(12)
`
`United States Patent
`Dahod et al.
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 7,372,826 B2
`May 13, 2008
`
`USOO7372826B2
`
`(54) PROVIDING ADVANCED
`COMMUNICATIONS FEATURES
`
`(75) Inventors: Ashraf M. Dahod, Andover, MA (US);
`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, Westborough, MA
`(US)
`
`(73) Assignee: site Networks Corp., Tewksbury,
`
`(*) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`(21) Appl. No.: 10/210,897
`
`(22) Filed:
`
`Aug. 1, 2002
`
`(65)
`
`Prior Publication Data
`US 2004/0022208 A1
`Feb. 5, 2004
`(51) Int. Cl
`(2006.01)
`into 7/00
`(52) U.S. Cl. ...................... 79%;
`s
`s
`(58) Field of Classification Search ................ 370/312,
`370/328,335,342, 352-353, 5. 356,432,
`370/441, 466, 349,390, 401, 338,389; 455/524,
`$5,542,569. 404.1, 412. 412.2, 41.4.1,
`455/517,520; 705/26, 27; 3790, 88.03,
`379/88.04, 88.16, 265.01, 265.02; 709/207,
`lication file f
`let
`R2. 238
`S
`ee appl1cauon Ille Ior complete searcn n1story.
`References Cited
`
`(56)
`
`U.S. PATENT DOCUMENTS
`
`4,677,656 A *
`5,513,181 A *
`
`6, 1987 Burke et al. ................ 455,403
`4, 1996 Bresalier et al. ............ 370/465
`
`
`
`5/1997 Alford ......................... 455.18
`5,634,196 A *
`5,717,830 A * 2/1998 Sigler et al.
`... 455,426.1
`5,838,748 A * 11/1998 Nguyen ...................... 375/370
`
`(Continued)
`FOREIGN PATENT DOCUMENTS
`
`EP
`
`4f1995
`O 650284
`(Continued)
`OTHER PUBLICATIONS
`Schulzrinne, H. “The Session Initiation Protocol.” http://www.cs.
`columbia.edu/ucoms618.1/slides/11/sip long?.pdf, May 2001.
`(Continued)
`Primary Examiner Joseph Feild
`Assistant Examiner Inder Pal Mehra
`(74) Attorney, Agent, or Firm Wilmer Cutler Pickering
`Hale and Dorr LLP
`
`(57)
`
`ABSTRACT
`
`Advanced communications features are provided in a mobile
`communications 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
`duplex 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 communications
`apparatus for use in full-duplex mobile communications
`sessions. The half-duplex mobile communications session
`relies on the first and second mobile station Subsystems, and
`all of the reliance is only on the full-duplex communications
`apparatus. Mobile communications telephone calls are
`established with the first mobile station subsystem and the
`second mobile station subsystem. One of the first and second
`mobile station Subsystems is selected as a voice signal
`Source in the half-duplex communications session.
`
`27 Claims, 13 Drawing Sheets
`
`^ 400
`
`SOFTSWITCH
`
`EX2001
`Microsoft v. Uniloc
`IPR2019-01559
`
`

