JP2012199996A - System and apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow a radio terminal constituting a tree structure network to communicate with a radio base station when a highest-order radio terminal cannot continue a direct communication with the radio base station in the tree structure network where the radio terminal which performs a direct communication with the radio base station is determined as the highest-order radio terminal.SOLUTION: The radio terminal of the present invention comprises: a communication determination part 131 which determines whether or not a direct communication with a radio base station can continue; a message processing part 132 which transmits a search instruction inquiring whether or not a direct communication with the radio base station can be made to a lower-order radio terminal in a tree structure network when the communication determination part 131 determines that a direct communication with the radio base station cannot continue; and a master management part 133 which registers the lower-order radio terminal as a higher-order radio terminal in the tree structure network when receiving a response message from the lower-order radio terminal which indicates that a direct communication with the radio base station can be made.

Description

  The present invention relates to a system and a device constituting a tree-structured network having a wireless terminal directly communicating with a wireless base station as the highest level.

  Conventionally, an ad hoc network that is a wireless network autonomously configured by a plurality of wireless terminals (devices) having a relay function is known. In addition, a method has been proposed in which wireless terminals constituting an ad hoc network communicate with a wireless base station (see, for example, Patent Document 1). Specifically, the wireless terminal communicates with the wireless base station via another wireless terminal.

  That is, a tree-structured network having a wireless terminal directly communicating with a wireless base station as the highest level is configured by a plurality of wireless terminals. Since the lower radio terminal communicates with the radio base station via the upper radio terminal, the lower radio terminal can communicate with the radio base station even if it is outside the radio wave reachable range of the radio base station.

Japanese Patent Laid-Open No. 2003-124876 (page 6-7, FIG. 7)

  By the way, in the tree-structured network described above, the highest-level wireless terminal cannot always continue direct communication with the wireless base station. For example, when the highest radio terminal moves out of the radio wave reach of the radio base station, there is a problem that direct communication between the radio terminal and the radio base station cannot be continued.

  In addition, when direct communication between the highest-level wireless terminal and the wireless base station cannot be continued, the lower-level wireless terminal communicating with the wireless base station via the highest-level wireless terminal is There is a problem that a wireless terminal located outside the reachable range cannot communicate with the wireless base station.

  Therefore, the present invention has been made to solve the above-described problems. In a tree structure network in which a device directly communicating with a radio base station is the highest level, the highest-level device directly communicates with the radio base station. It is an object of the present invention to provide a system and a device that enables a device constituting a tree-structured network to communicate with a radio base station when the network cannot be continued.

  In order to solve the problems described above, the present invention has the following features.

  The system of the present invention includes a first device that communicates directly with a radio base station and a second device that communicates with the first device, and the first device is incapable of direct communication with the radio base station. If it is determined, it transmits a message inquiring whether direct communication with the radio base station is possible, and the second device performs direct communication with the radio base station when receiving the message. It is characterized by.

  When it is determined that direct communication with a radio base station is not possible, the device of the present invention sends a message asking whether or not direct communication with the radio base station is possible to other messages constituting the network including the device itself. It transmits to an apparatus, It is characterized by the above-mentioned.

  When the device of the present invention receives a message asking whether or not direct communication with the radio base station is possible from another device constituting the network including its own device, the device performs direct communication with the radio base station. It is characterized by doing.

  The system of the present invention includes a first device that communicates directly with a radio base station and a second device that communicates with the first device, and the first device is incapable of direct communication with the radio base station. If it is determined, a message for executing direct communication with the radio base station is transmitted, and the second device executes direct communication with the radio base station when receiving the message. .

  The device of the present invention is a device that directly communicates with a wireless base station, and when it is determined that direct communication with the wireless base station is impossible, a message for executing direct communication with the wireless base station is sent to the device. It transmits to the other apparatus which comprises the network containing this.

  The device of the present invention is a device constituting a network including a device that directly communicates with a wireless base station, and when a message for executing direct communication with the wireless base station is received from another device, the wireless base station It performs the direct communication with.

  The system of the present invention includes a first device that communicates directly with a radio base station and a second device that communicates with the first device, and the first device is incapable of direct communication with the radio base station. If it is determined, a search instruction is transmitted, and the second device performs a search when receiving the message.

  The device of the present invention is a device that directly communicates with a radio base station, and when it is determined that direct communication with the radio base station is impossible, a search instruction is transmitted to another device.

