CA2264790C - Mobile communication system - Google Patents

Abstract

A mobile communication system wherein a mobile station measures the distances between the mobile station and a plurality of adjacent radio base stations each from a time difference, eliminated by a fixed time difference, between the top time position of a time-divided CDMA burst signal received from a radio base station and the top time position of a time-divided CDMA burst signal transmitted to the radio base station in response to an instruction from the radio base station so that the top of the time-divided CDMA burst signal may come to the top time position of a time slot, and utilizes a result of the measurement for a hand-over discrimination, and frame synchronization between the radio base stations is established with a high degree of accuracy so that a plurality of radio base stations may operate in a same frame synchronization condition.

Description

CA 02264790 2001-09-14DescriptionMobile Communication SystemTechnical FieldThis invention relates to a mobile communication system which realizesfrequency channel sharing or time slot sharing using a time division multiple access(hereinafter referred to as TDMA) system or a time-divided code division multipleaccess (hereinafter referred to as time-divided CDMA) system, and more particularlyto measurement and utilization of the distance between a radio base station and amobile station or between radio base stations, and acquisition and keeping of framesynchronization between a radio base station and a mobile station or between radiobase stations.Background ArtA mobile communication system is formed principally from, for example, mobilevehicle-carried communication apparatus, mobile portable communication apparatusor like apparatus (hereinafter referred to as mobile stations) and radio base stationswhich communicate with the mobile stations by radio channels. In such a mobilecommunication system, sharing of a same radio frequency spectrum by different radiosystems (such sharing is hereinafter referred to as frequency channel sharing) issometimes performed between a frequency division multiple access (hereinafterreferred to as FDMA) or a TDMA system and a CDMA system. In the CDMA system,frequency channel sharing between different codes have already been put into practicalUSC.Here, a mobile communication system of the time slot sharing type that a TDMAsignal and a time-divided CDMA signal are shared in a same time slot is disclosed inU.S. Patent Application No. 08/524,974 separately filed for patent and so forth, nowissued as U.S. Patent No. 5,805,581. However, inCA 02264790 1999-02-24this patent application, measurement of the distance between a mobile station and a radiobase station is not mentioned, and no description of synchronization between radio basestations is given either.Meanwhile, also a technique regarding a mobile communication system of the timeslot sharing type and simultaneously of the frequency channel sharing type and anothertechnique regarding synchronization between radio base stations which employs asemi—fixed communication apparatus (hereinafter referred to as WLL station) whichemploys a wireless local loop (hereinafter referred to as WLL) or a like apparatus arepresent already. However, those techniques don't involve measurement of the distancebetween a mobile station and a radio base station or synchronization between radio basestations by a chip rate unit.A mobile communication system in which a plurality of CDMA signals are shared isknown by U.S. Patent No. 5,363,403. However, the specification of U.S. Patent No.5,363,403 describes nothing of a method of handling a time-divided CDMA signal.Another mobile communication system is known by U.S. Patent No. 5,511,068.However, U.S. Patent No. 5,511,068 relates to an adaptive filter for a time-dividedCDMA signal system, and the specification of U.S. Patent No. 5,511,068 does notdescribe that frequency channel sharing of a CDMA signal and a TDMA signal isperformed in one time slot.Meanwhile, a mobile communication system disclosed in International PublicationWO96/ 18277 relates to a macro diversity technique, and also an exchange is a simpleone which merely compares service qualities of information received simultaneously froma plurality of radio base stations to select a best one of them, but the results are notutilized for hand-over or the like. Further, the specification of International PublicationW096/18277 describes nothing of a combination with a tirne-divided CDMA technique.Further, a mobile communication system which measures the distance between amobile station and a radio base station using a chip code is disclosed by U.S. Patent No.5,506,864 and U.S. Patent No. 5,365,544. However, the U.S. patents relate to a mobileCA 02264790 1999-02-24communication system of the continuous CDMA system, and while the specifications ofthem describe that the mobile communication system is characterized in that it uses ageneric chip code in addition to a spread-spectrum chip code, they do not relate to amobile communication system which is based on the time-divided CDMA system and donot mention that the distance between a mobile station and a radio base station ismeasured making use of a frame structure or a characteristic of the time-divided CDMAsystem.Meanwhile, frame synchronization between radio base stations in a mobilecommunication system is known by U.S. Patent No. 5,440,561. However, thespecification of the U.S. patent merely describes a TDMA system but does not describe atirne-divided CDMA system. Also in regard to arrangement of radio base stations, it ispresumed that a radio base station is located at the center of a hexagonal cell, but noinvestigation is made for such a case that the distances between radio base stations arenot equal to each other.It is to be noted that, as other documents which relate to frame synchronizationbetween radio base stations of a mobile communication system, Japanese PatentLaid-Open Application No. 8-23569 and Japanese Patent Laid-Open Application No.8-33037 as well as Japanese Patent Laid-Open Application No. Hei 7-46660 are known.Each of Japanese Patent Laid-Open Application No. 8-23569 and Japanese PatentLaid-Open Application No. 8-33037 mentioned above describes, in the description of[Claims] in the specification thereof, that "so that the difference in timing may be equalto n times the one burst length of TDMA/TDD". This is a characteristic of the TDMAsystem which employs satellite communication, and has no relation to a mobilecommunication on the ground. In particular, in a mobile communication system on theground, since the distance between a mobile station and a radio base station does notbecome so long as the distance between a communications satellite and the earth, such asituation as described above does not occur, and also such a condition that a radio basestation transmits in a certain frame from among multiple frames whereas a tributary radioCA 02264790 1999-02-24base station transmits in another frame does not occur. Furthermore, the specificationsmentioned above describe nothing of frame synchronization by a chip plate unit of thetime-divided CDMA system.Meanwhile, Japanese Patent Laid-Open Application No. Hei 7-46660 discloses thatinformation representing to which one of time slots in a TDMA frame a TDMA controlsignal is transmitted is included in control information. Indeed where the frame length islong or in a system which requires provision of several control information time slots,such a prescription is required. However, where a mobile communication system whichpresupposes that a control signal is transmitted and received using a first time slot in aframe is considered, information indicating this explicitly need not be included in acontrol signal. Furthermore, a mobile communication system which can set a plurality ofTDMA control channels and a plurality of tirne-divided CDMA control channels in a firsttime slot need not use the technique disclosed in Japanese Patent Laid-Open ApplicationNo. Hei 7-46660 mentioned above.In this manner, as a mobile communication system which includes a plurality ofmobile stations and one or more radio base stations which communicate with the radiostations by radio channels, such various systems as described above are conventionallyknown already. In such radio communication systems, where both of the TDMA systemand the tirne—divided CDMA system are used, it becomes necessary to establish framesynchronization on the time axis between different radio base stations.It is to be noted that, while such establishment of frame synchronization betweenradio base stations can be performed using a time indication signal of the globalpositioning system (hereinafter referred to as GSP), to this end, it is required that allradio base stations be equipped with a GPS reception system and besides those radiobase stations are installed at locations at which a GPS signal can be received.However, in a personal communication system (hereinafter referred to as PCS) andso forth, a radio base station is sometimes installed indoors or in underground facilities.In order to utilize a GPS signal also in such a case, a complicated apparatus is required.CA 02264790 2001-09-14The conventional mobile communication systems have such problems as describedabove.Disclosure of the InventionThe present invention has been made to solve such problems as describedabove, and it is an object of the present invention to provide a mobile communicationsystem that a control channel is allocated to a TDMA signal or a time-divided CDMAsignal to establish frame synchronization between a plurality of radio base stationssuch as a plurality of operators (such a communication user which owns a systemwhich supplies a mobile communication service is normally called an operator) andthe distance between a mobile station and a radio base station is measured accuratelyso that discrimination of hand-over can be performed.In accordance with one aspect of the present invention, there is provided amobile communication system having a plurality of mobile stations and at least oneradio base station in which bidirectional communication using a time—divided codedivision multiple access (CDMA) system is performed between said mobile stationsand said at least one radio base station, wherein each of said mobile stations measuresa time difference having a fixed period of time subtracted therefrom, between a timethat a time-divided CDMA burst signal is received from said radio base station and atime that a time-divided CDMA burst signal is transmitted by that respective mobilestation in response to an instruction of said radio base station so that the transmittedtime-divided CDMA burst signal may arrive at said radio base station at a start timeposition of a time slot of said time-divided CDMA system, and transmits informationof the measured time difference to said radio base station.In accordance with another aspect of the present invention, there is provided amobile communication system having a plurality of mobile stations and at least oneradio base station in which bidirectional communication is performed between saidmobile stations and said at least one radio base station using a time division multipleaccess (TDMA)/time—divided code division multiple access (CDMA) sharing systemwherein a time slot of the time-divided CDMA system is inserted in time slots of aCA 02264790 2001-09-14frame construction of a TDMA system, wherein each of said mobile stations measuresa time difference having a fixed period of time subtracted therefrom, between a timethat a time-divided CDMA burst signal is received from said radio base station and atime that a time—divided CDMA burst signal is transmitted by that respective mobilestation in response to an instruction of said radio base station so that the transmittedtime—divided CDMA burst signal may arrive at said radio base station at a start timeposition of a time slot of said TDMA/time-divided CDMA sharing system, andtransmits information of the measured time difference to said radio base station.In accordance with yet another aspect of the present invention, there isprovided a mobile communication system having a plurality of mobile stations and atleast one radio base station in which bidirectional communication is performedbetween said mobile stations and said at least one radio base station using a timedivision multiple access (TDMA)/time-divided code division multiple access (CDMA)sharing system wherein a time slot of the time-divided CDMA system is inserted intime slots of a frame construction of a TDMA system, wherein each of said radio basestations includes: a first process of receiving, when first participating in said system, aTDMA control channel transmitted from said radio base station, transmitting controlinformation to said radio base station using a designated TDMA control channel basedon the received information, and performing communication of necessary controlinformation with said radio base station via the bidirectional TDMA control channels,a second process of communicating, when a TDMA speech channel is designated,using the TDMA speech channel, and a third process of communicating by using thetime—divided CDMA speech channel when a time-divided CDMA speech channel isdesignated.In accordance with still yet another aspect of the present invention, there isprovided a mobile communication system having a plurality of mobile stations and atleast one radio base station in which bidirectional communication is performedbetween said plurality of mobile stations and said at least one radio base station using atime division multiple access (TDMA)/time-divided code division multiple access(CDMA) sharing system that a time slot of the time-divided CDMA system is insertedCA 02264790 2001-09-14in time slots of a frame construction of a TDMA system, wherein each of said mobilestations measures a time difference having a fixed period of time subtracted therefrom,between a start time position of a TDMA burst or a time-divided CDMA burstreceived from said radio base station and a start time position of a TDMA burst or atime-divided CDMA burst transmitted by that mobile station to said radio base stationin a chip rate unit and transmits the time difference information to said radio basestation, and wherein a mobile switching center which accommodates a plurality ofradio base stations has a function of calculating distances between said radio basestations and said mobile stations based on the time difference information collectedfrom said radio base stations and storing distance information obtained from said timedifference information.In accordance with still yet another aspect of the present invention, there isprovided a mobile communication system having a plurality of mobile stations and aplurality of radio base stations in which bidirectional communication using a time-divided code division multiple access (CDMA) system is performed between saidplurality of mobile stations and said plurality of radio base stations, wherein when atime-divided CDMA control signal burst transmitted from a radio base station isreceived by a tributary base station, said tributary base station measures a timedifference having a fixed period of time subtracted therefrom, between a start timeposition of a time-divided CDMA burst signal received from said radio base stationand a start time position of a time-divided CDMA burst signal transmitted from saidtributary base station in response to an instruction from said transmitting radio basestation so that a beginning of the time-divided CDMA burst signal may arrive at saidtributary radio base position at a start time position of a time slot, and transmits themeasurement information therefrom to said transmitting radio base station.In accordance with still yet another aspect of the present invention, there isprovided a mobile communication system having a plurality of mobile stations and aplurality of radio base stations in which bidirectional communication is performedbetween said plurality of mobile stations and said plurality of radio base stations usinga time division multiple access (TDMA)/time-divided code division multiple accessCA 02264790 2001-09-14(CDMA) sharing system that a time slot of the time-divided CDMA system is insertedin time slots of a frame construction of a TDMA system, wherein when a TDMAcontrol signal burst or a time-divided CDMA control signal burst transmitted from aradio base station is received by a tributary base station, said tributary base stationmeasures a time difference having a fixed period of time subtracted therefrom,between a start time position of a TDMA burst signal or a time-divided CDMA burstsignal received from said radio base station and a start time position of a time-dividedCDMA burst signal transmitted from said tributary base station in response to aninstruction from said radio base station so that a start of the time-divided CDMA burstsignal may arrive at said radio base position at a start position of a time slot, andtransmits the measurement information therefrom to said transmitting radio basestation.In accordance with still yet another aspect of the present invention, there isprovided a mobile communication system having a plurality of mobile stations and aplurality of radio base stations in which bidirectional communication is performedbetween said plurality of mobile stations and said plurality of radio base stations usinga time division multiple access (TDMA)/time—divided code division multiple access(CDMA) sharing system that a time slot of the time-divided CDMA system is insertedin time slots of a frame construction of a TDMA system, and wherein a time divisionduplex mobile communication system in which a radio base station receives a time-divided CDMA control information signal burst transmitted from a tributary basestation discriminates that the received burst is at an appropriate burst position, andtransmits the discrimination information therefrom to said tributary base station via acontrol channel and said tributary base station transmits, after the discriminationinformation is received from said radio base station, information of a time differencebetween a start time position of a time-divided CDMA control signal burst transmittedfrom said radio base station and a start time position of a time—divided CDMA controlsignal burst transmitted from said tributary base station to said radio base station isconstructed, and wherein said radio base station performs transmission of one or bothof a TDMA control signal burst and a time-divided CDMA control signal burst oncefor two frames in a beginning slot of the frame.CA 02264790 2001-09-14In accordance with still yet another aspect of the present invention, there isprovided a mobile communication system having a plurality of mobile stations and aplurality of radio base stations in which bidirectional communication is performedbetween said plurality of mobile stations and said plurality of radio base stations usinga time division multiple access (TDMA)/time-divided code division multiple access(CDMA) sharing system that a time slot of the time-divided CDMA system is insertedin time slots of a frame construction of a TDMA system, wherein when a timedifference having a fixed period of time subtracted therefrom, between a start timeposition of a received burst position at a tributary base station of said plurality of basestations and a start time position of a TDMA burst signal or a time-divided CDMAburst signal transmitted from said tributary base station to said radio base station ismeasured in a chip rate unit of the time-divided CDMA by said tributary base stationwhen a TDMA control signal burst or a time-divided CDMA control signal bursttransmitted from a radio base station is received by said tributary base station, and themeasurement information is transmitted from said tributary base station to saidtransmitting radio base station to set frame synchronization between said radio basestations, frame synchronization between said radio base stations is first establishedusing a TDMA control channel, and then establishment of frame synchronizationbetween said radio base stations in a chip rate unit of the time-divided CDMA isperformed using a time-divided CDMA control channel, and then information of adisplacement time from a start time position of a time-divided CDMA control signalburst received from said transmitting radio base station by said tributary base stationwhen frame synchronization between said radio base stations is established in a chiprate unit of the time-divided CDMA to a top time position of a time-divided CDMAcontrol signal burst transmitted from said tributary base station to said transmittingradio base station is stored into a memory of at least one of said tributary base station,or a mobile switching center which accommodates said tributary base station.A mobile communication system according to a first aspect of the invention isconstructed such that a time difference, eliminated by a fixed time difference, betweena top time position of a burst received from a radio base station and a top time positionof a burst transmitted so that the burst may arrive at the radio base station at the top ofCA 02264790 2001-09-14a time slot, and information of the measured time difference is notified to the radiobase station. By the construction, a mobile communication system which can measurethe distance between a radio base station and a mobile station accurately can berealized.A mobile communication system according to a second aspect of the inventionis constructed such that, using a mobile communication system of the TDMA/time—divided CDMA sharing system in which a time slot of the time-divided CDMA systemis inserted in time slots of a frame construction of a TDMA system, each of the mobilestations measures a time difference, eliminated by a fixed time difference, between areceived burst from the radio base station and a top time position of a transmitted bursttransmitted so that the burst may arrive at the radio base station at the top of a