FILE HISTORY
`US 5,915,210
`
`5,915,210
`PATENT:
`INVENTORS: Cameron, Dennis Wayne
`Roehr, Jr., Walter Charles
`Bhagat, Jai P.
`Garahi, Masood
`Hays, William D.
`Ackerman, David W.
`
`TITLE:
`
`Method and system for providing
`multicarrier simulcast transmission
`
`APPLICATION
`NO:
`FILED:
`ISSUED:
`
`US1997899476A
`
`24 JUL 1997
`22 JUN 1999
`
`COMPILED:
`
`15 DEC 2016
`
`Aruba Networks et al. Exhibit 1002 Page 00001
`
`

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`% 5915210
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`Page 00003
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`08/760,457
`
`METHOD AND SYSTEM FOR PROVIDING MULTICARRIER
`SIMULCAST TRANSMISSION
`
`Transaction History
`
`Transaction Description
`Date
`Incoming Letter Pertaining to the Drawings
`12-06-1996
`12-06-1996 Preliminary Amendment
`12-06-1996 Preliminary Amendment
`01-03-1997
`Initial Exam Team nn
`02-21-1997 Application Captured on Microfilm
`03-07-1997 Case Docketed to Examiner in GAU
`04-25-1997 Mail Notice of Allowance
`04-25-1997 Notice of Allowance Data Verification Completed
`04-25-1997 Mail Examiner's Amendment
`04-25-1997 Examiner's Amendment Communication
`03-25-1998 Mail Abandonment for Failure to Correct Drawings/Oath
`03-25-1998 Abandonment for Failure to Correct Drawings/Oath/NonPub Request
`04-09-1998 Abandonment for Purposes of Filing an FWC - File Combined with Child Application
`
`Page 00004
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`