  The device of the present invention is a device that forms a network including a device that directly communicates with a radio base station, and performs a search when a search instruction is received from another device.

  According to the present invention, in a tree structure network in which a device directly communicating with a radio base station is the highest level, the tree structure network is configured when the highest level device cannot continue direct communication with the radio base station. It is possible to provide a system and a device that enable a device to communicate with a radio base station.

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 the radio | wireless terminal which concerns on embodiment of this invention. It is a functional block block diagram of the radio | wireless terminal which concerns on embodiment of this invention. It is a flowchart which shows the construction operation | movement of the ad hoc network performed by the radio | wireless terminal which concerns on embodiment of this invention. It is a figure for demonstrating the operation example 1 of the master-slave switching operation | movement which concerns on embodiment of this invention. It is a sequence diagram which shows the operation example 1 of the master / slave switching operation | movement which concerns on embodiment of this invention. It is a figure for demonstrating the operation example 2 of the master-slave switching operation | movement which concerns on embodiment of this invention. It is a sequence diagram which shows the operation example 2 of the master / slave switching operation | movement which concerns on embodiment of this invention.

  Next, an embodiment of the present invention will be described with reference to the drawings. Specifically, (1) the overall schematic configuration of the radio communication system, (2) the configuration of the radio terminal, (3) the operation of the radio terminal, (4) actions and effects, and (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 Radio Communication System FIG. 1 is an overall schematic configuration diagram of a radio communication system 10 according to the present embodiment. As shown in FIG. 1, the radio communication system 10 includes a radio base station BS and radio terminals MS1 to MS9.

  The radio base station BS constitutes a service area (radio wave arrival area) SA that is an area in which direct communication with a radio terminal is possible. In the example of FIG. 1, the radio base station BS communicates directly with the radio terminal MS1 located in the service area SA.

  The radio terminals MS1 to MS9 have a function of communicating directly with the radio base station BS (single-hop communication) and a function of communicating with the radio base station BS (multi-hop communication) via at least one other radio terminal. .

  In the present embodiment, an ad hoc network AH that is an autonomous wireless network is formed by the wireless terminals MS1 to MS9. The ad hoc network AH has a tree structure in which the radio terminal MS1 that communicates directly with the radio base station BS is the highest layer (root node).

  In the example of FIG. 1, in the ad hoc network AH having a tree structure, the wireless terminal MS2 and the wireless terminal MS5 connected to the wireless terminal MS1 are in the same hierarchy. The radio terminal MS3 and radio terminal MS4 connected to the radio terminal MS2 and the radio terminal MS6 connected to the radio terminal MS5 are in the same hierarchy. Note that the radio terminal MS8 and the radio terminal MS9 are the lowest hierarchy (leaf node).

  Further, the radio terminals MS1 to MS9 store the radio terminals belonging to the hierarchy immediately above as a master, and store the radio terminals belonging to the hierarchy directly below as a slave. For example, the radio terminal MS2 stores the radio terminal MS1 as a master, and stores the radio terminal MS3 and the radio terminal MS4 as slaves.

  Since the radio terminals MS1 to MS9 have the same configuration, in the following description, the radio terminals MS1 to MS9 are collectively referred to as radio terminals MS as appropriate.

(2) Configuration of Radio Terminal Next, the configuration of the radio terminal MS will be described using FIG. 2 and FIG. 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 radio terminal MS includes a base station communication unit 110, an ad hoc communication unit 120, a control unit 130, a display unit 143, an input unit 144, a microphone 141, a speaker 142, and a battery 150.

  The base station communication unit 110 is connected to the radio base station BS and performs direct communication with the radio base station BS. The base station communication unit 110 transmits and receives a radio signal (RF signal) in accordance with, for example, a CDMA scheme with the radio base station BS. In addition, the base station 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.

  The ad hoc communication unit 120 is connected to a wireless terminal configuring the ad hoc network AH, and communicates with the wireless base station BS via the wireless terminal. The ad hoc communication unit 120 has a configuration conforming to, for example, a wireless LAN (such as IEEE 802.11) or Bluetooth (registered trademark). The ad hoc 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 display unit 143 displays an image received via the control unit 130 and displays operation details (such as an input telephone number and an address). The input unit 144 includes a numeric keypad, function keys, and the like, and is used to input user operation details.

  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 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 battery 150 accumulates electric power for operating the wireless terminal MS and supplies the accumulated electric power to each block.

