JP2015089089A - Radio communication device, beacon transmission and reception method, and network system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radio communication device, a beacon transmission and reception method and a network system, reducing the probability of beacon transmission to reduce power consumption.SOLUTION: A network radio communication device 13 performs direct communication with another radio communication device 15 and time-synchronization by transmitting and receiving beacons on the basis of the beacon transmission timing of predetermined intervals. The other radio communication device 15 transmits a beacon at a random time in a certain period from the beacon transmission timing. The radio communication device 13 waits for the reception of the beacon transmitted from the other radio communication device 15 for the certain period, and transmits a beacon from the self-device in the event of failing to receive the beacon transmitted from the other radio communication device 15 in the certain period.

Description

  The present invention relates to a wireless communication device, a beacon transmission / reception method, and a network system in which a wireless communication device directly communicates.

  IEEE 802.11 standard wireless LAN (Local Area Network) modes include an infrastructure mode, an IBSS (Independent Basic Service Set) mode, and the like.

  The infrastructure mode is a mode in which an access point is provided, and broadcast information called a beacon is periodically transmitted from the access point to control the network.

  The IBSS mode is a mode in which wireless LAN devices communicate directly with each other without using an access point, and is used in an ad hoc network. The IEEE 802.11 standard IBSS refers to a group of wireless networks in an ad hoc network, and is an independent basic service set indicating wireless node groups communicating with each other.

  Here, for example, when considering an IBSS network composed of two wireless LAN devices A and B, beacon transmission of each of the wireless LAN devices A and B is performed with an equal probability. The wireless LAN devices A and B can know the subsequent beacon transmission timing TBTT (Target Beacon Transmission Time) from the time stamp value and the TBTT interval value included in the received beacon. Each of the wireless LAN devices A and B generates a random delay time and attempts to start beacon transmission after the random delay time with reference to TBTT. At this time, one wireless LAN device with a small delay time transmits a beacon, and the other wireless LAN device with a large delay time receives a beacon transmitted from the one wireless LAN device to receive a beacon from the own device. Stop sending beacons.

  By the way, as a wireless LAN device, for example, a technique as described in Patent Document 1 has been proposed.

Special table 2009-523378

  In a conventional IBSS network, beacon transmission of each wireless LAN device is performed with an equal probability, so even a wireless LAN device equipped with a battery with a smaller capacity than other wireless LAN devices has a beacon with an equal probability. There is a problem that power transmission cannot be reduced with a wireless LAN device equipped with a small capacity battery.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a wireless communication device, a beacon transmission / reception method, and a network system that reduce power consumption by reducing the probability of beacon transmission.

A wireless communication device according to an embodiment of the present invention is a wireless communication device in a network that performs direct communication with another wireless communication device (15) and transmits and receives beacons at a predetermined interval of beacon transmission timing to achieve time synchronization. And
While the other wireless communication device (15) transmits the beacon at a random time within a certain period from the beacon transmission timing, the beacon transmitted by the other wireless communication device (15) is transmitted during the certain period. It waits for reception and transmits a beacon from its own device when it cannot receive a beacon transmitted by the other wireless communication device (15) within the predetermined period.

  Preferably, the time from the beacon transmission timing to the start of transmission of the beacon is larger than the maximum time of the random time of the other wireless communication device (15).

  Preferably, the beacon transmission is performed when the beacon transmitted by the other wireless communication device (15) is waited for the certain period and the beacon transmitted by the other wireless communication device (15) is not received. From the timing, the beacon can be received in the awake state in which the beacon is waited for reception, and then the intermittent transmission / reception mode in which the low power consumption sleep state is maintained and the beacon transmitted by the other wireless communication device (15) can be received. In this case, the intermittent transmission / reception mode is always changed to the steady transmission / reception mode that maintains the awake state.

  Preferably, in the steady transmission / reception mode, a beacon transmitted by the other wireless communication device (15) is waited for the certain period, and a beacon transmitted by the other wireless communication device (15) is transmitted during the certain period. If reception fails, beacon transmission from the own device is stopped.

  Preferably, in the steady transmission / reception mode, a beacon lost count value is incremented when a beacon transmitted by the other wireless communication device (15) is not received in the predetermined period, and the beacon lost count value is equal to or greater than a threshold value. When it becomes, it changes to the intermittent transmission / reception mode.

