JP2011077634A - Wireless communication terminal and method - Google Patents

Abstract

A wireless communication terminal and a wireless communication method capable of confirming the communication status of another wireless communication channel without disconnecting a wireless network with a single wireless unit.
A wireless communication terminal 10 includes a communication unit 11a, a channel selection unit 11b, a frame generation unit 13, a communication status confirmation unit 12a, and a communication control unit 12b. The communication control unit 12b includes a channel selection unit 11b. After selecting one radio communication channel and using the first radio communication channel to transmit a use time setting frame indicating that the communication unit 11a uses the first radio communication channel for a certain period of time, use time setting is performed. The channel selection means 11b selects a second radio communication channel different from the first radio communication channel within the period of the radio communication channel use time set in the frame, and the communication status confirmation means 12a performs the second radio communication. After confirming the communication status in the channel, the channel selection means 11b executes a series of channel selection and confirmation processes for re-selecting the first wireless communication channel. It performs a control to.
[Selection] Figure 1

Description

  The present invention relates to a wireless communication terminal and a wireless communication method for performing control for confirming the communication status of a wireless communication channel.

  In recent years, wireless networks such as the IEEE802.11 standard have been widely used in businesses and homes because of the advantage that the troublesomeness of wiring in a wired network can be removed and the layout of terminals can be flexibly changed. In the IEEE 802.11 standard, access control to a wireless medium is mainly performed by a CSMA / CA (Carrier Sense Multiple Access / Collision Avidance) method. The CSMA / CA method is a connection method in which multiple access is performed based on carrier detection, and a wireless communication terminal confirms that communication frames of other wireless communication terminals are not transmitted, and then communicates with itself. By starting frame transmission, communication frame collision is avoided. The wireless communication terminal monitors the state of the wireless medium, and transmits a communication frame when there is no transmission signal for a predetermined fixed time or longer. The wireless communication terminal normally has a function of selecting and using a plurality of wireless communication channels. For example, the wireless communication terminal sets a wireless communication channel to be used when configuring a wireless network.

  Since the user normally sets the wireless communication channel, if the user does not know the communication status of the wireless communication channel to be used, the optimal wireless communication channel cannot be selected, and appropriate communication such as frequent occurrence of errors during communication. The state may not be maintained. Patent Document 1 discloses a technique for detecting an optimal wireless communication channel from a plurality of wireless communication terminals that can be used when configuring a wireless network and automatically switching the wireless communication channel to be used. However, since the technology of Patent Document 1 cannot confirm other wireless communication channels after the configuration of the wireless network, it cannot cope with changes in the wireless communication status after the configuration of the wireless network. In either case, in order to check the communication status of other wireless communication channels after configuring the wireless network, it is necessary to disconnect the wireless network once and switch the wireless communication channel. Is required.

  In order to cope with the above problem, Patent Document 2 includes two wireless units, a wireless unit for communication and a wireless unit for confirming the wireless communication status of the wireless communication channel, so that the optimal wireless communication channel is always detected. A method for switching a wireless communication channel used for communication to an optimal wireless communication channel is described.

JP 2004-096595 A JP 2006-345193 A

  However, in the case of the technique described in Patent Document 2, in order to detect an optimal wireless communication channel, a plurality of wireless units including a wireless unit for communication and a wireless unit for confirming the wireless communication status of the wireless communication channel are required. There was a problem of becoming.

  Accordingly, the present invention has been made to solve the above-described problems of the prior art, and an object of the present invention is to configure a wireless network with one wireless unit without disconnecting the wireless network. To provide a wireless communication terminal and a wireless communication method capable of confirming the communication status of wireless communication channels other than the wireless communication channel.

  A wireless communication terminal according to the present invention is a wireless communication terminal that forms part of a wireless network, and selects communication means for communicating with other wireless communication terminals and a wireless communication channel used for the communication. Station selection means, and a frame generation means for generating a use time setting frame indicating that the radio communication channel selected by the channel selection means is used for the communication for a predetermined radio communication channel use time period; A communication status confirmation unit for confirming a communication status of the radio communication channel selected by the channel selection unit; the channel selection unit selects the first radio communication channel; and the communication unit sets the usage time. After the frame is transmitted using the first wireless communication channel, the channel selection means performs the first wireless communication channel within the period of use of the wireless communication channel. A different second wireless communication channel is selected, the communication status confirmation unit confirms the communication status in the second wireless communication channel, and then the channel selection unit retunes the first wireless communication channel. It has a communication control means for performing control so as to execute a series of channel selection and confirmation processing.

