WO2017168539A1

WO2017168539A1 - Wireless communication system

Info

Publication number: WO2017168539A1
Application number: PCT/JP2016/060012
Authority: WO
Inventors: 一茂福嶋; 利明佐々木; 田中　宏明; 邦子遠藤; 藤原　孝則; 太樹関; 竜也大川
Original assignee: 株式会社日立国際電気
Priority date: 2016-03-29
Filing date: 2016-03-29
Publication date: 2017-10-05
Also published as: JPWO2017168539A1; JP6630816B2

Abstract

This wireless communication is provided with a plurality of subsystems configured from a master station and a plurality of slave stations. In each of the plurality of subsystems, the master station and the slave stations transmit/receive data using a superframe configured from a plurality of subframes. Each of the plurality of subframes is provided with a first time slot in which the master station transmits a beacon to the slave stations, a second time slot in which the master station detects carriers of other subsystems immediately before the first time slot, a third time slot in which the master station transmits data to the slave stations, and a fourth time slot in which the stave stations transmit data to the master station.

Description

Wireless communication system

The present disclosure relates to a wireless communication system, and is applicable to, for example, a wireless communication system in which a plurality of independent subsystems that complete communication between a master station and a slave station are collected.

When a wireless communication system is configured by a plurality of wireless communication devices, beacons necessary for maintaining the wireless communication system are transmitted at regular intervals.

JP 2007-5859 A

When a wireless communication system includes a plurality of adjacent wireless communication subsystems (subsystems), a beacon or the like may interfere between adjacent subsystems.
An object of the present disclosure is to provide a wireless communication system that reduces interference between adjacent subsystems.
Other problems and novel features will become apparent from the description of the specification and the accompanying drawings.

The outline of a representative one of the present disclosure will be briefly described as follows.
That is, the wireless communication system includes a plurality of subsystems each including a master station and a plurality of slave stations. In each of the plurality of subsystems, the master station and the slave station perform data transmission / reception in a superframe composed of a plurality of subframes. Each of the plurality of subframes includes a first time slot in which the master station transmits a beacon to the slave station, and a second time in which the master station detects a carrier of another subsystem immediately before the first time slot. A slot, a third time slot in which the master station transmits data to the slave station, and a fourth time slot in which the slave station transmits data to the master station.

According to the above wireless communication system, interference between subsystems can be reduced.

Configuration diagram of wireless communication system according to embodiment Configuration diagram of subframe and superframe according to the embodiment The figure which shows a mode that a different radio | wireless communication subsystem adjoins in the radio | wireless communications system which concerns on embodiment. The figure for demonstrating the case where the beacon of an adjacent wireless communication subsystem is detected The figure for demonstrating the case where the data of the adjacent radio | wireless communication subsystem are detected Configuration diagram of subframe according to another embodiment Illustration for explaining the shooting training system The figure which looked at the vehicle of FIG. 7 from the top Configuration diagram of presenting device and light receiver according to the embodiment Configuration diagram of subframe according to embodiment The figure which shows the sub-frame period at the time of link up The figure for demonstrating the case where the carrier of state data is detected The figure for explaining the case where the carrier of the beacon is detected The figure for demonstrating ARQ resending when data interference generate | occur | produces (when interference generate | occur | produces by ARQ resending) Enlarged view of FIG. 14A The figure for demonstrating ARQ resending when data interference generate | occur | produces (when interference does not generate | occur | produce by ARQ resending) Enlarged view of FIG. 15A The figure for demonstrating APL resending in case data interference generate | occur | produces Enlarged view of FIG. 16A Diagram for explaining link-up restart when beacon and status data interfere Enlarged view of FIG. 17A Enlarged view of FIG. 17A Diagram for explaining link-up restart when beacons interfere with each other Enlarged view of FIG. 18A Enlarged view of FIG. 18A Illustration for explaining the hidden terminal problem Illustration to explain the resolution of the hidden terminal problem when sending a beacon Enlarged view of FIG. 20A Enlarged view of FIG. 20A Diagram for explaining synchronization protection after linkup The figure for demonstrating the case where the vehicle of the same timing joins The figure for demonstrating the case where the vehicle of the same timing joins Configuration diagram of subframe according to modification The figure for demonstrating the link-up process by the sub-frame which concerns on a modification Enlarged view of FIG. 24A The figure for demonstrating the link-up process by the sub-frame which concerns on an Example. Enlarged view of FIG. 25A

Hereinafter, embodiments, examples, and modifications will be described with reference to the drawings. However, in the following description, the same components may be denoted by the same reference numerals and repeated description may be omitted.

FIG. 1 is a configuration diagram of a wireless communication system according to an embodiment. The wireless communication system 1 of the present embodiment includes one master station (coordinator) 10 and a plurality of slave stations (end devices) 20, and each slave station 20 and the master station 10 are wirelessly connected and communicate directly. Configured to do. That is, it is a star type configuration centering on the master station 10. The master station in the present embodiment is a radio station having a function of instructing the timing of radio transmission to other stations serving as slave stations by wirelessly transmitting a synchronization signal (beacon described later in this embodiment). Means.

