JP5267473B2 - Wireless communication apparatus and program, and communication system - Google Patents

Description

  The present invention relates to a wireless communication device, a program, and a communication system, and can be applied to a communication system that performs multi-hop communication with a plurality of wireless communication devices, for example.

  In recent years, a multi-hop wireless communication technology for performing communication via other wireless communication devices has been put into practical use, and sensor networks using the technology are becoming widespread. For example, IEEE 802.15.4 (see Non-Patent Document 1) is well known as an international standard for wireless systems for sensor networks, and is widely used in combination with network systems such as ZigBee.

  On the other hand, the 2.4 GHz band was mainstream in Japan as the frequency band that can use the sensor network, but the 950 MHz band that was assigned to the RFID (Radio Frequency IDentification) passive tag system due to the revision of the Radio Law in 2008. Also became available.

  If wireless communication is performed simultaneously at the same frequency (channel), radio wave interference occurs and communication cannot be performed correctly. For this reason, a technology called “carrier sense” that confirms that other systems do not use the frequency (channel) before transmission is defined in many standards including IEEE 802.15.4. As a radio wave method, it is essential to perform carrier sense in the 950 MHz band.

  Also, if multiple wireless communication devices start carrier sense at the same time, they will recognize that each other's wireless communication device is not using them and start transmission at the same time, causing radio wave interference despite carrier sense. There is a problem of doing.

  For example, in response to transmission of an initial signal (for example, a beacon request) in broadcast communication (broadcast or multicast) from one wireless communication device to another wireless communication device, two or more received the initial signal A case is assumed in which the wireless communication apparatus responds by unicast (beacon transmission) at the same time, or the initial signal is relayed to the next wireless communication apparatus by unicast, broadcast, or multicast. In this case, the transmission timings of the wireless communication apparatuses that have received the initial signal by the broadcast communication are likely to coincide with each other, and a lot of radio wave interference as described above occurs. In order to solve this problem, standards such as IEEE802.15.4 avoid radio wave interference by waiting for a random time called “random backoff” before carrier sense.

  FIG. 9 is a timing chart showing an operation of data transmission / reception by a wireless communication apparatus that does not support conventional random backoff.

  FIG. 10 is a timing chart showing a data transmission / reception operation by a wireless communication apparatus compatible with conventional random backoff.

  In FIG. 9 and FIG. 10, data of the initial signal (beacon request) is transmitted by broadcast from the wireless communication device A to the wireless communication devices B1 and B2, and unicast from the wireless communication devices B1 and B2 to the wireless communication device A, respectively. Shows an example of transmitting response (beacon) data.

  When the wireless communication devices B1 and B2 do not support random backoff, as shown in FIG. 9, after receiving the initial transmission of the broadcast from the wireless communication device A, the wireless communication devices B1 and B2 simultaneously receive carriers. Since sensing starts and transmission is performed at the same time, radio wave interference occurs.

  On the other hand, when the wireless communication devices B1 and B2 support random backoff, as shown in FIG. 10, the wireless communication devices B1 and B2 perform carrier sense after waiting for a random time. Since the wireless communication device B1 has a short back-off time, the carrier sense is started and transmitted immediately after a short standby, but the wireless communication device B2 has a longer back-off time than the B1, so the carrier sense is performed after a long standby. I do. At this time, since the wireless communication device B1 has already started transmission, the carrier sense of the wireless communication device B2 has failed and does not start transmission. When the wireless communication device B2 fails in carrier sense, it performs random backoff again and repeats carrier sense. In IEEE802.15.4 and the like, when a predetermined number of carrier senses are continuously failed, the back-off time is changed to be longer, and the standby time is gradually increased. Random backoff and carrier sense are repeated up to a predetermined maximum number of carrier senses, and transmission is started when carrier sense is successful. As a result, the wireless communication devices B1 and B2 can transmit by shifting the reply to the wireless communication device A without causing radio wave interference.

Tatetsu, “ZigBee Development Handbook”, Rick Telecom, February 22, 2006

  In standards such as IEEE 802.15.4, the carrier sense time (about 100 microseconds) and the backoff time (about several milliseconds) are set smaller than the transmission time (about several tens of milliseconds). It can operate stably without increasing the overall transmission delay so much.

  However, in the Japanese law, in the 950 MHz band, considering the influence on the RFID passive tag system sharing the same frequency band, it is 100 as compared with a standard such as IEEE 802.15.4, which is 10 milliseconds or more. Since the carrier sense time that is twice as long is specified, it leads to a large transmission delay and the power consumption of each wireless communication device also increases.

  FIG. 11 is a timing chart illustrating an example in which a long carrier sense leads to a large transmission delay in a conventional wireless communication apparatus that supports random backoff and has a long carrier sense time.

