This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2006-085846, filed on Mar. 27, 2006, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a technology for managing location of a mobile station.
2. Description of the Related Art
Various networks have been built as wireless access networks, and different kinds of networks, including old and new, depending on types of access, such as a general packet radio service (GPRS) and a wireless local area network (WLAN), depending on types of provided services, such as quality of service (QoS) and best effort, or according to a rate are in use at the same time.
To support these different types of communication services and to provide economical mobile communication over these access networks, connection of the networks using an IP protocol and location management of mobile stations using a Mobile Internet protocol (IP) have been proposed. With the progress of the wireless access networks, service areas of plural access networks are overlapped. A user of a mobile station can select an access network from plural networks, and can use different access networks at the same time. The user can switch among access networks to which the mobile station is connected based on use conditions of services, considering various conditions such as a charge condition (for example, Yuji Fukunaga, “Feature: Detailed Explanation on Mobile IP Technology”, [on line], Sep. 21, 2002, @IT, [retrieved on Mar. 10, 2006], the Internet <URL: http://www.atmarkit.co.jp/fnetwork/tokusyuu/15mobileip/mip01.html>).
When Mobile IP is used, a location managing node is a home agent (HA). The mobile node (MN) registers a home address (HoA) assigned fixedly by its home network and a care-of address (CoA) temporarily used in a visited network correlated to each other. According to a technique disclosed in Japanese Patent Laid-Open No. 2003-204330, the HA provided on the access network side manages a mobile station based on information (the home address and the care-of address) stored in a binding cache, when a location of the mobile station is registered, and when switching is requested due to a change of location of the mobile station. According to the technique, a processing load on HA can be reduced by controlling intervals for re-registration of an entry with respect to a valid entry that has already been registered.
A packet transmitted to HoA of MN by a communication correspondent node CN that is a counterpart of a communication is received by HA, and HA encapsulates and tunnels packet to CoA of MN. Thus, MN can communicate with CN even when MN moves to other network than the MN's home network (i.e. visited network). Although both IPv4 and IPv6 are defined as the Mobile IP, the basic operation is common. However, in IPv4, an external agent that is a foreign agent (FA) that terminates the tunnel in stead of MN is defined in a network at the mobile destination.
The access networks AN#a and AN#b are wireless access networks. When MN1 discovers the different access network AN#b as the MN1 changes a location and a condition of wireless communication changes, (1) MN1 checks a wireless quality of AN#b, and (2) requests switching from AN#a to AN#b based on a service that the user of MN1 desires. The switching is achieved by registering CoA_b captured/used in AN#b into HA, deleting a binding cache entry of CoA_a when the registration has been successfully completed, and switching the tunnel transfer to AN#b.
However, in the above conventional technique, it is difficult to reduce time required for switching communication paths (communication path setting time) at the location managing node HA. When MN1 requests the switching to AN#b based on wireless conditions such as a radio signal strength, a communication quality is expected to be maintained. However, when the line between AN#b and HA is congested (traffic is crowded), the communication quality can not be maintained. Therefore, when HA has received a switching request to switch to AN#b, this switching is permitted when the HA/AN#b communication path is not congested and the communication quality (e.g. bandwidth) desired by MN1 can be obtained in the communication path. Therefore, MN1 sends the switching request together with information on the desired communication quality (for example, Japanese Patent Laid-Open No. 2005-250096).
In the example shown in
As described above, according to the conventional technique, when the access network that is the destination of the requested switching is congested, quick switching can not be achieved even if the mobile station MN has requested switching. Not only for such switching of access networks but also for connection to a new access network, quick setting and connection of communication paths are demanded.
It is an object of the present invention to at least solve the above problems in the conventional technologies.
