JP2012049677A - Wireless communication device and data rate control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wireless communication device 20 capable of suppressing variations in characteristics of individual receivers and quickly determining a data rate increase, in a communication system 10 that controls PER to be equal to or smaller than a predetermined value by controlling data rate.SOLUTION: A wireless communication device 20 of this invention determines a data rate decrease using the PER of received packets, and determines a data rate increase using RSSI. After making a determination of data rate decrease, the wireless communication device 20 does not make a determination of data rate increase for a predetermined period of time.

Description

  The present invention relates to a technique for maintaining the quality of a received signal at a certain level or higher on the receiving side by controlling the data rate of the transmitting signal on the transmitting side.

  In wireless communication that supports multi-rate, the quality of the received signal can be kept above a certain level on the receiving side by adaptively controlling the data rate of the transmission packet on the transmitting side according to the radio wave environment of the propagation path. For example, when the radio wave environment of the propagation path is poor, stable wireless communication is ensured by transmitting packets at a low data rate, and when the radio wave environment of the propagation path is good, packets are transmitted at a high data rate. High-speed wireless communication can be realized.

  In order to realize such data rate adaptive control, it is necessary to estimate the radio wave environment. For estimation of the radio wave environment, a method using an error rate of data such as PER (Packet Error Rate) or information indicating a received signal state such as RSSI (Received Signal Strength Indicator) or SNR (Signal to Noise ratio) is used. The method is known.

For example, in Non-Patent Document 1 below, when the PER is less than a predetermined value on the receiving side, the data rate is increased on the transmitting side, and when the PER is larger than the predetermined value on the receiving side, the data rate is set on the transmitting side. Techniques for lowering are disclosed. For example, it is conceivable to perform control to lower the data rate when PER becomes larger than 10 ^{−3, and} to raise the data rate when PER becomes 10 ⁻⁵ or less, for example.

  Further, in Patent Document 2 below, a table in which the data rate that can suppress the PER to a certain value or less is created in association with the SNR, and the data rate is controlled on the transmission side according to the SNR measured on the reception side. Techniques to do this are disclosed.

A. Kamerman and L. Monteban. "WaveLAN-II: A High-performance wireless LAN for the unlicensed band" Bell Labs Technical Journal, pages 118-133, Summer 1997. G. Holland, N. Vaidya, P. Bahl, "A Rate-Adaptive MAC Protocol for Multi-Hop Wireless Networks", In Proceeding ACM MOBICOM, July 2001.

By the way, in the technique of Non-Patent Document 1 above, for example, whether or not PER becomes larger than 10 ⁻³ can be determined by measuring the number of error packets for every 10 ³ received packets. However, it is necessary to receive at least 10 ⁵ received packets, for example, in order to determine whether the PER is 10 ⁻⁵ or less. Therefore, even if the radio wave environment becomes good, it takes time to increase the data rate.

  In addition, the SNR measurement does not require much time as compared with the PER measurement. However, since the performance of the receiver is not exactly the same for each device, the SNR value that can suppress the PER to a predetermined value or less is Each may be different. Therefore, even if data is transmitted at a data rate corresponding to the measured SNR value with reference to a table showing a relationship between a preset SNR and a data rate, the PER exceeds a predetermined value on the receiving side. There is a case.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to suppress variations in characteristics among receivers in a communication system that controls PER to a predetermined value or less by controlling a data rate. At the same time, it is intended to make it possible to quickly determine the increase in data rate.

  In order to solve the above problems, in the present invention, in a communication system that maintains the quality of a received signal at a certain level or more by controlling the data rate, a data rate decrease determination is performed using an error rate of received data, and reception is performed. An increase determination of the data rate is performed using the signal strength.

