Transmission device, reception device, communication system, control circuit, storage medium, transmission method, reception method, and signal processing method

Abstract

A transmission device (10) that performs orthogonal frequency division multiplexing communication is provided with: a subcarrier mapping unit (113) that duplicates a subcarrier signal sequence and maps the duplicated plurality of subcarrier signal sequences with subcarrier spacing at equal intervals; and a transmission phase rotation unit (114) that divides each subcarrier signal sequence mapped with the subcarrier spacing into two or more subsets, and imparts a phase rotation that results in different time timings for each subset.

Description

Transmitting device, receiving device, communication system, control circuit, storage medium, transmitting method, receiving method, and signal processing method

[0001] The present disclosure relates to a transmitting device, a receiving device, a communication system, a control circuit, a storage medium, a transmitting method, a receiving method, and a signal processing method that perform Orthogonal Frequency Division Multiplexing (OFDM) communication.

[0002] OFDM communication, which is used in wireless LANs (Local Area Networks) and the like, is a transmission method that is resistant to multipath delays and can be used in wideband transmission. However, there are concerns about degradation of reception quality when communication quality deteriorates due to frequency selectivity of the transmission path, or when non-negligible interference within the signal band is superimposed on the received signal. As a countermeasure to cases where frequency selective fading causes a significant deterioration in communication quality in the transmission path, frequency diversity transmission, which transmits the same signal using multiple subcarriers, is being considered. Frequency diversity transmission is an optimal transmission method for open-loop systems in which a transmitter replicates and maps a subcarrier signal sequence at equal intervals to compensate for deterioration in communication quality in an unknown transmission path. Hereinafter, this type of transmission method will be referred to as frequency repetition.

[0003] Frequency repetition involves, for example, replicating a subcarrier signal sequence of length L into M subcarriers and dispersively mapping the M replicated subcarrier signal sequences at equal intervals with a subcarrier spacing of D. Applying frequency repetition can improve the aforementioned degradation in communication quality in the transmission path and resistance to interference. However, frequency repetition involves replicating and mapping the same signal onto multiple subcarriers, which can lead to a problem of a deterioration in the PAPR (Peak-to-Average Power Ratio) of the transmission waveform after inverse discrete Fourier transform, resulting in a decrease in transmission power efficiency. Various studies have been conducted on measures to address peaks in the transmission waveform in a transmitting device. For example, Patent Document 1 discloses a technology for a wireless communication device that can ensure signal quality while maintaining high amplifier efficiency even when the modulation method is adaptively changed.

[0004] Patent No. 4905463

[0005] However, the above-mentioned conventional techniques are concerned with measures to deal with peaks in general transmission waveforms, and have the problem that they do not disclose or suggest measures to deal with peaks in transmission waveforms specific to frequency repetition.

[0006] The present disclosure has been made in consideration of the above, and aims to provide a transmitting device that can suppress deterioration of the peak-to-average power ratio of the transmission waveform while suppressing a decrease in transmission power efficiency when frequency repetition is applied to OFDM communication.

[0007] In order to solve the above-mentioned problems and achieve the object, the present disclosure provides a transmitting device for performing orthogonal frequency division multiplexing communication, characterized in that the transmitting device includes a subcarrier mapping unit that replicates subcarrier signal sequences and maps the replicated subcarrier signal sequences at equal subcarrier intervals, and a transmission phase rotation unit that divides each subcarrier signal sequence mapped at the subcarrier intervals into two or more subsets and imparts phase rotation that results in different time timing for each subset.

[0008] A transmitting device according to the present disclosure has the advantage that, when frequency repetition is applied to OFDM communication, it is possible to suppress deterioration of the peak-to-average power ratio of the transmission waveform while suppressing a decrease in transmission power efficiency.

[0009] FIG. 1 shows an example of the configuration of a communication system according to embodiment 1. FIG. 2 shows an example of the signal waveform of a subcarrier signal sequence obtained by a transmission device that does not perform phase rotation, and the signal waveform of a time signal block after transformation by IDFT (Inverse Discrete Fourier Transform), as a comparative example. FIG. 3 shows an example of the signal waveform of a subcarrier signal sequence obtained by a transmission device of the communication system according to embodiment 1, and the signal waveform of a time signal block after transformation by IDFT. FIG. 4 shows an example of the complementary cumulative distribution function characteristic of instantaneous normalized signal power obtained by the communication system according to embodiment 1. FIG. 5 shows an example of the configuration of a processing circuit that realizes the transmission device according to embodiment 1 when configured with a processor and a memory. FIG. 6 shows an example of the processing circuit that realizes the transmission device according to embodiment 1 when configured with dedicated hardware. FIG. 7 shows an example of the configuration of a communication system according to embodiment 2.

