JP2011250023A - Wireless communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wireless communication system which improves using efficiency of a wireless signal by simplification of reception processing and reduction in power consumption in a wireless station, thereby shortening the preamble of the wireless signal.SOLUTION: A wireless communications system A comprises a relay device 2 and a plurality of reading meters 1 which wirelessly communicate using a predetermined wireless channel among a plurality of wireless channels of different frequencies. The relay device 2 allows a signal transmission unit 25 to transmit to the reading meter 1 a link establishment signal containing channel information indicating the wireless channel for data transmission allocated to each reading meter 1 by a channel allocation unit 23. Each reading meter 1 allows a channel setting unit 15 to set a wireless channel to be received, on the basis of the channel information contained in the received link establishment signal.

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, an automatic remote meter reading system, using a wireless station such as a specific low-power wireless station, sending and receiving measurement results of a measuring machine installed at a remote location, and starting the function of a device installed at a remote location, Wireless communication systems that transmit and receive control signals for termination have become widespread. This type of wireless communication system is also applied to lighting control systems, crime prevention systems, door phone systems, and the like, and Patent Document 1 describes an example in which this type of wireless communication system is applied to a fire alarm system. .

  In the fire alarm system described in Patent Document 1, a plurality of fire detectors provided with wireless communication functions are installed at multiple locations, and wireless signals are exchanged between the fire detectors. For example, when one of the fire detectors detects a fire, the fire detector sounds its own alarm and continuously transmits a wireless signal including fire detection information to the other fire detectors. In addition, other fire detectors that have received the wireless signal from the fire detector that has detected a fire sound an alarm based on the fire detection information included in the wireless signal. As described above, the plurality of fire detectors transmit and receive wireless signals to each other, so that the plurality of fire detectors operate in conjunction with each other so that the occurrence of a fire can be notified quickly and reliably.

  In this type of radio communication system, radio signals are exchanged between a plurality of radio stations. Therefore, a plurality of radio channels are provided in a specific frequency band used as radio signals, and radio signals are transmitted and received. Yes. Specifically, when a radio station transmits a radio signal, a radio channel to be used for transmission is selectively selected from a plurality of radio channels, and the radio signal is transmitted. In order for a radio station to receive a radio signal, the received signal strength (RSSI) for each radio channel is measured at a predetermined scan period. If the received signal strength is greater than a predetermined threshold, the radio signal Is detected and received.

  Here, for example, a format as shown in FIG. 3 is adopted for this radio signal, and apart from data DA which is binary data actually exchanged, preamble PA, unique word UW, device identification information AD, error detection code CR is included. The preamble PA is, for example, a bit string composed of a bit synchronization pattern in which 0 and 1 are alternately repeated. The first bit is set to 0 and the last bit is set to 1. The unique word UW is composed of a bit string different from the preamble PA, and a bit string determined in advance in the wireless communication system is used. In the device identification information AD, an identifier assigned to each of the wireless station that transmitted the wireless signal and the wireless station that is the destination of the wireless signal is set. The error detection code CR is, for example, a bit string made up of CRC (Cyclic Redundancy Check), and is set so that at least an abnormality such as bit inversion has occurred in the bit string constituting the data DA.

  When the radio station receives a radio signal, the preamble PA is detected on the radio channel to be received and bit synchronization is performed, and then the radio signal transmitted to the own device from the unique word UW and the device identification information AD It is judged whether it is. Thereafter, if the radio signal is a radio signal transmitted to the own station, the radio station detects that there is no abnormality in the data DA from the bit string of the data DA and the error detection code CR, and receives the data DA. Thereby, the radio signal transmitted using the radio channel arbitrarily selected by the radio station can be received, and the radio signal can be exchanged between a plurality of radio stations.