In the example of FIG. 1, the wireless communication system 1 is composed of one master station (CD) 10 and n (n: an integer of 2 or more) slave stations 20. A configuration in which the number of slave stations 20 is 1 is also possible. When the first slave station 20 (1),..., The nth slave station 20 (n) is described as a representative, it is referred to as a slave station 20. In the following description, the first slave station 20 (1) may be referred to as a first end device (ED1),..., And the nth slave station 20 (n) may be referred to as an nth end device (EDn).

In the wireless communication system according to the present embodiment, TDMA wireless communication is performed in accordance with the standard IEEE 802.15.4. That is, time division wireless communication is performed between the master station 10 and the slave station 20 according to the superframe.

FIG. 2 is a configuration diagram of a subframe and a superframe according to the embodiment. The subframe (Sub Frame) defines a period (time slot) in which the master station 10 and each slave station 20 can transmit frames. 3 includes a beacon transmission (TSb) 31, a first coordinator data transmission (TSc1) 32 (1),..., An m-th coordinator data transmission (TScm) 32 (m ), First end device (end device) data transmission (TS1) 33 (1),..., Nth end device data transmission (TSn) 33 (n), carrier sense (TScs) 34 time slots (Time Slot: TS). The number of time slots is determined by the amount of data transmitted between the master station 10 and the slave station 20 and the number of slave stations 20. Data transmission / reception between the master station 10 and the slave station 20 is performed by periodically repeating a super frame (Supper Frame) 300 including a plurality (k) of subframes 30. Carrier frequency (f1) of the first subframe (SBF1) 30 (1), carrier frequency (f2) of the second subframe (SBF2) 30 (2),..., Carrier frequency of the kth subframe (SBFk) (Fk) may be different from each other, or k may be divided into several groups so that carrier frequencies in the groups are different, thereby reducing interference with adjacent wireless communication systems.

∙ One frame can be transmitted in one time slot. The length of each time slot is determined as the time required for wireless transmission of this data based on the maximum data length of one frame. The length of each time slot may not be uniform. A guard time (not shown) is provided between a certain time slot and the next time slot. The guard time is provided to prevent interference between signals in different time slots, and transmission / reception is switched during the guard time. One frame includes one or a plurality of packets. The frame includes a header, transmission data, and a footer, and the header can accommodate the transmission source address and the transmission destination address of the frame. The footer includes communication error detection data.

The beacon transmission (TSb) 31 is a time slot in which the master station (coordinator) 10 outputs a frame including a beacon (synchronization reference signal). Each of the master station 10 and the slave station 20 is synchronized based on the synchronization reference signal output by the beacon transmission 31 and calculates a time slot in which the local station can transmit or receive data.

The first coordinator data transmission (TSc1) 32 (1),..., The m-th coordinator data transmission (TScm) 32 (m) is transmitted from the master station (coordinator) 10 to the slave station (end device) 20, respectively. It is a possible time slot. m is determined according to the amount of data transmitted from the master station 10 to the slave station 20. In a wireless communication system with a small amount of data transmitted from the master station 10, it is possible to set m = 1. When the first coordinator data transmission 32 (1),..., The m-th coordinator data transmission 32 (m) is described as a representative, it is referred to as a coordinator data transmission 32. In the present embodiment, in one coordinator data transmission 32 (for example, the first coordinator data transmission 32 (1)), data to a plurality of slave stations 20 can be multiplexed in one frame.

The first end device data transmission 33 (1),..., The nth end device data transmission 33 (n) are respectively transmitted from the slave stations (end devices) 20 (1) to 20 (n) to the master station 10 (coordinator). It is a time slot that can transmit data to. For example, the end device data transmission 33 (1) is the slave station 20 (1), that is, the time slot TS1 in which data can be transmitted from the end device 1 to the coordinator 10, and the end device data transmission 33 (n) is the slave station 20 ( n), that is, a time slot TSn in which data can be transmitted from the end device n to the coordinator 10. When the number of end devices n = 1, the number of end device data transmissions 33 can be 1. When the first end device data transmission 33 (1),..., The nth end device data 33 (n) is described as a representative, it is referred to as an end device data transmission 33.

Carrier sense (TScs) 34 is a time slot for detecting beacon transmission or data transmission of an adjacent wireless communication system. The function of the carrier sense 34 will be described below.

FIG. 3 is a diagram illustrating a state in which different wireless communication subsystems are adjacent to each other in the wireless communication system according to the embodiment. FIG. 4 is a timing diagram showing a case where a beacon of an adjacent wireless communication subsystem is sensed. FIG. 5 is a timing chart showing a case where data of an adjacent wireless communication subsystem is sensed. Here, the master station 10A, the first slave station 20A (1),..., The nth slave station 20A (n) constitutes a wireless communication subsystem (hereinafter simply referred to as “subsystem”) 1A. The station 10B, the first slave station 20B (1),..., The nth slave station 20B (n) constitute the subsystem 1B. The

subsystems

1A and 1B have the same configuration as that of the wireless communication system 1 in FIG. The number of slave stations of the subsystem 1B may be different from that of the subsystem 1A.