  According to the present invention, the communication status of another wireless communication channel different from the wireless communication channel being used is confirmed without using a plurality of wireless units and without disconnecting the wireless network. Can do. Therefore, by checking the communication status of other wireless communication channels, if the communication status of the wireless communication channel being used deteriorates, switch to the optimal wireless communication channel for which the communication status has been confirmed in advance. Is possible.

  In addition, according to the present invention, by configuring without using a plurality of wireless units, compared to the case of using a plurality of wireless units, product cost, device size reduction, power consumption reduction, etc. There is an effect that it can be realized.

It is a block diagram which shows roughly an example of a structure of the radio | wireless communication terminal which concerns on Embodiment 1 of this invention. 3 is a network diagram illustrating an example of a configuration of a wireless network including a wireless communication terminal according to Embodiment 1. FIG. 6 is a timing chart illustrating an example in which the wireless communication terminal according to Embodiment 1 transmits a usage time setting frame and NAV is set in another wireless communication terminal that has received the usage time setting frame. 3 is a flowchart showing an operation of confirming the communication status of the wireless communication terminal according to the first embodiment. 6 is a timing chart illustrating an example in which the NAV is reset in another wireless communication terminal that has transmitted the usage time reset frame and has received the usage time reset frame, according to the first embodiment. It is a flowchart which shows the operation | movement of the communication condition confirmation of the radio | wireless communication terminal which concerns on Embodiment 2 of this invention. Example in which wireless communication terminal according to Embodiment 2 transmits usage time setting frame and confirms wireless communication status of first and second wireless communication channels while NAV is set in other wireless communication terminals It is a timing chart which shows. It is a flowchart which shows the operation | movement of the communication condition confirmation of the radio | wireless communication terminal which concerns on Embodiment 3 of this invention. It is a timing chart which shows the communication sequence of Probe Request and Probe Response in IEEE802.11 specification.

Embodiment 1 FIG.
FIG. 1 is a block diagram schematically showing an example of the configuration of a radio communication terminal 10 according to Embodiment 1 of the present invention (that is, a device that can implement the radio communication method according to Embodiment 1). . As shown in FIG. 1, the wireless communication terminal 10 has, as a main configuration, a communication unit 11 that performs communication with other wireless communication terminals, a control unit 12, and a frame generation unit that generates a communication frame. Frame generation unit 13 and timer unit 14.

  The communication unit 11 selects a communication unit 11a that receives a communication frame from another wireless communication terminal and transmits a communication frame generated by the frame generation unit 13 in the own terminal, and a wireless communication channel used for communication. It has a channel selection unit 11b and a noise detection unit 11c that detects whether or not there is noise of a certain level or more in the selected radio communication channel.

  The control unit 12 includes a communication status confirmation unit 12a for confirming the communication status of the wireless communication channel selected by the channel selection unit 11b, and a communication control unit 12b. The communication control unit 12b selects the first wireless communication channel by the channel selection unit 11b, and transmits the usage time setting frame using the first wireless communication channel after the communication unit 11a transmits the usage time setting frame. Within the period, the channel selection unit 11b selects a second radio communication channel different from the first radio communication channel, the communication status confirmation unit 12a confirms the communication status in the second radio communication channel, and then The channel selection unit 11b performs control so as to execute a series of channel selection and confirmation processes for re-selecting the first wireless communication channel. For example, the control unit 12 analyzes the received communication frame, controls the communication procedure based on the communication protocol, controls the transmission timing of the communication frame generated by the frame generation unit 13, and determines the wireless communication channel used by the wireless communication terminal 10. Control settings.

  The frame generation unit 13 generates a communication frame for the wireless communication terminal 10 to perform communication. In the IEEE 802.11 standard, the time required for the wireless communication sequence can be set in the Duration / ID field of the header of the communication frame. The wireless communication terminal that has received the communication frame confirms the value set in the Duration / ID field, and sets a NAV (Network Allocation Vector) so as not to start the communication sequence during the period indicated by this value. That is, when the wireless communication terminal 10 generates a usage time setting frame that is a communication frame indicating that the wireless communication channel is used for a certain period of time, the wireless communication channel usage time is set in the Duration / ID field of the header of the communication frame. A value for setting time t is set. As the usage time setting frame, a unicast frame such as a CTS (clear to send) frame, an RTS (request to send) frame, or a data frame of the IEEE 802.11 standard is used, and the own terminal is used as a transmission destination address of the usage time setting frame. Set the address.

