GB2410855A - Telecommunication system communication sessions - Google Patents
Telecommunication system communication sessions Download PDFInfo
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- GB2410855A GB2410855A GB0402247A GB0402247A GB2410855A GB 2410855 A GB2410855 A GB 2410855A GB 0402247 A GB0402247 A GB 0402247A GB 0402247 A GB0402247 A GB 0402247A GB 2410855 A GB2410855 A GB 2410855A
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L65/00—Network arrangements, protocols or services for supporting real-time applications in data packet communication
- H04L65/10—Architectures or entities
- H04L65/102—Gateways
- H04L65/1023—Media gateways
- H04L65/103—Media gateways in the network
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L65/00—Network arrangements, protocols or services for supporting real-time applications in data packet communication
- H04L65/10—Architectures or entities
- H04L65/102—Gateways
- H04L65/1033—Signalling gateways
- H04L65/104—Signalling gateways in the network
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L65/00—Network arrangements, protocols or services for supporting real-time applications in data packet communication
- H04L65/1066—Session management
- H04L65/1069—Session establishment or de-establishment
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L65/00—Network arrangements, protocols or services for supporting real-time applications in data packet communication
- H04L65/1066—Session management
- H04L65/1083—In-session procedures
- H04L65/1095—Inter-network session transfer or sharing
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L67/00—Network arrangements or protocols for supporting network services or applications
- H04L67/14—Session management
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04M—TELEPHONIC COMMUNICATION
- H04M7/00—Arrangements for interconnection between switching centres
- H04M7/0024—Services and arrangements where telephone services are combined with data services
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04M—TELEPHONIC COMMUNICATION
- H04M7/00—Arrangements for interconnection between switching centres
- H04M7/12—Arrangements for interconnection between switching centres for working between exchanges having different types of switching equipment, e.g. power-driven and step by step or decimal and non-decimal
- H04M7/1205—Arrangements for interconnection between switching centres for working between exchanges having different types of switching equipment, e.g. power-driven and step by step or decimal and non-decimal where the types of switching equipement comprises PSTN/ISDN equipment and switching equipment of networks other than PSTN/ISDN, e.g. Internet Protocol networks
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W76/00—Connection management
- H04W76/10—Connection setup
- H04W76/12—Setup of transport tunnels
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L65/00—Network arrangements, protocols or services for supporting real-time applications in data packet communication
- H04L65/10—Architectures or entities
- H04L65/1016—IP multimedia subsystem [IMS]
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04M—TELEPHONIC COMMUNICATION
- H04M7/00—Arrangements for interconnection between switching centres
- H04M7/12—Arrangements for interconnection between switching centres for working between exchanges having different types of switching equipment, e.g. power-driven and step by step or decimal and non-decimal
- H04M7/1205—Arrangements for interconnection between switching centres for working between exchanges having different types of switching equipment, e.g. power-driven and step by step or decimal and non-decimal where the types of switching equipement comprises PSTN/ISDN equipment and switching equipment of networks other than PSTN/ISDN, e.g. Internet Protocol networks
- H04M7/1275—Methods and means to improve the telephone service quality, e.g. reservation, prioritisation or admission control
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W80/00—Wireless network protocols or protocol adaptations to wireless operation
Abstract
A telecommunications system is disclosed for establishing a communication session between two terminals 1 and 3. Information relating to the communication session exchanged between the terminals 1,3 includes a signalling component transmitted in a control plane and data components transmitted in a user plane. Signalling components are used by the telecommunications system to control the transmission of data components. The signalling components are transmitted by the telecommunications system to at least one of the terminals 1 by a packet switched connection. The signalling components selectively cause the data components to be exchanged between the telecommunications system and the terminal 1 by either a packet switched or a circuit switched connection, in dependence upon the circumstances. A circuit switched connection is used to transmit data between the telecommunication system and the terminal 1 when a high speed and high quality connection is required. In the embodiment the signalling components are transmitted using session initiation protocol (SIP). A SIP application server 29 receives instructions from an SIP router 11 in the control plane to control MSC server and media gateway 33 so that IP addressed data components received from the internet 15 in the user plane are converted into data of a suitable format and with suitable addressing to be transmitted by a circuit switched connection to the terminal 1 in the user plane.