When at least one of the subsystem 1A and the subsystem 1B moves, the master station 10B, the first slave station 20B (1), the seventh slave station 20B (7), and the nth slave station 20B ( n) may be in a position where radio waves from the master station 10A of the subsystem 1A can be received. At this time, as shown in FIG. 4, when the beacon timing of the subsystem 1A and the beacon timing of the subsystem 1B overlap, for example, a beacon collision occurs at the position of the first slave station 20B (1). Also, as shown in FIG. 5, if the beacon timing of the subsystem 1A and the data transmission timing of the subsystem 1B overlap, data interference occurs at the position of the first slave station 20B (1), for example.

Therefore, when the subsystem 1A detects the beacon transmission or data transmission (coordinator data transmission or end device data transmission) of the subsystem 1B in the carrier sense 34, the parent station in the beacon transmission 31 next to the detected carrier sense 34 10A does not perform beacon transmission but performs beacon transmission with a predetermined number of subframes shifted to avoid a beacon collision with the parent station 10B or interference between the beacon transmission of the parent station 10A and the data transmission of the subsystem 1B.

FIG. 6 is a configuration diagram of a subframe according to another embodiment. 6 includes a beacon transmission (TSb) 31, a first coordinator data transmission (TSc1) 32 (1),..., An m-th coordinator data transmission (TScm) 32 (m), and a first end device. Data transmission (TS1) 33 (1),..., First end device data transmission (TSn) 33 (n), and carrier sense (TScs) 34 are configured to include each time slot. Beacon transmission (TSb) 31, first coordinator data transmission (TSc1) 32 (1), ... m-th coordinator data transmission (TScm) 32 (m), first end device data transmission (TS1) 33 (1) ,..., Carrier sense (TScs) 34 is arranged in the time slot immediately before the n-th end device data transmission (TSn) 33 (n).

An example in which the wireless communication system according to the embodiment is applied to a shooting training system will be described below. The wireless communication system according to the embodiment is not limited to the shooting training system, but can be applied to a system including a plurality of adjacent wireless communication subsystems.

FIG. 7 is a diagram for explaining the shooting training system. FIG. 8 is a top view of the vehicle shown in FIG. The shooting training system includes a vehicle 110 including a light receiver (slave station) 111 (1) to 111 (8) and a presenter (master station) 112, and a laser transmitter 120. When the light receivers 111 (1) to 111 (8) are described as a representative, they are referred to as the light receiver 111. The number of light receivers 111 is eight in the example of FIG. 8, but is not limited to eight. In addition to the vehicle, the light receiver 111 and the indicator 112 can be installed in helicopters, ships, personnel, buildings, and the like.

In the shooting training, a laser beam 121 emitted from the laser transmitter 120 is used as a simulated bullet without using an actual bullet. The laser beam 121 includes information such as an identifier (ID) of the laser transmitter 120 that has emitted the laser beam 121, a firearm type, and a bullet type as the emission information.

The light receiver 111 attached to the vehicle 110 detects the laser beam 121 to detect the impact that the light receiver 111 has received. That is, when detecting the laser beam 121, the light receiver 111 reads the emission information included in the laser beam 121 and wirelessly transmits it to the display unit 112 together with the bullet information. The bulleted information is information such as a wear category indicating the degree of wear due to the bullet, and a worn part (shot position).

When receiving the bullet information from the light receiver 111, the presenter 112 displays the bulleted situation, that is, outputs the bulleted situation, using one or more of light emission, sound generation, and smoke according to the contents.

In this shooting training system, after bullet detection is performed by a plurality of light receivers 111, bullet information is wirelessly transmitted to the indicator 112, and the time until the indicator 112 is displayed is approximately 100 ms or less. There is a need to. Also, loss of bullet information due to data errors during wireless transmission affects normal training. In that case, it is necessary to reliably retransmit data.

Therefore, in this shooting training system, the wireless communication method of the standard IEEE 802.15.4 is used for data transmission between the light receiver (slave station) and the presenter (master station). In the standard IEEE 802.15.4, specifications of a communication method (access method, data transmission sequence, etc.) based on TDMA are established for a data link layer (MAC layer) of a wireless network.

When TDMA wireless communication is performed in accordance with the above standard, for example, when data transmission is performed between a master station and a slave station, time slots in which the master station and the slave station can transmit frames are set in advance in one superframe. The master station and the slave station perform transmission in the set time slots. The super frame indicates a structure on the time axis that defines time slots in which the master station and the slave stations can transmit frames.

FIG. 9 is a configuration diagram of the presenting device and the light receiving device according to the embodiment. As shown in FIG. 9, the presenter (coordinator) 112 includes a wireless module 11, a display unit 15, and a battery 16. The wireless module 11 includes a control unit 12, a transmission / reception unit 13, and a storage unit 14. The transceiver 13 includes an antenna 13 a for transmitting and receiving radio waves to and from the light receiver 111. The battery 16 supplies power to each component of the indicator 112.

The control unit 12 controls the operation of each component of the display unit 112 and the entire display unit 112. In addition, when wirelessly transmitting to the optical receiver 111, the control unit 12 transmits data such as status data, operation setting data, and ACK data based on the timing of the superframe time slot stored in the storage unit 14. Determine the timing. In addition, the control unit 12 causes the light receiver 111 to transmit a beacon for detecting a time slot for transmitting data and ACK data from the transmission / reception unit 13. That is, the control unit 12 notifies the light receiver 111 of the timing at which the light receiver 111 transmits data and ACK data. The ACK data is an acknowledgment (also referred to as a positive response) data, that is, an affirmative sent from the receiving side to the transmitting side in order to indicate that the data transmitted from the transmitting side has been normally received at the receiving side. It is a response data.

