JP7088762B2 - Beacon transmitting terminal, beacon receiving terminal and wireless communication system - Google Patents

Description

The present invention relates to a beacon transmitting terminal, a beacon receiving terminal, and a wireless communication system that avoid an increase in communication delay time due to radio wave interference with other wireless communication systems mounted in the same vehicle or in another vehicle.

Conventionally, a method of avoiding the occurrence of radio wave interference with a wireless device of another wireless communication system has been proposed.

For example, Patent Document 1 proposes a method in which a control device is arranged in a wireless network including one or more terminal devices, and the control device controls wireless communication using a plurality of frequency channels.
The control device includes a radio reception unit, a quality determination unit, and a beacon generation unit. The radio receiving unit can receive radio signals of a plurality of frequency channels, and the quality determination unit determines the usable frequency channel based on the reception state of the radio signal received by the radio receiving unit, and also determines the frequency channel of the frequency channel. Determine the order of use.
Then, the beacon generation unit generates a beacon including the usage order information of the frequency channel, and transmits the beacon to the terminal device. The channel setting unit of the terminal device that has received the beacon sets the frequency channel to be used according to the usage order information (see FIG. 19 (FIG. 14 of Patent Document 1)).
Further, in the superframe period consisting of an active period in which wireless communication is possible and an inactive period in which wireless communication is not performed, the active period is divided into a plurality of beacon transmission periods, and the beacon is periodically divided into beacon transmission periods. It is transmitted (see FIG. 16 (FIG. 4 of Patent Document 1), FIG. 17 (FIG. 6 of Patent Document 1), and FIG. 18 (FIG. 6 of Patent Document 1).

Further, for example, Patent Document 2 proposes a method based on a system that temporarily uses a frequency band not assigned to itself for communication. That is, it is a method of communicating by sharing a part of the license band assigned to the wireless communication system different from the own system. Specifically, before the start of communication, the first carrier sense is performed on the predetermined L (L ≧ 2) frequency bands, M frequency bands are selected from the carrier senses, and the time slot is selected. In the carrier sense section at the beginning of, a second carrier sense is performed on M frequency bands (L ≧ M ≧ 2), and the frequency band used for transmission is determined from the unused frequency bands. (See FIG. 20 (FIG. 7 of Patent Document 2) and FIG. 21 (FIG. 8 of Patent Document 2). At this time, if the frequency band used last time is among the final candidates, that frequency band is used. Alternatively, preferentially use the frequency band that has been used many times.
The wireless terminal is equipped with a matched filter, etc., and calculates the correlation value between the same signal sequence as the known sequence stored in advance and the first sequence of the received signal, so as to specify the frequency band used for transmission. It is configured (see FIG. 22 (FIG. 9 of Patent Document 2)).

Further, for example, in Patent Document 3, in an autonomous decentralized wireless communication network that does not require a specific control station, channels are periodically generated in synchronization with beacon reception in a communication environment in which a plurality of channels are prepared. By changing it, a method has been proposed in which communication can be performed on another communication channel even if the communication condition of a specific channel is poor.
That is, when communication is performed by staying on the same channel, communication cannot be performed if the communication status is poor due to interference, etc., but communication status is achieved by switching multiple channels in synchronization with the reception of the beacon. You can avoid the influence of bad channels.
Therefore, at the transmission timing of each wireless terminal, a beacon is transmitted and synchronized between the wireless terminals before data transmission. Immediately after transmitting the beacon, a priority allocation section for communication is given to the wireless terminal that transmitted the beacon so that another wireless terminal can transmit after a certain period of time (FIG. 3 of Patent Document 3). ), FIG. 24 (see FIG. 7 of Patent Document 3).
Further, since the channel is changed regularly, a mechanism for determining and notifying the communication channel between the terminals becomes unnecessary, and the operation becomes simple (see FIG. 25 (FIG. 13 of Patent Document 3)).

International Publication No. 2010/007738 Japanese Unexamined Patent Publication No. 2007-300421 Japanese Unexamined Patent Publication No. 2005-07985

However, according to the disclosures of Patent Document 1, Patent Document 2, and Patent Document 3, the frequency band being interfered with is independently avoided, and the increase in communication delay time when radio wave interference occurs for a long period of time is avoided. Can be difficult.
Therefore, an object of the present invention is to provide a means for solving such a problem.

In order to solve the above problems, the present invention adopts the following configuration.
That is, the invention according to claim 1 is a beacon of a wireless communication system in which one of a plurality of wireless terminals is used as a beacon transmitting terminal in a predetermined order each time the communication channel is switched, and the remaining wireless terminals are used as beacon receiving terminals. It ’s a transmitting terminal,
A beacon generator that generates start beacons, intermediate beacons, and end beacons,
A communication unit that transmits and receives the start beacon, data information, the intermediate beacon, and the end beacon.
A timer unit that measures the switching cycle of the communication channel of the communication unit, and a timer unit.
A channel switching unit that switches the communication channel of the communication unit according to a predetermined rule according to the switching cycle of the communication channel is included.
The beacon generation unit includes the timer information measured by the timer unit as time synchronization information in the start beacon, and includes channel switching information indicating the timing of switching the communication channel in the end beacon, and transmits / receives an intermediate beacon. When a transmission request is generated in the section, an intermediate beacon which is time information indicating the time when the transmission request is generated and includes the time information measured by the timer unit is generated.
The communication unit transmits the start beacon before the start of transmission / reception of the data information, transmits the intermediate beacon when a transmission request is generated in the intermediate beacon transmission / reception section, and after the end of transmission / reception of the data information. Send an end beacon,
At the end of the communication channel switching cycle, the channel switching unit switches the communication channel based on the predetermined rule and resets the timer unit.
The intermediate beacon transmission / reception section is characterized in that the reception of the response signal to the data information from the transmission of the data information on the communication channel cannot be completed before the transmission of the end beacon.

According to the above configuration, the beacon transmitting terminal switches the communication channel based on a predetermined rule at the end of the communication channel switching cycle, and thus autonomously avoids the communication channel in the frequency band being interfered with. be able to. Therefore, it is possible to avoid an increase in communication delay time by avoiding a communication channel in which radio wave interference occurs for a long period of time.
Further, even if the timing of the transmission frame of the beacon receiving terminal is deviated by a predetermined period, the time synchronization information for synchronizing the timer part of the beacon receiving terminal included in the start beacon with the beacon transmitting terminal and the channel switching included in the end beacon are performed. The information makes it possible to resynchronize between the beacon transmitting terminal and the beacon receiving terminal.
Furthermore, when the transmission / reception of data information is not completed in the transmission frame, the wireless terminal transmits the intermediate beacon in the intermediate beacon transmission / reception section, so that the communication delay time can be shortened and the transmission frame can be effectively used. Become. Further, by transmitting the intermediate beacon in advance, the period of the transmission / reception operation for the transmission request on the next communication channel can be omitted, so that the transmission frame can be effectively utilized.

In order to solve the above problem, in the invention according to claim 2, in the beacon transmission terminal according to claim 1, the beacon generation unit generates a transmission request included in the intermediate beacon transmitted / received by the communication unit. Based on the time information, the transmission order of the wireless terminal that transmits the data information on the next communication channel is determined in the time order of the time information when the transmission request is generated, and the transmission order information and the identification information of the wireless terminal are determined. Is included in the end beacon as transmission request information.

According to the above configuration, the transmission order of the wireless terminal that transmits the data information on the next communication channel is determined in the time order of the time information when the transmission request is generated, so that the wireless terminal having a long delay time is given priority first. Since the data information can be transmitted to, the delay time can be shortened.

In order to solve the above problem, the invention according to claim 3 is the beacon generation unit according to claim 2, when the communication unit receives the end beacon of the immediately preceding communication channel in the beacon transmission terminal according to claim 2. Uses the transmission request information included in the end beacon as the transmission request information included in the start beacon.
When the communication unit cannot receive the end beacon of the immediately preceding communication channel, the beacon generation unit is based on the time information in which the transmission request included in the intermediate beacon transmitted / received on the immediately preceding communication channel is generated. The transmission order of the wireless terminal for transmitting the data information is determined in the time order of the time information in which the transmission request is generated, and the transmission order information and the identification information of the wireless terminal are included in the start beacon as the transmission request information. It is a feature.

According to the above configuration, even if the beacon transmitting terminal of the next communication channel cannot receive the end beacon, the beacon transmitting terminal of the next communication channel that has received the intermediate beacon determines the transmission order of the wireless terminal. Then, the transmission order information can be transmitted by the start beacon.
Therefore, even if the end beacon is interfered with, if the wireless terminal can send and receive the start beacon including the transmission order information, the delay time until the wireless terminal in which the transmission request is generated transmits the data information can be shortened. Will be possible.

In order to solve the above problems, the invention according to claim 4 is started when the beacon transmitting terminal according to any one of claims 1 to 3 has the first transmission order. After transmitting the beacon, the data information is transmitted without providing a waiting time.

According to the above configuration, the wireless terminal can immediately transmit data information from the beginning of the transmission frame, so that the transmission frame can be effectively used. As an example, since the contention window adopted in the CSMA / CA method can be skipped and transmission can be performed, the time until the transmission starts can be shortened and the transmission frame can be effectively used. It will be possible.

In order to solve the above problems, the invention according to claim 5 further includes priority information indicating the priority of data information in the intermediate beacon in the beacon transmitting terminal according to any one of claims 2 to 4. The data information in which the data information having the higher priority of the priority information is transmitted earlier than the transmission order of the data information having the lower priority of the priority information is earlier and the priority of the priority information is the same. It is characterized in that the transmission order is determined in the time order of the time information in which the transmission request is generated.

According to the above configuration, it is possible to transmit data information having a high degree of urgency with priority over other data information. As an example, when a wireless communication system is mounted on a vehicle or the like, the vehicle is smoothly controlled by transmitting and receiving data information on vehicle control in preference to data information on entertainment such as music. Will be possible.

In order to solve the above problems, in the invention according to claim 6, one of a plurality of wireless terminals is predetermined in the beacon transmitting terminal according to any one of claims 1 to 5 each time the communication channel is switched. Among the wireless terminals included in the wireless communication system, the beacon transmitting terminals to be used as beacon transmitting terminals in the same order are within a predetermined range from the middle point on the line where the distance between the wireless terminals is the longest. It is characterized in that it is determined for wireless terminals.

