JP4918443B2 - Access network search system, wireless terminal, access network search method, and access network switching method - Google Patents

Description

  The present invention relates to an access network search system, a wireless terminal, an access network search method, and an access network switching method.

  Virtually most of the current services around the world run on the CS (Circuit Switched) domain. However, the number of IP (Internet Protocol) based networks connected to the core network continues to increase. Therefore, in the future, it will be important to provide a bridge path for shifting current services from the CS domain to the IMS domain.

  The VCC (Voice Call Continuity) is one of applications that provide such a bridge path, which allows a user to place a call from a CS domain to an IMS (IP Multimedia Subsystem) domain when entering the WLAN area. Can be transferred to. Conversely, when the user leaves the WLAN (Wireless LAN) area, the call is returned from the IMS domain to the CS domain. Many other applications such as video calls and video downloads can also be migrated between domains.

  In order for such a transition between domains to be performed, the user's communication device needs to communicate via a plurality of interfaces, and if possible, should be performed simultaneously.

  When communication is performed via a plurality of interfaces at the same time as described above, in the communication apparatus, it is necessary to turn on each interface so that a session can be transferred if a network is found. For this reason, the power consumption of the mobile phone becomes a big problem.

  By the way, power consumption during standby is larger in WLAN than in cellular (2G, 3G technology). Therefore, it is a waste of power to always turn on both the driver corresponding to the cellular and the driver corresponding to the WLAN in order for the communication device to search for an access network candidate around the current position. From the operator's point of view, it is important to make the delivery of media as much as possible to the cheaper access network. If the WLAN is used for calls, the operator can present a cheaper fee.

  A technique for realizing the transition between the domains is disclosed in Patent Document 1. This technique calls a mobile terminal from a wireless network without using a paging function.

  Specifically, the call control server of the IP network discovers a mobile terminal (UE) that is using an interface to the cellular network. The cellular network calls a mobile terminal requesting a connection to the IP network. When called by the cellular network to connect to the IP network, the mobile terminal connects to the wireless network. This eliminates the need for paging from the IP network to the mobile terminal. Therefore, since the mobile terminal can turn off the driver corresponding to the IP network, an effect of reducing wasteful power consumption can be obtained. However, in the technique disclosed in Patent Document 1, if the IP network is not available at the time of call setup, the call is processed by the cellular network all the time thereafter. That is, even when the user moves and the WLAN can be used, the call control server cannot request the mobile terminal to switch to the WLAN.

Another technique for realizing the transition between the domains is disclosed in Patent Document 2. This technique provides a method for performing handover based on the location of a mobile terminal. This method requires a constant comparison of the distance (position) between the mobile terminal and each WLAN location. If a match between the current location of the mobile terminal and the WLAN area is detected, the mobile terminal is requested to switch to WLAN.
US Patent Application Publication No. 2005/0221842 US Patent Application Publication No. 2004/00023669

  By the way, even in the technique disclosed in Patent Document 1, if there is a high real-time interface between two wireless networks, the call control server can switch from the cellular network to the WLAN even when the call is not set up. It is thought that you can. However, in order to perform this switching, it is necessary to switch paging between networks, which requires a close connection between the networks. Therefore, it is difficult to switch. In addition, the wireless system of each network needs to pay attention to other networks. This can lead to scale issues when multiple networks are taken into account.

  In the technique disclosed in Patent Document 2, it is necessary to always monitor the position of the mobile terminal and the area area of the WLAN regardless of whether the mobile terminal is actively transmitting. In addition, when the user is moving, the mobile phone may always be requested to switch to WLAN and switch back. Usually, WLAN coverage is as narrow as several tens of meters. Therefore, when using the technique disclosed in Patent Document 2, it is necessary for the mobile terminal to continuously perform handover without considering efficiency.

  The present invention has been made in view of the above point, and an access network search system, a wireless terminal, an access network search method, and an access network search method that realize flexible session transfer between networks while reducing power consumption of the wireless terminal, and An object is to provide an access network switching method.

