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

Abstract

To optimize transmission capacity while maintaining transmission quality.SOLUTION: The method comprises: identifying each roll-off rate using a predetermined relationship table, calculating a degraded SNR equivalent on the basis of the amount that the PAPR of a transmitting amplifier exceeds a backoff and a minimum Euclidean distance, and calculating an SNR for average transmit power; selecting either SC-FTN transmission or Nyquist transmission, using the calculated SNR; when SC-FTN transmission is selected, calculating transmission capacity that goes through the transmitting amplifier, using each of the identified roll-off rates and the SNR; and when SC-FTN transmission is selected, determining an optimum transmission capacity from among the calculated transmission capacities on the basis of a plurality of PAPR values, while sequentially changing the average transmit power, and determining the roll-off rate at which the optimum transmission capacity is achieved, as a final roll-off rate for the transmitting amplifier, and when Nyquist transmission is selected, determining that Nyquist transmission using the transmitting amplifier be performed.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a wireless communication method, a wireless communication device, and a wireless communication system using a transmission amplifier. [Background technology]

[0002] In a wireless communication device equipped with a transmission amplifier that amplifies a transmission signal, the smaller the roll-off factor α of the transmission amplifier, the narrower the transmission bandwidth that can be used. The PAPR (Peak to Average Power Ratio) of the wireless communication device is expressed as a function of the roll-off factor α and the compression factor τ.

[0003] For example, Non-Patent Document 1 discloses the contribution of square root raised cosine (SRRC) to PAPR for each roll-off rate α, and Non-Patent Document 2 discloses the change in PAPR with respect to compression rate for each roll-off rate α.

[0004] Furthermore, SC (single carrier)-FTN (faster-than-nyquist) transmission is known as one of the techniques for optimizing the transmission capacity of a wireless communication device that wirelessly transmits a transmission signal amplified using a transmission amplifier.

[0005] FTN transmission is a method of transmitting modulation symbols at a symbol rate exceeding the clock frequency, and is expected to reduce the PAPR more than higher-order Quadrature Amplitude Modulation (QAM) with the same number of transmission bits (see, for example, Non-Patent Documents 2 and 3). [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] Marco Baldi, et al., "A comparison between APSK and QAM inwireless tactical scenarios for land mobile systems", EURASIP Journal on Wireless Communications and Networking 2012 [Non-patent document 2] Jean-Alain Lucciardi, et al., "Trade-Off Between Spectral Efficiency Increase And PAPR Reduction When Using FTN Signaling: Impact Of Non Linearities", IEEE ICC 2016 SAC Satellite and Space Communications [Non-patent document 3] Fredrik Rusek, et al., "Constrained Capacities for Faster-Than-Nyquist Signaling", IEEE TRANSACTIONS ON INFORMATION THEORY, VOL. 55, NO. 2, FEBRUARY 2009 Summary of the Invention [Problem to be solved by the invention]

[0007] When a wireless communication device reduces the average transmission power by taking into account the backoff and PAPR of the transmission amplifier, the signal-to-noise ratio (SNR) decreases. Therefore, in order to optimize communication capacity, it is necessary to maintain communication quality by adjusting the roll-off rate α and the compression rate τ.

[0008] In wireless communication, if the PAPR value exceeds the backoff value and distortion is allowed to occur, quality degradation equivalent to a drop in SNR occurs. Also, in wireless communication devices that can switch modulation methods, the contribution of PAPR and the minimum Euclidean distance differ depending on the modulation method (e.g., 16QAM, 16APSK, etc.), and therefore the amount of degradation equivalent to SNR also differs.

[0009] An object of the present invention is to provide a wireless communication method, a wireless communication device, and a wireless communication system that can optimize transmission capacity while maintaining transmission quality. [Means for solving the problem]