`
`5,915,210
`
`METHOD AND SYSTEM FOR PROVIDING MULTICARRIER
`SIMULCAST TRANSMISSION
`
`Transaction History
`
`Transaction Description
`Date
`07-24-1997 Preliminary Amendment
`08-21-1997
`Initial Exam Team nn
`08-26-1997
`IFW Scan & PACR Auto Security Review
`09-12-1997 Amendment after Notice of Allowance (Rule 312)
`09-12-1997
`Information Disclosure Statement (IDS) Filed
`09-12-1997
`Information Disclosure Statement (IDS) Filed
`09-15-1997 Application Dispatched from OIPE
`12-19-1997
`Information Disclosure Statement (IDS) Filed
`12-19-1997
`Information Disclosure Statement (IDS) Filed
`04-09-1998 Case Docketed to Examiner in GAU
`04-16-1998 Mail Notice of Allowance
`04-16-1998 Notice of Allowance Data Verification Completed
`04-16-1998 Mail Examiner's Amendment
`04-16-1998 Examiner's Amendment Communication
`06-16-1998
`Issue Fee Payment Verified
`06-16-1998 Mailroom Date of Drawing(s)
`06-19-1998 Application Ordered to Match Drawing(s)
`06-19-1998 Drawing(s) Received at Publications
`06-24-1998 Application Received to Match Drawing(s)
`07-28-1998 Drawing(s) Processing Completed
`07-28-1998 Drawing(s) Matched to Application
`09-15-1998 Date Forwarded to Examiner
`09-23-1998 Mail Response to 312 Amendment (PTO-271)
`09-23-1998 Response to Amendment under Rule 312
`01-06-1999 Mailroom Date of Drawing(s)
`01-08-1999 Drawing(s) Received at Publications
`06-11-1999
`Issue Notification Mailed
`06-22-1999 Recordation of Patent Grant Mailed
`10-27-1999 Post Issue Communication - Certificate of Correction
`11-19-2013 Correspondence Address Change
`11-20-2013 Email Notification
`11-20-2013 Change in Power of Attorney (May Include Associate POA)
`06-27-2014 Petition Requesting Trial
`08-15-2014 Correspondence Address Change
`08-18-2014 Email Notification
`08-18-2014 Change in Power of Attorney (May Include Associate POA)
`10-03-2014 Petition Requesting Trial
`01-22-2015 Request for Trial Granted
`04-08-2015 Request for Trial Granted
`04-27-2015 Termination or Final Written Decision
`05-28-2015 Termination or Final Written Decision
`05-29-2015 Termination or Final Written Decision
`06-06-2015 Case Docketed to Examiner in GAU
`08-13-2015 Petition Requesting Trial
`08-13-2015 Petition Requesting Trial
`02-16-2016 Request for Trial Denied
`02-16-2016 Request for Trial Granted
`02-29-2016 File Marked Found
`03-16-2016 Petition Requesting Trial
`03-16-2016 Petition Requesting Trial
`05-03-2016 Termination or Final Written Decision
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`Page 00005
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`09-21-2016 Request for Trial Denied
`09-21-2016 Request for Trial Denied
`(cid:3)
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`Page 00006
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`Page 00010
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`INDEX OF CLAIMS
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`Page 00014
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`US0059152} i]A
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`United States Patent
`Cameron et 11!.
`
`[19]
`
`[11] Patent Number:
`[45] Date of Patent:
`
`5,915,210
`Jun. 22, 1999
`
`I54] METHOD AND SYSTEM FOR PROVIDING
`MULTICARRIER SIMULCAST
`TRANSMISSION
`
`{'75}
`
`Inventors: Denim Wayne Cameron, Jackson.
`Missx, Walter Charles Rnellr, Jr..
`Reaton, \Ih.; J3! P. Bhagal. Jackson,
`Miss; Mnsood Glnltl. Madison.
`Misss, Wililnm D. Hays. Jaclcsorl.
`M1355, David W. Ackermnn,
`Washington. D12.
`
`['13] As-signee: Datlnaer Corpnrallnn, Jackson, Mist
`
`1211
`122]
`
`.4pp1.No.: 04:71:99,474
`Filed:
`Jul. 24, 1997
`Related U.S. Application Data
`[63] Conmualion of application No. 087':'60,4$‘P, Dec. (1. 1996,
`abandoned, which is a wutinunlion of uppliuatiun Nu.
`071i9'1'3,915~. New. 12, 1992. Pat. No. 5,590,403.
`Inl.CI.‘
`1104131730
`[51]
`[523 U.s.cI.
`4531.159,-45571112:-45571113
`
`[53]
`Fleld ofsearch.
`. .............4s57502.s03.
`4557507. 509. 515. 510. 517, 524, 59, 60.
`02, 03, 07.1, 07.3, 57.6. 101. 102, 103;
`3757200. 267, 299; 3707343, 344
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`171970 Chung.
`1071975 Scinlcl.
`971930 Hullori 41.1.
`171931 Rcrkins.
`771933 Kai
`
`3,433,445
`3,914,554
`4,223,405
`4,244,047
`4,392,242
`
`..-4557101
`.4SS.'33.1
`
`455159
`455759
`
`4557512
`
`3757299
`
`459101
`
`4.490313 t27"l.9G4
`4,505,334
`371935
`
`4,570,205
`271934
`|t,?Ol,'l'58 101F198’? Dunkcnon et al. .
`771939 91333443.
`4,350,032
`4,968,950
`1171990 Juimki
`5,123,934
`771992 1311.311.
`5,163,181
`1111992 Koonu.
`971993 17.31 ,.
`5243.429
`
`5,143,499
`371994 Jnspe
`271995 Duis.
`5,192,452
`5,50-1,783
`471996 Tbminlo el II.
`FOREIGN PA'IEN'I' DOCUMENTS
`WO 90764131!
`411990 European Pet. Of
`177091710453
`1171991 wwo
`W09IJ'1l’1"07
`111992 WFPO ..
`
`Primary E.'.ur7r1.irner--'l'han|1 Cong Le
`Aaorney, 7132117, or F7'nr7—Finnegan. Henderson. Farnbow,
`t'larn:11 & Dunner
`ABSTRACT
`[51]
`A two-way Gtlrnmunicalion system for communication
`bclwncen 1: system network and 1 mobile unit. The syslcm
`network includes a plurality of base transmitters and base
`Ieucivers include in the network. The base transmitters are
`divided into mnal assignments and Iaxoadcaat in simulcast
`using mulu‘-carrier roudulaxion techniques. The syslem net-
`work controls the base Lmnsmiltcrs 1 bmadcast in suimul-
`cut during both systemw-id: and zone boundaries to maxi-
`mize information throughout. The preferred mobile unit
`inlcuées 3 noise detector circuit to prevenl unwanted Inns-
`Inissions. The system network further provides an adaptive
`registration feamre for mobile uniis which controls the
`registration operation by lbc mobile units to maxirnize
`inI‘unm1ic1u throughout.
`
`19 Claims, 30 Drawing Sheen
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`Page 00014
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`U.S. Patent
`
`Jun. 22, 1999
`
`Sheet 1 of 30
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`5,915,210
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`F/6‘. /
`WMRAM
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`Page 00015
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`U.S. Patent
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`Jun. 22, 1999
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`sheetz of30
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`5,915,210
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`Page 00018
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`
`

