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`US 2{){)4t)t)222(}8/\1
`
`(19) United States
`(12) Patent Application Publication (10; Pub. No.: US 2004/0022203 A1
`Dahod et al.
`(43) Pub. Date:
`Feb. 5, 2004
`
`(54)
`
`l’R()VIl)ING ADVANCICI)
`COMM UNICATI ONS FEATU RES
`
`(52) U.S. Cl.
`
`.......................................... .. 37l],v‘328; 3'r'0f4UI
`
`(75)
`
`Inventors: Ashraf M. Daltod. Andover, MA (US);
`Michael Silva, East Sandwich, MA
`(US); Peter Higgins, Sa ndwich, MA
`(US); Rajat Ghul, West Yarmouth, MA
`(US); John |)el’ietm, Brewster, MA
`(US); Nick Lopez, Sleepy Hollow, II.
`(US); Paul Shiell, Westborough, MA
`(US)
`
`Correspondence Address:
`1-I/\I.l'lANl) DORR, LLP
`60 S'l‘ATE STREET
`li()S'I"()N, MA {T2109
`
`(73)
`
`(31)
`
`Assignec: Starent Networks, Tewksbury, MA
`
`Appl. No.:
`
`l0;’2l0,897
`
`(33)
`
`l-'iled:
`
`Aug. 1, 2002
`
`I’t|I:tlieation Classification
`
`(51)
`
`1m.CI.’ __________________________ ..]-{04Q 7,100; 11041, 12.88:
`11041. 12156
`
`(57)
`
`ABS'l‘R/\C'l‘
`
`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
`tirst mobile station subsystem and a second
`mobile station subsystem. The first and second mobile
`station subsystems include full-duplex communications
`apparatus for use in fu||—cluplex mobile communications
`sessions. The haltlrluplex mobile communications session
`relies on the first and second mobile station subsystems, and
`all otthe 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 ol‘ the first and second
`mobile station subsystems is selected as a voice signal
`source in the hall’-duplex communications session.
`
`SOFT
`SWITCH
`
`K 400
`
`SOFFSWITCH
`
`001
`001
`
`Apple 1009
`Apple 1009
`U.S. Pat. 8,243,723
`U.S. Pat. 8,243,723
`
`

`
`Patent Application Publication
`
`Feb. 5, 2004 Sheet 1 of 13
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`US 2004/0022208 A1
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`Patent Application Publication
`
`Feb. 5, 2004 Sheet 2 of 13
`
`US 2004/0022208 Al
`
`FIG. 2
`PRIOR ART
`
`003
`003
`
`

`
`Patent Application Publication
`
`Feb. 5, 2004 Sheet 3 of 13
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`US 2004/0022203 A1
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`Patent Application Publication
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`Feb. 5, 2004 Sheet 5 of 13
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`US 2004/0022208 A1
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`530
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` FIG.4
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`Patent Application Publication
`
`Feb. 5, 2004 Sheet 6 of 13
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`US 2004/0022208 A1
`
`INDICATE THAT A PTT SESSION SHOULD COIVIMENCE
`
`2010
`
`
`
`ESTABLISH VOICE CONNECTION TO INITIATOR MS
`AND INTENDED RECIPIENT MS
`
`
`
`2015
`
`REFER TO PTT DIRECTORY
`
`2020
`
`DEFAULT TO LISTEN MODE
`
`
`
`SWITCH TO TALK MODE ON SIGNAL
`
`
`
`
`
`
`2030
`
`
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`CAUSE VOICE SIGNAL FROM MS TO BE
`TRANSMITTED TO ANOTHER MS
`
`2035
`
`
`
`
`
`
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`IGNORE OTHER VOICE SIGNALS
`
`
`
`2040
`
`
`
`2045
`
`SIGNAL REVERSION TO LISTEN MODE
`
`HALT TRANSMISSION OF VOICE SIGNAL
`
`
`
`
`
`
`
`2050
`
`
`
`2055
`
`
`
`INDICATE THAT PTT SESSION SHOULD TERMINATE
`
`CLOSE VOICE CONNECTIONS
`
`205°
`
`FIG. 5
`
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`

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`Sheet 7 of 13
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`US 2004/0022208 A1
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`Patent Application Publication
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`Feb. 5, 2004 Sheet 8 of 13
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`US 2004/[)022203 A1
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`
`
`3010
`
`3050
`
`
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`
