WO2014207998A1

WO2014207998A1 - Radio communication apparatus, radio communication system, and radio communication method

Info

Publication number: WO2014207998A1
Application number: PCT/JP2014/002781
Authority: WO
Inventors: 貴宏足立
Original assignee: 日本電気株式会社
Priority date: 2013-06-26
Filing date: 2014-05-27
Publication date: 2014-12-31
Also published as: JP6119855B2; JPWO2014207998A1

Abstract

Provided are a radio communication apparatus, a radio communication system and a radio communication method whereby when the transmission powers for respective modulation schemes are different from one another, changing modulation schemes can be stabilized. A radio communication apparatus (1) comprises a modulation scheme determination means (12) and a transmission means (14). The modulation scheme determination means (12) determines whether to change modulation schemes, on the basis of the reception power of a radio signal received from another radio communication apparatus that is, for example, a transmission station. The transmission means (14) transmits, to the other radio communication apparatus, determined modulation scheme information indicating a modulation scheme determined by the modulation scheme determination means (12). The modulation scheme determination means (12) is configured such that the determination result is fixed on the basis of a predetermined requirement.

Description

Wireless communication apparatus, wireless communication system, and wireless communication method

The present invention relates to a wireless communication device, a wireless communication system, and a wireless communication method, and more particularly, to a wireless communication device, a wireless communication system, and a wireless communication method that can change a modulation scheme according to received power.

As a technique for performing optimal wireless communication, there is an adaptive modulation system that changes a modulation system in accordance with a propagation path state. In the adaptive modulation scheme, a technique for switching the modulation scheme in accordance with received power has been proposed.

As a technique of the adaptive modulation system, for example, Patent Document 1 discloses a first means for calculating a mean value with a long time constant based on a means for detecting the strength of a received signal and the detected strength of the received signal. When the average calculation means, the second average calculation means for calculating an average value with a short time constant, and the output of the first average calculation means exceeds a first threshold value arbitrarily determined, When the modulation method is shifted to a modulation method having a larger number of modulation values than the currently selected modulation method, and the output of the second average calculation means falls below a second threshold value arbitrarily determined, An adaptive modulation method is disclosed in which a modulation method is shifted to a modulation method having a smaller number of modulation values than the currently selected modulation method.
Further, in Patent Document 2, when changing the modulation scheme in the direction in which the modulation multilevel number increases, the modulation scheme is changed so that the transmission power is first lowered and then the modulation multilevel number is increased. Discloses a technique for suppressing the occurrence of transmission distortion.

JP 2005-94605 A International Publication No. 2012/074041

In the adaptive modulation scheme, a high multi-level modulation scheme has a low tolerance to signal distortion, so that the maximum transmission power is set low so as not to cause a bit error. In other words, the transmission power is set to be different depending on the modulation method.

In such a case, when the maximum transmission power in the modulation scheme with a low multi-level number is set to the modulation scheme with a high multi-level number, the transmission power is the maximum transmission power in the modulation scheme after the change. There is a possibility of exceeding. Under such conditions, a bit error is likely to occur due to distortion in the modulated wave after power amplification. Therefore, as disclosed in Patent Document 2, when changing the modulation method in the direction in which the modulation multilevel number increases, the modulation is performed such that the transmission power is first lowered and then the modulation multilevel number is increased. There is a technology to change the method. The modulation multilevel number is the number of bits per symbol.

Here, in the technique of Patent Document 1, when the average value of the received signal exceeds the first threshold value, the modulation method shifts to a modulation method with a large number of modulation values. In such a case, in order to suppress the occurrence of bit errors as described above, if the modulation scheme is changed so as to reduce the transmission power first and then increase the modulation multilevel number, Since the transmission power decreases after exceeding the threshold value, the reception power decreases. Therefore, there is a possibility that the received power is lower than the first threshold value. In such a case, control is performed so as to return to the modulation scheme with a low multi-level number before the change.

When the modulation scheme is changed to a low multi-level number, the maximum transmission power is controlled to be high, so that the reception power may again exceed the first threshold value. The modulation scheme is changed so that the modulation multi-level number increases. That is, since the modulation scheme is controlled to be repeatedly switched in a short period, there has been a problem that the modulation scheme change is not stable.

An object of the present invention is to solve such problems, and a radio communication device, a radio communication system, and a radio communication apparatus capable of stabilizing a change in modulation scheme when transmission power differs for each modulation scheme To provide a wireless communication method.

A first wireless communication apparatus according to the present invention includes a modulation system determination unit that determines whether to change a modulation system based on reception power of a radio signal received from another wireless communication apparatus, and the modulation system determination Transmission means for transmitting to the other wireless communication apparatus, the modulation scheme determination means, based on a predetermined requirement, the determination modulation scheme information indicating the modulation scheme determined by the means The result is configured to be fixed.

The second wireless communication apparatus according to the present invention is a wireless communication apparatus, and whether or not to change the modulation scheme based on the received power of another wireless communication apparatus that receives a wireless signal transmitted from the wireless communication apparatus. A modulation scheme determining means for determining whether or not, a power control means for controlling the transmission power of the wireless communication apparatus to a predetermined power, and a modulation scheme is changed according to a determination result by the modulation scheme determining means. Modulation means for performing modulation using the above-described modulation system, and the modulation system determination means is configured to fix the determination result based on a predetermined requirement.

The wireless communication system according to the present invention preliminarily determines modulation scheme determining means for determining whether or not to change a modulation scheme based on reception power of a reception-side wireless communication device, and transmission power of a transmission-side wireless communication device. A power control means for controlling the power to the generated power, and a modulation means for changing the modulation method in accordance with a determination result by the modulation method determination means and performing modulation with the changed modulation method, the modulation method determination means comprising: The determination result is fixed based on a predetermined requirement.

The first wireless communication method according to the present invention determines whether to change the modulation method based on the received power of the wireless signal received from another wireless communication device, and based on a predetermined requirement, Processing is performed so that the determination result is fixed, and determination modulation scheme information indicating the determined modulation scheme is transmitted to the other wireless communication apparatus.

In the second wireless communication method according to the present invention, it is determined whether to change the modulation method based on the reception power of the reception-side wireless communication device, and the determination result is fixed based on a predetermined requirement. The transmission power of the wireless communication apparatus on the transmission side is controlled to a predetermined power, the modulation method is changed according to the determination result, and modulation is performed with the changed modulation method.

According to the present invention, it is possible to provide a radio communication device, a radio communication system, and a radio communication method that can stabilize the change of the modulation scheme when the transmission power is different for each modulation scheme.

It is a figure which shows the outline | summary of the radio | wireless communications system concerning embodiment of this invention. 1 is a diagram showing a wireless communication system according to a first exemplary embodiment. 1 is a diagram showing a configuration of a wireless communication apparatus according to a first exemplary embodiment. It is a figure for demonstrating the method to determine a modulation system according to received power. 3 is a flowchart illustrating processing of the wireless communication apparatus functioning as a determination station according to the first embodiment. 3 is a flowchart illustrating processing of the wireless communication apparatus functioning as a transmission station according to the first embodiment. FIG. 3 is a sequence diagram illustrating communication between a wireless communication device that is a transmitting station and a wireless communication device that is a determination station according to the first embodiment; 3 is a diagram illustrating a time chart according to the first exemplary embodiment; FIG. It is a figure which illustrates the time chart concerning a comparative example. 10 is a flowchart illustrating processing of a wireless communication apparatus functioning as a determination station according to the second embodiment. 10 is a flowchart illustrating processing of a wireless communication apparatus functioning as a determination station according to the third embodiment. FIG. 6 is a diagram illustrating a configuration of a wireless communication apparatus according to a fourth embodiment.

[Outline of Embodiment of the Present Invention]
Prior to the description of the embodiment, the outline of the embodiment according to the present invention will be described with reference to FIG. FIG. 1 is a diagram showing an outline of a wireless communication device 1 according to an embodiment of the present invention. As shown in FIG. 1, the wireless communication device 1 includes a modulation scheme determination unit 12 and a transmission unit 14. Note that the wireless communication device 1 may be a determination station (receiving station), for example.

