JP2011160484A - Portable communication terminal, method and program for switching radio station device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a period of time when communication is disabled, by efficiently switching a radio station device to be connected. <P>SOLUTION: While communicating with a first access point among a plurality of access points, a radio wave intensity E1 of a first channel is detected (step S21). In accordance with the detected radio wave intensity E1 of the first channel being below a first threshold value (S22:YES), a communication channel is temporarily switched from the first channel to a second channel, and a radio wave intensity E2 of the second channel is detected (S23). Based on the radio wave intensity E2 of the second channel, a second access point to next communicate therewith is determined from among the plurality of access points (S32) and in accordance with the radio wave intensity E1 of the first channel being below a second threshold value (S28:YES), a reassociation request for requesting connection by hand-off is transmitted to the second access point (S33). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a portable communication terminal, a radio station apparatus switching method, and a radio station apparatus switching program, and more particularly to a portable communication terminal connectable to a wireless LAN, a radio station apparatus switching method, and a radio station apparatus switching program.

  In recent years, local area networks (hereinafter referred to as “wireless LANs”) using wireless communication have become widespread. Further, a wireless communication terminal connected to a wireless LAN can be used as an IP (Internet Protocol) telephone. When a portable wireless communication terminal is used as an IP telephone, the wireless communication terminal must be located within a wireless LAN wireless communication station (access point).

  A technique called handoff (also referred to as handover) is known in which switching from a wireless communication station during wireless communication to communication with another wireless communication station is known. In this handoff, after it becomes impossible to communicate with the access point that has been communicating until then, the next access point that can be communicated is scanned and connected to the communicable access point determined by the scan. It takes time to connect to the next communicable access point after it cannot communicate with the access point that communicated first, and data cannot be transmitted or received during that time. For this reason, when a wireless communication terminal is used as an IP telephone, it is desirable to reduce the time during which data cannot be transmitted / received as short as possible so that the call is not interrupted.

  Japanese Patent Laying-Open No. 2005-175932 (Patent Document 1) includes a plurality of wireless LAN base stations and at least one wireless LAN terminal that is located and moves under each of the plurality of wireless LAN base stations. When the wireless LAN terminal performs a data transmission / reception process and a scanning process of the reception signal level of the surrounding wireless LAN base station in parallel in a time division manner when the reception signal level becomes weak, A wireless LAN handover processing method characterized by switching to a LAN base station is described.

  However, the conventional wireless LAN handover processing method switches to another wireless LAN base station even though the wireless LAN terminal can communicate even if it moves further away from the wireless LAN base station. For this reason, there is a problem that the performance of the wireless LAN base station cannot be fully utilized and the interval at which the wireless LAN base station is arranged must be narrowed.

  When a wireless communication terminal is used as an IP telephone, an IP address is assigned to the wireless communication terminal, but the IP address already assigned during a call is valid while connected to the same segment network. It is. Japanese Patent Laying-Open No. 2005-1224087 (Patent Document 2) detects that a mobile terminal that performs wireless communication complying with IPv4 via a wireless LAN system has changed BSS due to handover of the terminal itself. When the BSS change is detected by the detection means, the subnet information is inquired to the DHCP server while continuing to send and receive data, and the subnet found by the inquiry is a different subnet from that before the BSS change. In this case, there is described a mobile terminal that includes a control unit that obtains a new IP address from a DHCP server and performs Internet control using the IP address. However, since the inquiry about the subnet information to the DHCP server is performed using the UDP (User Datagram Protocol) communication protocol, there is a problem that it takes a long time to acquire the subnet and the period during which data communication cannot be performed becomes long. .

JP 2005-175932 A JP 2005-1224087 A

  The present invention has been made to solve the above-described problems, and one of the objects of the present invention is to enable efficient switching of connected radio station apparatuses and to shorten a period during which communication is not possible. Is to provide a portable communication terminal.

  Another object of the present invention is to provide a radio station apparatus switching method capable of efficiently switching between connected radio station apparatuses and shortening a period during which communication is not possible.

  Another object of the present invention is to provide a radio station apparatus switching program capable of efficiently switching radio station apparatuses to be connected and shortening a period during which communication is not possible.

  In order to achieve the above-described object, according to one aspect of the present invention, a mobile communication terminal includes a wireless communication unit capable of wireless communication with any one of a plurality of wireless station devices, and the wireless communication unit includes a plurality of wireless station devices. First radio field intensity detecting means for detecting the radio field intensity of the first channel during communication with the first radio station apparatus of the first channel, and the detected radio field intensity of the first channel is the first. The communication channel of the wireless communication means is temporarily switched from the first channel to a second channel different from the first channel in response to falling below the threshold value of the second channel to detect the radio field intensity of the second channel. Radio wave intensity detection means, determination means for determining a second radio station apparatus to communicate next from a plurality of radio station apparatuses based on the detected radio wave intensity of the second channel, and radio wave intensity of the first channel First Reconnection for sending a reconnection request for requesting connection by handoff to the second wireless station apparatus determined by the wireless communication means in response to falling below a second threshold value smaller than the threshold value Requesting means.

  According to this aspect, the radio field intensity of the first channel is detected while communicating with the first radio station apparatus of the plurality of radio station apparatuses via the first channel, and the radio field intensity of the first channel is In response to falling below the threshold value of 1, the channel is temporarily switched to the second channel, and the radio field intensity of the second channel is detected. Then, based on the detected radio field intensity of the second channel, a second radio station apparatus to be communicated next is determined from among the plurality of radio station apparatuses, and the radio channel intensity of the first channel reaches the second threshold value. In response to the decrease, a reconnection request for requesting connection by handoff is sent to the determined second radio station apparatus. Before the communication on the first channel becomes impossible, the second wireless station device is determined, and the communication with the second wireless station device can be performed immediately before communication on the first channel becomes impossible. For this reason, the second wireless communication station is determined before communication on the first channel becomes impossible. Therefore, the second wireless communication station is determined after communication on the first channel becomes impossible. Compared to the above, the period during which communication is interrupted can be shortened. If the second threshold value is set near the minimum value at which radio communication with the first radio station apparatus is possible, the performance of the first radio station apparatus can be utilized to the maximum. . As a result, it is possible to provide a mobile communication terminal capable of efficiently switching the connected radio station apparatus and shortening the period during which communication is not possible.

Preferably, the second radio field intensity detecting means is configured such that when the detected radio field intensity of the first channel falls below the first threshold value, the detected radio field intensity of the first channel is greater than the first threshold value. Until the third threshold value is exceeded, the radio field intensity of the second channel is repeatedly detected at predetermined time intervals.

  According to this aspect, if the radio field intensity of the first channel exceeds the third threshold value after the radio field intensity of the first channel falls below the first threshold value, the radio channel intensity of the second channel is not detected. . While detecting the radio field intensity of the second channel, it is impossible to communicate with the first radio station apparatus, so that a period during which communication cannot be performed when the radio field intensity of the first channel becomes sufficiently high is eliminated. be able to.

  Preferably, the reconnection requesting unit determines the radio field intensity of the second channel and the radio field intensity of the first channel when the radio field intensity of the first channel does not fall below the second threshold value which is smaller than the first threshold value. If the difference is larger than the fourth threshold value, the wireless communication means is made to send a reconnection request.