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`SIGNAL START OF RECORDING VOICE MESSAGE
`
`
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`DETECT SIGNAL
`
`
`
`3020
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`ESTABLISH VOICE CALL TO USER'S MS
`
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`RECORD VOICE MESSAGE
`
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`3040
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`DERIVE INSTANT TEXT MESSAGE FROM VOICE
`MESSAGE
`
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`3060
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`3070
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`CAUSE INSTANT TEXT MESSAGE TO BE DELIVERED
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`EXTRACT RECORDING FROM INSTANT TEXT MESSAGE
`
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`PLAY BACK RECORDING
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`3030
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`

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`Patent Application Publication
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`Feb. 5, 2004 Sheet 9 of 13
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`US 2004/0022208 A1
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`SUBSCRIBER
`
`THE SUBSCRIBER DEALS '1-800~888-VlM1'
`
`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
`
`1
`
`SUBSRIBER ENTERS 1
`
`—-5 1 1 1
`
`"PLEASE ENTER EACH NUMBER FOLLOWED BY THE # KEY, wHEN
`FINISHED PLEASE PRESS THE STAR KEY.‘
`
`DEFINING
`A NEW
`VG’
`
`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 OHANOE PRESS 2'
`
`SUBSCRIBER ENTERS 1
`
`“IF YOU WISH TO RECORD A MESSAGE, START RECORDING AT THE TONE,
`OTHERWISE STAY ON THE LINE FOR MORE OPTIONS. ONCE YOU'VE COMPLETED
`RECORDING, YOU MAY HANG—UP TO SEND YOUR MESSAGE."
`
`"PLEASE ENTER THE VIM GROUP ID TO RECORD A MESSAGE FOR.“
`
`SUBSCRIBER ENTERS THE VIM GROUD ID
`
`RECORD
`AND PLAY
`OUT A
`MESSAGE
`
`"AT THE TONE START RECORDING YOUR MESSAGE. 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.
`
`THE SUBSCRIBER DIALS '1-800-888-V|M1'
`
`N’
`ENTER 1 TO CREATE A NEW GROUP, ENTER 2 TO RECORD A MESSAGE,
`OR 3 TO OBTAIN STATUS FROM A PREVIOUS WM SESSION"
`
`OPTIONAL
`STATUS
`RETRIEVAL
`
`SUBSCRIBER ENTERS 3
`
`THE SYSTEM PLAYS OUT THE RECEIVE STATUS
`
`010
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`

`
`Patent Application Publication
`
`Feb. 5, 2004 Sheet ll} of 13
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`US 2004/0022208 A1
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`US 2004/l}{)22208 A1
`
`Feb. 5, 2004
`
`PROVIDING ADVANCED COMMUNICATIONS
`FI*lA'I'URES
`
`BACKG ROUND
`
`[0001] This invention relates to providing advanced com-
`munications features.
`
`[0002] Wireless telecommunication systems are able to
`provide wireless versions of information services tradition-
`ally provided by land—linc or copper wire systems. Examples
`of wireless communications applications include Advanced
`Mobile Phone Service (AMPS) analog cellular service and
`Code Division Multiple Access (C DMA) and Advanced
`Mobile Phone Service (AMPS-D) digital cellular service in
`North America, and Group Speciale Mobile (GSM) cellular
`service in Europe.
`
`[0003] Although the particular application may vary, the
`components of a wireless communication system are gen-
`erally 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 telephone switching ofice (MTSO), and a network to
`which the wireless communications system provides access,
`such as the Public Switched Telephone Network {PSTN).
`
`[0004] The various wireless communication applications
`use any of multiple modulation techniques for transmitting
`in formation to efiiciently 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 highcapacity multiple access systems. Telecommuni-
`cation systems designed to communicate with many mobile
`stations occupying a common radio spectrum are referred to
`as multiple access systems.