  The timer unit 14 sets an operation in which the wireless communication terminal 10 switches the wireless communication channel, confirms the wireless communication status of the wireless communication terminal 10, and resets the wireless communication channel of the wireless communication terminal 10 in the usage time setting frame. It is a timer used for performing within the period of radio communication channel use time t.

  FIG. 2 is a network diagram showing an example of a configuration of radio network 20 including the radio communication terminal according to Embodiment 1 of the present invention. As shown in FIG. 2, the wireless network 20 includes a wireless communication terminal 21, a wireless communication terminal 22, and a wireless communication terminal 23. The wireless communication terminal 21 has the same configuration as the wireless network 10 of FIG. The wireless communication terminals 22 and 23 may also have the same configuration as the wireless network 10 in FIG. Although the wireless network 20 in Embodiment 1 is described as being configured by the wireless communication terminals 21 to 23, the wireless network to which the present invention is applicable is not limited to this. The wireless network 20 may have other configurations as long as it is a wireless network including one or more wireless communication terminals. The wireless network 20 is, for example, a network that exists on a first wireless communication channel selected by the wireless communication terminal 21. In FIG. 2, another wireless network 20a different from the wireless network 20 is, for example, a network existing on a second wireless communication channel different from the first wireless communication channel selected by the wireless communication terminal 21. In the example illustrated in FIG. 2, the other wireless network 20 a includes the wireless communication terminal 24. When the wireless communication terminal 21 selects a second wireless communication channel and the wireless communication terminal 24 transmits a communication frame, the wireless communication terminal 21 can detect transmission of the communication frame by the wireless communication terminal 24. .

  FIG. 3 is a timing chart illustrating an example in which the wireless communication terminal 21 transmits a usage time setting frame and the NAV is set in the wireless communication terminal 22 and the wireless communication terminal 23. In the communication sequence of the IEEE802.11 standard, when a communication frame is transmitted, when the wireless communication channel is not used during the period of the sum of the DIFS (Distributed Inter Frame Space) time and the backoff time (DIFS + backoff), It is possible to start a communication sequence in the wireless communication channel.

  When the wireless communication terminal 21 confirms that the wireless communication channel is not used during the period of the sum of the DIFS time and the back-off time (DIFS + back-off), for example, in the Duration / ID field of the communication frame in the IEEE 802.11 standard A usage time setting frame in which a value for setting the usage time of the wireless communication channel as time t is set is transmitted. When each of the wireless communication terminal 22 and the wireless communication terminal 23 receives the usage time setting frame transmitted from the wireless communication terminal 21, it checks the Duration / ID field of the received usage time setting frame and sets the NAV. Since the NAV is set in all the wireless communication terminals that have received the usage time setting frame, after the usage time setting frame is transmitted from the wireless communication terminal 21, during the period of the wireless communication channel usage time t in which the NAV is set. A communication sequence from wireless communication terminals other than the wireless communication terminal 21 is not started. Therefore, during the wireless communication channel usage time t for which the NAV is set, communication with the wireless communication terminal 21 is not performed, and even if the wireless communication terminal 21 temporarily leaves the wireless network, The network connection with other wireless communication terminals (for example, wireless communication terminals 22 and 23) in the wireless network other than the wireless communication terminal 21 is maintained, and the wireless communication channel usage time t for which the NAV is set is maintained. Within the period, the wireless communication terminal 21 can perform processing such as switching the wireless communication channel. The value related to the wireless communication channel usage time set in the Duration / ID field of the communication frame is the wireless communication channel usage time t, the wireless communication terminal 21 selects another wireless communication channel, and the original wireless communication channel is set again. It is possible to set a value that is longer than the time required for re-tuning, for example, a maximum value that can be set in the Duration / ID field. In addition, the value related to the wireless communication channel usage time set in the Duration / ID field of the communication frame is the value when the wireless communication terminal transmits a frame at regular intervals, such as beacon transmission of a wireless access point. It can be set to a value that does not hinder communication.