  According to this aspect, even if the radio field intensity of the first channel does not fall below the second threshold value that is smaller than the first threshold value, the radio field intensity of the second channel and the radio field intensity of the first channel Is greater than the fourth threshold, a reconnection request is sent. For this reason, the occurrence of communication errors can be reduced.

  Preferably, an IP packet generation unit that generates packet data including an IP address and outputs the packet data to the wireless communication unit, and the reconnection request unit causes the wireless communication unit to transmit a reconnection request, and the second wireless station apparatus. After the wireless communication is established in step (b), the communication device further includes inquiry means for making an inquiry to the gateway of the network to which the first wireless station apparatus is connected. The connection request means generates packet data using the IP address used before sending the reconnection request to the wireless communication means.

  According to this aspect, after a reconnection request is transmitted and wireless communication is established with the second wireless station device, an inquiry is made to the gateway of the network to which the first wireless station device was connected. Therefore, it can be quickly determined whether the network to which the second radio station apparatus is connected is the same segment as the network to which the first radio station apparatus is connected.

  According to another aspect of the present invention, a radio station apparatus switching method is a radio station apparatus switching method executed by a mobile communication terminal provided with a radio communication unit capable of radio communication with any one of a plurality of radio station apparatuses. A step of detecting the radio field intensity of the first channel while the radio communication means is communicating with the first radio station device of the plurality of radio station devices via the first channel; In response to the radio field intensity of the channel being lower than the first threshold, the communication channel of the wireless communication means is temporarily switched from the first channel to a second channel different from the first channel. A step of detecting radio field intensity, a step of determining a second radio station apparatus to communicate next from a plurality of radio station apparatuses based on the detected radio field intensity of the second channel, A reconnection request for requesting a connection by handoff to the second radio station apparatus determined by the radio communication means in response to the strength falling below a second threshold value that is smaller than the first threshold value. Sending.

  According to this aspect, it is possible to provide a radio station apparatus switching method capable of efficiently switching the radio station apparatus to be connected and shortening the period during which communication is not possible.

According to still another aspect of the present invention, a radio station apparatus switching program is executed by a mobile communication terminal provided with a radio communication means capable of radio communication with any one of a plurality of radio station apparatuses. And the step of detecting the radio field intensity of the first channel while the radio communication means is communicating with the first radio station device of the plurality of radio station devices via the first channel, and the detected first In response to the radio field intensity of one channel being lower than the first threshold, the communication channel of the wireless communication means is temporarily switched from the first channel to a second channel different from the first channel, and the second channel Detecting a radio field intensity of the second radio station apparatus, determining a second radio station apparatus to communicate next from a plurality of radio station apparatuses based on the detected radio field intensity of the second channel, For requesting connection by handoff to the second radio station apparatus determined by the radio communication means in response to the radio field intensity of one channel being lower than a second threshold value that is smaller than the first threshold value. Causing the mobile communication terminal to execute a step of sending a reconnection request.

  According to this aspect, it is possible to provide a radio station apparatus switching program capable of efficiently switching the radio station apparatuses to be connected and shortening the period during which communication is not possible.

It is a figure which shows the outline | summary of the communication system in this Embodiment. It is a perspective view which shows the external appearance of the mobile telephone in one of embodiment of this invention. It is a functional block diagram which shows an example of the function of the mobile telephone in this Embodiment. It is a schematic diagram for demonstrating the relationship between the radio wave intensity of the radio wave transmitted by the access point, the scan start timing, and the transmission timing of the reassociation request. (A) is a figure which shows a measurement interval, FIG.5 (B) is a figure which shows a scanning interval. (A) is a figure for demonstrating the state of the data reception in execution of a scan, (B) is a figure for demonstrating the state of the data transmission in execution of a scan. It is a figure which shows the detail of a scanning period. (A) is a figure which shows the relationship between a radio wave intensity, a 1st threshold value, and a 2nd threshold value, (B) is a figure which shows the frequency | count of a scan at the time of using a 3rd threshold value. (C) is a figure which shows the frequency | count of scanning when not using a 3rd threshold value. It is a flowchart which shows an example of the flow of a wireless LAN connection process. It is a flowchart which shows an example of the flow of a radio wave intensity monitoring process.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

  FIG. 1 is a diagram showing an overview of a communication system in the present embodiment. Referring to FIG. 1, communication system 10 includes a mobile phone system 200 and a wireless LAN system 300. The mobile phone system 200 is a system provided by a communication carrier. Here, as an example, the mobile phone system 200 is a communication network 202, a base station device 201 connected to the communication network 202, and a mobile phone that performs wireless communication with the base station device 201. Phone 1. Here, one base station apparatus 201 is shown for explanation, but the number of units may be one or more, and the number of units is not limited. Base station apparatus 201 is a radio station apparatus that functions as a repeater of communication network 202. When the mobile phone 1 is located within the communicable area of the base station device 201, the mobile phone 1 communicates wirelessly with the base station device 201 and is connected to the communication network 202. Here, the communication network 202 provided by the communication carrier is referred to as a first network.

  The wireless LAN system 300 includes a mobile phone 1, three access points (APs) 100 to 102, a VoIP (Voice Internet Protocol) server 112, and a gateway (G / W) 111. The APs 100 to 102, the VoIP server 112, and the G / W 111 are respectively connected to the LAN cable 110 and constitute a second network capable of transmitting and receiving data to and from each other. Here, for the sake of explanation, three access points 100 to 102 are shown, but the number is sufficient as long as the number is one or more, and the number is not limited. Access points 100 to 102 are wireless station apparatuses that function as LAN repeaters. The mobile phone 1 can wirelessly communicate with any one of the access points 100 to 102. When wirelessly communicated with any one of the access points 100 to 102, the mobile phone 1 is connected to the second network, It becomes possible to communicate with the VoIP server 112 and the G / W 111.

  The second network is connected to the Internet 115 via the G / W 111. For this reason, the mobile phone 1 can communicate with the computer 116 connected to the Internet 115 while being connected to the second network.

  The access points 100 to 102 are normally fixed on the ground and each has a communicable area. The mobile phone 1 can wirelessly communicate with the access point 100 when located in the communicable area 100A of the access point 100, but wirelessly communicates with the access point 100 when located outside the communicable area 100A. I can't. The mobile phone 1 can wirelessly communicate with the access point 101 when located within the communicable area 101A of the access point 101, but wirelessly communicates with the access point 101 when located outside the communicable area 101A. I can't. The mobile phone 1 can wirelessly communicate with the access point 102 when located in the communicable area 102A of the access point 102, but wirelessly communicates with the access point 102 when located outside the communicable area 102A. I can't.

  The communicable area 100A of the access point 100, the communicable area 101A of the access point 101, and the communicable area 102A of the access point 102 are not overlapped with an area where three overlap and an area where two overlap. An area exists. When mobile phone 1 is present at the position shown in FIG. 1, the position is included in an area where communication areas 100 </ b> A to 102 </ b> A of access points 100 to 102 overlap. For this reason, the mobile phone 1 can wirelessly communicate with any of the access points 100 to 102. When the mobile phone 1 communicates with any of the access points 100 to 102, for example, an identifier such as SSID (Service Set Identifier) or ESSID (Extended SSID) is used. Thereby, the mobile phone 1 can be wirelessly connected to one selected by the mobile phone 1 from the access points 100 to 102 even if the mobile phone 1 is located in an area where the communicable areas 100A to 102A overlap.