Also, in the beacon transmission / reception method according to an embodiment of the present invention, the first wireless communication device (13) and the second wireless communication device (15) communicate directly and transmit / receive a beacon at every predetermined interval of beacon transmission timing. A network beacon transmission / reception method that synchronizes time,
The second wireless communication device (15) transmits the beacon at a random time within a certain period from the beacon transmission timing,
The first wireless communication device (13) waits for reception of a beacon transmitted by the second wireless communication device (15) for the certain period, and the second wireless communication device (15) for the certain period. When the beacon transmitted by cannot be received, the beacon is transmitted from the own device.

  Preferably, the time from the beacon transmission timing of the first wireless communication device (13) to the start of transmission of the beacon is greater than the maximum time of the random time of the second wireless communication device (15). It ’s a big time.

  Preferably, the first wireless communication device (13) waits for reception of a beacon transmitted by the second wireless communication device (15) during the predetermined period, and the second wireless communication device (15) When the beacon to be transmitted cannot be received, the intermittent transmission mode is maintained in the awake state in which the beacon is waited for reception for a certain period from the beacon transmission timing, and thereafter the sleep state with low power consumption is maintained. When the beacon transmitted by the second wireless communication device (15) can be received, the intermittent transmission / reception mode is changed to the steady transmission / reception mode that always maintains the awake state.

  Preferably, the first wireless communication device (13) waits for reception of a beacon transmitted by the second wireless communication device (15) during the certain period in the regular transmission / reception mode, and When the beacon transmitted by the second wireless communication device (15) cannot be received, the transmission of the beacon is stopped.

Preferably, in the steady transmission / reception mode, the first wireless communication device increments a beacon lost count value when the beacon transmitted by the second wireless communication device cannot be received in the certain period.
When the beacon lost count value becomes equal to or greater than a threshold value, the mode transits to the intermittent transmission / reception mode.

In the network system according to an embodiment of the present invention, the first wireless communication device (22A), the second wireless communication device (25), and the third wireless communication device (22B) directly communicate with each other at a predetermined interval. A network system that transmits and receives beacons at each beacon transmission timing to synchronize time,
The second wireless communication device (25) transmits the beacon at a random time within a certain period from the beacon transmission timing,
The first wireless communication device (22A) waits for reception of a beacon transmitted by the second wireless communication device (25) for the certain period, and the second wireless communication device (25) for the certain period. Sends a beacon from its own device when it fails to receive a beacon sent by
The third wireless communication device (22B) does not transmit a beacon from itself.

  Preferably, the time from the beacon transmission timing of the first wireless communication device to the start of transmission of the beacon is greater than the maximum time of the random time of the second wireless communication device.

  Note that the reference numerals in the parentheses are given for ease of understanding, are merely examples, and are not limited to the illustrated modes.

  ADVANTAGE OF THE INVENTION According to this invention, the probability of the beacon transmission of a wireless communication apparatus can be reduced and power consumption can be reduced.

It is a block diagram of one embodiment of a toy radio control system. It is a block diagram of one embodiment of a sports analysis system. 1 is a block diagram of an embodiment of a wireless LAN device. It is a figure which shows the example of a beacon frame structure. It is a flowchart of a mode control process. It is a flowchart of an intermittent transmission / reception process. It is a flowchart of a regular transmission / reception process. It is a figure for demonstrating operation | movement of the wireless LAN apparatus and smart phone at the time of IBSS network starting. It is a figure for demonstrating operation | movement of the smart phone which joined the IBSS network. It is a figure for demonstrating operation | movement of each apparatus in case a some wireless LAN apparatus participates in an IBSS network. It is a figure for demonstrating the data transmission in a toy radio control system. It is a figure for demonstrating the data transmission in a sports analysis system.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<Toyradicon system>
FIG. 1 shows a block diagram of an embodiment of a toy radio control system using a wireless LAN device which is a wireless communication device of the present invention. In FIG. 1, a toy radio control 10 is a toy such as a helicopter or an automobile. The toy radio control 10 includes a drive unit 11 including a motor and an LED, a sensor unit 12 such as a gyro sensor and a speed sensor, and a wireless LAN device 13. Have.

