Communication device, communication method, control circuit, and program storage medium

Abstract

In the present invention, a transmitter includes: a frequency repetition unit (63) that equally divides a communication band in a frequency domain by at least two, and allocates the same signal to each of the plurality of sub-bands generated by equal division to generate a frequency repetition signal; an IDFT unit (64) that, on the basis of the frequency repetition signal obtained by the frequency repetition unit (63), generates a transmission signal that becomes a pulse type in the time domain; and a transmission antenna (65) that transmits the transmission signal generated by the IDFT unit (64).

Description

[Technical Field]

[0001] The present disclosure relates to a communication device, a communication method, a control circuit, and a program storage medium. [Background technology]

[0002] In unlicensed bands (ISM (Industrial, Scientific, and Medical) bands) such as 2.4 GHz and 5 GHz, multiple wireless standards, including wireless local area network (WLAN) and Bluetooth®, are used. Terminals can be installed anywhere, making unlicensed bands a useful frequency band for a wide range of systems, regardless of their intended use. However, due to their versatility, unlicensed bands can sometimes cause interference between wireless terminals in crowded areas, resulting in temporary communication outages. This indicates that since each system operates autonomously and in a decentralized manner without cooperation, it is difficult to avoid mutual interference in an environment where multiple systems and devices coexist. As a result, transmission efficiency at wireless terminals decreases, and devices using WLAN, etc., cannot satisfy their own performance standards, and performance is specified on a best-effort basis.

[0003] In response to the above situation, specifications are being developed for wireless LAN and other systems to improve the efficiency of frequency resource utilization, and the allocation of available frequency resources is increasing from the 2.4 GHz band to the 5 GHz band and 6 GHz band, with ongoing technological development being carried out to maintain and improve communication connectivity.

[0004] For example, IEEE (Institute of Electrical and Electronics Engineers) 802.11ac has a sequence in which the sender sends an RTS (Request To Send) to the receiver, and the receiver responds by sending a CTS (Clear To Send). However, a communication control method is adopted in which the sender and receiver each add information about a channel that can be used without interference to the RTS and CTS, enabling efficient communication even in the presence of interference.

[0005] When determining whether communication is possible on a channel where interference exists, the receiving side can accurately obtain transmission path information that directly affects the transmission error rate, such as the signal-to-noise interference ratio (SINR), making it possible to more effectively utilize the above-mentioned communication control techniques.

[0006] Patent Document 1 discloses a method for selecting optimal communication parameters such as a frequency channel of a transmitter based on the SINR of a receiver in a shared radio frequency environment where a wireless LAN is used. This method makes it possible to accurately obtain the SINR, thereby enabling efficient wireless communication even in a shared radio frequency environment.

[0007] Patent Document 2 discloses a technique that enables a transmitter to transmit a known signal having specific characteristics, a receiver to detect the known signal from the signal received, and measure the SINR using information on the detected known signal and portions where no signal is present. The portions where no signal is present are null. Patent Document 3 discloses a method of measuring the SINR based on the power difference between the correlation peak and other portions, using the correlation power of a pilot signal as a reference. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent No. 7209292 [Patent Document 2] U.S. Patent No. 6,456,653 [Patent Document 3] Japanese Patent Application Laid-Open No. 2005-204307 Summary of the Invention [Problem to be solved by the invention]

[0009] In all of the techniques disclosed in Patent Documents 1, 2, and 3, the measurement of SINR is premised on first detecting a signal, but there is a problem in that signal detection is difficult under conditions where interference with the signal is so great that the SINR becomes a negative value.

[0010] The present disclosure has been made in view of the above, and aims to provide a communication device that can obtain good communication quality even when there is significant interference with signals. [Means for solving the problem]

[0011] In order to solve the above-described problems and achieve the object, a communication device according to the present disclosure has a receiving antenna that receives a received signal including a known signal sequence that becomes pulse-shaped in the time domain due to frequency repetition; an interference signal interval separation unit that assumes a sample position that becomes null in the received signal received by the receiving antenna and extracts the null position as a section containing only an interference signal; a discrete Fourier transform unit that performs a discrete Fourier transform on the section containing only the interference signal extracted by the interference signal interval separation unit to obtain a frequency spectrum; an interference measurement unit that performs frequency analysis on the frequency spectrum obtained by the discrete Fourier transform unit and measures the amount of interference power of each of a plurality of sub-bands obtained by dividing the communication bandwidth; a signal detection channel selection unit that selects a sub-band corresponding to an interference power amount that is equal to or less than a predetermined amount from the plurality of interference power amounts obtained by the interference measurement unit; a signal detection unit that extracts the sub-band selected by the signal detection channel selection unit from the received signal received by the receiving antenna and performs signal detection by correlation processing between the extracted sub-band and the known signal sequence; and a signal-to-interference-noise ratio measurement unit that measures a signal-to-interference-noise ratio based on the result of the signal detection performed by the signal detection unit. The communication device according to the present disclosure does not include a transmitter. The signal-to-interference ratio (SIR) measurement unit measures the SIR for each subband based on the interference power amount measured for each subband and the signal power measured at the timing of signal detection. The communication device according to the present disclosure feeds back to the transmitter the measurement result of the SIR for each subband measured by the SIR measurement unit. [Effects of the Invention]

[0012] The communication device according to the present disclosure has an effect of being able to obtain good communication quality even when there is a lot of interference with the signal. [Brief explanation of the drawings]

