PCT
`
`WORLD INTELLECTUAL PROPERTY ORGANIZATION
`lntemational Bureau
`
`
`
`INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT)
`
`(51) International Patent Classification 5 :
`
`(11) International Publication Number:
`
`W0 99!63’?"r'3
`
`H04Q 7/22
`
`A1
`
`(43) International Publication Date:
`
`9 December I999 (0912.99)
`
`(21) International Application Number:
`
`PCTiGB99i0l'.-'57
`
`(22) International Filing Date:
`
`3 June 1999 ({)3.06.99)
`
`(30) Priority Data:
`98! 1966.2
`
`3 June I998 (0106.98)
`
`GB
`
`(71) Applicant (for at! designated States except US): ORANGE
`PERSONAL COMMUNICATIONS SERVICES LIMITED
`IGBIGBJ; St. James Court, Great Park Road, Almondsbury
`Park, Bristol BSIZ 4Q] (GB).
`
`(72) Inventor; and
`(T5) Inventot-{Applicant [for US only]: STUBBS, Martin [GBICH]:
`Orange Communications S.A., World Trade Center, Avenue
`Gratta—Pail|e 2, Case postale 476, CH-1000 Lausanne 30
`Grey (CH).
`
`(74) Agents: SPAARGAREN. Jerome et al.; R.G.C. Jenkins & Co.,
`26 Caxton Street. London SWIH URJ (GB).
`
`(81) Designated States: AE, AL, AM, AT, AT (Utility model), AU,
`AZ. BA, BB, BG, BR, BY, CA, CH. CN. CU, CZ, CZ
`(Utility model), DE, DE (Utility model), DK, DK (Utility
`model), EE, EE (Utility model), ES, FI, Fl (Utility model),
`GB. GD, GE. GH. GM, HR, HU, ID, IL, IN, IS. JP. KE.
`KG, KP, KR, KZ, LC, LK. LR, LS, LT, LU. LV, MD, MG,
`MK, MN, MW, MX, NO. NZ. PL, PT. RO, RU. SD, SE,
`SG, SI, SK, SK (Utility model), 81., TJ, TM, TR, TT, UA,
`UG, US, UZ, VN, YU, ZA. ZW. ARIPO patent (GH, GM,
`KE, LS, MW, SD, SL, SZ, UG, ZW), Eurasian patent (AM,
`AZ, BY, KG, KZ, MD, RU, TJ, TM), European patent (AT.
`BE, CH, CY, DE, DK, ES, FI, FR, GB, GR.
`‘IE, IT, LU,
`MC, NL, PT, SE), OAPI patent (BF, BJ, CF, CG, CI, CM,
`GA, GN, GW, ML, MR. NE, SN, TD. TG).
`
`Published
`With international Search report.
`Before the expiration of the time iitnit for amemiing the
`claims and to be republished in the event of the receipt of
`amendments.
`
`(54) Title: DYNAMIC ALLOCATION OF RADIO RESOURCES IN A PACKET SWITCHED COMMUNICATIONS—SYS'I'EM
`
`
`
`
`
`
`
`
`
`
`
`i|Eli%lil‘:li
`
`-F I-‘F17 1-‘ll
`
`(57) Abstract
`
`Voice andtot image data packets are transferred by a packet handler between user stations in a GSM—type mobile communications
`system using a General Packet Radio Service {GPRS) data link. Control data for controlling a call is stored in a data store accessible by
`the packet handler. The control data identifies call participants and the identity of a participant who has currently seized the call. A mobile
`station capable of video conferencing is operable in a ha1f—duplex video conferencing mode, in which intennittent transmission of video
`data is controlled by depression of a transmit button.
`
`Apple 1022
`Apple 1022
`U.S. Pat. 8,243,723
`U.S. Pat. 8,243,723
`
`I
`
`

`
`FOR THE PURPOSES OF INFORMATION ONLY
`
`Codes used to identify States party to the PC!‘ on the front pages of pamphlets publishing international applications under the PCT.
`
`Albania
`Armenia
`Austria
`Australia
`iuerbaijan
`Bosnia and Herzegovina
`Barbados
`Belgium
`Burkina Faso
`Bulgaria
`Benin
`Brazil
`Belarus
`Canada
`Central African Republic
`Congo
`Switzerland
`Core d'Ivoite
`Cameroon
`China
`Cuba
`Czech Republic
`Cuznnarly
`Denmark
`Esnonia
`
`ES
`FI
`FR
`GA
`63
`GE
`GH
`GN
`GR
`IIU
`IE
`IL
`IS
`IT
`JP
`KF.