  The base station communication unit 110 includes an antenna 111, a base station communication RF processing unit 112, an encoding unit 113, and a decoding unit 114.

  The encoding unit 113 encodes the baseband signal from the control unit 130. The base station communication 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.

  Further, the base station communication RF processing unit 112 performs amplification and down-conversion of a radio signal input via the antenna 111, and generates a baseband signal. The decoding unit 114 decodes the generated baseband signal and inputs the decoded baseband signal to the control unit 130.

  The ad hoc communication unit 120 includes an antenna 121, an ad hoc communication RF processing unit 122, an encoding unit 123, and a decoding unit 124. The antenna 121, the ad hoc communication RF processing unit 122, the encoding unit 123, and the decoding unit 124 are the same as the antenna 111, the base station communication RF processing unit 112, the encoding unit 113, and the decoding unit 114, and thus overlap. Description is omitted.

(2.2) Functional Block Configuration of Radio Terminal FIG. 3 is a functional block configuration diagram of the radio terminal MS, specifically, a block diagram showing each function executed by the control unit 130. Hereinafter, points related to the present invention will be described.

  As shown in FIG. 3, the control unit 130 includes a communication determination unit 131, a message processing unit 132, a master management unit 133, a master storage unit 134, a slave management unit 135, a slave storage unit 136, a communication relay unit 137, and a communication control. Part 138.

  The communication determination unit 131 determines whether the direct communication can be continued based on at least one of the following (a) to (c) while performing direct communication with the radio base station BS. .

  (A) The communication determination unit 131 measures reception quality, which is the quality of a radio signal (for example, a broadcast signal such as a pilot signal) received from the radio base station BS, and compares the measured reception quality with a threshold value.

  As the reception quality, for example, RSSI (Received Signal Strength Indicator), SNR (Signal to Noise Ratio), CNR (Carrier to Noise Raito), or error rate can be used. The communication determination unit 131 determines that direct communication with the radio base station BS is not continued when the reception quality is lower than the threshold value.

  (B) The communication determination unit 131 detects the remaining amount of the battery 150 and compares the detected remaining amount with a threshold value. The communication determination unit 131 determines that direct communication with the radio base station BS cannot be continued when the remaining amount of the battery 150 is lower than the threshold value.

  (C) The communication determination unit 131 detects a transmission restriction that restricts direct communication with the radio base station BS. The communication determination unit 131 determines that direct communication with the radio base station BS cannot be continued if connection with the radio base station BS fails after the call regulation is detected by the transmission regulation detection unit.

  Further, when the ad hoc communication unit 120 and the message processing unit 132 receive a search instruction for the radio base station BS from the master, the communication determination unit 131 performs a base station search. In addition to the execution of the base station search, the determinations (a) to (c) may be performed.

  The message processing unit 132 mainly transmits and receives the following messages to and from the master and slave. A search instruction (inquiry message) for instructing a base station search. Search result (response message) that is a result of the base station search. Connection instruction (instruction message) instructing direct communication with the radio base station BS.

  The master management unit 133 stores identification information for identifying the master in the master storage unit 134. The slave management unit 135 stores identification information for identifying the slave in the slave storage unit 136. As identification information, a terminal ID or an address (IP address or MAC address) can be used.

  Further, the master management unit 133 reads the identification information stored in the slave storage unit 136 and stores the read identification information in the master storage unit 134 when the master / slave is switched.

  Similarly, the slave management unit 135 reads the identification information stored in the master storage unit 134 when the master / slave is switched, and stores the read identification information in the slave storage unit 136.

  The communication relay unit 137 relays communication between the slave and the master. That is, the communication relay unit 137 relays data (packets) transmitted / received between the slave and the master based on the identification information stored in the master storage unit 134 and the identification information stored in the slave storage unit 136.

  The communication control unit 138 controls the base station communication unit 110 and the ad hoc communication unit 120. When the master management unit 133 registers the master, the communication control unit 138 receives a radio signal (for example, a broadcast signal such as a pilot signal) transmitted from the radio base station BS to the base station communication unit 110. Stop.

(3) Operation of Wireless Terminal Next, the operation of the wireless terminal MS will be described with reference to FIGS. Specifically, (3.1) Ad hoc network construction operation and (3.2) Master / slave switching operation will be described.

(3.1) Ad Hoc Network Construction Operation FIG. 4 is a flowchart showing the construction operation of the ad hoc network AH executed by the wireless terminal MS.

