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 of each modulation scheme, with which a difference from P1dB can be accepted as a backoff, for the average transmit power P amplified by a transmitting amplifier; identifying each roll-off rate using a predetermined relationship table, for the calculated PAPR of each modulation scheme, calculating a degradation SNR converted amount on the basis of the amount that the PAPR of the transmitting amplifier exceeds backoff and the minimum Euclidean distance of each modulation scheme, and selecting a modulation scheme with which the degradation amount is small; calculating an SNR for the average transmit power; calculating transmission capacity that goes through the transmitting amplifier, using each of the identified roll-off rates and the calculated SNR; and 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 adopting 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 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 includes a transmission amplifier, and a signal is transmitted by switching modulation methods. SC-FTN In a wireless communication method using a wireless communication device that transmits, a difference from P1dB is allowed as a backoff for the average transmission power P amplified by the transmission amplifier. Multiple Modulation method each A tolerance calculation step of calculating the PAPR value of Multiple For the PAPR of the modulation method, The PAPR by SRRC for each modulation method is a modulation scheme selection step of specifying roll-off rates using a predetermined relationship table, calculating the amount of degradation SNR equivalent based on the amount by which the PAPR of the transmission amplifier exceeds the back-off and the minimum Euclidean distance for each modulation scheme, and selecting a modulation scheme with a small amount of degradation; an SNR calculation step of calculating an SNR for an average transmission power; and a modulation scheme selection step of calculating an SNR for an average transmission power using the specified roll-off rates and the calculated SNR. The SRRC and a capacity calculation step of calculating a transmission capacity through the transmission amplifier, and a 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 calculating a roll-off rate that results in the optimum transmission capacity. , the SRRC and the transmission amplifier SC-FTN transmission via and determining a final roll-off rate for the

[0011] Furthermore, a wireless communication device according to an aspect of the present invention includes a transmission amplifier, and transmits a signal by switching modulation methods. SC-FTN In a wireless communication device transmitting a signal, the difference from P1dB is allowed as a backoff for the average transmission power P amplified by the transmission amplifier. Multiple Modulation method each a tolerance calculation unit that calculates the PAPR value of the Multiple For the PAPR of the modulation method, The PAPR by SRRC for each modulation method is a modulation scheme selector that specifies each roll-off rate using a predetermined relationship table, calculates the amount of degradation SNR equivalent based on the amount by which the PAPR of the transmission amplifier exceeds the back-off and the minimum Euclidean distance for each modulation scheme, and selects a modulation scheme with a small amount of degradation; an SNR calculator that calculates an SNR for an average transmission power; and a modulation scheme selector that calculates an SNR for each average transmission power using each roll-off rate specified by the modulation scheme selector and the SNR calculated by the SNR calculator. The SRRC and a capacity calculation unit that calculates a transmission capacity via the transmission amplifier; and a roll-off rate that determines an optimum transmission capacity from the transmission capacities calculated by the capacity calculation unit based on a plurality of PAPR values ​​while sequentially changing the average transmission power. , the SRRC and the transmission amplifier SC-FTN transmission via and a determining unit for determining the final roll-off rate for the

[0012] Furthermore, a wireless communication system according to an aspect of the present invention includes a wireless communication device that includes a transmission amplifier and switches modulation methods to transmit a signal. SC-FTN In a wireless communication system, the difference from P1dB is allowed as a backoff for the average transmission power P amplified by the transmission amplifier. Multiple Modulation method each a tolerance calculation unit that calculates the PAPR value of the Multiple For the PAPR of the modulation method, The PAPR by SRRC for each modulation method isa modulation scheme selector that specifies each roll-off rate using a predetermined relationship table, calculates the amount of degradation SNR equivalent based on the amount by which the PAPR of the transmission amplifier exceeds the back-off and the minimum Euclidean distance for each modulation scheme, and selects a modulation scheme with a small amount of degradation; an SNR calculator that calculates an SNR for an average transmission power; and a modulation scheme selector that calculates an SNR for each average transmission power using each roll-off rate specified by the modulation scheme selector and the SNR calculated by the SNR calculator. The SRRC and a capacity calculation unit that calculates a transmission capacity via the transmission amplifier; and a roll-off rate that determines an optimum transmission capacity from the transmission capacities calculated by the capacity calculation unit based on a plurality of PAPR values ​​while sequentially changing the average transmission power. , the SRRC and the transmission amplifier SC-FTN transmission via and a determining unit for determining the final roll-off rate for the [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] 1A shows a constellation for 16APSK, and FIG. 1B shows a constellation for 16QAM. [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]

number

number

[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 FTN can 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] 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.