  For example, the wireless LAN device 13 is connected to the smart phone 15 by a wireless LAN. The smart phone 15 has a wireless LAN function and is used as a remote controller. An operation command from the smart phone 15 is transmitted to the wireless LAN device 13 via the wireless LAN, and the wireless LAN device 13 generates a control signal based on the operation command and supplies the control signal to the drive unit 11. The control signal may be a PWM (Pulse Width Modulation) signal or a GPIO (General Purpose Input / Output) signal.

  The detection signal output from each sensor in the sensor unit 12 is supplied to the wireless LAN device 13 through an SPI (Serial Peripheral Interface), I2C (Inter-Integrated Circuit), or the like, and is transmitted from the wireless LAN device 13 via the wireless LAN. It is supplied to the smart phone 15, and the smart phone 15 displays the state of the toy radio control 10 such as the posture and speed.

  Below, the operation | movement sequence of an example of a toy radio control system is demonstrated.

  1) IBSS network creation: In FIG. 1, when the power switch of the toy radio control 10 is turned on, the wireless LAN device 13 enters an intermittent transmission / reception mode for executing intermittent transmission / reception processing, and a beacon frame (hereinafter simply referred to as “beacon”) Send.

  2) Participation in the IBSS network: The smart phone 15 receives the beacon transmitted by the wireless LAN device 13 and connects to the IBSS network of the wireless LAN device 13. The wireless LAN device 13 detects that the smart phone 15 has been connected, transitions from the intermittent transmission / reception mode to the steady transmission / reception mode for executing the steady transmission / reception processing, and then maintains the steady transmission / reception mode. The smart phone 15 always operates in the steady transmission / reception mode.

  3) Preparation for data communication: Smartphone 15 sets an IP address. At this time, the wireless LAN device 13 serves as a DHCP (Dynamic Host Configuration Protocol) server. Thereafter, the smart phone 15 inquires about the MAC address and acquires the MAC address of the wireless LAN device 13.

  4) Data communication: The operation of the motor and LED of the drive unit 11 is controlled by an operation command from the smart phone 15.

  5) Disconnect: The wireless LAN device 13 transitions to the intermittent transmission / reception mode when the reception of the beacon from the smart phone 15 stops after a certain period.

<Sport analysis system>
FIG. 2 shows a block diagram of an embodiment of a sports analysis system using a wireless LAN device which is a wireless communication device of the present invention. 2, each of the sensor units 20A, 20B,..., 20X is attached to each part of the body such as the right wrist, left wrist, and head of the subject. Each of the sensor units 20A to 20X includes sensor units 21A to 21X such as a three-dimensional position sensor and wireless LAN devices 22A to 22X.

  The wireless LAN devices 22A to 22X are connected to the smart phone 25, for example, by a wireless LAN. The smart phone 25 has a wireless LAN function and is used as an analysis / display device. The position detection signals output from the sensor units 21A to 21X are supplied to the wireless LAN devices 22A to 22X through SPI, I2C, and the like, and are supplied from the wireless LAN devices 22A to 22X to the smart phone 25 via the wireless LAN. The three-dimensional position of each part of the body such as the right wrist, left wrist, and head is displayed, and the movement of the subject's body is analyzed and displayed.

  Below, the operation | movement sequence of an example of a sports analysis system is demonstrated.

  1) IBSS network creation: In FIG. 2, when the power switch of the sensor unit 20A is turned on, the wireless LAN device 22A enters an intermittent transmission / reception mode in which intermittent transmission / reception processing is executed, and performs beacon transmission.

  2) Participation in the IBSS network 1: The smart phone 25 receives the beacon transmitted by the wireless LAN device 22A and connects to the IBSS network of the wireless LAN device 22A. The wireless LAN device 22A detects that the smart phone 25 has been connected, transitions from the intermittent transmission / reception mode to the steady transmission / reception mode for executing the steady transmission / reception processing, and then maintains the steady transmission / reception mode. The smart phone 25 always operates in the steady transmission / reception mode.

  3) Data communication preparation 1: The smart phone 25 sets an IP address. At this time, the wireless LAN device 22A serves as a DHCP server. Thereafter, the smartphone 25 inquires about the MAC address and acquires the MAC address of the wireless LAN device 22A.