[0010] A transmitting device, a receiving device, a communication system, a control circuit, a storage medium, a transmitting method, a receiving method, and a signal processing method according to embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings.

[0011] Embodiment 1. Fig. 1 is a diagram showing an example of the configuration of a communication system 1 according to embodiment 1. The communication system 1 includes a transmitting device 10 and a receiving device 20. The communication system 1 is a system in which the transmitting device 10 and the receiving device 20 perform wireless communication using OFDM communication to which frequency repetition is applied. In the following description, OFDM communication may be referred to as orthogonal frequency division multiplexing communication. Note that Fig. 1 shows an example in which the communication system 1 includes one transmitting device 10 and one receiving device 20, but this is not limiting. The communication system 1 may include multiple transmitting devices 10 and multiple receiving devices 20.

[0012] The transmitting device 10 includes a transmitting baseband processing unit 110 that generates a baseband signal from a transmission bit sequence, a transmitting RF (Radio Frequency) unit 120 that converts the baseband signal generated by the transmitting baseband processing unit 110 into a high-frequency signal, and a transmitting antenna 130 that transmits the high-frequency signal converted by the transmitting RF unit 120. The transmitting baseband processing unit 110 includes an encoding unit 111, a primary modulation unit 112, a subcarrier mapping unit 113, a transmission phase rotation unit 114, an IDFT unit 115, a GI (Guard Interval) adding unit 116, a transmission waveform shaping unit 117, and a DAC (Digital-to-Analog Conversion) unit 118. Figure 2 is a flowchart showing the operation of the transmitting device 10 according to the first embodiment.

[0013] The encoder 111 applies encoding processing such as error correction encoding to the transmission bit sequence (step S11). The primary modulator 112 I / Q maps the transmission bit sequence encoded by the encoder 111 onto a PSK (Phase Shift Keying) modulated signal, a QAM (Quadrature Amplitude Modulation) modulated signal, or the like (step S12). The subcarrier mapper 113 replicates the length L of the primary modulated signal sequence into M copies and maps them to subcarriers (step S13). That is, the subcarrier mapper 113 replicates the subcarrier signal sequence and maps the replicated subcarrier signal sequences at equal subcarrier spacing D. Note that M is an integer equal to or greater than 1, and D is an integer equal to or greater than 1. The unit of the subcarrier spacing D is the same as the unit of the length L of the subcarrier signal sequence. Furthermore, since the length of the primary modulated signal sequence, i.e., the subcarrier signal sequence, is L, the subcarrier spacing D is an integer such that D≧L. The transmission phase rotation unit 114 divides each subcarrier signal sequence mapped at subcarrier spacing D into two or more subsets, and applies phase rotation to each subset so that the time timing differs (step S14). The detailed operation of the transmission phase rotation unit 114 will be described later.

[0014] The IDFT unit 115 converts the subcarrier signal sequence, i.e., the subcarrier signal block, after phase rotation by the transmission phase rotation unit 114 into a time signal block by IDFT (step S15). The GI adding unit 116 adds a guard interval, i.e., a GI, to each time signal block (step S16). The transmission waveform shaping unit 117 performs digital front-end processing, including upsampling, digital filtering, and orthogonal transform processing, on the time signal block after GI addition (step S17). The DAC unit 118 performs digital-to-analog conversion on the time signal block after digital front-end processing (step S18) and outputs a baseband signal.

[0015] The receiving device 20 receives a subcarrier signal sequence transmitted from the transmitting device 10 performing OFDM communication. The receiving device 20 includes a receiving antenna 230 that receives a radio frequency signal, a receiving RF unit 220 that converts the radio frequency signal received by the receiving antenna 230 into a baseband signal, and a receiving baseband processing unit 210 that generates a receiving bit sequence from the baseband signal. The receiving baseband processing unit 210 includes an ADC (Analog-to-Digital Conversion) unit 218, a receiving waveform shaping unit 217, a GI removal unit 216, a DFT (Discrete Fourier Transform) unit 215, a receiving phase rotation unit 214, a subcarrier demapping unit 213, a primary demodulation unit 212, and a decoding unit 211. Figure 3 is a flowchart showing the operation of the receiving device 20 according to the first embodiment.