`
`eat 5 of3|]
`
`5,915,210
`
`F/G.5PRIORART
`
`Page 00019
`
`Page 00019
`
`

`
`U.S. Patent
`
`Ju19. 22, 1999
`
`Sheet 6 am
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`5,915,210
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`Page00020
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`Page 00020
`
`
`
`
`
`
`

`
`U.S. Patent
`
`Jun. 22, 1999
`
`Sheet 7 M3!)
`
`5,915,210
`
`FIG. 7
`
`T00
`
`T02
`
`70:;
`
`Generating a system inlormation
`signal which includes a plurality of
`blocks of information
`
`Transmitting the system information
`signal to the plurality of transmitters
`
`time period
`
`Transmitting by the first and second
`
`sets oi transmitters a first block of
`information in simulcast during the first
`
`me
`
`time period
`
`Transmitting by the first set of
`transmitters a second block or
`inlormation during the second
`time period
`
`Transmitting by the second set of
`transmitters a third block of
`information during the second
`
`iii}
`
`!_.__.._/'
`
`Page 00021
`
`Page 00021
`
`

`
`
`
`US. Patent
`
`Jun. 22, 1999
`
`Sheet 8 of 30
`
`5,915,210
`
`FIG 8
`
`802
`
`304
`
`805
`
`Transmitting a message signal by a
`base transmitter servicing a zone
`where" the mobile transceiver was‘ last
`lrnown to be located
`
`base transmitter
`
`Transmitting a regional probe signal
`by a plurality of base transmitters
`servicing a plurality of zones if the
`mobile transceiver does not indicate
`
`receipt of the message signal from the
`
`
`
`Receiving the regional probe signal by
`the mobile transceiver
`
`
`
`
`
`800
`
` E03
`Transmitting an acknowledgment
`
`signal by the mobile transceiver in
`response to the received regional
`probe signat
`
`
`
`
`Fteceiving the acknowledgment signal
`from the mobile transceiver by a base
`receiver
`
`
`
`BID
`
`"A
`
`Page 00022
`
`Updating the data to reflect the zone
`
`
`of the base receiver that received the
`
`EH2
`acknowledgment signal as the last
`known location or the mobile
`transceiver
`
`
`
`Page 00022
`
`

`
`U-S- Patent
`
`Jun. "22, 1999
`
`Sheet 9 of 30
`
`5,915,210
`
`Page 00023
`
`Page 00023
`
`
`

`
`
`
`U.S. Patent
`
`Jun. 22, 1999
`
`Sheet 10 of 30
`
`5,915,210
`
`FIG‘. /0
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`F1 6)’ I012
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`Page00024
`
`Page 00024
`
`

`
`
`
`U.S. Patent
`
`Jun. 22, 1999
`
`Sheet 11 of 30
`
`5,915,210
`
`FIG. 11
`
`FREQUENCY
`CONTROL
`S|GNAL{
`
`Y
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`MODULATOR
`
`1102
`
`I112
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`1100
`
`Page 00025
`
`Page 00025
`
`