  The VoIP server 112 mediates communication between the mobile phone 1 connected to the second network and the counterpart device. The counterpart device includes a computer connected to the second network, an IP phone, and another mobile phone that communicates with any of the access points 100 to 102. The VoIP server 112 stores a user table in which device identification information for identifying the mobile phone 1 and an extension number assigned in advance to the mobile phone 1 are associated, and the mobile phone 1 is connected to the second network. When the mobile phone 1 is connected, the IP address assigned to the mobile phone 1 is associated with the extension number assigned to the mobile phone 1. For example, first device identification information and a first extension number are assigned to a first mobile phone, and second device identification information and a second extension number are assigned to a second mobile phone. The case will be described. When the first mobile phone is connected to the second network, a first IP address is assigned by a DHCP (Dynamic Host Configuration Protocol) server, and the first IP address is acquired from the DHCP server. Thereafter, when the first mobile phone requests registration of the first IP address from the VoIP server 112, the VoIP server 112 associates the first extension number with the first IP address. Similarly, when the second mobile phone is connected to the second network, the second IP address is assigned by the DHCP server, and the second IP address is acquired from the DHCP server. Thereafter, when the second mobile phone requests registration of the second IP address to the VoIP server 112, the VoIP server 112 associates the second extension number with the second IP address. If the first mobile phone 1 transmits the second extension number to the VoIP server 112, the VoIP server mediates between the first and second mobile phones, and the first and second mobile phones. Communication for transmitting and receiving IP packets to and from is possible. Thus, each of the first and second mobile phones functions as an IP phone and can make a call. In addition, the first mobile phone transmits the second extension number to the VoIP server 112, acquires the second IP address assigned to the second mobile phone from the VoIP server, and the first mobile phone An IP packet may be directly transmitted / received to / from the second mobile phone.

  FIG. 2 is a perspective view showing an appearance of the mobile phone according to one embodiment of the present invention. 2A shows the appearance of an open-style mobile phone, and FIG. 2B shows the appearance of a closed-style mobile phone. Referring to FIGS. 2A and 2B, mobile phone 1 includes an operation side portion 3 and a display side portion 2. The operation side unit 3 includes an operation key 14 including a power key 14A, a numeric keypad, a call key, and the like, and a microphone 13 on an inner surface, and a microphone terminal 16 and an earphone terminal 17 on a right side. In the display side section 2, a liquid crystal display (LCD) 15, a first speaker 11 constituting a receiver, and a camera 24 are arranged on the inner surface, and a camera 24A, a small LCD 15A, and a second speaker 12 are arranged outside. Located on the side. Although an example in which the mobile phone 1 includes the LCD 15 is shown here, an organic EL (Electro Luminescence) display may be used instead of the LCD 15. The operation side unit 3 and the display side unit 2 are rotatably connected by a hinge mechanism, and the operation side unit 3 and the display side unit 2 can be opened and closed. When the mobile phone 1 is folded and the operation side portion 3 and the display side portion 2 are in the closed state, the state of the mobile phone 1 is the closed style, and the mobile phone 1 is opened to open the operation side portion 3 and the display side portion. The state of the mobile phone 1 when 2 is in the open state is the open style.

  FIG. 3 is a functional block diagram illustrating an example of functions of the mobile phone according to the present embodiment. Referring to FIG. 3, mobile phone 1 includes a control unit 21 for controlling the entire mobile phone 1, a wireless circuit 22 connected to antenna 22A, a wireless LAN circuit 23 connected to antenna 23A, A codec unit 28 for processing audio data, a switching unit 29 for switching input / output of the codec unit 28, a microphone 13, a first speaker 11, a second speaker 12, and a microphone connected to the switching unit 29, respectively. A terminal 16, an earphone terminal 17, a camera 24, an operation key 14 for receiving an input of a user operation, an infrared communication unit 19, a vibration unit 26, a display control unit 30 for controlling display on the LCD 15, and a control A ROM (Read Only Memory) 31 for storing a program to be executed by the unit 21 and a work area for the control unit 21 A random access memory (RAM) 32, an EEPROM (Electronically Erasable and Programmable ROM) 33 for storing address book data, e-mail and the like in a nonvolatile manner, and a card interface (I / F) 27.

  The radio circuit 22 performs radio communication with the base station apparatus 201 connected to the communication network 202. A radio signal transmitted from the antenna by the base station apparatus 201 is received by the antenna 22A. The radio circuit 22 receives the radio signal received by the antenna 22 </ b> A and outputs an audio signal obtained by demodulating the radio signal to the codec unit 28. The radio circuit 22 receives the audio signal from the codec unit 28 and outputs a radio signal obtained by modulating the audio signal to the antenna 22A. A radio signal transmitted from the antenna 22A is received by the antenna of the base station apparatus 201 and output to the base station apparatus 201.

  The wireless LAN circuit 23 wirelessly communicates with any one of the access points 100 to 102. A radio signal transmitted from any of the access points 100 to 102 is received by the antenna 23A. The wireless LAN circuit 23 receives the wireless signal received by the antenna 23 </ b> A and outputs an audio signal obtained by demodulating the wireless signal to the codec unit 28. The wireless LAN circuit 23 receives the audio signal from the codec unit 28, and outputs a radio signal obtained by modulating the audio signal to the antenna 23A. The radio signal transmitted from the antenna 23A is received by any of the access points 100 to 102.

  The wireless LAN circuit 23 is controlled by the control unit 21 and executes scanning. The scan is an operation for inquiring whether or not there are access points in the vicinity among the access points 100 to 102. Specifically, a probe request is transmitted, and a probe response is received from an access point existing in the vicinity. The probe request is transmitted in order for every predetermined channel. A channel indicates a frequency band. However, at the time of handoff, a probe request is transmitted for every channel other than the channel currently used for communication. If there is an access point that communicates with the corresponding channel in the vicinity, a probe response corresponding to the probe request can be received. The wireless LAN circuit 23 cannot communicate on a plurality of channels at the same time. For this reason, for example, if the wireless LAN circuit 23 communicates with the access point 100 and executes a scan, the wireless LAN circuit 23 cannot communicate with the access point 100 during the scan, and the scan is completed. It will communicate with the access point 100 again later.

  The codec unit 28 decodes the audio signal input from the wireless circuit 22 or the wireless LAN circuit 23, converts the decoded digital audio signal to analog, amplifies it, and outputs it to the switching unit 29. The codec unit 28 receives an analog audio signal from the microphone 13 or the microphone terminal 16 via the switching unit 29, converts the audio signal to digital, encodes it, and converts the encoded audio signal into the radio circuit 22 or The data is output to the wireless LAN circuit 23.

