United States Patent [19]
`Jasinski et al.
`
`[11] Patent Number:
`[45] Date of Patent:
`
`4,968,966
`Nov. 6, 1990
`
`[54] HIGH DATA RATE SIMULCAST
`
`4,816,820 3/1989 Davis ............................ .. 340/825.44
`
`COMMUNICATION SYSTEM
`[75] Inventors: Leon Jasinski, Ft. Lauderdale;
`Francis R_ Steel’ deceased’ late of
`Parkland; Lynne A_ Steel, legal
`representative, Highland Beach’ all
`of Fla.
`[73] Assignee: Motorola, Inc., Schaumburg, Ill.
`[21] APPL No; 425,662
`'
`[22] Flled‘
`
`oct- 23’ 1989
`
`
`4,851,820 7/1989 Fernandez 4,88l,073 11/1989 Andros et al. ............... .. IMO/825.44
`,
`_
`Primary Exammer-—Donald J. Yusko
`.
`Assistant Examiner-Enc O._I_’udpud
`Attorney, Agent, or Firm—Phllip P. Macnak; Vmcent B.
`Ingrassia
`ABSTRACT
`[57]
`A system for transmitting long text messages includes a
`plurality of transmission cells de?ning different geo
`graphical areas, each having a transmitter for simulcast
`address transmission at a ?rst data bit rate and for trans
`mitting the address and a message at a second data bit
`rate higher than the ?rst data bit rate. A paging transa
`ceiver generates and transmits an acknowledgment
`signal in response to receiving a transmitted address at
`tat taat data at tata
`laaataa wtttaa aaaa at
`the transmission cells receive the transmitted acknowla
`edgmem Signal- An apparatus responsive 1° the re
`ceived acknowledgment signal identi?es the transmis
`sion cell in which the paging transceiver is located
`effecting the selection of the transmitter in the transmis
`sion cell in which the paging transceiver is located to
`transmit the address and message at the second data bit
`rate higher than the ?rst data bit met
`
`9 Claims, 16 Drawing Sheets
`
`[62]
`
`E5}
`
`[56]
`
`11:11::1:313::31131:::....iiiiiii'sia;aaai‘il‘ga%%‘l
`379/60; 455/33
`[58] Field of Search ......... .. 340/311.1, 825.44, 825.47,
`340/82549, 82552; 379/56, 57, 5g, 69, 60;
`455/33, 34, 31; 370/79, 34
`_
`References Cited
`US PATENT DOCUMENTS
`4,618,860 10/1986 Mori .................................... .. 379/57
`4,642,632 2/1987 Ohyagi et al.
`.
`4,811,376 3/1989 Davis et al. .................. .. 340/825.4-4
`
`Related [15- Application Data
`Division Of Ser. No. 257,904, Oct. 13, 1988, Pat. NO.
`4,918,437.
`5
`
`14
`STATIONS E®f
`
`REMOTE _
`
`CENTRAL _
`
`STATION “6
`
`12
`
`PORTABLE _ r18
`TRANSCEIVER -
`
`1
`
`Petitioner Samsung - SAM1013
`
`

`
`US. Patent Nov. 6, 1990
`
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`

`
`US. Patent Nov. 6, 1990
`
`Sheet 2 of 16
`
`4,968,966
`
`EMOTE
`TIONS
`
`CENTRAL
`STATION
`
`PORTABLE
`TRANSCEIVER
`
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`US. Patent
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`4,968,966
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`US. Patent
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`Nov. 6, 1990
`
`Sheet 4 of 16
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`4,968,966
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`US. Patent
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`Nov. 5
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`1/
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`1990
`
`Sheet 6 of 16
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`4,968,966
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`US. Patent
`
`Nov. 6,1990
`
`Sheet 7 of 16
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`4,968,966
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`
`Sheet 8 of 16
`
`4,968,966
`
`US. Patent Nov. 6, 1990
`( INITIALIZE !