For example, a first aspect of the present invention is a wireless communication apparatus used in a wireless communication system for controlling a data rate in order to keep the quality of a received signal at a certain level or more,
In association with information indicating the received signal strength, an allowable rate information storage unit that stores an allowable rate indicating a data rate that is allowed for an error rate of data received at the strength to be less than a predetermined threshold;
An error rate calculation unit for calculating an error rate of data included in a signal received from another wireless communication device on the transmission side as a communication partner;
A lowering determination unit that outputs a lowering signal indicating an instruction to lower the data rate when the error rate is greater than the threshold;
When the error rate is equal to or lower than the threshold, an allowable rate associated with the current received signal strength is extracted from the allowable rate information storage unit, and the extracted allowable rate is higher than the current data rate. A rising determination unit that outputs a rising signal indicating an instruction to increase the current data rate;
When a down signal is output from the down determination unit, if communication at a data rate lower than the current data rate is supported in the communication system, the down signal is transmitted to the other wireless communication device on the transmission side. When the rising signal is transmitted from the rising determination unit and the communication system supports communication at a data rate higher than the current data rate, the rising signal is transmitted to the other radio on the transmitting side. A rate control signal transmitter for transmitting to the communication device;
A transmission unit that transmits data to another wireless communication device on the receiving side that is a communication partner at an instructed data rate;
When a down signal is received from another wireless communication device on the receiving side, the transmitter is instructed to send a data rate lower than the current data rate, and an up signal is received from the other wireless communication device on the receiving side In this case, a wireless communication apparatus is provided, comprising: a data rate control unit that instructs the transmission unit to use a data rate higher than a current data rate.

A second aspect of the present invention is a data rate control method for a radio communication device used in a radio communication system for controlling a data rate in order to keep the quality of a received signal at a certain level or more,
The wireless communication device
Corresponding to information indicating the received signal strength, an allowable rate information storage unit for storing an allowable rate indicating a data rate allowed for an error rate of data received at the strength to be less than a predetermined threshold is provided. ,
An error rate calculation step for calculating an error rate of data included in a signal received from another wireless communication device on the transmission side as a communication partner;
A descent determination step of outputting a descent signal indicating an instruction to lower the data rate when the error rate is greater than the threshold;
When the error rate is equal to or lower than the threshold, an allowable rate associated with the current received signal strength is extracted from the allowable rate information storage unit, and the extracted allowable rate is higher than the current data rate. A rising determination step for outputting a rising signal indicating an instruction to increase the current data rate;
When the down signal is output in the down determination, if the communication system supports communication at a data rate lower than the current data rate, the down signal is transmitted to the other wireless communication device on the transmission side. When the rising signal is output in the rising determination step, if communication at a data rate higher than the current data rate is supported in the communication system, the rising signal is transmitted to the other wireless communication device on the transmission side. A rate control signal transmission step for transmitting;
When a down signal is received from another wireless communication device on the receiving side that is the communication partner, data is transmitted at a data rate lower than the current data rate, and an up signal is received from the other wireless communication device on the receiving side. In such a case, a data rate control method is provided that executes a transmission step of transmitting data at a data rate higher than a current data rate.

  According to the wireless communication apparatus of the present invention, in a communication system that controls the data rate to keep the PER below a predetermined value, it is possible to suppress variations in characteristics of each receiver and to quickly determine the increase in the data rate. It can be carried out.

1 is a system configuration diagram illustrating an example of a configuration of a communication system 10 according to an embodiment of the present invention. It is a block diagram which shows an example of a detailed functional structure of the radio | wireless communication apparatus 20 incorporated in each apparatus 11 in 1st Embodiment. It is a figure which shows an example of the structure of the data stored in the allowable rate information storage part. 6 is an explanatory diagram for explaining an operation of a rate control signal transmission unit 26. FIG. It is explanatory drawing for demonstrating operation | movement of the rate control signal transmission part 26 in 1st Embodiment. It is explanatory drawing for demonstrating operation | movement of the rate control signal transmission part 26 in 1st Embodiment. 6 is a flowchart illustrating an example of an operation of the radio communication device 20 on the receiving side in the first embodiment. It is a block diagram which shows an example of a detailed functional structure of the radio | wireless communication apparatus 20 incorporated in each apparatus 11 in 2nd Embodiment. 10 is a flowchart illustrating an example of an operation of the radio communication device 20 on the receiving side in the second embodiment. It is explanatory drawing for demonstrating operation | movement of the rate control signal transmission part 26 in 2nd Embodiment.

