CA2040061A1 - Adaptive diversity equipment arrangement for cellular mobile telephone systems - Google Patents
Adaptive diversity equipment arrangement for cellular mobile telephone systemsInfo
- Publication number
- CA2040061A1 CA2040061A1 CA002040061A CA2040061A CA2040061A1 CA 2040061 A1 CA2040061 A1 CA 2040061A1 CA 002040061 A CA002040061 A CA 002040061A CA 2040061 A CA2040061 A CA 2040061A CA 2040061 A1 CA2040061 A1 CA 2040061A1
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- CA
- Canada
- Prior art keywords
- receivers
- mode
- receiver
- signal
- signals
- 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.)
- Abandoned
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Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
- H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
- H04B7/08—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station
- H04B7/0802—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station using antenna selection
- H04B7/0817—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station using antenna selection with multiple receivers and antenna path selection
- H04B7/082—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station using antenna selection with multiple receivers and antenna path selection selecting best antenna path
Abstract
ABSTRACT
A method and apparatus utilizing adaptive diversity in the base station of a cellular telephone system where during a diversity period the signal strengths of two receivers assigned to three or more sectors are continuously compared and the stronger audio output signal is switched to be used in the station signal processing circuits and where during non-diversity, relatively short time periods, samples of adjacent sectors signal strengths are measured and compared so that the adjacent sector with the strongest signal is applied to one receiver while the other receiver supplies the central sector to the other receiver for transmission to the station audio processor.
A method and apparatus utilizing adaptive diversity in the base station of a cellular telephone system where during a diversity period the signal strengths of two receivers assigned to three or more sectors are continuously compared and the stronger audio output signal is switched to be used in the station signal processing circuits and where during non-diversity, relatively short time periods, samples of adjacent sectors signal strengths are measured and compared so that the adjacent sector with the strongest signal is applied to one receiver while the other receiver supplies the central sector to the other receiver for transmission to the station audio processor.
Description
;~ 0 6~
A~APTIVE DIVERSITY EQUIPMENT ARRANGEMENT
FOR CELLULAR MO~ILE TELEP~ONE SYSTEMS
FIELD OE T~E INVENTIO~
The invention relates to improvements in cellular telephone base stations.
BACKGROUND AND SUMMARY OF T~ INVENTION
Contemporary cellular mo~ile telephone systems conventionally include a "diversity" system of some nature in the base or ixed station receivers to redu~e the efects of multipath fading wherein large rapid fluctuations of signal level occur. In such diversity systems the signals received by two ~r more antenna~ are normally mada available to the receiving equipment and a process or scheme is provided whereby when the signal from one antenna is experiencing a large negative fluctuation or deep fade the signal from another antenna may be sub~tituted. Such switching thus produces a ~ignal level of higher average signal strength, and the ~uality of communicatiGns is inherently improved.
A typical such diversity system a~30ciated with receiving eguipment is illustrated in Figure 1 which is a sirnpliied block diagram illustrating a singl~
channel. In a typ~cal such system each antenna conventionally may ~erve many channels through a multicoupler. Although such multicoupler~ are not i~lustrated in sub~equent figuras, the exemplary embodiments found therein may be assumed to include such multicouplers. As illustrated in F:igure 1, ' :' ' ' ' '`
.
, 2 ;~ 6~
such system3 are provided with two receivers per RF
channel, and each receiver has an antenna input and audio o~tput a~ well as a received signal strength indicator ~RSSI) output. The latter output is an analog output which is indicative of or provides a measure of the received RF signal strength at the antenna input. A comparison o the RSSI receiver outputs i~ made to determine the larger of the two, and the generated high or low signal may be used to operate a switch such as SW1 50 as to select the input for the audio processing element from the receiver with the highest RSSI signal. Such a diversity scheme is known as a "post-detection receiver selection by RSSI" and is in common use.
It is also known to use the R5SI or "receiv~d signal strength indicator" for other purposes such as determining when it is nece~sary to hand off or transfer the communications function to another cell. Such a determination may be made by converting the RSSI measure to a digital ormat for transmission to a central processor for comparison with similar signals from other cells so that the cell having the ~trongest signal from the mobile unit may be determined. The RSSI signals may be used for these and other purposes through the use of a sampling switch means ~SW2~, an analog-to-digital converter and the logic unit a~ illustrated in Figur~ 1.
Diversity circuits where the instantaneou~ly larger of the input signals is passed to the receiver, operate with sufficient speed to follow the rather large and rapid fluctuations of the received signal strength that are present due to 2al~0~
multipath fading. Determining when to transer or hand off the communications function to another cell, however, is not dependent on rapid fluctuations but is dependent on the mobile position and average signal strength. Accordingly, both instantaneous and average signal strengths must be cletermined .
As seen in Figure 1 two receivers and two antenna~ are required for each area to be covered.
However, in areas where the number of subscribers is guite high it is necessary to provide smaller cells and re-use requencies in cells that are relatively close to each other in order to provide a suficiently high number of channels to handle the communication traffic. In such areas it is conventional to subdivide cells into sectors and use directional antennas to reduce interfering signals from other cells. Each sector would require two antennas and two receivers for maintainin~ diversity as noted above. Where a cell, for example, is divided into three 120 sectors, six receiving antennas would be re~uired. When the cell is further divided, maintaining diversity would lead to a prohibitively large number o antennas and overcrowding of support tower~ and the like.
Clearly, undar such circumstances it would be de#irabla to provide the benefits of diversity but with f~wer antennas being required in each sector of a cell.
We have discovered that efective diversity with only one receiver antenna in each sector of a sector~d cell may be obtained through the use of "adaptive" diver~ity. Such diversity dynamically ;~4~1~6~
adapts to changing signal conditions wherein an analog comparator acc~pts RSSI ~ignals from two receivers and the receivers operate to receive the signals from three sectors of a sectored cell; one receiver being connected to the center sector antenna and the other receiver being switchably connected between left and rlght adjacent sector antennas. Eff~ctive diversity is maintained ( for a large portio~ o the time3 between the center sector and one of the adjacent ~ectors. For very short periods of time the audio is taken from the center sector only while the second receiver measures RSSI
in the other adjacent sector. By keeping track of average signal levels in both adjacent sectors we can adaptively determine which adjacent sector ha~
the largest average signal and use it during the large time period when diversity i8 in effect.
Such adaptive diversity method and apparatus not only maintains diversity where large rapid fluctuations of ~ignal level occur but also dynamically adapt~ to changing conditions due to movement of the mobile unit. Thus, the shortcoming~
of the prior art are overcome.
These and further object~ and advantage~ of the present invention will become more apparent upon reerence to the following specification, appended cla~ms and drawings.