The modulation scheme determination means 12 determines whether or not to change the modulation scheme based on the received power of a radio signal received from another wireless communication device that is a transmitting station, for example. The transmission unit 14 transmits determination modulation scheme information indicating the modulation scheme determined by the modulation scheme determination unit 12 to another wireless communication apparatus. The modulation scheme determination unit 12 is configured so that the determination result is fixed based on a predetermined requirement.

According to the wireless communication apparatus 1 according to the embodiment of the present invention, it is possible to stabilize the change of the modulation scheme when the transmission power is different for each modulation scheme. In addition, even in a wireless communication system including a wireless communication device that is a determination station (receiving station) and a wireless communication device that is a transmission station, when the transmission power differs for each modulation method, the change of the modulation method is stabilized. Can do.
The modulation scheme determination unit 12 is provided in the wireless communication apparatus 1 that is a determination station (reception station), but may be provided in a wireless communication apparatus that is a transmission station. In this case, the change of the modulation scheme can be stabilized even when the transmission power is different for each modulation scheme, even by the wireless communication device that is the transmitting station.

[Embodiment 1]
The first embodiment will be described below with reference to the drawings.
FIG. 2 is a diagram of the wireless communication system 50 according to the first embodiment. The wireless communication system 50 includes a wireless communication device A100A and a wireless communication device B100B. The wireless communication device A100A and the wireless communication device B100B are connected via a wireless line so that wireless communication is possible.

Further, the wireless communication device A 100A and the wireless communication device B 100B are connected to the

data lines

60A and 60B, respectively. The data lines 60A and 60B are lines connected to a network such as a communication carrier or a provider carrier. The wireless communication device A 100A and the wireless communication device B 100B transmit and receive user data such as packets or frames via the

data lines

60A and 60B. Here, the wireless communication system 50 may conform to, for example, Ethernet (registered trademark).

The wireless communication device A100A and the wireless communication device B100B may be digital microwave communication devices, for example. Also, one of the wireless communication device A 100A and the wireless communication device B 100B may be a mobile terminal or a wireless LAN (Local Area Network) device, and the other may be a wireless base station or a wireless LAN base station.

Further, for example, the wireless communication device A100A may function as a transmitting station, and the wireless communication device B100B may function as a determination station (receiving station). That is, the wireless communication device A 100A transmits a wireless signal to the wireless communication device B 100B, and the wireless communication device B 100B as the determination station uses the modulation method based on the received power when the wireless communication device B 100B receives the wireless signal. It may be configured to determine whether or not to change.

The following description is based on the assumption that data is transmitted from the wireless communication device A100A to the wireless communication device B100B. However, a wireless signal may be transmitted from the wireless communication device B100B to the wireless communication device A100A. In this case, the wireless communication device B100B functions as a transmission station, and the wireless communication device A100A functions as a determination station.
Further, the wireless communication device A100A and the wireless communication device B100B may have the same components. Hereinafter, the wireless communication device A 100A and the wireless communication device B 100B will be described on the assumption that they have the same components. Hereinafter, the wireless communication device A 100A and the wireless communication device B 100B are collectively referred to as the wireless communication device 100.

FIG. 3 is a diagram illustrating a configuration of the wireless communication device 100 according to the first embodiment. The wireless communication apparatus 100 includes an antenna 102, a transmission baseband processing unit 112, a modulator 114, a variable attenuator 116, a transmission power control unit 118, an amplifier 120, a reception power detector 132, a demodulator 134, and a reception baseband processing unit 136. And a reception modulation method determination unit 138.

The transmission baseband processing unit 112 receives data (input data) to be transmitted via the data line 60. The input data may be data generated in the wireless communication device 100 or data transmitted from another device connected to the wireless communication device 100 via the data line 60.

Also, the transmission baseband processing unit 112 receives transmission modulation scheme control information from the transmission power control unit 118. In addition, the transmission baseband processing unit 112 receives determination modulation method information from the reception modulation method determination unit 138. Note that the transmission modulation scheme control information is information for designating a modulation scheme when the modulator 114 performs modulation. The determination modulation method information is information indicating the modulation method determined by the reception modulation method determination unit 138. These transmission modulation scheme control information and decision modulation scheme information will be described later.

Further, the transmission baseband processing unit 112 adds (multiplexes) transmission modulation scheme control information and determination modulation scheme information to the packet header or the control information area with respect to the input data, and generates transmission radio frame data. . Further, the transmission baseband processing unit 112 transmits the generated transmission radio frame data to the modulator 114.

The modulator 114 receives transmission radio frame data from the transmission baseband processing unit 112. The modulator 114 reads transmission modulation scheme control information from the received transmission radio frame data. The modulator 114 modulates the transmission radio frame data with the modulation scheme indicated in the read transmission modulation scheme control information, and generates a transmission modulation signal. Further, the modulator 114 transmits the generated transmission modulation signal to the variable attenuator 116.

The variable attenuator 116 changes transmission power according to control by the transmission power control unit 118. Here, the variable attenuator 116 only needs to be able to change the transmission power. For example, the transmission power may be changed by changing the voltage level, or the transmission power may be changed by changing the current value. May be changed.

The transmission power control unit 118 receives, from the reception baseband processing unit 136, the determination modulation method information from the wireless communication device 100 (wireless communication device B 100B) that functions as a determination station. Also, the transmission power control unit 118 controls the variable attenuator 116 so that the transmission power corresponds to the modulation scheme indicated in the determination modulation scheme information. Further, the transmission power control unit 118 generates transmission modulation scheme control information indicating the modulation scheme indicated in the determination modulation scheme information received by itself, and transmits the transmission modulation scheme control information to the transmission baseband processing unit 112. The processing of the transmission power control unit 118 will be described later.

The amplifier 120 may be an amplifier with a fixed amplification factor, for example. The amplifier 120 amplifies the transmission power (for example, voltage level) of the transmission signal attenuated by the variable attenuator 116 with a predetermined amplification factor. The antenna 102 transmits the transmission signal amplified by the amplifier 120 to the opposing wireless communication apparatus 100 as a radio wave via a wireless line.

Further, the antenna 102 receives a radio signal transmitted from the facing radio communication device 100. Here, the received signal is referred to as a received signal.
The reception power detector 132 detects the reception power (reception level) of the reception signal and transmits reception level information indicating the value of the reception power to the reception modulation method determination unit 138. Further, the received power detector 132 transmits the received signal to the demodulator 134.

As will be described later, the demodulator 134 demodulates the received signal using the modulation method indicated in the reception modulation method information received from the reception baseband processing unit 136 to generate received radio frame data. Further, the demodulator 134 transmits the generated reception radio frame data to the reception baseband processing unit 136.

The reception baseband processing unit 136 extracts data (input data) that is a transmission target in the wireless communication device 100 (wireless communication device A 100A) functioning as a transmission station from the received wireless frame data. Further, the reception baseband processing unit 136 transmits the extracted data as output data via the data line 60. The data output destination may be an information processing function included in the wireless communication device 100 or may be another device connected to the wireless communication device 100 via the data line 60.

Also, the reception baseband processing unit 136 extracts reception modulation method information from the reception radio frame data. This reception modulation method information is transmission modulation method control information added in the wireless communication device 100 of the transmission source (wireless communication device A100A functioning as a transmission station). That is, the reception modulation method information is information indicating the modulation method used by the modulator 114 of the wireless communication apparatus 100 that is the transmission source. The reception baseband processing unit 136 transmits the extracted reception modulation scheme information to the demodulator 134 and the reception modulation scheme determination unit 138.

Furthermore, the reception baseband processing unit 136 extracts the determination modulation method information from the reception radio frame data. This determination modulation method information is determination modulation method information added in the wireless communication apparatus 100 (wireless communication apparatus B100B) functioning as a determination station. The reception baseband processing unit 136 transmits the extracted determination modulation scheme information to the transmission power control unit 118.

The demodulator 134 receives the reception modulation method information from the reception baseband processing unit 136. Then, demodulator 134 demodulates the received modulated signal received at the next timing using the received received modulation scheme information. In other words, the demodulator 134 uses the modulation scheme indicated in the reception modulation scheme information included in the received radio frame data obtained by demodulating the reception modulation signal received at the previous timing, and performs reception modulation. Demodulate the signal.