  An access network search system of the present invention is used in a wireless communication system including a plurality of networks to which different communication methods are applied, and is an access network search system for searching for an access network to be accessed by a wireless terminal, The state of a session formed with an access network, and the priority transfer destination network of the session are managed for each wireless terminal, and information on the priority transfer destination network is obtained when the session state changes. When the priority transfer destination network included in the notification control information is different from the communication method of the current access network, the service control unit that notifies the notification information including the session transfer destination access network from the priority transfer destination network. Explore the candidates at a predetermined interval, a configuration searched access network candidate having a an access network discovery device for transmitting the candidate to said wireless terminal as a session transfer destination access network when unchanged over time.

  The wireless terminal of the present invention manages the state of a session formed between the wireless terminal and the access network and the priority transfer destination network of the session for each wireless terminal, and the session state changes. A service control unit for notifying information including information on the priority transfer destination network, and when the priority transfer destination network included in the notification information is different from the communication method of the current access network, An access network search device that searches for a session transfer destination access network candidate at a predetermined interval, and transmits the candidate as a session transfer destination access network to the wireless terminal when the searched access network candidate does not change for a certain period of time; A In Seth network discovery system, a wireless terminal, a session between the current access network, a configuration for switching a session between the session transition destination access network transmitted from the access network discovery system.

  The access network search method of the present invention includes a monitoring step for monitoring a state of a session formed between the wireless terminal and the access network, and a state change in the session formed between the current access network, and And an access network search step of searching for a session transfer destination access network candidate at a predetermined interval from the priority transfer destination network when the current access network is different from the priority transfer destination network.

  The access network switching method of the present invention includes a monitoring step for monitoring a state of a session formed between the wireless terminal and the access network, and a state change in the session formed between the current access network, and An access network search step of searching for a session transfer destination access network candidate from the priority transfer destination network at a predetermined interval when the current access network is different from the priority transfer destination network; and the searched access network candidate A notification step of notifying the wireless terminal of the candidate as a session transfer destination access network when it does not change for a certain period of time.

  According to the present invention, it is possible to provide an access network search system, a radio terminal, an access network search method, and an access network switching method that realize flexible session transfer between networks while reducing power consumption of the radio terminal. it can.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram showing a communication system configuration of the present embodiment. The communication system 5 shown in the figure triggers a session domain transfer {domain transfer} (that is, switching of a network that forms a session with a communication apparatus. Hereinafter, it may be referred to as “session transfer”). Give to the wireless terminal.

  A communication system 5 shown in the figure includes a communication device 10, a service control unit 11, and an access network search device 20 having an access network search function (ANSF).

  The communication device 10 is a multimode device capable of communicating with a plurality of networks (not shown) via a plurality of interfaces. As the plurality of interfaces, for example, wireless LAN, cellular (circuit switching domain or packet switching domain), WiMAX, Ethernet (registered trademark), Bluetooth, and the like can be considered.

  The communication device 10 includes a transfer unit 21, an AN information receiving unit 22, an AN1 communication unit 23, an AN control unit 24, an AN2 communication unit 25, and a session control unit 26.

  In FIG. 1, two access networks are selected. Correspondingly, the communication apparatus 10 has an AN1 (access network 1) communication unit and an AN2 (access network 2) communication unit. Each of the AN1 communication unit and the AN2 communication unit can independently take charge of communication via different interfaces.

  Without loss of generality, AN1 communication unit 23 is the default unit used for communication. That is, it is assumed that the AN1 communication unit 23 is always active and in the on state. This is based on the fact that the power consumption of the AN1 communication unit 23 (particularly the power consumption when waiting for a call from the network) is lower than the power consumption of the AN2 communication unit 25. On the other hand, communication using the network corresponding to the AN2 communication unit 25 has a lower communication fee than communication using the network corresponding to the AN1 communication unit 23. That is, the AN2 communication unit 25 becomes a desirable network interface for the user.

  One example is where AN1 is a cellular radio network and AN2 is a WLAN radio network. Generally, the power consumption of the AN1 communication unit 23 corresponding to the cellular radio network is lower than the power consumption of the AN2 communication unit 25 corresponding to the WLAN radio network. Therefore, waiting in the AN1 communication unit 23 corresponding to the cellular radio network while the AN2 communication unit 25 corresponding to the WLAN radio network is in the switch-off mode is highly efficient from the viewpoint of power consumption. On the other hand, the communication fee is cheaper when communicating using a WLAN wireless network, so communicating via WLAN is more cost effective than transmitting using cellular radio.

