WWWWWWW MMWWWWWW
`
`USOU?3?2826BZ
`
`(12) United States Patent
`Dahod et a].
`
`(IO) Patent No.:
`
`(45) Date of Patent:
`
`US 7,372,826 32
`May 13,2008
`
`(54) PROVIDING ADVANCED
`COMMUNICATIONS FEATURES
`
`(75)
`
`Dahed. Andover. MA (US):
`Inventors: Ashraf
`Michael Silva. East Sandwich. MA
`(US): Peter Higgins. Sandwich. MA
`(US); Rajat Ghai. West Yarmouth. MA
`(US); John DePietro. Brewster, MA
`(US): Nick Lopez. Sleepy Hollow. IL
`(US): Paul Shieh. Westb(mtugh. MA
`(US)
`
`(73} Assignee: Starent Networks. Corp.. Tewksbury.
`MA (US)
`
`( * } Notice:
`
`Subject to any disclaimer. the term oi'titis
`patent is extended or adjusted under 35
`U.S.C. 15403} by 0 days.
`
`(21) Appl. No; 101210.897
`
`(22)
`
`Filed:
`
`Aug. 1. 2002
`
`(65)
`
`Prior Publication Data
`US 20(l4f()0222()8 Al
`Feb. 5. 2004
`
`(51}
`
`Int. Cl.
`HMQ 7X0!)
`(52) U.S. Cl.
`
`(2006.01)
`370l328:3701349:370f3561
`370889;.37014011455517
`(58) Field of Classification Search
`370812.
`3701328. 335. 342. 352 353. 355. 356. 432.
`3701441. 466. 349. 390. 401. 338. 389; 4551524.
`455542. 560. 404.1. 412.]. 4E2.2. 414.1.
`455517. 520: 7'051’26. 27: 379(8801. 8803.
`379188.04. 88.16. 265.01. 265.02: T09f207.
`7091231. 238
`See application file for complete search history.
`
`(56)
`
`References Cited
`U.S. PA’I‘erN’l‘ DOCUMIIENTS
`
`4.6??.656 A *
`5.513.181 A *
`
`6-"198? Burke et al.
`451995 Bresalicr et' al.
`
`4553403
`3703465
`
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`
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`2-1998 Sigler et al.
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`
`455-"l8
`.. 45554361
`
`3?5-"370
`
`(Continued)
`FOREIGN PATIENT DOCUMENTS
`
`HP
`
`(1 650 284
`
`451995
`
`(Continued)
`01] 113R PUBLICATIONS
`
`Schulzl'inne. ll. “The Session Initiation Protocol.“ hltp:-"-"w‘w.cs.
`colmnbiacdtt-‘ttcontsfi[8| "sl ides-'11.-'sip _long.-".pdf. May 2001.
`
`(Continued)
`
`Priming: Iiit'rrminer
`Assistant Examiner
`
`
`Joseph I-‘eild
`Inder Pal Meltra
`
`('14) Anemia“ Agent. or Finn—Wilmer Cutler Pickering
`Hale and Dorr LLP
`
`(57)
`
`ABSTRACT
`
`Advanced communications features are provided in a mobile
`conmtunications network having at least one mobile switch—
`ing center and at least one mobile station subsystem. The
`mobile switching center and mobile station subsystem each
`communicate signaling messages according to a mobile
`signaling protocol. An indication is received that a half-
`dupiex mobile communications session is to be initiated
`between a first mobile station subsystem and a second
`mobile station subsystem. The first and second mobile
`station subsystems include full—duplex connnunications
`apparatus for use ill full-duplex mobile connnunications
`sessions. The hall-duplex mobile communications session
`relies on the first and second mobile station subsystems. and
`all of the reliance is onlyr on the hill-duplex communications
`apparatus. Mobile cmnmnnications telephone calls are
`established with the first mobile station subsystem and the
`second mobile station subsystem. One oi'the first and second
`mobile station subsystems is selected as a voice signal
`source in the half-duplex comnntnications session.
`
`27 Claims. 13 Drawing Sheets
`
`
`
`