According to the above configuration, the wireless communication system of this method can be smoothly operated by not using the wireless terminal whose communication environment may deteriorate as the beacon transmission terminal. As an example, when a wireless communication system is mounted on a vehicle or the like, the wireless terminal arranged in the center of the vehicle is used as a beacon transmission terminal to communicate with the wireless terminals arranged in the front and rear of the vehicle. It is possible to increase the success rate and operate the wireless communication system smoothly.

In order to solve the above problems, the invention according to claim 7 uses one of the plurality of wireless terminals as a beacon transmitting terminal in a predetermined order each time the communication channel is switched, and the remaining wireless terminals as a beacon receiving terminal. It is a beacon receiving terminal of a wireless communication system
Beacon generator that generates intermediate beacons and
A communication unit that receives a start beacon and an end beacon and transmits / receives data information and the intermediate beacon.
A timer unit that measures the switching cycle of the communication channel of the communication unit, and a timer unit.
A channel switching unit that switches the communication channel of the communication unit according to a predetermined rule according to the switching cycle of the communication channel is included.
When the communication unit receives the start beacon, the timer unit sets the time synchronization information included in the start beacon in the timer unit.
When the communication unit receives the end beacon, the channel switching unit switches the communication channel after a predetermined period after receiving the channel switching information indicating the timing for switching the communication channel included in the end beacon. , Reset the timer section,
When a transmission request is generated in the intermediate beacon transmission / reception section, the beacon generation unit generates time information indicating the time when the transmission request is generated, and generates an intermediate beacon including the time information measured by the timer unit. ,
The intermediate beacon transmission / reception section is characterized in that the reception of the response signal to the data information from the transmission of the data information on the communication channel cannot be completed before the reception of the end beacon.

According to the above configuration, the beacon receiving terminal switches the communication channel based on a predetermined rule at the end of the communication channel switching cycle, and therefore autonomously avoids the communication channel which is the frequency band being interfered with. be able to. Therefore, it is possible to avoid an increase in communication delay time by avoiding a communication channel in which radio wave interference occurs for a long period of time.
Further, even if the timing of the transmission frame of the beacon receiving terminal is deviated by a predetermined period, the timer part of the beacon receiving terminal is resynchronized with the beacon transmitting terminal by the time synchronization information included in the first start beacon of the transmission frame, and the transmission frame of the transmission frame. It becomes possible to resynchronize with the beacon transmitting terminal by the channel switching information included in the last end beacon.
Furthermore, when the transmission / reception of data information is not completed in the transmission frame, the wireless terminal transmits the intermediate beacon in the intermediate beacon transmission / reception section, so that the communication delay time can be shortened and the transmission frame can be effectively used. Become. Further, by transmitting the intermediate beacon in advance, the period of the transmission / reception operation for the transmission request on the next communication channel can be omitted, so that the transmission frame can be effectively utilized.

In order to solve the above problem, in the invention according to claim 8, in the beacon receiving terminal according to claim 7, the transmission order of the beacon receiving terminal is the best based on the transmission order information included in the start beacon. When becomes, it is characterized in that after receiving the start beacon, data information is transmitted without providing a waiting time.

According to the above configuration, the wireless terminal can immediately transmit data information from the beginning of the transmission frame, so that the transmission frame can be effectively used. As an example, since the contention window adopted in the CSMA / CA method can be skipped and transmission can be performed, the time until the transmission starts can be shortened and the transmission frame can be effectively used. It will be possible.

In order to solve the above problems, the invention according to claim 9 is the beacon receiving terminal according to any one of claims 6 to 8, wherein the communication unit is continuously connected to all communication channels, and the start beacon and the said are described. When the end beacon is not received, the channel switching unit waits for the reception of the start beacon or the end beacon in the communication channel set at the beginning of the switching order of the communication channels.

If the synchronization between the beacon receiving terminal and the beacon transmitting terminal deviates by more than the transmission frame period, the beacon receiving terminal cannot receive the start beacon and the end beacon, so that the period during which the beacon transmitting terminal cannot be resynchronized is long. The possibility of becoming a beacon increases.
However, according to the above configuration, the beacon receiving terminal stops the communication channel switching operation and waits on the initial communication channel, so that the start beacon or the end beacon can be received and resynchronized with the beacon transmitting terminal. Will be possible.

In order to solve the above problems, the invention according to claim 10 is characterized by including the beacon transmitting terminal according to any one of claims 1 to 6 and the beacon receiving terminal according to any one of claims 7 to 9. do.

According to the above configuration, the beacon transmitting terminal and the beacon receiving terminal switch the communication channel based on a predetermined rule at the end of the communication channel switching cycle. It can be avoided independently. Therefore, it is possible to avoid an increase in communication delay time by avoiding a communication channel in which radio wave interference occurs for a long period of time.
Further, even if the timing of the transmission frame of the beacon receiving terminal is deviated by a predetermined period, the timer part of the beacon receiving terminal is resynchronized with the beacon transmitting terminal by the time synchronization information included in the first start beacon of the transmission frame, and the transmission frame of the transmission frame. It becomes possible to resynchronize with the beacon transmitting terminal by the channel switching information included in the last end beacon.
Furthermore, if the transmission / reception of data information is not completed in the transmission frame, the wireless terminal sets the intermediate beacon transmission / reception section and transmits the intermediate beacon to shorten the communication delay time and effectively utilize the transmission frame. Will be possible. Further, by transmitting the intermediate beacon in advance, the period of the transmission / reception operation for the transmission request on the next communication channel can be omitted, so that the transmission frame can be effectively utilized.

According to the present invention, it is possible to independently avoid a communication channel which is a frequency band receiving interference and to avoid an increase in communication delay time when radio wave interference occurs for a long period of time.

Further, when the transmission / reception of the data information and the response signal is not completed in one transmission frame, the wireless terminal sets the intermediate beacon transmission / reception section and transmits the intermediate beacon to shorten the communication delay time and reduce the transmission frame. It will be possible to utilize it effectively.

This is an example of a wireless communication network constituting a wireless communication system. It is a block diagram which shows the configuration example of the hardware of a wireless terminal. It is a figure which shows the beacon transmission timing and the communication channel switching timing in an Example. It is a figure which shows the structure of the start beacon. It is a figure which shows the structure of the end beacon. It is a figure which shows the structural example of a data frame. This is an example of a transmission frame of a beacon transmission terminal. It is a flowchart which shows the initial operation after the wireless terminal is activated. It is a flowchart which showed the process after switching a communication channel. It is a flowchart when a wireless terminal operates as a beacon transmission terminal. It is a flowchart when a wireless terminal operates as a beacon transmission terminal. It is a flowchart when a wireless terminal operates as a beacon receiving terminal. It is a flowchart when a wireless terminal operates as a beacon receiving terminal. It is a figure which shows an example of a channel switching order when interference does not occur in a communication channel. It is a schematic diagram which shows the resynchronization of the beacon receiving terminal by the beacon reception. It is a schematic diagram which shows the intermediate beacon transmission / reception section. It is another example of the wireless communication network constituting the wireless communication system. It is a drawing for demonstrating patent document 1 which is a prior art. It is a drawing for demonstrating patent document 1 which is a prior art. It is a drawing for demonstrating patent document 1 which is a prior art. It is a drawing for demonstrating patent document 1 which is a prior art. It is a drawing for demonstrating patent document 2 which is a prior art. It is a drawing for demonstrating patent document 2 which is a prior art. It is a drawing for demonstrating patent document 2 which is a prior art. It is a drawing for demonstrating patent document 3 which is a prior art. It is a drawing for demonstrating patent document 3 which is a prior art. It is a drawing for demonstrating patent document 3 which is a prior art.

(Overview of wireless communication system)
In the wireless network composed of a plurality of wireless terminals of this embodiment, each wireless terminal regularly switches two or more communication channels (frequency bands) for communication, so that the frequency band is receiving interference. Can be communicated independently while avoiding. Each wireless terminal transmits a beacon at the beginning and end of a transmission frame in a preset beacon transmission order, and synchronizes with other wireless terminals. The channel switching cycle is predetermined, and each wireless terminal autonomously switches the frequency as soon as the switching time is reached. Even if the synchronization signal by the beacon cannot be received, since each wireless terminal can autonomously switch the frequency as described above, all the wireless terminals can communicate on the same communication channel.

Since the time spent in the communication channel is always constant, even if there is a transmission request immediately before the communication channel is switched, the communication may not be terminated before the communication channel is switched. In such a case, the wireless terminal cannot start communication even if a transmission request is generated. Therefore, if a transmission request occurs even though the communication cannot be terminated by the timing when the communication channel is switched, the wireless terminal in which the transmission request is generated transmits an intermediate beacon, so that all the wireless terminals have a transmission request. Notify that. Then, based on the information contained in the intermediate beacon, the wireless terminal that transmits the end beacon determines in advance the order of the wireless terminals that perform the transmission operation on the next communication channel. For example, when a plurality of transmission requests are generated, the wireless terminal that transmits the end beacon determines the transmission order so that the wireless terminal having the earlier transmission request can start the transmission operation preferentially. The transmission request generation time is based on the reception time of the start beacon immediately before the transmission request is generated. Further, the transmission order of the wireless terminal that has transmitted the intermediate beacon can be determined by the wireless terminal that transmits the start beacon after switching the communication channel, but the details will be described later.

The information of the wireless terminal performing the determined transmission operation is transmitted to all the wireless terminals by the end beacon and the start beacon after the communication channel is switched. Immediately after the start beacon is transmitted and received, the wireless terminal starts the transmission operation based on the determined order. In this case, the time until the start of transmission can be shortened by skipping the contention window or the like adopted in the CSMA / CA (Carrier Sense Multiple Access / Collection Assistance) method. Further, in the CSMA / CA method, a transmission wireless terminal is randomly selected, but according to this method, a wireless terminal having a long delay time can be preferentially transmitted first, so that the delay time can be shortened. As a basic operation of the wireless terminal, when other than data transmission, Ac (Acknowledgement) transmission, and beacon transmission operation, the user always waits in the reception state and detects the reception strength. Further, from the detected reception strength, it is determined whether the data, the beacon, the Ack, or the like is an interference.

