JPWO2016129271A1 - Communication terminal, communication control method and communication system in wireless communication network - Google Patents

Abstract

A communication terminal, a communication control method, and a communication system capable of efficiently improving connectivity between terminals are provided. A determination unit (104) for determining whether or not a communication terminal can be wirelessly connected to another communication terminal by Wi-Fi or Wi-Fi peer-to-peer, and whether the state of the communication terminal satisfies a predetermined condition. And a control unit (105) that changes a retransmission timeout of a control message transmitted / received when establishing a connection with another communication terminal according to the determination result. [Selection] Figure 2

Description

  The present invention relates to a wireless communication network including terminals that can be wirelessly connected to each other, and more particularly to a communication terminal, a communication control method, and a communication system of a wireless communication network.

  In recent years, Wi-Fi Direct as a terminal-to-terminal communication method has attracted attention from the viewpoints of broadbanding and security enhancement. Earlier Wi-Fi networks operate in infrastructure mode with a specific device as an access point (AP), whereas in a network compliant with the Wi-Fi Direct standard, any peer-to-peer (instead of a specific device) A P2P) terminal becomes a group owner, thereby enabling communication within the group (Non-Patent Document 1). The group owner is a P2P terminal that operates as an access point of the group, and a group having another P2P terminal as a child (client) can be formed as the parent of the group.

  In general, in wireless communication between wireless communication terminals, since there is a high possibility of packet loss due to radio wave interference or the like, a function of retransmitting the lost packet is provided. Usually, when a packet is lost, retransmission at the MAC (Media Access Control) layer occurs. However, in an environment where radio waves are congested, there is a case where recovery is not possible by only retransmission of the MAC layer, so a retransmission function at the software layer is essential.

  In the retransmission of the software layer, 1 second (minimum 200 milliseconds, maximum 20 seconds) is recommended as the initial value of retransmission timeout (RTO: Retransmission Time Out) (see “4.3 Retransmission Behavior” in Non-Patent Document 2). reference). Further, in Non-Patent Document 2, back-off control (see “5 Managing the RTO Timer” in Non-Patent Document 3) is recommended as retransmission control in which the retransmission timeout is doubled every time retransmission is repeated.

  FIG. 1 is a sequence diagram schematically showing the back-off control operation when the RTO initial value is 1. As shown in the figure, every time the number of retransmissions increases, the retransmission timeout increases twice as much as the previous time.

Wi-Fi Peer-to-Peer Technical Specification Version 1.1 (Wi-Fi Alliance Technical Committee PSP Task Group, Wi-Fi Peer-to-Peer (P2P) Technical Specification Version 1.1) RFC3748 (“Extensible Authentication Protocol (EAP)”, Network Working Group, June 2004) RFC 2988 ("Computing TCP's Retransmission Timer", Network Working Group, November 2000)

  However, in a place where the radio wave environment is so bad that retransmission at the software layer described above is necessary, if retransmission control and backoff control using the RTO initial value are executed, a delay in connection establishment between P2P terminals and a connection success rate Problems such as degradation and degradation of communication performance become significant. For example, if packet loss frequently occurs in a place where Wi-Fi hot spots are concentrated, there is a high possibility that the retransmission timeout value will increase twice, and it may take a considerable time (10 seconds or more) to establish a connection. Such a delay in connection establishment causes great frustration to the user, and causes an undesirable situation such as greatly reducing the connection success rate in a situation where two communication terminals are approaching each other at high speed.

  Therefore, an object of the present invention is to provide a communication terminal, a communication control method, and a communication system that can efficiently improve the connectivity between terminals.

The communication terminal according to the present invention is a communication terminal that can be wirelessly connected to other communication terminals by Wi-Fi or Wi-Fi peer-to-peer, and determines whether the state of the communication terminal satisfies a predetermined condition. And determining means and control means for changing a retransmission timeout of a control message transmitted / received when establishing a connection with another communication terminal according to the result of the determination.
The communication control method according to the present invention is a communication control method for a communication terminal that can be wirelessly connected to other communication terminals by Wi-Fi or Wi-Fi peer-to-peer, and the determination means determines that the condition of the communication terminal satisfies a predetermined condition. It is determined whether or not it is satisfied, and the control means changes a retransmission timeout of a control message transmitted and received when establishing a connection with another communication terminal according to the determination result.
The communication system according to the present invention is a communication system in which a first communication terminal and a second communication terminal can be wirelessly connected to each other by Wi-Fi or Wi-Fi peer-to-peer, and the first communication terminal and the second communication terminal. Any one of the terminals determines whether the condition of the terminal satisfies a predetermined condition, and either one of the first communication terminal and the second communication terminal determines whether the other terminal The retransmission timeout of a control message transmitted / received when establishing a connection with a terminal is changed.

  According to the present invention, connectivity between terminals can be efficiently improved by changing the retransmission timeout according to the situation.

FIG. 1 is a sequence diagram schematically showing an existing back-off control operation. FIG. 2 is a block diagram schematically showing a functional configuration of the terminal according to the first embodiment of the present invention. FIG. 3 is a sequence diagram illustrating an example of a retransmission timeout control operation according to the first embodiment. FIG. 4 is a block diagram schematically showing a functional configuration of a terminal according to the second embodiment of the present invention. FIG. 5 is a sequence diagram illustrating an example of a retransmission timeout control operation according to the second embodiment. FIG. 6 is a block diagram schematically showing a functional configuration of a terminal according to the third embodiment of the present invention. FIG. 7 is a sequence diagram illustrating an example of a retransmission timeout control operation according to the third embodiment. FIG. 8 is a block diagram schematically showing a functional configuration of a terminal according to the fourth embodiment of the present invention. FIG. 9 is a sequence diagram illustrating an example of a retransmission timeout control operation according to the fourth embodiment. FIG. 10 is a sequence diagram showing an example of a Wi-Fi Direct connection procedure to which retransmission timeout control according to the first embodiment of the present invention is applied. FIG. 11 is a sequence diagram showing an example of scan processing for explaining a first example of retransmission timeout control in FIG. FIG. 12 is a block diagram schematically showing the functional configuration of the client terminal in the first example of retransmission timeout control in FIG. FIG. 13 is a block diagram schematically showing a functional configuration of a group owner (GO) terminal in the first example of retransmission timeout control in FIG. FIG. 14 is a flowchart showing respective operations of the client terminal and the GO terminal in the first example of retransmission timeout control in FIG. FIG. 15 is a sequence diagram showing a second example of retransmission timeout control in FIG. FIG. 16 is a block diagram schematically showing the functional configuration of the GO terminal in the second example of retransmission timeout control in FIG. FIG. 17 is a flowchart showing the operation of the GO terminal in the second example of retransmission timeout control in FIG. FIG. 18 is a block diagram schematically showing a functional configuration of a terminal according to the second embodiment of the present invention. FIG. 19 is a sequence diagram showing an example of retransmission timeout control according to the second embodiment shown in FIG.