  FIG. 11 shows an example in which data is transmitted from the wireless communication device A by broadcast to the wireless communication devices B1 to B3, and response data is transmitted from the wireless communication devices B1 to B3 to the wireless communication device A by unicast. ing.

  In FIG. 11, transmission is performed in order from a wireless communication device having a short random back-off time, and a delay of [(number of devices × carrier sense time) + delay due to random back-off timing] occurs as a whole. In addition, since the reception function is used during carrier sense, power consumption increases, but a device with a large random backoff repeats long carrier sense many times, and power consumption is wasted.

  In IEEE 802.15.4, when a wireless communication apparatus connects to a relay apparatus (router), a “beacon request” is made, and the connection destination is selected by comparing the beacon quality returned from the router. However, the beacon from the router is stipulated that if the carrier sense fails once, the transmission is stopped without inserting the backoff and performing the second carrier sense. Therefore, despite the provisions for random backoff, it is not possible to receive beacons from multiple routers, and only the router with the smallest backoff random number will send a beacon, leading to poor quality routers. End up.

  In view of the above, in a communication system in which a plurality of receiving-side wireless communication devices each perform data transmission based on broadcast communication from a transmitting-side wireless communication device, it is possible to efficiently transmit and receive data. A communication device and program, and a communication system are desired.

The wireless communication device according to the first aspect of the present invention (1), when receiving predetermined broadcast data transmitted by broadcast communication from the transmission-side wireless communication device, transmits transmission data in response to reception of the broadcast data. (2) carrier sensing means for performing carrier sensing at least once after the broadcast data is received until the data transmitting means transmits the transmission data; and (3) at least the data transmission means transmitting unit time including such transmission time for the transmission of the transmission data and, by using the random value, the data transmission means have a timing control means for controlling the timing of data transmission, (4) When reception of the broadcast data is completed, the timing control means starts carrier sense by the carrier sense means, and the carrier sense ends. From after a time obtained by multiplying the random value to the transmission unit time, characterized in that to start the transmission of the transmission data to the data transmission means.
When the wireless communication device of the second aspect of the present invention receives (1) predetermined broadcast data transmitted by broadcast communication from the wireless communication device on the transmission side, (2) transmission according to reception of the broadcast data. Data transmission means for transmitting data, and (3) carrier sense means for performing carrier sense at least once after the broadcast data is received until the data transmission means transmits the transmission data; (4) Timing control means for controlling the timing at which the data transmission means transmits data using at least a transmission unit time including a transmission time required for transmission of the transmission data and a random value. (5) The carrier sense means performs carrier sense for a first carrier sense time at the end of reception of the broadcast data, and further sends data to the data transmission means. Immediately before data transmission, carrier sense is performed for a second carrier sense time shorter than the first carrier sense time. (6) The transmission unit time includes the transmission time and the second carrier sense time. (7) When the reception of the broadcast data is completed, the timing control unit causes the carrier sense unit to start carrier sense of the first carrier sense time, and the carrier sense After the elapse of time, the carrier sense means starts carrier sense for the second carrier sense time after elapse of the time obtained by multiplying the transmission unit time by the random value, and after the carrier sense ends, the data transmission And means for starting transmission of the transmission data.

The wireless communication program according to the third aspect of the present invention allows a computer installed in a wireless communication apparatus to (1) receive the predetermined broadcast data transmitted by broadcast communication from the wireless communication apparatus on the transmission side, Data transmission means for transmitting transmission data in response to data reception; and (2) one or more carrier senses from when the broadcast data is received until the data transmission means transmits the transmission data. Carrier sensing means for performing data transmission, and (3) using the transmission unit time including a transmission time required for transmission of the transmission data by the data transmission means and a random value to determine the timing at which the data transmission means transmits data. to function as a control for the timing control means, (4) the timing control means, when the reception of the broadcast data is completed, according to the carrier sense unit Yariasensu to start, after completion of the carrier sense after the elapse of time obtained by multiplying the random value to the transmission unit time, and wherein the Rukoto to initiate transmission of the transmission data to the data transmission means.
The wireless communication program according to the third aspect of the present invention allows a computer installed in a wireless communication apparatus to (1) receive the predetermined broadcast data transmitted by broadcast communication from the wireless communication apparatus on the transmission side, Data transmission means for transmitting transmission data in response to data reception; and (2) one or more carrier senses from when the broadcast data is received until the data transmission means transmits the transmission data. Carrier sensing means for performing data transmission, and (3) using the transmission unit time including a transmission time required for transmission of the transmission data by the data transmission means and a random value to determine the timing at which the data transmission means transmits data. (4) The carrier sense means performs a first carrier sense time at the end of reception of the broadcast data. Further, immediately before data transmission by the data transmission means, carrier sense is performed for a second carrier sense time shorter than the first carrier sense time, and (5) the transmission unit time is: (7) When the timing control means finishes receiving the broadcast data, the timing control means sends the first carrier sense time to the carrier sense means. Carrier sense is started, and after the completion of the carrier sense, the carrier sense means starts carrier sense for the second carrier sense time after elapse of time obtained by multiplying the transmission unit time by the random value. Then, after the end of the carrier sense, the data transmission means starts transmission of the transmission data .