  First, a first embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a system configuration diagram illustrating an example of a configuration of a communication system 10 according to an embodiment of the present invention. The communication system 10 includes a plurality of devices 11. Each device 11 is provided in a home, for example, and wirelessly communicates with each other using a built-in wireless communication device 20.

  FIG. 2 is a block diagram illustrating an example of a detailed functional configuration of the wireless communication device 20 built in each device 11 in the first embodiment. The wireless communication device 20 includes a PER calculation unit 21, a descending determination unit 22, an ascending determination unit 23, an allowable rate information storage unit 24, a decoder 25, a rate control signal transmission unit 26, a radio unit 27, a data rate control unit 28, and an encoder. 29.

  In FIG. 2, the wireless communication device 20a indicates the wireless communication device 20 provided on the receiving side in the two devices 11 that transmit and receive data, and the blocks indicated by broken lines in the wireless communication device 20a are received. Blocks that do not function when operating as a side are shown. Similarly, the wireless communication device 20b indicates the wireless communication device 20 provided on the transmission side, and the blocks indicated by broken lines in the wireless communication device 20b indicate blocks that do not function when operating as the transmission side. Yes.

  First, the radio communication device 20a when operating as the receiving side will be described. The radio unit 27 demodulates the radio wave received via the antenna and supplies it to the decoder 25, and modulates the signal received from the encoder 29 and transmits it via the antenna. In addition, the radio unit 27 measures RSSI and provides information indicating the measured RSSI to the ascent determination unit 23.

  The decoder 25 performs error correction or the like on the signal received from the wireless unit 27 and decodes it, and supplies the decoded data to the device 11. Each time the decoder 25 receives a data packet, the decoder 25 provides the PER calculator 21 with information indicating that the data packet has been received and whether the data packet is an error packet. In addition, the decoder 25 provides information indicating the current data rate to the rise determination unit 23 and the rate control signal transmission unit 26.

The PER calculation unit 21 receives from the decoder 25 and holds information indicating that the data packet has been received and whether or not the data packet is an error packet, and stores a predetermined number (for example, 10 ^{3) of} data packets. Each time it is received, PER is calculated and sent to the descent determining unit 22.

The descending determination unit 22 determines whether the received PER is larger than a predetermined threshold (for example, 10 ⁻³ ) when the PER is received from the PER calculation unit 21. When the received PER is larger than a predetermined threshold value, the decrease determination unit 22 outputs a decrease signal indicating an instruction to decrease the data rate to the rate control signal transmission unit 26. On the other hand, when the received PER is equal to or less than a predetermined threshold, the lowering determination unit 22 notifies the increase determination unit 23 to that effect.

  As described above, since the data rate decrease determination is performed based on the PER of the actually received packet, the wireless communication device 20a of the present embodiment relates to the performance variation of the wireless unit 27, reception of unnecessary radio waves, and the like. Therefore, the quality of the received signal can be kept above a certain level.

In the allowable rate information storage unit 24, for example, as shown in FIG. 3, in association with information indicating the RSSI range 240, the PER of the received data in the RSSI within the range 240 has a predetermined threshold (for example, An allowable rate 241 indicating the maximum data rate allowed to be less than 10 ⁻³ ) is stored. Note that all the data rate values supported in the communication system 10 are stored in the column of the allowable rate 241.