`
`U.S. Patent
`
`Jun. 22, 1999
`
`Sheet 12 of 30
`
`5,915,210
`
`FIG. 12
`
`I CONTROL
`SIGNAL1j?} 1202
`
`INPHASE
`OUADRATURE
`
`1200
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`
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`FOUR CARRIER OUADRATURE MODULATOR
`
`Page 00026
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`
`
`}
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`® OUADRATURE
`
`}
`
`1205
`
`EN PHASE
`
`CONTROL
`SIGNAL 2
`
`CONTROL
`SIGNAL 3
`
`
`
`
`Page 00026
`
`

`
`U.S. Patent
`
`wMB
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`012,51av5
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`Page 00027
`
`Page 00027
`
`
`
`
`

`
`U.S. Patent
`
`Jun. 22, 1999
`
`Sheet 14 of 30
`
`5,915,210
`
`83
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`Page 00028
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`Page 00029
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`
`
`
`

`
`U.S. Patent
`
`Jun. 22, 1999
`
`Sheet 16 or 30
`
`5,915,210
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`Page 00030
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`Page 00030
`
`
`
`

`
`U.S. Patent
`
`Jun. 22, 1999
`
`Sheet 17 0f3[}
`
`5,915,210
`
`FIG‘. /7
`
`Mobile Receiver
`
`I700
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`W08
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`Receiver
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`[T08
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`
`
`Display and
`Storage Logic
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`ISM
`
`Page 00031
`
`
`
`
`Display
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`
`Page 00031
`
`

`
`U.S. Patent
`
`Jun.22,1999
`
`Sheet 18 M30
`
`5,915,210
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`
`Page 00032
`
`
`
`
`
`
`
`

`
`Page 00033
`
`
`
`U.S. Patent
`
`Jun. 22, 1999
`
`Sheet 19 0!‘ 30
`
`5,915,210
`
`F/G. I9
`
`
`
`Analog
`Receiver
`
`
`
`1302
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`
`
`
`
`
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`Circuitry
`‘
`
`Page 00033
`
`

`
`U.S. Patent
`
`Jun. 22, 1999
`
`Sheet 20 of 30
`
`5,915,210
`
`
`
`
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`Page 00034
`
`Page 00034
`
`

`
`
`
`U.S. Patent
`
`Jun. 22, 1999
`
`Sheet 21 of30
`
`5,915,210
`
`FIG. 2/
`
`2:02
`
`ZIU4
`
`ZIUS
`
`Last
`Location
`
`
`Transmit
`Capability?
`
`
`2'00
`/
`
`M55539‘?
`_______________|.._.___
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`
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`
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`n-_—;-_.—_...—;——-p_~———.u..__—_
`
`
`
`User Database
`
`Page 00035
`
`Page 00035
`
`

`
`U.S. Patent
`
`Jun. 22, 1999
`
`Sheet 22 M30
`
`5,915,210
`
`ammm.wi
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`Page 00036
`
`Page 00036
`
`
`
`
`
`

`
`
`
`U.S. Patent
`
`Jun. 22, 1999
`
`Sheet 23 of 30
`
`5,915,210
`
`F7/Ci 213
`
`Service Queue
`
`C urrent Messag es
`
`Page00037
`
`Page 00037
`
`

`
`anU
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`tHW8D;
`
`Jun. 22, 1999
`
`Sheet 24 of 30
`
`5,915,210
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`oowm
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`Page 00038
`
`
`
`
`
`
`
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`
`
`
`
`
`

`
`U.S. Patent
`
`Jun. 22, 1999
`
`Sheet 25 M30
`
`5,915,210
`
`mwcom
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`Page 00039
`
`Page 00039
`
`

`
`U.S. Patent
`
`Jun. 22, 1999
`
`Sheet 20 ol-'30
`
`5,915,210
`
`FIG. 26
`
`
`
`
`
`2600
`
`2802
`
`
`
`
`
`
`
`
`
`Transmitting substantially
`simultarieousiy a first information
`signal and a second information
`signal, the first information signal
`being transmitted in simulcast by a
`first set of base transmitters
`assigned to a first zone. and the
`second information signal being
`transmitted in simulcast by a second
`set of base transmitters assigned to a
`second zone
`
`
`
`Dynamically reassigning one or more
`
`of the base transmitters in the first set
`
`
`
`
`
`
`
`
`
`
`
`2504
`
`
`
`2605
`
`
`
`of base transmitters assigned to the
`first zone to the second set of base
`transmitters assigned to the second
`zone, thereby creating an updated
`first set of base transmitters and an
`updated second set of base
`transmitters
`
`
`
`
`Transmitting substantially
`' simultaneously a third information
`
`signal and a fourth information signal,
`the third information signal being
`transmitted in simulcast by the
`updated first set of base transmitters,
`and the fourth information signal
`being transmitted in simuicast by the
`updated second set of base
`transmitters
` _
`
`Page 00040
`
`
`
`Page 00040
`
`

