United States Patent [191
`Ito
`[54] MOBILE RADIO COMMUNICATION
`SYSTEM HAVING MOBILE BASE AND
`PORTABLE DEVICES AS A MOBILE
`STATION
`[75] Inventor: Koichi Ito, Tokyo, Japan
`[73] Assignee: Kabushiki Kaisha Toshiba, Kawasaki,
`Japan
`[21] Appl. No.: 778,272
`[22] Filed:
`Oct. 17, 1991
`[30]
`Foreign Application Priority Data
`' Oct. 17, 1990 [JP]
`Japan ................................ .. 2477680
`[51] Int. Cl.5 .............................................. .. 1104.1 3/16
`[52] U.S. Cl. ................................... .. 370/95.1; 379/59;
`455/33.1
`[58] Field of Search ................. .. 370/95.1, 95.3, 85.13,
`370/8514; 455/58.1, 58.2, 33.1; 379/60, 61, 62,
`63, 59
`References Cited
`U.S. PATENT DOCUMENTS -
`4,056,779 11/1977 Toler ................................ .. 455/581
`4,894,856 l/1990 Nakanishi et a1.
`455/582
`
`[56]
`
`4,659,878 ‘4/ 1987 Dinkins . . . . . . . . . . . . .
`
`. . . . . . .. 370/71
`
`5,133,001 7/1992 Béihm . . . . . . . . . . . . . . . .
`
`. . . .. 455/33.l
`
`5,134,615 7/1992 Freeburg et a1. ................ .. 370/953
`FOREIGN PATENT DOCUMENTS
`“108904569 5/1989 PCT Int’l Appl..
`2241850 9/1991 United Kingdom.
`Primary Examiner-Douglas W. Olms
`
`US005276686A
`Patent Number:
`Date of Patent:
`
`[11]
`[45]
`
`5,276,686
`Jan. 4, 1994
`
`Assistant Examiner-Shick Hom
`Attorney, Agent, or Firm-Banner, Birch, McKie &
`Beckett
`ABSTRACT
`. [57]
`A mobile radio communication system according to the
`invention comprises a base station to be connected with
`a communication network by way of a wired communi
`cation path, a mobile base device to be connected with
`the base station by way of a ?rst radio channel selected
`from a plurality of ?rst radio channels and a portable
`device to be connected with the mobile base device by
`way of a second radio channel selected from a plurality
`of second radio channels. Each of the ?rst and second
`radio channels de?ned by a radio frequency and a time
`slot. The mobile base device comprises ?rst, second and
`third connection control circuits. The ?rst connection
`control circuit is used to select an idle ?rst radio chan
`nel out of the ?rst radio channels in cooperation with
`the base station and connect the mobile base device
`with the base station by the selected idle ?rst radio
`channel. The second connection control circuit is used
`to select a radio channel having an idle time slot show
`ing a speci?c relationship with the ?rst radio channel
`selected by the ?rst connection control circuit and con
`nect the mobile base device and the portable device by
`the selected idle second radio channel. The third con
`nection control circuit is used to connect the ?rst and
`second radio channels and establish a telephone com
`munication path between the base station and the porta
`ble device.
`
`29 Claims, 8 Drawing Sheets
`
`M53
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`1
`MOBILE RADIO COMMUNICATION SYSTEM
`HAVING MOBILE BASE AND PORTABLE
`DEVICES AS A MOBILE STATION
`BACKGROUND OF THE INVENTION
`1. Field of the Invention
`This invention relates to a radio communication sys
`tem to be used as an automobile telephone system, a
`portable radio telephone system or a cordless telephone
`system and more particularly it relates to a radio com
`munication system that enables installation of mobile
`base devices and portable device.
`2. Description of the Related Art
`A cellular type automobile telephone system has been
`known as a mobile radio communication system. Such a
`system normally comprises a control station, a plurality
`of base stations and a plurality of mobile stations, of
`which the control station is connected to a wired tele
`phone network by way of a wire communication path.
