Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W48/00—Access restriction; Network selection; Access point selection
  • H04W48/20—Selecting an access point
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W76/00—Connection management
  • H04W76/10—Connection setup
  • H04W76/12—Setup of transport tunnels
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W76/00—Connection management
  • H04W76/10—Connection setup
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W76/00—Connection management
  • H04W76/20—Manipulation of established connections
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W88/00—Devices specially adapted for wireless communication networks, e.g. terminals, base stations or access point devices
  • H04W88/14—Backbone network devices
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W92/00—Interfaces specially adapted for wireless communication networks
  • H04W92/02—Inter-networking arrangements
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W92/00—Interfaces specially adapted for wireless communication networks
  • H04W92/16—Interfaces between hierarchically similar devices
  • H04W92/24—Interfaces between hierarchically similar devices between backbone network devices

Definitions

• This invention relates to digital TDMA (Time Division Multiple Access) cellular radio mobile telecom ⁇ munications systems. More specifically, the present invention is directed towards apparatuses and mobile stations for providing packet data communications services in current TDMA cellular systems as defined in the preambles of claims 1, 30, 44 and 53.
• TDMA Time Division Multiple Access
• a mobile data network should:
• connectionless network datagram
• connection- oriented network virtual call
• TDMA Global System for Mobile communication
• the data services provided by or proposed for cellular systems in general are with few exceptions based on circuit mode of operation, using a dedicated radio channel for each activemobile user.
• the exceptions include the packet data concepts described in the following documents: a)US-A-4,887,265 and Proc. 38th IEEE Vehicular Technology Conference, June 88, Philadelphia (U.S.), pages 414-418: "Packet Switching in Digital Cellular Systems". These documents describe a cellular systemproviding shared packet data radio channels, each one capable of acco odating multiple data calls.
• a mobile station requesting packet data service is assigned to a particular packet data channel using essentially regular cellular signalling.
• the system may include PacketAccess Points (PAPs) for interfacing with packet data networks.
• PAPs PacketAccess Points
• each packet data radio channel is connected to one particular PAP and is thus capable of multiplexing data calls associated with that PAP.
• System initiated handover (handoff) is employed, to a large extent similar to the type of handover used in the same system for voice calls.
• a new type of handover is added for handling situations when the capacity of a packet channel is insuf ⁇ ficient.
• This document describes (for one of the embodiments) a new packet mode cellular radio system architecture, and a new procedure for routing (voice and/or data) packets to a mobile station.
• Base stations, public switches via trunk interface units, and a cellular control unit are linked together via a wide area network. The routing procedure is based on mobile station initiated handover and on adding to the header of any packet transmitted from a mobile station
• the mobile station may transmit extra control packets for the sole purpose of conveying cell location information.
• the cellular control unit is prima ⁇ rily involved at call establishment, when it assigns to the call a call control number. It then notifies the mobile station of the call control number and the trunk interface unit of the call control number and the identifier of the initial base station. During a call, packets are then routed directly between the trunk interface unit and the currently serving base station.
• CDPD Cellular Digital Packet Data
• CDPD is a new concept for providing packet data services, utilizing available radio channels on current Advanced Mobile Phone Service AMPS systems (i.e. the North American Analog Cellular System) .
• CDPD is a comprehensive, open specification endorsed by a group of U.S. cellular operators. Items covered include external interfaces, air interfaces, services, network architecture, network management, and administration.
• the CDPD system specified is to a large extent based on an independent infrastructure. Common denominators with AMPS systems are limited to utilization of the same type of radio frequency channels and the same base station sites (the base station itself, used by CDPD, is new and CDPD specific) , and employment of a signalling interface for coordinating channel assignments between the two systems.
• Routing a packet to a mobile station is based on, first routing the packet to a home network node (home Mobile Data Intermediate System, MD-IS) equippedwith a home location register (HLR) , based on the mobile station address; then, when necessary, routing the packet to a visited, serving MD-IS based on HLR information; and finally transferring the packet from the serving MD-IS via the current base station, based on the mobile station reporting its cell location to its serving MD-IS.
• a home network node home Mobile Data Intermediate System, MD-IS
• HLR home location register
• system initiated handover in GSM is based on allocating 1/26 of a traffic channel capacity during a call for signalling related to monitoring and controlling signal quality (for a single mobile station) in preparation for a possible handover.
• the overall object of the present invention is to provide system concepts for providing general purpose packet data communication services in current digital TDMA cellular systems, based on providing spectrum efficient shared packet data channels optimized for packet data and compatible with cellular requirements.
• Target systems include GSM systems, systems based on GSM architecture but operating in other frequency bands (e.g. the 1800 and 1900 MHz bands) , D-AMPS and PDC systems.
• an object of the invention is to provide an "integrated" system concept that provides the new packet data services in a closely integrated way, utilizing the current TDMA cellular infrastructure to the extent possible consistent with packet data functional and perfor- ance requirements.
• FIG.1 illustrates an embodiment of the "integrated" system concept applied to a GSM system ("Embodiment I") , by showing a block diagram of a GSM system enhanced with packet data (PD) functions, the major PD function blocks shown with bold contour lines.
• PD packet data
• FIG. 2 illustrates an intranetwork protocol and interworking example (Internet Protocol IP) for Embodiment I.
• FIG. 3 illustrates an intranetwork protocol and interworking example (X.25) for Embodiment I.
• FIG.4 illustrates a new PD state (PDmode) , introdu ⁇ ced in Embodiment I, in relation to regular GSM idle state (mode) and call-connected state (mode) .
• PDmode new PD state
• mode regular GSM idle state
• mode call-connected state
• FIG. 5 shows a sequence diagram illustrating establishment of PD state (PD mode) , initiated from a mobile station (MS) .
• PD mode PD state
• MS mobile station
• FIG. 6 shows an example of a 51-frame Master packet data channel (MPDCH) downlink multiframe, together with the multiframe cycle in FIG.7 provided for coordinating listening to MPDCH with listening to regular GSM broadcast channels
• MPDCH Master packet data channel
• FIG.7 shows an example of a multiframe cycle formed by 8 MPDCH downlink multiframes (illustrated in FIG. 6) , and an example of scheduling adequate times for listening to regular GSM broadcast channels.
• FIG. 8 shows a sequence diagram illustrating allocation of a packet data channel (PDCH) on demand, initia ⁇ ted from an MS (applicable to Embodiment I) .
• FIG. 9 shows a flow chart, illustrating the process of dynamically allocating PDCHs based on throughput measure ⁇ ments (applicable both to Embodiment I and II) .
• FIG. 10 shows a sequence diagram illustrating an example of a mobile originated packet transfer in Embodiment I.
• FIG. 11 shows a sequence diagram illustrating an example of a mobile terminated packet transfer (using "i- mmediate channel reservation") in Embodiment I.
• FIG. 12 shows a sequence diagram illustrating an example of a mobile terminated packet transfer (using paging) in Embodiment I.
• FIG. 13 shows examples of a mobile originated and a mobile terminated packet transfer on an MPDCH, thereby illustrating theprinciples of usingUplinkState Flags (USFs) and a type of paging that reserves an access slot for the MS to respond (applicable both to Embodiment I and II) .