  FIG. 4 is a flowchart showing an operation for confirming the communication status of the wireless communication terminal according to the first embodiment. Referring to FIG. 4, when the selected wireless communication channel is not used during the period of the sum of the DIFS time and the back-off time (DIFS + back-off), the wireless communication terminal 21 is connected to the selected wireless communication channel. An operation of transmitting a use time setting frame through a communication channel and confirming the communication status of another radio communication channel different from the selected radio communication channel will be described.

  When the wireless communication terminal 21 confirms that the wireless communication channel is not used during the period of the sum of the DIFS time and the back-off time (DIFS + back-off), the wireless communication terminal 21 starts the operation for confirming the communication state shown in FIG. The use time setting frame generated by the frame generation unit 13 is transmitted from the transmission unit 11 (step S101). Note that the communication status confirmation operation does not necessarily need to be performed at all times when it is confirmed that the wireless communication channel is not used during the period of the sum of the DIFS time and the back-off time (DIFS + back-off). Every time, the period of the sum of the DIFS time and the back-off time (DIFS + back-off), it may be confirmed that the wireless communication channel is not used, and the communication status confirmation operation may be started. Also, the communication status check operation starts when the communication error rate exceeds a certain level, confirming that the wireless communication channel is not used for the period of the sum of the DIFS time and the back-off time (DIFS + back-off). You may make it do. Alternatively, in the communication status confirmation operation, the wireless communication channel is not used at the timing after the random time elapses from the transmission of the previous use time setting frame and the sum of the DIFS time and the back-off time (DIFS + back-off). Then, the communication status confirmation operation may be started. With this configuration, when another wireless network that operates in the same manner as the wireless network in the first embodiment is operating on another wireless communication channel, the wireless network according to the first embodiment and the other The possibility that the wireless network operates at the same timing can be reduced. As a result, it is possible to make it difficult for a wireless communication terminal configuring one wireless network to detect a wireless communication terminal of the other wireless communication channel.

  When transmitting the use time setting frame, the wireless communication terminal 21 transmits another wireless communication channel (for example, different from the wireless communication channel used by the wireless network configured by the wireless communication terminal 21 (for example, reference numeral 20 in FIG. 2)). 2 is performed (step S102), and the wireless communication channel setting processing time (the selected wireless communication channel is determined from the wireless communication channel use time t set in the use time setting frame). A time obtained by subtracting the time required for switching to another wireless communication channel) and the time required for resetting the wireless communication channel (time required for switching the other wireless communication channel to the original wireless communication channel) as a set time. (In the timer unit 14 in FIG. 1) is activated (step S103). In the first embodiment, the wireless communication terminal 21 is configured such that the wireless communication channel setting process and the wireless communication channel resetting process are performed within a predetermined time for each wireless communication terminal. In the first embodiment, the wireless communication terminal 21 transmits a usage time setting frame and starts a timer after setting a wireless communication channel. However, the present invention is not limited to such processing. Control may be performed so that the timer is activated with the time obtained by subtracting the wireless communication channel reset processing time from the wireless communication channel use time t set in the time setting frame, and then the wireless communication channel is set.

  Further, the wireless communication terminal 21 may preferentially set the wireless communication channel set in step S102 in the order of the frequencies of the wireless communication channels supported by the wireless communication terminal. In addition, the wireless communication terminal 21 records the previous wireless communication status of the wireless communication channel, a list indicating the order of the wireless communication channels with a low frequency of occurrence of noise above a certain level, and / or other A list indicating the order of wireless communication channels with a low detection frequency of wireless communication may be created, and the wireless communication channels may be preferentially set, for example, in ascending order of frequency with reference to the list.

  Next, the wireless communication terminal 21 confirms whether the elapsed time from the start of the timer is the set time of the timer (step S104). If the set time of the timer is not reached, the wireless communication channel set in step S102 The communication status is confirmed (step S105). When the wireless communication terminal 21 detects at least one of noise of a certain level or higher and wireless communication of another wireless communication terminal by the communication state confirmation (step S106), the communication state of the wireless communication channel is not clean. It is determined that the wireless communication channel is not usable, the wireless communication channel is reset to the original channel, and the processing for confirming the communication status of the other wireless communication channel is terminated. If the wireless communication terminal 21 does not detect noise of a certain level or higher and wireless communication of other wireless communication terminals in step S106 in step S106, the wireless communication terminal 21 returns to the timer check process in step S104. . If the wireless communication terminal 21 does not detect noise of a certain level or higher and wireless communication of another wireless communication terminal even when the timer setting time is reached in step S104, the communication status of the wireless communication channel is clean. (Can be used), the wireless communication channel is reset to the original channel (step S107), and the process of confirming the communication status of the other wireless communication channel is terminated.

