Patent Publication Number: US-2009238159-A1

Title: Mobile communication system and communication control method

Description:
TECHNICAL FIELD 
     The present invention relates to a mobile communication system in which a terminal can be connected to a plurality of service networks at the same time. 
     BACKGROUND ART 
       FIG. 1  is a block diagram showing a configuration of a mobile communication system in which one terminal can be connected to a plurality of service networks at the same time. Referring to  FIG. 1 , the mobile communication system has GGSN (Gateway GPRS (General Packet Radio Service) Support Node)  95 , SGSN (Serving GPRS Support Node)  94 , RNC (Radio Network Controller)  93 , and base station  92 . GGSN  95  and SGSN  94  belong to a core network, and RNC  93  and base station  92  belong to a wireless access network. 
     GGSN  95  is a gateway device connected to two service networks  96  and  97 , and between the mobile communication system and service networks  96  and  97 . Service networks  96  and  97  are networks which provide packet service. 
     SGSN  94  is a node device for providing a GPRS service, connects to RNC  92  connected to terminal  91 , and also establishes tunnels  98  and  99  between SGSN  94  and GGSN  95  to allow terminal  91  to connect to service networks  96  and  97 . 
     RNC  93  is a controller for controlling base station  92 , and typically controls a plurality of base stations  92 . RNC  93  sets a call by performing call processing between itself and both the core network and terminal  91 . 
     Base station  92  wirelessly connects to terminal  91  and relays communications from terminal  91 . 
     In the state of  FIG. 1 , terminal  91  is receiving connection services from both service networks  96  and  97 . At this time, for the purpose of the connection of terminal  91 , GTP (GPRS Tunneling Protocol) tunnels  98  and  99  are established for connecting to service networks  96  and  97 , respectively, between SGSN  94  and GGSN  95 . 
       FIG. 2  is a diagram for describing an operation of the mobile communication system when terminal  91  shown in  FIG. 1  has moved and thereby a change is made to SGSN  94 . Although, in  FIG. 2 , the base station is omitted for the sake of clarity, suppose that terminal  91  is connected to RNC  93  via base station  92  (not shown) as shown in  FIG. 1 . Referring to  FIG. 2 , terminal  91  has moved from source RNC  93   1  to destination RNC  93   2 . At this time, signal  112  indicating the movement of terminal  91  is sent from moved terminal  91  or destination RNC  93   2  to new SGSN  94   2 . 
     Subsequently, new SGSN  94   2  sends to GGSN  95  switching request signal  113  for switching GTP tunnel  98  for service network  96  and switching request signal  114  for switching GTP tunnel  99  for service network  97 . 
     Having received two switching request signals  113  and  114 , GGSN  95  switches respective GTP tunnels  98  and  99  from old SGSN  94   1  to new SGSN  94   2 . 
     DISCLOSURE OF THE INVENTION 
     As described using  FIG. 2 , when terminal  91  which is connected to two service networks  96  and  97  has moved, new SGSN  94   2  containing destination RNC  93   2  sends two switching request signals to the same GGSN  95  for one movement of one terminal  91 . In order to make a request to the same GGSN  95  for switching tunnels for the same terminal  91 , it is quite wasteful to send a plurality of switching request signals for each tunnel. 
     In addition, when each request signal is sent for each tunnel, a status conflict will occur between tunnels if one of the request signals is lost. In this case, a system design in which such a status conflict is taken into account is required, making the device functions more complicated. 
     An object of the present invention is to provide a mobile communication system capable of performing tunnel switching associated with the movement of a terminal efficiently and easily. 
     In order to achieve the object described above, a mobile communication system according to one aspect of the present invention is a mobile communication system for connecting a terminal to service networks, comprising: 
     a wireless access network device for connecting to the terminal; 
     a gateway device for establishing a plurality of tunnels connecting the terminal to the service networks and for switching the plurality of tunnels as requested; and 
     a mobility management device for sending to the gateway device a request to collectively switch the plurality of tunnels. 
