JP2006333098A - Radio communications system, radio transmitter, and radio receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio communications system, radio transmitter, and radio receiver, reducing the collision ratio of either a signal from an RF tag or a response signal, when an RF tag reader performs data transmission/reception in one-to-n manner. <P>SOLUTION: The radio communication system includes a modulation for decoding data for transmission by using a clock, a clock for generating the clock, a carrier detector for detecting whether the carrier detection factor exceeds a preset threshold, a control unit for controlling the clock frequency, a preamble for adding clock information indicative of the clock frequency to the data and packetizing, a transmitter for modulating and transmitting the packet as a transmission signal, a receiver for demodulating the received signal to regenerate the packet, a preamble matching portion for performing preamble pattern matching and extracting the clock information, a data-sampling clock for controlling the decoded clock using the clock information, and a decoder for decoding the transmitted data by using the clock. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a wireless communication system including a wireless transmitter such as an RF tag and a wireless receiver such as an RF tag reader that transmit and receive data wirelessly, and a wireless transmitter and a wireless receiver used therefor.

Conventionally, when an RF tag reader performs identification processing of an RF tag existing in its own reception area, signals or response signals from a plurality of RF tags may collide, and a signal or response signal for identification may not be received. is there.
For this reason, as a transmission device that performs bidirectional communication using a radio device in a specific low-power data transmission frequency band, the electric field strength of received data is compared with a predetermined threshold, and the data block length is shortened / There is a configuration in which the length is changed to prevent collision of wireless communication (for example, see Patent Document 1).
JP-A-6-119538

  In the power transmission device shown in Patent Document 1, for example, when communication is performed between the data transmission device A and the data transmission device B, the distance at which the communication between the other data transmission device C and the data transmission device D is close When the data transmission apparatus A is implemented at the same frequency, the data transmission apparatus A controls the transmission data output and the data block length from the electric field strength based on the received signal level of the data transmission apparatus B. Interference with communication between C and the data transmission device D is suppressed. The receiving side estimates the block length of the transmission data by determining the threshold value of the electric field strength.

  However, the above-described transmission device controls communication between two devices, even if it is a plurality, and as in communication in identification processing between an RF tag reader and an RF tag, 1 to n (n> 1 is an integer). It is not configured to support the case of performing two-way communication.

  The present invention has been made in view of such circumstances. When the RF tag in the reception area increases and the RF tag reader transmits and receives data in a 1-to-n relationship, the RF tag in the reception area It is an object of the present invention to provide a radio communication system capable of reducing the ratio of signal or response signal collisions as compared with the prior art, and a radio transmitter and radio receiver used therefor.

  The radio transmitter according to the present invention includes a baseband modulation unit that performs baseband encoding of data to be transmitted based on an input clock, a clock unit that generates a clock for baseband encoding, and carrier detection within a predetermined period. A carrier detection unit that detects whether or not the rate exceeds a set threshold value, and a control unit that controls the frequency of the clock based on the detection result.

  The radio transmitter according to the present invention is characterized in that when the control unit detects that a carrier detection rate exceeds the threshold, the frequency of the clock is multiplied.

  The radio transmitter according to the present invention has a preamble section that adds a preamble to the data, and clock information indicating a clock frequency is added to the preamble section.

  The wireless transmitter of the present invention is characterized in that the clock information is a length of a terminal pulse length controlled according to a clock frequency, or a preamble pattern in which the clock information is controlled according to a clock frequency. And

  The radio transmitter according to the present invention includes a baseband modulation unit that performs baseband encoding of data to be transmitted based on an input clock, a clock unit that generates a clock for baseband modulation, and a carrier detection rate within a predetermined period. And a carrier detection unit for detecting whether or not a set threshold is exceeded, and a control unit for controlling the data length of the data to be transmitted according to the detection result.

  The radio transmitter according to the present invention is characterized in that when the control unit detects that a carrier detection rate exceeds the threshold, the data length of the data to be transmitted is shortened.

  The radio transmitter according to the present invention includes a preamble portion that adds a preamble to the data, and changes a preamble pattern according to a data length of data transmitted by the preamble portion.

  The wireless transmitter of the present invention has a flag insertion unit that adds a flag to baseband encoded data, and changes the flag to be inserted according to the data length of data transmitted by the flag insertion unit. And

  A radio receiver according to the present invention is a radio receiver that receives a packet in which the number of clocks of baseband encoding of a transmission signal is indicated by a preamble clock information added from the radio communication device, and the preamble of the packet A preamble matching unit for extracting preamble clock information, a data sampling clock unit for controlling a baseband decoding clock based on the clock information, and a base for performing baseband decoding of the data using the clock And a band decoding unit.

  The wireless communication system of the present invention includes a baseband modulation unit that performs baseband encoding of data to be transmitted based on an input clock, a clock unit that generates a baseband encoding clock, and carrier detection within a predetermined period. A carrier detection unit that detects whether or not a rate exceeds a set threshold; a control unit that controls the frequency of the clock according to the detection result; and a preamble to which clock information indicating a clock frequency is added. A wireless transmitter having a preamble portion that is attached to data and is used as a packet, and a transmitter that modulates the packet and is transmitted as a transmission signal; receives the transmission signal; demodulates the transmission signal into a packet Performs pattern matching of the preamble of the packet with the receiver, and extracts preamble clock information A radio receiver having a preamble matching unit, a data sampling clock unit that controls a clock of baseband decoding based on the clock information, and a baseband decoding unit that performs baseband decoding of data transmitted by the clock It is characterized by having.

  The wireless communication system of the present invention includes a baseband modulation unit that performs baseband encoding of data to be transmitted according to an input clock, a clock unit that generates a clock for baseband modulation, and a carrier detection rate within a predetermined period. A carrier detection unit that detects whether or not a set threshold is exceeded, a control unit that controls the data length of the data to be transmitted based on the detection result, and data length information that indicates the data length of the data to be transmitted A wireless transmitter having a preamble part that adds the added preamble to the data to form a packet, and a transmitting part that modulates the packet and transmits the packet as a transmission signal; receives the transmission signal; Performs pattern matching of the preamble of the packet with the receiving unit that demodulates the packet, and at the same time the preamble A preamble matching unit that extracts data information, a baseband decoding unit that performs baseband decoding of the packet using a clock, a control unit that detects a data length of transmitted data using the clock information, and a detected data length. And a radio receiver having a baseband decoding unit that performs baseband decoding of the transmitted data.