[0013] [Figure 1] A diagram for explaining frequencies that can be used as communication bands [Figure 2] A diagram for explaining a situation in which transmitters transmit sounding signals in sequence from CH1 to CH4. [Figure 3] A diagram showing multiple sub-channels obtained by dividing one channel of communication bandwidth. [Figure 4] A diagram showing an example of communication quality for all communication bands [Figure 5] This diagram shows a situation where a measurement sequence in which a sounding signal is transmitted via downlink and the communication quality measurement results are transmitted via uplink as sounding measurement data is repeated N times. [Figure 6] FIG. 1 shows the configuration of a transmitter and a receiver for generating a sounding signal and performing sounding in an embodiment. [Figure 7] A diagram showing multiple sub-channels obtained by dividing a channel into equal parts. [Figure 8] A diagram showing the presence of a signal every L samples [Figure 9] A diagram showing a received signal on which an interference signal is superimposed. [Figure 10] FIG. 10 is a diagram showing an extracted signal in an interference signal section. [Figure 11] A diagram showing an example of a band with little interference [Figure 12] FIG. 1 is a diagram showing an example of a signal used for signal detection performed by a signal detection unit according to an embodiment; [Figure 13] A diagram showing an example of a signal in which known sequence symbols are repeated. [Figure 14] FIG. 10 is a diagram showing another configuration of a receiver according to an embodiment; [Figure 15] FIG. 10 is a diagram showing another configuration of a transmitter and a receiver according to an embodiment; [Figure 16] FIG. 1 shows the configuration of a transmitter and a receiver in an embodiment where the receiver has a sounding result analysis unit. [Figure 17] 1 is a flowchart showing a series of steps from sounding processing to data transmission according to an embodiment of the present invention. [Figure 18] Diagram showing an example of signals transmitted from two transmit antennas [Figure 19] FIG. 1 is a diagram showing a processing circuit in the case where the functions of a transmitter and a receiver according to an embodiment are realized by the processing circuit; [Figure 20] FIG. 1 is a diagram showing a central processing unit (CPU) when the functions of a transmitter and a receiver according to an embodiment are implemented by the CPU; [Figure 21] FIG. 1 is a diagram showing a control circuit for controlling the operation of a transmitter according to an embodiment; [Figure 22] FIG. 1 is a diagram showing a program storage medium storing a program for controlling a transmitter according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] A communication device, a communication method, a control circuit, and a program storage medium according to embodiments will be described in detail below with reference to the accompanying drawings.

[0015] Embodiment First, an overview of the sounding process in this application will be described. Sounding is a process of measuring the propagation environment to measure the communication quality of a frequency band available for communication and search for communication parameters that will provide good communication characteristics before data communication is performed from a transmitter to a receiver. Both the transmitter and the receiver are communication devices.

[0016] Here, an example of an overview of sounding processing is shown. FIG. 1 is a diagram for explaining frequencies that can be used as a communication band. In FIG. 1, frequencies that can be used as a communication band are divided into four bands, and the channels are designated CH1 to CH4. In the example of FIG. 1, the entire usable frequency band is four consecutive channels, CH1 to CH4. Note that a channel may also be referred to as a band. In sounding processing, for example, a transmitter transmits a sounding signal for each of CH1 to CH4 in sequence as shown in FIG. 2, and a receiver measures the communication quality of each channel. FIG. 2 is a diagram for explaining a situation in which a transmitter transmits sounding signals in sequence for CH1 to CH4. The horizontal axis of FIG. 2 represents time.

[0017] When measuring communication quality, subchannels are defined by further dividing each channel as shown in FIG. 3, and the receiver measures the SINR value indicating the communication quality for each subchannel. FIG. 3 is a diagram showing multiple subchannels obtained by dividing one channel of a communication bandwidth. Each of the multiple subchannels is a unit of SINR measurement. The receiver may measure communication quality over the entire channel without generating subchannels. Alternatively, the receiver may use an evaluation index other than the SINR value, such as a signal-to-interference power ratio (SIR) value or a signal-to-noise ratio (SNR) value, instead of the SINR value. As a result of measuring each channel, the receiver can obtain communication quality for the entire communication band as shown in FIG. 4. FIG. 4 is a diagram showing an example of communication quality for the entire communication band. In the example of FIG. 4, the communication channel with the largest average communication quality value is considered to be a band with good communication quality. In the example of FIG. 4, a portion of CH1 and a portion of CH2 adjacent to that portion are bands with good communication quality.

[0018] To communicate using a band with good communication quality, a transmitter that transmits a sounding signal and a data signal must obtain information about the band. Therefore, as shown in FIG. 5, a measurement sequence in which a sounding signal is transmitted on the downlink and a communication quality measurement result is transmitted on the uplink as sounding measurement data is repeated a predetermined number of times. After obtaining communication quality information for the entire communication band, the transmitter analyzes the optimal channel and performs data communication. DL in FIG. 5 refers to the downlink, and UL in FIG. 5 refers to the uplink. FIG. 5 illustrates a situation in which a measurement sequence in which a sounding signal is transmitted on the downlink and a communication quality measurement result is transmitted on the uplink as sounding measurement data is repeated N times. N is an integer equal to or greater than 2. The communication packets shown in FIG. 5 are packets that constitute data transmitted by the transmitter. Note that, in order to communicate using the optimal channel, not only the transmitter but also the receiver must obtain information about the channel through which communication will be performed. Therefore, the optimal channel may be analyzed by the receiver that performs data communication, and the receiver may feed back the results of the analysis of the optimal channel to the transmitter. By performing the above-described processing, it is possible to perform communication control based on the sounding results after sounding. Next, the transmission and reception of a sounding signal per sounding will be described in order.