[0016] The ADC unit 218 performs analog-to-digital conversion on the baseband signal (step S21). The received waveform shaping unit 217 performs digital front-end processing on the digitally converted time signal, including quadrature demodulation, digital filtering, and downsampling (step S22). The GI removal unit 216 removes GIs from each time signal block after the digital front-end processing (step S23) and extracts DFT target blocks. The DFT unit 215 converts the time signal blocks after GI removal into subcarrier signal blocks using DFT (step S24).

[0017] The reception phase rotation unit 214 compensates for the phase rotation of the received subcarrier signal block, i.e., the subcarrier signal sequence, by inversely rotating the phase by the amount of phase rotation imparted by the transmission device 10 (step S25). The subcarrier demapping unit 213 combines the M copies of the subcarrier signal sequence created by the transmission device 10 (step S26) and extracts the resulting I / Q signal to be demodulated. That is, the subcarrier demapping unit 213 combines the subcarrier signal sequence whose phase rotation has been compensated for by the reception phase rotation unit 214 and extracts the resulting demodulated signal. The primary demodulation unit 212 performs PSK demodulation, QAM demodulation, or the like on the I / Q signal to calculate a soft decision value or a hard decision value (step S27). The decoding unit 211 performs decoding processing, such as error correction decoding, on the soft decision value or the hard decision value (step S28) and outputs a received bit sequence.

[0018] The inverse discrete Fourier transform (IDFT) performed by the IDFT unit 115 of the transmitting device 10 includes an inverse fast Fourier transform (IFFT) with points that are powers of 2. Similarly, the discrete Fourier transform (DFT) performed by the DFT unit 215 of the receiving device 20 includes an FFT (Fast Fourier Transform) with points that are powers of 2.

[0019] Before describing the effects obtained by the communication system 1 of this embodiment, i.e., the transmitting device 10 and the receiving device 20, the problems caused by the frequency repetition previously described in the background art will be described using figures. Fig. 4 shows, as a comparative example, an example of a signal waveform of a subcarrier signal sequence obtained by a transmitting device that does not perform phase rotation and a signal waveform of a time signal block after conversion by IDFT. A transmitting device that does not perform phase rotation is, for example, a transmitting device in which the transmission phase rotation unit 114 is removed from the transmitting device 10 shown in Fig. 1. In Fig. 4, the left side shows the signal waveform of the subcarrier signal sequence, and the right side shows the signal waveform of the time signal block after conversion by IDFT. The signal waveform of the subcarrier signal sequence on the left side of Fig. 4 shows an example in which the number of subcarrier signal sequence copies M=3, a subcarrier signal sequence of length L is copied into three copies, and the copies are mapped to subcarriers at equal intervals with a subcarrier spacing D.

[0020] Although the subcarrier signal sequence of length L is illustrated as one frequency-continuous signal block, this is not limited thereto, and the subcarrier signal sequence of length L may be dispersed. However, since the subcarrier signal sequence of length L is subcarrier-mapped at equal subcarrier intervals D, the subcarriers to be mapped do not overlap with those of neighboring signal blocks. When an N-point IDFT is performed on a subcarrier signal sequence to which frequency repetition is applied, in-phase synthesis of M signals occurs every N / D samples, resulting in increased peaks, and other time samples becoming nulls or side lobes. Note that N is an integer equal to or greater than 2. As such, applying frequency repetition increases the frequency and magnitude of peaks in the time waveform compared to an OFDM signal to which frequency repetition is not applied, resulting in a problem of reduced transmission power efficiency.

[0021] Next, in the communication system 1 to which the frequency repetition of this embodiment is applied, the processing of the transmission phase rotation unit 114 included in the transmission baseband processing unit 110 of the transmission device 10, which is a feature of this embodiment, will be described. Fig. 5 is a diagram showing an example of the signal waveform of a subcarrier signal sequence obtained by the transmission device 10 of the communication system 1 according to embodiment 1 and the signal waveform of a time signal block after conversion by IDFT. As in Fig. 4, in Fig. 5, the left side shows the signal waveform of the subcarrier signal sequence, and the right side shows the signal waveform of the time signal block after conversion by IDFT. The signal waveform of the subcarrier signal sequence on the left side of Fig. 5 shows an example in which the number of subcarrier signal sequence copies M=3, a subcarrier signal sequence of length L is copied into three, and the subcarriers are mapped at equal intervals with a subcarrier spacing D.

