JP2005210300A - Hand-off method based on geographical range, and mobile terminal and program thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hand-off method or the like, whereby a mobile terminal can receive a packet transmitted from a communication opposite terminal, even if the mobile terminal is in the middle of moving to a different network. <P>SOLUTION: The mobile terminal 2 has an IPv6 address, denoting a packet reception area C and position registration operating border information whose area D is narrower than the area C, when the mobile terminal 2 exceeds the geographical range, on the basis of the position registration operating border information of the area D, the mobile terminal decides a new IPv6 address denoting a new area wherein packets can be received, and the mobile terminal 2 registers its position by means of the decided IPv6 address to a home agent apparatus 20 as a "care of" address. Further, when the mobile terminal 2 detects changes in the access point to another base station, the mobile terminal 2 transmits vicinity advertisement information to routers connected to the other base station for the recognition of the mobile terminal 2 by the routers. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a handoff method in a system in which a plurality of base stations that can communicate with a mobile terminal, a router connected to the base station, and a home agent device in mobile IP (Mobile Internet Protocol) are connected via an IP network. The present invention relates to the mobile terminal and the program.

  FIG. 1 is a conventional system configuration diagram.

  According to FIG. 1, the system comprises a mobile terminal 2, base stations 4 and 6, a communication partner terminal 8, a home agent device 20 in mobile IP, and an IPv6 network 11. The IPv6 network 11 includes routers 10-16. The communication partner terminal 8 is connected to the router 10, the base station 4 is connected to the router 12, the base station 6 is connected to the router 16, and the home agent device 20 is connected to the router 14.

  According to the mobile IP, the home agent device exists in the home network of the mobile terminal and holds a “Care-Of Address” indicating the current connection position of the mobile terminal. Mobile IPv6 (Mobility Support in IPv6 draft-ietf-mobileip-ipv6-24) is a protocol that is being standardized in IETF (Internet Engineering Task Force). According to this protocol, communication can be continued even if the mobile terminal moves to a different network. The terminal always has a home address (Home Address) that is the same address and a care-of address that is determined each time the terminal moves to a different network. Each time the mobile terminal moves through a different network, the care-of address indicating its current location is registered with the home agent device. As a result, the packet sent to the home address of the terminal is transferred to the care-of address by the home agent device, and the mobile terminal can receive the packet (communication partner → Home Agent → mobile terminal in this order). Packet passes). In this way, a series of procedures for the terminal to register a new care-of address with the home agent and transfer the data transfer destination is called handoff. In addition, the mobile terminal directly notifies the communication partner terminal of the care-of address by a method called Route Optimization, and enables packet transmission / reception without going through the home agent device.

  According to FIG. 1, the mobile terminal 2 exists in a region A that is a radio wave reachable range of the base station 4. The mobile terminal 2 holds the care-of address in the network in the area A in the home agent 20. Thereby, even if the communication partner terminal 8 transmits a packet to the home network of the mobile terminal 20, the packet is transferred to the network of the base station 4 by the care-of address held in the home agent device 20.

  At this time, it is assumed that the mobile terminal 2 has moved to a region B that is a radio wave reachable range of another base station 6. At that time, the mobile terminal 2 connects to the IPv6 network 11 via the base station 6 and acquires a new care-of address. Then, the mobile terminal 2 requests the home agent device 20 for location registration of the acquired care-of address. Thus, even if the communication partner terminal 8 transmits a packet destined for the home network, it is transferred to the mobile terminal 2 existing in the area B.

  FIG. 2 is a sequence diagram of a conventional mobile IP handoff method based on the system of FIG.

(S21) The communication partner terminal 8 acquires the care-of address (old CoA) addressed to the mobile terminal 2 held in the home agent device 20, and transmits the packet to the mobile terminal 102 via the router 112.
(S22) At this time, the mobile terminal 2 recognizes that it exists in the network of the router 16 by receiving router advertisement information periodically broadcast from the router 16.
(S23) It is assumed that the mobile terminal 2 has moved to a region B that is a radio wave reachable range of another base station 6. At that time, the mobile terminal 2 connects to the router 16 and acquires a new care-of address (new CoA).
(S24) The mobile terminal 2 makes a location registration request (Binding Update) to the home agent device 20 and the communication partner terminal 8 in order to register a new care-of address.
(S25) In response to this, a location registration response (Binding Ack) is received from the home agent device 20 and the communication partner terminal 8.
(S26) Thereby, the communication partner terminal 8 transmits the packet to the mobile terminal 2 via the router 16 with the new care-of address.