The reception modulation method determination unit 138 corresponds to the modulation method determination unit 12. The reception modulation method determination unit 138 operates, for example, in the wireless communication device 100 (wireless communication device B100B) that functions as a determination station. The reception modulation method determination unit 138 determines the reception modulation method (the modulation method of the received signal) from the reception modulation method information received from the reception baseband processing unit 136. Then, the reception modulation scheme determination unit 138 determines the modulation scheme according to the reception modulation scheme and the reception power indicated in the reception level information from the reception power detector 132, as described with reference to FIG. To do.

FIG. 4 is a diagram for explaining a method of determining a modulation scheme according to received power. FIG. 4 illustrates a determination method when the reception modulation method is QPSK (QuadratureadPhase Keying) and 16QAM (Quadrature Amplitude Modulation). In the modulation scheme “QPSK”, a QPSK lower limit threshold that is a lower limit value of received power in QPSK and a QPSK upper limit threshold that is an upper limit value of received power in QPSK are set in advance. Also, in the modulation scheme “16QAM”, a 16QAM lower limit threshold that is a lower limit value of received power in 16QAM and a 16QAM upper limit threshold that is an upper limit value of received power in 16QAM are set in advance.

That is, when the reception modulation scheme is QPSK, the reception modulation scheme determination unit 138 maintains the modulation scheme when the reception power is equal to or lower than the QPSK upper limit threshold and equal to or higher than the QPSK lower threshold, that is, the modulation scheme is set to QPSK. judge. When the reception modulation scheme is QPSK, the reception modulation scheme determination unit 138 changes the modulation scheme, that is, determines that the modulation scheme is 16QAM when the reception power exceeds the QPSK upper limit threshold.

Similarly, when the reception modulation scheme is 16QAM, the reception modulation scheme determination unit 138 maintains the modulation scheme when the reception power is equal to or lower than the 16QAM upper threshold and equal to or higher than the 16QAM lower threshold, that is, the modulation scheme is set to 16QAM. Is determined. When the reception modulation scheme is 16QAM, the reception modulation scheme determination unit 138 changes the modulation scheme, that is, determines the modulation scheme to be QPSK when the reception power falls below the 16QAM lower limit threshold.

Note that the lower limit threshold of the upper modulation scheme (a modulation scheme having a large modulation multilevel number) and the upper limit threshold of the lower modulation scheme (a modulation scheme having a small modulation multilevel number) have hysteresis characteristics. That is, for example, in the example of FIG. 4, the QPSK upper limit threshold is larger than the 16QAM lower limit threshold. Thus, since each threshold value has a hysteresis characteristic, it is prevented that the change of the modulation system is repeated between QPSK and 16QAM in a short time due to a slight change in the environment.
4 illustrates QPSK and 16QAM as modulation schemes, the modulation scheme according to the present embodiment may be any modulation scheme such as 64QAM, 128QAM, or 256QAM.

For example, when the current reception modulation scheme is QPSK, the reception modulation scheme determination unit 138 (FIG. 3) determines whether or not the reception power is equal to or higher than the QPSK lower limit threshold and is equal to or lower than the QPSK upper limit threshold. To do. In this case, the reception modulation scheme determination unit 138 determines that the modulation scheme is changed from QPSK to 16QAM having a large modulation multilevel number when the reception power exceeds the QPSK upper limit threshold. Similarly, the reception modulation scheme determination unit 138 determines that the modulation scheme is changed to a modulation scheme having a smaller modulation multi-level number than QPSK when the received power becomes less than the QPSK lower limit threshold.

Also, for example, when the current reception modulation scheme is 16QAM, the reception modulation scheme determination unit 138 determines whether the reception power is equal to or greater than the 16QAM lower limit threshold and is equal to or less than the 16QAM upper limit threshold. In this case, the reception modulation scheme determination unit 138 determines that the modulation scheme is changed from 16QAM to QPSK having a small modulation multilevel number when the reception power becomes less than the 16QAM lower limit threshold. Similarly, reception modulation scheme determination section 138 determines that the modulation scheme is changed to a modulation scheme having a larger modulation multi-level number than 16QAM when the received power exceeds the 16QAM upper limit threshold.

Further, the reception modulation scheme determination unit 138 is configured to fix the determination result regardless of the reception power from the determination that the modulation scheme is changed until the determination result fixing period elapses. Here, the determination result fixed period is a predetermined period, and is a period from when it is determined that the modulation scheme is changed until at least the modulation scheme on the receiving side is changed. Specific processing will be described later.

Hereinafter, for processing such as when the modulation scheme is changed in the direction in which the modulation multilevel number increases, the wireless communication device 100 (wireless communication device B100B) that functions as a determination station and the wireless communication device 100 that functions as a transmission station Each of (wireless communication apparatus A100A) will be described.
FIG. 5 is a flowchart showing processing of the wireless communication device 100 (wireless communication device B100B) functioning as a determination station.

The wireless communication device 100 (wireless communication device B100B), which is the determination station, determines whether or not the received power exceeds the upper limit threshold during the determination period (S102). Here, the determination period is a period during which received power is measured in order to determine an optimal modulation scheme under the current environment. Specifically, reception modulation scheme determination section 138 determines whether or not the received power indicated in the reception level information has exceeded the upper limit threshold during the determination period.

More specifically, the reception modulation method determination unit 138 of the wireless communication apparatus B 100B that is the determination station uses the current reception modulation method from the modulation method indicated in the reception modulation method information received from the reception baseband processing unit 136. Judging. The reception modulation method determination unit 138 compares the upper threshold corresponding to the reception modulation method with the reception power indicated in the reception level information during the determination period.

Here, the reception level information may be an average value of received power in a certain period. That is, the reception power detector 132 may transmit the average value of reception power to the reception modulation scheme determination unit 138 as reception level information. Thus, by setting the reception level information as the average value of the reception power, it is possible to remove the noise of the reception power and smooth the reception power indicated in the reception level information.

Further, in this way, when the reception level information is the average value of the reception power, the reception power detector 132 sends the reception level information, which is the average value of the reception power, to the reception modulation scheme determination unit 138 for each fixed period. The reception modulation scheme determination unit 138 may compare the upper limit threshold value with the average value of the reception power indicated in the reception level information for each fixed period. Then, the reception modulation scheme determination unit 138 determines that the reception power has exceeded the upper limit threshold in the determination period when the average value of the reception power indicated in the reception level information exceeds the upper limit threshold, for example, five times. Good.

When it is determined that the received power does not exceed the upper limit threshold in the determination period (NO in S102), the wireless communication device B100B as the determination station does not change the determination modulation scheme (the modulation scheme corresponding to the determination result) The determination modulation scheme information indicating the determination modulation scheme is transmitted to the wireless communication apparatus A100A serving as the transmission station (S104). Specifically, the reception modulation scheme determination unit 138 sets the determination modulation scheme to “QPSK” when the reception modulation scheme is QPSK and the reception power does not exceed the QPSK upper limit threshold during the determination period. To do. The reception modulation scheme determination unit 138 transmits determination modulation scheme information indicating the current determination modulation scheme “QPSK” to the transmission baseband processing unit 112.

The transmission baseband processing unit 112 adds (multiplexes) the decision modulation method information to the packet header or the control information area and generates transmission radio frame data. Then, the wireless communication device B 100B as the determination station modulates the transmission wireless frame data by the modulator 114 to generate transmission modulation information, and transmits the transmission modulation information to the wireless communication device A 100A as the transmission station via a wireless line. As a result, the current determination modulation scheme information is transmitted from the wireless communication device B100B, which is the determination station, to the wireless communication device A100A, which is the transmission station.

On the other hand, when it is determined that the received power has exceeded the upper limit threshold during the determination period (YES in S102), the wireless communication device B100B, which is the determination station, changes the determination modulation scheme to a modulation scheme with a large number of modulation multi-values ( S106). Specifically, the reception modulation scheme determination unit 138 of the wireless communication apparatus B100B, for example, determines the determination modulation scheme when the reception modulation scheme is QPSK and the reception power exceeds the QPSK upper limit threshold during the determination period. Change from “QPSK” to “16QAM”.