In the communication system of the fifth aspect of the present invention, in the communication system having a plurality of first wireless communication apparatuses, the wireless communication apparatus of the first or second aspect of the present invention is applied as the first wireless communication apparatus. Features.

  According to the present invention, it is possible to efficiently transmit and receive data in a communication system in which a plurality of receiving-side wireless communication devices perform data transmission based on broadcast communication from a transmitting-side wireless communication device.

It is the block diagram shown about the functional structure of the radio | wireless communication apparatus which concerns on 1st Embodiment. 1 is a block diagram showing an overall configuration of a communication system according to a first embodiment. 3 is a timing chart illustrating the operation of each wireless communication device in the communication system according to the first embodiment. 6 is a timing chart showing the operation of each wireless communication device in a modified embodiment of the first embodiment. It is the block diagram shown about the functional structure of the radio | wireless communication apparatus which concerns on 2nd Embodiment. 6 is a timing chart showing the operation of each wireless communication device in the communication system according to the second embodiment. It is the timing chart (1) shown about operation | movement of each radio | wireless communication apparatus in the deformation | transformation embodiment of 2nd Embodiment. It is the timing chart (2) shown about operation | movement of each radio | wireless communication apparatus in the deformation | transformation embodiment of 2nd Embodiment. It is the timing chart which showed the operation | movement of the data transmission / reception by the radio | wireless communication apparatus which does not respond | correspond to the conventional random backoff. It is the timing chart which showed the operation | movement of the data transmission / reception by the radio | wireless communication apparatus corresponding to the conventional random backoff. It is the timing chart which showed the operation | movement of the data transmission / reception by the conventional radio | wireless communication apparatus with long carrier sense time.

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

(A-1) Configuration of the First Embodiment FIG. 2 is an explanatory diagram showing the overall configuration of the communication system 1 of the first embodiment. In FIG. 2, the reference numerals in parentheses are used only in the second embodiment to be described later.

  The communication system 1 includes a wireless communication device 200 and three wireless communication devices 100 (100-1 to 100-3). Note that the number of wireless communication devices 100 and 200 is not limited. Each wireless communication device in the communication system 1 may perform multi-hop communication.

  The wireless communication device 200 transmits data of an initial signal (for example, a beacon request) to the wireless communication devices 100-1 to 100-3 by broadcast communication such as broadcast or multicast.

  The wireless communication devices 100-1 to 100-3 receive an initial signal (for example, a beacon request) and return response data (for example, a beacon to the beacon request) to the wireless communication device 200 by unicast. However, the wireless communication apparatuses 100-1 to 100-3 relay the data received from the wireless communication apparatus 200 to another plurality of wireless communication apparatuses (not shown) by unicast, broadcast, or multicast (for example, the received beacon request is transmitted). Further, relay transmission may be performed by broadcast communication).

  Note that the carrier sense time supported by each wireless communication device of the communication system 1 is not limited. However, here, as an example, the long carrier sense time (10 ms or more), which is limited for communication in the 950 MHz band by Japanese law. ). For communication specifications (including beacon requests and beacon formats) other than the characteristic portions of the present invention, such as carrier sense time in each wireless communication apparatus, data transmission and carrier sense timing described below, and the like, for example, IEEE802. You may make it apply the thing corresponding to existing standards, such as 15.4.

  In FIG. 2, the wireless communication apparatus 200 includes a configuration that transmits an initial signal to the wireless communication apparatuses 100-1 to 100-3 by broadcast communication (here, it is assumed that it is broadcast). -1 to 100-3 are assumed to have a configuration in which a response signal to the received initial signal is transmitted to the wireless communication apparatus 200 by unicast. In the communication system 1, all wireless communication devices transmit an initial signal to another wireless communication device by broadcast communication, and when an initial signal using broadcast communication is received, a response signal to the initial signal is transmitted. You may make it provide both the structures to perform. However, in FIG. 2, to simplify the description, it is assumed that the wireless communication device 200 has a configuration on the side of transmitting an initial signal, and the configuration of the side on which the wireless communication device 100 receives and responds to an initial signal.

  FIG. 1 is a block diagram illustrating a functional configuration of the wireless communication device 100.

  The wireless communication devices 100-1 to 100-3 all have the same configuration, and are each shown in FIG.

