JP4946933B2 - Mobile communication system, session continuation determination server, and session continuation method - Google Patents

Description

  The present invention relates to a mobile communication system, a session continuation determination server, and a session continuation method. For example, FMC (Fixed Mobile Convergence) studied in 3GPP (Third Generation Partnership Project) is used. And session control continuity on the premise of VCC (Voice Call Continuity).

  Using a single mobile terminal, the phone service of the CS (Circuit Switching) network is used when going out, and the IMS (IP Multimedia Subsystem) of the PS (Packet Switching) network when at home or in the office A technical mechanism for using a multimedia telephone service has been established (the PS network and the IMS core network accommodating the PS network are collectively referred to as an IMS network in this specification). Mobility (call between networks) at the call (session) and service control level so that the selection of the CS network / IMS network for receiving a telephone call and the continuous use of a telephone call interrupted between the CS network / IMS network can be used. VCC) is a mechanism for providing (transfer).

In the VCC study of 3GPP, the cooperation between the CS network and the IMS network is defined as a session control method for realizing the service while continuing the session across the CS network / IMS network (Non-Patent Document 1). To 3).

Further, in general communication in the IMS network, it is considered to realize a service by sufficiently securing the QoS (Quality of Service) of the network. Patent Document 1 describes an example of a procedure for securing QoS when a service is realized across CS networks / IMS networks.
JP 2007-325191 A 3GPP TS 24.229 3GPP TR23.806 3GPP TS 23.206

  However, Non-Patent Document 1 to Non-Patent Document 3 do not sufficiently refer to a QoS reservation method in realizing a service across the CS network / IMS network.

  As described above, Patent Document 1 describes an example of a procedure for securing QoS. However, the operation when QoS cannot be secured is not mentioned, in other words, what happens when QoS cannot be secured. It is not considered whether to make it work. The case where QoS cannot be secured is, for example, a case where a user who has been communicating with a videophone becomes insufficient in bandwidth due to a change in the network. Some users may wish to be able to make a voice call even if they cannot communicate as a videophone due to lack of bandwidth.

  In addition, Patent Document 1 does not specifically describe resource reservation or bandwidth reservation on the IMS core network side.

  The present invention has been made in view of the above problems, and in realizing services across different access networks, mobility that can ensure session continuity by reflecting the demands of users considering QoS, etc. It is intended to provide a body communication system, a session continuation determination server, and a session continuation method.

According to the first aspect of the present invention, there are a plurality of different types of access networks, and the mobile terminal can move between different types of access networks even during session establishment. A mobile communication system having a session continuation determination server for determining whether or not to permit switching and a quality management system for managing communication service quality in each access network. The session continuation determination server provides (1) a first state of communication service quality capable of providing all communication services, a second state of communication service quality capable of providing only a part of communication services, and provision of communication services. For switching at the time of session switching request for each of the third states of unsuitable communication service quality Network policy management means for managing the first policy information by the network administrator in association with the action to be performed, and (2) for each movement direction between the access networks of the mobile terminals sent out by the session switching request. User policy management means for managing the second policy information by the user, in which the action related to switching at the time of session switching request is associated with each of the first state and the second state, and (3) session switching A communication service quality fetching means for fetching the status of the communication service quality in the destination access network from the quality management system when requested, (4) the fetched status of the communication service quality and the network policy management with brute groups in the first policy information managed by means, When the action of the first policy information to be used is “according to the second policy information”, the state of the taken communication service quality, the first policy information managed by the network policy management means and the user policy management means, based on the second policy information, it possesses a switching determination means for determining whether admission switching session (5) the network policy management means, for said first state and said second state , “Switch”, “no switch”, “follow the second policy information”, manage the candidates selected by the network administrator from among the three action candidates, and manage the network for the third state. (6) The above user policy management without managing the selection by the user and managing the fixed action “no switching” Stage, at arbitrary moving direction, to manage the relative first state and said second state, "switching", "no switching", the two candidate selected by the user from the action candidates It is characterized by that.