timeslot, and transmits information of the measured time difference to the radio basestation.A mobile communication system according to a third aspect of the invention isconstructed such that the time difference, eliminated by the fixed time difference,between the top time position of the received burst signal from the radio base stationand the top time position of the transmitted burst signal to the radio base station ismeasured in a chip rate unit which is used in time-divided CDMA communication.A mobile communication system according to a fourth aspect of the inventionis constructed such that a time difference, eliminated by a fixed time difference,between a top time position of a burst received from any other radio base station thanthe radio base station with which the mobile station is communicating and the top timeposition of the burst transmitted to the radio base station is measured, and informationof the measured time difference is transmitted to the radio base station with which themobile station is communicating.A mobile communication system according to a fifth aspect of the invention isconstructed such that each of the mobile stations includes a correlationreception/despread-spectrum coding calculation section for extracting an originalsignal from a spread-spectrum coded signal sent thereto from the radio base station, a10CA 02264790 2001-09-14CH reception/TDMA demodulation section for demodulating a despread—spectrumcoded time-divided CDMA signal and extracting a necessary signal, a digital-to-analogconversion section for decoding an information signal from the extracted signal into ananalog signal and forwarding the analog signal to a man—machine interface section, ananalog—to-digital conversion section for coding an information signal from the man-machine interface section into a digital code signal, a CH transmission/TDMAmultiplexing section for multiplexing the coded signal, a spread-spectrum codingcalculation section for spectrum-spreading the multiplexed information on a frequencyaxis, a burst control/intra-frame time setting and time measurement section forcontrolling and adjusting an emission time of a burst signal in response to aninstruction of the radio base station and measuring the time difference, subtracted bythe fixed time difference, between the top time position of the burst signal receivedfrom the radio base station and the top time position of the burst signal transmitted tothe radio base station, and a spread-spectrum code generator-chip rate generator forgenerating a chip rate and a spread-spectrum code allocated to the self station.A mobile communication system according to a sixth aspect of the invention isconstructed such that the radio base station includes a plurality of signal processingsections each including a correlation reception/despread-spectrum coding calculationsection, a CH reception/TDMA demodulation section, a conversion section foroutputting an information signal to a network man—machine interface section, anotherconversion section for inputting an information signal from the network man—machineinterface section, a CH transmission/TDMA multiplexing section, a spread-spectrumcoding calculation section, a burst control/intra-frame time setting and timemeasurement section, and a spread-spectrum code generator-chip rate generator, and asignal distribution and addition section for performing distribution and addition ofsignals inputted to and outputted from the signal processing sections.A mobile communication system according to a seventh aspect of the inventionis constructed such that, in at least one of the signal processing sections of the radiobase station, the conversion section for decoding the information signal is constructedas a digital-to—analog conversion section which decodes a signal extracted by the CH11CA 02264790 2001-09-14reception/TDMA demodulation section into an analog information signal and outputsthe analog information signal to an analog network interface section, and theconversion section for coding an information signal is constructed as an analog-to-digital conversion section which codes an information signal inputted from the analognetwork interface section into a digital code signal.A mobile communication system according to an eighth aspect of the inventionis constructed such that the CH reception/TDMA demodulation section of each of themobile stations includes a demultiplexing section for separating an information signaland control information included in a time slot destined for the self station, and aninformation signal memory and a control information memory for temporarily storingthe information signal and the control information, that the CH transmission/TDMAmultiplexing section of each of the mobile stations includes an information signalmemory and a control information memory for temporarily storing an informationsignal and control information to be transmitted, and a multiplexing section forcomposing the information signal and the control information and multiplexing thecomposed signal in a time slot allocated to the self station, and that the mobile stationincludes a control information processor for decoding the control information from theradio base station, instructing the mobile station of various functions based on thedecoded control information and transmitting a response to the control information tothe radio base station.A mobile communication system according to a ninth aspect of the invention isconstructed such that, in a first process, necessary control information is firstcommunicated with a radio base station using a designated TDMA control channel,and thereafter, if a time-divided CDMA speech channel is designated, then in a thirdprocess, a service is performed using the time-divided CDMA speech channel, but if aTDMA communication channel is designated, then a service is performed using theTDMA communication channel in a second process. By this construction, when amobile station first participates in this system, regarding frame information from theradio base station, it is possible to first use a TDMA control channel to establish framesynchronization at a TDMA symbol rate, with which it is easy to establish12, .,.,.............——.CA 02264790 2001-09-14synchronization rough in time and then establish synchronization at a chip rate of thetime-divided CDMA which is higher in accuracy in time.A mobile communication system according to a tenth aspect of the invention isconstructed such that, in the first process, the mobile station measures a timedifference, eliminated by a fixed time, between a top time position of a TDMA controlsignal burst transmitted from the radio base station and a top time position of a TDMAcontrol signal burst transmitted to the radio base station and transmits the timedifference information to the radio base station. By this construction, in the firstprocess, the distance between the mobile station and the radio base station can bemeasured only from a signal burst of the TDMA without using the time-dividedCDMA by measuring the time difference of the fixed time difference from the timedifference of the top time position of the transmission burst with a number ofinformation symbols.A mobile communication system according to an eleventh aspect of theinvention is constructed such that, in the second process, the mobile station measures atime difference, eliminated by a fixed time difference from a time difference, betweena top time position of a TDMA speech signal burst transmitted from the radio basestation and a top time position of a TDMA speech signal burst transmitted to the radiobase station in a time-divided CDMA chip rate unit and transmits the time differenceinformation to the radio base station. By this construction, although the speechchannel is the TDMA, time measurement can be performed in a chip rate unit of thetime-divided CDMA. In particular, a chip rate is usually by approximately several tentimes to several hundred times faster than a symbol rate of the TDMA, andaccordingly, if measurement is performed with the chip rate of the higher speed, thenthe accuracy in time difference can be increased by a degree corresponding to themultiple.A mobile communication system according to a twelfth aspect of the inventionis constructed such that, in the third process, the mobile station measures a timedifference, eliminated by a fixed time difference from a time difference, between a top13CA 02264790 2001-09-14time position of a time-divided CDMA speech signal burst transmitted from the radiobase station and a top time position of a time-divided CDMA speech signal bursttransmitted to the radio base station and transmits the time difference information tothe radio base station. By this construction, the communication channel is the time-divided CDMA, and also time difference measurement is performed at a high speed ata chip rate of the time-divided CI)MA.A mobile communication system according to a thirteenth aspect of theinvention is constructed such that each of mobile stations measures a time difference,eliminated by a fixed time difference from a time difference, between top timepositions of bursts transmitted to and received from a radio base station in a chip rateunit and transmits a resulting value to the radio base station, and a mobile switchingcenter calculates distances between radio base stations and mobile stations based ontime difference information collected from the radio base stations and stores thedistance information. By determining hand-over based on the distance information,the emission of unnecessarily strong radio waves from both of a mobile station and aradio base station can be prevented.A mobile communication system according to a fourteenth aspect of theinvention is constructed such that the mobile switching center supervises distancesbetween each of the mobile stations and a plurality of radio base stations around themobile station and forwards a hand-over starting instruction so as to newly set a radiochannel to the one radio base station if the distance to the mobile station is shorterfrom any other one of the radio base stations than from that radio base station to whichthe mobile station is connected.A mobile communication system according to a fifteenth aspect of theinvention is constructed such that, if the nearest radio base station is a radio basestation of a different operator, the mobile switching center transmits a hand-overstarting instruction to the radio base station via a public system and a mobile switchingcenter of the different operator. Consequently, hand-over can be performed alsobetween radio base stations owned by different operators.14CA 02264790 2001-09-14A mobile communication system according to a sixteenth aspect of theinvention is constructed such that a tributary base station measures a time difference,eliminated by a fixed time difference, between a top time position between burstsignals received from a radio base station and a top time position of a burst transmittedso that the burst may arrive at the radio base position at the top of a time slot, andtransmits the measurement information to the radio base station. By this construction,a mobile radio system which can measure the distance between a radio base stationand a tributary base station accurately can be realized.A mobile communication system according to a seventeenth aspect of theinvention is constructed such that as the mobile communication system, using a mobilecommunication system of the TDMA/time-divided CDMA sharing system that a timeslot of the time-divided CDMA system is inserted in time slots of a frame constructionof a TDMA system is used, a tributary base station measures a time difference,eliminated by a fixed time difference from a time difference, between a top timeposition between burst signals received from a radio base station and a top timeposition of a burst transmitted so that the burst may arrive at the radio base position ata top time position of a time slot, and transmits the measurement information to theradio base station. By this construction, in a time division duplex (TDD) mobilecommunication system of the TDMA system and the time-divided CDMA system,frame synchronization between radio base stations is established, and interferencebetween time slots can be eliminated.A mobile communication system according to an eighteenth aspect of theinvention is constructed such that a time difference, eliminated by the fixed timedifference, between a top time position of a burst signal received from the radio basestation and a top time position of a burst signal transmitted to the radio base station ismeasured in a chip rate unit which is used in time-divided CDMA communication.A mobile communication system according to a nineteenth aspect of theinvention is constructed such that it is discriminated whether or not a time-dividedCDMA control information reception burst from the tributary base station is at an14aCA 02264790 2001-09-14appropriate burst position, and when the received burst is at an appropriate burstposition, the discrimination information is transmitted to the radio base station, andthen the information of the time difference eliminated by the fixed time difference istransmitted to the radio base station.A mobile communication system according to a twentieth aspect of theinvention is constructed such that, when the received burst signal from the tributarybase station is displaced from the appropriate burst position, the displacementinformation measured in a chip rate unit of the time-divided CDMA system istransmitted to the tributary base station via a control channel, and the tributary basestation receiving the displacement information corrects a top time position of a burstsignal to be transmitted to the radio base station in time based on the information ofthe displacement. By repeating this process, frame synchronization between the radiobase stations can be established.A mobile communication system according to a twenty first aspect of theinvention is constructed such that, when the tributary base station detects a top timeposition of a received burst signal, the tributary base station stops transmission of aburst signal of a time slot which should originally be transmitted from the tributarybase station, and receives a time—divided CDMA control signal burst transmitted fromthe radio base station.A mobile communication system according to a twenty second aspect of theinvention is constructed such that a radio base station discriminates that a receivedburst is at an appropriate burst position and transmits the discrimination information toa tributary base station and the tributary base station receiving the discriminationinformation transmits information of a time difference between top time positions oftransmitted and received burst signals so as to form a TDD mobile communicationsystem, and the radio base station transmits a TDMA control signal burst and a time-divided CDMA control signal burst in a top slot of every other frame.A mobile communication system according to a twenty third aspect of theinvention is constructed such that, in a time slot in which a TDMA control signal burst14bCA 02264790 2001-09-14and a time-divided CDMA control signal burst are not transmitted in a top slot thereof,the radio base station receives a TDMA control signal burst and a time-divided CDMAcontrol signal burst from the tributary base station.A mobile communication system according to a twenty fourth aspect of theinvention is constructed such that, in a time slot in which the basic base stationreceives a TDMA control signal burst and a time-divided CDMA control signal bursttransmitted from the tributary base station, although the time slot originally belongs toa down-link of the radio base station, the transmission is stopped and the TDMAcontrol signal burst and the time-divided CDMA control signal burst from the tributarybase station are received.A mobile communication system according to a twenty fifth aspect of theinvention is constructed such that the radio base station transmits, whensynchronization information is to be propagated from the radio base station to aplurality of tributary base stations, a TDMA control signal burst and a time-dividedCDMA control signal burst, and each of the tributary base stations transmits, whensynchronization information is to be propagated from the tributary base station to theradio base station, a TDMA control signal burst or a time-divided CDMA controlsignal burst. By this construction, frame synchronization in the accuracy in a chip rateunit of the time-divided CDMA can be established between one radio base station anda plurality of tributary base stations at a time.A mobile communication system according to a twenty sixth aspect of theinvention is constructed such that frame synchronization between radio base stations isestablished first using a TDMA control channel and then using a time-divided CDMAcontrol channel, and a displacement time between top time positions of burst signalstransmitted and received by a tributary base station is stored into a memory. By thisconstruction, even in a situation that updating of control information cannot beperformed in cooperation with a radio base station, interference between time slots canbe easily prevented readily if a top time position of a time-divided CDMA controlsignal received and the stored information of the displacement time are utilized.14cCA 02264790 2001-09-14A mobile communication system according to a twenty seventh aspect of theinvention is constructed such that, after frame synchronization between the radio basestations by time-divided CDMA control channels is established, the radio base stationuses a time slot, in which the radio base station has received the time-divided CDMAcontrol signal from the tributary base station, as a speech channel to down-links to aplurality of mobile stations. By this construction, time slots can be utilized effectively.A mobile communication system according to a twenty eighth aspect of theinvention is constructed such that, when the traffic decreases, a time slot which hasbeen used as a speech channel for a down-link to a plurality of mobile stations is usedfor reception of a time-divided CDMA control signal burst from the tributary basestation to resume frame synchronization establishment between the radio base stations.A mobile communication system according to a twenty ninth aspect of theinvention is constructed such that, upon establishment of frame synchronizationbetween radio base stations, after frame synchronization by a TDMA control channelis established, it is discriminated whether or not use of a time-divided CDMA controlchannel is allowed, and if use of a time—divided CDMA control channel is not allowed,then frame synchronization by the TDMA control channel is repeated, but if use of thetime-divided CDMA control channel is allowed, then frame synchronization by thetime-divided CDMA control channel is performed. By this construction, even in asituation that a time slot of the time-divided CDMA cannot be used for communicationof control signals between radio base stations, at least the system can be operated byestablishing frame synchronization between the radio base stations using the TDMAcontrol channel.Brief Description of DrawingsFIG. 1 is a system constructive View showing a general construction of amobile communication system according to an embodiment 1 of the present invention;14dCA 02264790 2001-09-14FIG. 2 is a diagrammatic View illustrating a relationship of time delays at amobile station of radio waves emitted from different radio base stations of theembodiment 1;FIG. 3 is a diagrammatic View illustrating a relationship of time delays at radiobase stations by which radio waves emitted from a mobile station in the embodiment 1are received;FIG. 4 is a block diagram showing a construction of a TDMA/time-dividedCDMA mobile station in the embodiment 1;FIG. 5 is a block diagram showing a construction of the TDMA/time-dividedCDMA base station in the embodiment 1;14eCA 02264790 1999-02-24FIG. 6 is a block diagram showing an example of a burst time measuring and settingfunction of a mobile station of the embodiment 1;FIGS. 7 and 8 are diagrammatic views showing an example of a frame structure ofa TDMA/time-divided CDMA communication system according to an embodiment 2 ofthe present invention;FIG. 9 is a flow chart illustrating a process of burst top time measurement andcontrol of a mobile station in the embodiment 2;FIG. 10 is a block diagram showing a construction of a mobile switching center inan embodiment 3 of the present invention;FIG. 11 is a diagrammatic view illustrating distance information between mobilestations and radio base stations around them stored in a memory of a system settingprocessor in the embodiment 3;FIG. 12 is a flow chart illustrating a control process of distance measurementbetween a mobile station and a radio base station and hand-over starting in theembodiment 3;FIG. 13 is a diagrammatic view illustrating an example of TDMA controlchannels/tirne-divided CDMA control channels for frame synchronization in anembodiment 4 of the present invention;FIG. 14 is a diagrammatic view illustrating allocation of transmission/reception oftime slots shown in FIG. 13;FIG. 15 is a diagrammatic view illustrating an example of TDMA controlchannels/time-divided CDMA control channels for frame synchronization in anembodiment 5 of the present invention;FIG. 16 is a diagrammatic view illustrating allocation of transmission/reception oftime slots shown in FIG. 15;FIG. 17 is a diagrammatic view illustrating an example of TDMA controlchannels/tirne—divided CDMA control channels for frame synchronization in a15. .........,.......»....