  The rise determination unit 23 refers to the allowable rate information storage unit 24 based on the RSSI provided from the radio unit 27 when notified that the PER is less than a predetermined threshold value from the decrease determination unit 22. The allowable rate associated with the range including the current RSSI value is extracted. When the extracted allowable rate is higher than the current data rate provided from the decoder 25, the increase determination unit 23 outputs an increase signal indicating an instruction to increase the data rate to the rate control signal transmission unit 26.

  As described above, since the data rate increase determination is performed based on the current RSSI value, the data rate increase determination is performed based on the PER calculated from the reception result of tens of thousands of packets. This makes it possible to quickly determine whether the data rate has increased.

  When the rate control signal transmission unit 26 receives the down signal from the down determination unit 22, the rate control signal transmission unit 26 refers to the allowable rate information storage unit 24, and an allowable rate lower than the current data rate provided from the decoder 25 is an allowable rate. It is determined whether or not the information is stored in the information storage unit 24. When the allowable rate lower than the current data rate provided from the decoder 25 is not stored in the allowable rate information storage unit 24, that is, when the data rate cannot be lowered any more, the rate control signal transmission unit 26 Discards the descent signal received from the descent determination unit 22.

On the other hand, when the allowable rate lower than the current data rate provided from the decoder 25 is stored in the allowable rate information storage unit 24, that is, when the data rate can still be lowered, the rate control signal transmission unit 26 sends the lowering signal received from the lowering determination unit 22 to the encoder 29. Then, the rate control signal transmitter 26 resets and starts the built-in timer. The built-in timer counts up to a predetermined period T ₀ after the reset start, and when it reaches T ₀ , the value of the built-in timer stops at a value indicating the T ₀ . The predetermined period T ₀ is, for example, a period until 3 × 10 ³ packets are received.

Also, when receiving an increase signal from the decrease determination unit 22, the rate control signal transmission unit 26 refers to the allowable rate information storage unit 24 and allows an allowable rate higher than the current data rate provided from the decoder 25. It is determined whether or not the value stored in the rate information storage unit 24 and the value of the built-in timer is a value T ₀ indicating a predetermined period. When the allowable rate higher than the current data rate provided from the decoder 25 is stored in the allowable rate information storage unit 24 and the value of the built-in timer is T ₀ , the rate control signal transmission unit 26 sends the rising signal received from the lowering determination unit 22 to the encoder 29.

On the other hand, an allowable rate higher than the current data rate provided from the decoder 25 is not stored in the allowable rate information storage unit 24 (that is, the data rate cannot be increased any more), or a built-in timer When the value of T is not T ₀ , the rate control signal transmission unit 26 discards the rising signal received from the lowering determination unit 22.

Here, for example, when the RSSI value is within a range of −50 dBm to −35 dBm, the PER value is less than a threshold value (for example, 10 ⁻³ ) if the data rate is, for example, 320 Mbps. The allowable rate information shown in 3 is created. The relationship between RSSI and PER in this case is as shown by characteristic 30 in FIG.

However, the receiver performance varies, and if unnecessary radio waves are transmitted within the communication band, the PER value exceeds the threshold even if the RSSI value is within the above range. May end up. For example, as shown in FIG. 4, when the relationship between RSSI and PER becomes a characteristic 31 due to the influence of variations in receiver performance and reception of unnecessary radio waves, if the RSSI value is R ₁ , Despite being in the range of −50 dBm to −35 dBm, the PER cannot be kept below the threshold (P _TH ) at a data rate of 320 Mbps.

  Therefore, for example, as shown in FIG. 5, after the decrease determination unit 22 is instructed to decrease the data rate, the increase determination unit 23 is instructed to increase the data rate. As shown in FIG. 4, the RSSI value may not necessarily reflect the PER value. Therefore, after the ascent determining unit 23 increases the data rate based on the RSSI value, the descending determining unit 22 There is a possibility that the PER is larger than the threshold value until the data rate is lowered after detecting the deterioration.