<Outline of Embodiment>
According to the embodiment of the present invention, the retransmission timeout of a control message transmitted / received between terminals when a Wi-Fi or Wi-Fi peer-to-peer connection is established is changed according to the state of the terminal, radio wave environment, purpose of use, and the like. This makes it possible to efficiently improve the connectivity between terminals even in an environment where packet loss occurs.

  The status of the terminal, the radio wave environment, etc. can be detected by various methods. For example, for detection of the radio wave environment, the level of the received signal, the number of message retransmissions, the processing time from request to response, and the like can be used as indices. For detecting the state of the terminal, for example, the moving speed of the terminal, the remaining battery level of the terminal, a change in GPS position, and the like can be used as indices. If such a detection result satisfies a preset retransmission timeout changing condition, the retransmission timeout is changed.

  The retransmission timeout can be changed in various ways. For example, a method of switching between the initial value of retransmission timeout and a changed setting value smaller than the initial value, a method of preparing a plurality of changed setting values, selecting one of them according to the situation, and changing the multiplier And a method of switching a plurality of change setting values or a plurality of multipliers at random. Hereinafter, embodiments and examples of the present invention will be described in detail with reference to the drawings.

1. 1st Embodiment According to 1st Embodiment of this invention, the retransmission timeout at the time of Wi-Fi or Wi-Fi peer-to-peer connection establishment is shortened according to a condition. Since the retransmission frequency is increased by shortening the retransmission timeout, the possibility of connection can be increased even in an environment where the radio wave condition is not good, and as a result, the connection success rate is improved.

1.1) Terminal Configuration As illustrated in FIG. 2, the P2P terminal according to the present embodiment includes a Wi-Fi device 101, a Wi-Fi connection control unit 102, and an application unit 103 for performing Wi-Fi communication. The Wi-Fi connection control unit 102 has a function of controlling Wi-Fi Direct commands in place of existing communication applications, and automates control according to Wi-Fi Direct without modifying existing applications. It shall be possible.

  The application unit 103 has a function of realizing the determination unit 104 and the retransmission timeout control unit 105. The retransmission control unit 106 is provided in the Wi-Fi connection control unit 102 and implements the above-described retransmission function in the software layer, and functions when recovery cannot be performed by the retransmission function in the MAC layer.

  The determination unit 104 receives the radio wave environment information from the Wi-Fi connection control unit 102, determines whether or not the radio wave environment satisfies a predetermined retransmission timeout change condition, and if the change condition is satisfied, the retransmission timeout control Notification to the unit 105. The radio wave environment information includes, for example, the level of a received signal from a connection partner terminal, the number of retransmissions of a control frame during connection operation, the processing time from a request to a response during connection operation, or the number of retransmissions during retransmission control at the MAC layer. It is. Further, the determination unit 104 may input terminal state information and determine whether or not the terminal state satisfies a predetermined retransmission timeout change condition. For example, when the moving speed of the terminal exceeds a predetermined value, or when the relative moving speed with the connection partner terminal using the GPS information exceeds a predetermined value, it is determined that the retransmission timeout change condition is satisfied.

  When the retransmission timeout change condition is satisfied, the retransmission timeout control unit 105 switches the retransmission timeout value to a value shorter than the initial value and sets the retransmission timeout value in the retransmission control unit 106. The retransmission control unit 106 executes well-known retransmission control using the updated retransmission timeout value.

1.2) Retransmission time-out control As illustrated in FIG. 3, the terminal 1 and the terminal 2 start a connection procedure according to Wi-Fi Direct (operation S11), the terminal 1 is a client, the terminal 2 is a group owner ( GO). The determination unit 105 of the GO terminal 2 detects the radio wave environment from the received signal in the connection procedure with the terminal 1 to determine whether or not the radio wave environment has deteriorated, or considers the state of the terminal 2 itself and performs retransmission. It is determined whether or not a timeout change condition is satisfied (operation S12). For example, when the received signal strength is lower than the threshold value, or when the number of retransmissions of control messages transmitted and received in the connection procedure is greater than the threshold value, the radio wave environment is degraded (that is, the retransmission timeout change condition is satisfied). It is determined. This criterion can be determined depending on the purpose of communication between terminals, the relative movement state between terminals, and the like.

  Subsequently, when the retransmission timeout change condition is satisfied, the retransmission timeout control unit 105 switches the retransmission timeout value to a value (RTO1) shorter than the initial value (RTOinitial) and sets the retransmission timeout value in the retransmission control unit 106 (operation S13). . The shortened retransmission timeout value RTO1 may be a predetermined fixed value, or may be a value selected sequentially or randomly from a plurality of predetermined values depending on the situation.

  The retransmission control unit 106 performs known retransmission control. More specifically, when the Wi-Fi connection control unit 102 transmits a control frame according to Wi-Fi Direct, the retransmission control unit 106 starts a retransmission timer of RTO 1 (operation S14). If there is a complete control frame response from the terminal 1 before the retransmission timeout RTO1, the retransmission control unit 106 does not perform a retransmission operation, and if there is no complete control frame response within the retransmission timeout, the control frame is retransmitted. The Wi-Fi connection control unit 102 is instructed to do so. However, it is assumed that retransmission control in the MAC layer is performed independently of retransmission control by the retransmission control unit 106.

1.3) Application Example A case where the radio wave environment information is reception intensity will be described as a first example. The GO terminal 2 detects the strength of a signal received from the client terminal 1 by a connection procedure according to Wi-Fi Direct, and shortens the retransmission timeout when the received strength is equal to or less than a predetermined threshold value. As an example, if the received strength is RSSI (Received Signal Strength Indicator), the retransmission timeout is shortened when it is −80 dBm or less. As a result, the connection success rate can be improved even in an environment where the radio wave condition is not good.