  The wireless communication terminal 21 generates a use time reset frame in the frame generation unit 13 when the communication state confirmation operation flow of the wireless communication channel described with reference to FIG. 4 ends before the wireless communication channel use time t elapses. Then, as shown in FIG. 5, the transmission unit 11 transmits a usage time reset frame to reset the NAV of the wireless communication terminal in the wireless network. By doing in this way, it can prevent that the wireless communication terminal in a wireless network will be in a communication impossible state for a long time.

  As described above, in the wireless communication terminal and the wireless communication method according to the first embodiment, the wireless communication channel is used for the period of the wireless communication channel use time t at a timing when communication is not performed for a certain time or more. The wireless communication channel is transmitted within a period of the wireless communication channel usage time t, another wireless communication channel different from the wireless communication channel is selected, the wireless communication status is confirmed, and the original wireless communication channel is again transmitted. Operates to tune in. For this reason, according to the wireless communication terminal and the wireless communication method according to Embodiment 1, the wireless network is configured without using a plurality of wireless units and without disconnecting the wireless network. The communication status of another wireless communication channel different from the wireless communication channel can be confirmed.

  In addition, according to the wireless communication terminal and the wireless communication method according to the first embodiment, when the communication status of the wireless communication channel being used is deteriorated by confirming the communication status of another wireless communication channel. It is possible to quickly switch to another wireless communication channel whose communication status has been confirmed.

  Furthermore, according to the wireless communication terminal and the wireless communication method according to the first embodiment, by configuring without using a plurality of wireless units, compared with the case of using a plurality of wireless units, The device can be downsized and the power consumption can be reduced.

  Furthermore, according to the wireless communication terminal and the wireless communication method according to the first embodiment, the wireless communication terminal 21 wirelessly terminates the wireless communication status confirmation process before the wireless communication channel usage time t elapses. When it is reset to the wireless communication channel that configures the network, the wireless communication terminal in the wireless network becomes in a state where communication cannot be performed for a long time by transmitting a usage time reset frame for resetting the NAV. Can be prevented.

  In the above description, the case where the unused period of the wireless communication channel to be confirmed when starting the communication sequence is the sum of the DIFS time and the back-off time (DIFS + back-off) has been described. The configuration is not limited to this, and a value defined in the wireless network can be used depending on priority or the like. Specifically, an AIFS (Arbitration Inter Frame Space) time can be used instead of the DIFS time.

Embodiment 2. FIG.
FIG. 6 is a flowchart showing an operation of confirming the communication status of the wireless communication terminal according to Embodiment 2 of the present invention (that is, a device that can implement the wireless communication method according to Embodiment 2). In the flowchart of FIG. 6, the operation in which the wireless communication terminal transmits the usage time setting frame and starts checking the communication state of the wireless communication channel is the same as the operation in the first embodiment. Further, FIG. 7 shows that the first wireless communication channel (first CH) and the wireless communication terminal according to the second embodiment transmit the usage time setting frame while the NAV is set in the other wireless communication terminals. It is a timing chart which shows the example which confirms the radio | wireless communication condition of a 2nd radio | wireless communication channel (2nd CH). Note that FIG. 2 is also referred to in the description of the second embodiment.

  As shown in FIG. 6, in the second embodiment, the wireless communication terminal 21 confirms that the wireless communication channel is not used during the period of the sum of the DIFS time and the back-off time (DIFS + back-off). A situation confirmation operation is started and a usage time setting frame is transmitted (step S101). Next, the wireless communication terminal 21 starts a timer with a time set by subtracting the wireless communication channel reset processing time from the wireless communication channel use time t set in the use time setting frame (step S202). A process of setting to another wireless communication channel different from the wireless communication channel used by the wireless network composed of 21 is performed (step S203). The wireless communication terminal 21 may set the wireless communication channels set in step S203 in the frequency order of the wireless communication channels supported by the wireless communication terminal, or record the previous wireless communication status. In addition, a list of wireless communication channels is created in the order of low noise detection frequency above a certain level or in the order of low detection frequency of other wireless communication, and the wireless communication channels in the order of the list for each channel setting in step S203. May be set.

