JP2001258058A - Hand-over method, mobile station and base station - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hand-over method that allows a portable telephone to conduct efficient transmission of data. SOLUTION: Upon the receipt of a beacon signal sent from a base station agent BA, a terminal agent MA mounted on a portable telephone 10 makes a request for agent information to the base station agent BA and stores the agent information sent from the base station agent BA, in response to the request. In the case of conducting hand-over method, when a channel is selected in a data link layer, the terminal agent MA uses the agent information stored in advance, to switch IP connection in a network layer, following the channel switching.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile communication network handover method for providing a mobile station with a mobile Internet protocol connection, and a mobile station and a base station used in the method.

[0002]

2. Description of the Related Art In recent years, portable telephones that can be connected to the Internet via a portable communication network have become widespread. This type of mobile phone can perform packet communication, for example, browse a homepage provided by a server on the Internet, or download various contents from the server. By the way, in a communication service using a mobile phone, a cellular system in which a communication service area includes a large number of cells is generally adopted.
In this cellular system, a process of switching the radio channel each time the mobile phone moves to a different cell, that is, a so-called handover, is performed, whereby the mobile phone maintains a communication line connected state even when moving to a different cell. can do.

Hereinafter, referring to FIGS. 16 and 17,
This handover will be described in detail. In FIG.
The mobile phone MS performs packet communication by mobile IP (Internet Protocol) with the server ISP on the Internet INET via the base station BS and the mobile communication network MN. The base station BS holds a channel table in which the MS-ID of the mobile phone MS located in the wireless cell and the communication channel name assigned to the terminal are recorded in association with each other. The home memory HM includes identification information of the mobile phone MS (hereinafter, referred to as MS-ID),
It holds a routing table in which the IP address of a base station agent included in a base station BS that is performing wireless communication with the terminal is recorded in association with the IP address. Thus, the MS-ID of the mobile phone MS is stored in the home memory HM.
The storage of the IP address of the base station agent and the IP address of the base station agent are hereinafter referred to as mobile registration. The mobile communication network MN refers to the home memory HM, and the mobile phone M
Routing of data transmitted to S is performed. The operation of this routing is specifically as follows.

[0004] Now, base station BS1 and base station BS2,
Each transmits a beacon signal including identification information for identifying each base station BS (hereinafter referred to as BS-ID). On the other hand, the mobile phone MS has the base stations BS1 and B
While receiving the beacon signal transmitted from S2,
The radio wave intensity at the time of receiving the signal is measured. The mobile phone MS transmits the BS-
A base station list (not shown) for storing the ID and the radio wave intensity of the beacon signal in association with each other is provided, and the content of the base station list is updated each time a beacon signal is received. The mobile phone MS determines an optimal base station BS for performing wireless communication with reference to the base station list. When the optimum base station BS changes, the mobile phone MS determines that the mobile phone MS has moved to a different wireless cell C, and switches the wireless channel in the data link layer to the optimum base station BS. Hereinafter, the base station BS that is optimal for this wireless communication and that is to switch the wireless channel is referred to as a switching destination base station.

[0005] When the cellular phone MS is located in the wireless cell C1, it performs data communication with the server ISP via a wireless line with the base station BS1. FIG.
(A) is a schematic diagram showing a communication connection between the mobile phone MS and the base station BS1 at a communication protocol level.
As shown in the figure, a channel in the data link layer is connected between the mobile phone MS and the base station BS1, and an IP connection is made in a higher network layer. Here, the data link layer means a communication protocol for identifying and transferring data between directly connected communication devices, that is, between the mobile phone MS and the base station BS. The network layer is a communication protocol for managing addresses on the network and routing data transmitted on the network. Here, a mobile IP connection is made between the server ISP and the mobile phone MS. Meaning protocol.

Next, the operation of the mobile phone MS moving to the radio cell C2 and switching the IP connection accompanying the handover will be described with reference to the sequence shown in FIG. When the mobile phone MS receives the beacon signal from the base station BS2 (step Sf1), the base station list B
The BS-ID and the radio wave intensity included in the beacon signal are recorded on L (step Sf2). Then, the mobile phone MS refers to the base station list BL, and the radio wave intensity of the beacon signal received from the base station BS2 is higher than the base station B
When it is detected that the radio wave intensity of the beacon signal received from S1 has become stronger, it is determined that the mobile station is located in the radio cell C2 of the base station BS2, and a response signal including its own MS-ID is returned to the base station BS2. (Step Sf3). on the other hand,
Upon receiving the response signal, the base station BS2 specifies the mobile phone MS based on the MS-ID included in the signal, and performs a synchronization process with the mobile phone MS (step Sf4). As a result, as shown in FIG. 17B, the channel in the data link layer is switched from the base station BS1 to the base station BS2.

[0007] When the channel is switched to the base station BS2, the IP connection is switched from the base station BS1 to the base station BS2 in the network layer as follows. The base station BS1 and the base station BS2 intermittently transmit a message signal for switching the IP connection, separately from the above-described beacon signal. This message signal contains information necessary for the mobile phone MS to switch the IP connection to the base station BS2, that is, the base station BS2.
2 includes the IP address of the base station agent included in the base station agent 2. The mobile phone MS connects the channel in the data link layer with the base station BS2,
The message signal transmitted from the base station BS2 can be received. When the mobile phone 10 receives the message signal from the base station BS2 (step Sf5), it extracts an IP address from the message signal and adds a mobile registration request signal obtained by adding its own MS-ID thereto to the base station B.
Reply to S2 (step Sf6). This move registration request signal is a signal for requesting the home memory HM to perform move registration. When receiving the movement registration request signal, the base station BS2 transfers this to the home memory HM. In the home memory HM, the MS-I
D and the IP address are extracted, and movement registration is performed.
By this movement registration, data transmitted to the mobile phone MS can be routed. As a result, as shown in FIG.
This means that the P connection has been switched from the base station BS1 to the base station BS2.

