United States Patent [191
`Siwiak et al.
`
`[11] Patent Number:
`[45] Date of Patent:
`
`4,875,038
`Oct. 17, 1989
`
`[75]
`
`[54] FREQUENCY DIVISION MULTIPLEXED
`ACKNOWLEDGE BACK PAGING SYSTEM
`Inventors: Kazimierz Siwiak, Coral Springs;
`Leon Jasinski, Fort Lauderdale;
`Francis R. Steel, Parkland, all of Fla.
`[73] Assignee: Motorola, Inc., Schaumburg, Ill.
`[21] Appl. No.: 141,654
`[22] Filed:
`Jan. 7, 1988
`[51] Int. Cl.4 ............................................... H04Q 9/00
`[52] U.S. Cl . .......................... 340/825.44; 340/825.47;
`379/57; 370/76
`[58] Field of Search ...................... 340/825.44, 825.47,
`340/825.48, 311.1; 370/92, 93, 94, 50, 69.1, 73,
`76; 379/56, 57; 455/31, 89, 92
`References Cited
`U.S. PATENT DOCUMENTS
`3,573,379 4/1971 Schmitz ................................. 370/76
`3,973,200 8/1976 Akerberg ....................... 340/825.44
`4,194,153 3/1980 Masaki et al ..
`4,208,630 6/1980 Martinez ............................... 455/31
`4,352,955 10/1982 Kai et al ................................ 379/57
`4,392,242 7/1983 Kai .
`
`[56]
`
`4,466,001 8/1984 Moore et al .................... 340/825.47
`4,590,473 5/1986 Burke et al ..................... 340/825.44
`4,604,583 8/1986 Aoyagi et al ..
`4,636,741 1/1987 Mitzlaff .
`4,646,082 2/1987 Engel et al ..................... 340/825.44
`4,654,882 3/1987 Ikeda .
`4,713,808 12/1987 Gaskill et al .......................... 270/93
`
`Primary Examiner-Gerald Brigance
`Attomey, Agent, or Firm-William E. Zitelli; Vincent B.
`Ingrassia
`ABSTRACT
`[57]
`An acknowledge back (ack-back) paging system is pro(cid:173)
`vided which includes a central station which transmits a
`group of message signals to a group of ack-back pagers
`which are addressed as a group. The users of the group
`of addressed ack-back pagers indicate a response to
`their respective pagers thus providing ack-back data.
`The pagers in the group of addressed ack-back pagers
`then simultaneously transmit back to the central station
`their ack-back data on different frequency sub-bands, a
`different frequency sub-band being allocated to each of
`the pagers in the group.
`
`21 Claims, 9 Drawing Sheets
`
`llO
`
`CENTRAL
`STATION
`(PAGING
`lt:RMINAL)
`
`ACK BACK
`PAGER 122
`
`130
`
`NON
`ACK BACK
`PAGER
`
`ACK BACK
`PAGER P
`
`Apple Exhibit 1009
`Apple Inc. v. Rembrandt Wireless
`IPR2020-00033
`Page 00001
`
`

`

`U.S. Patent
`
`oct.11, 1989
`
`Sheet 1 of 9
`
`4,875,038
`
`FIG.1
`10
`
`D DD D
`
`D
`ON/OFF
`
`D DD D
`
`CJ
`ON/OFF
`
`1
`
`2
`
`CJ
`
`CJ CJ
`
`CJ
`
`3
`
`D
`ON/OFF
`
`• • • •
`
`D
`
`CJ D
`
`D
`
`N
`
`CJ
`ON/OFF
`
`20
`
`D
`
`KEYBOARD
`
`PAGING
`ENCODER 11---_...,. TRANSMITTER
`
`IPR2020-00033 Page 00002
`
`

`

`U.S. Patent
`
`oct.17, 1989
`
`Sheet 2 of 9
`
`4,875,038
`
`FIG.2
`100
`
`110
`
`CENTRAL
`STATION
`~PAGING
`T RMINAL)
`
`ACK BACK
`PAGER 121
`
`z
`
`...
`
`ACK BACK
`PAGER 122
`
`1.30
`
`NON
`ACK BACK
`PAGER
`
`ACK BACK
`PAGER P
`
`FIG.3
`110
`
`180
`
`141 T
`E
`L
`E
`142 p
`H
`0
`N
`•
`E
`•
`I
`• N
`T
`E
`149 R
`F 140
`A
`C
`E
`
`150C
`
`1500
`
`1508
`
`MICROCOMPUTER
`150
`
`150E
`
`190
`
`LEVEL
`SHIFTER
`
`210
`
`200
`
`TRANS-
`MITTER
`
`150A
`150G
`DATA
`
`150F
`CONTROL
`
`240C
`
`I
`
`Q
`
`220
`2.30
`
`230A
`
`RECEIVER
`
`240 240A
`DIGITAL
`SIGNAL
`PROCESSOR
`2400
`2408 2.30B
`
`IPR2020-00033 Page 00003
`
`