`The base stations are centeredon different radio com
`munication zones. Each of the mobile stations is con
`nected by a radio channel to the base station of a radio
`communication zone where it is currently located and
`further to a wire telephone network by way of the base
`station and the control station.
`Such a known system normally employs a so-called
`frequency division multiple access (FDMA) technique
`for connection between a base station and each of the
`mobile stations that belong to it. FDMA is a technique
`in which a number of radio frequencies are shared by a
`base station and a plurality of mobile stations. For com
`munication between a base station and a mobile station,
`the base station picks up an idle radio frequency when
`ever it calls or is called and then, if the call is successful,
`the calling and called stations are wirelessly connected
`by way of the picked up radio frequency. The operation
`of searching idle frequencies and assigning a particular
`frequency to a calling or called base station is con
`ducted by the control station.
`Now, each of the mobile stations of an automobile
`telephone system is equipped with an automobile tele
`phone main unit and peripheral equipment including a
`handset assembly. An automobile telephone main unit
`comprises radio transmission circuits, control circuits
`and other circuits. A handset assembly normally com
`prises a cradle and a handset, which in turn comprises a
`telephone transmitter, a receiver and a console unit. A
`console unit in turn comprises dial key, hook switch, an
`LCD display and other components. The automobile
`telephone main unit and the handset assembly are con
`nected by a signal cord. The cradle and the handset are
`connected by a curled cord.
`With such an arrangement, the curled cord can con
`stitutes an annoying obstacle when the driver drives and
`speaks into the telephone transmitter simultaneously.
`Moreover, the handset cannot be moved away beyond
`a limit posed by the curled wire, meaning that a passen
`ger sitting on the front or rear passenger seat is com
`pelled to stand up or take a crouching posture if he or
`she wants to speak over the phone.
`While the handset assembly of a conventional mobile
`station is placed within the passenger cabin of a car, the
`automobile telephone main unit is normally arranged in
`the trunk of the car, The signal cord connecting the
`telephone main unit and the handset assembly should be
`carefully arranged so as not to aesthetically damage the
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`appearance of the car, entailing a troublesome work to
`be done within a narrow space of the car.
`SUMMARY OF THE INVENTION
`It is therefore an object of the present invention to
`provide a mobile radio communication system that
`wirelessly connects not only between a base station and
`a mobile station but also between a mobile station, or a
`mobile base device, and a portable device by a radio
`channel in order to eliminate the necessity of wiring the
`mobile base device and portable device and enhance the
`maneuverability of an automobile telephone handset.
`Another object of the present invention is to provide
`a mobile radio communication system that can appro
`priately allocate radio channels for secure communica
`tion between base stations and mobile base devices and
`between mobile base devices and portable devices with
`out causing interference and other troubles among radio
`channels.
`According to the invention, the above objects are
`achieved by providing a mobile radio communication
`system comprising a base station to be connected with a
`communication network by way of a wired communi
`cation path, a mobile base device, to be connected with
`the base station by way of a ?rst radio channel selected
`from a plurality of ?rst radio channels, and a portable
`device to be connected with the mobile base device by
`way of a second radio channel selected from a plurality
`of second radio channels. Said mobile base device is
`provided with ?rst, second and third connection con
`trol means. The mobile base device cooperates with the
`base station to search an idle radio channel out of the
`?rst radio channels by using the ?rst connection means
`so that the base station and the mobile base device are
`mutually connected by way of the idle ?rst radio chan
`nel. Then, the second connection means is used to
`search an idle radio channel out of the second radio
`channels that has a de?nite relationship with the time
`slot of the selected idle ?rst radio channel so that the
`mobile base device and a portable device are mutually
`connected by way of said selected idle second radio
`channel. The third connection means is used to connect
`the selected ?rst and second radio channels to establish
`a communication through path between the base station
`and the portable device.