[0008]

As described above, after performing the handover, the mobile phone MS waits until a message signal intermittently transmitted from the base station BS is received, and receives the message signal. Starts the IP connection switching in the network layer. Therefore, a delay time DT as shown in FIG. 18 exists between the time when the mobile phone MS performs the handover and the time when the message signal is received. During a period corresponding to the delay time DT, as shown in FIG. 17B, the mobile phone MS is connected to the base station BS1 in the data link layer.
Channel connection with the base station BS2 in the network layer. In such a case, since the routing table of the home memory HM stores the BS-ID of the base station BS1 corresponding to the MS-ID of the mobile phone MS, the packet transmitted from the server IPS is It reaches BS1. However, as shown in FIG. 17B, since the channel in the data link layer is disconnected between the base station BS1 and the mobile phone MS, the base station B
The packet delivered to S1 loses its destination and is discarded as it is. The discarded packet is retransmitted to the mobile phone MS after the IP connection is switched from the base station BS1 to the base station BS2. As described above, since the switching of the IP connection in the network layer may be performed with a delay due to the switching of the channel in the data link layer, the packet is discarded unnecessarily, and the traffic of the network is reduced by the subsequent retransmission processing. For example, there is a problem that the data transmission efficiency is deteriorated, such as increase.

Incidentally, the data transmission speed of the wired transmission path between the base station BS and the switching center (not shown) differs depending on the traffic expected in the base station BS. For example, in FIG. 16, when the base station BS1 is installed in a downtown area and the base station BS2 is installed in a suburban area, the traffic is expected to be large at the base station BS1, and the traffic is expected to be large at the base station BS2. Expected to be small. In such a case, the wired transmission path CB1 connecting the base station BS1 and the mobile communication network MN, and the base station B
The data transmission speed is different from the wired transmission path CB2 connecting S2 and the mobile communication network MN. On the other hand, the mobile phone MS does not consider such a situation on the side of the base station BS, and based on the radio wave intensity of the beacon signal transmitted from the base station BS, the base station BS that is assumed to be closest to its own position.
Is designed to perform handover for As described above, since the mobile phone MS does not necessarily perform handover to the base station BS having a high data transmission speed, this may be inefficient in terms of data transmission to the mobile phone MS.

[0010] The present invention has been made in view of such a background, and an object of the present invention is to provide a handover method, a mobile station, and a base station for performing more efficient data transmission.

[0011]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the invention described in claim 1 is directed to a mobile internet protocol (hereinafter referred to as I) for a mobile station via a base station.
In a handover method of a mobile communication network for providing a connection, a handover switching destination base station is selected,
A first step of switching a channel to the switching destination base station in a data link layer, and a movement for a mobile IP connection in a communication layer higher than the data link layer in response to the channel switching in the data link layer. A second step of transmitting a registration message from the mobile station to the mobile communication network side; and a third step of performing switching processing of the mobile IP connection according to the mobile registration message. .

According to a second aspect of the present invention, in the handover method according to the first aspect, the second step includes the following:
Requesting the switching destination base station for the IP address of an agent existing ahead of the base station, including the IP address transmitted from the switching destination base station to the mobile station in response to the request Transferring the mobile registration message from the mobile station to the mobile communication network side.

According to a third aspect of the present invention, in a handover method of a mobile communication network for providing a mobile IP connection to a mobile station via a base station, a step of selecting a base station to be a candidate for a handover switching destination, Securing a channel connection in the data link layer at the selected base station as a switching destination candidate, and providing an IP of an agent existing ahead of the base station to the base station of the switching destination candidate connected to the channel. Requesting an address, storing an IP address transmitted from the base station to the mobile station in response to the request, selecting a handover switching destination base station, and selecting the switching destination base station in the data link layer. Switching the channel to the station, including the stored IP address, Transmitting a mobile registration message for a mobile IP connection in an upper communication layer from the mobile station to the mobile communication network; and performing a mobile IP connection switching process in accordance with the mobile registration message. It is characterized by doing.

According to a fourth aspect of the present invention, in the handover method according to the third aspect, the step of selecting the base station to be the switching destination candidate includes the step of the mobile station transmitting a beacon signal transmitted from the base station. The selection is made based on the radio wave intensity at the time of reception.

According to a fifth aspect of the present invention, in a handover method of a mobile communication network for providing a mobile IP connection to a mobile station via a base station, data transmission from the base station to the mobile station is performed at the base station. Transmitting a beacon signal including information about the mobile station, receiving the beacon signal at the mobile station, storing information about the data transmission included in the beacon signal, based on the information about the stored data transmission And a base station selecting step of selecting a handover switching destination base station.

According to a sixth aspect of the present invention, in the handover method according to the fifth aspect, the step of giving flow identification information for identifying the flow of the data to the data to be received by the mobile station is provided. The base station selecting step is characterized in that a handover switching destination base station is selected for each piece of the flow identification information.

According to a seventh aspect of the present invention, in a mobile station accommodated in a mobile communication network and performing a mobile IP connection through a base station of the network, a handover switching destination base station is selected and a data link layer is selected. Channel switching means for performing channel switching to the switching destination base station; and, in response to the channel switching in the data link layer, transmitting a mobility registration message for mobile IP connection in a communication layer higher than the data link layer. Message transmitting means for transmitting to the communication network side.

According to an eighth aspect of the present invention, in the mobile station according to the seventh aspect, the message transmitting means requests the switching destination base station for an IP address of an agent existing ahead of the base station. IP address request means;
Transfer means for transferring, to the mobile communication network, a mobility registration message including the IP address transmitted from the switching destination base station in response to the request.

