JP2015139190A - Radio communication device, radio communication system, and radio communication method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radio communication device, a radio communication system, and a radio communication method, capable of appropriately changing a modulation system depending on communication quality.SOLUTION: A radio communication device 1 comprises: a transmission power information acquisition unit 12 for acquiring, from another radio communication device, transmission power information showing a transmission power of the another radio communication device; a communication quality information acquisition unit 14 for acquiring communication quality information showing communication quality from a radio signal (a reception signal) received from the another radio communication device; a modulation system determination unit 16 for determining whether or not to change a modulation system, on the basis of a result of comparing the communication quality information with a changeover threshold set corresponding to the transmission power information; and a transmission unit 18 for transmitting determined modulation system information showing a modulation system determined by the modulation system determination unit 16 to the another radio communication device.

Description

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

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

  As a technique of an adaptive modulation system, for example, Patent Document 1 discloses a reception level measurement unit that measures a signal level of a signal and outputs a reception level, and a reception modulation system that outputs modulation system control information based on reception data. Based on the reception level, the extraction means, the designation information output means for outputting the modulation scheme designation information and the transmission power designation information associated with the modulation scheme, and the modulation scheme designation information and the transmission power designation information are transmitted to the transmission apparatus. A technique related to a communication apparatus including a transmission unit is disclosed. In Patent Document 1, the communication apparatus switches the modulation method by comparing a switching threshold determined for each modulation method with a reception level.

  In addition, in a wireless transmission device using an adaptive modulation scheme, a technique is known in which a line state (communication quality) is determined using a CNR (Carrier to Noise Ratio) to perform adaptive modulation. In this technique, a CNR is used as communication quality information, and a modulation scheme is selected by comparing the CNR with a determination threshold.

  On the other hand, when determining the channel state (communication quality) using only the CNR, when there is distortion in the received signal, it may not be possible to switch to a modulation scheme with a large modulation multi-level number as described below. There is a problem. In general, when the transmission output is increased, the waveform of the transmitted signal is distorted above a certain output power.

  In a modulation scheme with a small modulation multi-level number such as QPSK (Quadrature Phase Shift Keying), a modulation with a large CNR (required CNR) required for a predetermined BER (Bit Error Ratio) is large. Small compared to the method. For this reason, in a modulation scheme such as QPSK, even if a certain degree of CNR degradation occurs, the channel quality is not affected. Therefore, it is possible to increase the system gain (difference between the transmission power of the transmitting station and the specified reception level at the receiving station) by increasing the transmission power.

  If high transmission power is set in order to increase the system gain during transmission using a modulation scheme with a small number of modulation multi-values, the CNR deteriorates (saturates) due to waveform distortion during transmission. As a result, even when the radio propagation path state is good and the CNR deterioration due to the radio propagation path state hardly occurs during radio wave propagation, the CNR of the received signal has a modulation multilevel number. May fall below the required CNR for large modulation schemes. In such a case, for example, the CNR is improved by reducing the transmission power, thereby enabling communication using a modulation scheme having a large number of modulation multilevels. However, since the CNR of the current received signal is deteriorated, the modulation scheme cannot be changed to a modulation scheme having a large modulation multilevel number.

  Patent Document 2 discloses a technique for solving such a problem. Specifically, Patent Document 2 discloses a CNR modulation scheme determination unit that outputs a modulation scheme determined based on CNR information indicating a CNR of a received signal and a predetermined CNR threshold value as CNR determination information, and an RSL of the received signal. RSL modulation scheme determination means for outputting a modulation scheme determined based on RSL information indicating (Received Signal Level) and a predetermined RSL threshold as RSL determination information, and a reception modulation scheme indicating the modulation scheme of the received signal A technique relating to an apparatus including a composite modulation scheme determining unit that determines a modulation scheme used for modulation by a transmission source of a received signal based on information, CNR determination information, and RSL determination information is disclosed. Here, the CNR threshold is information indicating a minimum CNR allowed in each modulation scheme. The RSL threshold is information indicating the minimum RSL allowed in each modulation scheme. In Patent Document 2, when the modulation multilevel number of the modulation scheme indicated by the CNR determination information is less than the modulation multilevel number of the modulation scheme indicated by the RSL determination information, the modulation scheme indicated by the RSL determination information is the received signal. Is determined as a modulation scheme used for modulation.

  That is, in Patent Document 2, when the modulation multilevel number of the modulation scheme indicated by the RSL determination information is larger than the modulation multilevel number of the modulation scheme indicated by the CNR determination information, the modulation scheme having a large modulation multilevel number is set. It is possible to switch. In other words, as a result of increasing the transmission power of the received signal, the waveform of the radio signal is distorted, and even when the switching condition cannot be satisfied due to CNR degradation, it is possible to switch to a modulation scheme with a large modulation multi-level number. It becomes. In other words, even when the CNR is reduced due to transmission wave distortion caused by setting high transmission power, the modulation scheme can be determined by using RSL determination information that is less influenced by distortion. . That is, in Patent Document 2, it is possible to change to a more suitable modulation method even when the CNR of the received signal deteriorates due to distortion.

International Publication No. 2011-034193 International Publication No. 2011/0778097

  On the other hand, in wireless communication, even if the transmission power is the same, the reception level (RSL) may increase due to in-band interference that causes some interference component to enter the band of the local station. In other words, the reception level may increase because the radio propagation path state has deteriorated. In such a case, the modulation scheme should not be changed to a modulation scheme with a large modulation multilevel number. However, in Patent Literature 1 and Patent Literature 2, when the reception level (RSL) is equal to or higher than a threshold value determined for each modulation scheme, the modulation scheme is changed to a modulation scheme having a large modulation multi-level number. In this case, the CNR of the received signal may not satisfy the required CNR in the changed modulation scheme.

  In this way, there is a possibility that a bit error may occur due to the modulation scheme being changed to a modulation scheme having a large modulation multi-level number, despite the deterioration of the radio propagation path state. In addition, there is a possibility that the modulation method may change, such as changing to the original modulation method immediately after the modulation method is changed to a modulation method having a large multi-level number.

  On the other hand, when the received signal is distorted due to the transmission side as described above, the wireless channel state is not deteriorated. In such a case, the CNR is deteriorated (saturated), but communication can be performed appropriately even if the modulation method is changed to a modulation method with a large modulation multi-level number. Therefore, in such a case, it is desirable to change the modulation system to a modulation system with a large modulation multi-level number.

  An object of the present invention is to solve such a problem, and provides a wireless communication device, a wireless communication system, and a wireless communication method capable of appropriately changing a modulation scheme according to communication quality There is to do.

  A first wireless communication apparatus according to the present invention includes, from another wireless communication apparatus, transmission power information acquisition means for acquiring transmission power information indicating the transmission power of the other wireless communication apparatus, and the other wireless communication apparatus. Modulation based on a communication quality information acquisition means for acquiring communication quality information indicating communication quality from a received radio signal, and a comparison result between a switching threshold set corresponding to the transmission power information and the communication quality information A modulation method determination unit that determines whether or not to change the method, and a transmission unit that transmits determination modulation method information indicating the modulation method determined by the modulation method determination unit to the other wireless communication device. Have.

