JP6878972B2 - Wireless communication devices, wireless communication programs, and wireless communication methods - Google Patents

Description

The present invention relates to a wireless communication device, a wireless communication program, and a wireless communication method, and can be applied to, for example, a time division multiple access wireless network.

Conventionally, there is a wireless system that avoids frame collision by adopting a time division multiple access system and giving transmission rights only to wireless communication devices assigned to time slots.

Further, if frame transmission / reception is performed only on a certain channel, the transmission error rate of the wireless communication device may increase due to radio wave interference. Therefore, there is also a wireless channel hopping method in which the transmission channel is changed for each frame and a channel in which radio wave interference is unlikely to occur is also used to suppress the total transmission error rate.

As a method having both functions of such a time division multiple access method and a channel hopping method, there are Bluetooth (registered trademark), TSCH (Time Slotted channel hopping) (see, for example, Non-Patent Document 1) and the like.

In TSCH, there are individual time slots and shared time slots (broadcast time slots). In the individual time slot, the transmission / reception wireless communication device is fixed, and the wireless communication devices other than these do not need to stand by for reception. The shared time slot shares the time slot with all wireless communication devices, and if the broadcast frame or destination address is not assigned to an individual time slot, it is transmitted in the shared time slot, and the surrounding all-line communication device sends the wireless signal. Receive.

The coordinator device periodically transmits an extended beacon to a device (wireless communication device) within the range of radio waves. Extended beacons include synchronization time, channel hopping, time slots, links and slot information.

A device trying to connect to a new network first receives a beacon from a surrounding device. Then, the time slot for network participation is set using the information in the beacon, and the network participation procedure is performed with the host device.

After joining the network, receive information on new creation of slot frames and links for data communication from management entities in the upper layer.

In a star network, only the coordinator needs to be the device that transmits the extended beacon. In a mesh network, some devices cannot directly receive the extended beacon from the coordinator, so the router device also sends the extended beacon.

IEEE Standard for Local and metropolitan area network Part 15.4: Low-Rate Willless Personal Network Network (LR-WPANs) (LR-WPANs) (LR-WPANs) (LR-WPANs) (LR-WPANs) (LR-WPANs) (LR-WPANs) (LR-WPANs) (LR-WPANs) (LR-WPANs) 2.6 TSCH PAN formation: About the initial procedure)

However, in TSCH, as the number of devices (wireless communication devices) in the network increases, control messages such as beacons increase. Allocation of time slots so that all control messages can be sent causes a problem that the allocation of time slots for data frames is reduced.

If the beacon transmission cycle is lengthened, it is necessary to lengthen the scan cycle of the device that newly joins the network, and as a result, it takes time to connect to the network. In addition, power consumption increases because reception standby is performed during scanning.

Therefore, even if the number of wireless communication devices in the network increases, a wireless communication device, a wireless communication program, and a wireless communication method that can prevent an excessive increase in control frames and efficiently execute data communication are desired. There is.

The first invention employs a time-division multiplexing connection method, and there are two types of time-division time slot allocation, one for broadcasting and one for between individual wireless communication devices, and the destinations of data frames and control frames are In a wireless communication device that uses an individual time slot if specified, or a broadcast time slot if not specified, (1) the number of times the control frame is received by a broadcast received from a surrounding wireless communication device within a predetermined time. Control to determine the number of transmissions of the control frame to be broadcast within a predetermined time based on the reception control frame measuring means to be measured and (2) the number of times the control frame is received by the broadcast measured by the reception control frame measuring means. It is characterized by having means.

The second wireless communication program of the present invention employs a time division multiplexing connection method, and there are two types of time division allocation of time slots, one for broadcasting and one for between individual wireless communication devices, and data frames and controls. A computer mounted on a wireless communication device that uses an individual time slot if the frame destination is specified and a broadcast time slot if not specified is (1) received from a surrounding wireless communication device within a predetermined time. The reception control frame measuring means for measuring the number of times the control frame is received by broadcasting, and (2) the said broadcasting within a predetermined time based on the number of times the control frame is received by broadcasting measured by the receiving control frame measuring means. It is characterized in that it functions as a control means for determining the number of times a control frame is transmitted.

The third invention employs a time-division multiplexing connection method, and there are two types of time-division time slot allocation, one for broadcasting and one for between individual wireless communication devices, and the destination of the data frame and the control frame is. In a wireless communication method used for a wireless communication device that uses an individual time slot if specified and a broadcast time slot if not specified, it has a reception control frame measuring means and a control means, and (1) the reception control. The frame measuring means measures the number of times the control frame is received by the broadcast received from the surrounding wireless communication device within a predetermined time, and (2) the control means is the broadcast measured by the reception control frame measuring means. It is characterized in that the number of transmissions of the control frame to be broadcast within a predetermined time is determined based on the number of receptions of the control frame.

