Method for transferring the context of a mobile terminal in a wireless telecommunication network

The present invention relates to a method of transferring the context of a mobile terminal in a wireless communication network including a plurality of base stations linked to each other by a communication network.

A mobile communication network that provides communication services to a mobile terminal that moves around in an area consisting of a large number of wireless cells generally has the right to access the network before giving the relevant resources. Provide the mobile operator with a means to confirm that.

A mobile communication network generally consists of a large number of base stations connected to a large number of base station controllers, the controller itself is connected to a small number of VLRs (Visited Location Registry), and the VLRs are further connected. Connected to at least one common HLR (Home Location Registry).

In such a network, information about the authenticated mobile terminal, the so-called mobile terminal context, is stored in the mobile terminal and the HLR. The mobile terminal can be authenticated by comparing the information stored in the mobile terminal with the information stored in the HLR. Based on this information, the mobile communication network allows or denies access to the mobile terminal. Authentication by such centralized management causes some waiting time in the authentication process.

To reduce latency, the concept of VLR has been introduced to minimize the number of accesses to HLR. The HLR handles a large number of mobile terminals and will not be able to withstand the large amount of signaling required for access to allow all mobile terminals throughout the network. The VLR can be considered as a proxy for the HLR function, and more specifically, it handles the HLR function for all mobile terminals located in the area under the influence of the HLR. To do so, VLR and HLR delegate authority. Therefore, in many cases, the VLR can autonomously determine the access permission.

Even in such a hierarchical architecture, the base station has to relay the authentication request from the mobile terminal to the VLR, and the VLR has to process the requests from many mobile terminals in parallel, so there is still some waiting in the authentication process. Time will occur.

Authentication processing can be delegated to the base station to reduce latency, but such a solution is unacceptable as it does not fit into the concept of fast travel. Each time a mobile terminal moves from one cell of one base station to another cell of a base station, permissions must be re-negotiated between the mobile terminal and the other base station. Other base stations that do not know the mobile terminal context will request such information from the HLR. As a result, there will be a significant increase in signaling to be processed by the HLR. The signaling time for exchanging mobile terminal contexts is long. In fact, in the case of a mobile terminal moving at high speed, in the sense that the mobile terminal may have moved to another cell controlled by another base station before the mobile terminal context is received. In addition, the cell reselection function will not be realized efficiently.

For the above reasons, current technology limits the efficient reselection of cells within multiple cells controlled by a single VLR, and spans areas served by different VLRs. It is clear that mobility is unsatisfactory.

An access point in a wireless local area network as disclosed in the standard IEEE 802.11 includes several access control mechanisms, and a Radius server can be placed within the access point itself. However, such wireless local area networks do not propose any practical scheme capable of maintaining fast permissions between adjacent wireless local area networks and fast and efficient cell reselection.

New generation mobile communication networks, such as third generation cellular networks, provide high speed data rate transmission, but the latency of the authentication process has not been improved.

In addition, new mobile communication networks offer a large number of services with varying quality of service. Each time a handover is made, the new base station providing the service must set up the communication parameters used by the wireless and fixed network interfaces to carry the communication context. There are a wide variety of communication parameters, such as code numbers, frequencies, time slots, data formats, communication ports, and the like. These communication parameters are derived by the base station from higher level parameters in the communication context, such as quality of service. In that case, the new base station that provides the service must acquire the higher-level parameters of the communication context from either the mobile terminal or the previous base station that provided the service during the handover procedure. The new base station that provides the service must then derive communication parameters from this information. The transfer of such information about the mobile terminal delays the handover procedure. In addition, the process of deriving the communication parameter from the upper parameter of the communication context is time-consuming and may involve an additional signaling procedure. The time for exchanging mobile terminal information and the time for deriving communication parameters are combined to be long. In fact, in the sense that the mobile terminal may have moved to another cell controlled by another base station before the information about the mobile terminal is received or the communication parameters are derived. In the case of a mobile terminal that moves at high speed, the handover function may not be efficiently realized.

<p num="0012"> Therefore, an object of the present invention is to propose a method and a device that can reduce the waiting time of a movement process, such as a cell reselection process or a handover procedure.</p>