  The switching unit 29 is controlled by the control unit 21 and switches input / output of audio signals to the codec unit 28. The switching unit 29 outputs the audio signal received from the codec unit 28 to any one of the earphone terminal 17, the first speaker 11, and the second speaker 12. When the earphone is connected to the earphone terminal 17, the audio signal received from the codec unit 28 is output to the earphone terminal 17. When the earphone is not connected to the earphone terminal 17, if the mobile phone 1 is in the hands-free mode, the audio signal received from the codec unit 28 is output to the second speaker 12, and the mobile phone 1 is not in the hands-free mode. The audio signal received from the codec unit 28 is output to the first speaker 11. When the user operates the operation key 14, the mobile phone 1 is set to the hands-free mode. Further, even when the mobile phone 1 is in the open style and is not in the hands-free mode, when the mobile phone 1 changes to the closed style, the control unit 21 sets the hands-free mode. For this reason, the switching unit 29 outputs the audio signal received from the codec unit 28 to the first speaker 11 if the mobile phone 1 is not set to the hands-free mode when the mobile phone 1 is in an open style and is in a talking state. When the state changes to the closed style, the audio signal received from the codec unit 28 is output to the second speaker 12.

  The switching unit 29 outputs an audio signal output from either the microphone 13 or the microphone terminal 16 to the codec unit 28. The switching unit 29 outputs the audio signal received from the microphone terminal 16 to the codec unit 28 when the microphone is connected to the microphone terminal 16, and from the microphone 13 when the microphone is not connected to the microphone terminal 16. The received audio signal is output to the codec unit 28.

The display control unit 30 is controlled by the control unit 21 and controls the LCD 15 according to an instruction input from the control unit 21 to display an operation screen or an image on the LCD 15. The image displayed on the LCD 15 includes a moving image and a still image.

  A removable flash memory 27A is attached to the card I / F 27. The control unit 21 can access the flash memory 27A via the card I / F 27. Although an example in which a program to be executed by the control unit 21 is stored in the ROM 31 will be described here, the program is stored in the flash memory 27A, the program is read from the flash memory 27A, and the control unit 21 You may make it perform. The recording medium for storing the program is not limited to the flash memory 27A, but is a flexible disk, cassette tape, optical disk (CD-ROM (Compact Disc-ROM) / MO (Magnetic Optical Disc) / MD (Mini Disc) / DVD (Digital). Semiconductor memory such as an IC card, an optical card, a mask ROM, an EPROM (Erasable Programmable ROM), an EEPROM (Electronically EPROM), or the like. Alternatively, the mobile phone 1 may be connected to the Internet via the wireless circuit 22 or the wireless LAN circuit 23, and a program may be downloaded from a computer connected to the Internet and executed by the control unit 21. The program here includes not only a program directly executable by the control unit 21 but also a source program, a compressed program, an encrypted program, and the like.

The camera 24 includes a lens and a CMOS (Complementary Metal O
A photoelectric conversion element such as a xide (sensor) sensor is provided, and the light collected by the lens is imaged on the CMOS sensor. The CMOS sensor photoelectrically converts the received light and outputs image data to the control unit 21. The camera 24 is controlled by the control unit 21, starts imaging in response to an instruction from the control unit 21, and outputs the obtained still image data or moving image data to the control unit 21. The camera 24 includes an image processing circuit that executes image processing for improving the image quality of image data, and an A / D conversion circuit that converts image data from analog to digital. The control unit 21 outputs the still image data or moving image data output from the camera 24 to the display control unit 30 and displays it on the LCD 15 or encodes the still image data or moving image data using the compression encoding method, The data is stored in the flash memory 27A attached to the card I / F 27. The camera 24 images the user of the mobile phone 1 when the mobile phone 1 functions as a video phone.

  The infrared communication unit 19 transmits and receives data using infrared as a medium. For example, data is transmitted to and received from an external device in accordance with IrDA (Infrared Data Association) standards. Although an example in which data is transmitted and received using infrared rays as a medium is shown here, communication with an external device may be performed by wireless communication using electromagnetic waves. Further, instead of or in addition to the infrared communication unit 19, a serial interface or a parallel interface may be provided, connected to an external device via a communication cable, and data transmitted to and received from the external device.

<Handoff>
Next, handoff of the wireless LAN system 300 will be described with reference to FIG. Referring to FIG. 1, when mobile phone 1 communicates with access point 100 in a state of being located within communicable area 100 </ b> A of access point 100 and connected to the second network, mobile phone 1 communicates. When moving from the possible area 100A to a position outside the communicable area 100A, communication with the access point 100 is not possible. However, the mobile phone 1 can communicate with the access point 101 or the access point 102 if the moved position is located in either the access point 101 or the communicable area 101A or 102A of the access point 102. In this case, the mobile phone 1 selects an access point capable of communication among the access points 101 and 102, transmits a reassociation request (reconnection request) to the access point, and communicates with the access point. , Continue to connect to the second network. For example, when the mobile phone 1 selects the access point 101, a handoff is performed in which the mobile phone 1 is transferred between the access point 100 with which the mobile phone 1 was communicating and the access point 101 that transmitted the reassociation request. Is done. The reassociation request includes a MAC (Media Access Control) address as device identification information for identifying the mobile phone 1 and a MAC address as device identification information for identifying the access point 100 that has been communicating so far. included. When the access point 101 that has received the reassociation request acquires information necessary for permitting the connection of the mobile phone 1 from the access point 100 that is the handoff source and permits the connection, Send a reassociation response. The mobile phone 1 that has received the reassociation response from the access point 101 can communicate with the access point 101 and is reconnected to the second network. As described above, when the handoff is executed between the access point 100 and the access point 101, the communication destination of the mobile phone 1 is changed from the access point 100 to the access point 101. Can be kept connected to other networks.

  When the mobile phone 1 changes the communication destination from the access point 100 to the access point 101, both the access point 100 and the access point 101 are connected to the second network. For this reason, since it is connected to the network of the same segment before and after the handoff, the IP address assigned at the stage of connecting to the second network by communicating with the access point 100 before the handoff is used as it is after the handoff. Is possible. However, if the access point with which the mobile phone 1 communicates after handoff is connected to a network in a different segment from the second network to which the access point 100 with which the mobile phone 1 communicated before handoff is connected is connected to the second network. The IP address assigned at the stage that was assigned cannot be used as it is after handoff. For this reason, the mobile phone 1 confirms that the network segments connected before and after the handoff are the same.

  Specifically, the mobile phone 1 acquires the IP address of the G / W 111 by communicating with the access point 100 before the handoff, and the acquired IP address of the G / W 111 is correct via the access point that communicates after the handoff. Determine whether or not. The mobile phone 1 requests the MAC address of the IP address of the G / W 111 acquired previously according to the address resolution protocol (ARP) after handoff, and acquires the MAC address. The mobile phone 1 compares the acquired MAC address with the previously acquired MAC address of the G / W 111, and if the two match, the mobile phone 1 determines that it is connected to the second network. If it cannot be obtained, it is determined that it is connected to a network different from the second network.

  If the network segment connected before and after the handoff is the same, the cellular phone 1 uses the IP address acquired before the handoff as it is after the handoff, but if the network segment connected before and after the handoff is not the same, the DHCP server To assign a new IP address.

  In order to confirm that the network is in the same segment before and after handoff, there is a method of obtaining a subnet mask from the DHCP server. However, since communication with the DHCP server follows UDP, compared with communication according to ARP. Communication takes time. This is because communication according to UDP is communication in the transport layer of the OSI reference model, whereas communication according to ARP is communication in a network layer lower than the transport layer.