FIG. 1 shows a configuration example of a wireless communication network constituting the wireless communication system of this embodiment. In FIG. 1, wireless terminals 11 to 20 construct a wireless communication network 1000. The CSMA / CA method is assumed as the wireless communication method.

FIG. 2 shows an example of a block diagram of the hardware of the wireless terminal 200 of this embodiment. The beacon transmitting terminal and the beacon receiving terminal according to the claim are realized as a wireless terminal 200. The wireless terminal 200 is a general computer including a communication unit 210, a determination unit 220, a control unit 230, an I / F (interface) unit 240, and an information recording unit 250. The function shown in FIG. 2 is realized by executing a communication program by a general computer. Further, the control unit 230 is a CPU (Central Processing Unit). The control unit 230 reads / writes data stored in the information recording unit 250, inputs / outputs data to / from the communication unit 210, and executes processing in the wireless terminal 200.

The communication unit 210 includes a transmission / reception switching unit 211, a wireless transmission unit 212, and a wireless reception unit 213, and when the wireless terminal 200 is in the transmission mode, the transmission / reception switching unit 211 connects the antenna and the wireless transmission unit 212. When the wireless terminal 200 is in the reception mode, the transmission / reception switching unit 211 connects the antenna and the wireless reception unit 213.

The transmission / reception switching unit 211 switches the wireless terminal 200 to the transmission mode when transmitting data or a beacon, and switches the wireless terminal 200 to the reception mode at other times.

The wireless transmission unit 212 has a function of transmitting wireless signals such as data, a start beacon, an intermediate beacon, and an end beacon.

The wireless reception unit 213 has a function of receiving processing of wireless signals such as data received by an antenna from another wireless terminal 200, a start beacon, an intermediate beacon, and an end beacon.

The determination unit 220 includes a reception intensity determination unit 221 and an interference determination unit 222.

The reception intensity determination unit 221 has a function of determining whether or not the power of the received signal exceeds the threshold level.

The interference determination unit 222 has a function of determining whether the received signal exceeding the threshold level is in the own wireless communication system or is due to another wireless communication system. If it is a received signal from another wireless communication system, it is determined that interference has occurred in the current communication channel.

The control unit 230 includes a beacon generation unit 231, a data generation unit 232, a beacon analysis unit 233, a channel switching unit 234, a data processing unit 235, and a timer unit 236. Then, the control unit 230 transmits / receives data to / from the I / F (interface) unit 240, transmits / receives information to / from the information recording unit 250, transmits data and beacon information to the wireless transmission unit 212, and receives data from the wireless reception unit 213. Receives data and beacon information.

The beacon generation unit 231 starts the beacon when it is time to transmit the beacon as the beacon transmission terminal from the beacon transmission order information, the channel switching cycle information, and the timer information stored in the information recording unit 250. Alternatively, it has a function of generating and transmitting an end beacon. Further, when a transmission request is generated in the own wireless terminal 200 in the intermediate beacon transmission / reception section, a function of generating an intermediate beacon for transmitting information indicating that the transmission request has occurred in the own wireless terminal 200 to another wireless terminal 200 is performed. Has.

That is, when a transmission request is generated to the own wireless terminal 200 and the transmission / reception of data information and the transmission / reception of Ac to the data information are not completed in the remaining period of the current communication channel, the beacon generation unit 231 is intermediate. Generate a beacon. The details of the conditions for generating the intermediate beacon will be described later.

The intermediate beacon includes identification information of the wireless terminal 200 that transmits the intermediate beacon and time information when a transmission request is generated. The time information at which the transmission request is generated is based on the reception time of the start beacon immediately before the transmission request is generated.

Further, the beacon transmitting terminal that has transmitted the start beacon receives the intermediate beacon and has the right to transmit which wireless terminal 200 to what order on the next communication channel in order from the wireless terminal 200 having the earliest time when the transmission request is generated. Determine the information you have. That is, the wireless terminal 200 that has transmitted the start beacon determines the transmission order in the next communication channel of the wireless terminal 200 that has transmitted the intermediate beacon, and associates the transmission order information with the identification information of the wireless terminal 200. The transmission request information is included in the end beacon.

The end beacon includes transmission request information in which the transmission order information of the wireless terminal 200 in the next communication channel described above and the identification information of the wireless terminal 200 are associated with each other, and channel switching information (CH switching) indicating the channel switching timing. Information) is included. Further, the address information of the beacon transmitting terminal that transmitted the end beacon is added to the head of the end beacon. The address information is the identification information of the beacon transmitting terminal.

Further, the start beacon includes transmission request information in which the transmission order information of the wireless terminal 200 in the communication channel to which the start beacon is transmitted / received and the identification information of the wireless terminal 200 are associated with each other, and synchronization between the wireless terminals 200. Contains time synchronization information to take. Further, the address information of the beacon transmitting terminal that transmitted the start beacon is added to the head of the start beacon. The address information is the identification information of the beacon transmitting terminal.

Here, the time synchronization information included in the start beacon may be the timer information of the beacon transmission terminal that transmitted the start beacon. The wireless terminal 200 that has received the start beacon writes the time synchronization information included in the start beacon to the timer unit 236 of the own wireless terminal 200. As a result, it becomes possible to synchronize between the beacon transmitting terminal that transmitted the start beacon and the wireless terminal 200 that received the start beacon.

The data generation unit 232 has a function of generating data to be transmitted when a transmission request is received from the I / F unit 240.

The beacon analysis unit 233 extracts the above-mentioned various beacon information contained in the start beacon, the intermediate beacon or the end beacon from the received start beacon, intermediate beacon or end beacon, and records the extracted information in the information recording unit 250. Has a function. Further, as described above, the beacon analysis unit 233 of the beacon receiving terminal writes the time synchronization information extracted from the start beacon to the timer unit 236 to synchronize with the beacon transmitting terminal.

The channel switching unit 234 switches the communication channel after a predetermined time has elapsed after the reception of the channel switching information included in the end beacon is finished. The predetermined time is the time until the channel switching cycle of the beacon transmitting terminal ends. Therefore, the beacon transmission terminal starts transmitting the end beacon so that the channel switching cycle ends after a predetermined time has elapsed from the transmission completion timing of the end beacon. The predetermined time can also be referred to as a channel switching grace period.

If the beacon receiving terminal cannot receive the end beacon, the timer information stored in the information recording unit 250 is read out, and the communication channel is switched when the channel switching cycle specified by the channel switching cycle information is reached. conduct. When switching the communication channel, the channel switching unit 234 specifies the communication channel to be changed next based on the channel switching order information stored in the information recording unit 250, and switches the communication channel.

The data processing unit 235 has a function of processing the received data and transmitting it to the I / F unit 240.

The timer unit 236 has a channel switching cycle from the time when the communication channel is switched and the timer is reset until the transmission / reception of the channel switching information included in the end beacon is completed and the communication channel is switched after the channel switching grace period has elapsed. Time as. Here, the channel switching cycle is also the transmission frame length (Tms). The time measured by the timer unit 236 is recorded in the information recording unit 250 as timer information.

Therefore, the timing at which the transmission / reception of the end beacon is completed is before the channel switching grace period from the channel switching cycle. Since the beacon transmitting terminal recognizes the end beacon length, the end beacon transmission is started so that the end timing of the end beacon transmission is completed before the channel switching grace period. Further, the channel switching grace period is predetermined in the wireless communication system, and all the wireless terminals 200 included in the wireless communication system record in the information recording unit 250.

The I / F unit 240 has an interface function with an external device. The external device can be any electronic device.

The information recording unit 250 stores various information including timer information, transmission request information, channel switching cycle information, channel switching order information, and beacon transmission order information, and sends and receives each information to and from the control unit 230. ..

The timer information records the elapsed time from the beginning of the channel switching cycle as time information in real time, with a predetermined channel switching cycle as a unit, based on the time measured by the timer unit 236. When the wireless terminal 200 extracts the time synchronization information from the received start beacon, the wireless terminal 200 that sets the time synchronization information in the timer unit 236 and transmits the start beacon and the wireless terminal 200 that receives the start beacon. Synchronize with. That is, the timer unit 236 restarts the time measurement from the time indicated by the time synchronization information, and records the time measurement information in the information recording unit 250 as the timer information.

Further, the wireless terminal 200 resets and initializes the timer unit 236 after switching the communication channel (see FIG. 9). All wireless terminals 200 tick the time in the predetermined channel switching cycle as a unit, and if the start beacon and the end beacon cannot be received, the communication channel is automatically changed in the channel switching cycle. do.

Further, the transmission request information of the information recording unit 250 includes the identification information of the wireless terminal 200 and the transmission order information associated with the identification information of the wireless terminal 200. The transmission request information of the information recording unit 250 is the same as the transmission request information included in the end beacon or the start beacon.

As described above, the transmission order is determined so that the wireless terminal 200 that has received the intermediate beacon can transmit in order from the wireless terminal 200 that has transmitted the intermediate beacon with the earlier time information that the transmission request included in the intermediate beacon has occurred. As the transmission request information, the identification information of the wireless terminal 200 may be arranged only in the order of transmission. Further, the transmission request information may be recorded in which the time information at which the transmission request is generated is associated with the identification information of the wireless terminal 200 that has transmitted the intermediate beacon.

In the channel switching cycle information, information indicating a predetermined communication channel switching cycle is recorded. That is, the time (Tms) from the timing when the switching of the communication channel is completed to the timing when the transmission / reception of the channel switching information included at the end of the end beacon is completed and the channel is switched after the channel switching grace period has elapsed is recorded. There is.

That is, as an example, the transmission frame length (Tms) is recorded in the information recording unit 250 as channel switching cycle information.

As the channel switching order information, a predetermined communication channel switching order is recorded. That is, when the communication channel does not interfere, the wireless terminal 200 switches the communication channel in the order of channel switching. For example, as shown in FIG. 12, the channel switching order is set so that all the communication channels prepared in one cycle are used once. When one cycle of the channel switching order is completed, the wireless terminal 200 selects the communication channel again from the beginning of the channel switching order.