<p num="0013"> To this end, the present invention acquires the context of a mobile terminal that is expected to be serviced by a first base station in a wireless communication network that includes multiple base stations linked together by the communication network. The steps include a step performed by a first base station that is expected to service the mobile terminal. A step of receiving a first message from a mobile terminal via a wireless interface, the message receiving the first message, including at least the identifier of the mobile terminal and the identifier of the second base station. Steps and A step of forwarding a second message over a communication network that contains at least one identifier contained within the received message, and With the step of receiving the context of the mobile terminal over the communication network The present invention relates to a method of acquiring the context of a mobile terminal, which comprises.</p><p num="0014"> The present invention is also a device that acquires the context of a mobile terminal that is expected to be serviced by a first base station in a wireless communication network that includes a plurality of base stations linked together by the communication network. Is included in the first base station that is expected to provide services to mobile terminals, A means of receiving a first message from a mobile terminal via a wireless interface, the message receiving the first message, including at least the identifier of the mobile terminal and the identifier of the second base station. Means and A means of forwarding a second message over a communication network that contains at least one identifier contained within a received message. As a means of receiving the context of a mobile terminal via a communication network It also relates to a device that acquires the context of a mobile terminal, which is characterized by having.</p><p num="0015"> Therefore, it is possible to shorten the waiting time for the movement process such as the cell reselection process or the handover procedure.</p><p num="0016"> When a mobile terminal in standby mode moves from one cell of one base station to one cell of another base station, the other base station requires a procedure as disclosed in the latest technology. You can get the mobile terminal context for the authentication procedure without having to. Since the HLR and VLR procedures for authentication are no longer required, other base stations can perform the authentication procedure by themselves so that the cell reselection process can be performed at high speed. become.</p><p num="0017"> Therefore, the number of messages handled by HLR and VLR can be reduced, and the complexity is reduced.</p><p num="0018"> When a mobile terminal in communication mode moves from one cell of one base station to one cell of another base station, the handover procedure is also shortened.</p><p num="0019"> According to certain characteristics, the second base station is a base station that provides services to mobile terminals.</p><p num="0020"> Therefore, when cell reselection processing is performed between adjacent base stations, the context is transferred over a short distance. This can also reduce the waiting time for executing the cell selection or the waiting time for executing the handover procedure.</p><p num="0021"> According to the first embodiment of the present invention, the second message is transferred to the second base station and includes at least the identifier of the second base station and the identifier of the mobile terminal, and the context of the mobile terminal is Received in the third message.</p><p num="0022"> Therefore, the waiting time for executing the cell selection or the waiting time for executing the handover procedure is shortened.</p><p num="0023"> According to certain features, the first message contains a certificate, which is the mobile terminal identifier, the second base station identifier, and these identifiers encrypted by the second base station's private key. Includes signatures obtained by encryption and / or signatures obtained by encrypting these identifiers with the private key of the mobile terminal. Before forwarding the second message, the first base station, which is expected to service the mobile terminal, checks to see if the certificate has been tampered with.</p><p num="0024"> Therefore, the first base station can identify the second base station that is currently servicing the mobile terminal, and in order to obtain the context of the identified mobile terminal, the second base station can be identified. Requests can be sent.</p><p num="0025"> If the certificate has been tampered with, the first base station may refuse to send a request to the second base station in order to obtain the context of the identified mobile terminal. Only the mobile terminal having the access right guaranteed by the second base station can realize the cell reselection of the handover with the first base station. This can protect the wireless cellular network from forwarding unwanted signaling associated with malicious mobile terminals that do not have access rights across multiple base stations.</p><p num="0026"> In addition, the time it takes for the mobile terminal to confirm the access right to access the network via the first base station is reduced.</p><p num="0027"> According to certain characteristics, when the third message is received, the first base station, which is expected to serve the mobile terminal, begins to serve the mobile terminal, at least to the mobile terminal. , The identifier of the first base station and the identifier of the mobile terminal are transferred.</p><p num="0028"> Therefore, the mobile terminal can store the identifier of the first base station, and can transmit this identifier to the third base station when another cell reselection or handover procedure is performed. Therefore, the waiting time for the authentication procedure is reduced.</p><p num="0029"> According to certain characteristics, when the first base station, which is expected to serve the mobile terminal, begins to serve the mobile terminal, the first base station moves through the communication network to the third base station. The fourth message is received from the base station of the above, and the message includes at least the identifier of the first base station that provides the service to the mobile terminal and the identifier of the mobile terminal, and the first base station is a communication network. The fifth message is transferred to the third base station via, the fifth message contains the context of the mobile terminal, and the first base station stops servicing the mobile terminal.</p><p num="0030"> Therefore, the first base station can identify the context associated with the mobile terminal before transmitting the context to the third base station.</p><p num="0031"> The mobile terminal context is then transferred to a third base station that is expected to service the mobile terminal.</p><p num="0032"> According to certain features, the fourth message contains a certificate, which encrypts the mobile terminal identifier, the first base station identifier, and these identifiers with the first base station's private key. Includes signatures obtained by encryption and / or signatures obtained by encrypting these identifiers with the private key of the mobile terminal.</p><p num="0033"> Therefore, it can be trusted that the first base station handled the context of the mobile terminal.</p><p num="0034"> Therefore, the first base station is not trying to remove the context by reusing an old certificate previously issued by the fourth base station, for example, why the third base station is not valid. You can trust that.</p><p num="0035"> According to a second embodiment of the invention, the first message includes at least the identifier of another third base station selected by the mobile terminal.</p><p num="0036"> Therefore, the route used by the mobile terminal to move between the first base station and the second base station can be determined.</p><p num="0037"> According to a particular feature of the second embodiment, the second message was forwarded to a third base station selected by the mobile terminal, and the second message was received, at least in the first message. Includes identifier.</p><p num="0038"> Therefore, even when the first base station and the second base station are not connected, the first base station knows the third base station that can be connected to the second base station.</p><p num="0039"> According to a particular feature of the second embodiment, the base station identifier is transferred in a list in which the mobile terminal is ordered based on the order in which the base stations are selected.</p><p num="0040"> Therefore, it is possible to accurately determine the history of the route used by the mobile terminal to move from the first base station to the second base station.</p><p num="0041"> According to a particular feature of the second embodiment, the identifiers of the plurality of third base stations are included in the first message, and the first base station is the third base station to which the second message is sent. Determine if it should be transferred and transfer the second message to the confirmed third base station.</p><p num="0042"> Therefore, the waiting time is shortened.</p><p num="0043"> According to a particular feature of the second embodiment, the first base station selects a third base station to which the second message should be transferred, based on the order of the base station identifiers in the list. Determine.</p><p num="0044"> According to a particular feature of the second embodiment, the first message includes a certificate, which is the mobile terminal identifier and the base station identifier, and these identifiers are the secret of the second base station. Service to the mobile terminal before forwarding the second message, including the signature obtained by encrypting with the key and / or the signature obtained by encrypting these identifiers with the private key of the mobile terminal. The first base station, which is expected to provide, checks to see if the certificate has been tampered with.</p><p num="0045"> Therefore, if the certificate has been tampered with, the first base station can refuse to request context.</p><p num="0046"> According to a particular feature of the second embodiment, the second message includes a certificate, which is the mobile terminal identifier and the base station identifier, and these identifiers are the secret of the second base station. Includes signatures obtained by encrypting with a key and / or signatures obtained by encrypting these identifiers with a mobile terminal's private key.</p><p num="0047"> Therefore, if the certificate has been tampered with, the second base station can refuse to send the context.</p><p num="0048"> According to a particular feature of the second embodiment, when the context is received in the third message, the first base station begins servicing the mobile terminal and at least the first to the mobile terminal. The base station identifier and the mobile terminal identifier are transferred.</p><p num="0049"> According to a particular feature of the second embodiment, when the first base station, which is expected to provide services to the mobile terminal, begins to provide services to the mobile terminal, the first base station becomes a communication network. The fourth message is received from the fourth base station via, and the message includes at least the identifier of the first base station that provides services to the mobile terminal and the identifier of the mobile terminal, and the first The base station transfers the fifth message to the fifth base station over the communication network, the fifth message contains the context of the mobile terminal, and the first base station serves the mobile terminal. Stop.</p><p num="0050"> According to a particular feature of the second embodiment, the fourth message contains a plurality of fifth base station identifiers, the first base station should transfer the message to which fifth base station. And forward the fifth message to the confirmed fifth base station.</p><p num="0051"> According to a particular feature of the second embodiment, the fifth base station to which the second message should be transferred is determined based on the order of the base station identifiers in the list.</p><p num="0052"> Further, the present invention is a method of requesting a base station to provide a service to a mobile terminal, in which the base station is a base station of a wireless communication network and the mobile terminal is another base of the wireless communication network. The method includes a step performed by a mobile terminal that is serviced by a station and requires that the method be serviced by a base station. The step of receiving the first message from the base station where the mobile terminal is currently serviced, the first message is at least the identifier of the base station where the mobile terminal is currently serviced. The step of receiving the first message, including the mobile terminal identifier, A step of transferring a second message to a base station that requires the mobile terminal to be serviced, the second message being at least the identifier of the base station to which the mobile terminal is currently serviced. And the step of transferring a second message, including the mobile terminal identifier It also relates to a method of requesting a mobile terminal to provide a service, which comprises.</p><p num="0053"> Further, the present invention is a device that requests a base station to provide a service to a mobile terminal, the base station is a base station of a wireless communication network, and the mobile terminal is another base of the wireless communication network. Serviced by the station, the device is included in the mobile terminal requesting to be serviced by the base station, A means of receiving at least the identifier of the base station to which the mobile terminal is currently serviced and the identifier of the mobile terminal from the base station to which the mobile terminal is currently serviced. A means of transferring a message to a base station that requires the mobile terminal to be serviced, at least including the identifier of the base station to which the mobile terminal is currently serviced and the identifier of the mobile terminal. It also relates to devices that require mobile terminals to be serviced, characterized in that they are equipped with.</p><p num="0054"> Therefore, the base station requested to provide the service by the mobile terminal obtains the information necessary for the base station requested to provide the service by the mobile terminal to provide the service to the mobile terminal. In addition, the mobile terminal can send a request to the base station currently being serviced. A base station that is required to be serviced by a mobile terminal does not need to send such a request to the server, thus reducing the delay in providing the service to the mobile terminal.</p><p num="0055"> According to certain characteristics, the first message contains a certificate, which is the mobile terminal identifier, the base station identifier, and these identifiers of the base station to which the mobile terminal is currently serviced. Includes signatures obtained by encrypting with a private key.</p><p num="0056"> Therefore, by checking the integrity of the certificate, a base station that is required to service a mobile terminal autonomously that the mobile terminal has access to be serviced by that base station. You can check. By revoking the tampered certificate, the capacity of the wireless cellular network can be saved.</p><p num="0057"> According to certain features, the second message contains a certificate, which is by encrypting the mobile terminal identifier, the base station identifier, and these identifiers with the private key of another base station. Includes signatures obtained and / or signatures obtained by encrypting these identifiers with the mobile terminal's private key.</p><p num="0058"> Therefore, by examining the integrity of the certificate, the base station to which the mobile terminal is currently serviced has the right to handle the mobile terminal context with the base station requesting the mobile terminal to provide the service. Can be confirmed autonomously. By revoking the tampered certificate, the capacity of the cellular mobile network can be saved.</p><p num="0059"> According to a particular feature of the second embodiment, the mobile terminal selects a third base station and stores the identifier of the selected base station. The second message also includes base station identifiers that are ordered based on the order in which the mobile terminal selects the base stations.</p><p num="0060"> According to a particular feature of the second embodiment, the mobile terminal is set to a first state in which signal transfer is interrupted. Also, when the mobile terminal is set to a state in which signal transfer is interrupted, a third base station is selected.</p><p num="0061"> Therefore, the power resources of the mobile terminal are saved.</p><p num="0062"> According to a particular feature of the second embodiment, the mobile terminal finds the number of selected third base stations, and if the found number is equal to a predetermined value, the mobile terminal can transfer the signal. Set to the second possible state.</p><p num="0063"> Therefore, the power resources of the mobile terminal are saved.</p><p num="0064"> According to a particular feature of the second embodiment, the second message is forwarded when the mobile terminal is set to the second state.</p><p num="0065"> Further, the present invention is a message transferred in a wireless cellular network composed of a plurality of base stations linked to each other by a communication network, and one base station is currently providing a service to a mobile terminal. The message also relates to a message, characterized in that it includes, at a minimum, an identifier of the mobile terminal and an identifier of a base station that is currently servicing the mobile terminal.</p><p num="0066"> According to certain features, the message further includes an ordered list of base station identifiers selected by the mobile terminal.</p><p num="0067"> According to certain features, the message is transferred between the mobile terminal and another base station that is expected to service the mobile terminal.</p><p num="0068"> According to certain characteristics, the first message contains a certificate, which is the identifier of the mobile terminal, the identifier of the base station currently servicing the mobile terminal, and these identifiers to the mobile terminal. Includes signatures obtained by encrypting with the private key of the base station currently providing the service, and / or signatures obtained by encrypting these identifiers with the private key of the mobile terminal.</p><p num="0069"> The features and advantages associated with the message are the same as those described above for the methods and devices according to the invention, so they are not repeated here.</p><p num="0070"> According to yet another aspect, the invention is a computer program that can be loaded directly into a programmable device and that, when executed in the programmable device, is a portion of an instruction or code that performs the steps according to the invention. Including computer programs.</p><p num="0071"> The features and advantages associated with computer programs are the same as those described above for methods and devices according to the invention, so they are not repeated herein.</p><p num="0072"> The features of the present invention will be further clarified by reading the following description of an example of an embodiment. The explanation will be given with reference to the attached drawings.</p>