`

`US 7,372,826 32
`Page 2
`
`U.S. PATENT DOCUMENTS
`
`6.1 12.083
`6.128.509
`6. l 3 1 . l 2 l
`6.2 98.0 58
`6.366.? 82
`6.4003316?Ir
`6.449.496
`6.477.150
`6.520.871
`6.606.305
`6.7 54. | 80
`7.058.036
`200110046234
`200 22007 5805
`20020025814
`2002.100? 58 25
`200 200771 36
`200 230028464
`200210085552
`200200853539
`2002:f00866 65
`2003100 1 78 36
`2003300 63 590
`20031008842 1
`2003:“0128696
`
`1’" $
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`131*
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`812000
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`6-2005
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`612002
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`612002
`6.12002
`712002
`1-2002
`2.12002
`1 2003
`4.-"2003
`5.0003
`2e'2003
`
`455F426]
`Sweet el al.
`115505561
`Veijola et al.
`7092227
`Maitaway et a].
`320890
`Maker 01 a].
`4553457
`I‘umm'olo c1 a].
`.. 455.563
`Nilsson ........ ..
` Beith et a1.
`4552563
`3701312
`Maggenti ct a1.
`320E356
`Schneider
`.. 3203260
` Christie
`Boyle 61 a].
`.
`3203236
`Yu el al.
`3201335
`Agrawal ct a].
`Gupta ct a].
`Desai et a1.
`Drawida et a].
`Maggenti et al.
`Dravida et a].
`Tandon
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`Wengrovitz et :11.
`
`4551517
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`
`370-352
`
`2001-0156688 Al’“
`200300185202 Al "
`200510286689 A1“
`2006-0002358 A1
`200610140151 Al‘“
`
`8:"2 003
`1012 003
`12.12 005
`1:2 006
`6.12 006
`
`McCarty et a1.
`Maenpm
`Vuori
`Ray et 31.
`Damn et a].
`
`379.5611
`.... .. 3701352
`379188.22
`
`
`
`370031
`
`FOREIGN PA'I‘EN'I‘ DOCUMENTS
`
`EP
`W0
`W0
`W0
`W0
`W0
`W0
`W0
`W0
`W0
`W0
`W0
`W0
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`0 845 894
`W0-98-"47298 A2
`W0-00f22792 AZ
`W0 01545335
`W0 00147005
`W0 0057601
`WO 00279826 A1
`W0-01r'31939 A2
`WO 01156236
`W0-01J'262'i'6 A2
`W0 02230010
`W0-02f45440 Al
`WO-02.-'054707 A2
`
`611998
`10.f 1998
`4-’2000
`612000
`812000
`9-"2000
`12.12000
`5,"2001
`8.32001
`[03200]
`4.32002
`6.-"2002
`2.12002
`
`OTI 111R PU]31..1CATIONS
`
`Handley. M. ct 31.. “SIP Session
`lctfiorg"html-'rfc2543. Mar. 1999.
`
`initiation Protocol.“ httpwftools.
`
`“‘ cited by examiner
`
`

`

`US. Patent
`
`May 13
`
`, 2008
`
`Sheet 1 of 13
`
`US 7,372,326 132
`
`.5”?MOEQ
`
`550.2
`
`«3.
`
`29.25
`
`

`

`US. Patent
`
`May 13,2008
`
`Sheet 2 of 13
`
`US 7,372,826 132
`
`
`
`FIG. 2
`PRIOR ART
`
`

`

`US. Patent
`
`May 13, 2008
`
`Sheet 3 of 13
`
`US 7,372,326 132
`
`
`
`IO._._>>m._.n_Om
`
`46.0E
`
`

`

`US. Patent
`
`May 13
`
`, 2008
`
`Sheet 4 of 13
`
`US 7,372,326 132
`
`Op
`
`.
`‘Q'
`
`Now
`
`
`
`mm.O_u_
`
`

`

`US. Patent
`
`May 13,2008
`
`Sheet 5 of 13
`
`US 7,372,826 132
`
`USER
`
`USER
`
`530
`
`525
`
`w w
`
`PTI'
`
`DIRECTORY
`
`FIG.4
`
`517
`
`515
`
`

`

`US. Patent
`
`May 13,2008
`
`Sheet 6 of 13
`
`US 7,372,826 132
`
`INDICATE THATA PTT SESSION SHOULD COMMENCE
`
`
`
`ESTABLISH VOICE CONNECTION TO INITIATOR MS
`AND INTENDED RECIPIENT MS
`
`2010
`
`
`
`TRANSMITTED TO ANOTHER MS
`
`2035
`
`REFER TO PTT DIRECTORY
`
`2020
`
`
`
`2030
`
`
`
`
`
`
`
`
`
`2015
`
`2°55
`
`
`
`
`
`
`SIGNAL REVERSION TO LISTEN MODE
`
`2045
`
`
`
`HALT TRANSMISSION OF VOICE SIGNAL
`
`INDICATE THAT PTT SESSION SHOULD TERMINATE
`
`CLOSE VOICE CONNECTIONS
`
`2060
`
`FIG. 5
`
`

