EP0500654A1 - Microcellule divisee en zones a balayage de secteurs pour systemes telephoniques cellulaires - Google Patents

Microcellule divisee en zones a balayage de secteurs pour systemes telephoniques cellulaires

Info

Publication number
EP0500654A1
EP0500654A1 EP90916653A EP90916653A EP0500654A1 EP 0500654 A1 EP0500654 A1 EP 0500654A1 EP 90916653 A EP90916653 A EP 90916653A EP 90916653 A EP90916653 A EP 90916653A EP 0500654 A1 EP0500654 A1 EP 0500654A1
Authority
EP
European Patent Office
Prior art keywords
cell
antenna
frequency
sub
transmission
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.)
Withdrawn
Application number
EP90916653A
Other languages
German (de)
English (en)
Other versions
EP0500654A4 (en
Inventor
William Chien-Yeh Lee
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Pactel Corp
Original Assignee
Pactel Corp
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Pactel Corp filed Critical Pactel Corp
Publication of EP0500654A1 publication Critical patent/EP0500654A1/fr
Publication of EP0500654A4 publication Critical patent/EP0500654A4/en
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W16/00—Network planning, e.g. coverage or traffic planning tools; Network deployment, e.g. resource partitioning or cells structures
    • H04W16/24—Cell structures
    • H04W16/26—Cell enhancers or enhancement, e.g. for tunnels, building shadow
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q21/00—Antenna arrays or systems
    • H01Q21/06—Arrays of individually energised antenna units similarly polarised and spaced apart
    • H01Q21/22—Antenna units of the array energised non-uniformly in amplitude or phase, e.g. tapered array or binomial array
    • 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
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W16/00—Network planning, e.g. coverage or traffic planning tools; Network deployment, e.g. resource partitioning or cells structures
    • H04W16/24—Cell structures
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W16/00—Network planning, e.g. coverage or traffic planning tools; Network deployment, e.g. resource partitioning or cells structures
    • H04W16/24—Cell structures
    • H04W16/28—Cell structures using beam steering
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/16—Performing reselection for specific purposes
    • H04W36/18—Performing reselection for specific purposes for allowing seamless reselection, e.g. soft reselection
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W88/00—Devices specially adapted for wireless communication networks, e.g. terminals, base stations or access point devices
    • H04W88/08—Access point devices
    • H04W88/085—Access point devices with remote components