`

`US 7,372,826 B2
`Page 2
`
`U.S. PATENT DOCUMENTS
`
`6,112,083
`6,128,509
`6,131,121
`6,298,058
`6,366,782
`6,400,967
`6,449,496
`6,477,150
`6,570,871
`6,606,305
`6,754,180
`7,058,036
`2001, 0046234
`2002fOO75805
`2002fOO75814
`20O2/OO75875
`2002fOO77136
`2002fOO78464
`2002fOO85552
`2002fOO85589
`2002fOO86665
`2003, OO17836
`2003, OO63590
`2003/0088421
`2003.0128696
`
`8, 2000
`10, 2000
`10, 2000
`10, 2001
`4, 2002
`6, 2002
`9, 2002
`11, 2002
`5/2003
`8, 2003
`6, 2004
`6, 2006
`11, 2001
`6, 2002
`6, 2002
`6, 2002
`6, 2002
`6, 2002
`T/2002
`T/2002
`T/2002
`1, 2003
`4, 2003
`5/2003
`T/2003
`
`Sweet et al. ............. 455,426.1
`Veijola et al. ........... 455/556.1
`Mattaway et al.
`... 709,227
`Maher et al.
`... 37Of 390
`Fumarolo et al. .
`... 455,457
`... 455,563
`Nilsson .........
`Beith et al. ....
`... 455,563
`Maggenti et al. .
`... 370,312
`Schneider ......
`... 370,356
`Boyle et al.
`370,260
`Christie ......
`370,236
`Yu et al. ..................... 370,335
`Agrawal et al.
`Gupta et al.
`Desai et al.
`Dravida et al.
`Maggenti et al.
`Dravida et al.
`Tandon
`Dravida et al.
`Maggenti et al.
`Vishwanathan et al. .... 455/517
`Mohan et al. .............. 370,338
`Maes et al.
`Wengrovitz et al. ........ 370,352
`
`2003/O156688 A1* 8, 2003
`2003/O1852O2 A1* 10, 2003
`2005/0286689 A1* 12, 2005
`2006, OOO2358 A1
`1, 2006
`2006, O140151 A1* 6, 2006
`
`
`
`McCarty et al. ........... 379 (67.1
`Maenpaa ....
`... 370,352
`Vuori ...................... 379.88.22
`Ray et al.
`Dantu et al. ................ 370,331
`
`FOREIGN PATENT DOCUMENTS
`
`EP
`WO
`WO
`WO
`WO
`WO
`WO
`WO
`WO
`WO
`WO
`WO
`WO
`
`O 845 894
`WO-98,47298 A2
`WO-OO,22792 A2
`WO O1/45335
`WOOOf 47005
`WOOO,576O1
`WOOOf79826 A1
`WO-01 (31939 A2
`WO O1, 56.236
`WO-O 1/76276 A2
`WO O2/30010
`WO-02/45440 A1
`WO-O2/O54707 A2
`
`6, 1998
`10, 1998
`4/2000
`6, 2000
`8, 2000
`9, 2000
`12/2000
`5, 2001
`8, 2001
`10, 2001
`4/2002
`6, 2002
`T 2002
`
`OTHER PUBLICATIONS
`Initiation Protocol.” http://tools.
`Handley, M. et al., “SIP Session
`letforg/html/rfc2543, Mar. 1999.
`* cited by examiner
`
`

`

`U.S. Patent
`U.S. Patent
`
`
`
`Sheet 1 of 13
`Sheet 1 of 13
`
`US 7,372,826 B2
`US 7,372,826 B2
`
`May 13
`2008
`May 13
`, 2008
`9
`
`LVYdOldd
`
`

`

`U.S. Patent
`
`May 13, 2008
`
`Sheet 2 of 13
`
`US 7,372,826 B2
`
`
`
`F.G. 2
`PRIOR ART
`
`

`

`U.S. Patent
`U.S. Patent
`
`00; -^
`
`Sheet 3 of 13
`Sheet 3 of 13
`
`US 7,372,826 B2
`US 7,372,826 B2
`
`May 13, 2008
`May13, 2008
`
`VeSlA
`
`
`
`
`
`

`

`Sheet 4 of 13
`Sheet 4 of 13
`
`US 7,372,826 B2
`US 7,372,826 B2
`
`0/17
`OLV
`
`89 "SO|-
`
`U.S. Patent
`U.S. Patent
`
`
`
`May 13
`, 2008
`May 13
`, 2008
`
`cOr
`
`

`

`U.S. Patent
`U.S. Patent
`
`May 13, 2008
`May13, 2008
`
`Sheet S of 13
`Sheet 5 of 13
`
`US 7,372,826 B2
`US 7,372,826 B2
`
`5.
`525
`
`
`
`g
`USER
`g
`cS
`
`:
`USER
`g
`co
`
`PTTDIRECTORY
`
`FIG.4
`
`:
`530
`
`517
`
`515
`
`