  4) Participation in the IBSS network 2: When the power switches of the sensor units 20B to 20X are turned on, the wireless LAN devices 22B to 22X enter the reception mode, and periodically switch the wireless channel to be received.

  5) Data communication preparation 2: The smart phone 25 acquires the MAC addresses of the wireless LAN devices 22B to 22X. At this time, the smart phone 25 transmits a MAC address inquiry frame, and the wireless LAN devices 22B to 22X transmit the MAC address of the own device to the smart phone 25 in response to this inquiry.

  6) Data communication: The smart phone 25 performs data communication with each of the wireless LAN devices 22A to 22X, and acquires position detection data detected by the sensor units 21A to 21X.

  7) Disconnect: The wireless LAN device 22A transitions to the intermittent transmission / reception mode when the reception of the beacon from the smart phone 25 is interrupted for a certain period. The wireless LAN devices 22B to 22X transition to the reception mode when the reception of the beacon from the smart phone 25 stops after a certain period.

<Block diagram of wireless LAN device>
FIG. 3 shows a block diagram of an embodiment of a wireless LAN apparatus which is a wireless communication apparatus of the present invention. This wireless LAN device is used as the wireless LAN devices 13, 22B to 22X. In FIG. 3, the wireless LAN device 30 includes an RF transmission / reception unit 31, a modem unit 32, a transmission / reception data buffer 33, an I / F unit 34, and a MAC processing unit 35.

  The RF transmitter / receiver 31 receives the RF signal from the antenna 36, converts it into an IF signal, and supplies it to the modem unit 32. The modem unit 32 demodulates the IF signal, obtains a received frame from the demodulated baseband signal, and stores it in the transmission / reception data buffer 33. The MAC processing unit 35 performs a MAC (Media Access Control) process on the received frame read from the transmission / reception data buffer 33. The control data read from the transmission / reception data buffer 33 under the control of the MAC processing unit 35 is supplied to the electronic device 37 via the I / F (interface) unit 34. The electronic device 37 corresponds to the drive unit 11, the sensor units 12, 21A to 21X, etc. shown in FIG.

  Further, detection data and the like supplied from the electronic device 37 are stored in the transmission / reception data buffer 33 via the I / F unit 34. The detected data and the like are mapped to a transmission frame by the MAC processing unit 35 and supplied to the modem unit 32. The transmission frame is modulated by the modem unit 32, converted into an RF signal by the RF transceiver unit 31, and transmitted from the antenna 36.

  The received frame analysis unit 41 in the MAC processing unit 35 analyzes received frames such as beacon frames and data frames. The transmission frame generation unit 42 generates a transmission frame such as a beacon frame or a data frame. The TBTT generator 43 generates beacon transmission timing. The beacon reception period management unit 44 manages the period during which the device itself receives a beacon. The beacon lost management unit 45 manages a beacon lost, that is, a state where a beacon cannot be detected. The power state control unit 46 performs switching control between an intermittent transmission / reception mode and a constant transmission / reception mode, which will be described later, and transmission power switching control in the RF transmission / reception unit 31.

<Configuration example of beacon frame>
A beacon is broadcast information, and time synchronization between devices can be achieved by transmitting and receiving beacons between devices participating in the IBSS network.

FIG. 4 is a diagram showing a configuration example of a beacon frame in the IEEE 802.11 standard. Note that the beacon frame includes optional functions required or broadcasted by the wireless device, such as information on frequency hopping (Hopping Pattern Parameters elements), information on wake-up schedules (Wakeup Schedule elements), and the like. Further, it may be added. In FIG. 4, an identifier indicating a beacon frame is set in the first Frame Control. Note that “2B” in the lower part of the figure indicates that the Frame Control is 2 bytes. Others are the same. The next Duration / ID is all '0'
Is set. Address 1 is set with a broadcast address (0xFF, where 0x indicates a hexadecimal display). Address 2 is set with the MAC address of the transmission source. Address 3 is set with a BSSID (Basic Service Set Identifier) of the identifier of the IBSS network. The BSSID is an identifier for identifying a network to which a frame to be transmitted / received belongs, generated based on the MAC address of the wireless device that created the BSSID of the IBSS network. The frame includes, for example, a data type frame, a management type frame, and a control type frame. BSSID is used in the data type frame, the management type frame, and some control type frames. The beacon frame is a management type frame.

