JP2009182697A - Wireless terminal and radio communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To properly select an ad hoc communication network of a connection destination when there exists a plurality of ad hoc communication networks connected with radio communication systems having the types different from each other. <P>SOLUTION: A radio communication method includes: a step S109 of acquiring first speed information showing a first communication speed determined according to the type of first radio communication system to which a first ad hoc communication network is connected; a step S109 of acquiring second speed information showing a second communication speed determined according to the type of second radio communication system to which a second ad hoc communication network is connected; and a step S111 of selecting the ad hoc communication network of a connection destination on the basis of the acquired first speed information and the acquired second speed information. In the step S111 of selecting the ad hoc communication network of a connection destination, the first communication speed and the second communication speed are compared with each other. When the first communication speed exceeds the second communication speed, the first ad hoc communication network is selected. When the second communication speed exceeds the first communication speed, the second ad hoc communication network is selected. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a wireless terminal and a wireless communication method capable of communicating with a wireless base station via another wireless terminal.

  In recent years, with the spread of wireless communication technology, an environment capable of connecting to a plurality of wireless communication systems having different communication methods is being prepared. For example, cdma 2000 nx evolution-data only (EV-DO), which is a kind of third generation mobile phone system, and wireless LAN system defined by IEEE802.11a / b / g etc. Provision of terminals is under consideration.

  Such a wireless LAN system can communicate at a higher speed than a mobile phone system such as EV-DO. In the wireless LAN system, an infrastructure mode in which a wireless terminal directly communicates with a wireless base station and an ad hoc mode in which communication is performed between wireless terminals without passing through the wireless base station are defined. In the ad hoc mode, an ad hoc communication network is formed by a plurality of wireless terminals.

  Also, in a wireless LAN system, a wireless terminal that communicates directly with a wireless base station (hereinafter “main wireless terminal”) and at least one wireless terminal that communicates with the wireless base station via the main wireless terminal (hereinafter “subordinate wireless terminal”). A method of forming an ad hoc communication network with a wireless terminal ") is known. Furthermore, a wireless terminal capable of selecting a connection destination ad hoc communication network from among a plurality of ad hoc communication networks has been proposed (see Patent Document 1).

Specifically, the wireless terminal described in Patent Document 1 acquires communication band information, which is information on a communication band (that is, effective value of communication speed) of wireless communication executed in the ad hoc communication network, for each ad hoc communication network. Then, a connection destination ad hoc communication network is selected based on the acquired communication band information.
Japanese Patent Laying-Open No. 2005-79827 ([Claim 1], FIG. 1)

  Generally, a communication band changes with changes in communication quality (for example, SNR). Communication quality of wireless communication executed in an ad hoc communication network frequently changes with the influence of interference sources and movement of wireless terminals. Therefore, in the method described in Patent Document 1 in which the connection destination ad hoc communication network is selected based on the communication band, the connection destination ad hoc communication network is not always appropriately selected because the communication band serving as the selection reference is unstable. There is a problem that cannot be done.

  In an ad hoc communication network, when the main wireless terminal is compatible with both the wireless LAN system and the mobile phone system, the mobile phone system is applied to the wireless communication between the main wireless terminal and the wireless base station, and the main wireless terminal It is also assumed that a wireless LAN system is applied to wireless communication between a terminal and a slave wireless terminal.

  In such an ad hoc communication network, since the communication speed of the mobile phone system is lower than that of the wireless LAN system, the wireless communication between the main wireless terminal and the wireless base station becomes a bottleneck, and the wireless communication between the primary wireless terminal and the secondary wireless terminal The communication speed inherent in the wireless LAN system cannot be exhibited in communication.

  However, since the wireless terminal described in Patent Literature 1 does not consider the connection band between the ad hoc communication network and the public network or the type of the wireless communication system to which the ad hoc communication network is connected, the ad hoc communication network is connected. There is a risk of connecting to an ad hoc communication network in which the communication speed decreases due to the type of the wireless communication system.

  Further, in the method described in Patent Document 1, since band information between all nodes (wireless terminals) in an ad hoc communication network is transmitted to wireless terminals attempting connection, the amount of information increases and a load is imposed on the network. There is also a problem.

  Therefore, the present invention has been made to solve the above-described problem, and when there are a plurality of ad hoc communication networks connected to different types of wireless communication systems, the connection destination ad hoc communication network is appropriately selected. An object is to provide a selectable wireless terminal and a wireless communication method.

  In order to solve the above-described problems, the present invention has the following features. First, the first feature of the present invention is that a first ad hoc communication network (ad hoc communication network AH1) connected to a first radio base station (radio base station BS1) constituting a first radio communication system (for example, EV-DO). ) Or a second ad hoc communication network (ad hoc communication) connected to a second radio base station (radio base station BS2) constituting a second radio communication system (for example, IEEE802.11b) of a different type from the first radio communication system A wireless terminal (wireless terminal MS10) capable of selecting any one of the networks AH2) as a connection destination ad hoc communication network, and a signal transmitted by the wireless terminals (wireless terminals MS1 to MS3) forming the first ad hoc communication network 1st information acquisition which acquires the 1st rate information (WAN rate information) which is the information contained in 1 and which shows the 1st communication speed defined according to the classification of the 1st radio communications system Unit (wireless LAN communication unit 120, control signal processing unit 131) and information transmitted in signals transmitted by wireless terminals (wireless terminals MS4 to MS6) forming the second ad hoc communication network, the second wireless A second information acquisition unit (wireless LAN communication unit 120, control signal processing unit 131) for acquiring second rate information (WAN rate information) indicating a second communication rate determined according to the type of communication system; An ad hoc communication network selection unit (selecting an ad hoc communication network to be connected) based on the first speed information acquired by the information acquisition unit and the second speed information acquired by the second information acquisition unit ( An ad hoc communication network selection unit 133), the ad hoc communication network selection unit compares the first communication speed with the second communication speed, and the first communication speed exceeds the second communication speed. The gist is to select the first ad hoc communication network when turning, and to select the second ad hoc communication network when the second communication speed exceeds the first communication speed.