[0019] 6 is a diagram showing the configurations of a transmitter and receiver for generating a sounding signal and performing sounding in an embodiment. The transmitter includes a communication parameter selection unit 61 that determines parameters of the sounding signal, a known sequence generation unit 62 that generates a known sequence to be assigned to the sounding signal, a frequency repetition unit 63 that imparts characteristics of a pulsed signal on the time axis to the generated signal, an IDFT (Inverse Discrete Fourier Transform) unit 64 that converts the signal obtained by the frequency repetition unit 63 into a time signal, and a transmission antenna 65 for transmitting the transmission signal. The known sequence is a known signal sequence. The IDFT unit 64 is an inverse discrete Fourier transform unit.

[0020] 6 is a communication device that includes a frequency repetition unit 63 that generates a frequency-repeated signal by equally dividing a communication band into two or more subbands in the frequency domain and assigning the same signal to each of a plurality of subbands generated by the equal division, an IDFT unit 64 that generates a pulse-shaped transmission signal in the time domain based on the frequency-repeated signal obtained by the frequency repetition unit 63, and a transmission antenna 65 that transmits the transmission signal generated by the IDFT unit 64. For example, the frequency repetition unit 63 generates the frequency-repeated signal using a CAZAC sequence that has a constant amplitude value and good correlation characteristics (autocorrelation is 0). For example, the transmission antenna 65 repeatedly transmits the same signal in the time domain.

[0021] The receiver has a receiving antenna 66 for receiving the received signal, an interference signal section separation unit 67 for extracting samples of only the interference signal, a DFT (Discrete Fourier Transformation) unit 68 for converting the interference signal into frequency space to perform spectral analysis of the interference signal, an interference measurement unit 69 for measuring the amount of interference power for each subchannel, a signal detection CH (channel) selection unit 610 for determining the subchannel to be used for signal detection from the results of the interference measurement, a signal detection unit 611 for detecting the signal from a sample sequence including the interference signal and the signal, an SINR measurement unit 612 for measuring the SINR from the results of the interference measurement and signal detection, and an average power measurement unit 613 for measuring the average power from samples of the received signal.

[0022] 6 includes a receiving antenna 66 that receives a received signal including a known signal sequence that becomes pulse-shaped in the time domain due to frequency repetition, an interference signal interval separation unit 67 that assumes sample positions that become null in the received signal received by the receiving antenna 66 and extracts the null positions as intervals containing only the interference signal, and a DFT unit 68 that obtains a frequency spectrum by performing a discrete Fourier transform on the interval containing only the interference signal extracted by the interference signal interval separation unit 67. The receiver of Fig. 6 further includes an interference measurement unit 69 that performs frequency analysis on the frequency spectrum obtained by the DFT unit 68 and measures the amount of interference power in each of a plurality of sub-bands obtained by dividing the communication bandwidth, and a signal detection CH selection unit 610 that selects a sub-band corresponding to an interference power amount that is equal to or less than a predetermined amount from the plurality of interference power amounts obtained by the interference measurement unit 69. The receiver of FIG. 6 further includes a signal detector 611 that extracts a subband selected by a signal detection CH selector 610 from a received signal received by a receiving antenna 66 and performs signal detection by correlating the extracted subband with a known signal, and an SINR measurement unit 612 that measures a signal-to-interference-plus-noise ratio (SNR) based on the result of signal detection performed by the signal detector 611. The interference measurement unit 69 measures the signal power of the subband selected by the signal detection CH selector 610 at the timing when the signal detector 611 performs signal detection. The SINR measurement unit 612 measures the SNR for each subband based on the amount of interference power measured for each subband and the signal power measured at the timing when signal detection is performed. The receiver of FIG. 6 feeds back the measurement result of the SNR for each subband measured by the SINR measurement unit 612 to the transmitter. The received signal is a transmission signal transmitted by the communication device of FIG. 6. The SINR measurement unit 612 measures the signal-to-interference-plus-noise ratio (SNR) of a received signal including a known signal sequence that is a pulse type for each of a plurality of communication parameters as a sounding sequence. The receiver of Fig. 6 accumulates and analyzes the SNR information obtained by the SINR measurement unit 612 to determine optimal communication parameters. Alternatively, the transmitter of Fig. 6 accumulates and analyzes the SNR information obtained by the SINR measurement unit 612 to determine optimal communication parameters.

[0023] The generation of a known sequence transmitted by a transmitter as a sounding signal will now be described. The known sequence is a preamble. Note that the same generation method may be used for data communication that is not a known sequence. In selecting communication parameters, the communication parameter selector 61 selects the communication band to be used for sounding, etc. As the known sequence, it is desirable to use a constant amplitude zero autocorrelation (CAZAC) sequence, which has a constant amplitude value and good correlation characteristics, such as a CAZAC sequence, from the viewpoint of the receiver performing synchronization processing and measuring the SINR for each frequency within the communication band, but other sequences may also be used.

[0024] As a sounding signal, a pulsed signal with periodic null samples is generated by frequency repetition so that the interference signal can be extracted on the time axis. A null sample is a sample whose signal power is 0. To generate the sounding signal, the channel is divided equally, as shown in FIG. 7, and the same signal is assigned to each subchannel. FIG. 7 is a diagram showing multiple subchannels obtained by dividing the channel equally. The horizontal axis of FIG. 7 represents frequency, and the vertical axis of FIG. 7 represents power. In order to divide the channel equally and assign the same signal to each subchannel, a signal that satisfies the following equation (1) is assigned to each subchannel.