[0022] The replication mapping in the subcarrier mapping unit 113 is the same as the example of frequency repetition shown in FIG. 4 , but in this embodiment, the transmission phase rotation unit 114 divides the subcarrier signal sequence of length L after replication mapping in the subcarrier mapping unit 113 into K subsets. Here, K is an integer satisfying the relationship 2≦K≦L. FIG. 5 shows an example in which the number of subsets K=3. In the example of FIG. 5 , each subset is shown as a single signal block with continuous frequency, but this is not limited thereto. Each subset may be a plurality of dispersed subcarrier signals, and the number of subcarrier signals included in each subset may be the same or different. Here, when a signal S(f) mapped to a subcarrier f with frequency f belongs to subset #k, the signal S′(f) after phase rotation processing in the transmission phase rotation unit 114 is expressed by the following equation (1). Here, the range of k is k∈0, ..., K−1.

[0023]

[0024] In equation (1), Φ ｋis the phase offset of subset #k. The processing using equation (1) means that the phase rotation is performed so that the timing of the time peak differs for each subset, while allowing for events that result in in-phase combination for each subset. This allows the transmission phase rotation unit 114 to evenly distribute the time timing that results in in-phase combination for each subset. In this way, when the number of subcarrier signal sequences replicated by the subcarrier mapping unit 113 is M, the subcarrier spacing is D, and the number of subsets to be divided is K, and signal S(f) mapped to subcarrier f with frequency f belongs to subset #k, the transmission phase rotation unit 114 performs the phase rotation processing expressed by equation (1) on signal S(f) and outputs signal S'(f).

[0025] Next, in the communication system 1 to which the frequency repetition of this embodiment is applied, the processing of the reception phase rotation unit 214 included in the reception baseband processing unit 210 of the receiving device 20, which is a feature of this embodiment, will be described. The reception phase rotation unit 214 compensates for the phase rotation in the transmission phase rotation unit 114 included in the transmission baseband processing unit 110 of the transmitting device 10 described above, and performs processing to return the phase-rotated signal to the signal state before the phase rotation. In other words, the reception phase rotation unit 214 performs a phase rotation opposite to the phase rotation of equation (1). The reception phase rotation unit 214 performs a phase rotation process expressed by the following equation (2) on the reception signal R(f) of subcarrier f, which is the output of the DFT unit 215, when the reception signal R(f) belongs to subset #k, and obtains a signal R'(f) as an output signal.

[0026]

[0027] In this way, the reception phase rotation unit 214 performs phase rotation processing expressed by equation (2) on the reception signal R(f), and outputs a signal R'(f), where M is the number of subcarrier signal sequences copied by the transmission device 10, D is the subcarrier spacing when the subcarrier signal sequences copied by the transmission device 10 are mapped at equal subcarrier spacing, and K is the number of subsets included in one subcarrier signal sequence when each subcarrier signal sequence is divided into subsets by the transmission device 10. When a reception signal R(f) of subcarrier f with frequency f belongs to subset #k, the reception phase rotation unit 214 performs phase rotation processing expressed by equation (2) on the reception signal R(f), and outputs a signal R'(f).

[0028] 6 is a diagram illustrating an example of a complementary cumulative distribution function characteristic of instantaneous normalized signal power obtained by the communication system 1 according to the first embodiment. To illustrate the effect of phase rotation by the communication system 1 according to the present embodiment, FIG. 6 shows a complementary cumulative distribution function (CCDF) of instantaneous normalized signal power during transmission by the transmitting device 10, calculated by computer simulation. In the computer simulation, the number of IDFT points is N=256, the length of the subcarrier signal sequence is L=56, the number of subcarrier signal sequence copies is M=4, and the frequency repetition of the copied subcarrier signal sequence is D=64. Furthermore, the number of subset divisions is K=7, and a phase rotation given by Equation (1) is applied. Furthermore, the primary modulation method is QPSK (Quadrature Phase Shift Keying).