  According to such a wireless terminal, when there are a plurality of ad hoc communication networks connected to different types of wireless communication systems, the connection destination ad hoc communication network can be appropriately selected. Specifically, it is possible to avoid selecting an ad hoc communication network that causes a decrease in communication speed due to the type of wireless communication system to which the ad hoc communication network is connected as a connection destination.

  A second feature of the present invention relates to the first feature of the present invention, wherein the first information acquisition unit includes a first beacon signal broadcasted by a wireless terminal forming the first ad hoc communication network at a predetermined period. When the first speed information is included, the first speed information is acquired from the first beacon signal, and the second information acquisition unit notifies the wireless terminals forming the second ad hoc communication network at a predetermined cycle. When the second speed information is included in the second beacon signal to be performed, the second speed information is acquired from the second beacon signal.

  A third feature of the present invention relates to the second feature of the present invention, wherein when the first speed information is not included in the first beacon signal, a wireless terminal forming the first ad hoc communication network is provided. A first request signal transmission unit (wireless LAN communication unit 120, control signal processing unit 131) for transmitting a first probe request signal for requesting transmission of first control information used for forming the first ad hoc communication network; When the second speed information is not included in the second beacon signal, the second control information used for forming the second ad hoc communication network is transmitted to the wireless terminals forming the second ad hoc communication network. A second request signal transmission unit (wireless LAN communication unit 120, control signal processing unit 131) for transmitting a second probe request signal for requesting transmission, wherein the first information acquisition unit is configured to transmit the first ad hoc communication. When the first probe response signal transmitted by the wireless terminal forming the network in response to the first probe request signal includes the first speed information, the first speed information is acquired from the first probe response signal. When the second information acquisition unit includes the second speed information in a second probe response signal transmitted by a wireless terminal forming the second ad hoc communication network in response to the second probe request signal. The gist is to obtain the second speed information from the second probe response signal.

  A fourth feature of the present invention is according to the third feature of the present invention, wherein the first request signal transmission unit includes the first request information when the first speed information is not included in the first probe response signal. A first speed information request signal for requesting transmission of the first speed information is transmitted to a wireless terminal forming an ad hoc communication network, and the second request signal transmission unit transmits the first speed information request signal to the second probe response signal. If the second speed information is not included, a second speed information request signal requesting transmission of the second speed information is transmitted to the wireless terminals forming the second ad hoc communication network, and the first information acquisition is performed. The unit acquires the first speed information from a first speed information response signal transmitted by a wireless terminal forming the first ad hoc communication network in response to the first speed information request signal, and the second information acquisition unit Forming the second ad hoc communication network Wireless terminal is to be required to obtain the second velocity information from the second speed information response signal transmitted in response to the second speed information request signal.

  A fifth feature of the present invention relates to the first feature of the present invention, wherein a reception sensitivity of a signal transmitted by a wireless terminal forming the first ad hoc communication network and a wireless terminal forming the second ad hoc communication network are provided. Further includes a reception sensitivity measurement unit (wireless LAN communication unit 120, control signal processing unit 131) for measuring the reception sensitivity of the signal transmitted by the ad hoc communication network selection unit, the first communication speed and the second communication. When the speed is equal, the higher one of the first ad hoc communication network and the second ad hoc communication network having the higher reception sensitivity measured by the reception quality measuring unit is selected as the connection destination ad hoc communication network. This is the gist.

  A sixth feature of the present invention relates to the first feature of the present invention, wherein the first information acquisition unit is a first system type indicating a type of the first wireless communication system instead of the first speed information. The second information acquisition unit acquires second system type information indicating a type of the second wireless communication system instead of the second speed information, and the ad hoc communication network selection unit Selecting the ad hoc communication network of the connection destination based on the first system type information acquired by the first information acquisition unit and the second system type information acquired by the second information acquisition unit; The gist.

  According to a seventh aspect of the present invention, there is provided a first ad hoc communication network connected to a first radio base station constituting the first radio communication system, or a second radio communication system having a different type from the first radio communication system. A wireless communication method for performing communication by selecting any of the second ad hoc communication networks connected to the second wireless base station as a connection destination ad hoc communication network, and transmitted by a wireless terminal forming the first ad hoc communication network A step of acquiring first speed information which is information included in the signal and indicates a first communication speed determined according to a type of the first wireless communication system; and a wireless terminal forming the second ad hoc communication network A step of acquiring second speed information, which is information included in a signal to be transmitted and indicates a second communication speed determined according to a type of the second wireless communication system; Selecting the connection destination ad hoc communication network based on the first speed information and the acquired second speed information, wherein the selecting step includes the first communication speed and the second communication. Comparing the speed, selecting the first ad hoc communication network when the first communication speed exceeds the second communication speed, and when the second communication speed exceeds the first communication speed. And a step of selecting the second ad hoc communication network.