JP 2009-177340 A

  By the way, assuming that the number of radio channels used in the above-described radio communication system is 30, and the measurement time of the received signal strength for one radio channel is 2 ms, the time required to detect the received signal strength of all the radio channels is as follows. At least 60ms are required. Here, in order for a radio station to detect a radio signal transmitted to an arbitrary radio channel within the above-described scan cycle, the total bit length of the preamble PA of the radio signal is scanned with the bit length necessary for bit synchronization. A bit length obtained by adding a bit length corresponding to the period is required. That is, the total bit length of the preamble PA needs a bit length of about 352 bits, which is obtained by adding, for example, 64 bits necessary for bit synchronization and about 288 bits corresponding to the scan cycle (60 ms) (see FIG. 3).

  For example, if the total bit length of the preamble PA is shorter than the above-described total bit length (about 352 bits), the receiving-side radio station cannot detect the preamble PA within a predetermined scan period, and as a result, the radio signal May not be received. Therefore, when the number of radio channels to be used increases, it is necessary to increase the bit length of the preamble PA in accordance with the number of radio channels. As a result, the ratio of actual data in the radio signal is reduced, and the use efficiency of the radio signal is reduced. There was a problem of being lowered.

  The present invention has been made in view of the above-described reasons, and an object thereof is to provide a wireless communication system in which the preamble of a wireless signal is shortened and the utilization efficiency of the wireless signal is high.

  In order to achieve the above object, a wireless communication system of the present invention includes a first wireless device that transmits a wireless signal using a first wireless channel and one or more second wireless channels having different frequencies, and One or a plurality of second radios that receive a radio signal transmitted from the first radio, and the first radio transmits data to the second radio for data transmission Allocating means for allocating the wireless channel from one to a plurality of second wireless channels, and link establishment signal generating means for generating a link establishment wireless signal in which channel information capable of identifying the wireless channel for data transmission is stored And a signal transmission means for transmitting a radio signal for data transmission including actual data and a radio signal for link establishment to the second radio device, and the second radio device receives the radio signal. Channel setting means for setting a radio channel to be received from the first and plural second radio channels, signal strength measuring means for measuring the signal strength of the radio channel to be received, and signal strength measured by the signal strength measuring means If the signal exceeds a predetermined threshold value, signal receiving means for receiving a wireless signal using the wireless channel is provided, and the first wireless device transmits a wireless signal for data transmission to the second wireless device to be transmitted. A link establishment signal generation unit generates a link establishment radio signal including channel information corresponding to the radio channel for data transmission, and the signal transmission unit uses the first signal transmission unit to generate the link establishment radio signal. When a link is established with the second radio by transmitting using the radio channel, the data transmission radio is transmitted using the data transmission radio channel. When the signal receiving means receives the wireless signal for link establishment in a state where the reception target wireless channel is set to the first wireless channel, the second wireless device converts the wireless signal for link establishment into the wireless signal for link establishment. The channel setting means sets the radio channel to be received based on the included channel information.

  ADVANTAGE OF THE INVENTION According to this invention, the radio | wireless communications system with high use efficiency of a radio signal can be provided by shortening the preamble of a radio signal.

It is a schematic block diagram which shows the radio | wireless communications system concerning embodiment of this invention. It is the schematic which shows the format of the communication signal used for the same radio | wireless communications system. It is the schematic which shows the format of the communication signal used for the conventional radio | wireless communications system.

  Hereinafter, an embodiment in which the technical idea of the present invention is applied to a power meter reading system will be described with reference to FIGS.

  The power meter reading system A according to the present embodiment collects the amount of power consumed by a plurality of dwelling units located at remote locations from the power company by operating a totaling server installed in the power company, for example. System. As shown in FIG. 1, the power meter reading system A includes a meter meter 1 installed in each dwelling unit and a relay device 2 that is installed in a utility pole or the like and receives meter data from the surrounding meter meter 1.

  The relay device 2 includes a control unit 21 that performs overall control of the relay device 2 and a control unit 22 that performs communication with a totaling server (not shown) installed in the power company via the wide area communication network WAN. A wireless communication unit 20 that performs wireless communication with the surrounding meter-reading meter 1 is provided.