  A case where at least one of the terminal 1 and the terminal 2 is an in-vehicle device will be described as a second example. In this case, the in-vehicle terminal is set to have a short retransmission timeout according to the terminal state information indicating that it is in-vehicle. For example, in the case of a terminal for car-to-car communication, shortening the retransmission timeout from the initial value of 1 second to 0.1 seconds dramatically improves the connection success rate even when cars pass each other at 60 km / h. Can be improved. Alternatively, the connection success rate can be improved according to a dynamic situation by changing the retransmission timeout value stepwise according to the speed of the vehicle.

1.4) Effect According to the above-described embodiment, the retransmission timeout value at the time of establishing Wi-Fi or Wi-Fi peer-to-peer connection is set to a predetermined value according to information indicating the radio wave environment of the terminal or the state of the terminal. Or by shortening to one of the predetermined multiple values, the possibility of connection can be increased regardless of changes in the situation of the terminal, radio wave environment, and the like.

2. Second Embodiment According to the second embodiment of the present invention, the retransmission timeout at the time of establishing a Wi-Fi or Wi-Fi peer-to-peer connection is controlled to turn on / off the high-speed retransmission mode according to the situation. The fast retransmission mode is an operation mode in which the retransmission timeout value in the retransmission operation in the application layer is shortened from the initial value. Since the retransmission frequency increases in the high-speed retransmission mode, the possibility of connection can be increased even in an environment where the radio wave condition is not good, and as a result, the connection success rate is improved. Further, if the radio wave state is sufficient for retransmission control in the MAC layer, frequent retransmissions can be suppressed by turning off the high-speed retransmission mode.

2.1) Terminal Configuration As shown in FIG. 4, in the terminal according to this embodiment, the high-speed retransmission mode ON / OFF control unit 107 replaces the retransmission timeout control unit 105 of the terminal shown in the first embodiment (FIG. 2). Is provided. Since the terminal according to the present embodiment has basically the same configuration and function as those of the first embodiment except for the above, the same reference numerals are assigned and description thereof is omitted.

  When the retransmission timeout change condition is satisfied, the high-speed retransmission mode ON / OFF control unit 107 sets the high-speed retransmission mode to ON (on), switches the retransmission timeout value to a value shorter than the initial value, and transmits to the retransmission control unit 106. If the retransmission timeout change condition is not satisfied, the high-speed retransmission mode is turned off and the retransmission timeout initial value is set in the retransmission control unit 106. The retransmission control unit 106 executes well-known retransmission control using the set retransmission timeout value.

2.2) Retransmission timeout control As illustrated in FIG. 5, the terminal 1 and the terminal 2 start a connection procedure according to Wi-Fi Direct (operation S11), the terminal 1 is a client, the terminal 2 is a group owner ( GO). The determination unit 104 of the GO terminal 2 detects the radio wave environment from the received signal in the connection procedure with the terminal 1 and determines whether or not the radio wave environment has deteriorated, or considers the state of the terminal 2 itself and performs retransmission. It is determined whether or not a timeout change condition is satisfied (operation S12).

  For example, when the received signal strength is lower than the threshold value, or when the number of retransmissions of control messages transmitted and received in the connection procedure is greater than the threshold value, the radio wave environment is degraded (that is, the retransmission timeout change condition is satisfied). It is determined. This criterion can be determined depending on the purpose of communication between terminals, the relative movement state between terminals, and the like. Note that the determination operation as to whether or not the retransmission timeout change condition is satisfied may be executed at a predetermined time interval, or the determination operation cycle may be changed depending on the state of the terminal (whether or not it is moving). Good.

  Subsequently, when the retransmission timeout change condition is satisfied, the high-speed retransmission mode ON / OFF control unit 107 turns on the high-speed retransmission mode (operation S13a), and sets the retransmission timeout value to a value shorter than the initial value (RTOinitial) (RTOinitial). RTO1) is set and the retransmission control unit 106 is set.

  The retransmission control unit 106 performs known retransmission control. More specifically, when the Wi-Fi connection control unit 102 transmits a control frame according to Wi-Fi Direct, the retransmission control unit 106 starts a retransmission timer of RTO 1 (operation S14). If there is a complete control frame response from the terminal 1 before the retransmission timeout RTO1, the retransmission control unit 106 does not perform a retransmission operation, and if there is no complete control frame response within the retransmission timeout, the control frame is retransmitted. The Wi-Fi connection control unit 102 is instructed to do so. However, it is assumed that retransmission control in the MAC layer is performed independently of retransmission control by the retransmission control unit 106.

  Subsequently, it is determined whether or not a second retransmission timeout change condition is satisfied after a predetermined time has elapsed from the determination operation (S12) of the retransmission timeout change condition (operation S15). If the retransmission timeout change condition is not satisfied in this determination, the high-speed retransmission mode is turned off (operation S16a), the retransmission timeout value is switched to the initial value (RTOinitial), and is set in the retransmission control unit 106. The retransmission control unit 106 starts an initial value (RTOinitial) retransmission timer (operation S17).

  FIG. 5 illustrates the case where the radio wave environment has been improved in the determination operation (S15) of the second retransmission timeout change condition. However, if the radio wave environment has not been improved even in this determination operation (S15). The fast retransmission mode is continued. Also, in the case of an in-vehicle terminal, when the moving speed is a predetermined value or less, the high-speed retransmission mode can be similarly turned off.

2.3) Effect According to the second embodiment of the present invention described above, the high-speed retransmission mode is turned on / off according to information indicating the radio wave environment of the terminal or the state of the terminal, as in the first embodiment. In addition, the possibility of connection can be increased regardless of changes in conditions such as the terminal state and the radio wave environment. Furthermore, according to the present embodiment, for example, if the radio wave environment is good enough to cope with retransmission control in the MAC layer, the high-speed retransmission mode can be turned off, so that frequent retransmissions can be avoided. The increase in traffic and the load on the communication terminal can be reduced.

3. Third Embodiment According to the third embodiment of the present invention, retransmission timeout when establishing a Wi-Fi or Wi-Fi peer-to-peer connection is controlled in stages according to the situation. Since the retransmission timeout value changes stepwise according to the situation, for example, retransmission control according to the degree of deterioration of the radio wave state is possible, and the connection success rate can be improved efficiently.

3.1) Terminal Configuration As shown in FIG. 6, the terminal according to the present embodiment is different from the terminal determination unit 104 and the retransmission timeout control unit 105 shown in the first embodiment (FIG. 2) in that a determination unit 108 and a retransmission A timeout selection unit 109 and an RTO table 110 are provided. Since the terminal according to the present embodiment has basically the same configuration and function as those of the first embodiment except for the above, the same reference numerals are assigned and description thereof is omitted.

