GB2408654A

GB2408654A - Synchronised circuit-switched and packet-switched communications

Info

Publication number: GB2408654A
Application number: GB0327466A
Authority: GB
Inventors: Gerry Foster; Howard Benn; Seiamak Vahid
Original assignee: Motorola Inc
Current assignee: Motorola Solutions Inc
Priority date: 2003-11-26
Filing date: 2003-11-26
Publication date: 2005-06-01
Anticipated expiration: 2023-11-26
Also published as: GB0327466D0; GB2408654B

Abstract

A cellular communication system 100 supports both packet-switched communication services and circuit-switched communication services. The system 100 includes a Mobile Switching Centre (MSC) 107, to provide a circuit-switched connection between mobile stations (MS) 101, 113, and a Serving GPRS Support Node (SGSN) 115, to provide a packet-switched connection. The system 100 may further comprise a synchronisation server 117 for synchronising a packet-switched user plane stream and a circuit-switched user plane stream. Alternatively, a communication link, such as a Gs interface, between the MSC and SGSN provides synchronisation between circuit-switched and packet-switched communications. Thus, enhanced setup of combined or coordinated packet-switched and circuit-switched services is provided.

Description

A CELLULAR COMMUNICATION SYSTEM AND A METHOD OF

OPERATION THEREFOR

Field of the invention

The invention relates to a cellular communication system and a method of operation therefor and in particular to a cellular communication system capable of supporting both packet switched and circuit switched services.

Background of the Invention

In a cellular communication system a geographical region is divided into a number of cells each of which is served by a base station. The base stations are interconnected by a fixed network which can communicate data between the base stations. A mobile station is served via a radio communication link by the base station of the cell within which the mobile station is situated.

As a mobile station moves, it may move from the coverage of one base station to the coverage of another, i.e. from one cell to another. As the mobile station moves towards base station, it enters a region of overlapping coverage of two base stations and within this overlap region it changes to be supported by the new base station. As the mobile station moves further into the new cell, it continues to be supported by the new base station. This is known as a handover or handoff of a mobile station between cells.

A typical cellular communication system extends coverage over typically an entire country and comprises hundreds or even thousands of cells supporting thousands or even millions of mobile stations. Communication from a mobile station to a base station is known as uplink, and communication from a base station to a mobile station is known as downlink.

The fixed network interconnecting the base stations is operable to route data between any two base stations, thereby enabling a mobile station in a cell to communicate with a mobile station in any other cell. In addition, the fixed network comprises gateway functions for interconnecting to external networks such as the Public Switched Telephone Network (PSTN), thereby allowing mobile stations to communicate with landline telephones and other communication terminals connected by a landline. Furthermore, the fixed network comprises much of the functionality required for managing a conventional cellular communication network including functionality for routing data, admission control, resource allocation, subscriber billing, mobile station authentication etc. Currently, the most ubiquitous cellular communication system is the 2nd generation communication system known as the Global System for Mobile communication (GSM). GSM uses a technology known as Time Division Multiple Access (TDMA) wherein user separation is achieved by dividing frequency carriers into 8 discrete time slots, which individually can be allocated to a user. A base station may be allocated a single carrier or a multiple of carriers. One carrier is used for a pilot signal which further contains broadcast information. This carrier is used by mobile stations for measuring of the signal level of transmissions from different base stations, and the obtained information is used for determining a suitable serving cell during initial access or hangovers. Further description of the GSM TDMA communication system can be found in 'The GSM System for Mobile Communications' by Michel Mouly and Marie Bernadette Pautet, Bay Foreign Language Books, 1992, ISBN 2960719007.

To further enhance the services and performance of the GSM communication system, a number of enhancements and additions have been introduced to the GSM communication system over the years.

One such enhancement is the General Packet Radio System (GPRS), which is a system developed for enabling packet data based communication in a GSM communication system. Thus, the GPRS system is compatible with the GSM (voice) system and provides a number of additional services including provision of packet data communication, which augments and complements the circuit switched communication of a traditional communication system.

Furthermore, the packet based data communication may also support packet based speech services. The GPRS system has been standardized as an add-on to an existing GSM communication system, and can be introduced to an existing GSM communication system by introducing new network elements.