     A communication control method according to one aspect of the present invention is a communication control method for connecting a terminal to service networks, comprising: 
     establishing a plurality of tunnels connecting the terminal to the service networks; 
     sending a request to collectively switch the plurality of tunnels; and 
     collectively switching the plurality of tunnels according to the request. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram showing a configuration of a mobile communication system in which one terminal can be connected to a plurality of service networks at the same time; 
         FIG. 2  is a diagram for describing an operation of the mobile communication system when terminal  1  shown in  FIG. 1  has moved and thereby a change is made to SGSN; 
         FIG. 3  is a block diagram showing a configuration of a mobile communication system according to a first exemplary embodiment; 
         FIG. 4  is a diagram for describing an operation of the mobile communication system when terminal  1  has moved according to the first exemplary embodiment; 
         FIG. 5  is a flow chart showing an operation of new SGSN  4   2  for processing a tunnel switching request; 
         FIG. 6  is a diagram for describing an operation of a mobile communication system when terminal  1  has moved according to a second exemplary embodiment; 
         FIG. 7  is a diagram for describing a configuration of a mobile communication system according to a third exemplary embodiment and an operation thereof when a terminal has moved; 
         FIG. 8  is a diagram for describing a configuration of a mobile communication system according to a fourth exemplary embodiment and an operation thereof when a terminal has moved; and 
         FIG. 9  is a diagram for describing a configuration of a mobile communication system according to a fifth exemplary embodiment and an operation thereof when a terminal has moved. 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     An exemplary embodiment will be described in detail with reference to the drawings. 
     First Exemplary Embodiment 
       FIG. 3  is a block diagram showing a configuration of a mobile communication system according to a first exemplary embodiment. In this figure, there is shown a mobile communication system in which one terminal can be connected to a plurality of service networks at the same time. 
     Referring to  FIG. 3 , the mobile communication system has GGSN  5  (Gateway GPRS (General Packet Radio Service) Support Node), SGSN  4  (Serving GPRS Support Node), RNC  3  (Radio Network Controller), and base station  2 . GGSN  5  and SGSN  4  belong to a core network, and RNC  3  and base station  2  belong to a wireless access network. 
     GGSN  5  is a gate device connected to two service networks  6  and  7 , serves to connect the mobile communication system to service networks  6  and  7 . Service networks  6  and  7  are networks which provide packet service. 
     SGSN  4  is a node device for providing a GPRS service, connects to RNC  2  that is connected to terminal  1 , and also establishes tunnels  8  and  9  between SGSN  4  and GGSN  5  to allow terminal  1  to connect to service networks  6  and  7 . 
     RNC  3  is a controller for controlling base station  2 , and typically controls a plurality of base stations  2 . RNC  3  sets a call by performing call processing between itself and both the core network and terminal  1 . 
     Base station  2  wirelessly connects to terminal  1  and relays communications from terminal  1 . 
     In the state of  FIG. 3 , terminal  1  is receiving connection services from both service networks  6  and  7 . At this time, for the purpose of connecting terminal  1 , GTP (GPRS Tunneling Protocol) tunnels  8  and  9  are established for making connections to service networks  6  and  7 , respectively, between SGSN  4  and GGSN  5 . 
       FIG. 4  is a diagram for describing an operation of the mobile communication system when terminal  1  has moved according to the first exemplary embodiment. Although, in  FIG. 4 , as in  FIG. 2 , the base station is omitted for the sake of clarity, suppose that terminal  1  is connected to RNC  3  via base station  2  (not shown) as shown in  FIG. 3 . Referring to  FIG. 4 , terminal  1  has moved from source RNC  3   1  to destination RNC  3   2 . Accordingly, a change of connection from old SGSN  4   1  to new SGSN  4   2  is made. 
     At this time, signals associated with the movement are sent/received between new SGSN  4   2 , destination RNC  3   2 , and terminal  1 . Upon receiving predetermined signal  10 , new SGSN  4   2  starts processing a tunnel switching request. Predetermined signal  10  for starting processing of a tunnel switching request includes a route area update signal from terminal  1  or a relocation completion signal from destination RNC  3   2 . 
     New SGSN  4   2  also obtains tunnel information about tunnels established for terminal  1  as a PDP (Packet Data Protocol) context from old SGSN  4   1 . For example, new SGSN  4   2  may send a PDP context request signal to old SGSN  4   1  and then old SGSN  4   1  may send a PDP context as the response. Alternatively, old SGSN  4   1  may notify new SGSN  4   2  of the tunnel information autonomously by means of a transfer relocation request signal. 
