CA2068430C - Frequency agile tdma communications system - Google Patents
Frequency agile tdma communications systemInfo
- Publication number
- CA2068430C CA2068430C CA002068430A CA2068430A CA2068430C CA 2068430 C CA2068430 C CA 2068430C CA 002068430 A CA002068430 A CA 002068430A CA 2068430 A CA2068430 A CA 2068430A CA 2068430 C CA2068430 C CA 2068430C
- Authority
- CA
- Canada
- Prior art keywords
- data
- frequencies
- devices
- node
- time slots
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J4/00—Combined time-division and frequency-division multiplex systems
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/24—Radio transmission systems, i.e. using radiation field for communication between two or more posts
- H04B7/26—Radio transmission systems, i.e. using radiation field for communication between two or more posts at least one of which is mobile
- H04B7/2615—Radio transmission systems, i.e. using radiation field for communication between two or more posts at least one of which is mobile using hybrid frequency-time division multiple access [FDMA-TDMA]
Abstract
An intelligent communications node (20) is capable of dynamically selecting frequency and time slot assignments for com-munications with remote communication devices (22, 24, 26) having different communication protocols including different avail-able frequencies and time slots in a TDMA system. A frequency agile transmitter (62) and receiver (32) combined with an adapt-able time slot selector (38, 60) enables communications with remote devices utilizing different protocols. The time and frequency management capabilities of the node (20) makes greater spectral efficiencies possible.
Description
wo 92/06546 ~ 0 6 8 ~ 3 o Pcr/US9l/06993 ~REQUENCY AGILE TDMA COMMUNICATIONS SYSTEM
Background of the Invention This invention is generally directed to time division multiple access (TDMA) communications systems and is more specifically directed to a TDMA system having nodes which are ~pAhlo of the time slot and frequency management thereby accommodating communications with different types of communication devices each having its own different 1 5 time and frequency characteristics.
A number of communications systems exist in which a node or controller can communicate with a plurality of remote communication devices. In a conventional RF communications network, a base station communicates with various mobile and portable units utilizing a 20 predetermined number of different frequency channels. In TDMA
systems a predetermined frequency with a defined bandwidth is utilized to transmit frames of data with predetermined time slots ~l!ocAted to different users.
RecAuse of the efficiencies available with TDMA systems, a 25 number of such systems exist and a variety of new systems are being developed, such as a digital European cordless telephone (DECT). A
TDMA device designed for one system cannot communicate when in a different TDMA system becAuse of different time slot protocols. The radio transmission of TDMA data adds yet another degree of complexity to 30 communication between different systems since different frequencies and bandwidths are utilized.
There exists a need for a common communications node which can manage both time and frequency in order to be compatible with different TDMA communications devices.
wo 92/06546 2 0 G 8 4 3 0 PCI/US91/06993 Brief Description of the Drawings FIG. 1 illustrates a communication system in accordance with the present invention.
FIG. 2 is a graph illustrative of the time and frequency management capabilities of a node in accordance with the present invention.
FIG. 3 is a block diagram of an embodiment of a node in accordance with the present invention.
FIG. 4 is a block diagram illustr~ting the clock generator of FIG. 3.
FIG. 5 is a block diagram illustrating an embodiment of a time slot selector (TSS) utilized in FIG. 3.
FIG. 6 is a block diagram of an embodiment of a frequency division multiplex receiver of FIG. 3.
FIG. 7 is a block diagram of an embodiment of a frequency division muHiplex transmitter of FIG. 3.
FIG. 8 is a flow chart of steps for the transmission of data by a node in accordance with the present invention.
FIG. 9 is a flow chart of steps for the reception of data by a node in acconJance with the present invention.
Description of a Preferred Embodiment FIG. 1 shows an exemplary RF communications system having a node 20 in accordance with the present invention ~p~hle of RF
communications with communication devices 22, 24, and 26. Each of the three different types of devices utilize a different TDMA protocol and communicate at different frequencies. Node 20 is ~p~hlQ of RF
communications over a subst~ntial range of frequencies including those used by the three different devices and is capable of managing the frequency and time factors in order to provide communications with each of the different types of devices. Although this illustrative system uses RF
wireless communications, the present invention is generally applicable to WO 92/06546 21~ 3 0 PCI-/US91/06993 communication systems which utilize modulated carriers for in a TDMA
environment.
FIG. 2 is a graph illustrating different iime slots T1-T4 repeated as frames versus different frequency channels CH1-CH4. In the 5 representative graph, three different types of TDMA devices are shown as being acco"""Gdate.J in each frame. In time slots T1 and T4, one type of device is accommo.Jale-~ by two time slots per frame and utilizes three conti~uous channels CH1-CH3. The data l-ans,nitle~l during these time slots is accom~GdAIe.~ by a carrier frequency at the center of channel 10 CH2 with a ban~J~ l, of 3 channels. In time slot T2 a second different device with less data throughput demand is acco"""o~te-J on only frequency channel CH2. In time slot T3, a third different device is accommo~ted by utilizing bandwidth of frequency channels CH3 and CH4. Time slot T4 represents a seconJ time slot ~IlQ~tion in addition to 15 T1 within the frame for carrying data ~ssoc~te~J with the first device.
It should be understood that the reprerontati-/e graph is shown in simplified form to better convey an aspect of the present invention. The number of time slots per frame, the number of channels, and the bandwidth per channel will vary depending upon the demands placed 20 upon and capacity of the communicatiGns system. Generally, a large number of time slots per frame is desired in order to have incr~ased flexibility in accommodating different TDMA devices and different data throughput requirements. Similarly, frequency considerations will vary depending upon the number and type of different devices being 25 accon""GJated within the system. The gre~test flexibility in managing the system accolJing to the present invention occurs when a continuous range of frequency spectrum is available in which varying bandwidths can be utilized.
It is becoming increasingly difficult to obtain sufficient frequency 30 spectrum in order to support our communication needs. The present invention provides the opportunity to increase the ability to communicate within a previously assigned frequency spectrum for one type of communications by interleaving additional communications capacity in available time slots and frequencies. A node in accordance with the Wo s2/06s46 2 0 1~ 8 4 3 0 PCI /US91/06993 present invention has the capability of dynamically reconfiguring its time and frequency resources in order to adapt to different demands.
Preferably the node will be preprogrammed with the definition of the communication protocols utilized by the different communication devices 5 to be accommo~ ed Thus, the node can make time and frequency assignments consistent with the ability of remote devices to adapt within the particular protocol for each type of device.