Description
1 2410855 T1FLF,COMMUNICATION SYSTEM COMMUNICATION SESSIONS The present
invention relates to a telecommunications system for establishing a communication session between two terminals, information relating to the communication session being exchanged between the terminals including data components and signalling components, the signalling components being used by the telecommunications system to control the transmission of the data components, and wherein the signalling components are transmitted by the telecommunications system to at least one of the terminals by a packet switched connection. The invention also relates to a device which allows the exchange of data between a telecommunications system and a terminal registered with that telecommunications system and to a method of establishing a communications session between two terminals.
When mobile or cellular telecommunication systems were initially launched communication between mobile devices was limited solely to voice communication. This was later supplemented by the Short Message Service (SMS) and more recently Multimedia Messaging Service (MMS) technology and other data services, allowing users to send text, pictures and other data to other devices.
Data transmission is separate to a standard voice call - data are sent by connecting a mobile terminal to a server over a General Packet Radio Service ((GPRS) data connection. Voice calls are transmitted conventionally by circuit switched connections, and GPRS data, of course, is transmitted by packet switched connections. Current GSM devices do not support simultaneous circuit switched and packet switched connections. Therefore, data can only be sent when a voice call is not underway. A user cannot send data during a voice call - the call would need to be terminated before the data can be sent.
The third generation partnership project (3GPP) has recently defined a new concept known as IMS (IP - based Multimedia Subsystem). The IMS is a set of core network servers sitting behind the GGSN (which will be briefly described below) in the packet switched domain. These servers are introduced in order to process signalling between end users. The aim of IMS is to allow users such as mobile telephone network operators to provide services to their subscribers as efficiently and effectively as possible. For example, the IMS architecture is likely to support the following communication types: voice, video, instant messaging, "presence" (a user's availability for contact), location-based services, email and web. Further communication types are likely to be added in the future.
This diverse collection of communication devices requires efficient session management due to the number of different applications and services that will be developed to support these communication types. The 3GPP has chosen Session Initiation Protocol (SIP) for managing these sessions.
The SIP protocol is a session-based protocol designed to establish IP based communication sessions between two or more end points or users. SIP is used as a means of signalling, end-to-end, the initiation, modification and termination of packet switched sessions. Once a SIP session has been established, communication between these end points or users can be carried out using a variety of different protocols (for example those designed for streaming audio and video). These protocols are deemed in the SIP session initiation messages.
With IMS, users are no longer restricted to a separate voice call or data session. Sessions can be established between mobile devices that allow a variety of communication types to be used and media to be exchanged. The sessions are dynamic in nature in that they can be adapted to meet the needs of the end users. For example, two users might start a session with an exchange of instant messages and then decide that they wish to change to a voice call, possibly with video. T his is all possible within the IMS framework. If a user wishes to send a file to another user and the users already have a session established between each other (for example, a voice session) the session can be redefined to allow a data file exchange to take place. This session redefinition is transparent to the end user.
Currently, GPRS operates with a fairly low bandwidth, and even with IMS, this limits data applications - such as high quality video conferencing. Even with the addition of IMS, the (SPRY network and the radio network are still limited as to what data can be reasonably carried, and in particular, what data can be carried efficiently. This means that IMS is only suitable, in the short to mid-term future, of handling non-real-time services.
According to a first aspect of the present invention, there is provided a telecommunications system for establishing a communication session between two terminals, information relating to the communication session being exchanged between the terminals including data components and signalling components, the signalling components being used by the telecommunications system to control the transmission of the data components, wherein the signalling components are transmitted by the telecommunications system to at least one of the terminals by a packet switched connection, and wherein the signalling components selectively cause the data components to be exchanged between the telecommunications system and that terminal by one of a packet switched or circuit switched connection.
According to a second aspect of the present invention, there is provided a mobile telecommunications system for establishing a communication session between two terminals, at least one of which is a mobile terminal capable of communicating wirelessly with the telecommunication system, wherein information relating to the communication session exchanged between the terminals includes data components exchanged in a user plane and signalling components exchanged in a control plane, the signalling components being used by the telecommunications system to control the transmission of the data components, and wherein the signalling components are transmitted by the telecommunication system to the mobile terminal by a packet switched connection, and wherein the signalling components selectively cause the data components to be exchanged between the telecommunications system and the mobile terminal by either a packet switched connection or a circuit switched connection.