  The determination unit 108 includes a plurality of predetermined thresholds TH1,... THn (TH1 <... <THn; n is an integer of 2 or more) and radio wave environment information input from the Wi-Fi connection control unit 102. To determine the level of the radio wave environment, and notifies the retransmission timeout selection unit 109 of the determination result. The radio wave environment information includes, for example, the strength of the received signal from the connection partner terminal, the number of retransmissions of the control frame during connection operation, the processing time from request to response during connection operation, or the number of retransmissions during retransmission control at the MAC layer. It is. Moreover, the determination part 108 can perform the same state determination also about a terminal state using the some threshold value provided previously. For example, the level of the moving speed of the terminal is determined, and the determined speed level is notified to the retransmission timeout selection unit 109.

  The retransmission timeout selection unit 109 searches the RTO table 110 using the determination result from the determination unit 108 and sets a retransmission timeout value corresponding to the determination result in the retransmission control unit 106. The retransmission control unit 106 executes well-known retransmission control using the set retransmission timeout value.

  The RTO table 110 can search for a plurality of predetermined determination situations (aaa, bbb, ... zzz) and retransmission timeout values (RTOa, RTOb, ... RTOinitial) suitable for each situation. Stored in Predetermined judgment situations (aaa, bbb, ... zzz) are classified according to predetermined judgment indices (such as radio wave condition and moving speed), and specify which level the situation judged by the judgment unit 108 belongs to it can. For example, if the field intensity is between two threshold values TH1 and TH2, it is determined that the signal belongs to the determination status aaa. Therefore, the retransmission timeout selection unit 109 can search the RTO table 110 using the determination result from the determination unit 108 as a key, and determine a retransmission timeout value suitable for the determination level.

  In this embodiment, as an example, it is assumed that the retransmission timeout value of the RTO table 110 is RTOa <RTOb <... <RTOinitial, which is smaller than the initial value RTOinitial. In this case, retransmission timeout values RTOa, RTOb,... Other than the initial value RTOinitial can be considered as retransmission timeout setting values in different high-speed retransmission modes.

3.2) Retransmission timeout control As illustrated in FIG. 7, the terminal 1 and the terminal 2 start a connection procedure according to Wi-Fi Direct (operation S11), the terminal 1 is a client, the terminal 2 is a group owner ( GO). The determination unit 108 of the GO terminal 2 detects the radio wave environment from the received signal in the connection procedure with the terminal 1, or determines the degradation level of the radio wave environment in consideration of the state of the terminal 2 itself (operation S12). Here, it is assumed that the current radio wave environment is determined to be the degradation level aaa.

  Subsequently, the retransmission timeout selection unit 109 selects the retransmission timeout value RTOa corresponding to the determination result by searching the RTO table 110 using the determination result aaa from the determination unit 108 (operation S13b). A retransmission timeout value is set in the retransmission control unit 106.

  The retransmission control unit 106 performs known retransmission control. More specifically, when the Wi-Fi connection control unit 102 transmits a control frame in accordance with Wi-Fi Direct, the retransmission control unit 106 starts a retransmission timer with a retransmission timeout value RTOa (operation S14). If there is a complete control frame response from the terminal 1 before the time corresponding to the retransmission timeout value RTOa elapses, the retransmission control unit 106 does not perform the retransmission operation, and the complete control frame response is received within the retransmission timeout. If not, it instructs the Wi-Fi connection control unit 102 to retransmit the control frame. However, it is assumed that retransmission control in the MAC layer is performed independently of retransmission control by the retransmission control unit 106.

  Subsequently, after a predetermined time has elapsed from the situation determination operation (S12), the second situation determination operation is executed (operation S15). If the current radio wave environment is improved from the previous time, for example, it is determined that the degradation level is bbb, the retransmission timeout selection unit 109 searches the RTO table 110 using the determination result bbb from the determination unit 108 to perform the determination. The retransmission timeout value RTOb corresponding to the result is selected (operation S16b), and the selected retransmission timeout value is set in the retransmission control unit 106. Thereby, the retransmission control unit 106 starts a retransmission timer for the retransmission timeout value RTOb (operation S17).

  FIG. 7 illustrates the case where the radio wave environment has been improved by one step in the second situation determination (S15), but is not limited to this, and may be improved by two or more steps. In some cases, it may deteriorate by one or more steps from the previous time. In either case, the basic operation is as described above.

3.3) Effect According to the third embodiment of the present invention described above, the retransmission timeout at the time of establishing a Wi-Fi connection is controlled stepwise according to information indicating the radio wave environment of the terminal or the state of the terminal. For example, retransmission control according to the degree of deterioration of the radio wave state becomes possible, and the connection success rate can be improved efficiently. Further, for example, by increasing the retransmission timeout stepwise as the radio wave environment becomes better, frequent retransmissions can be avoided, and the increase in traffic and the load on the communication terminal can be reduced.

4). Fourth Embodiment According to the fourth embodiment of the present invention, the retransmission timeout at the time of establishing a Wi-Fi connection is changed by changing the multiplier a of the back-off retransmission control according to the situation. As described in the background art, the normal retransmission timeout is set to a multiplier a = 2, and the retransmission timeout increases by a factor of 2 each time retransmission is performed. On the other hand, according to the present embodiment, the multiplier a is set within the range of 0 <a ≦ 2. For example, if the multiplier a is set to 1 <a <2, the rate of increase in retransmission timeout for each retransmission can be reduced. Conversely, if 0 <a <1 is set, the retransmission timeout is reduced for each retransmission. be able to.

  In this embodiment, the multiplier a of the back-off control is changed, but the multiplicand (the retransmission timeout initial value) of the back-off control can also be changed by the first to third embodiments described above.

4.1) Terminal Configuration As shown in FIG. 8, in the terminal according to the present embodiment, the retransmission timeout control unit 105 according to the first embodiment, the fast retransmission mode ON / OFF control unit 107 according to the second embodiment, and the third embodiment. A back-off retransmission control unit 111 is provided instead of the retransmission timeout selection unit 109 according to FIG. Since the terminal according to the present embodiment has basically the same configuration and function as those of the above-described embodiments except for the above, the same reference numerals are assigned and description thereof is omitted.

  The back-off retransmission control unit 111 can set the multiplier a of the back-off control to a fixed value within a range of 0 <a ≦ 2 or a predetermined value according to the determination result of the determination unit (104 or 108).

