JP2023015780A - Wireless communication system and wireless communication method - Google Patents

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 corresponding to the base signal point and the offset signal point. After that, the transmitter pre-codes each of the base modulated wave and the offset modulated wave and then amplifies them to a predetermined power. Then, the transmitter transmits a base radio wave and an offset radio wave. A receiver of the wireless communication system according to the present disclosure demodulates a combined signal of a received signal associated with the base radio wave and an offset radio wave of a received signal associated with the offset radio wave.SELECTED DRAWING: Figure 6

Description

TECHNICAL FIELD The present disclosure relates to a wireless communication system and a wireless communication method for transmitting data from a transmitter to a receiver using radio waves through single-carrier transmission.

Patent Document 1 discloses a method of estimating channel coefficients g11, g12, g21, and g22 related to transmission diversity channels in a wireless communication system using transmission diversity. A wireless communication system has a base station and at least one mobile station and includes a transmit diversity channel transmitted over at least two propagation paths from at least two antennas associated with the base station. The method disclosed in Patent Document 1 comprises the steps of supplying pilot symbol sequences for transmission from a base station to a mobile station via a transmit diversity channel for each of at least two antennas; receiving a sequence of symbols r1, r2, r3, r4 from the channel; setting a matrix P of values of the pilot symbol sequence; , g12, g21, g22.

Japanese translation of PCT publication No. 2003-505926

2. Description of the Related Art 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. Therefore, 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. Ultimately, there are effects such as an increase in average transmission output and a reduction in power consumption.

Performing wireless communication by single-carrier transmission can suppress the PAPR of modulated waves compared to performing wireless communication by multi-carrier transmission (for example, OFDMA (Orthogonal frequency-division multiple access)). However, even when performing wireless communication by single-carrier transmission, there is a problem that the PAPR increases as the modulation order of the modulated wave increases.

In addition, it is known that the transmission diversity technique disclosed in Patent Document 1 can improve the signal-noise ratio (SNR) by combining signals related to a plurality of propagation channels at the time of reception. there is This enables transmission by high-order modulation. However, there is still a problem that the PAPR becomes large.

The present disclosure has been made in view of the above problems, and aims to provide a wireless communication system and wireless communication method capable of suppressing the PAPR of a modulated wave input to an amplifier without lowering the modulation order. aim.

A first disclosure relates to a wireless communication system for transmitting data from a transmitter to a receiver by means of single-carrier transmission using radio waves based on quadrature amplitude modulation. The transmitter of this wireless communication system includes a signal space diagram defining the positions of transmission signal points in the divided parts for predetermined divisions that equally divide the signal range, and a base signal space diagram corresponding to the positions of the divided parts related to the division. A signal point calculator that calculates the base signal point and the offset signal point corresponding to the transmission signal point according to the offset signal space diagram that defines the offset, and a base modulated wave generator that generates the base modulated wave corresponding to the base signal point , a base modulated wave precoding unit that precodes the base modulated wave, a base modulated wave amplifier that amplifies the base modulated wave precoded by the base modulated wave precoding unit to a predetermined power, and a base modulated wave amplifier A base radio wave transmitting antenna that transmits a base radio wave using an amplified base modulated wave, an offset modulated wave generation section that generates an offset modulated wave corresponding to an offset signal point, and an offset modulated wave precoding section that precodes the offset modulated wave. an offset modulated wave amplifier that amplifies the offset modulated wave precoded by the offset modulated wave precoding unit up to a predetermined power; and an offset radio wave transmission antenna that transmits an offset radio wave by the offset modulated wave amplified by the offset modulated wave amplifier. , is equipped with Further, the receiver of this radio communication system includes a receiving antenna for receiving the base radio wave and the offset radio wave, and a demodulation section for demodulating a combined signal obtained by combining the received signal related to the base radio wave and the received signal related to the offset radio wave. ing. Here, the transmission signal point is a signal point corresponding to data to be transmitted, and the signal range is the range of signal points according to the signal space diagram on which the transmission signal point is based. Also, the base modulated wave precoding section and the offset modulated wave precoding section perform signal points indicated by the composite signal based on the base signal space diagram, the offset signal space diagram, and the propagation channel information between the transmitter and the receiver. The base modulated wave and the offset modulated wave are precoded so that is the transmission signal point.