  Here, the wireless communication device 100 includes, for example, an information processing device having an execution configuration of a program such as a CPU, ROM, RAM, EEPROM, and hard disk, and an interface for communicating with other communication devices. A wireless communication program or the like may be installed and constructed. Note that the wireless communication apparatus 200 may also be constructed by installing the wireless communication program of the embodiment (configuration required on the side that transmits the initial signal by broadcast communication) in the same information processing apparatus.

  The wireless communication apparatus 100 includes a transmission data identification unit 101, a standby time control unit 102, a transmission unit 103, a carrier sense control unit 104, and a reception unit 105.

  The transmission data identification unit 101 determines whether the data to be transmitted by the wireless communication device 100 is normal transmission data (for example, data to be transmitted based on control of an upper layer not shown) or other wireless communication device It is identified whether it is return data (beacon) or relay data (relay transmission of beacon request) in response to an initial signal (beacon request) by broadcast communication. Then, when the data to be transmitted is return or relay data, the transmission data identification unit 101 calculates the transmission time of the data and passes it to the standby time control unit 102, and passes the transmission data to the transmission unit 103. Is. Here, the transmission time is not calculated every time, but a value calculated in advance or a predetermined value may be passed.

  The standby time control unit 102 controls the standby time until the wireless communication device 100 starts data transmission next time.

  The standby time control unit 102 generates a random value, and sets [the sum of the carrier sense time and the transmission time obtained from the transmission data identification unit 101] as one unit time, and determines the standby time obtained from [random value × unit time]. Calculate and give to the transmission unit 103.

  The range of the random value generated by the standby time control unit 102 is not limited, but here, the range between the minimum value 0 and a predetermined maximum value is a random value range.

  Here, it is desirable that the maximum random value is larger than the number of wireless communication devices in the vicinity of the radio wave receiving range of the wireless communication device 100. In practice, for example, a value such as 16 or 32 is specified. Anyway.

  Further, when the carrier sense NG is notified from the transmission unit 103, a random standby time is calculated again and given to the transmission unit 103.

  Here, when retrying, considering that some of the other wireless communication devices 100 have already been transmitted, the standby time calculation for the second and subsequent times was used for the first calculation. The maximum random value may be reduced to half.

  The transmission unit 103 performs transmission control and transmission of data to be transmitted by the wireless communication apparatus 100.

  The transmission unit 103 stops transmission for the standby time given from the standby time control unit 102, and then notifies the carrier sense start to the carrier sense control unit 104 and receives a carrier sense completion notification from the carrier sense control unit 104. Later, the transmission data received from the transmission data identification unit 101 is transmitted.

  When the carrier sense NG is notified from the carrier sense control unit 104, the transmission unit 103 receives the standby time from the standby time control unit 102 again, and notifies the carrier sense control unit 104 of the carrier sense after waiting for the standby time. Transmit after successful carrier sense. When the carrier sense NG is continued many times, the above process is repeated up to the upper limit.

  In response to a request from the transmission unit 103, the carrier sense control unit 104 controls the reception unit 105 to perform carrier sense processing, and returns a result of the carrier sense to the transmission unit 103.

  Upon receiving an instruction to start carrier sense from the transmission unit 103, the carrier sense control unit 104 receives reception data from the reception unit 105, confirms that a signal having a preset reception level or higher has not been received for a certain period of time, The transmission unit 103 is notified of the completion of carrier sense. When a signal having a reception level or higher set within a certain time is received, the carrier sense NG is notified to the transmission unit 103, and when it is not, the carrier sense OK is notified.

  The receiving unit 105 takes in a signal based on radio waves received by an antenna (not shown) and outputs received data based on the signal. When there is a carrier sense instruction from the carrier sense control unit 104, carrier sense is started.

  The carrier sense performed by the receiving unit 105 may be the same procedure as that of an existing wireless communication apparatus. Here, the reception level confirmation performed by the reception unit 105 may be performed all at once for a certain period of time, or it may be confirmed in a short time and carrier sense may be continued when there is no signal. Also good. By checking every short time, carrier sense NG can be detected early.

(A-2) Operation of the First Embodiment Next, the operation of the communication system 1 of the first embodiment having the above configuration will be described.

  FIG. 4 shows a wireless communication device that transmits data of an initial signal (beacon request) by broadcast from the wireless communication device 200 to the peripheral wireless communication devices 100-1 to 100-3 and receives data from the wireless communication device 200. Reference numerals 100-1 to 100-3 denote operations for transmitting response (beacon) data in unicast communication. In the following, timings T11 to T16 in FIG. 4 indicate timings serving as a reference for explaining the operation of each wireless communication device.

  First, the wireless communication apparatus 200 performs carrier sense (at least 10 ms) from the timing T11, and transmits data of an initial signal (beacon request) by broadcast to the wireless communication apparatuses 100-1 to 100-3 during the timings T12 to T13. It is assumed that

  In wireless communication devices 100-1 to 100-3, standby time based on random values (random value × unit time) is received by standby time control unit 102 at the end of data reception from wireless communication device 200 (timing T13). Is required.

