JP7623641B2 - Wireless communication system and wireless communication method - Google Patents

Description

The present disclosure relates to a wireless communication system and a wireless communication method that transmit data from a transmitter to a receiver using single carrier transmission via radio waves.

Non-Patent Document 1 proposes a new modulation method that can apply Trellis Shaping (TS) technology, a peak power reduction technique, to the Single Carrier Frequency Division Multiple Access (SC-FDMA) modulation method.

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)

In a wireless communication transmitter, if the peak power of the modulated wave input to the amplifier exceeds the linear characteristics of the amplifier, nonlinear distortion occurs in the amplifier output, 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, by suppressing the peak-to-average power ratio (PAPR) of the modulated wave input to the amplifier, the backoff can be reduced. This in turn has the effect of increasing the average transmission output and reducing power consumption.

By performing wireless communication using single-carrier transmission, the PAPR of the modulated wave can be suppressed compared to wireless communication using multi-carrier transmission (e.g., OFDMA (Orthogonal frequency-division multiple access)). However, even when performing wireless communication using single-carrier transmission, there is an issue that the PAPR increases as the modulation order of the modulated wave increases.

The present disclosure has been made in consideration of the above 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.

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 division portion for 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 portion 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 also includes a receiving antenna that receives radio waves, and a demodulator that adjusts the scale of a received signal related to the received radio waves based on scale information that indicates the scale of the signal range and performs demodulation. Here, the transmission signal point is a signal point that corresponds to the data to be transmitted, and the signal range is a range of signal points related to the signal space diagram on which the transmission signal point is based.

The second disclosure relates to a wireless communication system including 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.

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.

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 specifies the position of a transmission signal point in a division portion for a predetermined division that equally divides a signal range and an offset signal space diagram that specifies the offset 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 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 radio waves using the transmission modulated wave, a reception process for receiving radio waves, and a demodulation process for adjusting the scale of a received signal related to the received radio waves based on scale information indicating the scale of the signal range and performing demodulation. Here, the transmission signal point is the signal point corresponding to the data to be transmitted, and the signal range is the range of signal points related to the signal space diagram on which the transmission signal point is based.

The fifth disclosure relates to a wireless communication method further including the following features in relation 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.

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.

According to the wireless communication system and wireless communication method disclosed herein, the modulation order for the base signal point and the modulation order for the offset signal point can be made smaller than the modulation order for 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.

FIG. 1 is a conceptual diagram showing an example of a signal space diagram for QAM. 1 is a conceptual diagram showing an example of a base signal space diagram and an offset signal space diagram. FIG. 10 is a conceptual diagram for explaining a base signal point and an offset signal point calculated according to a transmission signal point. FIG. FIG. 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 the base signal point and the offset signal point calculated according to the transmission signal point shown in FIG. 2 . FIG. 1 is a conceptual diagram showing an example where two offset constellation diagrams are given. 1 is a block diagram showing an example of the configuration of a wireless communication system according to an embodiment of the present invention. 5 is a flowchart showing a process executed in the wireless communication method according to the embodiment. 8 is a flowchart showing a process executed in step S110 shown in FIG. 7; 8 is a flowchart showing a process executed in step S120 shown in FIG. 7;

Below, the embodiments of the present disclosure will be described with reference to the drawings. However, when the numbers, quantities, amounts, ranges, etc. of each element are mentioned in the embodiments shown below, the idea of the present disclosure is not limited to the mentioned numbers unless otherwise specified 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 otherwise specified or the number is clearly specified in principle. In addition, the same reference numerals are used for the same or corresponding parts in each drawing, and duplicate explanations are appropriately simplified or omitted.

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").

As is well known, QAM is a modulation method in which the amplitude of two carrier waves, each of which has an orthogonal phase relationship, is modulated according to the data to be transmitted, and the resulting signal is combined to produce a modulated wave.

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. In addition, modulation of each of the two carrier waves according to the data is performed according to the constellation diagram.

Figure 1 shows an example of a QAM constellation diagram. 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 multiple signal points corresponding to data. The constellation diagram shown in Figure 1 includes 16 signal points, each of which corresponds to 4 bits of data. In other words, Figure 1 shows a constellation diagram related to 16QAM, and in accordance with the constellation diagram shown in Figure 1, the modulated wave can show 4 bits of data per symbol. For example, the data 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.

When performing single-carrier transmission based on QAM, it is known that 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 of the modulated wave and the required SNR for each modulation method (and the modulation order of the modulation method).