`
`U.S. Patent
`
`n.
`
`In.
`
`2.
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`Page 00041
`
`Page 00041
`
`
`
`
`
`

`
`
`
`U.S. Patent
`
`Jun. 22, 1999
`
`Sheet 28 or 30
`
`5,915,210
`
`I7/£2 £fi9Y3fl/
`
`2800
`
`2802
`
`2804
`
`
`
`Send a message to disable the
`registration feature
`
`
`
`
`
`
`Store the number of probe
`signals sent and a number of
`
`
`
`
`
`messages successfully
`delivered
`
`
`
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`probe signals and number of
`
`messages succesfully
`
`delivered to evaluate a
`
`
`
`
`
`
` 2306
`
`
`likelihood that a probe signal
`will be required to be sent by
`the network to locate the mobile
`transceiver
`
`
`
`
`
`transceivers capability to
`
`
`
`
`Send a message to the mobile
`unit to enable the mobile
`2808
`
`
`transmit a registration signal it
`
`
`the likelihood exceeds a
`selected value
`
`
`Page00042
`
`Page 00042
`
`

`
`
`
`U.S. Patent
`
`Jun. 22, 1999
`
`Sheet 29 of 30
`
`5,915,210
`
`FI 6'. 28/8}
`
`Send a message to enable the
`registration feature
`
`28|0
`
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`Store the number of registration
`signals received and a number
`of messages successfully
`delivered
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`ZEIE4
`
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`
`registration signals and
`number of messages
`succesiutly delivered to
`evaluate a likelihood that a
`
`ZSIE
`
`registration signal will be
`received by a base receiver in
`the network that will not be
`
`used by the network to
`determine a set of base
`
`transmitters to be operated to
`transmit a message to the
`mobile transceiver
`
`
`
`
`
`Page 00043
`
`
`
` Send a message to the mobile
`unit to disable the mobile
`
`I/28|3
`
`
`transceivers capability to
`transmit a registration signal it
`the likelihood exceeds a
`
`selected value
`
`
`Page 00043
`
`

`
`U.S. Patent
`
`Jufi. 22, 1999
`
`Sheet 30 of 30
`
`5.915310
`
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`Page 00044
`
`Page 00044
`
`
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`
`
`
`