• USFs UplinkState Flags
• FIG. 14 illustrates an example of routing from an interworking function (IWF) to an MS's currently serving Mobile services Switching Centre (MSC) in Embodiment I, when the addressing scheme chosen is such that an MS's IP address identifies the MS as belonging to a particular public land mobile network (or group of MSCs) .
• IWF interworking function
• MSC Mobile services Switching Centre
• FIG.15 illustrates an example of routing from an IWF to an MS's currently serving MSC in Embodiment I, when the addressing scheme chosen is such that an MS's IP address identifies the MS as belonging to a particular MSC.
• FIG. 16 illustrates an embodiment of the "separated" system concept applied to a GSM system ("Embodiment II") , by showing a block diagram of a GSM system with a Base Station
• BSS Backbone System
• GSM system Two different embodiments of the invention are described, both applied to a digital TDMA cellular systemwith a GSM type of architecture. Although this type of system may operate in another frequency band (such as the 1800 or 1900 MHz band) than that specified for GSM, it is in the following description referred to as a "GSM system".
• GSM system One of the em ⁇ bodiments (Embodiment 1) is directed towards providingthe new packet data services in a closely integrated way, utilizing the current infrastructure to the extent possible, consistent with functional and performance requirements.
• the second embodiment in order to minimize the impact on the current system, primarily utilizes the base station portion of the GSM system, for the remaining network parts relying on a separate mobile packet data infrastructure.
• FIG.1 illustrates a GSM system enhanced with packet data (PD) functions, the major PD function blocks shown with bold contour lines.
• PD packet data
• BTSs Base Stations
• MSC Mobile Services Switching Centre
• VLR Visitor Location Register
• PSTN Public Switched Telephone Network
• ISDN Integrated Services Digital Network
• An MSC equipped for routing incoming calls is referred to as a Gateway MSC (GMSC) .
• GMSC Gateway MSC
• MSC/VLR(s) are via a CCITT (International Canal & Telephone Consultative Committee) Common Channel Signalling (CCS) system No. 7 network connected to a Home Location Register (HLR) , which is a data base comprising information on all subscribers, including location infor ⁇ mation identifyingtheMSC/V Rwhere a subscriber is currently (or was last) registered.
• HLR Home Location Register
• AUC Authen ⁇ tication Centre
• EIR Equipment Identity Register
• OMC Operations and Maintenance Centre
• the packet data functionality added in BTS includes capability to provide one or more shared packet data channels
• PDCHs Downlink Control Channels
• a PDCH In a cell, only occasionally visited by a packet data user, a PDCH may be allocated temporarily on user demand. In a cell with con ⁇ tinuous packet data traffic demand on the other hand, one or more PDCHs may either be allocated on a semi-permanent basis, or be allocated dynamically, adapted to the current load situation. The allocation of PDCHs is controlled from BSC. The degree of PDCH support in a cell (continuous, on user demand, or no support at all) may be configurable. Information defining the support level and any PDCH, allocated for initiating packet transfer, is broadcasted on a regular GSM Broadcast Control Channel (BCCH) .
• BCCH Broadcast Control Channel
• a PDCH is a new type of logical channel on a physical TDMA channel (time slot) , optimized for shared packet transfer to and from multiple packet data capable MSs (supporting packet data only, or packet data combined with ordinary voice/circuit data services in different modes of operation) .
• PDCHs are used for data transfer and associated control signalling.
• a "rese- rvation-Aloha" type of protocol is employed.
• Uplinks and downlinks are basically used as independent channel resour ⁇ ces.
• a PDCH uplink may carry data from one MS and the downlink data to another.
• the packet data radio link protocol over the PDCH(s) allocated in a cell is handled by a "PD transfer controller" in BTS.
• the PD transfer controller In a BTS with at least one PDCH allocated, the PD transfer controller has a, normally unique, physical connection for packet transfer to and from MSC, utilizing ordinary internode trunks.
• a "PD router” is provided for routing packets to and from the MSC service area. Furthermore, a “PD controller” is provided for handling signalling exchange with the "circuit mode MSC", and for handling control, monitoring and parameter storage functions related to packet data MSs.
• the PD controller comprises processor, memory, signalling interface functions, and software.
• MSCs PD routers
• IWFs interworking functions
• IWFs provide internetworking with external networ (s) , such as Internet (i.e. IPnetwork) and/or PSPDN (Packet Switched Public Data Network, i.e. X.25 net- work) , thus interconnecting Fixed Stations (FSs) withtheMSs.
• An IWF may perform protocol conversion and address transla- tion, as required. It may also route packet data traffic between cooperating PLMNs. Packet data traffic between MSs in different MSC service areas in the same PI_MN is normally routed directly between the respective MSCs, across the backbone network.
• HLR may, via a "HLR interrogation server", be interrogated from entities on the backbone network.
• the HLR interrogation server provides necessary functions to enable such interrogation from the packet data network.
• HLR, AUC, EIR and OMC are also enhanced to support the new types of subscriptions, services and equipments.
• IP connectionless network
• IP is here used to denote the Internet Protocol (the de facto standard IP protocol used in the TCP/IP protocol suite) or the ISO (International Standards Organisation) Internetworkprotocol (ISO 8473) . (Possibly both these protocols may be supported.)
• Value-added services including multicast, broadcast and electronic mail services, may be provided by Network Ap ⁇ plication Server(s) (NAS(s)), attached to the backbone network and accessed by using higher layer protocols on top of IP.
• NAS(s) Network Ap ⁇ plication Server
• the PLMN basically appears as an IP network.
• the protocol ar- chitecture is illustrated in FIG. 2.
• the figure shows an example of communication between an MS and a fixed station (FS) , e.g. a host computer, attached to an external IP network.
• IWF and MSC then both have the role of IP (layer 3) routers, and MS and FS may communicate end-to-end using a TCP (Transmission Control Protocol) transport (layer 4) protocol.
• the MT and TE parts of the MS are in this example integrated in one unit.
• BTS acts as a link layer (layer 2) relay between the radio link protocol (denoted RL2 in the figure) and the link protocol (denoted L2) used across the trunk connection.
• the radio protocol handled by BTS is an ARQ (Automatic Repeat reQuest) type of protocol, based on dividing each frame in equal size blocks and retransmitting blocks in error.
• ARQ Automatic Repeat reQuest
• encryption/ decryption is performed between MT and MSC.
• An MS is iden ⁇ tified, on layer 3 with an IP address, and on layer 2 with standard GSM identities, International Mobile Subscriber Identity (IMSI) or, normally. Temporary Mobile Subscriber Identity (TMSI) .
• IMSI International Mobile Subscriber Identity
• TMSI Temporary Mobile Subscriber Identity
• Standardconnection-orientednetwork (X.25) services may also be provided by employing a connection- oriented transport protocol across the PLMN, on top of the IP protocol.
• an X.25 DCE-DTE interface is provided between MT and TE.
• IWF and MT both perform protocol conversion and map any X.25 virtual circuit on to a transport connection between the two entities, using the intra-PLMN transport protocol (denoted L4) .