__............u..._......._.._......n. . ......CA 02264790 1999-02-24TDMA/tirne-divided CDMA coexisting TDD system according to an embodiment 6 ofthe present invention;FIG. 18 is a diagrammatic view illustrating allocation of transmission/reception oftime slots shown in FIG. 17;FIG. 19 is a diagrammatic View illustrating another example of TDMA controlchannels/tirne-divided CDMA control channels for frame synchronization in theTDMA/time-divided CDMA coexisting TDD system according to the embodiment 6 ofthe present invention;FIG. 20 is a diagrammatic view illustrating allocation of transmission/reception oftime slots shown in FIG. 19;FIG. 21 is a flow chart illustrating a process of frame synchronizing controlbetween a radio base station and an adjacent tributary base station according to anembodiment 7 of the present invention;FIG. 22 is a flow chart illustrating a process of flame synchronization controlbetween a radio base station and an adjacent tributary base station according to anembodiment 8 of the present invention; andFIGS. 23 and 24 are diagrammatic views illustrating allocation oftransmission/reception of time slots in the embodiment 8.Preferred Embodiments of the InventionIn the following, in order to describe the present invention more in detail, bestforms for carrying out the present invention are described with reference to theaccompanying drawings.Embodiment 116CA 02264790 2001-09-14FIG. 1 is a system constructive view showing a general construction of a mobilecommunication system to which a time slot sharing and frequency channel sharing systemaccording to the present invention is applied. Referring to FIG. 1, reference numerals 1,2 and 3 denote each a radio base station, and 4 and 5 denote each a radio cover area(hereinafter referred to as cell) constructed by the radio base station 1 or 2. lt is to benoted that the cell 4 includes zones 11, 12 and 13, and the cell 5 includes zones 21, 22and 23. Reference numerals 31, 32, 33 and 34 denote each a mobile station (MS) suchas a mobile vehicle carried communication apparatus, a mobile portable communicationapparatus or the like which communicates with the radio base station 1 or 2 over a radiochannel. Reference numerals 41 and 42 denote each a WLL station (WS) whichcommunicates with the radio base station 1 or 2 over a radio channel.Reference numeral 6 denotes a mobile switching center (MSC) which controls theradio base stations 1 and 3, and 7 denotes a mobile switching center which controls theradio base station 2. Reference numeral 8 denotes a public switching telephone network(PSTN) to which the mobile switching centers 6 and 7 are connected by wires.The present embodiment 1 relates to a mobile station-radio base station distancemeasuring system for a TDMA/tirne-divided CDMA system and an apparatus therefor,and in the following, measurement of the distance between a mobile station and a radiobase station is described.It is to be noted that, in the mobile communication system according to the presentinvention, the mobile stations 31 to 34 and WLL stations 41 and 42 are communicatedwith the radio base stations 1, 2 and 3 such that accessing is performed based on amulti-carriers time division multiple access (Multi-carriers TDMA) system and atirne-divided CDMA system using a modulation signal according to a digital modulationsystem such as frequency shift keying (FSK), phase shift keying (PSK) such as BPSK,QPSK, DQPSK or TC-DQPSK or minimum phase shift keying (MSK) such as QAMSKor QGMSK, and they are radio connected to each other by TDMA/fiequency divisionduplex (hereinafter referred to as FDD), TDMA/time division duplex (hereinafter17CA 02264790 1999-02-24referred to as TDD) or by duplex according to time-divided CDMA/FDD ortime-divided CDMA/T DD.Further, the mobile communication system is a time slot sharing and frequencychannel sharing mobile communication system which has a time-divided CDMA signalchannel (hereinafter referred to as sharing channel) which shares a time slot and shares afrequency channel with an FDMA/TDD digital signal and a TDMA digital signal on thefrequency axis, and a frequency channel sharing and time slot sharing WLL and mobilecommunication system that a TDMA signal in a same time slot of a same frequencychannel is formed from a plurality of signals and the TDMA signals are synchronizationword sharing, time slot sharing and frequency channel sharing TDMA signal which canbe identified as they have synchronization words different from each other and have timeslot sharing and frequency channel sharing (including a case that the frequency is notshared) time-divided CDMA signal with the TDMA signal.FIG. 2 is a time chart illustrating a relationship of time delays at a mobile station ofradio waves emitted from different radio base stations. In FIG. 2, a relationship in timeafter radio waves of the burst type emitted from the radio base stations 1, 2 and 3 (BS1,BS2 and BS3) arrive at the mobile station 32 (MS32) where the mobile station 32 ispresent at a position shown in FIG. 1.Now, it is assumed that in FIG. 1 the mobile station 32 is radio connected to and iscommunicating with the radio base station 1. In this instance, radio waves of atime-divided CDMA burst signal emitted from the radio base station 1 arrive at themobile station 32 by a delay time based on the distance between the radio base station 1and the mobile station 32. In FIG. 2, the radio waves emitted from the radio base station1 are indicated as a burst 51 of a "TIME SLOT #0", and the radio waves arriving at themobile station 32 by the delay time are indicated as a burst 52 of a "DELAYED WAVEOF TIME SLOT #0". Further, the time delay is indicated by a time T2.It is to be noted that the delay time T2 cannot be measured directly by the radiobase station 1 or the mobile station 32. Therefore, as seen in FIG. 3, the emission time18CA 02264790 1999-02-24of radio waves of a time-divided CDMA burst signal to be transmitted from the mobilestation 32 to the radio base station 1 is adjusted forwardly or backwardly in response toan instruction of the radio base station 1 so that, when the radio waves arrive at the radiobase station 1, the top thereof may come to the top time position of a time slot. In thisFIG. 3, the radio waves transmitted from the mobile station 32 are denoted as a burst 61of "RADIO WAVES EMITTED FROM MOBILE STATION 32 SO AS TO ARRIVEAT RADIO BASE STATION 1 AT THE TOP OF TIME SLOT", and the radio wavesarriving at the radio base station 1 are denoted as a burst 62 of "DELAYED WAVESORIGINATING FROM RADIO WAVES EMITTED FROM MOBILE STATION 32PRIOR TO TOP VALUE OF TIME SLOT AND ARRIVING AT RADIO BASESTATION 1".In this instance, as seen in FIG. 3, the burst 61 to be transmitted by the mobilestation 32 is emitted prior by a time T8 to the top time position of a time slot so that theburst 62 may arrive at the radio base station 1 at the top time position of the time slot.Since the time difference T8 between the burst 61 and the burst 62 is a time in which theradio waves propagate over the same distance, it is equal to the time difference T2between the burst 51 and the burst 52 (T2 = T8). It is to be noted that the timedifference T7 between the top time position of the burst 52 and the top time position ofthe burst 61 can be measured in a chip rate unit by counting the number of clocks in themobile station 32. The information obtained is transmitted from the mobile station 32 tothe radio base station 1.Here, since the time difference T2 between the burst 51 and the burst 52 and thetime difference T8 between the burst 61 and the burst 62 are equal to each other asdescribed above, the following expression (1) stands. Accordingly, the top time positionof the time slot is present at the center of the time difference T7.T7=T2+T8=2xT2 ........ ..(1)CA 02264790 1999-02-24It is to be noted that the distance D1 between the mobile station 32 and the radiobase station 1 then is given, where the velocity of the radio waves is represented by C, bythe following expression (2).D1 = (T7/2) x C = T2 x C ........ .. (2)Meanwhile, a burst 53 of radio waves emitted from another radio base station, forexample, the radio base station 2, arrives as a burst 54 at the mobile station 32 after lapseof the time T4 as shown in FIG 2. Also in this instance, although the delay time T4cannot be measured directly, the time difference T3 between the top of the burst 54 fromthe radio base station 2 and the top of the burst 52 from the radio base station 1 can bediscriminated by counting clocks in the mobile station 32. Using the time difference T3,the distance D2 between the radio base station 2 and the mobile station 32 can becalculated, where the velocity of the radio waves is represented by C, in accordance withthe following expression (3).D2=T4xC=(T2-T3)xC ........ ..(3)Similarly, also the distance D3 between the other radio base station 3 and themobile station 32 can be calculated from the time difference T5 between the top of aburst 56 originating from a burst 55 of radio waves emitted from the radio base station 3and received after the time T6 and the top of the burst 52 from the radio base station 1,where the velocity of the radio waves is represented by C, in accordance with thefollowing expression (4).D3=T6xC=(T2—T5)xC ........ ..(4)It is to be noted that also such information is transmitted from the mobile station 32to the radio base station 1 to which the mobile station 32 is radio connected at present.Here, FIG. 4 is a block diagram showing a construction of a TDMA/time-dividedCDMA mobile station which has such a function of measuring the distance between amobile station and a radio base station as described above. Referring to FIG. 4,reference numeral 71 denotes an antenna, 72 a transmission/reception distribution section20CA 02264790 1999-02-24which effects distribution of a signal received by the antenna 71 and a signal to betransmitted from the antenna 71, 73 a RF (Radio Frequency) reception section whicheffects amplification of a signal received by the antenna 71, and 74 a RF transmissionsection which effects amplification of a signal to be transmitted from the antenna 71. Itis to be noted that the transmission/reception distribution section 72 is realized, for theTDD, by a transmission/reception change—over switch, but for the FDD, by a filterdiplexer.Reference numeral 75 denotes a correlation reception/despread—spectrum codingcalculation section having a (correlation reception) function of multiplying (reversecoding calculation) a spread-spectrum coded signal (CDMA signal) coded by andtransmitted from a radio base station by a spread-spectrum code allocated to the selfstation to extract an original signal not in a spread-spectrum coded state. It is to benoted that, for the TDMA, since despread—spectrum coding is unnecessary, thecorrelation reception/despread-spectrum coding calculation section 75 does not operate.Reference numeral 76 denotes a channel reception/TDMA demodulation section(hereinafter referred to as CH reception/TDMA demodulation section) having a functionof demodulating a despread—spectrum coded tirne-divided CDMA signal but, for aTDMA signal, demodulating a modulation signal and another function of extracting(demultiplexing) a necessary signal from a format of the demodulated signal andsupplying the extracted signal to processing sections for the signal.Reference numeral 77 denotes an error correction/voice decoding section serving asa digita1-to- analog conversion section for correcting an error of information (a digitalsignal) supplied from the CH reception/TDMA demodulation section 76, decoding avoice signal from the information and supplying the decoded voice signal as aninformation output to a man-machine interface section not shown. Reference numeral 78denotes an error correction/voice coding section serving as an analog-to-digitalconversion section for digitally coding a voice signal supplied from the man-machineinterface section and adding a code for error correction to the digitally coded voicesignal.21CA 02264790 1999-02-24Reference numeral 79 denotes a channel transmission/TDMA multiplexing section(hereinafter referred to as CH transmission/TDMA multiplexing section) having afunction of multiplexing error correction coded digital voice information and othercontrol information, incorporating the multiplexed information into a necessary time slotin a frame format and outputting a resulting signal. Reference numeral 80 denotes aspread-spectrum coding calculation section having a function of spectrum-spreading suchmultiplexed information on the frequency axis using a spread-spectrum code allocated tothe self station and outputting resulting information to the RF transmission section 74. Itis to be noted that, for the TDMA, since this spread-spectrum is not required, the spread-spectrum coding calculation section 80 does not operate.Here, those sections are similar to those of a mobile station of an ordinaryTDMA/time-divided CDMA system.Further, reference numeral 81 denotes a burst control/intra-frame time setting andtime measurement section having a function of controlling and adjusting the emissiontime of a burst signal (the burst 61 of FIG. 3 or the like) to be emitted from the selfstation based on information spread-spectrum coded by the spread-spectrum codingcalculation section 80 to set in w_h;ch time slot radio waves should be emitted(intra-frame time setting) and measuring (time measurement) the time difference T7 inFIG. 3 in a chip rate unit which is used in time-divided CDMA communication. The CHtransmission/FDMA multiplexing section 79 outputs a signal at a time controlled andadjusted by the burst control/intra-frame time setting and time measurement section 81.Reference numeral 82 denotes a spread-spectrum code generator-chip rate generatorwhich generate a chip rate to be used for such time-divided CDMA communication and aspread-spectrum code allocated to the self station and supplying them to the burstcontrol/intra-flame time setting and time measurement section 81, correlationreception/despread-spectrum coding calculation section 75, spread-spectrum codingcalculation section 80 and so forth.22”...........................»........«...... .CA 02264790 1999-02-24Subsequently, operation of the mobile station having such a construction asdescribed above is described.Radio waves coded and emitted from a radio base station are received by theantenna 71 and distributed by the transrnission/reception distribution section 72 so thatthey are sent to the RF reception section 73. The RF reception section 73 amplifies thesignal received by the antenna 71 and sends it to the correlation reception/despread-spectrum coding calculation section 75. The correlation reception/despread-spectrumcoding calculation section 74 multiplies the spread-spectrum coded tirne-divided CDMAsignal sent thereto from the RF reception section 73 by a spread-spectrum codegenerated by the spread-spectrum code generator—chip rate generator 82 and allocated tothe self station to effect despread-spectrum coding calculation to restore an originalsignal which is not in a spread-spectrum coded state.The time division CDMA signal despread-spectrum coded by the correlationreception/despread-spectrum coding calculation section 75 is sent to and demodulated bythe CH reception/TDMA demodulation section 76. The CH reception/TDMAdemodulation section 76 further extracts a necessary signal from a format of thedemodulated signal, and supplies the thus extracted signal to processing sections for thesignal such as the error correction/voice decoding section 77 and the burstcontrol/intra-frame time setting and time measurement section 81. The errorcorrection/voice decoding section 77 performs error correction of the information with adigital signal supplied thereto from the CH reception/TDMA demodulation section 76and effects analog conversion of the information to decode a voice signal, and suppliesthe voice signal as an information output to the man-machine interface section.On the other hand, a voice signal supplied from the man-machine interface sectionis converted into a digital code by the error correction/voice coding section 78 and acode for error correction is added to the digital code, and a resulting signal is sent to theCH transmission/TDMA multiplexing section 79. The CH transmission/TDMAmultiplexing section 79 multiplexes the digital voice information from the error23CA 02264790 1999-02-24correction/voice coding section 78 and other control information, incorporates themultiplexed information into a necessary time slot in a frame format, and outputs thesignal at a corrected time of radio wave emission designated from the radio base stationin accordance with control of the burst control/intra-frame time setting and timemeasurement section 81.Here, the burst control/intra-frame time setting and time measurement section 81controls and adjusts the emission time of a burst signal to be emitted from the selfstation, for example, the burst 61 shown in FIG. 3, in accordance with an instruction ofthe radio base station based on a signal supplied thereto from the CH reception/TDMAdemodulation section 76. Further, the burst control/intra-frame time setting and timemeasurement section 81 sets, by intra-frame timing setting, in which time slot radiowaves should be emitted, and further measures the time difference T7 in FIG. 3 by thetime measurement function.The signal outputted from the CH transrnission/TDMA multiplexing section 79 issent to the spread-spectrum coding calculation section 80, and the spread—spectrumcoding calculation section 80 spectrum-spreads the signal on the fi'equency axis using thespread-spectrum code allocated to the self station. The spread-spectrum code used bythe spread-spectrum coding calculation section 80 is generated by and supplied from thespread-spectrum code generator-chip rate generator 82. The signal spectrum-spread bythe spread—spectrum coding calculation section 80 is amplified by the RF transmissionsection 74, distributed by the transmission/reception distribution section 72, andtransmitted from the antenna 71.In this manner, the time position of the burst 52 of delayed waves emitted from theradio base station 1 shown in FIG. 3 and arriving at the mobile station 32 is measured bythe burst control/intra-frame time setting and time measurement section 81. On the otherhand, the burst 61 of radio waves emitted from the mobile station 32 so that it may arriveat the radio base station 1 at the top time position of the time slot illustrated in FIG. 3 isconstituted by the spread-spectrum code generator-chip rate generator 82 in response to24CA 02264790 1999-02-24an instruction of the burst control/intra-frame time setting and time measurement section81.Meanwhile, FIG. 5 is a block diagram showing a construction of theTDMA/tirne-divided CDMA radio base station. Referring to FIG. 5, reference numerals91 and 92 denote each a signal processing section equivalent to the functions of themobile station shown in FIG. 4 from which the antenna 71, transrnission/receptiondistribution section 72, RF reception section 73 and RF transmission section 74 areomitted. However, the present radio base station system not only inputs and outputs avoice signal, but also has a function of transmitting and receiving control information ofthe entire system and so forth, and also the processing sections for a control signal arerealized by similar functions to the signal processing sections 91 and 92 although they aresomewhat different in software.Reference numerals 93 and 94 denote each an adder for adding output signals fromthe signal processing sections including the signal processing sections 91 and 92.Reference numeral 95 denotes a signal distribution and addition section which performsdistribution and addition of reception signals inputted from the signal processing sections91 and 92 and so forth and transmission signals to be outputted from the signalprocessing sections 91 and 92 and so forth. Reference numeral 96 denotes a RFtransmission section as a transmission section, 97 a RF reception section asia receptionsection, 98 a transrnission/reception distribution section, and 99 an antenna. It is to benoted that the RF transmission section 96, RF reception section 97,transmission/reception distribution section 98 and antenna 99 are equivalent in functionto those of the mobile station shown in FIG. 4 although they may be different in size.Meanwhile, in the signal processing sections 91 and 92, reference numerals 101 and111 denote each an error correction/voice coding section, 102 and 112 denote each a CHtransrnission/TDMA multiplexing section, 103 and 113 denote each a spread-spectrumcoding calculation section, 104 and 114 denote each a burst control/intra-frame timesetting and time measurement section, 105 and 115 denote each a spread-spectrum code25CA 02264790 1999-02-24generator-chip rate generator, 106 and 116 denote each a correlationreception/despread-spectrum coding calculation section, 107 and 117 denote each a CHreception/TDMA demodulation section, and 108 and 118 denote each an errorcorrection/voice decoding section, and they are equivalent to the corresponding sectionsshown in FIG. 4. It is to be noted that, in the signal processing sections 91 and 92, theerror correction/voice coding sections 101 and 111 as analog-to-digital conversionsections and the error correction/voice decoding sections 108 and 118 as digital-to-analog conversion sections effect communication of an information signal in the form ofa voice signal not with the man-machine interface section but with an analog networkinterface section (not shown).Subsequently, operation of the mobile station constructed in this manner isdescribed.Here, basic operation of the signal processing sections 91 and 92 is similar tooperation of the corresponding sections of the mobile station, and each of the burstcontrol/intra-frame time setting and time measurement sections 104 and 114 effectssupervision and time measurement so that the top time position of radio waves from amobile station may be the top of a reception time slot and notifies a result of themeasurement to the mobile station. The mobile station controls the top time position ofradio waves to be emitted based on the information.To this end, a signal outputted from the spread—spectrum coding calculation section103 or 113 of the signal processing section 91 or 92 is added to a signal outputted fromanother signal processing section by the adder 93 or 94 and supplied to the RFtransmission section 96. However, in the case of the TDMA, the intermediate frequencycenter frequencies of the signals outputted from the signal processing sections 91 and 92are different from each other. This is because, even where a same time slot is used, thisis intended to prevent collision of signals. It is to be noted that, in the case of thetime—divided CDMA, since, even if a same time slot is used, two signals can be separatedfrom each other if spread-spectrum codes are different from each other, it is allowable26CA 02264790 1999-02-24that the intermediate frequency center frequencies of the signals outputted from thesignal processing sections 91 and 92 are identical with each other.The signals added by the adders 93 and 94 are amplified by the signal distributionand addition section 95 and transmitted from the antenna 99 via thetransmission/reception distribution section 98. On the other hand, a signal received bythe antenna 99 is sent via the transrnission/reception distribution section 98 to the RFreception section 97, by which it is amplified, whereafter it is inputted to the correlationreception/despread-spectrum coding calculation sections 106 and 116 and so forth of thesignal processing sections 91 and 92.In this manner, the radio base station can measure the distances to a plurality ofmobile stations using a plurality of signal processing sections such as the signalprocessing sections 91 and 92. Further, the radio base station sends out informationcommunicated with the mobile stations to the network side, that is, to the publicswitching telephone network 8 side from the mobile switching centers 6 and 7 shown inFIG. 