JP6372740B2 - Wireless communication device, transmission rate control method, and transmission rate control program - Google Patents

Description

  The present invention relates to a transmission rate control technique used for transmitting a signal from a transmission-side wireless communication device to a reception-side wireless communication device.

  For example, a radio frequency band of 2.4 GHz band may be used in wireless communication typified by IEEE (Institut of Electrical and Electronics Engineers) 802.11 standard or IEEE 802.15.4 standard. The radio frequency band of 2.4 GHz band is also called an ISM (Industry-Science-Medical) band.

The 2.4 GHz band is used not only for devices that perform wireless communication but also for devices such as a microwave oven. Radiation noise of a device such as a microwave oven becomes an interference wave for a transmission-side wireless communication device and a reception-side wireless communication device that perform wireless communication using the 2.4 GHz band, and causes a reception error.
In an environment where the influence of interference waves is large, it is possible to suppress reception errors by using a low transmission rate (sometimes described as “data transmission rate”). On the other hand, since a low transmission rate has a low transmission throughput, a limited frequency resource cannot be effectively used if a low transmission rate is always used.

Based on this fact, there is a transmission rate control technique that adaptively selects a transmission rate used for wireless communication from a plurality of transmission rates according to a transmission path state that changes due to changes in the surrounding environment.
For example, in the IEEE802.11b standard, four transmission rates of 1 Mbps, 2 Mbps, 5.5 Mbps, and 11 Mbps are defined depending on the modulation scheme. In the IEEE802.11g standard, eight transmission rates of 54 Mbps, 48 Mbps, 36 Mbps, 24 Mbps, 18 Mbps, 12 Mbps, 9 Mbps, and 6 Mbps are defined depending on the difference in modulation scheme and coding rate.

Note that a transmission rate determined by a physical layer (Physical Layer) modulation method and / or coding rate may be described as a “PHY rate”. The transmission rate is also called MCS (Modulation and Coding Scheme) in the IEEE 802.11 standard.
An example of a transmission rate control technique is disclosed in Patent Document 1. In Patent Document 1, a wireless communication device on the transmission side transmits a plurality of test packets at a plurality of transmission rates. The receiving-side wireless communication device that has received the test packet measures the PER (Packet Error Rate) at each of a plurality of transmission rates. Then, the reception-side wireless communication device assigns priorities to at least some transmission rates based on the measured PER, creates a priority table, and transmits the priority table to the transmission-side wireless communication device.

  The wireless communication device on the transmission side switches the transmission rate used for transmitting the signal to the wireless communication device on the reception side based on the received priority order table.

JP 2005-39722 A

However, in the transmission rate control technique disclosed in Patent Document 1, it is necessary to transmit a test packet at each of a plurality of prepared transmission rates. For this reason, the load of transmission and reception of the test packet increases for each of the wireless communication devices on the transmission side and the reception side.
The present invention has been made in view of the above-described problem, and a transmission-side wireless communication device selects a transmission rate used for transmitting a signal from a plurality of transmission rates to a reception-side wireless communication device. It is an object of the present invention to provide a wireless communication device that can reduce the communication load on the transmission side and the reception side.

In order to achieve the above object, a wireless communication device of the present invention is a wireless communication device on the transmission side that performs wireless communication with a reception device that is a wireless communication device on the reception side, and various signals transmitted from the reception device. , A first detector for detecting the signal strength of the desired signal wave received when the receiver receives the desired signal wave, an interference wave emitted from an external device, and the power of the interference wave A second detection unit that detects the interference wave power, a transmission unit that transmits a test signal to the reception device when the second detection unit detects an interference wave, and the reception unit is the reception device. An analysis unit that performs error detection of the response signal when a response signal to the test signal is received from, a detected value of the signal strength of the desired signal wave, a detected value of the interference wave power of the interference wave, and the test Number of transmissions related to signals and errors Not on the basis the the reception number of the response signal, to, e Bei a transmission rate control unit for selecting a transmission rate used to transmit the signal to the receiving device from among a plurality of transmission rates, and the transmission rate control The unit is configured to perform forward communication, which is communication from the transmitting-side wireless communication device to the receiving device, from the number of transmissions related to the test signal and the number of receptions related to the response signal without error, and from the receiving device to the transmitting side. An error rate calculation unit that calculates a reception error rate of round-trip communication combined with return path communication that is communication to the wireless communication device, a detection value of the signal strength of the desired signal wave, a detection value of the interference wave power, An interference wave power estimator for estimating the interference wave power in the receiving device, a detection value of the signal strength of the desired signal wave, and the interference wave power And an estimate of Therefore, a transmission rate selection unit that selects a transmission rate to be used, and when the estimated value of the interference wave power in the reception device is received from another wireless communication device, the transmission unit, Without transmitting the test signal to the receiving device, the transmission rate control unit selects the transmission rate using the estimated value of the interference wave power received from the other wireless communication device.

  According to the above-described wireless communication device, it is possible to reduce a communication load that occurs when the transmission-side wireless communication device selects a transmission rate for transmitting a signal from the plurality of transmission rates to the reception-side wireless communication device.

1 is a system configuration diagram of a wireless communication system 1 according to a first embodiment. The block diagram which shows the structure of the radio station 3 of FIG. The block diagram which shows the structure of the transmission rate control part 39 of FIG. The figure which shows the example of the content of the propagation characteristic table 110 of FIG. The block diagram which shows the structure of the wireless access point 5 of FIG. FIG. 2 is a sequence diagram illustrating an example of an operation of the wireless communication system 1 in FIG. 1. The flowchart which shows the process at the time of the radio station 3 detecting the received signal strength of a desired signal wave. 6 is a flowchart showing transmission rate control processing by the wireless station 3; 6 is a flowchart showing test signal transmission / reception processing by the wireless station 3; 6 is a flowchart showing test signal transmission / reception processing by the wireless access point 5; 9 is a flowchart showing a transmission rate control process by the wireless station 3 in Modification 1. 9 is a flowchart showing interference wave power reception processing by the wireless station 3 in Modification 2. 9 is a flowchart showing a transmission rate control process by the wireless station 3 in Modification 2. The flowchart which shows the estimated value notification process of the interference wave electric power of FIG. The block diagram which shows the structure of 39 A of transmission rate control parts which concern on 2nd Embodiment. The figure which shows the example of the content of the propagation characteristic table 115 of FIG. The flowchart which shows the transmission rate control process by the radio station containing the transmission rate control part 39A of FIG. The figure which shows an example of the radiation noise radiated | emitted from the interference apparatus of FIG.

<Examination by inventors>
In the transmission rate control technique disclosed in Patent Document 1, the transmission-side wireless communication device adaptively controls the transmission rate used for signal transmission from the plurality of transmission rates to the reception-side wireless communication device. In addition, it is necessary to transmit a test packet at each of a plurality of prepared transmission rates. For this reason, there is a problem that the load of transmission and reception of the test packet is large for each of the wireless communication devices on the transmission side and the reception side.

Therefore, the inventors have transmission rate control that allows the transmission-side wireless communication device to adaptively control the transmission rate by transmitting test packets at a part of a plurality of prepared transmission rates. The technology was examined.
Further, for example, in a home network, it is expected that various wireless communication devices such as old and new wireless communication devices and wireless communication devices from different manufacturers are mixed. In constructing such a home network, it is a restriction to install a function for adaptively controlling the transmission rate in both the transmitting side and receiving side wireless communication devices. Therefore, the inventors have a transmission capable of adaptively controlling the transmission rate only with the function of the transmitting-side wireless communication device without adding a new function to the receiving-side wireless communication device as much as possible. The rate control technology was studied.

As a result of these studies, the inventors can provide a plurality of prepared transmissions if the reception-side wireless communication device has a function of returning a test response signal to the test transmission signal from the transmission-side wireless communication device. By transmitting a test signal at one of the rates, a transmission rate control technology mechanism that can adaptively control the transmission rate in the wireless communication device on the transmission side has been obtained.
Furthermore, as a result of repeated studies, a wireless communication device on the receiving side can be used for testing by using an existing ICMP (Internet Control Message Protocol) ping, an IEEE 802.11 standard probe, or the like. In addition, they have found that it is not necessary to add a new function for controlling the transmission rate.

Hereinafter, a radio communication system including a radio communication device on the transmission side based on the result of the above examination will be described.
However, for example, communication from the wireless station (wireless STA) 3 to the wireless access point (wireless AP) 5 in FIG. 1 is “outward communication”, communication from the wireless AP 5 to the wireless STA 3 is “return communication”, and wireless STA 3 to wireless AP 5 The communication that combines the communication from the wireless AP 5 and the communication of the wireless STA 3 with the returned wireless AP 5 is referred to as “round-trip communication”.

<< Embodiment 1 >>
Embodiment 1 of the present invention will be described below with reference to the drawings.
FIG. 1 is a system configuration diagram of a radio communication system according to the first embodiment.
The wireless communication system 1 includes a wireless station (wireless STA) 3 that is a terminal and a wireless access point (wireless AP) 5 that is a base station. The wireless communication system 1 may include one or a plurality of wireless STAs other than the wireless STA 3, and may include one or a plurality of wireless APs other than the wireless AP 5.

In the first embodiment and the like, the wireless STA 3 and the wireless AP 5 correspond to the “transmission-side wireless communication device” and the “reception device that is the reception-side wireless communication device”, respectively, in the claims.
The interference device 7 in FIG. 1 is an external device that is a source of interference waves.
However, in the first embodiment, it is assumed that the interference device 7 is a device that generates periodic radiation noise, for example, as shown in FIG. 18, and is a home appliance such as a microwave oven. Even if the interference device 7 is a device that generates radiation noise having no periodicity, the transmission rate control technique described in the first embodiment can be used.

First, the configuration of the wireless STA 3 in FIG. 1 will be described with reference to the drawings.
FIG. 2 is a block diagram showing the configuration of the wireless STA 3 in FIG. In FIG. 2 and FIGS. 3, 5, and 15 to be described later, data lines are indicated by solid arrows, and control lines are indicated by dotted arrows.
The wireless STA 3 includes an antenna 31, a reception unit 32, a reception frame analysis unit 33, an upper layer processing unit 34, a transmission frame generation unit 35, a transmission unit 36, an RSSI detection unit 37, an interference wave detection unit 38, and a transmission rate control unit 39. Is provided.

  The receiving unit 32 mainly performs processing in a physical layer (Physical Layer) on radio waves received via the antenna 31. Examples of processing in the physical layer include signal wave detection processing, automatic gain control (Auto Gain Control: AGC), automatic frequency control (Auto Frequency Control: AFC), channel estimation, channel equalization, demodulation, and decoding.

