Wireless communication system, wireless terminal, wireless base station, wireless communication method, and wireless communication program

Abstract

The present disclosure relates to a wireless communication system pertaining to adaptive modulation technology for changing a wireless signal modulation scheme according to the communication quality of wireless communication. The purpose of the disclosure is to provide a wireless communication system in which a transmission waveform of a wireless signal is not accompanied by non-linear distortion degradation of an amplifier, even if the wireless signal is transmitted by a wireless terminal far from a wireless base station. In the wireless communication system of the present disclosure, an MCS index includes a single carrier modulation scheme as a secondary modulation scheme. A transmitter is configured so as to execute: a process for selecting one from among MCS indices, by comparing reception quality reported from a receiver and required reception quality prescribed for each MCS index; a process for modulating and encoding a transmission signal; and a process for transmitting the transmission signal to the receiver. The receiver is configured so as to execute: a process for calculating reception quality on the basis of an average transmission power reported from the transmitter and a non-linear distortion degradation amount; and a process for transmitting the reception quality to the transmitter.

Description

Technical Field

[0001] The present disclosure relates to an adaptive modulation technique for changing the modulation method of a wireless signal according to the communication quality of wireless communication, and relates to a wireless communication system, a wireless terminal, a wireless base station, a wireless communication method, and a wireless communication program.

Background Art

[0002] In wireless communication, an adaptive modulation technique for adaptively changing the modulation method of a wireless signal according to the communication line quality between a wireless base station and a wireless terminal is used. As the communication line quality, SINR (Signal-to-Interference plus Noise power Ratio) on the receiving side or the like is used. Note that SINR is the ratio of the received signal power of a desired wave signal to the sum of the power of other interfering wave signals and noise.

[0003] Non-Patent Document 1 discloses a technique in which the secondary modulation method is fixed to one type such as an OFDM (Orthogonal Frequency Division Multiple) method, and the primary modulation method is changed according to SINR. By this method, it becomes possible to transmit an appropriate wireless signal according to the wireless propagation environment.

[0004] Note that the PAPR (Peak to Average Power Ratio) characteristic of the OFDM method is disclosed in Non-Patent Document 2.

Prior Art Documents

Non-Patent Documents

[0005]

Non-Patent Document 1

[0006] However, in the prior art, when a wireless terminal far from a base station transmits a wireless signal, a large transmission power is required, so there is a problem that the transmission waveform of the wireless signal is accompanied by non-linear distortion degradation of the amplifier.

[0007] In order to solve the above problems, the present disclosure provides a wireless communication system in which even when a wireless terminal far from a base station transmits a wireless signal, the transmission waveform of the wireless signal is not accompanied by non-linear distortion degradation of the amplifier as a first object.

[0008] Furthermore, the present disclosure provides a wireless terminal in which even when a wireless terminal far from a base station transmits a wireless signal, the transmission waveform of the wireless signal is not accompanied by non-linear distortion degradation of the amplifier as a second object.

[0009] Furthermore, the present disclosure provides a base station in which even when a wireless terminal far from a base station transmits a wireless signal, the transmission waveform of the wireless signal is not accompanied by non-linear distortion degradation of the amplifier as a third object.

[0010] Furthermore, a fourth objective of this disclosure is to provide a wireless communication method that does not involve nonlinear distortion degradation of the amplifier in the transmitted waveform of a wireless signal, even when a wireless terminal located far from a wireless base station transmits a wireless signal.

[0011] Furthermore, a fifth objective of this disclosure is to provide a wireless communication program that does not involve nonlinear distortion degradation of the amplifier in the transmitted waveform of a wireless signal, even when a wireless terminal located far from a wireless base station transmits a wireless signal. [Means for solving the problem]

[0012] A first aspect of this disclosure is a wireless communication system that performs adaptive modulation of a radio signal transmitted by a transmitter by selecting one of the MCS indices, which are predetermined combinations of modulation schemes and coding rates, according to the reception quality of the receiver, The aforementioned transmitter is A nonlinear distortion degradation calculation process that calculates the amount of nonlinear distortion degradation of the amplified signal from the nonlinear characteristics of the amplifier itself, A process that notifies the receiver of information regarding its own average transmission power and the amount of nonlinear distortion degradation, A modulation coding scheme selection process is performed by comparing the reception quality notified by the receiver with the required reception quality defined for each of the MCS indices, and selecting one from among the MCS indices. A modulation coding process that modulates and encodes the transmission signal based on one MCS index selected in the modulation coding scheme selection process, A process of transmitting the transmission signal modulated and encoded in the above modulation coding process to the receiver, It is configured to perform, The aforementioned receiver is A reception quality calculation process that calculates the reception quality based on the average transmission power and the nonlinear distortion degradation amount notified from the transmitter, A process to transmit the reception quality calculated in the reception quality calculation process to the transmitter, It is configured to perform, The aforementioned MCS index preferably includes a single-carrier modulation scheme as the secondary modulation scheme.