1, and transmits information received from the network side to the mobile stationsfiom the antenna 99.It is to be noted that, while, in the foregoing description, the conversion section forperforming inputting and outputting of information signals is described as an apparatuswhich performs forwarding and reception of information signals by voice signals to andfrom the analog network interface section using the error correction/voice codingsections 101 and 111 serving as analog-to-digital conversion sections and the errorcorrection/voice decoding sections 108 and 118 serving as digital-to-analog conversionsections, as the conversion section for performing inputting and outputting ofinformation signals, a conversion section of another conversion form may be used toeffect forwarding and reception of information signals by some other signals to and fromthe network interface section, or those conversion sections may be used in a mixedcondition.27CA 02264790 1999-02-24Meanwhile, FIG. 6 is a block diagram showing an example of the burst timemeasuring and setting function of the mobile station. Referring to FIG. 6, referencenumeral 121 denotes a control information processor which effects decoding of controlinformation from a radio base station, instructs the mobile station of various functionssuch as, for example, distance measurement based on the decoded control information,and transmits the response to the radio base station. It is to be noted that this controlinformation processor 121 is omitted in FIG. 4.Reference numeral 122 denotes a correlator which multiplies a spread—spectrumcoded signal transmitted from a radio base station by the same spread-spectrum code toextract a signal from which the spread-spectrum code has been removed, and 123denotes an equalizer unit for removing interference of radio waves from a radio basestation by a multiplex propagation line. The correlation reception/despread-spectrumcoding calculation section 75 is composed of the correlator 122 and the equalizer unit123.Reference numeral 124 denotes a demultiplexing section for selecting a time slotdestined for the self station from among a plurality of time slots and separating aninformation signal and control information included in the time slot destined for the selfstation, 125 denotes an information signal memory into which the separated informationsignal is temporarily stored, and 126 a control information memory into which theseparated control information is temporarily stored. The CH reception/TDMAdemodulation section 76 is composed of the demultiplexing section 124, informationsignal memory 125 and control information memory 126.Reference numeral 127 denotes an information signal memory in which aninformation signal to be transmitted to a radio base station is temporarily stored, 128 acontrol information memory in which control information is temporarily stored, and 129a multiplexing section for composing the information signal and the control informationand multiplexing them into a time slot allocated to the self station. The CH28CA 02264790 1999-02-24transmission/TDMA multiplexing section 79 is composed of the information signalmemory 127, control information memory 128 and multiplexing section 129.Subsequently, operation of the mobile station having such a construction asdescribed above is described.Information transmitted thereto from a radio base station is inputted to thecorrelation reception/despread spectrum coding calculation section 75, in whichcorrelation reception and despread-spectrum coding are performed by the correlator 122and interference is removed by the equalizer unit 123. Then, the information is sent tothe CH reception/TDMA demodulation section 76, in which an information signal andcontrol information included in a time slot of the self station are separated by thedemultiplexing section 124 and the information signal is stored into the informationsignal memory 125 while the control information is stored into the control informationmemory 126. The control information processor 121 decodes the control informationstored in the control information memory 126 and sends a result of the decoding to theburst control/intra-frame time setting and time measurement section 81.Meanwhile, in the CH transmission/TDMA multiplexing section 79, an informationsignal and control information stored in the information signal memory 127 and thecontrol information memory 128 and to be sent to a radio base station are multiplexed bythe multiplexing section 129 and sent to the spread-spectrum coding calculation section80. The spread-spectrum code generator-chip rate generator 82 controls the top timeposition of a burst emission time of radio waves based on the information spread-spectrum coded by the spread-spectrum coding calculation section 80 to move the toptime position forwardly or rearwardly in time based on the signal from the burstcontrol/intra-frame time setting and time measurement section 81 having received theresult of decoding from the control information processor 121.As described above, according to the present embodiment 1, the distance between aradio base station and a mobile station can be measured accurately by measuring the timedifference between the top time position of a burst of radio waves received from the29CA 02264790 1999-02-24radio base station by the mobile station and the top time position of a burst of radiowaves transmitted by the mobile station so that the burst may arrive at the radio basestation at the top of a time slot in a chip rate unit of the time-divided CDMA.Embodiment 2Subsequently, as an embodiment 2 of the present invention, measurement of thedistance to a moving mobile station in a time-divided CDMA system is described.FIG. 7 is a diagrammatic view illustrating an example of a fiame structure of aTDMA/time-divided CDMA communication system for a PCS in the presentembodiment 2. This frame structure is similar to that of the PHS (Personal Handy PhoneSystem: a cordless system used in Japan), but is a little different in structure of time slots.In particular, the voice codec rate is assumed to be 16 kb/s, 8 kb/s or 4 kb/s. The datatransmission rate is 192 kb/s, and the information rate per one time slot is 23.2 kb/s. Bysetting the chip rate to 192 kb/s x 128 = 24.576 Mb/s, data of 192 kb/s mentioned aboveare spectrum-spreaded with orthogonal spread-spectrum codes having this chip rate.Accordingly, a plurality of time-divided CDMA signals having different orthogonalspread-spectrum codes in one time slot share a frequency channel, and the signals areused for communication between a ratio base station and a plurality of mobile stations.In the present system, if the system is used as a TDMA system and framesynchronization is to be established, synchronization in a symbol unit is used, andaccordingly, the synchronization accuracy relies upon the time of one symbol. In thisinstance, the one symbol length is 1/96 ksymbol/s = 10.41 s, and if it is assumed that thevelocity of radio waves is 300 m/1 us, then the distance which corresponds to onesymbol time exceeds 3 km, and accordingly, even if the position of a mobile station isrepresented in this accuracy, this is not practical. On the other hand, where the system isoperated with such a CDMA system that the modulation system is QPSK, the chip rate is24.567 Mb/s, the symbol rate is 12.283 Msymbol/s, the one symbol length is 0.0814 u s,30CA 02264790 1999-02-24and the distance is 24.4 m. Accordingly, in this CDMA system, it is practical to measurethe distance in a chip rate unit.Further, an example of a frame construction of the PDC (Personal Digital CellularTelecom System: a kind of cellular system) of Japan applied to a CDMA system is shownin FIG. 8. The chip rate is 10.752 Mb/s, the symbol rate is 5.376 Msymbol/s, the onesymbol length is 0.186 us, and the distance is 55.8 m. Since the PDC is a cellularsystem, if traveling of an automobile is taken into consideration, it has no problem inpractical use that the position accuracy is 56 m.Subsequently, position measurement in a chip rate unit by such a CDMA system as' described above is described. FIG. 9 is a flow chart illustrating a process of burst toptime measurement and control of a mobile station, and the process is performed by theapparatus shown in FIGS. 4, 5 and 6 in the embodiment 1 described hereinabove.A radio base station transmits a control channel of the TDMA system andsimultaneously transmits a control channel also of the tirne-divided CDMA system.However, a mobile station which does not acquire frame synchronization as yet firstperforms a connection starting procedure to the system by a control channel of theTDMA system. Accordingly, when the mobile station first participates in the systemfirst, it receives, in step ST1 which is the first process, the TDMA control channeltransmitted from the base station and transmits control information to the radio basestation using a designated TDMA control channel based on the received information sothat necessary control information is communicated between the mobile station and theradio base station through the bidirectional control channels.In particular, in this step ST1, the mobile station receives a TDMA control channelof the object radio base station and transmits an up—link TDMA control channel based ona top value of a frame of the TDMA control channel. The radio base station receivingthis up-link TDMA control channel measures the frame top time position of the receivedup-link signal and transmits an instruction to displace the frame top time positionforwardly or backwardly in a TDMA transmission timing unit to the mobile station.31CA 02264790 1999-02-24After TDMA synchronization is completed, the mobile station measures the timedifference between the top time positions of the transmission and reception bursts withthe number of information symbols and transmits the value of the information symbolnumber to the radio base station.Thereafter, in step ST2, the mobile station performs discrimination of whether theprocess should advance to a speech channel of the time-divided CDMA system or aspeech channel of the TDMA system. To which one of the speech channels the processshould advance is discriminated and processed based on a function of the mobile station,a traffic condition of a cell in which the mobile station is positioned at present and soforth.When it is discriminated that the process should advance to a speech channel of thetime-divided CDMA system, the mobile station performs, in step ST3, communication ofcontrol information with the radio base station using a time-divided CDMA controlchannel. During the communication by the time-divided CDMA control channel, timeslot position control in a chip rate unit is performed simultaneously with thecommunication of control information. It is to be noted that this corresponds tomeasurement of the time different T7 in a chip rate unit as indicated in FIG. 3 in theembodiment 1.In particular, in step ST3, the mobile station receives the time-divided CDMAcontrol channel of the object radio base station and transmits an up-link time-dividedCDMA control channel based on a top value of a frame of the time-divided CDMAcontrol channel. The radio base station receiving the up-link time-divided CDMAcontrol channel measures the frame top time position of the received up-link signal, andtransmits an instruction to displace the time-divided CDMA transmission timingforwardly or rearwardly in a chip rate unit to the mobile station. After framesynchronization by the time-divided CDMA is completed, the mobile station measuresthe time difference between the top time positions of the time-divided CDMA32CA 02264790 1999-02-24transmission and reception bursts in a chip rate unit and transmits a value of the timedifference to the radio base station.Thereafter, when the process advances to the designated time-divided CDMAspeech channel, a service is started using the tirne-divided CDMA speech channel in stepST4 which is the third step. It is to be noted that, in this instance, the radio base stationsuccessively receives a burst of the tirne-divided CDMA of the up-link duringcommunication, successively measures the distance between the mobile station and theradio base station for each frame and instructs the mobile station of the information ofthe emitting position of the burst.In this measurement, for the system for a PCS shown in FIG. 7, the symbol lengthof the time-divided CDMA signal chip rate is 0.814 us, and approximately 10 secondsare required for a person to move over the distance 24.4 m on foot. Therefore, the burstemission time in a chip rate unit may be adjusted once per 10 seconds, and in order tocontrol this, the occupying ratio of the process time is very low with both of the mobilestation and the radio base station. Accordingly, the distance measurement by a chip rateunit does not make an excessive burden to the processor processing.On the other hand, for the system for a cellular shown in FIG. 8, the symbol lengthof the time-divided CDMA signal chip rate is 0.186 us, and approximately 2 seconds arerequired for an automobile to run over the distance 55.8 m at 100 km/h. Therefore,adjustment of the burst emission time in a chip rate unit may be performed once per 2seconds, and in order to control this, the occupying ratio of the process time is very lowwith both of the mobile station and the radio base station. Accordingly, also in thisinstance, the distance measurement by a chip rate unit does not make an excessiveburden to the processor processing.On the other hand, when it is discriminated in step ST2 that the process shouldadvance to a speech channel of the TDMA system, a service is started using thedesignated TDMA speech channel in step ST5 which is the second process. It is to benoted that, when to measure the distance between the mobile station and the radio base33CA 02264790 1999-02-24station which are communicating in the TDMA system with each other, where the mobilestation and the radio base station have chip rate generators (the chip rate generators 82,105 and 115 shown in FIGS. 4 and 5 of the embodiment 1) in the insides thereof,emission of an up-link signal burst from the mobile station to the radio base station isadjusted and controlled in a chip rate unit of the time-divided CDMA. In other words,this signifies that the time T7 in the inside of the mobile station illustrated in FIG. 3 ofthe first embodiment is measured in a chip rate unit and this information is transmitted tothe radio base station via control information in the TDMA speech channel. This is easywith the mobile station and the radio base station of the TDMA/tirne-divided CDMAsharing system.After a service is started by the tirne-divided CDMA control channel or the TDMAspeech channel, the mobile station measures, in step ST6, the distances to a plurality ofradio base stations other than the radio base station with which the mobile station iscommunicating by the method described above, and transmits the distances to the radiobase station with which the mobile station is communicating. The information of thedistances between the mobile station and the radio base stations is used fordiscrimination of hand-over involved in movement of the mobile station by the mobileswitching center (MSC) together with information of reception electric field strengthsfiom the mobile station at the individual radio base stations and reception electric fieldstrengths at the mobile station of radio waves from the individual radio base stations. Itis to be noted that this processing is described in detail in a different embodiment.As described above, according to the present second embodiment, sincecommunication of necessary control information is first performed with a radio basestation by a designated TDMA control channel and then a service is performed using adesignated time-divided CDMA speech channel or TDMA speech channel, when amobile station first participates in this system, it is possible to establish framesynchronization at a TDMA symbol rate with which synchronization rough in time canbe established regarding frame information from the radio base station first using the34CA 02264790 1999-02-24TDMA control channel and then establish synchronization at a chip rate of thetime-divided CDMA which is higher in accuracy in time.Embodiment 3Subsequently, as an embodiment 3 of the present embodiment, a mobile stationhand-over system under a condition that radio base stations are installed not at equaldistances is described.Hand-over which changes over a mobile station to the nearest radio base station isusually performed based on electric field strengths of received signals from the mobilestation or radio base stations.However, in a mobile communication system in which the distances between radiobase stations are not necessarily equal to each other such as where radio base stations ofdifferent operators are installed in a mixed condition and cells (radio cover areas) of themoverlap with each other or where a large number of radio base stations are installed in anarrow area because of the communication loads, the following situation exists: it cannotbe discriminated that the distance from a mobile station to a neighboring radio basestation is shortest when the transmission power to the mobile station or the radio basestation is maximum.For example, when the mobile station 32 of FIG. 1 moves in the south-eastdirection (here, the upward direction of FIG. 1 is the north) while communicating withthe radio base station 2, the mobile station 32 approaches the neighboring radio basestation 1 while the transmission power of the radio base station 2 to the mobile station 32does not exhibit a maximum value. In an extreme case, also when the mobile station 32comes very near to the radio base station 1, there is the possibility that the mobile station32 keeps a communication channel with the radio base station 2. Accordingly, there isthe possibility that it may not be sufficient to determine hand-over only based on thetransmission power.35CA 02264790 1999-02-24FIG. 10 is a block diagram showing a construction of a mobile switching centeraccording to the embodiment 3 which controls mobile station hand-over under such acondition that radio base stations are installed not at equal distances as described above.It is to be noted that, while this FIG. 10 shows the mobile switching center 6 of FIG. 1,the radio base stations 1 and 3 are connected to this mobile switching centerwhile theradio base station 2 is connected to the different switching center 7. Referring to FIG.10, reference numeral 1 denotes a radio base station (BS1), 3 another radio base station(BS3), 6 a mobile switching center (MCSO1), and 8 a public system (PSTN). It is to benoted that those elements are same as those denoted by same reference numerals in FIG.1.Further, in the mobile switching center 6, reference numeral 131 denotes a PSTNinterface which eflects transmission and reception of information to and from the publicsystem 8 of the mobile switching center 6 and transmission and reception of signalingsignals (a dial signal, accounting information, password information and so forth).Reference numeral 132 denotes a channel switching section which transfers information(voice information/data information and so forth) sent from the public system 8 to theradio base station 1 or 3 in which the other party mobile station is present and transmitsinformation transmitted thereto from the mobile station via the radio base station to thepublic system 8. Reference numeral 133 denotes a system setting processor whichselects, from among radio systems which connect the radio base station and the mobilestation such as the TDMA system or the time-divided CDMA system, a system withwhich the mobile station of the destination of connection can communicate, and instructsthe radio base station and the mobile station to set the system. Reference numeral 134denotes a signaling processor which processes the number of a mobile station to beconnected, a password procedure for charging a mobile station of a destination ofconnection for the charge for a telephone call (to confirm whether or not the mobilestation of the destination of connection is illegally used) and so forth. Reference numeral135 denotes a base station interface which communicates information (voiceinformation/data information and so forth) to be transmitted to a mobile station via a36CA 02264790 1999-02-24radio base station, signaling