FIG. 1a is the first diagram showing the architecture of the mobile communication network according to the present invention.

In this mobile communication network, the server 20 is connected to a plurality of base stations 10a and 10b via the communication network 50. The communication network 50 is a dedicated wired network, or a public network such as a public exchange network, or an IP-based network, or a wireless network, or an asynchronous transfer mode network, or a combination of the above networks.

The communication network 50 connects the base stations 10 to each other. Further, according to the present invention, messages and information can be transferred between the base stations 10 or between the base stations 10 and the server 20.

The server 20 stores information related to each mobile terminal 30 of the mobile communication network. When the base station 10 requests a context for an unknown mobile terminal 30, the server 20 creates a context from the stored information associated with the mobile terminal 30, and the context of the mobile terminal 30 is passed through the communication network 50. And transfer to base station 10.

Each base station 10 can transfer and / or receive data via the radio area 15. From now on, such a radio area will be referred to as cell 15.

Although only one server 20 is shown in FIG. 1a, it can be understood that a larger number of servers 20 can be used in the present invention. Similarly, only two base stations 10a and 10b, and cells 15a and 15b, respectively, are shown, but it can be understood that a larger number of base stations 10 and 15 can be used in the present invention. it can.

In FIG. 1a, one mobile terminal 30 is shown. The mobile terminal 30 is serviced by the base station 10a and moves from the cell 15a of the base station 10a to the cell 15 of the base station 10b.

If the mobile terminal 30 is able to establish communication, receive communication, or continue communication through base station 10, mobile terminal 30 is serviced by base station 10. That is, the base station 10 provides the service to the mobile terminal 30.

When the mobile terminal is in idle mode and moves from one cell to an adjacent cell, for example from cell 15a to cell 15b, the cell reselection process is performed. When mobile terminal 30 is not communicating with another communication device, mobile terminal 30 is in standby mode, but the context is still in base station 10 servicing mobile terminal 30. If communication must be established when the mobile terminal 30 is in standby mode, the mobile terminal 30 must constantly reselect the best cell 15. Such a process is a cell reselection process.

In the cell reselection process, the context of the mobile terminal 30 is, for example, data used to authenticate the mobile terminal 30 and check access rights, later when communication is established on the mobile terminal 30 such as an encryption key. Details of the data used and the service access contract of the mobile terminal 30. The base station 10 uses the context of the mobile terminal 30 to register the mobile terminal 30 as a mobile terminal 30 existing in the cell 15 and as a terminal for which the base station 10 provides a service.

A handover procedure is performed when the mobile terminal 30 is communicating with another communication device through a given cell 15 of a given base station 10 and moves to an adjacent cell 15 of the base station 10. In the handover procedure, a given base station 10 must stop providing services to the mobile terminal 30, and an adjacent base station 10 must start providing services to the mobile terminal 30 so that communication can continue. .. In the soft handover procedure, the adjacent base station 10 must start providing the service to the mobile terminal 30 while the given base station 10 continues to provide the service to the mobile terminal 30. This enables macrodiversity and allows communication to continue across multiple cells at the same time.

In the handover procedure, the context of the mobile terminal 30 is required for the target base station 10 to configure its own wireless and network interfaces. As a result, the mobile terminal 30 can be connected to the communication network 50 and the flow of information regarding handover can be relayed.

More precisely, the context of the mobile terminal 30 related to the handover procedure is, for example, the public key of the mobile terminal 30 in an asymmetric encryption / authentication system, the secret encryption / decryption key in a symmetric flow encryption system, the average data speed. And service quality information that defines the communication flow in terms of peak data speed, granularity, time / latency constraints for the communication context of mobile terminal 30, to route communication from mobile terminal 30 to communication network 50 and vice versa. Includes a reference to the entry port of the network interface to be used for.

Such information is used to set up wireless and network interfaces. Once set up, the wireless interface will be able to synchronize with the mobile terminal 30, the mobile terminal 30 will be notified of the wireless interface configuration, and if synchronization with the wireless interface is established, the handover procedure will be completed.

Base station 10 must set up both a wireless interface and a network interface. For example, base station 10 determines the frequency / time slot / code that should operate. They may be significantly dependent on quality of service parameters such as average peak speed to provide to mobile terminal 30. In addition, the base station 10 checks the availability of hardware resources and software resources in both the wireless interface and the network interface, and sets up a connection between the hardware resources and the software resources.