FIG.3 illustrates an embodiment of a node 20 in accordance with the present invention. The illustrative e"lbodiment illustrates a node 10 capal~lc of accepting user data and transmitting that data to a remote communications device by an RF signal. The node is similarly capable of receiving an RF signal from a remote device which carries data that is demodulated and provided to a user network.
Signals from the remote devices are received by antenna 30 15 which is connected to frequency division multiplexer receiver 32. A
microprocessor controller 34 provides control of the frequency and bar,dwiJIh of the receiver by means of frequency selection (FS) and bandJ~iJlh size (BWS) inputs. The receiver provides recovered digital data to time slot selectors (TSS)36 and 38. The TSS 36 functions to 20 derive time synchronization information from the received signals. The TSS 38 serves to recover the TDMA encoded data by appropriate time slot selection. The controller 34 provides control information to the selectors 36 and 38 including defining the repetition rate (RR), i.e.
number of slots per frame containing the desired information, slot 25 position (SP) which defines the beginning of the time slot within the frame, and the slot size (SS) which defines the length of time of each slot.
It should be noted that several adjacent time slots may be defined as a single time slot for purposes of time management. The output of TSS 36 only contains time information which is utilized by clock generator 40 30 which provides an output digital clock reference 42 utilized for general timing and synchronization of the node. The TSS 38 provides an output of data which has been time segregated corresponding to the different data sources to demultiplexer 44. Input control signal MX from controller 34 provides the demultiplexer with select information for routing the wo 92/06546 2 0 6 3 4 ~ ~ Pcr/usg1/o6993 received data to corresponding data channels 46. The data on these channels is preferably buffered by elastic buffers 48 before being coupled to local area network (LAN) interface 50 such as suited for use in an Ethernet environment. This interface controls the flow of information 5 to and from the user data network 52 by which the individual data channels are ultimately routed to different users.
Summarizing the reception of signals from remote users a fre~usnc~ agile receiver 32 5el~cts different frequencies and bandwidths for corresponding time slots utili~ed for each different type device. The 1 0 data recovered by the receiver is further processed by the TSS to identify the different data infor",a~ion residing in the different time slots. This recovered infor."ation is then se9l~9iqls~l into corresponding different data outrlJts by the demultiplexing process and ultimately routed to the user by a data network.
1 5 The trans",ission of data from the user data network 52 to r~",ole devices is accG",plished as follows. The LAN intelface 50 ~ epls data ~J.I,esse-J to a ~ ."ote device from user data network 52 and transfers the data to elastic buffers 54. The buffers are preferably implemented as ",apped memory controlled by controller 34. The data stored in the 20 buffers is transferred to multiplexer 56 which multiplexes the different data information into a single data stream. Buffers 54 and multiplexer 56 each receive clock information from the LAN interface and clock generator 40 for the sy"chronized transfer of data. A selector 58 selects between input A from multiplexer 56 and input B from controller 34. Its 25 output is coupled to time slot selector 60. The control input to selector 58 is provided by controller 34. This permits the controller to insert relevant data to be communicated to the remote devices. The TSS 60 receives the output from sel~c~or 58 and organizes the r~ceived data in accordance with the frame and time slot protocol to be utilized similarly 30 to the decodirlg accomplished by TSS 38. The frequQncy division multiplex transmitter 62 receives the output data stream from TSS 60 and l,ans",its a modul~tQd signal using antenna 64. The frequency and bandwidth of FDM trans",itler 62 is del~""ined by controller 34 via inputs FS and BWS.
Wo s2/06s46 2 0 ~ 8 ~ 3 0 PCI/US91/06993 Summarizing the transmission of data to remote devices, data destined for remote devices is buffered and multiplexed together to form a single data stream which together with system contrGI data provlded by controller 34 is segmented into appropriate time slots by the TSS. The output of the TSS is received and modulated at an appropriate frequency and bandwidth compatible with the receiver of the corresponding remote device.
FIG. 4 is a block diagram illustrating an embodiment of a clock generator 40. The time synchronization output from TSS 36 is received 1 0 by a clock oscillator 68. Its phase is adjusted by this output and maintains time synchronization between the transmitted and received signals. A counter 70 receives the clock output pulses from clock osc~ Jor 68. The data clock output 42 consists of the basic clock rate C
and taps from each of the divide by two stages up to 2n of counter 70.
1 5 The clock output 42 consists of digital data which continues to periodically cycle from zero to 2n+1.
FIG. 5 is a block diagram of an exemplary embodiment of a time slot selector (TSS). A digital 2n+1 comparator 80 compares data clock 42 with the time slot position (SP) generated by controller 34 for each clock C. The SP position corresponds to the time slot of the selected data to be transmined or received. The exemplary system according to the present invention operates in a half duplex mode so that data from the node can be only transmitted or received in one direction at a given time. The output of the comparator consists of a digital control line which provides a true or false indication relative to each comparison. A match (true) by comparator 80 marks the beginning edge of the time slot positioned for the corresponding data and ~uses divider 82 to be reset, provides an enabling input to OR gate 84, and sets RS flip flop 86. A true output of OR gate 84 sets RS flip flop 88 and resets divider 90. Since both flip flops 86 and 88 have been set, both inputs to AND gate 92 are true causing the AND gate output to provide a control signal 94 to data transmission gate 96 causing it to open or pass data.
An enable input to flip flop 86 through inverter 98 is provided by controller 34. The enable signal is provided when the RR, SP, and SS
wo s2/06s46 2 0 ~ 8 4 3 0 PCr/US91/06993 control signals are being generated by the microprocessor and are stable. During transitions by the controller 34, these signals are not stable. The enable serves to reset flip flop 86 causing its output to change state and thereby causing AND gate 92 to be inhibited thereby 5 causing control 94 to block the flow of data. The divider 90 is programmed to divide by L which is set by the SS control and corresponds to the size or length of the time slot. The input clock C is di~iJ~J by divider 90 which provides an output resetting flip flop 88 upon reaching the count of L. This represents the length of time of the 1 0 corresponding time slot. This ~ses the output of flip flop 88 to change state thereby inhibiting AND gate 92 and causing t,a,)sn,ission gate 96 to block the flow of data. Thus, gate 96 permits the flow of data beginning with the recognition of the beginning of the proper time slot and ending with the ,ecogr,ilion of the end of the co-,espo.,Jing time slot.
1 5 The repetition rate (RR) provides an input to division function 100 which c~lc~ es one divided by the repe~ilion rate. It will be known that this function may be carried out either in conventional hardware or implemented as part of a software routine to provide the division function.