According to a ninth aspect of the present invention, in a mobile station accommodated in a mobile communication network and performing a mobile IP connection via a base station of the network, candidate selection for selecting a base station to be a handover switching destination candidate is provided. Means, first channel switching means for performing channel switching in the data link layer for the selected base station, and agent existing ahead of the base station for the channel switched base station IP address requesting means for requesting the IP address of the mobile station, storage means for storing the IP address transmitted from the base station to the mobile station in response to the request, and selecting a handover switching destination base station, A second channel switching unit for performing channel switching to the switching destination base station in a link layer, and a second channel switching unit that performs channel switching by the second channel switching unit. The mobile station transmits a mobile registration message for mobile IP connection in a communication layer higher than a data link layer, including the stored IP address of the switching destination base station, from the mobile station to the mobile communication network side. Message transmitting means.

According to a tenth aspect of the present invention, in the mobile station according to the ninth aspect, the candidate selecting means is configured to determine a beacon signal transmitted from the base station based on a radio wave intensity when the mobile station receives the beacon signal. And selecting a base station that is a switching destination candidate.

[0021] The invention according to claim 11 relates to data transmission transmitted from the base station in a mobile station accommodated in a mobile communication network and making a mobile IP connection via a base station of the network and transmitted by the base station. Receiving means for receiving a beacon signal containing information, a step of storing information on the data transmission included in the received beacon signal, and a handover switching destination base station based on the stored information on the data transmission. And selecting means for selecting.

[0022] According to a twelfth aspect of the present invention, in the mobile station according to the eleventh aspect, a flow identification for giving flow identification information for identifying a flow of the data to data to be received by the mobile station. An information providing unit is provided, and the switching request signal includes the flow identification information.

According to a thirteenth aspect of the present invention, in a base station performing wireless communication with a mobile station performing mobile IP connection via a mobile communication network, channel switching in the data link layer is performed between the mobile station and the base station. Channel switching means, request receiving means for receiving a request for an IP address of an agent existing ahead of the base station from a mobile station which has performed channel switching in the data link layer, and said IP address in response to the request. IP address transmitting means for transmitting to the mobile station, and a mobile registration message for mobile IP connection in a communication layer higher than the data link layer, including the transmitted IP address, is received from the mobile station and transferred to a predetermined device. And transfer means for performing the transfer.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A: Principle of Embodiment Before starting detailed description, the principle of the embodiment will be described. In this embodiment, instead of waiting for an IP address to be transmitted from a base station after channel switching in the data link layer as in the related art, the mobile phone mainly performs peripheral operations before starting handover. And obtains an IP address from the base station, and holds this on a list. Therefore, this list includes the I-type corresponding to the base station which is the candidate for the handover switching by the mobile phone.
The P address is stored, and this is called an address list in the embodiment. And mobile phones are
After performing channel switching in the data link layer to the base station that is a handover switching destination, the base station requests IP connection switching using an IP address obtained by referring to the address list.

B: First Embodiment A first embodiment of the present invention will be described below with reference to the drawings. B-1: Configuration (1) Overall Configuration of System FIG. 1 is a block diagram showing the overall configuration of the system according to the embodiment. As shown in FIG. 1, the system includes a mobile phone 10, a mobile communication network 20, an Internet 30,
And the information providing server 40.

The mobile phone 10 is accommodated in a mobile communication network 20 and performs voice communication and packet data communication through the network 20. This mobile phone 10 has an I
A terminal agent MA is installed as software for switching the P connection. The mobile communication network 20
Base stations 21-1 to 21-3, exchange 22, relay center 2
3 and a communication line connecting them. Base station 21-
1-21-3 are wireless cells 200-1 through 200, respectively.
-3, and performs wireless communication with the mobile phone 10 located in the wireless cells 200-1 to 200-3. Each of the base stations 21-1 to 21-3 incorporates base station agents BA1 to BA3 as software for performing IP connection switching accompanying handover in cooperation with the terminal agent MA of the mobile phone 10. The exchange 22
A predetermined number of base stations 21-1 to 21-3 are accommodated, and radio cells 200-1 to 200- of the base stations 21-1 to 21-3 are accommodated.
The exchange processing of the communication line of the mobile phone 10 located in the area 3 is performed. The relay center 23 is connected to the exchange 22 and
The Internet 30 via a gateway device (not shown)
It is connected to the. The relay center 23 relays data communication between the mobile phone 10 and the information providing server 40. The relay center 23 is a mobile phone 1 that performs data communication.
The home agent HA is installed as software for performing the routing of the “0”. The information providing server 40 is connected to the Internet 30 via a router (not shown).

(2) Configuration of Base Station 21 Next, the configuration of the base station 21 will be described. FIG. 2 is a block diagram illustrating a hardware configuration of the base station 21. As shown in the figure, the base station 21 includes a wireless communication unit 210, a network interface 211, a control unit 212, and a bus 213 connecting these components to each other. The wireless communication unit 210 includes an antenna (not shown), a wireless communication control circuit, and the like, and performs wireless communication with the mobile phone 10. The network interface 211 transmits and receives signals to and from the mobile communication network 20. The data transmission speed of the network interface 211 differs for each base station 21 in accordance with expected traffic. The control unit 212 includes a CPU (Ce
ntral Processing Unit), ROM (Read Only Memor)
y) and a RAM (Random Access Memory). ROM
Is a program memory. The CPU reads and executes a control program stored in the ROM,
It controls the entire base station 21. This control program includes:
The base station agent BA described above is included.

Next, the functional configuration of the base station 21 will be described. Here, one of the functions of the base station 21 will be described with reference to FIG.
One base station agent BA will be described. The other functions provided in the base station 21 are provided in a general base station and are well known, and thus description thereof is omitted. As shown in the figure, the base station agent BA is composed of a data link processing unit BDD for performing handover in the data link layer, and a network processing unit BND for switching IP connection in the network layer. The data link processing unit BDD includes a beacon signal transmission unit BT
And a synchronization processing unit BAD. The beacon signal transmission unit BT generates a beacon signal including base station information related to the base station 21 and transmits the beacon signal to the inside of the wireless cell 200.
This beacon signal is a signal that triggers a handover in the data link layer, and its configuration will be described later. The synchronization processing unit AD1 receives a response signal transmitted from the terminal agent MA that has received the beacon signal, and performs synchronization processing with the terminal agent MA in response to the response signal.