• IWF andMT also translate between X.121 and IP address.
• the L4 protocol may be utilized to provide optional data compression.
• this transport connection is then maintained for the duration of the X.25 virtual call, even if the MS moves to the service area of another MSC.
• this is achieved by, as part of the connection establishment procedure, informing the MT of the IP address of the IWF. MT then addresses all packets associated with this connection to this IWF. MSC, in its turn, merely routes packets based on their IP address.
• the IWF is updated with new routing information when the MS moves to a new MSC, as described below.
• TE and FS may communicate end-to-end via a transport protocol (such as ISO transport protocol Class 1) .
• the packet data services subscribed to are available to an MS after a procedure that brings the MS from an initial GSM idle mode to a new "PD mode".
• This procedure may be initiated either by the MS making a request for packet data service or by the MSC, currently serving the MS, receiving a packet addressed to the MS.
• the procedure is based on standard GSM signalling and utilizes standard GSM authentication.
• the PD mode establishment procedure also includes initiating parameters for packet encryption/ decryption in the MS and its currentMSC/VLR. After completed procedure, the MS is registe ⁇ red in its current MSC/VLR as being in PD mode. The system then provides access to PDCHs in any cell.
• an MS performs cell selection and location updating based on GSM idle mode procedures. (Hand ⁇ over, in the GSM sense, is not used.)
• the MS from information broadcasted on BCCH, iden ⁇ tifies the PDCH that may be used for intiating packet transfer in a cell.
• Initiation of packet transfer to an MS from its currently serving MSC is guided by monitoring the MS's cell location based on any previous packet transfer.
• the packet transfer may be initiated with or without paging.
• the PD mode registration and any associated information stored at the MS's currently serving MSC/VLR is transferred from the old to the new MSC/VLR.
• Peer entities of any routes established to the MS's current MSC are also updated with routing information to the new MSC. I.B Packet Data Mode (PD Mode) and Mobility Management
• PD Mode in relation to regular GSM idle mode and call-connected mode is illustrated in FIG. 4.
• the denomination "state” is used as a synonym for "mode”.
• the MS When a packet data MS is turned on, standard GSM power-on and registration procedures are used. After re ⁇ gistration, the MS is in attached, idle mode and performs idle mode cell selection and location updating. In order to stay attached to the system, the MS also regularly initiates periodic registration.
• An MS in idle mode may change to PD mode (transition (1) in FIG. 4) by a procedure based on regular GSM signalling and authentication.
• the procedure may be initiated either by the MS, or by the MSC, currently serving the MS, receiving a packet addressed to the MS.
• the procedure in the former case is exemplified by the sequence diagram in FIG. 5. Initiation of the procedure may, as determined by a system parameter, be allowed only in cells where a PDCH is allocated or is al- locatable on user demand.
• the signalling sequence (1)-(13) in the figure is based on standard GSM signalling and authen ⁇ tication procedures used for settingup regularGSMvoice/cir ⁇ cuit data calls.
• a new type of service request (signal (3)) is used to request PD mode establishment.
• the optional sequence (8)-(13) is employed to allocate the MS a TMSI (Temporary Mobile Subscriber Identity) and/or to initiate packet encryption/decryption parameters in the MS and its current MSC.
• TMSI Temporal Mobile Subscriber Identity
• the MS is registered in its current MSC/VLR as being in PD mode and (optional) encryption parameters are stored (block (14)).
• the sequence (15)-(17) also based on regular GSM signalling, confirms the PD mode registration and makes the MS change to PD mode. If a PDCH is not already allocated in the cell in question, the PDCH allocation controller in BSC (FIG. 1) attempts to allocate a PDCH on demand (blocks (18)- (20)) .
• BSC sends a command to BTS to activate a PDCH and to broadcast channel defining infor ⁇ mation on BCCH (block (21)) .
• An optional channel defining signal (not shown in the figure) may also be sent directly to the MS, in order to provide a faster notification that a PDCH is allocated.
• the MS determines if a PDCH is allocated. If this is the case, the MS may initiate a packet transfer on the defined PDCH. If no PDCH is allocated, the MS may proceed with a predefined procedure, such as periodically initiating a PDCH on demand allocation procedure
• MSC/VLR is then, via the signal denoted (23) , informed that the PD mode establishing procedure is completed.
• Signal (23) conveys information onthe
• This information is stored, linked to the PD mode registration (block (24)).
• PD mode registration As also indicated in block (24) , if PD mode is monitored by a timer and/or inac ⁇ tivity timer, these timers, located in the PD controller (FIG. 1) , are initiated.
• the PD mode establishment procedure described above, is primarily based on ordinary GSM signalling func ⁇ tions, controlled from the circuit mode MSC (FIG.1) , although some adaptations are required e.g. for handling the new type of service request and the new encryption parameters.
• This data base may be regarded as an extension of VLR for packet data MSs.
• An example of functional division betweenVLR and this PD controller data base is as follows (alternative realizations are not precluded) :
• VLR (as well as HLR) is enhanced with packet data subscrip ⁇ tion parameters such as IP address, multicast address, and timeout parameters. For anMS in idle mode, this information is always available in the current VLR by means of regular location updating procedures (adapted to handle the ad- ditional subscription parameters) . VLR is also extended with information on whether an MS is in PD mode.
• the PD controller data base provides: a) Storage of operational parameters related to any MS in PD mode, including encryption parameters, timers, cell location, list of peer entities of any routes es ⁇ tablished, and the MS's current submodes (e.g. mobile/- stationary mode, normal/sleep paging mode; see below) .
• b) In order to facilitate fast packet routing and limit the interrogation load of VLR, storage also of a duplicate from VLR of all relevant information stored for any MS in PD mode (including subscription parame ⁇ ters and location area identity) .
• c) To facilitate exchange of signalling information with the circuit mode MSC (FIG. 1) , capability to, for any packet data MS registered in the MSC/VLR, translate the MS's IP address to IMSI.
• d) As a support function to the PD router (FIG. 1) As a support function to the PD router (FIG. 1) , a table with routing information to any MS to which a route is established from the MSC. With the IP address of the MS as input, the table provides routing information to the MS's currently serving MSC.
• Location updating for an MS in PD mode is based on idle mode location updating procedures.
• the new VLR automatically receives the related subscription parame ⁇ ters (from HLR) , as part of regular idle mode location updating.
• the location updating procedure is enhanced such that the new MSC/VLR is informed that the MS is in PD mode, and is provided information onthe backbone network address of the previous MSC/VLR.
• the MS's operational parameters are thentransferred (across the backbone network) from the PD controller in the previous MSC/VLR, and the data bases of the two PD controllers are updated.
• the PD controller in the new MSC/VLR also provides updated routing information to peer entities of any routes established to the MS's current MSC.
• a PD mode establishment procedure may also be initiated when a PD router in an MSC, currently serving an MS in idle mode, receives a packet addressed to the MS.
• the PD router then signals to the PD controller identifying the destination IP address.
• the PD controller finds that the MS is not in PD mode and, after translating the IP address to IMSI, requests the circuit mode MSC to initiate a PD mode establish- ment procedure.