  The wireless communication system of the present invention includes a baseband modulation unit that performs baseband encoding of data to be transmitted according to an input clock, a clock unit that generates a clock for baseband modulation, and a carrier detection rate within a predetermined period. A carrier detection unit that detects whether or not the threshold value exceeds a set threshold, a control unit that controls the data length of the data to be transmitted based on the detection result, and a flag that indicates the data length of the data to be transmitted A radio transmitter having a flag insertion unit, a preamble unit that adds a preamble to data to which the flag is added to form a packet, and a transmission unit that modulates the packet and transmits the packet as a transmission signal; and the transmission signal And a receiver that demodulates the transmission signal into a packet and a packet pattern matching for the preamble. An amble matching unit, a flag identifying unit for identifying a flag, a control unit for detecting the data length of transmitted data by the flag, and baseband decoding of the transmitted data based on the detected data length And a wireless receiver having a baseband decoding unit.

  As described above, according to the radio communication system of the present invention, when the carrier detection rate is high, the collision probability of radio packets from a plurality of radio transmitters increases, so the carrier detection rate is set in advance. When the threshold is exceeded, the packet frequency can be shortened by multiplying the clock frequency for baseband encoding, and the probability that multiple wireless packets will collide during a given period can be reduced, which increases efficiency. Wireless communication can be performed.

  Further, according to the wireless communication system of the present invention, when the carrier detection rate is high, the collision probability of wireless packets from a plurality of wireless transmitters increases, so the carrier detection rate exceeds a preset threshold. In this case, by shortening the data length of the data to be transmitted, the packet length can be shortened, and the probability that a plurality of wireless packets collide in a predetermined period can be reduced, and efficient wireless communication is performed. Can do.

<First Embodiment>
A wireless communication system according to a first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration example of a wireless communication system according to the embodiment.
In FIG. 1, a transmitter 1 is a wireless transmitter using low-power radio such as an RF tag or an IC tag, and includes a wireless modulation unit 11, a carrier detection unit 12, a control unit 13, a preamble insertion unit 14, a baseband. It has an encoding unit 15, a clock unit 16, and a data memory unit 17.
The receiver 2 is a tag reader or the like that collects identification numbers and the like from the RF tag or IC tag and performs tag identification processing, and includes a radio demodulation unit 21, a preamble matching unit 22, a control unit 23, and a baseband decoding unit. 24, a data sampling clock unit 25, and an interface unit 26. Here, the clock unit 16 and the data sampling clock unit 25 are provided with a crystal oscillator, a switch, and a clock multiplier, and when the carrier detection rate exceeds a threshold, the switch increases the frequency via the clock multiplier. It has become.

Next, the operation of the wireless communication system according to the first embodiment will be described with reference to FIGS. 1, 2, 3, and 4. FIG. FIG. 2 is a flowchart showing an operation example of the transmitter 1, and FIG. 4 is a flowchart showing an operation example of the receiver 2. FIG. 3 is a conceptual diagram illustrating a packet configuration for explaining control of a clock used for baseband encoding based on a carrier detection rate.
First, the operation of the transmitter 1 will be described with reference to the flowchart of FIG.
In step S1, the carrier detection unit 12 receives a control signal for data collection from the receiver 2 and includes an ID (identification information) for identifying itself and information acquired by stored unique information or measurement. When transmission data (signal or response signal) is read from the data memory 17 and this transmission data is transmitted to the receiver 2, carrier detection is performed in the vicinity of the frequency band used for transmitting the transmission data of itself.

Next, in step S2, the carrier detection circuit 12 measures whether or not the carrier to be measured has been detected exceeding a preset time rate, that is, the time during which the carrier exists within a predetermined measurement time. It is detected whether the numerical value divided by time (hereinafter referred to as carrier detection rate) exceeds a threshold value.
At this time, when the carrier detection circuit 12 detects that the carrier detection rate does not exceed the set threshold value, the carrier detection circuit 12 outputs a notification signal indicating that the carrier detection rate does not exceed the threshold value to the control unit 13 and proceeds to step 3. On the other hand, if it is detected that the carrier detection rate exceeds the set threshold value, a notification signal indicating that the carrier detection rate has been exceeded is output to the control unit 13 and the process proceeds to step 8.
At this time, when the control unit 13 receives the notification signal, the control unit 13 reads the ID and payload of the transmitter 1 from the data memory 17 and outputs the ID and payload to the baseband encoding unit 15.

Next, in step S <b> 3, the control unit 13 outputs a control signal with a clock frequency used for baseband encoding of 1 / Td <b> 1 to the clock unit 16. Here, Td1 is a clock cycle.
Thereby, the clock unit 16 changes the frequency of the clock supplied to the baseband encoding unit 15 to a frequency corresponding to 1 / Td1 of the clock frequency.
Then, the baseband encoding unit 15 synchronizes the voltage state in the bit interval such as Manchester encoding, NRZ, NRZI, etc. with the clock with the frequency 1 / Td1, and the high and low voltage In order to change according to the level, the clock frequency is easily detected and the encoded baseband signal is output to the preamble insertion unit 14 (is this description all right)?

Next, in step S4, the preamble insertion unit 14 sets T1 as the pulse width of the preamble end pulse added to the baseband signal. This pulse width T1 indicates that the baseband encoding is performed with a clock having a frequency of 1 / Td1. The correspondence between the pulse width T1 and the pulse width Td1 is determined in advance between the transmitter 1 and the receiver 2 in the wireless communication system.
In step S5, as shown in FIG. 3, the preamble inserting unit 14 adds a preamble having a predetermined pattern with a terminal pulse frequency of 1 / T1 to the baseband signal, generates a packet, and generates a packet. Output to the modulation unit 11.

Next, in step S6, the wireless modulation unit 11 modulates the input packet with a modulation clock having a predetermined frequency.
In step S7, the wireless modulation unit 11 transmits the modulated wireless packet to the receiver 2 via the antenna.