`

`US. Patent
`
`May 13, 2008
`
`Sheet 7 of 13
`
`US 7,372,826 B2
`
`
`
`._.Xm_._.._.Z<._.wz_
`
`02.092
`
`me
`
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`US. Patent
`
`May 13,2008
`
`Sheet 8 of 13
`
`US 7,372,826 132
`
`
`
`3010
`
`3030
`
`3050
`
`3060
`
`3070
`
`
`
`
`SIGNAL START OF RECORDING VOICE MESSAGE
`
`
`
`DETECT SIGNAL
`
`
`
`3020
`
`
`
`ESTABLISH VOICE CALL TO USER'S MS
`
`
`
`
`
`RECORD VOICE MESSAGE
`
`
`
`3040
`
`
`
`DERIVE INSTANT TEXT MESSAGE FROM VOICE
`
`MESSAGE
`
`
`
`
`
`CAUSE INSTANT TEXT MESSAGE TO BE DELIVERED
`
`TO ANOTHER IMG
`
`
`
`
`
`EXTRACT RECORDING FROM INSTANT TEXT MESSAGE
`
`
`
`PLAY BACK RECORDING
`
`3080
`
`FIG. 7
`
`

`

`US. Patent
`
`May 13,2008
`
`Sheet 9 of 13
`
`US 7,372,826 B2
`
`SUBSCRIBER
`
`THE SUBSCRIBER DIALS '1-800-888—VIM1'
`
`IMG
`[ST-16)
`
`"ENTER 1 T0 CREATEA NEW GROUP, ENTER 2 TO RECORD A MESSA GE, OR 3 ACCESSING
`TO OBTAIN STATUS FROMA PREVIOUS VIM SESSION"
`SYSTEM
`
`_
`
`SUBSRIBER ENTERS I
`
`—b- - — -
`
`"PLEASE ENTER EACH NUMBER FOLLOWED BY THE# KEY, WHEN
`FINISHED PLEASE PRESS THE STAR KEY."
`
`THE SUBSCRIBER ENTERS EACH NUMBER AND ENDS WITH THE STAR KEY
`
`THE SYSTEM WOULD THEN PLAY BACK THE NUMBERS FOLLOWED BY...
`"TO ACCEPT PRESS 1, To CHANGE PRESS 2*
`
`SUBSCRIBER ENTERS 1
`
`
`
`"IT: YOU WISH TO RECORD A MESSAGE, START RECORDING A T THE TONE
`OTHERWISE STAY ON THE LINE FOR MORE OPTIONS. ONCE YOU'VE COMPLETED
`RECORDING, YOU MAYHANG—UP TO SEND YOUR MESSAGE."
`
`"PLEASE ENTER THE VIM GROUP ID TO RECORD A MESSAGE FOR."
`
`SUBSCRIBER ENTERS THE VIM GROUD ID
`
`“A T THE TONE START RECORDING YOUR NESSA GE. HANG-UP WHEN FINISHED"
`
`THE SUBSCRIBER RECORDS THE MESSAGE AND HANGS-UP
`
`THE SYSTEM STARTS PLACING OUT-BOUND CALLS TO
`THE MEMBERS OF THE VG.
`
`- 4-
`
`THE SUBSCRIBER DIALS ‘1-800-888—VIM1'
`"ENTER 1 T0 CREATEA NEW GROUP, ENTER 2 TO RECORD A MESSAGE,
`
`OR 3 To OBTAIN STATUS FROM A PREVIOUS YIN SESSION"
`
`SUBSCRIBER ENTERS 3
`
`THE SYSTEM PLAYS OUT THE RECEIVE STATUS
`IL; III] H: H In
`
`FIG. 8
`
`DEFINING
`A NEW
`VG
`
`RECORD
`AND PLAY
`OUT A
`MESSAGE
`
`— -
`
`OPTIONAL
`Rggfii
`
`

`

`US. Patent
`
`Rdayl3,2008
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`US 7,372,826 B2
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`May 13, 2008
`
`Sheet 11 of 13
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`US 7,372,826 132
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`US. Patent
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`May 13, 2008
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`US 7,372,826 132
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`