The transmission / reception unit 13 transmits or receives data or ACK data wirelessly with the light receiver 111 according to the control from the control unit 12.

The storage unit 14 stores the timing of the superframe time slot. Further, the storage unit 14 holds data received from the light receiver 111 and holds data to be transmitted to the light receiver 111 according to control from the control unit 12. Data to be transmitted to the light receiver 111 is input from the control unit 12, for example.

The display unit 15 is an output unit that outputs various types of information, and displays information received from the light receiver 111. For example, the display unit 15 includes a sound generation unit 151 that emits sound, a light emission unit 152 that emits light, and a smoke generation unit 153 that emits smoke, and outputs sounds such as sound generation, light emission, and smoke generation according to information received from the light receiver 111. Do. Information input to the display unit 15 is held in the storage unit 14.

The light receiver (end device) 111 includes a wireless module 21, a light receiving unit 25, and a battery 26. The wireless module 21 includes a control unit 22, a transmission / reception unit 23, and a storage unit 24. The transmission / reception unit 23 includes an antenna 23a for transmitting / receiving radio waves to / from the display unit 112. The battery 26 supplies power to each component of the light receiver 111.

The control unit 22 controls the operation of each component of the light receiver 111 and the entire light receiver 111. Further, the control unit 22 performs control so that the information input from the light receiving unit 25 is wirelessly transmitted to the indicator 112. In addition, when performing wireless transmission to the indicator 112, the control unit 22 determines the timing for transmitting data and ACK data based on the timing of the superframe time slot stored in the storage unit 24.

The transmission / reception unit 23 transmits or receives data or ACK wirelessly with the display unit 112 according to the control from the control unit 22.

The storage unit 24 stores the timing of the superframe time slot based on the beacon received from the display unit 112. The storage unit 24 holds data received from the display unit 112 and holds data to be transmitted to the display unit 112 in accordance with control from the control unit 22. Data to be transmitted to the indicator 112 is input from the light receiving unit 25, for example.

The light receiving unit 25 is an input unit that receives input of various types of information. For example, the light receiving unit 25 receives a laser beam and outputs information included in the received laser beam to the control unit 22. Information input to the light receiving unit 25 is held in the storage unit 24.

Each of the control unit 12 and the control unit 22 includes a CPU (Central Processing Unit) and a memory for storing an operation program of each control unit as a hardware configuration. The CPU operates according to the operation program.

The storage unit 14 and the storage unit 24 are each composed of a semiconductor memory (flash memory, RAM (Random Access Memory), ROM (read only memory), etc.), a magnetic disk, or the like.

For example, in the example of the shooting training system, the slave station 20 is a light receiver that receives a laser beam, acquires information included in the received laser beam, and wirelessly transmits the acquired information to the display device. . The master station 10 is a display device that is directly connected to a plurality of light receivers, receives information wirelessly transmitted from the plurality of light receivers, and performs output based on the received information. .

FIG. 10 is a configuration diagram of a subframe according to the embodiment. 10 includes a beacon transmission (TSb) 31, a first coordinator data transmission (TSc1) 32 (1), a second coordinator transmission (TSc2) 32 (2), and a first end. Device (end device) data transmission (TS1) 33 (1),..., Eighth end device data transmission (TS8) 33 (8), carrier sense (TScs) 34 time slots (Time Slot: TS) Configured to include. Therefore, the subframe of the example is a case where m = 2 and n = 8 in the subframe of the embodiment.

The time of each time slot is, for example,
tTScs = 0.9ms
tTSb = 0.9ms
tTSc1 = tTSc2 = 2.8 ms
tTS1 = tTS2 = ... = tTS8 = 1.27 ms
tGT = 0.2ms
tSD = 19.96ms
It is.

The link up (at the time of communication connection establishment) with the light receiver 111 and the indicator 112 is demonstrated using FIG. FIG. 11 is a diagram illustrating a subframe period at the time of link-up.

In subframe # 1, the indicator 112 transmits a beacon to the light receiver 111 when no carrier is detected. The light receiver 111 receives the beacon of its own master station and completes the synchronization.

In subframe # 2, the light receiver 111 transmits status data to the indicator 112. The indicator 112 receives the status data. In FIG. 11 and subsequent drawings, the state data is represented by solid arrows.

In subframe # 3, the indicator 112 transmits ACK data to the light receiver 111. The light receiver 111 receives ACK data. In FIG. 11 and subsequent drawings, ACK data is indicated by a broken-line arrow.

In subframe #n, the display unit 112 transmits operation setting data to the light receiver 111. The light receiver 111 receives the operation setting data and transmits ACK data to the display device 112. Complete the link up. In FIG. 11 and subsequent drawings, the operation setting data is represented by solid arrows.

In the above-mentioned shooting training system, the subsystems that perform independent communication are one master station and eight slave stations, and there are about nine subsystems in the radio notification area in one subsystem. The number of channels is 4 to 8, and it is assumed that interference will surely occur during operation. Therefore, the operation is divided into two patterns of link-up (when connection is established) and operation (normal operation), and a method for avoiding interference in each of them will be described. In the following description, as a frequency hopping of 4 channels, a super frame is composed of sub-frames of 4 types of frequencies.