  Next, the wireless communication terminal 21 confirms whether the elapsed time from the start of the timer is the set time of the timer (step S104). If the set time of the timer is not reached, the wireless communication channel set in step S102 The communication status is confirmed (step S105). When the wireless communication terminal 21 detects at least one of noise of a certain level or higher and wireless communication of another wireless communication terminal by the communication state confirmation (step S106), the communication state of the wireless communication channel is not clean. The wireless communication channel is reset to the original channel, and the detection process is terminated. If the wireless communication terminal 21 does not detect noise of a certain level or more and wireless communication of other wireless communication terminals in step S106 in step S106, the wireless communication terminal 21 returns to the timer confirmation process in step S104.

  Next, when the wireless communication terminal 21 detects at least one of noise of a certain level or higher and wireless communication of another wireless communication terminal in step S106, the communication status of the wireless communication channel is not clean (can be used). The remaining time until the elapsed time from the timer activation reaches the timer setting time is longer than the wireless communication channel setting processing time. Whether or not can be confirmed (step S204). If the wireless communication terminal 21 determines that the other wireless communication channel can be confirmed, the wireless communication terminal 21 returns to the wireless communication channel setting process in step S203, checks the communication status of the other wireless communication channel, and determines the other wireless communication channel. If it is determined that the wireless communication channel cannot be confirmed, the wireless communication channel is reset to the original channel (step S107), and the detection process is terminated.

  In FIG. 7, the wireless communication terminal 21 transmits a usage time setting frame in which the wireless communication channel usage time t is set in the Duration / ID field, and the NAV is set in the wireless communication terminal 22 and the wireless communication terminal 23. During the wireless communication channel usage time t, the wireless communication terminal 21 confirms the wireless communication status of the first wireless communication channel (first CH), and then a second wireless that is different from the first wireless communication channel. An example in which the wireless communication status of the communication channel (second CH) is confirmed is shown. In the operation flow shown in FIG. 6, when the wireless communication status confirmation of the first wireless communication channel ends in a time shorter than the wireless communication channel use time t, as shown in FIG. The wireless communication status of the wireless communication channel can be confirmed. Note that FIG. 7 shows an example of confirming the wireless communication status of two wireless communication channels, but if the operation flow shown in FIG. 6 can be processed within the wireless communication channel usage time t, It is also possible to check the wireless communication status of three or more wireless communication channels. Further, the wireless communication terminal 21 transmits the use time reset frame described in the first embodiment when the confirmation of the wireless communication status of a predetermined number of wireless communication channels is completed, and the wireless communication terminal 22 and Control may be performed so that the NAV set in the wireless communication terminal 23 is reset.

  As described above, in the wireless communication terminal and the wireless communication method according to the second embodiment, when confirming the wireless communication status of a wireless communication channel, the communication status confirmation processing for a certain wireless communication channel is performed using the wireless communication channel usage time. When the communication is completed before the period t, the communication status of another wireless communication channel different from the wireless communication channel for which the communication status has been confirmed is confirmed. For this reason, according to the radio | wireless communication terminal and radio | wireless communication method which concern on Embodiment 2, the confirmation of the communication condition of a some radio | wireless communication channel can be performed continuously.

  In addition, according to the wireless communication terminal and the wireless communication method according to the second embodiment, when the communication status of a plurality of wireless communication channels is confirmed, the communication status of the used wireless communication channel is deteriorated. It is possible to select an optimal wireless communication channel from other wireless communication channels capable of communication and switch to the optimal wireless communication channel.

Embodiment 3 FIG.
FIG. 8 is a flowchart showing an operation of confirming the communication status of the wireless communication terminal according to Embodiment 3 of the present invention (that is, a device that can implement the wireless communication method according to Embodiment 3). Referring to FIG. 8, when the wireless communication terminal according to Embodiment 3 does not detect noise of a certain level or more and wireless communication of other wireless communication terminals for a certain period of time when confirming the communication status of the wireless communication channel, the wireless network The operation of transmitting a Probe Request frame for confirming the presence / absence of a message will be described. The operation in which the wireless communication terminal transmits the usage time setting frame and starts confirming the communication state of the wireless communication channel is the same as the operation in the first embodiment. Note that FIG. 2 is also referred to in the description of the third embodiment.