According to the present invention, even if the number of wireless communication devices in the network increases, it is possible to prevent an excessive increase in control frames and efficiently execute data communication.

It is a block diagram which shows the structure of the wireless communication apparatus which concerns on 1st Embodiment. It is a block diagram which shows the example of the whole structure of the wireless communication system which concerns on 1st Embodiment. It is a flowchart which shows the characteristic operation (beacon transmission number control) of the wireless communication apparatus which concerns on 1st Embodiment. It is explanatory drawing which shows the number of times of transmission / reception of the beacon of the wireless communication apparatus (priority level 1) which concerns on 1st Embodiment. It is a block diagram which shows the example of the whole structure of the wireless communication system which concerns on 2nd Embodiment. It is explanatory drawing which shows the recorded data of the reception counter which concerns on 2nd Embodiment. It is explanatory drawing which shows the recorded data of the transmission counter which concerns on 2nd Embodiment. It is a flowchart which shows the characteristic operation (beacon transmission number control) of the wireless communication apparatus which concerns on 2nd Embodiment. It is a flowchart which shows the characteristic operation (control of the number of times of transmission of a beacon by another channel) of the wireless communication apparatus which concerns on 2nd Embodiment.

(A) First Embodiment Hereinafter, the first embodiment of the wireless communication device, the wireless communication program, and the wireless communication method according to the present invention will be described in detail with reference to the drawings.

(A-1) Configuration of First Embodiment (A-1-1) Overall Configuration FIG. 2 is a block diagram showing an example of an overall configuration of a wireless communication system according to the first embodiment.

In the wireless communication system 1, one coordinator 10 and eight wireless communication devices 20 (20-1 to 20-8) are arranged. In FIG. 2, for the sake of simplicity, the case where the wireless communication system 1 has one coordinator 10 and eight wireless communication devices 20 is illustrated, but of course, the coordinator 10 and the wireless communication device 20 are illustrated. The number of is not particularly limited. The communication method of the coordinator 10 and the wireless communication device 20 is not particularly limited, and for example, various wireless LAN interfaces can be applied. In this embodiment, it is premised that the coordinator 10 and the wireless communication device 20 perform wireless communication by the wireless communication method of TSCH. In the following, for convenience of explanation, the coordinator 10 and the wireless communication device 20 constituting the wireless communication system 1 (wireless network) will be collectively referred to as nodes.

The arrows connecting the nodes in FIG. 2 indicate the transmission / reception direction of the beacon frame. The topology (communication path) of the wireless communication system 1 in FIG. 2 is a communication path related to a beacon frame, but a control frame other than the beacon frame and a data frame may use another path.

The coordinator 10 has a network coordination function and periodically transmits a beacon frame immediately after activation. In this embodiment, the priority level is used as an index indicating the distance from the coordinator 10. The priority level is an index whose value gradually increases according to the distance. The priority level of the coordinator 10 is set to "0".

The wireless communication devices 20-1 to 2-4 are nodes that can directly communicate with the coordinator 10. The wireless communication devices 20-1 to 2-4 periodically transmit the beacon frame after synchronizing with the coordinator 10. The priority level of the wireless communication devices 20-1 to 20-4 is "1".

It is assumed that the wireless communication devices 20-5 to 20-8 are in a position where they can communicate with the coordinator 10 via any of the wireless communication devices 20-1 to 20-4. The wireless communication device 20-5 to 2-8 periodically transmits a beacon frame after synchronizing with any of the wireless communication devices 20-1 to 2-4. The priority level of the wireless communication device 20-5 to 2-8 is "2".

(A-1-2) Detailed Configuration of Wireless Communication Device 20 FIG. 1 is a block diagram showing a configuration of the wireless communication device according to the first embodiment. The wireless communication device according to the first embodiment may be configured as hardware such as a dedicated IC chip equipped with each component shown in FIG. 1, or may be mainly composed of a CPU and a program executed by the CPU. Although it may be configured as software, it can be functionally represented in FIG.

In FIG. 1, the wireless communication device 20 includes a transmission / reception control unit 11, a reception counter 12, a reception frame analysis unit 13, a transmission timer 14, and a wireless transmission / reception unit 15. In FIG. 1, only the part related to the control of the beacon frame, which is the characteristic part of the present embodiment, is illustrated, and the other configurations are omitted.