The quotient of this division pn~cass provides an input to divider 82 and 20 defines the division Z to be provided by the divider. The least significant bit C of clock 42 provides the clock input to divider 82. The output from co",pardtor 80 resets the divider. The output of the divider provides the other input to OR gate 84 and is thus ~p~hlQ of setting flip flop 88 every Z inteNal. This per",its periodic spece~ apart time slots for the same 25 data to be utilized within a frame. The first time slot is activated by the initial tnue output from comparator 84 by its input to gate 84. The time slot ends as determined by the count of L by divider 90. If another time slot is provided within a frame for the corresponding data, OR gate 84 will again enable flip flop 88 upon divider 82 reaching the Z count and will mark the 30 beginning of each time slot for every Z interval following the initial time slot determination by comparator 80. It will be apparent that the maximum repetilion rate (Z) must be greater than the size of the slot (L).
FIG. 6 is a block diagram of a illustrative embodiment of a frequency division multiplex receiver 32. Received signals from antenna 2 0 ~ 8 4 3 ~ PCI/US91/06993 30 provide one input to mixer 110. The other input to the mixer is provided by the output of frequency synthesizer 112. The frequency selected Dy the synthesizer is controlled in accordance with the frequency select (FS) input from controller 34. The mixer output is amplified by an intermediate frequency amplifier 1 14 which provides its output to n filters 116. The output of each filter is provided to a selector 118 capable of selecting one of n inputs to be coupled to its output. The input selected by ssl~tor 118 is controlled in accordance with the BWS
input r~caived from controller 34. The output signal from the selector is demo~ te~ by demo~ul~or 120 to provide a b~-cebAnd output to data decision 122. The dec;sion function 122 makes a desision based on the den.G~ ted output signal as to what original digital data was lldl)s."itled and provides a digital data output. The demodulation and data decision prucess is generally well-known and is implemented by RF
receivers and modems.
The receiver is capable of receiving different remote device frequencies by the controller 34 causing frequency synthesizer 112 to generate the proper injection trequency to mixer 110 for the proper IF
trequency output. The bandwidth of the trans",illecl signal is matched by solE-1iny an ap~,ropriate output trom one ot the filters 116 by selector 118 in accordance with the bandwidth selection signal provided by controller 34. It is generally desirable to use the na"uwest filter which can pass the desired signal in order to provide maximum attenuation to undesired signals outside the desired signal band.
FIG. 7 is a block diagram of an embodiment of an FDM transmitter in accordance with the present invention. Digital data to the transmitter is received by a symbol generator 130 which generates symbols reprdsentative of each bit or byte of data to be transmitted. Such generators are generally well-known. The output of generator 130 is attenuated by variable attenuator 132. The amount of attenuation provided is electrically controlled by the output from digital to analog converter 134 based upon the BWS input by controller 34. Following attenuation the attenuated symbol provides an input to frequency synthesizer 136 and more specifically to the modulation control input of wo 92/06546 2 0 ~ ~ ~ 3 0 PCI/US91/06993 voltage controlled oscillator 138 of the synthesizer. The conventional phase detector and divider circuits comprising a conventional frequency synthesizer is provided by control circuit 140. The FS input from controller 34 is utilized to set the carrier frequency of the synthesizer.
5 The output of the synthesizer is amplified by amplifier 142 which provides its output to antenna 64 for trans-"ission to remote devices.
The BWS input controls the level of attenuation and hence bandwidth thereby causing the maximum amount of modulation provided to synthesizer 136 to vary. The frequency of the synthesizer is controlled 10 by the FS input. Thus the carrier frequency and maximum modul~tion (bandwidth) can be varied in accordance with the present invention.
FIG. 8 is a flow diagram illustrating control exercised by the micr,.prucessor controller 34 in transmitting data from a node to a remote device. As indicated by step 150 the controller periodically looks for 15 data ready interrupts generated by the LAN which indicates there is data to be transmitted. Decision step 152 determines if an interrupt has occurred. If NO the flow ends at EXIT 154. If YES controller executes step 156 and determines the amount of data (AOD) to be trans"~illed.
The AOD may be available as information as part of the transmission 20 from the LAN or can be derived based on the amount of buffer memory occupied by the data. Then a determination is made as to the remote device destination (ADR) in step 158. This information is part of the header supplied by the LAN for routing. Next a determination is made of the frequencies bandwidth and step sizes comp~tiblo with the ADR in 25 step 160. To avoid collisions a check is then made for frequencies and bandwidths in use at step 162. In step 164 an available and compatible frequency bandwidth and slot size is selected. The selection of slot position and repetition rate based on AOD in previously parameters occurs in step 166. Decision step 168 determines if all AOD can be sent 30 in one time slot. If NO the AOD is divided into maximum segments that can be sent in one time slot by step 170. If decision 168 is YES the AOD
is defined as one time slot by step 172.
In accordance with step 174 new data trans",ission parameters are not entered until the beginning of a new frame. Thus the system can WO 92/06546 ~. ~) 6 8 ~ ~ ~ PCI/US91/06993 be reconfigured at the beginning of a frame to include the transmission of new information to be transmitted or the transmission of information which could not be accommod~ted in the preceding trame or frames.
The table of system parameters is upd~ted to reflect new slot 5 assigr""ents in step 176. A variable N is set equal to 1 in step 178. In step 180 the new parameters are set for slot N. The data corresponding to slot N is l~ans",i~led by step 182. The decisicn step 184 determines if N is the last slot. If NO then step 186 increments N and returns control to step 180 to form a loop. Upon a YES decision by step 184 .Jecision step 188 deter nines if all fragments have been sent. If YES these steps end at EXIT 190. A NO derisiQn in-' ~tes more fragments remain to be sent than could be accommod~ed during the preceding frame and control p~sses to MORE 192 which allows the remainder of fragments to be identified and retra"s",illed during the next frames.
Summarizing the transmission of data from the node to a remote device user information entering the node is cletec~e-J and appropriate frequency and time parameters are sels~ted to enable tra,)s",ission of the data to the destination device. The frequency and time char~1eristics of the remote device are known and stored in the node so that appr~priate time and frequency selections can be made within the ilities of each type of remote device. This permits time and frequency management to occur thereby enhancing spectral efficiencies where possible. The data or fragments of the data are transmitted on a time slot basis within each frame.
With the capability of the present invention maximum spectral efficiencies will exist where at least one of the remote device types has a su~st~ntial degree of frequency and time slot flexibility allowing communications with such a device at frequencies and during times at which other less flexible remote devices are not capable of operation.