The beacon transmission timing when a carrier is detected will be described with reference to FIGS. FIG. 12 is a diagram for explaining a case where a carrier of state data of an adjacent subsystem is detected. FIG. 13 is a diagram for explaining a case where a beacon carrier of an adjacent subsystem is detected.

In the A subsystem (A vehicle) shown in FIG. 12, the frequency of the subframe changes in the order of fA, fB, fC, fD, fA, fB, fC, fD,..., And in the B subsystem (B vehicle) The frequency of the subframe changes in the order of fC, fA, fD, fB, fC, fA, fD, fB,. The sub-frame with the frequency of vehicle A fA and the sub-frame with the frequency of vehicle B fA partially overlap. As shown in FIG. 12, the parent station of the vehicle A detects the carrier of the state data transmitted from the child station of the vehicle B to the parent station by carrier sense before the timing of beacon transmission to the child station. Therefore, the parent station of vehicle A delays the beacon transmission timing by 8 subframes to avoid interference. The child station of vehicle A continues to wait for a beacon on the reference channel when no beacon is received.

In the A subsystem (A vehicle) and B subsystem (B vehicle) shown in FIG. 13, the frequency of the subframe changes in the order of fA, fB, fC, fD, fA, fB, fC, fD,. The sub-frame with the frequency of vehicle A fA and the sub-frame with the frequency of vehicle B fA partially overlap. As shown in FIG. 13, the parent station of vehicle A detects the carrier of the beacon transmitted from the parent station of vehicle B to the child station by carrier sense before the timing of beacon transmission to the child station. Therefore, the master station of the A vehicle delays the beacon transmission timing (superframe start) by 8 subframes to avoid interference. The child station of vehicle A continues to wait for a beacon on the reference channel when no beacon is received.

ARQ (Automatic Repeat request) retransmission when data interference occurs between adjacent subsystems will be described with reference to FIGS. 14A, 14B, 15A, and 15B. FIG. 14A is a timing chart when interference occurs in ARQ retransmission but link-up is completed. FIG. 14B is an enlarged view of FIG. 14A. FIG. 15A is a timing diagram when link up is completed without interference in ARQ retransmission. FIG. 15B is an enlarged view of FIG. 15A.

In the A subsystem (A vehicle) shown in FIG. 14A, the subframe frequency changes in the order of fA, fB, fC, fD, fA, fB, fC, fD,..., And in the B subsystem (B vehicle). The frequency of the subframe changes in the order of fD, fC, fB, fA, fD, fC, fB, fA,. The subframe with the frequency of vehicle A being fB, the subframe with the frequency of vehicle B being fB, the subframe with the frequency of vehicle A being fD, and the subframe having a frequency of vehicle B being fD partially overlap, and the broken line portion Cause interference.

As shown in FIG. 14B, transmission of status data from the slave station of the A vehicle to the master station, transmission of ACK data from the master station of the B vehicle to the slave station, and status data transmission from the slave station to the master station are performed. have a finger in the pie. The first, sixth to eighth slave stations (ED1, 6 to 8) of the vehicle A perform ARQ retransmission, but the ACK data (CD1, 2) from the master station to the slave stations also interfere and cause a retry over. However, the link up is completed by receiving operational data. The slave stations 5 to 7 of the B vehicle perform ARQ retransmission, but ACK data (CD1, 2) from the master station to the slave station also interferes and a retry over occurs. However, link-up is completed by receiving operational data.

In the A subsystem (A vehicle) shown in FIG. 15A, the frequency of subframes changes in the order of fA, fB, fC, fD, fA, fB, fC, fD,..., And in the B subsystem (B vehicle) The frequency of the subframe changes in the order of fD, fC, fB, fA, fD, fC, fB, fA,. The subframe with the frequency of the vehicle A of fB and the subframe of the vehicle B with the frequency fB partially overlap, and interference occurs at the broken line portion.

As shown in FIG. 15B, transmission of status data from the slave station of the A vehicle to the master station interferes with transmission of ACK data from the master station of the B vehicle to the slave station. The seventh and eighth slave stations (ED7 and 8) of the A vehicle are ARQ retransmitted, and the status data is transmitted to complete the link up. The first to fourth slave stations of the B vehicle are ARQ retransmitted, and the status data is transmitted to complete the link up.

The timing at which link-up can be completed by a retransmission instruction (APL retransmission) from the application layer when data interference occurs will be described with reference to FIGS. 16A and 16B. FIG. 16A is a timing diagram in which linkup is completed by APL retransmission. FIG. 16B is an enlarged view of FIG. 16A.

In the A subsystem (A vehicle) shown in FIG. 16A, the frequency of subframes changes in the order of fA, fB, fC, fD, fA, fB, fC, fD,..., And in the B subsystem (B vehicle) The frequency of the subframe changes in the order of fB, fD, fA, fC, fB, fD, fA, fC,. The subframe with the frequency of vehicle A being fB, the subframe with the frequency of vehicle B being fB, the subframe with the frequency of vehicle A being fD, and the subframe having a frequency of vehicle B being fD partially overlap, and the broken line portion Cause interference.

