Wireless communication system and wireless communication method

Abstract

To provide a wireless communication system that transmits data from a transmitter to a receiver by single carrier transmission using radio waves and can suppress the PAPR of a modulated wave input into an amplifier without lowering a modulation order.SOLUTION: A transmitter of a wireless communication system according to the present disclosure calculates a base signal point and an offset signal point corresponding to a transmission signal point according to a base signal space diagram and an offset signal space diagram, and generates a base modulated wave and an offset modulated wave according to the base signal point and the offset signal point. After that, the transmitter amplifies them to a predetermined power, and transmits a radio wave by a transmission modulated wave obtained by combining the amplified base modulated wave and offset modulated wave. Then, a receiver adjusts the scale of a received signal associated with the received radio wave based on scale information and then demodulates the received signal.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present disclosure relates to a wireless communication system and a wireless communication method for transmitting data from a transmitter to a receiver by single carrier transmission via radio waves. [Background technology]

[0002] Non-Patent Document 1 proposes a new modulation scheme that enables the application of Trellis shaping (TS) technology, which is a peak power reduction technique, to a Single Carrier Frequency Division Multiple Access (SC-FDMA) modulation scheme. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Tae-woo Lee, Hideki Ochiai, "A Study on Peak Power Reduction of SC-FDMA Signal Using Trellis Shaping", IEICE Technical Report, pp.29-34, WBS-2012-6(2012-05) Summary of the Invention [Problem to be solved by the invention]

[0004] In a transmitter for wireless communication, when the peak power of a modulated wave input to an amplifier exceeds the linear characteristic of the amplifier, nonlinear distortion occurs in the output of the amplifier, degrading the quality of the transmitted radio wave. For this reason, the input power of the modulated wave input to the amplifier is backed off so that such nonlinear distortion does not occur. Therefore, the backoff can be reduced by suppressing the peak-to-average power ratio (PAPR) of the modulated wave input to the amplifier. This in turn has the effect of increasing the average transmission output and reducing power consumption.

[0005] By performing wireless communication using single-carrier transmission, the PAPR of a modulated wave can be suppressed compared to wireless communication using multi-carrier transmission (for example, orthogonal frequency-division multiple access (OFDMA)). However, even when performing wireless communication using single-carrier transmission, there is a problem that the PAPR increases as the modulation order of the modulated wave increases.

[0006] The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide a wireless communication system and a wireless communication method that are capable of suppressing the PAPR of a modulated wave input to an amplifier without lowering the modulation order. [Means for solving the problem]

[0007] The first disclosure relates to a wireless communication system that transmits data from a transmitter to a receiver by single carrier transmission using radio waves based on quadrature amplitude modulation. The transmitter of this wireless communication system includes a signal point calculation unit that calculates a base signal point and an offset signal point corresponding to a transmission signal point according to a signal space diagram that defines the position of a transmission signal point in a predetermined division that equally divides a signal range and an offset signal space diagram that defines an offset of the base signal space diagram according to the position of the division related to the division, a base modulated wave generation unit that generates a base modulated wave corresponding to the base signal point, a base modulated wave amplification unit that amplifies the base modulated wave to a predetermined power, an offset modulated wave generation unit that generates an offset modulated wave corresponding to the offset signal point, an offset modulated wave amplification unit that amplifies the offset modulated wave to a predetermined power, a synthesis unit that synthesizes the base modulated wave amplified by the base modulated wave amplification unit and the offset modulated wave amplified by the offset modulated wave amplification unit to obtain a transmission modulated wave, and a transmission antenna that transmits radio waves by the transmission modulated wave. The receiver of this wireless communication system includes a receiving antenna for receiving radio waves, and a demodulator for adjusting the scale of a received signal related to the received radio waves based on scale information indicating the scale of a signal range, and performing demodulation. Here, the transmission signal point is a signal point corresponding to data to be transmitted, and the signal range is a range of signal points related to a signal space diagram on which the transmission signal point is based.

[0008] The second disclosure relates to a wireless communication system that further includes the following features in addition to the wireless communication system according to the first disclosure. The scale information is sent from the transmitter to the receiver prior to transmission of data.

[0009] The third disclosure relates to a wireless communication system further including the following features in addition to the wireless communication system according to the first or second disclosure. The scale information is a sequence of the positions of signal points included in the signal range and the positions of the base signal point and the offset signal point relative to the signal points.