  A second wireless communication apparatus according to the present invention uses transmission power information transmitting means for transmitting transmission power information indicating the transmission power of the wireless communication apparatus to another wireless communication apparatus, and the transmission power information. Receiving means for receiving modulation method determination information indicating a modulation method determined by the other wireless communication apparatus; and modulation means for changing a modulation method according to the modulation method determination information and performing modulation with the changed modulation method And have.

  A third wireless communication apparatus according to the present invention corresponds to communication quality information acquisition means for acquiring communication quality information indicating communication quality from another wireless communication apparatus, and transmission power information indicating transmission power of the wireless communication apparatus. Based on a comparison result between the switching threshold value set in the above and the communication quality information, a modulation method determination unit that determines whether or not to change the modulation method, and a modulation method according to the determination by the modulation method determination unit And modulation means for performing modulation using the changed modulation method.

  A fourth wireless communication apparatus according to the present invention includes: communication quality information acquisition means for acquiring communication quality information indicating communication quality from a radio signal received from another wireless communication apparatus; Transmitting means for transmitting to the wireless communication device.

  A wireless communication system according to the present invention shows communication quality information acquisition means for acquiring communication quality information indicating communication quality from a wireless signal received by a receiving-side wireless communication device, and indicates transmission power of the transmitting-side wireless communication device. Based on the comparison result between the switching threshold set corresponding to the transmission power information and the communication quality information, the modulation method determining means for determining whether or not to change the modulation method, and the determination by the modulation method determining means And a modulation unit that changes the modulation method in response to the modulation and changes the modulation method.

  A first wireless communication method according to the present invention obtains transmission power information indicating transmission power of a transmission-side wireless communication apparatus, and indicates communication quality indicating communication quality from a wireless signal received from the transmission-side wireless communication apparatus. Information is obtained, and based on the comparison result between the switching threshold value set corresponding to the transmission power information and the communication quality information, it is determined whether or not to change the modulation method, and the determined modulation method is The determination modulation method information shown is transmitted to the wireless communication device on the transmission side.

  According to a second wireless communication method of the present invention, transmission power information indicating transmission power of a transmission-side wireless communication device is transmitted to a reception-side wireless communication device, and the reception-side information is transmitted using the transmission power information. Modulation scheme determination information indicating the modulation scheme determined by the wireless communication apparatus is received, the modulation scheme is changed according to the modulation scheme determination information, and modulation is performed with the changed modulation scheme.

  A third wireless communication method according to the present invention obtains communication quality information indicating communication quality from a receiving-side wireless communication apparatus, and is set in correspondence with transmission power information indicating transmission power of the transmitting-side wireless communication apparatus. Based on the comparison result between the switched threshold value and the communication quality information, it is determined whether or not to change the modulation method, the modulation method is changed according to the determination, and modulation is performed with the changed modulation method.

  According to a fourth wireless communication method of the present invention, communication quality information indicating communication quality is acquired from a wireless signal received from another wireless communication device, and the communication quality information is transmitted to the other wireless communication device. Send.

  ADVANTAGE OF THE INVENTION According to this invention, the radio | wireless communication apparatus, the radio | wireless communications system, and the radio | wireless communication method which can change a modulation system appropriately according to communication quality can be provided.

It is a figure which shows the outline | summary of the radio | wireless communication apparatus concerning this Embodiment. 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 which shows the relationship between the transmission power of a transmission station, and a switching threshold value. 3 is a flowchart illustrating processing of the wireless communication apparatus functioning as a receiving 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 receiving station according to the first exemplary embodiment; It is a figure for demonstrating operation | movement when the distortion of the radio signal resulting from the transmission side has not generate | occur | produced. It is a figure for demonstrating operation | movement when the distortion of the radio signal resulting from the transmission side has generate | occur | produced. FIG. 3 is a diagram illustrating a configuration of a wireless communication apparatus according to a second embodiment.

(Outline of this embodiment)
Prior to the description of the embodiment, an outline of the present embodiment will be described with reference to FIG. FIG. 1 is a diagram illustrating an outline of a wireless communication device 1 according to the present embodiment. As shown in FIG. 1, the wireless communication device 1 includes a transmission power information acquisition unit 12 (transmission power information acquisition unit), a communication quality information acquisition unit 14 (communication quality information acquisition unit), and a modulation scheme determination unit 16 (modulation). A system determination unit) and a transmission unit 18 (transmission unit). The wireless communication device 1 may be a receiving station, for example. The wireless communication device 1 communicates with other wireless communication devices (for example, transmission stations).

  The transmission power information acquisition unit 12 acquires transmission power information indicating the transmission power of the other wireless communication device from another wireless communication device. The communication quality information acquisition unit 14 acquires communication quality information indicating communication quality from a radio signal (received signal) received from another radio communication device. The modulation scheme determination unit 16 determines whether or not to change the modulation scheme based on the comparison result between the switching threshold set corresponding to the transmission power information and the communication quality information. The transmission unit 18 transmits determination modulation method information indicating the modulation method determined by the modulation method determination unit 16 to another wireless communication device. The communication quality information is preferably information indicating a ratio between a carrier wave or a radio signal and noise, for example, CNR or SNR (Signal to Noise ratio). Not limited.

  According to the wireless communication device 1 according to the present embodiment, the modulation scheme can be appropriately changed according to the communication quality. In addition, even in a wireless communication system including a wireless communication apparatus that is a receiving station and a wireless communication apparatus that is a transmitting station, changes in modulation scheme can be stabilized when transmission power differs for each modulation scheme. Although the modulation scheme determination unit 16 is provided in the wireless communication apparatus 1 that is a receiving station, it may be provided in the wireless communication apparatus that is a transmitting station. In this case, the modulation scheme can be appropriately changed according to the communication quality also by the radio communication apparatus which is a 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 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. Further, one of the wireless communication device A 100A and the wireless communication device B 100B may be a mobile terminal or a wireless local area network (LAN) 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 receiving station (determination station). That is, the wireless communication device A100A may transmit a wireless signal to the wireless communication device B100B, and the wireless communication device B100B may receive the wireless signal. And you may comprise so that radio | wireless communication apparatus B100B as a receiving station may determine whether the modulation system is changed from the received radio signal.

  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 transmitting station, and the wireless communication device A100A functions as a receiving 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 of 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 demodulator 134, a reception baseband processing unit 136, and a reception modulation scheme 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 and transmission power 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 transmission power information is information indicating the transmission power of the wireless communication device 100 (wireless communication device A100A) that functions as a transmission station. The determination modulation method information is information indicating the modulation method determined by the reception modulation method determination unit 138. The transmission modulation scheme control information, transmission power 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 the transmission power according to the 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 scheme information from the wireless communication device 100 (wireless communication device B 100B) that functions as a reception station (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.