However, the physical layer signal includes, for example, a PLC (Physical Layer Convergence Protocol) preamble, a PLCP header, and a PSDU (PLCP Service Data Unit) in the IEEE 802.11 standard.
For example, in the IEEE802.11 standard, the reception unit 32 outputs the transmission rate information included in the PLCP header to the transmission rate control unit 39.

The reception frame analysis unit 33 mainly performs processing in the MAC layer (Media Access control Layer) such as error inspection of the received MAC frame (hereinafter referred to as “reception frame”) and analysis of the contents of the MAC header.
For example, the received frame analysis unit 33 notifies the RSSI detection unit 37 when the received frame is a MAC frame without a frame error addressed to itself as a result of the error check of the received frame and the analysis of the MAC header. . (It is assumed that the received frame is transmitted from the antenna 51 of the wireless AP 5)
However, for example, in the IEEE 802.11 standard, there are a data frame including a MAC header, a frame body, and an FCS (Frame Check Sequence) for frame error inspection, a control frame including a MAC header, and an FCS. .

  For example, a type value and a subtype value are stored in the MAC header. The type value is a value indicating whether it is a data frame, a management frame, or a control frame. The subtype value is a value (for example, a Probe Request (probe request) frame or a Probe Response (specified in the management frame) specified in the management frame, which is one of a plurality of types of frames specified in the frame indicated by the type value. Probe response) value assigned to the frame).

  The MAC header stores “To DS (Distributed System)” and “From DS (Distributed System)”. In the case of the management frame and the control frame, “0” is set in both “To DS” and “From DS”. In the case of a data frame, “1” is set to “To DS” when the receiving station is a base station, “0” is set to be a terminal, and “From DS” is set to “0” when the transmitting station is a base station. When “1” is a terminal, “0” is set.

In the MAC header, a maximum of four address fields (Address 1) to (Address 4) are prepared. Address 1 stores the MAC address of the receiving station, Address 2 stores the MAC address of the transmitting station, Address 3 stores the source address or destination address, and Address 4 stores the source address.
For example, when the wireless STA 3 transmits a data frame to another wireless STA via the wireless AP 5 or the wireless AP 5 and another wireless AP, the receiving station is the wireless AP 5 and the transmitting station in the data frame transmitted from the wireless STA 3 to the wireless AP 5. Is a wireless STA3. When another wireless STA transmits a data frame to the wireless STA 3 via the wireless AP 5 or another wireless AP and the wireless AP 5, the receiving station is the wireless STA 3 or the transmitting station in the data frame transmitted from the wireless AP 5 to the wireless STA 3. Is a wireless AP5.

The upper layer processing unit 34 mainly executes protocol processing of an upper layer (such as an IP layer (Internet Protocol Layer)) than the MAC layer.
For example, the upper layer processing unit 34 generates a test transmission packet and outputs it to the transmission frame generation unit 35 when receiving a notification that the start of the generation of the interference wave is detected from the interference wave detection unit 38. Then, a test response packet is received from the received frame analysis unit 33 as a response to the test transmission packet, and an error check of the packet header is performed. Then, the transmission packet control unit 39 outputs the transmission packet number T1 of the test transmission packet and the reception packet number T2 of the test response packet having no packet error to the transmission rate control unit 39.

However, the packet includes a packet header and a payload. The packet header stores a source address and a destination address, and includes a header checksum for checking the packet header error.
The transmission frame generation unit 35 mainly performs processing in the MAC layer such as generation of a MAC frame (hereinafter referred to as “transmission frame”).

The transmission unit 36 mainly executes processing in the physical layer and transmits a signal wave via the antenna 31. For example, as processing in the physical layer, processing such as encoding and modulation for a transmission frame using the transmission rate set by the transmission rate control unit 39, and generation of a signal in the physical layer are performed.
The RSSI detection unit 37 performs detection processing of the received signal strength (RSSI) of the signal wave. When the RSSI detection unit 37 receives a notification from the reception frame analysis unit 33 that the received frame is a MAC frame without a frame error addressed to the own station, the RSSI detection unit 37 uses the RSSI detection value of the signal wave related to the received frame as a desired signal. It is held as the detected value of the RSSI of the wave.

  The interference wave detector 38 detects the interference wave emitted from the interference device 7 and the interference wave power of the interference wave. When the interference wave detection unit 38 detects the generation of the interference wave, the interference wave detection unit 38 outputs a notification to the effect that the generation of the interference wave is detected to the upper layer processing unit 34 and sends the detected value of the interference wave power to the transmission rate control unit 39. Output. Further, when detecting the end of the generation of the interference wave, the interference wave detection unit 38 notifies the transmission rate control unit 39 that the end of the generation of the interference wave is detected.

For example, when the radiation noise radiated from the interference device 7 such as a microwave oven has the periodicity shown in FIG. 18 as an example, the interference wave detection unit 38 detects the interference wave and detects the interference wave as follows. Interference wave power is detected.
The interference wave detection unit 38 detects an interference wave based on whether or not periodic noise is received.

Further, the interference wave detection unit 38 detects the maximum value as the interference wave power. Instead of detecting the maximum value of the interference wave power, for example, an average value of one cycle of the interference wave power may be detected as the interference wave power, or a period during which radiation noise is generated in one cycle. The average value of the interference wave power may be detected as the interference wave power.
When an interference wave is detected, the transmission rate control unit 39 receives the RSSI detection value of the desired signal wave from the RSSI detection unit 37 and the interference wave power detection value from the interference wave detection unit 38. Further, the upper layer processing unit 34 receives the transmission packet number T1 of the test transmission packet and the reception packet number T2 of the test response packet having no packet error. Then, the transmission rate control unit 39 wirelessly transmits from the wireless STA 3 among a plurality of transmission rates based on the detected value of RSSI of the desired signal wave, the detected value of interference wave power, the number of transmitted packets T1, and the number of received packets T2. The transmission rate used for transmission of the signal to AP 5 is selected, and the selected transmission rate is set in the transmission unit 36.

  Further, when the end of the generation of the interference wave is detected, the transmission rate control unit 39 receives the RSSI detection value of the desired signal wave from the RSSI detection unit 37 and sets the interference wave power of the interference wave in the wireless AP 5 to “0”. "(No interference wave). The transmission rate control unit 39 then transmits a signal from the wireless STA 3 to the wireless AP 5 out of a plurality of transmission rates based on the RSSI detection value of the desired signal wave and the interference wave power “0” of the interference wave in the wireless AP 5. A transmission rate to be used for transmission is selected, and the selected transmission rate is set in the transmission unit 36.

Hereinafter, the transmission rate control unit 39 of FIG. 2 will be further described with reference to FIGS.
FIG. 3 is a block diagram showing a configuration example of the transmission rate control unit 39 in FIG.
The transmission rate control unit 39 includes a propagation characteristic table 110, a PERrt calculation unit 120, a PERdwn calculation unit 130, a PERup calculation unit 140, an interference wave power estimation unit 150, a PER estimation unit 160, and a transmission rate selection unit 170.

However, when the start of the generation of the interference wave is detected, the propagation characteristic table 110, the PERrt measurement unit 120, the PERdwn estimation unit 130, the PERup estimation unit 140, the interference wave power estimation unit 150, the PER estimation unit 160, and the transmission rate selection The transmission rate is selected and set in the transmission unit 36 by the function of the unit 170.
When the end of the generation of the interference wave is detected, the transmission rate is selected and set in the transmission unit 36 by the functions of the propagation characteristic table 110, the PER estimation unit 160, and the transmission rate selection unit 170.

The propagation characteristic table 110 is a table for storing propagation characteristics indicating the relationship between RSSI of desired signal wave, interference wave power, and PER for each of a plurality of transmission rates, and is held in the storage unit. Note that the propagation characteristic table is created in advance, for example.
Examples of the contents of the propagation characteristic table are shown in FIGS. 4A and 4B for transmission rates of 1 Mbps and 11 Mbps, respectively. 4A and 4B, the horizontal axis is RSSI (dBm), and the vertical axis is PER.

For example, in the case of the wireless communication of the IEEE802.11b standard, four transmission rates of 1 Mbps, 2 Mbps, 5.5 Mbps, and 11 Mbps are defined as transmission rates in the IEEE802.11b standard. The propagation characteristics for each of the two transmission rates will be stored.
The PERrt calculation unit 120 receives, from the upper layer processing unit 34, the number of transmission packets T1 of test transmission packets and the number of reception packets T2 of test response packets without packet errors. The PERrt calculation unit 120 calculates PERrt, which is a PER for round-trip communication between the wireless STA 3 and the wireless AP 5, from the transmission packet number T1 and the reception packet number T2, and outputs the calculated value of PERrt to the PERup calculation unit 140. . PERrt is calculated by calculating (T1-T2) / T1.

  The PERdwn calculation unit 130 receives the RSSI detection value of the desired signal wave from the RSSI detection unit 37 and the detection value of the interference wave power from the interference wave detection unit 38. The PERdwn calculation unit 130 refers to the propagation characteristics at the transmission rate used for transmission of the desired signal wave, which are stored in the propagation characteristic table 110, and the detected value of the RSSI of the desired signal wave and the detected value of the interference wave power Then, PERdwn, which is the PER of the return communication, is calculated, and the calculated value of PERdwn is output to the PERup estimation unit 140. Note that the transmission rate used for transmitting the desired signal wave is stored in the PLCP header in the IEEE 802.11 standard, and is received from the receiving unit 32.

  The PERup calculation unit 140 receives the calculated value of PERrt from the PERrt calculation unit 120 and the calculated value of PERdwn from the PERdwn calculation unit 130. The PERup calculation unit 140 calculates PERup, which is a PER for forward communication, from the calculated value of PERrt and the calculated value of PERdwn, and outputs the calculated value of PERup to the interference wave power estimation unit 150. For example, PERup is calculated by calculating (PERdwn-PERrt) / (PERdwn-1).

  The interference wave power estimation unit 150 receives the RSSI detection value of the desired signal wave from the RSSI detection unit 37 and the PERup calculation value from the PERup calculation unit 140. Furthermore, the transmission rate (transmission rate set by the transmission rate selection unit 170 in the transmission unit 36 and used for transmitting the test transmission signal) is received from the transmission rate selection unit 170. The interference wave power estimation unit 150 refers to the propagation characteristic at the transmission rate used for transmitting the test transmission signal in the propagation characteristic table 110, and determines the radio wave from the detected RSSI value of the desired signal wave and the calculated PERup value. The interference wave power of the interference wave at AP 5 is estimated, and the estimated value of the interference wave power is output to PER estimation section 160.

