JP2006121468A - Mobile terminal and radio system switching control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mobile terminal and a radio system switching control method for preventing the execution of position registration which is made invalid as a result, and for preventing the deterioration of communicating efficiency. <P>SOLUTION: This mobile terminal for performing access through either a first radio base station belonging to a mobile telephone communication network or a second radio base station belonging to a radio LAN communication network to the Internet by selectively using two radio equipment such as a portable telephone and a radio LAN communication unit is configured to detect the validity/invalidity of the radio communication of each radio equipment from the reception strength of the transmission radio wave of the base station in the portable telephone and radio LAN communication equipment, and to detect the moving speed of the mobile terminal, and to decide the switching necessity/non-necessity of the radio communication system based on the valid/invalid state of the communication of the radio equipment, the moving speed and identification information showing the radio equipment which is selected at present, and to switch the radio equipment according to the decision result. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a mobile terminal and a radio system switching control method, and more particularly to a mobile terminal and a radio system switching control method provided with a plurality of radio communication apparatuses having different systems such as a mobile phone, a wireless LAN, and a DSRC.

  In recent years, car navigation with built-in mobile phone data communication function or mobile phone connection is becoming widespread, and the mobile phone function is used to connect car navigation to the Internet, and the server and information on the Internet. It has become possible to communicate. As wireless devices capable of data communication, there are, for example, a wireless LAN that can be used outdoors, a DSRC (Dedicated Short Range Communication) that is used in an automatic toll collection system on a highway, and the like in addition to a mobile phone. One mobile terminal such as car navigation is equipped with two wireless devices with different wireless communication methods as described above, and a technique for continuing communication while appropriately switching to a wireless device with good reception radio waves from a base station is as follows: This is called seamless roaming.

  As an example of a communication network to which seamless roaming is applied, there is a Mobile IP network schematically shown in FIG. Mobile IP is a technology standardized as “IP Mobility Support” in RFC (Request For Comment) 2002 related to Internet communication.

  In FIG. 5, 21 is a home network of the mobile terminal 10, 22 is a network to which the mobile terminal 10 is moved, 23 is a communication partner network to which a server 50 to be a communication partner of the mobile terminal 10 is connected, These networks are interconnected by the Internet 20. Connected to the home network 21 of the mobile terminal 10 is a home agent 40 for managing the current location of the mobile terminal 10 and controlling transfer of IP packets addressed to the mobile terminal 10 to the destination network.

  In Mobile IP, the IP address of the mobile terminal 10 assigned in the home network is defined as the home address, and the communication partner device communicates with the mobile terminal 10 via the home agent 40 as will be described later. Even when moving to another network other than the home network, packet communication using the home address is enabled. Here, the packet transfer operation when the mobile terminal 10 that has started packet communication with the communication partner server 50 while connected to the home network 21 moves from the home network 21 to the destination network 22 as shown in the figure will be described.

  The IP packet sent by the communication partner server 50 to the home address of the mobile terminal 10 is transferred to the home network 21. In the state shown in the figure, since the mobile terminal 10 has already left the home network 21 and is connected to the destination network 22, it cannot receive an IP packet addressed to itself that has reached the home network 21. In such a case, in Mobile IP, the home agent 40 receives the IP packet on behalf of the mobile terminal 10 and transfers it to the destination network 22 where the mobile terminal 10 is currently located.

  In order to realize the packet transfer described above, the home agent 40 needs to always grasp the connection destination network (location information) of the mobile terminal 10. In Mobile IP, when each mobile terminal 10 detects a change in the connection destination network and acquires a new IP address (hereinafter referred to as a care-of address) in the transfer-destination network 22, the care-of address is notified to the home agent 40 ( Location registration).

The home agent 40 recognizes that the connection destination network of the mobile terminal 10 has been changed by receiving the location registration message from the mobile terminal 10. When the location registration process is completed, the home agent 40 is in a state in which a care-of address effective in the destination network is stored in association with the home address of the mobile terminal 10.
When receiving the IP packet addressed to the mobile terminal 10, the home agent 40 encapsulates the received packet with an encapsulation header having the care-of address as the destination IP address and transmits the encapsulated packet to the home network 21. The encapsulated packet is transferred from the Internet 20 to the destination network 22 according to the care-of address indicated by the encapsulation header. Upon receiving the encapsulated packet, the mobile terminal 10 removes (decapsulates) the encapsulated header from the received packet and performs reception processing as an IP packet addressed to the home address.

  However, as described in RFC2002, the location registration in Mobile IP includes the authentication procedure of the mobile terminal. Therefore, it takes time to complete the location registration. It is unsuitable. In order to compensate for the shortcomings related to location registration of Mobile IP, various techniques have been proposed so far.