  The control unit 21 includes a microcomputer (not shown) as its main component, and operates based on a control command received from the aggregation server via the control unit 22. This control command includes various commands such as a command to acquire meter reading data from the meter meter 1 (meter reading data collection command) and a command to set the time to acquire meter reading data (time setting command). Sent in response to

  The control unit 21 has a timer (not shown), controls the wireless communication unit 20 based on the collection time set by the time setting command, and from the surrounding meter-reading meter 1 received via the wireless communication unit 20. The meter reading data is transmitted to the counting server using the control unit 22. In addition, when the meter reading data collection command is input, the control unit 21 receives meter reading data from the surrounding meter meter 1 and transmits it to the counting server regardless of the preset collection time. Thereby, the power consumption amount of each dwelling unit measured by the meter-reading meter 1 can be automatically measured and totaled from the totaling server of the electric power company installed in the remote place.

  The wireless communication unit 20 includes, for example, a specific low-power wireless station, and transmits and receives various wireless signals such as the above notification signal, request signal, and link establishment signal to and from the meter-reading meter 1. In wireless communication between the wireless communication unit 20 and each meter-reading meter 1, a plurality of wireless channels are provided in a predetermined frequency band, and wireless signals are transmitted and received using one wireless channel selected from the plurality of channels. Do. As a radio signal used here, a notification signal for notifying the measured meter reading data, a request signal for the relay device 2 requesting the meter meter 1 to transmit meter reading data, and establishing a wireless link with the relay device 2 There are various radio signals such as a link establishment signal for the purpose.

  The radio signal adopts the format shown in FIG. 2, and is composed of a preamble PA, a unique word UW, device identification information AD, data DA, and an error detection code CR. The preamble PA is, for example, a bit string composed of a bit synchronization pattern in which 0 and 1 are alternately repeated. The first bit is set to 0 and the last bit is set to 1. The total bit length of the preamble PA is set to the minimum length necessary for bit synchronization (64 bits in FIG. 2). The unique word UW is composed of a bit string different from that of the preamble PA, is determined in advance for each wireless communication system, and the same value is set in the meter-reading meter 1 and the relay device 2. The device identification information AD includes transmission source information for identifying a wireless signal transmission source and destination information for identifying a transmission destination device. The data DA is made up of a bit string including actual data such as meter reading data measured by the electric energy measuring unit 11 and a request command from the relay device 2, for example, and the bit length can be made variable as necessary. The error detection code CR is, for example, a bit string composed of CRC (Cyclic Redundancy Check), and is set so that at least the occurrence of an abnormality such as bit inversion in the bit string constituting the data DA can be detected at the time of reception.

  Further, the wireless communication unit 20 includes a channel assignment unit 23 that assigns a wireless channel for transmitting actual data such as a request signal to the metering meter 1 to be transmitted. In addition, the wireless communication unit 20 includes a link establishment signal generation unit 24 that generates a link establishment signal including channel information for identifying a wireless channel assigned by the channel assignment unit 23, and a signal transmission unit 25 that transmits and receives various wireless signals. As a component.

  Each meter-reading meter 1 (1a ... 1c) is the radio | wireless communication part 10 which communicates by radio | wireless with the relay apparatus 2, the electric energy measuring part 11 which measures the electric energy consumed by the dwelling unit, and electric power consumption. And a storage unit 12 that stores the data as meter reading data.

  The power amount measuring unit 11 measures the amount of power consumed in the dwelling unit by constantly measuring the amount of power flowing through a power supply path (not shown) that supplies power from the power company to the dwelling unit. It memorize | stores in the memory | storage part 12 as the meter-reading data of the said dwelling unit.

  The storage unit 12 includes a nonvolatile memory such as an EEPROM (Electrically Erasable Programmable ROM), for example, and the power amount measurement unit 11 and the wireless communication unit 10 write and read various information as necessary.