Definitions

  • the user places the called number into an originating register in the mobile unit, checks to see that the number is correct, and pushes a "send" button.
  • a request for service is sent on a selected set-up channel obtained from a self-location scheme as described above.
  • the cell site receives it, and in directional cell sites, selects the best directive antenna for the voice channel to use.
  • the cell site sends a request to the MTSO via a high-speed data link.
  • the MTSO selects an appropriate voice channel for the call, and the cell site acts on it through the best directive antenna to link the mobile unit.
  • the MTSO also connects the wire-line party through the telephone company zone office.
  • a call two parties are on a voice channel.
  • the present cell site requests a handoff via an appropriate signal, for example, a 100 ms burst on the voice channel.
  • the system switches the call to a new frequency channel in a new cell site without either interrupting the call or alerting the user.
  • the call continues as long as the user is talking. The user does not notice the handoff occurrences.
  • a zoned icrocell system with sector scanning providing a more uniform signal coverage contour, lowered interference levels, and relatively simple and economical contruction is presented.
  • the system includes a plurality of antenna sets, each set being suitably postioned within the periphery of a cell and having transmitting and receiving means directionally configured to limit propagation and reception of signals substantially to a zone with the boundaries of the cell.
  • the strength of the signal received by each of the antenna sets at each frequency in the assigned set of transmission frequencies for the cell is monitored. Transmission, for each frequency in the assigned set of transmission frequencies for the cell, is confined to a selected antenna set in the cell receiving the strongest signal at each such frequency. This confines transmission at each frequency to the zone associated with the selected antenna set.
  • FIG. 1 is a schematic diagram of an embodiment of a microcell configuration according to the system of the present invention.
  • Figure 2 is a schematic block diagram of the electronics of an embodiment of the present invention.
  • Figure 4 is a block diagram of the electronics associated with one of the slave sub-sites in an embodiment of the present invention.
  • Figure 5 is a schematic diagram of a signal processing section at a slave site.
  • Figure 1 is a schematic illustration of a cell 1 constructed in accordance with the present invention.
  • the outer boundary of cell 1 is delineated by a- circle 11 in solid line.
  • cells are often represented as hexagons in cell design schemes. In reality, however, due to the terrain and the presence of buildings and other structures, the actual boundary of cell 1 may have an irregular shape.
  • solid line circle 11 is intended to represent the locus at which a mobile telephone unit passes from the influence of the illustrated cell into the influence of an adjacent cell.
  • Each antenna set includes a transmitting antenna 13a, 15a, and 17a, respectively.
  • Each antenna set also includes two receiving antennas 13b and 13c, 15b and 15c, and 17b and 17c, respectively. Duplication of the receiving antennas at each sub-site is for diversity use to reduce signal fading by combining the signals.
  • antenna set 13 includes a control-channel transmitting antenna 13d for transmitting control signals, and duplicate control- channel receiving antennas 13e and 13f for receiving control signals, as will be explained below.
  • Antenna sub-site 14 is called a master sub-site, whereas antenna sub-sites 10, 16, and 18 are called slave sub-sites.
  • antenna set 13 is located at master sub-site 14, but it is understood that antenna set 13 may be located elsewhere within cell 1 as desired, depending upon the particular environment.
  • the determination of the locations of sub- sites and the number of sub-sites in a cell can be based on Lee's coverage prediction model published in IEEE Transactions on Vehicular Technology, February, 1988. Each antenna set has its own zone of major influence for transmitting and receiving signals.
  • antenna set 13 at slave sub-site 10, co-located with master sub-site 14, has a zone indicated by a dotted line 13z.
  • antenna set 15 at slave sub-site 16 has a zone of influence designated by a dotted line 15z
  • antenna set 17 at slave sub-site 18 has a zone of influence designated by a dotted line 17z. It may be seen from Figure 1 that the zones overlap in certain areas.
  • Directionality is provided to the antenna sets so that the zones of influence (i.e., the zones of propagation and reception of signals) are limited to be substantially within the boundaries of cell 1.
  • suitable means such as shown as a symbolic means 19 arranged at each antenna set or sub-site.
  • Directionality means 19 can be a reflector for each individual antenna, or any other suitable arrangement to provide the desired directionality and coverage.
  • the set of control-channel antennas 13d, 13e, and 13f is configured to have a greater zone of influence, this being indicated by a dash-dot line 21, substantially coextensive with the limits of cell 1 delineated by circle 11.
  • FIG. 2 is a schematic block diagram of the electronics of an embodiment of the present invention.
  • the three slave sub-sites 10, 16, and 18 are each coupled to master sub-site 14 and are controlled therefrom.
  • slave sub-site 10 is connected to master sub-site 14 via three cables 43, 51, and 59.
  • Slave sub-site 16 is connected to master sub-site 14 via three cables 23, 25, and 27.
  • the converters can up-convert or down-convert in frequency depending on the type of communication utilized between the slave sub-sites and the master sub- sites.
  • the illustrated embodiment depicts the communication between the slave sub-sites and the master sub-site as being via cable. It will be apparent to those skilled in the art that such cables may include, for example, Tl carrier cables, optical fibers, or the like.
  • the cables may also be replaced by microwave channels.
  • the converter-converter operation between the slave sub-site and the master sub- site can be done by (1) converting 800 MHz up to microwave and then converting down to 800 MHz, (2) converting 800 MHz to optical wave and then converting down to 800 MHz, and (3) converting 800 MHz down to 14 MHz baseband and then converting up to 800 MHz.