Specifically, a number of Serving GPRS Support Nodes (SGSN) and Gateway GPRS Support Nodes (GGSN) may be introduced to provide a packet based fixed network communication.

Currently, 3rd generation systems are being rolled out to further enhance the communication services provided to mobile users. The most widely adopted 3rd generation communication systems are based on Code Division Multiple Access (CDMA) wherein user separation is obtained by allocating different spreading and scrambling codes to different users on the same carrier frequency. The transmissions are spread by multiplication with the allocated codes thereby causing the signal to be spread over a wide bandwidth. At the receiver, the codes are used to de-spread the received signal thereby regenerating the original signal. Each base station has a code dedicated for a pilot and broadcast signal, and as for GSM this is used for measurements of multiple cells in order to determine a serving cell. An example of a communication system using this principle is the Universal Mobile Telecommunication System (UMTS), which is currently being deployed.

Further description of CDMA and specifically of the Wideband CDMA (WCDMA) mode of UMTS can be found in 'WCDMA for UMTS', Harri Holma (editor), Antti Toskala (Editor), Wiley & Sons, 2001, ISBN 0471486876.

In a UMTS CDMA communication system, the communication network comprises a core network and a Radio Access Network (RAN). The core network is operable to route data from one part of the RAN to another, as well as interfacing with other communication systems. In addition, it performs many of the operation and management functions of a cellular communication system, such as billing. The RAN is operable to support wireless user equipment over a radio link being part of the air interface. The wireless user equipment may be a mobile station, a communication terminal, a personal digital assistant, a laptop computer, an embedded communication processor or any communication element communicating over the air interface. The RAN comprises the base stations, which in UMTS are known as Node Bs, as well as Radio Network Controllers (RNC) which control the Node Bs and the communication over the air interface.

Typically, cellular communication systems today support both traditional circuit switched services as well as packet switched services. In communication systems such as GSM/GPRS and UMTS systems, the functionality for supporting packet switched and circuit switched services tend to be separated. Mainly, consideration of legacy issues have led to separate domains being developed for circuit switched and packet switched functionality. For example the circuit switched domain comprises MSCs and circuit switched functionality of BSCs whereas the packet switched domain comprise SGSNs and GGSNs.

The circuit switched and packet switched domains are typically distinct domains in the core network and the protocols and processes used for managing and controlling the different domains are separate. For example, in a combined GSM/GPRS cellular communication system, circuit switched and packet switched services have completely different attach methods and strictly separate ways of establishing a time based association between calling and called parties. Thus, at present, two distinct call models exist for circuit switched and packet switched services. The two independent service models are Call Control for the circuit switched domain and domain Session Management for the packet switched domain. Both of these state models exist in addition to respective and distinct mobility models of the circuit switched and packet switched domains.

Also, currently a GSM mobile must have two transmitters to be able to support a full voice call and packet transmission simultaneously. However, this is expensive and cumbersome.

At present, operators are seeking to introduce new services such as multimedia services with voice and pictures. However, typically this is currently implemented by a full Session Initiation Protocol (SIP) session being initialised thereby resulting in the associated SIP signalling. The SIP offers an integrated packet switched domain for all service legs and types in a multimedia call. However, SIP is very inefficient in terms of signalling and set up speed and packet voice is not considered of acceptable and comparable quality to a GSM circuit switched voice call over the same bandwidth logical channel.

Hence, an improved cellular communication system would be advantageous and in particular a system allowing for increased flexibility, performance, enhanced services, additional services and/or improved compatibility, coordination and/or interworking between the packet switched domain and the circuit switched domain would be advantageous.

Summary of the Invention

Accordingly, the Invention seeks to preferably mitigate, alleviate or eliminate one or more of the above mentioned disadvantages singly or in any combination.

According to a first aspect of the invention there is provided a cellular communication system comprising: packet communication means for supporting packet switched communication services; circuit communication means for supporting circuit switched communication services; and synchronization means for synchronizing a packet switched user plane stream supported by the packet communication means and a circuit switched user plane stream supported by the circuit communication means.