[0025]

number

[0026] In equation (1), x(k) represents the signal of the kth subcarrier, and mod(p,q) represents the remainder when p is divided by q. n is an integer equal to or greater than 2. a(k) is the known sequence assigned to each subchannel. In this way, the frequency repetition unit 63 performs repetition processing on the known sequence, and the IDFT unit 64 performs an inverse discrete Fourier transform, thereby generating a pulse-type signal, as shown in FIG. 8, in which a signal exists every L samples, and if the base is a CAZAC sequence, the signal amplitude is constant and the rest is null. FIG. 8 is a diagram showing how a signal exists every L samples. The horizontal axis of FIG. 8 represents time, and the vertical axis of FIG. 8 represents power. Note that the larger the number of repetitions N / L, the more null samples there are on the time axis, and therefore the number of samples that can be used for interference measurement in processing by the receiver described later increases, improving the accuracy of interference measurement. However, since a longer preamble sequence length L is better in order to ensure synchronization accuracy for the signal, in the communication parameter selection described above, instead of providing a single fixed parameter, the communication parameters may be dynamically changed and a combination of multiple parameters may be used as the sounding signal. Alternatively, long-period control may be performed such that the communication parameters are changed when the receiver remains in an unsynchronized state and there is no response to reception for a while.

[0027] When the sounding signal generated as described above is received by the receiver, an interference signal is superimposed on it, resulting in a received signal as shown in FIG. 9. FIG. 9 is a diagram illustrating the received signal on which the interference signal is superimposed. The horizontal axis in FIG. 9 represents time, and the vertical axis in FIG. 9 represents power. A feature obtained by transmitting a pulsed signal from the transmitter is that, when extracting only the interference signal from the received signal, the interference signal section separator 67 can extract a section containing only the interference signal by extracting a portion of samples between pulses, as shown in FIG. 9. This section containing only the interference signal is the interference observation section. Note that if the reception timing of the received signal is unknown at this point, the pulse position is unknown. However, by performing subsequent processing using an arbitrary location as the pulse position and repeating the processing until signal detection is achieved, the timing at which the signal is detected can be treated as the timing at which the pulse position is correctly set. Incidentally, since the preamble itself may contain delayed waves due to multipath and synchronization timing deviations may occur in the receiver, the interference observation section is set to a portion between pulses of the pulsed signal, for example, half the pulse interval.

[0028] FIG. 10 is a diagram showing a signal in an extracted interference signal section. The horizontal axis of FIG. 10 represents time, and the vertical axis of FIG. 10 represents power. To measure the amount of interference for each subchannel, the DFT unit 68 performs a discrete Fourier transform on the signal in FIG. 10 from which the interference signal section has been extracted, to obtain a frequency spectrum. Note that the frequency spectrum obtained by extracting only a portion in space-time and performing a discrete Fourier transform has a broader bandwidth than the original spectrum. The amount of broadening of the bandwidth varies depending on the pulse interval L and the number of samples extracted as the interference observation section. The important point here is not only to calculate the interference power for each subchannel, but also to detect a band with sufficiently low interference, as shown in FIG. 11. FIG. 11 is a diagram showing an example of a band with low interference. The horizontal axis of FIG. 11 represents frequency, and the vertical axis of FIG. 11 represents power. The interference measurement unit 69 detects a band with low interference, and the signal detection CH selection unit 610 selects a subchannel with low interference power relative to the average power of the received signal samples, and the signal detection unit 610 performs signal detection in that band.

[0029] The signal detection unit 610 performs detection processing on a signal such as that shown in FIG. 12 , excluding the interval extracted as the interference observation interval. FIG. 12 is a diagram showing an example of a signal used for signal detection performed by the signal detection unit 610 according to the embodiment. The horizontal axis in FIG. 12 represents time, and the vertical axis in FIG. 12 represents power. Note that, since signal detection is possible if a signal component is present, the signal detection unit 610 may perform signal detection on the received signal itself. The signal detection method may be a detection method in time space or a detection method in frequency space. In the case of a detection method in frequency space, the DFT unit 68 performs a discrete Fourier transform on the signal for signal detection to generate a frequency spectrum, and then the interference measurement unit 69 calculates the cross-correlation between the known sequence and the interfering signal in a band where interference is sufficiently small. The signal detection unit 610 detects the signal by synchronization processing using a matched filter, etc., such that the timing at which peak power is obtained at which the correlation power is sufficiently large relative to the average value is set as the signal detection timing. In the case of a time-space detection method, the signal detector 610 prepares a filter that extracts only the bands with sufficiently low interference detected by the interference measurement unit 69, and detects the signal using a method similar to the above-mentioned method of performing signal detection based on cross-correlation processing between the known sequence and the interference signal for the filtered signal. By adopting this procedure, signals can be detected under conditions where the interference power in the received signal is greater than the signal power, i.e., even if SINR<0, as long as a subchannel with low interference exists. To facilitate detection, a signal in which the transmitter repeats OFDM (Orthogonal Frequency Division Multiplexing) symbols generated as pulsed signals, as shown in FIG. 13, can be used as a sounding signal. Even if the timing of the known sequence is unknown, the known sequence can be detected at a position where the timing of the CAZAC sequence is cyclically shifted in frequency space. Therefore, signal detection is possible as long as the position of the signal extracted for detection is within the section allocated to the repeated signal. FIG. 13 shows an example of a signal in which known sequence symbols are repeated. FIG. 13 illustrates the ability to detect a known sequence from any location. The horizontal axis in FIG. 13 represents time.