`KG
`KP
`
`KR
`[(1
`LC
`LI
`LK
`
`Spain
`Finland
`France
`Gabon
`United Kingdom
`Georgia
`Ghana
`Guinea
`Greece
`Hungary
`Ireland
`Israel
`Iceland
`lialy
`Japan
`Kenya
`Kyrgyzstan
`Democratic People's
`Republic of Korea
`Republic of Korea
`Kazalcstan
`Saint Lucia
`Liechtenstein
`Sri Lanka
`Liberia
`
`[.5
`LT
`LU
`LV
`MC
`MD
`MG
`MK
`
`MI.
`MN
`MR
`MW
`MX
`NE
`NI.
`N0
`N2’.
`PL
`PT
`RO
`RU
`SD
`SE
`SG
`
`Lesotho
`Lithuania
`Luxembourg
`Latvia
`Monaco
`Republic of Moldova
`Madagascar
`The former Yugoslav
`Republic of Macedonia
`Mali
`Mongolia
`Mauritania
`Malawi
`Mexico
`Niger
`Nelhexiands
`Norway
`New Zealand
`Poland
`Portugal
`Romania
`Russian Federation
`Sudan
`Sweden
`Singapore
`
`SI
`SK
`SN
`SZ
`TD
`TG
`TJ
`TM
`TR
`1'!‘
`UA
`UG
`US
`UZ.
`VN
`YU
`ZW
`
`Slovenia
`Slovakia
`Senegal
`Swaziland
`Chad
`Togo
`Tajikistan
`'I‘urkmenistarI
`Tilrlrcy
`Trinitlad and ‘Tobago
`Ukraine
`Uganda
`United States of America
`Uzbekistan
`Viet Nam
`Yugoslavia
`Zimbabwe
`
`
`
`II
`
`

`
`W0 99i‘63773
`
`PCT.’GB99.*'0l76'7
`
`DYNAMIC ALLOCATION OF RADIO RESOURCES IN A PACKET SNITCHED COMMUNICATIONS-
`SYSTEM
`
`This invention relates to mobile communications, such as cellular
`
`communications. The invention is particularly, but not exclusively, applicable
`
`5
`
`to GSM-type mobile communications systems.
`
`An example of a cellular communications system which provides
`
`voice dispatch services is
`
`the Motorola (trademark)
`
`integrated digital
`
`enhanced network, or iDEN (trademark), system.
`
`The system includes
`
`Enhanced Base Transceiver Systems (EBTSS) at cell sites which link mobile
`
`10
`
`terminals to the fixed network equipment via a TDMA radio interface, and
`
`which are connected to controlling base station controllers (BSCS). The BSCs
`
`provide a link with a mobile switching centre (MSC) which provides
`
`conventional circuit switching with a public services telephone network
`
`(PSTN), and a Metro Packet Switch (MPS) which provides switching for the
`
`15
`
`dispatch services. A Dispatch Application Processor (DAP) coordinates and
`
`controls dispatch communications, by registering the identifications and
`
`locations of mobile terminals active in the system.
`
`The iDEN system provides both voice dispatch services, circuit-
`
`switched call services and other data communications services, such as a short
`
`20
`
`message service.
`
`US-A-5,416,770 describes a voice dispatch cellular communications
`
`system, in which audio data packets are transported via frame relay links.
`
`1
`
`

`
`W0 99»’637'='3
`
`PCTfGB99!0l‘T6‘l'
`
`Communication is established between a plurality of communication units by
`
`replicating the transmitted data packets, and distributing the replicated packets
`
`to identified target base stations.
`
`US—A-5,448,620 describes a mobile terminal which is operable in both
`
`5
`
`a voice dispatch mode and a telephone interconnect mode.