information with a radio base station, and systeminformation which defines radio connection between a radio base station and a mobilestation.It is to be noted that the system setting processor 133 of the mobile switchingcenter 6 includes a memory (not shown) in the inside thereof, and distance informationbetween mobile stations and radio base stations around the mobile stations are stored inthe memory. FIG. 11 is a diagrammatic View illustrating an example of the distanceinformation stored in the memory, and here, it illustrates an example of distanceinformation between the mobile station 32 (MS32) and radio base stations around the' mobile station 32 in the system setting processor 133 of the mobile switching center 6.The memory of the system setting processor 133 of the mobile switching center 6 stores,as seen in FIG. 11, not only distance information to the radio base station 1 (BS1) andthe radio base station 3 (BS3) but also distance information to the radio base station 2(BS2). In other words, the mobile switching center 6 (MSCO1) acquires also suchinformation that the switching center 7 (MSC02) of another operator may startmeasurement from the switching center 7.While the distances of the mobile station 32 to the radio base stations 1, 2 and 3 areillustrated in FIG. 11, if a speech channel is set between the mobile station 32 (MS32)shown in FIG. 1 and the radio base station 2 (BS2) when the mobile station 32 moves inthe south-east direction until it comes to the position illustrated in FIG. 11, even thoughthe mobile station 32 arrives at this position, it remains connected to the radio basestation 2 and there is no trouble with the radio base station 2 itself. However, to theradio base station 1 (BS1), high power is transmitted in the proximity of the radio basestation. In the case of the CDMA system, since such a situation makes a factor ofdeteriorating the system performance regarding the radio base station 1, it is necessary toeliminate a high power transmission condition in the proximity of a radio base station.Subsequently, a process of eliminating such high power transmission of a mobilestation in the proximity of a radio base station as described above is described.37CA 02264790 1999-02-24Here, FIG. 12 is a flow chart illustrating a process of controlling distancemeasurement between a mobile station and a neighboring radio base station in such acase as described above and starting of hand—over. It is to be noted that processingsoftware for realizing the process is provided in the system setting processor 133 of themobile switching center 6 shown in FIG. 10.First, in step ST11, a mobile station measures the distance to an object radio basestation with which a speech channel is set and the distances to a plurality of otherneighboring radio base stations with which channel setting is possible, and transmits aresult of the measurement to the object radio base station. The distances between themobile station and the individual radio base stations are obtained each as a value which isequal to one half a time difference measured in step ST1, step ST4 or step ST5 of FIG. 9in the description of the embodiment 2 above multiplied by the velocity of light.For example, describing the mobile station 32 shown in FIG. 1 as an example, themobile station 32 measures the distance to the radio base station 1 with which it iscommunicating using the method described hereinabove, and transmits resulting distanceinformation to the radio base station 1. The mobile station 32 further measures thedistances to the other adjacent radio base station 2, with which it is not communicating,using a similar method, and transmits the distance information to the radio base station 1.Furthermore, the mobile station 32 calculates the distances to other radio base stationswith which channel setting is possible such as the radio base station 3 and transmitsdistance information to the radio base station 1.Then, in step ST12, the mobile switching center 6 collects the distance informationfrom the radio base station 1 and supervises presence of any other neighboring radio basestation which is nearer to the mobile station 32 than the radio base station with which themobile station 32 is communicating, and if it is discriminated in step ST13 that there isno nearer station, then the mobile station 32 returns its process to step ST11 to repeatthe processing described above. On the other hand, if it is discriminated in step ST13that there is a nearer station, then the mobile switching center 6 starts a procedure to38CA 02264790 1999-02-24hand over the destination of the communication of the mobile station to the nearest radiobase station.Here, if the mobile station 32 shown in FIG. 1 is communicating with the radio basestation 1 and both of the radio base station 1 and the mobile station 32 have necessaryreception signal strengths and besides the error rate of information communicatedbetween them satisfies predetermined criteria, the mobile station 32 need not performhand-over if the discrimination is based on conventional criteria. Actually, however, themobile station 32 may possibly be nearer in distance to the radio base station 2 than tothe radio base station 1 as seen in FIG. 1. Where there is a radio base station nearer tothe mobile station in this manner, the mobile switching center 6 causes the mobile station32 to start a procedure of hand-over to update the destination of communication of themobile station 32 to the nearer radio base station (in the example shown, the radio basestation 2).Next, the process advances to step ST15, in which, also after the hand-overprocedure is completed, the mobile station continues its measurement of the distances tothe radio base stations therearound and informs the mobile switching center of theobtained distance information via the new radio base station handed over.It is to be noted that, while, in the foregoing description, a case that agradio basestation of the destination of the hand-over is owned by the same operator is described,the operator which owns the radio base station of the destination of the hand-over maybe different from the operator which owns the radio base station with which the mobilestation is communicating. In particular, where the radio base station nearest to themobile station is owned by a different operator, the mobile switching center transmits ahand-over starting instruction to the nearest radio base station via the public system 8and a mobile switching center owned by the different operator. Consequently, hand-overto the radio base station owned by the different owner can be performed by a processsimilar to that of the hand-over to the radio base station owned by the same operator.39CA 02264790 1999-02-24As described above, according to the present embodiment 3, since a hand-overstarting instruction is forwarded based on a result of accurate measurement of thedistances between a mobile station and radio base stations, comparing with another casethat determination of hand-over is performed based on a discrimination in regard to thereception signal strength or the like in such a field that cells of radio base stations ofdifferent operators overlap with each other or in such a field that a large number of radiobase stations are installed within a narrow range from the reason of the communicationload or the like, hand-over to a radio base station nearest to the mobile station can beperformed with a higher degree of certainty, and it is possible to eliminate emission ofunnecessarily strong radio waves from both of the mobile station and the radio basestation emit.Embodiment 4Next, as an embodiment 4 of the present invention, a fiame synchronization controlchannel system between radio base stations in the case of the TDD is described.While the embodiment 1 is described such that the time difference between the toptime position of a burst signal received by a mobile station from a radio base station andthe top time position of another burst signal transmitted from the radio mobile station tothe radio base station is measured, the present embodiment 4 is constructed such that thetime difference between the top time position of a burst signal when burst radio wavestransmitted from one radio base station (hereinafter referred to as radio base station) arereceived by another radio base station (hereinafter referred to as tributary base station)and the top time position of another burst signal transmitted from the tributary basestation to the radio base station is measured by the tributary base station.FIG. 13 is a diagrammatic view illustrating an example of a TDMA controlchannel/tirne—divided CDMA control channel for frame synchronization between radiobase stations of a plurality of different operations in a TDMA/time-divided CDMAcoexistence TDD system.40.............,.....a..................................,.__...,. . . 2. ,. ,a....ta..............(.................._................,,.. V . . . - ., .._....._.._.l .....,...................__.......u.4..m..a.,..........._.,,. ... .. . . ., , . .,...................M........., CA 02264790 1999-02-24In this FIG. 13, as a control channel, a burst 204 is used for the TDMA, but anotherburst #201-0 is used for the tirne-divided CDMA. Those two bursts are radio wavesallocated to a transmission time slot To-1 and emitted from a radio base station (forexample, the radio base station 1) and correspond to the burst 51 of FIG. 3. Thetributary base station (for example, the radio base station 2) which receives the burstperforms transmission of burst radio waves prior to the top time position of the time slotsimilarly to the burst 61 of FIG. 3.Further, a control channel transmitted from the radio base station 2 to the radiobase station 1 is a burst 209 for the TDMA, but a burst #203-O for the time-dividedCDMA Those bursts are both allocated to a transmission time slot To-2.It is to be noted that, in FIG. 13, the top time position of the transmission time slotT0—1 and the top time position of the transmission time slot To-2 are spaced from eachother by 10 ms (a fixed time difference). In particular, since the axis of ordinate is a timeaxis in FIG. 13, the lower side edge of the transmission time slot To-1 is the top timeposition of the burst 204 of the TDMA or the burst #201—O of the tirne-divided CDMAemitted from the radio base station 1, and the lower side edge of the transmission timeslot To—2 is the top time position of the burst 209 of the TDMA or the burst #203-O ofthe tirne-divided CDMA emitted from the radio base station 2. While the two top timepositions are displaced by 10 ms of the fixed time difference in this manner, in FIG. 3, thetop time positions of the time slot are represented by the same time position eliminatingthe fixed time difference.Next, a construction method for a control channel regarding a system whichmaintains frame synchronization between radio base stations in the case of a PCS whichis a TDD similarly as in FIG. 7 and has the time slot structure illustrated in FIG. 13 andso forth are described.Here, FIG. 14 is a diagrammatic view that an example of allocation of transmission(TX) and reception (RX) to radio base station time slots of a TDMA controlchannel/time-divided CDMA control channel illustrated in FIG. 13 is indicated in the41CA 02264790 1999-02-24form of a table. Referring to FIG. 13 described above and this FIG. 14, when a TDMAcontrol channel 204 and a time-divided CDMA control channel #201-0 are transmitted toa transmission time slot T0 of the radio base station 1, the radio base station 2 mustreceive this control channel signal at the transmission time slot T0 of itself. Accordingly,when the radio base station 2 receives the control channel at the transmission time slotTo, the radio base station 2 cannot transmit with this time slot.In particular, the radio base station 2 receives a TDMA control signal in the TDMAtime slot 204, receives a time-divided CDMA control signal in the time-divided CDMAtime slot #201-O, transmits a TDMA control signal in the TDMA time slot 209, andtransmits a time-divided CDMA control signal in the time"-divided CDMA’ time slot#203-O.Here, when the radio base station receives the time-divided CDMA controlinformation signal from the tributary base station, it performs discrimination of whetheror not the received burst signal is at an appropriate burst position. As a result, if it isdiscriminated that the received burst signal is at an appropriate burst position, the radiobase station transmits the discrimination information to the tributary base station throughthe control channel. When the discrimination information from the radio base station isreceived, the tributary base station produces time difference information by subtractingthe fixed time difference from the time difference between the top time position of thetime-divided CDMA control signal burst transmitted from the radio base station and thetop time position of the tirne—divided CDMA control signal burst to be transmitted fromthe tributary base station to the radio base station, and transmits the time differenceinformation to the radio base station.In particular, only after the radio base station detects coincidence with the top timeposition of the burst 62 illustrated in FIG. 3 (while it is illustrated in FIG. 3 that this burst62 is emitted from the mobile station 32, here the mobile station is read as the tributarybase station) and the coincidence detection information is transmitted from the radio basestation to the tributary base station, the tributary base station transmits time difference42CA 02264790 1999-02-24information obtained by subtracting the fixed time difference (10 ms illustrated in FIG.13) from the time difference between the top time position of the reception burst signaland the top time position of the transmission burst signal to the radio base station.On the other hand, when the time-divided CDMA control information signal bursttransmitted from the tributary base station arrives at the radio base station, if it isdiscriminated that the burst signal received by the radio base station is displaced from anappropriate burst position, that is, if the top time position of the burst 62 illustrated inFIG. 3 is displaced from the top time position of the time slot, the radio base stationmeasures the displacement time in- a chip rate unit of the tirne-divided CDMA system andtransmits displacement information obtained to the tributary base station via the controlchannel. Based on the displacement information received from the radio base station, thetributary base station corrects the top time position of the time-divided CDMA controlsignal burst signal to be transmitted to the radio base station with reference to the toptime position of the time—divided CDMA control signal burst signal transmitted from theradio base station, and emits a burst signal to the radio base position at the timecorrected by the displacement.It is to be noted that, in such frame synchronization between radio base stations asdescribed above, as a cause by which synchronism is lost, if the frequency stability of anoscillator in a transmitter in the radio base station is 1 x 10'“, then since thelsymbol rateof the system of FIG. 7 is 12.283 Msynbol/s, displacement of approximately 13 symbolsper second occurs, and fluctuation of one symbol for each 1/13 = 0.769 = 76.9 Msecoccurs. Here, since the frame length is 10 ms, the timing must be corrected by 1 chipsymbol once for 7 frames.It is sufficient that the correction operation against chip rate displacement describedabove is performed once for 2 frames. In the construction of a control channel illustratedin FIGS. 13 and 14, synchronization correction between radio base stations and mobilestation position measurement by a tirne-divided CDMA control channel is performedCA 02264790 1999-02-24once for 2 frames, and a TDMA control channel is transmitted once for 2 frames so thatit is used for initial acquisition for synchronization information and control information.Here, while, in the embodiment 2 described above, synchronization displacement ofa chip rate by a mobile station carried on a moving automobile or carried by a walkingperson is argued, since correction necessitated as a result of displacement of an internaloscillator in the transmitter is much higher in frequency than correction necessitated as aresult of the synchronization displacement, the synchronization displacement correctioncan be made only against the displacement caused by the oscillator in the transmitter.It is to be noted that, since the time-divided CDMA burst #2091-0 illustrated in FIG.13 is a transmission time slot in the TDD system, the tributary base station shouldoriginally perform transmission of a time-divided CDMA burst signal. However, in orderto receive a time-divided CDMA burst signal transmitted from the radio base station,transmission with the time-divided CDMA burst #201—0 is interrupted. In a time-dividedCDMA time slot, many code multiplexed speech channels can be set and maycommunications (in this instance, transmissions) can be performed at a time. However,to establish frame synchronization between radio base stations is very important to sucha system which effects communication by time division on a time frame as illustrated inFIG. 13. Accordingly, setting of a large number of speech channels is temporarilysacrificed, and the time-divided CDMA burst #201-0 is used for reception of one controlchannel from the radio base station.As described above, according to the present embodiment 4, since a tributary basestation measures the time difference eliminated by the fixed time difference from the timedifference between the top time position of a reception burst signal and the top timeposition of a transmission burst signal in a chip rate unit and transmits the time differenceinformation to a radio base station, in a TDD mobile communication system of theTDMA system and the time-divided CDMA system, frame synchronization betweenradio base stations is established and interference between time slots can be eliminated.44CA 02264790 1999-02-24Embodiment 5It is to be noted that, while, in the embodiment 4 described above, a framesynchronization control channel system between radio base stations for the TDD isdescribed, as an embodiment 5 of the present invention, a frame synchronization controlchannel system between radio base stations for the FDD is described below.FIG. 15 is a diagrammatic View illustrating an example of a TDMA controlchannel/tirne-divided CDMA control channel for frame synchronization between radiobase stations of a plurality of different operators in a TDMA/tirne-divided CDMAcoexistence FDD system. It is to be noted that, also in this FIG. 15, the top timeposition of a time slot T/R0-1 and the top time position of another time slot T/R0-2 aredisplaced by 10 ms from each other.Subsequently, a construction method for a control channel regarding a systemwhich maintains frame synchronization between radio base stations in the case of acellular system which is an FDD similarly as in FIG. 8 and has the time slot structureillustrated in FIG. 15 and so forth are described. It is to be noted that FIG. 16 is adiagrammatic view which illustrates an example of transmission/reception (TX/RX)allocation to radio base station time slots of the TDMA control channel/tirne-dividedCDMA control channel illustrated in FIG. 15 in the form of a table.Referring to FIGS. 15 and 16, when a TDMA control channel 214 and atime-divided CDMA control channel #211-0 are transmitted to a transmission/receptiontime slot T/R0-1 of the radio base station 1, a tributary base station must receive thiscontrol channel signal in a transmission/reception time slot T/R0 of itself. Accordingly,when the tributary base station receives a control channel in the transmission/receptiontime slot T/R0, the tributary base station cannot transmit with this time slot.In particular, the radio base station 2 receives a TDMA control signal in a TDMAcontrol channel 214, receives a time-divided CDMA control signal in a time-dividedCDMA time slot #211-O, and transmits a TDMA control signal in a TDMA time slot 21645CA 02264790 1999-02-24or transmits a time-divided CDMA control signal in a time-divided CDMA time slot#212-0.Meanwhile, with the system shown in FIG. 8 which is an example of a time-dividedCDMA system for a cellular different from that shown in FIG. 15 described above, thesymbol rate is 5.376 Msynbol/s, and where the stability is 1 x 10", displacement byapproximately 5.4 symbols occurs for one second, and accordingly, correction by onesymbol must be performed for 1/5.4 = 0.185 = 185 ms. Since the frame length is 20 ms,from 185/20 = 9.2, correction must be performed once for 9 frames.It is sufficient if a correction operation against the chip rate displacement describedabove is performed once for 2 frames. In the construction of a control channel illustratedin FIGS. 15 and 16, synchronization correction between radio base stations and mobilestation position measurement by a time-divided CDMA control channel is performedonce for 2 frames, and in the remaining one of the two fiames, a TDMA control channelis transmitted and used for initial acquisition for synchronization information and controlinformation.In particular, according to the example illustrated in FIG. 15, the radio base station1 transmits, in the top transmission/reception time slot T/R0—1 of a flame, a burst 214 ofthe TDMA control channel and a burst #211—O of the time-divided CDMA controlchannel. However, in the top transmission/reception time slot T/R0-2 of a next frame,transmission of a burst of the TDMA control channel and a burst of the time-dividedCDMA control channel is not performed. Further, in the top transmission/reception timeslot T/R0-3 of a further next frame, a burst 217 of the TDMA control channel and a burst#213-0 of the time-divided CDMA control channel are transmitted. Thereafter,transrnission/stopping of a burst of the TDMA control channel and a burst of thetime-divided CDMA control channel are repeated alternately for each one frame in asimilar manner.It is to be noted that, in the top transmission/reception time slot T/R0-2 of a framein which a burst of the TDMA control channel and a burst of the time-divided CDMA46CA 02264790 1999-02-24control channel is not performed, the radio base station 1 receives a burst 216 of theTDMA control channel transmitted from the radio base station 2 and a burst #212-O ofthe tirne—divided CDMA control channel.Further, for frame synchronization acquisition between radio base stations, acontrol signal of the tributary base station must be received in a time slot in which theradio base station should originally transmit a control channel as described above.Accordingly, the reason of such special use of time slots is that the radio base station inthis instance has a function of a mobile station, and therefore, it relates only to adown-link, and no influence is had on an up-link channel by which a signal from a mobilestation is transmitted.Here, while, in the embodiment 2 described above, synchronization displacement ofa chip rate by a mobile station carried on a moving automobile or carried by a walkingperson is argued, since correction necessitated as a result of displacement of an internaloscillator in the transmitter is much higher in frequency than correction necessitated as aresult of the synchronization displacement, also in the case of the FDD, thesynchronization displacement correction can be made only against the displacementcaused by the oscillator in the transmitter similarly as in the case of the TDD.Further, as illustrated in FIG. 16, also in the case of the FDD, transmission andreception of a TDMA control channel and a tirne-divided CDMA control channel usedfor frame synchronization between radio base stations are all performed on the down-linkside, and the up-link side is not used. Therefore, in this frame synchronization processbetween radio base stations, no disturbance is hand on a transmission signal on theup-link side from a mobile station, and there is no necessity to limit transmission of amobile station specifically for this object.As described above, according to the present embodiment 5, since a tributary basestation transmits, after it is discriminated by a radio base station that a reception burst isat an appropriate burst position, time difference information between the top timepositions of burst signals transmitted from and received by the tributary base station to47... H... --..