As shown in FIG. 16B, transmission of status data from the slave station of the A vehicle to the master station interferes with transmission of operation setting data from the master station of the B vehicle to the slave station. The 4th to 7th slave stations (ED4 to 7) of the A vehicle are ARQ retransmitted, but the ACK data (CD1, 2) from the master station to the slave station also interferes and a retry over occurs. However, the link up is completed by receiving operational data. The operation setting data from the master station to the slave station of the B vehicle is ARQ retransmission, but the ACK data (ED4 to ED7) from the slave station to the master station also interferes and causes a retry over. However, at the time of ARQ retry over of the operation setting data at the master station, retransmission processing by the application layer is performed. The retransmission timing is determined by a delay time using random numbers. This is to prevent re-interference due to retransmission at the same timing in vehicles having the same frequency hopping (FH).

When random numbers are acquired at each slave station in APL retransmission at the slave station, a difference occurs in the slave station retransmission timing, and a lot of subframes are used for each retransmission data and ACK data from the master station. As a result, the rate of occurrence of re-interference increases. As a countermeasure, it is necessary to adjust the retransmission data from the slave station to be one subframe or two consecutive subframes. The delay time is determined by referring to the delay time table from the PAN-ID assigned with a unique number for each vehicle. The setting value of the delay time table is configured to be as inconsistent as possible with the FH pattern determined by the PAN-ID.

The timing at which link-up can be completed by restarting the wireless module at the time of beacon interference will be described with reference to FIGS. 17A, 17B, 17C, 18A, 18B, and 18C. FIG. 17A is a timing diagram when only one of the interfered subsystems completes link-up by restarting. 17B and 17C are enlarged views of FIG. 17A. 17C is connected next to FIG. 17B, and the right side part of FIG. 17B and the left side part of FIG. 17C overlap. FIG. 18A is a timing diagram when both interfering subsystems complete the link-up by restarting. 18B and 18C are enlarged views of FIG. 18A. 18C is connected next to FIG. 18B.

In the A subsystem (A vehicle) shown in FIG. 17A, the frequency of subframes changes in the order of fA, fB, fC, fD, fA, fB, fC, fD,..., And in the B subsystem (B vehicle) The frequency of the subframe changes in the order of fC, fA, fD, fB, fC, fA, fD, fB,. The subframe with the frequency of vehicle A is fA and the subframe with the frequency of vehicle B are fA partially overlap, and interference occurs at the broken line portion.

As shown in FIG. 17B, transmission of a beacon from the parent station of the A vehicle to the child station interferes with transmission of status data from the child station of the B vehicle to the parent station. The child station of the vehicle A cannot receive the beacon and cannot transmit the status data. On the other hand, the first slave station (ED1) of vehicle B performs ARQ retransmission, and status data is transmitted to complete link up. Therefore, as shown in FIG. 17C, when the master station of the vehicle A detects the incomplete operation data transmission even after a predetermined time (for example, 3 seconds) has passed since the beacon transmission, the link up process is restarted by using this as a trigger. to start. This restart process is implemented by transmitting an operation stop request from the control unit 12 to the transmission / reception unit 13 and then transmitting an operation start request after a delay time based on a random value. The slave station continues to wait for a beacon on the reference channel when no beacon is received.

In the A subsystem (A vehicle) shown in FIG. 18A, the subframe frequency changes in the order of fA, fB, fC, fD, fA, fB, fC, fD,..., And in the B subsystem (B vehicle). The subframe frequency changes in the order of fA, fB, fC, fD, fA, fB, fC, fD,. The sub-frames of all the frequencies of the A vehicle and the sub-frames of all the frequencies of the B vehicle overlap, and interference occurs at the broken line portion.

As shown in FIG. 18B, transmission of a beacon from the parent station of the A vehicle to the child station interferes with transmission of a beacon from the parent station of the B vehicle to the child station. The slave station of the A vehicle and the slave station of the B vehicle cannot receive the beacon and cannot transmit the status data. Therefore, as shown in FIG. 18C, when the master station of the A vehicle and the master station of the B vehicle detect the incomplete transmission of the operation data even after a predetermined time (for example, 3 seconds) has passed since the beacon transmission, this is triggered. Restart the link up process. This restart process is implemented by transmitting an operation stop request from the control unit 12 to the transmission / reception unit 13 and then transmitting an operation start request after a delay time based on a random value. By transmitting the operation start request after the delay time based on the random number value, as shown in FIG. 18C, the beacon transmission timings of the parent station of the A vehicle and the parent station of the B vehicle can be shifted. The slave station continues to wait for a beacon on the reference channel when no beacon is received.

The hidden terminal problem during beacon transmission will be described with reference to FIGS. 19, 20A, 20B, and 20C. FIG. 19 is a diagram illustrating a positional relationship of vehicles in which a hidden terminal problem occurs during beacon transmission. FIG. 20A is a timing diagram for explaining the hidden terminal problem during beacon transmission. 20B and 20C are enlarged views of FIG. 20A. After FIG. 20B, FIG. 20C is connected.

As shown in FIG. 19, the carrier of the B vehicle does not reach the master station 112A of the A vehicle 110A, but the fourth vehicle station 111A (4) and the fifth slave station 111A (5) of the A vehicle 110A May arrive. When the master station does not recognize the interference with the adjacent subsystem and the slave station interferes with the adjacent subsystem, it is called a hidden terminal problem.