  Here, it is assumed that the random value of the wireless communication device 100-1 is 0, the random value of the wireless communication device 100-2 is 1, and the random value of the wireless communication device 100-3 is 2.

  Here, since what each of the wireless communication devices 100-1 to 100-3 transmits to the wireless communication device 200 is beacon transmission in response to a beacon request, each of the wireless communication devices 100-1 to 100-3 The size of the data to be transmitted is the same or almost the same size. Therefore, in the following description, the following description will be given on the assumption that all the unit times calculated in the respective wireless communication apparatuses 100-1 to 100-3 are the same.

  Then, the wireless communication device 100-1 starts carrier sense immediately after the end of data reception from the wireless communication device 200 (timing T13), starts data transmission to the wireless communication device 200 after carrier sensing, and receives timing T14. At this point, data transmission ends.

  In this case, the period from the start of carrier sense (timing T13) to the completion of data transmission (timing T14) is between the unit time described above.

  Then, in the wireless communication device 100-2, carrier sense and data transmission are performed from the time point T14 after the lapse of one unit time from the data reception end point (timing T13), and the time point of the timing T15 after the lapse of one unit time. This completes the data transmission.

  Then, in the wireless communication device 100-3, carrier sense and data transmission are performed from the time point T15 after the elapse of 2 unit time from the data reception end time (timing T13), and further at the time point T16 after 1 unit time. Data transmission ends.

(A-3) Effects of First Embodiment According to the first embodiment, the following effects can be achieved.

  When the length of the return data from each wireless communication device 100 or the length of relay data is known to some extent, the delay due to the random backoff timing is eliminated, and the transmission delay generated for each device is [carrier sense time + Transmission time]. In addition, since the carrier sense is not repeatedly performed unlike the conventional method, power consumption can be suppressed in the wireless communication device 100.

  In addition, since the probability that the carrier sense of each wireless communication device 100 is successful at the first time is high, each wireless communication device 100 transmits a response (beacon) to the initial signal (beacon request) from the wireless communication device 200. Probability increases. As a result, the wireless communication device 200 can realize the original function of selecting a connection destination by comparing the quality from a plurality of beacons, and can configure a stable network.

  Furthermore, in the communication system 1, when another wireless communication device returns or relays an initial transmission by broadcast or multicast from a certain wireless communication device, a long carrier limited by the Japanese law for communication in the 950 MHz band. Multiple transmissions can be completed in a shorter amount of time without being significantly affected by sense.

(A-4) Modification of First Embodiment As for the first embodiment, the following modified embodiment can be further exemplified.

  4, as in FIG. 3, the wireless communication devices 100-1 to 100-3 perform response (beacon) data transmission based on data transmission of an initial signal (beacon request) from the wireless communication device 200. Show. FIG. 4 is different from FIG. 4 in that the reception operation is not performed while it is estimated that the wireless communication devices 100-1 to 100-3 are performing carrier sensing on the wireless communication device 200 side. Only the differences between FIG. 4 and FIG. 3 will be described below.

  4 is the same as that in FIG. 3 because the operations on the wireless communication apparatuses 100-1 to 100-3 are the same as those in FIG. 3, and only the operation on the wireless communication apparatus 200 will be described below.

  In FIG. 4, the wireless communication device 200 holds the information on the above-mentioned 1 unit time and carrier sense time calculated in the standby time control unit 102 of each of the wireless communication devices 100-1 to 100-3. It shall be. For example, when all the wireless communication devices on the communication system 1 have the same communication specification, one unit time and carrier sense time for beacon transmission may be registered in the wireless communication device 200 in advance. The same as the data identification unit 101 and the standby time control unit 102 may be provided in the wireless communication apparatus 200 for calculation.

  As shown in FIG. 4, the carrier sense time is started in one of the wireless communication devices 100 at the end of data transmission by the wireless communication device 200 (timing T13) and every other unit time from that time. On the wireless communication apparatus 200 side, the reception operation is stopped for every carrier time for every unit time, and the operation is performed with lower power consumption than when the reception operation is performed (hereinafter referred to as “power-saving operation state”). Shall be.

  As shown in FIG. 4, in the communication system 1, since the wireless communication devices 100-1 to 100-3 all determine the timing for performing carrier sense and data transmission based on the same rule, the wireless communication device 200 side Then we can grasp the timing. Thereby, in the wireless communication device 200, it is possible to estimate the timing at which none of the wireless communication devices 100-1 to 100-3 performs data transmission.

  That is, since the transmission from each wireless communication device 100 is repeated with a fixed length of carrier sense time and a fixed length of transmission time, as shown in FIG. 4, the wireless communication device 200 receives during the carrier sense period. Thus, the power saving effect can be further enhanced.