‘......................... . CA 02264790 1999-02-24the radio base station and the radio base station transmits a TDMA control signal burstand a time-divided CDMA control signal burst in the top slot of every other frame, in anFDD mobile communication system of the TDMA system and the tirne-divided CDMAsystem, frame synchronization between radio base stations is established, andinterference between time slots can be eliminated.Embodiment 6Subsequently, as an embodiment 6 of the present invention, frame synchronizationestablishment between a radio base station and a plurality of tributary base stations in thecase of the TDD and the FDD is described.FIG. 17 is a diagrammatic view illustrating an example of a TDMA controlchannel/tirne-divided CDMA control channel when, among radio base stations of aplurality of different operators, one radio base station establishes frame synchronizationwith a plurality of tributary radio base stations. Meanwhile, FIG. 18 is a diagrammaticview in which an example of transmission/reception (TX/RX) allocation of radio basestation time slots of the TDMA control channel/time-divided CDMA control channelillustrated in this FIG. 17 is illustrated in the form of a table.First, a process in which one radio base station establishes frame synchronizationwith a plurality of tributary base stations in a TDD system is described with reference toFIGS. 17 and 18.As seen in FIGS. 17 and 18, when synchronization information is to be propagatedfrom the radio base station 1 (BS1) to the tributary base station 2 (BS2) and the tributarybase station 3 (BS3), the radio base station 1 transmits a TDMA control signal burst anda time-divided CDMA control signal burst from a TDMA control channel and atirne-divided CDMA control channel in a transmission time slot To-1, and each of thetributary base stations 2 and 3 receives the TDMA control signal burst or thetirne-divided CDMA control signal burst of the TDMA control channel or the48CA 02264790 1999-02-24time—divided CDMA control channel. In this instance, down-links for a control channelfor frame synchronization between radio base stations are formed.On the other hand, when synchronization information is to be transmitted flom thetributary base station 2 or 3 to the radio base station 1, the tributary base station 2 or 3transmits a TDMA control signal burst or a time—divided CDMA control signal burstflom a TDMA control channel or a tirne-divided CDMA control channel in atransmission time slot To-2, and the radio base station 1 receives the TDMA controlsignal burst and the time-divided CDMA control signal burst of the TDMA controlchannel and the tirne-divided CDMA control channel. In this instance, up—links for acontrol channel for frame synchronization between radio base stations are formed.It is to be noted that a basic process for flame synchronization establishmentbetween radio base stations is similar to that in the case of the embodiment 4 describedhereinabove.Subsequently, a process that one radio base station establishes flamesynchronization with a plurality of tributary base stations in an FDD system is described.It is to be noted that, also in this instance, a basic process for frame synchronizationestablishment between radio base stations is similar to that in the case of the embodiment5 described above.Here, FIG. 19 is a diagrammatic view illustrating an example of a TDMA controlchannel/tirne—divided CDMA control channel in a TDMA/time-divided CDMAcoexistence FDD system when, among radio base stations of a plurality of differentoperators, one radio base station establishes flame synchronization with a plurality oftributary base stations. Meanwhile, FIG. 20 is a diagrammatic view that an example oftransrnission/reception (TX/RX) allocation to radio base station time slots of the TDMAcontrol channel/time-divided CDMA control channel illustrated in FIG. 19 is illustratedin the form of a table.As seen in FIGS. 19 and 20, when synchronization information is to be transmittedflom the radio base station 1 (BS1) to the tributary base station 2 (BS2) and the tributary49CA 02264790 1999-02-24base station 3 (BS3), the radio base station 1 transmits a TDMA control signal burst anda time-divided CDMA control signal burst from a TDMA control channel and atirne-divided CDMA control channel in a transmission/reception time slot T/R0-1, andeach of the tributary base stations 2 and 3 receives the TDMA control signal burst or thetime-divided CDMA control signal burst of the TDMA control channel or thetime-divided CDMA control channel. In this instance, down-links for a control channelfor frame synchronization between radio base stations are formed.On the other hand, when synchronization information is to be transmitted from thetributary base station 2 or 3 to the radio base station 1, the tributary base station 2 or 3transmits a TDMA control signal burst or a tirne-divided CDMA control signal burstfrom a TDMA control channel or a time—divided CDMA control channel in atransrnission/reception T/R0-2, and the radio base station 1 receives the TDMA controlsignal burst and the time-divided CDMA control signal burst of the TDMA controlchannel and the tirne—divided CDMA control channel. In this instance, up-links for acontrol channel for frame synchronization between radio base stations are formed.As described above, according to the present embodiment 6, since a radio basestation transmits a TDMA control signal burst and a tirne—divided CDMA control signalburst so that synchronization information is propagated from" the radio base station to aplurality of tributary base stations and each tributary base station transmits a TDMAcontrol signal burst or a tirne-divided CDMA control signal burst so that synchronizationinformation is propagated from each tributary base station to the radio base station,frame synchronization can be established between one radio base station and a pluralityof tributary base stations at a time in the accuracy in a time-divided CDMA chip rateunit, and interference between time slots from a plurality of radio base stations can beeliminated.Embodiment 750CA 02264790 1999-02-24Subsequently, as an embodiment 7 of the present invention, a process of framesynchronization control between a radio base station and an adjacent tributary basestation is described.FIG. 21 is a flow chart illustrating an example of a control process of framesynchronization between a radio base station and an adjacent tributary base station.Where a plurality of adjacent tributary base stations are involved, this control process isexecuted repetitively for the individual tributary base stations.In particular, in step ST21 of FIG. 21, a tributary base station first receives aTDMA control signal burst transmitted first by a TDMA control channel from the radiobase station, and transmits a TDMA control signal burst of the tributary base station by aTDMA control channel of an up-link toward the radio base station with reference to thetop time position of the received burst signal.The radio base station receiving the TDMA control signal burst of the tributarybase station sends, in step ST22, a transmission burst position control signal forcontrolling the TDMA control signal burst transmitted fiom the tributary base station sothat it may be accommodated into a time slot into which it should be accommodated by aTDMA control channel of a down-link transmitted from the radio base station.Then, in step ST23, the radio base station confirms that the TDMA control signalburst of the up-link transmitted from the tributary base station in response to thetransmission burst position control signal described above is entered in a time slotposition on the time axis of the receiver input of the radio base station in which thetransmission burst position control signal should be entered, and establishes framesynchronization between the radio base stations which use the TDMA control channels.After the radio base station establishes frame synchronization by the TDMA controlchannels, it transmits a time-divided CDMA control signal burst to the tributary basestation.When the time-divided CDMA control signal burst is received, the tributary basestation transmits, subsequently in step ST24, a time-divided CDMA control signal of the51CA 02264790 1999-02-24self station to the radio base station by a time-divided CDMA control channel of anup-link with reference to the top time position of the received time-divided CDMAcontrol signal burst. Then, in step ST25, the radio base station transmits a transmissionburst position control signal to the tributary base station by the time-divided CDMAcontrol channel of the down—link transmitted by the radio base station so as to controlthe time-divided CDMA control signal burst received from the tributary base station sothat it may be accommodated in a time slot in which it should be accommodated. Framesynchronization between the radio base stations in a chip rate unit of the time-dividedCDMA using the time-divided CDMA control channels is established in this manner.After frame synchronization measurement in a chip rate unit of the time-dividedCDMA between the radio base station and the tributary base station in steps ST23 andST24 is completed once, the displacement time information is stored into a memory inthe tributary base station or the mobile switching center. While this displacement timeinformation increases in proportion to the distance between the radio base station and thetributary base station, since those radio base stations do not move, the displacement timeinformation is fixed. Accordingly, if the tributary base station receives a time-dividedCDMA control signal burst from the radio base station, then since the displacement timeinformation from the top time position of the received burst is stored already, the toptime position of a frame of the tributary base station is set with the displacement timeinformation stored in the memory from the received burst signal.Here, once measurement of the displacement time is completed, transmission of atime-divided CDMA control signal burst by the up—link from the tributary base station tothe radio base station becomes unnecessary, and accordingly, the tributary base stationthereafter stops transmission of a time-divided CDMA control signal burst by theup-link. Accordingly, since the radio base station need not use a time slot of atime-divided CDMA control signal for reception any more, it can transmit a time-dividedCDMA communication signal burst using the time slot as an ordinary speech channel forthe down—link. This process is illustrated in step ST26 of FIG. 21.52CA 02264790 1999-02-24A time slot which can be used as an ordinary speech channel for the down-link asthe radio base station 1 (BS1) described above need not receive a time-divided CDMAcontrol signal burst by an up—link from the tributary base station 2 (BS2) any more is, forexample, "RX" of a time-divided CDMA control channel in the row of BS1 of thecolumn of To-2 in FIG. 18 and a time slot CDMA #203—O in FIG. 17. Further, it is "RX"of a time-divided CDMA control channel in the row of BS1 of the column T/R0-2 ofFIG. 20 and a time slot CDMA #212-0 in FIG. 19.Thereafter, if, in step ST27, the speech traffic decreases to such a degree that a timeslot of a time-divided CDMA control signal of the radio base station need not be utilizedas a speech channel, then the radio base station instructs the tributary base station totransmit a time-divided control signal burst through the up-link. For example, in themidnight or the like, since the speech traffic decreases, such time zone is a situationsuitable to effect measurement and confirmation of the displacement time informationdescribed above between radio base stations.As described above, according to the present embodiment 7, since flamesynchronization between radio base stations is established first using TDMA controlchannels and then using time-divided CDMA control channels and a displacement timebetween the top time positions of burst signals transmitted and received by a tributarybase station is stored into a memory of the tributary base station or a mobile switchingcenter, also in a situation in which updating of control information cannot be performedbetween the tributary base station and a radio base station, interference between timeslots can be eliminated by utilizing the top time position of a received time-dividedCDMA control channel and the information of the displacement time measured andstored in advance.Embodiment 8Subsequently, as an embodiment 8 of the present invention, a control process whenframe synchronization between a radio base station and an adjacent tributary base station53CA 02264790 1999-02-24is established using TDMA control channels when the speech traffic becomes excessivelylarge.FIG. 22 is a flow chart illustrating an example of a control process of framesynchronization between a radio base station and an adjacent tributary base station wheresuch a case that the speech traffic becomes excessively large is taken into consideration.Meanwhile, FIGS. 23 and 24 are diagrammatic views that the allocation of controlsignals in such an instance is indicated in the form of a table, and FIG. 23 illustrates anexample of transmission/reception (TX/RX) allocation in a TDMA/time-divided CDMAcoexistence TDD system while FIG. 24 illustrates an example of transrnission/reception(TX/RX) allocation in a TDMA/tirne-divided CDMA coexistence FDD system.In the following, a control process of frame synchronization between a radio basestation and a tributary base station is described with reference to FIG. 22.First in step ST31, the tributary base station receives, similarly as in the case of theembodiment 7, a TDMA control signal burst transmitted first by a TDMA controlchannel from the radio base station, and transmits a TDMA control signal burst of thetributary base station by a TDMA control channel of an up-link toward the radio basestation with reference to the top time position of the received burst signal.Then in step ST32, the radio base station sends a transmission burst positioncontrol signal for controlling the TDMA control signal burst transmitted from thetributary base station described above so that it may be accommodated into a time slotinto which it should be accommodated by a TDMA control channel of a down—1inktransmitted from the radio base station, and confirms that the TDMA control signal burstof the up-link transmitted from the tributary base station is entered in a time slot positionon the time axis of the receiver input of the radio base station in which the transmissionburst position control signal should be entered by emission time adjustment of atransmission burst of the tributary base station based on the transmission burst positioncontrol signal. Consequently, frame synchronization between the radio base stations inwhich the TDMA control channels are used is established.54CA 02264790 1999-02-24Then in step ST33, in a condition that frame synchronization between the radiobase stations by the TDMA control channels is established and actual operation isperformed, it is discriminated whether or not the speech traffic has changed to such acondition that a tirne-divided control charmel of the tributary base station can be used.As a result, if the tirne-divided control channel is not in a usable condition, then theprocess returns to step ST32 to perform actual operation while the framesynchronization between the radio base stations in which TDM control channels are usedis maintained.On the other hand, if it is discriminated in step ST33 that the tirne-divided controlchannel is in a usable condition, then the process advances to step ST34, in which theradio base station transmits a time-divided CDMA control signal burst to the tributarybase station.Thereafter, similarly as in the case of the embodiment 7, the tributary base stationreceiving the time-divided CDMA control signal burst sends a tirne-divided CDMAcontrol signal burst of the self control to the radio base station in step ST35, and in stepST36, the radio base station transmits a transmission burst position control signal to thetributary base station to perform establishment of frame synchronization by tirne-dividedCDMA control channels. Thereafter, in step ST37, measured displacement timeinformation is stored, and transmission of a tirne-divided CDMA control signal burstsince then is stopped. If the speech traffic decreases, then the radio base station instructsthe tributary base station of transmission of a time-divided CDMA control signal burstwhich has been stopped till then.Although it naturally is better that frame synchronization between radio basestations is performed at a time-divided CDMA chip rate by which a high degree ofsynchronization accuracy is obtained, when the speech traffic of the object radio basestation is very high at the point of time and a time slot of the time-divided CDMA cannotbe used for reception of tirne-divided CDMA control information as a control channel,the second best countermeasure is taken as follows: as described above, frame55CA 02264790 2001-09-14synchronization is established in a symbol rate unit of a TDMA control channel and, at apoint of time when the speech traffic of the radio base station decreases, a time slot ofthe time-divided CDMA is allocated as a control channel and used to receivetime-divided CDMA control information.It is to be noted that, while it is illustrated in FIGS. 23 and 24 that one time slot isused commonly for transmission (TX) and reception (RX), in order to commonly useone time slot for transmission and reception, it is required to displace the respectivefrequencies by a necessary amount from each other and use a steep filter diplexer.However, since it is not necessary to argue the matter here, its description is omitted.As described above, according to the present embodiment 8, since framesynchronization by TDMA control channels is repeated if time-divided CDMA controlchannels are not in a usable condition but frame synchronization by time-divided CDMAcontrol channels is performed if the time-divided CDMA control channels are in a usablecondition, also in a situation in which a time slot of the time-divided CDMA cannot beused for communication of control signals between radio base stations, at least thesystem can be operated by establishing frame synchronization between radio basestations using TDMA control channels and an increase in interference between time slotscan be prevented.Industrial ApplicabilityAs described above, a mobile communication system according to the presentinvention is useful where it is used for measurement of the distance between a mobilestation and a radio base station and for establishment of frame synchronization and alsofor measurement of the distance and establishment of frame synchronization betweenradio base stations in a mobile communication system which has time-divided CDMAsignal channels (shared channels) time slot shared and frequency channel shared withFDMA/T DD and TDM A digital communication on the frequency axis and wherein amobile station and a radio base station are radio connected to each other by duplex by56., . F491 .....w.....».w.t.m..-....._._......“........ ., .2 <\4 -Flt CA 02264790 1999-02-24the FDMA/TDD system, the multi-carrier TDMA system or the time-divided CDMAsystem which employs a modulation signal by a digital modulation system. Further, themobile communication system can be applied not only to a mobile communication systemwherein a mobile station and a radio base station are radio connected to each other, butalso to another mobile communication system wherein a mobile station and asemi-fixedWLL station are radio connected to a radio base station.57