  As a conventional route control method, there is a method that enables packet transfer to a terminal based on position information acquired by a GPS (Global Positioning System) (see, for example, Non-Patent Document 1). . There is also a method of including a geographic range in an IPv6 packet (see Non-Patent Document 2, for example).

T. Imielinski, J. Navas, Rutgers University, “GPS-Based Addressing and Routing”, IETF, RFC2009, Experimental, November 1996. “Mapping Universal Geographical Area Description to IPv6 Geo Based Unicast Adders”, [online], IETF, Internet-Draft, draft-vanmegen-ipv6-addr-00, [November 21, 2003 search], Internet <URL: http : //www.watersprings.org/pub/id/draft-vanmegen-ipv6-addr-00.txt>

  However, according to the conventional sequence diagram shown in FIG. 2, the mobile terminal 2 moves to a different network, acquires a new care-of address, and registers the location with the home agent device 20 and the communication partner terminal 8. In the period up to (for example, about 5 seconds), the packet is transmitted to the old CoA and cannot be normally received. This is a significant problem while multimedia multimedia data such as moving image data or audio data is being received.

  Accordingly, an object of the present invention is to provide a handoff method, a mobile terminal, and a program for reducing a reception interruption that occurs when a mobile terminal changes a connection destination network.

  Before describing the present invention, it is one technique for achieving the above-described object, and is based on location information (hereinafter referred to as “GIP (Geographical Internet Protocol) address”) developed by the present inventors. ) Describe the system.

  The GIP address is composed of a network prefix part and a position information part, and the position information part represents specific position information and range information. That is, a normal IPv6 address represents a single host, while a GIP address corresponds to a certain geographic range. When a packet having a GIP address is received, the network prefix portion of the GIP address of the packet matches the GIP address set in advance in the terminal, and the geographic range represented by the location information portion is superimposed. In this case, it is determined that the packet is transmitted. Therefore, this GIP address system makes it possible to provide a service for transmitting / receiving a packet having an IP address based on position information and range information, even if there is no position information management server. For example, the position information part of the GIP address can express the position by “latitude” and “longitude”, express the range information by “distance” from the position, and set a “shape” such as a square or a circle. it can. If the “distance” is zero, it represents a point position.

  According to the handoff method of the present invention, the mobile terminal has a first location information indicating a first geographical range in which a packet can be received and an IP address including the first range information, and a range narrower than the first geographical range. First location registration operation boundary information, and when the mobile terminal exceeds the geographical range based on the first location registration operation boundary information, new second location information and second range information are displayed. And a second step of the mobile terminal registering the determined IP address as a care-of address with the home agent device. Thereby, it is possible to reduce the reception interruption that occurs when the mobile terminal changes the connection destination network. In particular, by acquiring a new GIP address before exceeding the packet reception range indicated by the GIP address, it becomes possible to continue receiving packets thereafter.

  According to another embodiment of the handoff method of the present invention, when the mobile terminal detects a change in the access point from the first base station to the second base station, it connects to the second base station. In order to make the router recognize the mobile terminal, it is preferable to further include a step of transmitting neighborhood advertisement information. As a result, the router that has received the neighborhood advertisement information can recognize that the mobile terminal is in the range under management and acquire the physical address.

  The mobile terminal according to the present invention includes a first location information indicating a first geographic range in which a packet can be received and an IP address including the first range information, and a first range indicating a range narrower than the first geographic range. IP that has position registration operation boundary information and determines a new IP address based on the second position information and the second range information when the geographical range based on the first position registration operation boundary information is exceeded. It is characterized by having an address determination means and a location registration means for registering the determined IP address as a care-of address of the home agent device.