`
`For example, in an FDMA analog cellular system,
`[0005]
`such as an AMPS analog cellular radio system, the available
`frequency 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 I-‘DMA 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 FDMAsystem is generally divided into multiple cells,
`each cell having a set of frequency channels selected so as
`to help reduce oocharmel interference between cells.
`
`Frequency division is often combined with time
`[0006]
`division so that
`transmission circuits are distinguished in
`both the frequency and time domain, e.g., in a FDfl'DMA
`system. In a digital I"Dl'ITJMA (commonly referred to as
`TDMA) cellular system, a narrowband frequency channel is
`reformatted 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 tell: is
`generally used for AMPS-I) digital TDMA cellular systems.
`
`[0007] Another approach to cellular multiple access
`modulation is CDMA. CDMA is a spread spectrum tech-
`
`nique for transmitting information over a wireless commu-
`nication system in which the bandwidth occupied by the
`transmitted signal is significantly greater than the bandwidth
`required by the bascband information signal (eg, the voice
`signal). Thus, CDMA modulation spectrally spreads a nar-
`rowband infonnation 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 kl-Iz used in
`FDMA and TDMA modulation techniques, a CDMA system
`generally employs a bandwidth of approximately 1.25 MHz
`or greater.
`
`the mobile communication systems
`[0008] Typically,
`described above are arranged hierarchically such that a
`geographical "coverage area“ is partitioned into a number of
`smaller geographical areas called -~,;e]ls.” Referring to FIG.
`1, each cell
`is preferably served by a Base Transceiver
`Station {"BTS") 102:1. Several BTS 102:1-rt are centrally
`administered via fixed links l04rt-n by a Base Station
`Controller (“BSC”) 106:1. 'l'he B'I‘Ss and BSC are sometimes
`collectively referred to as the Base Station Subsystem
`(‘'BS”) 107. Several BSC's I06!)-rt may be centrally admin-
`istered by a Mobile Switching Center ("lVISC”} 110 via lixed
`links 108:1-rt.
`
`[0009] MSC.‘ 110 acts as a local switching exchange (with
`additional features to handle mobility management require-
`ments, discusscd below) and communicates with the phone
`network (“PS'IN") 120 through trunk groups. U.S. mobile
`networks include a home MSC and a serving MSC. ‘lhe
`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.
`
`[0010] The home MSC.‘ is responsible for a Home Location
`Register (“I-ILR") I18 discussed below. 'l'hc 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 (“VI.R“)
`116 is co-located with the MSC110 and a logically singular
`I-ILR 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 infonnation and profiles.
`
`[0011] Radio channels 112 are associated with the entire
`coverage area. As described above, the radio cha1'lncLs are
`partitioned 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.
`
`[0012] Mobile network signaling has at least two signifi-
`cant 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
`
`015
`015
`
`

`
`US 2004/0022208 A1
`
`Feb. 5, 2004
`
`technology, this signaling concerns access methods used by
`the MS (such as TDMA or CDMA), pertaining to,
`for
`example, assignment of radio channels and autl1cntication.A
`second aspect
`involves the signaling among the various
`entities in the mobile network, such as the signaling among
`the MSCS, BSCs, VLRs, and l~1LRs. This mcond part
`is
`sometimes referred to as the Mobile Application Part
`(“MAP”) especially when used in the context of Signaling
`System No. 7 ("SS'r"’). S57 is a common channel signaling
`system by which elements of the telephone network
`exchange information, in the form of messages.
`
`[0013] The various forms of signaling (as well as the data
`and voice communication) are transmitted and received in
`accordance with various standards. lior example, the Elec-
`tronics Industries Association (‘‘EIA‘') and Telecommunica-
`tions Industry Association ("TIA") help define many U.S.
`standards, such as IS-41, which is a MAP standard. Analo-
`gously, the CCITT and ITU help define international stan-
`dards, 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
`TI;iLl3.COMMUNlCA'l'10l\lS Nl_i'I'WORKS (Wiley 1998).
`
`[0014] 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 l’S'l‘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.