[0029] In Figure 6, CCDF = 10 －３The power value at this point is defined as the PAPR. When QPSK is used as the primary modulation, it has been confirmed that the transmission signal waveform of normal OFDM communication without frequency repetition has a PAPR of 8.1 dB. When frequency repetition is applied, in-phase synthesis of replica signals with a number M of replicas of the subcarrier signal sequence (M=4) occurs, resulting in a deterioration to PAPR of 12.6 dB. In contrast, when frequency repetition is applied while phase rotation for each subset is applied as in this embodiment, it has been confirmed that the PAPR is 8.1 dB, which is equivalent to that of normal OFDM communication. In other words, by applying frequency repetition while applying phase rotation for each subset as in this embodiment, the PAPR can be improved by 4.5 dB compared to when only frequency repetition is applied. This is the effect of phase rotation in the frequency domain so that the timing of the time peak differs for each subset, while allowing the time signal to be in-phase synthesized for each subset, as described above.

[0030] In the operation of the communication system 1, the operation of the transmitting device 10 is performed after the operation of the receiving device 20. Therefore, although a description using a flowchart will be omitted, the operation of the communication system 1 can be explained as a flow in which the operation of the transmitting device 10 shown in the flowchart of Fig. 2 is performed after the operation of the receiving device 20 shown in the flowchart of Fig. 3 is performed.

[0031] Next, the hardware configuration of the transmitting device 10 will be described. In the transmitting device 10, the transmitting RF unit 120 is a general RF module circuit. The transmitting antenna 130 is an antenna element. The transmitting baseband processing unit 110 is realized by a processing circuit. The processing circuit may be a processor and memory that executes a program stored in memory, or may be dedicated hardware. The processing circuit is also called a control circuit.

[0032] FIG. 7 is a diagram illustrating an example of the configuration of a processing circuit 90 that implements the transmitting device 10 according to the first embodiment, when the processing circuit is configured with a processor 91 and a memory 92. The processing circuit 90 illustrated in FIG. 7 is a control circuit and includes a processor 91 and a memory 92. When the processing circuit 90 is configured with the processor 91 and the memory 92, each function of the processing circuit 90 is implemented by software, firmware, or a combination of software and firmware. The software or firmware is written as a program and stored in the memory 92. In the processing circuit 90, each function is implemented by the processor 91 reading and executing the program stored in the memory 92. That is, the processing circuit 90 includes the memory 92 for storing a program that results in the processing of the transmitting device 10 being executed. This program can also be said to be a program that causes the transmitting device 10 to execute each function implemented by the processing circuit 90. This program may be provided by a storage medium on which the program is stored, or by other means such as a communication medium.

[0033] The above program can also be said to be a program that causes the transmitting device 10 to execute a subcarrier mapping step in which the subcarrier mapping unit 113 duplicates subcarrier signal sequences and maps the duplicated subcarrier signal sequences at equal subcarrier spacing D, and a transmission phase rotation step in which the transmission phase rotation unit 114 divides each subcarrier signal sequence mapped at subcarrier spacing D into two or more subsets and imparts phase rotation with different time timing to each subset.

[0034] Here, the processor 91 is, for example, a CPU (Central Processing Unit), a processing device, an arithmetic unit, a microprocessor, a microcomputer, or a DSP (Digital Signal Processor), etc. The memory 92 is, for example, a non-volatile or volatile semiconductor memory such as a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, an EPROM (Erasable Programmable ROM), or an EEPROM (Electrically EPROM), a magnetic disk, a flexible disk, an optical disk, a compact disk, a minidisk, or a DVD (Digital Versatile Disc).

[0035] FIG. 8 is a diagram illustrating an example of a processing circuit 93 that implements the transmitting device 10 according to the first embodiment when the processing circuit is configured with dedicated hardware. The processing circuit 93 illustrated in FIG. 8 corresponds to, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a combination thereof. The processing circuit may be partially implemented with dedicated hardware and partially implemented with software or firmware. In this way, the processing circuit can implement each of the above-described functions by dedicated hardware, software, firmware, or a combination thereof.

[0036] The hardware configuration of the transmitting device 10 has been described above, and the hardware configuration of the receiving device 20 is similar. In the receiving device 20, the receiving RF unit 220 is a general RF module circuit. The receiving antenna 230 is an antenna element. The receiving baseband processing unit 210 is realized by a processing circuit. The processing circuit may be a processor and memory that executes a program stored in memory, or may be dedicated hardware. The processing circuit is also called a control circuit.