  For example, Japanese Patent Laid-Open No. 2003-87848 (Patent Document 1) discloses that a wide wireless area is formed by a first foreign agent (wireless base station) belonging to a first subnetwork connected to a backbone IP network. The second foreign agent (wireless base station) belonging to the second subnetwork connected to the backbone IP network forms a narrow wireless area that overlaps within the wide wireless area, and the mobile terminal reaches the narrow wireless area. When the connection destination subnetwork is changed, the mobile terminal requests the home agent to perform pseudo location registration related to the original connection destination subnetwork, and then requests normal location registration related to the new connection destination subnetwork. Has proposed. According to this proposal, the home agent that has received the pseudo registration request stores the authentication result related to the mobile terminal that was performed when connecting to the first subnetwork, so that the mobile terminal that has passed through the narrow wireless area can When returning to a wide wireless area, it becomes possible to complete the location registration accompanying the change of the connection destination without the authentication procedure.

JP 2003-87848 A

  When a mobile terminal equipped with two wireless devices with different communication methods is mounted on an automobile, for example, the wireless communication area formed by a wireless LAN base station is a narrow area of about 100 m from the base station. The terminal passes through one wireless LAN communication area in a short time. Accordingly, when a mobile terminal communicating with a mobile phone detects intrusion into the wireless LAN communication area and performs mobile IP location registration to switch the wireless device from the mobile phone to the wireless LAN communication device, A situation occurs in which the mobile terminal passes through the wireless LAN area before the location registration in the area is completed or immediately after the location registration is completed.

  In this case, as a result, switching to the wireless LAN is wasted, and switching to the mobile phone occurs again before performing data packet communication on the wireless LAN, until the location registration on the mobile phone is completed. In the meantime, there is a possibility that a packet addressed to the mobile terminal captured by the home agent is discarded due to indefinite transfer destination. Note that the proposal of Patent Document 1 is intended to shorten the time required for location registration, and does not consider the transit time of the destination wireless communication area. Absent.

  An object of the present invention is to provide a mobile terminal and a radio system switching control method capable of avoiding execution of location registration that becomes invalid as a result and preventing a decrease in communication efficiency.

In order to achieve the above object, the present invention selectively uses first and second radio apparatuses having different radio communication schemes, and the first radio base station belonging to the communication network of the first radio communication scheme, In a radio system switching control method for a mobile terminal that accesses the Internet via any of the second radio base stations belonging to a communication network of 2 radio communication systems,
Detecting whether or not the first and second wireless devices are able to communicate wirelessly from the received intensity of the base station transmission radio waves in the first and second wireless devices; detecting the moving speed of the mobile terminal; 1. Based on the communication availability status of the second wireless device, the moving speed, and the identification information of the currently selected wireless device, it is determined whether the wireless communication method needs to be switched, and the wireless device is switched according to the determination result. It consists of steps.

Further, the present invention selectively uses the first and second radio apparatuses having different radio communication schemes, and uses the first radio base station belonging to the first radio communication scheme communication network or the second radio communication scheme. In a mobile terminal accessing the Internet via one of the second radio base stations belonging to the communication network,
A first communication control unit of a first wireless communication method coupled to the first wireless device;
A second communication control unit of the second wireless communication method coupled to the second wireless device;
A wireless device switching unit that selects one of the first and second communication control units to perform protocol processing for Internet access and data transmission / reception;
A wireless communication state detector that detects whether or not wireless communication of the first and second wireless devices is possible based on the received intensity of the base station transmission radio wave in the first and second wireless devices;
A moving speed detector for detecting the moving speed of the mobile terminal;
The communication availability information of the first and second wireless devices output from the wireless communication state detection unit, the moving speed of the mobile terminal output from the moving speed detection unit, and the wireless device switching unit currently selected And a wireless device switching determination unit that determines whether or not to switch the wireless communication method based on the identification information of the wireless communication method and gives a wireless communication method switching command to the wireless device switching unit.

  More specifically, in the mobile terminal of the present invention, the second radio communication area formed by the second radio base station is included in a part of the first radio communication area formed by the first radio base station. When the first communication control unit of the first wireless communication method is selected by the wireless device switching unit, the wireless device switching determination unit is configured so that the second wireless device is the second wireless base station. On the condition that the moving speed is lower than a predetermined threshold speed, the wireless device switching unit is instructed to switch the wireless communication method.