Claims (30)

1. A mobile communication system having a plurality of mobile stations and at least one radio base station in which bidirectional communication using a time-divided code division multiple access (CDMA) system is performed between said mobile stations and said at least one radio base station, wherein each of said mobile stations measures a time difference having a fixed period of time subtracted therefrom, between a time that a time-divided CDMA
burst signal is received from said radio base station and a time that a time-divided CDMA
burst signal is transmitted by that respective mobile station in response to an instruction of said radio base station so that the transmitted time-divided CDMA burst signal may arrive at said radio base station at a start time position of a time slot of said time-divided CDMA system, and transmits information of the measured time difference to said radio base station.

2. A mobile communication system having a plurality of mobile stations and at least one radio base station in which bidirectional communication is performed between said mobile stations and said at least one radio base station using a time division multiple access (TDMA)/time-divided code division multiple access (CDMA) sharing system wherein a time slot of the time-divided CDMA system is inserted in time slots of a frame construction of a TDMA system, wherein each of said mobile stations measures a time difference having a fixed period of time subtracted therefrom, between a time that a time-divided CDMA
burst signal is received from said radio base station and a time that a time-divided CDMA
burst signal is transmitted by that respective mobile station in response to an instruction of said radio base station so that the transmitted time-divided CDMA burst signal may arrive at said radio base station at a start time position of a time slot of said TDMA/time-divided CDMA sharing system, and transmits information of the measured time difference to said radio base station.

3. A mobile communication system according to claim 2, wherein the time difference having a fixed period of time subtracted therefrom, between the start time position of the time-divided CDMA burst signal received from said radio base station by each of said mobile stations and the start time position of the time-divided CDMA burst signal transmitted from the mobile station to said radio base station is measured in a chip rate unit which is used in time-divided CDMA
communication.

4. A mobile communication system according to claim 2, wherein each of said mobile stations is radio-connected to one radio base station, wherein during a communication, a time difference having a fixed period of time subtracted therefrom, is measured between a start time position of a time-divided CDMA burst signal received from any radio base station other than the one radio base station and the start time position of the time-divided CDMA burst signal received from the one radio base station to which the mobile station is radio connected, and wherein information of the measured time difference is transmitted to the one radio base station to which the mobile station is radio connected.

5. A mobile communication system according to claim 2, wherein each of said mobile stations includes:

a correlation reception/despread-spectrum coding calculation section for extracting an original signal, which is not in a spread-spectrum coded condition, from a spread-spectrum coded signal sent thereto from said radio base station;

a channel reception/TDMA demodulation section for demodulating a time-divided CDMA signal despread-spectrum coded by said correlation reception/despread-spectrum coding calculation section and extracting a necessary signal from a format of a signal obtained by the demodulation;

a digital-to-analog conversion section for decoding an information signal from the signal extracted by said channel reception/TDMA demodulation section into an analog signal and forwarding the analog signal to a man-machine interface section;

an analog-to-digital conversion section for coding an information signal from said man-machine interface section into a digital code signal;

a channel transmission/TDMA multiplexing section for multiplexing the signal coded by said analog-to-digital conversion section;
a spread-spectrum coding calculation section for spectrum-spreading the information multiplexed by said channel transmission/TDMA multiplexing section on a frequency axis using a spread-spectrum code allocated to the self station;
a burst control/intra-frame time setting and time measurement section for controlling and adjusting an emission time of a burst signal which emits the information spread-spectrum coded by said spread-spectrum coding calculation section in response to an instruction of said radio base station and measuring the time difference, eliminated by the fixed time difference, between the top time position of the time-divided CDMA burst signal received from said radio base station and the top time position of the time-divided CDMA burst signal transmitted to said radio base station in a chip rate unit which is used in time-divided CDMA communication;
and a spread-spectrum code generator-chip rate generator for generating a chip rate to be used for the time-divided CDMA communication and the spread-spectrum code allocated to the self station and for supplying the chip rate and the spread-spectrum code to said burst control/intra-frame time setting and time measurement section or said correlation reception/despread-spectrum coding calculation section and spread-spectrum coding calculation section.

6. A mobile communication system according to claim 2, wherein said radio base station includes:

a plurality of signal processing sections each including a correlation reception/despread-spectrum coding calculation section for extracting an original signal from a spread-spectrum coded signal, a channel reception/TDMA
demodulation section for demodulating a despread-spectrum coded time-divided CDMA signal and extracting a necessary signal, a conversion section for decoding the extracted signal into an information signal and outputting the information signal to a network interface section, another conversion section for coding an information signal inputted from said network interface section, a channel transmission/TDMA multiplexing section for multiplexing the coded signal, a spread-spectrum coding calculation section for spectrum-spreading the multiplexed information on a frequency axis, a burst control/intra-frame time setting and time measurement section for controlling and adjusting an emission time of a burst signal which emits the spread-spectrum coded information and for performing time setting and time measurement in a frame, and a spread-spectrum code generator-chip rate generator for generating a chip rate to be used for the time measurement and the spread-spectrum code allocated to the self station; and a signal distribution and addition section for adding signals outputted from said signal processing sections and outputting a result of the addition to a transmission section and for distributing a signal received by a reception section to said signal processing sections.