The transmission / reception control unit 11 generates a transmission frame when there is a transmission request from a higher layer in the own device or a transfer request from another device. Then, the transmission / reception control unit 11 determines the transmission timing using information such as the reception counter 12 and the transmission timer 14, and outputs a transmission request to the wireless transmission / reception unit 15. The transmission / reception control unit 11 controls the number of transmissions of the beacon frame to be broadcast within a predetermined time based on the value of the reception counter 12.

The reception counter 12 records the number of times the beacon frame is received within a predetermined time.

The reception frame analysis unit 13 analyzes the type of the input frame from the wireless transmission / reception unit 15 and gives the frame to the transmission / reception control unit 11 if it is a frame to be captured in the own device. Further, the reception frame analysis unit 13 has a function of notifying the reception counter 12 when a beacon frame is received from another wireless communication device having the same priority level as itself.

The transmission timer 14 is a periodic timer that sets the beacon transmission cycle. Then, the transmission timer 14 has a function of notifying the transmission / reception control unit 11 of the beacon transmission time. In this embodiment, the transmission / reception control unit 11 can control the number of beacon transmissions within a predetermined time by changing the beacon transmission cycle of the transmission timer 14. An example in which the transmission / reception control unit 11 controls the number of beacon transmissions will be described in detail in the section of operation.

The radio transmission / reception unit 15 performs demodulation processing on a radio signal from an antenna (not shown), converts it into digital data (frames), and gives it to the reception frame analysis unit 13. Further, the wireless transmission / reception unit 15 converts the transmission data (transmission request) given by the transmission / reception control unit 11 into a wireless signal (performs modulation processing) and gives it to an antenna (not shown).

Since the coordinator 10 has the same configuration as the wireless communication device 20 and the network coordinator function is the same as the conventional one, the description thereof will be omitted.

(A-2) Operation of First Embodiment Next, the operation of the wireless communication system 1 of the first embodiment having the above configuration will be described with reference to the drawings. Since this embodiment has a feature regarding the processing of the beacon frame of each wireless communication device 20 constituting the wireless communication system 1, the processing of the beacon frame of the wireless communication device 20 will be described below.

FIG. 3 is a flowchart showing a characteristic operation (control of the number of beacon transmissions) of the wireless communication device according to the first embodiment.

The wireless communication device 20 updates the reception counter 12 based on the frame received from the coordinator 10 or another wireless communication device 20 (S101). Specifically, when the wireless transmission / reception unit 15 receives a wireless signal, it performs a predetermined process to convert it into a frame and gives it to the reception frame analysis unit 13. If the received frame is a frame for its own device, the reception frame analysis unit 13 gives the frame to the transmission / reception control unit 11. If the reception frame analysis unit 13 determines that the beacon frame has been received, the reception frame analysis unit 13 checks the priority level of the transmission source (coordinator 10 or other wireless communication device 20) from the payload of the beacon or the source address. If the reception frame analysis unit 13 has the same priority level as itself, the reception frame analysis unit 13 notifies the reception counter 12. The reception counter 12 adds 1 to the counter.

The wireless communication device 20 (transmission / reception control unit 11) determines whether or not the transmission count change time has come (transmission timer 14 has timed out) (S102). When the transmission timer 14 times out, the wireless communication device 20 executes the next process, and when the transmission timer 14 does not time out, the wireless communication device 20 continues the frame reception standby state.

The transmission / reception control unit 11 determines whether or not the number of beacon receptions (value of the reception counter 12) is equal to or greater than a predetermined upper limit threshold value (S103). When the number of beacon receptions is equal to or greater than the upper limit threshold value, the wireless communication device 20 executes the next process (S104), and when it is less than the upper limit threshold value, executes the process of step S105 described later. However, even if the number of times the beacon is received is less than the upper limit threshold value, the wireless communication device 20 executes the next process (S104) if it is lower than the lower limit threshold value.

The transmission / reception control unit 11 changes the transmission cycle of the beacon frame (changes the setting of the transmission timer 14) (S104). Specifically, the transmission / reception control unit 11 extends the set time of the transmission timer 14 when the number of beacon receptions exceeds the upper limit threshold value (that is, the transmission cycle of the beacon frame is widened and the number of transmissions is reduced). Further, when the number of beacon receptions becomes equal to or less than the lower limit threshold value, the transmission / reception control unit 11 shortens the set time of the transmission timer 14 (that is, narrows the transmission cycle of the beacon and increases the number of transmissions).