  However, the interference wave power estimation unit 150 is such that the RSSI value in the wireless STA 3 of the signal wave transmitted from the antenna 51 by the wireless AP 5 is equal to the RSSI value in the wireless AP 5 of the signal wave transmitted from the antenna 31 by the wireless STA 3. Works as. However, if the RSSI value in the wireless STA 3 and the RSSI value in the wireless AP 5 are not equal and it is previously known that there is a difference between the constant values, the detected value of the RSSI of the desired signal wave is corrected for the difference and corrected. It is also possible to set the later value as the RSSI value of the desired signal wave in the wireless AP 5. For example, the difference in RSSI value due to the difference between the gain value of the antenna 51 of the wireless AP 5 and the gain value of the antenna 31 of the wireless STA 3 or the difference between the transmission power value of the wireless AP 5 and the transmission power value of the wireless STA 3. May always occur several dBm.

The PER estimation unit 160 performs the following operation at the start of generation of interference waves.
The PER estimation unit 160 receives a notification indicating that an interference wave has been detected from the interference wave detection unit 38. Further, the RSSI detection value of the desired signal wave is received from the RSSI detection unit 37, and the interference wave power estimation value in the wireless AP 5 is received from the interference wave power estimation unit 150. Then, the PER estimation unit 160 refers to the propagation characteristics at each transmission rate in the propagation characteristics table 110, and determines the transmission rate from the detected value of the RSSI of the desired signal wave and the estimated value of the interference wave power in the wireless AP 5 by radio. The PER is estimated when it is used to transmit a signal from the STA 3 to the wireless AP 5. Then, the estimated PER of each transmission rate is output to transmission rate selection section 170 in association with the transmission rate.

The PER estimation unit 160 associates the PER value estimated by the PERup estimation unit 140 with the transmission rate for the transmission rate used for transmitting the test transmission signal, without performing the PER estimation process. You may make it output to the transmission rate selection part 170. FIG.
The PER estimation unit 160 performs the following operation at the end of generation of the interference wave.
The PER estimation unit 160 receives a notification of detection of the end of generation of interference waves from the interference wave detection unit 38. Further, the RSSI detection value of the desired signal wave is received from the RSSI detector 37, and the interference wave power of the interference wave in the wireless AP 5 is regarded as “0” (no interference wave). Then, the PER estimation unit 160 refers to the propagation characteristics at each transmission rate in the propagation characteristic table 110, detects the RSSI value of the desired signal wave, and the interference wave power “0” of the interference wave in the wireless AP 5 (no interference wave). Thus, the PER is estimated when the transmission rate is used for signal transmission from the wireless STA 3 to the wireless AP 5. Then, the estimated PER of each transmission rate is output to transmission rate selection section 170 in association with the transmission rate.

  However, the PER estimation unit 160, like the interference wave power estimation unit 150, has the RSSI value in the wireless STA3 of the signal wave transmitted from the antenna 51 by the wireless AP 5 and the wireless AP 5 of the signal wave transmitted from the antenna 31 by the wireless STA3. It is assumed that the RSSI value is equal. However, if the RSSI value in the wireless STA 3 and the RSSI value in the wireless AP 5 are not equal and it is previously known that there is a difference between the constant values, the detected value of the RSSI of the desired signal wave is corrected for the difference and corrected. It is also possible to set the later value as the RSSI value of the desired signal wave in the wireless AP 5. For example, the difference in RSSI value due to the difference between the gain value of the antenna 51 of the wireless AP 5 and the gain value of the antenna 31 of the wireless STA 3 or the difference between the transmission power value of the wireless AP 5 and the transmission power value of the wireless STA 3. May always occur several dBm.

The transmission rate selection unit 170 selects a transmission rate having the smallest estimated PER value from a plurality of transmission rates as a transmission rate used for transmission of a signal from the wireless STA 3 to the wireless AP 5, and transmits the selected transmission rate to the transmission unit. Set to 36.
Next, the configuration of the wireless AP 5 in FIG. 1 will be described with reference to the drawings.
FIG. 5 is a block diagram showing a configuration of the wireless AP 5 of FIG.

The wireless AP 5 includes an antenna 51, a reception unit 52, a reception frame analysis unit 53, an upper layer processing unit 54, a transmission frame generation unit 55, and a transmission unit 56.
The receiving unit 52 mainly executes processing in the physical layer for radio waves received via the antenna 31.
The received frame analysis unit 53 mainly performs processing in the MAC layer, such as error checking of received frames and analysis of the contents of the MAC header.

The upper layer processing unit 54 mainly executes protocol processing of an upper layer (such as an IP layer) than the MAC layer.
For example, the upper layer processing unit 54 receives a test transmission packet from the received frame analysis unit 53 and performs an error check on the packet header. If there is no packet error, the upper layer processing unit 54 generates a test response packet and outputs the test response packet to the transmission frame generation unit 55.

The transmission frame generation unit 55 mainly performs processing in the MAC layer such as generation of a transmission frame.
The transmission unit 56 mainly performs processing in the physical layer and transmits a signal wave via the antenna 51.
Next, an example of the operation of the wireless communication system in FIG. 1 will be described with reference to the drawings.

FIG. 6 is a sequence diagram showing an example of the operation of the wireless communication system of FIG.
The wireless STA 3 uses the transmission rate #A (initially set transmission rate or the transmission rate previously selected by the wireless STA 3 itself) to transmit data signals to other wireless STAs via the wireless AP 5 and other wireless APs. Send. Then, the wireless STA 3 receives an ACK (Acknowledgement) signal for the data signal from the other wireless STA via the other wireless AP and the wireless AP 5 (step S11).

The RSSI detector 37 of the wireless STA 3 detects the RSSI of the signal wave related to the ACK signal relayed by the wireless AP 5 as the RSSI of the desired signal wave from the wireless AP 5 (step S12).
Note that the signal wave from the wireless AP 5 to the wireless STA 3 may be a signal wave transmitted from the antenna 51 to the own station, and other than the signal wave related to the ACK signal relayed by the wireless AP 5, for example, wireless There are signal waves related to data signals relayed by AP5, signal waves related to beacon signals periodically transmitted by wireless AP5, and the like.

The operation switch of the interference device 7 is turned on (step S13), and radiation noise is emitted from the interference device 7.
This radiation noise becomes an interference wave for the wireless STA 3, and the interference wave detection unit 38 of the wireless STA 3 detects the start of the generation of the interference wave and the interference wave power of the interference wave (step S 14). Note that radiation noise emitted from the interference device 7 also appears as an interference wave in the wireless AP 5.

  The wireless STA 3 transmits a test transmission signal to the wireless AP 5, and the wireless AP 5 transmits a test response signal as a response. The wireless STA 3 receives the test response signal from the wireless AP 5. Then, the upper layer processing unit 34 of the wireless STA 3 determines the transmission packet number T1 of the test transmission packet related to the test transmission signal and the reception packet number T2 of the test response packet related to the test response signal without a packet error. It outputs to the PERrt calculation part 120 (step S15). The PERrt calculation unit 120 of the wireless STA 3 calculates the PERrt for round-trip communication using the transmission packet number T1 and the reception packet number T2 (step S16).

The relationship between the test transmission signal and the test response signal may be such that the wireless AP 5 that has received the test transmission signal returns and returns the test response signal to the wireless STA 3.
The PER dwn calculation unit 130 of the wireless STA 3 calculates PER dwn of the return communication that is communication from the wireless AP 5 to the wireless STA 3 (step S17), and the PERup calculation unit 140 calculates PER up of the forward communication that is communication from the wireless STA 3 to the wireless AP 5. Calculate (step S18). Subsequently, the interference wave power estimation unit 150 of the wireless STA 3 estimates the interference wave power of the interference wave in the wireless AP 5 (step S19).

  The PER estimation unit 160 of the wireless STA 3 estimates PER for each of the plurality of transmission rates when the transmission rate is used for signal transmission from the wireless STA 3 to the wireless AP 5 (step S20). Then, the transmission rate selection unit 170 of the wireless STA 3 selects the transmission rate #B having the smallest estimated PER value from the plurality of transmission rates as the transmission rate used for signal transmission from the wireless STA 3 to the wireless AP 5. It sets to the transmission part 38 (step S21).

The wireless STA 3 transmits a data signal to another wireless STA via the wireless AP 5 and another wireless AP using the transmission rate #B. Then, the wireless STA 3 receives an ACK signal for the data signal from the other wireless STA via the other wireless AP and the wireless AP 5 (step S22).
The operation switch of the interference device 7 is turned off (step S23), and no radiation noise is emitted from the interference device 7.

The wireless STA 3 detects the end of the generation of the interference wave (step S24).
The PER estimation unit 160 of the wireless STA 3 regards the interference wave power of the interference wave in the wireless AP 5 as 0 (no interference wave), and transmits the transmission rate from the wireless STA 3 to the wireless AP 5 for each of a plurality of transmission rates. The PER in the case of being used for is estimated (step S25). Then, the transmission rate selection unit 170 of the wireless STA 3 selects the transmission rate #C having the smallest estimated PER value from the plurality of transmission rates as the transmission rate used for signal transmission from the wireless STA 3 to the wireless AP 5. The transmission unit 38 is set (step S26).

The wireless STA 3 transmits a data signal to another wireless STA via the wireless AP 5 and another wireless AP using the transmission rate #C. Then, the wireless STA 3 receives an ACK signal for the data signal from the other wireless STA via the other wireless AP and the wireless AP 5 (step S27).
The RSSI detector 37 of the wireless STA 3 detects the RSSI of the signal wave related to the ACK signal relayed by the wireless AP 5 (the signal wave transmitted from the antenna 51 by the wireless AP 5) as the RSSI of the desired signal wave from the wireless AP 5 (step S28). ).

Next, operations related to transmission rate control of the wireless STA 3 in FIGS. 2 to 4 will be described with reference to the drawings.
FIG. 7 is a flowchart of processing in which the wireless STA 3 detects the received signal strength of the desired signal wave.
However, in the flowchart of FIG. 7, when the interference wave is generated and the RSSI detection value of the desired signal wave is already stored, the content of the RSSI detection value is not updated. Even in such a case, the detected value of RSSI may be updated.