  In the mobile terminal of the present invention, when the second communication control unit of the second wireless communication method is selected by the wireless device switching unit, the wireless device switching determination unit is configured so that the first wireless device is the first communication unit. The wireless device switching unit is instructed to switch the wireless communication method on condition that communication with one wireless base station is possible and the moving speed is higher than a predetermined threshold speed.

When the mobile terminal of the present invention accesses the Internet by selectively using the first and second wireless devices having different communication methods, such as a mobile phone and a wireless LAN communication device, the mobile terminal and the base station In addition to the state of the radio link with the station, the mobile terminal is controlled in consideration of the moving speed of the mobile terminal, so that the mobile terminal has a relatively small area, for example. When entering the wireless communication area of the wireless LAN at a high speed, by suppressing switching from the mobile phone to the wireless LAN communication device, the Mobile IP location registration procedure with the wireless LAN compatible ISP is being executed. Immediately after the location registration is completed, it is possible to avoid a situation in which the mobile terminal passes through the wireless LAN communication area E31 and consequently switching to the wireless LAN becomes invalid. Therefore, according to the present invention, it is possible to prevent a reduction in communication efficiency due to unnecessary switching of wireless devices, and to realize more effective seamless roaming.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows an example of a network configuration to which the present invention is applied. Elements identical to those of the network described in FIG. 5 are assigned the same reference numerals as in FIG.
The mobile terminal 10 of this embodiment includes a mobile phone 30 and a wireless LAN communication device 31 as wireless devices. The mobile phone 30 communicates with a mobile phone base station 303 connected to the mobile phone communication network 302 via a wireless line, and the wireless LAN communication device 31 communicates with a wireless LAN base station 313 connected to the wireless LAN communication network 310 and a wireless line. Communicate with.

  When the Internet 20 is accessed by the mobile phone 30 and the wireless LAN communication device 31, it is generally necessary to connect the mobile terminal 10 to an Internet connection service provider (ISP). In the illustrated example, the mobile phone communication network 302 is connected to the Internet 20 via a public line network 300 and a mobile phone compatible ISP 301. The mobile phone compatible ISP 301 is a server of a service provider that enables connection between the mobile phone 30 and the Internet. In this embodiment, the user of the mobile terminal 10 has a service contract with the mobile phone compatible ISP 301. Shall. Although only one mobile phone base station 303 is shown here, the mobile phone communication network 302 generally accommodates a plurality of mobile phone base stations, and a line between each mobile phone base station and the public line network 300. Exchange control is performed. The mobile phone base station 303 transmits a radio wave of a specified frequency that can be received by the mobile phone 30, and the reachable range of the radio wave is a mobile phone communication area E 30.

  The wireless LAN communication network 310 is connected to the Internet 20 via a wireless LAN compatible ISP 311. The wireless LAN compatible ISP 311 is a server of a service provider that enables connection between the wireless LAN communication device 31 and the Internet, similar to the mobile phone compatible ISP 301. Here, the user of the mobile terminal 10 is allowed to connect to the wireless LAN compatible ISP 311. It is assumed that a service contract is also made. Similar to the mobile phone communication network 302, the wireless LAN communication network 310 accommodates a plurality of wireless LAN base stations and is connected to an external network. E31 indicates the reach of radio waves transmitted from the wireless LAN base station 313, and is a wireless LAN communication area in which the wireless LAN communication device 31 and the wireless LAN base station 313 can communicate. The wireless LAN communication device 31 is connected to the wireless LAN compatible ISP 311 via the wireless LAN base station 313 and the wireless LAN communication network 310.

Based on the above network configuration, Mobile IP seamless roaming by the mobile terminal 10 of the present invention will be described with reference to the communication sequence shown in FIG.
First, a communication sequence when the mobile terminal 10 connects to the Internet 20 using the mobile phone 30 and applies a pre-assigned home address to communicate with the communication partner server 50 via the home network 21 will be described. .

  When the mobile terminal 10 detects that it has entered the mobile phone communication area E30 (step 401), it makes a dial-up connection from the mobile phone 30 to the mobile phone compatible ISP 301 in order to connect to the Internet 20. The mobile phone compatible ISP 301 is an access point for receiving a mobile phone, and the mobile terminal 10 makes a call to the access point using the auto dial function of the mobile phone 30.

  A call from the mobile phone 30 is transmitted to the mobile phone base station 303 via a wireless line, and arrives at the mobile phone compatible ISP 301 via the mobile phone communication network 302 and the public line network 302. When the cellular phone compatible ISP 301 responds to the incoming call, a telephone line is established between the cellular phone 30 and the cellular phone compatible ISP 301. Thereafter, the cellular phone 30 and the ISP 301 perform data communication using a modem (not shown). Possible CONNECT state.