  For example, when the determination unit 104 determines that the retransmission timeout has been changed as in the first or second embodiment, the back-off retransmission control unit 111 fixes the multiplier a of the back-off control, for example, within a range of 0 <a <1. Set to value. That is, when the high-speed retransmission mode is turned on in the second embodiment, the back-off retransmission control unit 111 according to the present embodiment sets the multiplier a to 0.8, for example, so that the next retransmission occurs. Reduce the retransmission timeout by 20%.

  Similarly to the third embodiment, a plurality of multipliers are prepared in advance, and the back-off retransmission control unit 111 determines one multiplier from the plurality of multipliers a according to the level of the radio wave environment determined by the determination unit 108. You can also choose. Specifically, similarly to the third embodiment, multipliers a1, a2,... Corresponding to the radio wave environment are stored in advance in the RTO table 110, and the backoff retransmission control unit 111 is a multiplier value corresponding to the determination result. To determine the retransmission timeout.

4.2) Retransmission time-out control Hereinafter, the operation when the back-off retransmission control unit 111 sets the normal multiplier a to the multiplier value a1 in the high-speed retransmission mode according to the situation will be described with reference to FIG.

  As illustrated in FIG. 9, the terminal 1 and the terminal 2 start a connection procedure according to Wi-Fi Direct (operation S11), and the terminal 1 is determined to be a client and the terminal 2 is determined to be a group owner (GO). And The determination unit 108 of the GO terminal 2 detects the radio wave environment from the received signal in the connection procedure with the terminal 1, or determines the degree of deterioration of the radio wave environment in consideration of the state of the terminal 2 itself (operation S12). For example, it is assumed that it is determined that the current radio wave environment is deteriorated below a predetermined threshold (retransmission timeout change condition is satisfied).

  When the retransmission timeout change condition is satisfied, the back-off retransmission control unit 111 sets the multiplier for the back-off control to a fixed value a1 that is smaller than 1 (operation S13c). In the first transmission, the retransmission control unit 106 sets a normal retransmission timeout value (RTO) (operation S14_0). If there is a complete control frame response from the terminal 1 before the retransmission timeout RTO, the retransmission control unit 106 does not perform the retransmission operation. If there is no response of the complete control frame within the retransmission timeout RTO, the retransmission control unit 106 instructs the Wi-Fi connection control unit 102 to retransmit the control frame. At this time, the retransmission timeout value is set to RTO1 = RTO × Shorten to a1 (operation S14_1). If there is still no response of the complete control frame within the retransmission timeout RTO1, the retransmission control unit 106 instructs the Wi-Fi connection control unit 102 to retransmit the control frame, and the retransmission timeout value is set to RTO2 = Further shortening to RTO1 × a1 (operation S14_2). Similarly, if there is no complete response, the retransmission timeout value is shortened until a predetermined lower limit is reached.

  In addition, it is determined whether or not the second retransmission timeout change condition is satisfied after a predetermined time has elapsed from the determination operation (S12) of the retransmission timeout change condition, and the retransmission timeout change condition is not satisfied (the radio wave condition is improved) The backoff retransmission control unit 111 resets the multiplier a to the normal value.

  In addition, as described above, the same applies to the case where the back-off retransmission control unit 111 sequentially selects one multiplier from a plurality of multipliers a according to the determination result of the determination unit 108 as in the third embodiment. Back-off control.

4.3) Effect According to the above-described fourth embodiment of the present invention, the first to third embodiments are configured by changing the multiplier of the back-off control according to information indicating the radio wave environment of the terminal or the state of the terminal. Similarly to the above, it is possible to increase the possibility of connection regardless of changes in the state of the terminal, radio wave environment, and the like.

5. First Embodiment As already described, the status of the terminal, the radio wave environment, and the like can be detected by various methods. Hereinafter, as a first embodiment of the present invention, a radio wave environment determination method using scan processing in a connection procedure between P2P terminals will be described.

5.1) Connection procedure between P2P terminals In FIG. 10, first, a neighboring P2P terminal is searched by Device Discovery processing (operation S21), and when a P2P terminal is found, one of them is a group owner (by GO Negotiation processing). GO) and the other is a client (operation S22). Here, it is assumed that the terminal 1 is a client and the terminal 2 is a GO. The GO terminal 2 sets an SSID (“DIRECT-XX”: XX is two random characters) and starts to operate as an access point.

  In order to acquire information as an access point of the GO terminal 2, the client terminal 1 broadcasts a Probe Request and waits for a Probe Response corresponding thereto (Operation S23). Hereinafter, the handshake operation including Probe Request broadcast and Probe Response reception is referred to as “scan processing”. The scan process is not defined in the Wi-Fi Direct standard, but is included in the connection procedure in the implementation in order to update the internal information of the kernel after the GO Negotiation process.

  After the scan process (operation S23), the WPA2 common key generation and group authentication process, which is a security technology, are performed (operation S24), and once disconnected, the scan process is performed again (operation S25). After the second scan process S15, an AES encryption key generation process is executed (operation S26), and the connection between the terminal 1 and the terminal 2 is completed. Note that the second scan process S15 may not be executed depending on the environment.

  As shown in FIG. 11, since the probe request for scan processing is a broadcast packet, retransmission control in the MAC layer does not work even if the probe request is discarded. Therefore, there is a high possibility that the scan process will fail and be repeatedly executed where the radio wave quality is poor. Normally, if a probe request is not returned even after a certain time (approximately 100 milliseconds) has elapsed, the scanning process is executed again. Therefore, the number of repetitions of this scanning process or the time taken until the scanning process is successful can be used as an indicator of the wireless environment.

  Further, when the result of the scan process is used as a wireless environment index, the retransmission timeout value can be changed by using the radio wave environments detected by the first scan process S23 and the second scan process S25 in FIG. . For example, in the second embodiment, when the deterioration of the radio wave environment is detected in the first scanning process S23, the high-speed retransmission mode is turned on. If the radio wave environment is improved in the second scanning process S25, the high-speed retransmission mode is set. Control to return to OFF is possible.

  Hereinafter, a first example in which the number of scan processing repetitions is used as a wireless environment index and a second example in which the time taken until the scanning process is successful will be described.

5.2) First example Retransmission control in the application layer is a technique on the Wi-Fi access point side (GO side), but in the first example, the client terminal determines the number of repetitions of the scanning process, and the determination The GO terminal executes retransmission control according to the result. Hereinafter, an example of the functional configuration of the client terminal and the GO terminal will be shown using FIG. 12 and FIG. 13, respectively, and an example of the overall operation will be described using FIG. However, in FIG. 12 and FIG. 13, only functions necessary for explaining the operation of the present embodiment are shown, and the others are omitted.