As described above, by changing the transmission cycle of the beacon frames, even if the number of wireless communication devices 20 in the network increases, the number of beacon frames is unlikely to increase. Further, even when the number of wireless communication devices 20 in the network is small, the number of beacon frames is secured, and the wireless communication device 20 newly trying to connect to the network can maintain a state in which it is easy to receive the beacon frames.

The amount of change in the number of transmissions is not particularly limited. For example, normally, the amount of change may be set to once, and may be changed twice or more if the number of receptions is significantly changed when the number of receptions is determined in S103 described above. Further, the transmission timing after the reduction in the number of beacon transmissions is not limited. Considering the timing of beacon transmission from the surrounding wireless communication device 20, control may be added so that the beacons are evenly spaced in the entire network.

The transmission / reception control unit 11 clears the transmission timer 14 and returns the reception counter 12 (beacon reception count) to 0 each time the transmission timer 14 times out (S105).

Next, the operation of the wireless communication device 20-1 in steps S103 and S104 described above will be described with reference to specific examples (number of times the beacon of each wireless communication device 20 is transmitted and received). FIG. 4 is an explanatory diagram showing the number of transmissions and receptions of the beacon of the wireless communication device (priority level 1) according to the first embodiment. It is assumed that the wireless communication devices 20-1 to 20-4 can receive frames from three other wireless communication devices 20 (20-1 to 20-4) other than themselves. As described above, the priority level of the wireless communication devices 20-1 to 20-4 is 1. When the wireless communication device 20-1 receives the beacon frame from the wireless communication devices 20-1 to 20-3, the wireless communication device 20-1 counts at the reception counter 12. Even if the wireless communication device 20-1 receives the beacon frame from the coordinator 10, the priority level of the coordinator 10 is 0, so the wireless communication device 20-1 does not count at the reception counter 12 (similarly, the wireless communication device 20-1 has a lower priority level than its own device). Even if it is received from the communication device 20-5 to 20-8, it is not counted). The initial number of beacon transmissions is 5 times / second. The upper limit threshold value is 10 times / second, and the lower limit threshold value is 3 times / second.

At time T1, the number of times the beacon is received by the wireless communication device 20-1 is 5 times received from the wireless communication device 20-2, which is equal to or less than the upper limit threshold value. Therefore, the wireless communication device 20-1 continues the number of beacon transmissions at 5 times / second (the transmission timer 14 is not changed). Similarly, the number of beacon transmissions of the wireless communication device 20-2 does not change.

At time T2, the number of times the beacon is received by the wireless communication device 20-1 is 10 times in total from the wireless communication devices 20-2 and 20-3, so that the upper limit threshold value has been reached. Therefore, the wireless communication device 20-1 changes the setting of the transmission timer 14 and reduces the number of beacon transmissions to 4 times / second. As for the wireless communication devices 20-2 and 2-3, since the upper limit threshold value is reached when the number of beacon receptions is 10, the number of beacon transmissions is reduced to 4 times / second.

At time T3, the total number of transmissions of the wireless communication device 20 having a priority level of 1 is reduced from 15 to 12.

At time T4, the number of times the beacon is received by the wireless communication device 20-1 is 12 times in total from the wireless communication devices 20-2 to 2-4, so that the upper limit threshold value is reached. Therefore, the wireless communication device 20-1 changes the setting of the transmission timer 14 and reduces the number of beacon transmissions to 3 times / second. As for the wireless communication devices 20-2 to 2-4, since the upper limit threshold value is reached when the number of beacon receptions is 12, the number of beacon transmissions is reduced to 3 times / second.

At time T5, the total number of transmissions of the wireless communication device 20 having a priority level of 1 is reduced from 16 to 12.

At time T6, the number of times the beacon is received by the wireless communication device 20-1 is three times received from the wireless communication device 20-2, so that it falls below the lower limit threshold value. Therefore, the wireless communication device 20-1 changes the setting of the transmission timer 14 to increase the number of beacon transmissions to 4 times / second (increase by 1 from the time T5). As for the wireless communication device 20-2, the number of beacon receptions is 3 times, which is below the lower limit threshold value, so that the number of beacon transmissions is increased to 4 times / second.

At time T7, the total number of transmissions of the wireless communication device 20 having a priority level of 1 increases from 6 to 8.

In this way, if the total number of transmissions increases, the number of beacon transmissions per device decreases, but if the total number of transmissions decreases too much, the number of individual transmissions increases, so the amount of change in the total number of transmissions should be suppressed. (About 10 times in this example).

(A-3) Effect of First Embodiment According to the first embodiment, the following effects are exhibited.