The user plane streams are communicated end to end and may be routed by any intervening switches, routers, base stations etc. Specifically, the user plane streams originate and/or terminate in a user equipment. The user plane streams may specifically comprise information presented to the user of a user equipment and/or be used in a user application interfacing with a user. The user plane streams may comprise signalling information associated with a user application or the presentation of information to a user. As an example, the user plane streams may comprise audio and/or visual data. Specifically, the user plane streams may be user plane streams as specified for the UMTS 3rd generation cellular communication system. The synchronization may include a plurality of packet switched user plane streams and/or a plurality of circuit switched user plane streams.

The means for supporting packet switched communication services may comprise all or some network elements used for routing, switching, managing and/or controlling communication of data packets in the cellular communication system including functionality for setting up packet communication sessions or frameworks. The means for supporting circuit switched communication services may comprise all or some network elements used for routing, switching, managing and/or controlling communication of circuit switched data in the cellular communication system including functionality for setting up circuit switched calls.

The invention allows an improved compatibility and co-operation between the circuit switched and the packet switched domains of a cellular communication system. Enhanced, improved and/or additional performance of the communication system as a whole may be achieved. Specifically, the invention may allow facilitated and/or improved provision of combined circuit switched and packet switched services. Alternatively or additionally, improved, enhanced and/or additional combined circuit switched and packet switched services may be provided.

According to a feature of the invention, the synchronization means is operable to synchronise the packet switched user plane stream and the circuit switched user plane stream during a communication setup process. This may allow facilitated and/or improved setup of combined circuit switched and packet switched services. It may further allow improved, enhanced and/or additional combined circuit switched and packet switched services to be setup. Thus, the combined circuit switched and packet switched services may be enabled right from the start of a new service being setup.

According to a different feature of the invention, the communication setup process is a circuit switched call setup process. The process of setting up combined circuit switched and packet switched services may be circuit switch anchored. This may allow a simple and easy to implement process for setting up packet communication(s) or session(s) in connection with setting up a circuit switched call.

According to a different feature of the invention, the communication setup process is a packet session setup process. The process of setting up combined circuit switched and packet switched services may be packet switch anchored.

This may allow a simple and easy to implement process for setting up circuit switched communication in connection with setting up a packet data session.

According to a different feature of the invention, the synchronisation means comprises a communication link between the packet communication means and the circuit communication means operable to carry synchronisation information. This provides a suitable means of implementation allowing for a practical and efficient synchronisation between the packet switched and the circuit switched domain.

According to a different feature of the invention, the communication link comprises a G9 interface link. This provides a suitable means of implementation which is compatible with many current cellular communication systems such as GSM/GPRS and/or UMTS. The invention may provide both for bearer control signalling and bearer synchronisation in addition to the already specified traditional mobility signalling currently defined for the Gs interface.

According to a different feature of the invention, the synchronisation means comprises a wireless Intelligent Network (IN) server for synchronizing the packet switched user plane stream and the circuit switched user plane stream.

This may provide a suitable and advantageous implementation. In particular it may facilitate provision of the synchronisation in existing communication systems that comprise IN functionality, such as e.g. communication systems such as GSM/GPRS and/or UMTS wireless. It may specifically allow for a server external to an MSC to interface to the MSC to provide synchronisation input. Thus, the wireless IN server may specifically be compatible with wireless IN as specified for the UMTS communication system.

According to a different feature of the invention, the synchronization means comprises a supplementary services server for synchronizing the packet switched user plane stream and the circuit switched user plane stream. This may provide a suitable and advantageous implementation. In particular it may facilitate provision of synchronization in existing communication systems comprising supplementary services functionality and protocols. For example it provides for a practical and advantageous implementation in communication systems such as GSM/GPRS and/or UMTS. It may specifically allow a suitable implementation of a server as a functional entity of an MSC. Specifically, the supplementary services server may be compatible with the supplementary service protocol as defined for the UMTS communication system.

According to a different feature of the invention, the synchronization means comprises a dedicated synchronization server for synchronizing the packet switched user plane stream and the circuit switched user plane stream. This may provide a suitable and advantageous implementation. In particular it may allow a very flexible, efficient and high performance interworking between the packet switched and circuit switched domains.