A second disclosure relates to a wireless communication system that is different from the wireless communication system according to the first disclosure and further includes the following features.
The base modulated wave precoding section and the offset modulated wave precoding section apply predetermined weights given according to the base signal space diagram, the offset signal space diagram, and the propagation channel information between the transmitter and the receiver to the base modulated wave. and the offset modulation wave are multiplied for precoding.

A third disclosure relates to a wireless communication method for transmitting data from a transmitter to a receiver by means of single-carrier transmission using radio waves based on quadrature amplitude modulation. This wireless communication method includes a signal space diagram that defines the positions of transmission signal points in the divided portions for a predetermined division that equally divides the signal range, and an offset of the base signal space diagram that corresponds to the positions of the divided portions related to the division. According to the defined offset signal space diagram, signal point calculation processing for calculating base signal points and offset signal points corresponding to transmission signal points, base modulated wave generation processing for generating base modulated waves corresponding to base signal points, base Base modulated wave precoding processing for precoding the modulated wave, base modulated wave amplification processing for amplifying the precoded base modulated wave by the base modulated wave precoding processing to a predetermined power, and base amplified by the base modulated wave amplification processing Base radio wave transmission processing for transmitting a base radio wave using a modulated wave, offset modulated wave generation processing for generating an offset modulated wave according to an offset signal point, offset modulated wave precoding processing for precoding the offset modulated wave, and offset modulation offset modulated wave amplification processing for amplifying the offset modulated wave precoded by the wave precoding processing to a predetermined power, offset radio wave transmission processing for transmitting the offset radio wave by the offset modulated wave amplified by the offset modulated wave amplification processing, and base radio wave and a reception process for receiving the offset radio wave, and a demodulation process for demodulating a combined signal obtained by combining the received signal related to the base radio wave and the received signal related to the offset radio wave. Here, the transmission signal point is a signal point corresponding to data to be transmitted, and the signal range is the range of signal points according to the signal space diagram on which the transmission signal point is based. In addition, the base modulated wave precoding process and the offset modulated wave precoding process are performed based on the base signal space diagram, the offset signal space diagram, and the propagation channel information between the transmitter and the receiver. The base modulated wave and the offset modulated wave are precoded so that is the transmission signal point.

A fourth disclosure relates to a wireless communication method including the following features in addition to the wireless communication method according to the third disclosure.
The base modulated wave precoding process and the offset modulated wave precoding process are performed by applying predetermined weights according to the base signal space diagram, the offset signal space diagram, and the propagation channel information between the transmitter and the receiver. and the offset modulation wave are multiplied for precoding.

According to the radio communication system and radio communication method according to the present disclosure, 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. As a result, the PAPR of the modulated waves (base modulated wave and offset modulated wave) input to the amplifier can be suppressed without lowering the modulation order.

1 is a conceptual diagram showing an example of a signal space diagram of QAM; FIG. FIG. 4 is a conceptual diagram showing an example of a base signal space diagram and an offset signal space diagram; FIG. 2 is a conceptual diagram for explaining base signal points and offset signal points calculated according to transmission signal points; 3 is a conceptual diagram showing that a transmission signal point is given by linear combination of the base signal point and the offset signal point, 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. FIG. 4 is a conceptual diagram showing an example when two offset signal space diagrams are given; 1 is a block diagram showing a configuration example of a radio communication system according to this embodiment; FIG. 4 is a flow chart showing processing executed in the wireless communication method according to the present embodiment; FIG. 8 is a flowchart showing a process executed in step S110 shown in FIG. 7; FIG. FIG. 8 is a flow chart showing a process executed in step S120 shown in FIG. 7; FIG.

Embodiments of the present disclosure will be described below with reference to the drawings. However, when referring to the number, quantity, amount, range, etc. of each element in the embodiments shown below, unless otherwise specified or the number is clearly specified in principle, the reference The idea according to the present disclosure is not limited to the number. In addition, the configurations and the like described in the embodiments shown below are not necessarily essential to the concept of the present disclosure, unless otherwise specified or clearly specified in principle. In each figure, the same or corresponding parts are denoted by the same reference numerals, and redundant description thereof will be appropriately simplified or omitted.