On the other hand, in step S8, the control unit 13 outputs to the clock unit 16 a control signal for setting the frequency of the clock used for baseband encoding to 1 / Td2.
Thereby, the clock unit 16 changes the frequency of the clock supplied to the baseband encoding unit 15 to a frequency corresponding to the pulse width Td2 of the clock.
Then, the baseband encoding unit 15 synchronizes the voltage state in the bit period such as Manchester encoding, NRZ, NRZI, etc. with the clock with the frequency of 1 / Td2, and the high and low voltage In order to change according to the level, a code format in which the clock frequency is easy to detect is performed, and the encoded baseband signal is output to the preamble insertion unit 14.

Next, in step S9, the preamble insertion unit 14 sets the pulse width of the end pulse of the preamble added to the baseband signal to T2. This pulse width T2 indicates that the baseband encoding is performed by a clock having a frequency of the pulse width Td2. The correspondence between the pulse width T2 and the pulse width Td2 is determined in advance between the transmitter 1 and the receiver 2 in the wireless communication system.
In step S5, as shown in FIG. 3, the preamble inserting unit 14 adds a preamble having a predetermined pattern with a pulse width T2 of the terminal pulse to the baseband signal, generates a packet, and performs radio modulation. To the unit 11.

As described above, when the carrier detection rate does not exceed the set threshold, the pulse width of the clock used for baseband encoding is Td1, and when the carrier detection rate exceeds the set threshold, the baseband encoding is performed. The frequency of the clock to be used is 1 / Td2, Td1> Td2 (generally, Td1 = N × Td2 (N = 2, 3, 4,...), And if N = 2, the data length becomes 1/2. (This is effective for shortening the packet).
For this reason, the time length of the baseband signal after baseband encoding has exceeded the threshold value for which the carrier detection rate has been set, compared to the case where the carrier detection rate has not exceeded the threshold value for which the carrier detection rate has been set. In this case, the probability of collision of radio packets from a plurality of transmitters 1 can be reduced.

Here, the threshold is the transmission timing, for example, when the carrier is detected at 5 out of 10 times (50%) or more, that is, the timing at which the wireless packet is actually transmitted next, that is, the wireless without detecting the carrier. At a transmission timing for transmitting a packet, a process of increasing the frequency of a clock used for baseband encoding (or reducing the data length (number of bits) of transmission data) is performed.
Then, after performing the process of increasing the frequency of the clock used for baseband encoding (or reducing the data length (number of bits) of transmission data), 5 out of 10 times (50%) in the subsequent transmission timing If the carrier is detected at less than 1, the frequency (or transmission data length) of the changed clock is restored to the original timing at the time when the radio packet is actually transmitted next.

Next, the operation of the receiver 2 will be described with reference to the flowchart of FIG.
In step S11, the radio demodulation unit 21 demodulates the radio packet received via the antenna using a demodulation clock having the same frequency as the modulation clock used by the radio modulation unit 11 of the transmitter 1. Reproduce.

Next, in step S12, the preamble matching unit 22 performs preamble pattern matching in the input packet, detects whether or not the received packet is received by the receiver 2, and the pattern is received by the receiver. When 2 is not received, the packet is discarded and the subsequent processing is not performed. On the other hand, when it is detected that the pattern is received by the receiver 2, detection (measurement) of the end pulse width of the preamble is performed. The detected terminal pulse width is output to the control unit 23.
Then, the preamble matching unit 22 deletes the preamble from the packet and outputs it as a baseband signal to the baseband decoding unit 24.

Next, in step S13, the control unit 23 detects an input terminal pulse width, that is, detects whether the input terminal pulse width is T1 or T2.
At this time, if the control unit 23 detects that the input terminal pulse width is T1, the process proceeds to step S14. On the other hand, if the control unit 23 detects that the input terminal pulse width is T2, Advances to step S17.

Next, in step S14, the control unit 23 outputs a control signal to the data sampling clock unit 25 so that the frequency of the data sampling clock supplied to the baseband decoding unit 24 becomes 1 / Td1.
Thereby, the data sampling clock unit 25 supplies a clock having a frequency of 1 / Td1 to the baseband decoding unit 24, and the process proceeds to step S15.

  Next, in step S15, the baseband decoding unit 24 performs data sampling processing or the like using the clock, and the baseband encoding unit 15 of the transmitter 1 performs the baseband signal input from the preamble matching unit 22. Decoding is performed by performing decoding processing corresponding to the encoding (Manchester encoding, decoding processing for NRZ, NRZI, etc.), error correction is performed as necessary, and transmission data is reproduced as a processing result.

Next, in step S <b> 16, the baseband decoding unit 23 transmits the reproduced transmission data to the interface unit 16.
The interface unit 16 is a serial interface, an Ethernet (registered trademark) interface, or the like, and changes transmission data to a data format of each interface and outputs the data to an external device.

In step 17, the control unit 23 outputs a control signal to the data sampling clock unit 25 so that the frequency of the data sampling clock supplied to the baseband decoding unit 24 becomes 1 / Td 2.
Thereby, the data sampling clock unit 25 supplies a clock having a frequency of 1 / Td2 to the baseband decoding unit 24, and the process proceeds to step S15.

<Second Embodiment>
Hereinafter, a radio communication system according to a second embodiment of the present invention will be described with reference to the drawings. FIG. 5 is a block diagram showing a configuration example of the wireless communication system according to the embodiment.
In FIG. 5 of the wireless communication system according to the second embodiment, the same components as those of the wireless communication system according to the first embodiment are denoted by the same reference numerals, and description thereof is omitted.
In FIG. 5, a transmitter 1 is a wireless transmitter using low-power radio such as an RF tag or an IC tag, and includes a wireless modulation unit 11, a carrier detection unit 12, a control unit 13, a preamble insertion unit 14, a baseband. It has an encoding unit 15, a clock unit 16, and a data memory unit 17.
The tag reader or the like collects identification numbers from the RF tag or IC tag and performs tag identification processing, and includes a radio demodulation unit 21, a preamble A matching unit 22A, a preamble B matching unit 22B, a control unit 23, A baseband decoding unit 24, a data sampling clock unit 25, and an interface unit 26 are provided.