`
`
`
`1
`METHOD AND SYSTEM FOR PROVIDING
`MULTICARRIER SIMIJLCAST
`TRANSMISSION
`
`5
`
`ID
`
`13
`
`JD
`
`50
`
`55
`
`This application is a continuation of application Ser. No.
`D8fl6fl.457. filed Dec. 6, 1996. now abandoned. which is a
`Rule 60 continuation of prior application Ser. No. OTIQTJ.
`918, filed Nov. 12., 1992, now U.S. Pat. No. 5,590,403.
`BACKGROUND OF THE lNV'EN'I'[{)N
`A. Field of the invention
`The present invention relates to methods and systems for
`providing two-way communication capability between a
`central network and a mobile unit over a relatively large
`area, and more particularly to such methods and systems
`which allow for rapid nommunication oflarge messages and
`efficient use of system resources.
`B. Description of the Related Art
`Conventional two-way portablcfmobik wireless messag-
`ing systems often provide a variety of senrices to subscrib-
`crs. Conventional messaging systems in particular provide
`out-.—way services using store and forward techniques to
`mobile receivers carried by the subscriber. A fundamental
`goal of Iwoway messaging systems is to provide l network
`of interconnected transmitters and receiver: which provides
`sulficient transmitted signal strength and receive capability
`to uniformly cover a geographic region. Some conventional
`rnemaging systems provide the message to the utter on a
`small viewing screen on the mobile unit.
`However. such conventional systems often stllfer lrorn
`problems associated with low system throughput, evide need
`by slow message delivery and message alzc limitations and
`do not provide an acknowlodgtnent
`feature wherein the
`mobile unit
`transmits an acknowledgment signal
`to the
`system to acknowledge receipt of the message from the
`system. Generally, system Ltarougtput refers to overall com-
`munication capability of a system as defined by the total
`amount of message data from the system to the mobile units
`transferred by the system during a given period of lime
`divided by the frequency bandwidth necessary to transmit
`the message data and may be measured in bits lrattsfened
`per Hz. Further. such conventional systems sufier from
`technical problems preventing ootuistent wide area cover-
`age and would require extremely wide portions of valuable
`frequency bandwidth to achieve acceptable system through-
`put mes.
`technology in communication systems was
`Simulcast
`originally developed to extend Iransmitlcr coverage beyond
`that which could be obtained irorn 5 single transmitter. Over
`time. however, eimulcasting has evolved into a technique
`capable of providing continuous coverage to a large area.
`Generally, simulcast
`technology provides multiple
`transmitters, operating on substantially the same frequencies
`and transmitting the same iuforrrtation positioned to cover
`extended areas. As shown in FIG. I, transmitter 190 gener-
`ally provides coverage over area A. D. and E. transmitter
`102 generally provides coverage over area B, D. and E. and
`transmitter 104 generally provides coverage over area (I, E,
`and F. In some cases. the coverage area of a first transmitter
`maybe entirely enclosed within the.-coverage area of another
`trnnsrnittensltcb as in building interiors and valleys. In areas
`where one [and only one) transmitter dominates (c.g.. areas
`A. B. and C in FIG. 1). simulcast is efiective because the
`other transmitters do not sigttiflcanlly alfect receivers in
`those areas.
`However. in “overlap” areas D. E. and Fshown in FlG.1,
`where the signals from two or more transmitters are approxi-
`
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`2
`mately equal. probles can arise because destructive inter-
`ference of goals occurs in these overlap areas such as areas
`D, E, and F. Destructive interference occurs when the two
`signals are equal in magnitude and 130‘ out of phase and
`coplelely cancel each other. While there were some
`successes. reliable design procedures were not available.
`Attempting to precisely synchronize the carrier frequen-
`cies of all simulcast trousrnilters does not overcome the
`problem because points (in. nodes) at which destntctive
`summing occurred persisted for tong periods of time. At
`such points, a mobile receiver can not receive the simulcast
`signal.
`Deliberately ofllselting the carrier frequencies of adjacent
`transmitters can ensure that destructive interference does not
`persist atone point for an extended period ofIitne.The slight
`errors in frequency displayed by high quality reference
`oscillators (c.g., 20 hertz more in 100 MHZ signals or a few
`parts in HIT} tender deliberate olf.-netting unnecessary.
`Further, merely olisetting the carrier frequencies could not
`guarantee acceptable quality demudtuatinn because proper
`alignment of the modulating signals in time is also required.
`FIG. 2 displays the situation at. for example. point D in
`FIG. 1 when rnedulating waveforms are synchronized and
`includes coverage boundary ZEEZ from a first transmitter and
`a second transmitter coverage boundary Zlltl from a second
`adjacent
`transmitter. An cqui-signal boundary Zlltl exists