In the beacon transmission order information, the order in which the wireless terminal 200 becomes a beacon transmission terminal is recorded. For example, if the identification information of the wireless terminal 200 is recorded in the beacon transmission order information in order, the wireless terminal 200 can recognize which wireless terminal 200 becomes the beacon transmission terminal each time the communication channel is switched. When one cycle of the beacon transmission order is completed, the wireless terminal 200 to be the beacon transmission terminal is determined again from the beginning of the beacon transmission order.

All the wireless terminals 200 included in the wireless communication system become beacon transmission terminals in order, some wireless terminals 200 included in the wireless communication system become beacon transmission terminals in order, and beacon transmission terminals. The wireless terminal 200 may be fixed.

For example, the beacon transmission terminal in which one of the plurality of wireless terminals 200 is used as the beacon transmission terminal in a predetermined order each time the communication channel is switched is the wireless terminal 200 among the wireless terminals 200 included in the wireless communication system. Determined for the wireless terminal within a predetermined range from the midpoint on the line with the longest distance between

That is, by not using a wireless terminal that may deteriorate the communication environment as a beacon transmitting terminal, it is possible to smoothly operate the wireless communication system of this method.

As an example, when a wireless communication system is mounted on a vehicle or the like, the wireless terminal arranged in the center of the vehicle is used as a beacon transmission terminal to communicate with the wireless terminals arranged in the front and rear of the vehicle. It is possible to increase the success rate and operate the wireless communication system smoothly. That is, by not using the wireless terminal 200 on the periphery of the communicable range of the wireless communication system as the beacon transmission terminal, the wireless communication system can be operated more stably.

FIG. 3 is a diagram schematically showing a transmission cycle and a channel switching cycle of the start beacon and the end beacon.

First, the wireless terminal 11 acts as a beacon transmission terminal and transmits a start beacon on CH (channel: Channel) 1, which is an initial communication channel arranged at the beginning of the channel switching order information, transmits / receives data, and ends the beacon. To send. Within Tms, which is the channel switching cycle, transmission of the start beacon to transmission of the end beacon is executed. At this time, the wireless terminals 12 to 20 receive the start beacon and the end beacon on CH1 as the beacon receiving terminal. Tms is also a transmission frame period, which is a data transmission / reception period. Further, Tms is a fixed period during the operation of the wireless communication system.

After the wireless terminal 11 transmits the end beacon, all the wireless terminals are switched to CH2, and the wireless terminal 12, which is the next wireless terminal of the wireless terminal 11, becomes the beacon transmitting terminal and transmits the start beacon. Similarly, transmission / reception of the start beacon and the end beacon and switching of the communication channel are repeated.

In FIG. 3, a start beacon and an end beacon are transmitted in a Tms cycle. The communication channel is changed after the transmission / reception of the end beacon is completed and the channel switching grace period has elapsed, and the start beacon is transmitted after the communication channel is switched. As described above, this cycle time T is a transmission frame period and is predetermined in the wireless communication system. Further, the wireless communication system cannot change the specified period time T while the wireless terminal is operating.

Further, in FIG. 3, 10 wireless terminals from the wireless terminal 11 to the wireless terminal 20 are used, and the number of the wireless terminals does not change during the operation of the wireless terminals. That is, the wireless terminal is basically a fixed station, and the mobile station is not considered. Therefore, the increase or decrease of wireless terminals in the wireless communication network is not taken into consideration, and the wireless terminal to be assigned as the wireless terminal 20 from the wireless terminal 11 must be specified first. Further, as described above, there are cases where all or some of the wireless terminals in the wireless communication system become beacon transmission terminals in order, and there are cases where the beacon transmission terminals are fixed.

When the wireless terminal is not operating, the wireless communication system can add or reduce new wireless terminals. For example, when the wireless communication system adds a new wireless terminal, the wireless terminal newly added by the wireless communication system is assigned as the wireless terminal 21 in the following order of the wireless terminal 20, and the beacons of all the wireless terminals are assigned. Information such as transmission order information is also updated.

FIG. 3 shows a basic communication channel switching cycle, in which the initial channel is CH1 and all wireless terminals are simultaneously switched in the order of CH1 → CH2 → CH3 at Tms intervals. Further, the beacon transmitting terminal that transmits the beacon may also switch from the wireless terminal 11 to the wireless terminal 20 in order in the Tms cycle.

In this case, it is desirable that all wireless terminals can be synchronized by the beacon. However, even if the beacon cannot be received, the communication channel is automatically switched at Tms intervals, so that synchronization can be achieved between the wireless terminals.

That is, if the beacon receiving terminal can receive the end beacon, the reception of the channel switching information of the end beacon is completed, and the beacon receiving terminal switches the communication channel after the channel switching grace period has elapsed. If the beacon receiving terminal cannot receive the end beacon, the communication channel is switched based on the timer information of the information recording unit 250.

FIG. 4 shows a block diagram of the start beacon. The start beacon contains the source address, transmission request information, and time synchronization information. The start beacon is transmitted at the beginning of a transmission frame period, which is a period in which the wireless terminal 200 as a beacon transmission terminal for transmitting a beacon transmits / receives data.

The source address is the address of the wireless terminal 200 that transmitted the start beacon.

The transmission request information includes the identification information of the wireless terminal 200 and the transmission order information associated with the identification information of the wireless terminal 200. When the wireless terminal 200 that has received the start beacon has transmitted the intermediate beacon on the immediately preceding communication channel, the data transmission operation is performed according to the transmission order information included in the start beacon.

When the wireless terminal 200 that transmits the start beacon can receive the immediately preceding end beacon, the transmission request information included in the end beacon is transmitted as the transmission request information included in the start beacon.

When the wireless terminal 200 that transmits the start beacon cannot receive the immediately preceding end beacon, the transmission request information is created from the intermediate beacon received in the immediately preceding communication channel. That is, the wireless terminal 200 that transmits the start beacon determines information as to which wireless terminal 200 has the right to transmit in the current communication channel in order from the wireless terminal 200 in which the transmission request is generated earlier. do. In other words, the wireless terminal 200 that has transmitted the start beacon determines the transmission order of the wireless terminal 200 on the communication channel that has transmitted the start beacon, and includes the wireless terminal 200 identification information and the transmission order information in the start beacon as transmission request information. No, broadcast the start beacon.

As an example, the transmission request information may only be arranged according to the transmission order of the identification information of the wireless terminal 200.

Further, as another example, the delimiter is arranged at the end of the source address information, the identification information of the wireless terminal and the number as the transmission order information are arranged next to the delimiter, and the delimiter is arranged after the number. Then, the identification information of the other wireless terminal 200 is arranged next to the delimita, the number as the transmission order information of the other wireless terminal 200 is arranged next to the identification information of the other wireless terminal 200, and the delimita is arranged next to the number. The configuration in which is arranged may be repeated. The number between the delimiters indicates the transmission order of the wireless terminals 200 specified by the identification information of the wireless terminals 200 between the delimiters. Further, the time information when the transmission request occurs between the delimiters may be included.

The time synchronization information is timer information recorded in the information recording unit 250 of the wireless terminal 200 that transmits the start beacon. The wireless terminal 200 that has received the start beacon can synchronize between the wireless terminals 200 by setting the timer unit 236 at the time indicated by the time synchronization information included in the start beacon. If there is a synchronization gap between the wireless terminals 200, this time synchronization information enables resynchronization between the wireless terminal 200 that has transmitted the start beacon and the wireless terminal 200 that has received the start beacon.

FIG. 5 shows a configuration diagram of the end beacon. The end beacon includes a source address, transmission request information, and channel (CH) switching information. The end beacon is transmitted by the beacon transmitting terminal at the end of the transmission frame.

The source address is the address of the wireless terminal 200 as the beacon transmitting terminal that transmitted the end beacon.

The transmission request information includes the identification information of the wireless terminal 200 and the transmission order information associated with the identification information of the wireless terminal 200. When the wireless terminal 200 that has received the end beacon has transmitted the intermediate beacon on the communication channel that has received the end beacon, the wireless terminal 200 executes a data transmission operation on the next communication channel according to the transmission order information. Further, the wireless terminal 200 that has received the end beacon records the transmission request information included in the end beacon in the information recording unit 250.

However, when the wireless terminal 200 receives the start beacon on the next communication channel, the transmission operation is executed based on the transmission order information of the transmission request information of the start beacon.

The channel (CH) switching information is timing information for switching to the next communication channel, and after the transmission / reception of the channel (CH) switching information is completed and the channel switching grace period has elapsed, all the wireless terminals 200 are next to the communication channel. Switch to the communication channel of.

If there is a deviation in synchronization between the wireless terminals 200, this channel (CH) switching information enables resynchronization between the wireless terminals 200. That is, if the beacon receiving terminal can receive the end beacon, the communication channel is switched at the reception completion timing of the channel (CH) switching information of the end beacon, so that the start timing of the communication channel is synchronized. Further, the beacon receiving terminal resets the timer unit 236 at the timing when the communication channel is switched.

FIG. 6 shows a configuration example of a data frame. At the beginning of the data frame, there is a bit synchronization signal for synchronizing in bit units, then there is a frame synchronization signal for synchronizing in frame units, and then there is an ID unique to the wireless communication system. There is a header to include. Next to the header is the payload, which is the body of the data, and finally there is an error detection and correction code for detecting and correcting errors in the data. In the transmission / reception of data information in the intermediate beacon transmission / reception section, the data frame is said to have a fixed length. The wireless communication system can set the data frame length to any length.

As shown in FIG. 6, since the data frame includes an ID unique to the wireless communication system, the unique ID is used to determine whether the wireless signal received by the wireless terminal 200 is the wireless signal of the own wireless communication system. It can be determined by whether or not it was received.

FIG. 7 shows a transmission frame of the beacon transmission terminal X. The beacon transmission terminal X transmits a start beacon at the beginning of the transmission frame and an end beacon at the end of the transmission frame. A wireless terminal with a transmission request performs a transmission operation in the other data transmission area.

Here, the transmission frame length (Tms) indicates a channel switching cycle. Further, the transmission timing of the start beacon and the end beacon in the transmission frame is determined in advance by the wireless communication system.