An apparatus according to one aspect of the present invention performs location management for a mobile station connected thereto through a plurality of networks, and determines whether to permit or reject a request for connection to a desired network made by the mobile station. The apparatus includes a storing unit configured to store information on rejection of the request for the connection when congestion has occurred on a communication path of the desired network; a searching unit configured to search in the recording unit, when the congestion is resolved, to retrieve a mobile station of which the request has been rejected; and a notifying unit configured to notify retrieved mobile station that the desired network is available.
A method according to another aspect of the present invention is of performing location management for a mobile station connected through a plurality of networks in which whether to permit or reject a request for connection to a desired network made by the mobile station is determined. The method includes storing information on rejection of the request for the connection when congestion has occurred on a communication path of the desired network; retrieving, when the congestion is resolved, a mobile station of which the request has been rejected, from the information; and notifying retrieved mobile station that the desired network is available.
The other objects, features, and advantages of the present invention are specifically set forth in or will become apparent from the following detailed description of the invention when read in conjunction with the accompanying drawings.
Exemplary embodiments according to the present invention will be explained in detail with reference to the accompanying drawings. In the explanation, Mobile IPv4 and Mobile IPv6 will be described without especially distinguishing therebetween except for the external agent (FA) described in a third embodiment.
The embodiments of the present invention have the following characteristic:
1. As soon as a congestion state at a destination to which a mobile station has requested to connect is resolved, the location managing apparatus notifies the mobile station that switching of access networks to the destination is possible.
2. When the location managing apparatus has rejected registration due to insufficient bandwidth resources of an access network at the requested destination, the location managing apparatus stores the condition of the rejection, and as soon as enough resources get available, notifies the mobile station accordingly to provide an opportunity to switch access networks to the requested destination.
3. The notice to the mobile station is incorporated in an existing location control message (adding an availability notice flag).
4. When the location control is based on Mobile IP, the notice is piggybacked to a Mobile IP control message.
5. For switching of existing communication paths, whether the resources are secured is judged based on actually measured values retained by the location managing apparatus.
6. A quality request (for example, QoS declaration) from the mobile station, and extraction/analysis thereof by the location managing apparatus are not required to reduce response time to the mobile station.
The input processing unit 101 receives a packet from a network connected thereto. The packet type identifying unit 102 identifies the type of the received packet. When this received packet is not a location managing protocol message, the packet is sent to the BC searching unit 103. The BC searching unit 103 searches the BC table 104 using the addressee address of the packet as a key. When a valid entry is present in the BC table 104, the unit 103 notifies the encapsulating unit 106 of CoA in the entry. The encapsulating unit 106 executes IP encapsulation of the received packet using CoA as the addressee. The output path determining unit 107 determines an output path by the ordinary IP routing based on the addressee address (CoA in the above example) of the packet inputted from the encapsulating unit 106, and transmits the received packet that has been encapsulated from the output processing unit 108 corresponding to the output path to a connected network.
When no valid entry is present in the BC table 104, the received packet is transmitted through the encapsulating unit 106 without executing the encapsulation, and the output path determining unit 107 executes routing to the received packet as it is.
The output path determining unit 107 has a function of monitoring the traffic amount for each access network (line) to be connected with and notifies the QoS processing unit 109 of the monitoring result. The QoS processing unit 109 retains the AN line use amount monitored value 109b for each access line as well as the predetermined AN line amount (e.g. capacity) 109a. Using these values, the QoS processing unit 109 executes acceptance control (i.e. admission control) of connection/switching request to the access network.
A message for the location management control is identified by the packet type identifying unit 102 in the latter stage of the input processing unit 101. When the packet type identifying unit 102 has received the location management control message, the packet type identifying unit 102 delivers the received data to the mobile message processing unit 110. The mobile message processing unit 110 further identifies the type of the message and executes a process according to the message.