`
`600
`
`/602
`v
`WAIT FOR
`PAGE REQUEST _’®
`
`V
`PAGE REQUEST
`ENTERED
`
`604
`/
`
`F]G.8A
`
`' N
`
`616
`T
`\
`ASSIGN FUNCTIONAL
`ADDRESS 3 (FA3)
`
`V
`SToRE FA3, MESSAGE
`AND EOM MARKER
`IN CURRENT FRAME
`MESSAGE FILE
`\
`618
`
`V
`610\
`ASSIGN FUNCTIONAL
`ADDRESS 1 (FA1)
`
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`612
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`MESSAGE IN ACTIvE
`PAGE FILE
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`v
`ASSIGN FUNCTIONAL f2‘)
`ADDRESS 2 (FA2)
`
`V
`ASSIGN ACK-BACK jzz
`CHANNEL TO FA2
`,
`
`v
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`FORMAT ACTIvE PAGE FILE WITH
`FA2 AND A-B CHANNEL INFO‘
`
`614"
`
`62f
`
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`RECovER CURRENT FRAME-1
`MESSAGE FILE
`
`FORMAT ACTIVE PAGE FILE WITH
`CURRENT FRAME-1 MESSAGE FILE
`
`9
`
`

`
`US. Patent Nov. 6, 1990
`
`Sheet 9 of 16
`
`4,968,966 ,
`
`(630
`DECREMENT
`FRAME TIMER
`
`N
`
`628
`TIME
`TO TRANSMIT
`
`634
`
`636
`
`INTERLEAVE ACTIVE PAGE
`FILE/GENERATE BLOCK
`ERROR CHECK
`
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`\
`SWITCH TO BURST RATE
`
`7
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`TRANSMIT ACTIVE PAGE
`FILE TO REMOTE STATIONS
`(BURST)
`
`<5
`
`F] G. 83
`
`10
`
`

`
`US. Patent Nov. 6, 1990
`
`Sheet 10 of 16
`
`4,968,966
`
`DE-KEY PAGING
`TRANSMITTER
`
`V
`SWITCH TO REMOTE
`STATION OPERATION
`
`638
`/
`
`640
`J
`
`642
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`OPERATION
`
`644
`V
`RECEIVE ENCODED SIGNAL J
`STRENGTH AND
`ACKNOWLEDGE RESPONSES
`
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`CORRELATE ENCODED
`SIGNAL STRENGTH ‘DATA,
`SELECT REMOTE STATIONS
`
`646
`/
`
`652
`K
`
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`
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`PAGE FILE
`
`RECEIVER NOT
`RESPODNDING
`
`DELETE CORRESPONDING
`‘ MESSAGE FROM CURRENT
`FRAME MESSAGE FILE
`
`650 /
`
`RECOVER CURRENT
`FRAME MESSAGE FILE
`
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`
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`FRAME MESSAGE FILE —>@
`STORE IN CURRENT
`FRAME-1 MESSAGE FILE
`
`FIG.8C
`
`11
`
`

`
`US. Patent Nov. 6, 1990
`
`Sheet 11 of 16
`
`4,968,966
`
`RECEIVE REMOTE SITE
`SYNCHRONIZATION
`SIGNALLING
`
`704
`+
`SYNCHRONIZE REMOTE J
`SITE CLOCKS
`
`DE-INTERLEAVE
`I ACTIVE PAGE FILE
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`
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`ADDRESSES IN LOCAL
`ADDRESS FILE
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`
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`
`718
`K
`STORE FRAME-1
`MESSAGES IN LOCAL
`MESSAGE FILE
`
`SELECT SIMULCAST
`TRANSMISSION BIT RATE
`I
`KEY PAGING TRANSMITTER
`+
`SIMULCAST SYNC (so)
`+
`SIMULCAST CURRENT
`FRAME ADDRESSES
`
`J24
`
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`
`12
`
`

`
`US. Patent Nov. 6, 1990
`
`Sheet 12 of 16
`
`4,968,966
`
`(I?