The RSSI detector 37 turns off the RSSI detected flag (step S101). However, when the RSSI detected flag is on, it indicates that the RSSI detection value of the desired signal wave from the wireless AP 5 is held, and when it is off, the RSSI detection value of the desired signal wave from the wireless AP 5 is held. Indicates not.
The receiving unit 32 performs detection processing of a signal wave transmitted by any of the wireless communication devices including the wireless AP 5, and the RSSI detection unit 37 performs detection processing of the RSSI of the signal wave (Step S102). Until the signal wave is detected in the signal wave detection process in step S102 (S103: No), the reception unit 32 continues the signal wave detection process in step S102, and the RSSI detection unit 37 performs the signal wave detection in step S102. The RSSI detection process is continuously performed. When a signal wave is detected (S103: Yes), the receiving unit 32 performs predetermined processing such as demodulation and decoding on the detected signal wave. Then, the received frame analysis unit 33 analyzes the error of the received frame and the contents of the MAC header, and determines whether or not the received frame is a frame error MAC frame with the wireless AP 5 as a transmitting station, that is, the detected signal wave is It is determined whether or not the desired signal wave is transmitted from the antenna 51 to the own station by the wireless AP 5 (step S104).

For example, when the received frame is a data frame, it can be determined whether or not the received frame is a MAC frame addressed to the own station using the wireless AP 5 as a transmitting station based on Address 1, Address 2, and the like.
For example, when the received frame is an ACK frame, there is only Address 1 for storing the MAC address of the receiving station as an address field in the ACK frame. However, the transmitting station of the ACK frame addressed to itself is a receiving station that stores the MAC address in Address 1 of the data frame. From this, it can be determined whether or not the ACK frame is a MAC frame destined for the own station having the wireless AP 5 as a transmitting station.

  If it is determined that the signal is not the desired signal wave (S104: No), the process returns to step S102. On the other hand, when it is determined that the signal is a desired signal wave (S104: Yes), the RSSI detector 37 determines whether or not the interference wave generation flag is on (step S105). However, when the interference wave generation flag is on, it indicates that an interference wave is being generated, and when it is off, it indicates that no interference wave is being generated. The interference wave generation flag is turned on / off in the transmission rate control process of FIG.

When it is determined that the interference wave generation flag is on (S105: Yes), the RSSI detection unit 37 determines whether the RSSI detected flag is on (step S106). If it is determined that the RSSI detected flag is on (S106: Yes), the process returns to step S102.
When it is determined that the interference wave generation flag is off (S105: No), or when it is determined that the RSSI detected flag is off (S106: No), the RSSI detector 37 sets the RSSI detected flag. While turning on, the RSSI detection value detected in step S102 is held as the RSSI detection value of the desired signal wave (step S107), and the process returns to step S102.

For example, the interference wave detection unit 38 may turn off the RSSI detected flag every time the wireless STA 3 and the wireless AP 5 are wirelessly connected, and turn off the RSSI detected flag every predetermined period. You may do it.
FIG. 8 is a flowchart of transmission rate control processing by the wireless STA 3 in FIGS.
The transmission rate selection unit 170 arbitrarily selects one transmission rate from a plurality of transmission rates, and initializes the selected transmission rate in the transmission unit 36 (step S151).

  If the wireless STA 3 receives the desired signal wave transmitted from the antenna 51 by the wireless AP 5 before the start of the generation of the interference wave after the initial setting, the detected value of the RSSI of the desired signal wave and the wireless AP 5 The transmission rate may be selected and set in the transmission unit 36 by performing the processes of steps S165 and S166 using the interference wave power “0” (no interference wave) of the interference wave in FIG.

The interference wave detection unit 38 turns off the interference wave generation flag (step S152).
The interference wave detection unit 38 performs a detection process of the interference wave and the interference wave power (step S153). The interference wave detection unit 38 continues the detection process of the interference wave and the interference wave power in step S153 until the start of the generation of the interference wave is detected in the process of step S153 (S154: No).

When the start of the generation of the interference wave is detected (S154: Yes), the interference wave detection unit 38 turns on the interference wave generation flag (step S155).
The wireless STA 3 transmits a signal wave related to the test transmission packet to the wireless AP 5 by the processing of the upper layer processing unit 34, the transmission frame generation unit 35, and the transmission unit 36. The wireless STA 3 receives the test response packet as a response to the test transmission packet by the processing of the reception unit 32, the reception frame analysis unit 33, and the upper layer processing unit 34. This is performed for the test transmission packet having the transmission packet number T1. Then, the upper layer processing unit 34 calculates the transmission packet number T1 of the test transmission packet and the reception packet number T2 of the test response packet having no packet error obtained as a result of transmission / reception of the test transmission packet and the test response packet. And output to the PERrt calculation unit 120 (step S156). An example of processing of the wireless STA 3 and an example of processing of the wireless AP 5 regarding step S156 will be described later with reference to FIGS.

The PERrt calculation unit 120 calculates PERrt, which is a PER for round-trip communication, from the number of transmission packets T1 and the number of reception packets T2 received from the upper layer processing unit 34 in the process of step S156 (step S157).
The PERdwn calculation unit 130 refers to the propagation characteristic at the transmission rate used for transmission of the desired signal wave in the propagation characteristic table 110, detects the RSSI detected value of the desired signal wave held in step S107 in FIG. From the detected value of the interference wave power detected in S153, PERdwn, which is the PER for return path communication, is calculated (step S158). The transmission rate used for transmitting the desired signal wave is stored in the PLCP header in the IEEE 802.11 standard.

The PERup calculation unit 140 calculates PERup, which is the PER for outbound communication, from the calculated value of PERrt calculated in step S157 and the calculated value of PERdwn calculated in step S158 (step S159).
The interference wave power estimation unit 150 refers to the propagation characteristic at the transmission rate used for transmitting the test transmission signal in the propagation characteristic table 110, and the detected value of the RSSI of the desired signal wave held in step S107 in FIG. Then, the interference wave power of the interference wave in the wireless AP 5 is estimated from the calculated value of PERup calculated in step S159 (step S160).

  The PER estimation unit 160 refers to the propagation characteristics at each transmission rate in the propagation characteristic table 110, detects the RSSI detection value of the desired signal wave held in step S107 in FIG. 7, and the interference in the wireless AP 5 estimated in step S160. The PER in the case where the transmission rate is used for signal transmission from the wireless STA 3 to the wireless AP 5 is estimated from the estimated value of the interference wave power of the waves (step S161).

The transmission rate selection unit 170 selects a transmission rate having the smallest estimated PER value from a plurality of transmission rates as a transmission rate used for transmission of a signal from the wireless STA 3 to the wireless AP 5, and transmits the selected transmission rate to the transmission unit. 36 is set (step S162).
The interference wave detection unit 38 performs a detection process of the interference wave and the interference wave power (step S163). The interference wave detection unit 38 continues the detection process of the interference wave and the interference wave power in step S163 until it detects the end of the generation of the interference wave in the process of step S163 (S164: No).

  When the end of the generation of the interference wave is detected (S164: Yes), the PER estimation unit 160 regards the interference wave power of the interference wave in the wireless AP 5 as “0” (no interference wave). Then, the PER estimation unit 160 refers to the propagation characteristics at each transmission rate in the propagation characteristics table 110, detects the RSSI detection value of the desired signal wave held in step S107 in FIG. 7, and the interference wave of the interference wave in the wireless AP 5 From the power “0” (no interference wave), the PER is estimated when the transmission rate is used for signal transmission from the wireless STA 3 to the wireless AP 5 (step S165).

The transmission rate selection unit 170 selects a transmission rate having the smallest estimated PER value from a plurality of transmission rates as a transmission rate used for transmission of a signal from the wireless STA 3 to the wireless AP 5, and transmits the selected transmission rate to the transmission unit. It is set to 36 (step S166).
The interference wave detection unit 38 turns off the interference wave generation flag (step S167). Then, the process returns to step S153.

FIG. 9 is a flowchart showing the processing of transmission / reception S156 of the test signal of FIG. 8 by the wireless STA3.
The upper layer processing unit 34 generates a test transmission packet including a header checksum (step S201). In Embodiment 1 or the like, the test transmission packet can be identified by the upper layer processing unit 54 of the wireless AP 5 by analyzing the contents of the payload. And

  The transmission frame generation unit 35 generates a test transmission frame including a MAC header, a frame body storing data related to the test transmission packet, and the FCS (step S202). In Embodiment 1 or the like, the test transmission frame is determined whether the reception frame analysis unit 53 of the wireless AP 5 analyzes the contents of the type value and the subtype value to determine whether the reception frame is a test transmission frame. Assume that you are able to understand. Further, it is assumed that the receiving station and the transmitting station can be understood by analyzing the contents of Address 1 and Address 2.

The transmission unit 36 performs predetermined processing such as encoding and modulation on the test transmission frame portion using the transmission rate set by the transmission rate control unit 39, adds a PLCP preamble and a PLCP header, and performs a test. A signal wave related to the transmission signal is transmitted from the antenna 31 (step S203).
The receiving unit 32 performs a signal wave detection process (step S204), and determines whether a signal wave is detected in the detection process of step S204 (step S205). When the signal wave is not detected (S205: No), the upper layer processing unit 34 determines whether or not a predetermined time has elapsed since the transmission packet was generated in step S201 (step S206). If it is determined that the predetermined time has not elapsed (S206: No), the process returns to step S204. If it is determined that the predetermined time has elapsed (S206: Yes), the process proceeds to step S210.

  When the signal wave is detected (S205: Yes), the receiving unit 32 performs predetermined processing such as demodulation and decoding on the detected signal wave. The received frame analysis unit 33 analyzes the error of the received frame and the contents of the MAC header, and determines whether the received frame is a test response frame addressed to the own station without any frame error (step S207). In the first embodiment and the like, the test response frame is determined whether the received frame is a test response frame by analyzing the contents of the type value and the subtype value by the received frame analysis unit 33 of the wireless STA 3. Assume that you are able to understand. Further, it is assumed that the receiving station and the transmitting station can be understood by analyzing the contents of Address 1 and Address 2.

If it is determined that the received frame is not a test response frame addressed to the own station without a frame error (S207: No), the process proceeds to step S210.
When it is determined that the received frame is a test response frame addressed to the own station without a frame error (S207: Yes), the upper layer processing unit 34 checks the packet header for error and analyzes the contents of the payload of the received packet. Then, it is determined whether the received packet is a test response packet with no packet error (step S208). In the first embodiment, etc., the test response packet can be determined whether or not the test response packet is a test response packet by the upper layer processing unit 34 of the wireless STA 3 analyzing the contents of the payload. And

If it is determined that the received packet is not a test response packet with no packet error (S208: No), the process proceeds to step S210.
When it is determined that the received packet is a test response packet having no packet error (S208: Yes), the upper layer processing unit 34 sets the received packet number T2 of the test response packet having no packet error received so far. The received packet count T2 is updated by adding the received packet count of the test response packet received this time without a packet error (step S209). Then, the process proceeds to step S210.