Next, the wireless communication device B 100B, which is a determination station, performs determination result fixing processing (S108). Specifically, the reception modulation method determination unit 138 of the wireless communication apparatus B 100B fixes the determination result to the changed modulation method when the modulation method is changed in the direction in which the modulation multilevel number increases. When the modulation scheme is changed in the direction in which the number of modulation multilevels increases, for example, the reception modulation scheme determination unit 138 outputs the output from the reception modulation scheme determination unit 138 to the transmission baseband processing unit 112 as the modulation scheme after the change. The determination result may be fixed by performing a mask process that replaces the modulation method information indicating. For example, the reception modulation scheme determination unit 138 may fix the determination result by interrupting the modulation scheme determination process.

Next, the wireless communication device B 100B as the determination station transmits determination modulation method information indicating the changed modulation method to the wireless communication device A 100A as the transmission station (S110). Specifically, for example, when the determination modulation method is changed from “QPSK” to “16QAM”, the reception modulation method determination unit 138 sends the determination modulation method information indicating “16QAM” to the transmission baseband processing unit 112. Send to.

The transmission baseband processing unit 112 adds (multiplexes) the decision modulation method information to the packet header or the control information area or the like, similarly to the processing of S104, and generates transmission radio frame data. Then, the wireless communication device B 100B as the determination station modulates the transmission wireless frame data by the modulator 114 to generate transmission modulation information, and transmits the transmission modulation information to the wireless communication device A 100A as the transmission station via a wireless line. As a result, the changed determination modulation method information (16QAM) is transmitted from the wireless communication device B100B as the determination station to the wireless communication device A100A as the transmission station.

Next, the wireless communication device B100B, which is the determination station, determines whether or not the determination result fixed period has elapsed (S120). Specifically, the reception modulation method determination unit 138 of the wireless communication apparatus B 100B determines whether or not the determination result fixed period has elapsed after determining that the determination modulation method is to be changed in S106 described above. Here, the determination result fixed period is a period sufficient to change the modulation scheme of the wireless communication apparatus B 100B, which is the determination station, after the modulation scheme is determined to be changed, and can be arbitrarily set.

If it is determined that the determination result fixing period has elapsed (YES in S120), the wireless communication device B100B as the determination station releases the determination result fixing process (S122). Specifically, the reception modulation method determination unit 138 of the wireless communication apparatus B100B cancels the determination result fixing process. For example, the reception modulation scheme determination unit 138 may cancel the determination result fixing process by canceling the mask processing described above. Also, for example, the reception modulation scheme determination unit 138 may cancel the determination result fixing process by canceling the interruption of the modulation scheme determination process and restarting the determination process.

FIG. 6 is a flowchart illustrating processing of the wireless communication device 100 (wireless communication device A 100A) functioning as a transmission station.
The wireless communication device A100A that is the transmitting station receives the determination modulation method information from the wireless communication device B100B that is the determination station (S202). Specifically, the wireless communication device A100A receives the determination modulation scheme information transmitted from the wireless communication device B100B to the wireless communication device A100A in S104 or S110 of FIG. More specifically, the wireless communication device A100A receives the modulation signal including the determination modulation method information transmitted from the wireless communication device B100B as a reception modulation signal. The demodulator 134 of the wireless communication apparatus A 100 </ b> A demodulates the reception modulation signal and transmits the obtained reception radio frame data to the reception baseband processing unit 136. Further, the reception baseband processing unit 136 extracts the determination modulation method information included in the reception radio frame data, and transmits it to the transmission power control unit 118.

The wireless communication device A100A, which is a transmitting station, determines whether or not the determination modulation method has been changed in a direction in which the modulation multilevel number increases (S204). Specifically, the transmission power control unit 118 of the wireless communication apparatus A100A compares the determination modulation scheme indicated in the determination modulation scheme information with the current transmission modulation scheme (transmission signal modulation scheme). Further, the transmission power control unit 118 compares the modulation multi-level numbers in the respective determination modulation schemes. For example, when the current transmission modulation scheme is “QPSK” and the modulation scheme indicated in the determination modulation scheme information is “16QAM”, the modulation multilevel number of “QPSK” is 2 (2 bits per symbol) , “16QAM” has a modulation multilevel number of 4 (4 bits per symbol). Therefore, the transmission power control unit 118 determines that the modulation multilevel number increases.

When it is determined that the modulation multi-level number increases (YES in S204), the wireless communication device A100A as the transmitting station first controls transmission power (S206). Specifically, the transmission power control unit 118 of the wireless communication apparatus A100A controls the variable attenuator 116 so that the transmission power corresponds to the modulation scheme indicated in the determination modulation scheme information. The variable attenuator 116 changes the transmission power according to the control by the transmission power control unit 118. For example, when the modulation scheme indicated in the determination modulation scheme information is “16QAM”, the transmission power control unit 118 sets the variable attenuator 116 so that the transmission power is reduced to a transmission power (for example, 15 dBm) corresponding to “16QAM”. Control.

Next, the wireless communication device A100A that is the transmitting station determines whether or not the control of the transmission power is finished (S208). Specifically, the transmission power control unit 118 of the wireless communication apparatus A 100A determines whether or not the transmission power has decreased to a transmission power corresponding to the modulation scheme indicated in the determination modulation scheme information.
If the transmission power control is not completed, that is, if the transmission power has not decreased to the transmission power corresponding to the modulation scheme indicated in the determination modulation scheme information (NO in S208), the processing in S206 is repeated.

On the other hand, when the transmission power control is completed, that is, when the transmission power is reduced to the transmission power corresponding to the modulation method indicated in the determination modulation method information (NO in S208), the wireless communication device A100A that is the transmission station The transmission power control unit 118 outputs transmission modulation scheme control information indicating the changed modulation scheme (S210). Specifically, for example, when the modulation scheme indicated in the determination modulation scheme information is “16QAM” and the transmission power is reduced to a transmission power (for example, 15 dBm) corresponding to “16QAM”, the transmission power control unit 118 transmits transmission modulation scheme control information indicating the changed modulation scheme (16QAM) to the transmission baseband processing unit 112.

Next, the wireless communication device A100A that is the transmitting station changes the modulation method (S212). Specifically, the transmission baseband processing unit 112 of the wireless communication apparatus A 100A adds (multiplexes) transmission modulation scheme control information indicating the modulation scheme after the change to a packet header or a control information area, and transmits the transmission radio. Generate frame data. The modulator 114 reads transmission modulation scheme control information indicating the changed modulation scheme from the transmission radio frame data, and modulates the transmission radio frame data with the modulation scheme indicated in the read transmission modulation scheme control information. As a result, the modulation scheme (transmission modulation scheme) of the wireless communication apparatus A100A that is the transmitting station is changed.

On the other hand, when it is determined that the modulation multi-level number does not increase (NO in S204), the transmission power control unit 118 of the wireless communication device A100A, which is the transmission station, outputs transmission modulation scheme control information (S220). Specifically, transmission power control section 118 transmits transmission modulation scheme control information indicating the modulation scheme indicated in the determination modulation scheme information to transmission baseband processing section 112.

Next, the wireless communication device A100A, which is a transmitting station, determines whether or not the modulation method has been changed (S222). Specifically, the transmission power control unit 118 compares the determination modulation scheme indicated in the determination modulation scheme information with the current transmission modulation scheme, and determines whether or not they are different. When it is determined that the modulation method is not changed (that is, when the modulation multilevel number does not change) (NO in S222), the process ends.

On the other hand, when it is determined that the modulation method is changed (that is, when the modulation multi-value number decreases) (YES in S222), the wireless communication device A100A as the transmitting station changes the modulation method (S224). Specifically, as in S212, the transmission baseband processing unit 112 of the wireless communication apparatus A100A adds (multiplexes) transmission modulation scheme control information indicating the modulation scheme after the change to a packet header or a control information area. Then, transmission radio frame data is generated. The modulator 114 reads transmission modulation scheme control information indicating the changed modulation scheme from the transmission radio frame data, and modulates the transmission radio frame data with the modulation scheme indicated in the read transmission modulation scheme control information. As a result, the modulation scheme (transmission modulation scheme) of the wireless communication apparatus A100A that is the transmitting station is changed.

