Abstract:
There is disclosed a method and apparatus for establishing multiple PDP contexts in a mobile communication system. The method comprises determining the number of PDP context requests required. Preferably this step is performed by the UE. The method comprises receiving all the required PDP context requests. This step is preferably performed in the network, i.e. in the SGSN and/or the GGSN. The method comprises establishing radio access resources for all the PDP context requests. This step is preferably initiated by the SGSN, and the RNC then preferably allocates the radio access resources based on SGSN requests.

Description:
FIELD OF THE INVENTION 
     The present invention relates to the establishment of connections between a user equipment and a communication network, and particularly but not exclusively to the establishment of PDP contexts. 
     BACKGROUND OF THE INVENTION 
     An application session, e.g. an IP (Internet protocol) multimedia session may consist of multiple media components, for example video, voice and data. In the communication network specified by 3GPP, each media component may require a PDP context of its own. This requires a user equipment (UE) to activate multiple PDP contexts for an application session consisting of multiple media components. 
     There has been a suggestion in the art that there should be provided the flexibility to allow multiplexing of multiple media components onto a single PDP context. Such multiplexing would theoretically allow a single PDP context for all media components which have similar requirements for the PDP context, e.g. similar quality of service requirements. 
     However, even if a multiplexing solution was implemented, a user equipment must activate multiple PDP contexts e.g. if the quality of service requirements of the media components of an application session are different. For example, an IP multimedia session consisting of video, voice and data would most likely require three distinct qualities of service levels, which in turn requires three PDP contexts. 
     It is an object of the present invention to provide an improved technique in which one or more of the above-stated problems are addressed. 
     SUMMARY OF THE INVENTION 
     According to the present invention there is provided a method of establishing multiple connections between a user equipment and a communications network over a radio interface, comprising the step of establishing the radio access resources for the multiple connections in a single step. 
     The multiple connections may correspond to bearers having different levels of service. The multiple connections may correspond to bearers carrying different media components. The media components may include one or more of video, voice or data. The radio access resources may be radio access bearers. 
     The method may further comprise receiving a request for the multiple connections. The request is at least one PDP context request. The method may further comprise receiving a request for the multiple connections in a single step. 
     The request may be one of: an activate PDP context request identifying multiple PDP contexts; an activate secondary PDP context request identifying multiple PDP contexts; a modify PDP context request identifying multiple PDP contexts; a deactivate PDP context request identifying multiple PDP contexts. 
     A create PDP context request identifying multiple PDP contexts may be created responsive to the request. A create PDP context response identifying multiple PDP contexts may be created responsive to the create PDP context request. The radio access resources may be established responsive to the create PDP context response. An activate PDP context accept identifying multiple PDP contexts may be created following establishment of the radio access resources. 
     The method may further comprise receiving requests for the multiple connections in corresponding multiple successive steps. Each request may be an activate PDP context request identifying a PDP context. 
     Each request may be one of: an activate secondary PDP context request identifying a PDP context; a modify PDP context request identifying a PDP context; a deactivate PDP context request identifying a PDP context. 
     The activate request may include an indication of whether a further request follows. The further request may be the corresponding one of: an activate secondary PDP context request identifying a PDP context; a modify PDP context request identifying a PDP context; a deactivate PDP context request identifying a PDP context. A create PDP context request may be created responsive to each successive request. The create PDP context request may include an indication of whether a further PDP context request follows. The further request may be one of: an activate secondary PDP context request identifying a PDP context; a modify PDP context request identifying a PDP context; a deactivate PDP context request identifying a PDP context. A create PDP context response may be created responsive to each successive create PDP context request. The create PDP context response may include an indication of whether a further PDP context response follows. The further response may be one of: an activate secondary PDP context request identifying a PDP context; a modify PDP context request identifying a PDP context; a deactivate PDP context request identifying a PDP context. The radio access resources may be established responsive to receipt of all successive PDP context responses. Successive activate PDP context accepts may be created following establishment of the radio access resources. 