`In a mobile radio communication system according to
`the invention and having a con?guration as described
`above, a radio channel can be established not only be
`tween the base station and a mobile base device but also
`between a mobile base device and a portable device for
`mutual communication. If such a system is used for an
`automobile telephone, connection between an automo
`bile telephone main unit that operates as a mobile base
`device and a handset assembly that constitutes a porta
`ble device does not involve a signal cord nor curled
`cord to consequently enhance the maneuverability of
`the telephone handset and eliminate any possible nui
`sance to the driver due to the curled cord. Moreover,
`with such a system, a passenger on the rear seat can
`speak into the telephone transmitter of the handset
`without leaving the seat. Since no signal cord needs to
`be laid between an automobile telephone main unit and
`a handset assembly, the work of installing an automobile
`telephone terminal can be signi?cantly simpli?ed.
`According to the invention, a second radio channel is
`selected as a function of the time slot of a selected ?rst
`radio channel. Therefore, the selected second radio
`channel is always appropriate for a secure communica
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`tion path between the base station and the portable
`can be branched from a wired telephone terminal of a
`telephone network and jointly participate in a common
`device and never constitutes a source of interference
`telephone talk that takes place among the connected
`and/or other troubles.
`terminals.
`The effect of a mobile radio communication system
`In another preferred embodiment of the invention, a
`according to the invention will be particularly remark
`mobile base device searches out of the second radio
`able when the transmission time slot of the ?rst radio
`channels a plurality of idle radio channels to accommo
`channel and that of the second radio channel are se
`date a number of portable devices to be mutually con
`lected with a difference of timing so that any two differ
`nected whenever such a search operation is requested
`ent operations of signal transmission may not take place
`by portable devices. Then, the mobile base device is
`simultaneously in a mobile base device and conse
`connected with the request issuing portable devices by
`quently occurrence of any undesirable spurious trans
`way of the selected respective second radio channels so
`mission output may be effectively avoided. Besides, the
`peak value of energy consumption by a mobile base
`that any two or more than two portable devices may be
`put through to one another. With such an arrangement,
`device may be reduced to alleviate the load for power
`supply.
`portable devices that belong to a mobile base device can
`A system according to the invention may ?nd a vari
`operate as so many extension terminals branched from a
`ety of applications. In a ?rst conceivable application of
`local switch board, which is in fact a mobile base de
`a system according to the invention, a mobile base de
`vice.
`In still another preferred embodiment of the inven
`vice may be constituted by an automobile telephone
`tion, the length of a time slot in a second radio channel
`20
`main unit installed in a car and a portable device may
`is made longer than the length of a time slot in a ?rst
`correspond to a portable radio telephone handset to be
`radio channel. In other words, the number of time slots
`used with the main unit in a mobile radio communica
`tion system according to the invention. The portable
`comprised in a time frame of a second radio channel is
`made smaller than that of time slots comprised in a time
`radio telephone handset is connected with the automo
`frame of a ?rst radio channel. With such an arrange
`bile telephone main unit by a radio channel to set up a
`ment, the bit rate of data transmitted by way of a second
`communication channel leading to a telephone net
`radio channel can be set to a relatively low level to
`work. It is a known fact that a conventional portable
`radio telephone handset arranged in a car normally
`allow the use of a CPU having a relatively low process
`ing speed in a portable device. The circuit con?guration
`needs to be taken out of the car and placed somewhere
`of such a portable device can be made rather simple to
`outside the car or an adaptor should be put to it in order
`reduce the cost of the station. Since the volume of traf
`to make it operable relative to a matching telephone
`main unit in the car. A portable radio telephone handset
`?c between a mobile base device and a portable device
`is by far smaller than that of traffic between a base
`of a system according to the invention, however, is not
`station and a mobile base device, a radio channel con
`required to be placed outside the car nor does it need an
`necting them does not need to have a large channel
`adaptor to be put on it to become operable.