  The wireless communication unit 10 includes, for example, a specific low-power wireless station, and performs communication using a wireless signal with the relay device 2. The wireless communication unit 10 also includes a signal strength detection unit 13 that measures the signal strength of the wireless channel to be received, and reception that receives a wireless signal if the signal strength detected by the signal strength detection unit 13 is greater than a predetermined threshold. A signal receiving unit 14 having a function is provided as a component. Furthermore, the radio communication unit 10 includes a channel setting unit 15 that sets a radio channel to be received based on a link establishment signal as a component.

  The signal strength detection unit 13 measures the signal strength in the radio channel to be scanned set by the channel setting unit 15. The measurement of the signal strength is performed based on, for example, a received signal strength display signal (RSSI), and the signal strength detector 13 outputs signal information including the measured signal strength and the wireless channel to the signal receiver 14.

  When signal information is input from the signal strength detector 13, the signal receiver 14 compares the signal strength included in the signal information with a preset threshold value. In addition, when the signal strength is greater than the threshold value, the signal receiving unit 14 receives a radio signal using the radio channel included in the signal information as a radio channel to be received.

  In receiving a radio signal, first, the signal receiving unit 14 detects the preamble PA in the radio channel to be received and performs bit synchronization. When the preamble PA is detected and bit synchronization is normally performed, the unique word UW, the data DA The error detection code CR is received. Here, the signal receiving unit 14 compares the bit string of the unique word UW with a preset bit string, and determines whether the radio signal is transmitted from the device identification information AD to the own device. Further, when the signal receiving unit 14 determines that the received radio signal is a radio signal addressed to itself, the signal receiving unit 14 obtains a CRC value from the bit string of the data DA, compares the CRC value with the error detection code CR, and compares the radio signal. Detect anomalies that occur in the bit string. In this way, the signal receiving unit 14 can receive only a valid radio signal transmitted to the own device without receiving a radio signal transmitted to a device other than the own device or a radio signal having an incorrect bit string. .

  When the signal receiving unit 14 receives a link establishment signal as a radio signal by the above-described reception operation, the channel setting unit 15 determines the radio channel to be scanned based on the channel information included in the link establishment signal as the signal strength detection unit 13. Set to. As a result, the signal strength detection unit 13 detects the signal strength in the newly set radio channel to be scanned, so that the radio signal received by the radio channel assigned by the relay device 2 is the radio channel to be received. Is called.

  Here, the operation when the wireless communication unit 20 transmits a request signal toward each meter-reading meter 1 (1a... 1c) will be described with reference to FIG. In the following description, channels CH0 to CH6 having different frequencies are provided as radio channels used for radio communication, and channel CH0 is set as a radio channel for transmitting and receiving a link establishment signal. Further, in the signal intensity detection unit 13 of the meter-reading meter 1, the channel CH0 is set as an initial value of the reception target wireless channel for detecting the signal intensity.

  First, the signal transmission unit 25 sets the channel CH0 for link establishment as a wireless channel for transmission, and transmits a link request signal including a preamble PA or the like. In this link request signal, device identification information AD is set so that all meter-reading meters 1 are the destination, and is broadcast toward the meter-reading meters 1 in the vicinity (S1 in FIG. 2).

  Receiving this link request signal, each meter-reading meter 1 transmits a response signal to the link request including the preamble PA to the relay device 2 (S2 in FIG. 2). This response signal includes an address for identifying each meter-reading meter 1, and by using this address as the device identification information AD, the destination is designated in the subsequent transmission / reception of the radio signal. be able to.

  Next, the channel allocation unit 23 allocates a radio channel for transmitting a request signal to the meter-reading meter 1 according to the response signal received by the signal transmission unit 25. Here, channel CH1 is assigned as a radio channel for transmitting the request signal. Thereafter, the link establishment signal generation unit generates a link establishment signal in which channel information indicating the assigned radio channel is stored in the data DA, and transmits the link establishment signal to the meter-reading meters 1a to 1c via the signal transmission unit 25 (FIG. 2). S3).