1. Introduction A wireless communication system according to the present disclosure is a wireless communication system (hereinafter referred to as such wireless communication system is referred to simply as a "wireless communication system").

As is well known, QAM is a modulation method in which the amplitudes of two carrier waves having a relationship of orthogonal phases are modulated according to data to be transmitted, and the combination thereof is used as a modulated wave.

In QAM, the relationship between the data to be transmitted and the modulation of each of the two carriers is generally given by a signal space diagram. Also, according to the signal space diagram, each of the two carriers is modulated according to the data.

FIG. 1 shows an example of a signal space diagram of QAM. The signal space diagram consists of an in-phase axis (I-axis) indicating the amplitude of one carrier wave, a quadrature-phase axis (Q-axis) indicating the amplitude of the other carrier wave, and a plurality of signal points corresponding to data. be. The signal space diagram shown in FIG. 1 includes 16 signal points, and 4-bit data corresponds to each signal point. That is, FIG. 1 shows a signal space diagram relating to 16QAM, and when following the signal space diagram shown in FIG. 1, the modulated wave can indicate 4-bit data per symbol. For example, 0110 data is indicated by a modulated wave modulated such 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.

It is known that when single-carrier transmission is performed based on QAM, the higher the modulation order (the number of bits per symbol) employed, the higher the PAPR of the modulated wave. It is also known that the required SNR increases as the modulation order increases. Table 1 shows a comparison of the degree of PAPR and required SNR of modulated waves with respect to modulation schemes (and modulation orders of modulation schemes).

Here, the PAPR of the modulated wave and the degree of required SNR (minimum to maximum) indicate the comparative relationship among the five modulation schemes shown in Table 1. Also, QPSK indicates quadrature phase-shift keying (QPSK). QPSK can also be implemented as 4QAM.

As shown in Table 1, a modulated wave with a smaller modulation order has a smaller PAPR. If PAPR can be suppressed, backoff can be reduced. As a result, it is possible to increase the average transmission power and reduce the power consumption. Also, a modulated wave with a small modulation order requires a small SNR and can improve the SNR. However, if wireless communication is performed using a transmission radio wave modulated with a small modulation order, the data transmission speed naturally decreases.

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

2. Radio communication system 2-1. Overview First, a radio communication system according to the present embodiment will be described. In the radio communication system according to the present embodiment, first, according to the signal point corresponding to the data to be transmitted (hereinafter also referred to as "transmission signal point"), the signal point related to the base signal space diagram (hereinafter, "base signal point ”), and signal points related to the offset signal space diagram (hereinafter also referred to as “offset signal points”). Here, the base signal space diagram equally divides the signal point range (hereinafter also referred to as "signal range") related to the signal space diagram based on the transmission signal points (hereinafter also referred to as "transmission signal space diagram"). Fig. 4 is a signal space diagram defining the locations of transmitted signal points in the division portion, for a given division of the signal; Also, the offset signal space diagram is a signal space diagram that defines the offset of the base signal space diagram according to the position of the divided portion.

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

In FIG. 2, signal range 1 is a square range (range surrounded by dotted lines) surrounding 64 signal points. The division of the signal range 1 is given by dividing the square range into four equal parts (chain lines), as shown in FIG. Therefore, each divided portion contains 16 signal points.

At this time, the base signal space diagram consists of 16 signal points, as shown in FIG. Here, each of the 16 signal points forming the base signal space diagram corresponds to each of the 16 signal points included in the divided portion, and defines the position of the transmission signal point in the divided portion.

Also, the offset signal space diagram is composed of four signal points, as shown in FIG. Here, each of the four signal points forming the offset signal space diagram corresponds to each of the quartered divisions and defines the offset of the base signal space diagram.

Note that the base signal space diagram and the offset signal space diagram are given so that their linear combinations become the transmission signal space diagram. That is, the transmission signal space diagram is the sum of the base signal space diagram multiplied by a constant and the offset signal space diagram multiplied by a constant. Geometrically, the signal range on the base signal-space diagram gives the similitude of the split parts, and the offset signal-space diagram gives the translation of the signal range on the base signal-space diagram.