  The upper layer processing unit 34 determines whether or not the number of transmitted test transmission packets has reached the number of transmitted packets T1 (step S210). If it is determined that the number of transmission packets T1 has not been reached (S210: No), the processing returns to step S201. On the other hand, when it is determined that the number of transmitted packets T1 has been reached (S210: Yes), the upper layer processing unit 34 outputs the number of transmitted packets T1 and the number of received packets T2 to the transmission rate control unit 39 (step S211). ).

Next, operations related to control of the transmission rate of the wireless AP 5 in FIG. 5 will be described with reference to the drawings.
FIG. 10 is a flowchart of the test signal transmission / reception processing by the wireless AP 5 of FIG. 5 corresponding to the processing of the test signal transmission / reception S156 of FIG.
The receiving unit 52 performs detection processing of a signal wave transmitted by any of the wireless communication devices including the wireless STA 3 (Step S251). Until the signal wave is detected in the signal wave detection process in step S251 (S252: No), the receiving unit 52 continues the signal wave detection process in step S251. When a signal wave is detected (S252: Yes), the receiving unit 52 performs predetermined processing such as demodulation and decoding on the detected signal wave. Then, the received frame analysis unit 53 analyzes the error of the received frame and the contents of the MAC header, and determines whether or not the received frame is a test transmission frame addressed to the own station with no frame error (step S253). When it is determined that the received frame is not a test transmission frame addressed to the own station without a frame error (S253: No), the process returns to step S251.

  When it is determined that the received frame is a test transmission frame addressed to the own station without a frame error (S253: Yes), the upper layer processing unit 54 analyzes the error of the packet header and the content of the payload of the received packet, It is determined whether the received packet is a test transmission packet having no packet error (step S254). If it is determined that the received packet is not a test transmission packet with no packet error (S254: No), the process returns to step S251.

  When it is determined that the received packet is a test transmission packet with no packet error (S254: Yes), the upper layer processing unit 54 generates a test response packet including a header checksum (step S255). The transmission frame generation unit 55 generates a test response frame including a MAC header, a frame body storing data related to the test response packet, and the FCS (step S256). The transmitting unit 56 performs predetermined processing such as encoding and modulation on the test transmission frame portion, adds a PLCP preamble and a PLCP header, and transmits a signal wave related to the test response signal from the antenna 51. (Step S257). Then, the process returns to step S251.

According to the first embodiment, the wireless STA 3 and the wireless AP 5 transmit and receive test signals at one of a plurality of defined transmission rates, so that the wireless STA 3 can transmit signals from the wireless STA 3 to the wireless AP 5. The transmission rate to be used can be selected. For this reason, the communication load of the test signal when selecting the transmission rate can be reduced.
Further, if the wireless AP 5 has a function of returning a test response signal by returning to the test transmission signal, the wireless STA 3 can adaptively select a transmission rate, Restrictions on building can be reduced.

<< Modification of Embodiment 1 >>
<Modification 1>
When the interference device 7 is, for example, a microwave oven, it is assumed that the installation locations of both the wireless AP 5 and the interference device 7 are not changed much.
For example, the level of radiation noise emitted from a microwave oven or the like usually does not change much.

Considering these things, the level of the interference wave power of the interference wave in the wireless AP 5 does not change so much, for example, when a power source is newly turned on, for example, when a microwave oven is turned on in the past. It is considered a thing.
Therefore, the first embodiment has described the function of selecting the transmission rate using the estimated value of the interference wave power of the interference wave in the wireless AP 5 estimated when the start of the generation of the interference wave is detected. You may make it add to a transmission rate control technique.

According to this, if the interference wave power of the interference wave in the wireless AP 5 has been estimated before, the processing from step S156 to step S160 can be omitted when the start of the generation of the interference wave is detected, and the wireless STA3 In addition, the processing load of the wireless AP 5 can be reduced, and the transmission rate can be selected and set in a short time.
The operation flow of the transmission rate control process by the wireless STA 3 will be described with reference to FIG.

FIG. 11 is a flowchart of a transmission rate control process by the wireless STA 3 in the first modification. In the first modification, processing steps that perform substantially the same processes as those in the first embodiment are denoted by the same reference numerals, and the description thereof can be applied.
The interference wave detection unit 38 turns off the interference wave generation flag, and the interference wave power estimation unit 150 turns off the interference wave power estimation completed flag (step S152A). However, when the interference wave power estimated flag is on, it indicates that the interference wave power of the interference wave in the wireless AP 5 has already been estimated and the estimated value is held, and when it is off, interference of the interference wave in the wireless AP 5 The wave power is not estimated and the estimated value is not retained.

The upper layer processing unit 34 determines whether or not the interference wave power estimated flag is on (step S181).
If it is determined that the interference wave power estimated flag is not on (S181: No), the interference wave power estimation unit 150 turns on the interference wave power estimated flag after the processing from step S156 to step S160 is executed. Then, the estimated value of the interference wave power of the interference wave in the wireless AP 5 estimated in step S160 is held (step S182). And the process of step S161 is performed.

  If it is determined that the interference wave power estimated flag is on (S181: Yes), the PER estimation unit 160 refers to the propagation characteristics at each transmission rate in the propagation characteristic table 110, and in step S107 of FIG. The transmission rate is transmitted from the wireless communication apparatus 3 to the wireless AP 5 based on the detected RSSI value of the desired signal wave and the estimated interference wave power of the interference wave in the wireless AP 5 held in step S182. The PER when used is estimated (step S183).

The transmission rate selection unit 170 selects a transmission rate having the smallest estimated PER value from a plurality of transmission rates as a transmission rate used for transmission of a signal from the wireless STA 3 to the wireless AP 5, and transmits the selected transmission rate to the transmission unit. It is set to 36 (step S184). Then, the process of step S163 is executed.
Note that in the wireless communication using the selected transmission rate, the wireless STA 3 may perform the processing from step S156 to step S162 again when the communication success rate of the round-trip communication does not satisfy a predetermined condition.

  For example, in the wireless communication using the selected transmission rate, the wireless STA 3 determines the communication success rate R1 = round-trip communication from the transmission packet number A of transmission packets and the reception packet number B of packet without error as a response. B / A is calculated. In addition, the wireless STA 3 determines the round-trip communication success rate R2 = (1) from the calculated value of PERdwn for return path communication in step S158 and the estimated value of PER for outbound communication in step S161 or step S183 regarding the selected transmission rate. -PER) * (1-PERdwn) is calculated.

  Then, when the communication success rate R1 is less than a value obtained by subtracting a predetermined value (for example, 0.1) from the communication success rate R2, the wireless STA 3 performs the processing from step S156 to step S162 again. Note that, when the communication success rate R1 is less than a value obtained by multiplying the communication success rate R2 by a predetermined value (for example, 0.9), the wireless STA 3 may perform the processing from step S156 to step S162 again.

In this example, the predetermined condition is “the communication success rate R1 is equal to or greater than a value obtained by subtracting a predetermined value (for example, 0.1) from the communication success rate R2”, “the communication success rate R1 is equal to the communication success rate R2 by a predetermined value ( For example, it is equal to or greater than a value obtained by multiplying 0.9). As described above, when the predetermined condition is not satisfied, many communication errors occur.
These are merely examples and are not particularly limited. In addition, a communication error rate may be used instead of the communication success rate, but this is substantially equivalent only by changing the view from the communication success rate.

According to this, for example, when the installation environment of the wireless STA 3 and the wireless AP 5 changes, there is an advantage that wireless communication can be performed at a transmission rate suitable for the new installation environment.
Further, when a certain time has elapsed since the interference wave power of the interference wave at the wireless AP 5 is estimated, or when the number of detections of the start of generation of the interference wave exceeds a predetermined number, the processing from step S156 to step S162 is performed again. You may make it perform.

According to this, for example, when the installation environment of the wireless STA 3 and the wireless AP 5 changes, there is an advantage that wireless communication can be performed at a transmission rate suitable for the new installation environment.
<Modification 2>
When the radiation noise emitted from the interference device 7 becomes an interference wave to the wireless AP 5, the estimated value of the interference wave power in the wireless AP 5 estimated by the wireless STA 3 performing the processing from step S156 to step S160, and other wireless STAs It is assumed that the estimated value of the interference wave power in the wireless AP 5 estimated by performing the processing from step S156 to step S160 is almost the same value.

Therefore, when the start of the generation of the interference wave is detected, if the estimated value of the interference wave power of the interference wave in the wireless AP 5 has already been received from another wireless STA, the interference wave power of the interference wave in the wireless AP 5 The function of selecting the transmission rate using the estimated value may be added to the transmission rate control technique described in the first embodiment or the modification 1 thereof.
According to this, if the estimated value of the interference wave power of the interference wave in the wireless AP 5 has already been received from another wireless STA, the processing from step S156 to step S160 is omitted when the start of the generation of the interference wave is detected. It is possible to reduce the processing load on the wireless STA 3 and the wireless AP 5 and to select and set the transmission rate in a short time.

The operation relating to the control of the transmission rate of the wireless STA 3 will be described with reference to the drawings.
FIG. 12 is a flowchart illustrating processing in which the wireless STA 3 according to the second modification receives interference wave power.
The upper layer processing unit 34 turns off the interference wave power received flag (step S301). However, when the interference wave power received flag is on, it indicates that the estimated value of the interference wave power of the interference wave in the wireless AP 5 has already been received from another wireless STA, and that the estimated value is held, and when it is off Indicates that the estimated value of the interference wave power of the interference wave in the wireless AP 5 is not received from another wireless STA, and the estimated value is not held.

  The receiving unit 32 performs processing for detecting a signal wave transmitted by any of the wireless communication devices including the wireless STA 3 (step S302). Until the signal wave is detected in the signal wave detection process in step S302 (S303: No), the receiving unit 32 continues the signal wave detection process in step S302. When a signal wave is detected (S303: Yes), the receiving unit 32 performs predetermined processing such as demodulation and decoding on the detected signal wave. Then, the received frame analysis unit 33 analyzes the error of the received frame and the content of the MAC header, and determines whether or not the received frame is a broadcast interference power notification frame without a frame error (step S304). In the second modification, the interference wave power notification frame is obtained by analyzing whether the reception frame analysis unit 33 of the wireless STA 3 analyzes the contents of the type value and the subtype value, and whether or not the reception frame is an interference wave power notification frame. Assume that you are able to understand. Also, it is assumed that it is possible to know whether the MAC frame is broadcast by looking at the address.