  As illustrated in FIG. 12, the terminal that has become a client by the GO Negotiation process is provided with a repetitive determination unit 104 in the application unit 103. When the above-described scan processing is executed, the Wi-Fi connection control unit 102 notifies the determination unit 104 of the application unit 103 of the number of repetitions n. The determination unit 104 compares the scan repetition count n with the threshold value Nth, and notifies the GO terminal of the comparison result as determination information.

  As illustrated in FIG. 13, a terminal that has become GO through GO Negotiation processing includes a retransmission timeout control unit 105 and a retransmission control unit 106 in the application unit 103. When receiving the determination information from the client terminal, the retransmission timeout control unit 105 switches the retransmission timeout value and sets it in the retransmission control unit 106 as described in the first to fourth embodiments. Hereinafter, the operations of the client terminal and the GO terminal will be described in more detail with reference to FIG.

  As shown in FIG. 14, it is assumed that the terminal 1 becomes a client and the terminal 2 becomes a GO by GO Negotiation processing (operation S22).

  First, the Wi-Fi connection control unit 102 of the client terminal 1 broadcasts a Probe Request at the start of scanning described above and increments the number of transmissions n (operation S201). If the probe response is not received within a predetermined time after transmission (operation S202; No), the Wi-Fi connection control unit 102 transmits the probe request again and repeats operation S201.

  When the probe response to the probe request is received within the predetermined time (operation S202; Yes), the determination unit 104 compares the transmission repetition count n notified from the Wi-Fi connection control unit 102 with the threshold Nth (operation). S203). If the number of transmission repetitions n is equal to or greater than the threshold value Nth (Operation S203; No), the determination unit 104 notifies the Wi-Fi connection control unit 102 of determination information indicating deterioration of the radio wave environment (Operation S204). If the number of transmission repetitions n is less than the threshold value Nth (operation S203; Yes), determination information indicating that the radio wave environment has not deteriorated is notified to the Wi-Fi connection control unit 102 (operation S205). Hereinafter, as an example, according to the second embodiment, the fast retransmission flag is set to “1” when the deterioration of the radio wave environment is detected, and the fast retransmission flag is set to the default “0” when the deterioration is not deteriorated. Assume that the set judgment information is used. However, determination information according to other embodiments can also be used.

  Upon receiving the determination information from the determination unit 104, the Wi-Fi connection control unit 102 transmits the determination information on the first control frame after the scanning process and transmits the determination information to the GO terminal 1, and then the remaining connection establishment shown in FIG. Processing is executed (operation S206). The first frame after the scan process is the first frame of the operation S24 or S26 shown in FIG. 10, for example, an Association Request frame. Hereinafter, as an example, it is assumed that the determination information is included in the P2P attribute (P2P Attributes) in the information element (IE) of the Association Request frame (see Figure 16 on page 78 of Non-Patent Document 1).

  On the other hand, when receiving the probe request from the client terminal (operation S301), the Wi-Fi connection control unit 102 of the GO terminal 2 transmits a probe response (operation S302). Thereafter, when the first frame after the scan process (here, an Association Request frame) is received from the client terminal 1 (operation S303), the determination information included in the frame is notified to the retransmission timeout control unit 105 of the application unit 103.

  The retransmission timeout control unit 105 determines whether or not the high-speed retransmission flag that is the determination information is “1” (operation S304). If the high-speed retransmission flag is “1” (operation S304; Yes), the retransmission control is performed. The high-speed retransmission of the unit 106 is set to ON (operation S305), and if the high-speed retransmission flag = “0” (operation S304; No), the high-speed retransmission of the retransmission control unit 106 is set to OFF (operation S306). Thus, the remaining connection establishment processing shown in FIG. 10 is subsequently executed according to the set high-speed retransmission mode (ON or OFF) (operation S307). The high-speed retransmission mode is as described in the second embodiment.

5.3) Second Example Next, a second example in which the time taken until the scanning process is successful is used as a wireless environment index will be described. In the second example, the GO terminal determines the success of the scanning process, and the GO terminal takes the lead in executing retransmission timeout control. Therefore, in the second example, it is not necessary for the client terminal 1 to notify the determination information to the GO side.

  As shown in FIG. 15, when the terminal 1 becomes a client and the terminal 2 becomes GO by GO Negotiation processing, the GO terminal 2 sets an SSID (“DIRECT-XX”: XX is two random characters) and serves as an access point. And a timer for counting the time until the scanning process is successful is started (operation S401).

  In the scanning process, as described above, the client terminal 1 broadcasts a Probe Request in order to acquire information as an access point of the GO terminal 2, and waits for a Probe Response to the information (Operation S23). As described above, the probe request broadcast is repeated up to a predetermined number of times until a probe response is received. When the probe response is received and the scan process is successful, the client terminal 1 starts the subsequent WPA2 common key generation and group authentication process (operation S24). The GO terminal 2 reads the timer count when receiving the first control frame after returning the Probe Response, and uses the elapsed time Ts as a radio environment index.

  As illustrated in FIG. 16, the timer determination unit 104 of the terminal that has become GO by the GO Negotiation process starts the timer at the timing when the GO Negotiation ends, and the first control frame after returning the Probe Response of the scan process Timer determination is performed at the timing when (Association Request) is received here. This timer value Ts is notified to the retransmission timeout control unit 105 as a radio environment index, and retransmission timeout control and retransmission control are executed as described above. Hereinafter, the operation of the GO terminal will be described using the second embodiment as an example, but other embodiments may be applied.

  In FIG. 17, when GO is obtained by GO Negotiation processing (Operation S22), the timer determination unit 104 starts a timer at the timing when GO Negotiation is completed (Operation S401). Subsequently, when a Probe Request is received from the client terminal, a Probe Response is transmitted in response thereto (Operation S402). After that, when the first frame after scan processing (Association Request in this case) is received from the client terminal 1 (Operation S403), the timer determination unit 104 compares the elapsed time Ts of the timer with the threshold Tth (Operation S404). ). If the elapsed time Ts is equal to or greater than the threshold Tth (Operation S404; No), the retransmission timeout control unit 105 sets the high-speed retransmission mode of the retransmission control unit 106 to ON (Operation S405). If the elapsed time Ts is smaller than the threshold Tth (operation S404; Yes), the retransmission timeout control unit 105 sets the high-speed retransmission mode of the retransmission control unit 106 to OFF (operation S406). Thus, the remaining connection establishment processing shown in FIG. 10 is subsequently executed according to the set high-speed retransmission mode (ON or OFF) (operation S407). The high-speed retransmission mode is as described in the second embodiment.