The node is capable of communicating with such a flexible remote device by sending instnuctions at a predetermined frequency and time slot instructing the remote device which frequency and time slot(s) are to be utilized in order to minimize contention for frequencies and times utilized 20~843~
by other devices. This allows maximum utilization of the communications ability of the node over its frequency and time management capacit~.
FiG. g is a fiow diagram iliustrating a method in accordance with the present invention for receiving information from the remote devices.
5 In step 200 the node polls each type of remote device every X frames for a status indication. Each of the r~",ole device types will be assigned to preJ~termined frequencies and time slots for receiving the corresponding poll with different devices of the same type being assigned different time slots. In step 202 frame X+1 is r~caived by the 10 node using predeter~nined frequency and time parameters est~hlished for each type of remote device. During this frame each remote device needing to transmit data to the node will send its request containing app,~,,iale information such as amount of data to be transmitted. This request ;nforl"~tion is .Jec~-Jed by the node.
1 5 In decision step 204 a .J~c;sicn is made if any remote device has made a request to send data to the node. If NO the p,~cess ends at EXIT
206 since no further information is to be recaived from the remote devices. If YES a det~r",indlion is made to de~6-",ine cG",palible frequencies bandwidths and slot sizes for each RD re~luesting to transmit data in step 208. Frequencies and bandwidths in use by other devices are checked by step 210 to avoid conflicting assignments. In step 212 the node selects an appropriate frequency and bandwidth of each reqlJssting remote device. The repetition rate slot position and slot size are selected by the node based on a stored remote device profile and the previously identified amount of information to be trans",i~led from the remote device in step 214.
In step 216 the node transmits at frame X+2 on predetermined frequency and time slots to the remote dovices the system parameter information to be utilized by each remote device for data trans",ission to the node during frame X+3. In step 218 the node waits for frame X+3 and then initializes parameter N equal to 1 at step 220. In step 222 the node sets parameters to be used for slot N for receiving transmissions from remote devices using parameters previously defined for such transmissions. Data is received in slot N in step 224. Decision step 226 wo 92/06~ 2 0 6 8 4 ~ PCT/US91/06993 determines if N is the last slot in frame X+3. If NO N is incremented in step 228 and control retumed to step 222 for reception of further data. If decision step 226iS YES decision step 230 determines if aii data has been received from the remote devices. This determination is possible 5 since in the preceding poll response trom the remote devices included the length of data to be transl"i~le.l. If YES i.e. all data to be transmitted from remote devices has been received then the steps end at EXIT 232.
If the decisiQn of step 230iS NO which indicates that more data is to be received the node waits for the next frame at step 234 and then repeats 10 the r~ception cycle by retuming to step 220. This permits the remainder of the data to be trans",i~le.l from the remote devices to be received in succeeding frames.
Summarizing the reception of data from remote devices the node periodically polls the devices to determine if information is to be 15 transmitted. In the frame following the polling frame information is received from the remote devices on predetermined signalling frequencies and times containing status or request to transmit data information. Selection of a~propriate signal parameters to be utilized for the data trans",ission is made. This parameter information is transmitted 20 to the remote devices during a following frams. The succeeding frames are utilized for the ~ce~ion of data from the remote devices until the trans",ission of this infor",ation is complete.
Although embodiments of the present invention have been shown and illuslral~d the scope of the invention is defined by the claims which 25 follow.
Background of the Invention This invention is generally directed to time division multiple access (TDMA) communications systems and is more specifically directed to a TDMA system having nodes which are ~pAhlo of the time slot and frequency management thereby accommodating communications with different types of communication devices each having its own different 1 5 time and frequency characteristics.
A number of communications systems exist in which a node or controller can communicate with a plurality of remote communication devices. In a conventional RF communications network, a base station communicates with various mobile and portable units utilizing a 20 predetermined number of different frequency channels. In TDMA
systems a predetermined frequency with a defined bandwidth is utilized to transmit frames of data with predetermined time slots ~l!ocAted to different users.
RecAuse of the efficiencies available with TDMA systems, a 25 number of such systems exist and a variety of new systems are being developed, such as a digital European cordless telephone (DECT). A
TDMA device designed for one system cannot communicate when in a different TDMA system becAuse of different time slot protocols. The radio transmission of TDMA data adds yet another degree of complexity to 30 communication between different systems since different frequencies and bandwidths are utilized.
There exists a need for a common communications node which can manage both time and frequency in order to be compatible with different TDMA communications devices.
wo 92/06546 2 0 G 8 4 3 0 PCI/US91/06993 Brief Description of the Drawings FIG. 1 illustrates a communication system in accordance with the present invention.
FIG. 2 is a graph illustrative of the time and frequency management capabilities of a node in accordance with the present invention.
FIG. 3 is a block diagram of an embodiment of a node in accordance with the present invention.
FIG. 4 is a block diagram illustr~ting the clock generator of FIG. 3.
FIG. 5 is a block diagram illustrating an embodiment of a time slot selector (TSS) utilized in FIG. 3.
FIG. 6 is a block diagram of an embodiment of a frequency division multiplex receiver of FIG. 3.
FIG. 7 is a block diagram of an embodiment of a frequency division muHiplex transmitter of FIG. 3.
FIG. 8 is a flow chart of steps for the transmission of data by a node in accordance with the present invention.
FIG. 9 is a flow chart of steps for the reception of data by a node in acconJance with the present invention.
Description of a Preferred Embodiment FIG. 1 shows an exemplary RF communications system having a node 20 in accordance with the present invention ~p~hle of RF
communications with communication devices 22, 24, and 26. Each of the three different types of devices utilize a different TDMA protocol and communicate at different frequencies. Node 20 is ~p~hlQ of RF
communications over a subst~ntial range of frequencies including those used by the three different devices and is capable of managing the frequency and time factors in order to provide communications with each of the different types of devices. Although this illustrative system uses RF
wireless communications, the present invention is generally applicable to WO 92/06546 21~ 3 0 PCI-/US91/06993 communication systems which utilize modulated carriers for in a TDMA
environment.