`
`730
`
`SIMULCAST UNMODULATED /
`CARRIER (cw)
`
`V
`
`‘732
`SWITCH TO BIT RATE / '
`FOR NON-SIMULCAST
`TRANSMISSION
`
`"
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`TRANSMIT TIMER
`
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`TRANSMIT CURRENT
`FRAME-1
`PAGE FILE
`
`734
`J
`
`736
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`
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`
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`
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`TRANSMIT TIMER
`
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`
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`RESPONSE TIMER
`
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`
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`
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`
`13
`
`

`
`US. Patent Nov. 6, 1990
`
`Sheet 13 Of 16
`
`4,968,966
`
`DETERMINE RESPONSE /
`SIGNAL STRENGTHS
`
`750
`"
`DECODE AND ERROR /
`CORRECT ACKNOWLEDGE
`RESPONSES
`
`"
`ENCODE SIGNAL
`STRENGTH, STORE WITH
`ACKNOWLEDGE RESPONSE
`
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`
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`RESPONSE TIMER
`
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`J
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`SITE TRANSMITTER
`
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`TRANSMIT ENCODED
`SIGNAL STRENGTH AND
`ACKNOWLEDGE RESPONSE
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`
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`
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`
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`
`14
`
`

`
`US. Patent Nov. 6, 1990
`
`Sheet 14 of 16
`
`4,968,966 ,
`
`800
`
`INITIALIZE
`
`SET SIMULCAST
`RECEIVE RATE
`
`SAMPLE RECEIVED DATA
`AND CORRELATE FOR SYNC
`
`\
`802
`804
`
`LOAD ADDRESS TIMER
`T
`SAMPLE RECEIVED DATA
`AND CORRELATE FOR ADDRESS
`
`818
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`
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`
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`
`ADDRESS
`
`ADDRESS TIMER
`TIMEOUT
`'.>
`
`816
`
`ADDRESSES
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`
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`
`*
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`\ SET NON-SIMULCAST
`REGEIvE RATE
`
`+
`828
`\ LOAD CARRIER TIMER
`
`15
`
`

`
`US. Patent Nov. 6, 1990
`
`Sheet 15 of 16
`
`4,968,966
`
`@—> LOCK ON TO CARRIER (CW)
`\
`
`832
`
`CARRIER TIMER
`TIMEOUT
`'?
`
`Y
`
`MESSAGE TIMER
`
`TIMEOUT
`
`SAMPLE RECEIVED
`DATA AND CORRELATE
`FOR ADDRESS
`
`RECEIVER DATA
`
`T
`DE—INTERLEAVE DATA
`
`TY
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`
`TV
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`
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`
`6
`
`MESSAGE TIMER
`
`TIMEOUT
`
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`
`FIG. 1 OB
`
`16
`
`

`
`US. Patent
`
`Nov. 6, 1990
`
`Sheet 16 0f 16
`
`4,968,966
`
`SWITCH TO
`TRANSMIT MODE
`
`"
`860
`\ TRANSMIT ACK 1
`OR ACK 2 RESPONSE
`
`V
`
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`
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`
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`
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`
`17
`
`

`
`1
`
`HIGH DATA RATE SIMULCAST
`COMMUNICATION SYSTEM
`
`4,968,966
`
`2
`0nd, or even higher are required. However, most pag
`ing systems in use today employ simulcast transmission
`of information to provide wide area coverage. Such
`paging systems employ a number of transmitters geo
`graphically separated, which are located in a cellular, or
`pseudo-cellular, fashion to provide the required cover
`age, and all transmitters transmit the same information
`simultaneously in all cells or zones. While conventional
`frequency modulated (FM) simulcast transmission sys
`tems can provide adequate message transmission at data
`rates below 2400 bits per second, they become dif?cult
`to set up and have not reliably been used to transmit
`messages at higher data rates. Problems, such as with
`providing proper phase equalization and synchroniza
`tion of the transmission of the transmitters within the
`system become substantially more dif?cult at higher
`data rates.