`

`U.S. Patent
`
`May 13, 2008
`
`Sheet 6 of 13
`
`US 7,372,826 B2
`
`INDICATE THAT APTT SESSION SHOULD COMMENCE -200
`
`
`
`
`
`ESTABLISH VOICE CONNECTION TO INTEATORMS
`AND INTENDED RECIPIENT MS
`
`REFER TO PTT DIRECTORY - 2020
`
`2015
`
`
`
`
`
`
`
`
`
`
`
`
`
`TRANSMTTED TO ANOTHERMS
`
`
`
`
`
`SIGNAL REVERSION TO LISTEN MODE
`
`
`
`
`
`2030
`
`2035
`
`
`
`2045
`
`HALT TRANSMISSION OF VOICE SIGNAL
`
`2050
`
`
`
`INDICATE THAT PTT SESSION SHOULD TERMINATE H'
`
`CLOSE VOICE CONNECTIONS -2060
`FIG. 5
`
`

`

`U.S. Patent
`
`May 13, 2008
`
`Sheet 7 of 13
`
`US 7,372,826 B2
`
`
`
`
`
`„LXELL LNW LSN||
`
`5) NÆ)SW
`
`X{R+O/VALEN
`
`
`
`
`
`
`
`

`

`U.S. Patent
`
`May 13, 2008
`
`Sheet 8 of 13
`
`US 7,372,826 B2
`
`SIGNAL START OF RECORDING VOICE MESSAGE
`
`
`
`
`
`DETECTSGNAL
`
`3020
`
`ESTABLISH VOICE CALL TO USER'S MS
`
`
`
`
`
`RECORD VOICE MESSAGE
`
`3040
`
`
`
`
`
`3010
`
`3030
`
`
`
`
`
`
`
`DERIVE INSTANT TEXT MESSAGE FROM VOICE
`MESSAGE
`
`3050
`
`
`
`
`
`CAUSE INSTANT TEXT MESSAGE TO BE DELIVERED
`TO ANOTHER IMG
`
`3060
`
`EXTRACT RECORDING FROM (NSTANT TEXT MESSAGE
`
`PLAYBACK RECORDING
`
`3O80
`
`FIG. 7
`
`

`

`U.S. Patent
`
`May 13, 2008
`
`Sheet 9 of 13
`
`US 7,372,826 B2
`
`SUESCRIBER
`
`THE SUBSCRIBERDIALS1-800-888-VIM1'
`"ENTER TO CREATEA NEW GROUP, ENTER2TO RECORDAMESSAGE, OR3 ACCESSING
`TO OBTAINSTATUS FROMA PREVIOUS WIMSESSION"
`SYSTEM
`
`IMG
`(ST-16)
`
`
`
`SUBSRIBER ENERS 1
`
`"PLEASE ENTEREACH NUMBER FOLLOWED BY THE # KEY, WHEN
`FINISHED PLEASE PRESS THE STARKEY."
`
`X
`
`DEFINING
`A NEW
`WG.
`
`THE SUBSCRIBERENTERSEACH NUMBERAND ENDS WITH THE STAR KEY
`
`THE SYSTEMWOULD THEN PLAYBACK THENUMBERS FOLLOWED BY.
`"TO ACCEPT PRESS 1, TO CHANGE PRESS 2"
`
`SUBSCRIBERENTERS 1
`
`"IF YOU WISHTO RECORDAMESSAGE STARTRECORDING AT THE TONE
`OTHERWISE STAY ON THE LINE FORMOREOPTIONS ONCE YOU WECOMPLETED
`RECORDING, YOU MAYHANG-UPTO SEND YOUR MESSAGE."
`
`"PLEASE ENTER THE WIMGROUPID TO RECORDAMESSAGE FOR."
`
`SUBSCRIBERENTERS THE VIM GROUDID
`
`RECORD
`AND PLAY
`OUTA
`MESSAGE
`
`"AT THE TONESTART RECORDING YOUR MESSAGE HANG-UPWHENFINISHED"
`
`THE SUBSCRIBER RECORDS THE MESSAGE AND HANGS-UP
`THE SYSTEM STARTS PLACING OUT-BOUND CALLS TO
`THE MEMBERS OF THE WG.
`
`THE SUBSCRIBER DALS"1-800-888-VIM1
`"ENTER TO CREATEA NEW GROUP, ENTER2TO RECORDAMESSAGE,
`OR3 TO OBTAINSTATUS FROMA PREVIOUS WIMSESSION"
`
`OPTIONAL
`RTREil
`
`SUBSCRIBERENTERS 3
`THE SYSTEMPLAYS OUT THE RECEIVE STATUS
`FOREACH MEMBER OF THE WO
`
`FIG. 8
`
`