Next, the wireless communication device A100A, which is a transmitting station, controls transmission power (S226). Specifically, the transmission power control unit 118 of the wireless communication apparatus A100A controls the variable attenuator 116 so that the transmission power corresponds to the modulation scheme indicated in the determination modulation scheme information. The variable attenuator 116 changes the transmission power according to the control by the transmission power control unit 118. For example, when the modulation scheme indicated in the determination modulation scheme information is “QPSK”, the transmission power control unit 118 sets the variable attenuator 116 so as to increase the transmission power corresponding to “QPSK” (for example, 20 dBm). Control.

Next, the wireless communication device A100A that is the transmitting station determines whether or not the control of the transmission power is finished (S228). Specifically, the transmission power control unit 118 of the wireless communication apparatus A 100A determines whether or not the transmission power has increased to a transmission power corresponding to the modulation scheme indicated in the determination modulation scheme information.
If the transmission power control is not completed, that is, if the transmission power has not increased to the transmission power corresponding to the modulation scheme indicated in the determination modulation scheme information (NO in S228), the processing in S226 is repeated. On the other hand, when the control of the transmission power is completed, that is, when the transmission power is increased to the transmission power corresponding to the modulation scheme indicated in the determination modulation scheme information (YES in S228), the processing is terminated.

5 and 6, the determination result is fixed until the determination result fixing period elapses in the wireless communication device B100B as the determination station. Therefore, even when the reception power is reduced in radio communication apparatus B100B, which is the determination station, because radio communication apparatus A100A, which is the transmission station, has reduced transmission power, the modulation scheme is not changed. Therefore, it is possible to stabilize the change of the modulation method.

Hereinafter, the overall operation of the wireless communication system 50 will be further described.
FIG. 7 is a sequence diagram showing communication between the wireless communication device A100A as a transmitting station and the wireless communication device B100B as a determination station. FIG. 8 is a diagram illustrating a time chart according to the present embodiment.

In FIG. 8, the transmission power of the wireless communication device A100A, which is a transmission station, is indicated by a solid line. Also, the received power of the wireless communication device B100B, which is the determination station, is indicated by a broken line. 7 and 8 illustrate a case where the modulation scheme is changed from QPSK to 16QAM. Further, the transmission power of the radio communication apparatus A100A when the modulation scheme is QPSK is 20 dBm, and the transmission power of the radio communication apparatus A100A when the modulation scheme is 16QAM is 15 dBm. In addition, the QPSK upper limit threshold (QPSK → 16QAM switching threshold) of the received power in the radio communication apparatus B100B serving as a determination station is set to −65 dBm, and the 16QAM lower limit threshold (16QAM → QPSK switching threshold) is set to −75 dBm.

The wireless communication device A100A as a transmitting station transmits a wireless signal to the wireless communication device B100B as a determination station during the determination period T1 (S302-1 to S302-k) (k is an arbitrary natural number). At this time, the transmission modulation scheme is QPSK. During the determination period T1, the wireless communication device B 100B, which is the determination station, receives a radio signal from the wireless communication device A 100A, which is the transmission station, and compares the received power with the QPSK upper limit threshold value to determine the modulation scheme.

Then, when the received power exceeds −65 dBm which is the QPSK upper limit threshold during the determination period T1, the wireless communication device B100B as the determination station changes the modulation scheme from “QPSK” to “16QAM” at time t1 ( S304). This processing corresponds to the processing in S102 and S106 in FIG.
Next, the wireless communication device B 100B, which is a determination station, performs determination result fixing processing (S306). This process corresponds to the process of S108 in FIG. As a result, as shown in FIG. 8, during the determination result fixed period T2, the determination modulation scheme in the determination station is fixed to 16QAM.

Next, at time t2, the wireless communication device B 100B as the determination station transmits determination modulation scheme information (16QAM) to the wireless communication device A 100A as the transmission station (S308). This process corresponds to the process of S110 in FIG. When wireless communication apparatus A100A, which is a transmitting station, receives the determination modulation scheme information, it starts control of transmission power (S310). This processing corresponds to the processing of S202 to S206 in FIG. Since the determination modulation scheme is changed from “QPSK” to “16QAM”, that is, the modulation scheme is changed in the direction in which the modulation multi-value number increases, the radio communication apparatus A100A as the transmitting station first reduces the transmission power. To control. As a result, as shown in FIG. 8, the received power in the wireless communication device B100B, which is the determination station, decreases from time t2.

While the transmission power is being controlled, the wireless communication device A100A that is a transmission station transmits a wireless signal to the wireless communication device B100B that is a determination station (S312). The transmission modulation scheme at this time is QPSK since it is before the modulation scheme is changed. Therefore, the reception modulation method in radio communication apparatus B100B, which is the determination station, is also QPSK. Therefore, even after time t2, radio communication apparatus B100B, which is the determination station, compares the QPSK upper limit threshold value with the received power. In this case, as shown in FIG. 8, the received power may fall below the QPSK upper limit threshold, but the determination modulation scheme of the determination station is maintained at 16 QAM because of the determination result fixing process. That is, the wireless communication apparatus B100B that is the determination station does not transmit the determination modulation scheme information indicating QPSK to the wireless communication apparatus A100A that is the transmitting station during the determination result fixed period T2.

Next, when the transmission power is reduced to the transmission power (15 dBm) corresponding to 16QAM at time t3, the wireless communication device A100A as the transmission station changes the transmission modulation method from QPSK to 16QAM (S314). This process corresponds to the process of S212 in FIG. Then, at time t4, the wireless communication device A100A that is the transmitting station transmits a wireless signal to the wireless communication device B100B that is the determining station (S316). As a result, the wireless communication device B100B, which is the determination station, changes the reception modulation method from QPSK to 16QAM.

Furthermore, when the determination result fixing period has elapsed at time t5, the wireless communication device B100B, which is the determination station, cancels the determination result fixing process (S320). This process corresponds to the process of S122 of FIG. Accordingly, since the reception modulation scheme is 16QAM, the wireless communication device B100B serving as a determination station determines the modulation scheme by comparing the received power with the 16QAM lower limit threshold and the 16QAM upper limit threshold.

[Comparative example]
Hereinafter, a comparative example in which the determination result fixing process is not performed will be described.
FIG. 9 is a diagram illustrating a time chart according to the comparative example. In FIG. 9, as in FIG. 8, the transmission power of the transmission station is indicated by a solid line, and the reception power of the determination station is indicated by a broken line. In addition, FIG. 9 illustrates a case where the modulation scheme is changed from QPSK to 16 QAM, as in FIG. Similarly to FIG. 8, the transmission power of the transmission station when the modulation scheme is QPSK is 20 dBm, and the transmission power of the transmission station when the modulation scheme is 16 QAM is 15 dBm. Similarly to FIG. 8, the QPSK upper limit threshold (QPSK → 16QAM switching threshold) of received power at the determination station is set to −65 dBm, and the 16QAM lower limit threshold (16QAM → QPSK switching threshold) is set to −75 dBm.

During the determination period T1, the determination station receives a radio signal from the transmission station, and determines the modulation scheme by comparing the received power with the QPSK upper limit threshold. Then, when the received power exceeds −65 dBm, which is the QPSK upper limit threshold, during the determination period T1, as shown in the determination station determination modulation scheme in FIG. 9, the determination station changes the modulation scheme from “QPSK” at time t11. Change to “16QAM”.

When the determination station transmits the changed determination modulation method information (16QAM) to the transmission station, the transmission station starts control of transmission power from time t12 and performs control so as to decrease the transmission power. As a result, as shown in FIG. 9, the reception power at the determination station decreases from time t12. At time t13, when the transmission power decreases to the transmission power (15 dBm) corresponding to 16QAM, the transmission station changes the transmission modulation system from QPSK to 16QAM as shown in the transmission station transmission modulation system of FIG. Then, at time t15, the determination station changes the reception modulation method from QPSK to 16QAM.

On the other hand, the transmission station transmits a radio signal to the determination station while controlling the transmission power. The transmission modulation scheme at this time is QPSK since it is before the modulation scheme is changed. Therefore, the reception modulation method in the determination station is also QPSK. Therefore, even after time t12, the determination station compares the QPSK upper limit threshold value with the received power. In this case, as shown in FIG. 9, when the state where the received power is below the QPSK upper limit threshold continues during the determination period T1, as shown in the determination station determination modulation scheme of FIG. The decision modulation method is changed from 16QAM to QPSK. Note that time t15 is later than time t14. Thus, even if the determination station changes the modulation scheme from QPSK to 16QAM, the transmission station lowers the transmission power, so that the modulation scheme is returned to QPSK.