• the MS is in idle mode, the request is accepted and the circuit mode MSC initiates the procedure using regular GSM paging, but with a special "PD indicator".
• the procedure is then very similar to the one described above for the mobile originated case.
• the normal situation for an MS in PD mode is that it is located in a cell with at least one PDCH allocated.
• the first PDCH allocated in a cell, on which packet transfers are initiated, is here designated “Master PDCH” (MPDCH) .
• MPDCH Master PDCH
• the MS performs what is here referred to as “PDCH procedures” (the upper smaller circle in FIG. 4).
• PDCH procedures the upper smaller circle in FIG. 4.
• the cell selection criteria may be somewhat modified compared to idle mode, if a user (e.g. with a keyboard command) selects to operate the MS in "stationary mode". In stationary mode, the MS retains the current cell as long as the signal quality is above a certain threshold value. The purpose is to reduce the probability of "unnecessarily" changing cell due to fluc ⁇ tuations in the radio environment, e.g. caused by reflec ⁇ tions from moving objects.
• the MS automatically returns to normal "mobile mode" of operation.
• the MS informs the PD controller in its currently serving MSC/VLR of its mode of operation, by sending amobile/stationarymode indicator at least every time it changes from mobile to stationary mode, or vice versa.
• paging may then be limited to a single cell, or data may be sent directly (as "immediate data” / "immediate channel reser ⁇ vation” followed by data) without previous paging.
• the modified cell selection criteria may be employed also for an MS in mobile mode.
• packet transferto theMS may be initiated in a similar way as to a "stationary" MS. Listens to MPDCH and performs packet transfers as required. On MPDCH, an MS listens for:
• the MS explicitly or implicitly, informs the PD controller in its current MSC/VLR of its paging mode, by sending a normal/PD sleep mode indicator at least every time it changes paging mode.
• Multicast messages i.e. unacknowledged messages ad ⁇ dressed to a group of MSs
• PD sleep mode In normal or PD sleep mode.
• SMs GSM cell broadcast short messages
• Coordination of the above procedures may be ac ⁇ complished by employing for the MPDCH downlink a multiframe scheme similar to and synchronized with the 51-frame mul- tiframe schemes used for regular GSM downlink control chan ⁇ nels.
• a multiframe scheme similar to and synchronized with the 51-frame mul- tiframe schemes used for regular GSM downlink control chan ⁇ nels.
• an MS may listen to broad ⁇ cast channels at any time except during its assigned (sleep mode) paging block, more extensive coordination is required for an MS in PD mode, and specifically when the MS is in normal paging mode. In the latter case, the time an MS is available for downlink messages needs to be maximized, while allowing sufficient time for the broadcast listening tasks.
• a mul ⁇ tiframe coordination scheme with this purpose is exemplified in FIG. 6 and FIG. 7.
• FIG. 6 shows an example of a 51-frame MPDCH multiframe, synchronized with the corresponding GSM Broadcast Channel (BCH) / Common Control Channel (CCCH) and Stand-alone Dedicated Control Channel (SDCCH) multiframes.
• BCH GSM Broadcast Channel
• CCCH Common Control Channel
• SDCCH Stand-alone Dedicated Control Channel
• 8 MPDCH multiframes form a multiframe cycle (synchronized with the corresponding BCH/CCCH and SDCCH multiframe cycles) .
• FIG. 7 also illustrates an example of scheduling adequate times for the tasks of listening to and reading information from ordinary GSM broadcast channels.
• the MPDCH multiframe (FIG. 6) comprises: - Paging blocks (similar to GSM), marked P0-P7, each 4 TDMA frames long.
• an MS listens to one of the paging blocks (depending on its IMSI) in a subset of the mul ⁇ tiframes in the cycle, as determined by a system parameter (giving a sleep mode period ranging between approximately 0.25 and 2 seconds) .
• Multiframes 5 and 7 every Nth cycle are excluded, as these (as illustrated in FIG. 7) are scheduled for listening to adjacent BCCH.
• an MS may be paged in all paging blocks, and at any time not scheduled for other purposes (see below) .
• PDB used for PDCH broadcast (with the exceptions indicated in FIG. 7) .
• PDCH broadcast may, with a sleep mode parameter, be limited to a defined subset of the multiframes.
• the sleep mode parameter may be different from that used for paging.
• PDCH broadcast is used for providing system infor ⁇ mation, including PDCH specific parameters, and a flag indication when relevant information on current BCCH has changed. MSs should then read BCCH and "extended BCCH" (if any) , starting with the next multiframe and until the relevant information contents of all 8 multiframes have been read (see FIG. 7) .
• PDCH broadcast may also be used for different kinds of user information services. - Frames marked F0-F14 which can be grouped in different ways for various purposes (see FIG. 7) .
• block F3-F6 may (when not allocated for other purposes; see FIG. 7) be utilized for multicast messages. (Other multicast allocation alter- natives exist.)
• the BCH/CCCHmultiframe is included in FIG.6 to show the allocation of FCCH (marked F) , SCH (marked S) , and BCCH
• the purpose of showing the SDCCH multiframe in FIG. 6, is to indicate the allocation of cell broadcast SMs. These are allocated a subchannel utilizing the block marked "D2", in multiframes
• FIG.7 A possible way to schedule listening to these broadcast channels is shown in the diagram of FIG.7.
• the more precise block/frame allocation in the respective multiframe is defined in the column at the right hand side.
• opportunities are provided twice per cycle (i.e. approximately once per second) .
• the multiframes of adjacent cells may be unsynchronized with those of the current cell, 12 consecutive frames need to be assigned.
• An MS that needs to read information from BCCH of an adjacent cell should read at least one BCCH block from multiframes 2, 3, 6 or 7 in a multiframe cycle. This is achieved with the reading schedule in FIG. 7, again taking into account that multiframes of adjacent and current cells maybe unsynchronized.
• the time indicated for reading adjacent BCCH is assigned once every N:th cycle, where N is a system parameter.
• an MS in PD mode temporarily has to be "off PDCH” and use ordinary GSM channels and perform what is here denoted "GSM procedures”. It is then accessable by and has access to the same signalling as in idle mode. It also performs cell selection exactly as in idle mode.
• GSM procedures Common situations when the MS changes to these "GSM procedures" (transition marked (3) in FIG. 4) are: a) When the MS moves to a new location area. It then performs location updating based on idle mode procedures. Upon completion, the MS returns to "PDCH procedures" (transition (4) in the figure). b) At regular intervals, when the MS performs periodic registration as in idle mode. Upon completion, the MS returns to "PDCH procedures" (transition (4)). c) When the MS (on PDCH) receives a request from its current MSC to perform authentication or equipment
• the MS After granted and completed procedure, the MS returns to "PDCH procedures" (transition (4)). If the authentication or equipment identification is rejected, the procedure ends with the MS receiving a "PD mode termination command", returning the MS to idle mode (transition (5)) . d) When the MS moves to a cell where no PDCH is allocated but where a PDCH may be allocated on user demand. In such a cell, the MS may be paged via ordinary GSM paging channel.