  When the mobile phone compatible ISP 301 enters the CONNECT state, the mobile terminal 10 executes a data link request (SQ1) and a communication procedure (SQ2) for establishing a data link with the mobile phone compatible ISP 301. This is a negotiation for negotiating communication parameters required for data link layer communication.

  When the data link is established by the negotiation, an authentication request is transmitted from the mobile phone compatible ISP 301 to the mobile terminal 10 in order to confirm whether or not the user of the mobile terminal 10 is an authorized contractor (SQ3). In response to the request, the mobile terminal 10 returns an authentication response including the user ID and password to the cellular phone compatible ISP 301 (SQ4). The cellular phone compatible ISP 301 refers to the subscriber information registered in advance corresponding to the user ID, and checks whether or not the password matches that registered in advance. If it is determined by the above check that the user is a legitimate contractor, the cellular phone compatible ISP 301 returns an authentication confirmation to the mobile terminal 10 (SQ5) and completes the authentication procedure.

  Upon receiving the authentication confirmation, the mobile terminal 10 transmits an IP address acquisition request to the mobile phone compatible ISP 301 (SQ6). In response to the request, the cellular phone compatible ISP 301 dynamically assigns an IP address and distributes the IP address to the requesting mobile terminal 10 (SQ7). The mobile terminal 10 treats the IP address assigned by the cellular phone compatible ISP 301 as a care-of address, and transmits a location registration request including the care-of address to the home agent 40 (SQ8).

  Upon receiving the location registration request, the home agent 40 registers the care-of address indicated by the received message in correspondence with the home address of the mobile terminal (402). The registration process 402 includes an authentication process for confirming the location registration requesting source mobile terminal 10. If there is no problem in location registration, a location registration response is returned to the requesting mobile terminal 10 ( SQ9) The location registration procedure is completed, and the mobile terminal 10 and the communication partner server 50 can communicate with each other.

  When the information acquisition request is transmitted from the mobile terminal 10 to the communication partner server 50 (SQ10), the communication partner server 50 returns a response packet including the information requested from the mobile terminal 10 (SQ11). The response packet is transmitted in an IP packet format with the home address of the mobile terminal 10 as the destination address, and transferred to the home network 21 via the Internet 20. After the location registration of the mobile terminal 10 at the destination, the IP packet addressed to the mobile terminal 10 is captured (proxy reception) by the home agent 40, and the encapsulation header including the care-of address of the mobile terminal 10 as the destination address is used. IP encapsulation processing is performed (403). The encapsulated IP packet is transferred from the home network 21 to the Internet 20 according to the care-of address, and is received by the mobile phone compatible ISP 301 and transferred to the mobile terminal 10 communicating with the mobile phone 30 (SQ12).

  Upon receiving the encapsulated IP packet, the mobile terminal 10 executes a decapsulation process (404) for removing the encapsulation header from the received packet, and extracts distribution information from the original IP packet. Thereafter, each time an information acquisition request is transmitted from the mobile terminal 10, a response packet from the communication partner server 50 is transferred to the mobile terminal 10 via the home agent 40 described above.

Next, the operation when the mobile terminal 10 communicating with the mobile phone 30 enters the wireless LAN communication area E31 shown in FIG. 1 will be described.
The mobile terminal 10 detects that it has entered the wireless LAN communication area E31 based on the received radio wave from the wireless LAN base station 313 received by the wireless LAN communication device 31 (405). A feature of the present invention is that the mobile terminal 10 that has detected that it has entered the wireless LAN communication area E31 during communication with the mobile phone 30 takes into account the current moving speed of the mobile terminal 10 as will be described later. Is to determine whether or not to switch from the mobile phone 30 to the wireless LAN communication device 31 (406).

  As a result of the determination process, when it is determined that the wireless terminal 10 should be switched to the wireless LAN communication device 31, the mobile terminal 10 uses the wireless LAN communication device 31 and the communication sequence performed with the mobile phone compatible ISP 301 described above. Similarly, for communication parameter negotiation (SQ21, SQ22), authentication procedures (SQ23 to SQ25), and acquisition of an IP address used for wireless LAN communication with the wireless LAN compatible ISP 311. Negotiation (SQ26, SQ27).

  When receiving the IP address dynamically assigned by the wireless LAN compatible ISP 311, the mobile terminal 10 transmits a location registration request to the home agent 40 using this as a care-of address (SQ 28). When the home agent 40 completes the location registration process (402) corresponding to the location registration request, it returns a location registration response to the mobile terminal 10 (SQ29).