`Another problem that exists in the transmission of
`long messages, is insuring the message being transmit
`ted, has been received by the pager for which it is in
`tended, otherwise valuable air-time is wasted. Failure to
`receive the message can occur when the pager is out of
`range of the transmitters, has not been turned on by the
`user, has a dead battery, or has a battery that has died
`during the operating day. In providing a paging system
`capable of transmitting long messages, it is extremely
`important to know the messages being transmitted are
`likely to be received, otherwise valuable air-time is lost.
`
`SUMMARY OF THE INVENTION
`It is therefore an object of the present invention to
`provide a communication system providing increased
`message throughput.
`It is a further object of the present invention to pro
`vide a communication system providing increased mes
`sage throughput utilizing simulcast transmitter opera
`tion.
`It is a further object of the present invention to pro
`vide a communication system providing reliable mes
`sage throughput at high data transmission rates.
`Generally, a system for transmitting long text mes
`sages includes a plurality of transmission cells each
`having a transmitter for simulcast address transmission
`at a ?rst data bit rate and for transmitting the address
`and a message at a second data bit rate higher than the
`?rst data bit rate. A paging transceiver generates and
`transmits an acknowledgement signal having predeter
`mined characteristics in response to receiving the trans
`mitted address at the ?rst data bit rate. Receivers lo
`cated within each of the transmission cells receive the
`transmitted acknowledgement signal. A selecting means
`responsive to the received acknowledgement signals
`selects the transmission cell in- which the paging trans
`ceiver is located effecting the transmission of the ad
`dress and message at the second data bit rate higher than
`the ?rst data bit rate in the selected transmission cell in
`which the paging transceiver is located.
`Another embodiment of a system for transmitting
`long text messages includes a plurality of transmission
`cells each having a transmitter for simulcast address
`transmission at a ?rst data bit rate and for transmitting
`the address and a message at a second data bit rate
`higher than the first data bit rate. A paging transceiver
`generates and transmits an acknowledgement signal
`having predetermined characteristics in response to
`receiving the transmitted address at the ?rst data bit
`rate. Receivers located within each of the transmission
`cells receive the transmitted acknowledgement signal.
`
`This is a division, of application Ser. No. 07/257,904,
`?led Oct. 13, 1988 now US. Pat. No. 4,918,437.
`
`FIELD OF THE INVENTION
`This invention relates to the ?eld of data communica
`tion systems, and more particularly to a data communi
`cation system providing simulcast radio frequency data
`transmission capability for long data messages transmit
`ted at high data rates.
`
`20
`
`25
`
`35
`
`BACKGROUND OF THE INVENTION
`Numerous data communication systems are available
`providing data message delivery. One such system hav
`ing great popularity, the radio paging system, can de
`liver numeric and alphanumeric messages originated by
`a caller, using a telephone or an alphanumeric messag
`ing terminal. The messages are then transmitted to a
`numeric or alphanumeric display pager. Radio paging
`systems deliver the messages using a variety of signaling
`formats, such as the Golay Sequential Code (GSC) and
`POCSAG signaling formats to small portable receivers
`referred to as pagers. The POCSAG signaling format is
`shown in FIG. IA. As shown, a synchronization code
`(SC) is ?rst transmitted, which is used by all paging
`receivers, or pagers, within the system for maintaining
`synchronization with the transmitted information. The
`30
`synchronization code (SC) is followed by eight frames,
`F1~F8. Each frame provides for the transmission of
`address blocks (A) and data blocks (M). Pagers are
`assigned to a speci?c one of the eight frames, providing
`the pager a battery saving function. The pagers are
`generally con?gured as tone-only pagers (T) respond
`ing only with an audible alert when paged, numeric
`pagers (N) responding with an audible alert and a dis
`played numeric message, such as a telephone number
`when pages, or alphanumeric pagers (Alpha) respond
`ing with an audible alert and a displayed alphanumeric
`message when paged. The paging system transmits only
`the address identifying the pager being paged for tone
`only pagers, and an address identifying the pager to
`which a message is intended followed by the message
`for numeric and alphanumeric pagers. As shown in
`FIG. 1A, two tone-only address blocks can be transmit
`ted in a single frame, while a simple seven digit phone
`number, which is encoded using a four bit binary data
`format, requires transmitting an address block followed
`by two data blocks, continuing part of the message into
`the next POCSAG frame. Alphanumeric messages,
`which are encoded using a seven bit BCH data format,
`can extend into many frames and required substantially
`more air time to transmit than either the tone-only or
`numeric pages. Consequently, the transmission of mi
`men'c and alphanumeric messages on a paging system
`reduced the number of pagers that can be loaded into
`the system, and this problem is compounded when long
`alphanumeric messages are transmitted. One solution
`which has been proposed for this problem is to increase
`the data transmission rate to 1200 bits per second from
`the current standard 512 bits per second. However,
`even this solution has proven inadequate for transmit
`ting long data messages.