`US 2,372,826 B2
`
`2
`
`Thus, C DMA tnodulation spectrally spreads a narrowband
`information signal over a broad bandwidth by multiplex
`modulation. using a codeword to identify various signals
`sharing the same frequency chamtel. Recognition of the
`transmitted signal takes place by selecting the spectrally-
`coded signals using the appropriate codeword. In contrast to
`the narrowband channels of approximately 30 kHz used in
`FDMA and TDMA modulation teclmiques. a CDMA system
`generally employs a bandwidth of approximately 1.25 MI-lz
`or greater.
`Typically, the mobile connnunication systems described
`above are arranged hierarchically such that a geographical
`“coverage area" is partitioned into a number of smaller
`geographical areas called “cells.” Referring to FIG. 1. each
`cell
`is preferably served by a Base Transceiver Station
`(“B'l‘S”) 102a. Several B‘I'S lOZn-n are centrally adminis-
`tered via fixed links 104a-n by a Base Station Controller
`(“BSC”) 186a. The BTSs and BSC are sometimes collec-
`tively referred to as the Base Station Subsystem (“BS”) [07.
`' Several BSCs lflfib-rt may be centrally administered by a
`Mobile Switching Center (“MSC”) 110 via fixed links
`1030—”.
`MSC 110 acts as a local switching exchange (with addi-
`tional features to handle mobility management require-
`ments. discussed below) and communicates with the phone
`network (“PSTN”) 120 through trunk groups. US. mobile
`networks include a home MSC and a serving MSC. The
`hotne MSC is the MSC corresponding to the exchange
`associated with a Mobile Subscriber (also referred to above
`as a mobile station or “MS"); this association is based on the
`phone number. such as the area code, of the MS. Examples
`of an MS include a hand-held device such as a mobile phone.
`a PDA. a 2-way pager. or a laptop computer. or Mobile Unit
`Equipment. such as a tnobile unit attached to a refrigerator
`van or a rail car. a container. or a trailer.
`The home MSC is responsible for a Home Location
`Register (“HLR”) 118 discussed below. The serving MSC.
`on the other hand. is the exchange used to connect the MS
`call to the PSTN. Consequently. sometimes the home MSC
`and serving MSC functions are served by the same entity.
`but other times they are not (such as when the MS is
`roaming). Typically, a Visiting Location Register (“VLR”)
`116 is co-located with the MSC 110 and a logically singular
`HLR is used in the mobile network (a logically singular
`l-lLR may be physically distributed but is treated as a single
`entity). As will be explained below. the MIR and VLR are
`used for storing subscriber information and profiles.
`Radio channels 112 are associated with the entire cover-
`age area. As described above. the radio channels are parti~
`tioned into groups of channels allocated to individual cells.
`The channels are used to carry signaling information to
`establish call connections and related arrangements, and to
`carry voice or data information once a call connection is
`established.
`
`1
`PROVIDING ADVANCED
`COMM UN ICA'I‘IONS FEATURES
`
`BACKGROUND
`
`This invention relates to providing advanced communi-
`cations features.
`
`“Greless telecommunication systems are able to provide
`wireless versions of information services traditionally pro-
`vided by land-line or copper wire systetns. Examples of
`wireless cotnmunications applications include Advanced
`Mobile Phone Service (AMPS) analog cellular service and
`Code Division Multiple Access (CDMA) and Advanced
`Mobile Phone Service (AMPS—D) digital cellular service in
`North America. and Group Speciale Mobile (GSM) cellular
`service in Europe.
`Although the particular application may vary. the com-
`ponents of a wireless communication system are generally