In general QAM, the signal ranges of the signal space diagrams with different modulation orders are similar to each other, so the base signal space diagram can be realized by the signal space diagram of the conventional QAM. For example, the base signal space diagram shown in FIG. 2 may be the signal space diagram for 16QAM.

Also, the offset signal space diagram may be realized by a signal space diagram according to a conventional modulation scheme. For example, the offset signal space diagram shown in FIG. 2 may be a signal space diagram for 4PSK (or 4QAM). The offset signal space diagram can formally be realized by a signal space diagram for phase shift keying. However, the offset signal space diagram may be realized with the signal space diagrams of other conventional modulation schemes by appropriately providing the division of the signal range according to the transmission signal space diagram. For example, when dividing the signal range 1 shown in FIG. 2 into 16 equal parts, the offset signal space diagram may be realized by a signal space diagram according to 16QAM.

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

By constructing the base signal space diagram and the offset signal space diagram in this way, it is possible to provide combinations of base signal points and offset signal points that correspond one-to-one with transmission signal points. FIG. 3 is a conceptual diagram for explaining the base signal point 3 and the offset signal point 4 calculated according to the transmission signal point 2. As shown in FIG. FIG. 3 shows base signal points 3a, 3b, and 3c and offset signal points 4a, 4b, and 4c calculated according to three transmission signal points 2a, 2b, and 2c (black circles). Here, the transmission signal space diagram, base signal space diagram, and offset signal space diagram shown in FIG. 3 are equivalent to those shown in FIG. The positions of the signal points in the respective signal space diagrams are indicated by white circles surrounded by dotted lines.

Transmission signal point 2 a is included in the upper right subdivision of signal range 1 . Also, the transmission signal point 2a in the divided portion is located on the upper right of the inner four signal points among the 16 signal points. At this time, the base signal point 3a corresponds to the position of the transmission signal point 2a in the divided portion, as shown in FIG. The offset signal point 4a corresponds to the position of the divided portion including the transmission signal point 2a, and is the upper right position of the four signal points.

Transmission signal point 2 b is included in the lower left subdivision of signal range 1 . Also, the transmission signal point 2b in the divided portion is positioned at the upper left of the outer 12 signal points out of the 16 signal points. At this time, the base signal point 3b corresponds to the position of the transmission signal point 2b in the divided portion, as shown in FIG. The offset signal point 4b corresponds to the position of the divided portion including the 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 subdivision of signal range 1 . Also, the transmission signal point 2c in the divided portion is located at the lower right of the outer 12 signal points out 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 bottom right of the outer 12 signal points. The offset signal point 4c corresponds to the position of the divided portion including the transmission signal point 2c, and is located at the bottom right of the four signal points.

Next, in the radio communication system according to this embodiment, the base modulated wave and the offset modulated wave are precoded. Precoding is typically performed by multiplying predetermined weights.

Next, in the radio communication system according to the present embodiment, the precoded base modulated wave and offset modulated wave are input to the amplifier and amplified to a predetermined power. After that, the base modulated wave and the offset modulated wave are synthesized.

Thus, the base signal point 3 and the offset signal point 4 are calculated according to the transmission signal point 2 . As described above, the base signal space diagram and the offset signal space diagram are given so that their linear combination becomes the transmission signal space diagram. is given by a linear combination of That is, when the position vector of the transmission signal point 2 is s, the position vector of the calculated base signal point 3 is a, and the position vector of the offset signal point 4 is b, the following equation (1) holds. . Here, V1 and V2 are constants given according to the base signal space diagram and the offset signal space diagram.

FIG. 4 shows, 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. It conceptually shows that

A plurality of offset signal space diagrams may be provided. In this case, depending on the transmission signal points 2, a plurality of offset signal points 4 are calculated for respective offset signal space diagrams. s is the position vector associated with the transmission signal point 2, a is the position vector associated with the calculated base signal point 3, and bi (i=1, 2, . . . ) is the position vector associated with the plurality of calculated offset signal points 4 , N), the following equation (2) holds. where V1 and V2i are constants given according to the base signal space diagram and a plurality of offset signal space diagrams, and N is the number of offset signal space diagrams given.