[0010] A wireless communication method according to one aspect of the present invention is a wireless communication method using a wireless communication device that includes a transmission amplifier and transmits signals by switching between SC-FTN transmission and Nyquist transmission, wherein a difference from P1dB is used as a backoff for an average transmission power P amplified by the transmission amplifier. Distortion exceeds the backoff value. A tolerance calculation step of calculating the PAPR value of each modulation scheme, and a roll-off rate calculation step of calculating the roll-off rate of each PAPR using a predetermined relationship table. Identify, Calculate the amount of degradation in SNR based on the amount exceeding the backoff and the minimum Euclidean distance, and calculate the average transmission power Subtract the propagation loss, noise power, and the degradation SNR equivalent from An SNR calculation step of calculating an SNR, and Based on this, the characteristics are advantageous Either SC-FTN transmission or Nyquist transmission , as a method of transmitting signals a capacity calculation step of calculating a transmission capacity via the transmission amplifier using each of the identified roll-off rates and the SNR when SC-FTN transmission is selected; and a capacity calculation step of sequentially changing an average transmission power when SC-FTN transmission is selected. obtained by Based on multiple PAPR values, By the capacity calculation process From the calculated transmission capacity The maximum transmission quality that can be maintained Determine the transmission capacity, The largest and a determination step of determining a roll-off rate that becomes a transmission capacity as a final roll-off rate for the transmission amplifier, and, when Nyquist transmission is selected, determining to perform Nyquist transmission using the transmission amplifier.

[0011] Furthermore, a wireless communication device according to one aspect of the present invention includes a transmission amplifier, and transmits a signal by switching between SC-FTN transmission and Nyquist transmission. The wireless communication device transmits a signal by switching between SC-FTN transmission and Nyquist transmission. The wireless communication device further includes: a transmission amplifier configured to amplify an average transmission power P by amplified by the transmission amplifier, the average transmission power P being a difference from P1 dB as a back-off; Distortion exceeds the backoff value. A tolerance calculation unit calculates the PAPR value of each modulation scheme that is allowed, and a roll-off rate is calculated for each PAPR calculated by the tolerance calculation unit using a predetermined relationship table. Identify, Calculate the amount of degradation in SNR based on the amount exceeding the backoff and the minimum Euclidean distance, and calculate the average transmission power Subtract the propagation loss, noise power, and the degradation SNR equivalent from an SNR calculation unit for calculating an SNR; and Based on this, the characteristics are advantageous Either SC-FTN transmission or Nyquist transmission , as a method of transmitting signals a capacity calculation unit that, when the selection unit selects SC-FTN transmission, calculates a transmission capacity via the transmission amplifier using the roll-off rates and SNRs specified by the SNR calculation unit; and, when the selection unit selects SC-FTN transmission, sequentially changes the average transmission power. obtained by Based on a plurality of PAPR values, from among the transmission capacities calculated by the capacity calculation unit, The maximum transmission quality that can be maintained Determine the transmission capacity, The largest a decision unit that decides a roll-off rate that becomes a transmission capacity as a final roll-off rate for the transmission amplifier, and that decides to perform Nyquist transmission using the transmission amplifier when the selection unit selects Nyquist transmission.

[0012] In addition, a wireless communication system according to one aspect of the present invention is a wireless communication system that includes a transmission amplifier and transmits a signal using a wireless communication device that switches between SC-FTN transmission and Nyquist transmission, and a back-off is set to a difference from P1dB for an average transmission power P amplified by the transmission amplifier. Distortion exceeds the backoff value. A tolerance calculation unit calculates the PAPR value of each modulation scheme that is allowed, and a roll-off rate is calculated for each PAPR calculated by the tolerance calculation unit using a predetermined relationship table. Identify,Calculate the amount of degradation in SNR based on the amount exceeding the backoff and the minimum Euclidean distance, and calculate the average transmission power Subtract the propagation loss, noise power, and the degradation SNR equivalent from an SNR calculation unit for calculating an SNR; and Based on this, the characteristics are advantageous Either SC-FTN transmission or Nyquist transmission , as a method of transmitting signals a capacity calculation unit that, when the selection unit selects SC-FTN transmission, calculates a transmission capacity via the transmission amplifier using the roll-off rates and SNRs specified by the SNR calculation unit; and, when the selection unit selects SC-FTN transmission, sequentially changes the average transmission power. obtained by Based on a plurality of PAPR values, from among the transmission capacities calculated by the capacity calculation unit, The maximum transmission quality that can be maintained Determine the transmission capacity, The largest a decision unit that decides a roll-off rate that becomes a transmission capacity as a final roll-off rate for the transmission amplifier, and that decides to perform Nyquist transmission using the transmission amplifier when the selection unit selects Nyquist transmission. [Effects of the Invention]

[0013] According to the present invention, it is possible to optimize transmission capacity while maintaining transmission quality. [Brief explanation of the drawings]