[0037] As described above, according to the present embodiment, in communication system 1, transmission phase rotation unit 114 of transmitting device 10 divides each subcarrier signal sequence mapped at subcarrier spacing D into two or more subsets and imparts phase rotation that results in different time timing to each subset. Specifically, when frequency repetition is applied in which a subcarrier signal sequence of length L is replicated into M subsets and equally distributedly mapped at subcarrier spacing D, transmission phase rotation unit 114 divides the subcarrier signal sequence into K subsets and imparts phase rotation that results in different time timing to each subset so as to evenly distribute the time timing among the subsets. Reception phase rotation unit 214 of receiving device 20 compensates for the phase rotation in transmitting device 10 by reverse-rotating the phase of the received subcarrier signal sequence by the amount of phase rotation imparted by transmission phase rotation unit 114 of transmitting device 10. As a result, when frequency repetition is applied to OFDM communication, the communication system 1 can suppress deterioration of the peak-to-average power ratio of the transmission waveform while suppressing a decrease in transmission power efficiency.

[0038] Second Embodiment In the first embodiment, the case where the transmitting device 10 and the receiving device 20 perform wireless communication has been described. In the second embodiment, the case where the transmitting device and the receiving device perform wired communication will be described.

[0039] FIG. 9 is a diagram showing an example of the configuration of a communication system 1a according to the second embodiment. The communication system 1a includes a transmitting device 10a and a receiving device 20a. The communication system 1a is a system in which the transmitting device 10a and the receiving device 20a perform wired communication using OFDM communication to which frequency repetition is applied, and in the example of FIG. 9, optical communication using optical fiber. Note that FIG. 9 shows an example in which the communication system 1a includes one transmitting device 10a and one receiving device 20a, but this is not limiting. The communication system 1a may also include multiple transmitting devices 10a and multiple receiving devices 20a.

[0040] The transmitting device 10a includes a transmission baseband processing unit 110 and an E / O (Electrical-to-Optical) unit 140 that performs electrical-to-optical conversion. The processing content of the transmission baseband processing unit 110 in the second embodiment is the same as the processing content of the transmission baseband processing unit 110 described in the first embodiment. The E / O unit 140 converts the baseband signal generated by the transmission baseband processing unit 110 from an electrical signal to an optical signal, and outputs the converted signal to a transmission path, which is an optical fiber in the example of FIG. 9 .

[0041] The receiving device 20a includes an O / E (Optical-to-Electrical) unit 240 that performs optical-to-electrical conversion, and a receiving baseband processing unit 210. The O / E unit 240 converts a received signal acquired from a transmission path, which is an optical fiber in the example of FIG. 9 , from an optical signal to an electrical signal, and outputs the electrical signal to the receiving baseband processing unit 210. The processing content of the receiving baseband processing unit 210 in the second embodiment is the same as the processing content of the receiving baseband processing unit 210 described in the first embodiment.

[0042] The communication system 1a can obtain the same effects as the communication system 1 of the first embodiment even when performing wired communication with the configuration shown in FIG.

[0043] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, or different embodiments may be combined with each other. It is also possible to omit or modify parts of the configurations as long as they do not deviate from the gist of the invention.

[0044] 1, 1a communication system, 10, 10a transmitting device, 20, 20a receiving device, 90, 93 processing circuit, 91 processor, 92 memory, 110 transmitting baseband processing unit, 111 encoding unit, 112 primary modulation unit, 113 subcarrier mapping unit, 114 transmitting phase rotation unit, 115 IDFT unit, 116 GI adding unit, 117 transmitting waveform shaping unit, 118 DAC unit, 120 transmitting RF unit, 130 transmitting antenna, 140 E / O unit, 210 receiving baseband processing unit, 211 decoding unit, 212 primary demodulation unit, 213 subcarrier demapping unit, 214 receiving phase rotation unit, 215 DFT unit, 216 GI removing unit, 217 receiving waveform shaping unit, 218 ADC unit, 220 receiving RF unit, 230 Receiving antenna, 240 O / E part.

Claims

1. A transmitting device for performing orthogonal frequency division multiplexing communications, comprising: a subcarrier mapping unit that replicates subcarrier signal sequences and maps the replicated subcarrier signal sequences at equal subcarrier intervals; and a transmission phase rotation unit that divides each subcarrier signal sequence mapped at the subcarrier intervals into two or more subsets and imparts phase rotation that results in different time timing for each subset.