According to the second aspect of the present invention, there are a plurality of different types of access networks, and the mobile terminal can move between different types of access networks even during the session establishment, and one mobile terminal during the session establishment can access the access network. In a mobile communication system having a session continuation determination server that determines whether or not to permit switching, and a quality management system that manages communication service quality in each access network. In the session continuation determination server, (1) a first state of communication service quality capable of providing all communication services, a second state of communication service quality capable of providing only a part of communication services, and unsuitable for providing communication services For switching at the time of session switching request for each of the third states of communication service quality Network policy management means for managing the first policy information by the network administrator in association with the action to be performed, and (2) for each movement direction between the access networks of the mobile terminals sent out by the session switching request. User policy management means for managing the second policy information by the user, in which the action related to switching at the time of session switching request is associated with each of the first state and the second state, and (3) session switching A communication service quality fetching means for fetching the status of the communication service quality in the destination access network from the quality management system when requested, (4) the fetched status of the communication service quality and the network policy management with brute groups in the first policy information managed by means, When the action of the first policy information to be used is “according to the second policy information”, the state of the taken communication service quality, the first policy information managed by the network policy management means and the user policy management means, based on the second policy information, it possesses a switching determination means for determining whether admission switching session (5) the network policy management means, for said first state and said second state , “Switch”, “no switch”, “follow the second policy information”, manage the candidates selected by the network administrator from among the three action candidates, and manage the network for the third state. (6) The above user policy management without managing the selection by the user and managing the fixed action “no switching” Stage, at arbitrary moving direction, to manage the relative first state and said second state, "switching", "no switching", the two candidate selected by the user from the action candidates It is characterized by that.

According to a third aspect of the present invention, there are a plurality of different types of access networks, and the mobile terminal can move between different types of access networks even during session establishment. Of a mobile communication system having a session continuation determination server for determining whether or not to permit switching and a quality management system for managing communication service quality in each access network. In the session continuation method, the session continuation determination server includes network policy management means, user policy management means, communication service quality capture means, and switching determination means. (1) The network policy management means includes: First state of communication service quality that can provide all communication services, and part of communication For the second state of communication service quality that can provide only services, the network administrator selected from the three action candidates of “switch”, “no switch”, and “follow the second policy information” In addition to managing candidates, for the third state of communication service quality unsuitable for providing communication services, the network administrator manages the fixed action “no switching” without allowing selection by the network administrator. Thus, the first policy information by the network administrator that associates each state of the communication service quality with the action related to the switching at the time of the session switching request, and (2) the user policy management means , Regardless of the movement direction between the access networks of the mobile terminal sent by the session switching request, By managing the candidate selected by the user from the two action candidates “switch” and “no switch” for the first state and the second state, the first state and the second state are Managing the second policy information by the user in association with an action related to switching at the time of a session switching request for each state of the second state, and (3) the communication service quality capturing means, When the session switching request is given, the communication service quality state in the destination access network is fetched from the quality management system. (4) The switching determination means includes the fetched communication service quality state and the network policy. with brute groups in the first policy information managed by the management means, actions of the first policy information applied In If is "according to the second policy information" based and communication service quality state taken, the first and second policy information managed by the network policy management unit and the user policy management unit, a session It is characterized by determining whether or not to allow switching.

  According to the present invention, when a service is realized across different access networks, the continuity of a session can be ensured by reflecting the demands of users and the like considering communication service quality.

(A) Main Embodiment Hereinafter, an embodiment of a mobile communication system, a session continuation determination server, and a session continuation method according to the present invention will be described in detail with reference to the drawings. In the mobile communication system of this embodiment, a mobile terminal (FMC terminal) can move across a CS network / IMS network.

(A-1) Configuration of Embodiment FIG. 1 is a block diagram showing a schematic configuration of a network in the mobile communication system of the embodiment.

In FIG. 1, the mobile communication system according to the embodiment is one in which FMC terminals 7 (7-1, 7-2) can be accommodated in either a circuit switching network (for example, an existing mobile network) 1 or an IMS network 2. is there. The circuit switching network 1 has a switch (MSC (Mobile Switching Center) 3) for performing circuit switching, and the IMS network 2 has various functions (P, S, I) in charge of call session control functions. The CSCF (Call Session Control Function) has a corresponding session control server 4. In the case of this embodiment, in order to continue session control, the IMS network 2 is provided with a session continuation service server (session continuation determination server of the embodiment). The session continuation service server 5 is provided as one type of application server (AS). The QoS management system 6 corresponds to, for example, RACF (Resource and Admission Control Function ), and manages the bandwidth of the circuit switching network 1 and the IMS network 2. The FMC terminal 7 sends a switching instruction when it moves under the networks 1 and 2 .