According to a third aspect of the present invention, a device which allows the exchange of data between a telecommunications system and a terminal registered with that telecommunications system, the device including means for receiving from telecommunications system instructions for transmitting data to the terminal by means of a packet switched connection, means for receiving data including an address which allows that data to be transmitted to the terminal by means of a packet switched connection, and means for converting the address into a modified address suitable for transmitting the data to the terminal by means of a circuit switched connection.
According to a fourth aspect of the present invention, a method of establishing a communication session between two terminals in which information relating to the communication session exchanged between the terminals includes data components and signalling components, the signalling components controlling the transmission of the data components, the method including transmitting the signalling components to at least one of the terminals by a packet switched connection and transmitting the data components to that terminal selectively by a packet switched or circuit switched connection.
A telecommunication system embodying the invention, a device for use with such a system and a network of establishing a Communication session, will now be described by way of example, with reference to the accompanying drawings in which: Figure 1 A shows schematically the elements of a telecommunication system having an IMS control plane and a GPRS user plane; Figure lB shows in more detail selected elements of the telecommunications system of Figure lA; Figure 2A shows schematically the elements of a telecommunications system having a circuit switched control plane and a circuit switched user plane; Figure 2B shows in more detail selected elements of the telecommunications system of Figure 2A; Figure 3 shows schematically a known arrangement for allowing a connection to a circuit switched network from an IMS device; Figure 4A shows schematically the elements of a telecommunications system having a user plane circuit switched bearer and an IMS control plane; Figure 4B shows in more detail selected elements of Figure 4A; Figure 5 shows in more detail elements of Figure 4 used to control the user plane; Figure 6 shows signal flow between elements of a known IMS telecommunications system; Figure 7 shows signal flow between a telecommunications system in accordance with the invention; Figure 8 shows in more detail the operation of a media gateway device of the telecommunications network; Figure 9 shows the signal flows between components of the telecommunications system when a communications session is initiated by a mobile terminal; and Figure 10 shows the signal flow in a telecommunications system when a mobile terminal receives an invitation from another mobile terminal to begin a communication session.
Like elements appearing in the drawings are generally designated with the same reference signs.
IMS provides a separation of the "control plane" and the "user plane". The control plane performs the required signalling, and includes the relevant application protocol and the signalling bearer for transporting the application protocol messages. Among other things, the application protocol is used for setting up the radio access bearer in the radio network layer. The user plane transmits data traffic and includes data streams and data bearers for the data streams. The data streams are characterized by one or more frame protocols specified for that interface.
Generally speaking, the user plane carries data for use by a receiving terminal - such as data that allows a voice or picture to be reproduced and the control plane controls how the data is transmitted.
Figure 1A and lB show a known arrangement with an IMS control plane and a GPRS user plane.
Figure 1A shows a communication session established between a first terminal 1 and a second terminal 3. Figure 1B shows in more detail the various elements of the network that link with the terminal 1. The mobile terminal 1 communicates wirelessly with the radio access network (RAN 5).
The RAN 5 handles subscriber access, and includes base stations and concentration nodes. Each RAN 5 is associated with a serving GPRS support lO node (SGSN 7). The SGSN 7 handles the data traffic of users in a geographical service area. Gateway GPRS support node (GGSN) provides the interface between the radio network and an IP network (for example, it performs protocol conversion between the GPRS and IP environments). Call session control function element (CSCF 11) controls the assignment of resources to a communication session. IP gateway (IP GW) 13 provides a link to IP network 15.
Figures 1A and 1B show the elements linking mobile terminal l to a core network. Like elements link the mobile terminal 3 to a core network. The core networks for terminals 1 and 3 may be different. In the embodiments described a communication session is established between the two mobile telecommunications terminals 1 and 3. It should, however, be understood that the invention is also applicable to the establishment of a communication session where one of the terminals is operating in a mobile telecommunications network and the other of the terminals operates in a different type of network.
In order to establish a communication session, the terminal l generates a packet data protocol (PDP) context 17. The PDP context defines parameters that support the flow of data traffic to and from terminal 1. Among the parameters that are set are the identifier of the external packet data network with which the terminal 1 wishes to communicate, a PDP address recognised in that network (an IF address for service over the internet), the address of the GGSN 9, quality of service (QoS) parameters etc. IMS is a control plane for SIP. It assumes that an adequate lP network exists to carry the user plane. As indicated above, although, as a user plane, the underlying GPRS network is unable to offer the right quality of service for real-time packet switched communication sessions (such as would be sufficient, for example, for high quality video conferencing), the lMS is capable of signalling such sessions in the control plane.