`
`[0015] 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.
`standards, the PSTN 120 routes the call to the MS ’s home
`MSC {which may or may not he 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.
`
`the BS 107 and MS 114 may
`[0016] During a call,
`cooperate to change channels or B'l‘Ss 102, if needed, for
`example, because of signal conditions. These changes are
`known as “handolIs,“ and they involve their own types of
`known messages and signaling.
`
`[0017] One aspect of MAP involves "mobility manage-
`ment." Different 138s and MS(.‘s maybe 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. ‘lb this end, MSCS
`use VLR 116 and HLR 118. The HLR is used to store and
`retrieve the mobile identification number {“MlN"), the elec-
`tronic serial number ("ESN”), MS status, and the MS service
`profile, among other things. The VLR stores similar infor-
`mation in addition to storing an MSC identification that
`
`In addition, under appropriate
`identifies the home MSC.
`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
`ttscd 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 \/'[.R 116 via the BS 107 and MSC Ill]. The VLR 116
`
`sends a location update message to the HLR I18 serving the
`MS 114, and the subscriber profile is downloaded from the
`HLR 118 to the VLR 116. The MS 114 is sent an acknowl-
`edgement of a successful
`location update. The I-{LR 118
`requests the VLR (if any) that previously held profile data to
`delete the data related to the relocated MS 114.
`
`[0018] FIG. 2 shows in more detail the signaling and user
`trallit: interfaces between a BS 107 and an MSC 110 in a
`
`CDMA mobile network. The BS 107 communicates signal-
`ing information using an SS7—based interface for controlling
`voice and data circuits known as the “Al" interface. An
`interface known as “A2” carries user tratlic (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.
`Information about one or more ofAl., A2, A5 may be found
`in CDMA lnternetworking—Dcploying the Open-/\ Inter-
`face, Su—Lin Low, Ron Schneider, Prentice Hall, 2000, ISBN
`U-13-088922-9.
`
`[0019] Mobile communications providers are supplying
`newer services. c. v., “data calls" to the Internet. For at least
`some of these services, MSCs are not cost elfective because
`they were primarily designed for voice calls. Integration of
`new services into the MSC is diflicult or infeasible because
`of the proprietary and closed designs used by many MSC
`software architectures. That is, the software logic necessary
`to provide the services is not easy to add to the MSC 110.
`Often, a switch adjunct is used to provide such services. For
`example, an lnter—Working Function (“lWF") is an adjunct
`to route a data call
`to the Internet. Either approach-
`integrating functionality into the MSC or adding a trunk-side
`adjunct—involvcs 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.
`
`[0020] 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 logically 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 mechanism that may cause it to be discarded),
`may be duplicated, and may be lost.
`
`[0021] With respect to the Internet, multicast communi-
`cation refers to the transmission of identical data packets to
`
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`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.)
`[0022] Each participant in a multicast receives informa-
`tion transmitted 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 trans-
`mitted by the participants of the multieast. In this way, the
`mu lticast communication uses only the network components
`(e.g., switches and trunks) actually needed for the multicast
`transmission.
`
`In multicast processing, when a potential partici-
`[0023]
`pant ("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 mul-
`ticast group and receive infortnatiott 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 rnulticast group X.
`A router R propagates the request up to the multicast source
`if the data path is not already in place.
`for
`for group X,
`[0024] Upon receiving an IP packet
`example, the router R maps an IP multicast group address
`into an Ethernet multieast address. and sends the resultant
`Ethernet packet to the appropriate switch or switches.
`[0025] According to the Internet Group Management Pro-
`tocol (“IGMP”), a host’s membership in a multicast group
`expires when the router does not receive a periodic mem-
`bership report from the host.