BRI~F DESCRIPTION OE T~E DRA~INGS
FIGURE 1 i3 a diagram of a prior art base station inc~udiny a diversity ~y~tem whereby tha ~tronge~t of the two audio ~ig~al~ rece~ved by two 2~
antenna i8 used to maintain a higher average signal level;
FIGURE 2 show~ part of a cell which has been divided into a number of sectors with each sector including a directional antenna;
FIGURE 3 illustrates a manner in which adjacent sector diversity may be obtained using three directional antennas and three receivers;
FIGURE 4 shows an attempt to provide adjacent:
~ector diversity with only two receivers and three antenna~;
FIGURE 5 illustrate~ the preferred exemplary embodiment for obtaining adaptive diversity in a sectored cell;
FIGURES 6A to 6D show portions of a timing ~iagram of the methodology followed by the exemplary ~tructure of Eigure 5; and FI5URE 7 is an exemplary ambodiment simiLar l:o that which i~ found in Figure 5 illustrating additional variation~ thereof.
DETAII~D DESCRIPTlON OF T~ DR~WINGS
A3 .illu~trated in Figure 2, a call may be divided into a number of sector~ with each ~ector including a directional antenna. Ideallzed ~ignal level contour3 of equal signal level for two of the 20fl~ 6~
SeCtorB labelled S and RA are also illustrated.
Such contours show that although the maximum signal will normally be obtained by an antenna from a mobile located within the boundaries of the sector containing the antenna, signals of only a little less amplitude can be obtained by an antenna located in another sector. Similar antenna propagation patterns, although not illustrated, al~o apply to the left adjacent sector LA.
A3 illustrated in Figure 2, a particular mobile is located in sector S at the point M, and it is clear that the antenna in sector S will be receiving the mobile signal at some average level. The antenna in sector RA (right side adjacent sector~
will also be receiving the mobile signal but a rPduced average level. Depending on the location o the mobile the average signal level received at RA
will range from nearly eq~al to that detected by the antenna in ~ector S to a few dB lower than the ~ignal received at S. The former situation would occur, for example, when the mobile wa~ on the ~ector border; whereas, the latter would occur with the mobile in the center of sector S.
Under such circumstances if multipath fading phenomena occurred in sector S (fading in the range of 20 to 30 dB), the ~ignal from RA or the duration of the fade may be on the order of 10 or 20 dB
~trongsr. Similar ~ignal levels and condition~ ~ay be found in khe left adjacent sector LA when the mobile i~ on that side of sector S.
Clearly, by usiny the ~lgnal~ from the ~ector~
adjacent the S ~ector, effective diver3ity may be provided with only one receivin~ antenna in each 2f~ 6~
sector. Additionally, it is clear that if the average signal level in an adjacent sector such as RA becomes larger than the average signal in sector S, the conditions are such that a transfer to the former sector, i.~. a handoff, would be appropriate since the mobile is no longer truly within sector SO
Apparatus for obtaining such diversity and handoff tran~fers is illustrated in Figure 3 which differs from that which is shown in Figure 1 in that three receivers 1, 2 and 3 are provided with three RSSI branch paths being compared by element 4 where the latter element operates as a three pole switchin~ arrangement for feeding the stronge3t audio signal to the base station audio processing system 5. That is to say, if the strongest instantaneous signal is received by sector S antenna 6, switch SW1 connects receiver 2 of sector S to element 5. With multipath propagation fading phenomena present in sector S, either sector RA or sector LA would furnish the audio input to element 5 depending on which sector had the strongest signal.
Although such a system i5 clearly operable, it has the disadvantage o the additional expense incurred by reguiring a third receiver. As illu~trated in Figure 4, a two-receiver system for providiny adjacent ~ector diversity is obtainable by connecting the adjacent ~ector antennas 6 and 8 to the second receivor and controlling the illustrated switch position~ through the use of dig~tal logic 9. Tha dotted lines indicate one or more switch control signal3 which allow the logic circuits to exercise control over the sw.itches. Switch SW~
allows the analog-to-digital converter to measure 8 2~4~36~
RSSI samples from eikher receiver. The antenna switch ASW allows receiver 2 to be connected to either of the adjacent sector antennas (6 and 8).
Under initial conditions the audio is, as illustrated, connected from receiver 1 by way of SWl to audio processor 5. Additionally, the RSSI signal from receiver 1 i~ connected to converter 10 by way of 5W2. Logic 9 would measura the received ignal strength indicator (RSSI) of sector S and thereafter the logic would connect converter 10 to receiver 2 and make similar measurements in each of the adjacent sector~ in a s~quential manner.
A comparison of the measurement~ by the logic element would indicate the highest signal strength and set the switches appropriately. If the RSSI in sector S, for example, were the largest measured, the audio switching woul~ be as îllustrated in the figure. Thereafter, the measurement cycle would be repeated and an adjacent sector such as LA or RA
would be connected for providing the audio input to element 5 if it provided the strongest signal as indicated in the subsequent meaaurement~. Logic unit 9 operates the antenna switch in a fashion similar to SWl. That is to say,in each measurement cycle the adjacent sector having the largest measured RSSI would be connected to receiver 2 and would be changed only if a subsequent measurement irldicated that the other adjacent sector RSSI were s~ronger.
Although such a ~ystem requires only two receiver~, the analog comparator has been replaced by a sequential digital RSSI oeasurement routine wherein the receiver whose audio output i~ not being ;:
:
:
9 20~
transmitted to element 5 is being used to mea~ure signal strength in the adjacent sectors. Although this proce~s is workable in prin~iple as to providing audio improvement due to diversity switching, practical implementation present~ a problem since the measurements are no longer being made in a ~imultaneous manner. That is to say, aignificant fades in the sector signals may occur many times a second and last for only a few millisecond~. In order for diversity to provide improved signal quality substantially instantaneous switching i reguired when multipath fading is sensed. To obtain such instantaneous switching, t:he entire process of switchiny antennas, ac~uiring and evaluating new RSSI measurements and switching the I appropriate audio output signal to processor 5 must be completed in no more than a couple of microseconds in order for diversity to bs effective. Such high performance sequential circuit designs are difficult to obtain and expensive.
Accordingly, such circuit designs would not be well suited for obtaining competitive commercial product~.
As previously noted, we have di~covered a manner and means of overcoming the shortcomings of the praviously described arrangements. The exemplary embodiment of Figure 5 is an arrangement for obtainlng eective diversity with only one antenna in each ~ector of a sectored cell and with adaptive diversity obtained through the use of structure whi.ch dynamically adapts to chanying ~gnal condition~ due to movement o the mobile, a~
well a~ the effects of multipath adlng.
.
26~
The ~tructure uses an analog comparator which obtains RS5I signals from two receivera, wherein the comparator output is connected to switch SWl by way of a loyical OR-like switching structure 11 which is ~ymbolically shown. Such OR structure allows (under the control of logic element 9) a diversity operation between the output of receiver 1 and the output of receiver 2 or requires the audio output from rec~ive 1 to be pa~sed by way of switch SWl to processor 5 for short periodic intervals. During the short periodic intervals, receiver 2 is u~ed to measure the RSSI from the left and right adjacent sectors by using elements 9 and 10 to determine which adjacent sector is producing the strongest signal and, therefore, which sector antenna ia to be connected to receiver 2.
