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

Abstract

To optimize transmission capacity while maintaining transmission quality.SOLUTION: The method comprises: determining whether the required SNR for the current modulation index and roll-off rate is satisfied, and when it is determined that the required SNR is not satisfied, performing the process of lowering the modulation index; calculating transmission capacity that goes through the transmitting amplifier, using each of identified roll-off rates and the SNR, on the basis of the result of determination; 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 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 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 a signal by switching a modulation index, the method comprising: Distortion exceeds the backoff value. Each of the allowed modulations Index A tolerance calculation process for calculating the PAPR value of each of the following: Identify, The amount of SNR degradation based on the amount of backoff exceeded and the minimum Euclidean distance Calculate Average Transmit Power Subtract the propagation loss, noise power, and the degradation SNR equivalent from an SNR calculation step of calculating an SNR; The calculated SNR is Current modulation index, roll-off rate predetermined a determination process for determining whether a required SNR is satisfied, and if it is determined that the required SNR is not satisfied, performing a process for lowering the modulation index; <Modulation index and a capacity calculation step of calculating a transmission capacity through the transmission amplifier using the specified roll-off rates and SNR; and The modified average transmit power of each Based on the PAPR value, 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 determining step of determining a roll-off rate that becomes a transmission capacity as a final roll-off rate for 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 a modulation index. The wireless communication device transmits a signal by switching a modulation index by switching a modulation index. Distortion exceeds the backoff value. Each of the allowed modulations Index a tolerance calculation unit that calculates the PAPR value of the roll-off rate using a predetermined relationship table for the PAPR calculated by the tolerance calculation unit; Identify, The amount of SNR degradation based on the amount of backoff exceeded and the minimum Euclidean distance Calculate , average transmit power Subtract the propagation loss, noise power, and the degradation SNR equivalent from an SNR calculation unit for calculating an SNR; The calculated SNR is Current modulation index, roll-off rate predetermined a determination processing unit that determines whether a required SNR is satisfied, and performs processing to lower the modulation index if it is determined that the required SNR is not satisfied; <Modulation index and a capacity calculation unit that calculates a transmission capacity through the transmission amplifier using the roll-off rates and SNRs specified by the SNR calculation unit; and The modified average transmit power of each Based on the PAPR value, the capacity calculation unit calculates the transmission capacity. The maximum transmission quality that can be maintained Determine the transmission capacity, The largest and a determining unit that determines the roll-off rate that becomes the transmission capacity as the final roll-off rate for the transmission amplifier.

[0012] In addition, a wireless communication system according to one aspect of the present invention includes a transmission amplifier, and transmits a signal by a wireless communication device that switches a modulation index. In the wireless communication system, a difference from P1 dB is set as a back-off for an average transmission power P amplified by the transmission amplifier. Distortion exceeds the backoff value. Each of the allowed modulations Index a tolerance calculation unit that calculates the PAPR value of the roll-off rate using a predetermined relationship table for the PAPR calculated by the tolerance calculation unit; Identify,The amount of SNR degradation based on the amount of backoff exceeded and the minimum Euclidean distance Calculate , average transmit power Subtract the propagation loss, noise power, and the degradation SNR equivalent from An SNR calculation unit calculates the SNR, and the calculated SNR is compared with the current modulation index and roll-off rate. predetermined a determination processing unit that determines whether a required SNR is satisfied, and performs processing to lower the modulation index if it is determined that the required SNR is not satisfied; <Modulation index and a capacity calculation unit that calculates a transmission capacity through the transmission amplifier using the roll-off rates and SNRs specified by the SNR calculation unit; and The modified average transmit power of each Based on the PAPR value, the capacity calculation unit calculates the transmission capacity. The maximum transmission quality that can be maintained Determine the transmission capacity, The largest and a determining unit that determines the roll-off rate that becomes the transmission capacity as the final roll-off rate for the transmission amplifier. [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] FIG. 10 is a diagram illustrating a modulation index table used by the wireless communication device. [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 due to a transmission amplifier may occur. Note that the wireless communication device according to an embodiment can transmit signals by switching modulation indexes and switching between SC-FTN transmission and Nyquist transmission, for example, 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): In the wireless communication device, the PAPR is unique with respect to the roll-off rate α (a function of τ), and a table (such as a look-up table) relating the PAPR and the roll-off rate α for each modulation index is stored in advance.

[0030] 4 is a diagram illustrating a modulation index table used by a wireless communication device, in which transmission bits and modulation schemes are associated with each modulation index.

[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 (f) to select either SC-FTN transmission or Nyquist transmission that combines the optimal FTN efficiency, roll-off rate, SNR (degraded SNR equivalent amount), and modulation index, thereby optimizing the transmission capacity.

[0034] (a): For average transmission power P, the allowable PAPR is calculated using the difference from P1 dB as the backoff, and the final roll-off rate is determined from the relationship between the allowable PAPR, the actual PAPR, the modulation method, and the roll-off rate α.

[0035] (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.

[0036] (c): The wireless communication device calculates the SNR for the average transmission power P using the following equation (3).

[0037]

number

[0038] (d): If the wireless communication device determines that the required SNR for the current modulation index and roll-off rate α is not satisfied, it lowers the modulation index and recalculates the actual PAPR.

[0039] (e): The wireless communication device uses the specified roll-off rate α and the calculated SNR to calculate the transmission capacity C FTN Calculate.