  In the case of this embodiment, communication for continuing session control is performed by establishing a session between the exchange 3 of the circuit switching network 1 and the session control server 4 and the session continuation service server 5 of the IMS network (IP network) 2. This is realized by interlocking with the QoS management system 6 that manages the above. Further, the bandwidth for realizing the service is managed in real time by the QoS management system 6 and accessed from the service continuation service server 5 at the time of a session switching request or the like, and whether or not the session can be switched in cooperation with policy information described later. Judging.

  FIG. 2 is a block diagram showing an internal functional configuration of the session continuation service server 5. Even if the session continuation service server 5 is realized by installing a predetermined program on a server having a communication function, it can be functionally represented in FIG.

  In FIG. 2, the session continuation service server 5 includes a service control unit 11, a signal processing unit 12, a policy control unit 13, a user information management unit 14, and a policy information management unit 15.

The service control unit 11 performs session switching control. The signal processing unit 12 performs signal transmission / reception control. The policy control unit 13 determines policy information. The user information management unit 14 manages contract data with the user. The policy information management unit 15 manages network and user policy information. The policy information management unit 15 also registers and updates network and user policy information according to operations from a network administrator or the like.

  The session continuation service server 5 can communicate with the exchange 3, one or a plurality of session control servers 4, and the QoS management system 6. The session continuation service server 5 communicates with the portable exchange 3 of the circuit switching network 1 via SS7 (Signaling System No. 7; No. 7 common line signaling), and with the session control server 4 of the IMS network 2 Communication is performed on an IP (SIP) basis. The session continuation service server 5 can be accessed from the QoS management system 6 on the basis of IP and SS7 in accordance with the requirements of each network and operator.

3 and 4 are explanatory diagrams showing the data structures of the network and user policy information managed by the policy information management unit 15 , respectively.

In FIG. 3, the network policy information 15N describes the type of bandwidth state of the session switching destination provided from the QoS management system 6 and the action taken by the session continuation service server 5 (the service control unit 11). It is. In the example of FIG. 3, three types of bandwidth states are prepared: “service can be provided”, “voice call service only can be provided”, and “service cannot be provided”. The width of each type of specific bandwidth (free capacity) varies depending on the system to be constructed and the settings of the network administrator. However, when there is almost no bandwidth available, “service provision is not possible” and sufficient bandwidth is available. One time is “ service can be provided ”, and the middle is “only voice call service can be provided”. In the case of “providing service” and “providing only voice call service”, there are three types of actions that can be set: “according to user policy”, “execution of session switching”, and “no session switching”. A network administrator selects (sets) from the types. In the case of “service cannot be provided”, there is no room for selection, and the action is “no session switching”.

In FIG. 4, the user policy information 15U includes the switching direction captured based on information from the exchange 3 or the session control server 4, the type of bandwidth state of the session switching destination provided from the QoS management system 6, and the session continuation. It describes the actions that the service server 5 (the service control unit 11) takes. There are two types of switching directions: “direction from the circuit switched network 1 to the IMS network 2” and “direction from the IMS network 2 to the circuit switched network 1”. There are two types of bandwidth states in the user policy information 15U : “service can be provided” and “only voice call service can be provided”. In the case of “service cannot be provided”, priority is given to the action in the network policy information 15N . . There are two types of actions that can be set for both “Service can be provided” and “Voice call service can be provided”: “Perform session switching” and “No session switching”, and the user can select from these two types. (Set).

  FIG. 5 and FIG. 6 respectively show the data structures of the network information and user policy information that are specifically set.

(A-2) Operation of Embodiment Next, the session continuation operation (session continuation method of the embodiment) in the mobile communication system of the embodiment, particularly the operation according to the policy information will be described in detail with reference to the drawings. . FIG. 7 is a flowchart showing the session continuation operation in the session continuation service server 5.

  When a communication session is established between the FMC terminals 7-1 and 7-2, the process shown in FIG. 7 is started for the session (step S1).

  A session switching request is sent from the circuit switching network 1 to the IMS network 2 or from the FMC terminal 7 that has moved from the IMS network 2 to the circuit switching network 1 or from the switch 3 or the session control server 4 that accommodates it. The continuous service server 5 receives the switching request (step S2).

At this time, the session continuation service server 5 collects at least the state of the band at the switching destination from the QoS management system 6 (step S3). Then, the collected bandwidth state is compared with the network policy information 15N (step S4).

