IA UN3728
`
`(12)
`
`United States Patent
`Dahod etal.
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 7,372,826 B2
`May13, 2008
`
`(54)
`
`(75)
`
`PROVIDING ADVANCED
`COMMUNICATIONS FEATURES
`
`5,634,196 A *
`S/1997) Alford voce 455/18
`5,717,830 A ™
`. 455/426.1
`2/1998 Sigler et al.
`
`5,838,748 A * LI/L998 Nauyen qo... ccc 375/970
`
`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)
`
`(Continued)
`FOREIGN PATENT DOCUMENTS
`
`EP
`
`0 650 284
`
`4/1995
`
`(Continued)
`OTHER PUBLICATIONS
`
`(73)
`
`Assignee: Starent Networks, Corp., Tewksbury,
`MA(US)
`
`(*)
`
`Notice:
`
`Subject to any disclaimer, the termof this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0days.
`
`(21)
`
`Appl. No.: 10/210,897
`
`(22)
`
`Filed:
`
`Aug. 1, 2002
`
`(65)
`
`(51)
`
`(52)
`
`(58)
`
`(56)
`
`Prior Publication Data
`
`US 2004/0022208 Al
`
`Feb. 5, 2004
`
`Int. Cl.
`
`(2006.01)
`H04Q 7/00
`CS Cliisnaaaaaws 370/328; 370/349, 370/356;
`370/389; 370/401; 455/517
`Field of Classification Search................. 370/312,
`370/328, 335, 342, 352-353, 355, 356, 432,
`370/441, 466, 349, 390, 401, 338, 389; 455/524,
`455/542, 560, 404.1, 412.1, 412.2, 414.1,
`455/517, 520; 705/26, 27; 379/88.01, 88.03,
`379/88.04, 88.16, 265.01, 265.02; 709/207,
`709/231, 238
`See application file for complete search history.
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`Schulzrinne, H. “The Session Initiation Protocol,” http://www.cs.
`columbia.edu/ucoms6 1$ 1/slides/11/sip_long/.pdf, May 2001.
`
`(Continued)
`
`
`Primary Examiner—Joseph Feild
`Assistant Examiner—tInder Pal Mehra
`
`(74) Attorney, Agent, or Firm—Wilmer Cutler Pickering
`Hale and Dorr LLP
`
`(57)
`
`ABSTRACT
`
`Advanced communicationsfeatures 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 onthe full-duplex communications
`apparatus. Mobile communications telephone calls are
`established with the first mobile station subsystem and the
`second mobile station subsystem. Oneofthefirst and second
`mobile station subsystems is selected as a voice signal
`source in the half-duplex communications session.
`
`4,677,656 A *
`5,513,181 A *
`
`6/1987 Burke et al. .......u.. 455/403
`4/1996 Bresalier et al,
`............ 370/465
`
`27 Claims, 13 Drawing Sheets
`
`GOOGLE 1017
`
`GOOGLE 1017
`
`1
`
`