The network processing unit ND comprises a request message receiving unit RA, an agent message transmitting unit MT, and a movement registration request receiving unit MR. The request message receiving unit RA receives a request message transmitted from the terminal agent MA. This request message is a message indicating that the terminal agent MA is requesting an agent message.
Upon receiving the request message from the terminal agent MA, the agent message transmitting unit MT generates an agent message and transmits it to the terminal agent MA. This agent message contains agent information related to the base station agent BA,
The configuration will be described later. Transfer registration request reception unit MR
Receives the mobile registration request message transmitted from the terminal agent MA and transfers it to the home agent HA. This transfer registration request message is a message for requesting transfer registration to the home agent HA, and its configuration will be described later.

Structure of Beacon Signal Here, the structure of the above-described beacon signal will be described with reference to FIG. As shown in the figure, the beacon signal includes base station information including a BS-ID, a lifetime, and a transmission rate. This beacon signal is a signal that triggers handover in the data link layer, and each base station agent BA1 to BA3 transmits this beacon signal using a control channel that can be received by all terminal agents MA. Has become. BS-
The ID is identification information for identifying each base station 21. The lifetime is information indicating the expiration date of the base station information broadcast by the beacon signal. The transmission speed is the data communication speed of the communication unit BSb of the base station BS.

Next, the structure of the above-described agent message will be described with reference to FIG. As shown in the figure, the agent message includes agent information including an agent ID, a lifetime, an IP address, and a BS-ID. This agent message is a message necessary for handover at the network layer, and each base station agent BA transmits an agent message to the terminal agent MA in response to a request from the terminal agent MA. . The agent ID is identification information for specifying each base station agent BA. The lifetime is information indicating the expiration date of the agent information transmitted by the agent message. The IP address is the IP address of each base station agent BA as described above, and the BS-ID is the identification information of the base station 21.

Structure of Move Registration Request Message Next, the structure of the above move registration request message will be described with reference to FIG. As shown in the figure, the mobile registration request message includes the MS-I
D, the agent ID and the IP address of the base station agent. The mobile registration request message transmitted from the terminal agent is the base station agent BA
And is received and stored by the home agent HA.

(3) Configuration of Mobile Phone 10 Hardware Configuration of Mobile Phone 10 FIG. 7 is a block diagram showing a hardware configuration of the mobile phone 10. As shown in FIG.
It comprises a wireless communication unit 11, a user interface unit 12, a control unit 13, and a bus 14 interconnecting these. The wireless communication unit 11 includes an antenna (not shown) and a wireless communication control circuit, and performs wireless communication with the base station 21. The user interface unit 12 includes a microphone and a speaker (not shown) for the user to make a call, a keypad for the user to perform an input operation, and a liquid crystal display for displaying various information. The control unit 13 includes a CPU (not shown),
It consists of OM and RAM. The ROM is a program memory, and the CPU loads a control program stored in the ROM into the RAM and controls the entire mobile phone 10. This control program includes the terminal agent MA described above.
Is included.

Next, a functional configuration of the mobile phone 10 will be described. Here, the terminal agent MA, which is one of the functions of the mobile phone 10, will be described with reference to FIG. Note that other functions of the mobile phone 10 are omitted since they are well-known and provided by general mobile phones. As shown in FIG.
A is composed of a data link processing unit MDL that performs handover in the data link layer, and a network processing unit MNW that performs handover in the network layer.

The data link processing unit MDL includes a beacon signal receiving unit BR, a base station list management unit BLC, and a synchronization processing unit MAD. The beacon signal receiving unit BR receives a beacon signal transmitted from the base station agent BA. The base station list management unit BLC includes a base station list BL that stores base station information included in the received beacon signal, and updates the list BL. The terminal agent MA can determine the switching destination base station 21 by referring to the base station list BL. In addition to the switching destination base station 21, the terminal agent MA determines the base station 21 which is located relatively close to the mobile phone 10. You can also understand. The configuration of the base station list BL will be described later. Synchronization processing unit MAD
Performs a synchronization process with the synchronization processing unit BAD of the base station agent BA. When the synchronization processing unit MAD completes synchronization processing with the synchronization processing unit BAD of the base station agent BA, it means that handover in the data link layer has been performed.

The network processing unit MNW includes an agent message processing unit MD and an address list management unit AL
C and a move registration request unit RR. The message processing unit MD transmits a request message requesting an agent message to the base station agent BA, and receives an agent message transmitted from the base station agent BA in response to the request message. The address list management unit BLC has an address list AL that stores agent information included in the received agent message, and updates the list AL. Agent information that the terminal agent MA has collected in advance from the surrounding base station agent BA is stored in the address list AL. The configuration of the address list AL will be described later. The mobile registration request transmission unit RR generates a mobile registration request message requesting the home agent HA to perform mobile registration, and transmits this message.