  A frame number (serial number) is set in the Sequence Control. A timestamp value is set in Timestamp. A TBTT interval value is set in Beacon Interval. In Capability, a value indicating that the network is an IBSS network, and information of a function (QoS (quality of service), APSD (automatic power save delivery), etc.) used in the network are set. A network name is set in the SSID. A transfer rate is set in the supported rate. A radio channel is set in the DSSS Parameter Set. In the IBSS Parameter Set, an Annunciation Traffic Indication Message (ATIM) window length (1024 μsec unit) indicating a reception time after TBTT in the case of intermittent operation is set. In FCS, Frame Check Sequence is set.

<Flowchart of mode control processing>
FIG. 5 shows a flowchart of the mode control process executed by the MAC processing unit 35 of the wireless LAN device 30 of the present invention. FIG. 6 shows a flowchart of intermittent transmission / reception processing, and FIG. 7 shows a flowchart of steady transmission / reception processing.

  In FIG. 5, step S1 indicates the start of loop processing, and step S4 indicates the end of loop processing. When the power is turned on, the wireless LAN device 30 first executes the intermittent transmission / reception process of step S2, and when the intermittent transmission / reception process ends, the wireless LAN device 30 executes the steady transmission / reception process of step S3. Then, when the steady transmission / reception process ends, the intermittent transmission / reception process of step S2 is executed. Thereafter, the steady transmission / reception process and the intermittent transmission / reception process are repeated in the same manner.

  The intermittent transmission / reception process of FIG. 6 is executed in the intermittent transmission / reception mode. In step S11, the wireless LAN device 30 sets itself to a sleep state. In the sleep state, the power supply to the RF transmission / reception unit 31 and the modulation / demodulation unit 32 is reduced, so that the power consumption is low.

  Next, in step S12, the wireless LAN device 30 determines whether or not the own device is the beacon transmission timing TBTT, and if it is the beacon transmission timing TBTT, the wireless LAN device 30 sets the own device in an awake state in step S13. To do. In step S14, a beacon reception period timer is started. In the awake state, power is supplied to the RF transmission / reception unit 31 and the modulation / demodulation unit 32 as usual, so that power consumption increases compared to the sleep state.

  Next, in step S15, the wireless LAN device 30 determines whether a beacon has been received. Here, the smart phone transmits the beacon. If no beacon is received, it is determined in step S16 whether or not the beacon reception period T0 has ended. If the beacon reception period T0 has not ended, the process proceeds to step S15. If the beacon reception period T0 has ended, the process proceeds to step S11 after transmitting a beacon in step S17. That is, beacon reception is waited for in steps S15 and S16.

  On the other hand, if a beacon is received in step S15, the smart phone has joined the IBSS network, and therefore the transmission power during beacon transmission is reduced by a predetermined value α in step S18. In step S19, the transition to the steady transmission / reception mode is recognized, and the intermittent transmission / reception process is terminated. The regular transmission / reception process is started by the end of the intermittent transmission / reception process.

  The steady transmission / reception process of FIG. 7 is executed in the steady transmission / reception mode. Step S21 indicates the start of the loop process, and step S26 indicates the end of the loop process. In step S22, the wireless LAN device 30 determines whether or not the own device is the beacon transmission timing TBTT, and if it is the beacon transmission timing TBTT, the wireless LAN device 30 starts a beacon reception period timer in step S23.

  Next, in step S24, the wireless LAN device 30 determines whether a beacon has been received. Here, the smart phone transmits the beacon. If a beacon is received, the beacon lost count is cleared to zero, and the processes in steps S21 to S26 are repeated.

  On the other hand, if the beacon is not received in step S24, the wireless LAN device 30 determines in step S30 whether or not the beacon reception period T0 has ended. That is, beacon reception is waited for in steps S24 and S30. If the beacon reception period T0 has not ended, the process proceeds to step S24. If it has ended, the beacon lost count is incremented by 1 in step S31. Next, in step S32, it is determined whether or not the beacon lost count exceeds a predetermined threshold value. This threshold is a value corresponding to several seconds, for example.