`
`A known GSM network, referred to as a public land mobile network
`
`(PLMN), is schematically illustrated in Figure 1. A mobile switching centre
`
`(MSC) 2 is connected via communication links to a number of base station
`
`controller (BSCs) 4. The BSCs 4 are dispersed geographically across areas
`
`10
`
`served by the mobile switching centre 2. Each BSC 4 controls one or more base
`
`transceiver stations (BTSS) 6 located remote from, and connected by further
`
`communication links to, the BSC. Each BTS 6 transmits radio signals to, and
`
`receives radio signals from, mobile stations 8 which are in an area served by that
`
`BTS. That area is referred to as a "cell". A GSM network is provided with a
`
`15
`
`large number of such cells, which are ideally contiguous to provide continuous
`
`coverage over the whole network territory.
`
`A mobile switching centre 2 is connected via communications links to
`
`other mobile switching centres in the remainder of the mobile communications
`
`network 10, and to other networks such as a public service telephone network
`
`20
`
`(PSTN), which is not illustrated. The mobile switching centre 2 is provided
`
`with a home location register (HLR) 12 which is a database storing subscriber
`
`authentication data including the international mobile subscriber identity (IMSI)
`
`which is unique to each mobile station 8. The IMSI is also stored in the mobile
`
`

`
`WO 99163773
`
`PCTfGB99.’0l':'6'?
`
`station in a subscriber identity module (SIM) along with other subscriber-
`
`specific infonnation.
`
`The mobile switching centre is also provided with a visitor location
`
`register
`
`(VLR)
`
`14 which is a database temporarily storing subscriber
`
`5
`
`authentication data for mobile stations active in its area.
`
`GSM was originally designed to support full duplex, circuit-switched
`
`voice calls.
`
`A new element of functionality is added in the GSM Phase 2+
`
`Technical Specifications, which is referred to as the advanced speech call
`
`10
`
`items (ASCI). This provides for group calls which are broadcast to members
`
`within a group.
`
`In order to establish a broadcast group call, an originating
`
`mobile station sends a service request to the MSC. containing the requested
`
`group identity. The MSC authenticates the subscriber using the VLR.
`
`If
`
`the
`
`authentication check is
`
`successful,
`
`the MSC requests
`
`15
`
`identification data for the members of the group from a group call register.
`
`With this information, the MSC sets up connections between the receiving
`
`mobile stations and a group call dispatcher. Each of the cells in which
`
`recipient mobile stations are located pages a notification, containing the
`
`identity of the group being called and the description of the channel allocated
`
`20
`
`for the group call broadcast. The group call dispatcher transmits the group
`
`call data to each of those cells, for broadcast on the allocated channels.
`
`A further element of functionality which is added to GSM in the GSM
`
`Phase 2+ Technical Specification is the general packet radio service (GPRS).
`
`

`
`W0 99!63773
`
`PCTJGBQ9.-‘0176‘7
`
`GPRS provides a packet-mode service to transfer high-speed and low-
`
`speed data and signalling efficiently over the GSM radio network.
`
`It
`
`is
`
`designed to support a range of types of data transfer, from intermittent and
`
`bursty data transfers to the occasional transfer of large volumes of data.
`
`It is
`
`5
`
`envisaged for use in Internet services, e-mail and other data services.
`
`GPRS includes facilities for both point to point (PTP) and point to
`
`multipoint (PTM) data packet transfer.
`
`In PTM data packet transfer, the data
`
`packets are broadcast in all of the cells in a defined geographical area. In each
`
`case, GPRS transmits the data packets transparently, insofar as other than
`
`10
`
`ensuring that the data packets are received correctly at their destination, there
`
`is no knowledge of the contents of the data packets on the network side.
`
`The GPRS radio interface is placed in a flexible number of TDMA
`
`time slots of the GSM physical radio interface used for circuit-switched traffic
`
`channels and signalling channels. The same GPRS radio resources are shared
`
`15
`
`by all mobile stations in a cell, the radio resources being reserved by or for
`
`mobile stations only when there are data packets to be sent.
`
`The packet-oriented network infrastructure includes a packet data
`
`network having packet switches in the form of GPRS support nodes (GSNS)
`
`interconnected by a GPRS backbone network, and including a gateway GPRS
`
`20
`
`support node (GGSN) for routing data packets to and from an external packet
`
`data protocol (PDP) network, using a protocol such as TCPKIP, X25 and the
`
`like.