5.4) Third Example The second example described above can also be applied to the sequence of the first example. That is, the client terminal may measure the time required from the start of the scanning process to the success of the scanning process, determine the radio wave environment, and notify the GO terminal of the determination result.

6). Second Embodiment Hereinafter, retransmission timeout control based on the moving speed of a terminal will be described as a second embodiment of the present invention. The retransmission timeout control according to each of the above-described embodiments is particularly necessary for communication with a mobile object. For example, in wireless communication between a relatively moving vehicle and a vehicle or between a vehicle and a fixed station, in an environment where a large number of vehicles are running in parallel, crossing, or passing each other, radio wave interference increases and the high-speed retransmission described above. The method becomes effective.

  Therefore, in the system according to the second embodiment of the present invention, the speed information provided by the terminal or the speed information by the acceleration sensor, the speed information from the in-vehicle speedometer, the speed information notified from the outside, or the like is used. The retransmission timeout control according to each embodiment described above is executed.

  As illustrated in FIG. 18, the terminal according to the present embodiment includes a speed detection unit 112 in addition to the Wi-Fi device 101, the Wi-Fi connection control unit 102, and the application unit 103 that are the same as those of the terminal according to the first embodiment. .

  The speed detecting unit 112 may have a function of calculating the moving speed of the terminal using not only the speed sensor or the acceleration sensor equipped in the terminal but also the moving information or position information from the outside. For example, the position information can be obtained using GPS (Global Positioning System) or a nearby fixed base station, and the moving speed of the terminal can be calculated from this position information and time information. In addition, when the position information of the partner terminal can be acquired from the terminal of the connection partner, the relative speed and moving direction with respect to the own terminal can be specified, and the traveling relationship with the partner terminal (parallel running, crossing, Alternatively, it is possible to identify each other.

  The determination unit 104 determines whether or not the moving speed of the terminal detected by the speed detection unit 112 exceeds a predetermined threshold, that is, whether or not a retransmission timeout change condition is satisfied. When the retransmission timeout change condition is satisfied, retransmission timeout control section 105 switches the retransmission timeout value to a value shorter than the initial value and sets it in retransmission control section 106.

  As illustrated in FIG. 19, the terminal 1 and the terminal 2 start a connection procedure according to Wi-Fi Direct (operation S11), and the terminal 1 is determined as the client and the terminal 2 is determined as the group owner (GO). And The determination unit 104 of the GO terminal 2 determines whether or not the movement speed obtained by the speed detection unit 112 exceeds a predetermined threshold (operation S501), and moves at a speed exceeding the predetermined threshold. If so, the retransmission timeout is set to a short value (operation S13), and the high-speed retransmission mode is started (operation S14).

  Note that the retransmission timeout value can be set according to each of the embodiments described above as well as a single fixed value. Thus, by shortening the retransmission timeout value at the time of establishing a Wi-Fi connection according to the information indicating the moving speed of the terminal, the possibility of connection can be increased regardless of changes in the situation of the terminal, radio wave environment, and the like.

7). Other Examples The present invention is not limited to the above-described embodiment or examples, and various modifications having the features of the present invention are possible. For example, in the above-described embodiment, the Wi-Fi access point side (GO side) performs retransmission control, but a similar retransmission control function can also be implemented in the client terminal.

  The present invention can be applied to wireless communication control based on Wi-Fi Direct.

101 Wi-Fi Device 102 Wi-Fi Connection Control Unit 103 Application Unit 104 Judgment Unit 105 Retransmission Timeout Control Unit 106 Retransmission Control Unit 107 Fast Retransmission Mode ON / OFF Control Unit 108 Judgment Unit 109 Retransmission Timeout Selection Unit 110 RTO Table 111 Backoff Retransmission control unit 112 Speed detection unit

Claims (49)