The process may be understood by again considering the example illustrated in Figure 2 where the mobile is located at M which is closer to sector RA than to sector LA. Tha siynal in sector RA, accordingly, will be stronger than the ~ignal sensed by antenna 6 in sector LA. If the location of the mobile unit were known in advance, the operation of the antenna switch ASW to select RA for connection to receiver 2 would be a foregone conclusion and easily implemented. Although such information i9 not available in advance, the invantion take~ advantage of two facts; namely, (a) that tha location o the mobile unit within a ceLl change~ relatively slowly compared to the rathQr rapid fluctuations of multipath fadiny, and ~b) improvement~ in the recovered audio due to effective diversity ia a ~tati3tical proce~ which obtains .
:'~
11 2~
., improved quality of communications by reducing the averaqe noi3e level in the recovered audio. As to the fir~t noted fact, although mult~path fading mu~t be overcome by the rapid switching provided by a diversity sy~tem, since the averaqe signal level change~ 810wly, it is possible to determine the average ~i~nal level by making less frequent measurements than is required for maintaining diversity.
We have discovered that effective diverslty can be maintained for a larqe portion of the tim~, for e~ample 90% of the time, and that the resulting improvement in guality is substantially aqual to that obtained where diversity is maintained ~00% of th~ time. We have further discovered that average adjacent sector signal levels may be obtained by taking periodic short samples of the RSSI in the adjacent sectors and that such samples provide a measure which indicate~ which adjacent sector has the stronge~t signal and, therefore, the position which should be assumed by switch ASW. Under such circum~tances receiver 2 can be connected to the antenna of the adjacent sector with the strongest ~lgnal as well a~ the analog comparator and thereafter provide efective diversity between sector S and the ~trongest adjacent ~ector. As aformentioned, said diversity period~ are relatively long, ~uch as 90% of the period. During the ~hort periodic samplas when the relativs signal strengths of the adjacent sectors i~ measured, logic element 9 by way o OR ~tructure 11 forces switch SWl to connect the receiv~r 1 audio to proce~sor 5.
Accordlngly, during all portions of the period an - , .
audio signal is applied to the proce~or 5, albeit, without diversity during the short sampling or measuring periods. However, the wor~t that can happen during the short measuring period would be a deep fade in the ~ignal from the antenna in the S
sector, which, o course, could happen during the measurement process. Statistically, however, such deep fade~ occur much le~s than 50% of the time during multipath ading. As such the average signal strength~ may be maintained at a high signal level, and consequently, the ~uality of communications is improved through the use of a relatively simple and inexpensive circuit design which is well suited for inclu~ion in a competitive commercial product.
The proces~ of the exemplary embodiment of Figure 5 may be more fully under~tood from a consideration of the timing diagram~ illustrated in Figure~ 6A to ~D. Figure 6A illustrates that diversity i~ effective, i . e., SWl continually select~ the stronge~t of the two r~ceiv~r audio output signal~, except when me~surements are made during the relatively short sampling periods. Al illustrated in Figure 6B, during the relatively lonc3 diversi ty periods the swi tch SW1 may connect either of the receivers to the audio proce~or 5 but during the relatlvely short mea~uring perlods only receiver 1 i~ connected to element 5. Figure 6C indicate~
which antenna (6 or 8) 1~ connected to the ~econd receiver by way o~ ~witch ASW at any particular time. The particular antenna connected, o~ cour~a, wl,ll depend upon the mea~ured 3ignal strength from the antennas which are ~ampled in the timed manner illu~trated ln Figure 6D.
, ~1~)4~
Considering the timing cycles of Fi~ure~ 6A to 6~ together at time T0 when diversity is active between ~ectors S and LA, sector RA and it~ antenna are inactive in the sense of not being connected to receiver 2. At time Tl, although diversity is ~til~
active, the R5SI of the active sector LA i~ sampled and mea~ured at the converter 10, and logic 9 then control SWl to select the audio from receiver l for transmis3ion to processor 5. Simultaneously, the logic element 9 operate~ switch ASW to connect receiver 2 to the "inactive" RA sector and at time T2 the RSSI of ~ector RA is sampled and measured.
The time diference between Tl and T2 i~ critical only to the extent of allowing sufficient time for the signal ~trength of receiver 2 to settle to it~
new value after the operation of the antenna switch ASW. A comparison is then made by logic element 9 to determine whether the signal strength of sector LA or RA is strongest, and the po~itioniny of switch A5W is made in accordance with the determination.
Thereafter, logic 9 allows switch SWl to again operate in a diversity mode.
As illustrated in Figure 6C, the right adjacent sector at time T2 would be determined to be larger than the left adjacent sector LA such that when diver~ity i~ reactivated, the activ~ sector is changed ~rom adjacent sector LA to adjacent RA.
Addltionally, in the period between T2 and T3, diver~ity i~ active between sector S and ~ector RA
w~th LA "inactive'l. Moreover, aq clearly i~lu~trated in Eigure 6A, at the end of time T3 a new measurement cycle begin~ but with sector RA
msasured durlng the active diversity period and 14 ~1~4~
~ector LA measured when SWl is orced to connect receiver 1 to processor 5.
Accordingly, the exemplary embodiment of Figure 5 provides a circuit de~ign that not only provide~
high guality communications but provide3 such results with a design well suited to a competitive commercial product. Moreover, the problems of the prior art are avoided by dynamically adapting to changing signal conditions whereby efective diver~ity is obtained to combat the effects of multipath fading as well as changing signal conditions due to movement of the mobile unit. The latter condition i~ measured for the purpo~e of using the strongest sector signal as well a~
determining when cell-to-cell transfer or handoff should occur.
Fisure 7 illustrates variation~ of the exemplary embodiment of Figure 5. For example~ the RSSI of sector S and receiver 1 may be measured and stored in logic 9, and the RSSI of additional sector~ may also be measured during the periodic short ~amples of adjacent and other ~ectors, said other sectors being represented by sactor B and antenna 12. The measuring of additional ~uch ~ignal strength sample~ may be used for storing averaga or rolling value3 or for comparison purposes with the RSSI of ~ector S along with other RSSI's for determining, among other thiny~, the need or call-to-cell tran~fer or handing of. Additionally, the inclusion of other ~ector~ in the diver~ity may t~lca into consideration the RS~I of the sector diametrically oppo~i.te from the S ~ector in order to handle the case where the mobile unit is pa~ing . . , ,. . .. .
: , :: , :
15 ~ 6~
substantially directly under the antenna tower through ~he center of the cell.
Still other variations will o~cur to tho~e skilled in the art. For example, logic unit 9 may be advantageously designed to choose or ba3e its decision~ on more than one sample of RSSI from a particular sector. Such decision~ may be ba3ed upon maintaining average readings o RSSI from each ~ector and updating the average6 at each measurement cycle. The choice of which receiver to use when based upon such average signals is indicative of the po~ition of the mobile unit and such averages ~ould vary slowly.