  The operations in steps S101 and S102 in FIG. 8 are the same as the operations in the same steps in the first embodiment (FIG. 4). Next, the timer is started with the set time t1 (step S301). Here, the set time t1 is set to a value equal to the period (DIFS + backoff) of the sum of DIFS and backoff time. In addition, the wireless communication terminal according to Embodiment 3 starts the timer after setting the wireless communication channel, but is not limited to this, and is the sum of DIFS and backoff time (DIFS + backoff) ) To the wireless communication channel reset processing time is set as the set time t1 ′, and the control may be performed so that the wireless communication channel is set after that.

  Next, the wireless communication terminal confirms whether the elapsed time from the timer activation is the timer set time t1 (step S302). In step S302, the operations in steps S105 and S106 when the timer has not reached the set time are the same as the operations in the same steps in the first embodiment (FIG. 4). In step S302, when noise exceeding a certain level and wireless communication of other wireless communication terminals are not detected even when the timer set time t1 is reached, as shown in FIG. The sequence of Probe Request and Probe Response is performed.

  Next, the sequence of Probe Request and Probe Response in FIG. 9 will be described. The Probe Request is a communication frame transmitted by the wireless communication terminal 21 in order to make an inquiry as to whether or not a wireless network exists around the wireless communication terminal 21. The wireless communication terminal 21 confirms that there is no other communication during the period of the sum of the DIFS time and the back-off time (DIFS + back-off), and when it is confirmed that there is no other communication, the probe request frame is displayed. Send. When a wireless network exists, the period of the sum of the DIFS time and the back-off time after sending the Probe Request (DIFS + back-off), and when there is no other communication, a Probe Response frame is transmitted from an access point that is another wireless communication terminal Is done. That is, when another wireless network exists, a communication frame from the other wireless network is transmitted before the sum of the DIFS time and the maximum backoff time elapses.

  Since the wireless communication terminal 21 confirms that there is no other communication during the set time t1 of the timer in step S301, the period of the sum of the DIFS time and the back-off time (DIFS + back-off), the Probe Request transmission time and the DIFS The sum of the time, the maximum back-off time, and the probe response transmission time is set as t2, the set time t2 is reset in the timer (step S303), and the probe request frame is transmitted (step S304). Next, the wireless communication terminal 21 confirms whether the elapsed time from the timer activation is the timer set time t2 (step S305). If it is not the set time of the timer, the wireless communication terminal 21 checks the communication status of the wireless communication channel set in step S102 as in step S105 (step S306). When the wireless communication terminal 21 detects at least one of noise of a certain level or higher and wireless communication of another wireless communication terminal by the communication state confirmation (step S307), the communication state of the wireless communication channel is not clean. The wireless communication channel is reset to the original channel, and the detection process is terminated. If it is determined in step S307 that noise of a certain level or more and wireless communication of another wireless communication terminal are not detected by the communication status confirmation, the process returns to the timer confirmation processing in step S305. In step S305, if no wireless communication of other wireless communication terminals including a noise of a certain level or higher and a probe response frame is detected even when the set time of the timer is reached, the communication status of the wireless communication channel is clean (use The wireless communication channel is reset to the original channel (step S107), and the detection process is terminated.

  In the third embodiment, the wireless communication channel usage time t set in the usage time setting frame is equal to or longer than the sum of the above-described time t1, time t2, wireless communication channel setting processing time, and wireless communication channel resetting processing time. Set the time. For example, the wireless communication channel usage time t set in the usage time setting frame is set to a time equal to the sum of the time t1, the time t2, the wireless communication channel setting processing time, and the wireless communication channel resetting processing time. Compared with the case where the wireless communication channel usage time t is set to the maximum value that can be set in the Duration / ID field, the communication status confirmation process can be performed in a short time even when noise exceeding a certain level and other wireless communication are not detected. Can be performed.

  Similarly to the first embodiment, when the communication status confirmation operation flow of the wireless communication channel described with reference to FIG. 8 ends before the wireless communication channel usage time t elapses, a usage time reset frame is displayed. By transmitting and resetting the NAV of the wireless communication terminal in the wireless network, it is possible to prevent the wireless communication terminal in the wireless network from being unable to communicate for a long time.