[0013] A second aspect of this disclosure is a wireless terminal that performs adaptive modulation of a wireless signal to be transmitted by selecting one from among the MCS indices, which are combinations of modulation schemes and coding rates, according to the reception quality of the receiver, A process to calculate the amount of nonlinear distortion degradation of the amplified signal from the nonlinear characteristics of the amplifier itself, A process that notifies the receiver of information regarding its own average transmission power and the amount of nonlinear distortion degradation, A modulation coding scheme selection process is performed by comparing the reception quality notified by the receiver with the required reception quality defined for each of the MCS indices, and selecting one from among the MCS indices. A modulation coding process that modulates and encodes the transmission signal based on one MCS index selected in the modulation coding scheme selection process, A process of transmitting the transmission signal modulated and encoded in the above modulation coding process to the receiver, It is configured to perform, The aforementioned MCS index preferably includes a single-carrier modulation scheme as the secondary modulation scheme.

[0014] A third aspect of this disclosure is a process for calculating the fading margin value of a radio signal transmitted to itself by another radio station, A reception quality calculation process that calculates the reception quality for each of the MCS indices expected to be used by the other radio station, based on the fading margin value, the average transmit power notified by the other radio station, and all of the MCS indices expected to be used by the other radio station, and based on the amount of nonlinear distortion degradation of the amplifier provided by the other radio station notified by the other radio station, A process of transmitting all the reception quality calculated in the reception quality calculation process to the other radio station, It is preferable that the wireless base station is configured to perform the following actions.

[0015] A fourth aspect of this disclosure is a wireless communication method that selects one of the MCS indices, which are combinations of modulation schemes and coding rates, according to the reception quality of the receiver, and performs adaptive modulation of the wireless signal transmitted by the transmitter, The aforementioned transmitter is A process to calculate the amount of nonlinear distortion degradation of the amplified signal from the nonlinear characteristics of the amplifier itself, A process that notifies the receiver of information regarding its own average transmission power and the amount of nonlinear distortion degradation, A modulation coding scheme selection process is performed by comparing the reception quality notified by the receiver with the required reception quality defined for each of the MCS indices, and selecting one from among the MCS indices. A modulation coding process that modulates and encodes the transmission signal based on one MCS index selected in the modulation coding scheme selection process, A process of transmitting the transmission signal modulated and encoded in the above modulation coding process to the receiver, Execute, The aforementioned receiver is A reception quality calculation process that calculates the reception quality based on the average transmission power and the nonlinear distortion degradation amount notified from the transmitter, A process to transmit the reception quality calculated in the reception quality calculation process to the transmitter, Execute, The aforementioned MCS index preferably includes a single-carrier modulation scheme as the secondary modulation scheme.

[0016] A fifth aspect of this disclosure is a wireless communication program that is executed by a wireless terminal which performs adaptive modulation of a wireless signal to be transmitted by selecting one from among the MCS indices, which are combinations of modulation scheme and coding rate, according to the reception quality of the receiver, The aforementioned MCS index includes a single-carrier modulation scheme as a secondary modulation scheme. The aforementioned wireless terminal, A process for calculating the amount of nonlinear distortion degradation of the amplified signal from the nonlinear characteristics of the amplifier equipped in the wireless terminal, A process for notifying the receiver of information regarding the average transmission power of the wireless terminal and the amount of nonlinear distortion degradation, A modulation coding scheme selection process is performed by comparing the reception quality notified by the receiver with the required reception quality defined for each of the MCS indices, and selecting one from among the MCS indices. A modulation coding process that modulates and encodes the transmission signal based on one MCS index selected in the modulation coding scheme selection process, A process of transmitting the transmission signal modulated and encoded in the above modulation coding process to the receiver, It is preferable to include a program that executes [the specified action]. [Effects of the Invention]

[0017] According to the first to fifth aspects of this disclosure, it is possible to provide a wireless communication system, wireless terminal, wireless base station, wireless communication method, and wireless communication program that do not involve nonlinear distortion degradation of the amplifier in the transmitted waveform of a wireless signal, even when a wireless terminal located far from a wireless base station transmits a wireless signal. [Brief explanation of the drawing]

[0018] [Figure 1] This figure shows an example configuration of a conventional wireless communication system related to the comparative example of this disclosure. [Figure 2] This is an example of an MCS index disclosed in Non-Patent Document 1, relating to a comparative example of this disclosure. [Figure 3] This is a schematic diagram illustrating the details of the nonlinear strain degradation amount (PT) in (Equation 1). [Figure 4] This figure shows the PAPR characteristics of an OFDM signal as disclosed in Non-Patent Document 2, relating to a comparative example of this disclosure. [Figure 5] This is an example of the configuration of a wireless communication system according to Embodiment 1 of the present disclosure. [Figure 6] This is a block diagram showing an example of the functional configuration of a transmitter and receiver according to Embodiment 1 of the present disclosure. [Figure 7]This is a schematic diagram illustrating a method for deriving the phasing margin value F according to Embodiment 1 of this disclosure. [Figure 8] This is an example of a modified MCS index table according to Embodiment 1 of this disclosure. [Figure 9] This is a flowchart illustrating the processing performed by the transmitter and receiver according to Embodiment 1 of this disclosure. [Modes for carrying out the invention]

[0019] [Comparative Example] Here, we will first describe the prior art as a comparative example. Figure 1 is a diagram showing an example configuration of a conventional wireless communication system related to the comparative example of this disclosure. The conventional wireless communication system 100 comprises a wireless base station (hereinafter referred to as "base station") 110 and a wireless terminal device (hereinafter referred to as "terminal") 120.