When it is determined that the received frame is not a broadcast interference power notification frame without a frame error (S304: No), the process returns to step S302.
If it is determined that the received frame is a broadcast interference power notification frame without frame error (S304: Yes), the upper layer processing unit 34 analyzes the error of the received packet and analyzes the contents of the payload, and receives the received packet. Is an interference wave power notification packet with no packet error (step S305). In the second modification, the interference wave power notification packet can be determined whether the higher layer processing unit 34 of the wireless ASTA 3 analyzes the contents of the payload or not. And Furthermore, it is assumed that the estimated value of the interference wave power of the interference wave in the wireless AP 5 estimated by another wireless STA is obtained by analyzing the contents of the payload.

When it is determined that the received packet is not an interference wave power notification packet with no packet error (S305: No), the process returns to step S302.
When it is determined that the received packet is an interference wave power notification packet with no packet error (S305: Yes), the upper layer processing unit 34 turns on the interference wave power received flag and notifies with the received interference wave power notification packet The estimated value of the interference wave power of the interference wave in the wireless AP 5 is stored (step S306). Then, the process of step S302 is performed.

FIG. 13 is a flowchart of a transmission rate control process performed by the wireless STA 3 in the second modification. In the second modification, processing steps that perform substantially the same processes as those in the first embodiment or the first modification are denoted by the same reference numerals, and the description thereof can be applied to omit the description.
When it is determined that the interference wave power estimated flag is not on (S181: No), the upper layer processing unit 34 determines whether or not the interference wave power received flag is on (step S191). When it is determined that the interference wave power received flag is not on (S191: No), after the processing from step S156 to step S182 is executed, the interference wave power estimation unit 150 performs the wireless AP 5 estimation in step S160. The estimated value of the interference wave power is output to the upper layer processing unit 34. Then, the wireless STA 3 executes the process of notifying the estimated interference wave power value shown in FIG. 14 (step S192).

  As illustrated in FIG. 14, the upper layer processing unit 34 generates an interference wave power notification packet including the estimated value of the interference wave power of the interference wave in the wireless AP 5 received from the interference wave power estimation unit 150 in the payload (step S351). . The transmission frame generation unit 35 generates an interference wave power notification frame including a MAC header, a frame body storing data related to the interference wave power notification packet, and an FCS (step S352). The transmission unit 36 performs predetermined processing such as encoding and modulation on the interference wave power notification frame part, adds a PLCP preamble and a PLCP header, and transmits a signal wave related to the interference wave power notification signal from the antenna 31. (Step S353).

  If it is determined that the interference wave power received flag is on (S191: Yes), the PER estimation unit 160 refers to the propagation characteristics at each transmission rate in the propagation characteristic table 110, and in step S107 of FIG. Transmission of the signal from the wireless STA 3 to the wireless AP 5 based on the detected RSSI value of the desired signal wave and the estimated value of the interference wave power of the interference wave in the wireless AP 5 held in step S306 of FIG. The PER in the case of being used for the estimation is estimated (step S193).

The transmission rate selection unit 170 selects a transmission rate having the smallest estimated PER value from a plurality of transmission rates as a transmission rate used for transmission of a signal from the wireless STA 3 to the wireless AP 5, and transmits the selected transmission rate to the transmission unit. 36 is set (step S194). Then, the process of step S163 is executed.
Note that, as described in the first modification, the wireless STA 3 uses a wireless communication using the selected transmission rate when the communication success rate of the round-trip communication or the communication failure rate of the round-trip communication does not satisfy a predetermined condition. The processing from step S156 to step S162 may be performed again.

Further, when a certain time has elapsed since the interference wave power of the interference wave at the wireless AP 5 is estimated, or when the number of detections of the start of generation of the interference wave exceeds a predetermined number, the processing from step S156 to step S162 is performed again. You may make it perform.
<< Embodiment 2 >>
Hereinafter, Embodiment 2 according to the present invention will be described with reference to the drawings. In the second embodiment, constituent elements having substantially the same functions as those in the first embodiment and processing steps for performing substantially the same processing are denoted by the same reference numerals, and the description thereof can be applied, and the description thereof is omitted. To do.

The second embodiment is different from the first embodiment in the method of selecting the transmission rate using the estimated value of the interference wave power of the interference wave in the wireless AP 5, and the transmission rate control unit of the wireless STA 3 in FIG. 39 is replaced with a transmission rate control unit 39A. Except for this point, the same wireless STA 3 and wireless AP 5 of Embodiment 1 can be used.
FIG. 15 is a block diagram showing a configuration of transmission rate control unit 39A of the wireless STA according to the second embodiment.

The transmission rate control unit 39A adds a propagation characteristic table 115 to the transmission rate control unit 39 of FIG. 3, and replaces the PER estimation unit 160 and the transmission rate selection unit 170 with an SIR calculation unit 160A and a transmission rate selection unit 170A. It has a configuration.
The propagation characteristic table 115 is a table for storing propagation characteristics indicating a relationship between a signal-to-interference ratio (SIR) and a transmission rate, and is held in a storage unit. However, for example, it is assumed that the propagation characteristic table is created in advance.

  An example of the propagation characteristic table 115 is shown in FIG. For example, in the case of the wireless communication of the IEEE802.11b standard, four transmission rates of 1 Mbps, 2 Mbps, 5.5 Mbps, and 11 Mbps are defined in the IEEE802.11b standard. The propagation characteristic indicating the relationship between the two transmission rates and the SIR is stored. In FIG. 16, the horizontal axis represents the SIR, and the vertical axis represents the transmission rate (Mbps).

The SIR calculation unit 160A performs the following operation at the start of generation of interference waves.
The SIR calculation unit 160A receives a notification of detection of the start of generation of interference waves from the interference wave detection unit 38. Furthermore, the RSSI detection value of the desired signal wave is received from the RSSI detection unit 37, and the interference wave power estimation value of the interference wave in the wireless AP 5 is received from the interference wave power estimation unit 150. Then, SIR calculation section 160A calculates a ratio (SIR) between the detected value of RSSI of the desired signal wave and the detected value of interference wave power of the interference wave, and outputs the calculated value of SIR to transmission rate selection section 170A.

The SIR calculation unit 160A performs the following operation at the end of the generation of the interference wave.
The SIR calculation unit 160A receives a notification of detection of the end of the generation of the interference wave from the interference wave detection unit 38. Furthermore, the SIR calculation unit 160A receives the RSSI detection value of the desired signal wave from the RSSI detection unit 37, and uses the interference wave power detection value detected by the interference wave detection unit 38 when there is no interference wave as an interference wave in the wireless AP 5. It is regarded as the value of the interference wave power. Then, SIR calculation section 160A calculates a ratio (SIR) between the detected value of RSSI of the desired signal wave and the detected value of interference wave power of the interference wave, and outputs the calculated value of SIR to transmission rate selection section 170A.

  However, similar to the interference wave power estimation unit 150, the SIR calculation unit 160A has the RSSI value of the signal wave transmitted from the antenna 51 by the wireless AP 5 and the wireless AP 5 of the signal wave transmitted by the wireless STA 3 from the antenna 31. It is assumed that the RSSI value is equal. However, if the RSSI value in the wireless STA 3 and the RSSI value in the wireless AP 5 are not equal, and it is previously known that a certain difference occurs, the detected value of the RSSI of the desired signal wave is corrected for the difference, and after the correction Can be set as the RSSI value of the desired signal wave in the wireless AP 5. For example, the difference in RSSI value due to the difference between the gain value of the antenna 51 of the wireless AP 5 and the gain value of the antenna 31 of the wireless STA 3 or the difference between the transmission power value of the wireless AP 5 and the transmission power value of the wireless STA 3. May always occur several dBm.

  The transmission rate selection unit 170A receives the calculated SIR value from the SIR calculation unit 160A. Then, the transmission rate selection unit 170A refers to the propagation characteristic stored in the propagation characteristic table 115, and uses the transmission rate corresponding to the calculated value of SIR as the transmission rate used for signal transmission from the wireless STA 3 to the wireless AP 5. The selected transmission rate is set in the transmission unit 36.

When the end of the generation of the interference wave is detected, the SIR calculation unit 160A and the transmission rate selection unit 170A do not perform the above processing, and the transmission rate selection unit 170A selects the fastest transmission rate among a plurality of transmission rates. You may make it do.
FIG. 17 is a flowchart showing transmission rate control processing by the wireless STA including the transmission rate control unit 39A of FIG.

SIR calculation section 160A calculates SIR from the RSSI detection value of the desired signal wave held in step S107 of FIG. 7 and the interference wave power estimation value of the interference wave in wireless AP 5 estimated in step S160. (Step S161A).
The transmission rate selection unit 170A refers to the propagation characteristic of the propagation characteristic table 115 and selects the transmission rate corresponding to the calculated value of SIR in step S161A as the transmission rate used for signal transmission from the wireless STA 3 to the wireless AP 5. The selected transmission rate is set in the transmitter 36 (step S162A).

  The SIR calculation unit 160A regards the detected value of the interference wave power detected by the interference wave detection unit 38 when there is no interference wave as the value of the interference wave power of the interference wave in the wireless AP 5. Then, SIR calculating section 160A calculates SIR from the RSSI detection value of the desired signal wave held in step S107 of FIG. 7 and the value of the interference wave power of the interference wave in wireless AP 5 (step S165A).

The transmission rate selection unit 170A refers to the propagation characteristic of the propagation characteristic table 115 and selects the transmission rate corresponding to the calculated value of SIR in step S165A as the transmission rate used for signal transmission from the wireless STA 3 to the wireless AP 5. The selected transmission rate is set in the transmitter 36 (step S166A).
The contents described in <Modification 1> and <Modification 2> of the modification of the first embodiment can be applied to the second embodiment.

≪Supplement (Part 1) ≫
The present invention is not limited to the contents described in the above embodiment, and can be implemented in any form for achieving the object of the present invention and the object related thereto or incidental thereto. .
(1) In addition to using a newly defined dedicated packet as a test transmission packet and a test response packet used for calculating PERrt in the first embodiment, etc., packets defined for other functions are used. It may be.

  For example, packets defined in ICMP may be used as the test transmission packet and the test response packet. For example, an Echo Message (echo request notification) packet and an Echo Reply Message packet that are transmitted and received by executing a Ping command may be used as the test transmission packet and the test response packet.