FIG. 2 is a graph illustrating different iime slots T1-T4 repeated as frames versus different frequency channels CH1-CH4. In the 5 representative graph, three different types of TDMA devices are shown as being acco"""Gdate.J in each frame. In time slots T1 and T4, one type of device is accommo.Jale-~ by two time slots per frame and utilizes three conti~uous channels CH1-CH3. The data l-ans,nitle~l during these time slots is accom~GdAIe.~ by a carrier frequency at the center of channel 10 CH2 with a ban~J~ l, of 3 channels. In time slot T2 a second different device with less data throughput demand is acco"""o~te-J on only frequency channel CH2. In time slot T3, a third different device is accommo~ted by utilizing bandwidth of frequency channels CH3 and CH4. Time slot T4 represents a seconJ time slot ~IlQ~tion in addition to 15 T1 within the frame for carrying data ~ssoc~te~J with the first device.
It should be understood that the reprerontati-/e graph is shown in simplified form to better convey an aspect of the present invention. The number of time slots per frame, the number of channels, and the bandwidth per channel will vary depending upon the demands placed 20 upon and capacity of the communicatiGns system. Generally, a large number of time slots per frame is desired in order to have incr~ased flexibility in accommodating different TDMA devices and different data throughput requirements. Similarly, frequency considerations will vary depending upon the number and type of different devices being 25 accon""GJated within the system. The gre~test flexibility in managing the system accolJing to the present invention occurs when a continuous range of frequency spectrum is available in which varying bandwidths can be utilized.
It is becoming increasingly difficult to obtain sufficient frequency 30 spectrum in order to support our communication needs. The present invention provides the opportunity to increase the ability to communicate within a previously assigned frequency spectrum for one type of communications by interleaving additional communications capacity in available time slots and frequencies. A node in accordance with the Wo s2/06s46 2 0 1~ 8 4 3 0 PCI /US91/06993 present invention has the capability of dynamically reconfiguring its time and frequency resources in order to adapt to different demands.
Preferably the node will be preprogrammed with the definition of the communication protocols utilized by the different communication devices 5 to be accommo~ ed Thus, the node can make time and frequency assignments consistent with the ability of remote devices to adapt within the particular protocol for each type of device.
FIG.3 illustrates an embodiment of a node 20 in accordance with the present invention. The illustrative e"lbodiment illustrates a node 10 capal~lc of accepting user data and transmitting that data to a remote communications device by an RF signal. The node is similarly capable of receiving an RF signal from a remote device which carries data that is demodulated and provided to a user network.
Signals from the remote devices are received by antenna 30 15 which is connected to frequency division multiplexer receiver 32. A
microprocessor controller 34 provides control of the frequency and bar,dwiJIh of the receiver by means of frequency selection (FS) and bandJ~iJlh size (BWS) inputs. The receiver provides recovered digital data to time slot selectors (TSS)36 and 38. The TSS 36 functions to 20 derive time synchronization information from the received signals. The TSS 38 serves to recover the TDMA encoded data by appropriate time slot selection. The controller 34 provides control information to the selectors 36 and 38 including defining the repetition rate (RR), i.e.
number of slots per frame containing the desired information, slot 25 position (SP) which defines the beginning of the time slot within the frame, and the slot size (SS) which defines the length of time of each slot.
It should be noted that several adjacent time slots may be defined as a single time slot for purposes of time management. The output of TSS 36 only contains time information which is utilized by clock generator 40 30 which provides an output digital clock reference 42 utilized for general timing and synchronization of the node. The TSS 38 provides an output of data which has been time segregated corresponding to the different data sources to demultiplexer 44. Input control signal MX from controller 34 provides the demultiplexer with select information for routing the wo 92/06546 2 0 6 3 4 ~ ~ Pcr/usg1/o6993 received data to corresponding data channels 46. The data on these channels is preferably buffered by elastic buffers 48 before being coupled to local area network (LAN) interface 50 such as suited for use in an Ethernet environment. This interface controls the flow of information 5 to and from the user data network 52 by which the individual data channels are ultimately routed to different users.
Summarizing the reception of signals from remote users a fre~usnc~ agile receiver 32 5el~cts different frequencies and bandwidths for corresponding time slots utili~ed for each different type device. The 1 0 data recovered by the receiver is further processed by the TSS to identify the different data infor",a~ion residing in the different time slots. This recovered infor."ation is then se9l~9iqls~l into corresponding different data outrlJts by the demultiplexing process and ultimately routed to the user by a data network.
1 5 The trans",ission of data from the user data network 52 to r~",ole devices is accG",plished as follows. The LAN intelface 50 ~ epls data ~J.I,esse-J to a ~ ."ote device from user data network 52 and transfers the data to elastic buffers 54. The buffers are preferably implemented as ",apped memory controlled by controller 34. The data stored in the 20 buffers is transferred to multiplexer 56 which multiplexes the different data information into a single data stream. Buffers 54 and multiplexer 56 each receive clock information from the LAN interface and clock generator 40 for the sy"chronized transfer of data. A selector 58 selects between input A from multiplexer 56 and input B from controller 34. Its 25 output is coupled to time slot selector 60. The control input to selector 58 is provided by controller 34. This permits the controller to insert relevant data to be communicated to the remote devices. The TSS 60 receives the output from sel~c~or 58 and organizes the r~ceived data in accordance with the frame and time slot protocol to be utilized similarly 30 to the decodirlg accomplished by TSS 38. The frequQncy division multiplex transmitter 62 receives the output data stream from TSS 60 and l,ans",its a modul~tQd signal using antenna 64. The frequency and bandwidth of FDM trans",itler 62 is del~""ined by controller 34 via inputs FS and BWS.
Wo s2/06s46 2 0 ~ 8 ~ 3 0 PCI/US91/06993 Summarizing the transmission of data to remote devices, data destined for remote devices is buffered and multiplexed together to form a single data stream which together with system contrGI data provlded by controller 34 is segmented into appropriate time slots by the TSS. The output of the TSS is received and modulated at an appropriate frequency and bandwidth compatible with the receiver of the corresponding remote device.
FIG. 4 is a block diagram illustrating an embodiment of a clock generator 40. The time synchronization output from TSS 36 is received 1 0 by a clock oscillator 68. Its phase is adjusted by this output and maintains time synchronization between the transmitted and received signals. A counter 70 receives the clock output pulses from clock osc~ Jor 68. The data clock output 42 consists of the basic clock rate C
and taps from each of the divide by two stages up to 2n of counter 70.
1 5 The clock output 42 consists of digital data which continues to periodically cycle from zero to 2n+1.