The mobile message processing unit 110 receives the location registration message, extracts information of quality request such as a requested bandwidth, and executes the acceptance judgment of whether the requested bandwidth can be accommodated in the line of the access network corresponding to CoA for which registration is requested in the location registration message. The process of this acceptance judgment is executed using information on the access line from the QoS processing unit 109. When the requested bandwidth can not be accommodated, a location registration response message to which the failure of the registration is coded is created to be transmitted to the mobile station MN. When the requested bandwidth can be accommodated, the requested CoA is registered in the BC table 104. A location registration response message to which the success of the registration is coded is created to be transmitted to the mobile station MN.
When the received location registration message is a switching request of access networks, the entry of CoA having the same home address for which communication is currently executed is deleted from the BC table 104. When no switching is specified, no process for switching is executed because the message is for updating the existing connection. The above specification/coding of new connection/switching or success of registration/failure of registration are represented by flags or codes in each message.
In addition to the above processes based on the reception of the location registration message, the mobile message processing unit 110 executes an entry management control of the BC table 104.
Whether the requested bandwidth can be accommodated in the access network AN corresponding to CoA of which registration is requested in the location registration message is judged (steps S204). This acceptance judgment process judges whether congestion has occurred referring information on the access line of the QoS processing unit 109 and using, for example, the following Equation 1.
requested bandwidth+AN line use amount>AN line (1)
When it is judged that the requested bandwidth can not be accommodated (step S204: YES), a location registration response message in which the failure of the registration is coded is created (step S205), registration of an entry indicating the failure of the registration is executed by recording home address and CoA of the requesting mobile station MN with setting a failure flag in the BC table 104 (step S206), the message is transmitted to the mobile station MN (step S212), and the above process is ended. The failure of the registration is notified to the mobile station MN1 as a connection rejection to the access network AN#b.
When it is judged that the requested bandwidth can be accommodated (step S204: NO), an entry of the requested information is created in home address and CoA of the BC table 104 (step S207), a location registration response message in which the success of the registration is coded is created (step S208), a process for transmission to the mobile station MN is executed (step S212), and the above process is ended.
It is judged whether the received message (location registration message) is a switching request of the access network AN (step S209). When the message is a switching request (step S209: YES), the entry of CoA having the same home address for which communication is currently executed is deleted from the BC table 104 (step S210), and the transmission at step S212 is executed. On the other hand, when the message is not a switching request (step S209: NO), because the message is for updating the existing connection after the process at step S208, the transmission at step S212 is executed and the above process is ended.
The transmission process at step S212 corresponds to the process executed at the units from the mobile message processing unit 110 through the output path determining unit 107 to the output processing unit 108. The above specification/coding of new connection/switching or success of registration/failure of registration are represented by flags or codes in each message.
The BC searching unit 103 of the location managing apparatus 100 periodically processes the BC table 104 (step S401). In this periodical process, the BC table 104 is checked by a periodic trigger using a timer.
When the process is triggered, each entry in the BC table 104 is checked one by one. First the target entry is checked whether it is a entry having an expired life time (step S402). As a result of the checking, when a valid entry having an expired life time are present (step S402: YES), a location registration request message for this entry is created and is transmitted to the mobile station MN (step S403). Then, this entry is invalidated (step S404), and the process is moved to step S412.
When the target entry is not a valid entry having an expired life time (step S402: NO), the processes at steps S405 to S411 are executed. At step S405, it is judged whether this entry is the candidate entry for access network switching/connecting. The candidate entry has an invalid flag, a failure flag, and a life time that is not expired. When this entry is not the above candidate (step S405: NO), the process is moved to step S412. When this entry is the above candidate (step S405: YES), it is judged whether this entry contains the quality request information (step S406). When this entry contains the quality request information (step S406: YES), a requested bandwidth registered in the quality request information of the BC table 104 (see
At step S409, it is judged whether congestion has occurred in the access network AN corresponding to CoA. In this judging process, information on the access line of the QoS processing unit 109 is referred and the Equation 1 is used. When it is judged that the congestion has occurred (step S409: YES), the process is moved to step S412. When it is judged that no congestion has occurred (step S409: NO), a location registration request message concerning a corresponding entry is created to be transmitted to the mobile station MN as an availability notice (step S410). Then, this entry is invalidated (step S411) and the process is moved to step S412.