  As described above, the wireless LAN circuit 23 starts scanning in accordance with an instruction from the control unit 21. When the mobile phone 1 communicates with the access point 100 and functions as an IP phone, if the scan is started after moving outside the communicable area 100A, there is a period during which the mobile phone 1 is not connected to the second network. It will be long. When the mobile phone 1 is functioning as an IP phone, the call is interrupted if the period during which the mobile phone 1 is not connected to the second network becomes longer. For this reason, the mobile phone 1 according to the present embodiment shortens the period when the mobile phone 1 is not connected to the second network by executing this scan before communication with the access point 100 becomes impossible.

  While communicating with the access point 100, the control unit 21 measures the radio field intensity of the radio wave transmitted by the access point 100 at predetermined intervals, and determines the timing for executing the scan based on the measured radio field intensity. . The radio wave intensity is RSSI (Receive Signal Strength Indication), and its unit is dBm. If there is no obstacle that affects radio waves, the radio wave intensity decreases as the distance between the access point 100 and the mobile phone 1 increases. Using this property of the radio wave, the timing for executing the scan is determined.

  Further, the control unit 21 sets the timing of transmitting a reassociation request for instructing the handoff to the access point 101 to the radio wave intensity of the radio wave transmitted by the access point 100 in order to shorten the period of time when the access point 100 is not connected to the second network. Determine based on.

  FIG. 4 is a schematic diagram for explaining the relationship between the radio wave intensity of the radio wave transmitted by the access point, the scan start timing, and the reassociation request transmission timing. The figure shows a case where there is no obstacle that affects radio waves. Referring to FIG. 4, the position of access point 100 is shown at the center, three concentric circles 401, 402, 403 centered on the position of access point 100, and communicable area 100A. A concentric circle 401 indicates a position where the radio wave intensity of the access point 100 becomes the first threshold value. The radio field intensity inside the concentric circle 401 becomes larger than the first threshold value, and the radio field intensity outside the concentric circle 401 becomes smaller than the first threshold value. A concentric circle 402 indicates a position where the radio wave intensity of the access point 100 becomes the second threshold value. The radio field intensity inside the concentric circle 402 is larger than the second threshold value, and the radio field intensity outside the concentric circle 401 is smaller than the second threshold value. Therefore, the second threshold value is smaller than the first threshold value. Further, the second threshold value is better as it is closer to the communicable area 100A, and the mobile phone 1 may be set to the minimum value of the radio wave intensity at which communication with the access point 100 is possible. A concentric circle 403 indicates a position where the radio wave intensity of the access point 100 becomes the third threshold value. The radio field intensity is larger than the third threshold value inside the concentric circle 403, and the radio field intensity is smaller than the third threshold value outside the concentric circle 403. The concentric circle 403 is inside the concentric circle 401, and the third threshold value is larger than the first threshold value.

  The control unit 21 measures the radio wave intensity of the access point 100 during communication at a predetermined time interval. Here, the interval at which the radio wave intensity of the access point 100 during communication is measured is called a measurement interval. When the radio field intensity of the access point 100 falls below the first threshold, in other words, when the mobile phone 1 moves outside the concentric circle 401, the control unit 21 causes the wireless LAN circuit 23 to transmit a predetermined time interval (hereinafter referred to as “scan”). An instruction to execute a scan is output at an interval). The wireless LAN circuit 23 performs scanning at scan intervals. The control unit 21 determines the next access point to be connected based on the radio field intensity for each channel received from the wireless LAN circuit 23 every time scanning is executed. Here, it is assumed that the control unit 21 has determined that the access point 101 is the next access point to be connected.

  Then, when the radio field intensity of the access point 100 is lower than the second threshold value, in other words, when the mobile phone 1 moves outside the concentric circle 402, the control unit 21 determines that the access to be connected next is made. A reassociation request is transmitted to the point 101. Thereby, handoff is executed between the access point 100 and the access point 101. Therefore, the association request is a request for instructing the access point 101 to perform handoff. The control unit 21 also communicates with the radio wave intensity of the access point 101 determined to be connected next by scanning even if the radio wave intensity of the access point 100 does not fall below the second threshold value. If the difference from the radio wave intensity of the point 100 is larger than the fourth threshold value, a reassociation request is transmitted to the access point 101 determined to be connected next.

  Further, when the radio field intensity of the access point 100 falls below the first threshold value, the control unit 21 outputs an instruction to execute scanning at a scan interval to the wireless LAN circuit 23, but thereafter the radio field intensity of the access point 100. Exceeds the third threshold without falling below the second threshold, in other words, when the mobile phone 1 moves inside the concentric circle 403, the wireless LAN circuit 23 is scanned at a scan interval. An instruction to stop the operation is output. Since the communication with the access point 100 cannot be performed during the scan period in which the scan is executed, when the radio wave intensity of the access point 100 is sufficiently recovered, the execution of the scan is stopped to cancel the scan with the access point 100. It is possible to secure the communication period as much as possible.

  FIG. 5A is a diagram showing the measurement interval, and FIG. 5B is a diagram showing the scan interval. Referring to FIGS. 5A and 5B, the scan interval T is set longer than the measurement interval. The scan interval is a period from the end of the scan period to the start of the next scan period. It is desirable to make the scan interval as long as possible so that the ratio of the scan period during which communication with the access point 101 cannot be as small as possible.

  FIG. 6A is a diagram for explaining the state of data reception during the execution of scanning. FIG. 6B is a diagram for explaining the state of data transmission during the execution of scanning. Referring to FIG. 6A, in the scan period, wireless LAN circuit 23 measures the radio field intensity of a channel different from the channel communicating with access point 100, so that access point 100 transmits during the scan period. The data cannot be received. For this reason, the access point 100 continuously transmits data that was transmitted but not received by the wireless LAN circuit 23 in a short period after the end of the scan period. For this reason, the wireless LAN circuit 23 receives data that should have been received in the scan period after the end of the scan period, after the end of the scan period.

  Referring to FIG. 6B, in the scan period, the wireless LAN circuit 23 measures the radio field intensity of a channel different from the channel communicating with the access point 100, and therefore transmits data to the access point 100 during the scan period. Cannot send. For this reason, the wireless LAN circuit 23 discards the data output by the codec unit 28 during the scan period without transmitting it. As a result, the other party's device cannot receive the data discarded by the wireless LAN circuit 23 during the scan period, and therefore, there is no sound. However, since the scan period is a short period of about 200 msec, a silent state is detected by human hearing, but it is not a period in which sound is interrupted. In order to prevent a silent state from occurring, a buffer memory is provided in front of the wireless LAN circuit 23, and the wireless LAN circuit 23 stores data input from the codec unit 28 during the scan period in the buffer memory. The data stored in the buffer memory may be continuously transmitted after the scan period.

  FIG. 7 is a diagram for explaining the details of the scan period. FIG. 7A is a diagram showing a scan period and a scan interval, FIG. 7B is a diagram showing details of the scan period, and FIG. 7C is a scan period per channel. FIG. Referring to FIG. 7B, the scan period per time includes a scan period for each channel. In the figure, an example including a scan period of three channels is shown. The three channels are channels other than the channel through which the wireless LAN circuit 23 communicates with the access point 100, and are predetermined channels.