[0014] [Figure 1] 10 is a graph illustrating the contribution of SRRC to PAPR for each roll-off factor α. [Figure 2] 10 is a graph illustrating an example of a change in PAPR with respect to compression ratio for each roll-off ratio α. [Figure 3] 1A shows a constellation for SC-64QAM, and FIG. 1B shows a distorted constellation for SC-64QAM. [Figure 4] 10A and 10B are diagrams illustrating SNRs with advantageous characteristics for optimizing transmission capacity while maintaining the transmission quality of SC-FTN transmission and Nyquist transmission, respectively. [Figure 5]10 is a graph illustrating input / output characteristics of a transmission amplifier included in a wireless communication device according to an embodiment. [Figure 6] 1 is a functional block diagram illustrating functions that a wireless communication device according to an embodiment has for optimizing transmission capacity while maintaining transmission quality. [Figure 7] 10 is a flowchart illustrating an example of an operation of a wireless communication device according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] In one embodiment, a wireless communication system is configured such that a transmitter (wireless communication device) equipped with a transmission amplifier transmits a signal to a receiver, for example, via SC-FTN. Here, a roll-off factor α is calculated to optimize the transmission capacity of the wireless communication device.

[0016] First, we explain the PAPR of SC-FTN transmission. PAPR is expressed as a function of the roll-off rate α and the compression rate τ.

[0017] Fig. 1 is a graph illustrating the contribution of SRRC to PAPR for each roll-off rate α. In Fig. 1, the increase in PAPR due to SRRC with respect to the roll-off rate α is illustrated (see Non-Patent Document 1).

[0018] Fig. 2 is a graph illustrating the change in PAPR with respect to the compression ratio for each roll-off ratio α. Fig. 2 shows that the PAPR changes due to signal overlap depending on the compression ratio τ (see Non-Patent Document 2).

[0019] Next, we will explain the transmission capacity of SC-FTN and distortion caused by the transmission amplifier. FTN is expressed by the following equation (1) and is maximized when the following equation (2) holds (see Non-Patent Document 3).

[0020]

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[0021]

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[0022] where τ is the compression ratio of FTN, α is the roll-off rate, W is the bandwidth, T is the symbol duration, P is the received power, N0 is the noise power, SNR is the signal-to-noise ratio (P / N0), and H(·) is the frequency response of the communication channel.

[0023] Assuming the above formula (2), the transmission capacity C FTN can be viewed as a function of two variables, SNR and roll-off rate α.

[0024] However, if the average transmission power is reduced in consideration of the back-off of the transmission amplifier and the PAPR, the SNR will decrease.

[0025] For example, the SC-64QAM constellation shown in FIG. 3(a) will be distorted as shown in FIG. 3(b) if the PAPR value exceeds the backoff value of the transmission amplifier.

[0026] Therefore, in order to optimize communication capacity while maintaining transmission quality, it is necessary to maintain communication quality by adjusting the roll-off rate α and the compression rate τ.

[0027] For example, if the PAPR value exceeds the backoff value and distortion is allowed to occur, quality degradation equivalent to a decrease in SNR occurs, so parameters such as the roll-off rate α and compression rate τ must be adjusted.

[0028] Therefore, a wireless communication device according to an embodiment is configured to optimize transmission capacity while maintaining transmission quality even when distortion due to a transmission amplifier may occur. Note that the wireless communication device according to an embodiment can transmit signals by switching between SC-FTN transmission and Nyquist transmission, for example, and is based on the following four conditions (A) to (D).

[0029] (A): In wireless communication devices, there exists an SNR at which the characteristics of SC-FTN transmission are advantageous over those of ordinary Nyquist transmission.

[0030] Fig. 4 shows the SNRs that are advantageous for optimizing transmission capacity while maintaining transmission quality for SC-FTN and Nyquist transmission. SC-FTN transmission is advantageous at high SNRs, while Nyquist transmission is advantageous at low SNRs.

[0031] (B): When SC-FTN transmission is applied, the wireless communication device has a transmission capacity of C FTN The relationship in equation (2) above is maintained so that is maximized.

[0032] (C): The wireless communication device has a unique PAPR for each modulation scheme with respect to the roll-off rate α (a function of τ), and stores a table (such as a look-up table) that contains a relationship between the PAPR and the roll-off rate α for each modulation scheme (e.g., 16QAM and 16APSK).

[0033] (D) The wireless communication device allows the PAPR value to exceed the backoff value of the transmission amplifier, causing distortion.