  In step S101, the radio terminal MS performs a base station search in order to find a radio base station BS capable of direct communication. For example, when the reception level of a radio signal received from the radio base station BS is stable and the reception level is equal to or higher than a certain level, the radio terminal MS determines that it can communicate directly with the radio base station BS. To do.

  In step S102, the radio terminal MS determines whether a radio base station BS capable of direct communication has been found. When a radio base station BS capable of direct communication is found, the radio terminal MS enters a standby state in step S103.

  On the other hand, if a radio base station BS capable of direct communication is not found, the radio terminal MS searches the ad hoc network AH in step S104. For example, the radio terminal MS broadcasts a connection request signal within a certain range, and determines whether another radio terminal MS in the ad hoc network AH has responded.

  In step S105, the radio terminal MS determines whether or not the ad hoc network AH has been found.

  When the wireless terminal MS discovers the ad hoc network AH, the wireless terminal MS joins the discovered ad hoc network AH in step S106. On the other hand, if the ad hoc network AH is not found, the process returns to step S101.

  In step S107, the radio terminal MS constructs an ad hoc network AH. Specifically, when the radio terminal MS is connected to the radio base station BS, the radio terminal MS registers the radio base station BS as a master. Further, when the wireless terminal MS is connected to another wireless terminal MS, the wireless terminal MS registers the other wireless terminal MS as a master.

  In step S108, the radio terminal MS determines whether or not a connection request has been received from another radio terminal MS. When receiving a connection request from another wireless terminal MS, the wireless terminal MS registers the other wireless terminal MS as a slave in step S109.

(3.2) Master / slave switching operation Next, a master / slave switching operation executed by the radio terminal MS, specifically, (3.2.1) Operation Example 1 and (3.2.2) Operation example 2 will be described.

  Here, the operation example 1 is an operation when master / slave switching is performed in two layers. The operation example 2 is an operation when master / slave switching is performed in three layers.

(3.2.1) Operation example 1
Operation example 1 of the master / slave switching operation will be described. In the operation example 1, it is assumed that the master / slave switching operation is performed in the situation shown in FIG. FIG. 6 is a sequence diagram showing an operation example 1 of the master / slave switching operation.

  In FIG. 5, the radio terminal MS1 and the radio terminal MS2 can directly communicate with the radio base station BS. The radio terminal MS1 is a master of the radio terminal MS2 and the radio terminal MS3. The radio terminal MS2 and the radio terminal MS3 are slaves of the radio terminal MS1.

  Therefore, as shown in FIG. 6, in the radio terminal MS1, the radio base station BS is registered as a master, and the radio terminal MS2 and the radio terminal MS3 are registered as slaves. In the radio terminal MS2, the radio terminal MS1 is registered as a master. In the wireless terminal MS3, the wireless terminal MS1 is registered as a master.

  Here, it is assumed that the radio terminal MS1 moves from the service area SA of the radio base station BS to the outside of the service area SA.

  In step S201, the radio terminal MS1 determines that direct communication with the radio base station BS cannot be continued.

  In step S202, the radio terminal MS1 transmits a search instruction to the slaves (that is, the radio terminal MS2 and the radio terminal MS3). When receiving the search instruction, the radio terminal MS2 and the radio terminal MS3 execute a base station search.

  In step S203, the radio terminal MS3 fails in the base station search. On the other hand, in step S204, the radio terminal MS2 succeeds in the base station search.

  In step S205, the radio terminal MS3 reports to the radio terminal MS1 a search result indicating that the base station search has failed. In step S206, the radio terminal MS2 reports to the radio terminal MS1 a search result indicating that the base station search has been successful.

  In step S207, the radio terminal MS1 transmits a connection instruction for instructing connection to the radio base station BS to the radio terminal MS2. When receiving the connection instruction, the wireless terminal MS2 connects to the wireless base station BS in step S208. When connected to the radio base station BS, the radio terminal MS2 transmits a completion report indicating that the connection to the radio base station BS is completed to the radio terminal MS1 in step S209.

  In step S210, the wireless terminal MS1 transmits to the wireless terminal MS2 a master / slave cancellation instruction that instructs cancellation of the master / slave relationship. In step S211, the wireless terminal MS1 cancels registration of the wireless terminal MS2 as a slave.