  According to the features of the present invention, there are provided a wireless terminal and a wireless communication method capable of appropriately selecting a connection destination ad hoc communication network when there are a plurality of ad hoc communication networks connected to different types of wireless communication systems. be able to.

  Next, an embodiment of the present invention will be described with reference to the drawings. Specifically, (1) overall schematic configuration of communication system, (2) configuration of wireless terminal, (3) operation of wireless terminal, (4) action / effect, (5) other embodiments will be described.

  In the description of the drawings in the following embodiments, the same or similar parts are denoted by the same or similar reference numerals.

(1) Overall Schematic Configuration of Communication System FIG. 1 is an overall schematic configuration diagram of a communication system according to the present embodiment. As shown in FIG. 1, the communication system includes wireless terminals MS1 to MS6 and MS10, wireless base stations BS1 and BS2, and a wide area network (WAN) 10. The wireless terminals MS1 to MS6 and MS10 are compatible with both EV-DO, which is a kind of mobile phone system, and a wireless LAN system.

  The radio base station BS1 is connected to the WAN 10 and forms a service area (radio wave arrival area) SA1, which is an area in which direct communication with a radio terminal is possible. In the present embodiment, the radio base station BS1 is configured according to EV-DO. The communication speed of EV-DO is a maximum of 2.4 Mbps (theoretical value).

  In the example of FIG. 1, a radio terminal MS1 located in the service area SA1 is connected to the radio base station BS1 and can directly communicate with the radio base station BS1. EV-DO is applied to wireless communication between the wireless terminal MS1 and the wireless base station BS1.

  The radio base station BS2 is connected to the WAN 10 and forms a service area SA2 that is an area that can directly communicate with the radio terminal. The wireless base station BS2 is an access point (AP) configured according to IEEE802.11b, which is a type of wireless LAN system. The communication speed of IEEE802.11b is a maximum of 11 Mbps (theoretical value).

  In the example of FIG. 1, a radio terminal MS4 located in the service area SA2 can connect to the radio base station BS2 and directly communicate with the radio base station BS1. IEEE802.11b is applied to wireless communication between the wireless terminal MS4 and the wireless base station BS2.

  The radio terminals MS1 to MS3 form an ad hoc communication network AH1. The ad hoc communication network AH1 has a tree structure with the radio terminal MS1 being the main radio terminal directly communicating with the radio base station BS1 as the highest level. The radio terminal MS2 and the radio terminal MS3 are slave radio terminals that communicate with the radio base station BS1 via the radio terminal MS1.

  IEEE802.11g, which is a type of wireless LAN system, is applied to wireless communication between the wireless terminal MS1 and the wireless terminal MS2 and wireless communication between the wireless terminal MS1 and the wireless terminal MS3. The maximum communication speed of IEEE802.11g is 54 Mbps (theoretical value).

  However, since EV-DO is applied to wireless communication between the wireless terminal MS1 and the wireless base station BS1, wireless communication between the wireless terminal MS1 and the wireless terminal MS2, and wireless communication between the wireless terminal MS1 and the wireless terminal MS3. In this case, the maximum communication speed is limited to the EV-DO communication speed (2.4 Mbps at the maximum) or less. Therefore, the original communication speed of IEEE802.11g cannot be exhibited.

  The radio terminals MS4 to MS6 form an ad hoc communication network AH2. The ad hoc communication network AH2 has a tree structure with the radio terminal MS4 being the main radio terminal directly communicating with the radio base station BS2 as the highest level. The radio terminal MS5 and the radio terminal MS6 are slave radio terminals that communicate with the radio base station BS2 via the radio terminal MS4.

  IEEE802.11b is applied to the wireless communication between the wireless terminal MS4 and the wireless terminal MS5 and the wireless communication between the wireless terminal MS4 and the wireless terminal MS6. Here, IEEE802.11b is also applied to wireless communication between the wireless terminal MS4 and the wireless base station BS2, and wireless communication between the wireless terminal MS4 and the wireless terminal MS5 and wireless communication between the wireless terminal MS4 and the wireless terminal MS6. Then, the original communication speed of IEEE802.11b can be demonstrated.

  The wireless terminal MS10 corresponds to a wireless LAN system including IEEE802.11b and IEEE802.11g and a mobile phone system (EV-DO), and has a function of directly communicating with the wireless base station BS1. In the example of FIG. 1, since the radio terminal MS10 is located outside the service area SA1, it cannot communicate directly with the radio base station BS1, but can be connected to either the ad hoc communication network AH1 or the ad hoc communication network AH2. It is.

  Since the radio terminals MS1 to MS6 and MS10 have the same configuration, in the following description, the radio terminals MS1 to MS6 and MS10 are collectively referred to as a radio terminal MS as appropriate. In the following description, the ad hoc communication network AH1 and the ad hoc communication network AH2 are also referred to as an ad hoc communication network AH.

(2) Configuration of Radio Terminal Next, the configuration of the radio terminal MS will be described with reference to FIGS. Specifically, (2.1) the hardware configuration of the wireless terminal and (2.2) the functional block configuration of the wireless terminal will be described.