Also, at time t14, the determination station returns the modulation scheme to QPSK and transmits the determination modulation scheme information to the transmission station. In this case, since the modulation scheme is changed in the direction in which the number of modulation multilevels decreases, the transmitting station first changes the transmission modulation scheme from 16QAM to QPSK at time t16, and then increases the transmission power to 20 dBm at time t17. Control to raise. This process corresponds to the processes of S224 and S226 in FIG. Further, as the transmission modulation scheme is changed to QPSK, the reception modulation scheme of the determination station is changed to QPSK at time t18.

Then, when the transmission power of the transmission station rises to 20 dBm and the reception power of the determination station again exceeds the QPSK upper limit threshold, the modulation scheme such as QPSK → 16QAM → QPSK as described above is performed from time t21 to t24. Changes (switches) are frequently repeated. That is, the change (switching) of the modulation method becomes unstable.

On the other hand, in the first embodiment described above, by performing the determination result fixing process, the switching of the modulation method is not repeated frequently as in the comparative example, and the change of the modulation method is stabilized. Furthermore, since the change of the modulation method is stabilized, it is possible to prevent the radio band from fluctuating unnecessarily.

[Embodiment 2]
Next, a second embodiment will be described. In the second embodiment, instead of determining whether or not the determination result fixed period has elapsed, it is determined whether or not the received power has decreased by a predetermined received power drop value. Different from the embodiment. The received power drop value will be described later.

FIG. 10 is a flowchart illustrating processing of the wireless communication device 100 (wireless communication device B100B) functioning as a determination station according to the second embodiment.
The wireless communication device 100 (wireless communication device B 100B), which is the determination station, determines whether or not the received power exceeds the upper limit threshold during the determination period, similar to the process of S102 of FIG. 5 (S402). Specifically, reception modulation scheme determination section 138 determines whether or not the received power indicated in the reception level information has exceeded the upper limit threshold during the determination period.

When it is determined that the received power does not exceed the upper limit threshold during the determination period (NO in S402), the wireless communication device B100B that is the determination station does not change the determination modulation method, similarly to the process of S104 in FIG. The determination modulation method information indicating the current determination modulation method is transmitted to the wireless communication apparatus A100A that is the transmitting station (S404). Specifically, the reception modulation scheme determination unit 138 sets the determination modulation scheme to “QPSK” when the reception modulation scheme is QPSK and the reception power does not exceed the QPSK upper limit threshold during the determination period. To do. The reception modulation scheme determination unit 138 transmits determination modulation scheme information indicating the current determination modulation scheme “QPSK” to the transmission baseband processing unit 112.

On the other hand, if it is determined that the received power has exceeded the upper limit threshold during the determination period (YES in S402), the wireless communication device B100B, which is the determination station, sets the determination modulation method to the modulation-multiple as in the process of S106 in FIG. The modulation method is changed to a modulation method with a large value (S406). Specifically, the reception modulation scheme determination unit 138 of the wireless communication apparatus B100B, for example, determines the determination modulation scheme when the reception modulation scheme is QPSK and the reception power exceeds the QPSK upper limit threshold during the determination period. Change from “QPSK” to “16QAM”.

Next, the wireless communication device B 100B, which is a determination station, performs determination result fixing processing in the same manner as the processing of S108 in FIG. 5 (S408). Specifically, the reception modulation method determination unit 138 of the wireless communication apparatus B 100B fixes the determination result to the changed modulation method when the modulation method is changed in the direction in which the modulation multilevel number increases. At this time, for example, the reception modulation scheme determination unit 138 outputs the output from the reception modulation scheme determination unit 138 to the transmission baseband processing unit 112 as the modulation scheme indicating the modulation scheme after the change, similarly to the processing of S108 in FIG. The determination result may be fixed by performing mask processing to be replaced with information. For example, the reception modulation scheme determination unit 138 may fix the determination result by interrupting the modulation scheme determination process.

Next, similarly to the processing of S110 of FIG. 5, the wireless communication device B 100B that is the determination station transmits determination modulation method information indicating the changed modulation method to the wireless communication device A 100A that is the transmission station ( S410). Specifically, for example, when the determination modulation method is changed from “QPSK” to “16QAM”, the reception modulation method determination unit 138 sends the determination modulation method information indicating “16QAM” to the transmission baseband processing unit 112. Send to.

The transmission baseband processing unit 112 adds (multiplexes) the determination modulation method information to the packet header or the control information area or the like, similarly to the processing of S404, and generates transmission radio frame data. Then, the wireless communication device B 100B as the determination station modulates the transmission wireless frame data by the modulator 114 to generate transmission modulation information, and transmits the transmission modulation information to the wireless communication device A 100A as the transmission station via a wireless line. As a result, the changed determination modulation method information (16QAM) is transmitted from the wireless communication device B100B as the determination station to the wireless communication device A100A as the transmission station.

Next, the wireless communication device B 100B, which is the determination station, determines whether or not the received power has decreased by the received power drop value (S420). Specifically, the reception modulation scheme determination unit 138 of the wireless communication apparatus B100B determines whether or not the reception power has decreased from the reception power when it is determined to change the determination modulation scheme to the reception power that is decreased by the reception power drop value. Determine whether. Here, the “reception power drop value” means that the transmission station changes when the modulation scheme is changed from a modulation scheme having a small modulation multilevel number (for example, QPSK) to a modulation scheme having a large modulation multilevel number (for example, 16QAM). This is a value indicating the difference in received power, indicating how much the received power of the wireless communication device B 100B, which is the determination station, decreases as the transmission power of a certain wireless communication device A 100A decreases.

For example, when the modulation scheme is changed from QPSK to 16QAM, in the example of FIG. 8, when the modulation scheme is QPSK, the transmission power of the wireless communication device A100A is 20 dBm, and the reception power of the wireless communication device B100B at this time Is −64 dBm. Further, it is assumed that the transmission power of radio communication apparatus A100A when the modulation scheme is 16QAM is 15 dBm, and the reception power of radio communication apparatus B100B at this time is −69 dBm. In this case, when the modulation method is changed from QPSK to 16QAM, the reception power of the wireless communication device B 100B as the determination station decreases as the transmission power of the wireless communication device A 100A as the transmission station decreases. The received power drops by 5 dBm (−64 dBm − (− 69 dBm)). That is, the received power drop value when the QPSK is changed to 16QAM is 5 dBm.

When the modulation scheme is changed from a modulation scheme with a small modulation multilevel number to a modulation scheme with a large modulation multilevel number (for example, QPSK → 16QAM, 16QAM → 64QAM, 64QAM → 256QAM) Each received power drop value is stored. Note that the received power drop value may be finely adjusted as appropriate according to the superiority or inferiority of the environment of wireless communication.

If it is determined that the received power has decreased by the received power drop value (YES in S420), the wireless communication device B100B, which is the determination station, cancels the determination result fixing process, similarly to the process in S122 of FIG. 5 (S422). ). Specifically, the reception modulation method determination unit 138 of the wireless communication apparatus B100B cancels the determination result fixing process. For example, the reception modulation scheme determination unit 138 may cancel the determination result fixing process by canceling the mask processing described above. Also, for example, the reception modulation scheme determination unit 138 may cancel the determination result fixing process by canceling the interruption of the modulation scheme determination process and restarting the determination process.

When the received power is reduced by the received power drop value, the modulation scheme is changed in the radio communication apparatus A100A as the transmitting station, and soon thereafter, the reception modulation scheme in the radio communication apparatus B100B as the determination station is also changed. .
In Embodiment 1, if the modulation scheme of the transmitting station is not changed during the determination result fixed period due to some cause of the wireless communication apparatus A100A that is the transmitting station, the determination is made before the modulation scheme of the determining station is changed. The result fixing process may be canceled. However, in the second embodiment, it is possible to fix the determination result more reliably until the reception modulation scheme is changed in the direction in which the modulation multilevel number increases. Furthermore, in Embodiment 2, the determination result fixing process is canceled soon after the modulation scheme is changed in radio communication apparatus A100A, which is the transmitting station, so the period of the determination result fixing process can be further shortened. It is.