[0020] Base station 110 is a radio station that receives radio waves from terminal 120 and establishes a wired connection to the core network, or conversely, converts signals from the core network into radio waves and transmits them to terminal 120. If the applicable wireless communication system is Wi-Fi (registered trademark), base station 110 corresponds to an access point. The base station notifies terminal 120 of its own SINR.

[0021] Terminal 120 communicates wirelessly with base station 110. Terminal 120 is, for example, a smartphone. When terminal 120 transmits a wireless signal to base station 110, it performs adaptive modulation based on SINR information notified by base station 110. In this process, only the primary modulation scheme is controlled, and the secondary modulation scheme is fixed to one type, such as OFDM.

[0022] The SINR of base station 110, which is notified to terminal 120, is calculated based on the following (Equation 1). Here, P T D(P) is the average transmit power of terminal 120 notified to base station 110 from terminal 120, L is the propagation loss, I is the interference noise power, and N is the noise power. Furthermore, D(P) T) is the amount of nonlinear strain degradation notified from terminal 120 to base station 110. SINR(P T )=P T -LIND(P T ) (Formula 1)

[0023] At base station 110, propagation loss L, interference noise power I, and noise power N are measured, and the average transmission power P is reported from terminal 120. T and nonlinear distortion degradation amount D(P T The SINR is calculated based on (Equation 1) using ( ). This allows us to estimate the wireless signal propagation environment between the base station 110 and the terminal 120.

[0024] Here, propagation loss L is the amount of loss when a radio signal propagates between base station 110 and terminal 120, and is a quantity that depends on the distance between base station 110 and terminal 120. Propagation loss L can be determined, for example, by base station 110 acquiring the location information of terminal 120 and calculating the distance to itself. Propagation loss L increases as terminal 120 is farther from base station 110, and in (Equation 1), it acts in the direction of lowering the SINR. Therefore, in order for the receiving base station 110 to satisfy the desired reception quality, terminal 120 must have a large average transmit power P T It is necessary to transmit a wireless signal.

[0025] As explained above, in the conventional wireless communication system 100, the terminal 120 controls the primary modulation scheme based on the SINR calculated by the receiving base station 110.

[0026] In the example shown in Figure 1, there is only one terminal, but multiple terminals may be provided.

[0027] FIG. 2 is an example of the MCS index disclosed in Non-Patent Document 1 according to the comparative example of the present disclosure. In FIG. 2, combinations of modulation methods (Modulation) and coding rates (Code Rate) are tabulated according to the SINR. The terminal 120 selects one from the MCS (Modulation and Coding Scheme) index tabulated in this way and switches it to perform primary modulation and coding.

[0028] FIG. 3 is a schematic diagram for explaining the details of the non-linear distortion degradation amount D(P T ) of (Equation 1). FIG. 3 shows the input-output characteristics of the amplifier used when the terminal 120 transmits a signal. The horizontal axis and the vertical axis represent the input intensity and output intensity of the amplifier, respectively, and the unit is, for example, dBm. The output intensity of the amplifier responds linearly in a region where the input intensity is small (linear region). However, when the intensity of the input signal exceeds a certain region, the response becomes non-linear, and the actual output intensity becomes smaller than that when assuming a linear response (non-linear region).

[0029] As described above, the loss of output due to the distortion of the amplified waveform that occurs when the amplifier operates in the non-linear region is the non-linear distortion degradation amount.

[0030] When the remote terminal 120 transmits a radio signal from the base station 110, that is, when the terminal 120 transmits with a large average transmission power P T , the response in the non-linear region cannot be avoided, and the effect of non-linear distortion appears particularly significantly.

[0031] Furthermore, in the prior art, since the secondary modulation method is fixed to the OFDM method, the PAPR, which is the ratio of the maximum transmission power to the average transmission power of the modulation signal, is high. Therefore, the non-linear response of the amplifier cannot be avoided, and the problem is that the radio signal is degraded by non-linear distortion.

[0032] FIG. 4 is a diagram showing the PAPR characteristics of a signal of the OFDM method disclosed in Non-Patent Document 2 according to the comparative example of the present disclosure. In FIG. 4, the secondary modulation is fixed to the OFDM method NextThe PAPR characteristics when the modulation order is changed are shown. It is clear that the PAPR cannot be reduced even when the order of the primary modulation scheme is decreased in the order of 64-QAM, 16-QAM, and QPSK.