• the MS may be required to report to its current MSC/VLR when it moves from a cell with PDCH allocated to one without, and vice versa.
• This information is stored in the PD controller (FIG. 1) which thus monitors the procedures used by the MS.
• paging is made on either MPDCH or ordinary GSM paging channel.
• paging has to be made in parallel on both MPDCH and ordinary GSM paging channel, if the paging area comprises cells of both kinds.
• a PDCH may be allocated when an actual need for packet transfer arises as described in section I.C below.
• the MS returns to "PDCH procedures" (transistion (4)) when a PDCH is allocated, or when the MS moves to a cell with PDCH allocated.
• e) When the MS moves to a cell not supporting PDCH. This case is similar to d) above with the difference that no PDCH may be allocated.
• packet data paging using ordinary GSM paging channel
• An MS in PD mode may make or receive a regular GSM (voice/circuit data/point-to- point short message) call with the PD mode maintained as "pending" during the call and returned to "active" when the call is completed.
• GSM procedures voice/circuit data/point-to- point short message
• the MS if it was using "PDCH procedures”, first changes to "GSM procedures" (tra ⁇ nsition (3) in FIG. 4).
• GSM procedures the MS initiates a call in a regular GSM manner and, when the call is set up, changes to call-connected mode (transition (6)).
• the circuit mode MSC FIG. 1
• the PD mode is marked as "pending" in VLR and in the data base portion of the PD controller (FIG. 1) .
• the MS returns to "active" PD mode (transition (7) in FIG. 4) and is marked accordingly in VLR and the PD controller.
• the circuit mode MSC If an ordinary GSM call to an MS in PD mode is received by a circuit mode MSC, the circuit mode MSC, after finding from VLR that the MS is in PD mode, requests the PD controller to initiate paging of the MS. If the PD controller has information on the procedures used by the MS, paging is initiated accordingly using either MPDCH, for which special paging types are provided to convey GSM calls, or ordinary GSM paging channel (via the circuit mode MSC) . Should such information not be available in the PD controller, paging may involve both types of channels in different cells. If the MS indicates "accept” in its paging response, the call, after the MS having changed to "GSM procedures" as required, is set up and PD mode is kept “pending" during the call in a similar way as discribed above for a mobile initiated call.
• PD mode for an MS may be monito ⁇ red by a timer and/or inactivity timer, handled by the PD controller in the MSC/VLR currently serving the MS.
• timeout period a predetermined period of time
• the inac ⁇ tivity timer is reset and reinitiated for any packet received from or sent to the MS.
• the time out periods may be subscrip ⁇ tion parameters. Termination of PD mode and return to idle mode (transition (2) in FIG. 4) may be initiated by a ter- mination request from the MS, or by a termination command from the PD controller when a timeout occurs.
• the PD mode is terminated, by first changing the MS mode to idle (transition (2)) , and then marking the MS as "detached” in VLR according to ordinary idle mode procedures.
• An MS wishing to initiate an explicit “detach” first initiates a change to idle mode (transition (2)) and then sends an "IMSI detach" as an idle mode.
• the main function blocks involved in providing PDCHs are (see FIG. 1) :
• the PD transfer controller in BTS which is processor-based and comprises both software and hardware. It: - Controls allocation/release of PDCHs on command from the PDCH allocation controller in BSC.
• the PDCH allocation controller in BSC which is processor- based and comprises both software and hardware. Together with the "circuit mode BSC", which has the overall respon ⁇ sibility for radio channel resources, it coordinates allocation of PDCHs such that, from a common pool of physical channels (time slots) , a variable mix of TCHs and PDCHs may be allocated determined by demand.
• the PDCH allocation controller :
• the first PDCH in a cell (the "master PDCH” MPDCH) , that is capable of carrying the necessary control signalling for initiating packet transfer as well as packet data and that is defined by cell specific information on BCCH, may be allocated either by system configuration or on user demand. "PDCH on demand" support may be of particular interest in a low capacity (e.g. single carrier) cell, only occasionally visited by a packet data user.
• an MPDCH may be allocated when an actual need for packet transfer arises: a)When PD mode is established for an MS (located in the cell) , an MPDCH is allocated (if a channel is available) as the last part of the PD mode establishment procedure as described in section I.B. The PDCH allocation is initiated by a command from the circuit mode BSC to the PDCH al ⁇ location controller. b)When an MS in PD mode (located in the cell) has data to send, it makes a "PDCH allocation request" using "GSM procedures” as illustrated in FIG. 8.
• the signalling sequence (l)-(4) is based on standard GSM signalling with the addition of a new type of service request (signal (3)) .
• the service request is- received by the circuit mode BSC which, if a channel is available, generates a PDCH al ⁇ location command to the PDCH allocation controller.
• AnMPDCH is then allocated (block (6)) and channel defining infor ⁇ mation is broadcasted on BCCH (block (7)).
• An optional channel defining signal (not shown in the figure) may also be sent directly to the MS, in order to provide a faster response.
• the MS determines if a PDCH is allocated. If this is the case, it may proceed with initiating a packet transfer on the defined MPDCH. If no PDCH is allocated, the MS may proceed with a predefined procedure, such as periodically repeating the PDCH al ⁇ location request.
• the request is transferred to the PD controller in MSC/VLR, from which it is forwarded to the PDCH allocation controller in BSC, and from there to the circuit mode BSC. If the request is granted, the MS may not need to change to "GSM proce ⁇ dures".
• MSC/VLR MSC/VLR
• SPDCHs slave PDCHs
• the PDCHs may be used as a set of "trunked" channels utilizing a dynamic assignment protocol.
• MPDCH is then used for access control signalling (including channel request, channel reservation and paging) and, as far as capacity admits, data, whereas SPDCH(s) are used for reserved data transfer.
• each MS is then assigned to a particular MPDCH determined by an algorithm based on the MS's identity (IMSI) and on control information broadcasted on BCCH and/or one or more of the MPDCHs.
• IMSI MS's identity
• the process of dynamically allocating/releasing PDCH(s) in a cell is based on measuring throughput and comparing with predetermined limits as illustrated in FIG.9.
• the upper dotted part of the flowchart illustrates allocation of a first MPDCH either on demand or as a result of system configuration.
• the counts of allocated MPDCHs are based on measuring throughput and comparing with predetermined limits as illustrated in FIG.9.
• BTS sends an SPDCH allocation request to BSC (block (17)).
• BSC determines if a channel is available (block (18)).
• an SPDCH is allocated in BTS (blocks (19) and (20)).
• the packet data protocol schedu ⁇ ling in BTS is readjusted to the new PDCH configuration (block (14)).
• the process then proceeds with throughput measurements across MPDCH(s) (block (2)) and in a similar way across SPDCH(s) (block (15)).
• MPDCH release request to BSC. After notifying MSs by means of broadcast information (block (10)) , anMPDCH is released
• FIG. 1 and MSs in the MSC service area is to a large extent determined by the radio link (layer 2) service provided by PDCHs.
• Variable length packets up to some maximum size (such as approximately 600 octets, depending on the PDCH protocol) from layer 3 are accepted by the layer 2 entity in the PD router and by the MT part of MSs respectively.