Configuration of Base Station List BL Here, with reference to FIG.
The contents of L will be described. As shown in the figure, the base station list BL stores a lifetime, a reception time, a transmission speed, a radio field intensity, and a communication flag corresponding to each BS-ID. The BS-ID, the lifetime, and the transmission speed are base station information included in the beacon signal received by the terminal agent. The signal strength is the terminal agent M
This is a value indicating the strength of the radio wave of the signal when A receives the beacon signal. Since each base station agent BA transmits a beacon signal with a common strength, the beacon signal received with the strongest signal strength is transmitted to the terminal agent MA.
Can be determined to have been transmitted from the base station agent BA located closest to the base station. Accordingly, the terminal agent MA sets the base station agent BA corresponding to the strongest radio field intensity on the base station list BL as the switching destination base station agent BA to which the handover is to be switched, and sets the communication flag corresponding to the agent BA. Set to ON.
The reception time indicates the time at which the terminal agent MA has received the beacon signal. When the lifetime has elapsed from the reception time, the base station information including the lifetime, the radio field intensity and the communication flag corresponding to the base station information are displayed. , Are deleted from the base station list BL. That is, old base station information for which a certain period has elapsed is deleted, and only relatively new base station information is held on the base station list BL.

Structure of Address List AL Next, the contents stored in the address list AL will be described with reference to FIG. As shown in the figure, the address list ML includes a lifetime, a reception time, an IP address, a BS-
The ID is stored. The agent ID, the lifetime, and the IP address are agent information included in the agent message received by the terminal agent. The reception time indicates the time at which the terminal agent MA has received the agent message. When the lifetime elapses from the reception time, the agent information corresponding to the lifetime is deleted from the address list ML. That is, similarly to the base station list BL, on the address list ML, old information whose fixed period has elapsed is deleted, and only relatively new information is retained.

Thus, on the address list AL,
Terminal agent MA is in the vicinity of base station agent B
Agent information collected from A is stored. The terminal agent MA is a switching destination base station agent BA
When performing an IP connection in the network layer between the home agent HA and the home agent HA, agent information corresponding to the base station agent BA is acquired with reference to the address list BL. Send. That is, since the terminal agent MA holds the agent information on the address list AL in advance, it is possible to eliminate the trouble of requesting the agent information when performing the IP connection in the network layer with the base station agent BA. Thus, the processing can be executed quickly.

(4) Configuration of Home Agent HA Next, the configuration of the home agent HA will be described. FIG. 11 is a block diagram showing the configuration of the home agent. As shown in FIG.
A includes a routing processing unit RD and a routing table RT. Routing table RT
Stores the MS-ID of the mobile phone 10, the agent ID and the IP address of the base station agent BA in association with each other. The routing processing unit RD includes:
The data transmitted to the mobile phone 10 is routed with reference to the routing table RT.

B-2: Operation Next, the operation of the embodiment having the above configuration will be described. When voice communication or data communication of the mobile phone 10 is started, the terminal agent MA executes a main routine shown in FIG. 12 and updates the base station list BL according to a beacon signal transmitted from the base station agent BA. . Further, the terminal agent MA collects the agent information from the base station agent BA, and performs a handover process with the base station agent BA using the previously collected agent information when the terminal agent MA is located in a different wireless cell 210. In the following, (1) base station list BL
, Update of (2) collection of agent information, and (3) handover processing.

(1) Update of Base Station List BL In FIG. 12, when voice communication or data communication of the mobile phone 10 is started, the processing of the terminal agent MA proceeds to step Sc1. In step Sc1, the terminal agent MA receives a beacon signal transmitted from the base station agent BA via the control channel, and measures the radio field intensity when the signal is received.

Next, the process proceeds to step Sc2. In step Sc2, the terminal agent MA extracts base station information from the received beacon signal, and extracts this information together with the reception time and the measured radio field intensity in the base station list B.
L. Then, the terminal agent MA refers to the base station list BL and sets the communication flag on for the base station information including the strongest radio field intensity.

Next, the process proceeds to step Sc3, where the terminal agent MA determines whether or not the switching destination base station agent BA has been changed on the base station list BL.
Here, if the switching destination base station agent BA has been changed, the terminal agent MA shifts to a handover process described later in order to perform a handover to the switching destination base station agent BA.

On the other hand, if the switching destination base station agent BA has not been changed, the process proceeds to step Sc5. In step Sc5, the terminal agent MA refers to the base station list BL and sets a predetermined threshold value indicating that the radio field intensity of the beacon signal received in step Sc1 is a radio field level at which data communication is possible. It is determined whether or not this is the case. Here, if the radio wave intensity is less than the threshold, the process returns to step Sb1. On the other hand, if the signal strength is equal to or greater than the threshold, the terminal agent MA
And base station agent B that transmitted the beacon signal
Since data communication with A is possible, the process shifts to agent information collection processing to be described later in order to collect agent information of the base station agent BA.

(2) Collection of Agent Information Next, the operation of the terminal agent MA to collect agent information will be described with reference to the flow shown in FIG. In step Sd1 shown in the figure, the terminal agent MA refers to the address list AL and the BS-ID included in the received beacon signal, and
Is determined in the address list AL. Here, if the agent information is stored in the address list AL, it is not necessary to further collect the already held agent information, so that the processing is performed in step S of the main routine described above.
Return to c1. On the other hand, if the agent information is not stored in the address list AL, the processing of the terminal agent MA proceeds to step S in order to collect the agent information.
Proceed to d2.

In step Sd2, the terminal agent MA performs a synchronization process with the base station agent BA that has transmitted the beacon signal, and performs channel connection in the data link layer. In this synchronization processing, the multiple access method of the mobile communication network is, for example, TDMA (Time Division Multiple).
In the case of iple Access), the process is performed using a free time other than the time slot used by the mobile phone 10 during communication. Similarly, the processing in steps Sc3 to Sc4 described below is also performed using a free time other than the time slot used by the mobile phone 10.

When the channel connection is made in the data link layer, the process proceeds to step Sd3. Step Sd
In 3, the terminal agent MA transmits a request signal requesting an agent message to the base station agent BA connected to the channel.

Then, in step Sd4, the terminal agent MA receives an agent message transmitted from the base station agent BA in response to the request signal.

Next, in step Sd5, the terminal agent MA extracts the agent information from the received agent message, adds the reception time thereto, and stores it in the address list AL.

