GB2450321A

GB2450321A - Mobile communication with packet switched and circuit switched radio systems or sub-systems

Info

Publication number: GB2450321A
Application number: GB0711750A
Authority: GB
Inventors: Chen-Ho Chin; Craig Kelvin Bishop
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 2007-06-18
Filing date: 2007-06-18
Publication date: 2008-12-24
Anticipated expiration: 2027-06-18
Also published as: GB0711750D0; GB2450321B

Abstract

In a packet switched wireless communications network for carrying voice calls, a method of signaling data indicating application-level capabilities of user equipment to the network comprising transmitting message data in the form of a Network Capability record which also contains data on the Network Capability of the user equipment.

Description

MOBILE COMMUNICATIONS

This invention relates to mobile communications. More specifically, this invention relates to mobile communications with both packet switched and circuit switched radio systems or sub-systems, and to inter-working between such sub-systems.

Many mobile communication systems (public land mobile networks or PLMNs) at present provide voice communications via a circuit-switched arrangement, in which a circuit connection to mobile user equipment is established, and maintained as the user moves. GSM networks, for example, provide circuit switched voice communications. Such networks may also provide data communications which operate on a packet switched basis; for example, GPRS is an example of a packet switched data network. Packet switched voice communications are known in non-mobile communication systems. For example, IP phones such as SKYPETM, operating over connected IP networks are becoming well known. However, packet switched data communications have not until recently been considered for mobile voice communications.

Currently under development is an all IP, packet switched, PLMN system known as SAE (system architecture evolution), described on the website of the third generation partnership project (3GPP), intended to work over a new air interface referred to as 3GPP Long Term Evolution(LTE), see http://www.3gpp.org/highlights/lte/lte.htm.

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3GPP papers TSG SA WG2 architecture S2-071505 and its predecessor, S2-071 178 (both available from http://www.3gpp.org/ftp/tsgsalWG2Arch]TSGS256c-Aj-J-warsaw/ljocs/ explain that the SAE system has to support both host-based mobility, i.e. client mobile 1P (CMIP) and network based mobility, i.e. proxy mobile IF (PMIP). It is therefore necessary for the packet switched system to know whether or not the user equipment (UE) supports CMIP in order to determine the mobility mode to use when communicating with the user equipment. It may also be desirable or necessary for the system to take into account other parameters in determining the mobility mode. One view is that the IP capabilities of the user equipment can be inferred from its communications behaviour. Another point of view is that it is necessary for the user equipment to communicate its IP capabilities to the system.

There are, in practice, many possibilities for signalling the user equipment mobile IP capabilities to the relevant packet switch network entity (the "enhanced packet core", EPC, and in particular the packet data network gateway, PDN GW or P-GW).

One method which has been contemplated (it is not known whether the discussions were published or available to the public) is to use the Mobile Station Classmark (MS Classmark). The MS Classmark information elements are used within GSM networks to describe the information that should be known by the base station to handle radio resources for that mobile station. It is therefore a container for several fields of information, such as multi slot

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capability, power class, supported frequency band, and encryption algorithms.

Classmark information elements (lEs) are carried in various defined messages. It would be possible to expand Classmark 3, for example, to include additional information elements.

Another possibility (not known in the prior art) would be to use the MS radio access capability information element which is signalled in various messages in the GPRS radio system.

By way of contrast, according to the present invention there are provided two alternative solutions. A solution according to a first aspect of the invention is to provide new information elements (signalled from the user equipment to the packet switched network), which are specifically for application level capabilities such as mobile IP capabilities. This violates the normal mindset for all current radio standards, which is to group and provide all the capability information relating to the user terminal into specific capability information elements, to minimise signalling traffic. However, it has advantages in this context. By selecting an appropriate message to carry application level capability information, the system can ensure that the message reaches the appropriate part of the packet switched network (i.e. the gateway which sets up the packet switched communications with the user equipment). Since the messages are specifically packet switched system messages, rather than expansions of circuit switched domain information elements (such as the MS Classmark information elements), this solution is more suited to pure packet switched networks such as SAE networks.

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Further, and more importantly, the information elements can, if delivered in appropriate messages, be passed transparently through to and handled at the application level at which the information is designed to be used. Messages and formats carrying the information elements concerned are described in greater detail below. The application level information comprises, at least, an indication of the mobile IF capability (i.e. host-based IP capability or proxy only IF capability) of the user equipment.