[Embodiment 3]
Next, Embodiment 3 will be described. The third embodiment is different from the other embodiments in that a threshold value switching process is performed instead of the determination result fixing process. The threshold switching process will be described later.

FIG. 11 is a flowchart illustrating processing of the wireless communication device 100 (wireless communication device B100B) functioning as a determination station according to the third embodiment.
The wireless communication device 100 (wireless communication device B 100B), which is the determination station, determines whether or not the received power exceeds the upper limit threshold during the determination period, similarly to the process of S102 of FIG. 5 (S502). Specifically, reception modulation scheme determination section 138 determines whether or not the received power indicated in the reception level information has exceeded the upper limit threshold during the determination period.

When it is determined that the received power does not exceed the upper limit threshold in the determination period (NO in S502), the wireless communication device B100B that is the determination station does not change the determination modulation method, similarly to the process of S104 in FIG. The determination modulation method information indicating the current determination modulation method is transmitted to the wireless communication apparatus A100A that is the transmitting station (S504). Specifically, the reception modulation scheme determination unit 138 sets the determination modulation scheme to “QPSK” when the reception modulation scheme is QPSK and the reception power does not exceed the QPSK upper limit threshold during the determination period. To do. The reception modulation scheme determination unit 138 transmits determination modulation scheme information indicating the current determination modulation scheme “QPSK” to the transmission baseband processing unit 112.

On the other hand, when it is determined that the received power has exceeded the upper limit threshold in the determination period (YES in S502), the wireless communication device B100B, which is the determination station, sets the determination modulation method to the modulation-multiple as in the process of S106 in FIG. The modulation method is changed to a modulation method with a large number of values (S506). Specifically, the reception modulation scheme determination unit 138 of the wireless communication apparatus B100B, for example, determines the determination modulation scheme when the reception modulation scheme is QPSK and the reception power exceeds the QPSK upper limit threshold during the determination period. Change from “QPSK” to “16QAM”.

Next, the wireless communication device B 100B, which is a determination station, performs threshold switching processing (S508). Specifically, the reception modulation scheme determination unit 138 of the wireless communication apparatus B 100B switches the threshold used for the modulation scheme determination to a threshold corresponding to the modulation scheme after the determination.

As described with reference to FIG. 4, in another embodiment, a threshold corresponding to a reception modulation method is used for determination of a modulation method. For example, when the reception modulation scheme is QPSK, even if the determination modulation scheme is 16QAM, the reception power is compared with the QPSK upper limit threshold and the QPSK lower limit threshold.

On the other hand, in Embodiment 3, for example, when the determination modulation scheme is changed from QPSK to 16QAM, reception modulation scheme determination section 138 performs modulation after determination even if the reception modulation scheme remains QPSK. The threshold value is switched to 16QAM, which is a method. That is, in this case, the reception modulation scheme determination unit 138 compares the received power with the 16QAM upper limit threshold and the 16QAM lower limit threshold.

For example, with reference to the example of FIG. 8, when the received modulation scheme determination unit 138 changes the determination modulation scheme from QPSK to 16QAM at time t1, the threshold used for determining the modulation scheme is changed to a threshold corresponding to 16QAM. Switch. That is, thereafter, reception modulation scheme determination section 138 compares the received power with the 16QAM upper limit threshold and the 16QAM lower limit threshold. For example, in FIG. 8, the received power decreases between time t2 and t3, but the received power after the decrease is larger than the 16QAM lower limit threshold. Therefore, in this case, the reception modulation scheme determination unit 138 determines that the modulation scheme is “16QAM”.

Next, similarly to the processing of S110 of FIG. 5, the wireless communication device B 100B that is the determination station transmits determination modulation method information indicating the changed modulation method to the wireless communication device A 100A that is the transmission station ( S510). Specifically, for example, when the determination modulation method is changed from “QPSK” to “16QAM”, the reception modulation method determination unit 138 sends the determination modulation method information indicating “16QAM” to the transmission baseband processing unit 112. Send to.

Next, the wireless communication device B 100B, which is a determination station, determines whether or not the determination modulation scheme matches the reception modulation scheme (S520). Specifically, the reception modulation scheme determination unit 138 of the wireless communication apparatus B 100B matches the modulation scheme indicated in the determination modulation scheme information with the modulation scheme indicated in the reception modulation scheme information included in the reception radio frame data. Determine whether or not.

When it is determined that the determination modulation method and the reception modulation method match (YES in S520), the wireless communication device B100B that is the determination station releases the threshold value switching process (S522). Specifically, the reception modulation method determination unit 138 of the wireless communication apparatus B 100B cancels the threshold value switching process. That is, reception modulation scheme determination section 138 returns the threshold used for modulation scheme determination from the threshold corresponding to the modulation scheme after determination to the threshold corresponding to the reception modulation scheme.

In the example of FIG. 8, at time t4, the reception modulation method is changed from QPSK to 16QAM. Therefore, the reception modulation scheme determination unit 138 determines that the determination modulation scheme and the reception modulation scheme match at time t4, and cancels the threshold value switching process. That is, at this time, the reception modulation scheme determination unit 138 switches to a threshold value corresponding to the reception modulation scheme (16QAM). However, since the decision modulation method and the reception modulation method are identical (16QAM), the threshold value itself is not changed.

As described above, also in the third embodiment, after the radio communication apparatus B100B that is the determination station determines that the modulation scheme is changed from QPSK to 16QAM, the reception modulation scheme of the radio communication apparatus B100B that is the determination station is changed from QPSK to 16QAM. The determination result is fixed to 16QAM until the time is changed to. That is, also in the third embodiment, the determination result is from when it is determined that the wireless communication device B100B as the determination station changes the modulation method to when the reception modulation method of the wireless communication device B100B as the determination station is changed. Is supposed to be fixed.

In Embodiment 1, the determination result fixing process is not canceled unless the determination result fixing period elapses. However, in the third embodiment, the threshold switching process is canceled when the reception modulation scheme is changed in radio communication apparatus B100B, which is the determination station, so that the period during which the determination result is fixed can be further shortened. It is.

[Embodiment 4]
Next, a fourth embodiment will be described. The fourth embodiment is different from the other embodiments in that the wireless communication apparatus that is a transmitting station determines the modulation scheme.
FIG. 12 is a diagram of a configuration of the wireless communication apparatus 200 according to the fourth embodiment. The wireless communication apparatus 200 includes an antenna 102, a transmission baseband processing unit 112, a modulator 114, a variable attenuator 116, a transmission power control unit 118, an amplifier 120, a reception power detector 232, a demodulator 134, and a reception baseband processing unit 136. And a reception modulation method determination unit 238. Note that components that are substantially the same as those in the first embodiment are given the same reference numerals, and descriptions thereof are omitted.
In the fourth embodiment, the transmitting station is wireless communication apparatus A200A, and the receiving station is wireless communication apparatus B200B.

The reception power detector 232 of the radio communication apparatus B 200B, which is a reception station, detects the reception power (reception level) of the reception signal and transmits reception level information indicating the value of the reception power instead of the reception modulation method determination unit 138. Transmit to the baseband processing unit 112. Further, the reception power detector 232 transmits the reception signal to the demodulator 134.
The transmission baseband processing unit 112 adds (multiplexes) reception level information to input data to generate transmission radio frame data. Further, the wireless communication device B 200B as the receiving station modulates the transmission wireless frame data by the modulator 114 to generate a transmission modulated signal, and transmits the transmission modulated signal to the wireless communication device A 200A as the transmitting station.

Radio communication apparatus A200A as a transmitting station receives a modulated signal including reception level information from radio communication apparatus B200B as a receiving station. Then, wireless communication apparatus A200A, which is a transmitting station, demodulates the modulated signal (received modulated signal) to generate received wireless frame data.
The reception modulation method determination unit 238 of the wireless communication apparatus A 200A serving as the transmission station extracts reception level information indicating the reception power of the wireless communication apparatus B 200B serving as the reception station from the reception baseband processing unit 136. Furthermore, the reception modulation method determination unit 238 determines the modulation method according to the reception modulation method and the received power indicated in the reception level information from the wireless communication device B 200B that is the receiving station. The determination method is the same as that of the reception modulation method determination unit 138.