For example, the start beacon is transmitted with a delay of a predetermined regular time from the beginning of the transmission frame. This is because, when the wireless terminals 200 are out of synchronization, the timing at which the communication channels are switched may vary. The predetermined rule time is also called the start beacon transmission grace period. By transmitting the start beacon after the start beacon transmission grace period is delayed by the start beacon transmission grace period after the communication channel is switched, the probability that the wireless terminal 200 out of synchronization can receive the start beacon is increased. Then, the wireless terminal 200 that has received the start beacon can be resynchronized with the wireless terminal 200 that has transmitted the start beacon by the time synchronization information included in the start beacon.

For example, if the switching timing of the communication channel of the wireless terminal 200 that could not receive the end beacon immediately before the start beacon is slightly delayed, and the start beacon is transmitted with a delay of the start beacon transmission grace period, the start beacon is transmitted. The probability of being received increases.

Further, the end beacon is transmitted so that the transmission / reception completion timing of the end beacon is before the end of the transmission frame by the channel switching grace period. This is because when the synchronization between the wireless terminals 200 is out of sync, the timing at which the communication channels are switched may vary. For example, the wireless terminal 200 in which the elapsed time of the timer information is early may not be able to receive the end beacon because the communication channel is switched quickly. However, if the transmission / reception completion timing of the end beacon is transmitted so as to be before the channel switching grace period from the end of the transmission frame, the probability that the wireless terminal 200 out of synchronization can receive the end beacon increases. Then, the wireless terminal 200 that has received the end beacon can be resynchronized with the wireless terminal 200 that has transmitted the end beacon by the channel switching information included in the end beacon.

The start beacon transmission grace period from the beginning of the transmission frame until the start beacon is transmitted and the channel switching grace period from the end of the transmission frame to the completion of transmission / reception of the end beacon may be the same or different. , Any time can be set.

If there is no transmission / reception of the intermediate beacon in the immediately preceding communication channel, the transmission right is given to all the wireless terminals 200 after the start beacon is transmitted, and all the wireless terminals 200 make a transmission request by CSMA / CA or the like. .. Further, after the transmission of all the wireless terminals 200 requested to be transmitted by the intermediate beacon is completed and before the intermediate beacon transmission / reception section described later, the transmission right is given to all the wireless terminals, and all the wireless terminals are CSMA /. Make a transmission request with CA or the like.

FIG. 8 shows a flowchart showing the initial operation at the time of starting the wireless terminal 200.

In step S801, when the wireless terminals 200 are activated, each wireless terminal 200 sets the communication channel to a predetermined initial channel in the wireless communication system. This is executed by each wireless terminal 200 referring to the channel switching order information of the information recording unit 250 and setting the first communication channel of the channel switching order information to the initial channel. Next, the wireless terminal 200 proceeds to step S802.

In step S802, it is determined whether or not the wireless terminal 200 is the initial wireless terminal 200 in the preset beacon transmission order. Since the beacon transmission order information is stored in the information recording unit 250, the wireless terminal 200 recognizes the identification information of the wireless terminal 200 at the head of the beacon transmission order information, so that the wireless terminal 200 is the initial wireless terminal 200. It can be determined whether or not. If the wireless terminal 200 is the initial wireless terminal 200 (step S802: YES), the wireless terminal 200 proceeds to step S803, and if it is not the initial wireless terminal 200 (step S802: NO), the process proceeds to step S809.

In step S803, before the beacon transmission terminal, which is the initial wireless terminal 200, transmits the start beacon, it is determined whether or not the reception intensity is detected by the reception intensity determination unit 221. If the reception strength is detected (step S803: YES), the initial wireless terminal 200 proceeds to step S804, and if the reception strength is not detected (step S803: NO), the initial wireless terminal 200 proceeds to step S805.

In step S804, if the reception intensity is detected, the initial wireless terminal 200 cannot transmit the start beacon. Therefore, the initial wireless terminal 200 proceeds to step S803 again in order to wait in the initial channel until the reception intensity is not detected. During the period when the initial wireless terminal 200 communicates, the other wireless terminals 200 are arranged not to communicate. Therefore, if the reception strength is detected, the received signal is a radio signal from another wireless communication system, and the initial wireless terminal 200 can determine that interference has occurred in the communication channel.

Since the reception intensity is not detected in step S805, the initial wireless terminal 200 transmits a start beacon and proceeds to step S806.

In step S806, the initial wireless terminal 200 waits until the predetermined period of the preset transmission frame elapses, and then proceeds to step S807.

In step S807, before the initial wireless terminal 200 transmits the end beacon, it is determined whether or not the reception intensity is detected by the reception intensity determination unit 221. If the reception strength is not detected (step S807: NO), the initial wireless terminal 200 proceeds to step S808. When the reception strength is detected (step S807: YES), the initial wireless terminal 200 does not transmit the end beacon. However, when the timer information recorded in the information recording unit 250 reaches the channel switching cycle, the channel switching unit 234 switches the communication channel based on the channel switching order information.

In step S808, since the reception intensity is not detected, the initial wireless terminal 200 includes the necessary information in the end beacon and transmits the end beacon. Then, when the channel switching grace period elapses after the transmission of the end beacon is completed, the channel switching unit 234 executes a process of switching the communication channel to the next channel based on the channel switching order information.

In step S809, since the initial wireless terminal 200 is a beacon receiving terminal, it waits in the receiving state and determines whether or not the beacon has been received. When the initial wireless terminal 200 receives the beacon (step S809: YES), the initial wireless terminal 200 proceeds to step S811, and when the initial wireless terminal 200 does not receive the beacon (step S809: NO), the process proceeds to step S810.

In step S810, the initial wireless terminal 200, which is a beacon receiving terminal, proceeds to step S809 in order to wait on the initial channel until the beacon is received.

In step S811, the initial wireless terminal 200 that has received the beacon analyzes whether or not the received beacon is the start beacon. If the received beacon is the start beacon (step S811: YES), the initial wireless terminal 200 proceeds to step S812. When the received beacon is not the start beacon (step S811: NO), the received beacon is the end beacon, so that the channel switching unit 234 of the initial wireless terminal 200 switches the communication channel to the next channel and ends the process. do. The start and end beacons contain beacon identification information.

In step S812, since the received beacon is the start beacon, the initial wireless terminal 200 sets the timer unit 236 based on the time synchronization information included in the start beacon, and waits in the reception state until the transmission frame period ends. Next, the initial wireless terminal 200 proceeds to step S813.

In step S813, the initial wireless terminal 200 determines whether or not the end beacon has been received. When the initial wireless terminal 200 receives the end beacon (step S813: YES), the communication channel is switched to the next channel after the channel switching grace period has elapsed, and the process ends. That is, when the reception of the channel switching information of the end beacon is completed, the channel switching unit 234 switches the communication channel to the next channel based on the channel switching order information after the channel switching grace period elapses, and ends the process.

When the initial wireless terminal 200 does not receive the end beacon (step S813: NO), the channel switching unit 234 switches the communication channel based on the channel switching order information at the end of the communication channel switching cycle.

The above operation is the initial operation at the time of starting the wireless terminal 200, and when the initial operation is completed, the transmission frame period has elapsed. At the time of the initial operation, the transmission operation other than the beacon is not performed.

FIG. 9 is a flowchart showing the processing after switching the communication channel. It should be noted that which communication channel the wireless terminal 200 switches to can be determined by referring to the channel switching order information of the information recording unit 250.

In step S901, the wireless terminal 200 resets the timer unit 236, sets the timer information of the information recording unit 250 to the initial value, and proceeds to step S902. As an example, the initial value is "0".

In step S902, it is determined whether or not the wireless terminal 200 is in the order of transmitting the beacon. If the wireless terminal 200 is in the order of transmitting the beacon (step S902: YES), the process proceeds to process A, and if it is not the order of transmitting the beacon (step S902: NO), the process proceeds to process B. .. Whether or not the wireless terminal 200 is in the order of transmitting the beacon can be determined by referring to the beacon transmission order information of the information recording unit 250.

10A and 10B show a flowchart of process A. The process A is a process flow in which the wireless terminal 200 is in the order of transmitting the beacon and functions as the beacon transmission terminal.

In step S1001, before the wireless terminal 200 transmits the start beacon, it is determined whether or not the reception intensity is detected by the reception intensity determination unit 221. If the reception strength is not detected (step S1001: NO), the wireless terminal 200 proceeds to step S1002, and if the reception strength is detected (step S1001: YES), the wireless terminal 200 proceeds to step S1003 and waits for reception.

In step S1002, since the reception intensity is not detected, the wireless terminal 200 transmits the start beacon, proceeds to step S1003, and enters the reception mode. In this case, the transmission request information recorded in the information recording unit 250 is transmitted as the transmission request information included in the start beacon. Further, the timer information recorded in the information recording unit 250 is transmitted as the time synchronization information included in the start beacon.

In step S1003, since the wireless terminal 200 is in the reception mode, the reception strength determination unit 221 determines whether or not the reception strength is detected. When the reception strength is detected (step S1003: YES), the wireless terminal 200 proceeds to step S1004, and when the reception strength is not detected (step S1003: NO), the radio terminal 200 proceeds to step S1007.

Since the reception strength is detected in step S1004, the wireless terminal 200 determines whether or not an ID unique to the wireless communication system is detected from the received signal. If the unique ID is detected (step S1004: YES), the wireless terminal 200 proceeds to step S1005, and if the unique ID is not detected (step S1004: NO), the wireless terminal 200 proceeds to step S1010.

In step S1005, the wireless terminal 200 determines whether or not the data information can be normally received from the received signal. If the wireless terminal 200 can normally receive the data information (step S1005: YES), the wireless terminal 200 proceeds to step S1006, and if the data information cannot be normally received (step S1005: NO), the wireless terminal 200 proceeds to step S1010. Proceed to.

Since step S1006 is a case where the wireless terminal 200 can normally receive the data information, the wireless terminal 200 transmits an Ac signal to the wireless terminal 200 that has transmitted the data information, and the process proceeds to step S1010.