[0033] As explained above using Figures 1 to 4, in the conventional technology, the secondary modulation scheme was fixed to OFDM, so it was necessary to amplify the high PAPR OFDM signal with an amplifier. Therefore, nonlinear distortion degradation of the amplifier could not be avoided. This problem was particularly pronounced when transmitting wireless signals from a terminal 120 far from the base station 110.

[0034] Embodiment 1 Figure 5 shows an example of the configuration of a wireless communication system according to Embodiment 1 of this disclosure. The wireless communication system 200 includes a base station 110 and terminals 120, similar to the conventional wireless communication system 100. However, for the sake of explanation, it is assumed that there are two terminals 120(1) and 120(2) that are at different distances from the base station 110.

[0035] In the wireless communication system 200 of this disclosure, when terminal 120 transmits a wireless signal to base station 110, adaptive modulation is performed according to the SINR notified by the receiving base station 110, similar to the comparative example. However, in the wireless communication system of this disclosure, the SINR is calculated based on the following (Equation 2). SINR(P T ,MCS')=P T -LIND(P T ,MCS')-F(Equation 2)

[0036] Similar to the comparative example, P T is the average transmit power of terminal 120, L is the propagation loss, I is the interference noise power, and N is the noise power. On the other hand, D(P T Unlike the comparative example, MCS' has an average transmit power P TIn addition, it is a nonlinear distortion degradation amount that takes into account the MCS index including secondary modulation switching (hereinafter referred to as the modified MCS index, and denoted as MCS' when it is explicitly stated that it is an argument of a function). Furthermore, F is a fading margin value that takes into account the power loss due to fading of the wireless signal, and is a loss amount that was not considered in the comparative example.

[0037] In (Equation 2), propagation loss L, interference noise power I, and noise power N are quantities measured at base station 110, as in the comparative example. Also, average transmission power P T and nonlinear distortion degradation amount D(P T Similarly, MCS') is the amount notified from terminal 120. The fading margin value F is a quantity predetermined by simulation at base station 110.

[0038] In this embodiment, the nonlinear distortion degradation amount is simply the average transmitted power P. T Furthermore, it is determined taking into consideration that it actually depends on the modulation scheme and coding rate of the transmitted signal. In other words, in this embodiment, the average transmitted power P T In addition, the nonlinear strain degradation amount D(P) is a function that also depends on the deformation MCS index. T The SINR (Signal Integrity Rate) is calculated. By using this, a more realistic SINR can be calculated, improving the accuracy of the estimation of the wireless signal propagation environment.

[0039] As explained above, the wireless communication system 200 of this disclosure is a SINR (P) shown in (Equation 2). T The nonlinear distortion degradation amount D(P) is calculated, taking into account the modulation scheme and coding rate of the wireless signal. T By considering the MCS' and the fading margin value F, it is possible to estimate the propagation environment of wireless signals with greater accuracy than conventional techniques. This makes it possible to select the optimal modulation scheme according to the actual propagation environment in the control of adaptive modulation based on SINR.

[0040] Figure 6 is a block diagram showing an example of the functional configuration of a transmitter and receiver according to Embodiment 1 of this disclosure. Here, terminal 120 is replaced with transmitter 220, and base station 110 is replaced with receiver 210.

[0041] First, let's explain the function of the transmitter 220. The information bit generation unit 221 generates data information bits that the transmitter 220 wants to transmit to the receiver 210. The generated data information bits include the average transmission power P of the transmitter 220, which is notified by the power information notification unit 222. T , and the nonlinear strain degradation amount D(P) of the transmitter 220 notified by the nonlinear strain degradation amount information notification unit 223. T The information of ,MCS' is also included. The modulation coding unit 224 applies error correction coding processing to the information bits generated in the information bit generation unit 221 based on the modified MCS index determined by the modulation coding scheme selection unit 225. Furthermore, it generates digital data signals with primary and secondary modulation. The digital-to-analog conversion unit 226 is the part that converts the digitally modulated data signal from the modulation coding unit 224 into an analog signal.

[0042] The transmit power control unit 227 controls the transmit power of the analog-converted data signal according to the modified MCS index selected by the modulation coding scheme selection unit 225, according to the desired communication quality. The signal amplification unit 228 amplifies the transmit signal input from the transmit power control unit 227 and inputs it to the antenna 229. The antenna 229 transmits a radio signal toward the receiver 210, or receives a radio signal transmitted from the receiver 210.

[0043] Furthermore, the modulation coding scheme selection unit 225 of the transmitter 220 selects one of the modified MCS indices based on the SINR information notified from the SINR information processing unit 230 and notifies the modulation coding unit 224 and the transmission power control unit 227. The power information notification unit 222 is responsible for the average transmission power P T This is the part that transmits the information to the information bit generation unit 221. The nonlinear distortion degradation amount information notification unit 223 transmits the nonlinear distortion degradation amount D(P TThis part calculates the SINR (P) contained in the radio signal transmitted from the receiver 210 and notifies the information bit generation unit 221 of the calculation result. T The information of ,MCS') is processed and notified to the modulation encoding scheme selection unit 225.