According to a feature of the present invention a mechanism is provided that allows a network operator to use the IMS control plane (SIP signalling) to establish communication sessions between terminals that use the circuit switched user plane to carry data traffic instead of the packet switched user plane shown in Figures lA and 1B.
The network architecture used to establish a voice call (for example) in the circuit switched domain will be briefly described with reference to Figures 2A and 2B to assist in understanding the present invention. Conventionally voice calls are carried by circuit switch connections.
As shown in Figures 2A and 2B, the circuit switched domain also has a decoupled control plane and user plane. The control plane is provided by routing signalling messages to a mobile switching centre (MSC) server 19.
As can be seen by the more detailed view in Figure 2B, the control plane signalling is transmitted wirclessly between the terminal l and the RAN 5.
Subsequently this signalling is transmitted from the RAN 5 to the MSC server l 9.
The user plane is provided by means of a dedicated circuit between the terminal 1 and a media gateway (MGW 21). The MGW 21 connects to the public switch telephone network (PSTN) 23.
The elements described above connected to the terminal 1 are also provided in association with terminal 3.
Conventionally the packet switched and circuit switched domains are completely separate. A (}PRS enabled GSM mobile terminal may be capable of circuit switched communications (for example to handle a conventional voice call) and also, separately and not simultaneously, the transmission and reception of packet data (for example, to allow the display of data from the internet by means of WAP - wireless application protocol).
In an IMS network, in order to allow a connection to a circuit switched network (for example to allow a subscriber with an IMS terminal to call another user that has a terminal capable of only handling circuit switched communications), the arrangement shown in Figure 3 is provided, which allows inter-working between the circuit switched control plane and the IMS control plane.
A SIP application server 29 performing a media gateway control function (MGCF) controls an enhanced media gateway (MOW) 31 that is able to interwork the IMS user plane with the circuit switched user plane. The signalling protocol used in the circuit switched control plane is ISDN user part (ISUP).
The ISUP defines the protocol and procedures used to set up, manage, and release trunk circuits and carry voice and data calls over the PSTN/ISDN and GSM networks. The MGCF performs protocol mapping between the SIP and the ISUP at the control plane level in order that call set up, maintenance and call release procedures can be supported. ISUP signals received from the MSC server 19 in their circuit switched control plane are received by the MGCF. The MGCF controls, using H.248 signalling, the MGW 31 to essentially map circuit switched user plane data associated with a particular MSISDN (i.e. mobile telephone number) to a corresponding TP address for use in the IP user plane. This allows the terminal 1 to communicate wirelessly with the network using circuit switched technology, but then allows conversion in the MGW 31 from the circuit switched domain to the packet switched domain.
The arrangement of Figure 3 therefore enables a terminal 1 supporting only circuit switched technology to exchange data with an IMS network. Such an arrangement is obviously desirable during a transition period when terminals supporting only circuit switched technology will be in use within IMS networks.
As discussed above, packet data is transmitted at fairly low speed over current packet switched mobile telecommunications connections. On the other hand, existing circuit switched bearers have high capacity and quality and have been refined and improved over a long period of time.
According to an aspect of the present invention, an arrangement is provided that allows the capacity and quality of the circuit switched bearer to be used to provide a circuit switched user plane in combination with an IMS control plane. This is shown in Figures 4A and 4B.
The elements of Figures 4A and 4B correspond to the similarly referenced elements of Figures lA,lB,2A,2B and 3. In Figures 4A and 4B the CSCF element 11 is labelled "SIP ROUTER". These are the same element.
The MGW 21 of Figures 2A and 2B is replaced with MSC server and MGW 33, further details of which will be described below.
From the point of view of the network of the terminal 3 (and the destination network), the IMS session must have the appearance of a normal IMS session (with a packet switched user plane). This packet switched user plane may well be converted back into a circuit switched user plane by the destination network, but this cannot be assumed. The solution proposed by the present invention is applicable whether or not the packet switched user plane will be converted into a circuit switched user plane by the destination network.