`
`

`
`wo 99l63773
`
`PCT!'GB99.-‘M767
`
`In accordance with one aspect of the present
`
`invention there is
`
`provided a method of controlling communication between user stations using
`
`a mobile communications system having a radio interface, said method
`
`comprising:
`
`5
`
`providing a data packet handler connected to a packet data network;
`
`holding control data, indicating a state of a call between a first user
`
`station and a second user station;
`
`dynamically assigning radio resources for the transfer of data packets
`
`carrying call data for said call over said radio interface, such that the amount
`
`10
`
`of radio resources assigned varies in accordance with the amount of call data
`
`to be transferred at different points in said call; and
`
`controlling the transfer of data packets between said first and second
`
`user stations, using said data packet handler, in accordance with said control
`
`data.
`
`15
`
`The state of a call may be held in a network-side store, to allow control
`
`of the communication between the mobile stations.
`
`The functionality
`
`provided by a packet data network, and the nature of radio resource allocation
`
`and control, is such that data transfer is possible throughout a call, even when
`
`the transfer of data is intermittent, without requiring an ongoing circuit-
`
`20
`
`switched connection between the user stations. The data transferred may be
`
`voice call data, or video call data. -
`
`

`
`W0 99.363773
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`PCT;"GB99l'0l767
`
`In accordance with a further aspect of the invention there is provided a
`
`method of handling the
`
`transfer of data
`
`in a GSM-type mobile
`
`communications system, said method comprising:
`
`receiving a first data packet from a first user station, said first data
`
`5
`
`packet containing a recipient ID;
`
`mapping said recipient ID to a packet network protocol address
`
`whereby routing to a second user station is identified by a gateway GPRS
`
`support node; and
`
`transmitting a second data packet to said gateway GPRS support node,
`
`10
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`said second data packet containing said packet network protocol address.
`
`This aspect provides functionality allowing the transfer of data packets
`
`between user stations using GPRS, wherein a known recipient ID, rather than
`
`a packet network protocol address (which may be only temporarily allocated),
`
`may be used by the first user station to identify the second user station.
`
`15
`
`In accordance with a further aspect of the invention there is provided a
`
`method of conducting communications between user stations using a mobile
`
`communications system, each said user station comprising a camera for
`
`picking up an image of the user and a display for displaying an image of a
`
`remote party, saidumethod comprising establishing a data transfer connection
`
`20
`
`between said userstations, and controlling said connection in a half-duplex
`
`mode such that a user station may perform one of either only receiving or only
`
`transmitting image data for a first period sufficient to receive or transmit
`
`image data fonning an image, and perfonn the other of only receiving or only
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`

`
`W0 99363773
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`PCT.-’GB99f01 767
`
`transmitting video image data for a second period following said first period
`
`and sufiicient to transmit or receive image data forming an image.
`
`In accordance with a still further aspect of the invention there is
`
`provided a mobile station adapted to conduct video image communications,
`
`5
`
`said mobile terminal having a half-duplex communications mode controlled
`
`by a data processor which in that mode prevents the transmission of video
`
`image data during the reception of video image data and which allows the
`
`transmission of video image data during a period selected by a user.
`
`These aspects provide a method of conducting communications, and a
`
`10
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`mobile station, which may be used for video conferencing in a novel and
`
`advantageous fashion. By limiting the communications to a half—duplex
`
`mode, the bandwidth and mobile station power requirements needed for the
`
`call may be reduced.
`
`In addition, operation in a dispatch communications mode, wherein
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`15
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`the video data is distributed amongst groups of recipients which may each
`
`both transmit and receive data, is possible. One party may seize the call to
`
`transmit video data which is received by the remaining participants. The call
`
`may then be subsequently seized by different participants.
`
`Further aspects of the invention are defined in the appended claims,
`
`20
`
`and features thereof will be apparent from the following description.