Next, the operation of the wireless communication system according to the second embodiment will be described with reference to FIG. 5, FIG. 6, FIG. 7, and FIG. FIG. 6 is a flowchart showing an operation example of the transmitter 1, and FIG. 8 is a flowchart showing an operation example of the receiver 2. FIG. 7 is a conceptual diagram illustrating a packet configuration for explaining control of a clock used for baseband encoding based on a carrier detection rate.
First, the operation of the transmitter 1 will be described with reference to the flowchart of FIG.
Here, the processing in steps S1, S2, S3, S6, S7, and S8 is the same as that in the flowchart of FIG.

From step S1 to step S3, step S8, a clock used for baseband encoding is set.
Next, in step S24, the preamble insertion unit 14 sets the pattern type of the preamble added to the baseband signal as the pattern A. This pattern A indicates that baseband encoding is performed with a clock having a frequency of 1 / Td1. The correspondence between the pattern A and the pulse width Td1 is determined in advance between the transmitter 1 and the receiver 2 in the wireless communication system.
In step S25, the preamble insertion unit 14 adds the preamble of the pattern A to the baseband signal, generates a packet, and outputs the packet to the radio modulation unit 11, as shown in FIG.
The data of the pattern A and the pattern B used here are stored in advance in the data memory unit 17, and the preamble insertion unit 14 reads out the data of the pattern A and the pattern B from the data memory unit 17 and uses them each time.

Next, in step S29, the preamble insertion unit 14 sets the pattern type of the preamble added to the baseband signal as the pattern B. This pattern B indicates that the baseband encoding is performed with a clock having a frequency of 1 / Td2. The correspondence between the pattern B and the pulse width Td2 is determined in advance between the transmitter 1 and the receiver 2 in the wireless communication system.
In step S25, the preamble insertion unit 14 adds the pattern B preamble to the baseband signal, generates a packet, and outputs the packet to the radio modulation unit 11, as shown in FIG.

  As described above, also in the second embodiment, as in the first embodiment, the time length of the baseband signal after baseband encoding is equal to the threshold at which the carrier detection rate is set. Compared to the case where it does not exceed, the carrier detection rate is shortened when the set threshold value is exceeded, and the probability of collision of radio packets from the plurality of transmitters 1 can be reduced.

Next, the operation of the receiver 2 will be described with reference to the flowchart of FIG.
Here, similarly to the description of the operation of the transmitter 1, the processing of S14 to S17 is the same as the flowchart of FIG.
In step S11, the radio demodulation unit 21 demodulates the radio packet received via the antenna using a demodulation clock having the same frequency as the modulation clock used by the radio modulation unit 11 of the transmitter 1. Reproduce.

Next, in step S22, the preamble matching unit 22A performs preamble pattern matching in the input packet, detects whether or not the received packet is received by the receiver 2, and the pattern is received by the receiver. 2 is not received, the packet is discarded and the subsequent processing is not performed. On the other hand, when it is detected that the pattern is received by the receiver 2, whether the preamble pattern is pattern A or not. Detection (measurement) of
When the preamble matching unit 22A detects that the type of the preamble pattern is A, the preamble matching unit 22A outputs a pattern confirmation signal indicating that the pattern is A to the control unit 23, and detects that the preamble pattern is not A. Then, a pattern confirmation signal indicating that the pattern is not A is output to the control unit 23.
Then, the preamble matching unit 22A deletes the preamble from the packet and outputs it as a baseband signal to the baseband decoding unit 24.

In addition, the preamble matching unit 22B performs preamble pattern matching in the input packet, detects whether or not the received packet is received by the receiver 2, and the pattern is received by the receiver 2. If not, the packet is discarded and the subsequent processing is not performed. On the other hand, if it is detected that the pattern is received by the receiver 2, detection (measurement) of whether the preamble pattern is the pattern B or not. I do.
When the preamble matching unit 22B detects that the type of the preamble pattern is B, the preamble matching unit 22B outputs a pattern confirmation signal indicating that the pattern is B to the control unit 23, and detects that the preamble pattern is not B. Then, a pattern confirmation signal indicating that the pattern is not B is output to the control unit 23.
Then, preamble matching unit 22B deletes the preamble from the packet and outputs it as a baseband signal to baseband decoding unit 24.

Next, in step S23, the control unit 23 detects the type of the preamble pattern based on the input pattern confirmation signal, that is, whether the pattern confirmation signal indicates the pattern A or the pattern B. Detection is performed.
At this time, if the control unit 23 detects that the pattern type based on the input pattern confirmation signal is A, the process proceeds to step S14, while the pattern type based on the input pattern confirmation signal is B. If it is detected that there is, the process proceeds to step S17.
Since the subsequent steps S14 to S17 are the same as the operation of the receiver 2 of the first embodiment shown in FIG.

<Third Embodiment>
Hereinafter, a wireless communication system according to a third embodiment of the present invention will be described with reference to the drawings. FIG. 9 is a block diagram showing a configuration example of the wireless communication system according to the embodiment.
In FIG. 9 of the wireless communication system according to the third embodiment, the same components as those of the wireless communication system according to the second embodiment are denoted by the same reference numerals, and description thereof is omitted.
In FIG. 9, a transmitter 1 is a wireless transmitter using low-power radio such as an RF tag or an IC tag, and includes a radio modulation unit 11, a carrier detection unit 12, a control unit 13, a preamble insertion unit 14, a baseband. It has an encoding unit 15, a clock unit 16, and a data memory unit 17.

The receiver 2 is a tag reader or the like that collects identification numbers from the RF tag or IC tag and performs tag identification processing, and includes a radio demodulation unit 21, a preamble A matching unit 22A, and a preamble B matching unit 22B. , A control unit 23, a baseband decoding unit 24, a data sampling clock unit 25, and an interface unit 26.
In the third embodiment, unlike the first and second embodiments, the data length (number of bits) of the transmission data is reduced, the packet length of the wireless packet transmitted by the transmitter 1 is shortened, and a plurality of The collision of radio packets from the transmitter 1 is reduced.
For this reason, the clock unit 16 and the data sampling clock unit 25 receive a clock having a predetermined frequency without being subjected to frequency change control from the corresponding control units 13 and 23, respectively, and a baseband encoding unit 15 and a baseband decoding unit, respectively. 24.