In Figure 5 the MSC server and MGW 33 is capable of circuit switched to lo packet switched interworking (like the MGW 31 of Figure 3). The SIP application server 29 controls the MSC server and MGW 33 using the media gateway control function of the SIP application server 29 as described in relation to Figure 3. The signalling between the SIP application server 29 and the circuit switched domain (MSC server) is also possible using the mobile gateway control function of the SIP application server 29. The call session control function element 11 operates as a SIP router and is controlled by the SIP server 29. The SIP server 29 controls the MSC server and MGW 33 using H.248 signalling.
The MSC server is part of the control plane for the establishment of the circuit switched under plane, but it is not involved in the control plane carrying the SIP signalling. Therefore, the MSC server is shown in the user plane only as part of the mobile gateway as the "MSC server + MGW" 33 in Figure 5.
For a better understanding of the invention, the flow of messages for establishing a real-time session in a conventional IMS network will be described with reference to Figure 6.
Terminal I invites terminal 3 (which may or may not be in another network or domain) by generating a SIP INVITE message at the 40. The SIP INVITE message comprises a session description protocol (SDP). This describes to terminal 3 the type of communication session that the terminal l wishes to establish (for example what media type should be used, such as voice or video). The SDP also carries the address to which user terminal 3 should send its data packets during the communication session. In TMS this will be an IP address and a port number to which the data packets from terminal 3 should be sent. The SIP INVITE 40 message is transmitted to CSCF 11 of the network or domain with which terminal l is associated. The CSCE element l l analyses the address information in the SIP INVITE message 40 and determines the appropriate CSCF element 1 l' to which the SIP INVITE message should be forwarded. When the CSCF element l l' (associated with mobile terminal 3) receives the SIP INVITE message 40, this is then passed to the terminal 3. In response to the SIP INVITE message, the terminal 3 will then issue a SIP INVITE RESPONSE message 42, which is forwarded via CSCF elements ll' and It to terminal 1. The SIP INVITE RESPONSE message 42 provides data that allows a session description to be negotiated between terminals l and 3. For example, this may allow the type of communication media to be selected. The terminal 3 may indicate that it will only join the communication session if it is limited to just voice (this may be because the terminal 3 only has the capability for voice communications or for some other reason). The SIP INVITE REQUEST message 42 contains SDP, and this will include the address to which the terminal 1 should send data packets so that they can be received by the terminal 3.
As a result of the SIP INVITE message 40 and SIP INVITE RESPONSE message 42 exchanged between the terminals I and 3, the two end points (i.e. the terminals) now both have an address to which data packets should be sent during the communication session. This address is an IF address. The terminal I then establishes a packet switched connection 43 with the CSCF element 11 which allows data packets to be transmitted from the terminal I to the IP address specified by the terminal 3 in the SIP INVITE RESPONSE message 42.
The terminal 1 then issues a further message 44, indicating that it agrees to establish a communication session on the basis of the information contained in the SIP INVITE RESPONSE message 42. The message 44 is passed via the CSCF elements l l and l l' to the terminal 3. The terminal 3 then sets up a packet switched user plane connection 45 with the CSCF l l' that will allow data packets to be transmitted from the terminal 3 to the terminal l using the IP address supplied by the terminal l. At this stage the mobile terminal 3 will ring (or provide some other indication to the user that a communication session has been initiated by mobile terminal l). User terminal 3 transmits to user terminal 1 a message 46 indicating that user terminal 3 is ringing (or the like) and a message 48 indicating that the terminal 3 accepts the negotiated invite message from terminal 1. A packet switched user plane connection then is established for the communication session 50 between the terminals 1 and 3.
The packet switched data connections between the terminals l and 3 and their respective CSCF elements It and ll' are GPRS connections. As indicated above, such connections are not at the present time sufficiently fast to allow high quality real time video data to be transmitted in the user plane.
The embodiment of the present invention seeks to mitigate this disadvantage, and this will be explained in more detail with reference to Figure 7. In the embodiment the command to set-up packet switched user plane connection 43 is replaced with set-up circuit switched user plane command 52.
The terminal 1 is made aware by the IMS network that a circuit switched bearer will be established rather than a packet switched bearer. To achieve this the SIP messages and the IMS control plane are modified in accordance with an aspect of the invention. SIP application server 29 performs this modification.
In a conventional IMS system, as shown in Figure lA,lB and 6, an IF address is passed to the MGW 21 in the user plane, and this is passed from the MGW 21 via MSC server 19 to PSTN 23 and onwardly to terminal 3, as shown in Figures lA and IB. This of course allows transmission of data packets in the packet switched user plane.