[0030] The reason for performing signal detection in sounding is to accurately calculate the ratio of signal power to interference plus noise power in the subsequent SINR measurement. Because the interference power has already been measured by the interference measurement unit 69 in the preceding stage, the remaining signal power must be measured. In signal detection, the signal power of subchannels with low interference is calculated at the time of detection, thereby suppressing the effects of interference and measuring the signal power. The signal power of the remaining subchannels not extracted is then set to the same signal power value as the subchannel with low interference, and the result of multiplying the signal power value of the subchannel with low interference by the number of subchannels is used as the signal power value of the entire channel, thereby enabling accurate calculation of signal power. In this way, the SINR measurement unit 612 calculates the SINR for each subchannel using the signal power calculated in conjunction with signal detection and the measurement results of the interference power measured by the interference measurement unit 69. The calculated SINR is used as feedback information to the transmitter.

[0031] 14 is a diagram showing another configuration of a receiver according to an embodiment. The difference between FIG. 14 and FIG. 6 is that the input for signal detection is a received signal received by a receiving antenna 141. In the configuration of FIG. 14, signal detection is performed without interference reduction. The receiver of FIG. 14 includes a receiving antenna 141 for receiving the received signal, an interference signal section separation unit 142 for extracting samples of only the interference signal, an FFT (Fast Fourier Transform) unit 143 for fast Fourier transforming the interference signal into frequency space to perform spectral analysis of the interference signal, an interference measurement unit 144 for measuring the amount of interference power for each subchannel, a signal detection CH selection unit 145 for determining a subchannel to use for signal detection based on the results of the interference measurement, a signal detection unit 146 for detecting a signal from a sample sequence including the interference signal and the signal, an SINR measurement unit 147 for measuring the SINR based on the results of the interference measurement and signal detection, and an average power measurement unit 148 for measuring the average power from samples of the received signal.

[0032] Next, a configuration for obtaining sounding measurement results and feeding back the information to control communications will be described. FIG. 15 illustrates another configuration of a transmitter and receiver according to an embodiment. FIG. 15 illustrates a configuration for performing feedback and communication control. The transmitter is the side that transmits data, and the receiver is the side that performs sounding measurements. The transmitter includes a communication parameter selector 151 that receives the sounding results and selects optimal parameters for communications, a data modulator 152 that performs data modulation according to the information bit input and the selected communication parameters, a switch 153 that switches between transmission and reception, a transmit / receive antenna 154 that transmits a transmit signal or receives a receive signal according to the state of the switch 153, and a sounding result analyzer 155 that analyzes the received sounding information and analyzes a communication band with a good SINR. The receiver includes a transmit / receive antenna 156 that receives a receive signal or transmits a transmit signal, a switch 157 that switches between transmission and reception, a data demodulator 158 that demodulates data and outputs demodulated bits, and a notification signal generator 159 that generates a modulated notification signal to feed back the sounding measurement results to the transmitter as notification information. In FIG. 15, the switch is labeled "SW."

[0033] The process of controlling communications based on sounding measurement results will now be described. In order for the receiver to feed back the sounding measurement results to the transmitter, the receiver generates a transmission signal for notifying the results in a notification signal generator 159. The modulation method for the notification signal may be any method suited to the signal propagation environment from the receiver to the transmitter, and may be a pulse signal format method similar to that used for the sounding signal transmitted from the transmitter to the receiver, or a method using an OFDM modulated signal that does not have such characteristics. The generated notification signal passes through a switch 157 and is transmitted from a transmitting / receiving antenna 156.

[0034] In the transmitter, the notification signal received by the transmit / receive antenna 154 passes through the switch 153 and is input to the sounding result analyzer 155. Because sounding is performed for multiple communication parameters, the above-described processes are repeated, and the sounding result analyzer 155 accumulates sounding measurement results for the multiple communication parameters. After the sounding measurement results are compiled for a predetermined set of communication parameters, the sounding result analyzer 155 performs an analysis process. Specifically, the sounding result analyzer 155 maps SINR values ​​on a subchannel basis for all frequency channels as shown in FIG. 4 and analyzes the band with the best communication quality for data communication. There may be multiple criteria for selecting the band with the best communication quality. The selection criteria may be, for example, selecting a band with the highest average SINR value, selecting a band that does not contain an SINR value below a certain level, or a combination of these criteria. Any criteria may be used as long as they ultimately select a band with a good SINR value for data communication. Information indicating a band with good communication quality as a result of analysis by the sounding result analysis unit 155 is input to the communication parameter selection unit 151, which selects and outputs communication parameters for data modulation according to the analysis results.

[0035] In this case, the communication parameter selector 151 may use the communication band indicated by the information obtained from the sounding result analyzer 155 as is, but may also change the modulation scheme depending on the SINR value. That is, if the SINR value is high, a modulation scheme with a high required SINR value, such as QAM (Quadrature Amplitude Modulation) modulation and a high modulation order, such as 256QAM, is selected. If the SINR value is lower than the required SINR value of 256QAM, a modulation scheme with a lower required SINR, such as 64QAM or 16QAM, or QPSK (Quadrature Phase Shift Keying) modulation, is selected. After the communication parameters selected by the communication parameter selector 151 are established as set values, a data modulator 152 modulates the information bits. The generated transmission signal is transmitted from a transmitting / receiving antenna 154 via a switch 153.

[0036] Subsequently, in the receiver, the signal received by the transmit / receive antenna 156 and carrying data passes through the switch 157, and the data demodulator 158 demodulates the received signal. During demodulation, the receiver must know the communication parameters selected by the transmitter. For example, one possible method is for the transmitter to add a header field before the data, transmitted using a fixed modulation scheme, and include communication parameter information in the header. However, since the selected frequency channel cannot be notified via the header, the receiver must be notified of the frequency channel in advance. This requires a notification signal, but since the notification signal cannot convey communication parameters in advance, communication must be performed using a specific frequency channel that has been determined in advance. To eliminate the need for such prior notification, a sounding result analyzer 169 must be located in the receiver, as shown in FIG. 16, and the receiver must determine communication parameters for data communication and notify the transmitter by feeding back the determined results. FIG. 16 is a diagram showing the configurations of a transmitter and receiver when the receiver has a sounding result analyzer 169 in an embodiment.