`

`US 7,372,826 B2
`Page 2
`
`U.S. PATENT DOCUMENTS
`
`2003/0156688 Al *
`2003/0185202 Al*
`2005/0286689 Al *
`2006/0002358 Al
`2006/0140151 Al*
`
`$/2003
`10/2003
`12/2005
`1/2006
`6/2006
`
`McCartyet al.
`............ 379/67.1
`Maenpaa wicccssiscsssscvsese 370/352
`
`WUOTL ooecedeeesseeseeeceeee 379/88,22
`Rayet al.
`Dantu et al. wc. 370/331
`
`FOREIGN PATENT DOCUMENTS
`
`EP
`wo
`WO
`WoO
`WO
`WoO
`WO
`WO
`WO
`WO
`WO
`WO
`WO
`
`0 845 894
`WO-98/47298 A2
`WO-00/22792 A2
`WO01/45335
`WO 00/47005
`WO 00/57601
`WO 00/79826 Al
`WO-01/31939 AZ
`WO 01/56236
`WO-01/76276 A2
`WO 02/30010
`WO-02/45440 Al
`WO-02/054707 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
`7/2002
`
`OTHER PUBLICATIONS
`
`Handley, M. et al., “SIP Session
`letforg/html/rfc2543, Mar. 1999,
`
`Initiation Protocol,” http:///tools.
`
`* cited by examiner
`
`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
`200 1/0046234
`2002/0075805
`2002/0075814
`2002/0075875
`2002/0077 136
`2002/0078464
`2002/0085552
`2002/0085589
`2002/0086665
`2003/0017836
`2003/0063590
`2003/0088421
`2003/0128696
`
`A *
`A ®
`A *
`BI*
`Bl*
`BL*
`Bl *
`Bl*
`BI*
`BI*
`BL*
`BL*
`Al
`Al
`Al
`Al
`Al
`Al
`Al
`Al
`Al
`Al*
`Al*
`Al*
`Al*
`
`8/2000
`10/2000
`10/2000
`10/2001
`/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
`7/2002
`7/2002
`7/2002
`1/2003
`4/2003
`5/2003
`7/2003
`
`
`
`wee 455/426. 1
`........
`Sweet et al.
`wee 455/556.1
`.......
`Veijola et al.
`709/227
`Mattawayet al.
`..........
`370/390
`Maheret al.
`........css000
`Fumarolo et al.
`455/457
`Nilsson ..........
`»- 455/563
`455/563
`Beith et al......ccc.c4-022
`370/312
`Maggenti et al.
`........0..
`we 370/356
`Schneider .......
`
`- 370/260
`Boyle et al.
`.
`Christie caaivsicanccs
`370/236
`Wu et ab. ..... cece
`370/335
`Agrawal et al.
`Gupta et al.
`Desaiet al.
`Dravida et al.
`Maggenti et al.
`Dravida et al.
`Tandon
`Dravida et al.
`Maggenti et al.
`vee 455/517
`Vishwanathan etal.
`Mohan et al.
`.......
`severe 370/338
`Maesetal.
`Wengrovitz et al.
`
`seesees 370/352
`
`.
`
`2
`
`

`

`Sheet 1 of 13
`
`LYVYOld (
`
`U.S. Patent
`
`!!l|IlI|!!|!t'It({l1tti1!|!L
`
`May13
`
`, 2008
`
`US 7,372,826 B2
`
`3
`
`
`

`

`May13, 2008
`
`Sheet 2 of 13
`
`U.S. Patent
`
`US 7,372,826 B2
`
`FIG. 2
`PRIOR ART
`
`4
`
`4
`
`

`

`U.S. Patent
`
`May13, 2008
`
`Sheet 3 of 13
`
`US 7,372,826 B2
`
`OOV4
`
`
`VOLYV9L-LS
`
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`
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`
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`
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`

`

`May13
`
`, 2008
`
`US 7,372,826 B2
`
`U.S. Patent
`
`cOV
`
`Sheet 4 of 13
`
`deSls
`
`6
`
`

`

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

`

`U.S. Patent
`
`May13, 2008
`
`Sheet 6 of 13
`
`US 7,372,826 B2
`
`INDICATE THAT A PTT SESSION SHOULD COMMENCE
`
`
`
`AND INTENDED RECIPIENT MS
`
` ESTABLISH VOICE CONNECTIONTO INITIATOR MS
`
`REFER TO PTT DIRECTORY[—2020
`
`INDICATE THAT PTT SESSION SHOULD TERMINATE[~229°
`
`CLOSE VOICE CONNECTIONS
`
`[2260
`
`FIG. 5
`
`8
`
`8
`
`

`

`U.S. Patent
`
`May13, 2008
`
`Sheet 7 of 13
`
`US 7,372,826 B2
`
`
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`

`U.S. Patent
`
`US 7,372,826 B2
`
`
`
`May13, 2008
`
`Sheet $ of 13
`
`PLAY BACK RECORDING
`
`3080
`
`FIG. 7
`
`10
`
`10
`
`