`similar. as described in more detail below. For example. a
`wireless communication system usually includes a radio
`terminal or mobile station. a radio base station. a switch or
`network control device. often referred to as a mobile tele
`phone switching oflice (M'l'SO), and a network to which the
`wireless connnunications system provides access. such as
`the Public Switched Telephone Network (PSTN).
`The various wireless communication applications use any
`of multiple modulation techniques for transmitting informa-
`tion to efliciently utilize the available frequency spectrum.
`For example. frequency division multiple access (FDMA).
`time division multiple access (‘1‘DMA)_. and code division
`multiple access modulation techniques are used to build
`high-capacity multiple access systems. "lelcconmtunication
`systems designed to communicate with tnany mobile sta-
`tions occupying a common radio spectrum are referred to as
`multiple access systems.
`For example. in an FDMA analog cellular system. such as
`an AMPS analog cellular radio system. the available fre-
`quency spectrum is divided into a large number of radio
`channels. e.g.. pairs of transmit and receive carrier frequen-
`cies. each of which corresponds to a message transmission
`channel. The bandwidth of each transmit and receive fre-
`quency channel is narrowband. generally 2530 kHz. Thus.
`the FDMA system permits information to be transmitted in
`a bandwidth comparable to the bandwidth of the transmitted
`information. such as a voice signal. The cellular service area
`in the FDMA system is generally divided into multiple cells.
`each cell having a set of frequency channels selected so as
`to help reduce co-channel interference between cells.
`Frequency division is often combined with time division
`so that transmission circuits are distinguished in both the
`frequency and time domain. e.g.. in a FDFTDMA system. In
`a digital
`l" 1):"[‘DMA (connnonly referred to as 'I‘DMA)
`cellular system. a narrowband frequency channel is refor-
`matted as a digital transmission path which is divided into a
`nutnber of time slots. The data signals frotu different calls
`are interleaved into assigned time slots and sent out with a
`correspondingly higher bit rate. the time slot assigned to
`each mobile station being periodically repeated. Although
`the TDMA bandwidth may be somewhat larger than the
`1“ DMA bandwidth. a bandwidth of approximately 30 kHz is
`generally used for AMPS-D digital TDMA cellular systems.
`Another approach to cellular multiple access tnodulation
`is CDMA. C DMA is a spread spectrum technique for
`transmitting information over a wireless communication
`system in which the bandwidth occupied by the transmitted
`signal is significantly greater than the bandwidth required by
`the baseband information signal (e.g.. the voice signal].
`
`ll]
`
`3o
`
`35
`
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`
`45
`
`50
`
`55
`
`on
`
`two significant
`least
`Mobile network signaling has at
`aspects. One aspect involves the signaling between an MS
`and the rest of the network. In the case of 2G (“26" is the
`industry term used for “second generation”) and later tech—
`nology. this signaling concerns access methods used by the
`MS (such as TDMA or CDMA), pertaining to. for example.
`assignment of radio channels and authentication. A second
`aspect involves the signaling among the various entities in
`the mobile network. such as the signaling among the MSCs.
`BSCs. V’L-Rs. and HLRs. This second part
`is sometimes
`referred to as the Mobile Application Part (“MAP”) espe—
`cially when used in the context of Signaling System No. 7
`(“SS7“). SS? is a common channel signaling system by
`
`