Therefore, in the present embodiment, as shown in FIG. 6, after the PER deterioration is detected and a data rate decrease is instructed, the data rate increase is suppressed for a certain period (T <T ₀ period). Thus, the frequency of occurrence of a state in which the PER is larger than the threshold value is kept low.

  Returning to FIG. 2, the description will be continued. The encoder 29 performs processing such as adding or encoding an error correction code to the ascending signal or descending signal received from the rate control signal transmission unit 26, and sends the data subjected to these processings to the radio unit 27. The radio unit 27 outputs a radio wave modulated based on the data received from the encoder 29 to the radio communication device 20b on the transmission side via the antenna.

  Next, the radio communication device 20b when operating as a transmission side will be described. The radio unit 27 demodulates the radio wave received via the antenna and supplies it to the decoder 25, and modulates the signal received from the encoder 29 and transmits it via the antenna.

  The decoder 25 performs error correction or the like on the signal received from the radio unit 27 and decodes the signal, and supplies the decoded data to the data rate control unit 28. When the data received from the decoder 25 includes an ascending signal, the data rate control unit 28 instructs the encoder 29 to have a data rate that is one step higher than the current data rate used for data transmission. If the data received from the decoder 25 includes a down signal, the data rate control unit 28 instructs the encoder 29 to use a data rate that is one step lower than the current data rate used for data transmission.

  The encoder 29 performs processing such as adding an error correction code to the data received from the main body of the device 11 or encoding at the data rate instructed by the data rate control unit 28, and wirelessly processing the data subjected to these processing. Send to part 27. The radio unit 27 outputs a radio wave modulated based on the data received from the encoder 29 to the radio communication device 20a on the reception side via an antenna.

  FIG. 7 is a flowchart showing an example of the operation of the radio communication device 20 on the receiving side in the first embodiment. The wireless communication device 20 starts the operation shown in this flowchart by starting reception.

First, PER calculating unit 21, information indicating a variable n for counting the number of packets, the variable n _e for counting the number of error packets is initialized to 0 (S100), that it has received a packet from the decoder 25 Is determined (S101).

  When the information indicating that the packet has been received is received from the decoder 25 (S101: Yes), the PER calculation unit 21 increases the variable n by 1 (S102), and receives the information from the decoder 25 together with the information indicating that the packet has been received. Referring to information indicating whether or not the packet is an error packet, it is determined whether or not the received packet is an error packet (S103).

If the received packet is not an error packet (S103: No), the PER calculation unit 21 executes the process shown in step S105. On the other hand, if the received packet is an error packet (S103: Yes), the PER calculation unit 21 increases the variable _ne by 1 (S104). Then, the PER calculation unit 21 determines whether or not the variable n has reached the predetermined value n ₀ (S105). The predetermined value n ₀ is, for example, 10 ³ . If the variable n has not reached the predetermined value n ₀ (S105: No), the PER calculation unit 21 executes the process shown in step S101 again.

On the other hand, if the variable n has reached the predetermined value _{n 0 (S105: Yes),} PER calculating unit 21 calculates a PER by dividing the variable n _e in the variable n (S106), lowering the calculated PER determination unit 22 Send to. The descending determination unit 22 determines whether the PER received from the PER calculation unit 21 is larger than a threshold value P _TH (for example, 10 ⁻³ ) (S107). When the PER is larger than the threshold value P _TH (S107: Yes), the decrease determination unit 22 outputs a decrease signal that instructs the decrease of the data rate to the rate control signal transmission unit 26.

  If the data rate can be lowered, the rate control signal transmitter 26 sends the received lowering signal to the encoder 29. The encoder 29 performs processing such as adding or encoding an error correction code to the descending signal received from the rate control signal transmission unit 26, and sends the data subjected to these processing to the radio unit 27. The radio unit 27 outputs the radio wave modulated based on the data received from the encoder 29 via the antenna (S108). Then, the rate control signal transmission unit 26 resets and starts the built-in timer (S109), and the PER calculation unit 21 executes the process shown in step S100 again.