  • the slave sub-sites each contain a signal processing ensemble of components as shown at 35 for slave sub-site 10. It is understood that substantially identical signal processing ensembles are contained in slave sub-sites 16 and 18, although such ensembles are not shown in Figure 2 for simplicity.
  • Signal processing ensemble 35 includes a filter 37, an amplifier 39, and a converter 41 interposed between antenna 13a and cable output 43. .
  • filter 45, amplifier 47, and converter 49 are interposed between antenna 13b and output cable 51
  • filter 53, amplifier 55, and converter 57 are interposed between antenna 13c and output cable 59.
  • the filters, amplifiers, and converters filter, enhance, and convert signals as desired and may be of any type suitable for the stated purpose.
  • Scanning receiver 63 at master sub-site 14 scans all of the sub-sites 10, 16, and 18, and all of the frequency channels allocated in the particular set assigned to that cell. It then chooses the strongest signal levels among all sub-sites for each frequency channel.
  • a zone exchanger or zone switch 61 links the transmit signal for a respective frequency to the desired sub-site and terminates the old sub-site transmitter. The received signal is also switched to the same new sub-site.
  • the control- channel signal antennas cover the entire cell and are used for setting up calls in the conventional manner known to those skilled in the art. Further elaboration on such procedure, as well as on cellular telephone systems in general, may be found in the book Mobile Cellular Telecommunications Systems, by William C.Y.
  • Scanning receiver 63 provides an output control signal via a suitable connector 71 to the zone switch 61.
  • Zone switch 61 may be of any suitable construction to provide switching between the respective sub-sites,, which switching depends upon the strength of the signal being received at a sub-site as determined by scanning receiver 63.
  • Master sub-site 14 further includes carrier frequency modules 73, 75, and 77. Module 73 is assigned to the transmitters and modules 75 and 77 are assigned to the receivers. Each module provides for the assigned set of carrier frequencies for the particular cell. For example, a portion of the 395 voice channels and one of the 21 control channels may be assigned to an individual cell.
  • Controller 79 also provides signals to transmitter module 73. Controller 79 also determines which of the cables is connected to provide the received voice signals to the MTSO. Controller 79 is connected via suitable connections to and from the MTSO. In addition, controller 79 is connected to a transceiver 81 which transmits and receives signals on the three control antennas 13d, 13e, and 13f.
  • Controller 79 measures the signal strength of a channel requested by the MTSO. If the initial call is in this particular cell, or if the call is handed off to this particular cell through controller 79, the controller initiates transmission at a particular frequency assigned by the MTSO to that call. The frequency assigned is the one which has the lowest noise level as determined by the controller. If, during the call, the signal strength received from all the antenna sets is below a preselected level, the controller initiates a handoff procedure from the MTSO.
  • a mobile unit operating on an assigned frequency f ⁇ - in the cell will typically be moving within the cell. All sub-sites within the cell will receive signal levels, but not necessarily the voice signals from the mobile unit. Only the sub-site at which the received signal level is the strongest will transmit and receive signals to the mobile unit and set up a call. When the mobile unit moves so that another sub-site receives the strongest signal, the system turns off the transmitter at the weaker sub-site and turns on the transmitter at the sub-site where the strongest signal is being received. The two-diversity receiver antennas are also switched to the proper sub-site to receive the call. The frequency, however, does not change and remains at f 1 . Thus no handoff has occurred in the traditional sense and the MTSO is not involved.
  • the cell design of the present invention includes a significant improvement in uniformity of coverage as opposed to cells in which only a single antenna site in each cell is employed. This becomes particularly advantageous in connection with a small cell, i.e., a cell having a radius of less than one mile. Since, by reducing the effective radiation area covered by each sub-site, the effective radiation radius for each frequency is reduced, a consequent lowering of the interference level also results. All of this accomplished without the necessity of handoffs within the cell itself.
  • the frequency at which transmission occurs does not change in a cell, although the active sub-site in a cell switches from one to another according to signal level. This is accomplished in a relatively simple and economical way, and enables the size of a cell to be reduced to as low as 500 to 1000 feet in radius.
  • Figure 3 shows schematically a further embodiment of the present invention wherein a cell, as in the case illustrated by Figure 1, includes three separate antenna sets designated as 113, 115, and 117.
  • the outer boundary of the cell is defined by a circle 111 (solid line) .
  • the cell in reality, may be irregular in shape.
  • the solid line 111 represents the boundary at which a mobile telephone unit passes from the influence of the illustrated cell to the influence of an adjacent cell.
  • antenna set 113 is located at a master sub-site 114, whereas the antenna sets 115 and 117 are located at sub-sites 116 and 118, respectively.
  • Master sub-site 114 can be co-located with any one of the slave sub-sites as desired. It is also understood that other numbers of antenna sets may be usefully employed and that the three sets shown in Figure 3 are illustrative only.
  • antenna sets 113, 115, and 117 each include a plurality of sub-sets of antennas which, in the illustrated embodiment, constitute three sub-sets at each sub-site.
  • Each antenna sub-set includes a transmitting antenna designated respectively as 113a, 113a', 113a", 115a, 115a', 115a", 117a, 117a', and 117a", respectively.
  • Each antenna set also includes two receiving antennas, designated as 113b, 113b', 113b", 113c, 113c', 113c", 115b, 115b', 115b", 115c, 115c', 115c", 117b, 117b', 117b", and 117c, 117c', 117c", respectively.
  • Duplication of the receiving antennas at each sub-set is for diversity use to reduce signal fading by combining the signals.