`
`Embodiments of the invention will now be described, by way of
`
`example only, with reference to the accompanying drawings, wherein:
`
`

`
`W0 99!63’!73
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`PC'I‘!GB99:'01767
`
`Figure 1 is a schematic block diagram of a known public land mobile
`
`network;
`
`Figure 2 is a schematic block diagram of a mobile station in
`
`accordance with a first embodiment of the invention;
`
`5
`
`Figure 3 is a schematic block diagram of a mobile communications
`
`network arranged in accordance with the present invention;
`
`Figure 4 is a schematic illustration of a call group record used in
`
`connection with embodiments of the present invention;
`
`Figure 5 is a schematic illustration of a mobile subscriber record store
`
`10
`
`in connection with embodiments of the present invention;
`
`Figures 6, 7 and 9 are flow diagrams illustrating procedures carried out
`
`by mobile stations in accordance with embodiments of the present invention;
`
`Figures 8, 10 and 11 are flow diagrams illustrating procedures carried
`
`out by a data packet handler
`
`in accordance with embodiments of the
`
`15
`
`invention; and
`
`Figure 12 is a schematic block diagram of a second embodiment of a
`
`mobile station in accordance with the present invention.
`
`Referring to Figure 2, a GSM-compliant mobile station 8 in accordance
`
`with an embodiment of the present invention is a handset which comprises a
`
`20
`
`transmitheceive aerial 16, a radio frequency transceiver 18, a GPRS module 19
`
`which includes
`
`a packetiserfdepacketiser
`
`and
`
`buffer
`
`store,
`
`a
`
`speech
`
`coderfdecoder 20 connected to a loudspeaker 22 and a microphone 24, a
`
`processor circuit 26 and its associated memory 28, an LCD display 30, a manual
`
`

`
`W0 99f63'?'73
`
`PCTlGB99!fll767
`
`input port (keypad) 32 and a push—to—talk button 34. The mobile station is
`
`connected to a removable subscriber identity module (SIM) not shown, via
`
`electrical contacts.
`
`Figure 3 is a schematic illustration of a GSM-type PLMN arranged in
`
`5
`
`accordance with an embodiment of the present
`
`invention.
`
`The PLMN
`
`includes GPRS support nodes, including one or more serving GPRS support
`
`nodes (SGSNS) 40, and a gateway GPRS support node (GGSN) 44. The
`
`PLMN includes all of the components described in relation to Figure l.
`
`The mobile station 8 may conduct circuit—switched calls, via the MSC
`
`10
`
`2, immediately after camping on to a serving cell, as in the prior art.
`
`The GGSN 44 is the node provided to interface the PLMN with an
`
`external packet data network 46, such as a TCPEIP network.
`
`It contains
`
`routing infonnation for active GPRS users in the PLMN, which is used to
`
`transmit data packets, referred to as packet data protocol protocol data units
`
`15
`
`(PD? PDUs) to the current point of attachment of a mobile station in the
`
`PLMN from the packet data network.
`
`The GGSN provides a mapping
`
`function for mapping a packet data protocol (PDP) address, whereby a mobile
`
`user is identified in the packet data network 46, to a mobile station identity,
`
`whereby the mobile user is identified in the PLMN. The PDP address of a
`
`20
`
`mobile user conforms with the standard addressing scheme of the respective
`
`network layer service used in the packet data network 46, for example an IP
`
`version 4 address, an IP version 6 address or an X.12l address.
`
`

`
`W9 9953773
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`PCT!GB99![I1767
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`A mobile user may be allocated a permanent, or “static” PDP address,
`
`which is stored in the mobile station 8 and the HLR 12, or may be allowed to
`
`request a temporary, or “dynamic” PDP address, which is allocated by the
`
`GGSN 44 on request.
`
`5
`
`The SGSNs 40, 42 are referred to as serving GPRS support nodes, in
`
`that these nodes are those which serve mobile stations 8 in their routing areas.
`
`On logon to the GPRS service of a mobile station, the SGSN establishes a
`
`mobility management context containing information pertaining to mobility
`
`and security for the mobile station. The SGSN also establishes a routing
`
`10
`
`context, referred to in GPRS as a “PDP context”, with the GGSN 44 to be
`
`used by the mobile station 8 to access the packet data network 46.
`
`The SGSN and the GGSN functionalities may be combined in the
`
`same physical node, or they may reside in different physical nodes.
`
`The packetdata network 46 may be the public Internet, an intranet
`
`15
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`connection or a leased line. The packet data network 46 may also provide
`
`connections with other elements, such as a GGSN 56 of other PLMNS or fixed
`
`terminals 58.