[0034] 5 is a graph illustrating the input / output characteristics of a transmission amplifier included in a wireless communication device according to one embodiment. Here, the difference between P1dB (1 dB compression point) and the average transmission power, which is the operating point, is defined as the back-off. The PAPR value exceeds the back-off value of the transmission amplifier.

[0035] Then, the wireless communication device according to one embodiment performs the following processes (a) to (f) to select either SC-FTN transmission or Nyquist transmission that combines the optimal FTN efficiency, roll-off rate, and SNR (degraded SNR equivalent amount), thereby optimizing the transmission capacity.

[0036] (a): The wireless communication device specifies the roll-off factor α for each PAPR of each modulation scheme (for example, 16QAM and 16APSK) from a relationship table.

[0037] (b) The wireless communication device calculates the amount of degradation in SNR based on the amount by which the PAPR of the transmission amplifier exceeds the backoff and the minimum Euclidean distance for each modulation scheme.

[0038] (c): The wireless communication device calculates the SNR for the average transmission power P using the following equation (3).

[0039]

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[0040] (d): In order to optimize transmission capacity while maintaining transmission quality, the wireless communication device selects either SC-FTN transmission or Nyquist transmission, which has advantageous characteristics, based on the calculated SNR (see FIG. 4).

[0041] (e): When the wireless communication device selects SC-FTN transmission, it calculates the transmission capacity C by using the specified roll-off rate α and the calculated SNR according to the above formula (1). FTN Calculate.

[0042] (f): The wireless communication device selects the optimal C from multiple PAPR values. FTN Determine the optimal C FTN The roll-off rate α is determined as the final roll-off rate α for the transmitting amplifier.

[0043] Next, a specific example of functions provided in the wireless communication device according to an embodiment will be described. Fig. 6 is a functional block diagram illustrating functions provided in the wireless communication device according to an embodiment for optimizing transmission capacity while maintaining transmission quality.

[0044] As shown in FIG. 6, the wireless communication device according to one embodiment includes a storage unit 10, a tolerance calculation unit 11, an SNR calculation unit 12, a selection unit 13, a capacity calculation unit 14, and a determination unit 15.

[0045] The storage unit 10 is a memory or the like that stores information, such as the above-mentioned relationship table, that is necessary for the wireless communication device to optimize the transmission capacity while maintaining the transmission quality.

[0046] The tolerance calculation unit 11 calculates the allowable PAPR value for the average transmission power P of the transmission amplifier, using the difference from P1 dB as the backoff, and outputs the calculation result to the storage unit 10 and the SNR calculation unit 12.

[0047] That is, the tolerance calculation unit 11 calculates the PAPR value of each modulation scheme that is tolerable as a back-off, the difference from P1 dB for the average transmission power P amplified by the transmission amplifier.

[0048] The SNR calculation unit 12 specifies the roll-off rate α for each PAPR of each modulation scheme, such as 16QAM or 16APSK, using a relationship table stored in the memory unit 10, calculates the amount of degradation in SNR based on the amount by which the PAPR of the transmitting amplifier exceeds the backoff and the minimum Euclidean distance, calculates the SNR for the average transmission power using the above equation (3), and outputs the calculated SNR to the memory unit 10 and the selection unit 13.

[0049] The selection unit 13 uses the SNR calculated by the SNR calculation unit 12 to select either SC-FTN transmission or Nyquist transmission, which has advantageous characteristics for optimizing transmission capacity while maintaining transmission quality, and outputs the selection result to the memory unit 10 and the capacity calculation unit 14.

[0050] When the selector 13 selects SC-FTN transmission, the capacity calculator 14 accesses the memory 10 and calculates the transmission capacity C FTN and outputs the calculation result to the storage unit 10 and the determination unit 15. For example, the capacity calculation unit 14 calculates the value of the allowable PAPR in SC-FTN transmission.

[0051] That is, when the selector 13 selects SC-FTN transmission, the capacity calculator 14 calculates the transmission capacity via the transmission amplifier using each roll-off factor and the SNR identified by the SNR calculator 12.

[0052] The determination unit 15 accesses the storage unit 10, and when the selection unit 13 selects SC-FTN transmission, determines the optimal transmission capacity CFTN from a plurality of PAPR values ​​while sequentially changing the average transmission power P, and determines the optimal C FTN as the final roll-off rate α for the transmitting amplifier. Furthermore, when the selecting unit 13 selects Nyquist transmission, the determining unit 15 determines that the wireless communication device will perform Nyquist transmission using the transmitting amplifier.