  • the determination of the locations of sub-sites, the number of sub-sites in a cell, and the number of antenna sub ⁇ sets at each sub-site can be based on the Lee coverage prediction model published in IEEE Transactions on Vehicular Technology, February, 1988.
  • Cell 111 also includes an antenna set (not shown) for transmitting and receiving control signals as explained above in connection with antenna set 13 of Figure 1 for transmitting and receiving signals to a suitable controller (not shown) .
  • a suitable controller not shown
  • control-channel antennas are configured to have a zone of influence substantially coextensive with the limits of cell 111 as indicated by the dash-dot line 121.
  • each antenna set has its own zone of major influence for transmitting and receiving signals. Unlike the embodiment of Figure 1, however, each antenna set in the embodiment of Figure 3 has its zone of major influence sub-divided into a plurality of substantially separate sectors.
  • the zone of influence related to sub- site 114 is comprised of three sectors 113x, 113y, and 113z.
  • Sector 113x is serviced by the antenna sub-set 113a, 113b, and 113c.
  • Sector 113y is serviced by the antenna sub-set 113a", 113b", and 113c".
  • Sector 113z is serviced by the antenna sub-set 113a', 113b', and -
  • the antenna sub-sites are positioned displaced inwardly from the periphery of cell 111 and that the sectors overlap in certain areas.
  • Directionality is provided to the antenna sub-set so that the sectors associated with the sub-sets, i.e., the zones of propagation and reception of signals, are limited to be substantially within the boundaries of the zone serviced by that particular sub- site.
  • the sectors are also limited to be substantially within the boundaries of cell 111.
  • Directionality is provided by suitable means such as shown by a symbolic means 119 arranged at each antenna set or sub-site. As illustrated in Figure 3, directionality means 119 constitutes reflectors at each sub-site which divide the respective sectors at approximately 120° segments.
  • any other suitable arrangement to provide a desired directionality and coverage including omni-directional antennas, may be employed within the spirit and scope of the invention.
  • the strength of the signal transmitted at each antenna sub-site may also be appropriately adjusted to provide the desired sector coverage.
  • Figure 4 is a block diagram of the electronics associated with one of the slave sub-sites 117 of Figure 3. It is to be understood that slave sub-site 118 illustrated in Figure 4 is connected in the system of the invention substantially as shown in Figure 2 in connection with slave sub-site 18. To clarify this, leads 29, 31, and 33 have been designated in Figure 4. Generally, cable 29 carries transmitter antenna signals whereas cables 31 and 33 carry receiver antenna signals. It is to be understood that, in the case of a master sub-site, in addition to the elements illustrated in Figure 4, elements as illustrated and described in connection with Figure 2 would also be incorporated. The three sub-sets of the antenna set are designated with the identical nomenclature of Figure 3.
  • Each of the antenna sub-sets is connected to a respective one of a plurality of sector sub-sites 134, 135, and 136.
  • Each of the sector sub-sites contains a signal processing section substantially similar to the signal processing section 35 illustrated in Figure 2 but "without the converters. This is shown in Figure 5 for exemplary slave sub-site 136.
  • Filter 181 and amplifier 191 are coupled between antenna 117a" and cable connection 143
  • filter 182 and amplifier 192 are coupled between antenna 117b'' and cable connection 151
  • filter 183 and amplifier 193 are coupled between antenna 117c" and cable connection 159.
  • suitable cable connections 123, 125, 127, 129, 131, 133, 143, 151, and 159 provide connection between the various sector sub-sites and a three 3-port sector switch 161.
  • connection is made for receiver signals via cables 125, 131, and 151, to a scanning receiver 163 via connections 165, 167, and 169, respectively.
  • Scanning receiver 163 provides an output * control signal, via a suitable connector 171, to the sector switch 161.
  • the sector switch 161 may be of any suitable construction to provide switching between the respective sector sub-sites 134, 135, and 136, which switching depends upon the strength of the signal being received at a respective sector sub-site as determined by scanning receiver 163.
  • the present invention thus provides two levels of discrimination for the strength of the signals at each of the frequencies within the assigned set for the cell.
  • Signal strength discrimination occurs at each antenna sub-site and determines which sub-set of antennas at that sub-site will be operational.
  • only that sector within the cell at which the strongest signal is being received will transmit and receive signals to the mobile unit and set up a call.
  • the system operates to turn off the transmitter associated with the weaker sector and turn on the transmitter associated with the sector at which the strongest signal level is being received.
  • the two diversity receiver antennas associated with that particular sector are also switched to receive the call.
  • the receivers at each sector need not be turned off.
  • the frequency does not change and remains the same throughout the cell for a given mobile unit.
  • no handoff occurs in the traditional sense and the MTSO is not involved.
  • No additional handoff load is added to the MTSO switching equipment as a result of the foregoing described sub-division of the cells.
  • the advantages accruing from the division of cells into sub-site zones and then subset sectors in accordance with the present invention include a significant improvement in the uniformity of coverage over systems utilizing only a single antenna site in each cell. This becomes particularly advantageous in connection with a small cell, i.e., a cell having a radius of less than one mile. Since, by reducing the effective radiation area covered by each sub-site over each zone and sector, the effective radiation radius for each frequency is reduced, a consequent lowering of the interference level also results. All of this is accomplished without the necessity of handoffs within the cell. The frequency at which transmission occurs does not change in a cell, although the active sub-site in a cell switches from one to another according to signal level.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