  According to another embodiment of the mobile terminal of the present invention, when a change in the access point from the first base station to the second base station is detected, the router connected to the second base station In order to recognize the mobile terminal, it is preferable to further include means for transmitting neighborhood advertisement information.

  The mobile terminal program according to the present invention includes a first location information indicating a first geographical range in which a packet can be received and an IP address including the first range information, and a first range indicating a narrower range than the first geographical range. 1 location registration operation boundary information, and when the geographical range based on the first location registration operation boundary information is exceeded, a new IP address is determined based on the second location information and the second range information. The computer is caused to function as an IP address determining means for performing location registration for registering the determined IP address as a care-of address of the home agent device.

  According to another embodiment of the mobile terminal program of the present invention, when a change in the access point from the first base station to the second base station is detected, the mobile terminal is connected to the second base station. In order for the router to recognize the mobile terminal, it is also preferable to have the computer function so as to further include means for transmitting neighborhood advertisement information.

  Furthermore, according to another embodiment of the present invention described above, it is also preferable that the position information is composed of latitude and longitude acquired by the global positioning system. Thereby, position information can be acquired easily.

  Furthermore, according to the other embodiments of the present invention described above, the IP address is preferably based on an IPv6 address. Thereby, it is possible to sufficiently secure the designated areas for the position information and the range information in the IP address.

  According to the present invention, even when the mobile terminal is moving to a different network, the mobile terminal can receive the packet transmitted from the communication counterpart terminal. In particular, by acquiring a new GIP address before exceeding the packet reception range indicated by the GIP address, it becomes possible to continue receiving packets thereafter.

  In addition, when the mobile terminal detects a change in the access point, the router recognizes that the mobile terminal exists in the managed range by transmitting the neighborhood advertisement information to the router, and acquires the physical address. Can do.

  Furthermore, according to the present invention, position information can be easily acquired by GPS, and by applying to an IPv6 address, a designated area for position information and range information can be sufficiently secured.

  Hereinafter, the best embodiment of the present invention will be described with reference to the drawings.

  FIG. 3 is an explanatory diagram of a GIP address system which is one component of the present invention.

  According to FIG. 3, the GIP address is composed of a 64-bit network prefix part and a 64-bit position information part.

  The network prefix part is exactly the same as the network prefix in normal IPv6. Therefore, as a matter of course, the route control for the network having the predetermined network prefix can be performed by the existing router. The network prefix is assigned to a service unit provided in a certain network. It is assumed that the terminal that wants to receive the service information knows the corresponding network prefix. For example, when a user selects a service information item to be acquired on the display screen, a network prefix based on the service information is selected.

  The location information part corresponds to a part called a host identifier in normal IPv6. According to FIG. 1, the position information section includes “latitude” and “longitude”, “distance (range)”, “form” bit, and “partial / complete match” bit.

For example, 47 bits are required to express the position on the earth with accuracy of 0.1 seconds (about 3.0 m) for “latitude” and “longitude” as follows.
(Latitude) 180 degrees × 60 minutes × 600 (in units of 0.1 seconds) = 6480000 ≈ 23 bits (Longitude) 360 degrees × 60 minutes × 600 (in units of 0.1 seconds) = 1299600000≈24 bits
47 bits in total

  Here, an actual application example of latitude and longitude will be described. For example, a case will be described in which a certain terminal acquires information on its own position as 48 degrees 07.038247 north latitude and 11 degrees 31.324523 east longitude. This value is converted to a hexadecimal number in units of 0.1 seconds.

48 degrees 07.038247 minutes (north latitude) → (48 + 90) x 36000 + 7.038247 x 600
= 4968623 (decimal)
= 4BD0AF (Hexadecimal: last 23 bits)
11 degrees 31.324523 minutes (east longitude) → 11 × 36000 + 31.324523 × 600
= 414794 (decimal)
= 06544A (Hexadecimal: 24 bits)

According to FIG. 3, the following GIP address is obtained.
3FFE: 0: 0: 1: 2328: 4BD0: AF06: 544A
(Network prefix) | (Distance) | (Latitude: North latitude) | (Longitude: East longitude)
This GIP address has a network prefix of “3FFE: 0: 0: 1 :: / 64”, and a terminal located at 48 degrees 07.038247 north latitude and 11 degrees 31.324523 east longitude is 15 minutes away (16 in 0.1 second increments). Representing a geographic range of 2328 in decimal). Here, latitude information is expressed by 24 bits (the most significant bit is fixed at 0) for simplicity.