In Figure 7, in order to allow the circuit switched user plane to be used with the IMS control plane, the SIP application server 29 in the network associated with the terminal 1 alters the way that the addresses are passed from the CSCF element (SIP router) 11 associated with the network of terminal 1 to the CSCF element (SIP router) 11' of the network of terminal 3. Eissentially, these modifications comprise: (1) providing the terminal 1 with the telephone number (MSISDN) of a media gateway towards which a circuit switched bearer should be established in the user plane, and (2) providing terminal 3 with an IP address of the same media gateway.
As described in relation to Figure 3, there are known IMS procedures that allow SIP routing functions to allow a SIP application server 29 to be added to the signalling path.
The labelled procedures performed by the SIP application server 29 in Figure 7 will now be described in more detail.
PROCEDURE A: The SIP INVITE message 40 is passed by the CSCF element 11 to the SIP application server 29. As discussed above, the SIP INVITE message includes the IP address to which terminal 3 should send its user plane data packets during the communication session to be established.
The SIP application server 29 modifies the SIP INVITE message 40 to replace the reply IP address given by terminal I with an IP address of the MSC server and MGW 33. The MSC server and media gateway 33 is described in relation to Figures 4A,4B and 5.
The SIP INVITE message 40, SIP INVITE: RESPONSE message 42 and the other messages 43,44,45,46 and 48 are transmitted in the IMS control plane.
PROCESS B: When the SIP INVITE RESPONSE message 42 is received by the CSCF element 11 the message is passed to SIP application server 29. In the SIP INVITE RESPONSE message 42 the IP address that terminal 3 wishes terminal 1 to send its data packets to during the data session is provided. The SIP application server 29 alters the SIP INVITE RESPONSE message 42 to replace the IP address provided by terminal 3 with a telephone number (MSISDN) of MSC server and MGW 33. A circuit switched user plane connection 52 is established between the RAN 5 and the mobile terminal 1 using the telephone number. The SIP INVITE RESPONSE message 42 from the terminal 3 has been received by the MSC server and MGW 33 because that message was addressed to the IP address of the MSC server and MGW 33 by virtue of process A. Figure 8 shows how the MSC server and MGW 33 maps IP addresses in the IP user plane to telephone numbers (MSISDN's) in the circuit switched user plane. It can be seen that IP address 10.10.10.C is mapped to telephone number +44 7898 124abx. Therefore, the SIP INVITE RESPONSE message 42 received from the terminal 3 because it is addressed to the basic 1P address (10.10.10) of the MSC server and MGW 33. The suffix C indicates to the MSC server and MOW 33 which particular telephone number (+44 7898 124abx) of the MSC server and media gateway 33 should be used for routing data in the user plane to the IP address 10.l0.10.C. The SIP application server 29 may also add a flag to the message sent to the terminal 1 to inform the terminal 1 that the terminal 1 should not establish a packet switched bearer but should instead establish a circuit switch bearer. The modified SIP INVITE RESPONSE message 42 is then transmitted to the terminal 1.
PROCESS C: The message 44 transmitted from the terminal 1 to the CSCF element l I is to indicate to the terminal 3 that the terminal l has the right user plane resources reserved to proceed with the communication session.
The CSCF element 11 forwards this message to the SIP application server 29.
The SIP application server again changes the reply IP address indicating where terminal 3 should send its reply from the IP address according to the l5 IMS control plane to the relevant IP address of the MSC server and media gateway 33.
The terminal 3 then establishes a packet switched user plane 45 in the conventional manner for an IMS network (although a circuit switched user plane could also be established here).
PROCESS D: Terminal 3 then issues a response message 46 for terminal 1 which indicates that terminal 3 is ringing (or the like). This message passes through the SIP application server 29, where the IP address of the message is converted by MSC server and MOW 33 into an appropriate telephone number for onward transmission to the terminal l. The SlP application server 29 may at this point need to instruct the MSC server and MOW 29 to generate a signal to command the terminal l to ring (or the like). PROCESS E: When the user of terminal 3 accepts the call to establish the
communication session a message 48 is generated by the terminal 3, which passes through the SIP application server 29. The SIP application server 29 informs the MSC server and MGW 33 that the call shall begin so that the MSC server and MGW 33 can connect through the circuit switched user plane (from terminal 1 to the telephone number of the MSC server and MGW 33) to the packet switched user plane (from appropriate IP address of the MSC server plus MGW 33 to the terminal 3).