By performing the processing described above, the terminal agent MA can hold the agent information of the peripheral base station agent BA in the address list AL in advance.

(3) Handover Processing Next, an operation in which the terminal agent MA performs handover with the base station agent BA will be described with reference to the flow shown in FIG. Step Se1 shown in FIG.
In, the terminal agent MA performs a synchronization process with the switching destination base station agent BA to perform channel switching in the data link layer.

Next, the process proceeds to Step Se2. In step Se2, the terminal agent MA refers to the BS-ID included in the received beacon signal and determines whether or not the agent information of the base station agent BA corresponding to the BS-ID is stored in the address list AL. I do. Here, as described above, since the agent information should have been collected from the base station agent BA that is a switching destination candidate, in this step Se2, the switching destination base station agent BA is included in the address list AL. Agent information should be present.
However, when the mobile phone 10 starts communication immediately after the power is turned on, or when the mobile phone 10 starts communication immediately after moving from the outside of the communication range to the communication range, the agent information is obtained in advance from the switching destination base station agent BA. It is assumed that there is no case. In such a case, the terminal agent MA needs to acquire the agent information again. Therefore, if the agent information is not stored in the address list AL, the processing proceeds to step Se3 in order for the terminal agent MA to acquire the agent information. On the other hand, if the agent information is stored in the address list AL, the process of the terminal agent MA proceeds to Step Se6 described later.

In step Se3, the terminal agent MA transmits a request signal requesting an agent message to the switching destination base station agent BA.

Then, in step Se4, the terminal agent MA receives an agent message transmitted from the switching destination base station agent BA in response to the request signal.

Next, at step Se5, the terminal agent MA extracts the agent information from the received agent message, adds the reception time to the agent information, and stores it in the address list AL.

Then, in step Se6, the terminal agent MA transmits a movement registration request message to the switching destination base station agent BA with reference to the address list AL. The mobile registration request message includes the MS-ID of the mobile phone 10, the agent ID of the base station agent BA, and the IP address. The transmitted mobile registration request message is transmitted to the base station agent BA.
To the home agent HA, and stored in the routing table RT of the home agent HA. This means that an IP connection has been made at the network layer between the terminal agent MA and the base station agent BA. Then, when an IP connection is made in the network layer, the process returns to the main routine described above.

According to the above-described first embodiment, the agent information necessary for handover in the network layer is collected in advance, and when the channel is switched in the data link layer, the network layer immediately follows the switch. Is performed, the discarded packet data is reduced.

C: Second Embodiment C-1: Configuration and Operation of Second Embodiment The configuration and operation of the second embodiment will be described below. The hardware configuration of the second embodiment is the same as the hardware configuration of the first embodiment, and a description thereof will not be repeated. The second embodiment is different from the first embodiment in that the terminal agent MA does not perform the handover based on the radio wave intensity of the beacon signal, but the switching destination base station agent BA based on the transmission speed included in the beacon signal. And performs handover with the base station agent BA. Specifically, in step Sc2 of the main routine in FIG. 12 described above, the terminal agent MA refers to the base station list BL and sets the presence flag on for the base station agent BA corresponding to the highest transmission rate. I do. Then, when the switching destination base station agent BA changes, the terminal agent MA performs handover with the new switching destination base station agent BA. Also, in the second embodiment, the same processing as in the first embodiment is performed for collecting the agent information.

As described above, according to the second embodiment, since the handover is performed with the base station 21 having the highest transmission speed among the base stations 21 located within a distance in which data communication is possible, the mobile phone 10 is more capable of performing the handover. High-speed data communication can be performed, and data transmission efficiency is improved.

C-2: Application Example of Second Embodiment In the above-described second embodiment, the terminal agent MA
On the other hand, instead of uniquely assigning the base station agent BA that performs handover, the base station agent BA may be assigned for each data flow received by the mobile phone 10. That is, for each data flow received by the mobile phone 10, a flow ID for identifying the flow is assigned, and the base station agent BA of the base station 21 having a data transmission capacity suitable for the data amount of the data flow. The handover is performed by designating the flow ID. Hereinafter, this operation will be described in detail.

FIG. 15 is a sequence showing the operation of the entire system for performing handover for each data flow. First, when the mobile phone 10 is communicatively connected to the information providing server 40, the user selects a desired content from a content menu provided by the information providing server, and performs an operation of requesting download of the content. The mobile phone 10 accepts the operation and assigns a flow ID to the content download process to distinguish the content download process from other data flows (step Sg1).
Then, the mobile phone 10 transmits a content request signal including the flow ID and identification information for identifying the content (hereinafter, referred to as C-ID) to the information providing server 40 (step Sg2).

Now, the content menu also includes information indicating the data amount of each content, so that the terminal agent MA can know the data amount of the content requested to be downloaded. Therefore, the terminal agent MA refers to the base station list BL and extracts the base station agent BA corresponding to the data transmission capacity suitable for the data amount of the content (step Sg).
3). That is, if the data amount of the content is relatively large, the base station agent BA with a high transmission rate included in the base station information is extracted. The base station agent BA having a low transmission rate is extracted. The association between this data amount and the base station agent BA is appropriately determined according to the average data amount of the content and the transmission capacity in the network.

Next, the terminal agent MA generates a response signal in response to the beacon signal transmitted from the extracted base station agent BA, and transmits this to the base station agent BA. The base station agent BA receives this response signal and synchronizes with the mobile phone 10 (step Sg4). This means that handover at the data link layer has been performed between the terminal agent MA and the base station agent BA.

Next, the terminal agent MA transmits a movement registration request signal including the flow ID, the MS-ID, the agent ID, and the IP address (step Sg).
5). This movement registration request signal is hereinafter referred to as a flow-specific movement registration request signal in a sense to distinguish it from the above-mentioned normal movement registration request signal.