FIG. 5 is a block diagram of an exemplary embodiment of a time slot selector (TSS). A digital 2n+1 comparator 80 compares data clock 42 with the time slot position (SP) generated by controller 34 for each clock C. The SP position corresponds to the time slot of the selected data to be transmined or received. The exemplary system according to the present invention operates in a half duplex mode so that data from the node can be only transmitted or received in one direction at a given time. The output of the comparator consists of a digital control line which provides a true or false indication relative to each comparison. A match (true) by comparator 80 marks the beginning edge of the time slot positioned for the corresponding data and ~uses divider 82 to be reset, provides an enabling input to OR gate 84, and sets RS flip flop 86. A true output of OR gate 84 sets RS flip flop 88 and resets divider 90. Since both flip flops 86 and 88 have been set, both inputs to AND gate 92 are true causing the AND gate output to provide a control signal 94 to data transmission gate 96 causing it to open or pass data.
An enable input to flip flop 86 through inverter 98 is provided by controller 34. The enable signal is provided when the RR, SP, and SS
wo s2/06s46 2 0 ~ 8 4 3 0 PCr/US91/06993 control signals are being generated by the microprocessor and are stable. During transitions by the controller 34, these signals are not stable. The enable serves to reset flip flop 86 causing its output to change state and thereby causing AND gate 92 to be inhibited thereby 5 causing control 94 to block the flow of data. The divider 90 is programmed to divide by L which is set by the SS control and corresponds to the size or length of the time slot. The input clock C is di~iJ~J by divider 90 which provides an output resetting flip flop 88 upon reaching the count of L. This represents the length of time of the 1 0 corresponding time slot. This ~ses the output of flip flop 88 to change state thereby inhibiting AND gate 92 and causing t,a,)sn,ission gate 96 to block the flow of data. Thus, gate 96 permits the flow of data beginning with the recognition of the beginning of the proper time slot and ending with the ,ecogr,ilion of the end of the co-,espo.,Jing time slot.
1 5 The repetition rate (RR) provides an input to division function 100 which c~lc~ es one divided by the repe~ilion rate. It will be known that this function may be carried out either in conventional hardware or implemented as part of a software routine to provide the division function.
The quotient of this division pn~cass provides an input to divider 82 and 20 defines the division Z to be provided by the divider. The least significant bit C of clock 42 provides the clock input to divider 82. The output from co",pardtor 80 resets the divider. The output of the divider provides the other input to OR gate 84 and is thus ~p~hlQ of setting flip flop 88 every Z inteNal. This per",its periodic spece~ apart time slots for the same 25 data to be utilized within a frame. The first time slot is activated by the initial tnue output from comparator 84 by its input to gate 84. The time slot ends as determined by the count of L by divider 90. If another time slot is provided within a frame for the corresponding data, OR gate 84 will again enable flip flop 88 upon divider 82 reaching the Z count and will mark the 30 beginning of each time slot for every Z interval following the initial time slot determination by comparator 80. It will be apparent that the maximum repetilion rate (Z) must be greater than the size of the slot (L).
FIG. 6 is a block diagram of a illustrative embodiment of a frequency division multiplex receiver 32. Received signals from antenna 2 0 ~ 8 4 3 ~ PCI/US91/06993 30 provide one input to mixer 110. The other input to the mixer is provided by the output of frequency synthesizer 112. The frequency selected Dy the synthesizer is controlled in accordance with the frequency select (FS) input from controller 34. The mixer output is amplified by an intermediate frequency amplifier 1 14 which provides its output to n filters 116. The output of each filter is provided to a selector 118 capable of selecting one of n inputs to be coupled to its output. The input selected by ssl~tor 118 is controlled in accordance with the BWS
input r~caived from controller 34. The output signal from the selector is demo~ te~ by demo~ul~or 120 to provide a b~-cebAnd output to data decision 122. The dec;sion function 122 makes a desision based on the den.G~ ted output signal as to what original digital data was lldl)s."itled and provides a digital data output. The demodulation and data decision prucess is generally well-known and is implemented by RF
receivers and modems.
The receiver is capable of receiving different remote device frequencies by the controller 34 causing frequency synthesizer 112 to generate the proper injection trequency to mixer 110 for the proper IF
trequency output. The bandwidth of the trans",illecl signal is matched by solE-1iny an ap~,ropriate output trom one ot the filters 116 by selector 118 in accordance with the bandwidth selection signal provided by controller 34. It is generally desirable to use the na"uwest filter which can pass the desired signal in order to provide maximum attenuation to undesired signals outside the desired signal band.
FIG. 7 is a block diagram of an embodiment of an FDM transmitter in accordance with the present invention. Digital data to the transmitter is received by a symbol generator 130 which generates symbols reprdsentative of each bit or byte of data to be transmitted. Such generators are generally well-known. The output of generator 130 is attenuated by variable attenuator 132. The amount of attenuation provided is electrically controlled by the output from digital to analog converter 134 based upon the BWS input by controller 34. Following attenuation the attenuated symbol provides an input to frequency synthesizer 136 and more specifically to the modulation control input of wo 92/06546 2 0 ~ ~ ~ 3 0 PCI/US91/06993 voltage controlled oscillator 138 of the synthesizer. The conventional phase detector and divider circuits comprising a conventional frequency synthesizer is provided by control circuit 140. The FS input from controller 34 is utilized to set the carrier frequency of the synthesizer.
5 The output of the synthesizer is amplified by amplifier 142 which provides its output to antenna 64 for trans-"ission to remote devices.
The BWS input controls the level of attenuation and hence bandwidth thereby causing the maximum amount of modulation provided to synthesizer 136 to vary. The frequency of the synthesizer is controlled 10 by the FS input. Thus the carrier frequency and maximum modul~tion (bandwidth) can be varied in accordance with the present invention.
FIG. 8 is a flow diagram illustrating control exercised by the micr,.prucessor controller 34 in transmitting data from a node to a remote device. As indicated by step 150 the controller periodically looks for 15 data ready interrupts generated by the LAN which indicates there is data to be transmitted. Decision step 152 determines if an interrupt has occurred. If NO the flow ends at EXIT 154. If YES controller executes step 156 and determines the amount of data (AOD) to be trans"~illed.
The AOD may be available as information as part of the transmission 20 from the LAN or can be derived based on the amount of buffer memory occupied by the data. Then a determination is made as to the remote device destination (ADR) in step 158. This information is part of the header supplied by the LAN for routing. Next a determination is made of the frequencies bandwidth and step sizes comp~tiblo with the ADR in 25 step 160. To avoid collisions a check is then made for frequencies and bandwidths in use at step 162. In step 164 an available and compatible frequency bandwidth and slot size is selected. The selection of slot position and repetition rate based on AOD in previously parameters occurs in step 166. Decision step 168 determines if all AOD can be sent 30 in one time slot. If NO the AOD is divided into maximum segments that can be sent in one time slot by step 170. If decision 168 is YES the AOD
is defined as one time slot by step 172.