  If the beacon lost count is less than the threshold, the wireless LAN device 30 transmits a beacon in step S33, and then proceeds to step S22. If the beacon lost count is greater than or equal to the threshold value, the smart phone has left the IBSS network in step S34, and in step S34, the transmission power during beacon transmission is increased by a predetermined value α. Then, in step S35, the transition to the intermittent transmission / reception mode is recognized, and the steady transmission / reception process is terminated. The intermittent transmission / reception process is started by the end of the steady transmission / reception process.

  In the above embodiment, the transmission power at the time of beacon transmission is reduced by a predetermined value α in step S18 to reduce the beacon transmission power in the steady transmission / reception process to save power, and the transmission power at the time of beacon transmission in step S34. By increasing the predetermined value α, the beacon transmission power in the intermittent transmission / reception process is increased so that the smart phone can easily receive the beacon. However, step S18 and step S34 may be deleted, and the beacon transmission power in the steady transmission / reception process and the intermittent transmission / reception process may be the same.

  The wireless LAN device 30 may be configured so that the wireless LAN device 30 does not transmit a beacon once the beacon is received from the smart phone. This can be realized by deleting step S33. The reason for this configuration is that it is possible to maintain the IBSS network even if the beacon transmitted by the smartphone is missing.

<At IBSS network startup>
The operation of the wireless LAN device 13 and the smart phone 15 when the IBSS network is started will be described with reference to FIG. Here, a toy radio control system is taken as an example. In FIG. 8, the wireless LAN device 13 transmits a beacon B1 after a delay time T1 from the beacon transmission timing TBTT (1). The delay time T1 is a value exceeding the beacon reception period T0.

  By the way, when receiving the beacon B1 from the wireless LAN device 13, the smart phone 15 recognizes the next beacon transmission timing TBTT (2) from the time stamp value and the TBTT interval value included in the beacon, and the beacon transmission timing TBTT (2). Beacon B2 is transmitted after a random delay time TR. The random delay time TR is expressed by the equation (1) according to the IEEE 802.11 standard.

TR = DIFS + 2 × SlotTime × RN (1)
DIFS is, for example, 50 μsec, SlotTime = 20 μsec, and RN is an integer from 0 to 31.

  Since the wireless LAN device 13 performs beacon transmission only when the smart phone 15 does not perform beacon transmission, the beacon receiving period T0 is set to the maximum value TRmax of the random delay time of the smart phone 15 or longer, and the wireless LAN device 13 The delay time T1 is set to a value larger than TRmax. Note that TRmax = DIFS + 2 × SlotTime × 31. As a result, the wireless LAN device 13 can quickly recognize the participation of the smart phone 15 in the IBSS network.

<When a smartphone is participating in the IBSS network>
The operation of the smart phone 15 participating in the IBSS network started up by the wireless LAN device 13 will be described with reference to FIG. In FIG. 9, the smart phone 15 transmits the beacon B1 within the beacon reception period T0 of the wireless LAN device from the beacon transmission timing TBTT (1). Similarly, the smart phone 15 transmits beacons B2 and B3 from the TBTTs (2) and (3), respectively, within the beacon reception period T0 of the wireless LAN device. The wireless LAN device 13 does not perform beacon transmission by receiving these beacons B1, B2, and B3.

  When the wireless LAN device 13 cannot receive a beacon within the beacon reception period T0 from the beacon transmission timing TBTT (4), the wireless LAN device 13 transmits the beacon B4 after the delay time T1 from TBTT (4).

  As described above, the smart phone 15 preferentially transmits the beacon. Thereby, it becomes possible to reduce the beacon transmission probability of the wireless LAN device 13 and reduce the power consumption. This is because the wireless LAN device 13 is assumed to have a smaller battery capacity than the smart phone 15, and it is desired to reduce the power consumption of the wireless LAN device 13 as much as possible.