`Alternatively in a second possible application that
`capacity. Therefore, a relatively small number of time
`slots in a second radio channel would not give rise to a
`uses a system according to the invention for a cordless
`telephone system, a mobile base device, may be consti
`channel shortage condition. .
`In a still another preferred embodiment of the inven
`tuted by a stationary unit of a cordless telephone system
`tion a ?xed communication device at least capable of
`while a portable device may correspond to a cordless
`telephone handset. In a cordless telephone system, sta
`calling other subscribers is connected to a mobile base
`device by way of a cable line for talking. Such a ?xed
`tionary telephone units are connected to a telephone
`communication device may be operated in different
`exchange by way of subscribers’ wire lines and each of
`modes. In one possible mode, the ?xed communication
`the stationary units is connected to a handset by way of
`device and a wired telephone terminal is connected by
`a radio channel. With a system according to the inven
`tion, additional stationary telephone units can be wire
`way of a ?rst radio channel and a telephone network. In
`another possible mode, the ?xed communication device
`lessly connected to a telephone exchange without incur
`and a portable device is connected by way of a second
`ring any additional cost of installing new subscribers’
`lines and/or removing existing subscribers’ lines.
`radio channel to use the portable device as an extension
`terminal. In still another possible mode, a portable de
`In a third possible application of a system according
`vice and a wired telephone terminal connected to a
`to the invention, a mobile base device and a portable
`telephone network are mutually connected to establish
`device may respectively correspond to an automobile
`telephone main unit and a cordless telephone handset.
`a communication path and then a ?xed communication
`device is further connected to the establish communica
`With such an arrangement, a codeless telephone hand
`tion path so that the three terminals can jointly partici
`set whose service area is normally limited to the inside
`pate in a telephone talk.
`of a home or an of?ce can be used in a car.
`Additional objects and advantages of the invention
`In preferable embodiment of the invention, a mobile
`will be set forth in the description which follows, and in
`base device searches out of the second radio channels a
`plurality of idle radio channels having a particular rela
`part will be obvious from the description, or may be
`learned by practice of the invention. The objects and
`tionship with a single ?rst radio channel in order to
`advantages of the invention may be realized and ob
`accommodate a number of portable devices to be con
`tained by means of the instrumentalities and combina
`nected to said ?rst radio channel whenever such a
`search operation is requested by portable devices. Then,
`tions particularly pointed out in the appended claims.
`the mobile base device is ?rstly connected with the
`BRIEF DESCRIPTION OF THE DRAWINGS
`request issuing portable device by way of the selected
`The accompanying drawings, which are incorpo
`respective second radio channels, which are subse
`rated in and constitute a part of the speci?cation, illus
`quently connected with the ?rst radio channel. With
`trate presently preferred embodiments of the invention,
`such an arrangement, those connected portable device
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`and together with the general description given above
`a control system. Reference numeral 40 denotes a
`and the detailed description of the preferred embodi
`power source, which is a battery.
`ments given below, serve to explain the principles of the
`The transmission system comprises a telephone trans
`invention.