Next, the operation of the wireless communication system according to the third embodiment will be described with reference to FIG. 9, FIG. 10, FIG. 11, and FIG. FIG. 10 is a flowchart showing an operation example of the transmitter 1, and FIG. 12 is a flowchart showing an operation example of the receiver 2. FIG. 11 is a conceptual diagram showing a packet configuration for explaining the control of the data length (number of bits of transmission data) in a packet used for baseband encoding based on the carrier detection rate.
First, the operation of the transmitter 1 will be described with reference to the flowchart of FIG.
Here, the processing in steps S1, S6, S7, and S8 is the same as the flowcharts of FIGS. 2 and 6 of the first and second embodiments, and thus description thereof is omitted.

In step S32, the carrier detection circuit 12 measures whether or not the carrier measured in step S1 has been detected exceeding a preset time rate, that is, the time during which the carrier exists within a predetermined measurement time. It is detected whether the numerical value divided by time (hereinafter referred to as carrier detection rate) exceeds a threshold value.
At this time, when the carrier detection circuit 12 detects that the carrier detection rate does not exceed the set threshold value, the carrier detection circuit 12 outputs a notification signal indicating that the carrier detection rate does not exceed the threshold value to the control unit 13 and the process proceeds to step 33. On the other hand, if it is detected that the carrier detection rate exceeds the set threshold value, a notification signal indicating that the carrier detection rate has been exceeded is output to the control unit 13 and the process proceeds to step 38.

Next, in step S33, the control unit 13 reads data including the ID of the transmitter 1 and the payload (data unique to the transmitter 1 and data measured by the sensor) from the data memory unit 17 as transmission data. The data is output to the baseband encoding unit 15.
Then, the baseband encoding unit 15 encodes transmission data including the ID and payload of the input transmitter 1 according to the clock supplied from the clock unit 16 (in a bit interval such as Manchester encoding, NRZ, NRZI). In order to change the voltage state at high and low voltage levels in synchronization with the clock, a clock format in which the clock frequency is easy to detect is performed, and the encoded baseband signal is output to the preamble insertion unit 14.

Next, in step S34, the preamble insertion unit 14 sets the pattern type of the preamble added to the baseband signal as the pattern A. This pattern A indicates that the baseband signal (that is, the transmission signal) includes the ID of the transmitter 1 and the payload. The correspondence between the pattern A and the data length of the transmission data is determined in advance between the transmitter 1 and the receiver 2 in the wireless communication system.
In step S25, the preamble insertion unit 14 adds the pattern A preamble to the baseband signal as shown in FIG. 11, generates a packet, and outputs the packet to the radio modulation unit 11.
The data of the pattern A and the pattern B used here are stored in advance in the data memory unit 17, and the preamble insertion unit 14 reads out the data of the pattern A and the pattern B from the data memory unit 17 and uses them each time.

Next, in step S <b> 38, the control unit 13 reads only the ID of the transmitter 1 from the data memory unit 17 and outputs the ID to the baseband encoding unit 15.
The baseband encoding unit 15 encodes only the ID of the input transmitter 1 using the clock supplied from the clock unit 16 and outputs the encoded baseband signal to the preamble insertion unit 14. .

Next, in step S39, the preamble insertion unit 14 sets the pattern type of the preamble added to the baseband signal as the pattern A. This pattern B indicates that the baseband signal (that is, the transmission signal) is only the ID of the transmitter 1. The correspondence between the pattern B and the data length of the transmission data is determined in advance between the transmitter 1 and the receiver 2 in the wireless communication system.
In step S35, the preamble insertion unit 14 adds the preamble of the pattern B to the baseband signal as shown in FIG. 11, generates a packet, and outputs the packet to the radio modulation unit 11.

  As described above, in the third embodiment, the radio packet length is not shortened by multiplying the frequency of the clock when performing baseband encoding as in the first and second embodiments. In this case, the data length (number of bits) of transmission data to be transmitted is reduced to shorten the wireless packet length. However, the baseband after baseband encoding is performed as in the first and second embodiments. The time length of the signal is shorter when the carrier detection rate exceeds the set threshold than when the carrier detection rate does not exceed the set threshold, and radio signals from a plurality of transmitters 1 are transmitted. The probability of packet collision can be reduced.

  Further, in order to perform error correction in the baseband encoder 15, when the carrier detection rate is low compared to the threshold, an error detection code such as CRC32 is added to the transmission data, but when the payload is deleted, This error detection code can also be shortened by reducing the number of bits by using a short one corresponding to the case where the carrier detection rate is high exceeding the threshold, for example, CRC16. The probability of collision can be reduced.

Next, the operation of the receiver 2 will be described with reference to the flowchart of FIG.
Here, similarly to the description of the operation of the transmitter 1, the processes of S11, S22, and S16 are the same as those in the flowchart of FIG.
In step S23, the control unit 23 detects the type of the preamble pattern based on the input pattern confirmation signal, that is, detects whether the pattern confirmation signal indicates the pattern A or the pattern B. Do.
At this time, if the control unit 23 detects that the pattern type based on the input pattern confirmation signal is A, the process proceeds to step S44, while the pattern type based on the input pattern confirmation signal is B. If it is detected that there is, the process proceeds to step S47.

  Next, in step S44, since the pattern type is A, the control unit 23 detects the data length (number of bits) and the baseband signal includes the ID and payload of the transmitter 1, and an error. It detects that the detection code is CRC32, and outputs a control signal to the baseband decoding unit 24 so as to perform decoding processing corresponding to the data length and error detection corresponding to the error detection code. At this time, even if the data lengths are different, the bit lengths of the data contents (ID, payload, CRC code) are fixed, so that they are recognized in advance on the wireless transmitter side and the wireless receiver side. Therefore, even if the payload is deleted, the control unit 23 can identify the entire bit length, and therefore performs the decoding process using the identified bit length.