`

`3
`
`4
`
`US T372326 B2
`
`which elements of the telephone network exchange infor-
`mation, in the form of messages.
`The various forms of signaling {as well as the data and
`voice conununication) are transmitted and received in accor-
`dance with various standards. For example. the l'ilectronics
`Industries Association (“151A”) and 'I'elecommunications
`Industry Association ("TIA") help define many U.S. stan-
`dards. such as 18—41 . which is a MAP standard. Analogously,
`the CCITT and ITU help define intemational standards. such
`as GSM-MAI’. which is an international MAP standard.
`Information about these standards is well known and may be
`found from the relevant organizing bodies as well as in the
`literature. see. e.g.. Bosse, SIGNALING IN TTiI..Ii(.‘OM-
`MUNICATIONS NETWORKS {Wiley 1998).
`To deliver a call front an MS 114. a user dials the number
`and presses “send” on a cell phone or other MS. The MS 114
`sends the dialed number indicating the service requested to
`the MSC 110 via the BS 107. The MSC 110 checks with an
`associated VLR 116 (described below) to determine whether
`the MS 114 is allowed the requested service. The sewing
`MSC routes the call to the local exchange of the dialed user
`on the PS'I‘N 120. The local exchange alerts the called user
`terminal. and an answer back signal is routed back to the MS
`114 through the serving MSC 110 which then completes the
`speech path to the MS. Once the setup is completed the call
`may proceed.
`To deliver a call to an MS 114. (assuming that the call
`originates from the PS'I'N 120) the PS’IN user dials the MS’s
`associated phone number. At least according to US. stan-
`dards. the PSTN 120 routes the call to the MS’s home MSC
`[which may or may not be the MSC serving the MS}. The
`MSC then interrogates the HLR 118 to determine which
`MSC is currently serving the MS. This also acts to inform
`the serving MSC that a call is forthcoming. The home MSC
`then routes the call to the serving MSC. The serving MSC
`pages the MS via the appropriate BS. The MS responds and
`the appropriate signaling links are set up.
`During a call. the BS 107 and MS 114 may cooperate to
`change channels or BTSs 102.
`if needed.
`for example.
`because of signal conditions. These changes are known as
`“handoifs.” and they involve their own types of known
`messages and signaling.
`One aspect of MAP involves “mobility management."
`Difl'erent l-3Ss and MSCs may be needed and ttsed to serve
`an MS. as the MS 114 roams to different locations. Mobility
`tnanagement helps to ensure that the serving MSC has the
`subscriber profile and other infonnalion the MSC needs to
`service (and bill) calls correctly. To this end, MSCs use VLR
`116 and HLR 118. The HLR is used to store and retrieve the
`mobile identification number (“MIN”). the electronic serial
`number (“BSN”), MS status, and the MS service profile.
`among other things. The V’LR stores similar information in
`addition to storing an MSC identification that identifies the
`hotne MSC. In addition. under appropriate MAP protocols.
`location update procedures [or registration notifications) are
`performed so that the home MSC of a Mobile Subscriber can
`locate its users. These procedures are used when an MS
`roams from one location to another or when an MS is
`
`powered on and registers itself to access the network. For
`example. a location update procedure may proceed with the
`MS 114 sending a location update request to the Vl.-R 116
`via the BS 10‘? and MSC 110. The VLR 116 sends a location
`
`(ifany) that previously held profile data to delete the data
`related to the relocated MS 114.
`
`FIG. 2 shows in more detail the signaling and user traflic
`interfaces between a BS 101Ir and an MSC 110 in a CDMA
`
`mobile network. The BS 107 communicates signaling in for-
`mation using an SST-based interface for controlling voice
`and data circuits known as the
`1“ interface An interface
`
`10
`
`known as “A2” carries user trafiic (such as voice signals)
`between the switch component 204 of the MSC and the BS
`107. An interface known as "AS" is used to provide a path
`for user traffic for circuit-switched data calls [as opposed to
`voice calls) between the source BS and the MSC. lnfonua-
`tion about one or more of A], A2, A5 may be found in
`CDMA Intemetworking—Deploying the Open—A Interface.
`Su-Lin Low. Ron Schneider. Prentice Hall. 2000. ISBN
`0-13-088922-9.
`
`Mobile communications providers are supplying newer
`services, e.g.. “data calls“ to the Intemet. For at least sortie
`ol'these services. MSCs are not cost effective because they
`' were primarily designed for voice calls. Integration of new
`services into the MSC is difficult or infeasible because of the
`
`proprietary and closed designs used by many MSC software
`architectures. "that is, the software logic necessary to pro-
`vide the services is not easy to add to the MSC 1111. Often.
`a switch adjunct
`is used to provide such services. For
`example. an Inter-Working Function (“IWF”) is an adjunct
`to route a data call
`to the Internet. Either approach-
`iutegrating functionality into the MSC or adding a trunk—side
`adjunct—involves the MSC in the delivery of service.
`Integrating new services via MSC? design changes or through
`trunk-side adjuncts can increase network congestion at the
`MSC and consume costly MSC. resources.
`Data calls typically make use of the Internet. which is an
`example ofa packet-switching medium. A packet-switching
`medium operates as follows. A sequence ofdata is to be sent
`from one host to another over a network. The data sequence
`is segmented into one or more packets. each with a header
`containing control infomiation, and each packet is routed