     In a further aspect the present invention provides a method of establishing multiple PDP contexts in a mobile communication system. The method comprises determining the number of PDP context requests required. Preferably this step is performed by the UE. The method comprises receiving all the required PDP context requests. This step is preferably performed in the network, i.e. in the SGSN and/or the GGSN. The method comprises establishing radio access resources for all the PDP context requests. This step is preferably initiated by the SGSN, and the RNC then preferably allocates the radio access resources based on SGSN requests. 
     In accordance with further aspects of the invention there is provided means adapted to perform the method steps defined herein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a better understanding of the present invention and as to how the same can be carried into effect, reference will now be made by way of example to the accompanying drawings in which: 
         FIG. 1  illustrates an exemplary network scenario within which embodiments of the present invention may be implemented; 
         FIG. 2  illustrates the method steps in a first embodiment of the present invention; 
         FIG. 3  illustrates the signaling between network elements in a first embodiment of the present invention; 
         FIG. 4  illustrates the method steps in a second embodiment of the present invention; and 
         FIG. 5  illustrates the signaling between network elements in a second embodiment of the present invention 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     The present invention is described herein with reference to a particular illustrative embodiment. However, such embodiment is presented for the purposes of illustrating the present invention, and does not limit the scope thereof. 
     The present invention is described herein by way of reference to an example implementation in a 3G UMTS (universal mobile telecommunication system) network. One skilled in the art will appreciate, however, from reading the following description that the present invention is not limited in its broad applicability to such an implementation. 
     Referring to  FIG. 1 , there is illustrated the main elements of a UMTS network, necessary for understanding embodiments of the present invention. It should be noted that  FIG. 1  does not represent a full implementation of a UMTS network, which implementation will be familiar to one skilled in the art. Rather  FIG. 1  represents some of the main elements of such a UMTS network necessary for placing the present invention into an appropriate context. 
     A user equipment (UE)  100  communicates over a radio interface with a UTRAN (UMTS radio access network)  102 . As is known in the art, the UTRAN  102  includes a base transceiver station (BTS)  104  and a radio network controller (RNC)  106 . In the UMTS network the UTRAN  102  is connected to a serving GPRS support node (SGSN)  108 , which in turn is connected to a gateway GPRS support node (GGSN)  110 . The GGSN  110  is further connected to at least one external network, e.g. multimedia IP network, represented by reference numeral  112  in  FIG. 1 . Both the SGSN and the GGSN may be considered to be network elements. 
     In general terms, a PDP context is activated in order to establish a logical connection between a user equipment and the GGSN. 
     In known implementations, the UE  100  initiates a logical connection by requesting a PDP context activation by transmitting session management messages to the SGSN  108  via the UTRAN  102 . Responsive thereto, the SGSN  108  requests RAB (radio access bearer) establishment from the RNC  106  using the radio access network application protocol (RANAP). The SGSN  108  also requests PDP context creation with GPRS tunneling protocol (GTP) from the GGSN  110 . This procedure is repeated for each PDP context which the UE  100  requires. 
     As well as requesting PDP context activation, the UE  100  may also request secondary PDP context activations, PDP context modifications, or PDP context deactivations. The specific implementation of PDP context activations, secondary PDP context activations, PDP context modifications, and PDP context deactivations is well known in the art. 
     A first embodiment of the present invention is now described with reference to  FIGS. 2 and 3 .  FIG. 2  illustrates a flowchart for the procedures followed in the exemplary embodiment, and  FIG. 3  illustrates the signaling flow in the exemplary embodiment. 
     In accordance with the first embodiment of the present invention, the activation (or modification) of multiple PDP contexts is provided for by a single session management message and a single GTP message. In this way, the UE  100  indicates all required PDP contexts at the same time to the SGSN  108 . The SGSN  108  can also request creation of all required PDP contexts at the same time from the GGSN  110 . Advantageously, the SGSN  108  does not have to perform multiple RAB establishment procedures corresponding to multiple PDP context activations, which saves time when activating the required PDP context. 
     Referring to  FIG. 3 , as represented by signal  300  the UE  100  transmits an activate PDP context request to the SGSN  108 , through the UTRAN  102 . In accordance with the first embodiment of the present invention, the activate PDP context request includes multiple PDP context requests. As represented by step  200  in  FIG. 2 , the SGSN receives the activate PDP context request with multiple PDP contexts. 
     In this embodiment, the activate PDP context request session management message comprises e.g. the following parameters for the PDP context:
         NSAPI   TI   PDP Type   PDP Address   Access Point Name   QoS Requested   PDP Configuration Options       