`

`TIME
`
`..
`
`Tl ME
`
`-
`
`CENTRAL STATION RBCEIVBR
`
`FIG.4D
`
`TIME
`
`-,
`I
`
`.
`
`EOM
`
`TRANSMITTER
`MESSAGE M
`
`• • •
`
`'\
`
`430
`
`'
`EOM
`
`T4-
`
`TRANSMITTER
`MESSAGE 2
`
`,-
`
`I
`
`'
`
`EOM
`
`TRANSMITTER
`MESSAGE 1
`
`.
`)"
`370
`
`'\
`
`330
`
`FIG.4C
`
`I _l_L_n --TIM;
`
`-----ii
`
`I l~I JI L...L...L.. _I I ...LL.LI
`
`i'll.......L....J.1_1.1........1..-LI 1 _1-1-.LJ.I
`
`310d-L.....l-Jr_,
`
`FIG. 4 Bl i----_
`
`_______ __,,.,....___ _____ _
`
`ADDRESSES
`
`CENTRAL STATION TRANSMITTER
`
`...
`
`T4-
`
`1,2 ........ M
`MESSAGES
`
`SENT
`
`•
`
`Tl
`
`(Fioo
`CARRIER
`REFERENCE
`
`..
`
`.,..-330
`
`,,,-320
`
`,,,-310
`
`FIG.4A
`
`T2
`
`I~
`
`-j T1
`
`PAGER ADDRESSES
`
`1,2 •••••••• M
`
`SENT
`
`30Q..,...
`
`PREAMBLE
`
`{
`
`IPR2020-00033 Page 00004
`
`

`

`TIME
`
`.,I
`
`T5
`
`~..
`
`T6
`
`•I ..
`
`1-.. --n
`
`1-T3 -1
`
`-I T1 114-•---12 -------.i .. l
`
`AB-M
`
`FIG.4G
`
`•SLEEP"
`GOTO
`
`450
`
`SUB CHANNEL M
`
`SEND ACK BACK
`
`.
`
`ON
`
`• • •
`
`RECEIVED 380
`REFERENCE
`
`(FR)()
`
`420
`
`• • •
`
`340
`
`RECBVED
`MESSAGE M
`440
`
`410
`
`360
`
`RECEIVED
`ADDRESS M
`
`RECEIVED 350 400
`PREAMBLE
`
`TIME
`
`TS----~
`
`~•
`
`T6
`
`AB-2
`
`"SLEEP"
`GOTO
`
`450
`
`SUB CHANNEL 2
`
`SEND ACK BACK
`
`ON
`
`RESPONSE
`INDICATES
`
`USER
`
`415
`
`410
`
`RECENED
`MESSAGE 2
`
`360
`
`FIG.4F
`
`-I T1 -1•---T2---•I
`
`400
`
`340
`
`RECEIVED
`ADDRESS 2
`
`RECEIVED 350
`PREAMBLE
`
`TIME
`
`TS-----•I
`
`•I ..
`
`1-.. ---n ----• .... l•--Ts
`
`-In -l•---12-----1
`
`AB-1
`
`FIG.4E
`
`"SLEEP"
`GO TO
`
`390
`
`SUB CHANNEL 1
`
`SEND ACK BACK
`
`ON
`
`RESPONSE
`INDICATES
`
`USER
`
`• • •
`
`RECEIVED
`REFERENCE
`
`(FR)C)
`
`385
`
`350
`
`340
`
`RECEIVED
`ADDRESS 1
`
`RECEIVED
`PREAMBLE
`
`IPR2020-00033 Page 00005
`
`

`

`TIME
`
`~
`
`.
`
`UNPAGED PAGER
`
`AB-U
`
`.
`
`"SLEEP''
`GO TO
`
`FIG.4I
`
`RECEIVED
`ADDRESS
`NO VALID
`
`(
`
`(
`480
`
`RECEIVED
`PREAMBLE
`
`1
`
`'
`-(
`340
`
`\.0
`00
`\.0
`~
`"'
`-l
`~
`
`0 p.
`("0 a
`~ f"'+-
`~ r.n
`
`•
`
`TIME
`
`'-l•---T4-------'•I
`
`NO~ ACK BACK PAGER
`
`AB-3
`
`,
`
`FIG.4H
`
`RECEIVED
`PREAMBLE
`
`380
`
`460
`
`340
`
`RECEIVED
`MESSAGE 3
`
`410
`
`RECEIVED
`RECEIVED 350 400 ADDRESS 3
`PREAMBLE
`
`IPR2020-00033 Page 00006
`
`