FIG. 5 conceptually shows an example where two offset signal space diagrams (a first signal space diagram and a 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 the transmission signal point 2. FIG. FIG. 5 shows, for example, the case of dividing the signal range 1 shown in FIG. 2 into 16 equal parts.

As described above, in the radio communication system according to this embodiment, base signal points and offset signal points are calculated according to transmission signal points. Next, in the radio communication system according to the present embodiment, a modulated wave corresponding to the calculated base signal point (hereinafter also referred to as "base modulated wave") and a modulated wave corresponding to the calculated offset signal point (hereinafter referred to as " Also referred to as "offset modulated wave").

Suitable well-known techniques may be used to generate modulated waves corresponding to the base signal point and the offset signal point. For example, when providing a base signal space diagram and an offset signal space diagram as described in FIG. Generation of the modulated wave may be realized by a conventional QPSK modulator.

Next, in the wireless communication system according to the present embodiment, radio waves related to base-modulated waves (hereinafter also referred to as "base radio waves") and radio waves related to offset-modulated waves (hereinafter also referred to as "offset radio waves") are Send out. That is, the transmitter of the wireless communication system according to the present embodiment includes a transmission antenna for transmitting base radio waves (hereinafter also referred to as "base radio wave transmission antenna") and a transmission antenna for transmitting offset radio waves (hereinafter , also referred to as an “offset radio wave transmission antenna”).

When a plurality of offset signal space diagrams are given, a plurality of offset modulated waves are generated according to each of the plurality of offset signal points. Then, an offset radio wave corresponding to each of the plurality of offset modulated waves is transmitted. In this case, the radio communication system according to this embodiment includes a plurality of offset radio wave transmission antennas.

Next, in the wireless communication system according to this embodiment, the receiver receives the base radio wave and the offset radio wave with the receiving antenna to obtain a received signal.

Then, in the radio communication system according to the present embodiment, a signal obtained by combining the received signal related to the base radio wave and the received signal related to the offset radio wave (hereinafter also referred to as "combined signal") is demodulated, and data indicated by the combined signal is demodulated. get

Here, precoding is performed based on the base signal space diagram, the offset signal space diagram, and the propagation channel information between the transmitter and the receiver so that the signal points indicated by the combined signal become the transmission signal points. . For example, let h1 be the propagation channel information between the base radio wave transmitting antenna and the receiving antenna, and h2 be the propagation channel information between the offset radio wave transmitting antenna and the receiving antenna. At this time, when precoding is performed so as to multiply predetermined weights, predetermined weights W1 and W2 to be multiplied by the base modulated wave and the offset modulated wave can be given by the following equation (3), respectively.

By multiplying the base modulated wave and the offset modulated wave by the weights W1 and W2 given by equation (3), when the base radio wave and the offset radio wave propagate from the transmitter to the receiver, the signal indicated by the received signal related to the base radio wave The point is V1·a, and the signal point indicated by the received signal related to the offset radio wave is V2·b. Therefore, according to equation (1), the signal point indicated by the synthesized signal point becomes the transmission signal point.

In addition, when a plurality of offset signal space diagrams are given, the propagation channel information between each of the plurality of offset radio wave transmission antennas and the reception antenna is h2i (i = 1, 2, ..., N), and the base modulation The predetermined weights W1 and W2i (i=1, 2, .

By multiplying the base modulated wave and a plurality of offset modulated waves by the weights W1 and W2i given by equation (4), when the base radio wave and the offset radio waves propagate from the transmitter to the receiver, the received signal related to the base radio wave is The indicated signal point is V1·a, and the respective signal points indicated by the received signals related to the plurality of offset radio waves are V2i·b (i=1, 2, . . . , N). Therefore, according to equation (2), the signal point indicated by the combined signal point becomes the transmission signal point.

Thus, in the radio communication system according to this embodiment, the modulation order of the signal to be demodulated (combined signal) is the modulation order related to the transmission signal point.