  The transfer unit 21 controls the transfer process of the session from AN1 to AN2, and conversely, the transfer process of the session from AN2 to AN1. The transfer unit 21 performs session transfer processing between networks in cooperation with the session control unit 26 via the interface I100.

  The session control unit 26 is a session layer module that interacts with the transfer unit 21 to enable signaling for a particular session. In addition, the session control unit 26 works in cooperation with the AN control unit 24 and performs a cooperative operation with an appropriate AN communication unit during communication. Signals are transmitted and received between the session control unit 26 and the transfer unit 21 via the interface I100. Signals are transmitted and received between the session control unit 26 and the AN control unit 24 via the interface I102. Signal transmission / reception is performed between the AN control unit 24 and an appropriate AN communication unit during communication via the interface I101 or the interface I106.

  The AN control unit 24 interoperates with the transfer unit 21 and informs the transfer unit 21 of the possibility of session transfer when a new AN communication unit is activated. Note that signal transmission / reception is performed between the AN control unit 24 and the transfer unit 21 via the interface I104.

  The AN information receiving unit 22 receives information on availability of the access network (that is, information on access network candidates currently available to the communication device 10) from the access network search device 20 via the interface I111. The AN information receiving unit 22 acquires the network type of the access network corresponding to the received information, and sends the network type information to the AN communication unit corresponding to the network type.

  The service control unit 11 includes a session state management unit 27 and an AN search notification unit 13. Basically, the service control unit 11 is a place where signaling for setting up a session between the communication device 10 and the access network is moored. Therefore, all signaling for session setup passes through the service control unit 11. That is, information regarding the session is transmitted to the service control unit 11 via the interface I29 from all the networks included in the communication system 5.

  The session state management unit 27 manages the state of a session formed between the communication device 10 and the access network. The session state management unit 27 holds the call state of the session such as whether or not the session is active.

  The session state management unit 27 receives all signaling related to the setting of the session, regardless of whether the session is formed by a request from the called side or requested from the calling side. . That is, even if the session state management unit 27 starts the session with another user existing in the same domain in response to a request from the user existing in the same domain, Even when a request from a specific user in the same domain (this user is a called party) and a user existing in another domain (this user is a calling party) is started. , Handle all signaling.

  Furthermore, the session state management unit 27 holds information related to the access network used for the session to be managed.

  The session state management unit 27 notifies the AN search notification unit 13 of information for notifying the occurrence of a session every time a session occurs. In addition, when a new session occurs, the session state management unit 27 notifies the access network corresponding to the session of information notifying the formation of the new session.

  In addition, when the session to be managed is terminated, the session state management unit 27 notifies the AN search notification unit 13 of information for notifying the end of the session. Also, the session state management unit 27 notifies the AN search notification unit 13 of information for changing the access network when the access network used for the session to be managed changes. The session is identified by an appropriate session identifier. In addition, signals are transmitted and received between the session state management unit 27 and the AN search notification unit 13 via the interface I110.

  The AN search notification unit 13 transmits instruction information for instructing the access network search apparatus 20 to perform access network candidate search processing. The AN search notification unit 13 holds a list of desired access networks (that is, priority transfer destination access networks) corresponding to each communication device 10 for all the communication devices 10. In the example of the communication device 10 described above, the access network 2 that is advantageous in terms of cost efficiency is a desired access network.

  When the AN search notification unit 13 receives information for notifying the occurrence of a session from the session state management unit 27, a session corresponding to the information is formed between the communication device 10 and a desired access network for the communication device 10. Check if it has been done. For this check, the above-mentioned list of desired access networks is used.