In step S107, if the PER is less than the threshold value P _TH (S107: No), falling determination unit 22 notifies the rise judgment unit 23. The rise determination unit 23 refers to the allowable rate information storage unit 24 based on the RSSI provided from the radio unit 27, and extracts the allowable rate associated with the range including the current RSSI value (S110). .

  Next, the increase determination unit 23 determines whether the extracted allowable rate is higher than the current data rate provided from the decoder 25 (S111). If the extracted allowable rate is equal to or lower than the current data rate provided from the decoder 25 (S111: No), the PER calculation unit 21 executes the process shown in step S100 again.

  On the other hand, when the extracted allowable rate is higher than the current data rate provided from the decoder 25 (S111: Yes), the increase determination unit 23 sends the increase signal instructing the increase of the data rate to the rate control signal transmission unit. 26 (S112).

Next, the rate control signal transmitter 26 refers to the value of the built-in timer and determines whether or not the value of the built-in timer is a value T ₀ indicating a predetermined period (S113). When the value of the built-in timer is not T ₀ (S113: No), the rate control signal transmission unit 26 discards the rising signal received from the rising determination unit 23, and the PER calculation unit 21 returns to step S100 again. Execute the process.

On the other hand, when the value of the built-in timer is T ₀ (S113: Yes), the rate control signal transmission unit 26 sends an increase signal to the encoder 29 if the data rate can be increased. The encoder 29 performs processing such as adding or correcting an error correction code to the rising signal received from the rate control signal transmission unit 26, and sends the data subjected to these processing to the radio unit 27. The radio unit 27 outputs a radio wave modulated based on the data received from the encoder 29 via the antenna (S114), and the PER calculation unit 21 executes the process shown in step S100 again.

  The first embodiment of the present invention has been described above.

  As is apparent from the above description, according to the wireless communication device 20 of the present embodiment, in the communication system 10 that controls the data rate to keep the PER below a predetermined value, it is possible to suppress variations in characteristics among receivers. In addition, it is possible to quickly determine whether the data rate has increased.

  Next, a second embodiment of the present invention will be described with reference to the drawings.

  FIG. 8 is a block diagram illustrating an example of a detailed functional configuration of the wireless communication device 20 built in each device 11 in the second embodiment. The wireless communication device 20 includes a decrease determination unit 22, an increase determination unit 23, an allowable rate information storage unit 24, a decoder 25, a rate control signal transmission unit 26, a wireless unit 27, a data rate control unit 28, and an encoder 29.

  Except for the points described below, in FIG. 8, the components denoted by the same reference numerals as those in FIG. 2 have the same or similar functions as those in FIG. The configuration of the wireless communication device 20 according to this embodiment is different from the wireless communication device 20a according to the first embodiment in the case of operating as a receiving side.

  Each time the decoder 25 receives a data packet from the radio communication device 20b on the transmission side, the decoder 25 notifies the descending determination unit 22 of the information indicating that the data packet has been received and whether the data packet is an error packet. .

The descending determination unit 22 receives and holds that the data packet has been received from the decoder 25, and notifies the ascending determination unit 23 every time a predetermined number (eg, 10 ³ ) of data packets are received. Further, when the decoder 25 is notified that the error packet has been received, the descending determination unit 22 outputs a descending signal indicating an instruction to lower the data rate to the rate control signal transmitting unit 26 and holds the data Resets information indicating the number of received packets.

  FIG. 9 is a flowchart illustrating an example of the operation of the radio communication device 20 on the receiving side according to the second embodiment. The wireless communication device 20 starts the operation shown in this flowchart by starting reception.

  First, the descending determination unit 22 initializes a variable n for counting the number of packets to 0 (S200), and determines whether information indicating that a packet has been received from the decoder 25 has been received (S201). When receiving the information indicating that the packet has been received from the decoder 25 (S201: Yes), the descending determination unit 22 increases the variable n by 1 (S202), and receives the information from the decoder 25 together with the information indicating that the packet has been received. Referring to information indicating whether or not the packet is an error packet, it is determined whether or not the received packet is an error packet (S203).