• Each packet normally after encryption, forms the information field of a layer 2 frame.
• each frame is divided into fixed size blocks (of approximately 25 information octets, corresponding to 4 TDMA bursts) .
• BTS or MT For each block, BTS or MT respectively performs channel coding, burst formatting, and interleaving (per block) .
• a selective repeat type of ARQ protocol between BTS and MT then provides retransmission of blocks in error.
• the TDMA structure and the need to allow for the same degree of timing disalignment at first MS access as in ordinary GSM have lead to the selection of a "reservation- Aloha" type of protocol.
• an MS makes a random access request (signal (1) in the figure) on the MPDCH uplink (using the same type of access burst as in ordinary GSM) , when allowed to do so, as determined by "uplink state flags" (USFs) on the MPDCH downlink.
• the access burst includes a random number providing an initial identification of the MS, and may also include class of service type of information.
• BTS normally responds with a channel reservation command (signal (2)) on the MPDCH downlink, reserving channel capacity for uplink data transfer and downlink ack ⁇ nowledgement (ACK) .
• ACK downlink ack ⁇ nowledgement
• the channel reservation command includes the same random number as received in the access burst, and timing alignment/power control (TA/PC) commands.
• TA/PC timing alignment/power control
• the timing alignment/power control functions are performed in BTS, not only the measurements part (as in ordinary GSM) but also, for performance reasons, the processing and command generation parts (located in the PD transfer controller) .
• the data frame (signal (3) in the figure) from the MS is followed by a positive acknowledgement (signal (4)) from BTS (as no retransmissions are assumed in this example) , and the frame is relayed to the PD router in MSC/VLR.
• the MS's cell location is determined by associating the frame (which includes the MS's identity TMSI in the frame header) with the (for each cell unique) physical connection on which the frame is received.
• the MS's cell location may be identified by providing in the PD transfer controller in BTS the additional function of inser- ting a cell identifier in the frame header, in a similar way as described in the cited US.A-4,916,691.
• the cell location identity and the associated time when the frame was received are, together with MS parameters (such as mobile/stationary indicator, class of service) that may be conveyed in the frame header from BTS, stored in the PD controller data base, linked to the MS's identity.
• MS parameters such as mobile/stationary indicator, class of service
• the packet normally after decryption, is then available at the layer 3 entity of the PD router for
• the packet is first fragmented, as required, to match the maximum packet size across PDCHs. The way the packet transfer to the MS is initiated then depends on the MS operational parameters available in the PD controller data base:
• the PD controller uses a software algorithm to select method for initiating the packet transfer: a)Transferring the data frame directly to a specific BTS (without previous paging) .
• This method is used if the MS is in stationary mode. It may be used also when the MS is in mobile mode, provided that the modified cell selection criteria employed in stationary mode (described in section I.B) is employed also for MSs in mobile mode, and provided that the cell location information is sufficiently recently updated.
• the frame header in the transfer to BTS includes TMSI, an indicator of the MS's paging mode, IMSI (if the MS is in PD sleep mode) , and possible class of service infor ⁇ mation. If the MS is in PD sleep mode, BTS then initiates the data transfer across PDCH(s) using paging (in a single cell) . Otherwise, the data transfer is initiated with "immediate channel reservation", or data may be sent directly as "immediate data” on MPDCH.
• the MPDCH downlink informs the MS of the channel on which the data frame (signal (6)) is to be received. If the data transfer takes place on an MPDCH, channel reservation may not be needed.
• the data frame includes reservation of an access slot on the MPDCH uplink for the MS to respond.
• the response burst (signal (7)), one bit is allocated for acknowledging the data frame. If, as in the example, the acknowledgement is positive, the sequence is completed.
• BTS sends a channel reservation for a more specified negative acknowledgement from the MS (defining blocks to be retransmitted) , and for retransmission from BTS. This channel reservation also includes TA/PC commands.
• the retransmission then includes channel reservation for the MS to acknowledge and for a possible further retransmission. Paging over a group of cells
• paging is limited to the smallest possible group of cells based on available cell location information. Paging is initiated by a "high level command" (including information on IMSI, TMSI, location area, cell location and recentness of this information, and paging mode) from the PD controller to the PD signalling controller (FIG. 1) in affected BSC(s) . (Alternative divisions of paging functions between MSC and BSC are not precluded.) As described in section I.B, depending on system configuration, the paging may include paging on both MPDCH and ordinary GSM paging channel and may thus involve also the "circuit mode" portion of BSC(s) .
• a special type of paging message may be employed which combines paging with reser ⁇ vation of an access slot for the MS to respond.
• An example of using this type of paging is shown in the sequence diagram in FIG. 12.
• the PD transfer controller in BTS then generates a paging message (signal (7)) on the MPDCH downlink which includes reservation of an access slot on the MPDCH uplink for the MS to send a response burst (signal (8)).
• the paging response (signal (9) and (12)) transferred back to MSC includes information on the MS's cell location, which information
• the paging response (with the associated time when the paging response was received) is stored in the PD controller data base.
• the paging response also results in a channel reservation (signal 10) ) on the MPDCH downlink for the data transfer.
• the channel reservation also includes TA/PC commands.
• data is received from MSC (signal (13))
• it is transferred on the reserved PDCH downlink (signal (16)).
• Channel reservation for an acknowledgement fromtheMS (signal (17)) and for possible retransmission may either be combined with the data frame (signal (16)) or included in the initial channel reservation (signal (10)).
• the need for renewal within a certain period of time imposes restric- tions on maximum packet size.
• the TA/PC commands included in the channel reservation (signal (10)) in FIG. 12 should, with a maximum size packet in the data frame (signal (16)), allow adequate timing alignment and power control at least until the acknowledgement (signal (17) ) is received from the MS.
• a maximum packet size of approximately 600 octets, should provide sufficient margins.
• additional TA/PC commands (as well as channel reservation commands) may be included in later parts of a sequence, combined with negative acknowledgement(s) or retransmission(s) .
• the principles for the mentioned uplink state flags (USFs) and for the type of paging that reserves an access slot for the MS to respond are illustrated by the examples in FIG. 13.
• the series of slots that depict MPDCH downlink and uplink respectively represent time slots in consecutive TDMA frames.
• the figure shows two simple transfer examples, one mobile originated (with index 1) and one mobile terminated (with index 2) . All control messages (except access bursts) comprise one block (i.e. 4 bursts) .
• An USF on the MPDCH downlink marks a corresponding access slot on the MPDCH uplink as either "free" (for random access) or "reserved".
• USFs are coded individually per MPDCH downlink burst (by allocating a group of redundant bits, carrying one bit of information, for this purpose) .
• the mobile originated data transfer starts with a random access burst from mobile station MS 1 in an access slot that is marked as "free" by an USF.
• BTS responds with a channel reservation command on the downlink and changes USF to "reserved” for the duration of the subsequent uplink data transfer.
• a downlink acknowledgement then completes the transfer sequence.
• the mobile terminated transfer is initiated by a paging message to mobile station MS 2 providing the MS a reserved slot for its response burst.
• the paging response is followed by a channel reservation command and a subsequent downlink data transfer.