The wireless communication device 20 (transmission / reception control unit 11) reduces the number of beacon transmissions of each device as the number of wireless communication devices increases and the total number of beacon transmissions increases. Even if the number of wireless communication devices increases, the number of times the beacon is transmitted by the entire network does not change much, and it is possible to prevent the increase in the time slot for the beacon. Therefore, it is possible to obtain an effect that each device can sufficiently secure the allocation of the data transmission time slot.

Further, the wireless communication device 20 (transmission / reception control unit 11) controls the number of times of beacon transmission by using the priority level. Therefore, the installation position of the wireless communication device 20 can be easily taken into consideration, and the probability that the beacon cannot be received within the scan time can be further reduced because the number of devices in the vicinity of a certain receiving wireless communication device is small.

(B) Second Embodiment Hereinafter, a second embodiment of the wireless communication device, the wireless communication program, and the wireless communication method according to the present invention will be described in detail with reference to the drawings.

(B-1) Configuration of Second Embodiment FIG. 5 is a block diagram showing an example of the overall configuration of the wireless communication system according to the second embodiment. In FIG. 5, in the wireless communication system 1A, a noise source N is added (generated) in addition to the configuration of the wireless communication system 1 of FIG. The wireless communication device 20 (20-1 to 20-3) within the range surrounded by the dotted line around the noise source N is affected by the noise. In this embodiment, the wireless communication device 20 uses three channels, but the present invention is not limited to this. Further, the influence of the noise source N on each channel is not constant and is different from each other.

The wireless communication device 20 of the second embodiment can be applied with the same configuration as that shown in FIG. 1 described above, except for the following points.

Unlike the second embodiment, the reception counter 12 of the second embodiment stores the number of times the beacon is received for each of the source wireless communication device 20 and the reception channel. FIG. 6 is an explanatory diagram showing the recorded data of the reception counter according to the second embodiment. In FIG. 6, the reception counter data D1 counts the number of beacon frames received by the wireless communication device 20-1 within a predetermined time for each of the other wireless communication devices 20-1 to 20-3 and the channel. An example in which the transmission / reception control unit 11 of the second embodiment uses the reception counter data D1 will be described in the section of operation.

Further, the transmission / reception control unit 11 of the second embodiment has a data transmission counter that records information on the transmitted frame. FIG. 7 is an explanatory diagram showing the recorded data of the transmission counter according to the second embodiment. In FIG. 7, the transmission counter data D2 sets the number of data frames transmitted by the wireless communication device 20-1 to the number of transmissions for each of the other wireless communication devices 20-1 to 20-3 and the channel (when transmission fails). It is counted as the number of errors). An example in which the transmission / reception control unit 11 of the second embodiment uses the transmission counter data D2 will be described in the section of operation. Regarding the types of frames to be counted, control frames may be counted in addition to data frames.

(B-2) Operation of Second Embodiment Next, the operation of the wireless communication system 1A (wireless communication device 20) of the second embodiment having the above configuration will be described with reference to the drawings. In this embodiment, there is a feature regarding the processing of the beacon frame of each wireless communication device 20 constituting the wireless communication system 1A. Therefore, the processing of the beacon frame of the wireless communication device 20 will be described below.

FIG. 8 is a flowchart showing a characteristic operation (control of the number of beacon transmissions) of the wireless communication device according to the second embodiment.

The wireless communication device 20 updates the reception counter 12 (reception counter data D1) based on the frame received from the coordinator 10 or another wireless communication device 20 (S201). For example, the wireless communication device 20 refers to the reception counter data D1 and adds only one counter corresponding to the reception channel of the source address (wireless communication device 20) of the beacon frame.

When the transmission data exists, the wireless communication device 20 (transmission / reception control unit 11) transmits the transmission data via the wireless transmission / reception unit 15 and updates the transmission counter (transmission counter data D2) (S202). When the wireless communication device 20 transmits data, the wireless communication device 20 adds an ACK (Acknowledgement / acknowledgment) request to perform the data transmission. When the wireless communication device 20 (transmission / reception control unit 11) receives the ACK from the wireless communication device 20 of the data transmission destination, the wireless communication device 20 (wireless communication device 20) sets only one counter for the number of transmissions corresponding to the channel used by the data transmission destination address (wireless communication device 20). to add. On the other hand, when the wireless communication device 20 (transmission / reception control unit 11) cannot receive the ACK from the wireless communication device 20 of the data transmission destination, the wireless communication device 20 corresponds to the channel used by the data transmission destination address (wireless communication device 20). Add 1 to the error count counter.

The wireless communication device 20 (transmission / reception control unit 11) determines whether or not the transmission frequency change time has come (whether the transmission timer 14 has timed out) (S203). When the transmission timer 14 times out, the wireless communication device 20 executes the next process, and when the transmission timer 14 does not time out, the wireless communication device 20 proceeds to step S201 described above.