`

`U.S. Patent Oct. 17, 1989
`
`Sheet 6 of 9
`
`4,875,038
`
`INITIALIZATION AND
`POWER ON RESET
`
`I=O
`M=20
`
`FIG.5
`
`INPUT MESSAGE
`
`STORE MESSAGE IN RAM
`
`COUNT MESSAGES I=I+ 1
`
`540
`
`N
`
`TRANSMIT PREAMBLE
`
`LOOK UP AND RETRIEVE ADDRESSES
`CORRESPONDING TO M PAGERS FROM MEMORY
`
`RESET I= 1
`
`RETRIEVE ADR I
`
`TRANSMIT ADR I
`
`600
`
`N
`
`I= I+ 1
`
`TRANSMIT REFERENCE CARRIER FR
`
`RESET I= 1
`
`RETRIEVE MESSAGE I
`
`TRANSMIT MESSAGE I
`
`TRANSMIT EOM MARKER
`
`670
`
`N
`
`690
`
`680
`
`I= I+ 1
`
`700
`
`PAUSE INDICATE RESPONSE
`
`RECEIVE ACK BACK SIGNALS FROM
`THE GROUP OF M ADDRESSED PAGERS
`
`IPR2020-00033 Page 00007
`
`

`

`QC
`Q w
`-...
`Ul
`-....,l
`QC
`-...
`.a;.
`
`\0
`
`s,
`-l
`~
`=-
`~
`
`TJ.l
`
`\0
`QO
`\0
`1--1-
`..,,
`-l
`1--1-
`p.
`0
`
`a
`n>
`fl""+,-
`~
`•
`rJJ.
`~
`
`950
`
`960
`
`920
`
`USER REPLY
`
`INPUT
`
`CLOCK
`
`EEPROM
`MEMORY
`
`RAM
`
`DISPLAY
`
`G F C
`0
`0
`2
`2
`8
`8
`
`0
`2
`8
`
`DATA
`REPLY
`8201
`
`MCC1468705G2
`
`820E
`
`820
`
`SUPPORT
`
`LINEAR
`
`MICRO COMPUTER
`
`820L
`
`1020A
`
`N
`FLO
`
`: N
`
`1010
`FLD
`
`FLO
`
`990
`
`DATA
`
`DETECTOR
`THRESHOLD
`
`Fe
`
`1050
`
`8508
`
`870
`
`AUDIO
`
`DEMOD.
`
`940
`
`930
`
`900
`
`890
`
`FILTER
`
`840
`
`FRX
`
`830
`
`FILTER
`
`1030
`
`FIG.6
`
`121
`
`1040
`
`1040A
`
`810C
`
`810D
`
`SWITCH
`RECEIVE
`TRANSMIT
`
`8108
`
`810
`
`800
`
`IPR2020-00033 Page 00008
`
`

`

`U.S. Patent
`
`oct.11, 1989
`
`Sheet 8 of 9
`
`4,875,038
`
`AB PAGER
`
`SUB-BAND#
`
`FREQUENCY
`(MHz)
`
`OFFSET (Pn)
`(MHz)
`
`AB-1
`
`AB-2
`
`AB-3
`
`AB-4
`
`AB-5
`
`AB-6
`
`AB-7
`
`AB-8
`
`AB-9
`
`AB-10
`
`AB-11
`
`AB-12
`
`AB-13
`
`AB-14
`
`AB-15
`
`AB-16
`
`AB-17
`
`AB-18
`
`AB-19
`
`AB-20
`
`1
`
`2
`
`3
`
`4
`
`5
`
`6
`
`7
`
`8
`
`9
`
`10
`
`11
`
`12
`
`13
`
`. 14
`
`15
`
`16
`
`17
`
`18
`
`19
`
`20
`
`149.9905
`
`149.9915
`
`149.9925
`
`149.99.35
`
`149.9945
`
`149.9955
`
`149.9965
`
`149.9975
`
`149.9985
`
`149.9995
`
`150.0005
`
`150.0015
`
`150.0025
`
`150.0035
`
`150.0045
`
`150.0055
`
`150.0065
`
`150.0075
`
`150.0085
`
`150.0095
`
`-.0095
`
`-.0085
`
`-.0075
`
`-.0065
`
`-.0055
`
`-.0045
`
`-.0035
`
`-.0025
`
`-.0015
`
`-.0005
`
`.0005
`
`.0015
`
`.0025
`
`.0035
`
`.0045
`
`.0055
`
`.0065
`
`.0075
`
`.0085
`
`.0095
`
`FIG.7
`
`IPR2020-00033 Page 00009
`
`