• a paging message may include paging of more than one MS and then includes reservations of individual access slots for the MSs to respond. The reservations may be explicit (in the form of pointers) or implicit, in which case the next few reserved slots are allocated to the MSs in the order they appear in the paging message.
• USFs may alternatively be included in the block channel coding and interleaving, and thus be provided on a per block basis. After receiving a block, an MS then knows the USFs (which may still be associated with individual access slots) for the 4 following access slots.
• Routing of packets from entities on the backbone network (FIG. 1) to an MS in PD mode is, as mentioned, based on establishing and maintaining routes to the MS's currently serving MSC, by means of: - From initiating entities, initially interrogating HLR, via the HLR interrogation server. - In the PD controller data base in the MS's current MSC/VLR, storing a list of peer entities of any routes established, linked to the MS's PD mode registration. - When the MS moves to a location area belonging to a new MSC/VLR, transferring the list of peer entities (and other parameters related to the MS) from the old to the new MSC/VLR, and updating the peer entities with routing information to the new MSC.
• HLR is enhanced to provide, at the initial inter ⁇ rogation when a route is being established, the IP address of the MSC currently serving the MS in question. HLR is informed of this IP address by means of an extension, for packet data MSs, of the procedure used when an MS registers in an MSC/VLR. The information sent from MSC/VLR to HLR at registration is then extended to include the MSC's IP address.
• each route may be monitored by an inactivity timer, handled by the PD controller in the MSC/VLR currently serving the MS.
• the inactivity timer is initiated to count a predetermined period of time (timeout period) .
• the inactivity timer is reset and reinitiated for any packet received from the route, addressed to the MS.
• the timer is reset and reinitiated also for any packet from the MS to the route, when the route is a bi ⁇ directional route between the MS's current MSC and another MS's current MSC, linked to the two MSs' respective PD mode registrations.
• the timeout period may be a subscription parameter.
• the method used for routing packets in the mobile terminated direction to an MS•s currently serving MSC depends on the IP addressing scheme chosen for the packet data PLMN. If the addressing scheme i ⁇ such that the network identifying portion of an MS's IP address identifies the MS as belonging to a particular PI_MN, or subdomain of a PI_MN including a group of MSCs, the routingmethod illustrated by the example in FIG. 14 may be used. Referring to the sequential steps indicated in the figure:
• IWF 1 receives a packet addressed to MS 1.
• IWF 1 performs protocol conversion and address translation (from the external network to the intra-PLMN IP network) .
• the address translation data base may be available locally at the IWF or via remote access. When a route has been established for an MS, the address translation is performed locally.
• IWF 1 determines, from an internal data base that stores routing information for any MS for which a route is established, if a route is established to MS l's current MSC. If a route is established, the sequence proceeds with
• IWF 1 interrogates HLR via the HLR interrogation server.
• the response from HLR includes the IP address of MS l's current MSC (MSC 2) .
• the packet is encapsulated with MSC 2's IP address as destination address and IWF l's IP address as source address.
• the encapsulated packet is routed to MSC 2.
• the packet is decapsulated and address information is analysed by the PD router and PD controller in MSC/VLR 2 respectively (FIG. 1) .
• the PD controller determines if MS 1 is in PD mode.
• a PD mode establishment procedure is initiated (discribed in section I.B). - If yes: The PD controller determines if a route from IWF 1 (IWF 1 being identified by the source address in the encapsulated packet) is established for MS 1 (i.e. if IWF 1 is included in the list of peer entities linked to MS 1) . If yes: If the route is monitored by an inactivity timer, the timer is reset and reinitiated. The sequence then proceeds with transferring the packet to the MS (as described in section I.D) .
• IP address of IWF 1 is stored (linked to MS l's identity), indicating that a route is being established. If the route is to be monitored by an inactivity timer, the timer is initiated. The sequence then proceeds with 9) .
• MSC 2 notifies IWF 1 that a route segment is established. 10) IWF 1 acknowledges.
• IWF 1 stores (linked to MS l's identity) the IP address of MSC 2 (MS l's current MSC) .
• the PD router in an MSC/VLR receives a packet instead originated from an MS (MS 1) within the MSC service area
• the network identifying portion of the des ⁇ tination IP address is first analysed. If the destination address is not within the range of addresses assigned to MSs belonging to the PI_MN, the packet is routed according to normal IP routing rules. If, on the other hand, the des ⁇ tination address is within this range of addresses and thus belongs to an MS (MS 2) , the "extended VLR data base" in the PD controller is interrogated.
• the routing method may then comprise the following steps: l)The PD controller (in MSC/VLR 1) determines if a route is established to MS 2's current MSC, linked to MS l's PD mode registration (and to MS 2's identity) .
• the route is monitored by an inactivity timer, the timer is reset and reinitiated.
• the packet is then either transferred to MS 2, if MS 2 is registered in the same MSC (MSC 1), or routed to MSC 2's current MSC using the encapsulation technique described above.
• MS 2's current MSC linked to any of the other MSs registe- red in MSC/VLR 1.
• the packet is either transferred to MS 2, if MS 2 is registered in the same MSC (MSC 1) , or routed to
• MS 2's current MSC using the encapsulation technique described above.
• MS 2's current MSC then initiates establishment of a (bidirectional) route between the two MSs' current MSCs, linked to their respective PD mode registrations. If the route is to be monitored by inac ⁇ tivity timer(s) (at one or both ends of the route), the timer(s) are initiated. - If no: The sequence proceeds with 3) .
• the PD controller determines if MS 2 is registered in MSC/VUR 1.
• a procedure for establishing PD mode for MS 2 is initiated. If or when PD mode is established, a (bidirectional) route is established as a linkage between the two MSs' respective PD mode registrations. In this way, the route between the two MSs' respective current MSCs can be maintained if any of the MSs moves to another MSC/VLR.
• the sequence proceeds with 4) .
• the PD controller initiates a procedure, including HLR interrogation, for establishing a route to MS 2's current MSC, in a similar way as in the above example of route establishment from an IWF. If successful, the procedure ends with a (bidirectional) route being established between the two MSs' respective currentMSCs, linked to their respective PD mode registrations.
• the network identifying portion of an MS's IP address identifies the MS as belonging to a specific MSC/VLR. Routing of packets in the mobile terminated direction may in this case be based on the method exemplified in FIG. 15. The sequential steps indicated in the figure are as follows: 1)IWF 1 receives a packet addressed to MS 1.
• IWF 1 performs protocol conversion and address translation in a similar way as described for the example in FIG. 14. (For an "active" MS, the address translation is performed locally.) 3)The packet is routed based on its destination address (as a normal IP packet) . In this example, MS 1 is assumed to have an IP address belonging to the set of addresses assigned to MSC 1. Thus, the packet is routed to this "predetermined MSC". If the external network is an IP network, particular
• the backbone network may then be a part of the "external network", and packets may be routed directly to the respective MSC, based on destination address. 4)
• the PD controller in MSC 1 determines if a route is estab ⁇ lished to MS l's current MSC (even if, at the moment, the current MSC should be the same as the "predetermined MSC 1") . If a route is established, the sequence proceeds with 9) . Otherwise, it proceeds with 5) .