[0025] 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.

[0026] 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.

[0027] 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).

[0028] (A): The wireless communication device has a transmission capacity of C FTN The relationship in equation (2) above is maintained so that is maximized.

[0029] (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).

[0030] 4A and 4B are diagrams illustrating constellations of different modulation schemes. FIG. 4A is a diagram illustrating a constellation of 16APSK. FIG. 4B is a diagram illustrating a constellation of 16QAM. As shown by comparing FIGS. 4A and 4B, when the modulation schemes are different, the PAPR contribution amount and the minimum Euclidean distance are different.

[0031] (C) The wireless communication device allows the PAPR value to exceed the backoff value of the transmission amplifier, causing distortion.

[0032] 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.

[0033] Then, the wireless communication device according to one embodiment performs the following processes (a) to (d) to select the optimal combination of FTN efficiency, roll-off rate, SNR (degraded SNR equivalent amount) and modulation method, thereby optimizing the transmission capacity.

[0034] (a): The wireless communication device identifies the roll-off rate α for each PAPR of each modulation method (e.g., 16QAM and 16APSK) from a relationship table, calculates the degradation SNR equivalent amount based on the amount by which the PAPR of the transmitting amplifier exceeds the backoff and the minimum Euclidean distance for each modulation method, and selects the modulation method with the least degradation amount.

[0035] (b) The wireless communication device calculates the SNR for the PAPR using the following equation (3).

[0036]

number

[0037] (c): The wireless communication device uses the specified roll-off rate α and the calculated SNR to calculate the transmission capacity C FTN Calculate.

[0038] (d): 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.

[0039] 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.

[0040] As shown in FIG. 6, the wireless communication device according to one embodiment includes a storage unit 10, a tolerance calculation unit 11, a modulation scheme selection unit 12, an SNR calculation unit 13, a capacity calculation unit 14, and a determination unit 15.

[0041] 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.

[0042] 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 modulation scheme selection unit 12.

[0043] 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.

[0044] The modulation scheme selector 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 of each modulation scheme, and selects a modulation scheme with the least degradation amount.The modulation scheme selector 12 then outputs information indicating the selected modulation scheme to the storage unit 10 and the SNR calculator 13.

[0045] That is, the modulation scheme selector 12 specifies the roll-off rate for each PAPR of each modulation scheme calculated by the tolerance calculator 11 using a predetermined relationship table, calculates the degradation SNR equivalent amount based on the amount by which the PAPR of the transmitting amplifier exceeds the backoff and the minimum Euclidean distance for each modulation scheme, and selects the modulation scheme with the least degradation amount.

[0046] The SNR calculation unit 13 accesses the storage unit 10, calculates the SNR for the average transmission power P using the above equation (3), and outputs the calculated SNR to the storage unit 10 and the capacity calculation unit 14.

[0047] 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. For example, the capacity calculation unit 14 calculates the PAPR value of each modulation scheme allowed in SC-FTN transmission.

[0048] That is, the capacity calculation unit 14 calculates the transmission capacity via the transmission amplifier using each roll-off factor identified by the modulation scheme selection unit 12 and the SNR calculated by the SNR calculation unit 13.

[0049] 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 FTNThe roll-off rate α is determined as the final roll-off rate α for the transmitting amplifier.

[0050] 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.

[0051] In this way, the wireless communication device according to one embodiment selects an optimal combination of FTN efficiency, roll-off rate α, SNR (degraded SNR equivalent amount), and modulation method, thereby achieving a transmission capacity C FTN This achieves optimization.

[0052] 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.

[0053] 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.

[0054] In step 102 (S102), the modulation scheme selection 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 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 selects the modulation scheme with the least degradation amount.