In an alternative aspect of the invention, the application level data is carried in an expanded version of the GPRS mobile station (MS) Network Capability information element (IE). That delivers the application level data to the right network entity to use since the Network Capability information element is used (in UMTS systems) by the serving GPRS support node (SGSN) so that, in the equivalent SAE packet switched network, the Network Capability data will reach the serving gateway which also uses the application level data to set up packet services for the user equipment. Although the information arrives in a message intended to be acted on by a different level protocol, it is at least possible to unpack the message and use the data at the applications level without requiring it to be signalled to a further network node elsewhere. Further, if the Network Capability information element is transmitted in messages equivalent to the GPRS ATTACH_REQUEST and ROUTING_AREA_UPDATE_REQUEST messages, it can arrive early; in the former case, before any possible session is requested so that a session, when requested, can be set in the correct IP mobility mode.

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It is expected that, in the longer term, voice services will be carried over packet switched radio networks, and that the need for circuit switched voice communications will be reduced. However, in the meantime, whilst packet switched voice communications are rolled out, packet switched voice communications will co-exist with circuit switched networks, and user equipment will need to be able to communicate using both. Additionally, mobile user equipment conducting a voice call will need to be capable of handovers between a packet switched domain (provided by an SAE network) and a circuit switched domain (provided by, for example, a GSM network).

As the SAE system is deployed, there will be "islands" of SAE packet switched voice coverage surrounded by "oceans" of GSM circuit switched voice coverage, so that there will need to be handovers from the packet switched domain to the circuit switched domain. In order to hand over the mobile terminal to a circuit switched domain, the packet switched system should be able to emulate a circuit switched network component (e.g. a mobile switching centre (MSC) in the GSM system). It is therefore desirable for the packet switched network to known the circuit switched capabilities of the user equipment, as a circuit switched network would do, but these are signalled in "Mobile Station Classmark" information elements within a circuit switched network, and are not signalled within the packet switched network (which, of itself, makes no use of them).

Accordingly, in a second aspect of the invention, circuit switched capability information (such as user equipment capability and Classmark

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information), usable in a circuit switched network but of itself not usable in a packet switched network, is provided by the user equipment to the packet switched network, in predetermined messages.

Particularly preferably, such circuit switched capability information is packaged together with the application level information of the first aspect.

However, this second aspect of the invention could be used separately of the first, and vice versa. This aspect of the invention is conveniently used with the embodiments described in our co-pending application GB, filed on the same day and having the same assignee as the present invention, agents' reference J000050098GB, the contents of which are incorporated herein by reference in their entirety.

Other aspects, embodiments and preferred features of the invention, and their associated advantages, will become apparent from the following

description, claims and drawings.

Embodiments of the invention will now be disclosed, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows schematically the interconnection of a packet switched network according to the present invention with other networks and with terminals; Figure 2 shows schematically the elements of a packet switched network according to the present invention (known per se); Figure 3 shows schematically the elements of circuit switched networks of Figure 1 (known per se);

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Figure 4 shows schematically the layers into which communications protocols are divided in networks according to the present invention (known per se); Figure 5 (comprising Figure 5a and Figure Sb) shows schematically the capability messages transmitted in a first embodiment of the invention; Figure 6 is a flow diagram showing the operation of the packet switched network in a first embodiment of the invention; Figure 7 is a diagram showing the structure of an information element defined according to the first embodiment; Figure 8 (comprising Figures 8a to 8d) shows schematically the capability messages transmitted in a third embodiment; Figure 9a is a diagram showing the structure of a first information element defined according to a fourth embodiment; and Figure 9b is a diagram showing the structure of a second information element defined according to the fourth embodiment; Figure 10 shows schematically the capability request and reply messages transmitted in a fifth embodiment of the invention; Figure 11 is a flow diagram showing the operation of the packet switched network according to a second embodiment of the invention on signalling capability information to the network; and Figure 12 is a flow diagram showing the operation of the packet switched network according to the second embodiment on handover;

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Figure 13 is a flow diagram showing schematically the process performed by the packet switched network in a sixth embodiment; Figure 14a is a flow diagram showing schematically the process performed by user equipment in the sixth embodiment; and Figure 1 4b is a flow diagram expanding part of Figure 1 4a.