From the discussion above, it should be clear to those skilled in the art that the embodiment described allows the IMS control plane (the SIP signalling path) to be used but without the packet switched user plane bearer (which at the present time cannot offer the speed or quality of service of the present circuit switched user plane bearers).
Therefore, even though packet switched user connections do not currently have sufficient speed to allow high quality video conferencing, faster data communication can be provided in accordance with the embodiment by replacing this packet switched user plane bearer with a circuit switched user plane bearer.
Examples of services which require a real time bearer are voice, video telephony, rich voice, multimedia fade-in and peer-to-peer gaming.
In addition to the advantages described above over a conventional all packet switched IMS system, the embodiment also provides an improvement over known all circuit switched systems. For example in circuit switched video telephony it is very difficult to signal from end-to-end the desire (for example, user initiated) or necessity (for example, due to hand over from 3G to 2G) to modify the call from voice and video down to just voice.
In the embodiment, SIP allows the two end-points (terminals 1 and 3) to re- negotiate the session at any time during the session. The embodiment provides an end-to-end SIP signalling path in the control plane to allow the video session, in the circuit switched user plane, to be modified between voice only and voice and video.
The decision as to whether to send data using the circuit switched user plane may be made because this provides the required speed or quality. The circuit switched user plane connection may be used, for example, when the data are such that they can be more efficiently carried by the circuit switched user plane, such as by the removal of IP and other protocol headers from the data sent over the wireless link, and/or by providing Unequal Error Protection for the data sent over the wireless link.
Some data may be exchanged by the packet switched connection but those other data which need improved radio quality or efficiency are exchanged by a circuit switched connection.
Figures 9 and 10 show more detailed flow diagrams of a mobile originating case and a mobile terminating case, respectively.
The signalling flows use the following key: - The message names are in capitals - The information encapsulated in "( )" is the specifics in SIP header - The information encapsulated in "[ 1" is the specifics in SDP information - "S=" - represents source address - "D=" - represents destination address - A represents the IP address of A - B represents the IP address of B - AS represents the 1P address of AS (application server).
Claims (24)
1. A telecommunications system for establishing a communication session between two terminals, information relating to the communication session being exchanged between the terminals including data components and signalling components, the signalling components being used by the telecommunications system to control the transmission of the data components, wherein the signalling components are transmitted by the telecommunications system to at least one of the terminals by a packet l O switched connection, and wherein the signalling components selectively cause the data components to be exchanged between the telecommunications system and that terminal by one of a packet switched or circuit switched connection.
2. The telecommunications system of claim 1, wherein the signalling components are transmitted in a control plane.
3. The telecommunications system of claim 1 or 2, wherein the data components are transmitted in a user plane.
4. The telecommunications system of claim 1, 2 or 3, wherein the signalling components include session initiation protocol (SIP) components.
5. The telecommunications system of claim 1,2,3 or 4, including an IP multimedia subsystem (IMS).
6. The telecommunications system of any one of the preceding claims, wherein the packet switched data connection is transmitted by a general packet radio system (GPRS) bearer.
7. The telecommunications system of any one of the preceding claims, wherein the data components are exchanged between the telecommunications system and the terminal by a circuit switched connection or a packet switched connection in dependence upon the nature of the data components.
8. The telecommunications system of claim 7, wherein the data components are exchanged by a circuit switched connection when the data components are such that a higher communication speed or quality is required.
9. The telecommunications system of claim 7, wherein the data components are exchanged by a circuit switched connection when the data components are such that can be more efficiently carried by a circuit switched connection.
10. The telecommunications system of claim 7,8 or 9, wherein some of said data components are exchanged by a packet switched connection and other of said data components which need improved radio quality or efficiency are exchanged by a circuit switched connection.
11. The telecommunications system of claim 7,8,9 or 10, wherein the data components are transmitted by a circuit switched connection when the data components comprise voice data, video telephony data or peer-to-peer gaming data.
12. The telecommunications system of any one of the preceding claims, wherein the data components include an address indicative of the terminal to which they are to be transmitted by the telecommunications system.
13. The telecommunications system of claim 12, wherein the address is an address suitable for transmitting the data to the terminal by a packet switched connection.