  When receiving the master / slave cancellation instruction, the wireless terminal MS2 cancels the registration of the wireless terminal MS1 as a master in step S212. In step S213, the wireless terminal MS2 transmits a completion report indicating that the master registration has been canceled to the wireless terminal MS1.

  In step S214, the radio terminal MS1 registers the radio terminal MS2 as a master.

  In step S215, the radio terminal MS2 registers the radio base station BS as a master. In addition, in step S216, the wireless terminal MS2 registers the wireless terminal MS1 as a slave.

  With the above operation, the wireless terminal MS1 is registered as a master and the wireless terminal MS3 is registered as a slave in the wireless terminal MS1. In the radio terminal MS2, the radio base station BS is registered as a master, and the radio terminal MS1 is registered as a slave.

  When the master / slave switching operation is completed, the radio terminal MS1 communicates with the radio base station BS via the radio terminal MS2. The radio terminal MS1 relays communication between the radio terminal MS3 and the radio base station BS. The radio terminal MS2 relays communication between the radio terminal MS1 and the radio base station BS.

(3.2.2) Operation example 2
Operation example 2 of the master / slave switching operation will be described. In the operation example 2, it is assumed that the master / slave switching operation is performed in the situation shown in FIG. It is assumed that the radio terminal MS1 has moved from the service area SA of the radio base station BS to the outside of the service area SA. The radio terminal MS3 can directly communicate with the radio base station BS.

  FIG. 8 is a sequence diagram showing an operation example 2 of the master / slave switching operation.

  In FIG. 7, the radio terminal MS1 is the master of the radio terminal MS2. The radio terminal MS2 is a slave of the radio terminal MS1. The radio terminal MS2 is a master of the radio terminal MS3. The radio terminal MS3 is a slave of the radio terminal MS2.

  Therefore, as shown in FIG. 8, in the radio terminal MS1, the radio base station BS is registered as a master and the radio terminal MS2 is registered as a slave. In the wireless terminal MS2, the wireless terminal MS1 is registered as a master, and the wireless terminal MS3 is registered as a slave. In the wireless terminal MS3, the wireless terminal MS2 is registered as a master.

  In step S301 in FIG. 8, the radio terminal MS1 determines that direct communication with the radio base station BS cannot be continued.

  In step S302, the radio terminal MS1 transmits a search instruction to the slave (that is, the radio terminal MS2). When receiving the search instruction, the radio terminal MS2 performs a base station search.

  In step S303, the radio terminal MS2 fails in the base station search.

  In step S304, the radio terminal MS2 reports to the radio terminal MS1 a search result indicating that the base station search has failed. Further, in step S305, the radio terminal MS2 transmits a search instruction to the slave (that is, the radio terminal MS3).

  When receiving the search instruction, the radio terminal MS3 performs a base station search. In step S306, the radio terminal MS3 succeeds in the base station search.

  In step S307, the radio terminal MS3 transmits a search result indicating that the base station search is successful to the radio terminal MS2. In step S308, the radio terminal MS2 transmits the received search result to the radio terminal MS1.

  When receiving the search result indicating that the base station search is successful, the radio terminal MS1 transmits a connection instruction for instructing connection to the radio base station BS to the radio terminal MS2 in step S309. In step S310, the radio terminal MS2 transmits the received connection instruction to the radio terminal MS3.

  When receiving the connection instruction, the wireless terminal MS3 connects to the wireless base station BS in step S311. When the wireless terminal MS3 is connected to the wireless base station BS, in step S312, the wireless terminal MS3 transmits a completion report indicating that the connection to the wireless base station BS is completed to the wireless terminal MS2. In step S313, the radio terminal MS2 transmits the received completion report to the radio terminal MS1.

  In step S314, the wireless terminal MS1 transmits to the wireless terminal MS2 a master / slave cancellation instruction that instructs cancellation of the master / slave relationship. In addition, in step S315, the radio terminal MS1 cancels registration of the radio terminal MS2 as a slave.

  When receiving the master / slave release instruction, the wireless terminal MS2 cancels the registration of the wireless terminal MS1 as the master in step S316. In step S317, the radio terminal MS2 transmits a completion report to the effect that the master registration has been canceled to the radio terminal MS1. In step S322, the wireless terminal MS1 registers the wireless terminal MS2 as a master.

  In step S318, the radio terminal MS2 transmits a master / slave release instruction to the radio terminal MS3. In addition, in step S319, the wireless terminal MS2 cancels registration of the wireless terminal MS3 as a slave.