[0040] (f): The wireless communication device changes the average transmission power P to obtain the transmission capacity C FTN The average transmission power P, roll-off rate α, and compression rate τ that maximize the

[0041] 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.

[0042] 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 determination processing unit 13, a capacity calculation unit 14, and a determination unit 15.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] The SNR calculation unit 12 specifies the roll-off rate α for each PAPR of each modulation method, such as 16QAM or 16APSK, using a relationship table stored in the storage unit 10, calculates the SNR degradation amount and modulation index based on the amount by which the PAPR of the transmission 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 storage unit 10 and the determination processing unit 13.

[0047] The determination processing unit 13 determines whether or not the required SNR for the current modulation index and roll-off rate α is satisfied, and outputs the determination result to the storage unit 10, the SNR calculation unit 12, and the capacity calculation unit 14. For example, when the determination processing unit 13 determines that the required SNR is not satisfied, it lowers the modulation index and, for example, causes the SNR calculation unit 12 to recalculate the actual PAPR.

[0048] 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 value of the allowable PAPR in SC-FTN transmission.

[0049] The determination unit 15 accesses the storage unit 10, and while sequentially changing the average transmission power P, determines the optimum transmission capacity CFTN from a plurality of PAPR values, and determines the optimum C FTN The 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 SC-FTN transmission or Nyquist transmission that combines the optimal FTN efficiency, roll-off rate α, SNR (degraded SNR equivalent amount), and modulation index, 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 SNR calculation unit 12 identifies the roll-off rate α using the relationship table stored in the storage unit 10, calculates the SNR degradation amount and modulation index 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 calculates the SNR for the average transmission power.

[0055] In step 104 (S104), the judgment processing unit 13 judges whether the required SNR for the current modulation index and roll-off rate α is met, and if it is judged that it is met (S104: Yes), proceeds to processing of S108, and if it is judged that it is not met (S104: No), proceeds to processing of S106.

[0056] In step 106 (S106), the decision processing unit 13 decreases the modulation index, and returns to the process of S102.

[0057] 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.

[0058] 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.

[0059] In step 112 (S112), the storage unit 10 stores the C FTN Remember.

[0060] 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.

[0061] 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 <···).

[0062] That is, when the required SNR is not satisfied for a predetermined roll-off rate α, the determining unit 15 lowers the modulation index and determines the roll-off rate α or the like.

[0063] In this way, when a wireless communication device equipped with a transmission amplifier that amplifies a transmission signal selects SC-FTN transmission, it can determine the combination of roll-off rate α, SNR degradation equivalent amount, and modulation index, and optimize transmission capacity while maintaining transmission quality.

[0064] 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.

[0065] 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]

[0066] 10. Storage unit, 11. Tolerance value calculation unit, 12. SNR calculation unit, 13. Judgment processing 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 indexes, a tolerance calculation step of calculating a PAPR value for each modulation index 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 determination process step of determining whether the calculated SNR satisfies a predetermined required SNR for the current modulation index and roll-off rate, and performing a process of lowering the modulation index when it is determined that the calculated SNR does not satisfy the required SNR; a capacity calculation step of calculating a transmission capacity through the transmission amplifier using a modulation index based on the determined result, each of the specified roll-off factors, and an SNR; a determination step of determining a maximum transmission capacity that maintains a predetermined transmission quality from the transmission capacities calculated in the capacity calculation step based on a PAPR value for each of the changed average transmission powers while sequentially changing the average transmission power, and determining the roll-off rate that results in the maximum transmission capacity as a final roll-off rate for the transmission amplifier; A wireless communication method comprising:

2. A wireless communication device including a transmission amplifier and transmitting a signal by switching a modulation index, a tolerance calculation unit that calculates a PAPR value for each modulation index 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 determination processing unit that determines whether the calculated SNR satisfies a predetermined required SNR for the current modulation index and roll-off rate, and performs processing to lower the modulation index when it is determined that the required SNR is not satisfied; a capacity calculation unit that calculates a transmission capacity through the transmission amplifier using a modulation index based on the result of the determination by the determination processing unit, and each of the roll-off rates and the SNR specified by the SNR calculation unit; a determination unit that determines a maximum transmission capacity that maintains a predetermined transmission quality from the transmission capacities calculated by the capacity calculation unit based on a PAPR value for each of the changed average transmission powers while sequentially changing the average transmission power, and determines a roll-off rate that results in the maximum 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 that has a transmission amplifier and switches a modulation index, a tolerance calculation unit that calculates a PAPR value for each modulation index 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 determination processing unit that determines whether the calculated SNR satisfies a predetermined required SNR for the current modulation index and roll-off rate, and performs processing to lower the modulation index when it is determined that the required SNR is not satisfied; a capacity calculation unit that calculates a transmission capacity through the transmission amplifier using a modulation index based on the result of the determination by the determination processing unit, and each of the roll-off rates and the SNR specified by the SNR calculation unit; a determination unit that determines a maximum transmission capacity that maintains a predetermined transmission quality from the transmission capacities calculated by the capacity calculation unit based on a PAPR value for each of the changed average transmission powers while sequentially changing the average transmission power, and determines a roll-off rate that results in the maximum transmission capacity as a final roll-off rate for the transmission amplifier; A wireless communication system comprising:

Images