The transmission / reception control unit 11 determines whether or not the number of beacon receptions (value of reception counter data D1) for each channel is equal to or higher than a predetermined upper limit threshold value (S204). The number of times the beacon is received for each channel is the total value of each wireless communication device 20 for each channel of the reception counter data D1 (for example, the number of times the channel 1 is received is 10 times of the wireless communication device 20-2 and wireless communication. A total of 20 times, including 10 times of the device 20-2). When the number of beacon receptions is equal to or greater than the upper limit threshold value (when there is a channel equal to or greater than the upper limit threshold value), the wireless communication device 20 executes the following process (S205), and when the number is less than the upper limit threshold value. (When there are only channels less than the upper limit threshold value), the process of step S207 described later is executed. However, even if the number of times the beacon is received is less than the upper limit threshold value, the wireless communication device 20 executes the following processing (S205, S206) if it is lower than the lower limit threshold value.

The transmission / reception control unit 11 refers to the transmission counter data D2 and determines whether or not the transmission error rate is less than the threshold value (S205). When the transmission error rate is less than the threshold value, the transmission / reception control unit 11 executes the next process (S206), and when the transmission error rate is greater than or equal to the threshold value, the transmission / reception control unit 11 executes the process of step S207 described later. The transmission error rate (ratio of the number of errors to the number of transmissions) may be determined by either the average of the wireless communication devices 20 of all transmission destinations or each of the wireless communication devices 20 of the transmission destinations. When the transmission error rate is equal to or higher than the threshold value, a modified example of transmitting the beacon on another channel whose transmission error rate is less than the threshold value will be described later in the description of FIG. Even if it is equal to or more than the threshold value, the process of step S206 is executed).

The transmission / reception control unit 11 changes the number of transmissions of the beacon frame of the corresponding channel (S206). The means for changing the number of transmissions is not limited, but for example, if the beacon frame of the corresponding channel is transmitted at a ratio of 2 times / 1 second, one time is treated as cancellation internally. You may control (change) the number of times the beacon frame is transmitted. Further, when the transmission / reception control unit 11 manages the beacon transmission cycle for each channel, the transmission / reception control unit 11 extends the set time of the transmission timer 14 if the number of beacon receptions of the corresponding channel exceeds the upper limit threshold value (that is,). The transmission cycle of the beacon frame may be widened to reduce the number of transmissions). If the number of beacon receptions is equal to or less than the lower limit threshold value, the transmission / reception control unit 11 increases the number of transmissions.

The transmission / reception control unit 11 clears the transmission timer 14 and returns the reception counter 12 (transmission counter data D2) to 0 each time the transmission timer 14 times out (S207). The timing for clearing the transmission counter data D2 (number of transmissions, number of errors) is not limited, and it does not have to be linked with the clearing of the reception counter 12.

Next, the details of the procedure for changing the number of transmissions (transmission cycle) of the beacon frame (mainly the processing of steps S204 and S205 described above) will be described again with specific examples. The number of beacons received for each channel of each wireless communication device 20 is shown in FIG. 6 (reception counter data D1), and the number of transmissions and the number of errors for each channel are shown in FIG. 7 (transmission counter data D2). ). Further, the upper limit threshold value of the number of times the beacon is received is "30" for each channel, and the lower limit threshold value is "10". Further, the threshold value of the data transmission error rate is set to "6%". It is assumed that the wireless communication device 20-1 transmits a beacon at a rate of 10 times / second for each channel from channels 1 to 3.

The transmission / reception control unit 11 of the wireless communication device 20-1 determines whether or not the number of beacon receptions for each channel is equal to or greater than a predetermined upper limit threshold value. With reference to the reception counter data D1 in FIG. 6, the total number of beacon receptions on channel 1 is "20", the total number of beacon receptions on channel 2 is "30", and the total number of beacon receptions on channel 3 is "40". is there. Therefore, the number of beacon receptions on channels 2 and 3 is equal to or higher than the upper limit threshold value (30).

Next, the transmission / reception control unit 11 determines whether or not to reduce the number of beacon transmissions of channels 2 and 3. With reference to the transmission counter data D2 in FIG. 7, the transmission error rate of channel 2 (the total transmission error rate of the wireless communication devices 20-2 to 20-4) is (40 + 10 + 0) / (200 + 200 + 100) × 100 = 10 (%). ). Therefore, since the transmission error rate of the channel 2 is equal to or higher than the threshold value (6%) of the transmission error rate, the process of reducing the number of transmissions on the channel 2 is not performed. The transmission error rate of channel 3 is (10 + 5 + 0) / (300 + 200 + 100) × 100 = 2.5 (%). Therefore, the transmission error rate of channel 3 is lower than the threshold value of the transmission error rate. Therefore, the transmission / reception control unit 11 performs the process of reducing the number of transmissions (step S206 described above) only for the channel 3.