`

`U.S. Patent
`
`·oct.11, 1989
`
`Sheet 9 of 9
`
`4,875,038
`
`POWER ON RESET
`
`1100
`
`FIG.B
`
`RECEIVE PREAMBLE
`
`WAKE-UP PAGER
`
`ADRCOUNT = 0/ADR MAX = M
`
`1150
`
`COUNT PAGER ADDRESSES
`ADR COUNT=
`ADR COUNT+ 1
`
`COUNT PAGER ADDRESSES
`ADR COUNT = ADR COUNT + 1
`
`COUNT FREQUENCY OF REFERENCE
`CARRIER Fe AND STORE Fe
`
`N
`
`1190
`
`MEASURE AND STORE SIGNAL
`STRENGTH OF CARRIER Fe
`
`1200
`
`1320
`
`1170
`
`ENTER
`BATTERY
`SAVER
`MODE
`
`MSG COUNT= 0
`
`RECEIVE NEXT MESSAGE
`
`MSG COUNT = MSG COUNT + 1
`
`COMPUTE N= F RX - Fe
`Fo + Fe
`
`SET DIVIDER TO N VALVE TO
`SET FREQUENCY OF ACK BACK TX
`
`1330
`
`N
`
`N
`
`1J60
`
`y
`
`DUPLICATE MESSAGE
`
`DETERMINE ACK BACK DATA
`
`WAIT FOR ACK BACK FIELD
`
`TURN TRANSMITTER CIRCUITS ON
`
`TRANSMIT ACK BACK
`DATA AT LOW POWER
`VIA
`FDM
`
`1380
`
`SELECT ONE OF M SUB-BANDS FOR
`ACK BACK BASED ON ADR COUNT
`
`LOOK UP FREQUENCY OFFSET
`F0 CORRESPONDING TO THE
`SELECTED SUB-BAND
`
`1290
`
`LOOK UP FRX
`
`RETRIEVE Fe
`
`TURN TRANSMITTER CIRCUITS ON
`
`TRANSMIT ACK BACK
`DATA AT HIGH POWER
`VIA
`FDM
`
`TURN TRANSMITTER CIRCUITS OFF
`
`IPR2020-00033 Page 00010
`
`

`

`1
`
`4,875,038
`
`2
`one of the sub-bands exhibiting a predetermined rela(cid:173)
`tionship to the order of the address of the pager within
`the batch of M addresses.
`The features of the invention believed to be novel are
`5 specifically set forth in the appended claims. However,
`the invention itself, both as to its structure and method
`of operation, may best be understood by referring to the
`following description and the accompanying drawings.
`
`FREQUENCY DMSION MULTIPLEXED
`ACKNOWLEDGE BACK PAGING SYSTEM
`
`BACKGROUND OF THE INVENTION
`This invention relates in general to radio communica(cid:173)
`tions systems. More particularly, the invention relates
`to radio paging systems.
`In the past several years, radio paging technology has
`advanced from the rather simple tone-only pager (tone 10
`alert only, no voice), to the tone and voice pager (tone
`alert with a voice message) and more recently to the
`alphanumeric display pager. In a typical conventional
`alphanumeric display paging system such as that shown
`as system 10 in FIG. 1, a central transmitter or paging 15
`terminal 20 is used to generate the radio pages which
`are transmitted via a radio link to a fleet of paging re(cid:173)
`ceivers 1, 2, 3 ... N, wherein N is the total number of
`pagers in system 10. A unique digital address is associ(cid:173)
`ated with each of paging receivers 1, 2, 3 .. . N. A page 20
`which is transmitted by paging terminal 20 consists of
`the unique digitally encoded address of the particular
`pager to which the page is targeted, immediately fol(cid:173)
`lowed by a corresponding digitally encoded numeric or
`alphanumeric page message which is intended for dis- 25
`play on the target pager.
`Typically, the numeric or alphanumeric page mes(cid:173)
`sage is stored in a memory within the paging receiver
`for later recall and display by the pager user. Paging
`receivers are available with a wide range of message 30
`storage capabilities which range from the ability to
`store just a few rather short numeric page messages to
`the ability to store a relatively large number of longer
`alphanumeric page messages.
`However, conventional display paging systems are 35
`generally one way systems. That is, the user receives a
`paging message from the central terminal but has no
`way of responding to that message with his or her
`pager. Instead, the pager user must seek out a telephone
`or other means of responding to the originator of the 40
`paging message.
`
`BRIEF SUMMARY OF THE INVENTION
`Accordingly, it is one object of the present invention
`is to provide a paging system in which the radio pager 45
`is capable of respqnding back to the paging terminal and
`the caller.
`Another object of the present invention is to provide