• the PD controller finds that MS 1 is not registered in MSC/VLR 1. It therefore initiates a procedure for establishing a route to MS l's current MSC (MSC 2), in the same way as described for the example in FIG. 14.
• the procedure includes HLR interrogation (steps 5)-8) in the figure) , and routing of an encapsulated packet to MSC 2 (step 9) ) .
• the routing method may comprise the following steps: l)The PD router determines if the destination address (the IP address of a mobile station MS 2) "belongs to" MSC/VLR 1. - If yes: Routing is then performed in the same way as described for the examle in FIG. 15 (as required, inclu ⁇ ding route establishment to MS 2's current MSC) .
• the PD controller may initiate route establish ⁇ ment by:
• HLR interrogation for any subsequent response packet e.g. in query/response type of applications
• a PLMN that provides connection-oriented (X.25) network services between MSs and an external X.25 network, and that employs an addressing scheme of the first type described above.
• the PD router in an MS's current MSC, from the MS receives a packet carrying a "transport connection request" (e.g. identified by a "class of service identifier" in the frame header)
• the X.25 IWF to which the packet is to be routed is determined based on stored routing information.
• the packet is "encapsulated" (with the IWF's IP address as destination address and the MSCs IP address as source address) and routed to the IWF. This initiates establishment of a route from the IWF to the MS's current MSC. HLR interrogation can thus be avoided for the response packet from the IWF. (In case a route is already established, the packet may be routed from the MSC to the IWF without encapsulation bymerely inserting the IWF's IP address as destination address.)
• MS I.F Mobile Station
• a packet data MS (“PD only", or combining PD with ordinary GSM functions) comprises: - Mobile Termination (MT) which is based on current GSM MT technology, but adapted toprovide the necessary PD functiono ⁇ nality.
• MT Mobile Termination
• TE Terminal Equipment
• PDA Personal Digital Assistant
• SIM Subscriber Identity Module
• a range of MT versions providing different standard interfaces towards TE will be available, depending on market requirements. Examples include:
• APIs Application Program Interfaces
• synchronous serial interface e.g. IP, X.25
• the MT comprises two main function blocks:
• - Terminal adapter typically microprocessor and software based, providing the TE interface as exemplified above.
• - Transceiver handling the radio interface. It is in the transceiver that most of the MS-related PD functions described in previous sections are performed, to a large extent realized with microprocessor software.
• the major PD functions that the transceiver performs may be summarized as follows:
• BCCH information identifies the degree of PDCH support provided in a cell and the MPDCH allocated (if any) for initiating packet transfer.
• - Performs cell selection in PD mode based on GSM idle mode procedures but with cell selection criteria, in stationary mode and (depending on chosen realization alternative) possibly also in mobile mode, modified such that the currently selected cell is retained as long as the signal quality is above a predefined threshold value.
• - Performs location updating in PD mode based on regular GSM procedures.
• FIG. 16 A schematical representation of this embodiment is shown in FIG. 16, with the major PD function blocks in the GSM system (as in FIG. 1) depicted with bold contour lines.
• the PD functions in BTS are almost the same as in Embodiment 1, as are the PDCH allocation functions in BSC.
• the packet data transfer connection of a BTS is coupled to a separate Mobile Packet Data Infrastructure (MPDI) (instead of, as in Embodiment 1, to the PD router in MSC/VLR) .
• MPDI Mobile Packet Data Infrastructure
• the MPDI provides the necessary packet routing, mobility management, authentication, and network management functions.
• the MPDI and the portions of BSS(s) utilized for packet data constitute a mobile packet data system.
• the system may be regarded as a separate system, and a GSM operator may choose to lease radio channel capacity to a separate packet data system operator. An MS requiring both packet data and regular GSM services may then need a separate subscription in each system.
• the packet data services provided by the system may (depending on the functionality of the MPDI) be the same as described for Embodiment 1.
• the only radio channels avai ⁇ lable for MSs are PDCHs and regular GSM broadcast channels. Registration, locationupdating (or cell location reporting) , authentication and similar signalling are thus performed via PDCHs. Furthermore, allocation of the first MPDCH on user demand, using ordinary GSM signalling as in Embodiment 1, is thus not possible. With this exception, the functions for providing PDCHs are the same as described for Embodiment 1.
• the first MPDCH in a cell is normally allocated by system configuration, although the method (outlined for Embodiment 1) of using a PDCH of an adjacent cell for requesting al ⁇ location of an MPDCH in a "PDCH on demand cell", prior to moving into that cell, is theoretically feasible.
• the allocation request would be transferred to a system entity in the MPDI.
• This system entity would then send an allocation request to the BTS of the "PDCH on demand cell" in question which, in its turn, would convey the request to the PDCH allocation controller in BSC.
• Regular GSM broadcast control channels are used in the same way as in Embodiment 1, i.e. for:
• Embodiment 1 Packet transfer across PDCHs may be performed according to the principles described for Embodiment 1, including using a multiframe scheme for coordinating with listening to broadcast channels, although adapted to the specific requirements of this separated system concept.
• BTS are also adapted to the interconnection requirements of the MPDI, e.g. to allow interconnection via a routing network.
• the functions of the MS are basically the same as in Embodiment 1, except for functions related to regular GSM signalling and PD mode which are not applicable in Embodiment 2.
• IP INTRANETWORK PROTOCOL AND INTERWORKING EXAMPLE
• Rm RANDOM ACCESS BURST
• Rd ace RESERVED ACCESS BURST
• SUBSTITUTESHEET 1 MOBILE ORIGINATED PACKET TRANSFER

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• 1993
  • 1993-12-10 SE SE9304119A patent/SE9304119D0/xx unknown
• 1994
  • 1994-11-23 TW TW083110908A patent/TW276382B/zh not_active IP Right Cessation
  • 1994-11-23 CA CA002153871A patent/CA2153871C/en not_active Expired - Lifetime
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  • 1994-11-23 KR KR1019950703333A patent/KR100353773B1/ko not_active Expired - Lifetime
  • 1994-11-23 AU AU12515/95A patent/AU675898B2/en not_active Expired
  • 1994-11-23 EP EP01128387A patent/EP1191800B1/en not_active Expired - Lifetime
  • 1994-11-23 ES ES95903477T patent/ES2188650T3/es not_active Expired - Lifetime
  • 1994-11-23 DE DE69434250T patent/DE69434250T2/de not_active Expired - Lifetime
  • 1994-11-23 CN CN94191082A patent/CN1092010C/zh not_active Expired - Lifetime
  • 1994-11-23 SG SG1996000606A patent/SG43755A1/en unknown
  • 1994-11-23 JP JP7516134A patent/JPH08506713A/ja active Pending
  • 1994-11-23 EP EP95903477A patent/EP0683963B1/en not_active Expired - Lifetime
  • 1994-11-23 WO PCT/SE1994/001120 patent/WO1995016330A1/en not_active Ceased
  • 1994-12-09 US US08/354,874 patent/US5590133A/en not_active Expired - Lifetime
• 1995
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