JP5313818B2 - Wireless communication system - Google Patents

Description

  The present invention relates to a wireless communication system that performs wireless communication using a plurality of wireless channels.

  In recent years, for example, using a radio station such as a specific low-power radio station, a control signal for starting, changing, or terminating the function of a device installed at a remote location, or a measuring machine installed at a remote location Wireless communication systems that transmit and receive measurement results are widely used. This type of wireless communication system is adapted to a wide variety of systems such as a lighting control system, a crime prevention system, a door phone system, a fire alarm system, and an automatic remote meter reading system. For example, the fire alarm system described in Patent Document 1 There is.

  In this fire alarm system, multiple fire detectors (radio units) with wireless communication functions are installed at multiple locations. A radio signal including fire detection information is continuously transmitted to other fire detectors. Other fire detectors receive the radio signal and sound an alarm based on the fire detection information included in the radio signal.

  Here, the radio signal transmitted / received by the fire detector includes a synchronization bit (preamble), a frame synchronization pattern (unique word), a destination address, a transmission source address, a message, and an error detection code. The preamble is a bit pattern for bit synchronization in which, for example, 0 and 1 are alternately arranged, and in this fire alarm system, the bit length is set to 8 bits. The unique word is a bit string having a bit pattern different from that of the preamble, and a bit pattern that is difficult to be included in a message or the like is used. In addition, each fire detector detects the preamble and unique word to detect that the wireless signal is a wireless signal used in its own system. The destination address, the source address, and , Receive messages and get necessary information such as control commands. The error detection code is, for example, an error detection code made up of CRC (Cyclic Redundancy Check) or the like, and confirms the consistency of the received radio signal, and there is an abnormality such as bit inversion due to some cause during transmission and reception of the radio signal It is possible to detect what has occurred.

  In this type of radio communication system, it is necessary to exchange radio signals between a plurality of radio stations (transmitters / receivers), and a plurality of radio channels are provided in a specific frequency band. Alternatively, a radio channel is selected and a radio signal is transmitted, and a receiver receives a radio signal from each transmitter by scanning all radio channels at a predetermined time period by, for example, time division. Taken. Here, the receiver measures the signal strength in each radio channel based on a received signal strength indication signal (Received Signal Strength Indication (RSSI)) every predetermined time period. A preamble consisting of bits is detected, and when a correct synchronization bit is detected, a unique word, a destination address, a source address, etc. following the preamble are received.

JP 2009-177340 A

  By the way, this type of radio transmission system can also share a radio station on the receiver side in a plurality of systems. For example, one receiver receives a detection signal from a human body detection sensor of a door phone system. At the same time, it can be applied to a system that receives a dimming signal for operating the dimming level of the lighting control system and operates the dimming level of the lighting fixture. A plurality of transmitters can be connected to the door phone system and the lighting control system, respectively.

  However, in the conventional radio transmission system, the bit length of the preamble is set to the minimum bit length necessary for bit synchronization (8 bits in the above-described fire notification system). For this reason, when the number of transmitters that transmit radio signals increases, the probability that the receiver side is scanning other radio channels when transmitting a radio signal at a certain transmitter increases, and the receiver side The possibility of missing the preamble increases. In this case, the transmitter side continuously transmits the same radio signal again. However, if the data length of the message to be transmitted is long, the time required from when the preamble is overlooked until it is retransmitted is very long. As a result, there is a problem that the time required for transmission and reception of radio signals becomes long.

  The present invention has been made in view of the above-mentioned reasons, and the object of the present invention is to reduce the possibility of missing a preamble of a radio signal transmitted by a transmitter and to transmit and receive a radio signal in a short time. It is to provide a wireless communication system.

In order to achieve the above object, according to the first aspect of the present invention, one or a plurality of transmitters for selectively selecting a plurality of radio channels having different frequencies and transmitting a radio signal are transmitted from the transmitter. and a receiver for receiving a radio signal, the radio signal has a preamble in which a predetermined bit synchronization pattern is repeatedly arranged, and a data arranged subsequent to the preamble, the receiver scans and channel setting means for setting a plurality of the radio channels of the target, for each predetermined scan cycle, and scanned divided sequentially switching the radio channels to be scanned by the time, detecting the bit synchronization pattern for each of the radio channel a synchronous bit detection unit for, when the bit synchronization pattern is detected, to receive the data following the preamble And a data receiving unit, the preamble is at least closed and bit length corresponding to one period of time of the scan cycle, the bit length corresponding to the sum and the bit length necessary for the detection of the bit synchronization pattern, the The transmitter may change the length of the preamble according to the number of the radio channels set by the channel setting means .