[0010] The fourth disclosure relates to a wireless communication method for transmitting data from a transmitter to a receiver by single carrier transmission using radio waves based on quadrature amplitude modulation. This wireless communication method includes a signal point calculation process for calculating a base signal point and an offset signal point corresponding to a transmission signal point according to a base signal space diagram that defines the position of a transmission signal point in a predetermined division that equally divides a signal range and an offset signal space diagram that defines an offset of the base signal space diagram according to the position of the division related to the division, a base modulated wave generation process for generating a base modulated wave corresponding to the base signal point, a base modulated wave amplification process for amplifying the base modulated wave to a predetermined power, an offset modulated wave generation process for generating an offset modulated wave corresponding to the offset signal point, an offset modulated wave amplification process for amplifying the offset modulated wave to a predetermined power, a synthesis process for synthesizing the base modulated wave amplified by the base modulated wave amplification process and the offset modulated wave amplified by the offset modulated wave amplification process to obtain a transmission modulated wave, a transmission process for transmitting a radio wave using the transmission modulated wave, a reception process for receiving a radio wave, and a demodulation process for adjusting the scale of a received signal related to the received radio wave based on scale information that indicates the scale of the signal range and performing demodulation. Here, a transmission signal point is a signal point corresponding to data to be transmitted, and a signal range is a range of signal points related to a signal space diagram on which the transmission signal point is based.

[0011] The fifth disclosure relates to a wireless communication method further including the following features with respect to the wireless communication method according to the fourth disclosure. The scale information is sent from the transmitter to the receiver prior to transmission of data.

[0012] The sixth disclosure relates to a wireless communication method further including the following features with respect to the wireless communication method according to the fourth or fifth disclosure. The scale information is a sequence of the positions of signal points included in the signal range and the positions of the base signal point and the offset signal point relative to the signal points. Effect of the Invention

[0013] According to the wireless communication system and wireless communication method of the present disclosure, the modulation order of the base signal point and the modulation order of the offset signal point can be made smaller than the modulation order of the transmission signal point. This makes it possible to suppress the PAPR of the modulated wave (base modulated wave and offset modulated wave) input to the amplifier without lowering the modulation order. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a conceptual diagram showing an example of a signal space diagram of QAM. [Diagram 2] 1 is a conceptual diagram showing an example of a base signal space diagram and an offset signal space diagram. FIG. [Diagram 3] 10 is a conceptual diagram for explaining a base signal point and an offset signal point calculated according to a transmission signal point. FIG. [Figure 4] 3 is a conceptual diagram showing that a transmission signal point is given by multiplying the sum of a base signal point and an offset signal point by a constant, taking as an example a base signal point and an offset signal point calculated according to the transmission signal point shown in FIG. 2. [Diagram 5] FIG. 13 is a conceptual diagram showing an example in which two offset constellation diagrams are given. [Figure 6] 1 is a block diagram showing an example of the configuration of a wireless communication system according to an embodiment of the present invention. [Figure 7] 5 is a flowchart showing a process executed in the wireless communication method according to the embodiment. [Figure 8] 8 is a flowchart showing the process executed in step S110 shown in FIG. 7. [Figure 9] 8 is a flowchart showing the process executed in step S120 shown in FIG. 7. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, the embodiments of the present disclosure will be described with reference to the drawings. However, when the number, quantity, amount, range, etc. of each element is mentioned in the embodiments shown below, the idea of ​​the present disclosure is not limited to the mentioned number unless it is specifically stated or the number is clearly specified in principle. Furthermore, the configurations etc. described in the embodiments shown below are not necessarily essential to the idea of ​​the present disclosure unless it is specifically stated or the number is clearly specified in principle. In addition, the same reference numerals are attached to the same or corresponding parts in each drawing, and the duplicated explanation is appropriately simplified or omitted.

[0016] 1. Introduction The wireless communication system according to the present disclosure is applied to a wireless communication system that transmits data from a transmitter to a receiver by single-carrier transmission using radio waves based on quadrature amplitude modulation (QAM) (hereinafter, such a wireless communication system will be simply referred to as a "wireless communication system").

[0017] As is well known, QAM is a modulation method in which the amplitude of each of two carrier waves, which are orthogonal in phase, is modulated in accordance with the data to be transmitted, and the resulting signal is combined to produce a modulated wave.