`
`Thus, with the additional functionality of the SGSNS 40 and the
`
`GGSN 44 in the PLMN, and the GPRS module 19 in the mobile stations 8,
`
`20
`
`the mobile networks and users are GPRS enabled, whereby the mobile users
`
`may transmit and receive packet mode data. For example, the mobile user
`
`may use the mobile station 8 in order to access Web pages, using terminal
`
`equipment attached to the mobile station 8, on the public Internet, via the
`
`10
`
`

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`W0 99553773
`
`PCT!GB99f01 767
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`gateway functionality provided by the GG SN 44 and the packet mode transfer
`
`functionality provided in the remainder of the network including the SGSNS
`
`40, 42, the BSCS 4, the —BTSs 6 and the GPRS radio interface.
`
`The GPRS radio interface is described in GSM 03.64 Version 5.1.0,
`
`5
`
`entitled “Digital Cellular Communications System (Phase 2+)”; General
`
`Packet Radio Service (GPRS); Overall Description of the GPRS Radio
`
`Interface; Stage 2, published by European Telecommunications Standard
`
`Institute, the contents of which are incorporated herein by reference.
`
`The GPRS architecture and transmission mechanism, mobility
`
`10
`
`management functionality, network management functionality, radio resource
`
`functionality, packet routing and transfer
`
`functionality,
`
`transmission and
`
`information storage using GPRS are described in GSM 03.60 Version 5.2.0,
`
`entitled “Digital Cellular Telecommunications System (Phase 2+)”; General
`
`Packet Radio Service (GPRS); Service Description; Stage 2, published by the
`
`15
`
`European Telecommunications Standard Institute, the contents of which are
`
`incorporated herein by reference.
`
`In addition to the standard GPRS infrastructure, this embodiment of
`
`mobile communications system of the present invention includes a dispatch
`
`packet handler 48, a packet store 50, a packet user database (PUD) 52 and a
`
`20
`
`service management terminal 54.
`
`The packet handler 48 is responsible for setting up virtual connections
`
`between GPRS users in the PLMN, and for copying packets when data
`
`packets are to be distributed to groups of users.
`
`ll
`
`

`
`W0 99l‘637"r'3
`
`PCTI'GB99:'0l '76?
`
`The packet store 50 is responsible for storing data packets which are
`
`intended for distribution to GPRS users within the PLMN who are
`
`uncontactable via GPRS at
`
`the time of receipt of data packets for the
`
`uncontactable user at the packet handler 48.
`
`5
`
`The packet user database 52 holds service data records used by the
`
`packet handler 43 to set up and manage virtual connections between GPRS
`
`users in the PLMN. The service management terminal 54 is used to update
`
`the service data in the PUD 52.
`
`The PUD 52 holds call group records for identifying the members of a
`
`10
`
`call group. Referring to Figure 4, which shows an exemplary call group
`
`record, a field for a single call group is identified by a call group ID
`
`containing fields 60, two or more mobile station IDs, MSIDI, MSID2
`
`MSIDn are contained in fields 62, and each mobile station ID field 62 has an
`
`associated call seize field 64 flagged to indicate that the associated mobile
`
`15
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`station has currently seized the call group.
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`In addition to call group records, the packet user database 52 stores
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`identification records for each mobile subscriber in the PLMN who has a valid
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`subscription to the GPRS virtual connection service of the present invention.
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`Referring to Figure 5, each such subscriber has a mobile subscriber record
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`20
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`including a field 66 containing a permanent mobile station ID 66, a field 68
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`for containing an allocated PDP address, if current, and a field ‘F0 for
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`containing a call group ID, if current, for the mobile subscriber in question. If
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`the PDP address field 68 is empty, this indicates that the mobile station is not
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`wo 99:63m
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`PCTiGB99i01767
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`currently attached to the GPRS service. If the current call group ID field 70 is
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`empty, this indicates that the subscriber is not currently participating in a
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`GPRS virtual connection call.
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`Figure 6 illustrates procedures carried out in the mobile station 8 in
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`5
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`order to participate in the GPRS virtual connection service of the present
`
`invention.
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`In order to utilise the GPRS service, the user initiates a GPRS logon
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`procedure from the mobile station 8, step 100.
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`The GPRS logon signalling procedure is described in GSM 03.60
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`10
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`V.S.2.D, part 6.5 entitled “Attach Function", which part is incorporated herein
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`specifically by reference.
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`This part also refers to part 9.2.2 entitled
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`“Activation Procedures” of the same document, which describes the PDP
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`context activation procedure at logon, which part is also incorporated herein
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`specifically by reference.