According to the present invention, each mobile terminal 30 serviced by the base station 10 receives the identifier of the base station 10 from the base station 10. When the cell reselection process or handover procedure is performed, the mobile terminal 30 transfers the identifier of the base station 10 that it is currently servicing to the base station 10 that it expects to be serviced. .. The base station 10 expected to provide the service to the mobile terminal 30 acquires the context of the mobile terminal 30 from the base station 10 currently providing the service to the mobile terminal 30.

Although only one mobile terminal 30 is shown in FIG. 1a, it can be understood that the wireless network of the present invention manages a large number of mobile terminals 30.

FIG. 1b is a second diagram showing the architecture of a mobile communication network according to the present invention.

In the mobile communication network, the server 120 is connected to a plurality of base stations 110a to 110e via the communication network 150. The communication network 150 is a dedicated wired network, or a public network such as a public exchange network, or an IP-based network, or a wireless network, or an asynchronous transfer mode network, or a combination of the above networks.

The communication network 150 connects several base stations 110 to each other so that messages and information can be transferred between the connected base stations 110 or between the base station 110 and the server 120.

As an example, but not limited to, the connection 151ab between the base station 110a and the base station 110b is established, the connection 151ac between the base station 110a and the base station 110c is established, and the base station 110b and the base station 110c Connection 151bc between base station 110b is established, connection 151bd between base station 110b and base station 110c is established, connection 151cd between base station 110c and base station 110d is established, base station 110d and base station 110e Connection 151de with is established.

Server 120 is exactly the same as Server 20 and will not be described further.

Each base station 110 can transfer and / or receive data via the radio area 115. Such a radio area is hereafter referred to as cell 115.

Although only one server 120 is shown in FIG. 1b, it can be understood that a larger number of servers 120 can be used in the present invention. Similarly, only five base stations 110a-110e and their respective cells 115a-115e are shown, but it can be understood that a larger number of base stations 110 and cells 115 can be used in the present invention. ..

FIG. 1b shows one mobile terminal 130. The mobile terminal 130 is serviced by base station 110a and passes from cell 115a of base station 110a through cell 115b of base station 110b, cell 115c of base station 110c, and cell 115d of base station 110d to base station 110e. Move to cell 115e. Such movement is indicated by arrow 131, labeled 131 in FIG. 1b.

If the mobile terminal 130 is capable of establishing, receiving, or continuing communication through the base station 110, the mobile terminal 130 is serviced by the base station 110. That is, the base station 110 provides a service to the mobile terminal 130.

When the base station 110 services the mobile terminal 130, the base station 110 holds the context associated with the mobile terminal 130. For example, base station 110a provides services to mobile terminal 130.

When mobile terminal 130 is in active mode, communication with mobile terminal 130 can be established, data can be transferred to base station 110, and / or data can be received at base station 110. Can be done.

When the mobile terminal 130 is in the operating mode and no data is being transferred in the established communication, the mobile terminal 130 can switch to the dormant state, and the mobile terminal 130 saves its power energy. To stop wireless transmission. In the hibernate state, the mobile terminal 130 continues to measure the level of the received signal, selects a new base station 110, stores the identifier of the selected base station, but does not cause signaling with these base stations 110.

For example, if mobile terminal 130 is dormant as it travels through cells 115b-115d, mobile terminal 130 is not serviced by base stations 110b-110d. Base stations 110b to 110d do not have the context of mobile terminal 130. The mobile terminal 130 stores the identifiers of the base stations 110b to 110d.

The mobile terminal 130 can execute the cell reselection process or the handover as disclosed in the case of the mobile terminal 30 with reference to FIG. 1a.

The context of the mobile terminal 130 is the same as the context disclosed in the case of the mobile terminal 30 with reference to FIG. 1a.

Base station 110 uses the context of mobile terminal 130 in the same manner as disclosed for base station 10 with reference to FIG. 1a.

FIG. 2 is a block diagram of a base station according to the present invention.

Base station 10 has, for example, an architecture based on components connected to each other by bus 201 and processor 200 controlled by a program as disclosed in FIG. 5a.

Bus 201 connects processor 200 to read-only memory ROM 202, random access memory RAM 203, network interface 204, and wireless interface 206.

Memory 203 includes registers. This register contains variables, identifiers of some base stations 10, the content of messages transferred by mobile terminal 30 or another base station 10 or server 20, and mobile terminals serviced by base station 10. It is intended to receive 30 contexts and program instructions for algorithms as disclosed in Figure 5a.

The processor 200 controls the operation of the network interface 204 and the wireless interface 206.

The read-only memory 202 contains program instructions related to the algorithm as disclosed in FIG. 5a, which are transferred to the random access memory 203 when the base station 10 is powered on.

The base station 10 is connected to the communication network 50 via the network interface 204. For example, the network interface 204 is a DSL (Digital Subscriber Line) modem, an ISDN (Integrated Services Digital Network) interface, or the like. Through such an interface, the base station 10 exchanges information with the server 20 of the wireless cellular communication network and other base stations 10. The communication established or received by the mobile terminal 30 included in the cell 15 of the base station 10 goes through the network interface 204 and the wireless interface 206.

Through the wireless interface 206, the base station 10 obtains at least the identifier of the base station 10 currently servicing the mobile terminal 30 from the mobile terminal 30 expected to be serviced by the base station 10. Receive.

Base station 110 is exactly the same as base station 10. Each base station 110 has, for example, an architecture based on components connected to each other by bus 201 and a processor 200 controlled by a program as disclosed in FIGS. 5b and 5c.

FIG. 3 is a block diagram of a mobile terminal according to the present invention.

The mobile terminal 30 has, for example, an architecture based on components connected to each other by bus 301 and a processor 300 controlled by a program as disclosed in FIG. 4a.

Bus 301 connects processor 300 to read-only memory ROM 302, random access memory RAM 303, and wireless interface 306.

Memory 303 includes registers. This register contains variables, the identifier of the base station 10 currently servicing the mobile terminal 30, the content of the message received from the base station 10 currently servicing the mobile terminal 30, and FIG. 4a. It is intended to receive program instructions and instructions relating to the algorithm as disclosed in.

The processor 300 controls the operation of the network interface 304 and the wireless interface 306.

The read-only memory 302 contains program instructions related to the algorithm as disclosed in FIG. 4, which are transferred to the random access memory 303 when the base station 10 is powered on.

Through the wireless interface 306, the mobile terminal 30 establishes or receives communication with another communication device via the base station 10 servicing the mobile terminal 30, or by a base station 10 located nearby. Measure the power strength of the signal to be transferred, the mobile terminal 30 receives a message from the serviced base station 10, or the mobile terminal 30 is expected to be serviced to the base station 10. Forward the message.

The mobile terminal 130 is exactly the same as the mobile terminal 30. The mobile terminal 130 has, for example, an architecture based on components connected to each other by bus 301 and a processor 300 controlled by a program as disclosed in FIG. 4b.

FIG. 4a is an algorithm executed by a mobile terminal according to the first embodiment of the present invention.

This algorithm is executed by each mobile terminal 30. More precisely, when the mobile terminal 30 forwards the cell update message to the base station 10, it is executed by the processor 300 of the mobile terminal 30.

In step S400, processor 300 detects the receipt of a message forwarded by the serviced base station 10 by mobile terminal 30 via wireless interface 306. As indicated by the arrows in FIG. 1a, the mobile terminal 30 is moving from cell 15a to cell 15b. Base station 10a provides services to mobile terminal 30, and base station 10b is expected to provide services to mobile terminal 30.