[0044] Here, the nonlinear strain degradation amount D(P) is calculated by the nonlinear strain degradation amount information notification unit 223. T ,MCS') is a quantity that is calculated for each of the deformed MCS indices that are expected to be used from the pre-tabled deformed MCS indices. Therefore, the nonlinear strain degradation amount D(P) that the transmitter 220 notifies the receiver 210 of T Note that there are as many ',MCS' elements as there are modified MCS indices that are intended for use.

[0045] Next, the functions of the receiver 210 will be explained. The signal amplification unit 211 is the part that amplifies the received signal received by the antenna 212. The analog-to-digital conversion unit 213 is the part that digitizes the analog received signal in order to demodulate it digitally. The demodulation and decoding unit 214 demodulates the received data signal and performs error correction decoding, and outputs the acquired information bits to the information bit detection unit 215. Furthermore, the average transmission power P of the transmitter 220 included in the received data T and nonlinear distortion degradation amount D(P T The information of ,MCS') is notified to the SINR information notification unit 216. The information bit detection unit 215 detects the information bits.

[0046] Furthermore, the simulator unit 217 determines the fading margin value F of the transmission signal transmitted by the transmitter 220 through simulation and notifies the SINR information notification unit 216 of the calculated fading margin value F.

[0047] Furthermore, the SINR information notification unit 216 notifies the transmitter 220 of the average transmit power P, which has been notified by the demodulation / decoding unit 214. T and nonlinear distortion degradation amount D(P T Based on (Equation 2), SINR(P TThe SINR calculation (MCS') is performed to generate SINR information. The generated SINR information from receiver 210 is sent to antenna 212 and transmitted as a radio signal to transmitter 220.

[0048] Here, the SINR(P) calculated by the SINR information notification unit 216 T Note that ,MCS') is required for each of the modified MCS indices that are expected to be used in transmitter 220.

[0049] As described above, in the wireless communication system 200 of this embodiment, the transmitter 220 transmits its average transmission power P simultaneously with the information data to be transmitted. T and nonlinear distortion degradation amount D(P T A wireless signal containing information (,MCS') is transmitted to the receiver 210. The receiver 210 uses this information and the fading margin value F determined by simulation to calculate the SINR (P) using (Equation 2). T The SINR(P) calculated by receiver 210 is calculated. T The information of ,MCS') is transmitted to the transmitter 220 by radio signal. The transmitter 220 receives the SINR(P T Based on the MCS', the modulation coding scheme selection unit 225 selects one from the modified MCS indices. Furthermore, based on the selected modified MCS index, primary and secondary modulation and coding of the data signal and control of the transmission power are performed.

[0050] In this disclosure, the processing performed by the base station 110 (receiver 210) and the terminal 120 (transmitter 220) may be executed by a program using a computer equipped with a CPU and memory, in which the program is stored in memory. Alternatively, the program may be executed using an integrated circuit such as an FPGA (Field Programmable Gate Array). The program may be provided by recording it on a storage medium or by providing it over a network.

[0051] Figure 7 is a schematic diagram showing a method for deriving the fading margin value F according to Embodiment 1 of this disclosure. Figure 7 shows how a simulator unit 217, located inside the receiving base station 110, determines the fading margin value F for each of the terminals 120(1) and 120(2) by simulation. In the simulation, parameters such as the CP (Cyclic Prefix) length, Rician factor, or Doppler variation for the delay spread of the radio signals from each of the terminals 120(1) and 120(2) are input.

[0052] In Figures 6 and 7, the case where the base station 110, which is the receiver 210, is equipped with a simulator unit 217 and performs the simulation was explained. However, each terminal 120(1) and 120(2), which are the transmitters 220, may also be equipped with a simulator unit. In this case, terminal 120 will have its own average transmission power P T and nonlinear distortion degradation amount D(P T At the same time as the MCS', the result of the fading margin value F should be notified to the base station 110.

[0053] Figure 8 is an example of a modified MCS index table according to Embodiment 1 of this disclosure. In Figure 8, the modified MCS index is determined according to the required SINR. Here, the required SINR is the receiving SINR necessary to receive the radio signal transmitted with the target modified MCS index. Hereafter, the required SINR determined for each modified MCS index will be denoted as required SINR(MCS'), and the SINR(P) in (Equation 2) will be expressed as required SINR(P T We will distinguish this from MCS'.

[0054] The modulation coding scheme selection unit 225 of terminal 120 selects the required SINR(MCS') and the SINR(P) notified by base station 110. T The ,MCS') are compared to determine whether the target modified MCS index is selectable or not.

[0055] For example, for the required SINR (MCS'=C-1), the SINR (P) notified by base station 110 T If MCS'=C-1 is large, the modulation coding scheme selection unit 225 of terminal 120 can adopt a modified MCS index of MCS'=C-1.