FIRST EMBODIMENT

Figure 1 depicts schematically a number of inter-operating communications systems. A fixed line telephone 2 is connected to a plain old telephony system (POTS) or Integrated Services Digital Network (ISDN) public switched telephone network (PS1'N) 4. A computer 6 is connected to the Internet 8, as is an Internet phone 10. Mobile telephony user equipment 12 is in radio communication with a circuit switched (CS) public land mobile network (PLMN) 14 such as a GSM network, and with a packet switched (PS) PLMN 16 such as an SAE/LTR 3G network. Each of the networks are connected together via gateways. Thus, the user of the user equipment 12 can conduct a voice call with the user of telephone 2 or the Internet phone 10 or another mobile user equipment (not shown).

The user equipment 12 is mobile, and may therefore provide voice communications via the packet switched PLMN where coverage is available, or the circuit switched PLMN 14 (for which coverage is almost universal) where there is no packet switched coverage. The user equipment 12 is therefore capable of registering on either the CS-PLIvIN 14 or the PS-PLIvIN

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16, and those networks are arranged to be capable of handing over a voice call between the networks whilst it is in progress. It will be understood that the user equipment 12 may also be capable of non-voice data communications in various modes, not here discussed.

Referring to Figure 2, the components of an SAE network 16 are illustrated. The user equipment 12 communicates with an evolved node B (eNB) which provides a radio relay or base station defining one or more cells.

A plurality of eNBs 162 are provided. The eNB communicates with a serving gateway ( S-GW) 164 and with a mobility management entity (MME) 166.

The serving gateway is the point through which packets to and from the user equipment 12 are routed, via the eNB 162. The serving gateway 164 is connected to a packet data network (PDN) gateway 168 via which it communicates with IF services provided by the network operator (e.g. IP multimedia services, IMS, packet switched services and others, indicated generically as 170). The mobility management entity 166 tracks the location of user equipment 12 and distributes paging messages to the relevant eNBs.

The MME also manages and stores the TIE control plane context, handles UE authentication, and various other functions.

A policy and charging rules function (PCRF) node 172 stores rules indicating which services can be used by different users (not relevant to the present invention). A home subscriber service (HSS) node 174 provides the main data storage for subscriber and service related data including user ( identities, registration in formation, access parameters and service-triggering information.

The serving gateway 164, mobility management entity 166, packet data network gateway 168 and home subscriber service database 174 comprise the elements of the evolved packet core (EPC) of the SAE network.

The EPC together with the eNB 162 makes up the enhanced packet system (EPS) of the SAE communications network.

A serving GPRS support node (SGSN) 176 interconnects the packet switched network with the packet switched domains of a GPRS/EDGE radio access network (GERAN) 14a and a IJMTS radio access network (UTRAN) 1 4b.

As shown in Figure 3, the GERAN 14a comprises a plurality of base transceiver stations (BTS) 142a, 142b each generating one or more respective radio cells, coupled to a base station controller (BSC) 144. Similarly, in the UTRAN 14b, there are provided a plurality of node Bs 143a, 143b coupled to a radio network controller (RNC). The base station controller 144 and RNC are connected via circuit switched links to a mobile switch centre (MSC) 146 and circuit switched media gateway (CS-MGW) 148. The MSC server 146 comprises the call control and mobility parts of a mobile switching centre and the CS-MGW 148 interfaces the data transport from the BSC 144 or RNC with the core network. The CS-MGW therefore contains the codecs, echo cancellers, and other format conversion components (not shown) necessary for the network to ineroperate with others.

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The various nodes of the networks shown comprise switching and control logic, in practice provided by one or more computers performing each function, together with network interface chips for data reception and transmission. Each of the identified functions may be provided by a physically separate computer, a single function may be distributed between several computers, or several computers collectively may provide one or more of the functions, as is generally known in the art.

The user equipment 12 may take a variety of forms, but is typically a handheld mobile communications terminal comprising conventional components (omitted for clarity) including an aerial, radio transmission and reception circuits, a codec, a modem, a keypad for dialling or data input, a screen for control and data display, a microphone and loudspeaker or earpiece for telephonic voice communications, a battery, a computer interface, a subscriber identity module (SIM), and so on. Controlling these are one or more suitably programmed control devices such as microcomputer or DSP chips, executing a control program that implements network signalling and data communications protocols.