  According to the present invention, since the possibility that the receiver detects the bit synchronization pattern of the radio signal transmitted by the transmitter is increased, the possibility of missing the preamble of the radio signal transmitted by the transmitter is reduced, and in a short time. Wireless signals can be transmitted and received.

In addition , since the preamble length of the transmitter can be increased or decreased according to the number of scans of the radio channel set by the receiver, a more optimal preamble length can be selected, and the radio signal transmitted by the transmitter can be selected. Wireless signals can be transmitted and received in a shorter time while reducing the possibility of missing the preamble.

In the invention of claim 2, in the invention described in claim 1, wherein the receiver includes a priority setting unit that sets a priority for each wireless channel scan target, the synchronous bit detecting unit includes radio channel The number of scans of the wireless channel in the scan period is set based on the priority for each.

  According to the present invention, for example, a radio signal in a high-priority wireless channel is detected a plurality of times in one scan cycle, so that a radio signal from a high-priority transmitter is further detected. The possibility increases.

According to the invention of claim 3, in the invention of claim 1 or 2, wherein the receiver includes a priority setting unit that sets a priority for each wireless channel scan target, the synchronous bit detecting unit Is configured to set the scan time of the radio channel in the scan cycle based on the priority for each radio channel.

  According to the present invention, for example, in one scan cycle, the period for detecting a radio signal in a radio channel with a high priority becomes long, so that a radio signal from a transmitter with a high priority may be detected more. Will increase.

According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the radio signal has a frame synchronization pattern comprising a bit pattern different from the bit synchronization pattern as the bit synchronization pattern. The receiver includes a signal strength detection unit that detects a signal strength of a radio channel, and a frame detection unit that detects the frame synchronization pattern, and the signal strength detection unit is a signal having a predetermined strength or higher. If the frame synchronization pattern is not detected before a predetermined time elapses after the intensity is detected, scanning of the wireless channel is started again.

  According to the present invention, when the frame synchronization pattern is not detected, the wireless signal is detected again, so that it is possible to avoid a situation in which another normal wireless signal cannot be received due to an unauthorized wireless signal.

According to the invention of claim 5, in the invention according to any one of claims 1 to 4 , the receiver includes a signal strength detector that detects a signal strength of a radio channel, and the data receiver When receiving the data, if the signal strength detected by the signal strength detection unit is lower than a predetermined strength, reception of the wireless signal is interrupted and scanning of the wireless channel is started again. And

  According to the present invention, if the signal strength weakens during reception of the radio signal, the reception is interrupted and the radio signal is detected again, so that another normal radio signal cannot be received by an unauthorized radio signal. Can be avoided.

  As described above, in the present invention, there is a high possibility that the preamble of the radio signal transmitted from the transmitter is detected on the receiver side. Therefore, the radio communication in which the time required for transmitting and receiving the radio signal is shortened. A system can be provided.

(A) is schematic which shows the format of the radio signal of the radio | wireless communications system concerning Embodiment of this invention, (b) (c) is schematic which shows the time which scans the same radio signal. It is a schematic block diagram which shows the structure of the radio | wireless communications system. It is a table which shows the setting content set to the receiver of the radio | wireless communications system.

  Embodiments of the present invention will be described below with reference to FIGS.

  As shown in FIG. 2, the radio communication system according to the present embodiment includes one receiver 10 and a plurality of transmitters 20. In the present embodiment, description will be made on the assumption that the transmitter 20 is connected to a total of seven transmitters 20a to 20d and 20x to 22z.

  The transmitters 20a... 20d constitute a door phone system together with the receiver 10. Each transmitter 20a... 20d includes a door phone sub-unit, such as a camera, that transmits a call signal in response to a visitor's operation. It is a human body detection sensor that transmits a detection signal, or a lock that is attached to a door such as an entrance and transmits a key opening / closing signal. The transmitters 20x... 20z constitute an illumination control system together with the receiver 10. Each transmitter 20x... 20z transmits a dimming signal in accordance with a user operation, and the lighting state of the light source. It is a lighting fixture that outputs a lighting signal, or an illuminance sensor that outputs an illuminance detection signal that is attached to a ceiling surface or the like and indicates the brightness of the illumination area.

  Each transmitter 20 includes a transmission unit 21 composed of, for example, a specific low-power radio station, and transmits a radio signal including information according to the type of each transmitter 20 and the type of the system to which the transmitter 20 belongs to the receiver 10. doing. The transmission unit 21 selectively selects a specific radio channel from a plurality of radio channels provided in the specific frequency band, and transmits a radio signal to the receiver 10. In this embodiment, ch1, ch2,... Ch7 are selected for the transmitters 20a... 20d, 20x.