  If the session is not formed with the desired access network as a result of the check, the AN search notification unit 13 accesses the access network search apparatus 20 for the specific communication apparatus 10 corresponding to the session. Search process start instruction information for instructing start of a search process for network candidates is transmitted. The search processing start information includes user identification information for identifying the specific communication device 10 and desired access network type information corresponding to the specific communication device 10. Further, when the session ends, the AN search notification unit 13 transmits search process stop instruction information for instructing to stop the search process for the access network candidate to the access network search apparatus 20. In addition, the AN search notification unit 13 provides the access network search device 20 with instruction information for instructing to stop the access network candidate search processing even when the communication device 10 independently shifts the session to the desired access network. Send to.

  The access network search device 20 performs access network candidate search processing triggered by reception of instruction information transmitted from the service control unit 11 and instructing start of access network candidate search processing. The access network search device 20 includes an AN search unit 14, an AN information acquisition unit 15, a mapping unit 16, a timer 17, a memory 18, and an AN selection unit 19.

  The timer 17 is started when the search processing start instruction information transmitted from the service control unit 11 is received via the AN search unit 14. The timer 17 has an appropriate time interval set in advance, and sends a notification signal to the AN search unit 14 every time the time interval elapses. Signal transmission / reception is performed between the AN searching unit 14 and the timer 17 via the interface I190 and the interface I191.

  Each time the AN search unit 14 receives a notification signal from the timer 17, the AN search unit 14 outputs the user identification information included in the search processing start instruction information that is the output trigger of the notification signal to the AN information acquisition unit 15. Signals are transmitted and received between the AN search unit 14 and the AN information acquisition unit 15 via the interface I193.

  The AN information acquisition unit 15 starts by receiving user identification information from the AN search unit 14. The AN information acquisition unit 15 acquires from the mapping unit 16 access network candidates that can be used at the current location of the user related to the received user identification information. The AN information acquisition unit 15 stores the acquired access network candidates in the memory 18 with an index.

  The mapping unit 16 stores location information and access network candidates that can be used at the location indicated by the location information for each type of desired access network. That is, the mapping unit 16 stores access network candidates corresponding to the position information for each type of desired access network. The mapping unit 16 has a function of acquiring the current position information of each communication device 10 and holds the acquired current position information.

  The mapping unit 16 receives the user identification information and the desired access network type from the AN information acquisition unit 15, and indicates the access network candidates that can be used by the communication device 10 corresponding to the user identification information and the desired access network type. The information is output to the AN information acquisition unit 15. Specifically, the mapping unit 16 first receives the user identification information from the AN information acquisition unit 15 and specifies the current position information of the communication device 10 corresponding to the user identification information. Then, the mapping unit 16 specifies information indicating access network candidates that can be used with the specified current position information. The specified information is output to the AN information acquisition unit 15 as an output. Note that any method may be used for obtaining the user's current location information and mapping the user's current location and access network candidates. That is, the current position information of the user specified by the GPS of the communication device 10 can be acquired from the communication device 10. Further, the acquisition process may be performed only when the access network search apparatus 20 receives the search process start instruction information. This limits the location signaling that the communication device 10 must do to update its exact location.

  The AN selection unit 19 checks access network candidates stored in the memory 18. When the access network candidate does not change for a predetermined period, the AN selection unit 19 determines that the user corresponding to the access network candidate is unlikely to move from the area corresponding to the access network candidate for a long period of time, and Information regarding network candidates is transmitted to the communication device 10. Signal transmission / reception is performed between the AN selection unit 19 and the communication device 10 via the interface I111.

  Next, the operation of the access network search device 20 will be described with reference to the flow of FIG.

  In step S90, the access network search apparatus 20 waits for a notification from the service control unit 11, and upon receiving this notification, in step S91, determines whether the notification is search process start instruction information or search process stop instruction information. To do. Note that the search process start instruction information includes the identification information of the communication device (user) and the type of the desired access network as described above.

  As a result of the determination, if the notification is search process stop instruction information, the search process ends in step S97. The search process stop instruction information is notified from the service control unit 11 when the session is ended or when the communication apparatus 10 is automatically switched to a desired access network.

  On the other hand, as a result of the determination, if the notification is search process start instruction information, in step S92, the AN information acquisition unit 15 determines the current position of the target user related to the received user identification information for each appropriate time interval T1. The search process for finding an access network candidate that can be used in is performed. That is, here, the selection of T1 is based on the type of access network and how often the check needs to be performed.