According to a different feature of the invention, the synchronization means is operable to associate packet data with a circuit switched call at call setup. This allows improved and/or additional services to be associated with a circuit switched call at setup. For example, when setting up a new circuit switched call, additional packet data may be selectively pushed to the called party.

Similarly additional packet data may be selectively pushed to the calling party from the called party once the anchored call or session is established between the calling and called parties.

According to a different feature of the invention, the synchronization means is operable to retrieve the packet data from a data store in response to a characteristic associated with the circuit switched call. This allows for packet data to be stored and retrieved and coordinated with a circuit switched call at setup. The retrieval and association of packet data may be automated. Thus, when setting up a circuit switched call, additional information may be automatically provided to a party by efficient packet switched communication.

According to a different feature of the invention, the data store is external to the synchronization means. Specifically, a suitable interface may be provided for interfacing the synchronization means to the data store. The data store may be external to the cellular communication system and may be managed directly by a third party.

According to a different feature of the invention, the packet data comprises a picture. For example, the picture may provide additional information related to the circuit switched call thus allowing for a user to be provided with visual information at call setup. The picture may for example be a picture of a user of a user equipment involved in the call.

According to a different feature of the invention, the synchronization means is operable to synchronize the packet switched user plane stream and the circuit switched user plane stream during a circuit switched call setup and to effect a packet data communication if the circuit switched call setup is not setup.

This may allow additional services dependent on whether a call is set up or not. The packet data communication may depend on the reason for the call not being set up. Specifically, the call may not be setup because a given set of requirements cannot be met or because a called party does not accept the call.

The packet data communication may provide an efficient communication of additional information when a call setup fails for any reason. Specifically, the packet data communication may provide information that is stored and provided to and/or retrieved by a user at a different time.

According to a different feature of the invention, the packet data may be data associated with an entity initializing the call. For example, the packet data may comprise personal information related to the identity or other characteristics of the caller. As another example, the packet data also comprise advertising information. Specifically, the packet data may comprise information selected by the caller to be provided to the called party if the circuit switched communication is not setup as requested (e. g. because of the called party not accepting the incoming call).

According to a different feature of the invention, the circuit switched user plane stream comprises a voice user plane stream. Thus, the invention may allow a very efficient and high performance association of packet switched services to a voice call thus providing for improved and/or additional services.

Preferably the cellular communication system comprises a 3rd Generation cellular communication network, a GSM cellular communication network and/or a GPRS cellular communication network. The circuit communication means preferably comprises at least one GPRS Support node and in particular preferably comprises at least one Serving GPRS Support Node and/or one Gateway GPRS Support Node.

According to a second aspect of the invention, there is provided a method of operation for a cellular communication system having packet communication means for supporting packet switch communication services and circuit communication means for supporting circuit switch communication services, the method comprising the step of synchronizing a packet switched user plane stream supported by the packet communication means and a circuit switched user plane stream supported by the circuit communication means.

These and other aspects, features and advantages of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter.

Brief Description of the Drawings

An embodiment of the invention will be described, by way of example only, with reference to the drawings, in which FIG. l illustrates a cellular communication system in accordance with an embodiment of the invention; and FIG. 2 illustrates an example of a signal flow for a circuit switch call setup process in accordance with an embodiment of the invention.

Detailed Description of a Preferred Embodiment of the Invention The following description focuses on an embodiment of the invention applicable to a combined GSM and GPRS cellular communication system.

However, it will be appreciated that the invention is not limited to this application but may be applied to many other cellular communication systems including for example a 3rd Generation cellular communication system such as UMTS.

FIG. 1 illustrates a cellular communication system in accordance with an embodiment of the invention.

The cellular communication system of FIG. l is specifically a GSM communication system which has been enhanced by introduction of GPRS packet communication functionality. The example of FIG. 1 illustrates elements involved in an example communication between subscriber units.

Specifically, FIG. 1 shows a first subscriber unit 101 which is communicating with a first base station 103 over the air interface. The first base station 103 is coupled to a first base station controller 105. The first base station controller is further coupled to a Master Switch Centre (MSC) 107. The MSC 107 is coupled to a second base station controller 109 which again is coupled to a second base station 111. The second base station 111 communicates with a second subscriber unit 113 over the air interface.