[0037] The transmitter in FIG. 16 includes a communication parameter selector 161 that receives sounding results and selects optimal parameters for communication; a data modulator 162 that performs data modulation based on information bit input and the selected communication parameters; a switch 163 that switches between transmission and reception; and a transmit / receive antenna 164 that transmits a transmission signal or receives a reception signal based on the state of the switch 163. The receiver in FIG. 16 includes a transmit / receive antenna 165 that receives a reception signal or transmits a transmission signal; a switch 166 that switches between transmission and reception; a data demodulator 167 that performs data demodulation; a notification signal generator 168 that generates a notification signal as a modulated signal to feed back the sounding measurement results to the transmitter as notification information; and a sounding result analyzer 169 that analyzes the received sounding information to identify a communication band with a good SINR. In FIG. 16, the switch is labeled "SW." The communication parameters determined by the receiver include, at a minimum, the frequency channel to be used. After the receiver acquires communication parameter information for data communication using one of the methods, the data demodulator 167 performs demodulation processing based on the communication parameters. In this way, demodulated bits are obtained, and communication control is realized for data communication in which optimal communication parameters are selected through sounding by the series of processes described above.

[0038] FIG. 17 is a flowchart showing a series of steps from sounding processing to data transmission in an embodiment. First, the transmitter selects a communication parameter by selecting one parameter from a group of parameters to be sounded (S1), performs modulation processing corresponding to the selected communication parameter, and generates a transmission signal (S2). The transmitter transmits a transmission signal. The receiver receives the transmission signal from the transmitter (S3) and performs interference signal separation by extracting samples containing only interference signals (S4). The receiver performs a discrete Fourier transform on the extracted samples, then performs frequency spectrum analysis, and measures interference for each subchannel (S5). The receiver then selects a subchannel with low interference power in signal detection CH selection 610 (S6). In FIG. 17, the operation of step S6 is referred to as "signal detection CH selection." The receiver performs signal detection from the received signal for the selected subchannel (S7). If the receiver detects a signal (Yes in S7), the receiver performs the operation of step S8. If the receiver cannot detect a signal (No in S7), it performs the operation of step S4 again.

[0039] In step S8, the receiver measures interference-plus-noise power based on the results of interference measurement and signal detection, and measures the SINR for each subchannel based on the signal power measurement results. The receiver generates a notification signal to be fed back to the transmitter based on the SINR measurement results (S9). The receiver transmits the generated notification signal to the transmitter (S10). The transmitter receives the notification signal transmitted from the receiver (S11). If the transmitter is the transmitter shown in FIG. 15, the notification signal transmitted from the receiver to the transmitter is stored in the sounding result analyzer 155 (S12). In FIG. 17, the operation of step S12 is indicated by the phrase "sounding result analysis." The transmitter determines whether processing of all sounding parameters has been completed (S13). If the transmitter determines that processing of all sounding parameters has not been completed (No in S13), that is, until processing of all sounding parameters has been completed, the transmitter returns to step S1, and the transmitter and receiver perform the sounding process again. When the transmitter determines that processing of all sounding parameters has been completed (Yes in S13), that is, after all sounding parameter results have been accumulated in the sounding result analysis unit 155, the transmitter analyzes the optimal parameters for data communication from the sounding results and concludes that sounding is complete. The transmitter selects communication parameters from the obtained sounding results (S14), determines parameters for data communication, and finally transmits data (S15), completing the series of processes. Here, a description of the data demodulation process is omitted.

[0040] As described above, the transmitter and receiver according to the embodiment have means for accurately measuring the SINR for each sub-band when the communication band is divided into multiple sub-bands in response to sounding of a frequency channel where radio wave interference exists. Therefore, the receiver feeds back the measurement results to the transmitter, allowing the transmitter to select a channel that can provide good communication quality. In other words, the transmitting device according to the embodiment can provide good communication quality even when there is significant interference with the signal.

[0041] Note that this sounding process can be performed in the same way even if the number of transmitting antennas is increased. As shown in FIG. 18, the signals transmitted from two transmitting antennas 1 and 2 are designated as transmitting antenna 1 signals and transmitting antenna 2 signals, and the transmitting antenna 1 signals and transmitting antenna 2 signals are pulse-type signals that are transmitted with timing staggered so that the pulses of each signal do not overlap. This enables separate signal detection and maintains the interference observation period between pulses, making it possible to perform a sounding process similar to the above-mentioned sounding process. Note that the signal for one antenna may be time-shifted to prevent interference between the signals on the time axis, or the signals may be superimposed assuming that the pulse position of the signal transmitted from one antenna is the same as the pulse position of the signal transmitted from the other antenna when transmission path coding such as STBC (Space-Time Block Coding) coding is performed. FIG. 18 is a diagram showing an example of signals transmitted from two transmitting antennas 1 and 2. The horizontal axis of FIG. 18 represents time, and the vertical axis of FIG. 18 represents power.

[0042] Next, the hardware configuration of the transmitter and receiver according to the embodiment will be described. The transmitting antenna 65, the receiving antennas 66 and 141, and the transmitting and receiving antennas 154, 156, 164, and 165 are each realized by an antenna device. Each component of the transmitter and receiver is realized by a processing circuit. The processing circuit may be realized by a dedicated circuit or by a control circuit using a CPU. When the processing circuit is realized by a dedicated circuit, as shown in FIG. 19, each of the transmitter and receiver has a processing circuit 91 corresponding to each component, and each function of the transmitter and receiver is realized by the processing circuit 91. FIG. 19 is a diagram showing a processing circuit 91 when each function of the transmitter and receiver according to the embodiment is realized by the processing circuit 91. When the processing circuit is realized by a dedicated circuit, the processing circuit 91 may be, 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.