  Next, in step S <b> 45, the baseband decoding unit 24 performs data sampling processing or the like using the clock from the data sampling clock unit 25, and converts the baseband signal input from the preamble matching unit 22 into the base of the transmitter 1. Decoding is performed by performing decoding processing corresponding to the encoding performed by the band encoding unit 15 (decoding processing for Manchester encoding, NRZ, NRZI, etc.), and error detection processing corresponding to the control signal from the control unit 23, Error detection using CRC32 is performed, transmission data is reproduced as a processing result, and the process proceeds to step S16.

  Next, in step S47, since the pattern type is B, the control unit 23 detects only the ID of the transmitter 1 as the baseband signal, detects this data length (number of bits), and sets error detection information. A CRC 16 is detected, and a control signal is output to the baseband decoding unit 24 so that decoding processing corresponding to the data length and error detection corresponding to the error detection code are performed.

  Next, in step S <b> 48, the baseband decoding unit 24 performs data sampling processing or the like with the clock from the data sampling clock unit 25, and converts the baseband signal input from the preamble matching unit 22 into the base of the transmitter 1. Decoding is performed by performing decoding processing corresponding to the encoding performed by the band encoding unit 15, error detection processing corresponding to the control signal from the control unit 23, that is, error detection using the CRC 16, and transmission as a processing result The data is reproduced and the process proceeds to step S16.

<Fourth Embodiment>
Hereinafter, a wireless communication system according to a fourth embodiment of the present invention will be described with reference to the drawings. FIG. 13 is a block diagram showing a configuration example of the wireless communication system according to the embodiment.
In FIG. 13 of the wireless communication system according to the fourth embodiment, the same components as those of the wireless communication system according to the third embodiment are denoted by the same reference numerals, and description thereof is omitted.
In FIG. 13, a transmitter 1 is a wireless transmitter using low power radio such as an RF tag or an IC tag, and includes a radio modulation unit 11, a carrier detection unit 12, a control unit 13, a preamble insertion unit 14, a baseband. It has an encoding unit 15, a clock unit 16, a data memory unit 17, and a flag insertion unit 18.

The receiver 2 is a tag reader or the like that collects identification numbers from the RF tag, IC tag, etc., and performs tag identification processing. The radio demodulation unit 21, preamble matching unit 22, control unit 23, baseband A decoding unit 24, a data sampling clock unit 25, an interface unit 26, and a flag identification unit 28 are provided.
In the fourth embodiment, the method of shortening the radio packet length is the same as that of the third embodiment, and the clock unit 16 and the data sampling clock unit 25 are frequency change from the corresponding control units 13 and 23, respectively. A clock having a predetermined frequency is supplied to the baseband encoding unit 15 and the baseband decoding unit 24 without being controlled.

Next, the operation of the wireless communication system according to the fourth embodiment will be described with reference to FIG. 13, FIG. 14, FIG. 15, and FIG. FIG. 14 is a flowchart showing an operation example of the transmitter 1, and FIG. 16 is a flowchart showing an operation example of the receiver 2. FIG. 15 is a conceptual diagram illustrating a packet configuration for explaining control of a data length (number of bits of transmission data) in a packet used for baseband encoding based on a carrier detection rate.
First, the operation of the transmitter 1 will be described with reference to the flowchart of FIG.
Here, the processing in steps S1, S6, and S7 is the same as that in the flowchart of FIG. 10 of the third embodiment, and thus description thereof is omitted.

In step S52, the carrier detection circuit 12 measures whether or not the carrier measured in step S1 has been detected exceeding a preset time rate, that is, the time during which the carrier exists within a predetermined measurement time. It is detected whether the numerical value divided by time (hereinafter referred to as carrier detection rate) exceeds a threshold value.
At this time, when the carrier detection circuit 12 detects that the carrier detection rate does not exceed the set threshold value, the carrier detection circuit 12 outputs a notification signal indicating that the carrier detection rate does not exceed the threshold value to the control unit 13 and the process proceeds to step 53. On the other hand, if it is detected that the carrier detection rate exceeds the set threshold value, a notification signal indicating that the carrier detection rate has been exceeded is output to the control unit 13 and the process proceeds to step 58.

In step S53, the control unit 13 reads data including the ID of the transmitter 1 and the payload (data unique to the transmitter 1, data measured by the sensor, etc.) from the data memory unit 17 as transmission data. To the conversion unit 15.
Then, the baseband encoding unit 15 encodes transmission data including the ID and payload of the input transmitter 1 according to the clock supplied from the clock unit 16 (in a bit interval such as Manchester encoding, NRZ, NRZI). In order to change the voltage state at a high and low voltage level in synchronization with the clock, the clock frequency is easily detected, and the encoded baseband signal is output to the flag insertion unit 18.

Next, in step S54, the flag insertion unit 18 inserts a flag indicating the data length as shown in FIG. 15, for example, transmission data having a long data length (a large number of bits) including the ID and payload of the transmitter 1 Therefore, the flag bit is set to “0”, this flag is added to the baseband signal, and the process proceeds to step S55.
This flag “0” indicates that the baseband signal (that is, the transmission signal) includes the ID and payload of the transmitter 1. The correspondence relationship between the bit “0” of the flag and the data length of the transmission data is determined in advance between the transmitter 1 and the receiver 2 in the wireless communication system.

In step S55, the preamble insertion unit 14 adds a predetermined pattern of preamble to the baseband signal, generates a packet, and outputs the packet to the radio modulation unit 11, as shown in FIG.
The flag data used here is stored in the data memory unit 17 in advance, and the flag insertion unit 18 reads the flag value from the data memory unit 17 and uses it each time.

Next, in step S <b> 58, the control unit 13 reads only the ID of the transmitter 1 from the data memory unit 17 and outputs it to the baseband encoding unit 15.
The baseband encoding unit 15 encodes only the ID of the input transmitter 1 using the clock supplied from the clock unit 16 and outputs the encoded baseband signal to the flag insertion unit 18. .