`

`U.S. Patent
`U.S. Patent
`
`May 13, 2008
`May13, 2008
`
`Sheet 10 of 13
`Sheet 10 of 13
`
`US 7,372,826 B2
`US 7,372,826 B2
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`U.S. Patent
`
`May 13, 2008
`May13, 2008
`
`Sheet 11 of 13
`Sheet 11 of 13
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`US 7,372,826 B2
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`2008
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`Sheet 12 of 13
`
`372,826 B2
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`May13, 2008
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`Sheet 13 of 13
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`US 7,372,826 B2
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`US 7,372,826 B2
`
`1.
`PROVIDING ADVANCED
`COMMUNICATIONS FEATURES
`
`BACKGROUND
`
`2
`Thus, CDMA modulation spectrally spreads a narrowband
`information signal over a broad bandwidth by multiplex
`modulation, using a codeword to identify various signals
`sharing the same frequency channel. 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 techniques, a CDMA system
`generally employs a bandwidth of approximately 1.25 MHz
`or greater.
`Typically, the mobile communication 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
`(“BTS) 102a. Several BTS 102a-n are centrally adminis
`tered via fixed links 104a-n by a Base Station Controller
`(“BSC) 106a. The BTSs and BSC are sometimes collec
`tively referred to as the Base Station Subsystem (“BS”) 107.
`Several BSCs 106b-n may be centrally administered by a
`Mobile Switching Center (“MSC) 110 via fixed links
`108a-n.
`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. U.S. mobile
`networks include a home MSC and a serving MSC. The
`home 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 mobile 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
`HLR may be physically distributed but is treated as a single
`entity). As will be explained below, the HLR 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.
`Mobile network signaling has at least two significant
`aspects. One aspect involves the signaling between an MS
`and the rest of the network. In the case of 2G (2G” 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, VLRs, 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). SS7 is a common channel signaling system by
`
`15
`
`25
`
`30
`
`35
`
`40
`
`This invention relates to providing advanced communi
`cations features.
`Wireless telecommunication systems are able to provide
`wireless versions of information services traditionally pro
`vided by land-line or copper wire systems. Examples of 10
`wireless communications 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 office (MTSO), and a network to which the
`wireless communications 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 efficiently utilize the available frequency spectrum.
`For example, frequency division multiple access (FDMA),
`time division multiple access (TDMA), and code division
`multiple access modulation techniques are used to build
`high-capacity multiple access systems. Telecommunication
`systems designed to communicate with many 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 25-30 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 FD/TDMA system. In
`a digital FD/TDMA (commonly referred to as TDMA)
`cellular system, a narrowband frequency channel is refor
`matted as a digital transmission path which is divided into a
`number of time slots. The data signals from 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
`FDMA bandwidth, a bandwidth of approximately 30 kHz is
`generally used for AMPS-D digital TDMA cellular systems.
`Another approach to cellular multiple access modulation
`is CDMA. CDMA 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).
`
`45
`
`50
`
`55
`
`60
`
`65
`
`