<When multiple wireless LAN devices participate in the IBSS network>
By the way, the wireless LAN device 13 of FIG. 1 and the wireless LAN device 22A of FIG. 2 execute the flowcharts shown in FIGS. In contrast, the wireless LAN devices 22B to 22X in FIG. 2 are set not to transmit beacons. In order to realize this, for example, a micro switch is provided in the wireless LAN device, the micro switch is set to ON in the wireless LAN devices 13 and 22A, and the micro switch is set to OFF in the wireless LAN devices 22B to 22X. Then, the wireless LAN devices 13 and 22A in which the microswitch is on execute the flowcharts of FIGS. In the wireless LAN devices 22B to 22X in which the micro switch is off, the intermittent transmission / reception process of step S2 in FIG. 5 is not jumped and executed, and the step S33 of the steady transmission / reception process of FIG. 7 is not jumped and executed. Set.

  The operation of each device when a plurality of wireless LAN devices participate in the IBSS network will be described with reference to FIG. Here, a sports analysis system is taken as an example. In FIG. 10, when the power of the wireless LAN device 22A is turned on at time t1, the wireless LAN device 22A transmits a beacon to start up the IBSS network. Thereafter, when the smart phone 25 joins the IBSS network at time t2, the smart phone 25 preferentially transmits a beacon. Furthermore, even if any of the wireless LAN devices 22B to 22X joins the IBSS network at time t3, the smart phone 25 transmits the beacon preferentially without transmitting the beacon. When the beacon of the smart phone 25 is lost, the wireless LAN device 22A transmits a beacon.

<Data transmission with toy radio control system>
Data transmission in the toy radio control system will be described with reference to FIG. In FIG. 11, the interval of the beacon transmission timing TBTT is, for example, 128 msec. Smart phone 15 transmits beacons B1 and B2 after random delay time TR from beacon transmission timings TBTT (1) and (2). Following the transmission of the beacon B1, the smart phone 15 transmits data frames C1 and C2 of operation data to the wireless LAN device 13. When the wireless LAN device 13 receives the data frames C1 and C2, the wireless LAN device 13 transmits response frames D1 and D2 to the smart phone 15, respectively.

<Data transmission with sports analysis system>
Data transmission in the sports analysis system will be described with reference to FIG. In FIG. 12, the interval of the beacon transmission timing TBTT is, for example, 128 msec, the maximum value TRmax of the random delay time is, for example, 1.3 msec, and the beacon transmission / reception time is, for example, 1 msec. Here, it is assumed that the smart phone 25 and the wireless LAN device 22B participate in the IBSS network set up by the wireless LAN device 22A.

  The smart phone 25 transmits beacons B1 and B2 after a random delay time TR from the beacon transmission timings TBTT (1) and (2). After this beacon transmission, the smart phone 25 transmits a data transmission request E1 addressed to the wireless LAN device 22A. When the wireless LAN device 22A receives the data transmission request E1, the smart phone 25 transmits a data frame F1 addressed to the smart phone 15. When the data transmission from the wireless LAN device 22A is completed, the smart phone 25 transmits a data transmission request E2 to the wireless LAN device 22B. When the wireless LAN device 22B receives the data transmission request E2, the data frame is transmitted to the smart phone 15. Send F2.

  In the above-described embodiment, the wireless LAN of the IEEE 802.11 standard has been described as an example. However, if the wireless communication apparatuses transmit and receive a beacon at every predetermined beacon transmission timing and perform time synchronization, the wireless LAN is used. It may be applied to any network other than.

DESCRIPTION OF SYMBOLS 10 Toy radio control 11 Drive part 12,21A-21X Sensor part 13,22A-22X, 30 Wireless LAN apparatus 15,25 Smartphone 20A-20X Sensor unit 31 RF transmission / reception part 32 Modulation / demodulation part 33 Transmission / reception data buffer 34 I / F part 35 MAC processing unit 36 antenna 37 electronic device 41 received frame analysis unit 42 transmission frame generation unit 43 TBTT generation unit 44 beacon reception period T0 management unit 45 beacon lost management unit 46 power state control unit

Claims (12)