2. Let M and D be integers equal to or greater than 1, let K be an integer equal to or greater than 2, and let the range of k be k∈0, ..., K-1; and when the number of the subcarrier signal sequences replicated by the subcarrier mapping unit is M, the subcarrier interval is D, and the number of subsets to be divided is K, and a signal S(f) mapped to subcarrier f of frequency f belongs to subset #k, the transmission phase rotation unit calculates Φ ｋ 2. The transmitting device according to claim 1, wherein, when a phase offset of subset #k is a phase offset of subset #k, a phase rotation process represented by the following equation is performed on the signal S(f), and a signal S'(f) is output.

3. A receiving device that receives a subcarrier signal sequence transmitted from a transmitting device that performs orthogonal frequency division multiplexing communication, comprising: a receiving phase rotation unit that compensates for the phase rotation in the transmitting device by inversely rotating the phase of the received subcarrier signal sequence by the amount of phase rotation imparted by the transmitting device; and a subcarrier demapping unit that combines the subcarrier signal sequences whose phase rotation has been compensated for by the receiving phase rotation unit and extracts them as a demodulated signal.

4. Let M and D be integers equal to or greater than 1, let K be an integer equal to or greater than 2, and let k be in the range of k∈0, ...,K-1; and in the receiving phase rotation unit, let M be the number of the subcarrier signal sequences copied by the transmitting device, let D be the subcarrier spacing when the subcarrier signal sequences copied by the transmitting device are mapped at equal subcarrier spacing, and let K be the number of subsets included in one subcarrier signal sequence when each subcarrier signal sequence is divided into subsets by the transmitting device; and when a received signal R(f) of subcarrier f with frequency f belongs to subset #k, then Φ ｋ is a phase offset of subset #k, the receiving device according to claim 3, wherein the receiving device performs a phase rotation process on the received signal R(f) expressed by the following equation to output a signal R'(f).

5. A communication system including a transmitting device and a receiving device that perform orthogonal frequency division multiplexing communication, wherein the transmitting device comprises: a subcarrier mapping unit that copies a subcarrier signal sequence and maps the copied subcarrier signal sequences at equally spaced subcarrier intervals; and a transmitting phase rotation unit that divides each subcarrier signal sequence mapped at the subcarrier intervals into two or more subsets and imparts a phase rotation that results in a different time timing for each subset; and the receiving device comprises: a receiving phase rotation unit that compensates for the phase rotation in the transmitting device by reverse-rotating the phase of the received subcarrier signal sequence by the amount of phase rotation imparted by the transmitting device; and a subcarrier demapping unit that combines the subcarrier signal sequences whose phase rotation has been compensated for in the receiving phase rotation unit and extracts them as a demodulated signal.

6. Let M and D be integers equal to or greater than 1, let K be an integer equal to or greater than 2, and let k be in the range of k∈0, ...,K-1; and when the number of the subcarrier signal sequences replicated by the subcarrier mapping unit is M, the subcarrier interval is D, and the number of subsets to be divided is K, and a signal S(f) mapped to subcarrier f of frequency f belongs to subset #k, the transmission phase rotation unit calculates Φ ｋ is a phase offset of subset #k, the signal S(f) is subjected to a phase rotation process expressed by the following equation to output a signal S'(f).

7. Let M and D be integers equal to or greater than 1, let K be an integer equal to or greater than 2, and let k be in the range of k∈0, ...,K-1; and in the receiving phase rotation unit, let M be the number of the subcarrier signal sequences copied by the transmitting device, let D be the subcarrier spacing when the subcarrier signal sequences copied by the transmitting device are mapped at equal subcarrier spacing, and let K be the number of subsets included in one subcarrier signal sequence when each subcarrier signal sequence is divided into subsets by the transmitting device; and when a received signal R(f) of subcarrier f with frequency f belongs to subset #k, Φ ｋ is a phase offset of subset #k, the received signal R(f) is subjected to a phase rotation process expressed by the following equation to output a signal R'(f).

8. A control circuit for controlling a transmitting device that performs orthogonal frequency division multiplexing communications, the control circuit causing the transmitting device to perform the following: duplicating a subcarrier signal sequence, and mapping the multiple copies of the subcarrier signal sequence at equal subcarrier intervals; dividing each subcarrier signal sequence mapped at the subcarrier intervals into two or more subsets; and imparting phase rotation to each subset so that the subset has a different time timing.

9. A control circuit for a receiving device that receives a subcarrier signal sequence transmitted from a transmitting device that performs orthogonal frequency division multiplexing communications, characterized in that the control circuit causes the receiving device to perform the following operations: compensate for the phase rotation in the transmitting device by inversely rotating the phase of the received subcarrier signal sequence by the amount of phase rotation imparted by the transmitting device; and synthesize the subcarrier signal sequence whose phase rotation has been compensated for, and extract it as a demodulated signal.