7. A mobile communication system according to claim 6, wherein in at least one of said signal processing sections of said radio base station, said conversion section for decoding the information signal is constructed as a digital-to-analog conversion section for decoding the signal extracted by said channel reception/TDMA demodulation section into an analog information signal and outputting the analog information signal to an analog network interface section, and said conversion section for coding an information signal is constructed as an analog-to-digital conversion section for coding an information signal inputted from said analog network interface section into a digital code signal.

8. A mobile communication system according to claim 5, wherein said channel reception/TDMA demodulation section of each of said mobile stations includes a demultiplexing section for separating an information signal and control information included in a time slot selected from among a plurality of time slots and destined for the self station, an information signal memory for temporarily storing the information signal and a control information memory for temporarily storing the control information, wherein said channel transmission/TDMA multiplexing section includes an information signal memory for temporarily storing an information signal to be transmitted, a control information memory for temporarily storing control information to be transmitted, and a multiplexing section for composing the information signal and the control information and multiplexing the composed signal in a time slot allocated to the self station, and wherein the mobile station includes a control information processor for decoding the control information from said radio base station, instructing the mobile station of various functions based on the decoded control information and transmitting a response to the control information to said radio base station.

9. A mobile communication system having a plurality of mobile stations and at least one radio base station in which bidirectional communication is performed between said mobile stations and said at least one radio base station using a time division multiple access (TDMA)/time-divided code division multiple access (CDMA) sharing system wherein a time slot of the time-divided CDMA system is inserted in time slots of a frame construction of a TDMA system, wherein each of said radio base stations includes:

a first process of receiving, when first participating in said system, a TDMA control channel transmitted from said radio base station, transmitting control information to said radio base station using a designated TDMA control channel based on the received information, and performing communication of necessary control information with said radio base station via the bidirectional TDMA control channels, a second process of communicating, when a TDMA speech channel is designated, using the TDMA speech channel, and a third process of communicating by using the time-divided CDMA
speech channel when a time-divided CDMA speech channel is designated.

10. A mobile communication system according to claim 9, wherein in said first process of each of said mobile stations, after said radio base station receiving a TDMA
control information signal burst from a respective mobile station discriminates that the received burst is at an appropriate burst position and transmits the discrimination information to the respective mobile station via the control channel, the mobile station measures a time difference between a start time position of a TDMA control signal burst transmitted from said radio base station and a start time position of a TDMA
control signal burst transmitted from the respective mobile station to said radio base station in an information symbol rate unit and transmits the time difference information to said radio base station.

11. A mobile communication system according to claim 9, wherein in said second process of each of said mobile stations, after said radio base station receiving a TDMA speech information signal burst from a respective mobile station discriminates that the received burst is at an appropriate burst position and transmits the discrimination information to the respective mobile station via a control channel in a speech channel, the mobile station measures a time difference having a fixed period of time subtracted therefrom between a start time position of a TDMA speech signal burst transmitted from said radio base station and a start time position of a TDMA
speech signal burst transmitted from the respective mobile station to said radio base station in a time-divided CDMA chip rate unit and transmits the time difference information to said radio base station.

12. A mobile communication system according to claim 9, wherein in said third process of each of said mobile stations, after said radio base station receiving a time-divided CDMA speech information signal burst from a respective mobile station discriminates that the received burst is at an appropriate burst position and transmits, if it is discriminated that the received burst is at an appropriate burst position, the discrimination information to the respective mobile station via a control channel in a speech channel, the mobile station measures a time difference having a fixed period of time subtracted therefrom, between a start time position of a time-divided CDMA
speech signal burst transmitted from said radio base station and a start time position of a time-divided CDMA speech signal burst transmitted from the respective mobile station to said radio base station in a time-divided CDMA chip rate unit and transmits the time difference information to said radio base station.

13. A mobile communication system having a plurality of mobile stations and at least one radio base station in which bidirectional communication is performed between said plurality of mobile stations and said at least one radio base station using a time division multiple access (TDMA)/time-divided code division multiple access (CDMA) sharing system that a time slot of the time-divided CDMA system is inserted in time slots of a frame construction of a TDMA system, wherein each of said mobile stations measures a time difference having a fixed period of time subtracted therefrom, between a start time position of a TDMA
burst or a time-divided CDMA burst received from said radio base station and a start time position of a TDMA burst or a time-divided CDMA burst transmitted by that mobile station to said radio base station in a chip rate unit and transmits the time difference information to said radio base station, and wherein a mobile switching center which accommodates a plurality of radio base stations has a function of calculating distances between said radio base stations and said mobile stations based on the time difference information collected from said radio base stations and storing distance information obtained from said time difference information.

14. A mobile communication system according to claim 13, wherein said mobile switching center measures distances between each of said mobile stations and a plurality of radio base stations around each mobile station, supervises the measured distances, and if the distance to a respective mobile station is shorter from any other one of the radio base stations than from the radio base station to which the mobile station is connected, forwards to the respective mobile station a hand-over starting instruction so as to newly set a radio channel to the one radio base station.

15. A mobile communication system according to claim 14, wherein when said mobile switching center tries to forward a hand-over starting instruction to the radio base station nearest to the respective mobile station, if that radio base station is a radio base station of a different operator than the radio base station to which said respective mobile station is presently radio-connected, said mobile switching center transmits a hand-over starting instruction to the radio base station nearest to the respective mobile station via a public system and a mobile switching center of the different operator.

16. A mobile communication system having a plurality of mobile stations and a plurality of radio base stations in which bidirectional communication using a time-divided code division multiple access (CDMA) system is performed between said plurality of mobile stations and said plurality of radio base stations, wherein when a time-divided CDMA control signal burst transmitted from a radio base station is received by a tributary base station, said tributary base station measures a time difference having a fixed period of time subtracted therefrom, between a start time position of a time-divided CDMA burst signal received from said radio base station and a start time position of a time-divided CDMA burst signal transmitted from said tributary base station in response to an instruction from said transmitting radio base station so that a beginning of the time-divided CDMA
burst signal may arrive at said tributary radio base position at a start time position of a time slot, and transmits the measurement information therefrom to said transmitting radio base station.

17. A mobile communication system having a plurality of mobile stations and a plurality of radio base stations in which bidirectional communication is performed between said plurality of mobile stations and said plurality of radio base stations using a time division multiple access (TDMA)/time-divided code division multiple access (CDMA) sharing system that a time slot of the time-divided CDMA system is inserted in time slots of a frame construction of a TDMA system, wherein when a TDMA control signal burst or a time-divided CDMA control signal burst transmitted from a radio base station is received by a tributary base station, said tributary base station measures a time difference having a fixed period of time subtracted therefrom, between a start time position of a TDMA burst signal or a time-divided CDMA burst signal received from said radio base station and a start time position of a time-divided CDMA burst signal transmitted from said tributary base station in response to an instruction from said radio base station so that a start of the time-divided CDMA burst signal may arrive at said radio base position at a start position of a time slot, and transmits the measurement information therefrom to said transmitting radio base station.

18. A mobile communication system according to claim 17, wherein a time difference having a fixed period of time subtracted therefrom, between start time positions of burst signals transmitted and received to and from said transmitting radio base station by said tributary base station is measured in a chip rate unit which is used in time-divided CDMA communication.

19. A mobile communication system according to claim 17, wherein said transmitting radio base station receives a time-divided CDMA control information signal burst transmitted from said tributary base station, discriminates whether or not the received burst is at an appropriate burst position, and transmits the discrimination information to said tributary base station via a control channel when it is discriminated that the received burst is at an appropriate burst position, and wherein said tributary base station transmits, after receiving the discrimination information, information of a time difference having a fixed period of time subtracted therefrom, between a start time position of a time-divided CDMA control signal burst transmitted from said radio base station and a start time position of a time-divided CDMA control signal burst transmitted from said tributary base station to said transmitting radio base station.

20. A mobile communication system according to claim 18, wherein said radio base station receives a time-divided CDMA control information signal burst transmitted from said tributary base station, discriminates whether or not the received burst is at an appropriate burst position, and transmits the displacement information measured in a chip rate unit of said time-divided CDMA
system to said tributary base station via a control channel when it is discriminated that the received burst is displaced from the appropriate burst position, and wherein said tributary base station corrects a top time position of a time-divided CDMA control signal burst to be transmitted from said tributary base station to said radio base station, based on the information of the displacement received from said radio base station, by a time corresponding to the displacement with reference to a top time position of a time-divided CDMA control signal burst transmitted from said tributary base station to said radio base station and transmits the corrected time-divided CDMA control signal burst to said radio base station.

21. A mobile communication system according to claim 20, wherein when said tributary base station receives a time-divided CDMA control information signal burst transmitted from said radio base station and detects a start time position of the received burst signal, said tributary base station stops transmission of a burst signal of a time slot which should originally be transmitted from said tributary base station, and receives the time-divided CDMA control signal burst transmitted from said radio base station.

22. A mobile communication system having a plurality of mobile stations and a plurality of radio base stations in which bidirectional communication is performed between said plurality of mobile stations and said plurality of radio base stations using a time division multiple access (TDMA)/time-divided code division multiple access (CDMA) sharing system that a time slot of the time-divided CDMA system is inserted in time slots of a frame construction of a TDMA system, and wherein a time division duplex mobile communication system in which a radio base station receives a time-divided CDMA control information signal burst transmitted from a tributary base station discriminates that the received burst is at an appropriate burst position, and transmits the discrimination information therefrom to said tributary base station via a control channel and said tributary base station transmits, after the discrimination information is received from said radio base station, information of a time difference between a start time position of a time-divided CDMA control signal burst transmitted from said radio base station and a start time position of a time-divided CDMA control signal burst transmitted from said tributary base station to said radio base station is constructed, and wherein said radio base station performs transmission of one or both of a TDMA control signal burst and a time-divided CDMA control signal burst once for two frames in a beginning slot of the frame.

23. A mobile communication system according to claim 22, wherein when said basic base station tries to transmit one or both of a TDMA control signal burst and a time-divided CDMA control signal burst once for two frames in a beginning slot, in a time slot in which a TDMA control signal burst and a time-divided CDMA control signal burst are not transmitted in a beginning slot thereof, said radio base station receives one or both of a TDMA control signal burst and a time-divided CDMA
control signal burst transmitted from said tributary base station.

24. A mobile communication system according to claim 23, wherein in a time slot that said basic base station receives one or both of a TDMA control signal burst and a time-divided CDMA control signal burst transmitted from said tributary base station, even if the time slot is one or both of a TDMA speech signal burst and a time-divided CDMA speech signal burst which should originally be transmitted as a down-link by said radio base station, the transmission is stopped and one or both of the TDMA control signal burst and the time-divided CDMA control signal burst from said tributary base station are received.

25. A mobile communication system according to claim 17, wherein said transmitting radio base station has a function of transmitting, when synchronization information is to be propagated from said radio base station to a plurality of tributary base stations, one or both of a TDMA control signal burst and a time-divided CDMA
control signal burst by one or both of a TDMA control channel and a time-divided CDMA control channel, and wherein each of said tributary base stations has a function of transmitting a TDMA control signal burst or a time-divided CDMA control signal burst by a TDMA
control channel or a time-divided CDMA control channel when synchronization information is to be propagated from a respective tributary base station to said radio base station.

26. A mobile communication system having a plurality of mobile stations and a plurality of radio base stations in which bidirectional communication is performed between said plurality of mobile stations and said plurality of radio base stations using a time division multiple access (TDMA)/time-divided code division multiple access (CDMA) sharing system that a time slot of the time-divided CDMA system is inserted in time slots of a frame construction of a TDMA system, wherein when a time difference having a fixed period of time subtracted therefrom, between a start time position of a received burst position at a tributary base station of said plurality of base stations and a start time position of a TDMA
burst signal or a time-divided CDMA burst signal transmitted from said tributary base station to said radio base station is measured in a chip rate unit of the time-divided CDMA by said tributary base station when a TDMA control signal burst or a time-divided CDMA control signal burst transmitted from a radio base station is received by said tributary base station, and the measurement information is transmitted from said tributary base station to said transmitting radio base station to set frame synchronization between said radio base stations, frame synchronization between said radio base stations is first established using a TDMA control channel, and then establishment of frame synchronization between said radio base stations in a chip rate unit of the time-divided CDMA is performed using a time-divided CDMA
control channel, and then information of a displacement time from a start time position of a time-divided CDMA control signal burst received from said transmitting radio base station by said tributary base station when frame synchronization between said radio base stations is established in a chip rate unit of the time-divided CDMA to a top time position of a time-divided CDMA control signal burst transmitted from said tributary base station to said transmitting radio base station is stored into a memory of at least one of said tributary base station, or a mobile switching center which accommodates said tributary base station.

27. A mobile communication system according to claim 26, wherein after frame synchronization between said radio base stations is established in a chip rate unit of the time-divided CDMA, said tributary base station stops transmission of a time-divided CDMA control signal burst therefrom to said radio base station and adjusts top time positions of time-divided CDMA control signal bursts to be transmitted to a plurality of mobile stations in accordance with the information of the time of displacement stored in said memory from a start time position of the time-divided CDMA control signal burst received from said transmitting radio base station, and said transmitting radio base station uses a time slot, in which said radio base station has received the time-divided CDMA control signal from said tributary base station, as a speech channel to down-links to said plurality of mobile stations, and transmits a time-divided CDMA speech signal burst.

28. A mobile communication system according to claim 27, wherein after frame synchronization between said radio base stations is established in a chip rate unit of the time-divided CDMA, when, while said radio base station uses a time slot, with which said radio base station has received a time-divided CDMA control signal from said tributary base station, as a speech channel for a down-link to a plurality of mobile stations, a call request to the mobile station which has used the down-link disappears, transmission of a time-divided CDMA speech signal burst to the mobile station is stopped in the time slot, and reception of a time-divided CDMA control signal burst from said tributary base station is resumed to effect frame synchronization establishment between said radio base stations.

29. A mobile communication system according to claim 26, wherein when one of said radio base stations tries to establish frame synchronization with another one of said radio base stations, frame synchronization between the radio base stations is established first using a TDMA control channel, and then it is discriminated whether or not use of a time-divided CDMA control channel is allowed, and if use of a time-divided CDMA control channel is not allowed, then frame synchronization between the radio base stations using the TDMA control channel is repeated, and, after use of the time-divided CDMA control channel becomes allowed, establishment of frame synchronization between the radio base stations is performed in a chip rate unit of the time-divided CDMA using the time-divided CDMA control channel.

30. A mobile communication system according to claim 22, wherein said transmitting radio base station has a function of transmitting, when synchronization information is to be propagated from said radio base station to a plurality of tributary base stations, one or both of a TDMA control signal burst and a time-divided CDMA
control signal burst by one or both of a TDMA control channel and a time-divided CDMA control channel, and wherein each of said tributary base stations has a function of transmitting a TDMA control signal burst or a time-divided CDMA control signal burst by a TDMA
control channel or a time-divided CDMA control channel when synchronization information is to be propagated from a respective tributary base station to said radio base station.