  Referring to FIG. 7C, the scan period per channel includes a time δ until a probe request (ProbeRequest) is sent and a waiting time until a probe response (ProbeResponse) is received. The time δ includes a time for switching the channel frequency and a time for waiting until the traffic becomes free. The wireless LAN circuit 23 transmits a probe request after the elapse of time δ. The time until the probe response (ProbeResponse) is received is a fixed time after the probe request is transmitted. This is because the probe response may not be received, and it is determined that the probe response is not received by waiting for a predetermined time. For this reason, the waiting time until the probe response is received is a fixed time even when the probe response is received.

  Next, the principle of reducing the number of scans will be described. FIG. 8A is a diagram showing the relationship between the radio wave intensity and the first threshold value and the second threshold value, and FIG. 8B shows the number of scans when the third threshold value is used. FIG. 8C illustrates the number of scans when the third threshold value is not used. In FIG. 8A, the horizontal axis represents time, and the vertical axis represents radio wave intensity. When the radio wave intensity is in the vicinity of the first threshold value, a phenomenon in which the first threshold value is exceeded after the radio wave intensity falls below the first threshold value occurs. In the figure, the number of times that the radio field intensity falls below the first threshold value during the period from T1 to T7 is five. For this reason, when the third threshold value is not used, scanning is started at each of the times T1, T2, T3, T4, and T6. On the other hand, when the third threshold value is used, the first scan is executed at the time T1 when the radio wave intensity first falls below the first threshold value, and the next scan is executed. This is a time T5 at which the scan interval T has elapsed since the end of the second scan. Further, at time T7 before the next scan is executed, if the radio wave intensity exceeds the third threshold value, the execution of the scan is stopped. Therefore, when the third threshold is not used, five scans are executed as shown in FIG. 8C, whereas when the third threshold is used, 2 scans are performed. Scans are performed. By reducing the number of scans to be executed, the period during which the wireless LAN circuit 23 can communicate with the access point 100 can be lengthened.

FIG. 9 is a flowchart illustrating an example of the flow of wireless LAN connection processing. The wireless LAN connection process is a process executed by the control unit 21 when the control unit 21 executes a wireless LAN connection program stored in the ROM 31. Referring to FIG. 9, control unit 21 is in a standby state until the power is turned on (NO in step S01), and when the power is turned on, the process proceeds to step S02. In step S02, the wireless LAN circuit 23 starts scanning in order to detect connectable access points. Then, an access point to be connected is determined based on the radio wave intensity detected by the scan, and a connection request (Association Request) is transmitted to the access point (step S03). For example, the access point to be connected may be determined to be the access point having the highest radio wave intensity. Here, a case where a connection request is transmitted to the access point 100 will be described as an example. Upon receiving the connection request, the access point 100 executes an authentication process defined by the standard IEEE 802.1X in order to authenticate the mobile phone 1. In response to this, the control unit 21 causes the wireless LAN circuit 23 to transmit information necessary for the authentication process to the access point 100 (step S04). If the authentication is successful at the access point 100, the control unit 21 controls the wireless LAN circuit 23 to exchange encryption information including the encryption key with the access point 100 (step S05). This protocol for exchanging encrypted information is known as a 4-way handshake.

  And the control part 21 acquires an IP address (step S06). Specifically, the wireless LAN circuit 23 is controlled to acquire an IP address from a DHCP server connected to the second network. Then, the acquired IP address is registered in the VoIP server 112 (step S07). The control unit 21 controls the wireless LAN circuit 23 to cause the VoIP server 112 to transmit the MAC address assigned to the mobile phone 1 and the acquired IP address. Thereby, the mobile phone 1 is registered in the VoIP server 112 and functions as an IP phone in the second network.

  And the control part 21 will be in a standby state (step S08), and if there exists a transmission or an incoming call (it is YES at step S09), a process will be advanced to step S10. If there is no outgoing call or no incoming call (NO in step S09), the process returns to step S08 to enter a standby state. The transmission is accepted by the control unit 21 when the user of the mobile phone 1 operates the operation key to operate the extension number. An incoming call is received by the control unit 21 by receiving an incoming call signal from the access point 100. In step S10, a line is connected and a call is started. The control unit 21 generates an IP packet including the IP address acquired in step S06 and the voice signal input from the codec unit 28 during a call, and outputs the IP packet to the wireless LAN circuit 23 for transmission. Moreover, the control part 21 performs a radio field intensity monitoring process during a call (step S11).

  In step S12, it is determined whether or not the line connected in step S10 is disconnected as a result of executing the radio field intensity monitoring process. If the line is disconnected, the process returns to step S06, and the line is not disconnected. The process proceeds to step S13. If the line is not disconnected by handoff, an IP packet including the IP address acquired in step S06 is generated before the handoff, and the IP packet is output to the wireless LAN circuit 23 for transmission. For this reason, since it is not necessary to acquire an IP address after handoff is performed, the time for acquiring an IP address can be shortened.

  In step S13, it is determined whether or not the call has ended. If the call has ended, the process proceeds to step S14; otherwise, the process returns to step S11. The end of the call is input to the cellular phone 1 when the user presses the call end button of the operation key and is accepted by the control unit 21 or the wireless LAN circuit 23 receives a signal indicating the end of the call from the access point 100. Then, the control unit 21 receives from the wireless LAN circuit 23. In step S14, it is determined whether or not the power is turned off. If the power is turned off, the process ends. If not, the process returns to step S08.

  FIG. 10 is a flowchart illustrating an example of the flow of the radio wave intensity monitoring process. The radio wave intensity monitoring process is a process executed in step S11 of FIG. Referring to FIG. 10, control unit 21 acquires radio wave intensity E1 of connected access point 100 (step S21). Then, it is determined whether or not the radio wave intensity E1 of the access point 100 is smaller than the first threshold value (step S22). If radio wave intensity E1 of access point 100 is smaller than the first threshold value, the process proceeds to step S23; otherwise, the process proceeds to step S27. In step S27, it is determined whether or not the measurement interval has elapsed since the radio field intensity E1 was measured. The process waits until the measurement interval time elapses (NO in step S27). If the measurement interval time elapses, the process returns to step S21. As a result, while the radio field intensity of the access point 100 is equal to or higher than the first threshold value, the radio field intensity E1 of the access point 100 is measured every time the measurement interval elapses.

  In step S23, the wireless LAN circuit 23 is caused to execute scanning. As a result, the radio LAN circuit 23 measures the radio field intensity of all channels except the channel communicating with the connected access point 100. The maximum value of the measured radio field intensity is acquired as the radio field intensity E2. While communication with the access point 100 is possible, a scan can be performed to determine an access point to be connected next.

  Then, it is determined whether or not the measurement interval has elapsed since the radio field intensity E1 was measured (step S24). The process waits until the measurement interval time elapses (NO in step S24). If the measurement interval time elapses, the process proceeds to step S25.

  In step S25, the radio field intensity E1 of the connected access point 100 is acquired. Then, it is determined whether or not the radio wave intensity E1 of the access point 100 is larger than the third threshold value (step S26). If radio wave intensity E1 of access point 100 is greater than the third threshold value, the process proceeds to step S27; otherwise, the process proceeds to step S28. If the radio wave intensity E1 of the access point 100 is greater than the third threshold, it is a sufficient condition to communicate with the access point 100, so the scan is stopped at every scan interval, This is to reduce the period during which communication with the connected access point 100 is not possible.