`a radio paging system in which a group of addressed
`pagers are capable of simultaneously transmitting ac- 50
`knowledge back signals on a plurality of respective
`predetermined sub-band frequencies.
`In one embodiment of the invention, an acknowledge
`back pager is provided which has a unique address
`associated therewith. The pager includes a receiver for 55
`receiving paging signals from a central station. Such
`paging signals include a batch of M pager addresses
`transmitted in a sequential order during a first time
`frame, wherein M is the number of pager addresses in
`the batch. The pager further includes a decoder, cou- 60
`pied to the receiver, for detecting the presence of the·
`pager's address within the batch of M addresses. An
`address order determining apparatus is coupled to the
`decoder for determining the order of the pager's ad(cid:173)
`dress within the batch of M addresses. The pager fur- 65
`ther includes a sub-band transmitter for transmitting an
`acknowledge back signal on a selected one of a plurality
`of M predetermined frequency sub-bands, the selected
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 is a block diagram of a conventional display
`type radio paging system.
`FIG. 2 is a block diagram of the ack-back paging
`system of the present invention.
`FIG. 3 is a block diagram of the central station em(cid:173)
`ployed in the paging system of FIG. 2.
`FIG. 4A is a time vs. event representation of the
`transmissions from the central station of the system of
`the invention.
`FIG. 4B is a representation of an address block used
`in the paging protocol of the paging system of the in(cid:173)
`vention.
`FIG. 4C is a representation of a message block used in
`the paging protocol of the paging system of the inven(cid:173)
`tion.
`FIG. 4D is a time vs. event representation of the
`receiver portion of the central station.
`FIG. 4E is a time vs. event representation of the
`activity of ack-back pager AB-1.
`FIG. 4F is a time vs. event representation of the
`activity of ack-back pager AB-2.
`FIG. 4G is a time vs. event representation of the
`activity of ack-back pager AB-M.
`FIG. 4H is a time vs. event representation of the
`activity of a non ack-back pager in the paging system of
`the invention.
`FIG. 41 is a time vs. event representation of the activ(cid:173)
`ity of an unpaged ack-back pager in the paging system
`of the invention.
`FIG. 5.is a flowchart depicting the operation of the
`central station in the paging system of the invention.
`FIG. 6 is a block diagram of one of the ack-back
`pagers employed in the paging system of the invention.
`FIG. 7 is subchannel frequency look-up table em(cid:173)
`ployed by the ack-back pagers in the system of the
`invention.
`FIG. 8 is a flowchart of the operation of the ack-back
`pagers of the paging system of the invention.
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`FIG. 2 is a simplified block diagram of the acknowl(cid:173)
`edge back paging system 100 of the present invention.
`Paging system 100 includes a central station or paging
`terminal 110 which is capable of both transmitting out(cid:173)
`going paging signals and of receiving acknowledge
`back (ack-back) paging signals. Paging system 100 in(cid:173)
`cludes a plurality of ack-back pagers 121, 122 ... P,
`wherein P is the total number of ack-back pagers in the
`pager population of system 100. Each of ack-back pag(cid:173)
`ers 121, 122 ... P has the capability of receiving paging
`signals from central station 110 and of permitting the
`pager user to respond to such paging signals. That is,
`pagers 121, 122 ... P permit the user to reply or ac(cid:173)
`knowledge back to a page from central station 110. It is
`noted that conventional non ack-back pagers such as
`pager 130 are also ineluctable in system 100. In FIG. 2,
`
`IPR2020-00033 Page 00011
`
`