[0056] Furthermore, in the example in Figure 8, the modified MCS index includes not only primary modulation but also switching of secondary modulation schemes. The secondary modulation schemes include not only OFDM schemes such as CP-OFDM (CP: Cyclic Prefix) and DFT-spread (DFT: Discrete Fourier Transform), but also single-carrier modulation schemes. As a result, terminal 120 can adopt modified MCS indices S-1, S-2, ..., S-4, which include single-carrier schemes as secondary modulation.

[0057] For example, if terminal 120 is located far from base station 110, a large average transmission power P is required to transmit a radio signal from terminal 120 to base station 110. T This is necessary. In this case, in order to avoid nonlinear distortion degradation in the signal amplification unit 228, it is desirable that the secondary modulation be a single-carrier method. Therefore, the SINR (P) notified from the base station 110 T If MCS' (S-1, ..., S-4) is higher than the required SINR (MCS' = S-1, ..., S-4), terminal 120 can select one of S-1, ..., or S-4. By employing this single-carrier secondary modulation scheme, although the frequency utilization efficiency decreases, the PAPR of the signal can be reduced.

[0058] Conversely, if terminal 120 is sufficiently close to base station 110, a large average transmission power P is used when transmitting a radio signal from terminal 120 to base station 110. T This is not required. In this case, the effect of nonlinear distortion degradation in the signal amplification unit 228 is small, so the secondary modulation can be OFDM. Therefore, for example, the SINR (P) notified from the base station 110 TIf the MCS' (C-1, ..., C-4) is greater than the required SINR (MCS' = C-1, ..., C-4), terminal 120 can adopt any one of C-1, ..., or C-4. By adopting the CP-OFDM method as the secondary modulation scheme in this way, normal multi-carrier transmission with good frequency utilization efficiency can be achieved.

[0059] As described above, the wireless communication system 200 of this embodiment can select the optimal primary / secondary modulation and encoding method according to the distance between the base station 110 and the terminal 120. As a result, even when the terminal 120 is located far from the base station 110, wireless signals can be transmitted without nonlinear distortion in the transmitted waveform of the wireless signal.

[0060] Figure 9 is a flowchart illustrating the processing performed by the transmitter and receiver according to Embodiment 1 of this disclosure. Here, as in Figure 6, the terminal 120 is replaced with the transmitter 220, and the base station 110 is replaced with the receiver 210.

[0061] First, the nonlinear distortion degradation amount information notification unit 223 of the transmitter 220 calculates the nonlinear distortion degradation amount D(P) from the nonlinear characteristics of the amplifier for all deformation MCS indices that are expected to be used. T Calculate the MCS' and MCS' respectively (step 240). Next, calculate the data you want to transmit and the average transmission power P. T and nonlinear distortion degradation amount D(P T The information of ,MCS') is transmitted to the receiver 210 (step 241). Next, the receiver 210, having received this information, measures the propagation loss L, interference noise power I, and noise power N (step 242). Furthermore, the simulator unit 217 of the receiver 210 determines the fading margin value F by simulation (step 243). Furthermore, the SINR information notification unit 216 of the receiver 210 determines the SINR(P) for each of the modified MCS indices that are expected to be used in the transmitter 220. T Calculate ,MCS') respectively (step 244). Furthermore, receiver 210 calculates SINR(P TSend ,MCS') to transmitter 220 (step 245).

[0062] Next, SINR(P T Information received from MCS') Transmitter 220 In this case, the modulation encoding scheme selection unit 225 is set to SINR(P T The system compares the MCS' with the required SINR (MCS') and selects one modified MCS index that satisfies the conditions (step 246). Furthermore, based on the modified MCS index selected by the modulation coding scheme selection unit 225, the system performs primary and secondary modulation and coding of the data signal to be transmitted (step 247). After step 247, the system returns to step 240.

[0063] As described above, in the wireless communication system 200 of this embodiment, the transmitter 220 transmits its average transmission power P to the receiver 210. T and nonlinear distortion degradation amount D(P T The receiver 210 transmits information about ,MCS'). Based on this information, the SINR(P T The transmitter 220 calculates the SINR(P) notified by the receiver 210. T By comparing the modified MCS' with the required SINR(MCS'), one is selected from the modified MCS indices. Furthermore, primary and secondary modulation and coding are performed based on the selected modified MCS index.

[0064] As described above, according to the first to fifth aspects of this disclosure, it is possible to provide a wireless communication system, wireless terminal, wireless base station, wireless communication method, and wireless communication program in which the transmitted waveform of the wireless signal is not affected by the nonlinear distortion degradation of the amplifier, even when a terminal 120 located far from the base station 110 transmits a wireless signal.

[0065] [Differentiation] In the embodiments described herein, a method was described using SINR as the reception quality of the base station 110 in order to estimate the wireless signal propagation environment between the base station 110 and the terminal 120. However, the reception quality of the base station 110 is not limited to SINR.

[0066] Furthermore, in the embodiments described herein, the case in which terminal 120 is a transmitter 220 and base station 110 is a receiver 210 has been described. However, the roles of transmission and reception may be reversed. That is, terminal 120 may be a receiver 210 and base station 110 may be a transmitter 220.