A circuit switched connection may be established from the first subscriber unit 101 to the second subscriber unit 113 through the MSC 107 as is known in the art. In particular, a standard GSM voice call may be set up and thus a circuit switched user plane voice stream may established between the users of the first and second subscriber unit 101, 113 thereby allowing a high quality voice communication with suitable quality of service parameters.

The first base station controller 105 is furthermore coupled to a Serving GPRS Support Nodes (SGSN) 115 which is also coupled to the second base station controller 109. A packet switched service may be set up between the first subscriber unit 101 and the second subscriber unit 113 through the SGSN 115.

For example, a text, voice or image messaging service may be set up between the users of the first and the second subscriber unit 101, 113. Thus, a packet switched user plane stream may be set up between the first and second subscriber unit 101, 113. It will be appreciated that the example of FIG. 1 for clarity and brevity illustrates only a single SGSN but that a plurality of SGSNs may be involved in packet communication between two subscriber units.

Conventionally, the circuit switched user plane voice stream will be set up using a standard GSM circuit switched call setup procedure. This functionality resides in the MSC 107 and the circuit switch elements of the BSC 105. Thus, the circuit switched user plane stream is set up and controlled exclusively from a circuit switched domain of the core network. Likewise, the packet switched user plane stream is conventionally, set up using a standard GPRS packet session setup procedure. This functionality resides in the SGSN 115 and the packet switch elements of the BSC 105. Thus, the packet switched user plane stream is set up and controlled exclusively from a packet switched domain of the core network.

However, in accordance with an embodiment of the current invention, the cellular communication system of FIG. 1 comprises a synchronization server 117 which is coupled to the MSC 107 and the SGSN 115 and which is operable to synchronise one or more packet switched user plane streams and one or more circuit switched user plane streams. In the embodiment, the services and connections of the packet switched domain and the circuit switched domain may thus be coordinated. Hence, services using both circuit switched user plane streams and packet switched user plane streams may be set up and/or controlled and/or managed together.

For example, the first subscriber unit 101 may set up a circuit switched call which has associated packet data services. Thus, the first subscriber unit 101 may request that a circuit switched call is set up. However, contrary to a normal request, the call request may further comprise packet switch parameters that specify a packet switch requirement or service associated with the circuit switch call. It will be appreciated that any suitable method or means of communicating the association or parameters of the packet switch request may be used.

The synchronisation server 117 may be provided with the parameters associated with the packet switch requirements. For example, the synchronisation server 117 may intercept the circuit call request or the MSC 107 may be operable to extract this information and feed it to the synchronisation server 117. In response, the synchronisation server 117 accesses the packet switch domain in the form of the SGSN 116 and causes the required packet switch session to be set up. Thus, a synchronized setup of both circuit switch and packet switch user plane streams may be achieved. This synchronized set up facilitates set up of combined packet and circuit switch services and provides for combined services to be active already during set up.

Thus, for example, packet switched user plane streams may be used during call set up to provide a user with additional information related to the call being setup.

In the example of FIG. 1, the synchronisation server 117 is shown as a separate dedicated synchronisation server. However, it will be appreciated that depending on the specific embodiment, the functionality illustrated by the synchronisation server 117 may be implemented in any suitable way and at any suitable location. Specifically, the functionality may be distributed between the packet switched domain and the circuit switched domain.

In a GSM/GPRS communication system, a communication link may exist between the MSC 107 and the SGSN 116. This communication link is known as a Gs interface, and in the described embodiment, the synchronisation server 117 comprises the Gs interface and is operable to communicate synchronisation information over the Gs interface. The synchronisation information may comprise any information required or desired to coordinate between the packet switch domain and the circuit switch domain including for example packet data requirements associated with a circuit call setup, user identification or resource allocation information or confirmation,.

It will be appreciated that the synchronization information may flow in both directions and that the synchronization process may be instigated and/or controlled by the packet switch domain and/or the circuit switch domain.

Specifically, the communication setup process may be circuit switch anchored or packet switch anchored.