`

`25
`
`3
`double arrows between central station 110 and each of
`ack-back pagers 121, 122 ... P are used to denote that
`two way communication exists between central station
`110 and such ack-back pagers. A single arrow denotes
`that only one way communication exists between sta- 5
`tion 110 and pager 130.
`FIG. 3 is a more detailed block diagram of central
`station or paging terminal 110. Central station 110 in(cid:173)
`cludes a conventional telephone interface 140 of the
`type generally used for central paging terminals. Tele- 10
`phone interface 140 couples outside telephone lines 141,
`142, etc. to an input 150A of a microcomputer 150.
`Telephone interface 140 converts message signals from
`lines 141, 142, etc. to digital signals which microcom(cid:173)
`puter 150 can process. For example, a caller wishing to 15
`send an alphanumeric page to an ack-back pager user
`uses dual tone multi frequency (DTMF) to key in a
`desired message. Telephone interface 140 then converts
`such analog DTMF alphanumeric message to its digital
`equivalent which microcomputer 150 processes as dis- 20
`cussed later in more detail. Central station 110 further
`includes a keyboard 160 coupled to a data input 150B of
`microcomputer 150. Keyboard 160 permits an operator
`to directly input messages into microcomputer 150 for
`transmission to pagers within the pager population.
`A read only memory (ROM) 170 is coupled to a
`memory port 150C of microcomputer 150. ROM 170
`includes a control program which controls the opera(cid:173)
`tion of microcomputer 150 and the circuits coupled
`thereto. A random access memory (RAM) 180 is cou- 30
`pied to a memory port 150D microcomputer 150. RAM
`180 provides temporary storage space for microcom(cid:173)
`puter 150 as it carries out the instructions of the control
`program within ROM 170.
`When a paging message and the identity of the partic- 35
`ular pager to be addressed are provided to microcom(cid:173)
`puter 150, the control program causes microcomputer
`150 to generate digital paging signals at its output 150E
`according to the protocol later described. Microcom(cid:173)
`puter output 150E is coupled via a level shifter 190 to 40
`the input of a transmitter 200. The output of transmitter
`200 is coupled to an antenna 210 having dimensions and
`characteristics appropriate to the particular paging fre(cid:173)
`quncy channel selected for the operation of central
`station 110. Level shifter 190 serves to adjust the signal 45
`level of the paging signals generated at microcomputer
`output 150E to a level appropriate for the input of trans(cid:173)
`mitter 200.
`For purposes of this example, it will be assumed that
`ack-back pagers 121, 122-P are acknowledging back via 50
`phase shift keyed (PSK) digital modulation. Those
`skilled in the art will appreciate that other forms of
`modulation as well may be employed by acknowledge
`back pagers 121, 122-P to respond to the paging signals
`transmitted by central station 110. In such a PSK em- 55
`bodiment, central station 110 includes a receive antenna
`220 for receiving the ackback signals transmitted by
`ack-back pagers 121, 122-P. In actual practice, antenna
`210 may also be employed as antenna 220. Receive
`antenna 220 is coupled to the input of a PSK receiver 60
`230 which includes an in-phase (I) output 230A and a
`quadrature (Q) output 230B. Receiver outputs 230A
`and 230B are respectively connected to inputs 240A and
`240B of digital signal processor 240. One digital signal
`processor which may be employed as processor 240 is 65
`the model DSP56000 manufactured by Motorola, Inc.
`Digital signal processor 240 includes a control input
`240C which is coupled to a control output 150F of
`
`4,875,038
`
`4
`microcomputer 150 to permit microcomputer 150 to
`control processor 240. Digital signal processor 240 fur(cid:173)
`ther includes a data output 240D which is coupled to
`the data input 1500 of microcomputer 150. Thus, it is
`seen that digital signal processor 240 decodes the digital
`data received at the I and Q inputs 240A and 240B
`thereof and transforms such information into digital
`data which is provided to microcomputer data input
`1500.
`FIG.'s 4A-4I are timing diagrams which show the
`signaling protocol employed by central station 110 and
`ack-back pagers 121, 122-P. More specifically, FIG. 4A
`is a simplified timing diagram of the paging protocol
`transmitted by central station 110. In FIG. 4A, time is
`represented on the horizontal axis and respective events
`are denoted as they occur at designated points in time
`along such time axis. Central station 110 first transmits
`a preamble signal 300 during a time interval Tl. In one
`embodiment, preamble symbol 300 consists of a plural(cid:173)
`ity of alternating O's and 1 's transmitted for a duration of
`time Tl. For example, preamble symbol is a 010101 •••
`signal.
`In accordance with the present invention, central
`station 110 groups paging addresses into groups of M
`wherein M is the number of paging addresses in a partic(cid:173)
`ular group. For purposes of this example, and not by
`way of limitation, the number of paging addresses and
`thus the number of messages corresponding to such
`addresses is selected to be 20 (that is, M=20). That is, as
`messages are called into central station 110 via tele(cid:173)
`phone interface 140 or keyboard 160, such paging mes(cid:173)
`sages and corresponding address information are held
`or stored in RAM 180 until a group of up to M = 20
`messages has been provided to station 110. In alterna(cid:173)
`tive embodiments of the invention, non ack-back pages
`may be interspersed with ack-back pages to increase the
`efficient throughput of the paging system if desired as
`will be discussed later. The group of M=20 ack-back
`pagers is a subgroup of the overall population of P
`pagers. Once station 110 has received 20 or M paging
`messages, microcomputer 150 sequentially transmits the