       FIG. 5  is a flow chart showing an operation of new SGSN  4   2  for processing a tunnel switching request. New SGSN  4   2  obtains the number of tunnels to be switched from the tunnel information obtained from old SGSN  4   1  and determines whether or not the number of tunnels is two or more (step  101 ). If the number of tunnels is two or more, new SGSN  4   2  then determines whether or not there are two or more GTP tunnels between new SGSN  4   2  and the same GGSN  5  (step  102 ). 
     As a result of the determination of step  102 , if there are two or more GTP tunnels between new SGSN  4   2  and the same GGSN  5 , new SGSN  4   2  sends to GGSN  5  switching request signal  11  including a request to switch the plurality of GTP tunnels from old SGSN  4   1  to new SGSN  4   2  (step  103 ). 
     The switching request signal, which includes a pair of TEIDs (Tunnel Endpoint Identifiers) for the plurality of GTP tunnels to be switched, is sent on one update PDP context request signal. 
     If the number of GTP tunnels to be switched is one or less as a result of the determination of step  101  or if there are no two or more GTP tunnels between new SGSN  4   2  and the same GGSN  5  as a result of the determination of step  102 , new SGSN  4   2  sends each switching request signal for switching each GTP tunnel to GGSN  5  corresponding to each GTP tunnel (step  104 ). 
     Having received the switching request signal sent from new SGSN  4   2  in this way, GGSN  5  analyzes the switching request signal and then switches the GTP tunnels indicated by the TEID from old SGSN  4   1  to new SGSN  4   2 . 
     According to the exemplary embodiment, as described above, when SGSN  4  needs to be switched due to the movement of terminal  1 , new SGSN  4   2  makes a request to GGSN  5  for collectively switching the plurality of GTP tunnels between the same GGSN  5  and SGSN  4  for the same terminal  1  by means of one switching request signal. Therefore, the amount of communications between new SGSN  4   2  and GGSN  5  is reduced, thereby allowing the switching of GTP tunnels with increased line performance. The time requesting for switching the GTP tunnels is also reduced because the switching of the plurality of GTP tunnels can be requested by one switching request signal. In addition, the functions of GGSN  5  and SGSN  4  are simplified because the status of GTP tunnel switching requests from SGSN  4  to GGSN  5  is always the same between tunnels, resulting in simple switching operations. 
     Second Exemplary Embodiment 
     A mobile communication system of a second exemplary embodiment can take a Direct Tunnel extended configuration which establishes GTP tunnels between an RNC and a GGSN directly. The configuration of a mobile communication system of the exemplary embodiment is the same as that of the first exemplary embodiment shown in  FIG. 3 . However, GTP tunnels  8  and  9  are established between RNC  3  and GGSN  5 . The operation of the mobile communication system of the exemplary embodiment is the same as that of the first exemplary embodiment except for the operation of establishing the Direct Tunnel extended configuration. 
       FIG. 6  is a diagram for describing an operation of a mobile communication system when terminal  1  has moved according to the second exemplary embodiment. Although, in  FIG. 6 , the base station is omitted for the sake of clarity, suppose that terminal  1  is connected to RNC  3  via base station  2  (not shown) as in  FIG. 4 . Referring to  FIG. 6 , terminal  1  is connected to a plurality of service networks  6  and  7  using one GGSN  5 . In this status, terminal  1  is moving from source RNC  3   1  to destination RNC  3   2 . Accordingly, it becomes necessary to switch GTP tunnels  8  and  9  established between source RNC  3   1  and GGSN  5  to the location between destination RNC  3   2  and GGSN  5 . 
     At this time, signals associated with the movement are sent/received between SGSN  4 , destination RNC  3   2 , and terminal  1 . Upon receiving movement completion notification  21  of terminal  1  from destination RNC  3   2 , SGSN  4  starts processing a tunnel switching request. 
     The processing of a tunnel switching request is the same as that of the first exemplary embodiment shown in  FIG. 5 . However, SGSN  4  may use tunnel information held by SGSN  4  itself for the determination of step  101 . With the processing of a tunnel switching request according to the second exemplary embodiment, if there is a plurality of GTP tunnels that need to be switched for the same GGSN  5 , SGSN  4  will make a request to switch the plurality of GTP tunnels by means of one switching request signal  22 . 