[0067] Furthermore, in step 240, the nonlinear strain degradation amount information notification unit 223 of terminal 120 notifies the nonlinear strain degradation amount D(P) for all deformation MCS indices that are expected to be used. T It was explained that the SINR(P) is calculated for each of the modified MCS indices expected to be used in the transmitter 220. Furthermore, in step 244, the SINR information notification unit 216 of the base station 110 calculates the SINR(P) for each of the modified MCS indices expected to be used in the transmitter 220. T The calculation of ,MCS') was explained. It is also possible to extract the invention from these disclosures and provide a novel wireless communication system different from the wireless communication system 200 of this disclosure. That is, it is also possible to provide a novel wireless communication system comprising a terminal configured to include the processing of step 240 and a base station configured to include the processing of step 244, wherein it is not necessary to use a modified MCS index that includes a single-carrier scheme for the secondary modulation scheme.

[0068] Similarly, in step 243, it was explained that the simulator unit 217 of the base station 110 determines the fading margin value by simulation. The invention can be extracted from this function to provide a wireless communication system different from the wireless communication system 200 of this disclosure. That is, a new wireless communication system can be provided comprising a terminal 120 and a base station configured to include the processing of step 243, which does not require the use of a modified MCS index including a single-carrier scheme for the secondary modulation scheme.

[0069] [Correspondence with terms used in claims] As explained in Figure 9, the nonlinear distortion degradation amount information notification unit 223 of the transmitter 220 calculates the nonlinear distortion degradation amount D(P) from the nonlinear characteristics of the amplifier. T The process of calculating ,MCS') is called the nonlinear distortion degradation calculation process. In other words, the nonlinear distortion degradation calculation process is the process in step 240. Similarly, the modulation coding scheme selection unit 225 of the transmitter 220 is called SINR(P T The process of comparing the MCS' with the required SINR(MCS') and selecting one from the modified MCS indices is called the modulation coding scheme selection process. In other words, the modulation coding scheme selection process is the process in step 246. Similarly, the process in which the transmitter 220 performs primary and secondary modulation and coding based on the modified MCS index is called the modulation coding process. The modulation coding process is the process performed by each part of the transmitter 220 shown in Figure 6, and is the process in step 247.

[0070] As explained in Figure 9, the SINR information notification unit 216 of the receiver 210 performs the SINR(P T The process of calculating the MCS' is called the reception quality calculation process. In other words, the reception quality calculation process is the process in step 244. [Explanation of Symbols]

[0071] 100, 200 wireless communication systems 110 Wireless base stations 120 wireless terminals 210 Receiver 211 Signal Amplification Section 212 Antenna 213 Analog-to-Digital Conversion Section 214 Demodulation and Decoding Section 215 Information bit detection unit 216 SINR Information Notification Department 217 Simulator Department 220 Transmitter 221 Information Bit Generation Unit 222 Electric power information notification section 223 Nonlinear Distortion Degradation Amount Information Notification Unit 224 Modulation Encoding Section 225 Modulation Encoding Scheme Selection Section 226 Digital-to-analog conversion section 227 Transmit Power Control Unit 228 Signal Amplification Section 229 Antenna 230 SINR Information Processing Unit

Claims

1. A wireless communication system that selects one of a predetermined MCS index according to the reception quality of the receiver and performs adaptive modulation of the wireless signal transmitted by the transmitter, The aforementioned MCS index is a combination of the primary modulation scheme, the secondary modulation scheme, and the coding rate. The aforementioned transmitter is A nonlinear distortion degradation calculation process that calculates the amount of nonlinear distortion degradation of the amplified signal from the nonlinear characteristics of the amplifier itself, A process that notifies the receiver of information regarding its own average transmission power and the amount of nonlinear distortion degradation, A modulation coding scheme selection process is performed by comparing the reception quality notified by the receiver with the required reception quality defined for each of the MCS indices, and selecting one from among the MCS indices. A modulation coding process that performs primary modulation, secondary modulation, and coding on the transmitted signal based on one MCS index selected in the modulation coding scheme selection process, A process of transmitting the transmission signal modulated and encoded in the above modulation coding process to the receiver, It is configured to perform, The aforementioned receiver is A reception quality calculation process that calculates the reception quality based on the average transmission power and the nonlinear distortion degradation amount notified from the transmitter, A process to transmit the reception quality calculated in the reception quality calculation process to the transmitter, It is configured to perform, The aforementioned MCS index is a wireless communication system that includes a single-carrier modulation scheme as a secondary modulation scheme.