  When the received packet is an error packet (S203: Yes), the decrease determination unit 22 outputs a decrease signal instructing a decrease in the data rate to the rate control signal transmission unit 26. If the data rate can be lowered, the rate control signal transmitter 26 sends the received lowering signal to the encoder 29. The encoder 29 performs processing such as adding or encoding an error correction code to the descending signal received from the rate control signal transmission unit 26, and sends the data subjected to these processing to the radio unit 27.

  The wireless unit 27 outputs a radio wave modulated based on the data received from the encoder 29 via the antenna (S204). Then, the rate control signal transmission unit 26 resets and starts the built-in timer (S205), and the descent determination unit 22 executes the process shown in step S200 again.

If the received packet is not an error packet (S203: No), falling determination unit 22, the variable n is equal to or it has reached the predetermined value n ₀ (S206). When the variable n has not reached the predetermined value n ₀ (S206: No), the descent determination unit 22 executes the process shown in step S201 again. On the other hand, when the variable n reaches the predetermined value n ₀ (S206: Yes), the decrease determination unit 22 notifies the increase determination unit 23 to that effect.

  Next, the rise determination unit 23 refers to the allowable rate information storage unit 24 based on the RSSI provided from the radio unit 27, and extracts the allowable rate associated with the range including the current RSSI value. (S207). Then, the increase determination unit 23 determines whether or not the extracted allowable rate is higher than the current data rate provided from the decoder 25 (S208). When the extracted allowable rate is equal to or lower than the current data rate provided from the decoder 25 (S208: No), the descent determination unit 22 executes the process shown in step S200 again.

On the other hand, when the extracted allowable rate is higher than the current data rate provided from the decoder 25 (S208: Yes), the increase determination unit 23 sends the increase signal instructing the increase of the data rate to the rate control signal transmission unit. 26 (S209). The rate control signal transmission unit 26 refers to the value of the built-in timer and determines whether or not the value of the built-in timer is T ₀ (S210). When the value of the built-in timer is not T ₀ (S210: No), the descent determination unit 22 executes the process shown in step S200 again.

On the other hand, when the value of the built-in timer is T ₀ (S210: Yes), the rate control signal transmitter 26 sends an increase signal to the encoder 29 if the data rate can be increased. The encoder 29 performs processing such as adding or correcting an error correction code to the rising signal received from the rate control signal transmission unit 26, and sends the data subjected to these processing to the radio unit 27. The wireless unit 27 outputs the radio wave modulated based on the data received from the encoder 29 via the antenna (S211), and the descending determination unit 22 executes the process shown in step S200 again.

  In the present embodiment, when the error packet is received, the descent determination unit 22 immediately outputs a descent signal. Therefore, as shown in FIG. 10, the period during which PER is larger than the threshold may be shortened. it can. In addition, even when the PER deteriorates in a short time, the data rate can be lowered more quickly.

  The second embodiment of the present invention has been described above.

  In addition, this invention is not limited to above-described embodiment, Many deformation | transformation are possible within the range of the summary.

  For example, in each of the embodiments described above, PER is used as an index indicating an error rate. However, the present invention is not limited to this, and BER (Bit Error Rate), FER (Frame Error Rate), or the like is used as an index indicating an error rate. It may be used. In each of the above embodiments, RSSI is used as an index indicating the quality of the received signal. However, the present invention is not limited to this, and SNR or the like may be used as an index indicating the quality of the received signal.

  In the above-described embodiment, the increase / decrease of the data rate is determined on the reception side. However, the value of PER or RSSI measured on the reception side is fed back to the wireless communication device 20 on the transmission side, and the wireless on the transmission side is determined. The communication device 20 may determine whether the data rate has increased or decreased.