By using a packet defined for another function, it is not necessary to add a function used only for transmission rate control to the wireless AP 5.
(2) In the first embodiment and the like, it has been described that the error rate (PER) at the packet level is used when selecting the transmission rate. However, the present invention is not limited to this, for example, at the MAC layer level. An error rate, that is, a frame error rate (FER) may be used.

By using FER at the MAC layer level, even when the wireless communication device on the reception side does not have a function higher than the MAC layer, the wireless communication device on the transmission side is the wireless communication device on the transmission side. Thus, it is possible to select a transmission rate used for signal transmission from the wireless communication device on the receiving side.
Further, when using FER, for example, a dedicated frame may be defined and used as a test transmission frame and a test response frame used for measuring the FER of round-trip communication, for other functions. You may make it utilize the frame defined in (1).

For example, an IEEE802.11 standard Probe (probe) request frame and Probe response frame may be used as a test transmission frame and a test response frame.
By using frames defined for other functions, it is not necessary to add a function used only for transmission rate control to the wireless AP 5.

(3) If the wireless STA 3 transmits a transmission packet with the transmission packet number T1, the wireless STA 3 will be described in the first embodiment or the like as long as the wireless STA 3 can measure the reception packet number of the reception packet with no packet error. The method is not limited to the above.
(4) In Embodiment 1 or the like, the transmission time of a predetermined portion of the test transmission signal transmitted from the antenna 31 may be a time corresponding to one cycle of the interference wave emitted from the interference device 7. . Further, the transmission time of a predetermined portion of the test response signal transmitted from the antenna 51 may be set to a time corresponding to one period of the interference wave emitted from the interference device 7.

The predetermined portion is a portion that is encoded or modulated at a modulation scheme and / or a coding rate corresponding to a transmission rate to be used among a plurality of transmission rates. For example, the IEEE 802.11 standard PSDU (PLCP Service Data Unit).
According to this, PERrt of the round-trip communication becomes almost the same value in the same environment regardless of the transmission timing of the test transmission signal and the test response signal, and an appropriate transmission rate can be selected.

  (5) In Embodiment 1 or the like, when the RSSI of the desired signal wave is detected before the generation of the interference wave, the RSSI of the desired signal wave is not detected during the generation of the interference wave. It has been described that the RSSI detection value of the desired signal wave before generation is used for transmission rate control. However, the present invention is not limited to this. Even when the RSSI of the desired signal wave is detected before the generation of the interference wave, the RSSI of the desired signal wave is detected during the generation of the interference wave, and the interference wave is being generated. The detected value of RSSI of the desired signal wave may be used to control the transmission rate.

(6) In the first embodiment and the like, the transmission rate of the test transmission signal is described as the transmission rate used for transmission of the signal from the wireless STA 3 to the wireless AP 5 before detecting the start of the generation of the interference wave. . However, the present invention is not limited to this, and the transmission rate of the test transmission signal may be a transmission rate other than this, for example, a lower transmission rate.
(7) In the first embodiment and the like, the transmission rate is selected by performing the processing of step S25 and step S26 in FIG. However, the present invention is not limited to this. For example, the transmission rate used before the detection of the start of the generation of the interference wave is retained and used after the detection of the end of the generation of the interference wave. Also good.

(8) The transmission rate selection mechanism described in the first embodiment is not limited to the IEEE802.11 standard such as the IEEE802.11b standard, but is used for transmission from the transmission-side wireless communication device to the reception-side wireless communication device. This is applicable when there are a plurality of transmission rates that can be used.
(9) If the wireless STA that has estimated the interference wave power of the interference wave in the wireless AP 5 can notify the other wireless STAs of the interference wave power estimation value in the wireless AP 5, the signals used for the notification are particularly limited. Is not to be done.

  (10) Each component of the transmitting-side wireless communication device and the receiving-side wireless communication device in the first embodiment may be realized by an LSI (Large Scale Integration) that is an integrated circuit. At this time, each component may be individually made into one chip, or may be made into one chip so as to include a part or all of them. In addition, although it is referred to as LSI here, it may be referred to as IC (Integrated Circuit), system LSI, super LSI, or ultra LSI depending on the degree of integration. Further, the method of circuit integration is not limited to LSI, and implementation with a dedicated circuit or a general-purpose processor is also possible. An FPGA (Field Programmable Gate Array) or a reconfigurable processor capable of reconfiguring connection and setting of circuit cells inside the LSI may be used. Furthermore, if integrated circuit technology comes out to replace LSI's as a result of the advancement of semiconductor technology or a derivative other technology, it is naturally also possible to carry out function block integration using this technology.

(11) At least a part of the operation procedure of the wireless STA and the wireless AP described in the first embodiment is described in the program, and for example, the CPU (Central Processing Unit) reads and executes the program stored in the memory Alternatively, the program may be stored in a recording medium and distributed.
(12) The contents described in the first embodiment and the like may be appropriately combined.

≪Supplement (Part 2) ≫
The wireless communication device on the transmission side, the transmission rate control method, the transmission rate control program, and the effects thereof in the embodiments and modifications will be summarized.
(1) The first wireless communication device is a transmission-side wireless communication device that performs wireless communication with a reception device that is a reception-side wireless communication device, and a reception unit that receives a signal transmitted from the reception device; A first detection unit that detects a signal intensity of the received desired signal wave when the receiving unit receives the desired signal wave, an interference wave emitted from an external device, and an interference wave power that is power of the interference wave A second detection unit to detect, a transmission unit that transmits a test signal to the receiving device when the second detection unit detects an interference wave, and a response from the receiving device to the test signal from the receiving device An analysis unit that performs error detection of the response signal when a signal is received, a detection value of the signal strength of the desired signal wave, a detection value of interference wave power of the interference wave, and the number of transmissions related to the test signal, Receiving the response signal without error. The number, based on, and a transmission rate control unit for selecting a transmission rate used to transmit the signal to the receiving device from among a plurality of transmission rates.

  The transmission rate control method is a transmission rate control method performed in a transmission-side wireless communication device that performs wireless communication with a reception device that is a reception-side wireless communication device, and receives a signal transmitted from the reception device, When the signal strength of the received desired signal wave is detected when the desired signal wave is received, the interference wave emitted from the external device and the interference wave power that is the power of the interference wave are detected, and the interference wave is detected , Transmitting a test signal to the receiving device, performing error detection of the response signal when a response signal to the test signal is received from the receiving device, and detecting the signal strength of the desired signal wave, Based on the detected value of the interference wave power of the interference wave, the number of transmissions related to the test signal, and the number of receptions related to the response signal without error, the signal of the signal to the receiving device from a plurality of transmission rates Sending Selecting a transmission rate to be used for.

  The transmission rate control program is received when a signal transmitted from the receiving device is received and a desired signal wave is received by a transmitting wireless communication device that performs wireless communication with a receiving device that is a receiving wireless communication device. The signal strength of the desired signal wave is detected, the interference wave emitted from the external device and the interference wave power that is the power of the interference wave are detected, and when the interference wave is detected, the test signal is sent to the receiving device. When the response signal to the test signal is received from the receiving device, error detection of the response signal is performed, and the detection value of the signal strength of the desired signal wave and the detection value of the interference wave power of the interference wave And, based on the number of transmissions related to the test signal and the number of receptions related to the response signal without error, a transmission rate used for signal transmission to the receiving device is selected from a plurality of transmission rates. This To the execution.

According to these, it is possible to reduce a signal communication load for a test when the transmission-side wireless communication device selects a transmission rate used for transmitting a signal to the reception-side wireless communication device from a plurality of transmission rates. Figured.
Further, if the receiving-side wireless communication device has a function of returning a response signal to the test signal from the transmitting-side wireless communication device, the transmitting-side wireless communication device to the receiving-side wireless communication device (receiving device). It is possible to appropriately select the transmission rate used for transmitting the signal at the transmitting-side wireless communication device.

  (2) The second wireless communication device is the first wireless communication device, wherein the transmission rate control unit determines the transmission side from the number of transmissions related to the test signal and the number of receptions related to the response signal without error. An error rate calculation unit that calculates a reception error rate of round-trip communication including forward communication that is communication from the wireless communication device to the reception device and return communication that is communication from the reception device to the wireless communication device on the transmission side And estimating the interference wave power at the receiving device based on the detected value of the signal strength of the desired signal wave, the detected value of the interference wave power, and the calculated value of the reception error rate of the round-trip communication. An interference wave power estimation unit; and a transmission rate selection unit that selects a transmission rate to be used based on the detected value of the signal strength of the desired signal wave and the estimated value of the interference wave power.

According to this, since the transmission rate is selected by estimating the interference wave power at the receiving device, it is possible to select an appropriate transmission rate.
(3) The third wireless communication device is the second wireless communication device, wherein the error rate calculation unit is based on a detected value of the received signal strength of the desired signal wave and a detected value of the interference wave power. Calculating the reception error rate of the return communication, and the error rate calculation unit includes a calculated value of the reception error rate of the round-trip communication and a calculated value of the reception error rate of the return communication by the return error rate calculation unit. The interference wave power estimation unit calculates the reception error rate of the desired signal wave and the calculation value of the reception error rate of the outbound communication based on Based on this, the interference wave power in the receiving device is estimated.

This makes it possible to select an appropriate transmission rate.
(4) The fourth wireless communication device is the third wireless communication device, wherein the transmission rate control unit is configured to detect a signal intensity detection value of the desired signal wave and the receiving device for each of the plurality of transmission rates. And an error rate estimation unit that estimates a reception error rate of the forward communication when the transmission rate is used based on the estimated value of the interference wave power in the transmission rate selection unit, the transmission rate selection unit, The transmission rate with the smallest estimated rate is selected as the transmission rate.

This makes it possible to select an appropriate transmission rate.
(5) The fifth wireless communication device is the third wireless communication device, wherein the transmission rate selection unit includes a detected value of the received signal strength of the desired signal wave and an estimated value of the interference wave power in the receiving device. And the transmission rate is selected based on the calculated value of the ratio.
This makes it possible to select an appropriate transmission rate.

(6) In the first wireless communication device, the sixth wireless communication device transmits the test signal to the receiving device when the interference wave detection unit detects an interference wave for the first time in the first wireless communication device. To do.
According to this, when the installation location of both the external device and the receiving device is not changed so much, the estimation process of the interference wave power of the interference wave in the receiving device can be omitted, and the processing load of the wireless communication device is reduced. In addition, the transmission rate can be selected and set in a short time.