Un système (1) de microcellules divisé en zones, à balayage de secteurs, pour systèmes téléphoniques cellulaires, comporte une pluralité de cellules contiguës, ayant chacune un ensemble différent et assigné de canaux de fréquences de transmission, et une capacité de transfert permettant de maintenir une communication de cellule à cellule. Le système comprend au moins une cellule (11) dotée d'une pluralité d'ensembles d'antennes (13, 15, 17). Chaque ensemble est positionné au niveau d'un sous-site (10, 16, 18) respectif et est configuré de sorte que la propagation et la réception de signaux sont limitées à une zone (13z, 15z, 17z) de transmission se trouvant dans les limites de la cellule, et représentant moins en superficie que cette dernière. Un dispositif (79) de commande contrôle l'intensité du signal reçu par chaque ensemble d'antennes. La transmission, au niveau de chaque canal de fréquence, est confinée à l'ensemble d'antennes ayant le signal reçu le plus fort, limitant ainsi la propagation du signal à cette zone de transmission. Dans un mode de réalisation, le contrôle d'intensité du signal est prévu au niveau de chaque sous-site, ainsi la transmission est limitée à un sous-ensemble spécifique d'antennes au niveau du sous-site, et à un secteur (115x, 115y, 115z) limité dans la zone de transmission.
EP19900916653 1989-11-07 1990-10-18 Zoned microcell with sector scanning for cellular telephone systems Withdrawn EP0500654A4 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US43251189A 1989-11-07 1989-11-07
US432511 1989-11-07
CA002106017A CA2106017A1 (fr) 1989-11-07 1993-09-13 Systeme de radiotelephonie numerique a microcellules