DESCRIPTION OF SYMBOLS 10 ... Communication system, 11 ... Apparatus, 12 ... Communication line, 20 ... Wireless communication apparatus, 21 ... PER calculation part, 22 ... Decrease determination part, 23 ... Ascent determination , 24 ... allowable rate information storage unit, 240 ... range, 241 ... allowable rate, 25 ... decoder, 26 ... rate control signal transmitter, 27 ... radio unit, 28. ..Data rate control unit, 29 ... encoder, 30 ... characteristic, 31 ... characteristic

Claims (3)

A wireless communication device used in a wireless communication system for controlling a data rate in order to keep the quality of a received signal at a certain level or more,
In association with information indicating the received signal strength, an allowable rate information storage unit that stores an allowable rate indicating a data rate that is allowed for an error rate of data received at the strength to be less than a predetermined threshold;
An error rate calculation unit for calculating an error rate of data included in a signal received from another wireless communication device on the transmission side as a communication partner;
A lowering determination unit that outputs a lowering signal indicating an instruction to lower the data rate when the error rate is greater than the threshold;
When the error rate is equal to or lower than the threshold, an allowable rate associated with the current received signal strength is extracted from the allowable rate information storage unit, and the extracted allowable rate is higher than the current data rate. A rising determination unit that outputs a rising signal indicating an instruction to increase the current data rate;
When a down signal is output from the down determination unit, if communication at a data rate lower than the current data rate is supported in the communication system, the down signal is transmitted to the other wireless communication device on the transmission side. When the rising signal is transmitted from the rising determination unit and the communication system supports communication at a data rate higher than the current data rate, the rising signal is transmitted to the other radio on the transmitting side. A rate control signal transmitter for transmitting to the communication device;
A transmission unit that transmits data to another wireless communication device on the receiving side that is a communication partner at an instructed data rate;
When a down signal is received from another wireless communication device on the receiving side, the transmitter is instructed to send a data rate lower than the current data rate, and an up signal is received from the other wireless communication device on the receiving side In this case, the wireless communication apparatus includes: a data rate control unit that instructs the transmission unit to use a data rate higher than a current data rate. The wireless communication device according to claim 1,
The rate control signal transmitter is
When a descending signal is output from the descending determination unit, the rising signal is output even if an ascending signal is output from the ascent determining unit until a predetermined period elapses after the descending signal is output. The wireless communication device is discarded without transmitting to the other wireless communication device on the transmission side. A data rate control method for a radio communication device used in a radio communication system for controlling a data rate in order to keep the quality of a received signal at a certain level or more,
The wireless communication device
Corresponding to information indicating the received signal strength, an allowable rate information storage unit for storing an allowable rate indicating a data rate allowed for an error rate of data received at the strength to be less than a predetermined threshold is provided. ,
An error rate calculation step for calculating an error rate of data included in a signal received from another wireless communication device on the transmission side as a communication partner;
A descent determination step of outputting a descent signal indicating an instruction to lower the data rate when the error rate is greater than the threshold;
When the error rate is equal to or lower than the threshold, an allowable rate associated with the current received signal strength is extracted from the allowable rate information storage unit, and the extracted allowable rate is higher than the current data rate. A rising determination step for outputting a rising signal indicating an instruction to increase the current data rate;
When the down signal is output in the down determination, if the communication system supports communication at a data rate lower than the current data rate, the down signal is transmitted to the other wireless communication device on the transmission side. When the rising signal is output in the rising determination step, if communication at a data rate higher than the current data rate is supported in the communication system, the rising signal is transmitted to the other wireless communication device on the transmission side. A rate control signal transmission step for transmitting;
When a down signal is received from another wireless communication device on the receiving side that is the communication partner, data is transmitted at a data rate lower than the current data rate, and an up signal is received from the other wireless communication device on the receiving side. And a transmission step of transmitting data at a data rate higher than the current data rate.

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