`In order to obtain the message throughput required to
`handle long alphanumeric messages, substantially
`higher data rates, such as at 2400 or 4800 bits per sec
`
`45
`
`50
`
`55
`
`65
`
`18
`
`

`
`10
`
`35
`
`45
`
`50
`
`4,968,966
`3
`4
`A selecting means responsive to the received acknowl
`System 10, as shown in FIG. 2A, is arranged in a sub
`edgement signals selects the transmission cell in which
`stantially cellular pattern, comprising a plurality of
`transmission cells 16 de?ning different geographical
`the paging transceiver is located, and further selects one
`or more transmission cells adjacent the transmission cell
`areas wherein the central station 12 and remote stations
`in which the paging transceiver is located for effecting
`14 are located, thereby providing wide area coverage
`the simulcast transmission of the address and message at
`for a plurality of communication transceivers, such as
`paging transceivers 18, operating within the system.
`the second data bit rate higher than the ?rst data bit rate
`in the selected transmission cell in which the paging
`While system 10 shows a regular arrangement of trans
`transceiver is located and in the selected adjacent trans
`mission cells 16, it will be appreciated by one of ordi
`mission cells.
`nary skill in the art, that the arrangement of transmis
`These and other objects and advantages of the pres
`sion cells 16 need not be regularly distributed to provide
`ent invention will become more apparent to those
`a wide area simulcast transmission system for a particu
`skilled in the art by referring to the following detailed
`lar geographical area. It will also be appreciated that
`description and accompanying diagrams.
`the number of remote stations which is shown is for
`example only, and depending upon the area of cover
`BRIEF DESCRIPTION OF THE DRAWINGS
`age, the system may have more or less remote stations
`than shown. It will also be appreciated, that the location
`The features of the invention which are believed to be
`novel are set forth with particularity in the appended
`of central station 12 relative to that of remote stations
`claims. The invention itself, together with its further
`14, need not necessarily be centrally located, as shown,
`objects and advantages thereof, may be best understood
`so long as central station 12 be able to communicate
`by reference to the following description when taken in
`with remote stations 14 in the manner to be described
`shortly.
`conjunction with the accompanying drawings, in the
`several ?gures of which like reference numerals identify
`Messages are entered into system 10 via central sta
`identical elements, in which and wherein:
`tion 12 and formatted into a predetermined signaling
`FIG. 1 is a timing diagram showing an example of
`format having address and message segments, to be
`25
`data transmission utilizing the POCSAG signaling for
`described in detail shortly. The formatted messages are
`stored for a predetermined time interval, also to be
`mat.
`FIG. 2A is a line drawing depicting the simulcast
`described in detail shortly, after which they are trans
`transmission mode in the preferred embodiment of the
`mitted as a burst signal, or packet of information, at a
`present invention.
`very high data rate, such as 19.2 or 38.4 kilobits per
`FIG. 2B is a line drawing depicting the non-simulcast
`second for the preferred embodiment of the present
`transmission mode for high data rate messages in the
`invention, from central station 12 to remote stations 14.
`preferred embodiment of the present invention.
`The address segments of the burst signal are then simul
`FIG. 2C is a line drawing depicting the pseudo-simul
`cast from remote station 14 ‘and central station 12 on a
`cast transmission mode for high data rate messages in
`common radio (R.F.) frequency in a manner well
`the preferred embodiment of the present invention.