`through the network. A common type of packet switching is
`datagram service. which offers little or no guarantees with
`respect to delivery. Packets that may belong together logi-
`cally at a higher level are not associated with each other at
`the network level. A packet may arrive at the receiver before
`another packet sent earlier by the sender. may arrive in a
`damaged state (in which case it may be discarded). may be
`delayed arbitrarily (notwithstanding an expiration mecha-
`nism that may cause it to be discarded]. may be duplicated.
`and may he lost.
`tnulticast conununicatiou
`to the Internet.
`With respect
`refers to the transmission of identical data packets to
`selected. multiple destinations on an Internet Protocol net-
`work. (In contrast, broadcast communication refers to the
`indiscriminate transmission of data packets to all destina-
`tions. and unicast communication refers to the transmission
`of data packets to a single destination.)
`Each participant in a multicast receives information trans«
`mitted by any other participant
`in the multicast. Users
`connected to the network who are not participants in a
`particular multicast do not receive the information transmit-
`ted by the participants of the multicast.
`In this way. the
`tnulticast communication uses only the network components
`(e.g.. switches and trunks) actually needed for the multicast
`transmission.
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`update message to the HLR 118 serving the MS 114, and the
`subscriber profile is downloaded from the HLR 118 to the
`VLR 116. The MS 114 is sent an acknowledgement of a
`successful location update. The 11th 118 requests the VLR
`
`In multicast processing, when a potential participant
`(“host”) is directed to join a particular 11’ multicast group,
`the host sends a “request to join" message to the nearest
`multicast-capable router to request
`to join the multicast
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`1;
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`US 2,372,826 B2
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`6
`
`to this group. For
`group and receive iniormation sent
`example, a host A sends a message to join multicast grottp
`Y, and a host B sends a message to join multicast group X.
`A router R propagates the request up to the multicast source
`if the data path is not already in place.
`Upon receiving an IP packet for group X, for example. the
`router R maps an IP multicast group address into an lithcmet
`multicast address, and sends the resultant Ethernet packet to
`the appropriate switch or switches.
`According to the Internet Group Management Protocol
`(“IGMP”). a host‘s membership in a mu lticast group expires
`when the router does not receive a periodic membership
`report from the host.
`With respect to interaction among MSs, a Nextel service
`(known as Nextel Direct Connect®. using Specialized
`Mobile Radio technology. and described at http:llwww.nex-
`tel.conv‘phone_servicesldirectconnectshtmlJ
`having
`two
`versions has been proposed for special connection calls
`among MSs. Both versions of the special connection calls
`require special—purpose MSs. In the first version, a one to
`one conversation is allowed between two mobile telephone
`subscribers, e.g., A and 13. When A wishes to have special
`connection communication with B. A enters B‘s private
`identification number, holds down a push to talk (“PTT”)
`button. waits for an audible alert signifying that B is ready
`to receive. and starts speaking. To listen. A releases the PTT
`button. If B wishes to speak. B holds down the PTT button
`and waits for an audible confirmation that A is ready to
`receive. The service allows a subscriber to choose private
`identification numbers from scrollable lists displayed on
`tnobile telephone handsets or to search a list of pre-stored
`names of subscribers.
`
`In the second version, conversations are allowed among
`members of a predefined group of subscribers. known as a
`Talkgroup. which is identified by a number. The mobile
`telephone handset may allow ’lalkgroup numbers to be
`searched through the control surface of the handset. In order
`to place a group call. the initiating subscriber. e.g.. A. locates
`a Talkgroup ntunber in the handset. holds down the PTT
`button, and. upon receiving an audible confirmation such as
`a chirp, can start speaking. All of the other Talkgroup
`members on the group call can only listen while .A is holding
`down the lyl’l‘ button. IfA releases the P’IT button, another
`member on the group call may hold down the FIT button.
`acquire control signaled by the audible confirmation, and
`start speaking.
`Technology on the Internet includes instant text messag-
`ing (1M). which lets users receive text messages moments
`alter the messages are sent. IM provides a way to chat with
`friends and also provides a useful tool for business. IM
`provides the convenience ol‘electronic mail (chinail) and the
`immediacy of a telephone call. The text messages arrive in
`real time (or nearly so) because both parties are constantly
`connected to the network. Recipients receive messages as
`fast as the data can travel across the Internet. (Email is less
`immediate. E—mail technology sends messages to a server
`that stores the items until the messages are downloaded by
`the recipient‘s e-mail software.) When a user logs on to an
`[M service. the sofiware lets a server know that the user is
`available to receive messages. To send a message to some-
`one else. the user begins by selecting that person‘s name,
`usually from a contact list the user has built. The user then
`enters the message and clicks a “Send” button. A data packet