  The receiver 10 also serves as a control master unit in both the door phone system and the lighting control system. For example, the control unit 11 including a microcomputer, the reception unit 12 including a specific low-power radio station, and a nonvolatile A storage unit 13 including a semiconductor memory and an operation input unit 14 including a liquid crystal panel and a switch are provided.

  The receiving unit 12 operates according to the control of the control unit 11, and when a radio channel to be scanned is designated, the signal strength in the radio channel is measured based on, for example, RSSI. When the measured signal strength is higher than a predetermined threshold value, the wireless signal flowing in the wireless channel is received and output to the control unit 11, but when the signal strength is lower than the predetermined threshold value, Reception is not performed, and the control unit 11 waits until a wireless channel is designated again.

  The storage unit 13 stores information recorded by the control unit 11, and stores information such as priority of each transmitter 20, identification address, and radio channel number. In the present embodiment, setting information shown in FIG. 3 is stored based on an operation input of the operation input unit 14 described later, and the transmitter 20a includes an identification address 001, a radio channel ch1, and The priority is set to “2”, and the same setting is made for the transmitters 20b... 20d, 20x. The priority is assumed to be higher as the number is smaller, and “1” is the highest priority.

  The operation input unit 14 outputs an operation input signal to the control unit 11 in accordance with a user input operation. The user operates a switch or the like of the operation input unit 14 based on characters / graphics displayed on the liquid crystal panel or the like of the operation input unit 14 to identify the address, priority, Settings such as addition, change, and deletion of the wireless channel number and the total number of transmitters 20 can be changed. The setting information performed by the user using the operation input unit 14 is stored in the storage unit 13 via the control unit 11, and the control unit 11 performs an operation based on the information recorded in the recording unit 13.

  Here, the radio signal transmitted from the transmitter 20 to the receiver 10 has a format as shown in FIG. 1A, and includes a preamble PA, a unique word UW, data DA, and an error detection code CR. It is configured. The preamble PA is, for example, a bit string composed of a bit synchronization pattern in which 0 and 1 are alternately repeated. The leading bit is set to 0, the last bit is set to 1, and the bit string is preambled only when this bit string is continuous for 64 bits or more. It can be regarded as PA. The unique word UW consists of bits different from the preamble PA, and is set to a length of 32 bits in the present embodiment. The data DA is a bit string including the identification address of the transmitter 20 that has been transmitted and the transmission information that the transmitter 20 transmits, and the bit length can be made variable according to the content of the transmission information that is transmitted. . The error detection code CR is a bit string made up of CRC, and is set so that an abnormality such as bit inversion can be detected at least in the bit string constituting the data DA at the time of transmission / reception.

  The control unit 11 activates the reception unit 12 every predetermined time interval (scan cycle) by a built-in timer (not shown), sequentially scans a preset wireless channel, and either transmitter The radio signal transmitted from 20 is received. In the present embodiment, as shown in FIG. 1B, based on the setting information stored in the storage unit 13, each radio channel is scanned every 2 ms. At this time, since the priority of the radio channels ch5 to ch7 set in the transmitters 20x to 20z is set to “1”, it is set to scan twice in one cycle. The time for one scanning period necessary for scanning the wireless channel is 20 ms.

  As a specific method of scanning each radio channel, the control unit 11 controls the receiving unit 12 to detect the signal strength in a predetermined radio channel. If the detected signal strength is sufficient, the receiving unit 12 A radio signal is input to the control unit 11. Next, the control unit detects the above-described bit synchronization pattern in the radio signal input from the receiving unit 12. If a bit synchronization pattern is not detected in 2 ms in each wireless channel, the wireless channel to be scanned is switched to the next wireless channel, and the bit synchronization pattern is detected again. If a bit synchronization pattern is detected within 2 ms, the radio channel to be scanned is fixed to that radio channel, and the preamble PA and unique word UW are detected continuously for a predetermined time. In this embodiment, 40 ms from the start of detection of the bit synchronization pattern is set as the predetermined time for detection, which is 20 ms for one cycle necessary for scanning all the radio channels. The time obtained by adding 13.3 ms corresponding to 64 bits necessary to determine that the bit string is the preamble PA and 6.7 ms corresponding to 32 bits which is the bit length of the unique word UW.

  Next, when the unique word UW is not detected, the receiver 10 stops receiving the radio signal on the radio channel and starts scanning each radio channel again. On the other hand, when the unique word UW is detected, the subsequent data DA is received, and the presence or absence of signal information is confirmed with the error correction code CR. If there is no abnormality, the information stored in the radio signal is acquired. . The receiving unit 12 periodically detects the signal intensity even when receiving the data DA, and if the signal intensity becomes lower than a predetermined threshold, the control unit 11 notifies the signal intensity. A signal indicating the decrease is output, reception of the radio signal in the radio channel is terminated, and scanning of the radio signal in the next radio channel is started.