Additionally, the artisan will recognize that the sequence in which the switches are operated and the measurements taken may be varied within the teachings of our disclosure. In Figur~s 6A to 6D, for example, the time during which diversity is active can be maximized by makinq the order in which the adjacent sector~ are measured dependent upon which ~ector i currently active. Such an operation, however, is ~ot necessary and the logic may be 3implified by making the order fixed and extending the diversity inactive period to cover measurements of both adjacent sector~. Still further, the artisan will recogni~e that contemporary circult element~ may be used to implement the exemplary embodiment~ illustrated and descr.ibed. For example, the ~witches ~uch a~ SWl could be implemented with commercially availabla ~lid ~tate device~ such as CMOS tran~mi~ion gate~. Additionally, the antenna switch ASW could also be a ~olld ~tate device such a~ a pin diode RF
switch. Still further, the logic element 9 could be ea~lly implemented by way of programming conventional microproce~sor~.
While the invention has been de~cribed in connection with what i~ presently considered to be the mo8t practical and preferred embodiment, it is to be understood that the invention 1~ not to be limited to khe disclosed embodiment, but on the contrary, i~ intended to cover variou9 modifications and eguivalent arxangements included within the 8pirit and scope of the appended claim~.
:
A~APTIVE DIVERSITY EQUIPMENT ARRANGEMENT
FOR CELLULAR MO~ILE TELEP~ONE SYSTEMS
FIELD OE T~E INVENTIO~
The invention relates to improvements in cellular telephone base stations.
BACKGROUND AND SUMMARY OF T~ INVENTION
Contemporary cellular mo~ile telephone systems conventionally include a "diversity" system of some nature in the base or ixed station receivers to redu~e the efects of multipath fading wherein large rapid fluctuations of signal level occur. In such diversity systems the signals received by two ~r more antenna~ are normally mada available to the receiving equipment and a process or scheme is provided whereby when the signal from one antenna is experiencing a large negative fluctuation or deep fade the signal from another antenna may be sub~tituted. Such switching thus produces a ~ignal level of higher average signal strength, and the ~uality of communicatiGns is inherently improved.
A typical such diversity system a~30ciated with receiving eguipment is illustrated in Figure 1 which is a sirnpliied block diagram illustrating a singl~
channel. In a typ~cal such system each antenna conventionally may ~erve many channels through a multicoupler. Although such multicoupler~ are not i~lustrated in sub~equent figuras, the exemplary embodiments found therein may be assumed to include such multicouplers. As illustrated in F:igure 1, ' :' ' ' ' '`
.
, 2 ;~ 6~
such system3 are provided with two receivers per RF
channel, and each receiver has an antenna input and audio o~tput a~ well as a received signal strength indicator ~RSSI) output. The latter output is an analog output which is indicative of or provides a measure of the received RF signal strength at the antenna input. A comparison o the RSSI receiver outputs i~ made to determine the larger of the two, and the generated high or low signal may be used to operate a switch such as SW1 50 as to select the input for the audio processing element from the receiver with the highest RSSI signal. Such a diversity scheme is known as a "post-detection receiver selection by RSSI" and is in common use.
It is also known to use the R5SI or "receiv~d signal strength indicator" for other purposes such as determining when it is nece~sary to hand off or transfer the communications function to another cell. Such a determination may be made by converting the RSSI measure to a digital ormat for transmission to a central processor for comparison with similar signals from other cells so that the cell having the ~trongest signal from the mobile unit may be determined. The RSSI signals may be used for these and other purposes through the use of a sampling switch means ~SW2~, an analog-to-digital converter and the logic unit a~ illustrated in Figur~ 1.
Diversity circuits where the instantaneou~ly larger of the input signals is passed to the receiver, operate with sufficient speed to follow the rather large and rapid fluctuations of the received signal strength that are present due to 2al~0~
multipath fading. Determining when to transer or hand off the communications function to another cell, however, is not dependent on rapid fluctuations but is dependent on the mobile position and average signal strength. Accordingly, both instantaneous and average signal strengths must be cletermined .
As seen in Figure 1 two receivers and two antenna~ are required for each area to be covered.
However, in areas where the number of subscribers is guite high it is necessary to provide smaller cells and re-use requencies in cells that are relatively close to each other in order to provide a suficiently high number of channels to handle the communication traffic. In such areas it is conventional to subdivide cells into sectors and use directional antennas to reduce interfering signals from other cells. Each sector would require two antennas and two receivers for maintainin~ diversity as noted above. Where a cell, for example, is divided into three 120 sectors, six receiving antennas would be re~uired. When the cell is further divided, maintaining diversity would lead to a prohibitively large number o antennas and overcrowding of support tower~ and the like.
Clearly, undar such circumstances it would be de#irabla to provide the benefits of diversity but with f~wer antennas being required in each sector of a cell.
We have discovered that efective diversity with only one receiver antenna in each sector of a sector~d cell may be obtained through the use of "adaptive" diver~ity. Such diversity dynamically ;~4~1~6~
adapts to changing signal conditions wherein an analog comparator acc~pts RSSI ~ignals from two receivers and the receivers operate to receive the signals from three sectors of a sectored cell; one receiver being connected to the center sector antenna and the other receiver being switchably connected between left and rlght adjacent sector antennas. Eff~ctive diversity is maintained ( for a large portio~ o the time3 between the center sector and one of the adjacent ~ectors. For very short periods of time the audio is taken from the center sector only while the second receiver measures RSSI
in the other adjacent sector. By keeping track of average signal levels in both adjacent sectors we can adaptively determine which adjacent sector ha~
the largest average signal and use it during the large time period when diversity i8 in effect.
Such adaptive diversity method and apparatus not only maintains diversity where large rapid fluctuations of ~ignal level occur but also dynamically adapt~ to changing conditions due to movement of the mobile unit. Thus, the shortcoming~
of the prior art are overcome.
These and further object~ and advantage~ of the present invention will become more apparent upon reerence to the following specification, appended cla~ms and drawings.
BRI~F DESCRIPTION OE T~E DRA~INGS
FIGURE 1 i3 a diagram of a prior art base station inc~udiny a diversity ~y~tem whereby tha ~tronge~t of the two audio ~ig~al~ rece~ved by two 2~
antenna i8 used to maintain a higher average signal level;
FIGURE 2 show~ part of a cell which has been divided into a number of sectors with each sector including a directional antenna;
FIGURE 3 illustrates a manner in which adjacent sector diversity may be obtained using three directional antennas and three receivers;
FIGURE 4 shows an attempt to provide adjacent:
~ector diversity with only two receivers and three antenna~;
FIGURE 5 illustrate~ the preferred exemplary embodiment for obtaining adaptive diversity in a sectored cell;
FIGURES 6A to 6D show portions of a timing ~iagram of the methodology followed by the exemplary ~tructure of Eigure 5; and FI5URE 7 is an exemplary ambodiment simiLar l:o that which i~ found in Figure 5 illustrating additional variation~ thereof.
DETAII~D DESCRIPTlON OF T~ DR~WINGS
A3 .illu~trated in Figure 2, a call may be divided into a number of sector~ with each ~ector including a directional antenna. Ideallzed ~ignal level contour3 of equal signal level for two of the 20fl~ 6~
SeCtorB labelled S and RA are also illustrated.
Such contours show that although the maximum signal will normally be obtained by an antenna from a mobile located within the boundaries of the sector containing the antenna, signals of only a little less amplitude can be obtained by an antenna located in another sector. Similar antenna propagation patterns, although not illustrated, al~o apply to the left adjacent sector LA.