As a result of the comparison, if the bandwidth cannot be secured and “service provision is not possible”, it is determined that the switching process is not performed (cannot be performed), and an NG response is made to the request (step S5). On the other hand, if it is determined as a result of the comparison that “service can be provided” or “only a voice call service can be provided”, the setting of the policy information 15N of the network is referred to (step S6 ).

As a result of referring to the network policy information 15N , when “session switching is performed”, switching processing is performed (step S7). As a result of referring to the network policy information 15N , if “no session switching”, the switching process is not performed and an NG response is made to the request (step S8). As a result of referring to the network policy information 15N , in the case of “according to the user policy”, in accordance with the setting conditions of the user policy information 15U , a process matching the moving direction of the terminal, the bandwidth state, etc. is performed (step S9).

FIG. 8 is a sequence diagram of each part illustrating a first example of the session continuation operation in the embodiment. This example is an example in the case where the network and user policy information 15N and 15U have the setting contents shown in FIGS.

  Initially, the FMC terminal 7-1 under the circuit switching network 1 and the FMC terminal 7-2 under the IMS network 2 are in a state in which a session is established between the IMS network 2 and the circuit switching network 1 (steps). S51) Assume that the FMC terminal 7-1 has moved to the IMS network 2 from this state (step S52).

  The FMC terminal 7-1 that has moved to the IMS network 2 sends a session switching request to the session control server 4 (step S53), and the session control server 4 transfers the received session switching request to the session continuation service server 5. (Step S54).

  The session continuation service server 5 that has received the session switching request captures the bandwidth state in the IMS network 2 from the QoS management system 6 (step S55). Here, it is assumed that the bandwidth state is “only voice call service can be provided”.

Referring to the policy information 15N of the network (NW), it is assumed that the band state “only voice call service can be provided” is “according to user policy” (step S56). Therefore, the session continuation service server 5 refers to the user policy information 15U (step S57). If the action for the bandwidth state “only voice call service can be provided” in the switching direction “circuit switching network 1 → IMS network 2” is “no session switching”, the session continuation service server 5 “switches” to the session control server 4. "NG" is returned (step S58), and the session control server 4 responds "switching NG" to the requesting FMC terminal 7-1 (step S59).

  Thus, even if the FMC terminal 7-1 moves to the IMS network 2, similarly to the initial state, in other words, the state in which the session is established between the IMS network 2 and the circuit switching network 1 (the session is Communication is continued (without opening) (step S60).

FIG. 9 is a sequence diagram of each part illustrating a second example of the session continuation operation in the embodiment. This example is also an example in the case where the network and user policy information 15N and 15U have the setting contents shown in FIGS.

  Initially, both the FMC terminals 7-3 and 7-4 under the IMS network 2 are in a state of establishing a session in the IMS network 2 (step S101). From this state, the FMC terminal 7-3 is switched over. Suppose that it moved to the network 1 (step S102).

  The FMC terminal 7-3 that has moved to the circuit switching network 1 sends a session switching request to the exchange 3 (step S103). The session switching request is sent to the session via the exchange 3 and the session control server 4 in sequence. The continuation service server 5 is reached (steps S104 and S105).

  The session continuation service server 5 that has received the session switching request takes in the bandwidth state in the circuit switching network 1 from the QoS management system 6 (step S106). Here, it is assumed that the bandwidth state is “service can be provided”.

When referring to the policy information 15N of the network (NW), it is assumed that the bandwidth state “service can be provided” is “according to user policy” (step S107). Therefore, the session continuation service server 5 refers to the user policy information 15U (step S108). If the action regarding the bandwidth state “service can be provided” in the switching direction “IMS network 2 → circuit switching network 1” is “session switching performed”, the session continuation service server 5 sends a “switching response” to the session control server 4. Sending out (step S109), the “switching response” arrives at the requesting FMC terminal 7-3 via the session control server 4 and the exchange 3 in sequence (steps S110 and S111).

  Thereby, a session is established between the IMS network 2 and the circuit switching network 1 for the FMC terminals 7-3 and 7-4 (step S112).

  When the session continuation service server 5 sends a “switching response”, the session control server 4 then instructs the session control server 4 to release the IMS session of the requesting FMC terminal 7-3 (step S113). The IMS session of the FMC terminal 7-3 is released (step S114).

  Note that the sequence after deciding to switch sessions is the same as the existing one. This embodiment is characterized in a method for determining whether or not to switch a session with movement.