  In this way, the receiver 10 receives the radio signal by detecting the preamble PA included in each radio channel every predetermined scan period (20 ms).

Here, the bit length of the preamble PA is set to 160 bits, which is 96 bits corresponding to the scanning period (20 ms) in the receiver 10 and 64 bits necessary for detecting the preamble PA. In this way the child, the receiver 10 from the head between the 96-bit preamble PA is likely to detect the bit synchronization pattern, further thereafter, 64-bit required for the detection of at least the preamble PA Since the bit synchronization pattern continues, the receiver 10 can detect the preamble PA and receive a radio signal. Thereby, since the probability that the radio signal transmitted by the transmitter 20 is received by the receiver 10 is increased, the transmitter 20 is less required to retransmit the same radio signal, and the time required for transmission / reception can be reduced. it can.

  As shown in FIG. 1C, the receiver 10 may scan radio channels ch5 to ch7 with high priority for a longer time than radio channels ch1 to ch4 with low priority. ch1 to ch4 are set to 2 ms, and ch5 to ch7 are set to 4 ms.

  In this embodiment, the bit length of the preamble PA of each transmitter 20 is a fixed length of 160 bits. However, the number of radio channels set in the receiver 10 by providing setting means in each transmitter 20. Or, it may be possible to change according to the length of one cycle in which each radio channel is scanned. As the changing means, when the user changes the setting of the receiver 10 via the operation input unit 14, The receiver 10 may transmit an instruction signal for instructing the preamble length to the transmitter 20, and the preamble length of the radio signal transmitted by itself may be changed according to the instruction signal received by the transmitter 20.

  In this embodiment, the example in which the wireless communication system is applied to a door phone system and a lighting control system has been described. However, remote meter reading is performed through a wide-area communication network, and maintenance and meter reading are performed by a maintenance terminal. It may be adapted to the system.

DESCRIPTION OF SYMBOLS 10 Receiver 11 Control part 12 Receiving part 13 Storage part 14 Operation input part 20a ... 20d, 20x ... 20z Transmitter 21 Transmitter PA Preamble UW Unique word DA Data CR Error detection code

Claims (5)

One or more transmitters that selectively select a plurality of radio channels having different frequencies and transmit radio signals;
A receiver for receiving a radio signal transmitted from the transmitter;
The radio signal has a preamble in which a predetermined bit synchronization pattern is repeatedly arranged, and a data arranged subsequent to the preamble,
The receiver includes a channel setting means for setting a plurality of the radio channels to be scanned, for each predetermined scan cycle, the time sharing scanned sequentially switching the radio channels to be scanned, for each of the radio channel a synchronous bit detection unit for detecting the bit synchronization pattern, if the bit synchronization pattern is detected, and a data reception unit for receiving the data following the preamble,
The preamble and at least perforated with the bit length corresponding to one period of time of the scan cycle, the bit length corresponding to the sum and the bit length necessary for the detection of the bit synchronization pattern,
The wireless communication system, wherein the transmitter changes the length of the preamble according to the number of channels of the wireless channel set by the channel setting means . The receiver includes a priority setting unit configured to set a priority for each radio channel to be scanned, and the synchronization bit detection unit is configured to perform the radio in the scan cycle based on the priority for each radio channel. 2. The wireless communication system according to claim 1, wherein the number of channel scans is set . The receiver includes a priority setting unit that sets a priority for each of the radio channels of the scan target, the synchronous bit detecting unit, based on the priority of each of the wireless channels, the in the scan cycle The radio communication system according to claim 1 or 2, wherein a scan time of the radio channel is set. In the wireless signal, a frame synchronization pattern composed of a bit pattern different from the bit synchronization pattern is arranged following the bit synchronization pattern,
The receiver includes a signal strength detection unit that detects a signal strength of the wireless channel and a frame detection unit that detects the frame synchronization pattern, and the signal strength detection unit detects a signal strength equal to or higher than a predetermined strength. The scanning of the wireless channel is started again if the frame synchronization pattern is not detected before a predetermined time elapses. The wireless communication system described. The receiver includes a signal strength detection unit that detects the signal strength of the wireless channel, and the signal strength detected by the signal strength detection unit when the data reception unit is receiving the data is a predetermined strength. The wireless communication system according to any one of claims 1 to 4 , wherein reception of a wireless signal is interrupted and scanning of the wireless channel is started again when the wireless communication signal is lower .

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