`

`U.S. Patent
`
`May13,2008
`
`Sheet 9 of 13
`
`US 7,372,826 B2
`
`SUBSCRIBER
`
`THE SUBSCRIBER DIALS '1-800-888-VIM1'
`
`IMG
`(ST-16)
`
`“ENTER 1 TO CREATE A NEW GROUP, ENTER 2 TO RECORD A MESSAGE, OR 3|ACCESSING
`TO OBTAIN STATUS FROM A PREVIOUS VIM SESSION"
`SYSTEM
`
`=a
`
`SUBSRIBER ENTERS1
`
`[SS= DEFINING
`
`"PLEASE ENTER EACH NUMBER FOLLOWED BY THE # KEY, WHEN
`FINISHED PLEASE PRESS THE STAR KEY."
`
`ANEW
`VG,
`
`THE SUBSCRIBER ENTERS EACH NUMBER AND ENDS WITH THE STAR KEY
`
`THE SYSTEM WOULD THEN PLAY BACK THE NUMBERS FOLLOWEDBY...
`"TO ACCEPT PRESS 1, TO CHANGE PRESS 2"
`
`SUBSCRIBER ENTERS1
`
`‘IF YOU WISH TO RECORD A MESSAGE, START RECORDING AT THE TONE,
`OTHERWISESTAY ON THE LINE FOR MORE OPTIONS. ONCE YOU'VE COMPLETED
`RECORDING, YOU MAY HANG-UP TO SEND YOUR MESSAGE."
`
`SUBSCRIBER ENTERS THE VIM GROUDID
`
`"AT THE TONE START RECORDING YOUR MESSAGE. HANG-UP WHENFINISHED"
`
`RECORD
`AND PLAY
`OUTA
`MESSAGE
`
`THE SUBSCRIBER RECORDS THE MESSAGE AND HANGS-UP
`
`THE SYSTEM STARTS PLACING OUT-BOUND CALLS TO
`THE MEMBERSOF THE VG.
`
`_ =o
`
`= =
`
`THE SUBSCRIBERDIALS '1-800-888-VIM1'
`OPTIONAL
`"ENTER 1 TO CREATEA NEWGROUP, ENTER2 TO RECORD A MESSAGE, Rea
`
`OR 3 TO OBTAIN STATUS FROM A PREVIOUS VIM SESSION"
`
`SUBSCRIBER ENTERS3
`
`THE SYSTEM PLAYS OUT THE RECEIVE STATUS
`FOR EACH MEMBER OF
`TH
`
`FIG. 8
`
`11
`
`

`

`U.S. Patent
`
`May13, 2008
`
`Sheet 10 of 13
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`US 7,372,826 B2
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`May13, 2008
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`