  When the mobile terminal 10 moves in the wireless LAN communication area E31 and transmits an information acquisition request (IP packet) to the communication partner server 50 via the wireless LAN communication device 31 (SQ30), the information acquisition request is The data is transferred to the Internet 20 through the LAN base station 313, the wireless LAN communication network 310, and the wireless LAN compatible ISP 311, and reaches the communication partner server 50 connected to the communication partner network 23.

  The response IP packet (SQ31) for request information delivery sent to the home address of the mobile terminal 10 by the communication partner server 50 is captured (proxy reception) by the home agent 40, and is encapsulated with the care-of address of the wireless LAN as the destination After IP encapsulation processing (403) using the header, it is transmitted to the home network 21. The encapsulated IP packet is transferred from the home network 21 to the Internet 20 according to the care-of address, and the wireless LAN compatible ISP 311 receives this and transfers it to the mobile terminal 10 that is performing wireless LAN communication (SQ32). When the wireless LAN communication device 31 receives the encapsulated IP packet, the mobile terminal 10 decapsulates the received packet (404), and extracts distribution information from the original IP packet.

  When the mobile terminal passes through the wireless LAN communication area E31 and returns to the mobile phone communication area E30, the sequence after the process 401 shown at the beginning of FIG. 2 is repeated, and the packet communication mode by the mobile phone 30 is set again.

  According to the present invention, when entering a wireless LAN communication area that is narrow in area, the mobile LAN determines whether or not to switch from the currently used mobile phone communication to the wireless LAN communication according to the current moving speed of the mobile terminal. Only when it is determined that switching to is effective, the care-of address of the wireless LAN is acquired and the location registration of Mobile IP is performed. According to the present invention, while the mobile terminal is moving at a high speed, the switching to the wireless LAN is suppressed, thereby avoiding the disconnection of the communication path between the mobile terminal 10 and the communication partner server 50 and continuing the communication. Guarantee.

  FIG. 3 is a block configuration diagram showing an embodiment of the mobile terminal 10 according to the present invention that enables the selective switching of the above-described wireless devices. The mobile terminal 10 shown here includes a system control unit 11 that controls the overall operation of the terminal system, an information display unit 12, a user operation unit 13, a clock unit 14, and a local terminal position detection unit 15.

  The system control unit 11 is actually composed of a processor (CPU), a ROM, a RAM, and the like except for some dedicated circuits, and controls the overall operation of the mobile terminal 10 by software processing by the processor. The information display unit 12 includes a display for displaying communication data, an operation menu of the mobile terminal 10, and the like. The user operation unit 13 is used by the user to input an operation setting of the mobile terminal 10 or a command such as a data transmission request by wireless communication, and a remote controller may be employed. The clock unit 14 notifies the system control unit 11 of the current time. The own terminal position detection unit 15 is for detecting the current position of the mobile terminal 10, and, for example, GPS is used.

The system control unit 11 includes a communication information processing unit 111 coupled to the information display unit 12 and the user operation unit 13, a moving speed detection unit 112 coupled to the clock unit 14 and the own terminal position detection unit 15, and the mobile phone 30. A mobile phone communication control unit 113 coupled to the wireless LAN communication device 31 and a wireless LAN communication control unit 114 coupled to the wireless LAN communication device 31.
The system control unit 11 further includes a wireless device switching unit 110 and a wireless communication state detection unit 115 coupled to the mobile phone communication control unit 113 and the wireless LAN communication control unit 114, and the moving speed detection unit 112 and the wireless communication state. Wireless device switching determination unit 116 coupled to detection unit 115, reference speed setting unit 117 coupled to wireless device switching determination unit 116, and communication in progress coupled to wireless device switching unit 110 and wireless device switching determination unit 116 And a wireless device storage unit 118.

  These components 110 to 118 of the system control unit 11 are realized by a dedicated LSI, a memory, or a program (processing routine) executed by a processor. When implemented by a processing routine, the connection relationship between components is determined by a control routine executed by the processor.

  The mobile phone communication control unit 113 performs command processing for mobile phone control for controlling transmission of data packets from the mobile phone 30, line disconnection, etc., and wireless communication with the mobile phone base station 303 in accordance with instructions from the user operation unit 13. A predetermined protocol process required, a transmission / reception process of communication data adapted to the external connection interface provided in the mobile phone 30, and received signal strength information of the outgoing radio wave from the mobile phone base station 303 acquired from the mobile phone 30 The out-of-service information is notified to the wireless communication state detection unit 115.