  When receiving the master / slave cancellation instruction, the wireless terminal MS3 cancels the registration of the wireless terminal MS2 as a master in step S320. In step S321, the radio terminal MS3 transmits a completion report to the effect that the master registration has been canceled to the radio terminal MS2.

   In step S323, the radio terminal MS2 registers the radio terminal MS3 as a master. In addition, the wireless terminal MS2 registers the wireless terminal MS1 as a slave in step S325.

  In step S324, the radio terminal MS3 registers the radio base station BS as a master. In addition, in step S326, the wireless terminal MS3 registers the wireless terminal MS2 as a slave.

  With the above operation, the wireless terminal MS2 is registered as a master in the wireless terminal MS1. In the wireless terminal MS2, the wireless terminal MS3 is registered as a master, and the wireless terminal MS1 is registered as a slave. In the radio terminal MS3, the radio base station BS is registered as a master, and the radio terminal MS2 is registered as a slave.

(4) Action / Effect According to the present embodiment, the radio terminal MS determines whether or not direct communication with the radio base station BS can be continued, and direct communication with the radio base station BS cannot be continued. If it is determined, a search instruction for inquiring whether direct communication with the radio base station BS is possible is transmitted to the slave. When receiving a search result indicating that direct communication with the radio base station BS is possible from the slave, the radio terminal MS registers the slave as a master.

  That is, when the direct communication between the master and the radio base station BS cannot be continued and the slave can directly communicate with the radio base station BS, the ad hoc network AH is configured by switching the relationship between the master and the slave. The wireless terminal MS can communicate with the wireless base station BS.

  According to the present embodiment, when the wireless terminal MS receives a search result indicating that direct communication with the radio base station BS is possible from the slave, the connection instruction that instructs the start of direct communication with the radio base station BS. To the slave. That is, by instructing a slave capable of direct communication with the radio base station BS to connect to the radio base station BS, the radio terminal MS constituting the ad hoc network AH can continue communication.

  According to the present embodiment, the radio terminal MS communicates with the radio base station BS via the master registered by the master management unit 133. Therefore, when the wireless terminal MS becomes a slave due to the replacement of the master and the slave, the wireless terminal MS can continue communication by communicating with the wireless base station BS via the master.

  According to this embodiment, when the slave is registered as a master by the master management unit 133, the radio terminal MS stops the base station search. As described above, when the wireless terminal MS that has become a slave stops the base station search, power consumption in the wireless terminal MS is reduced.

  According to the present embodiment, the radio terminal MS measures the reception quality that is the quality of the radio signal received from the radio base station BS, and compares the reception quality with a threshold value. If the reception quality is below the threshold, the radio terminal MS determines that direct communication with the radio base station BS cannot be continued. Therefore, when the wireless terminal MS that communicates directly with the wireless base station BS moves out of the service area SA, the wireless terminal MS and the wireless terminal MS before the communication cannot be completely continued. In the slave, the master / slave can be switched.

  According to the present embodiment, the radio terminal MS detects the remaining amount of the battery 150 and compares the remaining amount with a threshold value. Then, when the remaining amount of the battery 150 falls below the threshold, the radio terminal MS determines that direct communication with the radio base station BS cannot be continued. As a result, before the operation of the wireless terminal MS stops when the battery 150 is exhausted, the master / slave can be replaced in the wireless terminal MS and the slave of the wireless terminal MS.

  According to the present embodiment, the radio terminal MS detects a call restriction that restricts direct communication with the radio base station BS. The wireless terminal MS determines that direct communication with the radio base station BS cannot be continued if the connection with the radio base station BS fails after the call restriction is detected. Therefore, when the wireless terminal MS becomes unable to communicate due to outgoing restrictions, the master / slave can be switched between the wireless terminal MS and the slave of the wireless terminal MS.

  According to the present embodiment, the radio terminal MS can directly communicate with the radio base station BS when receiving a search instruction for inquiring whether or not direct communication with the radio base station BS is possible from the master. It is determined whether or not. When it is determined that direct communication with the radio base station BS is possible, the radio terminal MS performs direct communication with the radio base station BS and registers the master as a slave.

  That is, when the direct communication between the master and the radio base station BS cannot be continued and the slave can directly communicate with the radio base station BS, the ad hoc network AH is configured by switching the relationship between the master and the slave. The wireless terminal MS can communicate with the wireless base station BS.