Since step S1007 is a case where the reception strength of the received signal is not detected, the wireless terminal 200 determines whether or not the own wireless terminal 200 has a request for transmitting data information. If there is no transmission request for data information, or if the own wireless terminal 200 is not in the transmission order in the transmission request information transmitted by the start beacon (step S1007: NO), the wireless terminal 200 proceeds to step S1010. Further, when there is a transmission request for data information and the own wireless terminal 200 is in the transmission order in the transmission request information transmitted by the start beacon (step S1007: YES), the wireless terminal 200 proceeds to step S1008. .. Further, even when there is a transmission request for data information and all transmissions of the wireless terminal 200 included in the transmission request information transmitted by the start beacon are completed (step S1007: YES), the wireless terminal 200 also has. The process proceeds to step S1008.

Since step S1008 has data information to be transmitted to the wireless terminal 200, the wireless terminal 200 transmits the data information and proceeds to step S1009. In this case, when the transmission order of the own wireless terminal 200 is the first in the transmission request information transmitted by the start beacon, the operation related to the contention window or the like is skipped and the data information is transmitted. For example, when the transmission order of the own wireless terminal 200 is No. 1, the wireless terminal 200 transmits data information immediately after the transmission of the start beacon.

In step S1009, the wireless terminal 200 determines whether or not an Ac signal for the transmitted data information has been received. If the wireless terminal 200 does not receive the Ac signal, the wireless terminal 200 sets the retransmission flag and proceeds to step S1010. If the wireless terminal 200 receives the Ac signal, the retransmission flag is cleared and the process proceeds to step S1010. As an example, the retransmission flag is represented by 1 bit, and setting the retransmission flag to "1" is referred to as setting the retransmission flag, and setting the retransmission flag to "0" is referred to as clearing the retransmission flag. If the retransmission flag is set, a transmission request is generated in step S1007 and step S1012.

In step S1010, the wireless terminal 200 confirms the elapsed time. That is, the wireless terminal 200 transmits data information within the remaining data frame period, and confirms whether or not Ac can be received for the transmitted data information. If there is no transmittable time for transmitting data information and receiving Ac (step S1010: NO), the wireless terminal 200 proceeds to step S1011. When there is a transmittable time (step S1010: YES), the wireless terminal 200 proceeds to step S1003 in order to transmit / receive data information.

In step S1011, the wireless terminal 200 determines whether or not the reception strength is detected by the reception strength determination unit 221. When the reception strength is detected (step S1011: YES), the wireless terminal 200 proceeds to step S1014, and when the reception strength is not detected (step S1011: NO), the radio terminal 200 proceeds to step S1012.

In step S1012, the wireless terminal 200 determines whether or not there is a transmission request. If the wireless terminal 200 has a transmission request (step S1012: YES), the wireless terminal 200 proceeds to step S1013, and if there is no transmission request (step S1012: NO), the wireless terminal 200 proceeds to step S1016.

In step S1013, the wireless terminal 200 transmits an intermediate beacon. The intermediate beacon includes the identification information of the wireless terminal 200 in which the transmission request is generated and the time information indicating the time when the transmission request is generated as the transmission request information.

In step S1014, the wireless terminal 200 determines whether or not the intermediate beacon has been received. When the wireless terminal 200 receives the intermediate beacon (step S1014: YES), the wireless terminal 200 proceeds to step S1015, and when the wireless terminal 200 does not receive the intermediate beacon (step S1014: NO), the process proceeds to step S1016.

In step S1015, the wireless terminal 200 records the identification information of the wireless terminal 200 included in the intermediate beacon and the time information indicating the time when the transmission request is generated in the information recording unit 250.

When the wireless terminal 200 has not received another intermediate beacon, the transmission request in which the transmission order of the wireless terminal 200 specified by the identification information of the wireless terminal 200 included in the intermediate beacon received in step S1014 is the first. Information is recorded in the information recording unit 250.

When the wireless terminal 200 has already received another intermediate beacon, the transmission order is determined from the wireless terminal 200 having the earliest time information indicating the time when the transmission request is recorded recorded in the information recording unit 250, and transmission is performed. It is recorded in the information recording unit 250 as request information. For example, in the wireless terminal 200, the transmission order of the wireless terminal 200 having the earliest transmission request is set to the first, and the transmission order of the wireless terminal 200 having the second earliest transmission request is set to the second. Set. In this way, the wireless terminal 200 preferentially determines the transmission order in the order of the time when the transmission request is generated.

In step S1016, the wireless terminal 200 confirms the elapsed time. That is, the wireless terminal 200 confirms whether or not the intermediate beacon transmission / reception section in which the intermediate beacon can be transmitted / received has elapsed. When the intermediate beacon transmission / reception section has elapsed, it is time to transmit the end beacon. When the intermediate beacon transmission / reception section has elapsed (step S1016: YES), the wireless terminal 200 proceeds to step S1017, and when the intermediate beacon transmission / reception section has not elapsed (step S1016: NO), the radio terminal 200 proceeds to step S1011.

In step S1017, the wireless terminal 200 determines whether or not the reception strength is detected by the reception strength determination unit 221. If the reception strength is not detected (step S1017: NO), the wireless terminal 200 proceeds to step S1018. When the reception strength is detected (step S1017: YES), the wireless terminal 200 performs the channel change process without transmitting the end beacon. In this case, at the end of the communication channel switching cycle, the channel switching unit 234 switches the communication channel based on the channel switching order information.

In step S1018, since there is no interference in the communication channel, the wireless terminal 200 transmits the end beacon and performs the channel switching process after the channel switching grace period elapses. The above is the processing flow of processing A.

11A and 11B show a flowchart of process B. The process B is a process flow when the wireless terminal 200 functions as a beacon receiving terminal.

Since step S1101 is immediately after the wireless terminal 200 has switched the communication channel, the wireless terminal 200 determines whether or not the start beacon has been received from the beacon transmitting terminal. When the wireless terminal 200 receives the start beacon (step S1101: YES), the wireless terminal 200 proceeds to step S1102, and when the wireless terminal 200 does not receive the start beacon (step S1101: NO), the process proceeds to step S1103.

In step S1102, the beacon analysis unit 233 of the wireless terminal 200 analyzes the information contained in the start beacon. That is, the wireless terminal 200 rewrites the transmission request information of the information recording unit 250 to the transmission request information included in the start beacon, and sets the timer unit 236 to the time synchronization information included in the start beacon. The wireless terminal 200 that has transmitted the intermediate beacon on the immediately preceding communication channel can recognize the transmission order by referring to the rewritten transmission request information.

In step S1103, since the wireless terminal 200 is in the reception mode, the reception strength determination unit 221 determines whether or not the reception strength is detected. When the reception strength is detected (step S1103: YES), the wireless terminal 200 proceeds to step S1104, and when the reception strength is not detected (step S1103: NO), the radio terminal 200 proceeds to step S1107.

Since the reception strength is detected in step S1104, the wireless terminal 200 determines whether or not an ID unique to the wireless communication system is detected from the received signal. If the unique ID is detected (step S1104: YES), the wireless terminal 200 proceeds to step S1105, and if the unique ID is not detected (step S1104: NO), the wireless terminal 200 proceeds to step S1110.

In step S1105, the wireless terminal 200 determines whether or not the data information can be normally received from the received signal. If the wireless terminal 200 can normally receive the data information (step S1105: YES), the wireless terminal 200 proceeds to step S1106, and if the data information cannot be normally received (step S1105: NO), the wireless terminal 200 proceeds to step S1110. Proceed to.

Since step S1106 is a case where the wireless terminal 200 can normally receive the data information, the wireless terminal 200 transmits the Ac signal to the wireless terminal 200 that has transmitted the data information, and proceeds to step S1110.

Since step S1107 is a case where the reception strength of the received signal is not detected, the wireless terminal 200 determines whether or not the own wireless terminal 200 has a request for transmitting data information. If there is no transmission request for data information, or if the own wireless terminal 200 is not in the transmission order in the transmission request information received by the start beacon (step S1107: NO), the wireless terminal 200 proceeds to step S1110. Further, when there is a transmission request for data information and the own wireless terminal 200 is in the transmission order in the transmission request information received by the start beacon (step S1107: YES), the wireless terminal 200 proceeds to step S1108. .. Further, even when there is a transmission request for data information and all transmissions of the wireless terminal 200 included in the transmission request information received by the start beacon are completed (step S1107: YES), the wireless terminal 200 also has. The process proceeds to step S1108.

Since step S1108 has data information to be transmitted to the wireless terminal 200, the wireless terminal 200 transmits the data information and proceeds to step S1109. In this case, when the transmission order of the own wireless terminal 200 is the first in the transmission request information received by the start beacon, the operation related to the contention window or the like is skipped and the data information is transmitted. For example, when the transmission order of the own wireless terminal 200 is No. 1, the wireless terminal 200 transmits data information immediately after receiving the start beacon.

In step S1109, the wireless terminal 200 determines whether or not an Ac signal for the transmitted data information has been received. If the wireless terminal 200 does not receive the Ac signal, the wireless terminal 200 sets the retransmission flag and proceeds to step S1110. If the wireless terminal 200 receives the Ac signal, the retransmission flag is cleared and the process proceeds to step S1110. As an example, the retransmission flag is represented by 1 bit, and setting the retransmission flag to "1" is referred to as setting the retransmission flag, and setting the retransmission flag to "0" is referred to as clearing the retransmission flag. If the retransmission flag is set, a transmission request is generated in step S1107 and step S1112.

In step S1110, the wireless terminal 200 confirms the elapsed time. That is, the wireless terminal 200 transmits data information within the remaining data frame period, and confirms whether or not Ac can be received for the transmitted data information. If there is no transmittable time for transmitting data information and receiving Ac (step S1110: NO), the wireless terminal 200 proceeds to step S1111. When there is a transmittable time (step S1110: YES), the wireless terminal 200 proceeds to step S1103 in order to transmit / receive data information.

In step S1111, the wireless terminal 200 determines whether or not the reception strength is detected by the reception strength determination unit 221. When the reception strength is detected (step S1111: YES), the wireless terminal 200 proceeds to step S1114, and when the reception strength is not detected (step S1111: NO), the radio terminal 200 proceeds to step S1112.

In step S1112, the wireless terminal 200 determines whether or not the own wireless terminal 200 has a transmission request. If the wireless terminal 200 has a transmission request (step S1112: YES), the wireless terminal 200 proceeds to step S1113, and if there is no transmission request (step S1112: NO), the wireless terminal 200 proceeds to step S1116.