  FIG. 4 is an explanatory diagram for determining the overlap of geographical ranges between the GIP address of the terminal itself and the GIP address of the received packet.

  A description will be given of determination as to whether or not a received packet can be received as a destination packet to the terminal (whether or not the packet can be notified to an upper layer). This determination is determined by comparing the geographic range represented by the GIP address of the received packet with the geographic range represented by the GIP address set in advance by the terminal, and whether or not there are overlapping portions. .

  According to FIG. 4, the geographical range is determined by the method in the upper part of FIG. The geographic range A0 in FIG. 4 is a geographic range based on the GIP address of the terminal. On the other hand, the GIP address of the received packet indicates the geographic range A1. At this time, there is a portion that overlaps (x1 to x1 + d1) and (x0 to x0 + d0) based on the x axis, and there is a portion that overlaps (y1 to y1 + d1) and (y0 to y0 + d0) based on the y axis. It is judged by whether or not. In this case, it is determined that the geographic range A0 and the geographic range A1 are partially overlapped. At this time, if the “partial match / complete match” bit is “partial match”, it is determined that the packet indicating the geographic range A1 can be received.

  Further, when the GIP address of the received packet indicates the geographic range A2, there is a portion overlapping (y2 to y2 + d2) and (y0 to y0 + d0) based on the y axis, but based on the x axis (x2 to x2 + d2). And (x0 to x0 + d0) do not overlap. Accordingly, it is determined that the packet cannot be received because there is no overlapping portion between the geographic range A0 and the geographic range A2.

  Further, when the GIP address in the received packet indicates the geographic range A3, (x3 to x3 + d3) based on the x axis is completely included in (x0 to x0 + d0) and (y3 to y3 + d3) based on the y axis is (Y0 to y0 + d0) are completely included. Therefore, since the geographical range A3 is completely included in the geographical range A1, if the “partial match / complete match” bit is “partial match”, it is determined that the packet can be received.

  According to the present invention, since the route control is performed for a packet having a GIP address, at least a router connected to the base station must control the route of the packet by the GIP address. The router has a routing table represented by a set of entries including a destination address and a next hop address. According to the present invention, the geographical ranges of the destination GIP address and the GIP address of the received packet are compared, and the packet is transferred to the next hop address for all the partially matching entries.

  Further, according to FIG. 4, the location registration operation boundary is indicated by a broken line inside the geographic range A1 indicated by the GIP address. When the distance from the geographic area A1 to the inside is ds, if the distance is within the range of (x0 + ds to x0 + d0-ds) and (y0 + ds to y0 + d0-ds), location registration does not work and the boundary is exceeded. A location registration request is activated.

  FIG. 5 is a system configuration diagram according to the present invention.

  According to FIG. 5, compared to FIG. 1, the mobile terminal 2 defines the area C indicated by the GIP address, and the mobile terminal 2 receives a packet targeting a geographical range overlapping with the area C. It is comprised so that. Area A represents the radio wave reachable range of the base station 4, and the source mobile terminal 2 is present. Area B represents the radio wave reachable range of the base station 6, and the mobile terminal 2 moves to that area. Here, it is assumed that the area A of the base station 4 and the area B of the base station 6 have a portion that overlaps a part thereof.