By the way, from the way 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. That is, the PAPRs of the base modulated wave and the offset modulated wave are smaller than the PAPR of the modulated wave generated according to the transmission signal point. Then, in the wireless communication system according to this embodiment, the base modulated wave and the offset modulated wave are input to the amplifier. That is, in the radio 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 A configuration example of the wireless communication system according to the present embodiment will be described below. FIG. 6 is a block diagram showing a configuration example of the radio 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 radio communication system 10 shown in FIG. 6 shows a configuration example for transmitting data based on 256QAM. That is, 8-bit data is transmitted per symbol.

Also, in the radio communication system 10 shown in FIG. 6, the base signal space diagram is given by the signal space diagram according to 64QAM, and the offset signal space diagram is given by the signal space diagram according to QPSK.

The transmitter 100 includes an information processing device 110, modulators 120a and 120b, multipliers 130a and 130b, amplifiers 140a and 140b, a base radio wave transmission antenna 160a, and an offset radio wave transmission antenna 160b.

The information processing device 110 (signal point calculator) 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 communicated to modulators 120a and 120b, respectively. Information processor 110 is typically a microcontroller embedded in transmitter 100 . In this case, the information processing device 110 calculates the base signal point and the offset signal point by causing the processor to execute the program stored in the memory. The program describes, for example, according to the base signal space diagram and the offset signal space diagram, the processing that gives the correspondence between the data to be transmitted (every 8 bits) and the base signal point and the offset signal point.

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

The modulator 120 b (offset modulated wave generator) generates an offset modulated wave corresponding to the offset signal point transmitted from the information processing device 110 . Modulator 120b may be implemented by a conventional QPSK modulator.

The multiplier 130a (base modulated wave precoding unit) multiplies the base modulated wave generated by the modulator 120a by a predetermined weight W1.

The multiplier 130b (offset modulated wave precoding unit) multiplies the offset modulated wave generated by the modulator 120b by a predetermined weight W2.

Multipliers 130a and 130b may be implemented with conventional electronic circuitry.

where W1 and W2 are given according to the base signal space diagram, the offset signal space diagram, and the propagation channel information between the transmitter and receiver, as described above.

The amplifier 140a (base modulated wave amplification section) amplifies the base modulated wave precoded by the multiplier 130a to a predetermined power.

The amplifier 140b (offset modulated wave amplification section) amplifies the offset modulated wave precoded by the multiplier 130b to a predetermined power.

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

The base radio wave transmitting antenna 160a transmits radio waves (base radio waves) by means of base modulated waves.

The offset radio wave transmission antenna 160b transmits radio waves (offset radio waves) by offset modulated waves.

As the base radio wave transmission antenna 160a and the offset radio wave transmission antenna 160b, suitable antennas may be adopted according to the environment in which the wireless communication system 10 is applied. For example, array antennas, dipole antennas, and the like are exemplified.

Receiver 200 comprises a receive antenna 260 and a demodulator 220 .

The receiving antenna 260 receives the base radio wave and the offset radio wave transmitted from the base radio wave transmitting antenna 160a and the offset radio wave transmitting antenna 160b, and obtains a received signal related to the base radio wave and a received signal related to the offset radio wave. The receiving antenna 260 may employ a suitable antenna according to the environment in which the wireless communication system 10 is applied. A received signal obtained by the receiving antenna 260 is transmitted to the demodulator 220 .

The demodulator 220 (demodulation unit) demodulates a combined signal of the received signal related to the base radio wave and the received signal related to the offset radio wave obtained by the receiving antenna 260, and obtains data indicated by the combined signal. Here, by precoding in the multipliers 130a and 130b, the signal points indicated by the combined signal become transmission signal points. That is, in the radio communication system 10 shown in FIG. 6, the synthesized signal is a modulated signal based on 256QAM. In this case, demodulator 220 may be implemented by a conventional 256QAM demodulator.

3. Wireless Communication Method Next, a wireless communication method according to this embodiment will be described. However, in the following description, matters that overlap with the content described above are omitted as appropriate.

FIG. 7 is a flowchart showing processing executed in the wireless communication method according to this embodiment. The processing shown in FIG. 7 is started 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 a signal point (transmission signal point) corresponding to data to be transmitted. After step S100, the process proceeds to step S110.