Next, an example will be described in which the number of beacon transmissions is controlled by another channel whose transmission error rate is less than the threshold value, instead of reducing the number of transmissions of the corresponding channel. FIG. 9 is a flowchart showing a characteristic operation (control of the number of times a beacon is transmitted by another channel) of the wireless communication device according to the second embodiment.

The transmission / reception control unit 11 of the wireless communication device 20-1 lists the wireless communication device 20 and the channel whose transmission error rate exceeds the upper limit threshold value (S301). For example, referring to the transmission counter data D2 in FIG. 7, the transmission error rate of the wireless communication device 20-2 on channel 2 is 40/200 × 100 = 20 (%). Since the transmission error rate of the wireless communication device 20-2 on channel 2 exceeds the threshold value (6%), it is subject to listing.

Next, the transmission / reception control unit 11 lists the channels for which the number of times the beacon is received is less than the upper limit threshold value (S302). For example, referring to the reception counter data D1 in FIG. 6, the number of times the beacon is received is below the upper limit threshold value only for channel 1. Further, referring to the transmission counter data D2 in FIG. 7, the transmission error rate (5%) to the wireless communication device 20-2 on the channel 1 is below the threshold value (6%).

Next, the transmission / reception control unit 11 calculates the number of changeable beacons (S303). For example, the transmission / reception control unit 11 is changed so as to increase the number of transmissions to the wireless communication device 20-2 on the channel 1 by the process of step S302 described above. With reference to the reception counter data D1 of FIG. 6, since the total value of the reception counters of channel 1 is 20 and the upper limit threshold value is 30, the beacon transmission can be increased if the number of times is 9 or less.

The transmission / reception control unit 11 changes the beacon transmission channel (S304). For example, a setting is made in which the number of beacon transmissions on channel 2 is decreased by one and the number of transmissions on channel 1 is increased by one.

(B-3) Effect of Second Embodiment According to the second embodiment, the following effects are exhibited in addition to the effect of the first embodiment.

The wireless communication device 20 (transmission / reception control unit 11) calculates the number of beacons received in consideration of the transmission error rate for each channel, and reduces the number of beacon transmissions when the number of receptions is large. It has become possible to control the number of beacons transmitted in consideration of the radio wave conditions around the wireless communication device.

Further, when the radio wave condition is different for each channel, as compared with the first embodiment, it is possible to prevent an excessive transmission of the number of transmissions due to omission of detection of the number of beacons received and a state in which the beacon cannot be received within the scan time due to the reduction of the number of transmissions. it can.

(C) Other Embodiments In addition to each of the above embodiments, modified embodiments as illustrated below can also be mentioned.

(C-1) In each of the above embodiments, an example in which the transmission / reception control unit 11 indirectly increases the time slot to the data frame by controlling the number of times the beacon is transmitted has been described, but as a modification, the time slot has been described. You may change the pattern. That is, the transmission / reception control unit 11 may reduce the number of time slots allocated for broadcasting and increase the number of individual time slots allocated after the number of beacon transmissions is reduced. For example, the coordinator (coordinator 10 in each of the above embodiments) collects the number of wireless communication devices and the number of beacons in the network, and when the number of wireless devices is large but the number of beacons decreases, a part of the broadcast time slot is used. A control signal for stopping the allocation of is transmitted (notified) to a wireless communication device in the network. The wireless communication device that receives the notification sets an empty slot. After that, the wireless communication device that wants to increase the individual time slots can be realized by newly allocating to this empty slot. This makes it easier to secure the time slot required for data frame transmission as compared with each of the above embodiments.

(C-2) In each of the above embodiments, an example in which the transmission / reception control unit 11 increases or decreases the number of times the beacon is transmitted has been described. However, as a modification, if the number of received beacons is large, the transmission output is lowered to reduce the reach of the beacon. By narrowing it, the number of beacons within a certain range may be reduced.

(C-3) In each of the above embodiments, an example of reducing the beacon transmission of a specific channel has been described, but as a modification, instead of reducing the number of transmissions (number of transmission requests), a time slot is assigned to that channel. You may try to reduce it.

(C-4) Although the control of the beacon frame has been described in each of the above embodiments, the applicable frame is not limited to this, and the control of the beacon frame is also applicable to other broadcast frames.