`[0026] With respect to interaction among MSs, a Nextel
`service (known as Nextel Direct Connect®, using Special-
`ized Mobile Radio technology, and described at httptfl
`www.rtextel.com;'phone__servicesr’directconnectshtml) hav-
`ing two versions has been proposed for special connection
`calls among MSS. Both versions of the special connection
`calls require special-purpose MSS. In the lirst version, a one
`to one conversation is allowed between two mobile tele-
`phone 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
`(“P'l'I"’) button, waits for an audible alert signifying that B
`is ready to receive, and starts speaking. To listen, A releases
`the 1’1'1‘ button. If B wishes to speak, B holds down the PT!‘
`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
`[0027]
`among members of a pre-delined group of subscribers,
`known as a Talkgroup, which is identified by a number. The
`mobile telephone handset may allow Talkgnoup 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 ‘Ialkgroup
`members on the group call can only listen while A is holding
`down the l’l'I‘ button. IfA releases the FIT button, another
`member on the group call may hold down the PTT button,
`acquire control signaled by the audible continuation, and
`start speaking.
`
`text
`includes instant
`[0028] Technology on the Internet
`messaging {lM), 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 convenience of electronic mail (e-mail) and
`the immediacy of a telephone call. The text messages arrive
`in real time (or nearly
`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 c—maiI 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. Adata 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 connection
`between the user and the recipient.
`
`[0029] An IM service typically uses one of three mecha-
`nisms 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 connected 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.
`
`[0030] 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 identities 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 com-
`puter 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 com-
`puters, which speeds transfers by helping to avoid network
`traffic.
`
`[0031] America Online, Inc. (AOL) supplies AOL Instant
`Messenger (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
`[0032]
`one wireless Internet system has been proposed that pro-
`vides reliable access to tens of megahertz of bandwidth
`across a wide geographic area, using local wireless trans-
`ceiver technology (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 trans-
`ccivers in the region. In such a system, each transceiver may
`cover. e.g., 0.05 square kilometers. which is about one-
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`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 trans-
`[0033]
`ceiver system network of 10,000 transceiver access points
`(cell centers), if each point provides its users with 1-Mbis
`collective throughput, 10 active devices per transceiver can
`be supported at 100 kbfs 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, hand-
`oifs, and any provision for asymmetric tralfic (e.g., in which
`more bits flow toward a device than from it).
`
`[0034] Each local wireless transceiver system access point
`may be or resemble access points [or wireless local area
`network (LAN) technology such as IEEE 802.11. An asyn-
`chronous 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). 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 aocess infrastructure serv-
`ing as a backbone.
`
`SUMMARY
`
`[0035] 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
`[0036]
`received that a half—duplex mobile communications session
`is to be initiated between a Iirst mobile station subsystem
`and a second mobile station subsystem. (As used herein,
`"half-duplex” refers to a session in which at most one M8 at
`a time is considered a transmission source; "half-duplex"
`does not necessarily mean the sharing, alternating or other-
`wise, 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 mobiie oommunications sessions. The half-du-
`ptex 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
`com munications 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.
`
`In another aspect of the invention, message data is
`[0037]
`derived from an audio signal originating at a mobile station
`subsystem. The message data is suitable for playback over a
`
`telephone system and constitutes a completed message.
`Based on an indication from the mobile station subsystem,
`a set of mobile station subsystem destinations is determined
`for the message data. For each of the mobile station sub-
`system destinations,
`it
`is determined whether the mobile
`station subsystem destination is ready to play back the
`message data. Each of the mobile station subsystem desti-
`nations includes real-time communications apparatus for use
`in real-time communications sessions. The readiness deter-
`mination relies on the mobile station subsystem destinations.
`All of the reliance is only on the real-time communications
`apparatus.
`
`Implementations of the invention may provide one
`[0038]
`or more of
`the
`following advantages. By supplying
`enhanced services that do not require new hardware at the
`user end, service providers can achieve additional revenue
`and profits with little or no investment oftime or resources
`into changes at the user end. Users gain mobility, flexibility,
`and time efliciency by being able to make more use of voice
`input for user control and content entry, so that interaction
`with communications resources is less demanding on eyes
`and fingers. The user experience is improved over conven-
`tional offerings so that the stability and loyalty of the user
`base is improved.
`
`[0039] Other advantages and features will become appar-
`ent Irom the following description, including the drawings,
`and from the claims.
`
`BRIEF DESCRIPTION OF THE DRAW