  In step S93, the AN information acquisition unit 15 determines whether an access network candidate is found by the search process at each time interval T1. If an access candidate is found (step S93: YES), in step S94, the AN information acquisition unit 15 stores the acquired access network candidate in the memory 18 with an index. The index information is checked for consistency by the AN selector 19 to confirm that the access network candidates are exactly the same over a predetermined time period (step S95). If no access candidate is found (step S93: NO), the processing step returns to step S92.

  When it is confirmed that the access network candidates are relatively the same (step S95: YES), in step S96, the AN selection unit 19 obtains information on the access network candidate as a target user of the access network candidate search process. It transmits to a certain communication device 10. By receiving this information, the communication device 10 can know that the access network candidate is available.

  When the information related to the access network candidate is transmitted, in step S97, the access network search apparatus 20 ends the search process for the communication apparatus 10 that is the transmission destination of the transmission information. The search processing of the communication device 10 is started again when the access network search device 20 receives search processing start instruction information including user identification information of the communication device 10. Here, although it is described that the search process is stopped in step S97, the access network search apparatus 20 transmits the information related to the access network candidate, but the communication apparatus 10 that is the transmission destination of the transmission information The search process may be repeated until the search process stop instruction information for is received from the service control unit 11.

  If the access network candidates are not consistently the same (step S95: NO), the AN information acquisition unit 15 continues the access network candidate search process.

  Next, the movement of the entire communication system 5 will be described with reference to FIG. FIG. 3 is a sequence diagram for explaining messages transmitted and received between the constituent devices of each system when a service for searching for an access network is executed in the communication system 5.

  As described above, the service control unit 11 collects all the signaling related to session setting from the network.

  Accordingly, when a new session is set in step S30, the service control unit 11 recognizes the state of the session. At the same time, the service control unit 11 specifies a default access network in the main communication device 10 that forms the new session. The default access network in each communication device 10 is stored in the session state management unit 27.

  In step S31, the service control unit 11 instructs the communication apparatus 10 to start the session via the default access network that is currently active.

  In step S32, the communication apparatus 10 appropriately starts a session through the default access network. That is, the communication device 10 actually starts transmitting media through the default access network.

  On the other hand, in step S <b> 33, the service control unit 11 transmits search process start instruction information for the communication apparatus 10 that has issued an instruction to start a session through the default access network to the access network search apparatus 20. As described above, the search processing start instruction information includes user identification information (for example, user device ID) and type information of the user's desired access network. For the user identification information (for example, the user device ID), for example, a device-specific identifier such as MSISDN, SIP URI, TEL URI, or IMEI, or a location-specific identifier can be used. The type information of the desired access network to be searched may use the type of technology applied to the access network such as WLAN or UWB, or the service type such as interworking WLAN or unspecified WLAN. Provider policy types may be used.

  When the search process start instruction information is received, the access network search apparatus 20 starts the search process shown in FIG. Steps S34 and S35 in FIG. 3 basically correspond to the processes in steps S92 to S95 in FIG.

  In step S <b> 34, the access network search apparatus 20 performs search processing at a predetermined time interval in the AN information acquisition unit 15.

  In step S35, the AN selection unit 19 checks that the access network candidate does not change for a certain period. If it is confirmed that the access network candidate does not change, information on the access network candidate is a target user of the access network candidate search process in step S96. It transmits to the communication apparatus 10. Access network candidate information includes access to wireless information, security specific information to confirm faster registration, and other reusable information necessary to ensure faster session transfer Network specific information can be included.

  The information transmitted in step S96 is transmitted as signaling information to the communication device 10 via the default access network.

  When receiving the information related to the access network candidate, the communication device 10 passes the information to the AN communication unit corresponding to the access network candidate, and performs a connection process with the access network candidate (step S38).

  If the communication device 10 succeeds in the connection process, the communication device 10 starts session transfer to the access network candidate that is the desired access network in step S39. Note that a step of confirming whether or not the session transfer process can be executed with respect to the user may be provided before the session transfer.