     TFT may also be included when, for example, a secondary PDP context is activated or when a PDP context is modified. TFT is not included, however, in the activate PDP context request message which is used to activate a primary PDP context. 
     All these parameters are known in a standard activate PDP context request session management message. In addition, the message is adapted to further include parameters for each required additional PDP context, e.g.:
         NSAPI 2   TI 2   QoS Requested 2   PDP Configuration Options 2   TFT 2   NSAPI 3   TI 3   QoS Requested 3   PDP Configuration Options 3   TFT 3       

     Thus, in this embodiment, the activate PDP context request contains the details of three PDP contexts requested by the UE  100 , being all the PDP contexts desired by the UE  100 . In other embodiments the activate PDP context request may, in accordance with this embodiment of the present invention, generally identify two or more PDP contexts. 
     Responsive to the activate PDP context request, as represented by step  202  the SGSN  108  transmits a create PDP context request GTP message  302  to the GGSN  110 . The create PDP context request contains, in accordance with the embodiment of the invention, the identity of multiple PDP contexts. In accordance with known procedures, the create PDP context request message  302  includes e.g. the following parameters for the PDP context:
         NSAPI   PDP Type   PDP Address   Access Point Name   QoS Profile   PDP Configuration Options   SGSN Address Data   SGSN Address Signaling   TEID Data   TEID Signaling   MSISDN   Charging Characteristics       

     Not all PDP context parameters are listed. The full list of PDP context parameters can be found from 3GPP specifications, and the list may even be different e.g. in 3GPP Rel5 than in 3GPP Rel4, because new parameters may be added in later releases. The above parameters are included as examples only. 
     In addition, in accordance with this embodiment of the invention the create PDP context request also includes e.g. the following parameters:
         NSAPI2   QoS Profile 2   PDP Configuration Options 2   SGSN Address Data 2   SGSN Address Signaling 2   TEID Data 2   TEID Signaling 2   Charging Characteristics 2   TFT 2   NSAPI 3   QoS Profile 3   PDP Configuration Options 3   SGSN Address Data 3   SGSN Address Signaling 3   TEID Data 3   TEID Signaling 3   Charging Characteristics 3   TFT 3       

     Thus the GGSN  110  similarly receives the details of all three of the PDP contexts requested in a single message. 
     Responsive to the create PDP context request message  302 , the GGSN  110  sends a create PDP context response message  304  to the SGSN  108 . As is known, this message includes e.g.:
         PDP Address   QoS Profile   PDP Configuration Options   GGSN Address Data   GGSN Address Signalling   TEID Data   TEID Signaling   Charging ID   Cause       

     In addition, in accordance with this embodiment of the invention the create PDP context response message  304  also includes e.g.:
         QoS Profile 2   PDP Configuration Options 2   GGSN Address Data 2   GGSN Address Signaling 2   TEID Data 2   TEID Signaling 2   Charging ID 2   Cause 2   QoS Profile 3   PDP Configuration Options 3   GGSN Address Data 3   GGSN Address Signaling 3   TEID Data 3   TEID Signaling 3   Charging ID 3   Cause 3       

     The receipt of the create PDP context response message  304  by the SGSN  108  is represented in  FIG. 2  by step  204 . 
     In a step  206 , the SGSN  108  requests RAB establishment with a message  306  to the RNC  106 . The request message  306  includes information identifying all required RABs. Responsive thereto, the SGSN  108  receives from the RNC  106  a response message  308 , as denoted by step  208 , providing information on all required RABs. 
     Thus, RAB establishment for all PDP contexts takes place in a single step. 
     Thereafter, the SGSN  108  transmits an activate PDP context accept message  310  to the UE  100 , as represented by step  210 . As is known, the activate PDP context accept message  310  includes e.g.:
         TI   PDP Type   PDP Address   QoS Profile   Radio Priority   Packet Flow ID   PDP Configuration Options   Cause       

     In addition, in accordance with this embodiment of the invention the activate PDP context accept further includes e.g.:
         TI 2   QoS Profile 2   Radio Priority 2   Packet Flow ID 2   PDP Configuration Options 2   Cause 2   TI 3   QoS Profile 3   Radio Priority 3   Packet Flow ID 3   PDP Configuration Options 3   Cause 3       