Such a message includes at least the identifier of the base station 10 and the unique identifier of the mobile terminal 30. The identifier of the base station 10 is unique to the base station 10 that is located at least near the base station 10 currently servicing the mobile terminal 30 and is currently servicing the mobile terminal 30 by another base station 10. To be able to identify. Such messages preferably include a certificate.

The certificate is based on at least the unique identifier of the mobile terminal 30, the identifier of the base station 10 currently providing the service to the mobile terminal 30, and the private key of the base station 10 currently providing the service to the mobile terminal 30. Includes signatures obtained by encrypting these identifiers. By using the public key of the base station 10 associated with the private key together with the contents of the certificate, the integrity of the contents of the certificate is guaranteed and the base station 10 currently providing the service to the mobile terminal 30 is authenticated. be able to. Public and private key specifications, signature generation, authenticity detection, and source authentication methods can be performed, for example, to comply with the RSA authentication algorithm.

In the next step S401, the processor 300 stores the contents of the received message in the RAM memory 303.

In the next step S402, processor 300 generates a command signal to wireless interface 306 to proceed to measure the power strength of the pilot signal transferred by the nearby base station 10. According to FIG. 1a, two base stations 10a and 10b are shown, and the radio interface 306 measures the power strength of the pilot signal transferred in cells 15a and 15b of base stations 10a and 10b.

In the next step S403, processor 300 determines whether mobile terminal 30 should change cell 15. According to this example, the power strength of the pilot signal transferred in cell 15b of base station 10b is transferred in a given threshold or in cell 15a of base station 10a currently servicing the mobile terminal 30. If it is higher than a given ratio of the power strength of the pilot signal, the processor 300 determines to change cell 15. That is, it is expected that the service will be provided by the base station 10 that controls the cell 15b. In that case, processor 300 proceeds to step S404.

The power strength of the pilot signal transferred in the cell of the other base station 10 is a given threshold, or the power strength of the pilot signal transferred in the cell 15 of the base station 10 currently servicing the mobile terminal 30. If it is lower than the given ratio of, processor 300 returns to step S402 already described.

In step S404, processor 300 creates a message containing the contents of the message stored in step S401.

According to a modification of an embodiment of the invention, the processor 300 creates a certificate, which at least provides the mobile terminal 30's unique identifier, the mobile terminal 30's public key, and the mobile terminal 30 now. The signature of the base station 10 and the signature of the base station obtained by encrypting these identifiers with the private key of the base station 10 currently providing the service to the mobile terminal 30, and the secret of the mobile terminal 30. Includes the signature of mobile terminal 30 obtained by encrypting these identifiers with a key.

Note that the signature of the base station 10 currently servicing the mobile terminal 30 may not be included in the created message.

According to another embodiment, the message created is encrypted with the public key of the base station 10 where the mobile terminal 30 expects to be serviced.

In the next step S405, the processor 300 forwards the created message to the base station 10 where the mobile terminal 30 expects to be serviced.

Note that each base station 10 of the wireless communication network broadcasts a signal containing information that allows the mobile terminal 30 to send a message to the base station 10. The mobile terminal 30 uses such information to transfer a message to the base station 10 where the mobile terminal 30 expects to be serviced.

The processor 300 then returns to step S400, which has already been described.

FIG. 4b is an algorithm executed by a mobile terminal according to a second embodiment of the present invention.

This algorithm is executed by each mobile terminal 130. More precisely, it is executed by the processor 300 of each mobile terminal 130.

In step S450, processor 300 detects the receipt of a message forwarded by the serviced base station 110 by mobile terminal 30 via wireless interface 306. According to the example of FIG. 1b, the mobile terminal 130 is serviced by the base station 110a. Such a message includes at least the identifier of base station 110a. The identifier of the base station 110a allows another base station 10 having a connection with the base station 110a to uniquely identify the base station 110a currently servicing the mobile terminal 130. The message also includes a unique identifier for the mobile terminal 130. Such a message preferably includes a certificate as disclosed with reference to FIG. 4a.

In the next step S451, the processor 300 stores the contents of the received message in the RAM memory 303.

In the next step S452, the processor 300 instructs the mobile terminal 130 to change the state. The mobile terminal 30 shifts from the operating state to the hibernation state. That is, the switch-off of the transmission unit of the wireless interface 306 is instructed.

In the next step S453, processor 300 instructs wireless interface 306 to proceed to measure the power strength of the pilot signal transferred by the nearby base station 110. According to FIG. 1b, the radio interface 306 measures the power strength of the pilot signal transferred in cells 115a and 115b of base stations 110a and 110b.

In the next step S454, processor 300 determines whether mobile terminal 130 should change cell 115. According to the example of FIG. 1b, the power strength of the pilot signal transferred in cell 115b of base station 110b is transferred at a given threshold or in cell 115a of base station 110a currently servicing the mobile terminal 130. If it is higher than a given ratio of the power strength of the pilot signal to be made, the processor 300 determines to change cell 115. In that case, processor 300 proceeds to step S455.

Otherwise, processor 300 returns to step S453, which has already been described.

In step S455, processor 300 receives a message from base station 110b. Such a message includes at least the identifier of base station 110b. The identifier of base station 110b allows other base station 110 having a connection with base station 110b to uniquely identify base station 110b.

In the next step S456, the processor 300 stores the identifier of the base station 110b in the RAM memory 303. More precisely, processor 300 updates the ordered list, which includes the identifier of base station 110b followed by the identifier of base station 110a.

In step S457, processor 300 checks to see if mobile terminal 130 should transition from hibernation to operational state. Such a situation occurs when the mobile terminal 130 is dormant for a predetermined time, for example, several seconds, or when the mobile terminal 130 selects a predetermined number of cells 115, or when the mobile terminal 130 moves data. Occurs when receiving a message intended to be forwarded to terminal 130, or when communication needs to be established with another mobile terminal 130 or a remote communication device not shown in Figure 1b.

If the mobile terminal 130 should transition from hibernation to operating state, processor 300 proceeds to step S458. Otherwise, processor 300 returns to step S453.

For example, the mobile terminal 130 remains dormant.

In step S453, processor 300 generates a command signal to wireless interface 306 to proceed to measure the power strength of the pilot signal transferred by the nearby base station 110.

In step S454, processor 300 determines whether cell 115 should be modified. According to the example of FIG. 1b, processor 300 determines that cell 115 is to be modified. In that case, processor 300 proceeds to step S455.

In step S455, processor 300 receives a message from base station 110c. Such a message includes at least the identifier of base station 110c. The identifier of the base station 110c allows another base station 110 having a connection with the base station 110c to uniquely identify the base station 110c.

In the next step S456, the processor 300 stores the identifier of the base station 110c in the RAM memory 303. More precisely, processor 300 updates the ordered list, which includes the identifier of base station 110c, followed by the identifier of base station 110b, followed by the identifier of base station 110a.

In the next step S457, the processor 300 checks whether the mobile terminal 130 should transition from hibernation to operating state.

For example, the mobile terminal 130 is kept in hibernation.

The processor 300 then returns to step S453, selects cell 115d in step S454, and in step S455 receives a message from base station 110d that includes at least the identifier of base station 110d. The identifier of the base station 110d allows another base station 110 having a connection with the base station 110d to uniquely identify the base station 110d.