In the embodiment of FIG. 1, the MSC 107 is further coupled to a billing server 119 which is operable to compile billing information associated with both the circuit switched and the packet switched element of the call. As an example, billing may be kept fundamentally the same as for a voice call for the voice call part of the service, but with the associated packet services being billed as an addition to the basic voice bill. Thiswill be suitable for most consumers as it is more akin to the conventional billing approach than a separate packet and circuit bill and is furthermore a per transaction based bill.

FIG. 2 illustrates an example of a signal flow for a circuit switch call setup process in accordance with an embodiment of the invention. The process is applicable to the communication system of FIG. 1 and will be described with reference to this.

The circuit switch call setup process initiates with the first subscriber unit 101 transmitting a service request to the first base station 103. The first base station 103 accordingly transmits a service request message 201 to the MSC 107.

When the MSC 107 receives the service request message 201, it transmits a paging message 203 to the second base station 111 which accordingly pages the second subscriber unit 113. If the second subscriber unit 113 proceeds with the call it transmits a paging acknowledge to the second base station 111 which accordingly transmits a paging acknowledge message 204 to the MSC 107.

It will be appreciated that the description of the call setup process for brevity and clarity focuses on aspects appropriate for a description of the current embodiment, and that a call setup process in accordance with the detailed GSM specifications may be more complex and involve more complex signalling.

For example, in a GSM communication system, the initial steps of a call setup process may comprise further signalling. Specifically, assignment request messages, assignment acknowledge messages, alert messages etc may be communicated as is well known in the art.

After receipt of the paging acknowledge message 204 the MSC 107 is aware that both subscriber units 101, 113 are ready for setting the call up. In the example, the service request is a request for a circuit switched user plane service setup but is also a service request for an associated packet switch user plane service to be setup. Accordingly, the MSC 107 communicates a packet setup trigger message 205 to the synchronization server 117.

In some embodiments, the communication of the associated packet switch information may be by use of wireless Intelligent Network (IN) protocols. In this case, the MSC 107 may detect the wireless IN messaging and forward these to the synchronization server 117 which specifically may be a wireless IN server. Thus, the synchronization server 117 may be an external wireless IN server which interfaces with the rest of the cellular communication system via a wireless IN protocol.

In other embodiments, communication of the associated packet switch information may be by use of a supplementary services protocol. In this case the synchronization server 117 may be implemented as a supplementary services server which may be comprised in the MSC 107.

In response to receiving the packet setup trigger message 205, the synchronization server 117 transmits a bearer request message 207 to the SGSN 115. The specific parameters and requirements of the bearer may be determined by the synchronization server 117 in response to the packet switch requirements included in the service request message 201.

In response, the SGSN 115 sets up the required radio bearers for the packet switched session and subsequently transmits a bearer confirmation message 209 to the synchronization server 117. If the first and second subscriber unit 101, 113 are not associated with the same SGSN, both serving SGSNs need to be contacted. However, no paging is required at either end as the addresses and location of both subscriber units are known through the normal circuit switch call setup and circuit switched paging processes.

Following the bearer confirmation message 209 GPRS packet data sessions for the first and second subscriber unit 101, 113 have automatically been setup synchronized with the circuit switched call. Accordingly, the synchronization server 117 transmits a packet setup trigger acknowledge message 211 to the MSC 107 informing it that the associated packet session has been successfully setup. Upon receiving this, the MSC 107 transmits an alert message to the first base station 103.

Thus, the request for a circuit switched call has resulted in a packet data session being setup before the circuit switch call set up has finished. This synchronized set up may not only facilitate the combined or coordinated setup between the circuit switched domain and the packet switched domain but may also enable additional services.

In the example of FIG. 1, the synchronization server 117 is specifically operable to associate packet data with a circuit switched call during call setup.

In the example, the associated packet data comprises data associated with the first subscriber unit 101, such as e.g. information related to a user of this, and/or of the second subscriber unit 113. Specifically, the associated data in the described example comprises a picture of the user of the subscriber units.