A3 illustrated in Figure 2, a particular mobile is located in sector S at the point M, and it is clear that the antenna in sector S will be receiving the mobile signal at some average level. The antenna in sector RA (right side adjacent sector~
will also be receiving the mobile signal but a rPduced average level. Depending on the location o the mobile the average signal level received at RA
will range from nearly eq~al to that detected by the antenna in ~ector S to a few dB lower than the ~ignal received at S. The former situation would occur, for example, when the mobile wa~ on the ~ector border; whereas, the latter would occur with the mobile in the center of sector S.
Under such circumstances if multipath fading phenomena occurred in sector S (fading in the range of 20 to 30 dB), the ~ignal from RA or the duration of the fade may be on the order of 10 or 20 dB
~trongsr. Similar ~ignal levels and condition~ ~ay be found in khe left adjacent sector LA when the mobile i~ on that side of sector S.
Clearly, by usiny the ~lgnal~ from the ~ector~
adjacent the S ~ector, effective diver3ity may be provided with only one receivin~ antenna in each 2f~ 6~
sector. Additionally, it is clear that if the average signal level in an adjacent sector such as RA becomes larger than the average signal in sector S, the conditions are such that a transfer to the former sector, i.~. a handoff, would be appropriate since the mobile is no longer truly within sector SO
Apparatus for obtaining such diversity and handoff tran~fers is illustrated in Figure 3 which differs from that which is shown in Figure 1 in that three receivers 1, 2 and 3 are provided with three RSSI branch paths being compared by element 4 where the latter element operates as a three pole switchin~ arrangement for feeding the stronge3t audio signal to the base station audio processing system 5. That is to say, if the strongest instantaneous signal is received by sector S antenna 6, switch SW1 connects receiver 2 of sector S to element 5. With multipath propagation fading phenomena present in sector S, either sector RA or sector LA would furnish the audio input to element 5 depending on which sector had the strongest signal.
Although such a system i5 clearly operable, it has the disadvantage o the additional expense incurred by reguiring a third receiver. As illu~trated in Figure 4, a two-receiver system for providiny adjacent ~ector diversity is obtainable by connecting the adjacent ~ector antennas 6 and 8 to the second receivor and controlling the illustrated switch position~ through the use of dig~tal logic 9. Tha dotted lines indicate one or more switch control signal3 which allow the logic circuits to exercise control over the sw.itches. Switch SW~
allows the analog-to-digital converter to measure 8 2~4~36~
RSSI samples from eikher receiver. The antenna switch ASW allows receiver 2 to be connected to either of the adjacent sector antennas (6 and 8).
Under initial conditions the audio is, as illustrated, connected from receiver 1 by way of SWl to audio processor 5. Additionally, the RSSI signal from receiver 1 i~ connected to converter 10 by way of 5W2. Logic 9 would measura the received ignal strength indicator (RSSI) of sector S and thereafter the logic would connect converter 10 to receiver 2 and make similar measurements in each of the adjacent sector~ in a s~quential manner.
A comparison of the measurement~ by the logic element would indicate the highest signal strength and set the switches appropriately. If the RSSI in sector S, for example, were the largest measured, the audio switching woul~ be as îllustrated in the figure. Thereafter, the measurement cycle would be repeated and an adjacent sector such as LA or RA
would be connected for providing the audio input to element 5 if it provided the strongest signal as indicated in the subsequent meaaurement~. Logic unit 9 operates the antenna switch in a fashion similar to SWl. That is to say,in each measurement cycle the adjacent sector having the largest measured RSSI would be connected to receiver 2 and would be changed only if a subsequent measurement irldicated that the other adjacent sector RSSI were s~ronger.
Although such a ~ystem requires only two receiver~, the analog comparator has been replaced by a sequential digital RSSI oeasurement routine wherein the receiver whose audio output i~ not being ;:
:
:
9 20~
transmitted to element 5 is being used to mea~ure signal strength in the adjacent sectors. Although this proce~s is workable in prin~iple as to providing audio improvement due to diversity switching, practical implementation present~ a problem since the measurements are no longer being made in a ~imultaneous manner. That is to say, aignificant fades in the sector signals may occur many times a second and last for only a few millisecond~. In order for diversity to provide improved signal quality substantially instantaneous switching i reguired when multipath fading is sensed. To obtain such instantaneous switching, t:he entire process of switchiny antennas, ac~uiring and evaluating new RSSI measurements and switching the I appropriate audio output signal to processor 5 must be completed in no more than a couple of microseconds in order for diversity to bs effective. Such high performance sequential circuit designs are difficult to obtain and expensive.
Accordingly, such circuit designs would not be well suited for obtaining competitive commercial product~.
As previously noted, we have di~covered a manner and means of overcoming the shortcomings of the praviously described arrangements. The exemplary embodiment of Figure 5 is an arrangement for obtainlng eective diversity with only one antenna in each ~ector of a sectored cell and with adaptive diversity obtained through the use of structure whi.ch dynamically adapts to chanying ~gnal condition~ due to movement o the mobile, a~
well a~ the effects of multipath adlng.
.
26~
The ~tructure uses an analog comparator which obtains RS5I signals from two receivera, wherein the comparator output is connected to switch SWl by way of a loyical OR-like switching structure 11 which is ~ymbolically shown. Such OR structure allows (under the control of logic element 9) a diversity operation between the output of receiver 1 and the output of receiver 2 or requires the audio output from rec~ive 1 to be pa~sed by way of switch SWl to processor 5 for short periodic intervals. During the short periodic intervals, receiver 2 is u~ed to measure the RSSI from the left and right adjacent sectors by using elements 9 and 10 to determine which adjacent sector is producing the strongest signal and, therefore, which sector antenna ia to be connected to receiver 2.
The process may be understood by again considering the example illustrated in Figure 2 where the mobile is located at M which is closer to sector RA than to sector LA. Tha siynal in sector RA, accordingly, will be stronger than the ~ignal sensed by antenna 6 in sector LA. If the location of the mobile unit were known in advance, the operation of the antenna switch ASW to select RA for connection to receiver 2 would be a foregone conclusion and easily implemented. Although such information i9 not available in advance, the invantion take~ advantage of two facts; namely, (a) that tha location o the mobile unit within a ceLl change~ relatively slowly compared to the rathQr rapid fluctuations of multipath fadiny, and ~b) improvement~ in the recovered audio due to effective diversity ia a ~tati3tical proce~ which obtains .
:'~
11 2~
., improved quality of communications by reducing the averaqe noi3e level in the recovered audio. As to the fir~t noted fact, although mult~path fading mu~t be overcome by the rapid switching provided by a diversity sy~tem, since the averaqe signal level change~ 810wly, it is possible to determine the average ~i~nal level by making less frequent measurements than is required for maintaining diversity.