[0043] When the processing circuit is realized using a CPU, as shown in FIG. 20 , each of the transmitter and receiver has a CPU 92 and a memory 93, and functions are written as programs stored in the memory 93. The CPU 92 realizes functions corresponding to the programs by reading and executing the programs stored in the memory 93. FIG. 20 is a diagram showing the CPU 92 when the functions of each of the transmitter and receiver according to the embodiment are realized by the CPU 92. The CPU 92 may be replaced with a processing system, an arithmetic system, a microprocessor, or a DSP (Digital Signal Processor). The memory 93 may be, for example, a non-volatile or volatile semiconductor memory such as a random access memory (RAM), a read-only memory (ROM), a flash memory, an erasable programmable read-only memory (EPROM), or an electrically erasable programmable read-only memory (EEPROM®), a magnetic disk, a flexible disk, an optical disk, a compact disk, a minidisk, or a digital versatile disk (DVD). It should be noted that some of the functions of the transmitter and receiver may be realized by dedicated circuits, and the remaining functions may be realized by a program and the CPU 92.

[0044] 21 is a diagram showing a control circuit 94 that controls the operations performed by the transmitter according to the embodiment. Specifically, the control circuit 94 causes the communication device to perform the following operations: equally dividing a communication band into two or more subbands in the frequency domain and assigning the same signal to each of multiple subbands generated by the equal division to generate a frequency-repeated signal; generating a pulsed transmission signal in the time domain based on the obtained frequency-repeated signal; and transmitting the generated transmission signal. The operations performed by the receiver according to the embodiment may also be controlled by a control circuit equivalent to the control circuit 94. the control circuit that controls the operations performed by the receiver causes the receiver to perform the following operations: receive a received signal including a known signal sequence that becomes pulse-shaped in the time domain due to frequency repetition; assume sample positions in the received signal that will become null and extract the null positions as sections containing only the interference signal; perform a discrete Fourier transform on the extracted section containing only the interference signal to obtain a frequency spectrum; perform frequency analysis on the obtained frequency spectrum and measure the amount of interference power of each of a plurality of sub-bands obtained by dividing the communication bandwidth; select a sub-band from the obtained plurality of amounts of interference power that corresponds to an amount of interference power that is equal to or less than a predetermined amount; extract the selected sub-band from the received signal and perform signal detection by correlation processing between the extracted sub-band and a known signal; measure the signal-to-noise-interference ratio based on the results of the signal detection; measure the signal power of the selected sub-band at the timing when signal detection is performed; measure the signal-to-noise-interference ratio for each sub-band based on the amount of interference power measured for each sub-band and the signal power measured at the timing when signal detection is performed; and feed back the measurement results of the signal-to-noise-interference ratio for each sub-band to the transmitter.

[0045] 22 is a diagram showing a program storage medium 95 storing a program for controlling a transmitter according to an embodiment. The program causes the transmitter to perform the following operations: equally dividing a communication band into two or more subbands in the frequency domain, assigning the same signal to each of a plurality of subbands generated by the equal division, thereby generating a frequency-repeated signal; generating a pulsed transmission signal in the time domain based on the obtained frequency-repeated signal; and transmitting the generated transmission signal. The receiver according to the embodiment may also be controlled by a program stored in a program storage medium equivalent to program storage medium 95. the program causes the receiver to perform the following operations: receive a received signal including a known signal sequence that becomes pulse-shaped in the time domain due to frequency repetition; assume sample positions in the received signal that will become null and extract the null positions as sections containing only the interference signal; perform a discrete Fourier transform on the extracted section containing only the interference signal to obtain a frequency spectrum; perform frequency analysis on the obtained frequency spectrum and measure the amount of interference power of each of a plurality of sub-bands obtained by dividing the communication bandwidth; select a sub-band from the obtained plurality of amounts of interference power that corresponds to an amount of interference power that is equal to or less than a predetermined amount; extract the selected sub-band from the received signal and perform signal detection by correlation processing between the extracted sub-band and a known signal; measure the signal-to-noise-interference ratio based on the results of the signal detection; measure the signal power of the selected sub-band at the timing when signal detection is performed; measure the signal-to-noise-interference ratio for each sub-band based on the amount of interference power measured for each sub-band and the signal power measured at the timing when signal detection is performed; and feed back the measurement results of the signal-to-noise-interference ratio for each sub-band to the transmitter.

[0046] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, and parts of the configurations may be omitted or modified without departing from the spirit of the invention. [Explanation of symbols]

[0047] 61,151,161 Communication parameter selection unit, 62 Known sequence generation unit, 63 Frequency repetition unit, 64 IDFT unit, 65 Transmitting antenna, 66,141 Receiving antenna, 67,142 Interference signal section separation unit, 68 DFT unit, 69,144 Interference measurement unit, 91 Processing circuit, 92 CPU, 93 Memory, 94 Control circuit, 95 Program storage medium, 143 FFT unit, 145,610 Signal detection CH selection unit, 146,611 Signal detection unit, 147,612 SINR measurement unit, 148,613 Average power measurement unit, 152,162 Data modulation unit, 153,157,163,166 Switch, 154,156,164,165 Transmitting and receiving antenna, 155,169 Sounding result analysis unit, 158,167 Data demodulation section, 159,168 Notification signal generation section.