The wireless LAN communication control unit 114 performs predetermined protocol processing necessary for wireless communication with the wireless LAN base station 313, transmission / reception processing of communication data adapted to the external connection interface of the wireless LAN communication device 31, and wireless LAN communication device The wireless communication state detection unit 115 is notified of the reception intensity information of the radio wave transmitted from the wireless LAN base station 313 acquired from 31.
The wireless device switching unit 110 switches wireless devices that are to execute Mobile IP location registration protocol processing in accordance with an instruction from the wireless device switching determination unit 116, and as a result of the location registration, the wireless device (cell phone 30 or The identification information of the wireless LAN communication device 31) is set in the communicating wireless device storage unit 118. Switching between wireless devices is achieved when the wireless device switching unit 110 selects one of the mobile phone communication control unit 113 and the wireless LAN communication control unit 114.

  The communication information processing unit 111 executes communication protocol processing such as TCP / IP, which is an upper layer of the mobile phone communication control unit 113 and the wireless LAN communication control unit 114, and receives an IP packet from the payload of the received packet when receiving the IP packet. Is extracted and output to the information display unit 12. In response to the data transmission request from the user operation unit 13, the communication information processing unit 111 sets user transmission information in the payload of the transmission packet, performs communication protocol processing such as TCP / IP, and then transmits the transmission packet to the wireless device. Output to the switching unit 110. The wireless device switching unit 110 sends the transmission packet to the currently selected mobile phone communication control unit 113 or wireless LAN communication control unit 114.

  The wireless communication state detection unit 115 determines the state of the wireless line between the mobile phone 30 and the wireless LAN communication device 31 based on input information from the mobile phone communication control unit 113 and the wireless LAN communication control unit 114. The detection of the wireless communication area shown as processes 401 and 405 in FIG. 2 corresponds to the determination result by the wireless communication state detection unit 115. In the wireless communication state detection unit 115, a reception radio wave intensity threshold for determining the state of the wireless line is set in advance corresponding to each of the mobile phone 30 and the wireless LAN communication device 31. As each threshold, for example, a value of about 10% of the received radio wave intensity peak value is set, and the wireless communication state detection unit 115 is periodically notified from the mobile phone communication control unit 113 and the wireless LAN communication control unit 114. The received radio wave intensity is compared with each threshold value. When the received radio wave intensity is greater than or equal to the threshold value, it is determined that wireless communication is possible, and when the received radio wave intensity is less than the threshold value, it is determined that wireless communication is impossible.

  The moving speed detection unit 112 calculates the moving speed of the mobile terminal 10 based on the time information acquired from the clock unit 14 and the position information of the mobile terminal acquired from the own terminal position detection unit 15. When the mobile terminal 10 is an in-vehicle terminal such as a car navigation, the moving speed detection unit 112 may use speed information input to a car speedometer instead of the time information and the position information.

  The wireless device switching determination unit 116 is for performing the process 406 in the communication sequence shown in FIG. 2, the state of the mobile phone and the wireless LAN wireless line indicated by the wireless communication state detection unit 115, and the movement speed detection unit Based on the moving speed of the mobile terminal indicated by 112 and the threshold speed indicated by the reference speed setting unit 117, it is determined whether or not the wireless device indicated by the communicating wireless device storage unit 118 should be switched to another wireless device. As a result of the determination, when the wireless device switching determination unit 116 determines to switch to another wireless device, a switching command is issued to the wireless device switching unit 110, and the wireless device switching unit 110 performs the cellular phone communication currently selected. The control unit 113 or the wireless LAN communication control unit 114 is switched to the other. Thus, ISP switching by the newly selected communication control unit and Mobile IP location registration processing are executed.

FIG. 4 is a flowchart illustrating an example of a control operation that the wireless device switching determination unit 116 periodically executes while the mobile terminal is accessing the Internet.
The wireless device switching determination unit 116 acquires the identification information of the wireless device in communication held in the wireless device storage unit 118 in communication (step 501), and the mobile phone 30 and the wireless LAN communication device 31 from the wireless communication state detection unit 115. The status information of the wireless line is acquired (502).

  The wireless device switching determination unit 116 determines whether the mobile terminal is communicating with the mobile phone 30 from the identification information of the wireless device being communicated (503). From the information, it is determined whether or not wireless LAN communication is possible (504). If communication via the wireless LAN is impossible, it is determined that switching of the wireless device is unnecessary, and this routine is terminated.

  When wireless LAN communication is possible, the wireless device switching determination unit 116 acquires the current moving speed from the moving speed detection unit 112 (505), and sets the switching threshold speed from the reference speed setting unit 117 to the wireless LAN communication device 31. (506), and the current moving speed of the mobile terminal 10 is compared with the switching threshold speed (507).