[0053] That is, the determination unit 15 sequentially changes the average transmission power, determines the optimal transmission capacity from the transmission capacities calculated by the capacity calculation unit 14 based on multiple PAPR values, and determines the roll-off rate that results in the optimal transmission capacity as the final roll-off rate for the transmitting amplifier.

[0054] In this way, the wireless communication device according to one embodiment selects SC-FTN transmission or Nyquist transmission that combines the optimal FTN efficiency, roll-off rate α, and SNR (degraded SNR equivalent amount), thereby achieving a transmission capacity C FTN This achieves optimization.

[0055] Next, an example of the operation of the wireless communication device according to an embodiment will be described with reference to a flowchart of FIG.

[0056] In step 100 (S100), the tolerance calculation unit 11 calculates a PAPR value that is tolerable for the average transmission power P of the transmission amplifier, with the difference from P1 dB as a backoff.

[0057] In step 102 (S102), the SNR calculation unit 12 determines the roll-off rate α for each PAPR of each modulation scheme, such as 16QAM or 16APSK, using a relationship table stored in the storage unit 10, calculates the degradation SNR equivalent amount based on the amount by which the PAPR of the transmission amplifier exceeds the backoff and the minimum Euclidean distance for each modulation scheme, and calculates the SNR for the average transmission power.

[0058] In step 104 (S104), the selection unit 13 determines whether the characteristics of SC-FTN transmission are more advantageous than Nyquist transmission in order to optimize transmission capacity while maintaining transmission quality. If it is determined that the characteristics are advantageous (S104: Yes), the selection unit 13 proceeds to processing of S108, and if it is determined that the characteristics are not advantageous (S104: No), the selection unit 13 proceeds to processing of S106.

[0059] In step 106 (S106), the selection unit 13 selects Nyquist transmission.

[0060] In step 108 (S108), the capacity calculation unit 14 calculates the transmission capacity C by the above formula (1) using the roll-off rates α and the SNR specified by the SNR calculation unit 12. FTN Calculate.

[0061] In step 110 (S110), the determination unit 15 determines the C FTN However, the memory unit 10 previously stored C FTN It is determined whether it is greater than the threshold value, and if it is greater (S110: Yes), the process proceeds to S112, otherwise (S110: No), the process proceeds to S114.

[0062] In step 112 (S112), the storage unit 10 stores the C FTN Remember.

[0063] In step 114 (S114), the decision unit 15 determines whether the average transmission power P is greater than Pmax (maximum transmission power), and if it is greater (S114: Yes), terminates the processing, otherwise (S114: No), proceeds to processing S116.

[0064] In step 116 (S116), the determination unit 15 determines the average transmission power P i P i+1 (however,··· <P i-1 <P i <P i+1 <···).

[0065] In other words, when the selector 13 selects Nyquist transmission, the determiner 15 determines the optimal transmission capacity CFTN from multiple PAPR values ​​while sequentially changing the average transmission power P, and determines the roll-off factor α that results in the optimal CFTN as the final roll-off factor α for the transmitting amplifier. Also, when the selector 13 selects Nyquist transmission, the determiner 15 determines that the wireless communication device will perform Nyquist transmission using a transmitting amplifier.

[0066] In this way, when a wireless communication device equipped with a transmission amplifier that amplifies a transmission signal selects SC-FTN transmission, it determines the combination of the roll-off factor α, the SNR degradation amount, and the modulation scheme, and can optimize the transmission capacity while maintaining the transmission quality. Also, when selecting Nyquist transmission is more advantageous, the wireless communication device selects Nyquist transmission and optimizes the transmission capacity.

[0067] Note that each of the components constituting the wireless communication device described above may be partially or entirely configured by hardware, or may be configured by having a processor execute a program stored in a memory or the like.