     Since SGSN  4  typically contains a plurality of RNCs  3 , using a Direct Tunnel extended configuration which establishes GTP tunnels between RNC  3  and GGSN  5  leads to an increase in the number of switching GTP tunnels compared to establishing GTP tunnels between SGSN  4  and GGSN  5 . Therefore, the exemplary embodiment can obtain more advantages because of the Direct Tunnel extended configuration. 
     Third Exemplary Embodiment 
     In a third exemplary embodiment, a SAE (System Architecture Evolution) system which extends the GPRS system will be exemplified. 
       FIG. 7  is a diagram for describing a configuration of a mobile communication system according to the third exemplary embodiment and an operation thereof when a terminal has moved. Although, in  FIG. 7 , the base station is omitted for the sake of clarity, suppose that terminal  1  is connected to RNC  3  via base station  2  (not shown) as in  FIG. 4 . Referring to  FIG. 7 , old SGSN  4   1  and new SGSN  4   2  are connected to serving SAE GW  31 . 
     A mobile communication system of the third exemplary embodiment has serving SAE GW  31  and PDN SAE GWs  32   1  and  32   2 , instead of GGSN  5  according to the first exemplary embodiment shown in  FIG. 3 . RNC  3  and base station  2  (not shown) are included in a UTRAN (Universal Terrestrial Radio Access Network), and SGSN  4 , serving SAE GW  31  and PDN SAE GWs  32   1  and  32   2  are included in a core network. In the SAE system, accessing from the UTRAN is connected to serving SAE GW  31  from SGSN  4  through GTP tunnels. 
     Serving SAE GW  31  and PDN SAE GW  32   1  may be integrally configured, and serving SAE GW  31  is connected to service network  6  via PDN SAE GW  32   1 . In the example of the figure, since serving SAE GW  31  and PDN SAE GW  32   1  are integrally configured, there is no GTP tunnel established between serving SAE GW  31  and PDN SAE GW  32   1 . 
     Serving SAE GW  31  is also connected to service network  7  via PDN SAE GW  32   2 . GTP tunnel  35  is established between serving SAE GW  31  and PDN SAE GW  32   2 . 
     Serving SAE GW (Gateway)  31  is a device for terminating GTP tunnels  33  and  34  between serving SAE GW  31  and SGSN  4 . 
     PDN (Packet Domain Network) SAE GWs  32   1  and  32   2  are gate devices for connecting to service networks  6  and  7 . 
     Referring to  FIG. 7 , terminal  1  has moved from source RNC  3   1  to destination RNC  3   2 . Accordingly, a change of the connection from old SGSN  4   1  to new SGSN  4   2  is made. 
     At this time, signals associated with the movement are sent/received between new SGSN  4   2 , destination RNC  3   2 , and terminal  1 . Upon receiving movement completion notification  36  of terminal  1  from destination RNC  3   2 , new SGSN  4   2  starts processing of a tunnel switching request. 
     The processing of a tunnel switching request is the same as that of the first exemplary embodiment shown in  FIG. 5 . In the SAE system, when one terminal  1  connects to a plurality of service networks  6  and  7 , tunnels are consolidated into one serving SAE GW  31 . After the consolidation, tunnel  35  will be established between serving SAE GW  31  and PDN SAE GW  32   2 . If there is a plurality of tunnels in serving SAE GW  31 , new SGSN  4   2  sends to serving SAE GW  31  one switching request signal  37  for making a request to switch the plurality of tunnels. 
     In the SAE system, when one terminal  1  connects to a plurality of service networks  6  and  7 , tunnels are consolidated into one serving SAE GW  31 . Therefore, in the third exemplary embodiment, it is more likely that a plurality of tunnel switching requests may be consolidated into one switching request signal than that in the first exemplary embodiment so that more advantages can be obtained. 
     Fourth Exemplary Embodiment 
     In a fourth exemplary embodiment, the SAE system shown in the third exemplary embodiment, to which the Direct Tunnel extended configuration shown in the second exemplary embodiment can be applied will be exemplified. 
       FIG. 8  is a diagram for describing a configuration of a mobile communication system according to the fourth exemplary embodiment and an operation thereof when a terminal has moved. Although, in  FIG. 8 , the base station is omitted for the sake of clarity, suppose that terminal  1  is connected to RNC  3  via base station  2  (not shown) as in  FIG. 4 . Referring to  FIG. 8 , tunnels  33  and  34  are established between RNC  3  and serving SAE GW  31 . The operation of a mobile communication system of the exemplary embodiment is the same as that of the third exemplary embodiment except for the operation for establishing the Direct Tunnel extended configuration. 