     Thus in the first described embodiment of the present invention, multiple PDP contexts are identified in all messages between the UE, the SGSN and the GGSN. Advantageously, therefore, at the time that the SGSN has to request RAB establishment for the first PDP context, the SGSN is able to provide the RNC with a request for all RAB establishments. 
     As a consequence, the amount of signaling messages and thus the amount of traffic are reduced in the radio interface. 
     A second embodiment of the present invention is now described by way of reference to the flowchart of  FIG. 4  and the signaling diagram of  FIG. 5 . Referring to  FIG. 5 , as represented by signal  502  the UE  100  sends an activate PDP context request message to the SGSN  108  in accordance with conventional techniques. The receipt of the message  502  is represented in  FIG. 4  by step  400 . In step  402  the SGSN  108  then forwards a create PDP context request message  504  to the GGSN  110 , again in accordance with conventional techniques. The GGSN  110  then replies to the SGSN  108  with a create PDP context response message  506 , again in accordance with conventional techniques. The receipt of such message by the SGSN  108  is represented in  FIG. 4  by step  404 . 
     In accordance with the second embodiment of the present invention, the activate PDP context request message  502  is adapted to include a flag to indicate whether any further PDP context requests are required by the UE  100 . In a step  406 , the SGSN  108  determines whether further PDP context requests are expected, based on the setting of the appropriate flag in the previous activate PDP context request. 
     In the present case, it is assumed that the UE  100  wishes to establish two PDP context requests. In step  406  therefore the SGSN returns to step  400 , and receives a further activate PDP context request message  508 . As before, the SGSN  108  sends a create PDP context request message  510  to the GGSN  110 , which replies with a create PDP context response message  512  to the SGSN  108 . 
     On this occasion, in step  406 , the SGSN  108  determines that there are no further PDP contexts requested, and moves on to step  408 . In step  408  the SGSN  108  requests RAB establishment with the RNC  106 , as represented by the request RAB establishment message  514 . Thereafter, in a step  410 , the SGSN  108  receives information on all required RABs in a step  410 , as represented by the reply RAB information message  516 . 
     After RAB establishment, in a step  412  the SGSN  108  transmits activate PDP context accept messages to the UE  100 . An accept message is transmitted for each original PDP context request message received from the UE  100 . In a step  412  the SGSN transmits the activate PDP context accept message  518 . In a step  414  the SGSN  108  determines whether further PDP context have been established. Step  412  is then repeated and a further activate PDP context accept message  520  is transmitted to the UE  100 . Thereafter, all PDP contexts are established. 
     Thus the second embodiment of the present invention, described hereinabove with reference to  FIGS. 4 and 5 , utilizes existing session management procedures between the UE  100  and the SGSN  108 , and existing GTP procedures between the SGSN  108  and the GGSN  110 . Such existing procedures include PDP context activation, secondary PDP context activation, PDP context modification, and PDP context deactivation. Using the techniques of the second embodiment, the existing procedures are modified merely to add a flag to the existing session management message transmitted from the UE  100  to the SGSN  108 . This flag is a “more PDP context requests” flag, which indicates to the SGSN that it should wait before initiating RAB establishment. In the preferred embodiment, the SGSN thus waits until it receives an activate PDP context request from the UE  100  which does not have the flag set, indicating that no further requests are expected. All RABs are then established in a single procedure. 
     As well as adapting the session management message from the UE  100  to the SGSN  108 , the second embodiment of the present invention requires the logic of the SGSN  108  to be adapted. Otherwise, existing session management and GTP messages are used. With the adapted logic, the SGSN  108  does not initiate RAB establishment immediately when receiving a session management request (i.e. an activate PDP context request), but waits until all requests are received based on the flag indication. 
     In this way, the SGSN does not initiate multiple RAB establishment procedures towards the RNC, but rather initiates a single RAB establishment procedure. This saves time which would normally be used to activate or modify several PDP contexts. 
     In general, both described embodiments of the invention provide a technique in which, for the establishment of multiple logical connections between a user equipment and a network over a radio interface, the radio access resources are established in a single step. 
     Although the present invention has been specifically described in relation to a 3G mobile communications network, a person skilled in the art will appreciate that the invention is not so limited in its general applicability. 
     Specifically, the present invention is not limited in its applicability to logical connections on the basis of PDP contexts. Nor is the present invention limited to networks using a SGSN or a GGSN for establishing logical connections. 
     The present invention is applicable for circuit switched and packet switched applications, including GPRS. 
     The present invention is described herein with reference to examples of preferred embodiments for the purpose of illustration, and is not limited to any such embodiments. The scope of the present invention is defined by the appended claims.