[0018] In QAM, the relationship between the data to be transmitted and the modulation of each of the two carrier waves is generally given by a constellation diagram. Also, the modulation of each of the two carrier waves according to the data is performed according to the constellation diagram.

[0019] FIG. 1 shows an example of a constellation diagram of QAM. The constellation diagram is composed of an in-phase axis (I axis) showing the amplitude of one carrier wave, a quadrature axis (Q axis) showing the amplitude of the other carrier wave, and a plurality of signal points corresponding to data. The constellation diagram shown in FIG. 1 includes 16 signal points, and each signal point corresponds to 4 bits of data. That is, FIG. 1 shows a constellation diagram related to 16QAM, and in accordance with the constellation diagram shown in FIG. 1, the modulated wave can show 4 bits of data per symbol. For example, data of 0110 is shown by a modulated wave modulated so that the amplitude of the carrier wave corresponding to the I axis is a and the amplitude of the carrier wave corresponding to the Q axis is b.

[0020] It is known that when single-carrier transmission is performed based on QAM, the PAPR of the modulated wave increases as the modulation order (number of bits per symbol) increases. It is also known that the required signal-to-noise ratio (SNR) increases as the modulation order increases. Table 1 shows a comparison of the PAPR and required SNR of the modulated wave for each modulation method (and modulation order of the modulation method).

[0021] [Table 1]

[0022] Here, the PAPR of the modulated wave and the required SNR (minimum to maximum) show the comparative relationship among the five modulation methods shown in Table 1. Also, QPSK stands for Quadrature phase-shift keying (QPSK). QPSK can also be implemented as 4QAM.

[0023] As shown in Table 1, a modulated wave with a small modulation order has a small PAPR. If the PAPR can be suppressed, the backoff can be reduced. In turn, this makes it possible to increase the average transmission power and reduce power consumption. In addition, a modulated wave with a small modulation order has a small required SNR, making it possible to improve the SNR. However, if wireless communication is performed using radio waves transmitted using a modulated wave with a small modulation order, the data transmission speed will naturally decrease.

[0024] The wireless communication system and the wireless communication method according to the present embodiment suppress the PAPR of a modulated wave input to an amplifier without lowering the modulation order. Hereinafter, the wireless communication system and the wireless communication method according to the present embodiment will be described.

[0025] 2. Wireless communication systems 2-1. Overview First, a wireless communication system according to this embodiment will be described. In the wireless communication system according to this embodiment, first, a signal point related to a base signal space diagram (hereinafter also referred to as a "base signal point") and a signal point related to an offset signal space diagram (hereinafter also referred to as an "offset signal point") are calculated according to a signal point corresponding to data to be transmitted (hereinafter also referred to as a "transmission signal point"). Here, the base signal space diagram is a signal space diagram that specifies the position of a transmission signal point in a divided portion for a predetermined division that equally divides the range (hereinafter also referred to as a "signal range") of a signal point related to a signal space diagram (hereinafter also referred to as a "transmission signal space diagram") on which the transmission signal point is based. Also, the offset signal space diagram is a signal space diagram that specifies an offset of the base signal space diagram according to the position of the divided portion.

[0026] Fig. 2 is a conceptual diagram showing an example of a base constellation diagram and an offset constellation diagram. The upper part of Fig. 2 shows a transmission constellation diagram, and the lower part of Fig. 2 shows a base constellation diagram and an offset constellation diagram according to the division of a signal range 1 related to the transmission constellation diagram. Note that Fig. 2 shows a case where data is transmitted based on 64QAM, and the transmission constellation diagram is composed of 64 signal points.

[0027] In Fig. 2, signal range 1 is a square range (range surrounded by dotted lines) that encloses 64 signal points. Signal range 1 is divided into four equal parts (dotted lines) as shown in Fig. 2. Therefore, each divided part contains 16 signal points.

[0028] In this case, the base constellation diagram is composed of 16 signal points as shown in Figure 2. Here, each of the 16 signal points constituting the base constellation diagram corresponds to each of the 16 signal points included in the divided parts, and defines the position of the transmission signal point in the divided parts.

[0029] Moreover, the offset constellation diagram is composed of four signal points as shown in Fig. 2. Here, each of the four signal points constituting the offset constellation diagram corresponds to each of the four equal parts, and defines the offset of the base constellation diagram.