It will be appreciated that many other forms of packet data may be associated including personal information, voice messaging, ring tones, advertising etc. In the specific embodiment, the associated data is stored in a data store comprised in the SGSN 115. The data store is preferably user accessible and thus each user of a subscriber unit may at their convenience upload a picture to the data store. This picture may accordingly be automatically retrieved when the corresponding subscriber unit is involved in a call.

In other embodiments, the data store may be comprised in other elements or may be external to the cellular communication system. For example, the picture may be stored on third party or personal computers accessible through the Internet.

In the specific example, the synchronization server 117 transmits a picture fetch message 215 comprising an identification of the first and second subscriber units 101, 113 to the sasN 115. In response to receiving the picture fetch message 215, the SGSN retrieves the stored picture for the first and second subscriber unit 101, 113 respectively. It then proceeds to transmit a data download message 217 comprising the picture associated with the first subscriber unit 101 to the second subscriber unit 113, and a data download message 219 comprising the picture associated with the second subscriber unit 113 to the first subscriber unit 101.

Thus, in the example, the user of the second subscriber unit 113 may automatically be presented with a picture of the user of the first subscriber unit 101 before the call has been answered. Similarly, the user of the first subscriber unit 101 may be presented with a picture of the user of the second subscriber unit 113. Thus, in the specific example, instant recognition of the user at the other end of the circuit switched connection is efficiently provided.

It will be appreciated that many other forms of associated data and means of retrieving these may be used. For example, the packet data may originate at the subscriber units and may be communicated from one subscriber unit to another as part of the call setup procedure.

The second subscriber unit 113 may select to answer the call which may then proceed as a normal circuit switched call. However, the packet data session may be used further during the call and new packet services or communications may be set up.

An example of a call termination process will be described. In the specific example, the first base station 103 transmits a disconnect message 221 to the MSC 107 when the first subscriber unit 101 terminates the call. In response, the MSC 107 transmits a packet setup release message 223 to the synchronization server 117.

The synchronization server 117 subsequently transmits a bearer release message 225 to the SGSN 115 which causes this to terminate the packet data session (or sessions) currently active and associated with the circuit switched call. When the radio bearers have been successfully released the SGSN 115 transmits a bearer release acknowledge message 227 to the synchronization server 117. When the synchronization server 117 receives this message, it transmits a packet setup release complete message 229 to the MSC indicating that all packet switched resources have been released and all sessions have been terminated. Accordingly, the MSC 107 proceeds to terminate the call as for a conventional circuit switch call. Thus, the circuit switch call clearing procedure automatically terminates the associated packet sessions.

It will be appreciated that although the description above has focused on a circuit switched call anchored setup procedure, a synchronized circuit switched user plane and packet switched user plane communication setup may equally be performed by a packet switch communication anchored setup procedure.

Specifically, a request for a packet data session may comprise associated requests for setting up a circuit switched call. The synchronization server 117 may use this information to interwork with the MSC 107 to setup a circuit switched call e.g. simultaneously with the setting up of the packet data session.

In some embodiments, the communication sessions or connections being set up may depend on the call setup process itself Specifically, when setting up a circuit switched call as outlined above, a packet data session may automatically be set up and a packet data communication may be instigated if the circuit switched call is not setup. Specifically, a packet data communication may automatically be instigated if the second subscriber unit 113 does not respond to the paging or if the user of the second subscriber unit 113 does not respond to the incoming call.

Thus, if a circuit switched call cannot be set up, associated data may automatically be sent to the user of the second subscriber unit 113. This data may specifically be push data such as advertising or may be voice or text messaging. Thus, if a call cannot be setup, a packet data message may automatically be communicated e.g. informing the second subscriber unit 113 that it was called by the first subscriber unit 101. Specifically, the data may include a picture of the user of the first subscriber unit 101 thus allowing for the user of the second subscriber unit to automatically be informed that he was called by the user whose image is displayed.

The invention can be implemented in any suitable form including hardware, software, firmware or any combination of these. However, preferably, the invention is implemented at least partly as computer software running on one or more data processors and/or digital signal processors. The elements and components of an embodiment of the invention may be physically, functionally and logically implemented in any suitable way. Indeed the functionality may be implemented in a single unit, in a plurality of units or as part of other functional units. As such, the invention may be implemented in a single unit or may be physically and functionally distributed between different units and processors.