  Also, the transmission power control unit 118 generates transmission power information indicating the transmission power controlled by the transmission power control unit 118 itself. Then, the transmission power control unit 118 transmits the generated transmission power information to the transmission baseband processing unit 112.

  The amplifier 120 may be an amplifier having 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 radio signal is referred to as a received signal.

  As will be described later, the demodulator 134 demodulates the received signal using the modulation scheme indicated in the reception modulation scheme 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.

  Further, the demodulator 134 generates CNR information from the received signal. Further, the demodulator 134 transmits the generated CNR information to the reception modulation scheme determination unit 138. Here, the CNR information is information related to the CNR of the received signal. The CNR information is communication quality information indicating communication quality. For example, the demodulator 134 may generate CNR information by detecting a modulation error ratio (MER) indicating how much the amplitude and phase of the received signal deviate from the ideal point on the constellation. .

  The reception baseband processing unit 136 extracts data (input data) that is a transmission target in the wireless communication device 100 (wireless communication device A100A) 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 scheme 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.

  Also, the reception baseband processing unit 136 extracts transmission power information from the received radio frame data. This transmission power information is transmission power information added in the wireless communication apparatus 100 (wireless communication apparatus A100A) functioning as a transmission station. The reception baseband processing unit 136 transmits the extracted transmission power information to the reception modulation scheme determination unit 138.

  Further, the reception baseband processing unit 136 extracts determination modulation scheme 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 receiving station (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 16. The reception modulation method determination unit 138 operates, for example, in the wireless communication device 100 (wireless communication device B100B) that functions as a reception station (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. Also, the reception modulation scheme determination unit 138 receives transmission power information from the reception baseband processing unit 136. Also, the reception modulation scheme determination unit 138 receives CNR information from the demodulator 134. Then, the reception modulation scheme determination unit 138 receives the reception modulation scheme information, the CNR information, and the transmission power indicated in the transmission power information from the reception baseband processing unit 136 (that is, the wireless communication device A100A functioning as a transmission station). The modulation scheme is determined according to the above. Specifically, the reception modulation scheme determination unit 138 performs modulation based on the comparison result between the switching threshold set corresponding to the transmission power information and the CNR information (communication quality information) as described below. Determine whether to change the method.

Then, reception modulation scheme determination section 138 transmits determination modulation scheme information indicating the determination result to transmission baseband processing section 112. That is, when it is determined that the modulation scheme is to be changed, the reception modulation scheme determination unit 138 transmits determination modulation scheme information indicating the modulation scheme after the change to the transmission baseband processing unit 112. On the other hand, when it is determined that the modulation scheme is not to be changed, the reception modulation scheme determination unit 138 transmits the reception modulation scheme indicated by the reception modulation scheme information, that is, the determination modulation scheme information indicating the current modulation scheme, to the transmission baseband processing section 112. Send to. Note that the above-described determination method can be applied when the modulation scheme is changed so that the modulation multi-level number becomes large.
When changing the modulation scheme so that the number of modulation multilevels becomes smaller, for example, the reception modulation scheme determination unit 138 compares the switching threshold provided for each modulation scheme with the CNR (or RSL), and determines the CNR. When (or RSL) is less than the switching threshold value, it may be determined that the modulation scheme is changed so that the modulation multi-level number becomes small.

  FIG. 4 is a diagram showing the relationship between the transmission power P of the transmitting station and the switching threshold Th. The reception modulation method determination unit 138 stores a switching threshold table in which the transmission power P and the switching threshold Th are associated with each other as illustrated in FIG. When the CNR indicated by the CNR information is equal to or greater than the switching threshold Th, the reception modulation scheme determination unit 138 determines to change to a modulation scheme with a large modulation multilevel number.

  Note that in a modulation scheme with a small number of modulation multilevels, the required CNR may be small because the distance between signal points on the constellation is large. In other words, in a modulation method with a large number of modulation multilevels, the required CNR increases because the distance between signal points on the constellation is small. Therefore, when the modulation scheme is changed to a modulation scheme having a large modulation multi-level number, the CNR is a switching threshold value (necessary for a modulation scheme having a large modulation multi-level number after the change). If it does not exceed the required CNR), a communication error such as a bit error may occur.

  Here, in the example of FIG. 4, for example, a switching threshold value indicating whether or not the modulation scheme is changed from QPSK (Quadrature Phase Shift Keying) to 16QAM (Quadrature Amplitude Modulation) is shown. In this case, the reception modulation scheme determining unit 138 determines to change the modulation scheme from QPSK to 16QAM when the CNR indicated by the CNR information is equal to or greater than the switching threshold Th. The switching threshold table illustrated in FIG. 4 is used when determining whether or not to change the modulation scheme from QPSK to 16QAM. For example, the modulation threshold table is further changed from 16QAM to 64QAM. Similarly, a switching threshold value table for determining whether or not may be separately provided.

  Here, the switching threshold Th is set to be different for each transmission power P. In other words, the switching threshold Th is set corresponding to the transmission power information. As illustrated in FIG. 4, for example, when the transmission power is P1 [dBm], the switching threshold is Th1 [dB]. For example, when the transmission power is P2 [dBm], the switching threshold is Th2 [dB]. Here, for example, P2 is configured to be greater than P1, and Th1 is configured to be greater than Th2. That is, the switching threshold Th is set to be smaller as the transmission power indicated by the transmission power information is larger. With this configuration, as will be described later, when the RSL is high and the CNR is low, distortion of the radio signal due to the transmission side has occurred, or in-band interference has occurred. It is possible to determine whether or not to change the modulation method depending on whether or not.

  When the modulation scheme indicated by the reception modulation scheme information is QPSK and the transmission power indicated by the transmission power information is P1, the reception modulation scheme determination unit 138 selects the switching threshold Th1 corresponding to the transmission power P1. At this time, the reception modulation scheme determination unit 138 compares the CNR indicated by the CNR information with the switching threshold Th1. Then, when the CNR is equal to or greater than the switching threshold Th1, the reception modulation scheme determination unit 138 determines to change the modulation scheme from QPSK to 16QAM having a large modulation multilevel number.

  Similarly, reception modulation scheme determination section 138 selects switching threshold Th2 corresponding to transmission power P2 when the modulation scheme indicated by reception modulation scheme information is QPSK and the transmission power indicated by transmission power information is P2. . At this time, the reception modulation scheme determination unit 138 compares the CNR indicated by the CNR information with the switching threshold Th2. Then, when the CNR is equal to or higher than the switching threshold Th2, the reception modulation scheme determination unit 138 determines to change the modulation scheme from QPSK to 16QAM having a large modulation multilevel number.

Hereinafter, each of the wireless communication device 100 (wireless communication device B100B) functioning as a receiving station and the wireless communication device 100 (wireless communication device A100A) functioning as a transmitting station will be described.
FIG. 5 is a flowchart showing processing of the wireless communication device 100 (wireless communication device B100B) functioning as a receiving station.

  The wireless communication device 100 (wireless communication device B100B) as a receiving station receives transmission power information from the wireless communication device 100 (wireless communication device A100A) as a transmitting station (S102). Specifically, the wireless communication device B 100B receives the transmission power information transmitted from the wireless communication device A 100A to the wireless communication device B 100B in S202 of FIG. More specifically, the wireless communication device B100B receives a modulated signal including transmission power information transmitted from the wireless communication device A100A as a reception signal. The demodulator 134 of the radio communication apparatus B 100B demodulates the received signal and transmits the received radio frame data obtained to the reception baseband processing unit 136. Further, the reception baseband processing unit 136 extracts transmission power information included in the reception radio frame data, and transmits the extracted transmission power information to the reception modulation scheme determination unit 138.

  The wireless communication device 100 (wireless communication device B100B), which is a receiving station, detects the CNR from the received signal (S104). Specifically, the demodulator 134 of the wireless communication apparatus B 100B detects CNR from the received signal and generates (acquires) CNR information. Further, the demodulator 134 transmits the generated CNR information to the reception modulation scheme determination unit 138.

  The wireless communication device 100 (wireless communication device B100B), which is a receiving station, selects a switching threshold corresponding to the transmission power information (S106). Specifically, the reception modulation scheme determination unit 138 of the wireless communication apparatus B 100B uses the switching threshold table to select the switching threshold Th corresponding to the transmission power indicated in the transmission power information. In the example of FIG. 4, for example, when the transmission power information indicates P1, the reception modulation method determination unit 138 selects the switching threshold Th1. In the example of FIG. 4, when the transmission power information indicates transmission power between P1 and P2, the reception modulation scheme determination unit 138 selects a value between Th1 and Th2 as a switching threshold Th by interpolation. Also good.

  The wireless communication device 100 (wireless communication device B 100B), which is a receiving station, determines whether or not the CNR detected in S104 is equal to or greater than the switching threshold Th selected in S106 (S108). Specifically, the reception modulation scheme determination unit 138 compares the CNR indicated in the CNR information with the selected switching threshold Th, and determines whether or not the CNR is greater than or equal to the selected switching threshold Th. to decide.

  Here, the CNR information may be an average value of CNR in a certain period. That is, the demodulator 134 may transmit the average value of CNR to the reception modulation scheme determination unit 138 as CNR information. In this way, by setting the CNR information to the average value of the CNR, it is possible to remove the CNR fluctuation and smooth the CNR indicated in the CNR information.

  Further, in this way, when the CNR information is the average value of the CNR, the demodulator 134 transmits the CNR information, which is the average value of the CNR, to the reception modulation scheme determination unit 138 for each predetermined period, and receives modulation. The method determination unit 138 may compare the selected switching threshold Th with the average value of CNR indicated in the CNR information for each fixed period. Then, for example, when the average value of the CNR indicated in the CNR information is equal to or greater than the switching threshold Th, the reception modulation scheme determination unit 138 may determine that the CNR is equal to or greater than the switching threshold Th.

  When it is determined that the CNR is not equal to or greater than the switching threshold Th (NO in S108), the wireless communication device B100B as the receiving station does not change the determination modulation scheme (the modulation scheme corresponding to the determination result), and the current determination modulation scheme Is transmitted to the wireless communication apparatus A100A, which is a transmitting station (S110). Specifically, the reception modulation scheme determination unit 138 keeps the determination modulation scheme as “QPSK” when the reception modulation scheme is QPSK and the CNR is not equal to or greater than the switching threshold Th. At this time, reception modulation scheme determination section 138 transmits determination modulation scheme information indicating the current determination modulation scheme “QPSK” to transmission baseband processing section 112.

  The transmission baseband processing unit 112 adds (multiplexes) the determination modulation method information to a packet header or a control information area, and generates transmission radio frame data. Then, the wireless communication device B 100B as the receiving 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 transmitting station via a wireless line. As a result, the current determination modulation scheme information is transmitted from the wireless communication device B 100B as the receiving station to the wireless communication device A 100A as the transmitting station.

  On the other hand, when it is determined that the CNR is greater than or equal to the switching threshold Th (YES in S108), the wireless communication device B100B that is the receiving station changes the determination modulation scheme to a modulation scheme with a large number of modulation multilevels (S120). . Specifically, the reception modulation scheme determination unit 138 of the wireless communication apparatus B 100B changes the determination modulation scheme from “QPSK” to “16QAM, for example, when the reception modulation scheme is QPSK and the CNR is greater than or equal to the switching threshold Th. Change to

  Next, the wireless communication device B 100B as the receiving station transmits determination modulation method information indicating the changed modulation method to the wireless communication device A 100A as the transmitting station (S122). 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.

  Similar to the processing of S110, the transmission baseband processing unit 112 adds (multiplexes) the determination 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 receiving 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 transmitting 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 receiving station to the wireless communication device A100A as the transmitting station.

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 as a transmitting station transmits transmission power information to the wireless communication device B100B as a receiving station (S202). Specifically, the transmission power control unit 118 generates transmission power information indicating the transmission power controlled by itself, and transmits the generated transmission power information to the transmission baseband processing unit 112.

  The transmission baseband processing unit 112 adds (multiplexes) transmission power information to a packet header or a control information area and generates transmission radio frame data. Then, the wireless communication device A100A that is a transmitting station modulates this transmission wireless frame data by the modulator 114 to generate transmission modulation information, and transmits it to the wireless communication device B100B that is a receiving station via a wireless line. As a result, the transmission power information is transmitted from the wireless communication device A100A as the transmitting station to the wireless communication device B100B as the receiving 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 receiving station (S204). 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 S110 or S122 of FIG. More specifically, the wireless communication device A100A receives the modulated signal including the determination modulation method information transmitted from the wireless communication device B100B as a received signal. The demodulator 134 of the wireless communication apparatus A 100 </ b> A demodulates the received signal and transmits the received wireless frame data obtained 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 as the transmitting station determines whether or not the determination modulation scheme has been changed (S206). 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). If it is determined that the determination modulation method has not been changed (NO in S206), the process ends.

  On the other hand, when it is determined that the determination modulation method has been changed (YES in S206), the wireless communication device A100A that is the transmitting station changes the modulation method (S208). 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.

Next, 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 receiving station. FIG. 7 shows an example in which the modulation scheme is changed from QPSK to 16QAM.
The wireless communication device A100A as a transmitting station transmits a wireless signal including transmission power information to the wireless communication device B100B as a receiving station (S302). This process corresponds to S202 of FIG. At this time, the transmission modulation scheme is QPSK.

  Next, the wireless communication device B 100B, which is the receiving station, determines the modulation scheme by comparing the switching threshold set corresponding to the transmission power information with the CNR information (S304). This processing corresponds to the processing of S104 to S108 in FIG. Then, the wireless communication device B 100B, which is the receiving station, determines that the CNR information is greater than or equal to the switching threshold, and thus determines to change the modulation method (S306). This processing corresponds to the processing of S108 YES and S120 in FIG. At this time, the wireless communication apparatus B 100B as the receiving station changes the determination modulation method from “QPSK” to “16QAM”.

  Next, the wireless communication device B 100B as the receiving station transmits determination modulation scheme information indicating “16QAM” to the wireless communication device A 100A as the transmitting station (S308). This process corresponds to the process of S122 of FIG. When wireless communication apparatus A100A, which is a transmitting station, receives the determination modulation method information, it changes the transmission modulation method from QPSK to 16QAM (S310). This process corresponds to S204 to S208 in FIG.

Next, a specific operation according to the first embodiment will be described.
FIG. 8 is a diagram for explaining an operation when radio signal distortion caused by the transmission side does not occur. FIG. 8 is a diagram illustrating an RSL-CNR characteristic curve when the transmission power is P1. Here, (a) shows an RSL-CNR characteristic curve when in-band interference does not occur, and (b) shows an RSL-CNR characteristic curve when in-band interference occurs. The transmission power P1 is smaller than the transmission power at which distortion occurs in the waveform of the transmitted signal. Therefore, when the transmission power is P1, no distortion occurs in the waveform of the transmitted signal. Further, the transmission power is P1 in both cases where the modulation scheme is QPSK and 16QAM. Therefore, the RSL-CNR characteristic curve is the same between QPSK and 16QAM.

  FIG. 8 shows an example in which the modulation scheme is changed from QPSK to 16QAM. Further, FIG. 8 shows an RSL-CNR characteristic curve showing the relationship between RSL and CNR when the horizontal axis is RSL [dBm] and the vertical axis is CNR [dB]. As shown in FIG. 8, when the RSL increases, the CNR also increases, but the CNR saturates at some point.

  At this time, in the example of FIG. 8A, the wireless communication device A100A as the transmitting station transmits transmission power information indicating the transmission power P1 to the wireless communication device B100B as the receiving station. Radio communication apparatus B100B, which is a receiving station, extracts transmission power information indicating transmission power P1. Then, as described above, the reception modulation scheme determination unit 138 selects the switching threshold Th1 corresponding to the transmission power P1. The reception modulation scheme determination unit 138 determines to change the modulation scheme from QPSK to 16QAM when the current CNR is equal to or greater than the switching threshold Th1. Here, the switching threshold Th1 is a CNR (required CNR) necessary for maintaining communication quality when the modulation scheme is changed to 16QAM. As shown in FIG. 8A, when no in-band interference occurs, the RSL when the CNR is Th1 [dB] is SL1 [dBm].

  On the other hand, as shown in FIG. 8B, even if the transmission power is the same P1 as in the example of FIG. 8A, the RSL increases when in-band interference occurs. Also at this time, the wireless communication device A100A that is the transmitting station transmits transmission power information indicating the transmission power P1 to the wireless communication device B100B that is the receiving station. Radio communication apparatus B100B, which is a receiving station, extracts transmission power information indicating transmission power P1. Then, as described above, the reception modulation scheme determination unit 138 selects the switching threshold Th1 corresponding to the transmission power P1. The reception modulation method determination unit 138 selects a switching threshold Th1 corresponding to the transmission power P1. The reception modulation scheme determination unit 138 changes the modulation scheme from QPSK to 16QAM when the current CNR is equal to or greater than the switching threshold Th1.

  Here, as shown in FIG. 8B, when in-band interference occurs, the RSL when the CNR is Th1 [dB] is SL2 [dBm]. SL2 is larger than SL1. Here, as in Patent Literature 1 and Patent Literature 2, it is assumed that the modulation scheme is changed depending on whether or not the RSL is high. At this time, assuming that the switching threshold is SL1, in the example of FIG. 8A, in SL1, the required CNR (switching threshold Th1) necessary for 16QAM is satisfied. On the other hand, in the example of FIG. 8B, SL1 does not satisfy the required CNR (switching threshold Th1) necessary for 16QAM. Therefore, at this time, there is a possibility that a bit error may occur or the modulation system may change. Therefore, stable communication cannot be realized.

  On the other hand, in the present embodiment, as shown in FIG. 8B, when the in-band interference occurs, the CNR when the RSL is SL1 [dBm] is smaller than the switching threshold Th1. Therefore, in this case, in this embodiment, reception modulation scheme determination section 138 does not determine that the modulation scheme is changed from QPSK to 16QAM. Therefore, in the present embodiment, when the CNR is lower than the required CNR required for 16QAM (switching threshold Th1), the modulation scheme is not changed to a modulation scheme with a large modulation multi-level number, so that occurrence of bit errors and modulation are performed. It is possible to suppress the occurrence of the flutter of the method change. Therefore, stable communication can be realized.

  FIG. 9 is a diagram for explaining an operation when radio signal distortion caused by the transmission side occurs. FIG. 9 is a diagram illustrating an RSL-CNR characteristic curve when the transmission power is P2. Here, (a) shows an RSL-CNR characteristic curve when in-band interference does not occur, and (b) shows an RSL-CNR characteristic curve when in-band interference occurs. The arrows shown in FIG. 9 will be described later. The transmission power P2 is larger than the transmission power that is a threshold value as to whether or not distortion occurs in the waveform of the transmitted signal. Therefore, when the transmission power is P2, the waveform of the transmitted signal is distorted. The transmission power when the modulation scheme is QPSK is P2, but the transmission power when the modulation scheme is changed to 16QAM is P1.

  FIG. 9 shows an example in which the modulation scheme is changed from QPSK to 16QAM. FIG. 9 also shows an RSL-CNR characteristic curve showing the relationship between RSL and CNR when the horizontal axis is RSL [dBm] and the vertical axis is CNR [dB]. As shown in FIG. 9, when the RSL increases, the CNR also increases, but the CNR saturates at some point.

  Here, in QPSK, which is the current modulation scheme, the transmission power is P2, so that the waveform of the transmitted signal is distorted. Therefore, in the RSL-CNR characteristic curve in the case of QPSK, the CNR is saturated at a position lower than the switching threshold Th1. On the other hand, after the modulation scheme is changed from QPSK to 16QAM, the transmission power is changed to P1. Therefore, the RSL-CNR characteristic curve in the case of 16QAM is the same as the example of FIG.

  At this time, in the example of FIG. 9A, the wireless communication device A100A as a transmitting station transmits transmission power information indicating the transmission power P2 to the wireless communication device B100B as a receiving station. Radio communication apparatus B100B, which is a receiving station, extracts transmission power information indicating transmission power P2. Then, as described above, the reception modulation scheme determination unit 138 selects the switching threshold Th2 corresponding to the transmission power P2. The reception modulation scheme determination unit 138 determines to change the modulation scheme from QPSK to 16QAM when the current CNR is equal to or greater than the switching threshold Th2. Here, as described above, the switching threshold Th2 is smaller than the switching threshold Th1. Therefore, in the present embodiment, the modulation scheme can be changed from QPSK to 16QAM even when the CNR is saturated at a position lower than the switching threshold Th1. As shown in FIG. 9A, when no in-band interference occurs, the RSL when the CNR is Th2 [dB] is SL3 [dBm].

  On the other hand, as shown in FIG. 9 (b), even if the transmission power is the same P2 as in the example of FIG. 9 (a), if in-band interference occurs, the RSL increases. Also at this time, the wireless communication device A100A as a transmitting station transmits transmission power information indicating the transmission power P2 to the wireless communication device B100B as a receiving station. Radio communication apparatus B100B, which is a receiving station, extracts transmission power information indicating transmission power P2. Then, as described above, the reception modulation scheme determination unit 138 selects the switching threshold Th2 corresponding to the transmission power P2. The reception modulation scheme determination unit 138 changes the modulation scheme from QPSK to 16QAM when the current CNR is smaller than Th1 and is greater than or equal to the switching threshold Th2.

  When the switching threshold is fixed by the modulation method, assuming that the switching threshold from QPSK to 16QAM is Th1 as in the example of FIG. 8, the waveform of the transmitted signal is distorted In addition, as shown in FIG. 9, the CNR does not exceed the switching threshold Th1. Therefore, in such a case, the modulation method cannot be switched from QPSK to 16QAM. On the other hand, in the present embodiment, the switching threshold is not fixed by the modulation scheme, and the switching threshold is set according to the transmission power information transmitted from the transmitting station. Therefore, even if the waveform of the transmitted signal is distorted, the switching threshold is set according to the transmission power information in consideration of the CNR saturation associated with the transmission power. The modulation method can be switched from 16 to 16QAM.

  Further, as shown in FIG. 9B, when in-band interference occurs, the RSL when the CNR is Th2 [dB] is SL4 [dBm]. SL4 is larger than SL3. As shown in FIG. 9B, when the in-band interference occurs, the CNR when the RSL is SL3 [dBm] is smaller than the switching threshold Th2. Therefore, in such a case, even when radio signal distortion caused by the transmission side occurs, in this embodiment, the reception modulation scheme determination unit 138 determines to change the modulation scheme from QPSK to 16QAM. do not do.

Here, a method for setting the switching threshold Th <b> 2 when the distortion of the radio signal due to the transmission side has occurred will be described.
In FIG. 9, the arrows indicate the points on the characteristic curve when the modulation method is changed from QPSK to 16QAM. As described above, when the modulation scheme is changed from QPSK to 16QAM, the transmission power is changed from P2 to P1. That is, the transmission power decreases by (P2−P1) = ΔP. Therefore, at this time, RSL also decreases by ΔP. Here, as described above, the required CNR required in 16QAM is the switching threshold Th1, and in FIG. 9A, the RSL at this time is SL1. Therefore, if the value obtained by adding the decrease ΔP to SL1 is SL3 (SL3 = SL1 + ΔP), the CNR when the RSL becomes SL3 is set as the switching threshold Th2.

  In other words, the switching threshold Th2 is set so that the required CNR (switching threshold Th1) can be maintained when the modulation scheme is changed from QPSK to 16QAM. In FIG. 9A, assuming that the point of RSL = SL3 on the characteristic curve is Pt11, the CNR is equal to Th2 at this time. When the modulation method is changed from QPSK to 16QAM in this state, as indicated by an arrow A, the point Pt12 is transitioned to. At this point Pt12, RSL is SL1, and CNR is Th1. Therefore, at this time, the required CNR (Th1) necessary for 16QAM is satisfied. Therefore, the switching threshold at the transmission power P2 is set as the switching threshold Th2. If the CNR is larger than this point Pt11, the required CNR (Th1) necessary for 16QAM is satisfied when the modulation method is changed from QPSK to 16QAM as shown by the arrow in FIG. That is, occurrence of a bit error or the like in 16QAM after the change is suppressed.

  On the other hand, when the modulation method is changed to 16QAM from the state of Pt13 where the RSL and CNR are lower than the point Pt11 (that is, the switching threshold value Th2 is not satisfied) on the QPSK characteristic curve, as shown by the arrow B, the point Pt14 Transition. At this point Pt14, the CNR is lower than Th1. In other words, at the point Pt14, the required CNR (Th1) necessary for 16QAM is not satisfied. Therefore, if the modulation method is changed from the state of the point Pt13 to 16QAM, a bit error or the like may occur. However, in this embodiment, since the CNR is lower than the switching threshold Th2 at the point Pt13, the modulation scheme is not changed from QPSK to 16QAM. Therefore, it is possible to suppress the occurrence of a bit error or the like.

  Similarly, also in FIG. 9B, the required CNR required in 16QAM is the switching threshold Th1, and the RSL at this time is SL2. Therefore, if the value obtained by adding the decrease ΔP to SL2 is SL4 (SL4 = SL2 + ΔP), the CNR when the RSL becomes SL4 is set as the switching threshold Th2.

  In other words, in FIG. 9B, assuming that the point of RSL = SL4 on the characteristic curve is Pt21, CNR is equal to Th2 at this time. When the modulation method is changed from QPSK to 16QAM in this state, as indicated by an arrow C, a transition is made to a point Pt22. At this point Pt22, RSL is SL2 and CNR is Th1. Therefore, as in the case of FIG. 9A, the required CNR (Th1) necessary for 16QAM is satisfied. If the CNR is larger than this point Pt21, as shown by the arrow in FIG. 9B, the required CNR (Th1) necessary for 16QAM is satisfied when the modulation method is changed from QPSK to 16QAM. That is, occurrence of a bit error or the like in 16QAM after the change is suppressed.

  On the other hand, when the modulation scheme is changed to 16QAM from the state of Pt23 where the RSL and CNR are lower than the point Pt21 (that is, the switching threshold Th2 is not satisfied) on the characteristic curve of QPSK, as shown by the arrow D, the point Pt24 Transition. At this point Pt24, the CNR is lower than Th1. In other words, at the point Pt24, the required CNR (Th1) necessary for 16QAM is not satisfied. Therefore, if the modulation method is changed from the state of the point Pt23 to 16QAM, a bit error or the like may occur. However, in the present embodiment, at the point Pt23, since the CNR is smaller than the switching threshold Th2, the modulation scheme is not changed from QPSK to 16QAM. Therefore, it is possible to suppress the occurrence of a bit error or the like.

  Here, whether or not the modulation scheme should be changed from QPSK to 16QAM at a point where the RSL is high and the CNR is lower than the point Pt1 where the RSL on the characteristic curve of FIG. 8A is SL1 and the CNR is Th1. Further explanation will be given. For example, the RSL of the point Pt2 on the characteristic curve of FIG. 8B is higher than the RSL of the point Pt1, and the CNR of the point Pt2 is lower than the CNR of the point Pt1. Here, as described above, in FIG. 8B, RSL is high because in-band interference has occurred. That is, the radio propagation path state has deteriorated. Further, the CNR of the point Pt2 is lower than the switching threshold Th1. Therefore, in such a case, the modulation scheme should not be changed from QPSK to 16QAM.

  On the other hand, the RSL of Pt11 on the characteristic curve of FIG. 9A is higher than the RSL of the point Pt1, and the CNR of the point Pt11 is lower than the CNR of the point Pt1. Here, as described above, since the distortion of the radio signal due to the transmission side has occurred, the CNR is saturated (decreased). That is, the radio propagation path state itself does not deteriorate. Further, the CNR of the point Pt11 is not less than the switching threshold Th2. Therefore, in such a case, the modulation method may be changed from QPSK to 16QAM.

  As described above, whether or not the modulation scheme may be changed in the same way between Pt2 in FIG. 8B and Pt11 in FIG. 9A, although the RSL is higher than the point Pt1 and the CNR is lower. Will be different. Here, as in Patent Document 1 and Patent Document 2, in the method of comparing with the switching threshold using RSL and CNR, as described above, when the RSL is high and the CNR is low, may the modulation method be changed? I cannot make a decision.

  On the other hand, in the present embodiment, the transmission threshold can be selected according to the transmission power of the transmitting station by transmitting the transmission power information to the receiving station. That is, as shown in FIG. 8B, when the RSL is high due to the occurrence of in-band interference, the switching threshold is the required CNR (Th1) required when the modulation scheme is changed to 16QAM. is there. On the other hand, as shown in FIG. 9A, when the CNR is low due to the distortion of the radio signal due to the transmission side, the switching threshold is Th2 lower than Th1. In other words, by transmitting the transmission power information from the transmitting station to the receiving station, it is possible to determine whether or not in-band interference occurs when the RSL is high and the CNR is low. Therefore, in the present embodiment, when in-band interference occurs and the RSL is high and the CNR is low, the modulation scheme is not changed, and the radio signal distortion caused by the transmission side occurs. When the RSL is high and the CNR is low, it is possible to perform processing so as to change the modulation method.

  As described above, in this embodiment, when the CNR is lower than the required CNR required for 16QAM (switching threshold Th1), the modulation scheme is not changed to a modulation scheme with a large modulation multi-value number, so that bit error It is possible to suppress the occurrence of fluttering and fluctuation of the modulation system. Therefore, stable communication can be realized.

(Embodiment 2)
Next, a second embodiment will be described. The second embodiment is different from the first embodiment in that the wireless communication apparatus that is a transmitting station determines the modulation method.
FIG. 10 is a diagram of a configuration of the wireless communication apparatus 200 according to the second embodiment. Radio communication apparatus 200 includes antenna 102, transmission baseband processing unit 212, modulator 114, variable attenuator 116, transmission power control unit 218, amplifier 120, demodulator 234, reception baseband processing unit 236, and transmission modulation scheme 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 second embodiment, the transmitting station is wireless communication apparatus A200A, and the receiving station is wireless communication apparatus B200B.

  The transmission power control unit 218 generates transmission power information indicating the transmission power controlled by the transmission power control unit 218 itself, and the generated transmission power information is not a transmission baseband processing unit but a transmission modulation scheme determination unit. 238 for transmission. The other functions of the transmission power control unit 218 are the same as those of the transmission power control unit 118.

  Demodulator 234 of radio communication apparatus B 200B, which is a reception station, generates (acquires) CNR information from the received signal and transmits the CNR information to transmission baseband processing unit 212 instead of the reception modulation scheme determination unit. . Other functions of the demodulator 234 are the same as those of the demodulator 134.

  Transmission baseband processing section 212 of radio communication apparatus B 200B that is a receiving station is different from transmission baseband processing section 112 in that it does not receive transmission power information from the transmission power control section and receives CNR information from demodulator 234. The transmission baseband processing unit 212 adds (multiplexes) the CNR information to the input data to generate transmission radio frame data. As a result, the wireless communication device B 200B as the receiving station transmits the CNR information to the wireless communication device A 200A as the transmitting station. The other functions of the transmission baseband processing unit 212 are the same as those of the transmission baseband processing unit 112. That is, in Embodiment 2, radio communication apparatus A200A that is a transmitting station does not transmit transmission power information to radio communication apparatus B200B that is a receiving station.

  Radio communication apparatus A200A as a transmitting station receives a modulated signal including CNR 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. Then, reception baseband processing section 236 extracts CNR information from the received radio frame data and transmits it to transmission modulation scheme determination section 238. That is, the reception baseband processing unit 236 of the wireless communication device B200B that is a receiving station does not extract transmission power information. Also, the reception baseband processing unit 236 of the wireless communication apparatus A200A that is the transmitting station does not extract the determination modulation scheme information.

  The transmission modulation scheme determination unit 238 of the wireless communication apparatus A 200 </ b> A that is a transmission station receives transmission power information from the transmission power control unit 218. Also, the transmission modulation scheme determination unit 238 receives CNR information in the radio communication apparatus B 200B that is a receiving station, from the reception baseband processing unit 236. Also, the transmission modulation scheme determination unit 238 receives transmission modulation scheme control information indicating the transmission modulation scheme from the transmission power control unit 218. Further, the transmission modulation scheme determination unit 238 determines the modulation scheme according to the transmission modulation scheme, the CNR information, and the transmission power indicated in the transmission power information. The determination method is the same as that of the reception modulation method determination unit 138. Further, the transmission modulation scheme determination unit 238 transmits the determination modulation scheme information to the transmission power control unit 218.

  As described above, also in the second embodiment, it is possible to determine the modulation method by the same determination method as in the first embodiment. It is possible to suppress the occurrence of change flutter. Therefore, stable communication can be realized. Furthermore, as in Embodiment 2, it is not necessary for the transmitting station to transmit the transmission power information to the receiving station by determining the modulation scheme at the transmitting station. By doing so, it becomes possible to include a larger amount of input data in the transmission radio frame by the amount of reduction in the data amount of the transmission power information.

  In the second embodiment, the process shown in FIG. 5 is executed by radio communication apparatus A 200A that is a transmitting station. In this case, instead of S102 of FIG. 5, a process of receiving CNR information from the wireless communication apparatus B 200B as a receiving station is added, and the processes of S110 and S122 are omitted.

  Further, in the second embodiment, a process of receiving CNR information from radio communication apparatus B 200B as a receiving station is added instead of S302 in FIG. Further, the processes of S304 and S306 are executed by the wireless communication apparatus A200A which is a transmitting station. Further, the process of S308 is omitted.

(Modification)
Note that the present invention is not limited to the above-described embodiment, and can be changed as appropriate without departing from the spirit of the present invention. For example, in the flowcharts described above, the order of processing (steps) can be changed as appropriate. One or more of the plurality of processes (steps) may be omitted. For example, the process of S104 in FIG. 5 may be performed before the process of S102, or may be performed after the process of S106.

  In the above-described embodiment, the CNR information is acquired as the communication quality information. However, the present invention is not limited to this. Examples of the communication quality information include SNR, bit error rate (BER), packet error rate (PER), frame error rate (FER), and the like in addition to CNR. However, it is not limited to these. Further, parity bits may be embedded in a radio signal, error detection and correction such as parity check may be performed, and the implementation rate may be used as communication quality information. It should be noted that by using CNR information as communication quality information, it is possible to grasp communication quality more easily and appropriately, and therefore to determine a modulation scheme more appropriately.

  In the above-described embodiment, the transmission power control unit generates the transmission power information indicating the transmission power controlled by the transmission power control unit itself, but is not limited thereto. For example, the transmission power control unit may generate transmission power information indicating the transmission power in the transmission signal after being amplified by the amplifier.

  In the above-described embodiment, it is determined whether or not to change the modulation scheme based on the correspondence between the transmission power information indicating the transmission power at the transmission station and the CNR threshold. However, the present invention is not limited to this. For example, in addition to the correspondence between the transmission power information and the CNR threshold value, whether or not to change the modulation scheme may be determined based on the correspondence between the RSL and the CNR threshold value. Specifically, in a state where the RSL is considerably low (for example, near the origin in FIG. 8), the CNR does not exceed the switching threshold Th1. Therefore, when the RSL is low, the switching threshold associated with the RSL may be compared with the CNR without using the transmission power information. At this time, the switching threshold associated with the RSL may be Th1 or a value larger than Th1. With this configuration, it is possible to determine the modulation scheme without using transmission power information in a range where the modulation scheme cannot be changed in practice.

  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 apparatus by causing a CPU (Central Processing Unit) to execute a computer program.

  In the above example, the program can be stored and supplied to a computer using various types of non-transitory computer readable media. Non-transitory computer readable media include various types of tangible storage media. Examples of non-transitory computer-readable media include magnetic recording media (for example, flexible disks, magnetic tapes, hard disk drives), magneto-optical recording media (for example, magneto-optical disks), CD-ROMs (Read Only Memory), CD-Rs, CD-R / W, semiconductor memory (for example, mask ROM, PROM (Programmable ROM), EPROM (Erasable PROM), flash ROM, RAM (Random Access Memory)) are included. The program may also be supplied to the computer by various types of transitory 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.

DESCRIPTION OF SYMBOLS 1 Wireless communication apparatus 12 Transmission power information acquisition part 14 Communication quality information acquisition part 16 Modulation system determination part 18 Transmission part 50 Wireless communication system 60 Data line 100 Wireless communication apparatus 102 Antenna 112 Transmission baseband process part 114 Modulator 116 Variable attenuator 118 Transmission Power Control Unit 120 Amplifier 134 Demodulator 136 Reception Baseband Processing Unit 138 Reception Modulation Method Determination Unit 200 Wireless Communication Device 212 Transmission Baseband Processing Unit 218 Transmission Power Control Unit 234 Demodulator 236 Reception Baseband Processing Unit 238 Transmission Modulation Method Judgment part

Claims (17)

Transmission power information acquisition means for acquiring transmission power information indicating the transmission power of the other wireless communication device from another wireless communication device;
Communication quality information acquisition means for acquiring communication quality information indicating communication quality from a radio signal received from the other radio communication device;
A modulation scheme determination means for determining whether to change the modulation scheme based on a comparison result between the switching threshold set corresponding to the transmission power information and the communication quality information;
A wireless communication apparatus comprising: a transmission unit configured to transmit determination modulation method information indicating the modulation method determined by the modulation method determination unit to the other wireless communication device. The wireless communication apparatus according to claim 1, wherein the communication quality information is information indicating a ratio between a carrier wave or a wireless signal and noise. The wireless communication apparatus according to claim 1, wherein the switching threshold is set to be smaller as transmission power indicated by the transmission power information is larger. A wireless communication device,
Transmission power information transmitting means for transmitting transmission power information indicating the transmission power of the wireless communication device to other wireless communication devices;
Receiving means for receiving modulation scheme determination information indicating a modulation scheme determined by the other wireless communication device using the transmission power information;
A wireless communication apparatus comprising: a modulation unit that changes a modulation method according to the modulation method determination information and performs modulation using the changed modulation method. A wireless communication device,
Communication quality information acquisition means for acquiring communication quality information indicating communication quality from other wireless communication devices;
Modulation scheme determining means for determining whether to change the modulation scheme based on a comparison result between a switching threshold set corresponding to transmission power information indicating transmission power of the wireless communication device and the communication quality information; ,
A radio communication apparatus comprising: a modulation unit that changes a modulation method in accordance with determination by the modulation method determination unit, and performs modulation using the changed modulation method. The wireless communication apparatus according to claim 5, wherein the communication quality information is information indicating a ratio between a carrier wave or a wireless signal and noise. The wireless communication apparatus according to claim 5, wherein the switching threshold is set to be smaller as transmission power indicated by the transmission power information is larger. Communication quality information acquisition means for acquiring communication quality information indicating communication quality from a wireless signal received from another wireless communication device;
A wireless communication apparatus comprising: a transmission unit that transmits the communication quality information to the other wireless communication apparatus. Communication quality information acquisition means for acquiring communication quality information indicating communication quality from a radio signal received by a receiving-side radio communication device;
Modulation method determination for determining whether or not to change the modulation method based on a comparison result between the switching threshold value set corresponding to the transmission power information indicating the transmission power of the wireless communication device on the transmission side and the communication quality information Means,
A radio communication system comprising: a modulation unit that changes a modulation method according to determination by the modulation method determination unit and performs modulation using the changed modulation method. The wireless communication system according to claim 9, wherein the communication quality information is information indicating a ratio between a carrier wave or a wireless signal and noise. The wireless communication system according to any one of claims 9 and 10, wherein the switching threshold is set to be smaller as transmission power indicated by the transmission power information is larger. The communication quality information acquisition unit and the modulation method determination unit are provided in the reception-side wireless communication device,
The wireless communication system according to claim 9, wherein the modulation unit is provided in the wireless communication device on the transmission side. The communication quality information acquisition means is provided in the wireless communication device on the receiving side,
The radio communication system according to any one of claims 9 to 11, wherein the modulation scheme determination unit and the modulation unit are provided in the radio communication device on the transmission side. Obtain transmission power information indicating the transmission power of the wireless communication device on the transmission side,
From the wireless signal received from the wireless communication device on the transmission side, obtain communication quality information indicating communication quality,
Based on the comparison result between the switching threshold set corresponding to the transmission power information and the communication quality information, it is determined whether to change the modulation scheme,
A wireless communication method for transmitting determination modulation method information indicating the determined modulation method to the transmission-side wireless communication device. Transmits transmission power information indicating the transmission power of the wireless communication device on the transmission side to the wireless communication device on the reception side,
Receiving modulation scheme determination information indicating a modulation scheme determined by the reception-side wireless communication device using the transmission power information;
A wireless communication method in which a modulation method is changed according to the modulation method determination information, and modulation is performed using the changed modulation method. Obtain communication quality information indicating communication quality from the wireless communication device on the receiving side,
Based on the comparison result between the switching threshold and the communication quality information set corresponding to the transmission power information indicating the transmission power of the wireless communication device on the transmission side, determine whether to change the modulation method,
A wireless communication method in which a modulation scheme is changed according to the determination, and modulation is performed using the changed modulation scheme. From wireless signals received from other wireless communication devices, obtain communication quality information indicating communication quality,
A wireless communication method for transmitting the communication quality information to the other wireless communication device.

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