Referring to Figure 4, it is well known that communications in communications systems such as the mobile systems with which the present invention is concerned, are handled by computer programs which execute protocols arranged in various layers. Thus, at the physical layer 102 is the air interface. Also within the "access stratum" (handled by the radio access network components) are the media and radio link control layers (grouped

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together here as 104). Above these is the radio resource control layer 106, and above that (in the "non access stratum") are the mobility management layer and the call or session control layers 108, 110. Above the non-access stratum is the application layer 112, with which applications such as email 114, chat 118 and other applications 120 communicate via application programming interfaces (API) 122.

Grouping protocols into layers, separate of each other, allows ready inter-connection of different systems. The protocols in the stack within the user equipment 12 therefore communicate with equivalent peer protocols within the network, each working transparently through those at lower levels.

Different functional entities within the network execute the different protocols. The physical layer protocols are handled within the base stations (i.e. the BTS of a GSM system, or the node B or eNB of a UMTS system or LTE system respectively). Mobility management is handled by the mobility management entity (MME). Applications themselves are provided at service providers. The application layer 112 is handled at gateways such as the serving gateway 164, the PDN gateway 168 and the SGSN 176.

Where user equipment can have different capabilities, the relevant entity within the network needs to know the terminal capability. Thus, the terminal Classmarks need to be known to the entities which handle the access stratum and the non access stratum. The IP capability and other application level capabilities need to be known at the network entities which handle the application layer and above.

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In this embodiment, the first issue addressed is making the network aware of the mobile IP capability of the user equipment 12; specifically, whether or not the user equipment 12 can support client MIP (CMIP, also known as host-based MIP). Accordingly, in this embodiment, the mobile station Network Capability information element (defined at 3GPP TS 24.008) is expanded by the addition of a "CMIP supported bit". Preferably, the MS Network Capability IE is expanded by the addition of a "UE application capability structure" part, within which the "CMIP supported:" bit is located, together with space for additional spare bits which may be used for other application level data as shown below. Potentially, the UE's CSICS (Circuit Switched and IMS combined service) could also be provided, as could the user equipment VCC (voice call continuity) capabilities.

<MS Network Capability value part> ::= <GEAI bits> <SM capabilities via dedicated channels: bit> <SM capabilities via GPRS channels: bit> <UCS2 support: bit> <SS Screening Indicator: bit stnng(2)> <SoLSA Capability: bit> <Revision level indicator: bit> <PFC feature mode: bit> <Extended GEA bits> <LCS VA capability: bit> <PS inter-RAT HO to UTRAN lu mode capability: bit> UEAppIication Capability: structure> L_.<cMw supported: bit kspare bits> <Spare bits>; Modified MS Network Capability JE decode Referring to Figure 5, the Network Capability information element (IE) is transmitted from the user equipment 12 to the core (i.e. the EPC) of the

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packet switched network 16 within SAE messages equivalent to the GPRS ATTACH REQUEST message, when the user equipment seeks to register with the network, and ROUTING AREA UPDATE REQUEST message transmitted when the user terminal wishes to indicate that it has detected a change of the routing area in which it is located ("routing area" here is simply an example of position information; the equivalent position information in the SAE system is currently referred to as the Tracking Area). The network 16 is therefore arranged to direct these messages to a gateway, which is the appropriate node to process the CMIP indication as discussed below. At that gateway node, the message is unpacked and the Ut Application Capability parts are passed up to the application level protocols.

Thus, when the user equipment registers with a packet switched PLMN 16, it transmits a message (equivalent to the ATTACH_REQUEST) to the network in step 1002 of Figure 6. Likewise when it indicates contact with a new position by the ROUTiNG_AREA_UPDATE_REQUEST message.

In step 1004, the HSS 174 (together with an authentication, authonsation and accounting function typically provided on the same server as the HSS 174) authenticates the user equipment as being entitled to use the network, and selects the appropriate PDN gateway 168 and IP mobility mode (i.e. client mobile IP (CMIP) or proxy mobile IF (PMIP)), based on the received CMIP indication, and typically also on various other criteria. The decision process may take into account the Ut 12 geographical location, and knowledge about the presence of non-3GPP access in that location (e.g.