A communication terminal that can wirelessly connect to other communication terminals by Wi-Fi or Wi-Fi peer-to-peer,
Determination means for determining whether or not the status of the communication terminal satisfies a predetermined condition;
Control means for changing a retransmission timeout of a control message transmitted / received when establishing a connection with another communication terminal according to the determination result;
A communication terminal comprising:   The communication terminal according to claim 1, wherein the control unit changes the retransmission timeout to a setting value smaller than an initial value.   2. The control unit according to claim 1, wherein the control unit switches between a high-speed retransmission mode in which the retransmission timeout is set to the small set value and a normal mode set to the initial value according to the determination result. 2. The communication terminal according to 2.   The communication terminal according to any one of claims 1 to 3, wherein the control means selects one of a plurality of different setting values for the retransmission timeout.   The communication terminal according to claim 4, wherein the plurality of different setting values correspond to a plurality of predetermined conditions of the determination unit, respectively.   The communication terminal according to claim 4, wherein the plurality of different setting values are selected at random when the predetermined condition of the determination unit is satisfied.   The said control means changes the said retransmission timeout by back-off control, and changes the multiplier of the said back-off control to a multiplier value smaller than an initial multiplier value, The one of Claim 1-6 characterized by the above-mentioned. Communication terminal.   8. The communication terminal according to claim 7, wherein the control means changes the retransmission timeout by selecting one from a plurality of different multiplier values.   The communication terminal according to claim 8, wherein the plurality of different multiplier values correspond to a plurality of predetermined conditions of the determination unit, respectively.   9. The communication terminal according to claim 8, wherein when the predetermined condition of the determination unit is satisfied, the plurality of different multiplier values are selected at random.   The communication terminal according to claim 1, wherein the determination unit performs the determination a plurality of times when the connection is established.   The communication terminal according to claim 1, wherein the determination unit determines a radio wave environment in which the connection establishment is performed as the situation.   13. The communication terminal according to claim 12, wherein the radio wave environment is detected from a received signal level, the number of times the control message is retransmitted, or a time required until the processing of the control message is completed.   The radio wave environment uses a scan process from transmission of a broadcast message to a group owner terminal by a client terminal determined by GO Negotiation processing compliant with Wi-Fi Direct and reception of a response message to the broadcast message. The communication terminal according to claim 13, wherein the communication terminal is detected.   The communication terminal according to claim 14, wherein the radio wave environment is detected from the number of retransmissions of the broadcast message in the scan process.   The communication terminal according to claim 14, wherein the radio wave environment is detected from a time required for the scanning process.   In the radio wave environment, a group owner terminal determined by GO Negotiation processing conforming to Wi-Fi Direct receives a control message first transmitted from the client terminal after completion of the GO Negotiation processing and after completion of the scanning processing. The communication terminal according to claim 14, wherein the communication terminal is detected from a required time until.   The communication terminal according to claim 1, wherein the determination unit determines a moving state of the communication terminal as the situation.   The communication according to claim 18, wherein the movement state is detected using at least one of a speed sensor, an acceleration sensor, and GPS (Global Positioning System) information that detects a movement speed of the communication terminal. Terminal. A communication control method for a communication terminal that can wirelessly connect to other communication terminals by Wi-Fi or Wi-Fi peer-to-peer,
The determination means determines whether the status of the communication terminal satisfies a predetermined condition,
The control means changes a retransmission timeout of a control message transmitted / received when establishing a connection with another communication terminal according to the determination result,
A communication control method characterized by the above.   21. The communication control method according to claim 20, wherein the control unit changes the retransmission timeout to a setting value smaller than an initial value.   21. The control unit according to claim 20, wherein the control unit switches between a high-speed retransmission mode in which the retransmission timeout is set to the small set value and a normal mode set to the initial value according to the determination result. The communication control method according to claim 21.   The communication control method according to any one of claims 20 to 22, wherein the control unit selects one of the retransmission timeouts from a plurality of different setting values.   The communication control method according to claim 23, wherein the plurality of different setting values respectively correspond to a plurality of predetermined conditions of the determination unit.   The communication control method according to claim 23, wherein the plurality of different setting values are selected at random when the predetermined condition of the determination unit is satisfied.   The said control means changes the said retransmission timeout by backoff control, and changes the multiplier of the said backoff control to a multiplier value smaller than an initial multiplier value, The one of Claim 20-25 characterized by the above-mentioned. Communication control method.   27. The communication control method according to claim 26, wherein the control means changes the retransmission timeout by selecting one from a plurality of different multiplier values.   28. The communication control method according to claim 27, wherein the plurality of different multiplier values respectively correspond to a plurality of predetermined conditions of the determination unit.   28. The communication control method according to claim 27, wherein, when the predetermined condition of the determination unit is satisfied, the plurality of different multiplier values are selected at random.   30. The communication control method according to claim 20, wherein the determination unit executes the determination a plurality of times when the connection is established.   The communication control method according to any one of claims 20 to 30, wherein the determination unit determines a radio wave environment in which the connection establishment is performed as the situation.   32. The communication control method according to claim 31, wherein the radio wave environment is detected from a received signal level, the number of times the control message is retransmitted, or a time required to complete the processing of the control message.   The radio wave environment uses a scan process from transmission of a broadcast message to a group owner terminal by a client terminal determined by GO Negotiation processing compliant with Wi-Fi Direct and reception of a response message to the broadcast message. The communication control method according to claim 32, wherein the communication control method is detected.   34. The communication control method according to claim 33, wherein the radio wave environment is detected from the number of retransmissions of the broadcast message in the scan process.   The communication control method according to claim 33, wherein the radio wave environment is detected from a time required for the scanning process.   In the radio wave environment, a group owner terminal determined by GO Negotiation processing conforming to Wi-Fi Direct receives a control message first transmitted from the client terminal after completion of the GO Negotiation processing and after completion of the scanning processing. 34. The communication control method according to claim 33, wherein the communication control method is detected from a required time until.   The communication control method according to any one of claims 20 to 36, wherein the determination unit determines a movement state of the communication terminal as the situation.   The communication according to claim 37, wherein the movement state is detected using at least one of a speed sensor, an acceleration sensor, and GPS (Global Positioning System) information that detects a movement speed of the communication terminal. Control method. A communication system in which a first communication terminal and a second communication terminal can wirelessly connect to each other by Wi-Fi or Wi-Fi peer-to-peer,
Whether one of the first communication terminal and the second communication terminal determines whether the status of the terminal satisfies a predetermined condition;
Either one of the first communication terminal and the second communication terminal changes a retransmission timeout of a control message transmitted and received when establishing a connection with the other terminal according to the determination result,
A communication system characterized by the above. It is determined that the first communication terminal operates as an access point and the second communication terminal operates as a client by negotiation between the first communication terminal and the second communication terminal,
The second communication terminal determines whether the status of the terminal itself satisfies a predetermined condition, and notifies the first communication terminal of the determination result;
The first communication terminal changes a retransmission timeout of a control message transmitted and received when establishing a connection with the second communication terminal according to the determination result,
40. The communication system according to claim 39. It is determined that the first communication terminal operates as an access point and the second communication terminal operates as a client by negotiation between the first communication terminal and the second communication terminal,
The first communication terminal determines whether the status of the terminal satisfies a predetermined condition by transmitting / receiving a control message to / from the second communication terminal, and connects to the second communication terminal according to the determination result Change the retransmission timeout for the remaining control messages for establishment,
40. The communication system according to claim 39.   The communication system according to any one of claims 39 to 41, wherein the situation is a radio wave environment in which the connection establishment is executed.   43. The communication system according to claim 42, wherein the radio wave environment is detected from a received signal level, the number of times the control message is retransmitted, or a time required until the control message is completely processed.   The radio wave environment uses a scan process from transmission of a broadcast message to a group owner terminal by a client terminal determined by GO Negotiation processing compliant with Wi-Fi Direct and reception of a response message to the broadcast message. 44. The communication system according to claim 43, wherein the communication system is detected.   45. The communication system according to claim 44, wherein the radio wave environment is detected from the number of retransmissions of the broadcast message in the scan process.   45. The communication system according to claim 44, wherein the radio wave environment is detected from a time required for the scanning process.   In the radio wave environment, a group owner terminal determined by GO Negotiation processing conforming to Wi-Fi Direct receives a control message first transmitted from the client terminal after completion of the GO Negotiation processing and after completion of the scanning processing. 45. The communication system according to claim 44, wherein the communication system is detected from a required time until.   The communication system according to any one of claims 39 to 47, wherein the situation is a relative movement state between the first communication terminal and the second communication terminal.   49. The communication according to claim 48, wherein the movement state is detected using at least one of a speed sensor, an acceleration sensor, and GPS (Global Positioning System) information that detects a movement speed of the communication terminal. system.

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