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`15
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`After having executed GPRS attach, the mobile station is in a “ready
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`state",
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`in which packet transfer may occur via the GPRS radio interface
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`between the mobile station 8 and the PLMN, and mobility management
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`contexts are established in the mobile station and the SGSN 40. The mobile
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`station then activates its PDP context, by transmitting an ‘Activate PDP
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`20
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`Context’ request to the SGSN 40. If the mobile station is using a static PDP
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`address, it transmits its static PDP address in the ‘Activate PDP Context’
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`request.
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`PCTl‘GB99.I'0l767
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`The SGSN 40 queries the HLR 12,
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`in which GPRS subscription
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`information is held for the subscriber, in order to check that the mobile station
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`8 is allowed to activate the PDP address contained in the request. If allowed,
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`the SGSN transmits a ‘Create PDP Context’ request to the GGSN 44, which
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`5
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`creates a new entry in a PDP context table held in the HLR 12 on behalf of the
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`GGSN 44. This PDP context table includes the mobile station identity and
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`the PDP address allocated to the mobile station, allowing the GGSN 44 to
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`map between these two identifies and thereby route data packets between the
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`SGSN 40 and the packet data network 46.
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`If the mobile station 8 is not using a static PDP address, the ‘Create
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`PDP Context’ request sent by the SGSN 40 to the GGSN 44 results in the
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`GGSN allocating a dynamic PDP address, which is signalled, via the SGSN
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`40, to the mobile station 8.
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`Whether the mobile station is using a static PDP address or a dynamic
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`15
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`PDP address, the mobile station 8 is provided in each case with a PDP address
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`whereby routing for packets arriving from the packet data network 46 is
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`identified. Routing within the PLMN is provided by the GPRS data packet
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`encapsulation procedure, which encapsulation is removed from the data
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`packets at the GGSN 44 and the mobile station 8. The encapsulation function
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`20
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`is described in part 9.6 of the document GSM 03.60 V.S.2.0, which part is
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`specifically incorporated herein by reference. GPRS transparently supports
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`the transfer of PDP PDUs between external networks and the mobile stations.
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`One encapsulation scheme (referred to herein as GSN-GSN encapsulation) is
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`PCTlGB99.~'01767
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`used for the GPRS backbone network between GSNs in the PLMN, and one
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`(referred to herein as SGSN-MS encapsulation)
`
`is used for the GPRS
`
`connection between the SGSN 40 and the mobile station 8.
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`The GGSN 44 is arranged such that once the PDP context entry has
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`5
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`been made in the HLR 12 by the GGSN 44 for a newly logged-on GPRS user,
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`the GGSN 44 transmits a logon message to the packet handler, informing the
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`packet handler 48 of the mapping between the mobile station identity, held in
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`field 66 of the mobile station record held in the PUD 52, whereby the user is
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`permanently identified in the PLMN, and the allocated PDP address. On
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`10
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`receipt of the logon message, the packet handler 48 enters the allocated PDP
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`address in field 68 of the mobile subscriber record for the subscriber in
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`question.
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`Once logged-on to the GPRS service, the mobile station may transmit
`
`data packets to, and receive data packets from, the packet handler 48.
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`15
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`Data packets originated in the mobile station 8 are transmitted over the
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`radio interface and via the BTS 6 and the BSC 4 to the SGSN 40. When the
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`SGSN 40 has received a packet completely and correctly,
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`it GSN-GSN
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`encapsulates the packet into a GPRS backbone network packet which is sent
`
`to the GGSN 44. The GGSN 44 decapsulates the packet and forwards the
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`20
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`data packet, using the PDP address allocated to the sender as the packet
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`originating address in a header portion of the data packet,
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`to the packet
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`handler 48.
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`PCT!GB99!0I767
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`Data packets originated in the packet handler 48 are transmitted to a
`
`mobile station 8 by attaching the allocated PDP address, which is held in the
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`PUD 52 for the recipient, to the data packet as a destination address in a
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`header portion of the data packet. The data packet is transmitted, via the
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`5
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`packet data network 46, to the GGSN 44.