`

`3
`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 communication) are transmitted and received in accor
`dance with various standards. For example, the Electronics
`Industries Association (“EIA) and Telecommunications
`Industry Association (“TIA) help define many U.S. stan
`dards, such as IS-41, which is a MAP standard. Analogously,
`the CCITT and ITU help define international standards, such
`as GSM-MAP, 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 TELECOM
`MUNICATIONS NETWORKS (Wiley 1998).
`To deliver a call from 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 serving
`MSC routes the call to the local exchange of the dialed user
`on the PSTN 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
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`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 PSTN 120) the PSTN user dials the MS’s
`associated phone number. At least according to U.S. stan
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`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
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`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
`“handoffs, and they involve their own types of known
`messages and signaling.
`One aspect of MAP involves “mobility management.”
`Different BSs and MSCs may be needed and used to serve
`an MS, as the MS 114 roams to different locations. Mobility
`management helps to ensure that the serving MSC has the
`subscriber profile and other information 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
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`mobile identification number (“MIN), the electronic serial
`number (“ESN), MS status, and the MS service profile,
`among other things. The VLR stores similar information in
`addition to storing an MSC identification that identifies the
`home 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 VLR 116
`via the BS 107 and MSC 110. The VLR 116 sends a location
`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 HLR 118 requests the VLR
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`(if any) 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 traffic
`interfaces between a BS 107 and an MSC 110 in a CDMA
`mobile network. The BS 107 communicates signaling infor
`mation using an SS7-based interface for controlling voice
`and data circuits known as the "A1 interface. An interface
`known as “A2 carries user traffic (such as Voice signals)
`between the switch component 204 of the MSC and the BS
`107. An interface known as “A5” 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. Informa
`tion about one or more of A1, A2, A5 may be found in
`CDMA Internetworking 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 Internet. For at least some
`of 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 110. 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—
`integrating 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 of a packet-switching medium. A packet-switching
`medium operates as follows. A sequence of data 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 information, 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 be lost.
`With respect to the Internet, multicast communication
`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
`multicast communication uses only the network components
`(e.g., Switches and trunks) actually needed for the multicast
`transmission.
`In multicast processing, when a potential participant
`(“host') is directed to join a particular IP 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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`group and receive information sent to this group. For
`example, a host A sends a message to join multicast group
`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 Ethernet
`multicast address, and sends the resultant Ethernet packet to
`the appropriate Switch or Switches.
`According to the Internet Group Management Protocol
`(“IGMP), a hosts membership in a multicast 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(R), using Specialized
`Mobile Radio technology, and described at http://www.nex
`tel.com/phone services/directeonnect.shtml) 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 B. 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
`mobile telephone handsets or to search a list of pre-stored
`names of Subscribers.
`In the second version, conversations are allowed among
`members of a pre-defined group of Subscribers, known as a
`Talkgroup, which is identified by a number. The mobile
`telephone handset may allow Talkgroup 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 number in the handset, holds down the PTT
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`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 PTT button. If A releases the PTT button, another
`member on the group call may hold down the PTT button,
`acquire control signaled by the audible confirmation, and
`start speaking.
`Technology on the Internet includes instant text messag
`ing (IM), which lets users receive text messages moments
`after the messages are sent. IM provides a way to chat with
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`friends and also provides a useful tool for business. IM
`provides the convenience of electronic mail (e-mail) 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. (E-mail 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
`IM service, the software 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
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`sage to the recipient or facilitates a direct connection
`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 of a centralized
`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.
`According to the peer-to-peer approach (used by, e.g.,
`ICO), 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.) After a user logs
`on, the server provides the user's computer with the IP
`addresses of each other user on the user's contact list who is
`currently logged on. When the user 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 senders and recipient’s computers, which speeds trans
`fers by helping to avoid network traffic.
`America Online, Inc. (AOL) supplies AOL 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 Internet 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 may cover, e.g.,
`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 accommodate 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 accommodates 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 1-Mb/s col
`lective throughput, 10 active devices per transceiver can be
`supported at 100 kb/s 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, although
`Some accounting would need to be made for bandwidth
`consumed by overhead for channel access, handoffs, and any
`provision for asymmetric traffic (e.g., in which more bits
`flow 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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`With respect to the siting of access devices, since each
`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 ser