  As described above, in the wireless communication apparatus and the wireless communication method according to Embodiment 3, when confirming the wireless communication status of the wireless communication channel, noise and other wireless communication terminals exceeding a certain level for a certain period of time When no wireless communication is detected, a communication frame for confirming the presence / absence of the wireless network is transmitted. Thus, according to the wireless communication device and the wireless communication method according to Embodiment 3, the time set in the usage time setting frame transmitted by the wireless communication terminal is set to the shortest possible value, and a plurality of wireless communication The communication status of the wireless communication channels other than the wireless communication channels constituting the wireless network can be confirmed without using the unit and without disconnecting the wireless network.

  In addition, according to the wireless communication device and the wireless communication method according to the third embodiment, when the communication state of the wireless communication channel being used is deteriorated by confirming the communication state of the wireless communication channel, it is optimal. It is possible to switch to a different wireless communication channel.

  Furthermore, according to the wireless communication device and the wireless communication method according to the third embodiment, the wireless communication terminal in the wireless network is set by setting the time set in the usage time setting frame transmitted by the wireless communication terminal to the shortest possible value. Can be prevented from communicating for a long time, and communication delay can be suppressed.

  DESCRIPTION OF SYMBOLS 10, 21-24 Wireless communication terminal, 11 Communication part, 11a Communication means, 11b Election zone means, 11c Noise detection means, 12 Control part, 12a Communication status confirmation means, 12b Communication control means, 13 Frame generation part (Frame generation means) ), 14 timer part, 20 wireless network, 20a other wireless network.

Claims (8)

A wireless communication terminal that forms part of a wireless network,
Communication means for communicating with other wireless communication terminals;
Channel selection means for selecting a wireless communication channel used for the communication;
A frame generation unit that generates a use time setting frame indicating that the radio communication channel selected by the channel selection unit is used for the communication during a predetermined radio communication channel use time period;
Communication status confirmation means for confirming the communication status of the wireless communication channel selected by the channel selection means;
After the channel selection unit selects the first wireless communication channel and the communication unit transmits the usage time setting frame using the first wireless communication channel, the period of the wireless communication channel usage time The channel selection unit selects a second radio communication channel different from the first radio communication channel, the communication status confirmation unit confirms the communication status in the second radio communication channel, and then A wireless communication terminal comprising: a communication control unit that performs control so that the channel selection unit executes a series of channel selection and confirmation processes for re-selecting the first wireless communication channel.   2. The wireless communication terminal according to claim 1, wherein transmission of the usage time setting frame from the communication unit is executed at a timing when communication is not performed for a predetermined time or more in the first wireless communication channel. . The usage time setting frame is a communication frame in the IEEE 802.11 standard,
The radio communication terminal according to claim 1, wherein the frame generation unit sets a value indicating the radio communication channel use time in a Duration / ID field of the use time setting frame.   The communication control means performs the next use time at a timing when the first wireless communication channel has not been communicated for a certain period of time after a random time has elapsed since the last use time setting frame was transmitted. The wireless communication terminal according to claim 1, wherein control is performed so as to transmit a setting frame.   When the communication status confirmation unit determines that noise of a specified level or higher and wireless communication of another wireless communication terminal are not detected for a certain period of time when selecting the second wireless communication channel, the communication control unit The frame generation means generates a network confirmation communication frame for confirming the presence / absence of a wireless network using the second wireless communication channel, and the communication means transmits the network confirmation communication frame. 5. The wireless communication terminal according to claim 1, wherein control is performed.   The wireless communication terminal according to claim 5, wherein the network confirmation communication frame is a Probe Request frame in the IEEE 802.11 standard.   The communication control means generates a use time reset frame for the frame generation means to reset the wireless communication channel use time when the communication status confirmation means completes the series of channel selection and confirmation processing, The wireless communication terminal according to any one of claims 1 to 6, wherein control is performed so that the communication unit transmits the usage time reset frame. A wireless communication method executed by a wireless communication terminal that forms part of a wireless network,
Selecting a first wireless communication channel;
Generating a use time setting frame indicating that the first wireless communication channel is used for communication during a predetermined wireless communication channel use time period;
Transmitting the usage time setting frame using the first wireless communication channel;
Within the period of use time of the wireless communication channel, a second wireless communication channel different from the first wireless communication channel is selected, a communication state in the second wireless communication channel is confirmed, and then the first wireless communication channel is checked. And a step of re-selecting a radio communication channel.

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