This flow-specific mobile registration request signal is transmitted to the home agent HA via the base station agent BA (step Sg6). Home agent 23
Upon receiving the flow-specific movement registration request signal, the flow controller updates a flow-specific routing table (not shown) (step Sg7). The MS-ID, the agent ID, and the agent address are stored in the routing table for each flow in correspondence with the flow ID.

Now, upon receiving the content request signal from the mobile phone 10, the information providing server 40 converts the content data indicated by the C-ID extracted from the signal into
It transmits to the home agent HA together with the flow ID and the MS-ID (step Sg8).

On the other hand, the home agent HA sends the content data, flow I
When D and MS-ID are received, an agent address corresponding to the flow ID is acquired by referring to the routing table for each flow. Home Agent H
A is an IP packet containing the acquired agent address for an IP packet composed of content data and MS-ID.
The packet is added to the P header and encapsulated, and transmitted to the base station agent BA (step Sg9).

The base station agent BA includes the encapsulated agent address, content data and MS
Upon receiving the -ID, only the IP packet composed of the content data and the MS-ID is extracted from these, and the IP packet is transmitted to the mobile phone 10 indicated by the MS-ID (step Sg10). When the mobile phone 10 receives the IP packet, the terminal agent MA sends a reception completion notification to the home agent HA (step Sg11). Upon receiving the content reception completion notification from the terminal agent MA, the home agent HA deletes the information in the flow-specific routing table in response to the notification (step Sg12).

C-3: Supplement In the above-described second embodiment, it has been described that the handover is performed based on the transmission speed based on the first embodiment. However, it can be said that the data transmission efficiency is improved by the process itself of performing the handover based on the transmission speed. Therefore, the handover process of the second embodiment does not necessarily have to be based on the first embodiment, and may be performed independently of the first embodiment.

D: Modification As described above, the present invention is not limited to the above-described embodiment.
The following various changes are possible. D-1: Arrangement of Base Station Agent BA In the embodiment, each base station 21 is connected to the base station agent BA.
Was implemented, but the present invention is not limited to such a form. The base station agent BA only needs to perform processing related to handover for each base station 21. For example, the exchange 2
2 may be provided with a base station agent BA, and this base station agent BA may perform processing related to handover for each base station 21.

D-2: Form of Mobile Station In the embodiment, the mobile phone 10 having a call function is used as the mobile station. However, the present invention is not limited to this. For example, a PHS (Personal Handyphone System) dedicated to data communication or the like may be used. There may be.

D-3: Arrangement of Information Providing Server 40 In the embodiment, the information providing server 40 is the Internet 3
Although the mobile communication network 20 is connected to the mobile communication network 20 through the network 0, the present invention is not limited to this arrangement. That is, the transmitting node that transmits data to the mobile phone 10 does not need to be on the Internet 30 and may be included in the mobile communication network 20 or may be included in the mobile communication network 20 via a network such as a LAN.
May be connected.

D-4: Selection of Switching Destination Base Station and Selection of Switching Destination Candidate Base Station In the embodiment, the switching destination base station is selected based on the radio wave intensity of the beacon signal received by the mobile phone. A base station as a switching destination candidate was selected. However, the criterion for this selection is not limited to the radio wave intensity, but may be another criterion such as the quality of a radio signal grasped by error control.

D-5: Modified Example of Second Embodiment In the embodiment, the base station agent BA at the switching destination is determined based on the transmission rate included in the beacon signal. However, the present invention is not limited to this. If the information is related to the information, it can be used as a basis for determining the switching destination base station agent BA. For example, information on traffic in the base station 21 may be included in the beacon signal, and the switching destination base station agent BA may be determined based on this information.

[0076]

According to the above-mentioned invention, the mobile Internet protocol connection in the upper communication layer is switched when the channel is switched in the data link layer.
The time required for connection is reduced. By shortening this period, the amount of discarded packet data is reduced, and efficient data transmission can be performed. Furthermore, since the IP address required for switching the mobile Internet protocol connection is acquired in advance from the base station which is a candidate for the switching destination of the handover and is stored, the mobile registration message can be promptly transmitted when the IP connection is switched. Can be generated. Further, since the mobile station performs the handover based on the information related to the data transmission, it is possible to perform higher-speed data communication.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an entire system according to a first embodiment of the present invention.

FIG. 2 is a block diagram illustrating a hardware configuration of a base station according to the embodiment.

FIG. 3 is a block diagram showing a functional configuration of a base station agent in the embodiment.

FIG. 4 is a diagram showing a configuration of a beacon signal in the embodiment.

FIG. 5 is a diagram showing a configuration of an agent message in the embodiment.

FIG. 6 is a diagram showing a configuration of a move registration request message in the embodiment.

FIG. 7 is a block diagram showing a configuration of the mobile phone according to the embodiment.

FIG. 8 is a block diagram showing a functional configuration of a terminal agent in the embodiment.

FIG. 9 is a format diagram showing an example of contents stored in a base station list in the embodiment.

FIG. 10 is a format diagram showing an example of contents stored in an address list in the embodiment.

FIG. 11 is a block diagram showing a functional configuration of a home agent in the embodiment.

FIG. 12 is a flowchart in the embodiment.

FIG. 13 is a flowchart in the embodiment.

FIG. 14 is a flowchart in the same embodiment.

FIG. 15 is a sequence showing an operation in the second embodiment.

FIG. 16 is a schematic diagram illustrating a conventional handover.

FIG. 17 is a schematic diagram illustrating a conventional handover and switching of an IP connection at a communication protocol level.

FIG. 18 is a sequence illustrating a conventional handover.