[0030] The sum of the base signal space diagram and the offset signal space diagram is similar to the transmission signal space diagram. In other words, the signal range related to the sum of the base signal space diagram and the offset signal space diagram is similar to the signal range of the transmission signal space diagram.

[0031] The base constellation diagram can be realized by a constellation diagram for a conventional QAM. For example, the base constellation diagram shown in FIG. 2 may be a constellation diagram for 16QAM.

[0032] The offset constellation diagram may also be realized by a constellation diagram related to a conventional modulation method. For example, the offset constellation diagram shown in FIG. 2 may be a constellation diagram related to 4PSK (or 4QAM). The offset constellation diagram can be formally realized by a constellation diagram related to phase shift keying. However, by appropriately dividing the signal range related to the transmission constellation diagram, the offset constellation diagram may also be realized by a constellation diagram related to another conventional modulation method. For example, when dividing the signal range 1 shown in FIG. 2 into 16 equal parts, the offset constellation diagram may also be realized by a constellation diagram related to 16QAM.

[0033] The division of the signal range related to the transmission constellation diagram, the base constellation diagram, and the offset constellation diagram may be given appropriately without relying on the constellation diagram related to the conventional modulation method.

[0034] In this way, by configuring the base constellation diagram and the offset constellation diagram, it is possible to provide a combination of base constellation points and offset constellation points that correspond one-to-one to the transmission constellation points. Fig. 3 is a conceptual diagram for explaining the base constellation point 3 and offset constellation point 4 calculated according to the transmission constellation point 2. Fig. 3 shows the base constellation points 3a, 3b, and 3c and the offset constellation points 4a, 4b, and 4c calculated according to the three transmission constellation points 2a, 2b, and 2c, respectively (black circles). Here, the transmission constellation diagram, the base constellation diagram, and the offset constellation diagram shown in Fig. 3 are the same as those shown in Fig. 2. Note that the positions of the constellation points in each constellation diagram are shown as white circles surrounded by dotted lines.

[0035] The transmission signal point 2a is included in the upper right divided portion of the signal range 1. Moreover, the transmission signal point 2a in the divided portion is located to the upper right of the inner four signal points of the 16 signal points. At this time, as shown in Fig. 3, the base signal point 3a corresponds to the position of the transmission signal point 2a in the divided portion, and is located to the upper right of the inner four signal points. And the offset signal point 4a corresponds to the position of the divided portion including the transmission signal point 2a, and is located to the upper right of the four signal points.

[0036] Transmission signal point 2b is included in the lower left divided portion of signal range 1. Moreover, transmission signal point 2b in the divided portion is located at the upper left of the outer 12 signal points out of the 16 signal points. At this time, as shown in Fig. 3, base signal point 3b corresponds to the position of transmission signal point 2b in the divided portion and is located at the upper left of the outer 12 signal points. And offset signal point 4b corresponds to the position of the divided portion including transmission signal point 2b and is located at the lower left of the four signal points.

[0037] The transmission signal point 2c is included in the lower right divided portion of the signal range 1. Moreover, the transmission signal point 2c in the divided portion is located at the lower right of the outer 12 signal points of the 16 signal points. At this time, the base signal point 3c corresponds to the position of the transmission signal point 2c in the divided portion, as shown in Fig. 3, and is located at the lower right of the outer 12 signal points. And the offset signal point 4c corresponds to the position of the divided portion including the transmission signal point 2c, and is located at the lower right of the four signal points.

[0038] In this way, the base signal point 3 and offset signal point 4 are calculated according to the transmission signal point 2. As described above, the sum of the base signal space diagram and the offset signal space diagram is a similar figure to the transmission signal space diagram, so the transmission signal point 2 is given by a constant multiple of the sum of the calculated base signal point 3 and offset signal point 4. In other words, when the position vector related to the transmission signal point 2 is s, the position vector related to the calculated base signal point 3 is a, and the position vector related to the calculated offset signal point 4 is b, the following equation (1) holds. Here, W is a constant that gives the constant multiple.

[0039]

number

[0040] Fig. 4 conceptually shows that the transmission signal point 2b is given by multiplying the sum of the base signal point 3b and the offset signal point 4b (5b in Fig. 4) by a constant, taking as an example the base signal point 3b and the offset signal point 4b calculated according to the transmission signal point 2b shown in Fig. 2. Note that 6 in Fig. 4 indicates the signal range related to the sum of the base signal space diagram and the offset signal space diagram.