`known to one of ordinary skill in the art. The address
`FIG. 3 is a timing diagram showing the signaling
`segments are transmitted at a ?rst data bit rate, such as
`format of the preferred embodiment of the present in
`512 or 1200 bits per second, thereby providing reliable
`vention.
`simulcast transmission to the plurality of paging trans
`FIG. 4 is a timing diagram showing the application of
`ceivers 18 operating within system 10. It will be appre
`40
`the signaling format of FIG. 3 in a simulcast transmis
`ciated that other bit rates may also be employed, partic
`sion system.
`ularly when other signaling formats are employed, and
`FIG. Sis a line drawing showing the ?ow of data and
`that the preferred embodiment of the present invention
`control information for the simulcast transmission sys
`is not limited to the data transmission rates indicated by
`example. Each paging transceiver 18 is assigned a
`tem described in FIG. 4.
`unique address to which it is responsive. Upon receiv
`FIGS. 6A and 6B are electrical block diagrams of the
`central station transmission facility and the remote site
`ing and detecting an address corresponding to the as
`transmission facilities of the preferred embodiment of
`signed address for each paging transceiver 18, each
`the present invention.
`addressed paging transceiver 18 generates an acknowl
`FIG. 7 is an electrical block diagram showing a pag
`edgement signal in a manner to be described in detail
`ing transceiver in the preferred embodiment of the pres
`shortly. The acknowledgment signals, which have pre
`ent invention.
`determined characteristics, such as a predetermined
`transmission frequency, signal strength and signal phase
`FIGS. 8A-C are ?ow charts showing the operation
`of the central station transmission facility.
`characteristics, are generated by paging transceivers 18.
`FIGS. 9A-C are ?ow charts showing the operation
`The transmitted acknowledgement signals are received
`of the remote site transmission facilities.
`at one or more remote stations 14 or central station 12.
`FIGS. 10A-C are flow charts showing the operation
`The received acknowledgment signals allow system 10
`of the paging transceivers of the present invention.
`to identify the transmission cells 16 in which each re
`sponding paging transceiver 18 is located. Once the
`location of paging transceivers 18 have been deter
`mined, the messages, which are stored at central station
`12, corresponding to each paging transceiver 18 are
`tagged identifying one or more remote stations 14 to be
`used in the subsequent transmission of the message.
`The tagged messages are transmitted at the burst
`signal data rate described previously to the remote sta
`tions on the next central station transmission cycle.
`While all remote stations 14 receive the tagged mes
`
`DESCRIPTION OF A PREFERRED
`EMBODIMENT
`With respect to the ?gures, FIGS. 2 through 10 illus
`trate in general several preferred embodiments of the
`present invention. Referring to FIG. 2A, a typical si
`mulcast communication system 10 is shown which in
`cludes a substantially centrally located central station
`12 (identi?ed by the letter C) surrounded by a plurality
`of remote stations 14 (identi?ed by the numbers 1-8).
`
`55
`
`60
`
`65
`
`19
`
`

`
`20
`
`25
`
`4,968,966
`5
`6
`sages, only those remote stations to which the messages
`FIG. 3 shows a timing diagram of the signaling for
`mat 100 of the preferred embodiment of the present
`are tagged, process the messages as will be described
`shortly. Messages received at the appropriate remote
`invention. Signaling format 100 comprises a transmis
`sion time interval for the burst signal 102, during which
`stations 14 are re-transmitted in one of two embodi
`the burst signal is transmitted at the very high data rate
`ments of the present invention by the remote stations at
`previously described, from the central station to the
`a second data bit rate higher than the ?rst data bit rate,
`remote stations. A detailed description of burst signal
`such as 2400 or 4800 bits per second. It will be appreci
`102 will be described in FIG. 4.