(7) The seventh wireless communication device is the sixth wireless communication device, wherein the transmission unit has a communication success rate or communication error rate of the round-trip communication at a predetermined condition at the transmission rate selected by the transmission rate control unit. If not, the test signal is transmitted to the receiving device.
According to this, when the installation location of at least one of the external device and the receiving device is changed and the interference wave power level of the interference wave in the opposite wireless communication device is changed, the interference wave in the receiving device after the change is changed. It becomes possible to change to a transmission rate suitable for the interference wave power level.

(8) The eighth wireless communication device is the sixth wireless communication device, wherein the transmission unit detects the start of a certain number of interference waves after a certain period of time has elapsed after transmitting the previous test signal. In this case, the test signal is transmitted to the receiving device.
According to this, when the installation location of at least one of the external device and the receiving device is changed, and the interference wave power level of the interference wave in the receiving device is changed, the interference of the interference wave in the changed receiving device is changed. It becomes possible to change to a transmission rate suitable for the wave power level.

(9) When the ninth wireless communication device receives the estimated value of the interference wave power in the receiving device from another wireless communication device in the second wireless communication device, the transmission unit receives the reception Without transmitting the test signal to the device, the transmission rate control unit selects the transmission rate using the estimated value of the interference wave power received from the other wireless communication device.
According to this, it is possible to omit the interference wave power estimation process of the interference wave in the receiving device, reduce the processing load of the wireless communication device, and shorten the selection and setting of the transmission rate. It becomes possible to carry out in time.

(10) In the tenth wireless communication device, in the first wireless communication device, the test signal and the response signal are packets defined in ICMP (Internet Control Message Protocol).
According to this, it is not necessary to install a new function only for transmission rate control in the opposed wireless communication device.

(11) In the eleventh wireless communication device, in the first wireless communication device, the test signal and the response signal are a probe request frame and a probe response frame defined in the IEEE 802.11 standard.
According to this, it is not necessary to install a new function only for transmission rate control in the opposed wireless communication device.

(12) In the twelfth wireless communication device, in the first wireless communication device, a modulation method, a coding rate, or a modulation method and a coding rate corresponding to a transmission rate among the test signal and the response signal. The transmission time of the part to be modulated, encoded, or encoded and modulated corresponds to one period of the interference wave emitted from the external device.
According to this, regardless of the transmission timing of the test signal and the response signal, the number of receptions related to the response signal is almost the same in the same environment.

  INDUSTRIAL APPLICABILITY The present invention can be used for controlling a transmission rate used when a signal is transmitted from a transmission-side wireless communication device to a reception-side wireless communication device in an environment where an external device serving as an interference source exists.

1 wireless communication system 3 wireless station (wireless STA)
5 Wireless access point (wireless AP)
7 Interfering device 31 Antenna 32 Receiving unit 33 Received frame analyzing unit 34 Upper layer processing unit 35 Transmission frame generating unit 36 Transmitting unit 37 RSSI detecting unit 38 Interference wave detecting unit 39 Transmission rate control unit 51 Antenna 52 Receiving unit 53 Received frame analyzing unit 54 Upper layer processing unit 55 Transmission frame generation unit 56 Transmission unit 110, 115 Propagation characteristic table 120 PERrt calculation unit 130 PERdwn calculation unit 140 PERup calculation unit 150 Interference wave power estimation unit 160 PER estimation unit 160A SIR calculation unit 170, 170A Transmission rate Select part

Claims (12)

A transmitting-side wireless communication device that performs wireless communication with a receiving device that is a receiving-side wireless communication device;
A receiving unit for receiving a signal transmitted from the receiving device;
A first detection unit that detects a signal strength of the received desired signal wave when the receiving unit receives the desired signal wave;
A second detection unit that detects an interference wave emitted from an external device and an interference wave power that is a power of the interference wave;
A transmitter that transmits a test signal to the receiving device when the second detector detects an interference wave;
An analysis unit that performs error detection of the response signal when the receiving unit receives a response signal to the test signal from the receiving device;
Based on the detection value of the signal strength of the desired signal wave, the detection value of the interference wave power of the interference wave, the number of transmissions related to the test signal, and the number of receptions related to the response signal without error, a plurality of A transmission rate control unit that selects a transmission rate used for transmitting a signal to the receiving device from among the transmission rates of:
With
The transmission rate control unit
From the number of transmissions related to the test signal and the number of receptions related to the response signal without error, forward communication that is communication from the wireless communication device on the transmission side to the reception device and wireless communication on the transmission side from the reception device An error rate calculation unit that calculates a reception error rate of round-trip communication including return path communication that is communication to a device;
An interference wave that estimates the interference wave power in the receiving device based on the detected value of the signal strength of the desired signal wave, the detected value of the interference wave power, and the calculated value of the reception error rate of the round-trip communication A power estimation unit;
A transmission rate selection unit that selects a transmission rate to be used based on the detected value of the signal strength of the desired signal wave and the estimated value of the interference wave power;
With
When receiving the estimated value of the interference wave power in the receiving device from another wireless communication device,
The transmission unit does not transmit the test signal to the receiving device, and the transmission rate control unit uses the estimated value of the interference wave power received from the other wireless communication device to determine the transmission rate. Select the wireless communication device. The error rate calculation unit includes:
Based on the detected value of the received signal strength of the desired signal wave and the detected value of the interference wave power, the reception error rate of the return communication is calculated,
The error rate calculation unit includes:
Based on the calculation value of the reception error rate of the round-trip communication and the calculation value of the reception error rate of the return communication by the return error rate calculation unit, the reception error rate of the forward communication is calculated,
The interference wave power estimation unit
Wherein the detection value of the received signal strength of the desired signal wave, the a calculated value of the reception error rate of the forward communication, based on the wireless communication device of claim 1, wherein performing the estimation of the interference power in the receiving device. The transmission rate control unit
For each of the plurality of transmission rates, based on the detected value of the signal strength of the desired signal wave and the estimated value of the interference wave power in the receiving device, the forward communication in the case of using the transmission rate An error rate estimation unit for estimating a reception error rate;
The transmission rate selector is
The radio communication apparatus according to claim 2 , wherein a transmission rate with a minimum estimated value of the reception error rate is selected as the transmission rate. The transmission rate selector is
The ratio between the detected value of the received signal strength of the desired signal wave and the estimated value of the interference wave power in the receiving device is calculated, and the transmission rate is selected based on the calculated value of the ratio. 2. The wireless communication device according to 2 . The wireless communication apparatus according to claim 1, wherein the transmission unit transmits the test signal to the receiving device when the interference wave detection unit detects an interference wave for the first time. The transmission unit transmits the test signal to the receiving device when a communication success rate or communication error rate of the round-trip communication does not satisfy a predetermined condition at the transmission rate selected by the transmission rate control unit. The wireless communication device according to claim 5 . And the transmission unit, from the transmission of the previous test signal, after a certain period of time, or, when detecting the start of an interference wave of a certain number of times, to claim 5 for transmitting the test signal to the receiving device The wireless communication device described. The wireless communication device according to claim 1, wherein the test signal and the response signal are packets defined by ICMP (Internet Control Message Protocol). The wireless communication device according to claim 1, wherein the test signal and the response signal are a probe request frame and a probe response frame defined in the IEEE 802.11 standard. Of the portion of the test signal and the response signal that is modulated, encoded, or encoded and modulated at the modulation scheme, coding rate, or modulation scheme and coding rate corresponding to the transmission rate The wireless communication device according to claim 1, wherein a transmission time corresponds to one period of an interference wave emitted from the external device. A transmission rate control method performed in a wireless communication device on a transmission side that performs wireless communication with a reception device that is a wireless communication device on a reception side,
Receiving a signal transmitted from the receiving device;
When the desired signal wave is received, the signal strength of the received desired signal wave is detected,
Detect the interference wave emitted from the external device and the interference wave power that is the power of the interference wave,
When an interference wave is detected, a test signal is transmitted to the receiving device,
When a response signal for the test signal is received from the receiving device, error detection of the response signal is performed,
Based on the detection value of the signal strength of the desired signal wave, the detection value of the interference wave power of the interference wave, the number of transmissions related to the test signal, and the number of receptions related to the response signal without error, a plurality of Select the transmission rate used to transmit the signal to the receiving device from the transmission rate of
In selecting the transmission rate,
From the number of transmissions related to the test signal and the number of receptions related to the response signal without error, forward communication that is communication from the wireless communication device on the transmission side to the reception device and wireless communication on the transmission side from the reception device Calculate the reception error rate of round-trip communication combined with return path communication that is communication to the device,
Based on the detection value of the signal strength of the desired signal wave, the detection value of the interference wave power, and the calculated value of the reception error rate of the round-trip communication, the interference wave power in the receiving device is estimated,
Based on the detected value of the signal strength of the desired signal wave and the estimated value of the interference wave power, the transmission rate to be used is selected,
When the estimated value of the interference wave power in the receiving device is received from another wireless communication device, the interference wave received from the other wireless communication device without transmitting the test signal to the receiving device. A transmission rate control method for selecting the transmission rate using an estimated power value . To the transmitting side wireless communication device that performs wireless communication with the receiving device that is the receiving side wireless communication device,
Receiving a signal transmitted from the receiving device;
When the desired signal wave is received, the signal strength of the received desired signal wave is detected,
Detect the interference wave emitted from the external device and the interference wave power that is the power of the interference wave,
When an interference wave is detected, a test signal is transmitted to the receiving device,
When a response signal for the test signal is received from the receiving device, error detection of the response signal is performed,
Based on the detection value of the signal strength of the desired signal wave, the detection value of the interference wave power of the interference wave, the number of transmissions related to the test signal, and the number of receptions related to the response signal without error, a plurality of Selecting a transmission rate used for signal transmission to the receiving device from among the transmission rates of
To do that ,
In selecting the transmission rate,
From the number of transmissions related to the test signal and the number of receptions related to the response signal without error, forward communication that is communication from the wireless communication device on the transmission side to the reception device and wireless communication on the transmission side from the reception device Calculate the reception error rate of round-trip communication combined with return path communication that is communication to the device,
Based on the detection value of the signal strength of the desired signal wave, the detection value of the interference wave power, and the calculated value of the reception error rate of the round-trip communication, the interference wave power in the receiving device is estimated,
Based on the detected value of the signal strength of the desired signal wave and the estimated value of the interference wave power, the transmission rate to be used is selected,
When the estimated value of the interference wave power in the receiving device is received from another wireless communication device, the interference wave received from the other wireless communication device without transmitting the test signal to the receiving device. The transmission rate is selected using the estimated power value.
Transmission rate control program for.

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