Claims

1. a receiving antenna for receiving a received signal including a known signal sequence that becomes a pulse in the time domain due to frequency repetition; an interference signal section separation unit that assumes a sample position that becomes null in the received signal received by the receiving antenna and extracts the null position as a section containing only an interference signal; a discrete Fourier transform unit that performs a discrete Fourier transform on the section containing only the interference signal extracted by the interference signal section separation unit to obtain a frequency spectrum; an interference measurement unit that performs frequency analysis on the frequency spectrum obtained by the discrete Fourier transform unit and measures the amount of interference power in each of a plurality of sub-bands obtained by dividing a communication bandwidth; a signal detection channel selection unit that selects a subband corresponding to an interference power amount that is equal to or less than a predetermined amount from among the plurality of interference power amounts obtained by the interference measurement unit; a signal detection unit that extracts the subband selected by the signal detection channel selection unit from the received signal received by the receiving antenna and performs signal detection by correlation processing between the extracted subband and the known signal sequence; a signal-to-interference-plus-noise ratio measurement unit that measures a signal-to-interference-plus-noise ratio based on a result of the signal detection performed by the signal detection unit; Transmitter not included the signal-to-interference-noise ratio measurement unit measures the signal-to-interference-noise ratio for each subband based on the amount of interference power measured for each subband and the signal power measured at the timing when the signal detection is performed; A measurement result of the signal-to-noise-and-interference ratio for each of the subbands measured by the signal-to-noise-and-interference ratio measurement unit is fed back to a transmitter. A communication device comprising:

2. the signal-to-interference-noise ratio measurement unit measures the signal-to-interference-noise ratio for a received signal including a known signal sequence that is the pulse type for each of a plurality of communication parameters as a sounding sequence; The information on the signal-to-interference-plus-noise ratio obtained by the signal-to-interference-plus-noise ratio measurement unit is accumulated and analyzed, and optimal communication parameters are determined.

2. The communication device according to claim 1.

3. receiving a received signal including a known signal sequence that is pulse-shaped in the time domain due to frequency repetition; A step of assuming a sample position in the received signal that becomes null and extracting the null position as a section containing only an interference signal; performing a discrete Fourier transform on the section containing only the extracted interference signal to obtain a frequency spectrum; performing a frequency analysis on the obtained frequency spectrum and measuring an amount of interference power in each of a plurality of sub-bands obtained by dividing the communication bandwidth; selecting a subband corresponding to an interference power amount that is equal to or less than a predetermined amount from among the plurality of interference power amounts obtained; extracting the selected sub-band from the received signal and performing signal detection by correlation processing between the extracted sub-band and the known signal sequence; measuring a signal-to-noise-and-interference ratio based on the signal detection results; and feeding back the signal-to-noise-and-interference ratio measurement result for each of the sub-bands to a transmitter; In the step of measuring the signal-to-interference-plus-noise ratio, the signal-to-interference-plus-noise ratio for each subband is measured based on the amount of interference power measured for each subband and the signal power measured at the timing when the signal detection is performed. A communication method comprising:

4. In the step of measuring the signal-to-interference-plus-noise ratio, the signal-to-interference-plus-noise ratio is measured for a received signal including a known signal sequence that is the pulse type for each of a plurality of communication parameters; The obtained signal-to-noise-and-interference ratio information is accumulated and analyzed to determine optimal communication parameters.

4. The communication method according to claim 3.

5. receiving a received signal including a known signal sequence that becomes pulse-shaped in the time domain due to frequency repetition; An operation of assuming a sample position that becomes null in the received signal and extracting the null position as a section containing only an interference signal; an operation of performing a discrete Fourier transform on a section containing only the extracted interference signal to obtain a frequency spectrum; an operation of performing a frequency analysis on the obtained frequency spectrum and measuring an amount of interference power in each of a plurality of sub-bands obtained by dividing the communication bandwidth; an operation of selecting a subband corresponding to an interference power amount that is equal to or less than a predetermined amount from among the plurality of interference power amounts obtained; an operation of extracting the selected sub-band from the received signal and performing signal detection by correlation processing between the extracted sub-band and the known signal sequence; an operation of measuring a signal-to-noise-and-interference ratio based on the result of the signal detection; An operation of measuring the signal-to-interference-noise ratio for each subband based on the interference power amount measured for each subband and the signal power measured at the timing when the signal detection is performed; and an operation of feeding back the measured signal-to-noise-and-interference ratio for each of the subbands to a transmitter; A control circuit that causes a communication device to implement the above.

6. A program storage medium storing a program for controlling a communication device, The program receiving a received signal including a known signal sequence that becomes pulse-shaped in the time domain due to frequency repetition; An operation of assuming a sample position that becomes null in the received signal and extracting the null position as a section containing only an interference signal; an operation of performing a discrete Fourier transform on a section containing only the extracted interference signal to obtain a frequency spectrum; an operation of performing a frequency analysis on the obtained frequency spectrum and measuring an amount of interference power in each of a plurality of sub-bands obtained by dividing the communication bandwidth; an operation of selecting a subband corresponding to an interference power amount that is equal to or less than a predetermined amount from among the plurality of interference power amounts obtained; an operation of extracting the selected sub-band from the received signal and performing signal detection by correlation processing between the extracted sub-band and the known signal sequence; an operation of measuring a signal-to-noise-and-interference ratio based on the result of the signal detection; An operation of measuring the signal-to-interference-noise ratio for each subband based on the interference power amount measured for each subband and the signal power measured at the timing when the signal detection is performed; and an operation of feeding back the measured signal-to-noise-and-interference ratio for each of the subbands to a transmitter; A program storage medium that causes a communication device to execute the program.

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