`US 7,372,826 B2
`
`BACKGROUND
`
`This invention relates to providing advanced communi-
`cations features.
`
`1
`PROVIDING ADVANCED
`COMMUNICATIONS FEATURES
`
`2
`Thus, COMA 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-
`codedsignals using the appropriate codeword. In contrastto
`the narrowband channels of approximately 30 kHz used in
`FDMAand TDMA modulation techniques, a CDMA system
`Wireless telecommunication systems are able to provide
`generally employs a bandwidth of approximately 1.25 MHz
`wireless versions of information services traditionally pro-
`or greater.
`vided by land-line or copper wire systems. Examples of
`‘Typically, the mobile communication systems described
`wireless communications applications include Advanced
`above are arranged hierarchically such that a geographical
`Mobile Phone Service (AMPS) analog cellular service and
`Code Division Multiple Access (CDMA) and Advanced
`“coverage area” is partitioned into a number of smaller
`geographical areas called “cells.” Referring to FIG, 1, each
`Mobile Phone Service (AMPS-D) digital cellular service in
`cell
`is preferably served by a Base Transceiver Station
`North America, and Group Speciale Mobile (GSM)cellular
`(“BTS”) 102a. Several BTS 102a-n are centrally adminis-
`service in Europe.
`tered via fixed links 104a-n by a Base Station Controller
`Although the particular application may vary, the com-
`(“BSC”) 106a. The BTSs and BSC are sometimes collec-
`ponents of a wireless communication system are generally
`tively referred to as the Base Station Subsystem (“BS”) 107.
`similar, as described in more detail below. For example, a
`Several BSCs 1064-7 may be centrally administered by a
`wireless communication system usually includes a radio 2
`terminal or mobile station, a radio base station, a switch or
`Mobile Switching Center (“MSC”) 110 via fixed links
`1084-1.
`network control device, often referred to as a mobiletele-
`MSC 110 acts as a local switching exchange (with addi-
`phone switching office (MTSO), and a network to which the
`tional features to handle mobility management require-
`wireless communications system provides access, such as
`ments, discussed below) and communicates with the phone
`the Public Switched Telephone Network (PSTN).
`network (“PSTN”) 120 through trunk groups. U.S. mobile
`‘The various wireless communicationapplications use any
`networks include a home MSCand a serving MSC. The
`of multiple modulation techniques for transmitting informa-
`home MSC is the MSC corresponding to the exchange
`tion to efficiently utilize the available frequency spectrum.
`associated with a Mobile Subscriber (also referred to above
`For example, frequency division multiple access (FDMA),
`as a mobile station or “MS”); this association is based on the
`time division multiple access (TDMA), and code division
`phone number, such as the area code, of the MS. Examples
`multiple access modulation techniques are used to build
`ofan MS include a hand-held device such as a mobile phone,
`high-capacity multiple access systems. Telecommunication
`a PDA, a 2-way pager, or a laptop computer, or Mobile Unit
`systems designed to communicate with many mobile sta-
`Equipment, such as a mobile unit attached toa refrigerator
`tions occupying a commonradio spectrum are referred to as
`van or a rail car, a container, or a trailer.
`multiple access systems.
`The home MSC is responsible for a Home Location
`For example, in an FDMAanalog cellular system, such as
`Register (“HLR”) 118 discussed below. The serving MSC,
`an AMPSanalog cellular radio system, the available fre-
`on the other hand, is the exchange used to connect the MS
`quency spectrum is divided into a large number of radio
`call to the PSTN. Consequently, sometimes the home MSC
`channels, e.g., pairs of transmit and receive carrier frequen-
`and serving MSC functions are served by the sameentity,
`cies, each of which corresponds to a message transmission
`channel. The bandwidth of each transmit and receive fre-
`but other times they are not (such as when the MS is
`roaming). Typically, a Visiting Location Register (“VLR”)
`quency channel is narrowband, generally 25-30 kHz. Thus,
`
`the FDMAsystempermits information to be transmitted in 116 is co-located with the MSC 110 andalogically singular
`a bandwidth comparable to the bandwidth of the transmitted
`HLR is used in the mobile network (a logically singular
`information, such as a voice signal. The cellular service area
`HLR may be physically distributed but is treated as a single
`in the FDMAsystemis generally divided into multiple cells,
`entity). As will be explained below, the HLR and VLR are
`each cell having a set of frequency channels selected so as
`used for storing subscriber information and profiles.
`Radio channels 112 are associated with the entire cover-
`to help reduce co-channel interference betweencells.
`Frequency division is often combined with time division
`age area. As described above, the radio channels are parti-
`so that transmission circuits are distinguished in both the s
`tioned into groups of channels allocated to individual cells.
`frequency and time domain, e.g., ina FD/TDMAsystem. In
`The channels are used to carry signaling information to
`a digital FD/TDMA (commonly referred to as TDMA)
`establish call connections and related arrangements, and to
`cellular system, a narrowband frequency channel is refor-
`carry voice or data information once a call connection is
`established,
`matted as a digital transmission path whichis divided into a
`two significant
`least
`number of time slots. The data signals from different calls 5
`Mobile network signaling has at
`are interleaved into assigned time slots and sent out with a
`aspects. One aspect involves the signaling between an MS
`and the rest of the network. In the case of 2G (“2G”is the
`correspondingly higher bit rate, the time slot assigned to
`each mobile station being periodically repeated. Although
`industry term used for “second generation”) and later tech-
`the TDMA bandwidth may be somewhat larger than the
`nology, this signaling concerns access methods used by the
`FDMAbandwidth, a bandwidth of approximately 30 kHz is
`MS(such as TDMA or CDMA), pertaining to, for example,
`generally used forAMPS-Ddigital TDMAcellular systems.
`assignment ofradio channels and authentication. A second
`Another approachto cellular multiple access modulation
`aspect involves the signaling among the various entities in
`is CDMA. CDMAis a spread spectrum technique for
`the mobile network, such as the signaling among the MSCs,
`transmitting information over a wireless communication
`BSCs, VLRs, and HLRs. This second part is sometimes
`system in which the bandwidth occupied by the transmitted
`referred to as the Mobile Application Part (“MAP”) espe-
`signal is significantly greater than the bandwidth required by
`cially when used in the context of Signaling System No. 7
`the baseband information signal (e.g., the voice signal).
`(“SS7"). SS7 is a common channel signaling system by
`
`ay
`
`0
`
`4
`
`45
`
`60
`
`65
`
`16
`
`16
`
`