We have discovered that effective diverslty can be maintained for a larqe portion of the tim~, for e~ample 90% of the time, and that the resulting improvement in guality is substantially aqual to that obtained where diversity is maintained ~00% of th~ time. We have further discovered that average adjacent sector signal levels may be obtained by taking periodic short samples of the RSSI in the adjacent sectors and that such samples provide a measure which indicate~ which adjacent sector has the stronge~t signal and, therefore, the position which should be assumed by switch ASW. Under such circum~tances receiver 2 can be connected to the antenna of the adjacent sector with the strongest ~lgnal as well a~ the analog comparator and thereafter provide efective diversity between sector S and the ~trongest adjacent ~ector. As aformentioned, said diversity period~ are relatively long, ~uch as 90% of the period. During the ~hort periodic samplas when the relativs signal strengths of the adjacent sectors i~ measured, logic element 9 by way o OR ~tructure 11 forces switch SWl to connect the receiv~r 1 audio to proce~sor 5.
Accordlngly, during all portions of the period an - , .
audio signal is applied to the proce~or 5, albeit, without diversity during the short sampling or measuring periods. However, the wor~t that can happen during the short measuring period would be a deep fade in the ~ignal from the antenna in the S
sector, which, o course, could happen during the measurement process. Statistically, however, such deep fade~ occur much le~s than 50% of the time during multipath ading. As such the average signal strength~ may be maintained at a high signal level, and consequently, the ~uality of communications is improved through the use of a relatively simple and inexpensive circuit design which is well suited for inclu~ion in a competitive commercial product.
The proces~ of the exemplary embodiment of Figure 5 may be more fully under~tood from a consideration of the timing diagram~ illustrated in Figure~ 6A to ~D. Figure 6A illustrates that diversity i~ effective, i . e., SWl continually select~ the stronge~t of the two r~ceiv~r audio output signal~, except when me~surements are made during the relatively short sampling periods. Al illustrated in Figure 6B, during the relatively lonc3 diversi ty periods the swi tch SW1 may connect either of the receivers to the audio proce~or 5 but during the relatlvely short mea~uring perlods only receiver 1 i~ connected to element 5. Figure 6C indicate~
which antenna (6 or 8) 1~ connected to the ~econd receiver by way o~ ~witch ASW at any particular time. The particular antenna connected, o~ cour~a, wl,ll depend upon the mea~ured 3ignal strength from the antennas which are ~ampled in the timed manner illu~trated ln Figure 6D.
, ~1~)4~
Considering the timing cycles of Fi~ure~ 6A to 6~ together at time T0 when diversity is active between ~ectors S and LA, sector RA and it~ antenna are inactive in the sense of not being connected to receiver 2. At time Tl, although diversity is ~til~
active, the R5SI of the active sector LA i~ sampled and mea~ured at the converter 10, and logic 9 then control SWl to select the audio from receiver l for transmis3ion to processor 5. Simultaneously, the logic element 9 operate~ switch ASW to connect receiver 2 to the "inactive" RA sector and at time T2 the RSSI of ~ector RA is sampled and measured.
The time diference between Tl and T2 i~ critical only to the extent of allowing sufficient time for the signal ~trength of receiver 2 to settle to it~
new value after the operation of the antenna switch ASW. A comparison is then made by logic element 9 to determine whether the signal strength of sector LA or RA is strongest, and the po~itioniny of switch A5W is made in accordance with the determination.
Thereafter, logic 9 allows switch SWl to again operate in a diversity mode.
As illustrated in Figure 6C, the right adjacent sector at time T2 would be determined to be larger than the left adjacent sector LA such that when diver~ity i~ reactivated, the activ~ sector is changed ~rom adjacent sector LA to adjacent RA.
Addltionally, in the period between T2 and T3, diver~ity i~ active between sector S and ~ector RA
w~th LA "inactive'l. Moreover, aq clearly i~lu~trated in Eigure 6A, at the end of time T3 a new measurement cycle begin~ but with sector RA
msasured durlng the active diversity period and 14 ~1~4~
~ector LA measured when SWl is orced to connect receiver 1 to processor 5.
Accordingly, the exemplary embodiment of Figure 5 provides a circuit de~ign that not only provide~
high guality communications but provide3 such results with a design well suited to a competitive commercial product. Moreover, the problems of the prior art are avoided by dynamically adapting to changing signal conditions whereby efective diver~ity is obtained to combat the effects of multipath fading as well as changing signal conditions due to movement of the mobile unit. The latter condition i~ measured for the purpo~e of using the strongest sector signal as well a~
determining when cell-to-cell transfer or handoff should occur.
Fisure 7 illustrates variation~ of the exemplary embodiment of Figure 5. For example~ the RSSI of sector S and receiver 1 may be measured and stored in logic 9, and the RSSI of additional sector~ may also be measured during the periodic short ~amples of adjacent and other ~ectors, said other sectors being represented by sactor B and antenna 12. The measuring of additional ~uch ~ignal strength sample~ may be used for storing averaga or rolling value3 or for comparison purposes with the RSSI of ~ector S along with other RSSI's for determining, among other thiny~, the need or call-to-cell tran~fer or handing of. Additionally, the inclusion of other ~ector~ in the diver~ity may t~lca into consideration the RS~I of the sector diametrically oppo~i.te from the S ~ector in order to handle the case where the mobile unit is pa~ing . . , ,. . .. .
: , :: , :
15 ~ 6~
substantially directly under the antenna tower through ~he center of the cell.
Still other variations will o~cur to tho~e skilled in the art. For example, logic unit 9 may be advantageously designed to choose or ba3e its decision~ on more than one sample of RSSI from a particular sector. Such decision~ may be ba3ed upon maintaining average readings o RSSI from each ~ector and updating the average6 at each measurement cycle. The choice of which receiver to use when based upon such average signals is indicative of the po~ition of the mobile unit and such averages ~ould vary slowly.
Additionally, the artisan will recognize that the sequence in which the switches are operated and the measurements taken may be varied within the teachings of our disclosure. In Figur~s 6A to 6D, for example, the time during which diversity is active can be maximized by makinq the order in which the adjacent sector~ are measured dependent upon which ~ector i currently active. Such an operation, however, is ~ot necessary and the logic may be 3implified by making the order fixed and extending the diversity inactive period to cover measurements of both adjacent sector~. Still further, the artisan will recogni~e that contemporary circult element~ may be used to implement the exemplary embodiment~ illustrated and descr.ibed. For example, the ~witches ~uch a~ SWl could be implemented with commercially availabla ~lid ~tate device~ such as CMOS tran~mi~ion gate~. Additionally, the antenna switch ASW could also be a ~olld ~tate device such a~ a pin diode RF
switch. Still further, the logic element 9 could be ea~lly implemented by way of programming conventional microproce~sor~.
While the invention has been de~cribed in connection with what i~ presently considered to be the mo8t practical and preferred embodiment, it is to be understood that the invention 1~ not to be limited to khe disclosed embodiment, but on the contrary, i~ intended to cover variou9 modifications and eguivalent arxangements included within the 8pirit and scope of the appended claim~.