  FIG. 4 is a sequence diagram in the case where the session of the user who is the processing target of the search process ends before the search process of the access network candidate is completed. Steps S30, S31, S32 and S33 are the same as the corresponding steps in FIG.

  The new event in FIG. 4 is in step S40 for ending the session that the communication device 10 was conducting. Of course, the session may be terminated by the communication partner. In either case, as shown in step S41, the service control unit 11 recognizes that the session has been terminated since all signaling passes there.

  In step S42, the service control unit 11 transmits search process stop instruction information that serves as a trigger for stopping the access network candidate search process for the communication device 10 that has ended the session. When this search process stop instruction information is received, in step S97, the access network search apparatus 20 stops the search process specified by the user identification information and the desired access network type information included in the search process stop instruction information.

  As described above, the communication system 5 of the present embodiment is an access network search system that includes a plurality of networks (not shown) to which different communication methods are applied, and searches for an access network accessed by the communication device 10. . In addition, the communication system 5 manages a state of a session formed between the communication device 10 and the access network, and notifies a notification information indicating that the state of the session changes, a service control unit 11; And an access network search device 20 for searching for a session transfer destination access network from a network having a communication method different from that of the current access network in accordance with the notification information from the service control unit 11.

  The access network search device 20 stores a mapping unit 16 that stores access network candidates according to the location information, and an AN information acquisition unit that acquires information about access network candidates according to the location information of the communication device 10 from the mapping unit 16. 15 and an AN selection unit 19 that selects an access network candidate corresponding to the information as a session transfer destination access network when the information about the access network candidate acquired by the AN information acquisition unit 15 does not change for a certain period of time. It has.

  Note that the communication system 5 described above can also be used to maintain a voice call. That is, a voice call can be seamlessly transferred from a CS (circuit switching) domain to an IMS (IP multimedia subsystem) domain.

  Normally, the transfer to the IMS domain is performed when the communication device 10 detects an interworking WLAN (I-WLAN). For this reason, the communication apparatus 10 must always search for I-WLAN. And the communication apparatus 10 can transfer to CS domain from CS domain, if I-WLAN is detected.

  The function of collecting session setting information of the service control unit 11 is executed by the VCC application server connected to the IMS domain. The VCC application server as the service control unit 11 maintains the call state of each VCC call so that the call can be transferred between domains when appropriate conditions occur.

  The above functions of the service control unit 11 can be another application server connected to the VCC application, or can be incorporated into the VCC application itself.

  Further, the information regarding the access network candidate transmitted from the access network search device 20 to the communication device 10 can be in the form of a standardized XML (Extensible Markup Language) document or other data structure. Software built in the AN information receiving unit 22 of the communication apparatus 10 can understand and acquire details from the XML document.

  In addition, several other methods are conceivable as transmission methods for transmitting information related to access network candidates from the access network search device 20 to the communication device 10.

  As one of the methods, information on access network candidates is transmitted by GPRS (General Packet Radio Service) on the cellular. If the communication device 10 is already connected to GPRS, the information regarding the access network candidate can be transmitted to the communication device 10 by HTTP (HyperText Transfer Protocol). If the communication device 10 is not connected to GPRS, the access network search device 20 can start a network-initiated GPRS connection and connect the communication device 10 to GPRS. Thereafter, the information related to the access network candidate can be transmitted by HTTP as described above.

  As another method, a method of transmitting information on access network candidates by SIP (Session Initiation Protocol) notification is conceivable. The premise here is that the communication device 10 is registered in the IMS domain on GPRS. Furthermore, basically, the communication device 10 may be subscribed to an event that the AN search unit 14 confirms that the access network candidate does not change for a certain period. In this case, the access network search apparatus 20 can transmit information on the access network candidate with a SIP notification message via the Gm interface or the Ut interface. The SIP notification message can have a document format indicating information on access network candidates. If the document format can be analyzed by software in the communication device 10, the communication device 10 can extract the details of the information related to the access network candidate from the file.

  The interface I111 may be a GPRS connection established on a cellular to enable transmission of information related to access network candidates to the communication device 10. When the communication device 10 is not previously connected to GPRS, the access network search device 20 can use a network-initiated GPRS connection procedure.