(2.1) Hardware Configuration of Radio Terminal FIG. 2 is a hardware configuration diagram of the radio terminal MS. As shown in FIG. 2, the wireless terminal MS includes a mobile phone communication unit 110, a wireless LAN communication unit 120, a control unit 130, a microphone 141, a speaker 142, a display unit 143, and an input unit 144.

  The cellular phone communication unit 110 transmits and receives a radio signal (RF signal) according to the CDMA system to and from the radio base station BS1. In addition, the mobile phone communication unit 110 performs conversion between a radio signal and a baseband signal, and transmits / receives the baseband signal to / from the control unit 130. Note that the radio signal includes a control signal used for communication control and an information signal (user data).

  The wireless LAN communication unit 120 is configured according to a wireless LAN system that can use an infrastructure mode and an ad hoc mode, such as IEEE802.11a / b / g. The wireless LAN communication unit 120 transmits and receives wireless signals according to the wireless LAN system to and from the wireless base station BS2 or the wireless terminal MS. The wireless LAN communication unit 120 performs conversion between a radio signal and a baseband signal, and transmits / receives the baseband signal to / from the control unit 130.

  The microphone 141 converts sound into an electric signal and inputs the electric signal to the control unit 130. The speaker 142 converts the electrical signal from the control unit 130 into sound and outputs the sound.

  The display unit 143 displays images received via the control unit 130 and operation details (such as input telephone numbers and addresses). The input unit 144 includes a numeric keypad, function keys, and the like, and accepts user operations.

  The control unit 130 includes a CPU and a memory, and controls various functions provided in the wireless terminal MS. The memory stores various information used for control in the radio terminal MS.

  The mobile phone communication unit 110 includes an antenna 111, a mobile phone system RF processing unit 112, an encoding unit 113, and a decoding unit 114. The mobile phone system RF processing unit 112 performs amplification and down-conversion of a radio signal input via the antenna 111, and generates a baseband signal. The encoding unit 113 encodes the baseband signal from the control unit 130. The mobile phone system RF processing unit 112 performs up-conversion and amplification of the encoded baseband signal. Thereby, a radio signal is generated. The generated radio signal is transmitted to the outside via the antenna 111. The decoding unit 114 decodes the generated baseband signal and inputs the decoded baseband signal to the control unit 130.

  The wireless LAN communication unit 120 includes an antenna 121, a wireless LAN system RF processing unit 122, an encoding unit 123, and a decoding unit 124. The antenna 121, the wireless LAN system RF processing unit 122, the encoding unit 123, and the decoding unit 124 have the same functions as the antenna 111, the mobile phone system RF processing unit 112, the encoding unit 113, and the decoding unit 114, respectively. Therefore, the description is omitted. The wireless LAN communication unit 120 transmits and receives control signals including control information used for forming the ad hoc communication network AH.

(2.2) Functional Block Configuration of Radio Terminal FIG. 3 is a block diagram showing each function executed by the control unit 130. In the following, points related to the present invention will be mainly described.

  As shown in FIG. 3, the control unit 130 includes a control signal processing unit 131, an ad hoc communication network selection unit 133, a communication speed information storage unit 134, a communication control unit 136, a reception sensitivity comparison unit 137, and a handoff control unit 138. .

  The control signal processing unit 131 acquires or generates a control signal that the wireless LAN communication unit 120 transmits / receives to / from another wireless terminal MS. In the present embodiment, the control signal processing unit 131 also functions as a reception sensitivity measurement unit that measures the reception sensitivity of the received control signal.

  Here, the control signal includes a beacon signal, a probe request signal, a probe response signal, a speed information request signal, and a speed information response signal. That is, in the present embodiment, the control signal processing unit 131 constitutes an information acquisition unit that acquires communication speed information described later. Hereinafter, a control signal compliant with IEEE802.11b will be described as an example.

<1> Beacon signal The beacon signal indicates that the wireless terminal MS is located at a distance where the ad hoc communication network AH can be formed. Each wireless terminal MS autonomously broadcasts a beacon signal at a predetermined cycle. The beacon signal includes control information used for forming the ad hoc communication network AH.

  FIG. 4 shows information elements included in the beacon signal. As shown in the figure, the beacon signal includes an SSID (Service Set ID) field, a Capability information field, a WAN rate information field, and the like. The SSID field stores an identifier for identifying the ad hoc communication network AH. That is, the wireless terminal MS can identify the ad hoc communication network AH formed by the wireless terminal MS that broadcasts the beacon signal based on the SSID field.

  FIG. 5 shows information elements included in the Capability information field. The Capability information field includes a WAN rate information include field indicating whether or not the WAN rate information field is included in the beacon signal. The value of the WAN rate information include field is 1 when the WAN rate information field is included in the beacon signal. On the other hand, the value of the WAN rate information include field is 0 when the WAN rate information field is not included in the beacon signal.

  FIG. 6 shows information elements included in the WAN rate information field. The WAN rate information field includes a WAN rate field. The field length of the WAN rate field is 8 bits.

  The WAN rate field stores communication speed information indicating a communication speed determined according to the type of the wireless communication system to which the ad hoc communication network AH is connected. In the present embodiment, information indicating the theoretical value of the maximum communication speed is stored as communication speed information. For example, in the communication speed information, “0x01” is defined as 100 kbps, “0x02” is defined as 100 kbps to 300 kbps, “0x03” is defined as 300 kbps to 500 kbps, and the like. The wireless terminal MS can recognize the communication speed of the wireless communication system to which the ad hoc communication network AH is connected based on the WAN rate field, that is, the communication speed information.