`20 corresponding addresses as a group 310 during a time
`interval T2 subsequent to time interval Tl as shown in
`FIG. 4A.
`FIG. 4B shows the sequential relationship of each of
`the addresses within group 310. The addess of the first
`pager of the group ofM pagers to be addressed is desig(cid:173)
`nated address 1 and is transmitted first in group 310 as
`shown. The pager to which address 1 corresponds is ·
`designated AB-1 for reference. The address of second
`pager of the group of M selected ack-back pagers -is
`designated address 2 and is transmitted immediately
`following address 1. The pager to which address 2 cor(cid:173)
`responds is designated pager AB-2. This process of
`address transmission continues sequentially in the same
`fashion until all of the addresses of the group of M
`pagers are transmitted ending with address M, the ad(cid:173)
`dress of the last or M'th pager in group 310. The pager
`to which address M corresponds ss designated pager
`AB-M. A non-ack back pager AB-3 is shown addressed
`in the block of M pages as will be described later in the
`discussion of FIG. 4H.
`In one embodiment of the invention, the duration of
`time during which preamble signal 300 is transmitted,
`namely Tl, is approximately equal to 10 msec. Those
`skilled in the art will appreciate that Tl may have val(cid:173)
`ues greater than or less than 10 msec providing Tl is
`sufficiently long to permit the ackback receivers 121,
`
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`4,875,038
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`20
`
`5
`122 ... P to synchronize to the paging signals transmit(cid:173)
`ted by central station 110. Apparatus for synchronizing
`paging receivers to paging signals is well known to
`those skilled in the art and is included in ack-back pag(cid:173)
`ers 121, 122 ... P.
`For purposes of example, the time duration T2 of the
`group 310 of addresses is selected to be approximately
`equal to 1 sec. Those skilled in the art will appreciate
`that T2 may actually be greater or less than 1 sec de(cid:173)
`pending upon the number of paging addresses M se- 10
`lected to be in the group 310 and the frequency of trans(cid:173)
`mission of the digital data comprising such paging ad(cid:173)
`dresses. The selection of the time period T2 in this ex(cid:173)
`ample should not be taken as in any way limiting the
`invention. To reiterate, the particular pagers of the 15
`population P which are addressed in address block 310
`are designated as pagers AB-1 (the first pager to be
`addressed), pager AB-2 (the second pager to be ad(cid:173)
`dressed) ... pager AB-M (the last pager addressed of the
`group of M pagers).
`After transmission of the group of M addresses, cen(cid:173)
`tral station 110 transmits a reference carrier signal at a
`frequency FRXat 320 during a time interval T3 follow(cid:173)
`ing time interval T2. Subsequent to transmission of
`reference carrier 320, central station 110 sequentially 25
`transmits the 20 paging messages corresponding to the
`20 paging addresses of address group or block 310.
`More specifically, these Mor 20 data messages are sent
`as a group or block 330 of messages. Each of the M
`messages in block 330 bears a predetermined relation- 30
`ship to the order of the pager addresses in block 310.
`For example, in one embodiment of the invention and as
`shown more clearly in FIG. 4C, message block 330
`includes message 1 data followed in time by an end of
`message (EOM) field. The EOM field of message 1 is 35
`followed sequentially in time by the message 2 data
`which is in turn followed by another EOM field. The
`process of sending the respective messages 3, 4, etc.
`within message block 330 continues until message M is
`transmitted followed by a respective EOM field as 40
`shown in FIG. 4C.
`In the embodiment of the invention described above,
`the predetermined relationship between the sequence of
`messages transmitted in message block 330 and the se(cid:173)
`quence of pager of addresses transmitted in address 45
`block 310, is conveniently selected such that address 1 is
`first transmitted in block 310 and the message 1 corre(cid:173)
`sponding to such address 1 is transmitted first in the
`later following message block 330 occurring during
`time slot T4. To illustrate this predetermined relation- 50
`ship further, address 2 is transmitted second, that is
`immediately after address 1 in address block 310. Corre(cid:173)
`spondingly, in the later following time slot T4, message
`2 is transmitted second, that is, immediately following
`message l's EOM field. The same relationship exists 55
`between the remaining addresses in block 310 and mes(cid:173)
`sages in block 330.
`The invention, however, is not limited to the particu(cid:173)
`lar predetermined relationship described above be(cid:173)
`tween the sequence of pager addresses in address block 60
`310 and corresponding messages in message block 330.
`For example, in another embodiment of the invention,
`the sequence of pager addresses would remain as illus(cid:173)
`trated in FIG. 4B with address 1 being sent first fol(cid:173)
`lowed by address 2 and so forth until address M is trans- 65
`mitted completing the block. However, the sequential
`order in which the messages in message block 330 are
`transmitted in such embodiment may commence with
`
`6
`transmission of message M first followed by message
`M-1 (or message 19) followed by message M-2 (18) and
`so forth until message 1 is final\y transmitted at the end
`of message block 310. (EOM fields are still situated
`5 between messages.) What is important here is that a
`predetermined relationship exists between the order in
`which the paging addresses are transmitted in address
`block 310 to the order in which the paging messages are
`transmitted in message block 330 so as to permit ac(cid:173)
`knowledge back pagers AB-1, AB-2, . . . AB-M to
`match a particular message within block 330 to a re-
`spective paging address of block 310. This enables a