`ated that the bit rates indicated are by way of example
`Returning to FIG. 3, a synchronization codeword
`only, and that other bit rates may be satisfactorily em
`(SC) 104 follows burst signal 102. Synchronization
`ployed. In the ?rst embodiment of the present invention
`codeword 104 is used by the paging transceivers to
`shown in FIG. 2B, the messages are transmitted only
`maintain synchronization with the system in a manner
`from the remote stations 14 transmitter within the trans
`well known to one of ordinary skill in the art. Such
`mission cell 16 where the acknowledging paging trans
`synchronization allows for decoding of addresses and
`ceiver 18 was located. This method allows interference
`messages to follow, as well as for battery saving pur
`free transmission of lengthy messages on a common
`poses.
`R.F. frequency without interference to the other paging
`Address segment 106, shown in FIG. 3, follows syn
`transceivers 18 also receiving lengthy messages in other
`chronization codeword 104. The POCSAG signaling
`transmission cells. Interference-free transmission is as
`format is shown for example in address segment 106 of
`sured by providing simultaneous message transmission
`the preferred embodiment of the present invention and
`in non-adjacent transmission cells. Where simultaneous
`comprises eight frames 108. Each frame includes two
`message transmission is anticipated within adjacent
`address codewords 110, providing for the transmission
`transmission cells, the transmission from one cell to the
`of two addresses per frame. Each address codeword 110
`next would be delayed so as to avoid interference of the
`is a thirty-two bit binary codeword comprising a 31,21
`two messages.
`BCH codeword and a single block error check bit, as is
`In the second embodiment of the present invention
`well known in the POCSAG signaling format. The
`shown in FIG. 2C, messages are transmitted in a man
`addresses are transmitted at the ?rst data bit rate previ
`ner similar to the description of FIG. 2B, except that
`ously described. It will be appreciated by one of ordi
`selected remote station transmitters in transmission cells
`nary skill in the art that other signaling formats, such as
`16 adjacent to the transmission cell in which portable
`the Golay Sequential Code, or GSC signaling format,
`transceiver 18 is located are used to provide a localized
`could also be used in the delivery of addresses during
`pseudo-simulcast transmission of the messages. Pseudo
`address segment 106.
`simulcast transmission requires the measurement of the
`Silent carrier (CW) 112, shown in FIG. 3, follows
`propagation delay of the acknowledgment signal to the
`address segment 106. During this time interval, unmod
`central station and each of the remote stations. Once the
`ulated or silent carrier is simulcast transmitted by the
`propagation delays have been determined, the differen
`central and remote stations in the system. Silent carrier
`tial propagation delays between the central station and
`(CW) 112 is used by the paging transceivers to adjust
`the remote stations can be determined. This information
`transmitter frequency and power output prior to the
`together with the location of the paging transceiver
`transmission of an acknowledgement signal acknowl
`determined using the received signal strength permits
`edging the reception of the address, thereby guarantee
`the selection of one or more additional transmitters in
`ing known acknowledgement response characteristics.
`adjacent transmission cells to be used for transmission
`The transmitter frequency adjustment process is de
`thereby allowing high data bit rate transmissions with
`scribed in detail in copending U.S. patent application
`out experiencing large differential propagation delays
`Ser. No. 07/141,655, ?led Jan. 7, 1988, entitled “Ac
`which would otherwise corrupt the transmission. Infor
`knowledge Back Pager with Apparatus for Controlling
`mation on differential propagation delays can be in
`Transmit Frequency”, and U.S. patent application Ser.
`cluded with the address and message information dur
`No. 07/ 141,653, ?led Jan. 7, 1988, entitled “Acknowl
`ing the transmission of the burst signal allowing phasing
`edge Back Pager with Frequency Control Apparatus”.
`corrections to be made for the transmissions of adjacent
`The power output level adjustment is described in co
`remote station transmitters. Such pseudo-simulcast
`pending U.S. patent application No. 07/ 141,370, ?led
`transmission is advantageous in providing more reliable
`Jan. 7, 1988, entitled “Acknowledge Back Pager with
`message delivery, especially in those geographic areas
`Adaptive Variable Transmitter Output Power”. The
`common between adjacent transmission cells 16, and in
`three applications are assigned to the assignee of the
`other locations such as buildings, where transmission
`present invention, and are hereby incorporated for ref
`losses from a particular transmitter may be extremely
`erence herein.