`where the siytals from the first and second trnnsrnitters have
`approximately equal signal strengths. A more realistic equi-
`signal boundary would talne into account natural and man-
`made topography and propagation conditions, and therefore
`would probably not be a straight line.
`FIGS. 3 and 4 generally illustrttte various signals as they
`may occur at or near the equi-signal boundary 200 as shown
`in FIG. 2. in particular, FIGS. 3 and Il» illustrate various
`aspects of modulation synchronization and how altering
`transmission parameters may afieet the synchronization. In
`general.
`there are at least three sources which cause the
`signals from the firet transmitter and the second transmitter
`to be out of synchronization: (1) Lirnirtg rrhifis in the delivery
`of the mochtlating waveform to each of the trartsn1illcrs;(2)
`timing shifts internal to each transmitter; and (3) Liming
`shifts caused by propagation distances and anomalies. From
`the perspective ofa receiver located in an overlap area. these
`three sources of timing shifts combine to produce an overall
`liming shifts between the received signals from the first and
`second Lransmitlcts
`In current commercial practice. the
`summation of these three components results in lime shifis
`of about 201'.) microseconds. The timing shifi present in
`simulcast systems disadvantageously limits the baud rate at
`which information may be transferred. In general. FIGS. 3
`and 4 will also illustrate how timing shifts prevents high
`baud rate transmissions
`'
`A time line representation at a signal 306 from a that
`transmitter is shown in FIG. 3(A) and a signal 308 from a
`second transmitter is shown in FIG. 3(3), both from the
`perspective of a receiver located in an overlap area. Vertical
`dashed lines 300 represent baud intervals on the time axis.
`As can be seen from FIGS. 3(A} and (B). the signals 306 and
`308 are frequency modulated between a high and a low
`frequency value and the signal: 306 and 308 are exactly in
`phase. As will be appreciated,
`the timing shift between
`signals 306 and 308 must be small when compared to the
`baud interval shown in FIGS. J(A) and (B) since signals 3116
`and 308 are in synchronization. Of course, as the baud
`interval decreases. the timing shifts will likely cause signals
`306 and 3E8 to be out of synchronization.
`
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`5,915,210
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`P165. 3(6). (D). and (E) show the summation of these
`two signal; 306 and 308 at an equi-signal boundary, such as
`boundary 100 in FIG. 2. FIG. 3(C) slztows a composite signal
`sltt indicating that
`the frequency intorrnaticn rcntains
`unchanged, FIG. 3(D) shows a linear graph 312 of lite
`relative phase diiference caused bya slight carrier frequency
`difference between the signals [tom the first transmitter and
`the second transmitter. FIG. 3(5) shows a composite ampli-
`tude signal 314. A noise threshold is indicated by the
`horizontal dashed line 304 in Fit}. 3(5).
`or interest. FIG. 30?.) shows the composite amplitude
`signal 314 dipping below the noise threshold 3-04 at so
`artli-phase condition 302 (e.g., when the relative pbasfl angle
`is :l8U'. as shown in F10. 3([))). As can beseen from FIG.
`3{E). the anti-phase condition 302. caused by the slight phase
`shift between transmitter 1 and transmitter 1 will not cause
`any loss ofdata because the anti-phase condition persists for
`only a small portion of the baud interval.
`The alight offset of the carrier [requencies between the
`lirst and second transmitters causes a slow drifi of the
`relative phase of the two signals, as shown in FIG. 3(1)).
`when the signals are :18lJ' out of phase. the temporary dip
`in the amplitude signal may cause the loss of a few bits in
`the oomposite signal, at wnrst.T|1esc errors can be counter-
`acted with a conventional crror correcting code, such as is
`commonly KDCIWD.
`HO. 4 shows a set of similar signals to those in FIG. 3.
`but wherein the signal 402 from the first transmitter is ofl'set
`from. or out of synchronization with, the signald-D4 Erom the
`second transmitter by a full band. In particular. signal 404
`lags signal 4412 by one baud interval. As previously
`discussed. tltt: offset of signals 402 and 404 may be caused
`by various Liming shifts in the delivery of both signals 402
`and -I-04 to a receiver in an overlap area. FIGS. 4(A] and [B)
`illustrate the extreme case where the sum of these timirtg
`shifts is equal to the baud interval shown by dashed lines
`400. As can be seen in FIG. Il(Q, composite signal 406
`includes a period of ittdetermirtate frequency whitit unde-
`sirably covers several entire baud intervals and. therefore,
`successful demodulation is impominle during those baud
`intervals. Iflhe baud interval were increased to minimize the
`eflect of these timing shifts. data loss would be less liltely.
`‘Therefore, it can be seen that the baud rate at which good
`data transfer can be accomplished is limited by the timing
`shifts between signals delivered to receiver: in overlap
`areas.
`Through these examples. it can be seen that high degrees
`of mod