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access to second generation systems such as GERAN networks). When the user equipment 12 is roaming, the visited PLMN (VPLMN) capability can be made known to the home PLMN (HPLMN) based on roaming agreements between the two, so that the home PLMN stores such information on a long term basis; access type, user equipment capability and so on, as discussed in 3GPP document S2-07 1178, available on the 3GPP website, may also be taken into account.

In step 1006 the selected mobility mode and PDN gateway (indicated either by a fully qualified domain name (FQDN) or IP address) is provided to the mobility management entity 166.

In step 1008, the MME 166 selects a serving gateway 164 and forwards the information on the selected PDN gateway 168 to it. The serving gateway 164 then sends a PMIP binding updating message to the PDN gateway 168 (or an equivalent message for the GTP variant used instead of PMIP in the S5 or S8 interfaces).

In step 1010, the MME determines whether the user equipment 12 has indicated that it supports CMIP, within the Network Capability information element transmitted by the user equipment 12. If not, in step 1012, the access request is processed to allow the user equipment 12 to access the system with proxy based mobile IP as the mobility mode to be used. On the other hand, if the user equipment 12 provides client mobile IP, then in step 1014, the MME forwards the PDN gateway information on to the user equipment 12 which can then use CMIP. (

Thus, access can be provided to the user equipment depending on its IP capabilities. Further information will be found in 3GPP document S2-07 11 78, referenced above.

SECOND EMBODIMENT

In the preceding embodiment, application level capability information relating to operation in packet switched mode was transmitted from the user equipment to the SAE packet switched network 16, to allow that network to set up access for the user equipment. In this embodiment, alternatively or additionally, information on the communications capabilities of user equipment 12 in circuit switched networks 14 is provided to the packet switched network 16. The packet switched network 16 makes no use of this information itself in communications, but uses it when handing the user equipment on to a circuit switched domain of another network.

Handover procedures are discussed in 3GPPTS 23.009 (available at www.3gpp.org/fIp/specsfhtml-info/23009.htm). When handing over user equipment 12 from a packet switched network 16 such as an SAB network to the circuit switched domain of another network 14 such as a GERAN or UTRAN network, the EPC part of the SAE network must be able to emulate the traditional handover functionality described in 3GPP TS 23.009; there has to be an entity which can emulate the mobile switching centre (MSC) of a GERAN within the EPC, and typically as a function within the MME 166, to implement an anchoring MSC. It will therefore be connected to the MSCs ( 146 of the circuit switched system 14a, 14b as if it were another MSC. As part of the handover requirements, this entity must therefore perform the specified handover preparation procedures of 3GPP TS 23.009, to prepare the target circuit switched system to take over the voice call. For this purpose it must know the circuit switched characteristics which are given in the MS Classmark information element held at user equipment 12.

Although the MS Classmark information is, as regards the circuit switched system 14, used at the access and non-access layers rather than the application level, it is not used at those layers within the packet switched network 16. Such information can therefore be placed into a container for application level and service related information, as described in the first embodiment.

In this embodiment, therefore, the MS Network Capability information element is expanded by adding a structure for the UE circuit switched domain capability information, which includes the circuit switched Classmark 1, Classmark 2 and optionally, Classmark 3 data structures. As is well known, 3GPP TS 24.008 contains a definition of MS Classmark 3 information including encryption algorithms, multi slot capability, arid so on. (

<MS Network Capability value part> ::= <GEAI bits> <SM capabilities via dedicated channels: bit> <SM capabilities via GPRS channels: bit> <UCS2 support: bit> <SS Screening Indicator: bit string(2)> <SoLSA Capability: bit> <Revision level indicator bit> <PFC feature mode: bit> <Extended GEA bits> <LCS VA capability: bit> <PS inter-RAT HO to UTRAN lu mode capability: bit> (liE Application Capability: structure> <CMIP supported: bit (spare bits> - <LIE CS Domain Capability Information: structure> <MS Classmark 1: structure> <MS Classmark 2: structure> [ 1nark 3:structure) <Spare bits>; Modified MS Network Capability IE decode It will be apparent that the CMIP indication (and, generally, other application level capability) and the CS domain capability information are independent of each other, but can conveniently be transmitted in the same signalling messages.