1, 1A ... wireless communication system, 10 ... coordinator, 11 ... transmission / reception control unit, 12 ... reception counter, 13 ... reception frame analysis unit, 14 ... transmission timer, 15 ... wireless transmission / reception unit, 20 (20-1 to 20-8) ) ... Wireless communication device, D1 ... Reception counter data, D2 ... Transmission counter data, N ... Noise source.

Claims (9)

A time-division multiple access method is adopted, and there are two types of time-division time slot allocation, one for broadcasting and one for between individual wireless communication devices. If the destination of the data frame and control frame is specified, it is for individual use. In a wireless communication device that uses a time slot, or a broadcast time slot if not specified,
A reception control frame measuring means for measuring the number of times the control frame is received by a broadcast received from a surrounding wireless communication device within a predetermined time, and a reception control frame measuring means.
A wireless communication device having a control means for determining the number of transmissions of the control frame to be broadcast within a predetermined time based on the number of receptions of the control frame by broadcasting measured by the reception control frame measuring means. .. It has a first threshold value for the number of times the control frame is received by broadcasting, and a second threshold value that is smaller than the first threshold value.
When the number of times the control frame is received by broadcasting is equal to or greater than the first threshold value, the control means reduces the number of times the control frame is transmitted to be broadcast, and when the number of times the control frame is broadcast is equal to or less than the second threshold value. The wireless communication device according to claim 1, wherein the number of transmissions of the control frame to be broadcast is increased. The control frame includes an index regarding the distance from the network coordinator to the wireless communication device that transmitted the control frame.
The claim is characterized in that the reception control frame measuring means measures the number of receptions of the control frame only when the index included in the control frame is at the same level as the index indicating the distance from the network coordinator to itself. Item 2. The wireless communication device according to item 1 or 2. The reception control frame measuring means measures the number of times the control frame is received by broadcasting from surrounding wireless communication devices within a predetermined time for each received channel.
The claim is characterized in that the control means determines the number of transmissions of the control frame to be broadcast within a predetermined time based on the number of receptions of the control frame measured by the reception control frame measuring means for each channel. The wireless communication device according to any one of 1 to 3. It has a transmission frame measuring means for measuring the number of transmissions of the data frame and the number of errors to the surrounding wireless communication device within a predetermined time for each channel.
The control means is characterized in that the number of transmissions of the control frame to be broadcast within a predetermined time is determined in consideration of the transmission error rate for each channel calculated based on the number of transmissions of the data frame and the number of errors. The wireless communication device according to claim 4. It has a third threshold value to be compared with the transmission error rate.
The control means compares the transmission error rate with the third threshold value, and as a result of the comparison, the control frame broadcasts the channel whose transmission error rate is equal to or higher than the third threshold value. The wireless communication device according to claim 5, wherein the number of transmissions of the control frame is reduced, and the number of transmissions of the control frame to be broadcast is increased for a channel whose transmission error rate is less than the third threshold value. .. It is characterized by transmitting a request for reducing or increasing the number of allocated broadcast time slots to the surrounding wireless communication device by using the reception information of the control frame by broadcasting from the surrounding wireless communication device and the information regarding the number of wireless communication devices. The wireless communication device according to any one of claims 1 to 6. A time-division multiple access method is adopted, and there are two types of time-division time slot allocation, one for broadcasting and one for between individual wireless communication devices. If the destination of the data frame and control frame is specified, it is for individual use. A computer installed in a wireless communication device that uses a time slot, or a broadcast time slot if not specified.
A reception control frame measuring means for measuring the number of times the control frame is received by a broadcast received from a surrounding wireless communication device within a predetermined time, and a reception control frame measuring means.
The radio is characterized in that it functions as a control means for determining the number of transmissions of the control frame to be broadcast within a predetermined time based on the number of receptions of the control frame by the broadcast measured by the reception control frame measuring means. Communication program. A time-division multiple access method is adopted, and there are two types of time-division time slot allocation, one for broadcasting and one for between individual wireless communication devices. If the destination of the data frame and control frame is specified, it is for individual use. In a wireless communication method used for a wireless communication device that uses a time slot, or a broadcast time slot if not specified.
It has a reception control frame measuring means and a control means,
The reception control frame measuring means measures the number of times the control frame is received by a broadcast received from a surrounding wireless communication device within a predetermined time.
The wireless communication method is characterized in that the control means determines the number of transmissions of the control frame to be broadcast within a predetermined time based on the number of receptions of the control frame by broadcasting measured by the reception control frame measuring means. ..

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