(A-3) Effect of Embodiment According to the above-described embodiment, the session continuation service server that provides the service determines whether to continue or switch the session based on the policy information of the user over the network and the bandwidth state. Therefore, it is possible to realize a service that meets the user's request while guaranteeing the quality to the user.

  For example, depending on the carrier (communication carrier) that provides the service, when communication in the IMS network is provided at a lower cost than communication in the circuit switching network, even when moving from the IMS network to the circuit switching network, It is also possible to communicate as much as possible within the range that can be communicated by the IMS network and not switch to the circuit switching network. In addition, for example, even if a user who is talking on a videophone can only make a voice call due to movement between networks, the service can be continued for a user who wants to continue communication even with a voice call alone. it can.

(B) Other Embodiments In the description of the above-described embodiment, various modified embodiments have been referred to. However, modified embodiments as exemplified below can be cited.

  In the above embodiment, the session control server 4 and the session continuation service server 5 have been described as separate from each other. However, the session control server 4 and the session continuation service server 5 may be physically the same server.

  In the above embodiment, the policy information is managed by the session continuation service server 5, but the policy information may be held in the mobile terminal. For example, at least some mobile terminals have policy information that describes whether or not to send a switching request for each moving direction (switching direction). When moving to another network, switching is performed according to the built-in policy information. It may be determined whether or not to send a request. In this case, the management of the user policy information in the session continuation service server 5 may be stopped. Even in this case, the session continuation service server 5 manages and uses the user policy information. Also good.

In the description of the above embodiment, a specific protocol for exchanging information between the session continuation service server 5 and the QoS management system 6 has not been mentioned. Is not dependent. For example, it is also conceivable to apply a linkage system with RACF, which is being studied by NGN (Next Generation Network).

  The management (storage) method of network policy information and user policy information is not limited to the method shown in FIGS. 3 to 6 described above, and the data configuration and storage method are arbitrary as long as necessary information can be managed. .

  In the above-described embodiment, the user policy information indicates that the “band state” is also a condition. However, the policy information may be set only on the “movement direction (switching direction)” condition.

  In the description of the above-described embodiment, the “band state” is described as a communication band margin state, but it may reflect not only the band but also an ambient noise environment such as an error rate. That is, the QoS evaluation value may be used as a condition for network policy information or user policy information.

  The application target of the mobile communication system of the present invention is not limited to the system related to FMC being studied by 3GPP. There are a plurality of different types of access networks, and the mobile terminals are different types of access networks. The present invention can be applied as long as it is movable.

  In the above embodiment, the network policy information that describes referring to the user policy information is described. However, the user policy information is referred to first, and if there is no provision, the network policy information reference is described. In this case, the network policy information may be referred to.

1 is a block diagram showing a schematic configuration of a network in a mobile communication system according to an embodiment. It is a block diagram which shows the functional structure inside the session continuation service server in embodiment. It is explanatory drawing which shows the data structure of the policy information of the network in embodiment. It is explanatory drawing which shows the data structure of the user's policy information in embodiment. It is explanatory drawing which shows the example of a setting of the policy information of the network in embodiment. It is explanatory drawing which shows the example of a setting of the user policy information in embodiment. It is a flowchart which shows the session continuation operation | movement in the session continuation service server of embodiment. It is each part sequence diagram which shows the 1st example of the session continuation operation | movement in embodiment. It is each part sequence diagram which shows the 2nd example of the session continuation operation | movement in embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Circuit switched network (existing mobile network), 2 ... IMS network, 3 ... Switch (portable switch), 4 ... Session control server, 5 ... Session continuation service server, 6 ... QoS management system, 7, 7-1, 7-2 ... FMC terminal, 11 ... service control unit, 12 ... signal processing unit, 13 ... policy control unit, 14 ... user information management unit, 15 ... policy information management unit.

Claims (4)