[0041] W gives the scale correction between signal range 1 and signal range 6, and indicates the scale of signal range 1. Also, considering that at least the four corners (positions where the sum of the amplitudes of the I axis and the Q axis is maximum) in signal range 1 and signal range 6 are signal points, W can be calculated from the positions of the signal points at the four corners of signal range 1 and the sequence of the positions of the base signal point 3 and offset signal point 4 corresponding to those signal points. For example, when the position of one of the signal points at the four corners of signal range 1 is (s1, s2), the position of the base signal point 3 corresponding to that signal point is (a1, a2), and the position of the offset signal point 4 is (b1, b2), W can be calculated by the following formula (2).

[0042]

number

[0043] A plurality of offset signal space diagrams may be provided. In this case, a plurality of offset signal points 4 related to each offset signal space diagram are calculated according to the transmission signal point 2. When the position vector related to the transmission signal point 2 is s, the position vector related to the calculated base signal point 3 is a, and the position vectors related to the calculated plurality of offset signal points 4 are respectively bi (i=1,2,...,N), the following formula (3) is established. Here, N is the number of offset signal space diagrams to be provided.

[0044]

number

[0045] Fig. 5 conceptually shows an example in which two offset signal space diagrams (first signal space diagram and second signal space diagram) are given. In Fig. 5, a base signal point 3, a first offset signal point 4s, and a second offset signal point 4t are calculated according to a transmission signal point 2. Fig. 5 shows, for example, a case in which the signal range 1 shown in Fig. 2 is divided into 16 equal parts.

[0046] As described above, in the wireless communication system according to this embodiment, a base signal point and an offset signal point are calculated according to a transmission signal point. Next, in the wireless communication system according to this embodiment, a modulated wave according to the calculated base signal point (hereinafter also referred to as a "base modulated wave") and a modulated wave according to the calculated offset signal point (hereinafter also referred to as an "offset modulated wave") are generated.

[0047] The generation of modulated waves corresponding to the base signal point and the offset signal point may be performed by using a suitable known technique. For example, when the base signal constellation diagram and the offset signal constellation diagram are given as shown in FIG. 2, the generation of modulated waves corresponding to the base signal point may be realized by a conventional modulator related to 16QAM, and the generation of modulated waves corresponding to the offset signal point may be realized by a conventional modulator related to QPSK.

[0048] Next, in the wireless communication system according to the present embodiment, the base modulated wave and the offset modulated wave are input to an amplifier and amplified to a predetermined power, after which the base modulated wave and the offset modulated wave are combined.

[0049] Next, in the wireless communication system according to this embodiment, a radio wave is transmitted using a modulated wave (hereinafter also referred to as a "transmission modulated wave") obtained by combining a base modulated wave and an offset modulated wave.

[0050] Next, in the wireless communication system according to this embodiment, the receiver receives radio waves to obtain a reception signal.

[0051] In the wireless communication system according to this embodiment, the scale of the received signal is adjusted based on the scale information, and then the received signal is demodulated to obtain data indicated by the received signal.

[0052] Here, the scale information may be the constant W described in equation (1) (or equation (3)). Alternatively, it is a sequence of the positions of the signal points included in signal range 1 and the positions of the base signal point 3 and offset signal point 4 corresponding to the signal points. In this case, the sequence is given so that the scale can be calculated as shown in equation (2). In particular, as described in equation (2), the signal points included in signal range 1 can be the signal points at the four corners of signal range 1.

[0053] In addition, the scale information may be provided to the receiver in advance, or the transmitter may be configured to transmit the scale information to the receiver before transmitting data. In this way, the scale information can be provided appropriately according to the data to be transmitted.

[0054] The signal point indicated by the scale-adjusted received signal becomes the transmission signal point as shown in formula (1) (or formula (3)). Therefore, in the wireless communication system according to this embodiment, the modulation order becomes the modulation order related to the transmission signal point.

[0055] By the way, because the base signal space diagram and the offset signal space diagram are given, the modulation order related to the base signal point and the modulation order related to the offset signal point are smaller than the modulation order related to the transmission signal point. In other words, the PAPR of the base modulated wave and the offset modulated wave is smaller than the PAPR of the modulated wave generated according to the transmission signal point. In the wireless communication system according to this embodiment, the base modulated wave and the offset modulated wave are input to the amplifier. In other words, in the wireless communication system according to this embodiment, the PAPR of the modulated wave input to the amplifier can be suppressed without lowering the modulation order.