[0055] In step 104 (S104), the SNR calculation unit 13 calculates the SNR for the average transmission power using the above equation (3).

[0056] 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 specified by the modulation scheme selection unit 12 and the SNR calculated by the SNR calculation unit 13.FTN Calculate.

[0057] In step 108 (S108), 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 (S108: Yes), the process proceeds to S110, otherwise (S108: No), the process proceeds to S112.

[0058] In step 110 (S100), the storage unit 10 stores the C FTN Remember.

[0059] 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.

[0060] 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 <···).

[0061] 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.

[0062] In this way, a wireless communication device equipped with a transmission amplifier that amplifies a transmission signal can determine a combination of the roll-off rate α, the degradation SNR equivalent amount, and the modulation method, and optimize the transmission capacity while maintaining the transmission quality.

[0063] 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.

[0064] 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]

[0065] 10. Storage unit, 11. Tolerance calculation unit, 12. Modulation method selection 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 signals by switching modulation methods using SC-FTN, a tolerance calculation step of calculating a PAPR value for each of a plurality of modulation schemes, the difference from P1 dB being a back-off allowable for an average transmission power P amplified by the transmission amplifier; a modulation scheme selection step of specifying a roll-off rate for each of the calculated PAPRs of the plurality of modulation schemes using a relationship table in which the PAPRs by the SRRC for the roll-off rates are predetermined for each modulation scheme, calculating an amount of degradation equivalent to an SNR based on the amount by which the PAPR of the transmission amplifier exceeds the back-off and the minimum Euclidean distance for each modulation scheme, and selecting a modulation scheme with a small amount of degradation; an SNR calculation step of calculating an SNR for an average transmission power; a capacity calculation step of calculating a transmission capacity through the SRRC and the transmission amplifier using each of the identified roll-off rates and the calculated SNR; a determining 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 factor resulting in the optimal transmission capacity as a final roll-off factor for SC-FTN transmission via the SRRC and the transmission amplifier; A wireless communication method comprising:

2. A wireless communication device that includes a transmission amplifier and transmits signals by switching modulation methods using SC-FTN, a tolerance calculation unit that calculates a PAPR value for each of a plurality of modulation schemes, the difference from P1 dB being a backoff for an average transmission power P amplified by the transmission amplifier; a modulation scheme selection unit that specifies roll-off rates for the PAPRs of the plurality of modulation schemes calculated by the tolerance calculation unit using a relationship table in which PAPRs by SRRC for each of the modulation schemes are predetermined relative to roll-off rates, calculates a degradation SNR equivalent amount based on the amount by which the PAPR of the transmission amplifier exceeds a back-off and the minimum Euclidean distance for each of the modulation schemes, and selects a modulation scheme with a small amount of degradation; an SNR calculation unit that calculates an SNR for an average transmission power; a capacity calculation unit that calculates a transmission capacity via the SRRC and the transmission amplifier using each roll-off rate specified by the modulation scheme selection 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 the roll-off rate that results in the optimal transmission capacity as a final roll-off rate for SC-FTN transmission via the SRRC and 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 equipped with a transmission amplifier and capable of switching modulation methods, a tolerance calculation unit that calculates a PAPR value for each of a plurality of modulation schemes, the difference from P1 dB being a backoff for an average transmission power P amplified by the transmission amplifier; a modulation scheme selection unit that specifies roll-off rates for the PAPRs of the plurality of modulation schemes calculated by the tolerance calculation unit using a relationship table in which PAPRs by SRRC for each of the modulation schemes are predetermined relative to roll-off rates, calculates a degradation SNR equivalent amount based on the amount by which the PAPR of the transmission amplifier exceeds a back-off and the minimum Euclidean distance for each of the modulation schemes, and selects a modulation scheme with a small amount of degradation; an SNR calculation unit that calculates an SNR for an average transmission power; a capacity calculation unit that calculates a transmission capacity via the SRRC and the transmission amplifier using each roll-off rate specified by the modulation scheme selection 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 the roll-off rate that results in the optimal transmission capacity as a final roll-off rate for SC-FTN transmission via the SRRC and the transmission amplifier; A wireless communication system comprising:

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