Sent when there are multiple different types of access networks and the mobile terminal can move between different types of access networks even during session establishment, and when one mobile terminal in session establishment moves through the access network In a mobile communication system having a session switching request, a session continuation determination server that determines whether to permit switching, and a quality management system that manages communication service quality in each access network,
The session continuation determination server
A first state of communication service quality capable of providing all communication services, a second state of communication service quality capable of providing only some communication services, and a third state of communication service quality unsuitable for providing communication services A network policy management means for managing the first policy information by the network administrator, in which the action related to the switching at the time of the session switching request is associated with the state of
For each movement direction between the access networks of the mobile terminal sent by the session switching request, the state related to the switching at the time of the session switching request is associated with each state of the first state and the second state, User policy management means for managing second policy information by a user;
A communication service quality fetching means for fetching the status of the communication service quality in the destination access network from the quality management system when a session switching request is given;
And communication service quality state taken together with brute group in the first policy information managed by the network policy management unit, the action of the first policy information applied is "according to the second policy information" In this case, it is determined whether or not to permit session switching based on the state of the acquired communication service quality and the first and second policy information managed by the network policy management unit and the user policy management unit. have a and the switching determination means,
For the first state and the second state, the network policy management means is a network administrator among three action candidates of “switch”, “no switch”, and “follow the second policy information”. Manages the selected candidates, and manages the fixed action “no switching” for the third state without allowing selection by the network administrator,
The user policy management means is selected by the user from two action candidates of “switching” and “no switching” for the first state and the second state regardless of the movement direction. A mobile communication system characterized by managing candidates . At least some of the mobile terminals
A terminal policy management means for managing third policy information in which a moving direction between access networks of the mobile terminal is associated with whether or not a session switching request is transmitted;
The request transmission determining means for determining whether or not to transmit a session switching request based on the third policy information when the mobile terminal moves to a different access network during session establishment. mobile communication system according to 1. Sent when there are multiple different types of access networks and the mobile terminal can move between different types of access networks even during session establishment, and when one mobile terminal in session establishment moves through the access network In a session continuation determination server in a mobile communication system having a session continuation determination server for determining whether or not to permit switching, and a quality management system for managing communication service quality in each access network.
A first state of communication service quality capable of providing all communication services, a second state of communication service quality capable of providing only some communication services, and a third state of communication service quality unsuitable for providing communication services A network policy management means for managing the first policy information by the network administrator, in which the action related to the switching at the time of the session switching request is associated with the state of
For each movement direction between the access networks of the mobile terminal sent by the session switching request, the state related to the switching at the time of the session switching request is associated with each state of the first state and the second state, User policy management means for managing second policy information by a user;
A communication service quality fetching means for fetching the status of the communication service quality in the destination access network from the quality management system when a session switching request is given;
And communication service quality state taken together with brute group in the first policy information managed by the network policy management unit, the action of the first policy information applied is "according to the second policy information" In this case, it is determined whether or not to permit session switching based on the state of the acquired communication service quality and the first and second policy information managed by the network policy management unit and the user policy management unit. have a and the switching determination means,
For the first state and the second state, the network policy management means is a network administrator among three action candidates of “switch”, “no switch”, and “follow the second policy information”. Manages the selected candidates, and manages the fixed action “no switching” for the third state without allowing selection by the network administrator,
The user policy management means is selected by the user from two action candidates of “switching” and “no switching” for the first state and the second state regardless of the movement direction. A session continuation determination server characterized by managing candidates . Sent when there are multiple different types of access networks and the mobile terminal can move between different types of access networks even during session establishment, and when one mobile terminal in session establishment moves through the access network In a session continuation method of a mobile communication system having a session switching request, a session continuation determination server that determines whether to permit switching, and a quality management system that manages communication service quality in each access network,
The session continuation determination server includes network policy management means, user policy management means, communication service quality capture means, and switching determination means.
The network policy management means performs “switch”, “switch”, “communication service quality first state capable of providing all communication services, and communication service quality second state capable of providing only a part of communication services. Manages the candidate selected by the network administrator from among the three action candidates of “no switching” and “according to the second policy information”, as well as the third state of communication service quality unsuitable for providing communication services. By managing the fixed action “no switching” without allowing selection by the network administrator, the action related to switching at the time of session switching request can be managed for each state of communication service quality. Is associated with the first policy information by the network administrator,
The user policy management means performs “switching” and “no switching” for the first state and the second state regardless of the moving direction of the mobile terminal between the access networks sent by the session switching request. ”, The candidate selected by the user from among the two action candidates can be switched at the time of session switching request for each of the first state and the second state for each movement direction. Managing the second policy information by the user in association with the action,
The communication service quality fetching means fetches the status of the communication service quality in the destination access network from the quality management system when a session switching request is given,
It said switching determining means, and the communication service quality state taken, the network policy with brute groups in the first policy information managed by the management means, the action of the first policy information applied is "second In the case of “according to the policy information”, the switching of the session is permitted based on the taken communication service quality state and the first and second policy information managed by the network policy management means and the user policy management means. A session continuation method characterized by determining whether or not.

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