:
Claims (20)
1. An apparatus for obtaining adaptive diversity in a multipath communication system, said apparatus comprising:
a plurality of directional signal detecting elements, each said element operable to detect signals propagating substantially from a single sector in a multisectored pattern;
at least two receivers, each receiver connected to at least one signal detecting element and producing an output signal indicative of the received signal strength;
logic means connected to said receivers and operable in a first mode for continuously determining which receiver output signal is indicative of the strongest received signal and connecting said strongest received signal for use in said communication system;
said logic means operable in a second periodic mode to connect a particular one of said receivers for inputting its received signal to said communication system regardless of whether it is receiving said strongest signal.
a plurality of directional signal detecting elements, each said element operable to detect signals propagating substantially from a single sector in a multisectored pattern;
at least two receivers, each receiver connected to at least one signal detecting element and producing an output signal indicative of the received signal strength;
logic means connected to said receivers and operable in a first mode for continuously determining which receiver output signal is indicative of the strongest received signal and connecting said strongest received signal for use in said communication system;
said logic means operable in a second periodic mode to connect a particular one of said receivers for inputting its received signal to said communication system regardless of whether it is receiving said strongest signal.
2. An apparatus as specified in claim 1 wherein said particular one of said receivers is connected to a single detecting element and another of said receivers is connected to at least two detecting elements.
3. An apparatus as specified in claim 2 wherein said logic means includes further means operable in said second mode for measuring the signals of a plurality of said detecting elements and for connecting the strongest of said signals to said another of said receivers.
4. An apparatus as specified in claims 1 or 2 wherein said logic means includes a comparator for continuously determining in said first mode which receiver output signal is indicative of the strongest received signal.
5. An apparatus as specified in claim 2 wherein said detecting elements are directional antenna means and said at least two detecting elements detect signals propagating from sectors adjacent the sector in which said single detecting element is operable.
6. An apparatus as specified in claim 5 wherein said communication system is a cellular mobile telephone system which includes a signal processor and the signals connected thereto from the receiver are audio signals.
7. An apparatus as in claim 6 where the logic means include analog to digital converter means and said logic means measures the received signal strength of said particular one of said receivers when in said first mode.
8. An apparatus as specified in claim 7 wherein the values of received signal strength measured by said logic means when in said first and second modes is used to determine when it is necessary to transfer communications to another cell.
9. An apparatus as specified in claim 8 wherein the first and second modes of operation occur for predetermined time periods and the time period for said first mode is substantially longer than that of said second mode.
10. An adaptive diversity apparatus for use with a signal processing element of a cellular telephone system, said apparatus comprising:
a plurality of directional antennas, each antenna operable to detect signals propagating primarily from a single sector of a multisectored cell;
a plurality of groups of receivers, each group including at least two receivers each of which receives signals from at least one of said antennas;
signal comparator means connected to each of said groups to determine which of said at least two receivers is producing the strongest output signal;
a switch element in each said group operable in a first mode and responsive to said comparator for connecting the receiver with the strongest output signal to said signal processing element;
logical processing means for periodically causing said switch element to operate in a second mode to connect a particular one of said receiver output signals of a group to said signal processing element for a predetermined time period whether or not the output signal of said particular one receiver is the strongest of said output signals.
a plurality of directional antennas, each antenna operable to detect signals propagating primarily from a single sector of a multisectored cell;
a plurality of groups of receivers, each group including at least two receivers each of which receives signals from at least one of said antennas;
signal comparator means connected to each of said groups to determine which of said at least two receivers is producing the strongest output signal;
a switch element in each said group operable in a first mode and responsive to said comparator for connecting the receiver with the strongest output signal to said signal processing element;
logical processing means for periodically causing said switch element to operate in a second mode to connect a particular one of said receiver output signals of a group to said signal processing element for a predetermined time period whether or not the output signal of said particular one receiver is the strongest of said output signals.
11. An apparatus as specified in claim 10 wherein during the periodic connection of said particular one receiver to the signal processing element said logical processing means measures the received signal strength for each antenna connected to another receiver of each group and then connects the antenna having the largest signal strength to said another receiver for the subsequent first mode operation.
12. An apparatus as specified in claim 11 wherein the first mode occurs for a predetermined period of time and the time period for said second mode is substantially shorter than that of said first mode.
13. The apparatus as specified in claim 11 wherein the antenna connected to said one particular receiver of a group is for a particular sector and the antennas connected to said another receiver are adjacent sectors.
14. The apparatus of claim 11 wherein the logical processing means measures the received signal strength of said particular one of said receivers when in the first mode.
15. An apparatus as specified in claim 14 wherein the values of received signal strength measured by said logical processing means when in said first and second modes are used to determine when it is necessary to transfer communications to another cell.
16. A method of obtaining adaptive diversity in a multipath communications system, said method comprising:
arranging plural signal detectors to detect signals propagating from a multisectored pattern where each detector is operable to detect signals coming primarily from a single sector;
connecting first signal receivers to ones of said detectors;
connecting second signal receivers to receive signals from a plurality of other ones of said detectors;
comparing in a first mode of operation the received signal strengths of said first receivers with the received signal strengths of said second receivers and transmitting to the communications system the signals from the receivers having the strongest received signal strengths;
comparing in a second periodic mode of operation the received signal strengths from each of said other ones of said detectors whereby the detectors providing the strongest signals are connected to said second receivers; and transmitting the signals from said first receivers to said communication system when in said second mode irrespective of the signals strengths of said receivers.
arranging plural signal detectors to detect signals propagating from a multisectored pattern where each detector is operable to detect signals coming primarily from a single sector;
connecting first signal receivers to ones of said detectors;
connecting second signal receivers to receive signals from a plurality of other ones of said detectors;
comparing in a first mode of operation the received signal strengths of said first receivers with the received signal strengths of said second receivers and transmitting to the communications system the signals from the receivers having the strongest received signal strengths;
comparing in a second periodic mode of operation the received signal strengths from each of said other ones of said detectors whereby the detectors providing the strongest signals are connected to said second receivers; and transmitting the signals from said first receivers to said communication system when in said second mode irrespective of the signals strengths of said receivers.
17. The method as specified in claim 16 wherein said other ones of said detectors are arranged to detect signals from sectors adjacent to the sectors containing said ones of said detectors.
18. The method of claim 16 further comprising the steps of:
measuring the received signal strengths of said first detectors in said first mode;
measuring the received signal strengths of said other ones of said detectors in said second mode; and utilizing said measured signal strengths to determine when it is necessary to transfer communications to another multisectored pattern.
measuring the received signal strengths of said first detectors in said first mode;
measuring the received signal strengths of said other ones of said detectors in said second mode; and utilizing said measured signal strengths to determine when it is necessary to transfer communications to another multisectored pattern.
19. The method as specified in claim 16 further comprising the step of:
controlling the first and second modes to periodically occur for first and second periods of time, respectively, and wherein said second period of time is substantially shorter than said first period of time.
controlling the first and second modes to periodically occur for first and second periods of time, respectively, and wherein said second period of time is substantially shorter than said first period of time.
20. The method of claim 16 wherein the communication system is a cellular mobile telephone system and said detectors are directional antennas for producing audio signals at the outputs of said receivers.