  Here, in the beacon signal, the WAN rate information field is an optional element. That is, the radio terminal MS can generate a beacon signal that does not include the WAN rate information field.

  Further, the WAN rate field is generated by the main radio terminal MS (radio terminals MS1 and MS4 in FIG. 1). The slave radio terminal MS can store the WAN rate field received from the master radio terminal MS in the WAN rate information field.

<2> Probe Request Signal The probe request signal is a control signal for requesting transmission of control information used for forming the ad hoc communication network AH. The radio terminal MS transmits a probe request signal to the radio terminal MS located at a distance where the ad hoc communication network AH can be formed. Therefore, the probe request signal can also be used to confirm whether or not there is a wireless terminal MS that can form the ad hoc communication network AH.

  FIG. 7A shows information elements included in the probe request signal. The probe request signal includes the SSID field described above.

  The wireless terminal MS can transmit the probe request signal at an arbitrary time (including a periodic time) regardless of whether or not the ad hoc communication network AH is currently formed.

<3> Probe Response Signal The probe response signal is a control signal that responds to the probe request signal when the wireless terminal MS receives the probe request signal. FIG. 7B shows information elements included in the probe response signal. As shown in the figure, the information element included in the probe response signal is the same as the control information included in the beacon signal. That is, the probe response signal includes an SSID field, Capability information field, and WAN rate information field.

  Here, in the probe response signal, the WAN rate information field is an optional element. The radio terminal MS may generate a probe response signal that does not include the WAN rate information field.

<4> Speed Information Request Signal The speed information request signal is a control signal transmitted from the radio terminal MS to the radio terminal MS located at a distance where the ad hoc communication network AH can be formed. FIG. 8A shows information elements included in the speed information request signal. The wireless terminal MS that has received the probe response signal transmits a rate information request signal when the WAN response information field is not included in the probe response signal. That is, the speed information request signal is a control signal that requests transmission of the WAN rate field included in the WAN rate information field.

<5> Speed Information Response Signal The speed information response signal is a control signal that the wireless terminal MS that has received the speed information request signal transmits in response to the speed information request signal. FIG. 8B shows information elements included in the speed information response signal. As shown in the figure, the rate information response signal includes a WAN rate information field. The WAN rate information field includes a WAN rate field that is communication speed information as an essential element.

  The control signal processing unit 131 acquires or generates each control signal as described above. The control signal processing unit 131 extracts the SSID information stored in the SSID field and the communication speed information stored in the WAN rate field from the control signal, and outputs them to the ad hoc communication network selection unit 133.

  The ad hoc communication network selection unit 133 selects the connection destination ad hoc communication network AH based on the communication speed indicated by the communication speed information. Specifically, the ad hoc communication network selection unit 133 identifies the ad hoc communication network AH having the highest communication speed indicated by the communication speed information from the plurality of ad hoc communication networks AH, and connects the identified ad hoc communication network AH. It is selected as the previous ad hoc communication network AH.

  The communication speed information storage unit 134 temporarily stores communication speed information. The stored communication speed information is used when the ad hoc communication network selection unit 133 selects the connection destination ad hoc communication network AH.

  When the wireless terminal MS is not connected to the ad hoc communication network AH and the ad hoc communication network selection unit 133 selects the connection destination ad hoc communication network AH, the communication control unit 136 And instructing generation of a connection request signal for requesting connection to the selected ad hoc communication network AH.

  In addition, when the wireless terminal MS is connected to the ad hoc communication network AH, the communication control unit 136 is selected by the control signal processing unit 131 when receiving a handoff instruction from a handoff control unit 138 described later. Instructing the generation of a connection request signal for requesting connection to the ad hoc communication network AH.

  The reception sensitivity comparison unit 137 compares the reception sensitivities of control signals transmitted from the wireless terminals MS that form the ad hoc communication network AH. The reception sensitivity comparison unit 137 is configured such that the reception sensitivity of the control signal transmitted from the wireless terminal MS forming the connected ad hoc communication network AH is the control signal transmitted from the wireless terminal MS forming the other ad hoc communication network AH. When the sensitivity is lower than the reception sensitivity, the handoff control unit 138 is notified of this.

  Based on the notification from the reception sensitivity comparison unit 137, the handoff control unit 138 notifies the communication control unit 136 that the connection destination is switched to another ad hoc communication network AH.

  When the wireless terminal MS is connected to the ad hoc communication network AH, the communication relay unit 139 relays data (packets) transmitted / received between the wireless terminals MS.

(3) Operation of Wireless Terminal Next, the operation of the wireless terminal MS10 will be described using FIG. 9 and FIG. Specifically, (3.1) an initial connection operation to an ad hoc communication network and (3.2) a handoff operation will be described.

(3.1) Initial Connection Operation to Ad Hoc Communication Network FIG. 9 is a flowchart showing an initial connection operation to the ad hoc communication network AH executed by the radio terminal MS10.

  In this embodiment, the radio terminal MS10 uses either an ad hoc communication network AH1 connected to the radio base station BS1 constituting EV-DO or an ad hoc communication network AH2 connected to the radio base station BS2 constituting IEEE802.11b. Select as the destination ad hoc communication network.

  In step S101, the radio terminal MS10 starts searching for an ad hoc communication network AH that is a connection destination candidate.