  In step S28, it is determined whether or not the radio wave intensity E1 measured in step S25 is smaller than the second threshold value. If radio wave intensity E1 of access point 100 is smaller than the second threshold value, the process proceeds to step S29; otherwise, the process proceeds to step S31. In step S31, it is determined whether or not the difference between the radio wave intensity E2 of the access point 101 acquired in step S23 and the radio wave intensity E1 of the access point 100 acquired in step S25 exceeds a fourth threshold value. If so, the process proceeds to step S29; otherwise, the process proceeds to step S41. Even if the radio wave intensity E1 of the connected access point 100 is not smaller than the second threshold value, if there is an access point whose radio wave intensity difference exceeds the second threshold value than the access point 100, the access point This is because it is preferable that communication is performed with less communication errors.

  In step S29, candidate access points that are candidates for the next access point are determined. The condition for becoming a candidate access point is that an access point whose radio wave intensity acquired in step S23 is larger than the fifth threshold value or a radio wave intensity E1 of the communicating access point 100 is set to a fourth threshold value. It is an access point with a radio field intensity greater than the added value. The fifth threshold value is a value for determining absolutely whether or not the radio wave intensity is a value sufficient for communication only from the radio wave intensity, and is a predetermined value. The fourth threshold value is a value for relatively determining whether or not the radio wave intensity is a value sufficient for communication as compared with the radio wave intensity E1 of the access point 100 that is communicating, and is determined in advance. Value.

  In the next step S30, it is determined whether or not a candidate access point has been determined in step S29. If the candidate access point is determined, the process proceeds to step S32. If not determined, the process proceeds to step S41. Candidate access points may not be determined, in which case handoff is not performed.

On the other hand, in step S41, it is determined whether it is a scan timing. If it is the scan timing, the process returns to step S23, and if it is not the scan timing, the process returns to step S24. Since the scan interval and the measurement interval are determined separately, the time after the scan interval time elapses and the time after the measurement interval time elapses,
Execute the process that comes first.

  In step S32, among the candidate access points determined in step S29, the access point with the maximum radio wave intensity acquired by the scan in step S23 is determined as the connection access point for the next connection. Then, a reassociation request is transmitted to the connection access point (step S33). Here, description will be made assuming that the access point 101 is determined as a connection access point. When the access point 101 receives the reassociation request, the access point 101 acquires information necessary for permitting the connection of the mobile phone 1 from the access point 100 based on the device identification information of the handoff source access point 100 included in the reassociation request. When the connection is permitted, a reassociation response is transmitted to the mobile phone 1. The mobile phone 1 that has received the reassociation response from the access point 101 can communicate with the access point 101 and is reconnected to the second network. As described above, when the handoff is executed between the access point 100 and the access point 101, the communication destination of the mobile phone 1 is changed from the access point 100 to the access point 101. Can be kept connected to other networks. Note that, when the mobile phone 1 does not receive a reassociation response, it cannot communicate with the access point 101. Therefore, another connection access point may be determined and step S33 may be executed.

  Next, it is determined whether an authentication request has been received from the access point 101 that has become communicable (step S34). When the mobile phone 1 transmits a reassociation request and communication with the access point 101 becomes possible, the access point 101 has the initiative to determine whether or not to execute the authentication process. Therefore, if an authentication request is received from access point 101, the process proceeds to step S35, and if no authentication request is received, the process proceeds to step S36. Is transmitted to the access point 100 according to the authentication request, the wireless LAN circuit 23 transmits information necessary for the authentication process (step S35). If the access point 101 does not transmit an authentication request, the authentication process can be omitted, so that the time required for the authentication process can be shortened, and the period during which the mobile phone 1 is not connected to the second network can be reduced. Can be shortened.

In the next step S <b> 36, the control unit 21 controls the wireless LAN circuit 23 to exchange encryption information including an encryption key with the access point 100. Then, G / W is detected (step S37). The mobile phone 1 confirms that the network segments connected before and after the handoff are the same. Specifically, the mobile phone 1 uses the IP address of the G / W 111 acquired by communicating with the access point 100 before handoff, and transmits it to the access point that communicates after handoff according to the Address Resolution Protocol (ARP). It is confirmed whether the G / W 111 is connected to the network to which the point 102 is connected (step S38). If the G / W 111 is connected to the network to which the access point 102 is connected, it is determined that the network segments to be connected before and after the handoff are the same, the process proceeds to step S39, and the access point 102 is connected. If the G / W 111 is not connected to the existing network, it is determined that the network segments connected before and after the handoff are not the same, and the process proceeds to step S40. If the network segments connected before and after handoff are the same, an IP packet can be generated using the IP address obtained before handoff as it is, but if the network segments connected before and after handoff are not the same, handoff This is because the previously acquired IP address cannot be used as it is, and it is necessary to generate an IP packet using the newly acquired IP address. If the network segments connected before and after handoff are the same, an IP packet can be generated using the IP address obtained before handoff as it is, so there is no need to obtain a new IP address, and an IP address is obtained. It is possible to avoid a state in which connection to the second network is not possible until this time.

  In step S39, the process is returned to step S12 in FIG. 9 by continuing the call, and in step S40, the process is returned to step S12 in FIG. 9 by disconnecting the line.

  As described above, the mobile phone 1 according to the present embodiment has the radio field intensity E1 of the first channel during communication with one of the three access points 100 to 102 via the first channel. In response to the detection, the radio wave intensity E1 of the first channel falls below the first threshold value, and temporarily switches to the second channel with which another access point 101 or 102 communicates, and the radio wave intensity E2 of the second channel Run a scan to detect. Then, based on the detected radio wave intensity E2 of the second channel, the access point 102 to be communicated next is determined from the access points 101 and 102, and the radio wave intensity E1 of the first channel is below the second threshold value. Accordingly, a reassociation request (reconnection request) for requesting connection by handoff is transmitted to the connection access point 102. The connection access point 102 is determined before communication with the access point 100 cannot be performed on the first channel, and communication with the connection access point 102 can be performed immediately before communication with the first channel cannot be performed. For this reason, since the connection access point 101 is determined before communication with the access point 100 becomes impossible, a period in which communication is interrupted as compared to when the connection access point 102 is determined after communication with the access point 100 becomes impossible Can be shortened. If the second threshold value is set near the minimum value at which radio communication with the first radio station apparatus can be performed, the performance of the access point 100 can be utilized to the maximum extent.

  Further, after the radio field intensity E1 of the access point 100 that is communicating falls below the first threshold value, if the radio field intensity E1 exceeds the third threshold value, scanning is not performed. Since communication with the access point 100 cannot be performed while the scan is being executed, communication is performed by stopping the scan when the radio wave intensity E1 of the access point 100 with which communication is performed becomes sufficiently high. You can eliminate periods when you can't.

  Even if the radio field intensity E1 of the access point 100 that is communicating does not fall below the second threshold value that is smaller than the first threshold value, the radio field intensity E2 of another access point 101 or 102 If the difference from the radio wave intensity E1 is larger than the fourth threshold value, a reconnection request is transmitted. Thereby, handoff is performed. By switching to communication with an access point with higher radio field intensity, the occurrence of communication errors can be reduced.