10. A control circuit for controlling a communication system including a transmitter and a receiver that perform orthogonal frequency division multiplexing communication, characterized in that the control circuit causes the communication system to perform the following: duplicating a subcarrier signal sequence, and mapping the multiple copies of the subcarrier signal sequence at equal subcarrier intervals; dividing each subcarrier signal sequence mapped at the subcarrier intervals into two or more subsets and imparting a phase rotation that results in a different time timing for each subset; compensating for the phase rotation by reverse-rotating the phase of the received subcarrier signal sequence by the amount of the imparted phase rotation; and combining the subcarrier signal sequences whose phase rotation has been compensated for and extracting them as a demodulated signal.

11. A storage medium storing a program for controlling a transmitting device that performs orthogonal frequency division multiplexing communications, wherein the program causes the transmitting device to perform the following: duplicating a subcarrier signal sequence, and mapping the multiple copies of the subcarrier signal sequence at equal subcarrier intervals; dividing each subcarrier signal sequence mapped at the subcarrier intervals into two or more subsets; and imparting phase rotation to each subset so that the subset has a different time timing.

12. A storage medium storing a program for controlling a receiving device that receives a subcarrier signal sequence transmitted from a transmitting device that performs orthogonal frequency division multiplexing communications, wherein the program causes the receiving device to perform the following operations: compensate for the phase rotation in the transmitting device by inversely rotating the phase of the received subcarrier signal sequence by the amount of phase rotation imparted by the transmitting device; and synthesize the subcarrier signal sequence whose phase rotation has been compensated for, and extract it as a demodulated signal.

13. A storage medium storing a program for controlling a communication system including a transmitting device and a receiving device that perform orthogonal frequency division multiplexing communication, wherein the program causes the communication system to perform the following: duplicating a subcarrier signal sequence, and mapping the multiple copies of the subcarrier signal sequence at equal subcarrier intervals; dividing each subcarrier signal sequence mapped at the subcarrier intervals into two or more subsets and imparting a phase rotation that results in a different time timing for each subset; compensating for the phase rotation by reverse-rotating the phase of the received subcarrier signal sequence by the amount of the imparted phase rotation; and combining the subcarrier signal sequences whose phase rotation has been compensated for and extracting them as a demodulated signal.

14. A transmission method for a transmitting device that performs orthogonal frequency division multiplexing communications, comprising: a subcarrier mapping step in which a subcarrier mapping unit replicates a subcarrier signal sequence and maps the replicated subcarrier signal sequences at equal subcarrier intervals; and a transmission phase rotation step in which a transmission phase rotation unit divides each subcarrier signal sequence mapped at the subcarrier intervals into two or more subsets and imparts phase rotation with different time timing to each subset.

15. A receiving method for a receiving device that receives a subcarrier signal sequence transmitted from a transmitting device that performs orthogonal frequency division multiplexing communications, comprising: a receiving phase rotation step in which a receiving phase rotation unit compensates for the phase rotation in the transmitting device by inversely rotating the phase of the received subcarrier signal sequence by the amount of phase rotation imparted by the transmitting device; and a subcarrier demapping step in which a subcarrier demapping unit combines the subcarrier signal sequences whose phase rotation has been compensated for by the receiving phase rotation unit and extracts them as a demodulated signal.

16. A signal processing method for a communication system including a transmitting device and a receiving device that perform orthogonal frequency division multiplexing communication, comprising: a subcarrier mapping step in which a subcarrier mapping unit of said transmitting device copies a subcarrier signal sequence and maps the copied subcarrier signal sequences at equally spaced subcarrier intervals; a transmission phase rotation step in which a transmission phase rotation unit of said transmitting device divides each subcarrier signal sequence mapped at said subcarrier intervals into two or more subsets and imparts a phase rotation with a different time timing to each subset; a reception phase rotation step in which a reception phase rotation unit of said receiving device compensates for the phase rotation in said transmitting device by reversely rotating the phase of the received subcarrier signal sequence by the amount of phase rotation imparted by said transmitting device; and a subcarrier demapping step in which a subcarrier signal sequence whose phase rotation has been compensated for in said reception phase rotation unit is combined and extracted as a demodulated signal.

Images