  In step S102, the radio terminal MS10 determines whether or not a beacon signal has been received. When the radio terminal MS10 receives a beacon signal, the process proceeds to step S103. If the wireless terminal MS10 does not receive a beacon signal, the process proceeds to step S104.

  In step S103, the radio terminal MS10 determines whether or not the WAN rate information field is included in the beacon signal. When the WAN rate information field is included in the beacon signal, the process proceeds to step S109. When the WAN rate information field is not included in the beacon signal, the process proceeds to step S104.

  In step S104, the radio terminal MS10 transmits (notifies) a probe request signal.

  In step S105, the radio terminal MS10 determines whether a probe response signal has been received. When the probe response signal is received, the process proceeds to step S106. If no probe response signal is received, the process returns to step S102.

  In step S106, the radio terminal MS10 determines whether or not the WAN rate information field is included in the probe response signal. When the WAN rate information field is included in the probe response signal, the process proceeds to step S109. On the other hand, if the WAN response information field is not included in the probe response signal, the process proceeds to step S107.

  In step S107, the radio terminal MS10 transmits a speed information request signal, and in step S108, receives the speed information response signal.

  In step S109, the radio terminal MS10 stores the communication speed information acquired from any of the beacon signal, the probe response signal, or the speed information response signal.

  In step S110, the radio terminal MS10 determines whether or not to end the search for the ad hoc communication network AH. When a certain time has elapsed since the search for the ad hoc communication network AH was started, the radio terminal MS10 ends the search for the ad hoc communication network AH.

  In step S111, the radio terminal MS10 selects a connection destination ad hoc communication network AH based on the stored communication speed information. In the present embodiment, the wireless terminal MS10 stores communication speed information from the ad hoc communication network AH1 as a connection destination candidate and communication speed information from the ad hoc communication network AH2 in the communication speed information storage unit 134.

  Since the radio communication system to which the ad hoc communication network AH1 is connected is EV-DO and the radio communication system to which the ad hoc communication network AH2 is connected is IEEE802.11b, the ad hoc communication network selection unit 133 of the radio terminal MS10 is EV- It is determined that the communication speed of IEEE802.11b is higher than DO, and the ad hoc communication network AH2 is selected as the connection destination.

  In step S112, the radio terminal MS10 transmits a connection request signal for requesting connection to the ad hoc communication network AH2. As a result, the radio terminal MS10 can join the ad hoc communication network AH2.

(3.2) Handoff Operation FIG. 10 is a flowchart showing a handoff operation in which the wireless terminal MS10 switches the connection destination from the currently connected ad hoc communication network AH2 to another ad hoc communication network AHx (not shown). In FIG. 10, the description of the same operation as that of FIG. 9 is omitted.

  Each process of step S201 to step S207 is performed in the same manner as step S102 to step S108 of FIG.

  In step S208, the radio terminal MS10 determines whether or not the condition of the other ad hoc communication network AHx is better than that of the currently connected ad hoc communication network AH2. Specifically, it is determined whether or not the communication speed of the wireless communication system to which the other ad hoc communication network AHx is connected is higher than the communication speed of the wireless communication system (IEEE802.11b) to which the connected ad hoc communication network AH2 is connected. judge.

  When the communication speed of the wireless communication system connected to the other ad hoc communication network AHx is higher than the communication speed of the wireless communication system (IEEE802.11b) connected to the currently connected ad hoc communication network AH2, the wireless terminal MS10 Assuming that the conditions of the other ad hoc communication network AHx are good, a connection request is transmitted to the other ad hoc communication network AHx in step S209.

  When the communication speed of the wireless communication system to which the other ad hoc communication network AHx is connected is equal to the communication speed of the wireless communication system (IEEE802.11b) to which the connected ad hoc communication network AH2 is connected, the wireless terminal MS10 Based on the reception sensitivity, it is determined whether or not to switch the connection destination to another ad hoc communication network AHx.

  Specifically, the radio terminal MS10 determines that the conditions of the other ad hoc communication network AHx are good when the reception sensitivity from the other ad hoc communication network AHx is higher than the reception sensitivity from the connected ad hoc communication network AH2. In step S209, a connection request is transmitted to another ad hoc communication network AHx.

(4) Operation / Effect According to the present embodiment, the radio terminal MS10 acquires communication speed information included in a signal transmitted by the radio terminals MS1 to MS3 forming the first ad hoc communication network AH1, and performs second ad hoc communication. Communication speed information included in signals transmitted by the wireless terminals MS4 to MS6 forming the network AH2 is acquired.

  Then, the wireless terminal MS10 has a communication speed of EV-DO that is a wireless communication system to which the first ad hoc communication network AH1 is connected, and a communication speed of IEEE802.11b that is a wireless communication system to which the second ad hoc communication network AH2 is connected. And the higher communication speed of the wireless communication system (infrastructure network) to be connected, that is, the second ad hoc communication network AH2 is selected as the connection destination.

  Therefore, when there are a plurality of ad hoc communication networks AH1 and AH2 connected to different types of radio communication systems, the radio terminal MS10 can appropriately select a connection destination ad hoc communication network.

  Further, since only the information on the communication speed between the ad hoc communication network and the infrastructure network to which the ad hoc communication network is connected is notified, the load on the ad hoc communication network can be reduced.