  According to the present embodiment, the radio terminal MS relays communication between the slave registered by the slave management unit 135 and the radio base station BS. Therefore, when the wireless terminal MS becomes a master by switching the master-slave relationship, the slave can communicate (connect) with the wireless base station BS by relaying communication between the slave and the wireless base station BS. It becomes.

  According to the present embodiment, when the radio terminal MS determines that direct communication with the radio base station BS is possible, the radio terminal MS transmits a search result indicating that direct communication with the radio base station BS is possible to the master. . Further, the radio terminal MS receives a connection instruction for instructing the start of direct communication with the radio base station BS from the master. The radio terminal MS is capable of direct communication with the radio base station BS, and executes direct communication with the radio base station BS when receiving a connection instruction. In this way, the wireless terminal MS can perform the master / slave switching more reliably by performing the master / slave switching after waiting for the connection instruction.

  According to the present embodiment, if the radio terminal MS determines that direct communication with the radio base station BS is not possible after receiving the search instruction, the radio terminal MS transmits the search instruction to the slave. Therefore, the search instruction can be propagated toward the lower-level radio terminal MS.

(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, it is determined whether or not direct communication between the radio base station BS and the radio terminal MS is possible using the criteria (a) to (c). It is not limited to ~ (c). For example, in the radio terminal MS that cannot execute data communication during a voice call, it may be determined that direct communication with the radio base station BS cannot be continued when the voice call is started.

  In the above-described embodiment, the master / slave switching operation is performed by the master, but may be performed by the slave.

  In the example of FIG. 1, a mobile phone terminal is exemplified as the wireless terminal MS, but a notebook PC having a wireless communication function, a personal digital assistance (PDA), or the like may be used. An ad hoc network AH including not only a portable wireless terminal but also a fixed wireless terminal may be configured.

  In the above ad hoc 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.

   AH: Ad hoc network, BS: Wireless base station, MS, MS1 to MS9 ... Wireless terminal, SA ... Service area, 10 ... Wireless communication system, 110 ... Base station communication unit, 111 ... Antenna, 112 ... RF processing for base station communication 113: Encoding unit, 114 ... Decoding unit, 120 ... Ad hoc communication unit, 121 ... Antenna, 122 ... RF processing unit for ad hoc communication, 123 ... Encoding unit, 124 ... Decoding unit, 130 ... Control unit, 143 ... Display unit 131 ... Communication determination unit 132 ... Message processing unit 144 ... Input unit 133 133 Master management unit 134 ... Master storage unit 135 ... Slave management unit 136 ... Slave storage unit 137 ... Communication relay unit 138: Communication control unit, 141 ... Microphone, 142 ... Speaker, 150 ... Battery

Claims (9)

A system including a first device that communicates directly with a radio base station and a second device that communicates with the first device,
The first device is:
If it is determined that direct communication with the radio base station is not possible, send a message to inquire whether direct communication with the radio base station is possible,
The second device is
A system for executing direct communication with a radio base station when the message is received. A device that, when it is determined that direct communication with a wireless base station is not possible, transmits a message for inquiring whether direct communication with the wireless base station is possible or not to other devices constituting the network including the device itself. A device that performs direct communication with a radio base station when a message for inquiring whether direct communication with the radio base station is possible is received from another device that configures the network including the device itself. A system including a first device that communicates directly with a radio base station and a second device that communicates with the first device,
The first device is:
When it is determined that direct communication with the radio base station is impossible, a message for executing direct communication with the radio base station is transmitted,
The second device is
A system for executing direct communication with a radio base station when the message is received. A device that communicates directly with a radio base station,
A device that, when it is determined that direct communication with a radio base station is not possible, transmits a message for executing direct communication with the radio base station to another device that configures the network including the device. A device constituting a network including a device directly communicating with a radio base station,
A device that performs direct communication with a radio base station when a message for executing direct communication with the radio base station is received from another device. A system including a first device that communicates directly with a radio base station and a second device that communicates with the first device,
The first device is:
If it is determined that direct communication with the radio base station is not possible, send a search instruction,
The second device is
A system that performs a search when the message is received. A device that communicates directly with a radio base station,
A device that sends search instructions to other devices when it is determined that direct communication with a radio base station is not possible. A device constituting a network including a device directly communicating with a radio base station,
A device that performs a search when it receives a search instruction from another device.

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