(Position P1) Since the mobile terminal 2 exists in the area A that can communicate with the base station 4, it is under the network management of the GIP router 12 via the base station 4. In addition, the mobile terminal 2 defines a region C and a region D based on the GIP address. Region C represents a receivable range of a packet indicated by a GIP address designated in advance by the mobile terminal 2. A region D is a boundary where the mobile terminal 2 operates a location registration operation, and represents a boundary narrower than the region C. The position registration operation boundary of the region D is represented by a value ds that is somewhat smaller inward from the boundary of the region C.
(Position P2) It is assumed that the mobile terminal 2 moves to a position beyond the area A and the position exists in the area B where the base station 6 can communicate. At this time, the mobile terminal 2 establishes a connection with the base station 6 by switching the access point. Thereafter, the mobile terminal 2 notifies the base station 6 that the mobile terminal 2 has moved under the network management of the GIP router 16 by transmitting neighbor advertisement information.
(Position P3) Furthermore, the mobile terminal 2 acquires a GIP address that is a care-of address of a new network when the area D that is a position registration operation boundary is exceeded. The new GIP address designates an area E that is a receivable area and an area F that is a location registration operation boundary. Then, the home agent apparatus 20 is requested to register the location using the GIP address as a care-of address.
(Position P4) Furthermore, the mobile terminal 2 is moving, and even at this position, it is under the network management of the GIP router 16 via the base station 6.

  As described above, when the mobile terminal 2 moves over the area D, it is assumed that the area C will also exceed the area C. Therefore, at this time, a GIP address indicating a new area E is acquired. Repairing is extremely effective. This is because, at a position beyond the area C, the connection is released even within the radio wave reachable range of the base station, and packets based on the GIP address cannot be received.

  FIG. 6 is a sequence diagram of the present invention based on the system of FIG.

(S61: Position P1) The mobile terminal 2 holds an area C indicating a packet reception range as a GIP address and an area D indicating a position registration operation boundary. In addition, the mobile terminal 2 exists in a region A that is a radio wave reachable range of the base station 4.
(S62) It is assumed that the mobile terminal 2 has moved to a position beyond the area A which is the radio wave reachable range of the base station 4. At this time, the mobile terminal 2 can no longer communicate with the base station 4, but is present in the region B that is the radio wave reachable range of the base station 6, so that the base station 6 can be found. Then, the mobile terminal 2 establishes a connection with the base station 6.
(S63: Position P2) The mobile terminal 2 transmits the neighborhood advertisement information to the GIP router 16 via the base station 6. The GIP router 16 that has received the neighborhood advertisement information recognizes that the mobile terminal 2 has moved into the network managed by the mobile terminal 2 itself. That is, the router 16 can obtain the physical address of the mobile terminal 2. In this case, the mobile terminal 2 can receive a packet from the base station 6 using the GIP address indicating the region C.
(S64) Furthermore, it is assumed that the mobile terminal 2 has moved to a location within the range of the region C indicating the packet reception range and beyond the region D indicating the location registration operation boundary.
(S65: Position P3) At this time, the mobile terminal 2 updates the GIP address indicating the area E of the new packet reception range. Then, the mobile terminal 2 transmits a location registration request message to the home agent device 20 using the updated GIP address as a care-of address. In response to this, the home agent device 20 transmits a location registration response message to the mobile terminal 2. Thereby, the packet transmitted to the home address of the mobile terminal 2 is received by the mobile terminal 2 existing at the position indicated by the care-of address.
(S66) After that, even if the mobile terminal 2 exceeds the range of the area C specified by the previous GIP address, communication is possible by the area E specified by the new GIP address.

  FIG. 7 is a functional block diagram of a mobile terminal according to the present invention.

  The mobile terminal 2 includes an input unit 201, a location information measurement unit 203, a geographic range information designation unit 204, a network prefix designation unit 205, a GIP address determination unit 206, a GIP address accumulation unit 207, and a current location determination unit. 208, a location registration operation boundary accumulation unit 209, and a location registration message transmission / reception unit 210. Furthermore, the mobile terminal 2 includes an access point change detection unit 202 and a neighborhood advertisement information transmission unit 212.

  The position information measuring unit 203 measures the position information “latitude” and “longitude” of the mobile terminal 2 based on data received from the GPS. The location information measurement unit 203 notifies the current location information determination unit 208 of the location information when the location information of the mobile terminal 2 changes. Of course, the position information may be notified every predetermined time period.