A wireless communication device of a network that performs direct communication with other wireless communication devices, transmits and receives beacons at a predetermined interval of beacon transmission timing, and takes time synchronization,
While the other wireless communication device transmits the beacon at a random time within a certain period from the beacon transmission timing, the certain period waits to receive a beacon transmitted by the other wireless communication device, and A wireless communication apparatus, wherein a beacon is transmitted from the own apparatus when a beacon transmitted by the other wireless communication apparatus cannot be received within a certain period. The wireless communication device according to claim 1, wherein
The wireless communication device, wherein a time from the beacon transmission timing to the start of transmission of the beacon is a time larger than a maximum time of the random time of the other wireless communication device. The wireless communication apparatus according to claim 1 or 2,
When waiting for reception of a beacon transmitted by the other wireless communication device in the certain period, and not receiving a beacon transmitted by the other wireless communication device, the certain period of time from the beacon transmission timing is In the awake state where waiting for reception, and then maintaining the intermittent transmission / reception mode which becomes a low power consumption sleep state, when the beacon transmitted by the other wireless communication device can be received, from the intermittent transmission / reception mode, always, A radio communication apparatus that shifts to a steady transmission / reception mode that maintains the awake state. The wireless communication device according to claim 3, wherein
In the steady transmission / reception mode, the device waits for reception of a beacon transmitted by the other wireless communication device during the certain period, and when the beacon transmitted by the other wireless communication device cannot be received during the certain period, The wireless communication apparatus is characterized by canceling transmission of the beacon. The wireless communication device according to claim 4, wherein
In the steady transmission / reception mode, the beacon lost count value is incremented when the beacon transmitted by the other wireless communication device cannot be received in the certain period, and the beacon lost count value is equal to or greater than a threshold value, A wireless communication apparatus that is shifted to an intermittent transmission / reception mode. A beacon transmission / reception method for a network in which a first wireless communication device and a second wireless communication device perform direct communication and transmit / receive a beacon at every predetermined interval of beacon transmission timing to achieve time synchronization,
The second wireless communication device transmits the beacon at a random time within a certain period from the beacon transmission timing,
The first wireless communication apparatus waits for reception of a beacon transmitted by the second wireless communication apparatus for the certain period, and cannot receive a beacon transmitted by the second wireless communication apparatus for the certain period. A beacon transmission / reception method characterized by transmitting a beacon from its own device. The beacon transmission / reception method according to claim 6,
The time from the beacon transmission timing of the first wireless communication device to the start of transmission of the beacon is longer than the maximum time of the random time of the second wireless communication device. Beacon transmission / reception method. The beacon transmission / reception method according to claim 6 or 7,
The first wireless communication device waits for reception of a beacon transmitted by the second wireless communication device in the predetermined period, and when the beacon transmitted by the second wireless communication device cannot be received, From the beacon transmission timing, the beacon can be received in the awake state in which the beacon is waited to be received, and then the intermittent transmission / reception mode in which the low power consumption sleep state is maintained. The beacon transmission / reception method is characterized by transitioning from the intermittent transmission / reception mode to the steady transmission / reception mode in which the awake state is always maintained. The beacon transmission / reception method according to claim 8,
In the steady transmission / reception mode, the first wireless communication apparatus waits for reception of a beacon transmitted by the second wireless communication apparatus for the certain period, and the second wireless communication apparatus transmits for the certain period. A beacon transmitting / receiving method, wherein transmission of the beacon is stopped when a beacon cannot be received. The beacon transmission / reception method according to claim 9,
In the steady transmission / reception mode, the first wireless communication device increments a beacon lost count value when the beacon transmitted by the second wireless communication device cannot be received in the predetermined period.
When the beacon lost count value becomes equal to or greater than a threshold value, the beacon transmission / reception method is switched to the intermittent transmission / reception mode. A network system in which a first wireless communication device, a second wireless communication device, and a third wireless communication device perform direct communication and transmit and receive beacons at a predetermined interval of beacon transmission timing to achieve time synchronization,
The second wireless communication device transmits the beacon at a random time within a certain period from the beacon transmission timing,
The first wireless communication apparatus waits for reception of a beacon transmitted by the second wireless communication apparatus for the certain period, and cannot receive a beacon transmitted by the second wireless communication apparatus for the certain period. If you send a beacon from your device,
The third wireless communication apparatus does not transmit a beacon from itself. The network system according to claim 11, wherein
The time from the beacon transmission timing of the first wireless communication device to the start of transmission of the beacon is longer than the maximum time of the random time of the second wireless communication device. Network system.

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