In step S1113, the wireless terminal 200 transmits an intermediate beacon. The intermediate beacon includes the identification information of the wireless terminal 200 in which the transmission request is generated and the time information indicating the time when the transmission request is generated as the transmission request information.

In step S1114, the wireless terminal 200 determines whether or not the intermediate beacon has been received. When the wireless terminal 200 receives the intermediate beacon (step S1114: YES), the wireless terminal 200 proceeds to step S1115, and when the wireless terminal 200 does not receive the intermediate beacon (step S1114: NO), the process proceeds to step S1116.

In step S1115, the wireless terminal 200 records the identification information of the wireless terminal 200 included in the intermediate beacon and the time information indicating the time when the transmission request is generated in the information recording unit 250.

When another intermediate beacon is not received, the transmission request information in which the transmission order of the wireless terminal 200 specified by the identification information of the wireless terminal 200 included in the intermediate beacon received in step S1114 is the first is recorded. Record in section 250.

When the wireless terminal 200 has already received another intermediate beacon, the transmission order is determined from the wireless terminal 200 having the earliest time information indicating the time when the transmission request is recorded recorded in the information recording unit 250, and transmission is performed. It is recorded in the information recording unit 250 as request information. For example, in the wireless terminal 200, the transmission order of the wireless terminal 200 having the earliest transmission request is set to the first, and the transmission order of the wireless terminal 200 having the second earliest transmission request is set to the second. Set. In this way, the wireless terminal 200 preferentially determines the transmission order in the order of the time when the transmission request is generated.

In step S1116, the wireless terminal 200 confirms the elapsed time. That is, the wireless terminal 200 confirms whether or not the intermediate beacon transmission / reception section in which the intermediate beacon can be transmitted / received has elapsed. When the intermediate beacon transmission / reception section has elapsed, it is time to transmit the end beacon. When the intermediate beacon transmission / reception section has elapsed (step S1116: YES), the wireless terminal 200 proceeds to step S1117, and when the intermediate beacon transmission / reception section has not elapsed (step S1116: NO), the radio terminal 200 proceeds to step S1111.

In step S1117, the wireless terminal 200 determines whether or not the end beacon is received. If the end beacon is received (step S1117: YES), the wireless terminal 200 proceeds to step S1118. When the end beacon is not received (step S1117: NO), the wireless terminal 200 performs a channel change process. In this case, at the end of the communication channel switching cycle, the channel switching unit 234 switches the communication channel based on the channel switching order information.

In step S1118, the wireless terminal 200 records the transmission request information included in the end beacon in the information recording unit 250. Next, the channel change process is performed. The above is the processing flow of processing B.

(Overview of channel switching order)
Next, an outline of the channel switching order will be described with reference to FIG.

FIG. 12 is a diagram showing the switching order indicated by the channel switching order information recorded in the information recording unit 250, and the communication channels are switched in the order of CH1 → CH2 → CH3. The number of communication channels may be any number as long as it is two or more channels. Further, the channel switching order may be uniformly defined for all wireless terminals 200, and the channel switching order can be arbitrarily set by the wireless communication system. Similarly, the initial channel may be uniformly defined for all wireless terminals 200, and any communication channel may be the initial channel. The channel switching order is recorded in the information recording unit 250 as channel switching order information.

If the wireless terminal 200 cannot receive the start beacon and the end beacon consecutively a specified number of times, the wireless terminal 200 stops switching the communication channel, returns to the initial channel, and initially receives the start beacon or the end beacon. Wait on the channel. The specified number of times can be set to any value by the wireless communication system.
For example, if the wireless terminal 200 cannot receive the start beacon and the end beacon in the order of CH3, CH1, and CH2 in any of the communication channels, it returns to CH1 which is the initial channel until the start beacon and the end beacon can be received. And wait.

(Correction method for synchronization deviation)
Next, a method for correcting the synchronization deviation will be described.
Since each wireless terminal 200 has a timer unit 236, the frequency channel can be regularly switched in a predetermined channel switching cycle (Tms) including the transmission / reception period of the start beacon and the transmission / reception period of the end beacon. .. However, it is basically synchronized by receiving the start beacon and the end beacon.

On the other hand, in addition to the case where the wireless terminal cannot receive the beacon due to interference or the like, there is a possibility that the channel switching timing may be too early or too late due to the deviation of the clock frequency of the timer unit 236 or the like.

Therefore, FIG. 13 shows a procedure for resynchronization by receiving a beacon.

The beacon receiving terminal 1301 of FIG. 13 is a diagram showing a case where the channel switching timing from CH1 to CH2 is too early. In this case, the beacon receiving terminal 1301 receives the start beacon at the normal timing on the channel switching destination CH2, and sets the timer unit 236 of the beacon receiving terminal 1301 as the time synchronization information of the start beacon to other wireless terminals. It can be resynchronized with 200. That is, since the time synchronization information is included at the end of the start beacon, the beacon receiving terminal 1301 rewrites the timer unit 236 to the time synchronization information of the start beacon when the reception of the start beacon is completed. As a result, synchronization can be achieved between the wireless terminal 200 that has transmitted the start beacon and the wireless terminal 200 that has received the start beacon.

The beacon receiving terminal 1302 of FIG. 13 is a diagram showing a case where the channel switching timing from CH1 to CH2 is too late. In this case, the beacon receiving terminal 1302 can receive the end beacon at the normal timing on the channel switching destination CH2. Therefore, the beacon receiving terminal 1302 can switch to CH3 and resynchronize with another wireless terminal after the channel switching grace period has elapsed from the completion of reception of the ending beacon based on the CH switching information included at the end of the ending beacon. ..

As shown in FIG. 13, when a deviation within the channel switching cycle (Tms), which is a predetermined transmission frame length, occurs, the wireless terminal 200 starts a beacon or ends at the channel to which it is switched. By receiving the beacon, it is possible to resynchronize with another wireless terminal 200. If the synchronization is out of sync for a time of Tms or longer, the wireless terminal 200 waits on the initial channel until the beacon can be received, as described above.

FIG. 14 shows an intermediate beacon transmission / reception section in which an intermediate beacon can be transmitted / received. The intermediate beacon transmission / reception section is a period during which the reception of the response signal to the data information from the transmission of the data information on the communication channel cannot be completed before the transmission / reception of the end beacon. In FIG. 14, the transmission / reception section of the intermediate beacon is theoretically until the wireless terminal 200 transmits data information for convenience and the reception of the Ac transmitted by the other wireless terminal 200 that has received the data information can be completed. It is a period and is shown as a fixed length.

The reason is that, in reality, synchronization between wireless terminals 200 rarely completely matches in units of CPU clocks, and there is a high possibility that transmission delay of wireless signals will occur. Therefore, the theoretical reason of FIG. The period is the transmission / reception section of the intermediate beacon.

As described above, all wireless terminals 200 set the above-mentioned predetermined fixed-length intermediate beacon transmission / reception section. Then, if a transmission request is made to the wireless terminal 200 while the timer information indicates the intermediate beacon transmission / reception section, the intermediate beacon is used to transmit the data information on the next communication channel without transmitting the data information. To send.

The intermediate beacon includes identification information of the wireless terminal 200 that transmits the intermediate beacon and time information when a transmission request is generated. The time information at which the transmission request is generated is based on the reception time of the start beacon immediately before the transmission request is generated.

The beacon transmitting terminal that has transmitted the start beacon receives the intermediate beacon, and which wireless terminal 200 has the right to transmit in the next communication channel in order from the wireless terminal 200 having the earliest transmission request. To determine the information. That is, the wireless terminal 200 that has transmitted the start beacon determines the transmission order in the next communication channel of the wireless terminal 200 that has transmitted the intermediate beacon, and associates the transmission order information with the identification information of the wireless terminal 200. The transmission request information is transmitted by the end beacon.

If the beacon transmission terminal of the next communication channel can receive the transmission request information of the end beacon of the beacon transmission terminal of the previous communication channel, the transmission request information is included in the start beacon and broadcast.

However, if the beacon transmitting terminal of the next communication channel cannot receive the transmission request information of the end beacon of the beacon transmitting terminal of the previous communication channel, the transmission request information is newly created.

That is, the beacon transmission terminal of the next communication channel newly creates transmission request information based on the intermediate beacon received in the previous communication channel, includes the transmission request information in the start beacon, and broadcasts the information.

As described above, according to this embodiment. Each wireless terminal can operate independently without installing a control station.
Further, since all the wireless terminals regularly change the frequency channel for communication, it is not necessary to wait for a long time on the same frequency channel, and it is not necessary to carrier sense the entire frequency band before the start of communication.
Further, since the frequency band used is unified for all wireless terminals, it is not necessary to estimate the frequency band used for transmission by correlation.
Further, even if there is a transmission request other than the beacon transmission terminal, priority transmission can be performed by the intermediate beacon, so that all wireless terminals can communicate efficiently.
Further, even if only a specific wireless terminal is interfered with, the channel is automatically switched, so that it is possible to synchronize with another wireless terminal by receiving the beacon of the channel switching destination.
Further, since synchronization is performed by the first and last two beas of the transmission frame, if there is a deviation within the transmission frame length, the beacon can be resynchronized. Moreover, even if the synchronization cannot be completely achieved, the device waits on the initial channel, so that it can be resynchronized with another wireless terminal.

(Modification 1)
In FIG. 1, all wireless terminals are included in the wireless communication network, but as shown in FIG. 15, there may be wireless terminals that cannot directly communicate with each other. In this case, a wireless communication network can be formed by using relay transmission.

For example, a case where the wireless terminal 11 belonging to the wireless communication network 1501 is a beacon transmitting terminal will be described. The wireless terminal 14 that has received the start beacon and / or the end beacon transmitted by the wireless terminal 11 relays the start beacon and / or the end beacon to the wireless terminals 15 to 20 that do not belong to the wireless communication network 1501. Alternatively, the wireless terminal 12 or 13 that has received the start beacon and / or the end beacon transmitted by the wireless terminal 11 relays and transmits to the wireless terminals 15 to 17, and the wireless terminal 17 relays the start beacon and / or to the wireless terminals 18 to 20. Relay the end beacon.