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

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, and the SNR can be improved. However, if wireless communication is performed using radio waves transmitted by a modulated wave with a small modulation order, the data transmission speed will naturally decrease.

The wireless communication system and wireless communication method according to this embodiment suppress the PAPR of the modulated wave input to the amplifier without lowering the modulation order. The wireless communication system and wireless communication method according to this embodiment are described below.

2. Wireless communication system 2-1. Overview First, a wireless communication system according to this embodiment will be described. In the wireless communication system according to this embodiment, 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.

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

In Figure 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 (dash-dotted lines) as shown in Figure 2. Therefore, each divided part contains 16 signal points.

In this case, the base signal space diagram is composed of 16 signal points, as shown in FIG. 2. Here, each of the 16 signal points constituting the base signal space diagram corresponds to each of the 16 signal points included in the divided parts, and specifies the position of the transmission signal point in the divided part.

The offset signal space diagram is composed of four signal points, as shown in FIG. 2. Here, each of the four signal points constituting the offset signal space diagram corresponds to one of the four equal parts, and defines the offset of the base signal space diagram.

The sum of the base signal space diagram and the offset signal space diagram is a similar figure 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 mutually similar to the signal range of the transmission signal space diagram.

The base constellation diagram can be realized by a constellation diagram related to conventional QAM. For example, the base constellation diagram shown in FIG. 2 may be a constellation diagram related to 16QAM.

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). Formally, the offset constellation diagram can be 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 other conventional modulation methods. 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.

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

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

Transmission signal point 2a is included in the upper right division of signal range 1. Furthermore, transmission signal point 2a in the division is located to the upper right of the four innermost signal points of the 16 signal points. At this time, as shown in FIG. 3, base signal point 3a corresponds to the position of transmission signal point 2a in the division, and is located to the upper right of the four innermost signal points. Furthermore, offset signal point 4a corresponds to the position of the division that includes transmission signal point 2a, and is located to the upper right of the four signal points.

Transmission signal point 2b is included in the lower left division of signal range 1. Furthermore, transmission signal point 2b in the division 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 division, and is located at the upper left of the outer 12 signal points. Furthermore, offset signal point 4b corresponds to the position of the division that includes transmission signal point 2b, and is located at the lower left of the four signal points.

Transmission signal point 2c is included in the lower right division of signal range 1. Furthermore, transmission signal point 2c in the division is located to the lower right of the outer 12 signal points out of the 16 signal points. At this time, as shown in FIG. 3, base signal point 3c corresponds to the position of transmission signal point 2c in the division, and is located to the lower right of the outer 12 signal points. Furthermore, offset signal point 4c corresponds to the position of the division that includes transmission signal point 2c, and is located to the lower right of the four signal points.

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 similar to the transmission signal space diagram, so the transmission signal point 2 is given by a constant multiplication 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 multiplication.

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

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 position of the signal point 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 that signal point. 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).

Note that multiple offset signal space diagrams may be provided. In this case, multiple 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 multiple offset signal points 4 are each bi (i = 1, 2, ..., N), the following formula (3) holds. Here, N is the number of offset signal space diagrams to be provided.

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

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.

The generation of modulated waves corresponding to the base signal point and offset signal point may be performed using any suitable known technology. For example, when the base signal space diagram and offset signal space diagram are given as described in FIG. 2, the generation of modulated waves corresponding to the base signal point may be realized by a conventional 16QAM modulator, and the generation of modulated waves corresponding to the offset signal point may be realized by a conventional QPSK modulator.

Next, in the wireless communication system according to this embodiment, the base modulated wave and the offset modulated wave are input to an amplifier and amplified to a predetermined power. After that, the base modulated wave and the offset modulated wave are combined.

Next, in the wireless communication system according to this embodiment, radio waves are transmitted using a modulated wave (hereinafter also referred to as a "transmission modulated wave") that is a combination of a base modulated wave and an offset modulated wave.

Next, in the wireless communication system according to this embodiment, the receiver receives radio waves and obtains a received signal.

The wireless communication system according to this embodiment adjusts the scale of the received signal based on the scale information, and then demodulates the received signal to obtain the data represented by the received signal.

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.

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. This allows the scale information to be provided appropriately according to the data to be transmitted.

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

However, due to the way in which the base signal space diagram and the offset signal space diagram are given, the modulation order associated with the base signal point and the modulation order associated with the offset signal point are smaller than the modulation order associated with 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.