[0056] 2-2. Configuration example An example of the configuration of the wireless communication system according to this embodiment will be described below. Fig. 6 is a block diagram showing an example of the configuration of the wireless communication system 10 according to this embodiment. The upper part of Fig. 6 shows an example of the configuration of the transmitter 100, and the lower part of Fig. 6 shows an example of the configuration of the receiver 200. The wireless communication system 10 shown in Fig. 6 transmits data from the transmitter 100 to the receiver 200 by radio waves. Here, the wireless communication system 10 shown in Fig. 6 shows an example of the configuration when transmitting data based on 256QAM. That is, 8 bits of data are transmitted per symbol.

[0057] In addition, in the wireless communication system 10 shown in FIG. 6, it is assumed that the base constellation diagram is given as a constellation diagram relating to 64QAM, and the offset constellation diagram is given as a constellation diagram relating to QPSK.

[0058] The transmitter 100 includes an information processing device 110, modulators 120a and 120b, amplifiers 140a and 140b, an adder 150, and a transmitting antenna 160.

[0059] The information processing device 110 (signal point calculation unit) calculates a base signal point and an offset signal point according to a signal point (transmission signal point) corresponding to data to be transmitted. The calculated base signal point and offset signal point are transmitted to the modulators 120a and 120b, respectively. The information processing device 110 is typically a microcontroller incorporated in the transmitter 100. In this case, the information processing device 110 calculates the base signal point and offset signal point by having a processor execute a program stored in a memory. The program describes a process for providing a correspondence between data to be transmitted (every 8 bits) and the base signal point and offset signal point according to, for example, a base signal space diagram and an offset signal space diagram.

[0060] The modulator 120a (base modulated wave generating unit) generates a base modulated wave according to a base signal point transmitted from the information processing device 110. The modulator 120a may be realized by a conventional modulator related to 64QAM.

[0061] The modulator 120b (offset modulated wave generating section) generates an offset modulated wave according to an offset signal point transmitted from the information processing device 110. The modulator 120b may be realized by a conventional modulator related to QPSK.

[0062] The amplifier 140a (base modulated wave amplifier) ​​amplifies the base modulated wave to a predetermined power.

[0063] The amplifier 140b (offset modulated wave amplifier) ​​amplifies the offset modulated wave to a predetermined power.

[0064] Here, the amplifiers 140a and 140b may be realized by known amplifiers.

[0065] The adder 150 (combiner) combines the base modulated wave and the offset modulated wave amplified by the amplifier 140a and the amplifier 140b to obtain a transmission modulated wave. The adder 150 may be realized by a general electronic circuit.

[0066] The transmitting antenna 160 transmits radio waves by modulating the transmission wave. The transmitting antenna 160 may be an antenna suitable for the environment in which the wireless communication system 10 is used. For example, an array antenna, a dipole antenna, etc. may be used.

[0067] The receiver 200 includes a receiving antenna 260 and a demodulator 220 .

[0068] The receiving antenna 260 receives the radio waves transmitted from the transmitting antenna 160 to obtain a received signal. The receiving antenna 260 may be an antenna suitable for the environment in which the wireless communication system 10 is used. The received signal obtained by the receiving antenna 260 is transmitted to the demodulator 220.

[0069] The demodulator 220 (demodulation unit) adjusts the scale of the received signal based on the scale information, and then demodulates the received signal to obtain data indicated by the received signal. Here, the signal point indicated by the scale-adjusted received signal becomes the transmission signal point. That is, in the wireless communication system 10 shown in FIG. 6, the modulation order is equivalent to 256QAM.

[0070] The scale information may be provided in advance to the demodulator 220, or may be provided in advance to a device such as a memory provided in the receiver 200, and the demodulator 220 may read out the scale information from the device. Alternatively, the transmitter 100 may transmit the scale information before transmitting data, and the receiver 200 may receive the scale information. The scale information is, for example, the constant W described in equation (1) (or equation (3)). Alternatively, it is a sequence of the positions of the signal points included in the signal range 1 and the positions of the base signal point 3 and the offset signal point 4 corresponding to the signal points. In this case, the sequence is provided so that the scale can be calculated as shown in equation (2). In particular, as described in equation (2), the signal points included in the signal range 1 can be the signal points at the four corners of the signal range 1.