Next, in step S59, the flag insertion unit 18 inserts a flag indicating the data length, as shown in FIG. 15, for example, transmission data with a short data length only for the ID of the transmitter 1 (the number of bits is small). Therefore, the bit of the flag is set to “1”, this flag is added to the baseband signal, and the process proceeds to step S55.
This flag “1” indicates that the baseband signal (that is, the transmission signal) is only the ID of the transmitter 1. The correspondence between the bit “1” of the flag and the data length of the transmission data is determined in advance between the transmitter 1 and the receiver 2 in the wireless communication system.

In step S55, the preamble insertion unit 14 adds a predetermined pattern of preamble to the baseband signal, generates a packet, and outputs the packet to the radio modulation unit 11, as shown in FIG.
The flag data used here is stored in the data memory unit 17 in advance, and the flag insertion unit 18 reads the flag value from the data memory unit 17 and uses it each time.

  As described above, in the fourth embodiment, as in the third embodiment, the data length (number of bits) of transmission data to be transmitted is reduced to shorten the wireless packet length. Similar to the first and second embodiments, the carrier detection rate is compared with the case where the time length of the baseband signal after baseband encoding does not exceed the set threshold value. Becomes shorter when the set threshold value is exceeded, and the probability of collision of radio packets from a plurality of transmitters 1 can be reduced.

  Also, the baseband encoder 15 performs error detection as in the third embodiment, so that error detection information such as CRC32 is added to the transmission data when the carrier detection rate is lower than the threshold. However, when the payload is deleted, this error correction information is also shortened by using a short one corresponding to the case where the carrier detection rate exceeds the threshold, for example, CRC16, thereby further reducing the packet length. Can be shortened, and the probability of radio packet collision can be reduced.

Next, the operation of the receiver 2 will be described with reference to the flowchart of FIG.
Here, similarly to the description of the operation of the transmitter 1, the processing of S16 is the same as the flowchart of FIG. 12 of the third embodiment, and thus the description thereof is omitted.
In step S11, the radio demodulation unit 21 demodulates the radio packet received via the antenna using a demodulation clock having the same frequency as the modulation clock used by the radio modulation unit 11 of the transmitter 1. Reproduce.

In step S62, the preamble matching unit 22 performs preamble pattern matching on the input packet, detects whether the received packet is received by the receiver 2, and the pattern is received by the receiver. When 2 is not received, the packet is discarded and the subsequent processing is not performed. On the other hand, when it is detected that the pattern is received by the receiver 2, the flag bit after the preamble bit string is detected. I do.
Then, the preamble matching unit 22 leaves the detected flag bit, deletes the preamble from the packet, and outputs it to the flag identifying unit 28 as a baseband signal with the flag added.

Next, in step S63, the flag identifying unit 28 detects the numerical value of the bit of the flag, that is, detects whether the bit is “0” or “1”.
At this time, if the flag identification unit 28 detects that the flag bit is “0”, the process proceeds to step S64. On the other hand, if the flag identification unit 28 detects that the flag bit is “1”, the process proceeds to step S64. Proceed to step S67.

  Next, in step S64, since the flag bit is “0”, the control unit 23 detects the data length of the baseband signal including the ID and payload of the transmitter 1, and detects the error detection code. Is detected as CRC32, and a control signal is output to the baseband decoding unit 24 so as to perform decoding processing corresponding to the data length and error detection corresponding to the error detection code.

  Next, in step S65, the baseband decoding unit 24 performs a data sampling process or the like using the clock from the data sampling clock unit 25, and converts the baseband signal input from the preamble matching unit 22 into the base of the transmitter 1. Decoding is performed by performing decoding processing corresponding to the encoding performed by the band encoding unit 15 (decoding processing for Manchester encoding, NRZ, NRZI, etc.), and error detection processing corresponding to the control signal from the control unit 23, Error detection using CRC32 is performed, transmission data is reproduced as a processing result, and the process proceeds to step S16.

  Next, in step S67, since the flag bit is “1”, the control unit 23 detects only the ID of the transmitter 1 as the baseband signal, detects this data length (number of bits), and detects errors. It detects that the code is CRC16, and outputs a control signal to the baseband decoding unit 24 so as to perform decoding processing corresponding to the data length and error detection corresponding to the error detection code.

  Next, in step S <b> 68, the baseband decoding unit 24 performs data sampling processing or the like with the clock from the data sampling clock unit 25, and converts the baseband signal input from the preamble matching unit 22 into the base of the transmitter 1. Decoding is performed by performing decoding processing corresponding to the encoding performed by the band encoding unit 15, error detection processing corresponding to the control signal from the control unit 23, that is, error detection using the CRC 16, and transmission as a processing result The data is reproduced and the process proceeds to step S16.

  In addition, a program for realizing a function of transmitting and receiving data by changing the packet length according to the carrier detection rate in the transmitter 1 or the receiver 2 in FIG. 1 is recorded on a computer-readable recording medium. The program recorded on the recording medium may be read into the computer system and executed to change the packet length according to the carrier detection rate and perform data transmission / reception. Here, the “computer system” includes an OS and hardware such as peripheral devices. The “computer system” includes a WWW system provided with a homepage providing environment (or display environment). The “computer-readable recording medium” refers to a portable medium such as a flexible disk, a magneto-optical disk, a ROM, and a CD-ROM, and a storage device such as a hard disk built in the computer system. Further, the “computer-readable recording medium” refers to a volatile memory (RAM) in a computer system that becomes a server or a client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. In addition, those holding programs for a certain period of time are also included.

  The program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the “transmission medium” for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line. The program may be for realizing a part of the functions described above. Furthermore, what can implement | achieve the function mentioned above in combination with the program already recorded on the computer system, and what is called a difference file (difference program) may be sufficient.