In step S456, processor 300 stores the identifier of base station 110d in RAM memory 303. More precisely, processor 300 updates the ordered list, which includes the identifier of base station 110d, followed by the identifier of base station 110c, followed by the identifier of base station 110b, and the subsequent base. Includes the identifier of station 110a.

In step S457, processor 300 checks to see if mobile terminal 130 should change from hibernate to operational.

For example, the mobile terminal 130 is kept in hibernation.

At that time, the processor 300 returns to step S453, selects cell 115e in step S454, and receives a message from base station 110e including at least the identifier of base station 110e in step S455. The identifier of the base station 110e allows another base station 110 having a connection with the base station 110e to uniquely identify the base station 110e.

In step S456, the processor 300 stores the identifier of the base station 110e in the RAM memory 303. More precisely, the processor 300 updates the ordered list, which includes the identifier of base station 110e, followed by the identifier of base station 110d, the identifier of base station 110c, and the identifier of base station 110b. And the identifier of the base station 110a.

In step S457, processor 300 checks to see if mobile terminal 130 should transition from hibernation to operational state.

For example, the mobile terminal 130 must change from a hibernate state to an operating state.

In step S458, processor 300 reads a list containing the stored identifier of base station 110.

The list is ordered and contains the identifier of base station 110 that manages cell 115 through which the mobile terminal has advanced. The first identifier in the list is the identifier for base station 110e, the second identifier in the list is the identifier for base station 110d, the third identifier in the list is the identifier for base station 110c, and the fourth identifier in the list. The identifier is the identifier of base station 110b, and the fifth identifier in the list is the identifier of base station 110a.

In the next step S459, the processor 300 creates a message containing the list read in step S459 and the identifier of the mobile terminal 130.

According to a modification of an embodiment of the invention, processor 300 creates a certificate. The certificate includes at least the unique identifier of the mobile terminal 130, the public key of the mobile terminal 130, the read list, and the signature of the base station 110 servicing the mobile terminal 130. The certificate encrypts the unique identifier of the mobile terminal 130 and the identifier of the base station 110a that provides the service to the mobile terminal 130 with the private key of the base station 110a that currently provides the service to the mobile terminal 130. Obtained by doing. Further, the signature of the mobile terminal 130 is obtained by encrypting these identifiers with the private key of the mobile terminal 130.

Note that the signature of base station 110a, which is currently servicing mobile terminal 130, may not be included in the created message.

According to another variant of the embodiment, the created message is encrypted with the public key of base station 110, i.e., base station 110e, where mobile terminal 130 expects to be serviced.

In the next step S460, the processor 300 transfers the created message to the base station 110e, which the mobile terminal 130 expects to be serviced.

Note that each base station 110 of the wireless communication network broadcasts a signal containing information that allows the mobile terminal 130 to send a message to the base station 110. The mobile terminal 130 uses such information to transfer a message to a base station 110 that the mobile terminal 130 expects to be serviced.

The processor 300 then proceeds to step S460 to check whether the acknowledgment message ACK has been received from the base station 110e, which the mobile terminal 130 expects to be serviced.

If the acknowledgment message is not received within the predetermined time, the processor 300 returns to step S460.

If an acknowledgment message is received, processor 300 proceeds to step S461 to reset the list of base station identifiers stored in steps S451 and S456.

The processor 300 then returns to step S450, which has already been described.

FIG. 5a is an algorithm executed by a base station according to the first embodiment of the present invention.

This algorithm is executed by each base station 10 of the wireless network. More precisely, it is executed by the processor 200 of each base station 10.

In step S500, processor 200 receives the message.

In the next step S501, the processor 200 checks whether the message is transmitted from the base station 10 or the mobile terminal 30. When the message is transmitted from the base station 10, it is received via the network interface 204. At that time, the processor 200 proceeds to step S513. Otherwise, the message has been received via wireless interface 206 and processor 200 proceeds to step S502.

In step S502, processor 200 checks to see if the received message contains the identifier of base station 10. The identifier of such a base station 10 is the identifier of the base station 10 that is currently providing services to the mobile terminal 30.

If the message does not include the identifier of base station 10, it means that the mobile terminal 30 is not serviced by base station 10. For example, the mobile terminal 30 is powered on in cell 15 of the base station 10 that receives the message, and the context for the mobile terminal 30 does not yet exist in the wireless communication network.

If the message contains the identifier of base station 10, processor 200 proceeds to step S506. If the message does not include the identifier of base station 10, processor 200 proceeds to step S503.

In step S503, the processor 200 acquires the context of the mobile terminal 30 that sent the message from the server 20. To that end, the processor 200 uses the identifier of the mobile terminal 30 included in the message received in step S500.

In the next step S504, processor 200 creates a message. Such a message includes at least the identifier of its base station 10. Such messages preferably include a certificate.

The certificate includes at least the unique identifier of the mobile terminal 30, the identifier of the base station 10 that received the message, and the signature. Here, the signature is made by using these identifiers with the private key of the base station 10 that received the message, that is, the base station 10 that is expected to service the mobile terminal 30 and is currently servicing the mobile terminal 30. Obtained by encrypting.

In the next step S505, the processor 200 transmits a message to the mobile terminal 30 that transmitted the message received in step S500 via the wireless interface 206. The processor 200 then returns to step S500 and waits for a new message.

If the message received in step S500 includes the identifier of base station 10, processor 200 proceeds from step S502 to step S506.

In step S506, the processor 200 uses the base station identifier included in the received message to determine the base station 10 currently providing service to the mobile terminal 30 that sent the message.

In the next step S507a, processor 200 processes the received message. The process consists of storing the content of the received message in RAM203, or, if it contains at least one signature, inspecting the integrity of the content of the message in step S507b before storing it. ..

If the message contains the signature of base station 10, processor 200 decrypts the signature with the public key of base station 10 whose identifier is included in the message, and the decrypted information is included in the certificate. Determine if they are the same. If the information is different, the certificate has been tampered with and processor 200 aborts the process and returns to step S500.

Note that the public key of base station 10 whose identifier is included in the message is received from server 20 or from another base station 10 when the base station 10 is set up.

If the message contains the signature of mobile terminal 30, processor 200 decrypts the signature with the public key of mobile terminal 30 obtained from server 20 or from mobile terminal 30 itself, and the decrypted information becomes a certificate. Determine if it is the same as the information contained. If the information is different, the certificate has been tampered with and processor 200 aborts the process and returns to step S500.

Note that both of the above checks are performed if the received message contains two signatures.

Malicious attacks can be avoided by examining the integrity of the message.

If step S507a, or steps S507a and S507b, is executed correctly, processor 200 proceeds to step S508.

In that step, the processor 200 gives the determined base station 10, the identifier of the base station 10 currently providing services to the mobile terminal 30, the identifier of the mobile terminal 30, and the identifier of the base station 10, that is, If the identifier of the base station 10 expected to service the mobile terminal 30 and one or more signatures in the message received in step S500, the signature of the base station 10 and / or the move. Forward messages containing the signature of terminal 30.

In the next step S509, the processor 200 receives the context of the mobile terminal 30 from the base station 10 currently servicing the mobile terminal 30.

In the next step S510, the processor 200 applies the context of the received mobile terminal 30 to ensure that the mobile terminal 30 is serviced by the base station 10.

In the next step S511, processor 200 creates a message.