Referring to Figure 11, within the network process which deals with UE sessions and transaction requests, 1050, in step 1052, a request is received from the UE for registration andlor access to the system, which provides its circuit switched domain capability data. In step 1054, this data is saved, together with other context data for the UE 12, and the process 1050 terminates (step 1056).

Referring to Figure 12, during the process for handling an ongoing packet switched voice call within the packet switched network (indicated as

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1060 in Figure 12), whilst a voice call is in progress (step 1062) measurements are received from the user equipment 12 in step 1064, and the EPC or the eNB makes a decision as to whether to hand over the UE 12 in step 1066. In step 1068, the various handover preparation processes performed by different elements of the network are invoked and, in step 1070, the process for handing over to the circuit switched domain 14 is initiated. In step 1072, the MIME 166, emulating an anchoring MSC, makes use of the saved UE circuit switched domain capability information which was stored in step 1054 when informing the target MSC within the target circuit switched network 14 of the data necessary to set up a voice circuit during the handover preparation signalling between the two to initiate the handover (for which, in greater detail, see ourabove-referenced application agent's reference J00050098GB). The handover task is then continued conventionally at step 1074.

THIRD EMBODIMENT

In this embodiment, therefore, a new information element is introduced into the SAlE system, which may be termed "UF Application and Service Capabilities" (UASC). Thus, in the first octet of the information element, the information element is identified. In the second octet, the length of the data which follows is identified. In the third octet, the application level data (specifically, here, the CMJP supported bit) is provided. In the fourth ( octet, the Classmark data (corresponding to the existing defined MS Classmarks 1, 2 and optionally 3) is provided.

This information element could be transported in the ATTACH_REQUEST and ROUTING AREA UPDATE REQUEST messages as described in the first embodiment, but is preferably carried in the SER VICE REQUEST and/or ACTI VAlE PDP CONTEXT REQUEST messages, as shown in Figure 8. Thus, in addition to the scenarios discussed above, the information is transferred when a user requests a particular type of service (e.g. video, fax, data) or makes a connection establishment request (which would indicate that the user might thereafter need to be handed over.

Thus, whenever a user might need to be handed over to a circuit switched network, the packet switched network has the data available to do so. Further, the information is delivered to the gateway which is the correct entity to use the data, and is carried at the correct protocol level (the applications level).

FOURTH EMBODIMENT

In the embodiment described above, Figure 7 shows a single information element which contains UE application indications and CS domain capability information indications. Figure 9a indicates the structure of the application capability information element and Figure 9b the structure of the CS domain capability information IE; these can be compared with Figure 7. It is envisaged that these would be transmitted in the same messages as illustrated in Figure 8. However, additional flexibility in the

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signalling and routing of the data is given by providing these information elements separately (at the cost of a slight potential increase in overhead) as they are used on separate occasions (session setup and handover to CS domain respectively).

FIFTH EMBODIMENT

In the above embodiments, the UE 12 proactively signals its capabilities with the packet switched (SAE) network equivalents of the ATTACH_REQUEST, ROUTING_AREA_UPDATE_REQUEST, andlor SERVICE_REQUEST and ACTIVATE PDP CONTEXT REQUEST messages. In this embodiment, the user equipment 12 is also arranged to provide the capability information concerned by query and respond methods, in response to a query from the network as shown in Figure 10. Thus, in response to a PROVIDE_CAPABILITY_QUERY message from the EPC of the packet switched network, the user equipment 12 is arranged to return a PROVIDE_CAPABILITY RESPONSE message containing either a single information element or two separate information elements as described above in relation to the first through fourth embodiments.

SIXTH EMBODIMENT

It is anticipated that, in SAE networks (as in previous known networks), user equipment 12 will autonomously check its own capabilities for changes (e.g. updates) and send a message indicating a capability change.

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For instance a UE may undergo a software or firmware upgrade. Equally, where a UE comprises two physically separate entities (for example a mobile phone connected to a computer on which the IP stack is implemented) and one of the entities is changed, or when an application is added or removed, capabilities may change.