In the A subsystem (A vehicle) shown in FIG. 20A, the frequency of subframes changes in the order of fA, fB, fC, fD, fA, fB, fC, fD,..., And in the B subsystem (B vehicle) The frequency of the subframe changes in the order of fA, fC, fD, fB, fA, fC, fD, fB,. The sub-frame with the frequency of vehicle A fA and the sub-frame with the frequency of vehicle B fA overlap, and interference occurs at the broken line portion.

As shown in FIG. 20B, beacon reception from the fourth and fifth child stations of the A vehicle interferes with transmission of a beacon from the parent station of the B vehicle to the child station. Depending on the timing of the B vehicle, beacon reception from the fourth and fifth child stations of the A vehicle may interfere with transmission of operation data and the like of the B vehicle (not shown). The fourth child station and the fifth child station of the A vehicle cannot receive the beacon and cannot transmit the status data. Further, the 4th slave station and the 5th slave station do not receive the beacon and ARQ retransmission is not performed. Therefore, when the master station of the vehicle A detects incomplete operation data transmission even after a predetermined time (for example, 3 seconds) has passed since the beacon transmission, the master station restarts the link-up process using this as a trigger. This restart process is implemented by transmitting an operation stop request from the control unit 12 to the transmission / reception unit 13 and then transmitting an operation start request after a delay time based on a random value. The interference generating slave station continues to wait for a beacon on the reference channel when no beacon is received. When the other slave station detects that no operational data has been received even after a predetermined time (for example, 3 seconds) has elapsed since the start of synchronization, the slave station shifts to a beacon wait on the reference channel using this as a trigger.

Synchronization protection after link-up will be described with reference to FIGS. 21, 22A and 22B. FIG. 21 is a timing chart when a beacon is not transmitted by carrier sense. 22A and 22B are timing diagrams when vehicles having the same timing merge. FIG. 22B is connected after FIG. 22A.

As shown in FIG. 21, when the master station of vehicle A cannot detect the carrier of another subsystem in the sense slot and transmit a beacon, it transmits the beacon with a shift of 8 subframes. The slave station of vehicle A receives the next beacon if synchronized. If the slave station cannot receive a beacon, it continues to transmit beacons at intervals of 8 subframes. The slave station shifts to beacon waiting on the reference channel as out-of-synchronization when no new beacon reception occurs in the period of 2 superframes from the previous beacon reception.

As shown in FIG. 22A, when the B vehicle of the same timing joins the A vehicle, the beacon of the A vehicle and the beacon of the B vehicle continue to collide, and the beacon not received by the slave station continues. As a result, slave station asynchrony occurs and the process shifts to beacon waiting. The master station transmits Keep-Alive data to the slave station, but there is no response if all the slave stations are asynchronous at this time. The wireless module is restarted when no response is received from the slave station for Keep-Alive data transmitted from the master station every 10 minutes. This is the same processing as link-up restart.

In this embodiment, carrier sense is performed before beacon transmission, and if detected, the specified frame is shifted to avoid collision with other subsystems. Also, by providing a link-up time and resetting (restarting) if the connection is not established within a predetermined time, the beacon transmission timing of the subsystem can be shifted by performing the link-up again. Can avoid a state in which communication cannot be performed at all due to overlapping transmission timings. Also, the hidden terminal problem can be solved.

<Modification>
FIG. 23 is a configuration diagram of a subframe according to a modification. The subframe 30A shown in FIG. 23 corresponds to FIG. 6, and includes a beacon transmission (TSb) 31, a first coordinator data transmission (TSc1) 32 (1), a second coordinator transmission (TSc2) 32 (2), 1 end device data transmission (TS1) 33 (1),..., Eighth end device data transmission (TS8) 33 (8), and carrier sense (TScs) 34. TScs is arranged in front of TSb and each TSc1, TSc2, TS1,..., TS8. Therefore, the subframe of the modified example is a case where m = 2 and n = 8 in the subframe of the embodiment.

The time slot time is, for example,
tTScs = 0.2ms
tTSb = 0.9ms
tTSc1 = tTSc2 = 2.8ms
tTS1 = tTS2 = ... = tTS8 = 1.27 ms
tGT = 0.2ms
tSD = 23.26ms
It is.

The effect of the modification will be described with reference to FIGS. 24A, 24B, 25A, and 25B. FIG. 24A is a timing diagram of link-up processing using subframes according to a modification. FIG. 24B is an enlarged view of FIG. 24A. FIG. 25A is a timing diagram of link-up processing using subframes according to the embodiment. FIG. 25B is an enlarged view of FIG. 25A.

In the A subsystem (A vehicle) shown in FIG. 24A, the frequency of subframes changes in the order of fA, fB, fC, fD, fA, fB, fC, fD,..., And in the B subsystem (B vehicle) The frequency of the subframe changes in the order of fD, fC, fB, fA, fD, fC, fB, fA,. The subframe with the frequency of the vehicle A of fB and the subframe of the vehicle B with the frequency fB partially overlap, and interference occurs at the broken line portion.