`mitter 11, a speech encoder (SPCOD) 12, an error cor
`rection encoder (CHCOD) 13, a digital modulator
`FIG. 1 is a schematic view of a ?rst embodiment of
`the mobile radio communication system of the inven
`(MOD) 14, a multiplier 15, a power ampli?er (PA) 16,
`tion, illustrating its basic concept;
`a high frequency switch circuit (SW) 17 and an antenna
`18. The speech encoder 12 encodes analog speech sig
`FIG. 2 is a block diagram showing the con?guration
`nals coming from the telephone transmitter 11 into
`of a portable device of the embodiment of FIG. 1;
`FIG. 3 is a block diagram showing the con?guration
`coded signals. The error correction encoder 13 detects
`and corrects errors in coded speech signals coming
`of a mobile base device of the embodiment of FIG. 1;
`from the speech encoder 12 and encoding control sig
`FIG. 4 is a block diagram showing the con?guration
`of a base station of the embodiment of FIG. 1;
`nals coming from a control circuit 31, which will be
`described later. The digital modulator 14 generates
`FIG. 5 is a timing chart to be used for selecting ?rst
`and second radio channels in the embodiment of FIG. 1;
`intermediate frequency signals and causes them to be
`modulated by encoded speech signals coming from the
`FIG. 6 is a schematic view of a second embodiment
`of the mobile radio communication system of the inven
`error correction encoder 13 before sending them out. A
`tion, illustrating its basic concept;
`method called rr/4 shifted differentially encoded quad
`rature phase shift keying is typically used for modula
`FIG. 7 is a timing chart to be used for selecting ?rst
`and second radio channels in the embodiment of FIG. 2;
`tion in the modulator 14. Then, in the multiplier 15,
`intermediate frequency signals generated by the digital
`FIG. 8 is a block diagram showing the con?guration
`modulator 14 are mixed with local oscillation signals
`of a mobile base device in a third embodiment of the
`transmitted from a frequency synthesizer 32 and then
`invention; and
`FIG. 9 is a block diagram showing the con?guration
`subjected to a frequency conversion process to produce
`radio transmission signals having a frequency that
`of a mobile base device in a fourth embodiment of the
`matches the frequency of the assigned radio channel.
`invention.
`The power ampli?er 16 ampli?es the power of radio
`DETAILED DESCRIPTION OF THE
`transmission signals coming from the multiplier 15 to a
`predetermined transmission power level. The high fre
`' PREFERRED EMBODIMENTS ‘
`lst Embodiment
`quency switch circuit 17 is a switch circuit which is
`closed only for the period of each transmission time slot
`FIG. 1 shows a schematic view of a ?rst embodiment
`assigned by the control circuit 31. Only in this period,
`of the mobile radio communication system of the inven
`tion, which is an automobile telephone system.
`radio transmission signals coming from said power am
`This embodiment comprises as components a number
`pli?er 16 are forwarded to the antenna 18, which sends
`of base stations 8881 through BSSn and mobile stations
`them out to a corresponding base station BSS.
`M81 through MSm. Said base stations BSSl through
`On the other hand, the reception system comprises a
`receiver (RX) 21, a digital demodulator (DEM) 22, an
`BSSn are connected to a wire telephone network NW
`by way of respective cable lines CL1 through CLn and
`error correction decoder (CH-DEC) 23, a speech de
`centered in different radio zones E1 through En. Each
`coder (SP-DEC) 24 and a telephone receiver or ear
`phone 25. High frequency signals received by the re
`of the mobile stations MSI through MSm comprises a
`40
`mobile base device M55 and a portable device PS8.
`ceiver 21 in each predetermined time slot are converted
`for frequency into intermediate frequency signals in the
`The mobile base device M85 is connected to a base
`receiver 21. The digital demodulator 22, after establish
`station BSS that covers the radio zone E where it is
`ing bit-synchronization and frame-synchronization for
`located by way of a ?rst radio channel, whereas the
`the incoming intermediate frequency signals from said
`portable device PS8 is connected to the mobile base
`receiver 21, demodulate them into coded speech signals.
`device MSS by way of a second radio channel.
`The information used for bit- and frame-synchroniza
`This embodiment utilizes a FDMA/TDMA tech
`tion in the digital demodulator 22 is fed to the control
`nique for connection between a base station and a mo
`circuit 31. The error correction decoder 23 decodes
`bile base device as well as for connection between a
`demodulated coded signals coming from said digital
`mobile base device M85 and a portable device PSS.