`high so as to degrade message delivery. Compared to
`Message segment 114, shown in FIG. 3, follows silent
`the single transmitter transmission of FIG. 2B, a 3 dB
`carrier (CW) 112. Message segment 114 includes a plu
`improvement in signal strength is obtained with two
`rality of message blocks 116 corresponding to addresses
`stations operating, a 5 dB improvement is obtained with
`transmitted during the previous transmission cycle.
`three, stations operating, and a 6 dB improvement is
`Each message block 116 includes transmitter control
`obtained with four stations operating. Beyond four sta
`information identifying one or more remote stations
`tions, the complexity of phase correcting the transmis
`which will be used to transmit each message, the ad
`sions of multiple stations'for the high bit rate transmis
`dress associated with the message, and an end of mes
`sions becomes extremely complex. Pseudo-simulcast
`sage indicator, which is shown in greater detail in FIG.
`transmission of messages also minimizes the problem of 65
`4. Unlike address segment 106, it will be appreciated
`transmitting different messages in adjacent transmission
`message segment 114 is not a ?xed number of data
`cells, as previously described in the non-simulcast mode
`blocks in length, but rather varies depending upon the
`of operation.
`length of the message to be transmitted. Message seg
`
`35
`
`45
`
`20
`
`

`
`7
`ment 114 is transmitted at the second data bit rate of
`2400 or 4800 bits per second, as previously described.
`The second data bit rate provides for the transmission of
`two to eight times the message length in a time interval
`equal to the first data bit rate of 512 or 1200 bits per
`second, thereby greatly increasing message throughput.
`Acknowledgement signals (PACKS) 118, shown in
`FIG. 3, are transmitted simultaneously by all paging
`transceivers having received and detected an address
`during address segment 106. PACKS 118 can be en-
`coded by several methods, one of which is described in
`copending U.S. patent application Ser. No. 07/141,654
`filed Jan. 7, 1988, entitled “Frequency Division Multi-
`plexed Acknowledge Back Paging System”, which is
`assigned to the assignee of the present invention, and is
`hereby incorporated for reference herein. Patent appli-
`cation Ser. No. 07/ 141,654 describes a frequency divi-
`sion multiplex method allowing a group of paging trans-
`ceivers to simultaneously acknowledge during a com-
`mon time interval. In the preferred embodiment of the
`present
`invention,
`sixteen paging transceivers are
`shown potentially responding, although it will be appre-
`ciated that more or less paging transceivers may ac-
`knowledge in the time interval provided. An alternate
`embodiment for encoding the acknowledgement signals
`for simultaneous transmission to the remote stations is
`described in copending U.S. patent application Ser. No.
`7/141,656, filed Jan. 7, 1988, entitled “Code Division
`Multiplexed Acknowledge Back Paging System”,
`which utilizes orthogonal codes to provide code divi-
`sion multiplexing of the encoded acknowledgement
`signals onto a common carrier frequency, which is
`hereby incorporated by reference herein.
`PACKS 118, received at the central and remote sta-
`tions, are processed to identify the responding paging
`transceivers, and to determined the received signal
`strength at each remote station. Processing of the re-
`ceived PACKS include decoding the PACKS, error
`correcting the resultant information, and re-encoding
`the resultant information for SACK transmission. This
`results in enhanced reliability in the location of respond-
`ing paging transceivers. Time of acknowledgement
`reception may also be obtained at this time, as will be
`described in detail later. The received signal strength
`and time of reception information is encoded into a
`suitable format for transmission from the remote sta-
`tions to the central station during the system acknowl-
`edgement time interval (SACKS) 120. SACKS 120 are
`transmitted from the remote stations to the central sta-
`tion also at a high data bit rate, such as 9600 bits per
`second. Once the received signal strength and time of
`reception information is received from all remote sta-
`tions in the system, the information is processed at the
`central station to identify the transmission