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

Abstract

To optimize transmission capacity while maintaining transmission quality.SOLUTION: The method comprises: calculating a PAPR value with which a difference from P1dB can be accepted as a backoff, for the average transmit power P amplified by a transmitting amplifier; calculating a roll-off rate on the basis of the relationship of the PAPR and the roll-off rate; calculating an SNR for the PAPR; calculating transmission capacity using the calculated roll-off rates and SNR; and determining 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.SELECTED DRAWING: Figure 4

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] 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]

[0009] A wireless communication method according to one aspect of the present invention is a wireless communication method using a wireless communication device that has a transmission amplifier and transmits a signal, and is characterized by including: an allowable value calculation step of calculating a PAPR value that is allowable as a back-off, the difference from P1 dB, for average transmission power P amplified by the transmission amplifier; an α calculation step of calculating a roll-off rate based on a relationship between the PAPR and the roll-off rate; an SNR calculation step of calculating an SNR for the PAPR; a capacity calculation step of calculating a transmission capacity using each of the calculated roll-off rates and the SNR; and a determination step of determining an optimal transmission capacity from the calculated transmission capacities based on a plurality of PAPR values while sequentially changing the average transmission power, and determining the roll-off rate that results in the optimal transmission capacity as a final roll-off rate for the transmission amplifier.

[0010] Furthermore, a wireless communication device according to one aspect of the present invention is a wireless communication device that includes a transmission amplifier and transmits a signal, and is characterized in that it comprises: an allowable value calculation unit that calculates a PAPR value that is allowable as a back-off, the difference from P1 dB, for average transmission power P amplified by the transmission amplifier; an α calculation unit that calculates a roll-off rate based on the relationship between the PAPR and the roll-off rate; an SNR calculation unit that calculates an SNR for the PAPR; a capacity calculation unit that calculates a transmission capacity using each of the roll-off rates calculated by the α calculation unit and the SNR calculated by the SNR calculation unit; and a determination unit that determines an optimal transmission capacity from the transmission capacities calculated by the capacity calculation unit based on multiple PAPR values while sequentially changing the average transmission power, and determines the roll-off rate that results in the optimal transmission capacity as a final roll-off rate for the transmission amplifier.

[0011] Furthermore, 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 from a wireless communication device, and includes: an allowable value calculation unit that calculates a PAPR value that is allowable as a back-off, the difference from P1 dB for average transmission power P amplified by the transmission amplifier; an α calculation unit that calculates a roll-off rate based on a relationship between the PAPR and the roll-off rate; an SNR calculation unit that calculates an SNR for the PAPR; a capacity calculation unit that calculates a transmission capacity using each of the roll-off rates calculated by the α calculation unit and the SNR calculated by the SNR calculation unit; and a determination unit that determines an optimal transmission capacity from the transmission capacities calculated by the capacity calculation unit based on multiple PAPR values while sequentially changing the average transmission power, and determines the roll-off rate that results in the optimal transmission capacity as a final roll-off rate for the transmission amplifier. [Effects of the Invention]

[0012] According to the present invention, it is possible to optimize transmission capacity while maintaining transmission quality. [Brief explanation of the drawings]

[0013] [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] 10 is a graph illustrating input / output characteristics of a transmission amplifier included in a wireless communication device according to an embodiment. [Figure 4] 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 5] 10 is a flowchart illustrating an example of an operation of a wireless communication device according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] 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.

[0015] 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.

[0016] 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).

[0017] 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).

[0018] 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).

[0019]

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[0020]

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[0021] 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.

[0022] Assuming the above formula (2), the transmission capacity C FTNcan be viewed as a function of two variables, SNR and roll-off rate α.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] Therefore, a wireless communication device according to an embodiment is configured to optimize transmission capacity while maintaining transmission quality even when distortion may occur due to a transmission amplifier. Note that the wireless communication device according to an embodiment can transmit signals by switching modulation methods, and is based on the following three conditions (A) to (C).

[0027] (A): The wireless communication device has a transmission capacity of C FTN The relationship in equation (2) above is maintained so that is maximized.

[0028] (B): 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).

[0029] (C) The wireless communication device defines the backoff of the transmission amplifier as the allowable PAPR.

[0030] 3 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 serving as the operating point is defined as the backoff. The backoff value of the transmission amplifier and the allowable PAPR value are the same.

[0031] Then, the wireless communication device according to one embodiment performs the following processes (a) to (d) to select an optimal combination of FTN efficiency and roll-off rate, thereby optimizing the transmission capacity.

[0032] (a): The wireless communication device determines the allowable PAPR from the back-off of the transmission amplifier, and determines the roll-off rate α based on the relationship between the actual PAPR and the roll-off rate α with respect to the allowable PAPR.

[0033] (b): The wireless communication device calculates the SNR for the average transmission power using the following equation (3).

[0034]

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[0035] (c): The wireless communication device uses the specified roll-off rate α and the calculated SNR to calculate the transmission capacity C FTN Calculate.

[0036] (d): The wireless communication device is configured to FTN is determined, and the final roll-off rate α is calculated based on the relationship between PAPR and roll-off rate α and the coding rate value that satisfies a predetermined frequency utilization efficiency.

[0037] Next, a specific example of functions provided in the wireless communication device according to an embodiment will be described. Fig. 4 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.