  In addition, a reassociation request is sent out, and after wireless communication is established with the connection access point 102, the existence is inquired to the gateway 111 of the network to which the access point 100 communicating before handoff was connected. Since it is determined whether or not the network to which the mobile phone 1 is connected before and after the handoff is the same segment depending on the presence or absence of the gateway 111, whether or not the network segment to be connected before and after the handoff is the same as compared with the inquiry to the DHCP server. Can be judged quickly.

  Further, if the network segments connected before and after handoff are the same, an IP packet is generated using the IP address used before handoff, in other words, before sending an association request, and transmitted to access point 101. . For this reason, since it is not necessary to acquire an IP address again, the time for acquiring an IP address can be shortened, and the call can be continued while maintaining the connection to the second network.

In the above-described embodiment, the communication system 10, particularly the mobile phone 1, has been described. However, the radio station apparatus switching method or the radio station apparatus for causing the mobile phone 1 to execute the processes shown in FIGS. Needless to say, the invention can be understood as a switching program.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

<Appendix>
(1) The determining means is that the radio field intensity of the second channel is greater than a fifth threshold value, or that the difference from the radio field intensity of the first channel is greater than a fourth threshold value. The mobile concession terminal according to claim 1, wherein the second radio station apparatus is determined on the condition of
(2) In (1), when there are a plurality of the second radio station apparatuses, the determination unit determines the radio station apparatus having the maximum radio field intensity of the second channel as the second radio station apparatus. .

DESCRIPTION OF SYMBOLS 1 Mobile phone 2 Display side part 3 Operation side part 10 Communication system 11 1st speaker 12 2nd speaker 13 Microphone 14 Operation key 15 LCD
16 Microphone terminal 17 Earphone terminal 19 Infrared communication unit 21 Control unit 22 Wireless circuit 23 Wireless LAN circuit 24, 24A Camera 26 Vibration unit 27 Card I / F
27A Flash memory 28 Codec unit 29 Switching unit 30 Display control unit 100 to 103 Access point 110 LAN cable 111 Gateway 112 VoIP server 115 Internet 116 Computer 200 Mobile phone system 201 Base station device 202 Communication network 300 Wireless LAN system system

Claims (7)

Wireless communication means capable of wireless communication by transmitting and receiving a packet including an audio signal with any one of a plurality of access points connected to the same gateway;
First radio field intensity detecting means for detecting the radio field intensity of the first channel while the wireless communication unit is communicating with the first access point of the plurality of access points on the first channel;
In response to the detected radio field intensity of the first channel falling below a first threshold, the communication channel of the wireless communication means is temporarily changed from the first channel to a second channel different from the first channel. A second radio field intensity detecting means for detecting the radio field intensity of the second channel,
Determining means for determining a second access point to communicate next from among the plurality of access points based on the detected radio field intensity of the second channel;
In response to the radio field intensity of the first channel being lower than a second threshold value that is smaller than the first threshold value, the wireless communication means is connected to the determined second access point by handoff. Reconnection request means for sending out a reconnection request for requesting, and
The second radio wave intensity detecting means is configured such that when the detected radio wave intensity of the first channel falls below a first threshold value, the detected radio wave intensity of the first channel is greater than the first threshold value. A portable communication terminal that repeatedly detects the radio field intensity of the second channel at a predetermined time interval until a third threshold value is exceeded. The reconnection requesting unit determines the radio wave intensity of the second channel and the radio wave of the first channel when the radio wave intensity of the first channel does not fall below a second threshold value that is smaller than the first threshold value. 2. The mobile communication terminal according to claim 1, wherein if the difference from the strength is greater than a fourth threshold value, the wireless communication unit is configured to send the reconnection request. A codec that combines audio signals;
A first radio circuit that receives a radio signal including a packet including an audio signal sent from any one of the plurality of access points, and outputs an audio signal obtained by demodulating the radio signal to the codec unit;
A second radio circuit that receives a radio signal transmitted from any one of a plurality of base stations connected to a mobile phone communication network, and outputs an audio signal obtained by demodulating the radio signal to the codec unit;
The mobile communication terminal according to claim 1, further comprising: An access point switching method executed by a mobile communication terminal having a wireless communication means capable of wireless communication by transmitting and receiving a packet including an audio signal with any one of a plurality of access points connected to the same gateway. ,
Detecting the radio field intensity of the first channel while the wireless communication means is communicating with the first access point of the plurality of access points on the first channel;
In response to the detected radio field intensity of the first channel falling below a first threshold, the communication channel of the wireless communication means is temporarily changed from the first channel to a second channel different from the first channel. And switching to detect the radio field intensity of the second channel;
Determining a second access point to communicate next from among the plurality of access points based on the detected radio field intensity of the second channel;
In response to the radio field intensity of the first channel being lower than a second threshold value that is smaller than the first threshold value, the wireless communication means is connected to the determined second access point by handoff. Sending a reconnection request to request,
The step of detecting the radio field intensity of the second channel includes the step of detecting the radio field intensity of the first channel when the detected radio field intensity of the first channel falls below a first threshold. An access point switching method including the step of repeatedly detecting the radio field intensity of the second channel at a predetermined time interval until a third threshold value greater than a threshold value is exceeded. The step of transmitting the reconnection request includes the step of transmitting the second channel radio wave intensity and the first channel if the radio wave intensity of the first channel does not fall below a second threshold value that is smaller than the first threshold value. 5. The access point switching method according to claim 4, further comprising the step of causing the wireless communication means to send out the reconnection request if the difference from the radio field intensity of the channel is greater than a fourth threshold value. An access point switching program executed by a mobile communication terminal having a wireless communication means capable of wireless communication by transmitting and receiving a packet including an audio signal with any one of a plurality of access points connected to the same gateway. ,
Detecting the radio field intensity of the first channel while the wireless communication means is communicating with the first access point of the plurality of access points on the first channel;
In response to the detected radio field intensity of the first channel falling below a first threshold, the communication channel of the wireless communication means is temporarily changed from the first channel to a second channel different from the first channel. And switching to detect the radio field intensity of the second channel;
Determining a second access point to communicate next from among the plurality of access points based on the detected radio field intensity of the second channel;
In response to the radio field intensity of the first channel being lower than a second threshold value that is smaller than the first threshold value, the wireless communication means is connected to the determined second access point by handoff. Sending a reconnection request to request,
A packet generating step of generating packet data including an IP address assigned to the own device in the network to which the first access point is connected, and outputting the packet data to the wireless communication unit; and the wireless communication unit requesting reconnection And inquiring a network gateway connected to the second access point after wireless communication is established with the second access point, further causing the portable communication terminal to execute ,
In the packet generation step, when the gateway specified by the response received in response to the inquiry is the same as the gateway of the network to which the first access point is connected, the wireless communication means sends a reconnection request An access point switching program including a step of generating packet data by using an IP address that has been used before performing.   The step of transmitting the reconnection request includes the step of transmitting the second channel radio wave intensity and the first channel if the radio wave intensity of the first channel does not fall below a second threshold value that is smaller than the first threshold value. The access point switching program according to claim 6, further comprising a step of causing the wireless communication means to send out the reconnection request if the difference from the radio field intensity of the channel is larger than a fourth threshold value.