[0071] Furthermore, for demodulation processing of the received signal after scale adjustment, conventional demodulation processing related to 256QAM may be applied.

[0072] 3. Wireless communication method Next, a wireless communication method according to the present embodiment will be described, with the exception that in the following description, matters that overlap with the above content will be omitted as appropriate.

[0073] Fig. 7 is a flowchart showing the process executed in the wireless communication method according to this embodiment. The process shown in Fig. 7 starts when data to be transmitted is provided and wireless communication is performed.

[0074] In step S100 (signal point calculation processing), a base signal point and an offset signal point are calculated according to a signal point (transmission signal point) corresponding to data to be transmitted. After step S100, the processing proceeds to step S110.

[0075] In step S110, a base modulated wave is generated according to the base signal point calculated in step S100, and the generated base modulated wave is processed.

[0076] FIG. 8 shows the process executed in step S110.

[0077] In step S111 (base modulated wave generation processing), a base modulated wave corresponding to a base signal point is generated. After step S111, the processing proceeds to step S113.

[0078] In step S113 (base modulated wave amplification process), the base modulated wave is amplified to a predetermined power. After step S113, the process executed in step S110 ends.

[0079] Referring again to Figure 7, after step S110, the process proceeds to step S120.

[0080] In step S120, an offset modulated wave is generated according to the offset signal point calculated in step S100. Furthermore, the generated offset modulated wave is processed.

[0081] FIG. 9 shows the process executed in step S120.

[0082] In step S121 (offset modulated wave generation process), an offset modulated wave corresponding to an offset signal point is generated. After step S121, the process proceeds to step S123.

[0083] In step S123 (offset modulated wave amplification process), the offset modulated wave is amplified to a predetermined power. After step S123, the process executed in step S120 ends.

[0084] Referring again to Figure 7, after step S120, the process proceeds to step S130.

[0085] The order of steps S110 and S120 may be reversed, that is, step S110 may be executed after step S120, or steps S110 and S120 may be executed in parallel.

[0086] In step S130 (synthesis process), the base modulated wave and the offset modulated wave amplified in steps S113 and S123 are synthesized to obtain a transmission modulated wave. After step S130, the process proceeds to step S140.

[0087] In step S140 (transmission processing), a radio wave corresponding to the transmission modulated wave is transmitted. After step S140, the process proceeds to step S150.

[0088] In step S150 (reception processing), the radio wave transmitted in step S140 is received to obtain a reception signal. After step S150, the process proceeds to step S160.

[0089] In step S160 (demodulation process), the received signal obtained in step S150 is scaled based on the scale information. The scaled received signal is then demodulated to obtain data represented by the received signal. This completes data transmission by wireless communication. After step S160, the process ends.

[0090] Here, the signal points indicated by the scale-adjusted received signal become the transmission signal points. The scale information is, for example, the constant W described in equation (1) (or equation (3)). Alternatively, it is a sequence of the positions of signal points included in signal range 1 and the positions of base signal point 3 and offset signal point 4 corresponding to the signal points. In this case, the sequence is given so that the scale can be calculated as shown in equation (2). In particular, as described in equation (2), the signal points included in signal range 1 can be the signal points at the four corners of signal range 1.

[0091] In addition, the scale information may be provided to the receiver in advance, or the scale information may be transmitted to the receiver before the transmitter transmits data. In this way, the scale information can be provided appropriately according to the data to be transmitted.

[0092] The wireless communication method shown in Fig. 7 can be realized by a configuration equivalent to that of the wireless communication system 10 shown in Fig. 6. However, it may also be realized by other configurations.

[0093] 4.Effects As described above, according to the wireless communication system 10 and the wireless communication method of this embodiment, the modulation order related to the base signal point and the modulation order related to the offset signal point can be made smaller than the modulation order related to the transmission signal point. This makes it possible to suppress the PAPR of the modulated wave (base modulated wave and offset modulated wave) input to the amplifier without lowering the modulation order. As a result, it is possible to reduce the backoff, increase the average transmission output, and reduce power consumption.

[0094] Furthermore, by reducing the modulation order of the modulated wave input to the amplifier, the required SNR can be reduced, and the SNR can be improved.