As shown in FIG. 24B, transmission of status data (ED1) from the first slave station of the A vehicle to the master station and transmission of ACK data (CD2) from the master station of the B vehicle to the slave station interfere. When transmission data (including a beacon) is generated in both the master station and the slave station, if a carrier of another station is detected by carrier sense (TScs) immediately before the corresponding time slot, transmission is postponed to the next subframe (hereinafter, Ts_Kick.)

In the A subsystem (A vehicle) shown in FIG. 25A, the frequency of subframes changes in the order of fA, fB, fC, fD, fA, fB, fC, fD,. In (B vehicle), the frequency of the subframe changes in the order of fD, fC, fB, fA, fD, fC, fB, fA,. The subframe with the frequency of vehicle A being fB, the subframe with the frequency of vehicle B being fB, the subframe with the frequency of vehicle A being fD, and the subframe having a frequency of vehicle B being fD partially overlap, and the broken line portion Cause interference.

As shown in FIG. 25B, transmission of status data from the slave station of the A vehicle to the master station, transmission of ACK data from the master station of the B vehicle to the slave station, and status data transmission from the slave station to the master station are performed. have a finger in the pie. The first, sixth to eighth slave stations (ED1, 6 to 8) of the A vehicle are ARQ retransmitted, but ACK data (CD1, 2) from the master station to the slave stations also interfere and retry over. However, the link up is completed when the operation setting data is received. The fifth to seventh slave stations of vehicle B perform ARQ retransmission, but ACK data (CD1, 2) from the master station to the slave stations also interfere and retry over. However, the link up is completed when the operation setting data is received.

In the modification, ARQ retransmission can be avoided, but in the embodiment, AR retransmission and ARQ retry over occur. Thereby, in vehicle B, the link-up is completed one subframe earlier in the modified example than in the example. On the other hand, in the embodiment, since the super frame is shorter than the modified example, the real-time property at the time of continuous shooting is superior to the modified example. In the embodiment, since the carrier sense is not performed before data transmission even in the slave station, the power saving is superior to the modified example.

According to the modified example, not only the master station but also the slave station performs carrier sense, and if a carrier is detected at the time of transmission of the slave station, the real-time property is slightly delayed by waiting until the next beacon transmission timing. Since the collision is eliminated, the lost data is reduced, and as a result, the data arrival rate can be increased.

Although the invention made by the present inventor has been specifically described based on the embodiments and examples, the present invention is not limited to the above-described embodiments and examples, and various modifications can be made. Not too long.

DESCRIPTION OF SYMBOLS 1 ... Wireless communication system 1A ... Wireless communication subsystem 1B ... Wireless communication subsystem 110 ...

Vehicle

10, 10A, 10B ... Master station 112 ... Indicator (master station)
DESCRIPTION OF SYMBOLS 11 ... Wireless module 12 ... Control part 13 ... Transmission / reception part 13a ... Antenna 14 ... Memory | storage part 15 ... Display part 151 ... Sound-producing part 152 ... Light emission part 153 ...・ Smoke generating part 16 ...

battery

20, 20A, 20B ... slave station 111 ... receiver (slave station)
21 ... Wireless module 22 ... Control unit 23 ... Transmission / reception unit 23a ... Antenna 24 ... Storage unit 25 ... Light receiving unit 26 ... Battery 30 ... Subframe 31 ... Beacon transmission 32 ... Coordinator data transmission 33 ... End device data transmission 34 ... Carrier sense 300 ... Superframe

Claims

Provided with a plurality of subsystems composed of a master station and a plurality of slave stations. In each of the plurality of subsystems, the master station and the slave stations perform data transmission / reception in a superframe composed of a plurality of subframes. ,
Each of the plurality of subframes is
A first time slot in which the master station transmits a beacon to the slave station;
A second time slot in which the master station detects a carrier of another subsystem immediately before the first time slot;
A third time slot in which the master station transmits data to the slave station;
A fourth time slot in which the slave station transmits data to the master station;
A wireless communication system comprising:
In claim 1,
When the master station detects a carrier of another subsystem in the second time slot, the beacon transmission is stopped in the subframe, and the other subsystem is used in the second time slot of the subframe after a predetermined number of subframes. A wireless communication system that checks for the presence or absence of a carrier, repeats until a carrier of another subsystem is not detected, and transmits a beacon when the carrier is not detected.
In claim 2,
In the communication connection establishment process between the master station and the slave station, a wireless communication system that restarts the communication establishment process when the master station detects incomplete transmission of operational data within the predetermined time after transmitting a beacon.
In claim 1,
The fourth time slot is a time slot for transmitting the status data of the slave station to the master station,
The wireless communication system, wherein the third time slot is a time slot for transmitting ACK data indicating that the master station has received the status data to the slave station.
In claim 1,
The third time slot is a time slot in which the master station transmits operation setting data to the slave station,
The fourth time slot is a wireless communication system, which is a time slot for transmitting ACK data indicating that the slave station has received the operation setting data to the master station.
In claim 1,
A wireless communication system in which carrier frequencies of the plurality of subframes in the superframe are different.
In claim 1,
Each of the plurality of subframes further includes
A fifth time slot for detecting a carrier of another subsystem immediately before the third time slot;
A sixth time slot for detecting a carrier of another subsystem immediately before the fourth time slot;
A wireless communication system comprising: