Wireless communication method, wireless communication system, and wireless transmission device

Abstract

The present invention uses a radio transmission device 10 and a radio reception device corresponding to QAM and APSK. The radio transmission device 10 comprises a power amplifier 24 that makes transmission power variable. A constellation calculation unit 22 calculates, on the basis of input / output characteristics of the power amplifier 24, an estimated constellation {QAM} expected to be generated when a QAM-modulated signal is amplified by the power amplifier 24 with a desired transmission power, and calculates, in the same manner, an estimated constellation {APSK} expected to be generated when an APSK-modulated signal is amplified with the desired transmission power. A modulation scheme selection unit 20 compares an estimated minimum Euclidean distance on the estimated constellation {QAM} and an estimated minimum Euclidean distance on the estimated constellation {APSK} to each other, and selects the modulation scheme with the longer distance.

Description

[Technical field]

[0001] The present disclosure relates to a wireless communication method, a wireless communication system, and a wireless transmission device, and more particularly to a wireless communication method, a wireless communication system, and a wireless transmission device suitable for use in an environment in which transmission power varies. [Background technology]

[0002] Non-Patent Document 1 below describes in detail QAM (Quadrature Amplitude Modulation), which is one of the multi-level modulation methods for wireless communication. Non-Patent Document 2 below describes in detail APSK (Amplitude Phase Shift Keying), which is another example of the multi-level modulation method. As typified by these methods, various multi-level modulation methods are used in the field of wireless communication.

[0003] Regarding the influence of the different multi-level modulation methods on the quality of wireless communication, the following non-patent document 3 discloses the following: 1. The PAPR (Peak to Average Power Ratio) differs for each multi-level modulation method; 2. The larger the PAPR, the more likely the signal is misrecognized at the receiving end when the transmitting power amplifier operates in the nonlinear region; 3. When comparing APSK with QAM, APSK, which has a smaller PAPR, is more robust when transmitted in the nonlinear region of the power amplifier. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] IEEE Std 802.11ac-2013, IEEE, 2013 [Non-Patent Document 2] ETSI EN 302 307-1 V1.4.1, Digital Video Broadcasting, November 2014 [Non-Patent Document 3] “M-APSK Modulation for SC-FDMA Communication Systems”, Juraj GAZDA, Denis DUPAK, Dusan KOCUR, Department of Electronics and Multimedia Communications, Faculty of Electrical Engineering and Informatics, Technical University of Kosice, Letna 9, 04200 Kosice, Slovakia, 2011 Summary of the Invention [Problem to be solved by the invention]

[0005] In the symbol constellation used in QAM, multiple symbols are arranged in a grid pattern. On the other hand, in the symbol constellation used in APSK, multiple symbols are arranged in one or more concentric circles. Comparing the two, if the number of symbols is the same, the minimum Euclidean distance between symbols arranged in a QAM constellation is longer than the minimum Euclidean distance in an APSK constellation.

[0006] In communication using the multi-level modulation method, the receiving side recognizes the received signal as one of the symbols on a pre-stored constellation. Specifically, the likelihood of the received signal and each of the symbols present around it on the constellation is calculated, and the symbol with the highest likelihood is recognized as the received signal. In this case, the longer the Euclidean distance between the symbols arranged on the constellation, the higher the identification accuracy of the received signal. Therefore, in an environment in which the received signal is transmitted without distortion, QAM with a long minimum Euclidean distance is more likely to ensure a superior BER (Bit Error Rate) than APSK.

[0007] In a situation where the power amplifier on the transmitting side can amplify the transmission signal in a linear region, the transmission signal is less likely to be distorted. Therefore, in such a situation, QAM is more likely to ensure good communication quality than APSK. On the other hand, in a situation where the transmission power is large and the power amplifier amplifies the signal in a nonlinear region, for the reasons described in Non-Patent Document 3, APSK is more likely to ensure better communication quality than QAM.

[0008] In this way, when comparing the suitability of each multi-level modulation scheme, the merits and demerits may be reversed depending on whether the power amplifier uses a linear region or a nonlinear region. However, in the past, there was no consideration of controlling the multi-level modulation scheme used in communication to be appropriately switched depending on the transmission power. In this respect, conventional wireless communication technology has room for further improvement by switching between multiple multi-level modulation schemes.

[0009] The present disclosure has been made in consideration of the above problems, and has as a first object to provide a wireless communication method that ensures excellent communication quality over a wide range of transmission power by appropriately switching between multiple multi-level modulation schemes depending on the transmission power.

[0010] A second object of the present disclosure is to provide a wireless communication system that ensures excellent communication quality over a wide range of transmission power by appropriately switching between a plurality of multi-level modulation schemes depending on the transmission power.

[0011] A third object of the present disclosure is to provide a wireless transmission device that ensures excellent communication quality over a wide range of transmission power by appropriately switching between a plurality of multi-level modulation schemes depending on the transmission power. [Means for solving the problem]

[0012] In order to achieve the above object, a first aspect is a wireless communication method using a wireless transmitting device and a wireless receiving device that support at least two multi-level modulation schemes, comprising: The at least two multi-level modulation methods include a first modulation method and a second modulation method, the wireless transmission device includes a power amplifier that varies transmission power; The wireless transmitting device, calculating a first estimated constellation that is expected to be generated when a signal modulated by the first modulation scheme is amplified by the power amplifier at a desired transmission power based on an input / output characteristic of the power amplifier; calculating, based on the input / output characteristics, a second estimated constellation that is expected to be generated when the signal modulated by the second modulation scheme is amplified by the power amplifier at the desired transmission power; calculating a first estimated Euclidean distance, which is a characteristic value of a distance between symbols in the first estimated constellation; calculating a second estimated Euclidean distance, which is a characteristic value of a distance between symbols in the second estimated constellation; Among the first estimated Euclidean distance and the second estimated Euclidean distance, long selecting a modulation scheme that generates the above-mentioned signal as a scheme to be used for communication; instructing the wireless receiving device to communicate in the selected modulation scheme; It is preferable that the method further includes a step of: the wireless receiving device communicating with the wireless transmitting device in the instructed modulation method.

[0013] A second aspect is a wireless communication system using a wireless transmitting device and a wireless receiving device that support at least two multi-level modulation schemes, The at least two multi-level modulation methods include a first modulation method and a second modulation method, The wireless transmission device includes: A power amplifier is provided to vary the transmission power, calculating a first estimated constellation that is expected to be generated when a signal modulated by the first modulation scheme is amplified by the power amplifier at a desired transmission power based on an input / output characteristic of the power amplifier; a process of calculating, based on the input / output characteristics, a second estimated constellation that is expected to be generated when the signal modulated by the second modulation scheme is amplified by the power amplifier at the desired transmission power; A process of calculating a first estimated Euclidean distance, which is a characteristic value of a distance between symbols in the first estimated constellation; A process of calculating a second estimated Euclidean distance, which is a characteristic value of a distance between symbols in the second estimated constellation; Among the first estimated Euclidean distance and the second estimated Euclidean distance, long A process of selecting a modulation method that generates the above-mentioned signal as a method to be used for communication; and instructing the wireless receiving device to communicate in the selected modulation scheme; It is preferable that the wireless receiving device is configured to communicate with the wireless transmitting device in the instructed modulation method.

[0014] A third aspect is a wireless transmission device that supports at least two multi-level modulation schemes and has a function of communicating with a wireless reception device that supports the at least two multi-level modulation schemes, The at least two multi-level modulation methods include a first modulation method and a second modulation method, A power amplifier is provided to vary the transmission power, calculating a first estimated constellation that is expected to be generated when a signal modulated by the first modulation scheme is amplified by the power amplifier at a desired transmission power based on an input / output characteristic of the power amplifier; a process of calculating, based on the input / output characteristics, a second estimated constellation that is expected to be generated when the signal modulated by the second modulation scheme is amplified by the power amplifier at the desired transmission power; A process of calculating a first estimated Euclidean distance, which is a characteristic value of a distance between symbols in the first estimated constellation; A process of calculating a second estimated Euclidean distance, which is a characteristic value of a distance between symbols in the second estimated constellation; Among the first estimated Euclidean distance and the second estimated Euclidean distance, long A process of selecting a modulation method that generates the above-mentioned signal as a method to be used for communication; A process of instructing the wireless receiving device to communicate using the selected modulation method; Preferably, the system is configured to execute: Effect of the Invention

[0015] According to the first to third aspects, in an environment in which a plurality of multi-level modulation schemes can be used, by appropriately switching between them according to the transmission power, it becomes possible to ensure excellent communication quality over a wide range of transmission power. [Brief description of the drawings]

[0016] [Figure 1] 1 is a diagram illustrating a configuration example of a wireless communication system according to a first embodiment of the present disclosure. [Diagram 2] This is a diagram showing a comparison between APSK constellations and QAM constellations. [Diagram 3] This is a diagram comparing the characteristics of QAM and APSK. [Figure 4] 2 is a diagram for explaining input / output characteristics of a power amplifier included in the wireless transmission device shown in FIG. [Diagram 5] This figure shows the suitability of QAM and APSK in contrast when the power amplifier uses a linear region and when it uses a nonlinear region. [Figure 6] 1 is a block diagram illustrating a configuration of a wireless transmission device according to a first embodiment of the present disclosure. [Figure 7] 7 is a flowchart illustrating the flow of main processes performed by the wireless transmission device shown in FIG. 6. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Embodiment 1 [Overall configuration of the first embodiment] Fig. 1 illustrates a configuration example of a wireless communication system according to a first embodiment of the present disclosure. As illustrated in Fig. 1, the system according to the present embodiment includes a wireless transmission device 10 and a wireless reception device 12. The wireless transmission device 10 may be, for example, a wireless communication base station managed by a telecommunications carrier, or an access point of a wireless LAN (Local Area Network). Meanwhile, the wireless reception device 12 may be a terminal device capable of communication in both or either of a licensed band and an unlicensed band.

[0018] [Features of the first embodiment] In this embodiment, the wireless transmitting device 10 and the wireless receiving device 12 have a function of supporting a plurality of multi-level modulation methods. Specifically, a case will be described in which the wireless transmitting device 10 and the wireless receiving device 12 support QAM (Quadrature Amplitude Modulation) and APSK (Amplitude Phase Shift Keying), respectively.

[0019] Figure 2 shows a comparison between APSK constellations and QAM constellations. More specifically, the left side of Figure 2 shows a 16APSK constellation that handles 16 symbols. The right side of Figure 2 shows a 16QAM constellation that also handles 16 symbols. The position of each symbol represents the amplitude and phase.

[0020] In a 16APSK constellation, 16 symbols are arranged on two concentric circles, with eight symbols at equal intervals. In a 16QAM constellation, on the other hand, 16 symbols are arranged at equal intervals in a grid pattern. In the figure, the minimum Euclidean distance between symbols in each constellation is indicated by a double-headed arrow. Comparing the two, it can be seen that the minimum Euclidean distance is greater in the case of QAM, where the symbols are arranged in a grid pattern, than in the case of APSK.

[0021] Next, we consider the PAPR (Peak to Average Power Ratio). The larger the amplitude of each symbol on the constellation, the more power is required to transmit it. Therefore, with APSK, a peak power occurs when transmitting the eight symbols arranged on the outer concentric circle. On the other hand, with QAM, a peak power occurs when transmitting the four symbols located at the four corners. For this reason, the ratio of the peak transmission power to the average transmission power for all symbols is smaller with APSK. Therefore, when APSK is used, the PAPR tends to be smaller than when QAM is used.

[0022] Figure 3 shows the minimum Euclidean distance and PAPR characteristics for QAM and APSK. The circles and crosses in the figure indicate the relative merits of each in terms of ensuring a good BER (Bit Error Rate) in wireless communication. The reasons for this difference in merit are explained below.

[0023] The wireless receiving device 12 shown in Fig. 1 receives an instruction from the wireless transmitting device 10 regarding the modulation method to be used for communication, and selects a modulation method according to the instruction. Regardless of the modulation method, the wireless receiving device 12 arranges the received signal on a constellation based on its amplitude and phase, and calculates the likelihood of the received signal for each of the multiple symbols located around it. Then, the wireless receiving device 12 recognizes the received signal as the symbol with the highest likelihood.

[0024] The longer the minimum Euclidean distance on the constellation, the greater the difference in the likelihood calculated for each symbol. For this reason, if the received signal is correctly placed on the constellation, it is easier to ensure a better BER by using QAM, which has a large minimum Euclidean distance, than by using APSK, which has a small minimum Euclidean distance. The rightmost column in Figure 3 shows this relationship as "〇 (large)" for QAM and "× (small)" for APSK.

[0025] Fig. 4 shows the input / output characteristics of the power amplifier included in the wireless transmission device 10 shown in Fig. 1. As shown in Fig. 4, the power amplifier has an input power of P B The input / output characteristics are linear in the following range, but when the input power is P B In the region exceeding this range, the characteristics become nonlinear. Then, distortion is superimposed on the signal amplified by the power amplifier using the nonlinear region. If distortion occurs in the received signal, the received signal is placed at a position on the constellation in the radio receiving device 12 that is shifted from its original position. As a result, the signal amplified in the nonlinear region is easily misrecognized as an incorrect symbol in the radio receiving device 12.

[0026] When the wireless transmission device 10 transmits a wireless signal, even if the average power is within the linear region, a signal with a large amplitude may enter the nonlinear region of the power amplifier. Such a phenomenon is more likely to occur as the PAPR of the multi-level modulation method used in communication increases. For this reason, from the viewpoint of preventing misidentification of signals caused by distortion without distorting the transmission signal, APSK, which has a small PAPR, is superior to QAM, which has a large PAPR. The center column of FIG. 3 indicates this relationship as "x (large)" for QAM and "o (small)" for APSK.

[0027] Figure 5 shows the suitability of QAM and APSK in comparison when the power amplifier uses the linear region and when it uses the nonlinear region. If the input power to the power amplifier falls within the linear region, no distortion problem will occur regardless of which modulation method is used. In this case, due to the minimum Euclidean distance relationship, a better BER can be obtained by using QAM than by using APSK. The center column of Figure 5 shows this relationship as QAM "Excellent" and APSK "Good".

[0028] In the nonlinear region of the power amplifier, the larger the input power, the larger the distortion superimposed on the transmission signal. Therefore, when the input power enters the nonlinear region, the larger the PAPR of the multi-level modulation method, the larger the distortion superimposed on the signal corresponding to the peak. And the larger the distortion superimposed on the transmission signal, the more likely the signal is to be misrecognized by the wireless receiving device 12. For this reason, in a situation where the power transmitting device uses the nonlinear region, QAM with a large PAPR is more likely to cause a large deterioration in communication quality than APSK with a low PAPR. The rightmost column of FIG. 5 shows this relationship as QAM "× (due to large PAPR)" and APSK "△ (due to low PAPR)".

[0029] As described above, the superiority or inferiority of QAM and APSK is reversed depending on whether the operating region of the power amplifier is a linear region or a nonlinear region. Therefore, in this embodiment, in response to this reversal, the multi-level modulation method used for communication is appropriately switched between QAM and APSK so as to obtain excellent communication quality in a real environment.

[0030] [Wireless transmitter configuration] Fig. 6 is a block diagram for explaining the configuration of the wireless transmission device 10 used in this embodiment to realize the above functions. Each element shown in Fig. 6 can be configured with dedicated hardware. Moreover, in addition to the dedicated hardware, these elements can also be configured using an arithmetic processing unit and a program for causing the arithmetic processing unit to execute desired processing.

[0031] 6, the wireless transmitting device 10 includes an information bit generating unit 14. The information bit generating unit 14 generates bit data corresponding to information to be transmitted to the wireless receiving device 12. The bit data generated by the information bit generating unit 14 is provided to a QAM modulating unit 16 and an APSK modulating unit 18.

[0032] The QAM modulation unit 16 modulates the received bit data in the QAM format. Meanwhile, the APSK modulation unit 18 modulates the bit data in the APSK format. In either case, the modulated signal is provided to a modulation scheme selection unit 20 and a constellation calculation unit 22.

[0033] The modulation scheme selection unit 20 has a function of determining whether QAM or APSK is appropriate as a modulation scheme to be used for communication. If it is determined that QAM is appropriate, it provides the modulated signal generated by the QAM modulation unit 16 to the power amplifier 24. On the other hand, if it is determined that APSK is appropriate, it provides the modulated signal generated by the APSK modulation unit 18 to the power amplifier 24. The process by which the modulation scheme selection unit 20 selects a modulation scheme will be described in detail later.

[0034] The power amplifier 24 amplifies the modulated signal generated by the QAM modulation unit 16 or the APSK modulation unit 18 to a desired transmission power and supplies the amplified signal to the antenna 26. As a result, the signal amplified to the desired power by the power amplifier 24 is transmitted from the antenna 26 in accordance with the modulation scheme selected by the modulation scheme selection unit 20.

[0035] The wireless transmission device 10 in this embodiment includes an input / output characteristic storage unit 28. The input / output characteristic storage unit 28 stores in advance the input / output characteristic of the power amplifier 24. For example, an input / output characteristic curve as shown in FIG. 4 is stored. The input / output characteristic storage unit 28 can provide the information on the input / output characteristic to the constellation calculation unit 22.

[0036] The constellation calculation unit 22 generates an estimated constellation {QAM} corresponding to the QAM modulated signal based on the QAM modulated signal acquired from the QAM modulation unit 16, the input / output characteristics acquired from the input / output characteristics storage unit 28, and the transmission power commanded to the power amplifier 24. That is, the type of distortion superimposed on each symbol included in the modulated signal can be estimated based on the input / output characteristics and transmission power of the power amplifier 24. Here, the estimated constellation {QAM} is generated by arranging all symbols included in the QAM modulated signal on the constellation coordinates, assuming that the distortion is superimposed on each symbol. The constellation calculation unit 22 similarly generates an estimated constellation {APSK} for the APSK modulated signal.

[0037] The modulation scheme selection unit 20 acquires the estimated constellation {QAM} generated by the constellation calculation unit 22, and calculates the estimated minimum Euclidean distance {QAM} for all symbols included therein. That is, the linear distance between the closest symbols in the estimated constellation {QAM} is estimated. In the same manner, the modulation scheme selection unit 20 calculates the estimated minimum Euclidean distance {APSK} based on the estimated constellation {APSK}.

[0038] When the power amplifier 24 amplifies a signal in a linear region, since a large distortion is not superimposed on the transmission signal, the estimated minimum Euclidean distance {QAM} is likely to be larger than the estimated minimum Euclidean distance {APSK}. On the other hand, when the power amplifier 24 uses a nonlinear region, the relationship is reversed due to differences in PAPR. In either case, the receiving side is more likely to correctly recognize the transmission signal when the minimum Euclidean distance is longer.

[0039] In this embodiment, the modulation scheme selector 20 compares the estimated minimum Euclidean distance {QAM} with the estimated minimum Euclidean distance {APSK} and selects the modulation scheme with the longer distance as the scheme to be used for communication. Therefore, according to the wireless transmission device 10 of this embodiment, regardless of the region in which the power amplifier 24 amplifies the modulated signal, it is possible to always adopt a modulation scheme that is advantageous for allowing the wireless reception device 12 to correctly recognize the signal.

[0040] [Processing flow in the first embodiment] Fig. 7 is a flowchart for explaining the flow of main processes performed by the wireless transmission device 10 shown in Fig. 6. More specifically, it is a flowchart for explaining the flow of processes executed in the modulation scheme selection unit 20 and the constellation calculation unit 22.

[0041] 7, the processes of steps 100 to 108 are executed in the constellation calculation unit 22. Specifically, first, the input / output characteristics of the power amplifier 24 are read from the input / output characteristics storage unit 28 (step 100). The process of step 100, that is, the process enclosed in a dashed box in FIG. 7, may be executed only once as an initialization process when the operation of the wireless transmission device 10 starts.

[0042] Next, the constellation calculation unit 22 acquires the QAM modulated signal from the QAM modulation unit 16 (step 102) and acquires the APSK modulated signal from the APSK modulation unit 18 (step 104). Then, the estimated minimum Euclidean distance {QAM} and the estimated minimum Euclidean distance {APSK} are calculated (steps 106 and 108).

[0043] In calculating the estimated minimum Euclidean distance {QAM}, first, the transmission power used in the current transmission and the QAM modulated signal obtained in step 102 are applied to the input / output characteristics of the power amplifier 24 to generate an estimated constellation {QAM}. Then, the minimum Euclidean distance in the estimated constellation {QAM} is set as the estimated minimum Euclidean distance {QAM}. The estimated minimum Euclidean distance {APSK} is calculated in a similar manner based on the APSK modulated signal obtained in step 104.

[0044] The processes of steps 110 to 114 are executed in the modulation scheme selection unit 20. That is, when the processes of steps 100 to 108 are completed, the modulation scheme selection unit 20 first determines whether or not the estimated minimum Euclidean distance {APSK} calculated in step 108 is greater than the estimated minimum Euclidean distance {QAM} calculated in step 106 (step 110).

[0045] If the estimated minimum Euclidean distance {APSK}>the estimated minimum Euclidean distance {QAM} is found, APSK is selected as the modulation scheme to be used for communication (step 112). On the other hand, if the above relationship is not found, QAM is selected as the modulation scheme to be used for communication (step 114). The above processes of steps 102 to 114 are repeatedly executed for each transmission frame.

[0046] As described above, according to the wireless communication system of the present embodiment, a plurality of multi-level modulation methods can be appropriately switched and used based on the minimum Euclidean distance estimated to be realized by each transmission signal. As a result, regardless of the transmission power used by the power amplifier 24, a modulation method advantageous for obtaining high communication quality is always selected. Therefore, according to the wireless communication system of the present embodiment, it is possible to stably ensure excellent communication quality over a wide range of transmission power.

[0047] [Modification of the first embodiment] Incidentally, in the above-mentioned first embodiment, two multi-level modulation methods, 16QAM and 16APSK, are used, but the present disclosure is not limited to this. The number of symbols is not limited to 16, and the number of symbols of the two modulation methods may be different. In addition, various transmission methods such as OFDM (Orthogonal Frequency Division Multiplexing) transmission, DFT-s-OFDM (Discrete Fourier Transform-Spread-OFDM) transmission, and SC (Single Carrier) transmission can be applied. Various system configurations such as SISO (Single Input and Single Output) configuration and MIMO (Multiple Input and Multiple Output) configuration can be applied. Furthermore, methods such as FTN (Faster-than-Nyquist) transmission and Nyquist transmission can also be applied. In addition, three or more modulation methods may be used, and an optimal modulation method may be appropriately selected from the modulation methods.

[0048] In the above-described first embodiment, the scheme to be used for communication is selected based on a comparison of the estimated minimum Euclidean distances calculated for QAM and APSK. However, the present disclosure is not limited to this. The comparison may be made on anything that represents the density of symbols on an estimated constellation. For example, either QAM or APSK may be selected based on a comparison of the estimated average Euclidean distance, which is the average of the distances between symbols on an estimated constellation.

[0049] In the above-described first embodiment, an estimated constellation {QAM} corresponding to a QAM modulated signal and an estimated constellation {APSK} corresponding to an APSK modulated signal are generated, and the estimated minimum Euclidean distances are calculated based on the estimated constellation. However, the present disclosure is not limited to this. For example, the constellation calculation unit 22 may generate estimated constellations for each of QAM and APSK by reflecting the influence of distortion on a regular constellation without taking in the QAM and APSK modulated signals.

[0050] In the above-mentioned first embodiment, the estimated Euclidean distance {QAM} obtained from the estimated constellation {QAM} and the estimated Euclidean distance {APSK} obtained from the estimated constellation {APSK} are directly compared, but the present disclosure is not limited to this. For example, a bias value set according to communication quality may be added to or subtracted from either one of the Euclidean distances. In this case, a modulation scheme that is not optimal depending on the situation will be selected, but the frequency of switching the modulation scheme can be reduced.

[0051] Furthermore, in the above-mentioned first embodiment, the estimated constellation is updated for each frame to select the optimal modulation scheme for each frame. However, the present disclosure is not limited to this. That is, the estimated constellation may be updated for each set of frames or for each fixed time period, and the modulation scheme may be switched less frequently than every frame.

[0052] In the above-described first embodiment, the wireless transmission device 10 does not include an adaptive transmission power control (ATPC), but the present disclosure is not limited to this. That is, the wireless transmission device 10 may incorporate an ATPC and have the ATCP specify the transmission power used by the power amplifier 24. [Explanation of symbols]

[0053] 10 Radio transmitting device 12 Radio receiving device 16 QAM Modulation Section 18 APSK Modulation Section 20 Modulation method selection section 22 Constellation calculation unit 24 Power Amplifier 28 Input / output characteristics storage section

Claims

1. A wireless communication method using a wireless transmitting device and a wireless receiving device that support at least two multi-level modulation methods, The at least two multi-level modulation methods include a first modulation method and a second modulation method, the wireless transmission device includes a power amplifier that varies transmission power; The wireless transmitting device, calculating a first estimated constellation that is expected to be generated when a signal modulated by the first modulation scheme is amplified by the power amplifier at a desired transmission power based on an input / output characteristic of the power amplifier; calculating, based on the input / output characteristics, a second estimated constellation that is expected to be generated when the signal modulated by the second modulation scheme is amplified by the power amplifier at the desired transmission power; calculating a first estimated Euclidean distance, which is a characteristic value of a distance between symbols in the first estimated constellation; calculating a second estimated Euclidean distance, which is a characteristic value of a distance between symbols in the second estimated constellation; selecting a modulation scheme that generates the longer of the first estimated Euclidean distance and the second estimated Euclidean distance as a scheme to be used for communication; instructing the wireless receiving device to communicate in the selected modulation scheme; a step of the wireless receiving device communicating with the wireless transmitting device in the instructed modulation method; A wireless communication method comprising:

2. The wireless transmission device, generating a first modulated signal by modulating information bits to be transmitted to the wireless receiving device using the first modulation method; and generating a second modulated signal by modulating the information bits with the second modulation scheme; the first estimated constellation is formed of a set of symbols generated when the first modulated signal is amplified by the power amplifier at the desired transmission power; the second estimated constellation is formed of a set of symbols generated when the second modulated signal is amplified by the power amplifier at the desired transmission power. The wireless communication method according to claim 1 .

3. the first estimated constellation is formed by a set of symbols that are generated when all symbols included in a normal constellation of the first modulation scheme are amplified by the power amplifier at the desired transmission power, the second estimated constellation is formed by a set of symbols generated when all symbols included in a normal constellation of the second modulation method are amplified by the power amplifier at the desired transmission power. The wireless communication method according to claim 1 .

4. the first estimated Euclidean distance is an estimated minimum Euclidean distance in the first estimated constellation; the second estimated Euclidean distance is an estimated minimum Euclidean distance in the second estimated constellation. A wireless communication method according to any one of claims 1 to 3.

5. the first estimated Euclidean distance is an estimated average Euclidean distance in the first estimated constellation; the second estimated Euclidean distance is an estimated average Euclidean distance in the second estimated constellation. A wireless communication method according to any one of claims 1 to 3.

6. The wireless transmission device, setting a bias value based on a required communication quality; adding or subtracting the bias value to the first estimated Euclidean distance or the second estimated Euclidean distance; The wireless communication method according to any one of claims 1 to 5, further comprising:

7. A wireless communication system using a wireless transmitting device and a wireless receiving device that are compatible with at least two multi-level modulation methods, The at least two multi-level modulation methods include a first modulation method and a second modulation method, The wireless transmission device includes: A power amplifier is provided to vary the transmission power, calculating a first estimated constellation that is expected to be generated when a signal modulated by the first modulation scheme is amplified by the power amplifier at a desired transmission power based on an input / output characteristic of the power amplifier; a process of calculating, based on the input / output characteristics, a second estimated constellation that is expected to be generated when the signal modulated by the second modulation scheme is amplified by the power amplifier at the desired transmission power; A process of calculating a first estimated Euclidean distance, which is a characteristic value of a distance between symbols in the first estimated constellation; A process of calculating a second estimated Euclidean distance, which is a characteristic value of a distance between symbols in the second estimated constellation; selecting a modulation scheme that generates the longer of the first estimated Euclidean distance and the second estimated Euclidean distance as a scheme to be used for communication; and instructing the wireless receiving device to communicate in the selected modulation scheme; A wireless communication system, wherein the wireless receiving device is configured to communicate with the wireless transmitting device in the instructed modulation method.

8. A wireless transmission device that supports at least two multi-level modulation methods and has a function of communicating with a wireless reception device that supports the at least two multi-level modulation methods, The at least two multi-level modulation methods include a first modulation method and a second modulation method, A power amplifier is provided to vary the transmission power, calculating a first estimated constellation that is expected to be generated when a signal modulated by the first modulation scheme is amplified by the power amplifier at a desired transmission power based on an input / output characteristic of the power amplifier; a process of calculating, based on the input / output characteristics, a second estimated constellation that is expected to be generated when the signal modulated by the second modulation scheme is amplified by the power amplifier at the desired transmission power; A process of calculating a first estimated Euclidean distance, which is a characteristic value of a distance between symbols in the first estimated constellation; A process of calculating a second estimated Euclidean distance, which is a characteristic value of a distance between symbols in the second estimated constellation; selecting a modulation scheme that generates the longer of the first estimated Euclidean distance and the second estimated Euclidean distance as a scheme to be used for communication; A process of instructing the wireless receiving device to communicate using the selected modulation method; 23. A wireless transmitting device configured to:

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