Such a message includes at least the identifier of the base station 10, that is, the identifier of the base station 10 currently servicing the mobile terminal 30, and the unique identifier of the mobile terminal 30 that transmitted the message received in step S500. including. Such messages preferably include a certificate.

The certificate includes, at a minimum, the unique identifier of the mobile terminal 30, the identifier of the base station 10 currently servicing the mobile terminal 30, and the signature. Here, the signature is obtained by encrypting these identifiers with the private key of the base station 10.

In the next step S512, the processor 200 transfers the message created in the previous step via the wireless interface 206. The content of the message is replaced with the content of the message previously received from the base station 10 that previously provided the service to the mobile terminal 30 in the memory 303 of the mobile terminal 30.

The processor 200 then returns to step S500 and waits for a new message to be processed.

If it is confirmed in step S501 that the message received in step S500 is the message transferred by the base station 10, processor 200 proceeds to step S513a.

In the next step S513a, processor 200 processes the received message. The process comprises storing the contents of the received message in the RAM memory 203, or checking the integrity of the contents of the message in step S513b before storing it.

The processor 200 checks whether the identifier of the base station 10 currently providing the service to the mobile terminal 30 is the same as the identifier of the base station 10. Also, it is examined whether or not the identifier of the mobile terminal 30 is one of the identifiers of the mobile terminal 30 for which the base station 10 is currently providing the service. If one of the checks in this way is incorrect, processor 200 stops processing the message and returns to step S500.

If the message contains the signature of base station 10, processor 200 decrypts the signature with its public key and determines whether the decrypted information is the same as the information contained in the certificate. If the information is different, the certificate has been tampered with and processor 200 stops processing the message and returns to step S500.

If the message contains the signature of mobile terminal 30, processor 200 decrypts the signature with the public key of mobile terminal 30 obtained from server 20 or from mobile terminal 30 itself, and the decrypted information is included in the certificate. It is determined whether or not the information is the same as the information to be received. If the information is different, the certificate has been tampered with and processor 200 aborts the process and returns to step S500.

If step S507a or steps S513a and S513b are executed correctly, the processor 200 proceeds to step S514 and reads the context of the mobile terminal 30 whose identifier is included in the message from the RAM memory 203.

In the next step S515, the processor 200 transfers the context of the mobile terminal 30 to the base station 10 which is expected to service the mobile terminal 30 via the network interface 204.

Base station 10 stops servicing mobile terminal 30, processor 200 removes the associated context from RAM memory, then returns to step S500 and waits for a message to be received.

Note that when the base station 10 starts or stops providing the service to the mobile terminal 30, the base station 10 notifies the server 20.

5b and 5c disclose an algorithm executed by a base station according to a second embodiment of the present invention.

This algorithm is executed by each base station 110 of the wireless network. More precisely, it is executed by the processor 200 of each base station 110.

In step S530, processor 200 detects the receipt of a message.

In the next step S531, the processor 200 checks whether the message is transmitted from the base station 110 or the mobile terminal 130. If the message is transmitted from base station 110, the message is being received via network interface 204, at which time processor 200 proceeds to step S550. Otherwise, the message has been received via wireless interface 206 and processor 200 proceeds to step S532.

In step S532, processor 200 checks to see if the received message contains a list of base station 110 identifiers.

If the message contains a list of base station 110 identifiers, processor 200 proceeds to step S536. If the message does not include a list of base station 110 identifiers, processor 200 proceeds to step S533.

Steps S533 to S535 are the same as steps S503 to S505 in FIG. 5a and will not be described thereafter. When step S535 is executed, processor 200 returns to step S530 and waits for a new message.

If the message received in step S530 includes a list of base station 110 identifiers, processor 200 proceeds from step S532 to step S536.

The message is the same as the message transferred in step S460 of FIG. 4b and is received by base station 110e.

According to the example disclosed with reference to FIG. 4b, the list of base station identifiers is ordered and includes the identifier of base station 110 in which mobile terminal 130 manages cell 115 that has advanced through it. The first identifier in the list is the identifier of base station 110e, the second identifier in the list is the identifier of base station 110d, the third identifier in the list is the identifier of base station 110c, in the list. The fourth identifier in is the identifier of base station 110b, and the last identifier in the list is the identifier of base station 110a.

In step S536, processor 200 determines whether there are multiple connections to and from base station 110 whose identifier is in the list of base station identifiers and whose rank in the list is lower than that of base station 110e's identifier. Find out.

If there are multiple connections, processor 200 proceeds to step S538 and selects the lowest ranked base station 110 identifier in the list of connected base station identifiers among the connected base station 110 identifiers. To do.

If there is only one connection established with one base station 110 whose identifier is included in the list of base station identifiers, processor 200 proceeds to step S539.

According to the example of FIG. 1b, the base station 110e is connected only to the base station 110d. At that time, the processor 200 proceeds to step S539 and selects the identifier of the base station 110d.

In the next step S540, processor 200 processes the received message. The process is to store the contents of the received message in RAM memory 203, or if it contains at least one signature, check the integrity of the message contents in step S541 before storing it. Consists of.

If the message contains the signature of base station 110a, the processor 200 decrypts the signature with the public key of base station 110a whose identifier is included in the message, and the decrypted information is included in the certificate. Judges whether or not it is the same as. If the information is different, the certificate has been tampered with and processor 200 aborts the process and returns to step S530.

If the message contains the signature of mobile terminal 130, the processor 200 decrypts the signature with the public key of mobile terminal 130 obtained from the server 120 or from the mobile terminal 130 itself, and the decrypted information is included in the certificate. It is determined whether or not the information is the same as the information to be received. If the information is different, the certificate has been tampered with and processor 200 aborts the process and returns to step S530.

Note that both of the above checks are performed when the received message contains two signatures.

By checking the integrity of the message, you can avoid malicious attacks.

If step S540, or steps 540 and S541, is executed correctly, processor 200 proceeds to step S542.

In that step, processor 200 includes a list of base station identifiers, an identifier for mobile terminal 130, and one or more signatures on the message received in step S530 on the finalized base station 110, i.e. base station 110d. If so, preferably transfer a message containing the signature of base station 110a and / or the signature of mobile terminal 130.

The processor 200 then returns to step S530.

If the message received in step S530 is transmitted from base station 110, processor 200 proceeds to step S550 to check whether the message includes the context of mobile terminal 130.

If the message contains the context of mobile terminal 130, processor 200 proceeds to step S551. If the message does not include the context of mobile terminal 130, processor 200 proceeds to step S558.

According to this example, base station 110d receives the message and processor 200 of base station 110d proceeds to step S558.

In step S558, processor 200 of base station 110d checks to see if the identifier of base station 110d is the last identifier in the list of base station identifiers. If the identifier of base station 110d is the last identifier in the list of base station identifiers, processor 200 proceeds to step S559, otherwise processor 200 proceeds to step S554.

According to this example, the identifier of base station 110d is not the last identifier in the list of base station identifiers, and processor 200 proceeds to step S554.

In step S554, processor 200 determines whether there are multiple connections to and from base station 110 whose identifier is in the list of base station identifiers and whose rank in the list is lower than that of base station 110d's identifier. Find out.

If there are multiple connections, processor 200 proceeds to step S556. If the identifier is included in the list and there is only one connection to and from base station 110 that has a lower rank in the list than the identifier of base station 110d, processor 200 proceeds to step S555 and that identifier. Select to proceed to step S557.