In the fourth embodiment, the process shown in FIG. 5 is executed by radio communication apparatus A 200A that is a transmitting station. In this case, a process of receiving reception level information from the wireless communication apparatus B 200B, which is a receiving station, is added before S102 of FIG. 5, and the processes of S104 and S110 are omitted.

[Modification]
As described above, a plurality of embodiments have been described separately, but these embodiments can be combined with each other. For example, in the fourth embodiment, the process of the second embodiment (the process shown in FIG. 10) or the process of the third embodiment (the process shown in FIG. 11) may be applied.
In the above-described embodiment, the received power is detected using the received power detector, but the present invention is not limited to such a configuration. For example, the received power may be detected based on CNR (carrier to noise ratio) information.

Moreover, in the flowchart mentioned above, the order of a process (step) can be changed suitably. One or more of the plurality of processes (steps) may be omitted. For example, the process of S108 in FIG. 5 may be performed after the process of S110. The same applies to FIGS. 10 and 11.
In the above-described embodiment, the determination result fixing process (threshold switching process) is performed when it is determined that the modulation method is changed so that the modulation multi-level number increases. Absent. Any wireless communication system in which transmission power varies depending on the modulation scheme, and any system that can stably change the modulation scheme by performing determination result fixing processing (threshold switching processing) may be used.

In the above-described embodiments, the present invention has been described as a hardware configuration, but the present invention is not limited to this. The present invention can also realize processing of each circuit in the wireless communication device by causing a CPU (Central Processing Unit) to execute a computer program.

In the above example, the program can be stored using various types of non-transitory computer-readable media and supplied to a computer. Non-transitory computer readable media include various types of tangible storage media (tangible storage medium). Examples of non-transitory computer-readable media include magnetic recording media (eg flexible disks, magnetic tapes, hard disk drives), magneto-optical recording media (eg magneto-optical discs), CD-ROMs (Read Only Memory), CD-Rs, CD-R / W, semiconductor memory (for example, mask ROM, PROM (Programmable ROM), EPROM (Erasable ROM), flash ROM, RAM (Random Access Memory)) are included. The program may also be supplied to the computer by various types of temporary computer-readable media. Examples of transitory computer readable media include electrical signals, optical signals, and electromagnetic waves. The temporary computer-readable medium can supply the program to the computer via a wired communication path such as an electric wire and an optical fiber, or a wireless communication path.

The present invention has been described above with reference to the embodiment, but the present invention is not limited to the above. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the invention.

This application claims priority based on Japanese Patent Application No. 2013-134068 filed on June 26, 2013, the entire disclosure of which is incorporated herein.

DESCRIPTION OF SYMBOLS 1 Wireless communication apparatus 12 Modulation system determination means 14 Transmission means 50 Wireless communication system 60 Data line 100 Wireless communication apparatus 102 Antenna 112 Transmission baseband processing part 114 Modulator 116 Variable attenuator 118 Transmission power control part 120 Amplifier 132 Reception power detector 134 Demodulator 136 Reception Baseband Processing Unit 138 Reception Modulation Method Determination Unit 200 Radio Communication Device 232 Reception Power Detector 238 Reception Modulation Method Determination Unit

Claims

Modulation scheme determining means for determining whether to change the modulation scheme based on the received power of a radio signal received from another radio communication device;
Transmission means for transmitting to the other wireless communication device, determination modulation method information indicating the modulation method determined by the modulation method determination unit;
The modulation system determination means is a wireless communication apparatus configured to fix a determination result based on a predetermined requirement.
The determination method of the modulation method is fixed so that the determination result is fixed at least until the modulation method in the wireless communication apparatus is changed after determining that the modulation method is changed so that the modulation multi-value number increases. The wireless communication apparatus according to claim 1, which is configured.
The wireless communication apparatus according to claim 1, wherein the modulation method determination unit fixes the determination result until a predetermined period elapses after it is determined that the modulation method is changed.
The wireless communication apparatus according to claim 1 or 2, wherein the modulation method determination unit fixes the determination result until it is determined that the modulation method is changed and the received power becomes a value corresponding to the modulation method after the change.
The modulation scheme determining means determines whether to change the modulation scheme based on the received power and the first threshold corresponding to the modulation scheme of the received signal;
The modulation scheme determination unit changes the modulation scheme based on received power and a second threshold value corresponding to the modulation scheme corresponding to the determination result by the modulation scheme determination unit after determining to change the modulation scheme. The wireless communication apparatus according to claim 1, wherein the wireless communication apparatus determines whether or not.
A wireless communication device,
A modulation method determination means for determining whether to change the modulation method based on the received power of another wireless communication device that receives a wireless signal transmitted from the wireless communication device;
Power control means for controlling the transmission power of the wireless communication apparatus to a predetermined power;
A modulation unit that changes a modulation method according to a determination result by the modulation method determination unit, and performs modulation with the changed modulation method; and
The modulation system determination means is a wireless communication apparatus configured to fix a determination result based on a predetermined requirement.
The power control means determines the transmission power of the wireless communication apparatus in advance before changing the modulation method when the modulation method determination means determines that the modulation method is changed so as to increase the number of modulation multivalues. Control to lower to the specified power,
The modulation means changes the modulation method after the transmission power is controlled by the power control means, performs modulation with the changed modulation method,
The determination result is fixed at least during the period from when it is determined that the modulation method is changed so that the modulation multi-value number increases, until the modulation method in the other wireless communication device is changed. The wireless communication apparatus according to claim 6.
A modulation scheme determination means for determining whether to change the modulation scheme based on the received power of the wireless communication device on the receiving side;
Power control means for controlling the transmission power of the wireless communication device on the transmission side to a predetermined power;
A modulation unit that changes a modulation method according to a determination result by the modulation method determination unit, and performs modulation with the changed modulation method; and
The modulation system determination means is a wireless communication system configured to fix a determination result based on a predetermined requirement.
When the modulation scheme determining unit determines that the modulation scheme is to be changed so that the number of modulation multilevels is increased, the power control unit transmits the transmission power of the transmitting-side radio communication apparatus before changing the modulation scheme. Is controlled to lower to a predetermined power,
The modulation means changes the modulation method after the transmission power is controlled by the power control means, performs modulation with the changed modulation method,
The determination result is fixed at least during the period from the determination that the modulation method is changed so that the modulation multi-value number is increased until the modulation method in the receiving-side radio communication device is changed. The wireless communication system according to claim 8, wherein the wireless communication system is configured as described above.
The wireless communication system according to claim 8 or 9, wherein the modulation method determination unit fixes a determination result until a predetermined period elapses after it is determined that the modulation method is changed.
10. The wireless communication system according to claim 8, wherein the modulation scheme determination unit fixes the determination result until it is determined that the modulation scheme is changed until the received power reaches a value corresponding to the modulation scheme after the change.
The modulation scheme determining means determines whether to change the modulation scheme based on the received power and the first threshold corresponding to the modulation scheme of the received signal;
The modulation scheme determination unit changes the modulation scheme based on received power and a second threshold value corresponding to the modulation scheme corresponding to the determination result by the modulation scheme determination unit after determining to change the modulation scheme. The wireless communication system according to claim 8 or 9, wherein it is determined whether or not.
The modulation method determining means is provided in the receiving-side wireless communication device,
The wireless communication system according to any one of claims 8 to 12, wherein the power control unit and the modulation unit are provided in the wireless communication device on the transmission side.
Determine whether to change the modulation scheme based on the received power of the radio signal received from another radio communication device,
Based on predetermined requirements, process so that the determination result is fixed,
A wireless communication method for transmitting determination modulation method information indicating the determined modulation method to the other wireless communication device.
Determine whether to change the modulation method based on the received power of the receiving wireless communication device,
Based on predetermined requirements, process so that the determination result is fixed,
Control the transmission power of the wireless communication device on the transmission side to a predetermined power,
A wireless communication method for changing a modulation method according to the result of the determination and performing modulation using the changed modulation method.