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US511,348 | 1990-04-19 | ||
US07/511,348 US5119501A (en) | 1990-04-19 | 1990-04-19 | Adaptive diversity equipment arrangement for cellular mobile telephone systems |
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CA2040061A1 true CA2040061A1 (en) | 1991-10-20 |
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CA002034401A Expired - Fee Related CA2034401C (en) | 1990-04-19 | 1991-01-17 | Adaptive diversity equipment arrangement for cellular mobile telephone systems |
CA002040061A Abandoned CA2040061A1 (en) | 1990-04-19 | 1991-04-08 | Adaptive diversity equipment arrangement for cellular mobile telephone systems |
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CA002034401A Expired - Fee Related CA2034401C (en) | 1990-04-19 | 1991-01-17 | Adaptive diversity equipment arrangement for cellular mobile telephone systems |
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JP (1) | JP2708137B2 (en) |
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JP2552928B2 (en) * | 1990-01-31 | 1996-11-13 | 三菱電機株式会社 | Antenna selection diversity receiver |
FI91344C (en) * | 1991-03-05 | 1994-06-10 | Nokia Telecommunications Oy | Cellular radio network, base station and method for regionally adjusting traffic capacity in a cellular radio network |
JP2949533B2 (en) * | 1991-09-03 | 1999-09-13 | 日本電信電話株式会社 | Mobile communication wireless zone configuration method |
GB2271246B (en) * | 1992-10-03 | 1997-02-12 | Motorola Ltd | Sectorized cellular radio base station antenna |
GB2281479B (en) * | 1993-08-27 | 1997-09-03 | Nokia Telecommunications Oy | Radio receiving apparatus |
FI934052A (en) * | 1993-09-15 | 1995-03-16 | Nokia Telecommunications Oy | Procedure furthermore monitors the function of a radio receiver unit as well as a radio receiver unit |
JP3989532B2 (en) * | 1993-09-30 | 2007-10-10 | スカイワークス ソリューションズ,インコーポレイテッド | Multi-antenna home base for digital cordless telephones |
US5481571A (en) * | 1993-11-12 | 1996-01-02 | Pacific Communication Sciences, Inc. | Method and apparatus for switching between radio frequency circuits |
US5740526A (en) * | 1994-06-01 | 1998-04-14 | Bonta; Jeffrey D. | Method and apparatus for selecting two antennas from which to receive a communication signal |
US5640695A (en) * | 1994-06-14 | 1997-06-17 | Electrocom Communication Systems L.P. | Multibranched selectively combined diversity controller |
US5737689A (en) * | 1994-06-14 | 1998-04-07 | Telefonaktiebolaget Lm Ericsson | Method for preventing calls of bad quality from being disconnected in a cellular mobile radio system |
US5586170A (en) * | 1994-08-19 | 1996-12-17 | Georgia Tech Research Corporation | Cellular devices, systems and methods using intercell macro-diversity and dynamic channel allocation |
US5649306A (en) * | 1994-09-16 | 1997-07-15 | Motorola, Inc. | Portable radio housing incorporating diversity antenna structure |
GB2294609B (en) * | 1994-10-26 | 1999-01-27 | Northern Telecom Ltd | A base station arrangement |
FI956060A (en) * | 1995-12-15 | 1997-06-16 | Nokia Telecommunications Oy | Sectored base station |
FI107485B (en) * | 1996-04-17 | 2001-08-15 | Nokia Mobile Phones Ltd | Diversity method, radio receiver and radio system |
JP3076252B2 (en) * | 1996-11-25 | 2000-08-14 | 日本電気株式会社 | Multi-sector switching control device in cellular mobile communication system |
US5991282A (en) * | 1997-05-28 | 1999-11-23 | Telefonaktiebolaget Lm Ericsson | Radio communication system with diversity reception on a time-slot by time-slot basis |
SE9702370L (en) | 1997-06-19 | 1998-12-20 | Ericsson Telefon Ab L M | Balanced diversity |
US5991643A (en) * | 1997-11-28 | 1999-11-23 | Acer Peripherals, Inc. | Radio transceiver having switchable antennas |
DE19825536B4 (en) * | 1998-06-08 | 2005-05-19 | IQ wireless GmbH, Entwicklungsgesellschaft für Systeme und Technologien der Telekommunikation | Method and apparatus for a full-duplex radio transmission system with CDMA access |
DE19906867C1 (en) * | 1999-02-18 | 2000-07-06 | Weidmueller Interface | Serial data communications method involves each slave filtering data frames provided for it from bus forward line and passing them directly to bus return line after processing |
US7024168B1 (en) | 1999-07-07 | 2006-04-04 | Telefonaktiebolaget L M Ericsson (Publ) | Controlled antenna diversity |
US7123876B2 (en) * | 2001-11-01 | 2006-10-17 | Motia | Easy set-up, vehicle mounted, in-motion tracking, satellite antenna |
US6862434B2 (en) * | 2002-07-26 | 2005-03-01 | Qualcomm Inc. | Transmission diversity systems |
DE10311836B4 (en) * | 2003-03-18 | 2006-10-05 | Integrated Electronic Systems !Sys Consulting Gmbh | Remote controlled industrial device |
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JPS60223336A (en) * | 1984-04-20 | 1985-11-07 | Matsushita Electric Ind Co Ltd | Angular diversity receiver |
JPS6163120A (en) * | 1984-09-05 | 1986-04-01 | Matsushita Electric Ind Co Ltd | Base station receiver |
US4823398A (en) * | 1985-12-23 | 1989-04-18 | Kazuya Hashimoto | Diversity receiver |
US4726050A (en) * | 1986-02-18 | 1988-02-16 | Motorola, Inc. | Scanning receiver allocation method and apparatus for cellular radiotelephone systems |
US4704734A (en) * | 1986-02-18 | 1987-11-03 | Motorola, Inc. | Method and apparatus for signal strength measurement and antenna selection in cellular radiotelephone systems |
US4694484A (en) * | 1986-02-18 | 1987-09-15 | Motorola, Inc. | Cellular radiotelephone land station |
US4797947A (en) * | 1987-05-01 | 1989-01-10 | Motorola, Inc. | Microcellular communications system using macrodiversity |
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1990
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1991
- 1991-01-17 CA CA002034401A patent/CA2034401C/en not_active Expired - Fee Related
- 1991-04-08 CA CA002040061A patent/CA2040061A1/en not_active Abandoned
- 1991-04-19 DK DK91303508.5T patent/DK0454368T3/en active
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- 1991-04-19 JP JP3088408A patent/JP2708137B2/en not_active Expired - Lifetime
- 1991-04-19 ES ES91303508T patent/ES2100932T3/en not_active Expired - Lifetime
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ES2100932T3 (en) | 1997-07-01 |
DE69126235D1 (en) | 1997-07-03 |
EP0454368B1 (en) | 1997-05-28 |
EP0454368A2 (en) | 1991-10-30 |
CA2034401A1 (en) | 1991-10-20 |
DE69126235T2 (en) | 1998-01-08 |
HK1007847A1 (en) | 1999-04-23 |
JP2708137B2 (en) | 1998-02-04 |
DK0454368T3 (en) | 1997-06-30 |
CA2034401C (en) | 1999-11-16 |
EP0454368A3 (en) | 1992-12-02 |
JPH066276A (en) | 1994-01-14 |
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