  Further, the communication device 10 may be configured to be able to execute a plurality of sessions simultaneously. In this case, the access network candidate search process starts at the start of the first session of the plurality of sessions and ends at the end of the last session of the plurality of sessions. That is, the search process is performed over the total duration of the session group in the communication device 10. In order to continue the search process for the total period length, the AN search notification unit 13 can hold a list of all sessions being executed in each communication device 10 at an arbitrary time point. The AN search notification unit 13 notifies the access network search device 20 of each communication device 10 at the start of one session, but notifies the access network search device 20 even when a new session is started by the same device. It is not necessary to notify again.

  Further, the AN search notification unit 13 may manage a plurality of sessions by attaching tabs to each of a plurality of sessions that are simultaneously executed in each communication device 10 and holding the tabs. Then, the AN search notification unit 13 manages a plurality of sessions corresponding to each communication device 10 using this tab, and accesses the search process stop instruction information when the last session ends for each communication device 10. You may make it transmit to the network search apparatus 20. FIG.

  Further, the search notification unit 13 can assign an index to each session of the same device by assigning a session ID in order to identify different sessions of the same device. The search notification unit 13 can also index each session of the same device by using clear session parameters (such as call origination, call arrival, and call ID).

(Example)
An embodiment of the communication system 5 described above will be described.

  Bob has a dual-mode mobile phone with WLAN and cellular radio capabilities. Bob's mobile phone can process both CS domain voice call signals and GPRS signals for PS services on cellular radio.

  Bob is a VCC subscriber. That is, when Bob's mobile phone enters the WLAN area, the call automatically switches from the CS domain to the IMS domain.

  Apart from internet access, Bob uses WLAN for VCC calls if WLAN is available. Bob normally decides to turn off the WLAN function of the mobile phone unless he is intentionally using the WLAN to conserve the battery of the mobile phone.

  This is true even when Bob is in the WLAN area. For example, his office may have a WLAN. However, since Bob normally turns off the WLAN function of the mobile phone, it is necessary to switch on the WLAN function when using the WLAN even in the office. He only wants to use WLAN when the application is running and it seems reasonable to use WLAN in terms of cost, battery efficiency, and so on.

  When a VCC call arrives, the network automatically starts signaling on the CS domain. At the same time, for example, a server including the above-described access network search device 20 searches for a WLAN at a location where Bob is currently located. As a result of the search, if a WLAN is detected in the area where Bob is located, it can be confirmed that Bob can be assumed not to switch to the WLAN himself or can be estimated to remain in the WLAN area for a certain period of time. The If it can be guessed in this way, the server provided with the access network search device 20 can inform Bob's mobile phone of the WLAN information (corresponding to the above-mentioned information regarding the access network candidate) so that the WLAN can be switched on. Judge that it is good.

  If it is determined that Bob's mobile phone may be notified, WLAN information is transmitted to Bob's mobile phone by either HTTP on GPRS or SIP on the Gm interface.

  When Bob's portable device receives this information, it immediately turns on the driver corresponding to that WLAN so that it can connect to that WLAN. After the portable device is connected to the WLAN, the mobile device can start shifting the session to the WLAN.

  The main advantage of the technology described above is that the WLAN driver can be turned off when the application is not running. That is, wasteful power consumption of the mobile phone can be prevented.

  Another advantage is that a search for a WLAN that is a candidate for an access network for a mobile phone that is the subject of the session is performed over the entire period from the start of a session to the end of the session. It is. That is, there is no possibility that session transfer can be performed only at the start of a session, and session transfer can be performed flexibly. When the mobile phone executes a plurality of sessions, the WLAN search is performed over the entire period from the start of the first session formed for the plurality of sessions to the end of the last remaining session. Is called.

  If no access network candidate is detected in the WLAN search process, the driver corresponding to the WLAN of the mobile phone can be kept off. That is, wasteful power consumption of the mobile phone can be prevented.