  According to the present embodiment, the radio terminal MS10 includes the beacon signal that the radio terminals MS1 to MS3 forming the first ad hoc communication network AH1 broadcast in a predetermined cycle, and the radio terminals MS4 to MS6 that form the second ad hoc communication network AH2. When the communication speed information is included in the beacon signal notified at a predetermined period, the communication speed information is acquired from the beacon signal. Therefore, the radio terminal MS10 can easily acquire the communication speed information without transmitting a transmission request for the communication speed information to the ad hoc communication networks AH1 and AH2.

  According to the present embodiment, the radio terminal MS10 transmits a probe request signal when the communication speed information is not included in the beacon signal. When the communication speed information is included in the probe response signal that is a response signal to the probe request signal, the radio terminal MS10 acquires the communication speed information from the probe response signal. Therefore, the wireless terminal MS10 can acquire the communication speed information even when the beacon signal does not include the communication speed information.

  According to the present embodiment, when the probe response signal does not include communication speed information, the wireless terminal MS10 transmits a speed information request signal that requests transmission of the communication speed information. The speed information response signal that is a response signal to the speed information request signal includes communication speed information. Accordingly, the wireless terminal MS10 can reliably acquire the communication speed information even when the communication speed information is not included in the beacon signal and the probe response signal.

  According to the present embodiment, the radio terminal MS10 measures reception sensitivities from a plurality of ad hoc communication networks AH2 and AHx. When the communication speeds of the wireless communication systems to which the plurality of ad hoc communication networks AH2 and AHx are connected are the same, the wireless terminal MS10 selects the one having the higher reception sensitivity among the plurality of ad hoc communication networks AH2 and AHx as the connection destination. Therefore, the radio terminal MS10 can more appropriately select a connection destination ad hoc communication network.

(5) Other Embodiments As described above, the present invention has been described according to the embodiment. However, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  In the above-described embodiment, the radio terminals MS1 to MS3 and MS4 to MS6 that form the ad hoc communication networks AH1 and AH2 broadcast control signals including communication speed information. However, the radio terminals MS1 to MS3 and MS4 to MS6 forming the ad hoc communication network AH, instead of the communication speed information, control signals including system type information indicating the type of the radio communication system to which the ad hoc communication networks AH1 and AH2 are connected. May be notified.

  For example, in the system type information, “0x01” is PHS (32 kbps), “0x02” is PHS (˜128 kbps), “0x10” is EV-DO (2 to 3 Mbps), “0x20” is IEEE802.11b (11 Mbps), etc. It is prescribed as follows.

  In the case of such a configuration, the communication speed information storage unit 134 of the wireless terminal MS10 stores in advance a table in which the types of wireless communication systems and communication speed information indicating the communication speed are associated with each other. Then, when receiving a control signal including system type information, the radio terminal MS10 refers to the table and converts the system type information into communication speed information.

  In the embodiment described above, the wireless terminal MS10 first determines whether or not a beacon signal has been received. However, the wireless terminal MS10 periodically notifies the probe request signal without waiting for the reception of the beacon signal. May be.

  In the embodiment described above, the wireless terminal MS10 uses the SSID field as identification information indicating the ad hoc communication network AH. However, a BSSID (Basic Service Set Identifier) field may be used instead of the SSID field.

  In the example of FIG. 1, a mobile phone terminal is illustrated as the wireless terminal MS. However, a notebook PC having a wireless communication function, a personal digital assistance (PDA), or the like may be used. In addition, the ad hoc communication network AH including a fixed wireless terminal is not limited to a portable wireless terminal.

  In the ad hoc communication network construction operation, an existing routing protocol such as DSR (Dynamic Source Routing) or AODV (Ad-hoc On-Demand Vector Routing) can be used.

  Thus, it should be understood that the present invention includes various embodiments and the like not described herein. Therefore, the present invention is limited only by the invention specifying matters in the scope of claims reasonable from this disclosure.

1 is an overall schematic configuration diagram of a wireless communication system according to an embodiment of the present invention. It is a hardware block diagram of radio | wireless terminal MS which concerns on embodiment of this invention. It is a functional block block diagram of radio | wireless terminal MS which concerns on embodiment of this invention. The information element contained in the beacon signal concerning the embodiment of the present invention is shown. The information element contained in the Capability information field of the beacon signal which concerns on embodiment of this invention is shown. 4 shows information elements included in a WAN rate information field of a beacon signal according to an embodiment of the present invention. 4 shows information elements included in a probe request signal and a probe response signal according to an embodiment of the present invention. 4 shows information elements included in a speed information request signal and a speed information response signal according to an embodiment of the present invention. It is a flowchart which shows the initial connection operation | movement to the ad hoc communication network performed by radio | wireless terminal MS10 which concerns on embodiment of this invention. It is a flowchart which shows the handoff operation | movement between the ad hoc communication networks performed by radio | wireless terminal MS10 which concerns on embodiment of this invention.