14. The telecommunications system of claim 13, wherein the address is an IF address.
15. The telecommunications system of claim 12,13 or l4, including means for controlling the transmission of data components between the telecommunications system and the terminal, including means for determining whether circuit switched connection will be used to transmit data components between the telecommunications system and the terminal and for converting said address into a modified address that allows the data to be received by the terminal by a circuit switched connection.
16. The telecommunications system of claim 15, wherein the modified address includes a telephone number or MSISDN.
17. A telecommunication system of any one of the preceding claims, wherein the telecommunications system comprises a mobile telecommunication system and wherein communications between the telecommunications system and at least one of said terminals is performed by a wireless connection.
18. The telecommunications system of any one of the preceding claims, wherein the telecommunication system is a UMTS (3G) telecommunication system.
19. A mobile telecommunications system for establishing a communication session between two terminals, at least one of which is a mobile terminal capable of communicating wirelessly with the telecommunication system, wherein information relating to the communication session exchanged between the terminals includes data components exchanged in a user plane and signalling components exchanged in a control plane, the signalling components being used by the telecommunications system to control the transmission of the data components, and wherein the signalling components are transmitted by the telecommunication system to the mobile terminal by a packet switched connection, and wherein the signalling components selectively cause the data components to be exchanged between the telecommunications system and the mobile terminal by either a packet switched connection or a circuit switched connection.
20. A device which allows the exchange of data between a telecommunications system and a terminal registered with that telecommunications system, the device including means for receiving from telecommunications system instructions for transmitting data to the terminal by means of a packet switched connection, means for receiving data including an address which allows that data to be transmitted to the terminal by means of a packet switched connection, and means for converting the address into a modified address suitable for transmitting the data to the terminal by means of a circuit switched connection.
21. A method of establishing a communication session between two terminals in which information relating to the communication session exchanged between the terminals includes data components and signalling components, the signalling components controlling the transmission of the data components, the method including transmitting the signalling components to at least one of the terminals by a packet switched connection and transmitting the data components to that terminal selectively by a packet switched or circuit switched connection.
22. A telecommunications system for establishing a communication session between two terminals, substantially as hereinbefore described with reference to and/or substantially as illustrated in any one of or any combination of the accompanying drawings. s
23. A device substantially as hereinbefore described with reference to and/or substantially as illustrated in any one of or any combination of the accompanying drawings.
24. A method substantially as hereinbefore described with reference to and/or substantially as illustrated in any one of or any combination of the accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB0402247A GB2410855A (en) | 2004-02-04 | 2004-02-04 | Telecommunication system communication sessions |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB0402247A GB2410855A (en) | 2004-02-04 | 2004-02-04 | Telecommunication system communication sessions |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB0402247D0 GB0402247D0 (en) | 2004-03-03 |
| GB2410855A true GB2410855A (en) | 2005-08-10 |
Family
ID=31971881
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB0402247A Withdrawn GB2410855A (en) | 2004-02-04 | 2004-02-04 | Telecommunication system communication sessions |
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| Country | Link |
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| GB (1) | GB2410855A (en) |
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| EP1920572A2 (en) * | 2005-08-22 | 2008-05-14 | Nortel Networks Limited | Multimedia subsystem service control for circuit-switched subsystem calls |
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| US8811954B1 (en) | 2005-10-31 | 2014-08-19 | Genband Us Llc | Network domain selection |
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| WO2008052598A1 (en) * | 2006-11-03 | 2008-05-08 | Telefonaktiebolaget Lm Ericsson (Publ) | Accessing a communications network |
| CN102695149B (en) * | 2006-11-03 | 2016-01-27 | 艾利森电话股份有限公司 | Access communications network |
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| US8879539B2 (en) | 2007-04-26 | 2014-11-04 | Telefonaktiebolaget L M Ericsson (Publ) | Method of and a system for establishing a call over an IP multi media communications system and a circuit switched communications system |
| CN101658010B (en) * | 2007-04-26 | 2013-12-18 | 艾利森电话股份有限公司 | Method of and system for establishing call over IP multi media communications system and circuit switched communications system |
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| US8644298B1 (en) | 2007-09-12 | 2014-02-04 | Genband Us Llc | Adding a service control channel after session establishment |
Also Published As
| Publication number | Publication date |
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| GB0402247D0 (en) | 2004-03-03 |
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