According to the example of FIG. 1b, the base station 110d is connected to the base stations 110c and 110b. At that time, the processor 200 proceeds to step S556 and selects the identifier of the base station 110 having the lowest rank in the list of the base station identifiers among the identifiers of the connected base stations 110, that is, the identifier of the base station 110b. To do.

In the next step S557, the processor 200 gives the determined base station, ie base station 110b, a list of base station identifiers, the identifier of the mobile terminal 130, and one or more signatures on the message received in step S530. If included, it preferably transfers a message including the signature of base station 110a and / or the signature of mobile terminal 130.

The processor 200 then returns to step S530.

The base station 110b receives such a message, executes steps S530, S531, S550, S558, S554 to S557, and receives the list of base station identifiers and the identifier of the mobile terminal 130 at the base station 110a. If the message contains one or more signatures, the message is preferably forwarded, including the signature of base station 110a and / or the signature of mobile terminal 130.

The base station 110a receives such a message and executes steps S530, S531, S550, and the processor 200 of the base station 110a is the last in the list of base station identifiers in which the identifier of the base station 110a is in step S558. Confirm that it is an identifier. The processor 200 then proceeds to step S559.

In the next step S559, processor 200 processes the received message. The process comprises storing the contents of the received message in the RAM memory 203, or checking the integrity of the contents of the message in step S560 before storing it.

Step S560 is the same as step S507b in FIG. 5a.

If step S559, or steps S559 and S560 are executed correctly, processor 200 proceeds to step S561.

In step S561, the processor 200 has a plurality of connections with the base station 110 whose identifier is included in the list of base station identifiers and whose rank is higher in the list of base station identifiers than that of the base station 110a. Check if it is.

If there are multiple connections, processor 200 proceeds to step S562. If the identifier is included in the list and there is only one connection established with one base station 110 that has a higher rank in the list than the identifier of base station 110a, processor 200 goes to step S561. Proceed, select the identifier, and proceed to step S563.

According to the example of FIG. 1b, the base station 110a is connected to the base stations 110b and 110c. The processor 200 proceeds to step S562 and selects the identifier of the base station 110c having the highest rank in the list of base station identifiers in the identification of the base stations 110d and 110c.

In the next step S563, the processor 200 reads from the RAM memory 203 the context of the mobile terminal 130 whose identifier is included in the message.

In the next step S564, processor 200 transfers the context of mobile terminal 130 to base station 110c with a list of base station identifiers via network interface 204.

Base station 110a stops servicing mobile terminal 130, and processor 200 removes the associated context from RAM memory 203. After that, the process returns to step S530 and waits for the message to be received.

Note that the base station notifies the server 120 when the base station 110 starts or stops providing services to the mobile terminal 130.

The base station 110c receives such a message, executes steps S530 and S531, and in step S550 determines that the message includes the context of mobile terminal 130. After that, the processor of the base station 110c proceeds to step S551.

In step S551, processor 200 of base station 110c checks to see if the identifier of base station 110c is the first identifier in the list of base station identifiers. If the identifier is the first identifier, processor 200 proceeds to step S570, otherwise processor 200 proceeds to step S554.

In step S554, processor 200 checks to see if there are multiple connections to and from base station 110 whose identifier is in the list of base station identifiers and whose rank is higher than that of base station 110c's identifier.

If there are multiple connections, processor 200 proceeds to step S556 and selects the highest ranked base station 110 identifier in the list of connected base station identifiers among the connected base station 110 identifiers. To do.

If the identifier is included in the list of base station identifiers and there is only one connection to and from base station 110 that has a higher rank in the list than the identifier of base station 110c, processor 200 goes to step S555. move on.

According to the example of FIG. 1b, the base station 110c is connected to a base station 110d whose identifier is included in the list of base station identifiers and has a higher rank than the identifier of the base station 110c in the list of base station identifiers. .. At that time, the processor 200 proceeds to step S555 and selects the identifier of the base station 110d.

In the next step S557, processor 200 transfers a message to the determined base station, i.e., base station 110d, containing a list of base station identifiers, the identifier of mobile terminal 130, and the context of mobile terminal 130.

The processor 200 then returns to step S530.

The base station 110d receives such a message and executes steps S530, S531, S550, S551, S554 to S557, and gives the base station 110e a list of base station identifiers, a mobile terminal 130 identifier, and a mobile terminal. Forward messages containing 130 contexts.

The base station 110e receives such a message, the processor 200 of the base station 110e executes steps S530, S531, S550, and in step S551, the identifier of the base station 110e is the first in the list of base station identifiers. Confirm that it is an identifier.

After that, the processor 200 of the base station 110e proceeds to step S570.

In step S570, processor 200 reads the context of mobile terminal 130 in the received message.

In step S571, processor 200 applies the context of the received mobile terminal 130 to ensure that the mobile terminal 130 is serviced by base station 110e.

In the next step S572, the processor 200 instructs the transfer of the acknowledgment message to the mobile terminal 130.

In the next step S573, processor 200 creates a message. Such a message includes at least the identifier of the base station 110, that is, the identifier of the base station 110e currently servicing the mobile terminal 130, and the unique identifier of the mobile terminal 130. Such messages preferably include a certificate.

The certificate is obtained by at least encrypting the unique identifier of the mobile terminal 130, the identifier of the base station 110e currently servicing the mobile terminal 130, and these identifiers with the private key of the base station 110e. Including signature.

In the next step S574, the processor 200 transfers the message created in the previous step via the wireless interface 206. The content of the message is replaced with the content of the message previously received from the base station 110a that previously provided the service to the mobile terminal 130 in the memory 303 of the mobile terminal 130.

The processor 200 then returns to step S530 and waits for a new message to be processed.

Here, in the first embodiment and the second embodiment of the present invention, the identifier of the base station is the identifier of the base station or the identifier of one or more cells managed by the base station 110. Please note.

Here, the list of base station identifiers is ordered from the last selected base station 110 to the first selected base station 110, while the list of base station identifiers is from the first selected base station 110 to the last. It can also be ordered in the order of the base stations 110 selected for. In such cases, processor 200 determines one or more identifiers with higher ranks instead of determining one or more base stations with lower ranks. Similarly, the processor 200 determines one or more identifiers with a lower rank instead of determining one or more identifiers with a higher rank. Instead of determining whether the base station identifier is the last identifier in the list, the processor 200 determines whether the base station identifier is the first identifier in the list, and the processor 200 determines whether the base station identifier is the first identifier in the list. Instead of determining if the base station identifier is the first identifier in the list, it determines if the base station identifier is the last identifier in the list.

Of course, many modifications can be made to the above embodiments of the present invention without departing from the scope of the present invention.

<figref num="1a">It is the first figure which shows the architecture of the mobile communication network by this invention.</figref><figref num="1b">It is a 2nd figure which shows the architecture of the mobile communication network according to this invention.</figref><figref num="2">It is a block diagram of a base station according to this invention.</figref><figref num="3">It is a block diagram of the mobile terminal according to this invention.</figref><figref num="4a">It is a figure which shows the algorithm executed by the mobile terminal by 1st Embodiment of this invention.</figref><figref num="4b">It is a figure which shows the algorithm executed by the mobile terminal by the 2nd Embodiment of this invention.</figref><figref num="5a">It is a figure which shows the algorithm executed by the base station by 1st Embodiment of this invention.</figref><figref num="5b">It is a figure which shows the algorithm executed by the base station by the 2nd Embodiment of this invention.</figref><figref num="5c">It is a figure which shows the algorithm executed by the base station by the 2nd Embodiment of this invention.</figref>