At step S110, a base modulated wave corresponding to the base signal point calculated at step S100 is generated. Also, the generated base modulated wave is processed.

FIG. 8 shows the processing executed in step S110.

In step S111 (base modulated wave generation processing), a base modulated wave corresponding to the base signal point is generated. After step S111, the process proceeds to step S112.

In step S112 (base modulated wave precoding process), the base modulated wave is precoded. After step S112, the process proceeds to step S113.

In step S113 (base modulated wave amplification process), the base modulated wave precoded in step S112 is amplified to a predetermined power. After step S113, the process executed in step S110 ends.

Please refer to FIG. 7 again. After step S110, the process proceeds to step S120.

At step S120, an offset modulated wave corresponding to the offset signal point calculated at step S100 is generated. Also, the generated offset modulated wave is processed.

FIG. 9 shows the processing executed in step S120.

In step S121 (offset modulated wave generation processing), an offset modulated wave corresponding to the offset signal point is generated. After step S121, the process proceeds to step S122.

In step S122 (offset modulated wave precoding process), the offset modulated wave is precoded. After step S122, the process proceeds to step S123.

In step S123 (offset modulated wave amplification processing), the offset modulated wave precoded in step S122 is amplified to a predetermined power. After step S123, the process executed in step S120 ends.

Please refer to FIG. 7 again. After step S120, the process proceeds to step S130.

Note that the order of the processes in steps S110 and S120 may be reversed. That is, step S110 may be executed after step S120. Alternatively, the processes of steps S110 and S120 may be executed in parallel.

In step S130 (base radio wave transmission processing), the base radio wave is transmitted by the base modulated wave amplified in step S113. After step S130, the process proceeds to step S140.

In step S140 (offset radio wave transmission processing), an offset radio wave is transmitted by the offset modulated wave amplified in step S123. After step S140, the process proceeds to step S150.

Note that the order of the processes in steps S130 and S140 may be reversed. That is, step S130 may be executed after step S140. Alternatively, the processes of steps S130 and S140 may be executed in parallel.

In step S150 (receiving process), the base radio wave and the offset radio wave transmitted in steps S130 and S140 are received, and a received signal related to the base radio wave and a received signal related to the offset radio wave are obtained. After step S150, the process proceeds to step S160.

In step S160 (demodulation processing), the combined signal of the received signal related to the base radio wave and the received signal related to the offset radio wave obtained in step S150 is demodulated to obtain data indicated by the combined signal. This completes the data transmission by wireless communication. After step S160, the process ends.

Note that the precoding in steps S112 and S122 is such that the signal points indicated by the combined signal are the transmission signal points according to the base signal space diagram, the offset signal space diagram, and the propagation channel information between the transmitter and the receiver. It is done so that For example, if precoding is done by multiplying predetermined weights, the predetermined weights are the constants W1 and W2 (or W1 and W2i) described in equation (3) (or equation (4)).

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

4. Effects As described above, according to the radio communication system 10 and the radio communication method according to the present embodiment, the modulation order related to the base signal point and the modulation order related to the offset signal point are higher than the modulation order related to the transmission signal point. can be made smaller. As a result, the PAPR of the modulated waves (base modulated wave and offset modulated wave) input to the amplifier can be suppressed without lowering the modulation order. As a result, backoff can be reduced, and average transmission power can be increased and power consumption can be reduced.

In addition, 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.

Note that the radio communication system 10 and the radio communication method according to the present disclosure suitably employ reception diversity technology and MIMO (Multiple-input and multiple-output) technology, and include multiple base radio wave transmission antennas 160a and multiple offset radio wave transmissions. Antenna 160b and multiple receive antennas 260 may be provided. Even in this case, similar effects can be obtained.