In accordance with step 174 new data trans",ission parameters are not entered until the beginning of a new frame. Thus the system can WO 92/06546 ~. ~) 6 8 ~ ~ ~ PCI/US91/06993 be reconfigured at the beginning of a frame to include the transmission of new information to be transmitted or the transmission of information which could not be accommod~ted in the preceding trame or frames.
The table of system parameters is upd~ted to reflect new slot 5 assigr""ents in step 176. A variable N is set equal to 1 in step 178. In step 180 the new parameters are set for slot N. The data corresponding to slot N is l~ans",i~led by step 182. The decisicn step 184 determines if N is the last slot. If NO then step 186 increments N and returns control to step 180 to form a loop. Upon a YES decision by step 184 .Jecision step 188 deter nines if all fragments have been sent. If YES these steps end at EXIT 190. A NO derisiQn in-' ~tes more fragments remain to be sent than could be accommod~ed during the preceding frame and control p~sses to MORE 192 which allows the remainder of fragments to be identified and retra"s",illed during the next frames.
Summarizing the transmission of data from the node to a remote device user information entering the node is cletec~e-J and appropriate frequency and time parameters are sels~ted to enable tra,)s",ission of the data to the destination device. The frequency and time char~1eristics of the remote device are known and stored in the node so that appr~priate time and frequency selections can be made within the ilities of each type of remote device. This permits time and frequency management to occur thereby enhancing spectral efficiencies where possible. The data or fragments of the data are transmitted on a time slot basis within each frame.
With the capability of the present invention maximum spectral efficiencies will exist where at least one of the remote device types has a su~st~ntial degree of frequency and time slot flexibility allowing communications with such a device at frequencies and during times at which other less flexible remote devices are not capable of operation.
The node is capable of communicating with such a flexible remote device by sending instnuctions at a predetermined frequency and time slot instructing the remote device which frequency and time slot(s) are to be utilized in order to minimize contention for frequencies and times utilized 20~843~
by other devices. This allows maximum utilization of the communications ability of the node over its frequency and time management capacit~.
FiG. g is a fiow diagram iliustrating a method in accordance with the present invention for receiving information from the remote devices.
5 In step 200 the node polls each type of remote device every X frames for a status indication. Each of the r~",ole device types will be assigned to preJ~termined frequencies and time slots for receiving the corresponding poll with different devices of the same type being assigned different time slots. In step 202 frame X+1 is r~caived by the 10 node using predeter~nined frequency and time parameters est~hlished for each type of remote device. During this frame each remote device needing to transmit data to the node will send its request containing app,~,,iale information such as amount of data to be transmitted. This request ;nforl"~tion is .Jec~-Jed by the node.
1 5 In decision step 204 a .J~c;sicn is made if any remote device has made a request to send data to the node. If NO the p,~cess ends at EXIT
206 since no further information is to be recaived from the remote devices. If YES a det~r",indlion is made to de~6-",ine cG",palible frequencies bandwidths and slot sizes for each RD re~luesting to transmit data in step 208. Frequencies and bandwidths in use by other devices are checked by step 210 to avoid conflicting assignments. In step 212 the node selects an appropriate frequency and bandwidth of each reqlJssting remote device. The repetition rate slot position and slot size are selected by the node based on a stored remote device profile and the previously identified amount of information to be trans",i~led from the remote device in step 214.
In step 216 the node transmits at frame X+2 on predetermined frequency and time slots to the remote dovices the system parameter information to be utilized by each remote device for data trans",ission to the node during frame X+3. In step 218 the node waits for frame X+3 and then initializes parameter N equal to 1 at step 220. In step 222 the node sets parameters to be used for slot N for receiving transmissions from remote devices using parameters previously defined for such transmissions. Data is received in slot N in step 224. Decision step 226 wo 92/06~ 2 0 6 8 4 ~ PCT/US91/06993 determines if N is the last slot in frame X+3. If NO N is incremented in step 228 and control retumed to step 222 for reception of further data. If decision step 226iS YES decision step 230 determines if aii data has been received from the remote devices. This determination is possible 5 since in the preceding poll response trom the remote devices included the length of data to be transl"i~le.l. If YES i.e. all data to be transmitted from remote devices has been received then the steps end at EXIT 232.
If the decisiQn of step 230iS NO which indicates that more data is to be received the node waits for the next frame at step 234 and then repeats 10 the r~ception cycle by retuming to step 220. This permits the remainder of the data to be trans",i~le.l from the remote devices to be received in succeeding frames.
Summarizing the reception of data from remote devices the node periodically polls the devices to determine if information is to be 15 transmitted. In the frame following the polling frame information is received from the remote devices on predetermined signalling frequencies and times containing status or request to transmit data information. Selection of a~propriate signal parameters to be utilized for the data trans",ission is made. This parameter information is transmitted 20 to the remote devices during a following frams. The succeeding frames are utilized for the ~ce~ion of data from the remote devices until the trans",ission of this infor",ation is complete.
Although embodiments of the present invention have been shown and illuslral~d the scope of the invention is defined by the claims which 25 follow.
Claims (10)
1. In a communications system having a node and at least first and second time division multiple access (TDMA) remote devices, the first device having a first communications protocol utilizing first frequencies and time slots, the second device having a second communications protocol utilizing second frequencies and time slots, the first protocol being different from the second protocol, the improvement in the node comprising:
means for selectively receiving signals from said first and second devices on said first and second frequencies and generating received composite data;
means for separating said received composite data into corresponding data channels in accord with said first and second time slots utilized by said first and second remote devices;
means for combining data from user data channels coupled to said node to form composite data in accord with said first and second time slots utilized by said first and second remote devices;
means for selectively transmitting signals representing said composite user data to said first and second devices on said first and second frequencies;
means for switching receiving and transmitting frequencies used by said receiving and transmitting means so that the former correspond to said transmitting and receiving frequencies, respectively, used by said first and second remote devices when signals are being communicated between said remote devices and the node.
means for selectively receiving signals from said first and second devices on said first and second frequencies and generating received composite data;
means for separating said received composite data into corresponding data channels in accord with said first and second time slots utilized by said first and second remote devices;
means for combining data from user data channels coupled to said node to form composite data in accord with said first and second time slots utilized by said first and second remote devices;
means for selectively transmitting signals representing said composite user data to said first and second devices on said first and second frequencies;
means for switching receiving and transmitting frequencies used by said receiving and transmitting means so that the former correspond to said transmitting and receiving frequencies, respectively, used by said first and second remote devices when signals are being communicated between said remote devices and the node.