Thus, referring to Figure 13, in step 1102, a user equipment 12 which is registered with the packet switched PLMIN 16 (either in idle or active state) checks its capabilities and, where a change is detected (step 1104), transmits a CAPABILITY_CHANGE_INDICATION message in step 1106 to the network 16, containing at least one information element indicating a new application level and/or CS domain capability. In step 1108, the network 16 transmits back a CAPABILITY CHANGE CONFLRM message to the LIE (in the absence of which, the T.JE may retransmit at step 1106 until such a message is received).

To summarise, in this embodiment, taken together with its predecessors, as shown in Figure 14a either when (step 1202) the user equipment 12 initiates registration or transaction requests, or (step 1204) where the UE 12 is connected but its capabilities change (typically, generating an interrupt which triggers an interrupt handler routine but periodic checking is also possible) or, in step 1206, when a message is received from the network querying the UE's capabilities, then in step 1208 the UE 12 initiates its capability and characteristic check procedure which is shown in Figure l4b, consisting of checking (step 1210) whether it is CMIP capable, and if so (step 1212) setting the "CMIP supportu bit in the relevant information element; likewise in step 1214, preparing the circuit switched capability information (consisting of MS Classmark indications) and storing it in the relevant information element; and finally (step 1218) sending these capabilities to the network as discussed in relation to the embodiments above.

OTHER EMBODIMENTS AND VARIATIONS

It will be understood that the foregoing embodiments are merely examples, and that the invention extends to any and all modifications, variations and substitutions which would be obvious to the skilled person in the light thereof.

In particular, names of messages, data and systems are purely exemplary.

Another packet switched system with which the present invention could be employed is 3GPP2 (for which see www.3gpp2.org).

Claims

C CLAIMS

1. In a packet switched wireless communications network for carrying voice calls, a method of signalling data indicating application-level capabilities of user equipment to the network comprising transmitting message data in the form of a Network Capability record which also contains data on the Network Capability of the user equipment.

2. In a packet switched wireless communications network for carrying voice calls, a method of signalling data indicating application-level capabilities of user equipment to the network, comprising transmitting message data in the form of a new information element which does not contain data on the network or radio capabilities of said user equipment in said packet network.

3. The method of claim I or claim 2 in which the application-level information is, or includes, an indication of whether the user equipment can conduct client mobile Internet protocol (CMIP) communications.

4. The method of any preceding claim, in which the user equipment is operable both with said packet switched network and with a circuit switched network, and in which the user equipment is operable to be

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handed over from the packet switched network to the circuit switched network during a voice call.

5. in a packet switched wireless communications system for providing voice calls to user equipment, said user equipment also being operable with a circuit switched wireless network, said packet switched network being arranged to hand over a voice call with said user equipment to said circuit switched network during said call, a signalling method comprising the step of transmitting to the packet switched network data indicating the capability of said user equipment to communicate with said circuit switched network in the form of a message containing said capability information.

6. The method of claim 5 in which said capability information comprises data on the radio and network capabilities of said user equipment.

7. The method of claim 5 or claim 6, in which said capability information comprises MS Classmark information.

8. The method of any preceding claim, in which the message is a message transmitted by the user equipment on registration with the packet switched network.

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9. The method of any preceding claim in which the message is transmitted by the user equipment on supplying a routing area update to the network.

10. The method of preceding claim in which the message is transmitted by the user equipment when requesting a service from the network.

11. The method of any preceding claim in which the message is transmitted from the user equipment indicating a connection establishment request.

12. The method of any preceding claim in which the packet switched network is arranged to send a message requesting information from said user equipment, and to receive in return the message containing said application level andlor circuit switched capability information.

13. The method of any preceding claim in which the user equipment is arranged to assess its capabilities and send a said message to the network on detecting a change in said capabilities.

14. The method of claim 5, in which the packet switched network is arranged to store said capability data for future use.

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15. The method of claim 14, in which the future use comprises use in a handover to a circuit switched network.

16. The method of any of claims I to 4 further comprising the step, by the the packet switched network, of using said message data to select a packet communications mobility mode.

17. The method of claim 16, further comprising the step, by the packet switched network, where a client based IP mode is selected, of signalling the identity of a selected network node to the user equipment.

18. The method of claim 17, further comprising the step, by the user equipment, of receiving said identity and storing said identity for future use in client-based IP mobility management.

19. User equipment for performing all or part of the method of any preceding claim.

20. A network core component of a packet switched network for performing all or part of the method of any preceding claim.