  Here, the signal intensity detection unit 13 of each meter-reading meter 1 measures the signal intensity of the channel CH0 for each predetermined scan period and outputs the signal intensity to the signal reception unit 14. When the link establishment signal is transmitted from the relay device 2, the signal strength input to the signal receiving unit 14 becomes larger than the threshold value, and thus the signal receiving unit 14 receives a radio signal using the channel CH0. . When the signal receiving unit 14 receives a link establishment signal using the channel CH0, the channel setting unit 15 acquires a radio channel corresponding to the own device included in the link establishment signal, and receives a radio channel (here, a channel). CH1) is set in the signal intensity detector 13.

  In addition, when the wireless communication unit 10 of each meter-reading meter 1 receives the link establishment signal from the relay device 2, the wireless communication unit 10 transmits a completion signal indicating that the link establishment has been normally completed to the relay device 2 as a destination (FIG. 2). S4). In the relay device 2 that has received this completion signal, the signal transmission unit 25 switches the wireless channel to be transmitted to the channel CH1, and transmits a request signal for requesting the meter reading meter 1 to transmit meter reading data.

  After that, the signal strength detection unit 13 of the meter-reading meter 1 in which the reception target wireless channel is set to the channel CH1 detects the signal strength of the channel CH1 and performs bit synchronization, and the signal reception unit 14 receives the wireless signal. Thus, the meter-reading meter 1 can receive the request signal. In addition, the meter-reading meter 1 which received the request signal transmits meter-reading data to the relay apparatus 2 by returning the meter-reading data memorize | stored in the memory | storage part 12 using this channel CH1.

  As described above, since the signal strength detection unit 13 has one wireless channel for detecting the signal strength at a predetermined scan period, it is ensured even if the bit length of the preamble of the wireless signal transmitted by the relay device 2 is shortened. The meter-reading meter 1 can receive a radio signal. As a result, the preamble of the radio signal can be shortened to improve the utilization efficiency of the radio signal, and the processing related to transmission / reception can be simplified.

  In this embodiment, an example in which the technical idea of the present invention is applied to an electric power meter reading system has been described. However, the present invention can be applied to various systems such as a gas meter metering system and a water meter metering system. .

1 (1a ... 1c) Meter-reading meter (second radio)
DESCRIPTION OF SYMBOLS 10 Wireless communication part 11 Electric energy measuring part 12 Storage part 13 Signal strength detection part 14 Signal receiving part 15 Channel setting part 2 Relay apparatus (1st radio | wireless machine)
DESCRIPTION OF SYMBOLS 20 Wireless communication part 21 Control part 22 Communication part 23 Channel allocation part 24 Link establishment signal generation part 25 Signal transmission part WAN Wide area communication network

Claims (1)

A first radio that transmits a radio signal using a first radio channel and one or more second radio channels that have different frequencies from each other, and a radio signal that is transmitted from the first radio 1 Or a plurality of second radios,
The first radio includes a channel assignment means for allocating a data transmission radio channel for transmitting actual data to the second radio from the one or more second radio channels, and the data transmission A link establishment signal generating means for generating a link establishment radio signal in which channel information capable of identifying the radio channel is stored, a data transmission radio signal including the actual data, and the link establishment radio signal. Signal transmitting means for transmitting to the second radio,
The second radio device sets channel setting means for setting a reception target radio channel for receiving a radio signal from the first and the plurality of second radio channels, and measures signal strength of the reception target radio channel. A signal strength measuring unit; and a signal receiving unit configured to receive a radio signal using the radio channel if the signal strength measured by the signal strength measuring unit exceeds a predetermined threshold,
The first radio device assigns the radio channel for data transmission to the second radio device to be transmitted, and transmits a radio signal for link establishment including channel information corresponding to the radio channel for data transmission. When the link establishment signal generation means generates, the signal transmission means transmits the link establishment wireless signal using the first wireless channel, and the link is established with the second wireless device, Transmitting a wireless signal for data transmission using a wireless channel for data transmission;
When the signal receiving means receives the radio signal for link establishment in a state where the radio channel to be received is set to the first radio channel, the second radio unit converts the radio signal for link establishment into the radio signal for link establishment. A radio communication system, wherein the channel setting means sets a radio channel to be received based on channel information included.

Images