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

(B-1) Configuration of Second Embodiment The overall configuration of the communication system 1A of the second embodiment can also be shown using FIG. In FIG. 2, the reference numerals in parentheses are used only in the second embodiment.

  Hereinafter, the difference between the second embodiment and the first embodiment will be described.

  In the communication system 1A of the second embodiment, a wireless communication device 200 and three wireless communication devices 100A (100A-1 to 100A-3) are arranged. Since the wireless communication device 200 is the same as that of the first embodiment, detailed description thereof is omitted.

  FIG. 5 is a block diagram showing the functional configuration of the wireless communication device 100A, and the same and corresponding parts as those in FIG.

  The wireless communication device 100A includes a transmission data identification unit 101, a standby time control unit 102A, a transmission unit 103A, a carrier sense control unit 104A, a reception unit 105, and a random backoff unit 106. Note that the transmission data identification unit 101 and the reception unit 105 are the same as those in the first embodiment, and thus detailed description thereof is omitted.

  The standby time control unit 102A generates a random value (similar to the first embodiment) between the minimum value 0 and a predetermined maximum value, and sets [transmission time obtained from the transmission data identification unit 101]. As one unit time, a standby time obtained from [random value × 1 unit time] is calculated and passed to the transmission unit 103A.

  First, the transmission unit 103A informs the carrier sense control unit 104A of the start of carrier sense, receives a carrier sense completion notification from the carrier sense control unit 104A, and then waits for the start of transmission for the standby time received from the standby time control unit 102A. Thereafter, the transmission data received from the transmission data identification unit 101 is transmitted.

  Upon receiving an instruction to start carrier sense from the transmission unit 103A, the carrier sense control unit 104A receives reception data from the reception unit 105, confirms that a signal having a predetermined reception level or higher has not been received for a certain period of time, Notify the transmission unit 103A of the completion of carrier sense. When a signal of a reception level or higher set within a certain time is received, the carrier sense NG is notified to the random backoff unit 106, and the carrier sense is resumed after a short random backoff time similar to the conventional method. When the carrier sense NG continues many times, the above-described processing may be repeated up to the upper limit.

  When the random backoff unit 106 receives the carrier sense NG notification from the carrier sense control unit 104A, the random backoff unit 106 waits for a short backoff time generated by a random number or the like and notifies the carrier sense control unit 104A. The back-off time may be controlled so as to be short at the beginning as in the conventional method and become longer as the number of times is repeated.

(B-2) Operation of Second Embodiment Next, the operation of the communication system 1A of the second embodiment having the above configuration will be described.

  FIG. 6 shows a wireless communication device that transmits data of an initial signal (beacon request) by broadcast from the wireless communication device 200 to the peripheral wireless communication devices 100A-1 to 100A-3 and receives data from the wireless communication device 200. 100A-1 to 100A-3 each show an operation of transmitting a response (beacon) data by unicast communication. In the following, timings T21 to T27 in FIG. 6 indicate timings serving as a reference for explaining the operation of each wireless communication device.

  First, it is assumed that the wireless communication apparatus 200 performs carrier sense (at least 10 ms) from timing T21 and transmits data to the wireless communication apparatuses 100A-1 to 100A-3 by broadcast during timings T22 to T23.

  Then, each of the wireless communication devices 100A-1 to 100A-3 performs carrier sense (10 ms or more) all at once from the end of data reception from the wireless communication device 200 (timing T23). And in each radio | wireless communication apparatus 100A-1 to 100A-3, the waiting time (random value x 1 unit time) from the time (timing T24) when carrier sense was completed is calculated | required.

  Here, it is assumed that the random value of the wireless communication device 100A-1 is 0, the random value of the wireless communication device 100A-2 is 1, and the random value of the wireless communication device 100A-3 is 2.

  Then, wireless communication apparatus 100A-1 starts data transmission to wireless communication apparatus 200 immediately after the end of carrier sense (timing T24), and ends data transmission at timing T25.

  In this case, the period from the start of carrier sense (timing T24) to the completion of data transmission (timing T25) is between the unit time described above.

  Then, wireless communication apparatus 100A-2 starts data transmission to wireless communication apparatus 200 from time T25 immediately after the end of carrier sense (timing T24) and after one unit time has elapsed, and data transmission at time T26. Ends.

  Furthermore, in the wireless communication device 100A-3, carrier sense is started from the time T26 after two unit times have elapsed from the end of data reception (timing T24), and data transmission is further performed at the time T27 one unit time later. Ends.

  As described above, each of the wireless communication devices 100A-1 to 100A-3 waits for a random value × unit time from the timing T24 as a standby time, and performs carrier sense and data transmission.

(B-3) Effects of Second Embodiment According to the second embodiment, the following effects can be obtained in addition to the effects of the first embodiment.