Although the present invention has been described in connection with the preferred embodiment, it is not intended to be limited to the specific form set forth herein. Rather, the scope of the present invention is limited only by the accompanying claims. In the claims, the term comprising does not exclude the presence of other elements or steps. Furthermore, although individually listed, a plurality of means, elements or method steps may be implemented by e.g. a single unit or processor. Additionally, although individual features may be included in different claims, these may possibly be advantageously combined, and the inclusion in different claims does not imply that a combination of features is not feasible and/or advantageous. In addition, singular references do not exclude a plurality. Thus references to "a", "an", "first", "second" etc do not preclude a plurality.

Claims

1. A cellular communication system comprising: packet communication means for supporting packet switched communication services; circuit communication means for supporting circuit switched communication services; and synchronization means for synchronizing a packet switched user plane stream supported by the packet communication means and a circuit switched user plane stream supported by the circuit communication means.

2. A cellular communication system as claimed in claim 1 wherein the synchronization means is operable to synchronise the packet switched user plane stream and the circuit switched user plane stream during a communication setup process.

3. A cellular communication system as claimed in claim 2 wherein the communication setup process is a circuit switched call setup process.

4. A cellular communication system as claimed in claim 2 wherein the communication setup process is a packet session setup process.

5. A cellular communication system as claimed in any previous claim wherein the synchronization means comprises a communication link between the packet communication means and the circuit communication means operable to carry synchronization information.

6. A cellular communication system as claimed in claim 5 wherein the communication link comprises a Gs interface link.

7. A cellular communication system as claimed in any previous claim wherein the synchronisation means comprises a wireless Intelligent Network (IN) server for synchronizing the packet switched user plane stream and the circuit switched user plane stream.

8. A cellular communication system as claimed in any previous claim 1 to 6 wherein the synchronisation means comprises a supplementary services server for synchronizing the packet switched user plane stream and the circuit switched user plane stream.

9. A cellular communication system as claimed in any previous claim 1 to 6 wherein the synchronisation means comprises a dedicated synchronisation server for synchronizing the packet switched user plane stream and the circuit switched user plane stream.

10. A cellular communication system as claimed in any previous claim wherein the synchronisation means is operable to associate packet data with a circuit switched call at call setup.

11. A cellular communication system as claimed in claim 10 wherein the synchronisation means is operable to retrieve the packet data from a data store in response to a characteristic associated with the circuit switched call.

12. A cellular communication system as claimed in claim 11 wherein the data store is external to the s

13. A cellular communication system as claimed in any of the claims 10 to 12 wherein the packet data comprises a picture.

14. A cellular communication system as claimed in any previous claim wherein the synchronisation means is operable to synchronise the packet switched user plane stream and the circuit switched user plane stream during a circuit switched call setup and to effect a packet data communication if the circuit switched call setup is not setup..

15. A cellular communication system as claimed in claim 14 wherein the packet data may be data associated with an entity initialising the call.

16. A cellular communication system as claimed in any previous claim wherein the circuit switched user plane stream comprises a voice user plane 1 0 stream.

17. A cellular communication system as claimed in any previous claim wherein the circuit communication means comprises at least one GPRS Support Node.

18. A cellular communication system as claimed in any previous claim wherein the circuit communication means comprises at least one Mobile services Switching Centre (MSC).

19. A cellular communication system as claimed in any previous claim wherein the cellular communication system comprises a 3rd Generation cellular communication network.

20. A cellular communication system as claimed in any previous claim wherein the cellular communication system comprises a GSM cellular communication network.

21. A cellular communication system as claimed in any previous claim wherein the cellular communication system comprises a GPRS cellular communication network.

22. A method of operation for a cellular communication system having packet communication means for supporting packet switch communication services and circuit communication means for supporting circuit switch communication services, the method comprising the step of synchronizing a packet switched user plane stream supported by the packet communication means and a circuit switched user plane stream supported by the circuit communication means.

23. A computer program enabling the carrying out of a method according to claim 22.

24. A record carrier comprising a computer program as claimed in claim 23.