  The switching threshold speed THv is requested from the mobile terminal within the wireless LAN communication area E31, for example, the standard diameter of the wireless LAN communication area E31 is D [m], the mobile IP location registration time is t1 [seconds]. Assuming that the minimum stay time is t2 [seconds], THv = D / (t1 + t2). If the above equation is modified, THv · t1 + THv · t2 = D is obtained, so the threshold speed THv is calculated by subtracting the moving distance within the time required for position registration (t1), and the mobile terminal 10 determines the remaining distance of the wireless communication area E31 The time required to pass is the moving speed at which the minimum stay time t2 at which the switching effect to the wireless LAN can be expected. The minimum stay time t2 is, for example, the standard communication speed of the wireless LAN communication device 31 to be used and the average data amount (or average IP packet length) that the mobile terminal receives from the communication partner server at one time. Determine based on.

  The wireless device switching determination unit 116 compares the current moving speed v with the threshold speed THv (507), and when the current speed v is equal to or lower than the threshold speed THv, the mobile terminal 10 communicates while staying in the wireless LAN communication area E31. It is determined that IP packets can be transmitted / received to / from the partner server 50, and the wireless device switching unit 110 is instructed to switch to the wireless LAN communication device 31 (508). If the current moving speed v exceeds the threshold speed THv, it is determined that the mobile terminal passes through the communication area E31 before receiving a response packet from the communication partner even if the mobile phone is switched to the wireless LAN. This routine is terminated without switching to.

  If it is determined in the determination step 503 that the wireless LAN 31 is currently in use from the identification information of the wireless device in communication indicated by the wireless device storage unit 118 in communication, the wireless device switching determination unit 116 determines that the wireless communication state detection unit 115 It is checked from the acquired wireless LAN line status information whether or not wireless LAN communication can be continued (509). If the wireless LAN line state is good and communication can be continued, it is determined that switching of the wireless device is unnecessary, and this routine is terminated. When it is determined that the line state of the wireless LAN has deteriorated and communication cannot be continued, the wireless device switching determination unit 116 instructs the wireless device switching unit 110 to switch to the mobile phone 30 (510).

  In the above embodiment, the switching threshold speed THv is calculated on the basis of the standard diameter D of the wireless LAN communication area E31, the position registration time t1, and the mobile terminal minimum stay time t2 in the wireless LAN communication area E31. The routes of the mobile terminal 10 in the wireless LAN communication area E31 are various and do not always pass through the center of the area E31. Therefore, in order to give a margin to the determination result in step 507, the value of the diameter D may be set to a value about the radius of the area E31 (the distance from the base station 313 located at the center). For simplification, the threshold speed THv may be set to a walking speed or a value close to 0, and the mobile terminal 10 may be switched from a mobile phone to a wireless LAN only when the mobile terminal 10 is moving at a low speed.

  In the embodiment, when the wireless device switching determination unit 116 determines the line state while using the wireless LAN and determines that the communication cannot be continued, the wireless device switching determination unit 116 instructs switching from the wireless LAN to the mobile phone. The moving speed may be checked while using the wireless LAN, and it may be detected that the moving speed has exceeded a certain speed and switched to the mobile phone 3.

  As is clear from the above description, according to the present invention, when the mobile terminal enters the wireless LAN communication area E30 while using the mobile phone line, the wireless LAN is taken into account in consideration of the current moving speed of the mobile terminal. Since it is determined whether or not to switch to communication, the mobile terminal sets the wireless LAN communication area E31 during the execution of the Mobile IP location registration procedure with the wireless LAN compatible ISP or immediately after the location registration is completed. It is possible to avoid the situation that the switching to the wireless LAN becomes invalid as a result. In the embodiment, the case where the mobile terminal includes a mobile phone and a wireless LAN communication device as a wireless device has been described. However, the present invention is also applicable to a mobile terminal equipped with another wireless communication device such as DSRC. Is possible. The mobile terminal to which the present invention is applied may be a general personal computer in addition to car navigation.

1 is a diagram showing an example of a network configuration to which the present invention is applied. The sequence diagram of the seamless roaming by the mobile terminal of this invention. The block block diagram which shows one Example of the mobile terminal to which this invention is applied. 4 is a flowchart showing the operation of the wireless device switching determination unit in FIG. 3. The network block diagram for demonstrating the outline | summary of Mobile IP.