[0068] Furthermore, when some or all of the components of the wireless communication device are configured by having a processor execute a program, the program may be recorded on a recording medium and supplied, or may be supplied via a network. [Explanation of symbols]

[0069] 10. Memory unit, 11. Tolerance calculation unit, 12. SNR calculation unit, 13. Selection unit, 14. Capacity calculation unit, 15. Determination unit

Claims

1. A wireless communication method using a wireless communication device that includes a transmission amplifier and transmits signals by switching between SC-FTN transmission and Nyquist transmission, a tolerance calculation step of calculating a PAPR value for each modulation scheme where distortion is allowed to exceed a backoff value that is a difference from P1 dB with respect to an average transmission power P amplified by the transmission amplifier; an SNR calculation step of specifying a roll-off rate for each calculated PAPR using a predetermined relationship table, calculating a degradation SNR equivalent amount based on the amount exceeding the back-off and the minimum Euclidean distance, and calculating an SNR by subtracting the propagation loss, noise power, and the degradation SNR equivalent amount from the average transmission power; a selection step of selecting, based on the calculated SNR, either SC-FTN transmission or Nyquist transmission, which has advantageous characteristics, as a signal transmission method; a capacity calculation step of calculating a transmission capacity through the transmission amplifier using each of the identified roll-off factors and the SNR when SC-FTN transmission is selected; a determination step of determining, when SC-FTN transmission is selected, a maximum transmission capacity that maintains a predetermined transmission quality from among the transmission capacities calculated in the capacity calculation step, based on a plurality of PAPR values ​​obtained by sequentially changing the average transmission power, determining a roll-off rate that results in the maximum transmission capacity as a final roll-off rate for the transmission amplifier, and, when Nyquist transmission is selected, determining to perform Nyquist transmission using the transmission amplifier; A wireless communication method comprising:

2. A wireless communication device that includes a transmission amplifier and transmits signals by switching between SC-FTN transmission and Nyquist transmission, a tolerance calculation unit that calculates a PAPR value for each modulation scheme where distortion is allowed to exceed a backoff value that is a difference from P1 dB with respect to an average transmission power P amplified by the transmission amplifier; an SNR calculation unit that specifies a roll-off rate for each PAPR calculated by the tolerance calculation unit using a predetermined relationship table, calculates a degradation SNR equivalent amount based on an amount exceeding the back-off and a minimum Euclidean distance, and calculates an SNR by subtracting a propagation loss, noise power, and the degradation SNR equivalent amount from an average transmission power; a selection unit that selects either SC-FTN transmission or Nyquist transmission, which has advantageous characteristics, as a signal transmission method based on the SNR calculated by the SNR calculation unit; a capacity calculation unit that calculates a transmission capacity through the transmission amplifier using each roll-off rate and the SNR specified by the SNR calculation unit when the selection unit selects SC-FTN transmission; a determination unit that, when the selection unit selects SC-FTN transmission, determines a maximum transmission capacity that maintains a predetermined transmission quality from among the transmission capacities calculated by the capacity calculation unit based on a plurality of PAPR values ​​obtained by sequentially changing the average transmission power, determines a roll-off rate that results in the maximum transmission capacity as a final roll-off rate for the transmission amplifier, and, when the selection unit selects Nyquist transmission, determines to perform Nyquist transmission using the transmission amplifier; A wireless communication device comprising:

3. In a wireless communication system in which a signal is transmitted by a wireless communication device that includes a transmission amplifier and switches between SC-FTN transmission and Nyquist transmission, a tolerance calculation unit that calculates a PAPR value for each modulation scheme where distortion is allowed to exceed a backoff value that is a difference from P1 dB with respect to an average transmission power P amplified by the transmission amplifier; an SNR calculation unit that specifies a roll-off rate for each PAPR calculated by the tolerance calculation unit using a predetermined relationship table, calculates a degradation SNR equivalent amount based on an amount exceeding the back-off and a minimum Euclidean distance, and calculates an SNR by subtracting a propagation loss, noise power, and the degradation SNR equivalent amount from an average transmission power; a selection unit that selects either SC-FTN transmission or Nyquist transmission, which has advantageous characteristics, as a signal transmission method based on the SNR calculated by the SNR calculation unit; a capacity calculation unit that calculates a transmission capacity through the transmission amplifier using each roll-off rate and the SNR specified by the SNR calculation unit when the selection unit selects SC-FTN transmission; a determination unit that, when the selection unit selects SC-FTN transmission, determines a maximum transmission capacity that maintains a predetermined transmission quality from among the transmission capacities calculated by the capacity calculation unit based on a plurality of PAPR values ​​obtained by sequentially changing the average transmission power, determines a roll-off rate that results in the maximum transmission capacity as a final roll-off rate for the transmission amplifier, and, when the selection unit selects Nyquist transmission, determines to perform Nyquist transmission using the transmission amplifier; A wireless communication system comprising:

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