[0095] The wireless communication system 10 and the wireless communication method according to the present disclosure can be applied to a multiple-input and multiple-output (MIMO) technology by providing a plurality of transmitting antennas 160 or a plurality of receiving antennas 260. In this case, the same effects can be achieved. [Explanation of symbols]

[0096] 1. Signal Range 2 Transmission signal points 3 Base signal point 4 Offset Signal Points 10. Wireless communication systems 100 Transmitter 110 Information processing device (signal calculation unit) 120a Modulator (base modulation wave generating section) 120b Modulator (offset modulation wave generator) 140a Amplifier (base modulation wave amplifier) 140b Amplifier (offset modulation wave amplifier) 150 Adder (combiner) 160 transmitting antenna 200 Receiver 220 Demodulator (Demodulation section) 260 Receiving Antenna

Claims

1. A wireless communication system that transmits data from a transmitter to a receiver by single carrier transmission using radio waves based on quadrature amplitude modulation, A transmission signal point is a signal point corresponding to the data to be transmitted, A signal range is a range of signal points according to a signal space diagram on which the transmission signal point is based; The transmitter includes: a signal point calculation unit that calculates a base signal point and N offset signal points according to a base signal space diagram that defines the position of the transmission signal point in a division portion for a predetermined division that equally divides the signal range and N offset signal space diagrams (N is an integer equal to or greater than 1) that define offsets of the base signal space diagram according to the position of the division portion related to the division; a base modulated wave generating unit that generates a base modulated wave according to the base signal point; a base modulated wave amplifier that amplifies the base modulated wave to a predetermined power; an offset modulated wave generating unit that generates N offset modulated waves corresponding to the N offset signal points; an offset modulated wave amplifier that amplifies the offset modulated wave to a predetermined power; a synthesizing unit that synthesizes the base modulated wave amplified by the base modulated wave amplifier unit and the N offset modulated waves amplified by the offset modulated wave amplifier unit to obtain a transmission modulated wave; a transmitting antenna for transmitting the radio wave by the transmission modulated wave; Equipped with The receiver includes: A receiving antenna for receiving the radio waves; a demodulation unit that adjusts the scale of a received signal related to the radio wave based on scale information indicating a scale of the signal range and performs demodulation; Equipped 1. A wireless communication system comprising:

2. 2. The wireless communication system according to claim 1, The scale information is transmitted from the transmitter to the receiver prior to transmission of the data.

1. A wireless communication system comprising:

3. 3. The wireless communication system according to claim 1, The scale information is a sequence of positions of signal points included in the signal range and the positions of the base signal point and the offset signal point relative to the signal points.

1. A wireless communication system comprising:

4. A wireless communication method for transmitting data from a transmitter to a receiver by single carrier transmission using radio waves based on quadrature amplitude modulation, comprising: A transmission signal point is a signal point corresponding to the data to be transmitted, A signal range is a range of signal points according to a signal space diagram on which the transmission signal point is based; a signal point calculation process for calculating a base signal point and N offset signal points according to a base signal space diagram that defines the position of the transmission signal point in a division portion for a predetermined division that equally divides the signal range and N offset signal space diagrams (N is an integer equal to or greater than 1) that define offsets of the base signal space diagram according to the position of the division portion related to the division; A base modulated wave generation process for generating a base modulated wave according to the base signal point; A base modulated wave amplifying process for amplifying the base modulated wave to a predetermined power; an offset modulated wave generation process for generating N offset modulated waves corresponding to the N offset signal points; an offset modulated wave amplification process for amplifying the offset modulated wave to a predetermined power; a synthesis process of synthesizing the base modulated wave amplified by the base modulated wave amplification process and the N offset modulated waves amplified by the offset modulated wave amplification process to obtain a transmission modulated wave; a transmission process of transmitting the radio wave by the transmission modulated wave; A receiving process for receiving the radio wave; a demodulation process for adjusting a scale of a received signal related to the radio wave based on scale information indicating a scale of the signal range and performing demodulation; A wireless communication method comprising:

5. 5. The wireless communication method according to claim 4, The scale information is transmitted from the transmitter to the receiver prior to transmission of the data.

23. A wireless communication method comprising:

6. 6. The wireless communication method according to claim 4, further comprising: The scale information is a sequence of positions of signal points included in the signal range and the positions of the base signal point and the offset signal point relative to the signal points.

23. A wireless communication method comprising:

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