`is sent that contains address information for the recipient, the
`message. and data identifying the sender. Depending on the
`particular service. the server either directly relays the mes-
`
`sage to the recipient or facilitates a direct cotutection
`between the user and the recipient.
`An IM service typically uses one of three mechanisms to
`transport messages: a centralized network. a peer-to-peer
`connection. or a combination of both a centralized network
`
`and a peer-to-peer connection. In the case ofa central ined
`network (used by, e.g.. MSN Messenger), users are con-
`nected to each other through a series of servers that are
`linked to form a large network. When a user sends a
`message. servers locate the recipient’s computer station and
`route the message through the network until the message
`reaches its destination.
`
`ll]
`
`According to the peer-to-pecr approach (used by.
`ICQ). a central server keeps track of which users are online
`and the users’ unique Internet Protocol (IP) addresses. (An
`IP addreSs identifies a computer. which allows the computer
`to send and receive data via the Internet.) Alter a user logs
`on,
`the server provides the user's computer with the IP
`addresses 0 f each other user on the user’s contact list who is
`
`currently logged on. When the U83! creates a message to
`send to another user, the user‘s computer sends the message
`directly to the recipient‘s computer. without involving the
`server. Messages traverse only the network portion between
`the sender’s and recipient’s computers, which speeds trans-
`fers by helping to avoid network traflic.
`America Online. Inc. (AOL) supplies ADI. Instant Mes-
`senger (AIM) which combines the centralized and peer-to-
`peer methods. When a user sends a text message.
`the
`message travels along AOL‘s centralized network. However,
`when the user sends a file. the users‘ computers establish a
`peer-to-peer connection.
`In another variation of Internet technology. at least one
`wireless lntemet system has been proposed that provides
`reliable access to tens of megahertz of bandwidth across a
`wide geographic area, using local wireless transceiver tech—
`nology (e.g.. in a nanocell system). In contrast to the cellular
`wireless voice system. which relies on tens or hundreds of
`cells in a region. the local wireless transceiver system relies
`on thousands or tens of thousands of transceivers in the
`
`region. In such a system. each transceiver tnay cover. cg.
`0.05 square kilometers, which is about one-hundredth the
`coverage of a conventional cell. High spatial reuse of the
`radio frequency (RF) spectrum allows the local wireless
`transceiver system to acconunodate many more active
`devices at a given data rate than a conventional cell system.
`In addition. since users are closer to access points. the local
`wireless transceiver system acconunodates lower-power
`transmissions. The local wireless transceiver system can
`support large numbers of devices. running at high speeds.
`with relatively little drain on the devices‘ batteries.
`For example,
`in a citywide local wireless transceiver
`system network of 10.000 transceiver access points (cell
`centers), if each point provides its users with l-Mbrs col-
`lective throughput. 10 active devices per transceiver can be
`supported at 100 kbls each. which amounts to 100.000 active
`devices in the city. If each device is active 10 percent of the
`time, such a network can support a million devices, altimugh
`some accounting would need to be made for bandwidth
`consumed by overhead for channel access. handol‘fs, and any
`provision for asynnnetric traffic (c.g..
`in which more bits
`llow toward a device than from it).
`Each local wireless transceiver system access point may
`be or resemble access points for wireless local area network
`(LAN) technology such as IEEE 802.11. An asynchronous
`digital subscriber line (ADSL). or a cable modem line may
`be used to provide a link between each access point and the
`Internet (a wireless link may be used as well or instead].
`
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`US 2,372,826 B2
`
`to the siting of access devices, since each
`With respect
`device requires electrical power and is preferably elevated
`for adequate radio frequency coverage. sites on utility poles
`and buildings are typical candidates, with the high-speed
`neighborhood Internet access infrastructure serving as a
`backbone.
`
`FIGS. 5. 7 are flow diagrams of procedures in cotruntt—
`nications systems.
`FIGS. 8. 12 are call
`conmtunications systems.
`
`liow diagrams of sequences in
`
`DIFFAIIJEI) DESCRIPTION
`
`SUMMARY
`
`Advanced communications features are provided in a
`mobile communications network having at least one mobile
`switching center and at least one mobile station subsystem.
`The mobile switching center and mobile station subsystem
`each communicate signaling messages according to a mobile
`signaling protocol.
`In an aspect of the invention. an indication is received that
`a half-duplex mobile communications session is to be ini-
`tiated between a first mobile station subsystem and a second
`tnobile station subsystem. (As used herein. “half-duplex"
`refers to a session in which at most one MS at a time is
`considered a transmission source; “ alf—duplex" does not
`necessarily tnean the sharing. alternating or otherwise. of
`any channel or medium for transmission and reception.) The
`first and second mobile station subsystems include full-
`duplex communications apparatus for use in full-duplex
`mobile conurttutications sessions. The half-duplex mobile
`commtutications session relies on the first and second
`mobile station subsystems. and all of the reliance is only on
`t