Publications (2)

Publication Number Publication Date
EP0500654A1 true EP0500654A1 (fr) 1992-09-02
EP0500654A4 EP0500654A4 (en) 1993-08-04

Family

ID=25676635

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19900916653 Withdrawn EP0500654A4 (en) 1989-11-07 1990-10-18 Zoned microcell with sector scanning for cellular telephone systems

Country Status (4)

Country Link
EP (1) EP0500654A4 (fr)
JP (1) JPH05503616A (fr)
CA (1) CA2106017A1 (fr)
WO (1) WO1991007019A1 (fr)

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US5349631A (en) * 1991-11-21 1994-09-20 Airtouch Communications Inbuilding telephone communication system
US5487101A (en) * 1993-03-26 1996-01-23 Celcore, Inc. Off-load cellular system for off-loading cellular service from a main cellular system to increase cellular service capacity
US5521961A (en) * 1993-03-26 1996-05-28 Celcore, Inc. Mobility management method for delivering calls in a microcellular network
KR960027576A (ko) * 1994-12-01 1996-07-22 리차드 탤런 육상 이동 무선 베이스 사이트에 사용되는 무선 신호 스캐닝 및 타겟팅 시스템
US5701596A (en) * 1994-12-01 1997-12-23 Radio Frequency Systems, Inc. Modular interconnect matrix for matrix connection of a plurality of antennas with a plurality of radio channel units
US5684491A (en) * 1995-01-27 1997-11-04 Hazeltine Corporation High gain antenna systems for cellular use
CA2164169A1 (fr) * 1995-01-31 1996-08-01 Sheldon Kent Meredith Systeme de balayage et de selection de signaux radio pour sites de radio mobile terrestre
JP3111906B2 (ja) * 1996-07-17 2000-11-27 日本電気株式会社 無線基地局装置
JP3076252B2 (ja) * 1996-11-25 2000-08-14 日本電気株式会社 セルラー移動通信システムにおける多セクター切替制御装置
FR2764140B1 (fr) * 1997-05-28 1999-08-06 Armand Levy Procede de communication entre une station de base a n antennes et un mobile et station de base permettant de mettre en oeuvre ce procede
JP3111992B2 (ja) 1998-07-07 2000-11-27 日本電気株式会社 自動車通信方法及びシステム
JP4191050B2 (ja) 2002-01-18 2008-12-03 富士通株式会社 閉ループ送信ダイバーシチにおけるフィードバック制御方法及び装置

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DE2326163A1 (de) * 1973-05-23 1974-12-12 Tekade Felten & Guilleaume Verfahren zum feststellen der grenzueberschreitung sendender beweglicher funksprechstellen
US4144411A (en) * 1976-09-22 1979-03-13 Bell Telephone Laboratories, Incorporated Cellular radiotelephone system structured for flexible use of different cell sizes
US4759051A (en) * 1987-03-16 1988-07-19 A. A. Hopeman, III Communications system

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Title
See also references of WO9107019A1 *

Also Published As

Publication number Publication date
JPH05503616A (ja) 1993-06-10
WO1991007019A1 (fr) 1991-05-16
CA2106017A1 (fr) 1995-03-14
EP0500654A4 (en) 1993-08-04

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