  The geographic area information designation unit 204 designates geographic area information based on the information received from the input unit 201. For example, with respect to the position information, it is a circular radius or the length of one side of a square. The designated geographical range information is notified to the GIP address determination unit 206.

  The network prefix designation unit 205 designates a network prefix based on the information received from the input unit 201. For example, it is uniquely determined by service information that the user wants to receive. The designated network prefix is notified to the GIP address designation unit 206.

  The GIP address determination unit 206 includes the location information “latitude” “longitude” from the location information measurement unit 203, the geographic range information “distance” from the geographic range information designation unit 204, and the network prefix from the network prefix designation unit 205. The GIP address is determined. The fact that the GIP address is determined by “latitude”, “longitude”, “range”, and “network prefix” has been described above with reference to FIG. The determined GIP address is notified to the GIP address accumulation unit 207, the location registration operation boundary accumulation unit 209, and the location registration message transmission / reception unit 210.

  The GIP address accumulation unit 207 stores the GIP address notified from the GIP address determination unit 206. The GIP address includes information on “latitude”, “longitude”, and “distance”, and the range specified by the information is specifically represented by (x0 to x0 + d0) and (y0 + y0 + d0). The

  The location registration operation boundary accumulation unit 209 stores location registration operation boundary information based on the GIP address from the GIP address determination unit 206. For example, the position registration operation boundary information has the same position information, and is obtained by reducing the value of the geographical range information (for example, the radius of the circular shape or the length of one side of the square) by a certain value. Since the location registration operation boundary is narrower than the range specified by the GIP address, it is determined as d0-ds. ds indicates a distance that becomes narrower inward than the designated range of the GIP address. Specifically, as shown in FIG. 4, information of (x0 + ds to x0 + d0−ds) and (y0 + ds to y0 + d0−ds) is accumulated.

  The current position determination unit 208 is based on the current position information of the mobile terminal from the position information measurement unit 203, the GIP address from the GIP address storage unit 207, and the position registration operation boundary information from the position registration operation boundary storage unit 209. judge. The current position determination unit 208 instructs the GIP address determination unit 206 to re-acquire the GIP address when the current position of the mobile terminal is within the packet reception range indicated by the GIP address and exceeds the position registration operation boundary. To do. On the other hand, when the current position of the mobile terminal 2 is inside the position registration operation boundary, the current position determination unit 208 does not instruct the GIP address determination unit 206 at all.

  Since the current location information of the mobile terminal is represented by “latitude” y and “longitude” x, the current location is included in the range specified by the GIP address beyond the location registration operation boundary. Can be determined. Specifically, “longitude” x of the current position is included in the range of (x0 to x0 + ds) or (x0 + d0−ds to x0 + d0), and in the range of (y0 + y0 + ds) or (y0 + d0−ds to y0 + d0). If the “latitude” y of the current position is included, it can be determined that the current position exceeds the position registration operation boundary and is included in the range specified by the GIP address.

  As described above, the current position determination unit 208 determines whether or not the current position has exceeded the position registration operation boundary every time new position information is notified from the position information measurement unit 203 as the mobile terminal 2 moves. doing. Thereby, the timing when the mobile terminal 2 is handed off can be detected.

  The location registration message transmission / reception unit 210 transmits a location registration request to the home agent device 20 when the notification of the GIP address is received from the GIP address determination unit 206, that is, when the care-of address is updated. Thereby, the home agent device 20 holds the care-of address updated for the mobile terminal 2. Thereby, handoff is realizable.

  Next, when the radio wave from the base station 4 stops reaching, the access point change detection unit 202 detects radio waves from other base stations. For example, when it is detected that the radio wave from the base station 6 has arrived, the neighborhood advertisement information transmitting unit 212 transmits the neighborhood advertisement information to the base station 6.

  The embodiments described above are all illustrative and do not limit the present invention, and the present invention can be implemented in other various modifications and changes. In particular, in FIG. 7, the characteristic functions of the mobile terminal are described as a block configuration, but it is within the scope of the creativity of those skilled in the art that each function can be realized by a program. Therefore, the scope of the present invention is defined only by the claims and their equivalents.