`particular pager to determine which of the 20 paging
`messages in block 330 is intended for it, as will be dis(cid:173)
`cussed subsequently in more detail. Although examples
`have been discussed above wherein the predetermined
`relationship between the order of the pager addresses of
`address block 310 and the paging messages of message
`block 330 are both ascending, and in the other example
`ascending/descending, those skilled in the art will ap(cid:173)
`preciate that an arbitrary relationship between the pag-
`ing addresses on block 310 and the paging messages of
`block 330 may also be selected as long as this predeter(cid:173)
`mined known relationship is programmed into acknowl(cid:173)
`edge back pagers 121, 122 . .. P.
`A reference carrier exhibiting a frequency of F RX is
`generated during a period of time T3 subsequent to the
`end of transmission of the pager addresses in address
`block 310. In one embodiment of the invention, T3 is
`equal to approximately 70 msec. Those skilled in the art
`will appreciate that T3 may be longer or shorter than 70
`msec providing the reference carrier shown at 320 ex(cid:173)
`hibits a time duration sufficiently long to enable fre(cid:173)
`quency determining circuitry, later described, in ack(cid:173)
`back pagers 121, 122 ... P to determine the frequency
`of reference carrier 320.
`FIG. 4D is a time vs. event diagram of the status of
`receiver 230 in central station 110. Subsequent to time
`period T4, receiver 230 at central station 110 is turned
`on to receive ack-back signals from the 20 pagers in the
`group of M during a time period TS. Each of the group
`of M ack-back message signals transmitted by the re(cid:173)
`spective ack-back pagers in the group of M are on a
`different respective frequency sub-band within a com(cid:173)
`mon frequency channel as will be discussed in more
`detail subsequently. Receiver 230 is thus capable of
`distinguishing and decoding message signals on each of
`the 20 or M different sub-band frequencies. The config(cid:173)
`uration and operation of receiver 230 is discussed in
`more detail later.
`FIG. 4E is a time versus event diagram for the status
`of ack-back pager AB-1, that is, the first addressed
`pager of the group ofM pagers. FIG. 4E is drawn to the
`same time scale as FIG. 4A. During the Tl time inter(cid:173)
`val, pager AB-1 receives the preamble at 340. During
`the following time period T2, pager AB-1 receives and
`decodes address 1, which in this example is the address
`of pager AB-1. It is noted that prior to reception of the
`preamble at 340, pager AB-1 is in a "sleep" or "battery
`saver" state. That is, prior to such Tl time period, pager
`AB-1 and the other pagers of the population of P pag-
`ers, have several of their power consuming circuits
`turned off or placed in low power consumption states.
`Those skilled in the art are already familiar with the
`powering down of radio pager circuits in order to
`achieve battery saving and thus exactly which circuits
`in the pager are powered down, and the degree to
`which they are powered down, are not discussed here
`
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`4,875,038
`
`7
`in detail. What is important, however, is that the ack(cid:173)
`back pagers of the population of P pagers are placed in
`a "battery saving" state or "sleep state" during pre(cid:173)
`scribed periods of time such as that mentioned above
`and which will be later specified.
`When pager AB-1 receives the preamble 340 during
`time period Tl, pager AB-1 is switched from a battery
`saving state to a fully operational state such that pager
`AB-1 is capable of receiving information transmitted
`thereto. That is, subsequent to reception of the pream- 10
`bleat 340, pager AB-1 is fully turned on such that pager
`AB-1 receives and decodes its address at 350 at the
`beginning of the T2 time period. In one embodiment of
`the invention, pager AB-1 conveniently returns to the
`"sleep state" for the remainder of the T2 time period 15
`during which pager addresses are transmitted. Prior to
`receiving the reference carrier F RX at time period T3,
`pager AB-1 is returned from the "sleep state" to the
`fully operational state. Upon reception of the reference
`carrier, FR at 360, pager AB-1 determines the fre- 20
`quency of such carrier in a manner described in more
`detail subsequently.
`Referring to FIG. 4E, in conjunction with 4C, it is
`seen that the message 1 transmitted during time period
`T4 at 370 is received by pager AB-1 at 380 as shown in 25
`FIG. 4E. Pager AB-1 receives message 1 at 380 and
`matches message 1 to address 1. That is, by means later
`described in more detail, pager AB-1 is programmed to
`determine that message 1 is the particular message of
`the group of M messages which is intended for pager 30
`AB-1. Subsequent to reception and display of message 1
`at 380 as shown in FIG. 4E, the user of pager AB-1
`indicates his or her response to message 1 during a time
`period T6 at 385. Time period T6 is not drawn to scale
`with respect to the other time periods discussed. Time 35
`period T6 is sufficiently long to permit indication of a
`response by the pager user. Subsequent to time period
`T6, pagers AB-1, AB-2 ... AB-M simultaneously trans(cid:173)
`mit acknowledge back signals on respective frequency
`subbands (subchannels) back to central station 110 as at 40
`390 during a time period TS. Subsequent to the ack-back
`transmission at 390, pagers AB-1, AB-2 ... AB-Mare
`placed in the "sleep state" until awakened again by a
`preamble as at 340. In an alternative embodiment of the
`invention, ack-back pagers AB-1 .. . AB-20 reply back 45
`automatically without action by the pager user. In such
`an embodiment, prior to being paged, the user prese(cid:173)
`lects a reply already stored in the pager or keys into the
`pager a predetermined message which the pager uses as
`the ack back reply when it is later addressed by central 50
`station 1