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 calculator)
120a modulator (base modulated wave generator)
120b modulator (offset modulated wave generator)
130a multiplier (base modulated wave precoding unit)
130b multiplier (offset modulation wave precoding unit)
140a amplifier (base modulated wave amplifier)
140b amplifier (offset modulated wave amplifier)
160a base radio wave transmission antenna 160b offset radio wave transmission antenna 200 receiver 220 demodulator (demodulator)
260 receiving antenna

Claims (4)

A wireless communication system for transmitting data from a transmitter to a receiver by single-carrier transmission using radio waves based on quadrature amplitude modulation,
the 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 points are based,
The transmitter is
A base signal space diagram that defines the position of the transmission signal point in the divided portion for a predetermined division that equally divides the signal range, and an offset of the base signal space diagram that corresponds to the position of the divided portion related to the division. a signal point calculator that calculates a base signal point and an offset signal point corresponding to the transmission signal point according to a defined offset signal space diagram;
a base modulated wave generation unit that generates a base modulated wave corresponding to the base signal point;
a base modulated wave precoding unit that precodes the base modulated wave;
a base modulated wave amplifying section for amplifying the base modulated wave precoded by the base modulated wave precoding section to a predetermined power;
a base radio wave transmission antenna for transmitting a base radio wave with the base modulated wave amplified by the base modulated wave amplifier;
an offset-modulated wave generator that generates an offset-modulated wave corresponding to the offset signal point;
an offset modulated wave precoding unit that precodes the offset modulated wave;
an offset modulated wave amplifier that amplifies the offset modulated wave precoded by the offset modulated wave precoding unit to a predetermined power;
an offset radio wave transmitting antenna for transmitting an offset radio wave by the offset modulated wave amplified by the offset modulated wave amplifier;
with
The receiver is
a receiving antenna that receives the base radio wave and the offset radio wave;
a demodulation unit that demodulates a combined signal obtained by combining the received signal related to the base radio wave and the received signal related to the offset radio wave;
with
The base modulated wave precoding unit and the offset modulated wave precoding unit,
Based on the base signal space diagram, the offset signal space diagram, and propagation channel information between the transmitter and the receiver, the base modulation is performed so that the signal point indicated by the combined signal becomes the transmission signal point. precoding a wave and the offset modulated wave. A wireless communication system according to claim 1,
The base modulated wave precoding unit and the offset modulated wave precoding unit,
By multiplying the base modulated wave and the offset modulated wave by a predetermined weight given according to the base signal space diagram, the offset signal space diagram, and propagation channel information between the transmitter and the receiver A wireless communication system characterized by precoding. 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,
the 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 points are based,
A base signal space diagram that defines the position of the transmission signal point in the divided portion for a predetermined division that equally divides the signal range, and an offset of the base signal space diagram that corresponds to the position of the divided portion related to the division. a signal point calculation process for calculating a base signal point and an offset signal point corresponding to the transmission signal point according to a defined offset signal space diagram;
a base modulated wave generation process for generating a base modulated wave corresponding to the base signal point;
a base modulated wave precoding process for precoding the base modulated wave;
a base modulated wave amplification process for amplifying the base modulated wave precoded by the base modulated wave precoding process to a predetermined power;
a base radio wave transmission process for transmitting a base radio wave using the base modulated wave amplified by the base modulated wave amplification process;
an offset-modulated wave generation process for generating an offset-modulated wave corresponding to the offset signal point;
an offset-modulated wave precoding process for precoding the offset-modulated wave;
an offset modulated wave amplification process for amplifying the offset modulated wave precoded by the offset modulated wave precoding process to a predetermined power;
an offset radio wave transmission process for transmitting an offset radio wave by the offset modulated wave amplified by the offset modulated wave amplification process;
a reception process for receiving the base radio wave and the offset radio wave;
a demodulation process for demodulating a combined signal obtained by combining the received signal related to the base radio wave and the received signal related to the offset radio wave;
including
The base modulated wave precoding process and the offset modulated wave precoding process are
Based on the base signal space diagram, the offset signal space diagram, and propagation channel information between the transmitter and the receiver, the base modulation is performed so that the signal point indicated by the combined signal becomes the transmission signal point. precoding a wave and the offset modulated wave. The wireless communication method according to claim 3,
The base modulated wave precoding process and the offset modulated wave precoding process are
By multiplying the base modulated wave and the offset modulated wave by a predetermined weight given according to the base signal space diagram, the offset signal space diagram, and propagation channel information between the transmitter and the receiver A wireless communication method characterized by precoding.

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