  Another advantage is that there is no need to immediately switch to WLAN just because the WLAN exists near the current location of the mobile phone. That is, in order to switch to a WLAN only when there is a WLAN near the current position, the mobile phone must always monitor neighboring WLANs. And since the power consumption of the driver corresponding to the WLAN of the mobile phone is larger than the power consumption of the driver corresponding to the cellular radio, for example, performing the switching wastes the power of the mobile phone. It will be. However, since the mobile phone according to the present embodiment performs session transfer to the WLAN only when certain conditions are satisfied, wasteful power consumption can be reduced. Note that the WLAN search is performed only when the application / service / session triggers to perform a WLAN search.

  The access network search system, wireless terminal, access network search method, and access network switching method of the present invention are useful for realizing flexible session transfer between networks while reducing the power consumption of the wireless terminal.

The block diagram which shows the communication system structure which concerns on embodiment of this invention Flow diagram for explaining operation of access network search device Sequence diagram for explaining the movement of the entire communication system Sequence diagram for explaining the movement of the entire communication system

Explanation of symbols

DESCRIPTION OF SYMBOLS 5 Communication system 10 Communication apparatus 11 Service control unit 13 AN search notification part 14 AN search part 15 AN information acquisition part 16 Mapping part 17 Timer 18 Memory 19 AN selection part 20 Access network search apparatus 21 Transfer unit 22 AN information reception part 23 AN1 Communication unit 24 AN control unit 25 AN2 communication unit 26 Session control unit 27 Session state management unit

Claims (9)

An access network search system for searching for an access network used by a wireless terminal, which is used in a wireless communication system including a plurality of networks to which different communication methods are applied,
The state of a session formed between a wireless terminal and an access network, and the priority transfer destination network of the session for each wireless terminal, and the priority transfer destination network when the state of the session changes A service control unit for notifying information including
When the priority transfer destination network included in the notification information is different from the communication method of the current access network, the access network candidate of the session transfer destination is searched from the priority transfer destination network at predetermined intervals, and the searched access An access network search device that transmits the candidate to the wireless terminal as a session transfer destination access network when the network candidate does not change for a certain period of time;
An access network search system comprising: The access network search device comprises:
A network location management unit for storing access network candidates according to location information;
An access network information acquisition unit for acquiring information on access network candidates according to the location information of the wireless terminal from the network location management unit;
An access network selection unit that selects an access network candidate corresponding to the information as the session transfer destination access network when the information about the access network candidate acquired by the access network information acquisition unit does not change for a certain period;
The access network search system according to claim 1, comprising: The service control unit is
A session state management unit that manages an active session formed by the wireless terminal;
When it is necessary to start or end the search for the destination access network, an access network search notification unit that notifies the access network search device of the notification information;
The access network search system according to claim 1, further comprising:   The access network search system according to claim 3, wherein the access network search notification unit notifies the notification information every time a new session is formed. The state of a session formed between a wireless terminal and an access network, and the priority transfer destination network of the session for each wireless terminal, and the priority transfer destination network when the state of the session changes When the priority transfer destination network included in the notification information is different from the communication method of the current access network, the service control unit that notifies the notification information including the information of An access network search device comprising: an access network search device that searches for access network candidates at predetermined intervals and transmits the searched access network candidates to the wireless terminal as a session transfer destination access network when the access network candidates do not change for a certain period of time. In the system, a wireless terminal,
A wireless terminal that switches a session with the current access network to a session with the session transfer destination access network transmitted from the access network search apparatus. A monitoring step for monitoring a state of a session formed between the wireless terminal and the access network;
When there is a state change in a session formed with the current access network, and the current access network is different from the priority transfer destination network, a session transfer destination access network candidate from the priority transfer destination network An access network search step for searching for a predetermined interval;
An access network search method comprising: A monitoring step for monitoring a state of a session formed between the wireless terminal and the access network;
When there is a state change in a session formed with the current access network, and the current access network is different from the priority transfer destination network, a session transfer destination access network candidate from the priority transfer destination network An access network search step for searching for a predetermined interval;
A notification step of notifying the wireless terminal as a session transfer destination access network when the searched access network candidate does not change for a certain period of time;
An access network switching method comprising:   The access network switching method according to claim 7, wherein the notifying step notifies the session transfer destination access network using a SIP notification message. The access network switching method according to claim 7, wherein the notifying step notifies the session transfer destination access network via http.