In this way, by using the relay transmission, one wireless communication network can be formed by the wireless communication network 1501, the wireless communication network 1502, and the wireless communication network 1503.

(Modification 2)
When a wireless communication network is formed in a vehicle, the above-mentioned communication control method can be adopted for all wireless terminals in the vehicle. As a result, it is possible to construct a wireless communication network that copes with interference from other wireless communication systems outside the vehicle and interference from other wireless terminals and wireless devices brought into the same vehicle. Further, regardless of the inside of the vehicle, the above-mentioned communication control method can be similarly adopted for wireless devices such as factories. As the wireless communication method, a method other than the CSMA / CA method can also be adopted.

(Modification 3)
As described above, the intermediate beacon includes the identification information of the wireless terminal 200 that transmits the intermediate beacon and the time information that the transmission request is generated, and the time information that the transmission request is generated is immediately before the transmission request is generated. Based on the reception time of the start beacon. However, it is also possible to include the priority in the data information in which the transmission request is generated. For example, in wireless communication in a vehicle, the wireless terminal 200 needs to transmit data information related to vehicle control earlier than data information such as music data. In such a case, it is preferable that the wireless terminal 200 grants the transmission right according to the importance of the data information rather than granting the transmission right in the next communication channel in the order of the time when the transmission request occurs. Therefore, it is preferable that the intermediate beacon contains information related to the priority.

For example, the wireless terminal 200 includes a priority information bit in the intermediate beacon, sets the priority information bit to "1" for a transmission request having a high priority, and priority information for a transmission request having a low priority. Set the bit to "0" to send an intermediate beacon.

The wireless terminal 200 that has received the intermediate beacon determines the transmission order in the order of the generation time of the transmission request from the transmission requests whose priority information bit is set to "1". Next, the wireless terminal 200 that has received the intermediate beacon determines the transmission order in the order of the transmission request occurrence time from the transmission requests whose priority information bits are set to "0".

In this way, the wireless terminal 200 can reduce the delay of important data information such as control information by including the priority information of the data information for which the transmission request has occurred in the intermediate beacon. The priority information does not have to be one bit, and the priority information may be composed of a plurality of bits and three or more priorities may be set.

(Modification example 4)
In the third modification, the priority information bit is added to the intermediate beacon, but the emergency information bit having the highest priority can be further added to the intermediate beacon.

For example, in order to avoid a situation related to a vehicle accident or the like, it may be necessary to send and receive data information for controlling the vehicle with the highest priority. In such a case, the intermediate beacon includes the emergency information bit, the emergency information bit is set to "1" for the transmission request having the highest priority, and the emergency information bit is set to "0" for the other transmission requests. Set to "Send an intermediate beacon."

The wireless terminal 200 that has received the intermediate beacon preferentially determines the transmission order of the transmission request in which the emergency information bit is set to "1". Therefore, the wireless terminal 200 in which the emergency information bit is set to "1" can preferentially transmit data information on the next communication channel.

In this way, the emergency information bit enables preferential transmission / reception of data information for controlling the vehicle in order to avoid a situation related to a vehicle accident or the like.

(Modification 5)
In the embodiment, as shown in FIG. 3, an example in which all the wireless terminals 200 included in the wireless communication system become beacon transmission terminals in order based on the beacon transmission order information has been mainly described. However, there are cases where only some of the wireless terminals 200 included in the wireless communication system are beacon transmission terminals.

For example, the radio waves of the wireless terminal 200 at the front or the rear of the vehicle may be difficult to reach the wireless terminal 200 at the rear or the front of the vehicle. In such a case, if the state in which the start beacon and the end beacon cannot be received continues, synchronization deviation is likely to occur, and communication delay may occur.

Therefore, among the wireless terminals 200 included in the wireless communication system, only the wireless terminal 200 within a predetermined range from the midpoint on the line where the distance between the wireless terminals 200 is the longest can be used as the beacon transmission terminal.

The wireless communication system can have any value within the predetermined range. As an example, the wireless communication system can set the predetermined range to 1 / n of the vehicle length (n is a natural number of 3 or more). In this way, by using only the wireless terminal 200 in the central part of the vehicle as the beacon transmitting terminal, the beacon receiving terminal can easily receive the start beacon and the end beacon, and the occurrence of communication delay is suppressed. Further, among the wireless terminals 200 in the central part of the vehicle, only the wireless terminal 200 having the best communication state can be used as the beacon transmission terminal. For example, only the wireless terminal 200 having the largest CNR (Carrier to Noise Ratio) in the wireless communication system can be used as the beacon transmission terminal.

Although various examples have been described above, some or all of these examples can be combined into new examples.

The present invention is extremely useful in a wireless network that controls communication to avoid an increase in communication delay time due to radio wave interference with another wireless communication system.

200 ... Wireless terminal 210 ... Communication unit 211 ... Transmission / reception switching unit 212 ... Wireless transmission unit 213 ... Wireless reception unit 220 ... Judgment unit 221 ... Reception strength determination unit 222 ... Interference determination unit 230 ... Control unit 231 ... Beacon generation unit 232 ... Data generation unit 233 ... Beacon analysis unit 234 ... Channel switching unit 235 ... Data processing unit 236 ... Timer Part 240 ・ ・ ・ I / F (interface) part 250 ・ ・ ・ Information recording part

Claims (10)

A beacon transmission terminal of a wireless communication system in which one of a plurality of wireless terminals is used as a beacon transmitting terminal in a predetermined order each time a communication channel is switched, and the remaining wireless terminals are used as beacon receiving terminals.
A beacon generator that generates start beacons, intermediate beacons, and end beacons,
A communication unit that transmits and receives the start beacon, data information, the intermediate beacon, and the end beacon.
A timer unit that measures the switching cycle of the communication channel of the communication unit, and a timer unit.
A channel switching unit that switches the communication channel of the communication unit according to a predetermined rule according to the switching cycle of the communication channel is included.
The beacon generation unit includes the timer information measured by the timer unit as time synchronization information in the start beacon, and includes channel switching information indicating the timing of switching the communication channel in the end beacon, and transmits / receives an intermediate beacon. When a transmission request is generated in the section, an intermediate beacon which is time information indicating the time when the transmission request is generated and includes the time information measured by the timer unit is generated.
The communication unit transmits the start beacon before the start of transmission / reception of the data information, transmits the intermediate beacon when a transmission request is generated in the intermediate beacon transmission / reception section, and after the end of transmission / reception of the data information. Send an end beacon,
At the end of the communication channel switching cycle, the channel switching unit switches the communication channel based on the predetermined rule and resets the timer unit.
The intermediate beacon transmission / reception section is a beacon transmission terminal characterized in that the reception of a response signal to the data information from the transmission of the data information on the communication channel cannot be completed before the transmission of the end beacon. Based on the time information in which the transmission request was generated included in the intermediate beacon transmitted / received by the communication unit, the beacon generation unit transmits data information in the next communication channel in the order of the time information in which the transmission request was generated. The beacon transmission terminal according to claim 1, wherein the transmission order of the wireless terminals to be transmitted is determined, and the transmission order information and the identification information of the wireless terminal are included in the end beacon as transmission request information. When the communication unit receives the end beacon of the immediately preceding communication channel, the beacon generation unit uses the transmission request information included in the end beacon as the transmission request information included in the start beacon.
When the communication unit cannot receive the end beacon of the immediately preceding communication channel, the beacon generation unit is based on the time information in which the transmission request included in the intermediate beacon transmitted / received on the immediately preceding communication channel is generated. The transmission order of the wireless terminal for transmitting the data information is determined in the time order of the time information in which the transmission request is generated, and the transmission order information and the identification information of the wireless terminal are included in the start beacon as the transmission request information. The beacon transmission terminal according to claim 2, which is characterized by this. 6. Beacon transmission terminal. The intermediate beacon further includes priority information indicating the priority of the data information, and the data information having a higher priority of the priority information than the transmission order of the data information having a lower priority of the priority information. Any of claims 2 to 4, wherein the data information having an earlier transmission order and the same priority of the priority information is determined in the time order of the time information in which the transmission request is generated. Beacon transmission terminal described in. Each time the communication channel is switched, one of the plurality of wireless terminals is used as a beacon transmission terminal in a predetermined order. The beacon transmission terminal according to any one of claims 1 to 5, wherein the wireless terminal within a predetermined range from the midpoint on the line having the longest distance is determined. A beacon receiving terminal of a wireless communication system in which one of a plurality of wireless terminals is used as a beacon transmitting terminal in a predetermined order each time a communication channel is switched, and the remaining wireless terminals are used as a beacon receiving terminal.
Beacon generator that generates intermediate beacons and
A communication unit that receives a start beacon and an end beacon and transmits / receives data information and the intermediate beacon.
A timer unit that measures the switching cycle of the communication channel of the communication unit, and a timer unit.
A channel switching unit that switches the communication channel of the communication unit according to a predetermined rule according to the switching cycle of the communication channel is included.
When the communication unit receives the start beacon, the timer unit sets the time synchronization information included in the start beacon in the timer unit.
When the communication unit receives the end beacon, the channel switching unit switches the communication channel after a predetermined period after receiving the channel switching information indicating the timing for switching the communication channel included in the end beacon. , Reset the timer section,
When a transmission request is generated in the intermediate beacon transmission / reception section, the beacon generation unit generates time information indicating the time when the transmission request is generated, and generates an intermediate beacon including the time information measured by the timer unit. ,
The intermediate beacon transmission / reception section is a beacon receiving terminal characterized in that the reception of a response signal to the data information from the transmission of the data information on the communication channel cannot be completed before the reception of the end beacon. When the transmission order of the beacon receiving terminal becomes the first based on the transmission order information included in the start beacon, the data information is transmitted without a waiting time after receiving the start beacon. The beacon receiving terminal according to claim 7. When the communication unit does not receive the start beacon and the end beacon continuously on all communication channels, the channel switching unit is the communication channel set at the beginning of the switching order of the communication channels, and the start beacon is used. The beacon receiving terminal according to claim 7 or 8, wherein the beacon receiving terminal waits for the reception of the end beacon. The beacon transmission terminal according to any one of claims 1 to 6 and
A wireless communication system comprising the beacon receiving terminal according to any one of claims 7 to 9.

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