     Referring to  FIG. 8 , terminal  1  has moved from source RNC  3   1  to destination RNC  3   2 . At this time, signals associated with the movement are sent/received between SGSN  4 , destination RNC  3   2 , and terminal  1 . Upon receiving movement completion notification  41  of terminal  1  from destination RNC  3   2 , SGSN  4  starts processing a tunnel switching request. 
     The processing of a tunnel switching request is the same as that of the first exemplary embodiment shown in  FIG. 5 . In the SAE system, when one terminal  1  connects to a plurality of service networks  6  and  7 , tunnels are consolidated into one serving SAE GW  31 . After consolidation, tunnel  35  will be established between serving SAE GW  31  and PDN SAE GW  32   2 . 
     In the exemplary embodiment, since the Direct Tunnel extended configuration is applied, SGSN  4  may use tunnel information held by SGSN  4  itself. 
     If there is a plurality of tunnels in serving SAE GW  31 , SGSN  4  sends to serving SAE GW  31  one switching request signal  42  for making a request to switch the plurality of tunnels. 
     Also in the exemplary embodiment, as with the third exemplary embodiment, it is more likely that a plurality of tunnel switching requests may be consolidated into one switching request signal than that in the first exemplary embodiment so that more advantages can be obtained. Moreover, in the exemplary embodiment, the same advantage as that of the second exemplary embodiment can also be obtained. 
     Fifth Exemplary Embodiment 
     In a fifth exemplary embodiment, a SAE system is exemplified in which an RNC and a base station (e NB (evolved Node-B)) are integrally configured and a MME (Mobile Management Entity) is provided instead of a SGSN. An eNB is included in a EUTRAN (Evolved UTRAN). 
       FIG. 9  is a diagram for describing a configuration of a mobile communication system according to the fifth exemplary embodiment and an operation thereof when a terminal has moved. Referring to  FIG. 9 , the configuration of the mobile communication system of the fifth exemplary embodiment differs from the system shown in  FIG. 8  in that base station  2  and RNC  3  shown in  FIG. 3  are integrally configured as eNB  51 , and there is MME  52  instead of SGSN  4  shown in  FIG. 8 . Since MME  52  does not have a function for processing a user plane, tunnels are established between eNB  51  and serving SAE GW  31  directly, as with the Direct Tunnel extended configuration shown in  FIG. 8 . 
     Referring to  FIG. 9 , terminal  1  has moved from source eNB  51   1  to destination eNB  51   2 . At this time, signals associated with the movement are sent/received between MME  52 , destination eNB  51   2 , and terminal  1 . Upon receiving movement completion notification  53  of terminal  1  from destination eNB  51   2 , MME  52  starts processing a tunnel switching request. 
     The processing of a tunnel switching request is the same as that of the first exemplary embodiment shown in  FIG. 5 . In the SAE system, when one terminal  1  connects to a plurality of service networks  6  and  7 , tunnels are consolidated into one serving SAE GW  31 . After consolidation, tunnel  35  will be established between serving SAE GW  31  and PDN SAE GW  32   2 . 
     Since the SAE system of the exemplary embodiment has a configuration in which tunnels are established between eNB  51  and serving SAE GW  31 , MME  52  may use tunnel information which is held by MME  52  itself. 
     If there is a plurality of tunnels in serving SAE GW  31 , MME  52  sends to serving SAE GW  31  one switching request signal  54  for making a request to switch the plurality of tunnels. 
     In the exemplary embodiment, the same advantage as that of the fifth exemplary embodiment can be obtained. 
     Hereinbefore, although the present invention has been described with reference to the exemplary embodiments, the present invention is not limited to the exemplary embodiments. It is also possible to combine or incorporate the descriptions of each exemplary embodiment. Various modifications, which those skilled in the art may appreciate, can be made within the scope of the invention to the configuration or to the details of the present invention defined in the claims. 
     This application claims benefit of priority based on Japanese Patent Application No. 2007-061935 filed on Mar. 12, 2007, the disclosure of which is hereby incorporated by reference in its entirety.