  In the wireless communication device 100A, since the carrier sense is performed all at once at different timings for each wireless communication device, the transmission delay that occurs for each wireless communication device can be reduced to the transmission time, and a shorter time Can complete the transmission of all devices.

In particular, when each wireless communication device supports a long carrier sense defined by Japanese 950 MHz law, the influence of the delay time can be only 10 milliseconds for performing carrier sense all at once.

(B-4) Modification of Second Embodiment Regarding the second embodiment, the following modified embodiment can be further exemplified.

(B-4-1) In the second embodiment, as shown in FIG. 6, the wireless communication devices 100A-1 to 100A-3 perform carrier sense all at once (between timing T23 and T24), and thereafter Although the carrier sense is individually omitted and the response data is transmitted to the wireless communication apparatus 200, the carrier sense may be individually performed for a very short time.

  FIG. 7 shows an operation in which the wireless communication devices 100A-1 to 100A-3 perform response (beacon) data transmission based on data transmission of an initial signal (beacon request) from the wireless communication device 200, as in FIG. Show. 7 is different from FIG. 6 in that radio communication apparatuses 100A-1 to 100A-3 individually perform short-time carrier sense. Hereinafter, only differences from FIG. 6 will be described with reference to FIG.

  In FIG. 7, after the wireless communication devices 100A-1 to 100A-3 perform carrier sense at the same time between timings T23 and T24, the wireless communication devices 100A-1 to 100A-3 are wireless communication devices at different timings. Response data transmission is performed to 200, but carrier sensing is performed individually for a short time (time shorter than timing T23 to T24) before data transmission.

  In FIG. 7, individual short-time carrier sense is also performed for the wireless communication device 100A-1 having a random value of 0. However, it may be omitted and data transmission may be started from timing T24. . In that case, in the wireless communication device 100A in which the random value is 1 or more, a time obtained by subtracting an individual short carrier sense may be applied to the standby time.

  In this case, the unit time used by each of the wireless communication apparatuses 100A-1 to 100A-3 for calculating the standby time is the sum of the short carrier sense time and the transmission time obtained from the transmission data identifying unit 101.

  Japanese law requires that transmission be completed within 1 second after 10 milliseconds of carrier sense, so there is no problem even if there is an interval between transmissions after carrier sense as described above. Although there is no actual transmission immediately after carrier sense, there is a possibility of interference with transmission of other wireless communication devices. Therefore, as shown in FIG. 7, by inserting a short carrier sense before transmission after the standby time, although the overall delay is slightly increased, it is possible to interfere with the radio communication apparatus having a long standby time.

(B-4-2) In the second embodiment, as illustrated in FIG. 6, the wireless communication device 200 continuously receives a response after data transmission to the wireless communication devices 100A-1 to 100A-3. Although it is in a possible state, the reception operation is stopped during a period during which it is estimated that none of the wireless communication devices 100A-1 to 100A-3 performs data transmission (for example, during simultaneous carrier sense at timings T23 to T24) You may make it be a power saving operation state.

  FIG. 8 shows an operation in which the wireless communication devices 100A-1 to 100A-3 perform response (beacon) data transmission based on data transmission of an initial signal (beacon request) from the wireless communication device 200, as in FIG. Although shown, the wireless communication apparatus 200 side stops the reception operation and is different from FIG. 6 in that a period of the power saving operation state is provided. Hereinafter, only differences from FIG. 6 will be described with reference to FIG.

  In FIG. 8, as described above, while the wireless communication devices 100A-1 to 100A-3 perform carrier sense all at the timing T23 to T24, the wireless communication device 200 stops the reception operation, and the power saving operation state It has become.

  In FIG. 8, as in the case of FIG. 4 (modified example of the first embodiment) described above, the wireless communication device 200 includes information on the carrier sense time of each of the wireless communication devices 100A-1 to 100A-3. Is held.

  As illustrated in FIG. 8, the wireless communication device 200 stops the reception operation and enters the power saving operation state only during a period during which it is estimated that none of the wireless communication devices 100A-1 to 100A-3 performs data transmission. As a result, the power saving effect can be further enhanced.

(C) Other Embodiments The present invention is not limited to the above-described embodiments, and may include modified embodiments as exemplified below.

(C-1) In each of the above embodiments, an example in which the wireless communication device of the present invention is applied to a wireless communication device that transmits a beacon request and a wireless communication device that responds to a beacon in response to a beacon request will be described. However, the present invention may be applied to a wireless communication apparatus that exchanges other control signals.

  For example, a signal requesting some response such as Ping (echo request) is transmitted from the transmission-side wireless communication device by broadcast, and the reception-side wireless communication device that has received the signal responds to the transmission-side wireless communication device ( For example, an echo reply signal is transmitted.