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`In the GGSN 44, the PDP address
`
`of the receiver is read, and the SGSN which is serving the mobile station is
`
`identified from routing data held in the HLR 12. The data packet is then
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`GSN-GSN encapsulated and sent to the identified SGSN. The SGSN strips
`
`the GPS backbone network encapsulation, and the original data packet is
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`10
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`SGSN~MS encapsulated and transmitted to the mobile station 8 via the BSC
`
`4, BTS 6 and GPRS radio interface.
`
`When the mobile station 8 receives the packet, it removes the SGSN-
`
`MS encapsulation and processes the data packet. If the data packet is a voice
`
`data packet, a sequence of packets are reassembled and a voice signal
`
`is
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`15
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`generated in the mobile terminal.
`
`The user may set up a call by selecting, via a man machine interface,
`
`eg. the keypad 32, of the mobile station 8, from a stored list of call groups of
`
`which the mobile user is a member, a call group for which a virtual
`
`connection is to be established. Such selection is part of the initiation of a call
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`20
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`set up-transmit procedure, step 102, which is to be described below in relation
`
`to Figure 7.
`
`Once logged-on to the GPRS service, the mobile station 8 is able to
`
`receive call set up—i-eceive requests from the packet handler 48, which initiates
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`16
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`W0 99:’63773
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`PCTIGBQ9.-‘I111-'6'!
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`a procedure to be described below in relation to Figure 9. Once participating
`
`in a call, the mobile station 8 is also able to start to receive call data packets,
`
`step 106, and start to transmit call data packets, step 108, to be described
`
`below in relation to Figures 7 and 8- In addition, a user has the facility to end
`
`5
`
`participation in a call, by interaction with a man machine interface, e.g. the
`
`keypad 32, of the mobile station 8, step 110, which causes the mobile station
`
`to transmit an end participation request to the packet handler 48, step 112, and
`
`to delete the call group ID from its current call record, step 114.
`
`The user may also logoff the GPRS service if desired, step 116, which
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`10
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`results in logoff procedures carried out by the mobile station 8, step 118,
`
`including the deletion of the allocated PDP address for the subscriber in the
`
`HLR records stored by the GGSN 44. The GGSN 44 is arranged such that, on
`
`receiving a logoff message from the SGSN 40, the GGSN 44 also transmits a
`
`logoff message to the packet handler 48, which results in the deletion of the
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`15
`
`previously allocated PDP address from the PDP address field 68 in the mobile
`
`subscriber record held for the subscriber in the PUD 52.
`
`Referring to Figure 7, when a user first instructs the mobile station 8 to
`
`set up a call for a particular call group, by the depression of the PTT button 34
`
`after the selection of a call group from a list of call groups stored in the SIM
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`20
`
`of the mobile station 8,
`
`the mobile station 8 transmits a set up request,
`
`containing the selected call group ID, as one or more GPRS data packets to
`
`the packet handler 48, step 200. The call handler conducts procedures to be
`
`described below in relation to Figure 8, and, depending on the success of
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`17
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`WO 99363773
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`PCT!GB99{01767
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`those call set up procedures, the packet handler 48 may transmit a set up
`
`confirmation message to the mobile station within a time-out set within the
`
`mobile station 8, or not. If the call set up confirmation is not received within
`
`the time-out at the mobile station, step 202, the mobile station returns to the
`
`5
`
`general GPRS logged-on state, and the mobile station 8 may reuy by
`
`transmitting a further call set up request.
`
`If the set up confirmation message is received from the packet handler
`
`48 within the time-out, the mobile station 8 provides an audio or visual
`
`indication to the user that a virtual connection has been established, step 204.
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`10
`
`In addition, the mobile station places the call group ID selected by the user in
`
`a current call record, step 206.
`
`At this point, the user may transmit voice data by speaking into the
`
`microphone 24 as long as the PTT button 34 remains depressed. The speech
`
`signals are coded by the codec 20 and passed on to the GPRS module 19, in
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`15
`
`which the speech data is packetised and buffered, step 208, and SGSN-MS
`
`encapsulated for transmission over the GPRS radio interface by the radio
`
`frequency transceiver 18 and onward to the packet handler 48, step 210.
`
`As soon as the PTT button 34 is released, step 212, the mobile station
`
`8 generates a transmit end message, in the form of a data packet, which is
`
`20
`
`transmitted to the packet handler 48, step 214.
`
`Referring to Figure 8, on receipt o