Explanation of symbols

10: mobile terminal, 11: system control unit, 12: information display unit, 13: user operation unit,
14: clock part, 15: own terminal position detection part, 20: internet,
21: home network, 22: destination network, 23: communication partner network, 30: mobile phone, 31: wireless LAN communication device, 40: home agent,
50: Communication partner server,
110: Wireless device switching unit, 111: Communication information processing unit, 112: Movement speed detection unit,
113: Mobile phone communication control unit, 114: Wireless LAN communication control unit,
115: Wireless communication state detection unit 116: Wireless device switching determination unit
117: Reference speed setting unit, 118: Wireless device storage unit during communication,
300: Public line network, 301: ISP corresponding to mobile phone, 302: Mobile phone communication network,
303: Mobile phone base station, 310: Wireless LAN communication network, 311: ISP corresponding to wireless LAN, 313: Wireless LAN base station, E30: Mobile phone communication area,
E31: Wireless LAN communication area.

Claims (9)

A first wireless base station belonging to the communication network of the first wireless communication system or a first wireless device belonging to the communication network of the second wireless communication system by selectively using the first and second wireless devices having different wireless communication systems. A mobile terminal that accesses the Internet via one of two radio base stations,
A first communication control unit of a first wireless communication method coupled to the first wireless device;
A second communication control unit of the second wireless communication method coupled to the second wireless device;
A wireless device switching unit that selects one of the first and second communication control units to perform protocol processing for Internet access and data transmission and reception;
A wireless communication state detector that detects whether the first and second wireless devices are wirelessly communicable from the received intensity of the base station transmission radio waves in the first and second wireless devices;
A moving speed detector for detecting the moving speed of the mobile terminal;
The communication availability information of the first and second wireless devices output from the wireless communication state detection unit, the moving speed of the mobile terminal output from the moving speed detection unit, and the wireless device switching unit currently selected And a wireless device switching determination unit that determines whether or not to switch the wireless communication method based on the identification information of the wireless communication method and provides a wireless communication method switching command to the wireless device switching unit. Terminal.   A part of the first radio communication area formed by the first radio base station is formed in a state in which the second radio communication area formed by the second radio base station is included. When the first communication control unit of the first wireless communication method is selected, the wireless device switching determination unit is configured such that the second wireless device can communicate with the second wireless base station and the moving speed is predetermined. 2. The mobile terminal according to claim 1, wherein the wireless device switching unit is instructed to switch the wireless communication method on condition that the speed is lower than a threshold speed of 2.   A part of the first radio communication area formed by the first radio base station is formed in a state in which the second radio communication area formed by the second radio base station is included. When the first communication control unit of the first wireless communication method is selected and the moving speed is higher than a predetermined threshold speed, the wireless device switching determination unit determines whether the wireless device switching unit uses the wireless communication switching unit. The mobile terminal according to claim 1, wherein switching is suppressed.   A part of the first radio communication area formed by the first radio base station is formed in a state in which the second radio communication area formed by the second radio base station is included. When the second communication control unit of the second wireless communication method is selected, the wireless device switching determination unit is configured so that the first wireless device can communicate with the first wireless base station and the moving speed is predetermined. 2. The mobile terminal according to claim 1, wherein the wireless device switching unit is instructed to switch the wireless communication system on condition that the speed is higher than a threshold speed.   The mobile terminal according to any one of claims 1 to 4, wherein the second wireless device has a higher communication speed than the first wireless device. A first wireless base station belonging to the communication network of the first wireless communication system or a first wireless device belonging to the communication network of the second wireless communication system by selectively using the first and second wireless devices having different wireless communication systems. A radio system switching control method for a mobile terminal that accesses the Internet via one of two radio base stations,
Detecting whether the first and second wireless devices can perform wireless communication from the received intensity of the base station transmission radio waves in the first and second wireless devices;
Detecting the moving speed of the mobile terminal;
Based on the communication enable / disable state of the first and second wireless devices, the moving speed, and the identification information of the currently selected wireless device, it is determined whether or not to switch the wireless communication method, and the wireless device is determined according to the determination result. And a method of controlling switching between wireless systems. When the second radio communication area formed by the second radio base station is included in a part of the first radio communication area formed by the first radio base station,
When the first radio device is selected, the first radio device is conditioned on the condition that the second radio device can communicate with the second radio base station and the moving speed is lower than a predetermined threshold speed. The radio system switching control method according to claim 6, wherein switching from the apparatus to the second radio apparatus is performed. When the second radio communication area formed by the second radio base station is included in a part of the first radio communication area formed by the first radio base station,
When the second wireless device is selected, the first wireless device can communicate with the first wireless base station, and the moving speed is higher than a predetermined threshold speed. 7. The radio system switching control method according to claim 6, wherein switching from the two radio apparatuses to the first radio apparatus is performed.   9. The mobile terminal according to claim 6, wherein when the second wireless device is selected, the mobile terminal communicates with the counterpart device at a higher communication speed than when the first wireless device is selected. The radio system switching control method described in 1.

Images