[Explanation of symbols]

 Reference Signs List 10: mobile phone, MA: terminal agent, 20: mobile communication network, 21-1 to 21-3: base station, BA: base station agent 22: switching station, 23 ... Relay center HA ... Home agent 30 ... Internet 40 ... Information server

 ──────────────────────────────────────────────────続 き Continuing on the front page F term (reference) 5K030 GA03 HA08 HB29 HC01 JL01 JT09 LB08 LC06 5K033 AA01 CA12 CB01 CB08 CB14 DA03 DA05 DA17 EC03 5K034 AA02 AA03 DD01 EE03 EE09 EE13 FF10 FF11 HH01 HH02 MM11 AA15 BB04 DD11 DD19 DD44 EE02 EE10 HH23 JJ31 JJ39 9A001 BB04 BB06 CC02 CC05 CC06 JJ12 JJ25 JJ27

Claims (13)

[Claims] 1. A handover method for a mobile communication network for providing a mobile Internet protocol (hereinafter, Internet Protocol is abbreviated as IP) connection to a mobile station via a base station, comprising the steps of: selecting a handover switching base station; A first step of performing channel switching to the switching destination base station in a link layer, and a mobile registration for a mobile IP connection in a communication layer higher than the data link layer in response to the channel switching in the data link layer A handover comprising: a second step of transmitting a message from the mobile station to the mobile communication network side; and a third step of switching the mobile IP connection in response to the mobile registration message. Method. 2. The handover method according to claim 1, wherein the second step includes: requesting the switching destination base station for an IP address of an agent existing ahead of the base station; Generating a mobile registration message including the IP address transmitted from the switching destination base station to the mobile station, and transferring the mobile registration message from the mobile station to the mobile communication network side. Handover method. 3. A handover method for a mobile communication network for providing a mobile IP connection to a mobile station via a base station, the method comprising the steps of: selecting a base station to be a handover switching destination candidate; In a base station, a step of securing a channel connection in a data link layer, and a step of requesting an IP address of an agent existing ahead of the base station to the base station of a switching destination candidate connected to the channel, Storing an IP address transmitted from the base station to the mobile station in response to the request; selecting a handover switching destination base station and performing channel switching to the switching destination base station in a data link layer And a communication layer that includes the stored IP address and is higher than the data link layer. Transmitting a mobile registration message for mobile IP connection from the mobile station to the mobile communication network side, and performing a mobile IP connection switching process according to the mobile registration message. The handover method is as follows. 4. The handover method according to claim 3, wherein the step of selecting a base station to be a switching destination candidate includes a step of selecting a base station as a switching destination candidate, based on a radio wave intensity when the mobile station receives a beacon signal transmitted from the base station. A handover method, wherein the selection is performed based on the following. 5. A handover method for a mobile communication network for providing a mobile IP connection to a mobile station via a base station, the base station transmits a beacon signal including information on data transmission in the base station to the mobile station. Transmitting, the mobile station receiving the beacon signal, and storing information on the data transmission included in the beacon signal, based on the stored information on data transmission, a handover switching destination base station And a base station selecting step of selecting a base station. 6. The handover method according to claim 5, further comprising a step of adding, to data to be received by the mobile station, flow identification information for identifying a flow of the data, wherein the base station selection is performed. The step is for each of the flow identification information,
A handover method comprising selecting a handover switching destination base station. 7. A mobile station accommodated in a mobile communication network and performing a mobile IP connection via a base station of the network, selects a handover switching destination base station, and selects a handover switching destination base station in a data link layer. Channel switching means for performing channel switching, and a message for transmitting, to the mobile communication network side, a mobile registration message for mobile IP connection in a communication layer higher than the data link layer in response to the channel switching in the data link layer. A mobile station comprising transmitting means. 8. The mobile station according to claim 7, wherein the message transmission unit requests the switching destination base station for an IP address of an agent existing ahead of the base station. Generating a mobile registration message including the IP address transmitted from the switching destination base station in response to the request,
Transfer means for transferring the data to the mobile communication network. 9. A mobile station accommodated in a mobile communication network and performing a mobile IP connection via a base station of the network, a candidate selecting means for selecting a base station to be a handover switching destination candidate, First channel switching means for performing channel switching in the data link layer with respect to the base station; and IP for requesting the IP address of an agent existing ahead of the base station to the base station in which the channel switching has been performed. Address requesting means, storing means for storing the IP address transmitted from the base station to the mobile station in response to the request, selecting a handover switching destination base station, and selecting the switching destination base station in the data link layer A second channel switching unit for performing channel switching to the station, and storing and storing the second channel switching unit in response to the channel switching by the second channel switching unit. Message transmission means for transmitting a mobile registration message for mobile IP connection in a communication layer higher than a data link layer from the mobile station to the mobile communication network side, including an IP address of a switching destination base station to be switched. A mobile station, characterized in that: 10. The mobile station according to claim 9, wherein the candidate selection unit is a switching destination candidate based on a radio wave intensity when the mobile station receives a beacon signal transmitted from the base station. A mobile station characterized by selecting a base station. 11. A mobile station accommodated in a mobile communication network and performing a mobile IP connection via a base station of the network, receives a beacon signal transmitted from the base station and including information on data transmission in the base station. Receiving means, and storing information on the data transmission included in the received beacon signal; based on the stored information on the data transmission,
A selection unit for selecting a handover switching destination base station. 12. The mobile station according to claim 11, further comprising: flow identification information assigning means for assigning, to data to be received by the mobile station, flow identification information for identifying a flow of the data, The mobile station, wherein the switching request signal includes the flow identification information. 13. A base station that performs wireless communication with a mobile station that makes a mobile IP connection via a mobile communication network, comprising: a channel switching unit that performs channel switching in a data link layer with the mobile station; Request accepting means for accepting a request for an IP address of an agent existing ahead of the base station from a mobile station that has performed channel switching in the link layer; and an IP address for transmitting the IP address to the mobile station in response to the request. A mobile registration message for a mobile IP connection in a communication layer higher than a data link layer, including a transmitting unit and the transmitted IP address,
And a transfer unit for receiving from the mobile station and transferring to a predetermined device.