[0038] As shown in FIG. 4, the wireless communication device according to one embodiment includes a storage unit 10, a tolerance calculation unit 11, an α calculation unit 12, an SNR calculation unit 13, a capacity calculation unit 14, and a determination unit 15.

[0039] 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.

[0040] 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 α calculation unit 12.

[0041] 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.

[0042] The α calculation unit 12 calculates the roll-off factor α based on the relationship between the PAPR and the roll-off factor α, and outputs the calculation result to the storage unit 10 and the SNR calculation unit 13.

[0043] The SNR calculation unit 13 accesses the storage unit 10, calculates the SNR for the PAPR using the above equation (3), and outputs the calculated SNR to the storage unit 10 and the capacity calculation unit 14.

[0044] The capacity calculation unit 14 accesses the storage unit 10 and calculates the transmission capacity C FTN and outputs the calculation result to the storage unit 10 and the determination unit 15.

[0045] The determination unit 15 accesses the storage unit 10, sequentially changes the average transmission power P, and determines the optimum transmission capacity C from a plurality of 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.

[0046] 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.

[0047] In this way, the wireless communication device according to one embodiment calculates the transmission capacity C based on the optimal FTN efficiency and the roll-off rate α. FTN This achieves optimization.

[0048] 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.

[0049] 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.

[0050] In step 102 (S102), the α calculation unit 12 calculates the roll-off factor α based on the relationship between the PAPR and the roll-off factor α.

[0051] In step 104 (S104), the SNR calculation unit 13 accesses the storage unit 10, calculates the SNR for the PAPR using the above equation (3), and outputs the calculated SNR to the storage unit 10 and the capacity calculation unit .

[0052] In step 106 (S106), the capacity calculation unit 14 calculates the transmission capacity C by the above formula (1) using the roll-off rates α calculated by the α calculation unit 12 and the SNR calculated by the SNR calculation unit 13. FTN Calculate.

[0053] In step 108 (S108), the determination unit 15 determines the C FTN However, the memory unit 10 previously stored C FTNIt is determined whether it is greater than the threshold value, and if it is greater (S108: Yes), the process proceeds to S110, otherwise (S108: No), the process proceeds to S112.

[0054] In step 110 (S110), the storage unit 10 stores the C FTN Remember.

[0055] In step 112 (S112), the decision unit 15 determines whether the average transmission power P is greater than Pmax (maximum transmission power), and if it is greater (S112: Yes), ends the processing, otherwise (S112: No), proceeds to processing S114.

[0056] In step 114 (S114), the determination unit 15 determines the average transmission power P i P i+1 (however,··· <P i-1 <P i <P i+1 <···).

[0057] That is, the determination unit 15 sequentially changes the average transmission power P and determines the optimal transmission capacity C from a plurality of 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.

[0058] In this way, a wireless communication device equipped with a transmission amplifier that amplifies a transmission signal realizes optimization of the transmission capacity CFTN based on the optimum FTN efficiency and roll-off rate α.

[0059] 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.

[0060] 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]

[0061] 10. Storage unit, 11. Tolerance calculation unit, 12. α calculation unit, 13. SNR calculation 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 a signal, a tolerance calculation step of calculating a PAPR value that is permissible as a backoff, the difference from P1 dB, for the average transmission power P amplified by the transmission amplifier; an α calculation step of calculating a roll-off factor based on a relationship between the PAPR and the roll-off factor; an SNR calculation step of calculating an SNR for the PAPR; a capacity calculation step of calculating a transmission capacity using each of the calculated roll-off factors and the SNR; a determining step of determining an optimum transmission capacity from the calculated transmission capacities based on a plurality of PAPR values while sequentially changing the average transmission power, and determining the roll-off rate resulting in the optimum transmission capacity as a final roll-off rate for the transmission amplifier; A wireless communication method comprising:

2. In a wireless communication device that transmits signals and is equipped with a transmission amplifier, a tolerance calculation unit that calculates a tolerance value for PAPR, which is a difference from P1 dB as a backoff, for an average transmission power P amplified by the transmission amplifier; an α calculation unit that calculates a roll-off rate based on a relationship between the PAPR and the roll-off rate; an SNR calculation unit that calculates an SNR for the PAPR; a capacity calculation unit that calculates a transmission capacity using each roll-off factor calculated by the α calculation unit and the SNR calculated by the SNR calculation unit; a determination unit that determines an optimal transmission capacity from among the transmission capacities calculated by the capacity calculation unit based on a plurality of PAPR values while sequentially changing an average transmission power, and determines a roll-off rate that results in the optimal transmission capacity as a final roll-off rate for 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 having a transmission amplifier, a tolerance calculation unit that calculates a tolerance value for PAPR, which is a difference from P1 dB as a backoff, for an average transmission power P amplified by the transmission amplifier; an α calculation unit that calculates a roll-off rate based on a relationship between the PAPR and the roll-off rate; an SNR calculation unit that calculates an SNR for the PAPR; a capacity calculation unit that calculates a transmission capacity using each roll-off factor calculated by the α calculation unit and the SNR calculated by the SNR calculation unit; a determination unit that determines an optimal transmission capacity from among the transmission capacities calculated by the capacity calculation unit based on a plurality of PAPR values while sequentially changing an average transmission power, and determines a roll-off rate that results in the optimal transmission capacity as a final roll-off rate for the transmission amplifier; A wireless communication system comprising:

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