2-2. Configuration Example Hereinafter, a configuration example of the wireless communication system according to this embodiment will be described. Fig. 6 is a block diagram showing a configuration example of the wireless communication system 10 according to this embodiment. The upper part of Fig. 6 shows a configuration example of the transmitter 100, and the lower part of Fig. 6 shows a configuration example 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 a configuration example when transmitting data based on 256QAM. In other words, 8 bits of data are transmitted per symbol.

Furthermore, in the wireless communication system 10 shown in FIG. 6, the base signal space diagram is given as a signal space diagram relating to 64QAM, and the offset signal space diagram is given as a signal space diagram relating to QPSK.

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.

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 the 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 the processor execute a program stored in the memory. The program describes, for example, a process that provides a correspondence between the data to be transmitted (every 8 bits) and the base signal point and offset signal point according to the base signal space diagram and the offset signal space diagram.

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

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

The amplifier 140a (base modulated wave amplifier) amplifies the base modulated wave to a predetermined power.

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

Here, amplifiers 140a and 140b may be realized using known amplifiers.

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.

The transmitting antenna 160 transmits radio waves using a transmission modulated wave. The transmitting antenna 160 may be an antenna suitable for the environment in which the wireless communication system 10 is used. Examples include an array antenna and a dipole antenna.

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

The receiving antenna 260 receives the radio waves transmitted from the transmitting antenna 160 and obtains 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.

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

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 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 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.

In addition, the demodulation process for the received signal after scale adjustment may be performed using conventional 256QAM demodulation processing.

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.

Figure 7 is a flowchart showing the processing executed in the wireless communication method according to this embodiment. The processing shown in Figure 7 starts when data to be transmitted is given and wireless communication is performed.

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

In step S110, a base modulated wave is generated according to the base signal point calculated in step S100. The generated base modulated wave is also processed.

Figure 8 shows the process performed in step S110.

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

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.

Referring again to FIG. 7, after step S110, processing proceeds to step S120.

In step S120, an offset modulated wave is generated according to the offset signal point calculated in step S100. The generated offset modulated wave is also processed.

Figure 9 shows the process performed in step S120.

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

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 is terminated.

Referring again to FIG. 7, after step S120, processing proceeds to step S130.

The order of steps S110 and S120 may be reversed. That is, step S110 may be executed after step S120. Alternatively, steps S110 and S120 may be executed in parallel.

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.

In step S140 (transmission process), radio waves corresponding to the transmission modulated wave are sent out. After step S140, the process proceeds to step S150.

In step S150 (reception processing), the radio waves transmitted in step S140 are received to obtain a received signal. After step S150, processing proceeds to step S160.

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 the data indicated by the received signal. This completes data transmission via wireless communication. After step S160, the process ends.

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 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.

The scale information may be provided to the receiver in advance, or the scale information may be sent to the receiver before the transmitter transmits the data. This allows the scale information to be provided appropriately according to the data to be transmitted.

The wireless communication method shown in FIG. 7 can be realized by a configuration equivalent to the wireless communication system 10 shown in FIG. 6. However, it may also be realized by other configurations.

4. Effects As described above, according to the wireless communication system 10 and the wireless communication method of the present 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.

In addition, by reducing the modulation order of the modulated wave input to the amplifier, the required SNR can be reduced, improving the SNR.

The wireless communication system 10 and wireless communication method according to the present disclosure can be applied to MIMO (Multiple-input and Multiple-output) technology by providing multiple transmitting antennas 160 or multiple receiving antennas 260. In this case, the same effect can be achieved.

1 Signal range 2 Transmission signal point 3 Base signal point 4 Offset signal point 10 Wireless communication system 100 Transmitter 110 Information processing device (signal calculation unit)
120a Modulator (base modulated wave generating unit)
120b Modulator (offset modulated wave generating unit)
140a Amplifier (base modulation wave amplifier)
140b Amplifier (offset modulated wave amplifier)
150 Adder (combiner)
160: Transmitting antenna 200: Receiver 220: Demodulator (demodulation section)
260 receiving antenna

Claims (6)

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;
A wireless communication system comprising: 2. The wireless communication system according to claim 1,
The wireless communication system according to claim 1, wherein the scale information is transmitted from the transmitter to the receiver before transmitting the data. 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 positions of the base signal point and the offset signal point relative to the signal points. 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. The wireless communication method according to claim 4,
The wireless communication method according to claim 1, wherein the scale information is transmitted from the transmitter to the receiver before transmitting the data. 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 positions of the base signal point and the offset signal point relative to the signal points.

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