2. The communications system according to claim 1 further comprising means for defining time slots to be used by the first and second devices.
3. The communications system according to claim 1 further comprising means for defining the frequencies to be used by the first and second devices.
4. The communications system according to claim 2 further comprising means for defining the frequencies to be used by the first and second devices.
5. The communications system according to claim 1 wherein said separating means comprises a time slot selector that synchronizes the received composite data into separate data bound for separate users.
6. The communications system according to claim 1 wherein said combining means comprises a time slot selector that synchronizes data from separate users into a single stream of data corresponding in time to the first and second time slots used by the first and second remote devices.
7. In a communications system having a node and at least first and second time division multiple access (TDMA) remote devices, the first device having a first communications protocol utilizing first frequencies and time slots, the second device having a second communications protocol utilizing second frequencies and time slots, the first protocol being different from the second protocol, a node communication method comprising the steps of:
selectively receiving signals from said first and second devices on said first and second frequencies and generating received composite data;
separating said received composite data into corresponding data channels in accord with said first and second time slots utilized by said first and second remote devices;
combining data from user data channels coupled to said node to form composite data in accord with said first and second time slots utilized by said first and second remote devices;
selectively transmitting signals representing said composite user data to said first and second devices on said first and second frequencies;
switching receiving and transmitting frequencies used by said receiving and transmitting steps so that the former correspond to said transmitting and receiving frequencies, respectively, used by said first and second remote devices when signals are being communicated between said remote devices and the node.
selectively receiving signals from said first and second devices on said first and second frequencies and generating received composite data;
separating said received composite data into corresponding data channels in accord with said first and second time slots utilized by said first and second remote devices;
combining data from user data channels coupled to said node to form composite data in accord with said first and second time slots utilized by said first and second remote devices;
selectively transmitting signals representing said composite user data to said first and second devices on said first and second frequencies;
switching receiving and transmitting frequencies used by said receiving and transmitting steps so that the former correspond to said transmitting and receiving frequencies, respectively, used by said first and second remote devices when signals are being communicated between said remote devices and the node.
8. The communications method according to claim 7 further comprising the step of defining time slots and the frequencies to be used by the first and second devices.
9. The communications method according to claim 7 wherein said separating step comprises synchronizing the received composite data into separate data bound for separate users.
10. The communications method according to claim 7 wherein said combining step comprises synchronizing data from separate users into a single stream of data corresponding in time to the first and second time slots used by the first and second remote devices.
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|---|---|---|---|
| US07/593,146 US5134615A (en) | 1990-10-05 | 1990-10-05 | Frequency agile tdma communications system |
| US593,146 | 1990-10-05 |
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|---|---|
| CA2068430A1 CA2068430A1 (en) | 1992-04-06 |
| CA2068430C true CA2068430C (en) | 1996-06-11 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002068430A Expired - Lifetime CA2068430C (en) | 1990-10-05 | 1991-09-25 | Frequency agile tdma communications system |
Country Status (12)
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| US (1) | US5134615A (en) |
| EP (1) | EP0504377B1 (en) |
| JP (1) | JP2729332B2 (en) |
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| AU (1) | AU644024B2 (en) |
| BR (1) | BR9105907A (en) |
| CA (1) | CA2068430C (en) |
| DE (1) | DE69133433T2 (en) |
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| MX (1) | MX9101459A (en) |
| TW (1) | TW199253B (en) |
| WO (1) | WO1992006546A1 (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA1227844A (en) * | 1983-09-07 | 1987-10-06 | Michael T.H. Hewitt | Communications network having a single node and a plurality of outstations |
| DE3527331A1 (en) * | 1985-07-31 | 1987-02-05 | Philips Patentverwaltung | DIGITAL RADIO TRANSMISSION SYSTEM |
| US4868811A (en) * | 1987-03-10 | 1989-09-19 | Kabushiki Kaisha Toshiba | Multiple access communication system |
| US4942570A (en) * | 1989-01-23 | 1990-07-17 | Motorola, Inc. | Multiple control slot TDM/FDM communication system |
-
1990
- 1990-10-05 US US07/593,146 patent/US5134615A/en not_active Expired - Lifetime
-
1991
- 1991-09-25 EP EP91918896A patent/EP0504377B1/en not_active Expired - Lifetime
- 1991-09-25 CA CA002068430A patent/CA2068430C/en not_active Expired - Lifetime
- 1991-09-25 WO PCT/US1991/006993 patent/WO1992006546A1/en active IP Right Grant
- 1991-09-25 DE DE69133433T patent/DE69133433T2/en not_active Expired - Lifetime
- 1991-09-25 KR KR1019920701331A patent/KR960007244B1/en not_active IP Right Cessation
- 1991-09-25 AU AU87474/91A patent/AU644024B2/en not_active Ceased
- 1991-09-25 JP JP3517200A patent/JP2729332B2/en not_active Expired - Lifetime
- 1991-09-25 BR BR919105907A patent/BR9105907A/en not_active IP Right Cessation
- 1991-10-02 IL IL99638A patent/IL99638A0/en unknown
- 1991-10-04 MX MX9101459A patent/MX9101459A/en unknown
-
1992
- 1992-03-02 TW TW081101573A patent/TW199253B/zh active
Also Published As
| Publication number | Publication date |
|---|---|
| EP0504377B1 (en) | 2004-12-29 |
| JP2729332B2 (en) | 1998-03-18 |
| JPH05503404A (en) | 1993-06-03 |
| KR960007244B1 (en) | 1996-05-29 |
| MX9101459A (en) | 1992-06-05 |
| KR920704471A (en) | 1992-12-19 |
| IL99638A0 (en) | 1992-08-18 |
| EP0504377A1 (en) | 1992-09-23 |
| WO1992006546A1 (en) | 1992-04-16 |
| DE69133433T2 (en) | 2005-06-02 |
| CA2068430A1 (en) | 1992-04-06 |
| TW199253B (en) | 1993-02-01 |
| EP0504377A4 (en) | 1993-08-11 |
| AU8747491A (en) | 1992-04-28 |
| BR9105907A (en) | 1992-10-13 |
| AU644024B2 (en) | 1993-12-02 |
| DE69133433D1 (en) | 2005-02-03 |
| US5134615A (en) | 1992-07-28 |
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