2. A wireless communication system that performs adaptive modulation of a wireless signal transmitted by a transmitter by selecting one from a predetermined combination of modulation scheme and coding rate, which is an MCS index, according to the reception quality of the receiver, The aforementioned transmitter is A nonlinear distortion degradation calculation process that calculates the amount of nonlinear distortion degradation of the amplified signal for each of the MCS indices that are expected to be used, based on the nonlinear characteristics of the amplifier itself, A process that notifies the receiver of information regarding its own average transmission power and the amount of nonlinear distortion degradation, A modulation coding scheme selection process is performed to select one of the MCS indices by comparing the reception quality of each of the MCS indices that are expected to be used and notified by the receiver with the required reception quality defined for each of the MCS indices, A modulation coding process that modulates and encodes the transmission signal based on one MCS index selected in the modulation coding scheme selection process, A process of transmitting the transmission signal modulated and encoded in the above modulation coding process to the receiver, It is configured to perform, The aforementioned receiver is A reception quality calculation process that calculates the reception quality for all of the MCS indices that are expected to be used, based on the average transmission power and the nonlinear distortion degradation amount notified from the transmitter, A process to transmit the reception quality calculated in the reception quality calculation process to the transmitter, It is configured to perform, The aforementioned MCS index is a wireless communication system that includes a single-carrier modulation scheme as a secondary modulation scheme.

3. The aforementioned receiver is The process further includes calculating the fading margin value of the wireless signal transmitted by the transmitter, In the aforementioned reception quality calculation process, The wireless communication system according to claim 1, wherein the reception quality is calculated based on the fading margin value.

4. The aforementioned reception quality is SINR, In the reception quality calculation process, the receiver uses the average transmission power as P Ｔ , the nonlinear distortion degradation amount is D(P Ｔ The wireless communication system according to claim 3, wherein SINR is calculated by the following formula, with L being the propagation loss, I being the interference noise power, N being the noise power, and F being the fading margin value. SINR(P Ｔ ,MCS‘)=P Ｔ -L-I-N-D(P Ｔ ,MCS‘)-F

5. A wireless terminal that selects one of a predetermined MCS index according to the receiver's reception quality and performs adaptive modulation of the wireless signal to be transmitted, The aforementioned MCS index is a combination of the primary modulation scheme, the secondary modulation scheme, and the coding rate. A process to calculate the amount of nonlinear distortion degradation of the amplified signal from the nonlinear characteristics of the amplifier itself, A process that notifies the receiver of information regarding its own average transmission power and the amount of nonlinear distortion degradation, A modulation coding scheme selection process is performed by comparing the reception quality notified by the receiver with the required reception quality defined for each of the MCS indices, and selecting one from among the MCS indices. A modulation coding process that performs primary modulation, secondary modulation, and coding on the transmitted signal based on one MCS index selected in the modulation coding scheme selection process, A process of transmitting the transmission signal modulated and encoded in the above modulation coding process to the receiver, It is configured to perform, The aforementioned MCS index includes a single-carrier modulation scheme as the secondary modulation scheme for the wireless terminal.

6. A wireless communication method that selects one of a predetermined MCS index according to the reception quality of the receiver and performs adaptive modulation of the wireless signal transmitted by the transmitter, The aforementioned MCS index is a combination of the primary modulation scheme, the secondary modulation scheme, and the coding rate. The aforementioned transmitter is A process to calculate the amount of nonlinear distortion degradation of the amplified signal from the nonlinear characteristics of the amplifier itself, A process that notifies the receiver of information regarding its own average transmission power and the amount of nonlinear distortion degradation, A modulation coding scheme selection process is performed by comparing the reception quality notified by the receiver with the required reception quality defined for each of the MCS indices, and selecting one from among the MCS indices. A modulation coding process that performs primary modulation, secondary modulation, and coding on the transmitted signal based on one MCS index selected in the modulation coding scheme selection process, A process of transmitting the transmission signal modulated and encoded in the above modulation coding process to the receiver, Execute, The aforementioned receiver is A reception quality calculation process that calculates the reception quality based on the average transmission power and the nonlinear distortion degradation amount notified from the transmitter, A process to transmit the reception quality calculated in the reception quality calculation process to the transmitter, Execute, The aforementioned MCS index is a wireless communication method that includes a single-carrier modulation scheme as a secondary modulation scheme.

7. A wireless communication program that is executed by a wireless terminal that performs adaptive modulation of the wireless signal to be transmitted by selecting one from a predetermined set of MCS indices according to the reception quality of the receiver, The aforementioned MCS index is a combination of the primary modulation scheme, the secondary modulation scheme, and the coding rate. The aforementioned MCS index includes a single-carrier modulation scheme as a secondary modulation scheme. The aforementioned wireless terminal, A process for calculating the amount of nonlinear distortion degradation of the amplified signal from the nonlinear characteristics of the amplifier equipped in the wireless terminal, A process for notifying the receiver of information regarding the average transmission power of the wireless terminal and the amount of nonlinear distortion degradation, A modulation coding scheme selection process is performed by comparing the reception quality notified by the receiver with the required reception quality defined for each of the MCS indices, and selecting one from among the MCS indices. A modulation coding process that performs primary modulation, secondary modulation, and coding on the transmitted signal based on one MCS index selected in the modulation coding scheme selection process, A process of transmitting the transmission signal modulated and encoded in the above modulation coding process to the receiver, A wireless communication program that includes a program to execute [the specified command / function].

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