1 is a block diagram illustrating a configuration example of a wireless communication system according to a first embodiment of the present invention. 3 is a flowchart showing an operation example of packet transmission of the transmitter 1 of FIG. 1. It is a conceptual diagram which shows the structure of the packet explaining control of the clock used for baseband encoding based on the carrier detection rate in 1st Embodiment. 3 is a flowchart showing an example of packet transmission operation of the receiver 2 of FIG. 1. It is a block diagram which shows the structural example of the radio | wireless communications system by the 2nd Embodiment of this invention. 6 is a flowchart showing an operation example of packet transmission of the transmitter 1 of FIG. 5. It is a conceptual diagram which shows the structure of the packet explaining control of the clock used for baseband encoding based on the carrier detection rate in 2nd Embodiment. 6 is a flowchart showing an example of packet transmission operation of the receiver 2 of FIG. 5. It is a block diagram which shows the structural example of the radio | wireless communications system by the 3rd Embodiment of this invention. 10 is a flowchart showing an operation example of packet transmission of the transmitter 1 of FIG. 9. It is a conceptual diagram which shows the structure of the packet explaining the control of the data length used for baseband encoding based on the carrier detection rate in 3rd Embodiment. 10 is a flowchart illustrating an operation example of packet transmission of the receiver 2 of FIG. 9. It is a block diagram which shows the structural example of the radio | wireless communications system by the 4th Embodiment of this invention. It is a flowchart which shows the operation example of transmission of the packet of the transmitter 1 of FIG. It is a conceptual diagram which shows the structure of the packet explaining the control of the data length used for baseband encoding based on the carrier detection rate in 4th Embodiment. It is a flowchart which shows the operation example of transmission of the packet of the receiver 2 of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Transmitter 2 ... Receiver 11 ... Radio modulation part 12 ... Carrier detection part 13, 23 ... Control part 14 ... Preamble insertion part 15 ... Baseband encoding 16 ... Clock part 17 ... Data memory part 21 ... Radio demodulation part 22 ... Preamble matching unit 22A ... Preamble A matching unit 22B ... Preamble B matching unit 24 ... Baseband decoding unit 25 ... Data sampling clock unit 26 ... Interface unit

Claims (12)

A baseband modulation unit that performs baseband encoding of data to be transmitted according to an input clock;
A clock unit for generating a baseband encoding clock;
A carrier detection unit that detects whether or not the carrier detection rate within a predetermined period exceeds a set threshold;
And a control unit that controls the frequency of the clock according to the detection result.   The radio transmitter according to claim 1, wherein when the control unit detects that a carrier detection rate exceeds the threshold, the frequency of the clock is multiplied.   The radio transmitter according to claim 1, further comprising: a preamble part that adds a preamble to the data, wherein clock information indicating a clock frequency is added to the preamble part.   4. The radio transmitter according to claim 3, wherein the clock information is a length of a terminal pulse length controlled according to a clock frequency or a preamble pattern. A baseband modulation unit that performs baseband encoding of data to be transmitted according to an input clock;
A clock unit for generating a baseband modulation clock;
A carrier detection unit that detects whether or not the carrier detection rate within a predetermined period exceeds a set threshold;
And a control unit that controls a data length of the data to be transmitted according to the detection result.   The radio transmitter according to claim 5, wherein when the control unit detects that a carrier detection rate exceeds the threshold, the data length of the data to be transmitted is shortened.   7. The radio transmitter according to claim 5, further comprising: a preamble part that assigns a preamble to the data, wherein the preamble pattern is changed according to a data length of data transmitted by the preamble part. .   6. A flag insertion unit that adds a flag to baseband encoded data, and changes the flag to be inserted according to the data length of data transmitted by the flag insertion unit. 6. The wireless transmitter according to 6. A wireless receiver that receives a packet indicating the number of clocks of baseband encoding of a transmission signal from a wireless communication device according to clock information of a preamble to be added,
A preamble matching unit that performs pattern matching of a preamble of the packet and extracts clock information of the preamble;
A data sampling clock unit for controlling a clock for baseband decoding according to the clock information;
And a baseband decoding unit that performs baseband decoding of the data by the clock. A baseband modulation unit that performs baseband encoding of data to be transmitted according to an input clock; a clock unit that generates a clock for baseband encoding;
A carrier detection unit that detects whether or not a carrier detection rate within a predetermined period exceeds a set threshold; a control unit that controls the frequency of the clock based on the detection result; and clock information that indicates a clock frequency A wireless transmitter having a preamble part to which a preamble with a packet added is formed as a packet, and a transmission part that modulates the packet and transmits the packet as a transmission signal;
A reception unit that receives the transmission signal and demodulates the transmission signal to form a packet; a preamble matching unit that performs preamble pattern matching of the packet and extracts preamble clock information; and A wireless communication system comprising: a data receiver that has a data sampling clock unit that controls a decoding clock; and a baseband decoding unit that performs baseband decoding of data transmitted by the clock. Whether the baseband modulation unit that performs baseband encoding of the data to be transmitted, the clock unit that generates the clock for baseband modulation, and the carrier detection rate within a predetermined period exceeded the set threshold depending on the input clock A carrier detection unit for detecting whether or not, a control unit for controlling the data length of the data to be transmitted based on the detection result, and a preamble to which data length information indicating the data length of the data to be transmitted is added to the data A wireless transmitter having a preamble part to be given as a packet and a sending part that modulates the packet and sends it as a transmission signal;
A receiving unit that receives the transmission signal and demodulates the transmission signal into a packet; a preamble matching unit that performs preamble pattern matching of the packet and extracts preamble clock information; and A baseband decoding unit for decoding; a control unit for detecting a data length of transmitted data based on the clock information; and a baseband decoding unit for performing baseband decoding of data transmitted based on the detected data length A wireless communication system comprising: a wireless receiver having: Whether the baseband modulation unit that performs baseband encoding of the data to be transmitted, the clock unit that generates the clock for baseband modulation, and the carrier detection rate within a predetermined period exceeded the set threshold depending on the input clock A carrier detection unit that detects whether or not, a control unit that controls the data length of the data to be transmitted based on the detection result, a flag insertion unit that adds a flag indicating the data length of the data to be transmitted, and the flag A wireless transmitter having a preamble part that adds a preamble to the added data and forms a packet, and a transmitting part that modulates the packet and transmits it as a transmission signal; receives the transmission signal; demodulates the transmission signal A packet receiving unit, a preamble matching unit for pattern matching of the packet preamble, and a frame A flag identifying unit that identifies the data, a control unit that detects the data length of the transmitted data using the flag, and a baseband decoding unit that performs baseband decoding of the transmitted data based on the detected data length A wireless communication system comprising: a wireless receiver including:

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