  DESCRIPTION OF SYMBOLS 1 ... Communication system, 100, 100-1 to 100-3, 200 ... Wireless communication apparatus, 101 ... Transmission data identification part, 102 ... Standby time control part, 103 ... Transmission part, 104 ... Carrier sense control part, 105 ... Reception Department.

Claims (6)

When receiving predetermined broadcast data transmitted by broadcast communication from the wireless communication device on the transmission side, data transmission means for transmitting transmission data in response to reception of the broadcast data;
Carrier sense means for performing carrier sense at least once after the broadcast data is received until the data transmission means transmits the transmission data;
A timing control means for controlling the timing at which the data transmission means transmits data using at least a transmission unit time including a transmission time required for transmission of the transmission data and a random value ;
When the reception of the broadcast data is completed, the timing control unit starts carrier sense by the carrier sense unit, and after the carrier sense is completed, the time obtained by multiplying the transmission unit time by the random value has elapsed. A wireless communication apparatus characterized by causing the data transmission means to start transmission of the transmission data later . Upon receiving predetermined broadcast data transmitted by broadcast communication from the transmitting wireless communication device,
Data transmission means for transmitting transmission data in response to reception of the broadcast data;
Carrier sense means for performing carrier sense at least once after the broadcast data is received until the data transmission means transmits the transmission data;
A timing control means for controlling the timing at which the data transmission means transmits data using at least a transmission unit time including a transmission time required for transmission of the transmission data and a random value;
The carrier sense means performs carrier sense for a first carrier sense time at the end of reception of the broadcast data, and further, immediately before the data transmission by the data transmission means, than the first carrier sense time. Perform carrier sense for a short second carrier sense time,
The transmission unit time is the sum of the transmission time and the second carrier sense time,
When the reception of the broadcast data is completed, the timing control unit causes the carrier sense unit to start carrier sense of the first carrier sense time, and after the completion of the carrier sense, at the transmission unit time. After the elapse of the time multiplied by the random value, the carrier sense means starts carrier sense for the second carrier sense time, and after the carrier sense ends, the data transmission means starts transmission of the transmission data.
A wireless communication apparatus. A computer installed in a wireless communication device
When receiving predetermined broadcast data transmitted by broadcast communication from the wireless communication device on the transmission side, data transmission means for transmitting transmission data in response to reception of the broadcast data;
Carrier sense means for performing carrier sense at least once after the broadcast data is received until the data transmission means transmits the transmission data;
At least the data transmission means transmitting unit time including the transmission time taken for the transmission of the transmission data, by using the random value, the data transmission means to function as a timing control means for controlling the timing of data transmission ,
When the reception of the broadcast data is completed, the timing control unit starts carrier sense by the carrier sense unit, and after the carrier sense is completed, the time obtained by multiplying the transmission unit time by the random value has elapsed. A wireless communication program for causing the data transmission means to start transmission of the transmission data later . A computer installed in a wireless communication device
When receiving predetermined broadcast data transmitted by broadcast communication from the wireless communication device on the transmission side, data transmission means for transmitting transmission data in response to reception of the broadcast data;
Carrier sense means for performing carrier sense at least once after the broadcast data is received until the data transmission means transmits the transmission data;
Using at least a transmission unit time including a transmission time required for transmission of the transmission data by the data transmission unit and a random value, the data transmission unit functions as a timing control unit that controls the timing of data transmission,
The carrier sense means performs carrier sense for a first carrier sense time at the end of reception of the broadcast data, and further, immediately before the data transmission by the data transmission means, than the first carrier sense time. Perform carrier sense for a short second carrier sense time,
The transmission unit time is the sum of the transmission time and the second carrier sense time,
When the reception of the broadcast data is completed, the timing control unit causes the carrier sense unit to start carrier sense of the first carrier sense time, and after the completion of the carrier sense, at the transmission unit time. After the elapse of the time multiplied by the random value, the carrier sense means starts carrier sense for the second carrier sense time, and after the carrier sense ends, the data transmission means starts transmission of the transmission data.
A wireless communication program characterized by the above. A communication system having a plurality of first wireless communication apparatuses, wherein the wireless communication apparatus according to claim 1 is applied as the first wireless communication apparatus . 1 or more second wireless communication device further Yes,
The second wireless communication device is
When predetermined broadcast data is received by broadcast communication, data transmission according to reception of the broadcast data is performed, and carrier sense is performed before data transmission. A wireless communication device for transmitting the broadcast data,
Using the property that each receiving-side wireless communication device determines carrier sense timing and transmission data transmission timing based on the same rule after the broadcast data reception is completed, Non-transmission period estimation means for estimating a non-transmission period in which all of the wireless communication devices on the side do not perform data transmission;
During the non-transmission period which is estimated by the non-transmission period estimating means, for the wireless communication device, to claim 5, characterized in that it comprises a reception stop means for stopping the data reception from the wireless communication device of the reception side The communication system described.

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