`demodulator for error correction. Coded speech signals
`With a FDMA/TDMA technique, a number of radio
`frequencies are shared by a plurality of stations. These
`from said error correction modulator 23 are fed to the
`speech demodulator 24, while coding control signals
`radio frequencies have a time division signal unit format
`where a time frame is divided into a number of time
`from the error correction modulator 23 are sent to the
`slots, e.g., six time slots TSl through TS6. When a
`control circuit 31. The coded speech signals are de
`coded in the speech decoder 24 to reproduce analog
`station tries to call another station in this system, the
`system searches for an idle radio frequency and then for
`speech signals, which are sent out of the telephone
`an idle time slot of the radio frequency and assigns the
`receiver 25 in audible loud voice.
`selected time slot to the calling and called stations to
`Finally, the control system comprises a control cir
`establish a radio telephone communication channel
`cuit (CONT) 31, a frequency synthesizer (SYN) 32, a
`between these stations.
`received electric ?eld strength sensor circuit (R581) 33
`Now, the stationary base stations BSSl through
`and a console unit (CU) 34. The frequency synthesizer
`BSSn mobile base devices M88 and portable devices
`generates an oscillation having a local oscillation fre
`quency that matches the radio channel speci?ed by the
`PSS of this embodiment will be described further for
`their con?gurations.
`control circuit 31. The received electric ?eld strength
`Referring to FIG. 2 showing a block diagram of a
`sensor circuit 33 senses the received ?eld strength of the
`portable device PS5 to be used for the embodiment, it
`electric wave transmitted from the base station BSS it
`belongs and sends signals representing the determined
`comprises a transmission system, a reception system and
`
`60
`
`65
`
`25
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`45
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`5,276,686
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`demodulated coded signals coming from said digital
`?eld strength to the control circuit 31. The console unit
`34 comprises transmission switches, dial keys, a liquid
`dulator for error correction. Coded speech signals from
`display panel and so on.
`said error correction modulator 63 are fed to the speech
`demodulator 64, while coding control signals from the
`The control circuit is normally a microcomputer that
`comprises a central processing unit (CPU), an input
`error correction modulator 63 are sent to the control
`circuit 71. The speech decoder 64 changes the data
`port, an output port, a program ROM and a data RAM.
`signaling rate for digital speech signals coming from
`The CPU executes control operations according to the
`error correction decoder 63 and the digital speech sig
`programs stored in the program ROM.
`nals whose data signaling rate has been changed are
`Referring to FIG. 3 showing a block diagram of a
`temporarily stored in the register circuit 65 and then
`mobile base device MSS, it comprises a ?rst transmitter
`receiver unit 50 and a second transmitter-receiver unit
`sent out to the second transmitter-receiver unit 80.
`Finally, the control system comprises a control cir
`80. The ?rst transmitter-receiver unit 50 is used for
`cuit (CONT) 71, a frequency synthesizer (SYN) 72 and
`radio communication with the base station 1358 it be
`longs by way of a ?rst radio channel, whereas the sec
`a received electric ?eld strength sensor circuit (RSS1)
`73. The control circuit 71 has a main control section
`ond transmitter-receiver unit 80 is used for radio com
`munication with its portable device PSS by way of a
`which is normally a microcomputer and executes con
`trol operations for connecting a base station 855 and a
`second radio channel.
`portable device PS8. The frequency synthesizer gener
`The ?rst transmitter-receiver unit 50 comprises a
`transmission system, reception system and a control
`ates under the control of the control circuit 71 an oscil
`lation having a local oscillation frequency required for
`system. The transmission system is constituted by a
`20
`register circuit (STR) 51, a speech encoder (SPCOD)
`radio communication with the base station it belongs.
`The received electric ?eld strength sensor circuit 33
`52, an error correction encoder (CHCOD) 53, a digital
`modulator (MOD) 54, a multiplier 55, a power ampli?er
`senses the received ?eld strength of the electric wave
`(PA) 56, a high frequency switch circuit (SW) 57 and an
`transmitted from the base station BSS it belongs and
`sends signals representing the determined ?eld strength
`antenna 58. The register circuit 51 temporarily stores
`25
`digital speech signals sent from the reception system of
`to the control circuit 31.