At step S412, it is judged whether this entry is the final entry of the BC table 104. When this entry is the final entry (step S412: YES), the above process is ended. When this entry is not the final entry (step S412: NO), a check on the next entry is executed (step S413). More specifically, this check corresponds to re-execution of the processes at step S402 and the succeeding steps.
According to the first embodiment, as shown in
When it is judged that the quality request information is not contained (step S201: NO), as the succeeding process, as shown in
It is assumed that the mobile station MN1 shown in
When the communication quality can be maintained even after switching the communication path to the access network AN#b, HA 100 permits the switching, and notifies the permission to the mobile station MN1. When the communication quality may be degraded after the switching, HA 100 rejects the switching to the access network AN#b and this rejection request is recorded. When it becomes possible to accommodate an amount corresponding to the amount of the communication through the access network AN#a in the communication path of the access network AN#b, HA 100 notifies the mobile station MN1 that has once been rejected the request for switching, that the communication path of the access network AN#b is available.
As described above, according to the second embodiment, when the quality request information is not contained in the location registration message, the congestion state is judged based on the information on the use amount monitored statistically up to that time point. When the mobile station MN1 desires a bandwidth equivalent to the access network AN that has been used by the mobile station MN1, even after the switching is achieved, the quality request information (for example, QoS declaration) from the mobile station MN1 can be made unnecessary. That is, when the communication quality (e.g. bandwidth) that the mobile station MN1 desires is not changed, the QoS declaration, etc., from the mobile station is not required, thereby reducing time necessary for the switching
In a third embodiment of the present invention, an external agent, which is a foreign agent (FA), of the mobile station MN1 is disposed in the access network AN, thereby, monitoring the congestion state of the communication path of the access network AN. FA rejects a request from the mobile station MN1 for connection to the access network when congestion has occurred. When the congestion state of the communication path of the access network AN has been resolved, FA notifies the mobile station MN1 that the communication path is available, using the recorded information of request rejection.
When it is judged that the congestion has occurred (step S204: YES), as the succeeding process, as shown in
In this case, FA extracts the quality information from the location registration response, and (A) records the rejection log of the request together with the quality information. FA sends (4-2) location registration response (switching rejection) that has been formed by removing the quality information from the location registration response of (4-1), to the mobile station MN1.
Then, (B) when the resolution of the congestion has been detected, FA searches for the above rejecting log similar to an entry in the BC table 104 of HA and notifies the mobile station MN1 of (C) availability. Thereby, the mobile station MN1 immediately transmits (5-1) a location registration request (re-request), and FA transmits (5-2) the location registration request (re-request) to HA and the switching to the access network AN#b can be smoothly executed.
As described above, according to the third embodiment, the location management (switching control) similar to that of the first embodiment and the second embodiment can be applied even in a configuration in which the external agent (FA), which performs an encapsulating process and a decapsulating process instead of the mobile station, is disposed, as in mobile Mobile IPv4. FA can transfer the message (2-2) and HA can notify the traffic amount (e.g. data rate) of the existing communication using the message (4-1). In this manner, according to the third embodiment, the retention of the unsuccessful entry and the management control of the availability notice, etc., that HA executes in the first and the second embodiments can be executed by the external agent. Therefore, expansion of the location management system is easily done.
In the embodiments described above, the case where Mobile IP is used as the location management protocol has been explained. However, the location registration and the location registration request procedures are equally applicable to all other location management systems.
According to the embodiments described above, it is possible to reduce a time necessary for switching networks without increasing resource consumption of a wireless network.
Although the invention has been described with respect to a specific embodiment for a complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art which fairly fall within the basic teaching herein set forth.
Number | Date | Country | Kind |
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2006-085846 | Mar 2006 | JP | national |