`

`US 7,372,826 B2
`
`3
`which elements of the telephone network exchange infor-
`mation, in the form of messages.
`The various forms ofsignaling (as well as the data and
`voice communication) are transmitted and received in accor-
`dance with various standards. For example, the Electronics
`Industries Association (“ELA”) and Telecommunications
`Industry Association (“TILA”) help define many U.S. stan-
`dards, such as IS-41, which is a MAPstandard. Analogously,
`the CCITT and ITU help define international standards, such
`as GSM-MAP. whichis an international MAP standard.
`Information about these standards is well known and may be
`found fromthe 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 numberindicating the service requested to
`the MSC 110 via the BS 107. The MSC110 checks with an
`
`associated VLR 116 (described below) to determine whether
`the MS 114 is allowed the requested service. The serving
`MSCroutes the call to the local exchange of the dialed user
`on the PSTN 120. The local exchangealerts the called user
`terminal, and an answerback signal is routed back to the MS
`114 throughthe serving MSC 110 which then completes the
`speech path to the MS. Oncethe 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 userdials the MS's
`associated phone number. At least according to U.S. 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
`MSCthen interrogates the HLR 118 to determine which
`MSCis currently serving the MS. This also acts to inform
`the serving MSCthat a call is forthcoming. The home MSC
`then routes the call to the serving MSC. The serving MSC
`pages the MSvia 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 ofsignal 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 roamsto different locations. Mobility
`management helps to ensure that the serving MSChas 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 HLRis used to store andretrieve the
`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 MAPprotocols,
`location update procedures (or registration notifications) are
`performed so that the home MSC ofa 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 andregisters 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 usertraflic
`interfaces between a BS 107 and an MSC 110 ina CDMA
`mobile network. The BS 107 communicates signaling infor-
`mation using an SS7-based interface for controlling voice
`and data circuits known as the “AI”interface. Aninterface
`known as “A2” carries user traffic (such as voice signals)
`between the switch component 204 of the MSCand the BS
`107. Aninterface known as “A5”is used to provide a path
`for user traflic for circuit-switched data calls (as opposed to
`voice calls) between the source BS and the MSC. Informa-
`tion about one or more of Al, A2, A5 may be found in
`CDMAInternetworking—Deploying the Open-AInterface,
`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
`ofthese services, MSCs are not cost effective because they
`were primarily designed for voice calls. Integration of new
`services into the MSCis difficult or infeasible because ofthe
`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 MSCdesign changesor 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 sequenceofdatais 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 commontype 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-
`nismthat may cause it to be discarded), may be duplicated,
`and may belost.
`to the Internet, multicast communication
`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
`ofdata 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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`US 7,372,826 B2
`
`5
`to this group. For
`group and receive information sent
`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.
`Uponreceiving 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 host's 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®, using Specialized
`Mobile Radio technology, and described at http://www.nex-
`tel.com/phone_services/directconnect.shtml)
`having
`two
`versions has been proposed for special connection calls
`among MSs. Both versions of the special connectioncalls
`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 ofsubscribers.
`
`In the second version, conversations are allowed among
`members of a pre-defined group of subscribers, knownas 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
`button, and, upon receiving an audible confirmation such as
`a chirp, can start speaking. All of the other Talkgroup
`members onthe group call can only listen while A is holding
`downthe PTTbutton. If A releases the PTT button, another
`memberon the group call may hold down the PTTbutton,
`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
`friends and also provides a useful tool for business. IM
`provides the convenienceof 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 knowthat the useris
`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 ofboth 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..
`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.) 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 whois
`currently logged on. When the user creates a message to
`send to anotheruser, the user’s computer sends the message
`directly to the recipient’s computer, without involving the
`server. Messagestraverse only the network portion between
`the sender’s and recipient’s computers, which speeds trans-
`fers by helping to avoid networktraffic.
`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
`messagetravels along AOL’s centralized network. However,
`whenthe user sendsa 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 systemrelies
`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 conventionalcell 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 ofdevices, 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 fromit).
`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 7,372,826 B2
`
`7
`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 serving as a
`backbone.
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`FIGS. 5, 7 are flow diagrams of procedures in commu-
`nications systems.
`FIGS. 8, 12 are call
`communications systems.
`
`flow diagrams of sequences in
`
`DETAILED DESCRIPTION
`
`SUMMARY
`
`Advanced communications features are provided in a
`mobile communications network having at least one mobile
`switching center and at least one mobilestation subsystem.
`The mobile switching center and mobile station subsystem
`each communicate signaling messages according to a mobile
`signaling protocol.
`In an aspect ofthe invention, anindication is received that
`a half-duplex mobile communications session is to be ini-
`tiated betweena first mobile station subsystem and a second
`mobile station subsystem. (As used herein, “half-duplex”
`refers to a session in which at most one MS at a timeis
`considered a transmission source; “half-duplex” does not
`necessarily mean the sharing, alternating or otherwise, of
`any channel or mediumfor transmissionand reception.) 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 commu-
`nications telephonecalls are established with the first mobile
`station subsystem and the second mobile station subsystem.
`Oneof the first and second mobile station subsystems is
`selected as a voice signal source in the half-duplex commu-
`nications session.
`In another aspectof the invention, messagedata is derived
`from an audio signa