`the second transmitter-receiver unit 80, which will be
`Like the ?rst transmitter-receiver unit 50, the second
`described in more detail later. The speech encoder 52
`transmitter-receiver unit 80 also comprises a transmis
`changes the data signaling rate for digital speech signals
`sion system, reception system and a control system. The
`transmission system is constituted by a speech encoder
`coming from said register circuit 51. The error correc
`tion encoder 53 detects errors in digital speech signals
`(SPCOD) 82, an error correction encoder (CHCOD)
`from said speech encoder 52 and digital control signals
`83, a digital modulator (MOD) 84, a multiplier 85, a
`power ampli?er (PA) 86, a high frequency switch cir
`from a control circuit 71, which will be described later.
`The digital modulator 54 generates intermediate fre
`cuit (SW) 87 and an antenna 88. The transmission power
`level of the power ampli?er 86 is set lower than the
`quency signals and causes them to be modulated by
`encoded speech signals coming from the error correc
`transmission power level of the power ampli?er 56 of
`the ?rst transmitter-receiver unit 50. The reception
`tion encoder 53 before sending them out. A method
`called 1r/4 shifted QPSK is typically used for modula
`system comprises a receiver (RX) 91, a digital demodu
`tion in the modulator 54. Then, in the multiplier 55,
`lator (DEM) 92, an error correction decoder (CHDEC)
`intermediate frequency signals generated by the digital
`93 and a speech decoder (SPDEC). The control system
`comprises a frequency synthesizer 102 and a received
`modulator 54 are mixed with local oscillation signals
`electric ?eld strength sensor circuit 103. The frequency
`transmitted from a frequency synthesizer 72 and then
`subjected to a frequency conversion process to produce
`synthesizer 102 generates under the control of the con
`radio transmission signals having a frequency that
`trol circuit 71 an oscillation having a local oscillation
`frequency required for radio communication with its
`matches the frequency of the assigned radio channel.
`The power ampli?er 56 ampli?es the power of radio
`portable device PS5. The received electric ?eld
`transmission signals coming from the multiplier 55 to a
`strength sensor circuit 103 senses the received ?eld
`predetermined transmission power level. The high fre
`strength of the electric wave transmitted from the por
`table device PSS and sends signals representing the
`quency switch circuit 57 is a switch circuit which is
`closed only for the period of each transmission time slot
`determined ?eld strength to the control circuit 71.
`assigned by the control circuit 71. Only in this period,
`Finally, referring to FIG. 4 showing a block diagram
`radio transmission signals coming from said power am
`of a base station BSS. Base station BSS comprises, like
`pli?er 56 are forwarded to the antenna 58, which sends
`a portable device PSS described above, a transmission
`system, a reception system, a control system and addi
`out them to a corresponding base station BOSS.
`On the other hand, the reception system comprises a
`tionally a hybrid circuit 111, which is used for connect
`ing the transmission system and the reception system to
`receiver (RX) 61, a digital demodulator (DEM) 62, an
`error correction decoder (CHDEC) 63, a speech de
`a cable line CL.
`The transmission system is constituted by a speech
`coder (SPDEC) 64 and a register circuit (STR) 65. In
`the receiver 61, high frequency signals received by way
`encoder (SPCOD) 112, an error correction encoder
`of the antenna 58 and the high frequency switch circuit
`(CHCOD) 113, a digital modulator (MOD) 114, a multi
`plier 115, a power ampli?er (PA) 116, a high frequency
`57 in each predetermined time slot are converted for
`frequency into intermediate frequency signals. The digi
`switch circuit (SW) 117 and an antenna 118. The speech
`tal demodulator 62, after establishing bit synchroniza
`encoder 112 encodes speech sign