Explanation of symbols

  AH, AH1, AH2, AHx ... ad hoc communication network, MS, MS1 to MS6, MS10 ... wireless terminal, BS1, BS2 ... wireless base station, 10 ... WAN, 111 ... antenna, 112 ... processing unit, 113 ... encoding unit, DESCRIPTION OF SYMBOLS 114 ... Decoding part 110 ... Mobile telephone communication part 120 ... Wireless LAN communication part 121 ... Antenna, 122 ... Processing part, 123 ... Encoding part, 124 ... Decoding part, 130 ... Control part, 131 ... Control signal processing part DESCRIPTION OF SYMBOLS 133 ... Ad hoc communication network selection part 134 ... Communication speed information storage part 136 ... Communication control part 137 ... Reception sensitivity comparison part 138 ... Handoff control part 139 ... Communication relay part 141 ... Microphone 142 ... Speaker 143 ... Display unit, 144 ... Input unit

Claims (7)

A first ad hoc communication network connected to a first radio base station constituting the first radio communication system, or a second radio base station constituting a second radio communication system different in type from the first radio communication system. A wireless terminal capable of selecting any one of two ad hoc communication networks as a connection destination ad hoc communication network,
First information for acquiring first speed information indicating a first communication speed determined according to a type of the first wireless communication system, which is information included in a signal transmitted by a wireless terminal forming the first ad hoc communication network. 1 information acquisition unit;
A second speed information that is information included in a signal transmitted by a wireless terminal forming the second ad hoc communication network and that indicates a second communication speed determined according to a type of the second wireless communication system. 2 information acquisition unit;
An ad hoc communication network that selects the connection destination ad hoc communication network based on the first speed information acquired by the first information acquisition unit and the second speed information acquired by the second information acquisition unit With a selection unit,
The ad hoc communication network selection unit compares the first communication speed with the second communication speed, and selects the first ad hoc communication network when the first communication speed exceeds the second communication speed, A wireless terminal, wherein the second ad hoc communication network is selected when a second communication speed exceeds the first communication speed. When the first speed information is included in a first beacon signal that is broadcast by a wireless terminal forming the first ad hoc communication network at a predetermined period, the first information acquisition unit performs the first information acquisition from the first beacon signal. 1 Get speed information,
The second information acquisition unit, when the second speed information is included in a second beacon signal broadcasted by a wireless terminal forming the second ad hoc communication network at a predetermined period, from the second beacon signal to the second information The wireless terminal according to claim 1, wherein two-speed information is acquired. When the first speed information is not included in the first beacon signal, transmission of first control information used for forming the first ad hoc communication network is transmitted to the wireless terminals forming the first ad hoc communication network. A first request signal transmitter for transmitting a first probe request signal for requesting,
When the second speed information is not included in the second beacon signal, transmission of second control information used for forming the second ad hoc communication network is transmitted to the wireless terminals forming the second ad hoc communication network. A second request signal transmitter for transmitting a second probe request signal for requesting,
When the first speed information is included in a first probe response signal transmitted by a wireless terminal forming the first ad hoc communication network in response to the first probe request signal, Obtaining the first velocity information from a first probe response signal;
When the second speed information is included in a second probe response signal transmitted by a wireless terminal forming the second ad hoc communication network in response to the second probe request signal, the second information acquisition unit, The wireless terminal according to claim 2, wherein the second speed information is acquired from a second probe response signal. The first request signal transmission unit transmits the first rate information to a wireless terminal forming the first ad hoc communication network when the first rate information is not included in the first probe response signal. A first speed information request signal for requesting
The second request signal transmission unit transmits the second rate information to a wireless terminal forming the second ad hoc communication network when the second rate information is not included in the second probe response signal. A second speed information request signal requesting
The first information acquisition unit acquires the first speed information from a first speed information response signal transmitted in response to the first speed information request signal by a wireless terminal forming the first ad hoc communication network,
The second information acquisition unit acquires the second speed information from a second speed information response signal transmitted by a wireless terminal forming the second ad hoc communication network in response to the second speed information request signal. The wireless terminal according to claim 3. A reception sensitivity measuring unit for measuring a reception sensitivity of a signal transmitted by a wireless terminal forming the first ad hoc communication network and a reception sensitivity of a signal transmitted by a wireless terminal forming the second ad hoc communication network;
The ad hoc communication network selection unit is measured by the reception quality measurement unit of the first ad hoc communication network and the second ad hoc communication network when the first communication speed and the second communication speed are equal. The wireless terminal according to claim 1, wherein the one having the higher reception sensitivity is selected as the ad hoc communication network of the connection destination. The first information acquisition unit acquires first system type information indicating a type of the first wireless communication system instead of the first speed information,
The second information acquisition unit acquires second system type information indicating a type of the second wireless communication system instead of the second speed information,
The ad hoc communication network selection unit is configured to connect the connection destination based on the first system type information acquired by the first information acquisition unit and the second system type information acquired by the second information acquisition unit. The wireless terminal according to claim 1, wherein an ad hoc communication network is selected. A first ad hoc communication network connected to a first radio base station constituting the first radio communication system, or a second radio base station constituting a second radio communication system different in type from the first radio communication system. A wireless communication method for communicating by selecting any one of two ad hoc communication networks as a connection destination ad hoc communication network,
A step of acquiring first speed information indicating a first communication speed determined according to a type of the first wireless communication system, which is information included in a signal transmitted by a wireless terminal forming the first ad hoc communication network; When,
Obtaining second speed information indicating a second communication speed determined according to a type of the second wireless communication system, which is information included in a signal transmitted by a wireless terminal forming the second ad hoc communication network; When,
Selecting the ad hoc communication network of the connection destination based on the acquired first speed information and the acquired second speed information;
The step of selecting includes
Comparing the first communication speed and the second communication speed;
Selecting the first ad hoc communication network when the first communication speed exceeds the second communication speed;
Selecting the second ad hoc communication network when the second communication speed exceeds the first communication speed; and a wireless communication method comprising:

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