It is a conventional system configuration diagram. FIG. 2 is a sequence diagram in a conventional mobile IP handoff method based on the system of FIG. 1. It is explanatory drawing of the GIP address system which is one component of this invention. It is explanatory drawing for determining the superimposition of the geographical range of the GIP address of an own terminal, and the GIP address of a received packet. 1 is a system configuration diagram according to the present invention. FIG. 6 is a sequence diagram of the present invention based on the system of FIG. 5. It is a function block diagram of the mobile terminal by this invention.

Explanation of symbols

2,102 Mobile terminal 4,104,6,106 Base station 7 GPS
8, 108 Communication partner terminal 10, 110, 12, 112, 14, 114, 16, 116 GIP router 11, 109 IPv6 network 20, 120 Home agent device 201 Input means 202 Access point change detection unit 203 Location information measurement unit 204 Geography Range information designation unit 205 Network prefix designation unit 206 GIP address determination unit 207 GIP address accumulation unit 208 Current location determination unit 209 Location registration operation boundary accumulation unit 210 Location registration message transmission / reception unit 212 Neighbor Advertisement information transmission unit

Claims (12)

In a handoff method in a system in which a plurality of base stations that can communicate with a mobile terminal, a router connected to the base station, and a home agent device in mobile IP are connected via an IP network,
The mobile terminal includes a first location information indicating a first geographic range in which a packet can be received, an IP address including the first range information, and a first location registration indicating a range narrower than the first geographic range. Operating boundary information,
A first step of newly determining an IP address based on second location information and second range information when the mobile terminal exceeds a geographic range based on the first location registration operation boundary information;
And a second step in which the mobile terminal registers the determined IP address as a care-of address of the home agent device.   When the mobile terminal detects a change in an access point from the first base station to the second base station, the mobile terminal is connected to the router connected to the second base station in order to recognize the mobile terminal. The handoff method according to claim 1, further comprising a step of transmitting advertisement information.   The handoff method according to claim 1 or 2, wherein the position information includes latitude and longitude acquired by a global positioning system.   The handoff method according to any one of claims 1 to 3, wherein the IP address is based on an IPv6 address. In a mobile terminal capable of communicating via a plurality of base stations between a router and a home agent device in mobile IP,
First location information indicating a first geographic range in which a packet can be received, an IP address including the first range information, and first location registration operation boundary information indicating a range narrower than the first geographic range. Have
IP address determining means for newly determining an IP address based on the second position information and the second range information when the geographical range based on the first position registration operation boundary information is exceeded;
A mobile terminal comprising: location registration means for registering the determined IP address as a care-of address with the home agent device.   When a change in the access point from the first base station to the second base station is detected, neighbor advertisement information is transmitted to cause the router connected to the second base station to recognize the mobile terminal The mobile terminal according to claim 5, further comprising means.   The mobile terminal according to claim 5 or 6, wherein the position information includes latitude and longitude, and further includes means for acquiring the position information by a global positioning system.   The mobile terminal according to any one of claims 5 to 7, wherein the IP address is based on an IPv6 address. A program in a mobile terminal capable of communicating via a plurality of base stations between a router and a home agent device in mobile IP,
First location information indicating a first geographic range in which a packet can be received, an IP address including the first range information, and first location registration operation boundary information indicating a range narrower than the first geographic range. Have
IP address determining means for newly determining an IP address based on the second position information and the second range information when the geographical range based on the first position registration operation boundary information is exceeded;
A program that causes a computer to function as location registration means for registering the determined IP address as a care-of address of the home agent device.   When detecting a change in the access point from the first base station to the second base station, the neighbor advertisement information is transmitted to make the router connected to the second base station recognize the mobile terminal. The program according to claim 9, wherein the computer is caused to function so as to further include means for performing the processing.   The program according to claim 9 or 10, wherein the position information includes latitude and longitude, and causes the computer to further include means for acquiring the position information by a global positioning system. The program according to any one of claims 9 to 11, wherein the IP address is based on an IPv6 address.

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