JP2006173764A - Multicarrier signal demodulation circuit and multicarrier signal demodulation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multicarrier signal demodulation circuit and a multicarrier signal demodulation method capable of demodulating signals subjected to space division multiplex transmission by establishing timing synchronization with high accuracy from signals transmitted independently by each packet. <P>SOLUTION: A multicarrier signal demodulation circuit includes: a timing detection means for receiving a multicarrier modulation signal from one of a plurality of reception antennas and detecting a timing by an autocorrelation arithmetic operation or a cross-correlation arithmetic operation; a timing discrimination means for discriminating a reception timing from a timing detection signal; a plurality of GI elimination means for receiving multicarrier-modulated received signals from the plurality of reception antennas and using a reception timing discrimination signal to eliminate the GI respectively from each received signal; a plurality of multicarrier demodulation means for respectively applying multicarrier demodulation to output signals of the plurality of GI elimination means; and a signal detection means for receiving subcarrier signals outputted from the plurality of multicarrier demodulation means and detecting transmission signals from the signals subjected to space division multiplex transmission. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a multicarrier signal demodulation circuit that demodulates a multicarrier signal in a digital wireless communication system. In particular, the present invention relates to a multicarrier signal demodulation circuit and a multicarrier signal demodulation method corresponding to an OFDM (Orthogonal Frequency Division Multiplexing) modulation scheme.

  The multicarrier modulation scheme is a wireless transmission scheme that transmits information using a plurality of subcarriers. The input data signal is modulated by QPSK (Quadrature phase shift keying) or the like for each subcarrier. Among the multicarrier modulation schemes, the OFDM modulation scheme in which the frequencies of the subcarriers are orthogonal is widely used in wireless communication systems where multipath propagation is a problem.

  The OFDM modulation method is a modulation method that is not easily affected by multipath and is suitable for high-speed transmission. However, in order to further improve the transmission speed, a spatial division multiplexing method that simultaneously transmits from a plurality of transmission antennas at the same frequency is used. It is being considered. This space division multiplexing system is also called SDM (Space division multiplexing) transmission or MIMO (Multi input multi output) transmission due to the characteristics of a transmission path using a plurality of transmission antennas.

  FIG. 12 shows a configuration example of a space division multiplex transmission system. In the figure, the transmitter is configured to transmit a transmission signal of each data series subjected to serial / parallel conversion (S / P) from a transmission antenna (here, four) via an encoder, an interleaver, and an OFDM modulator. The receiver processes the received signals of the receiving antennas (here, four) with an OFDM-MIMO demodulator, and outputs each data series by performing parallel-serial conversion (P / S) via a deinterleaver and a decoder. It is a configuration. In addition, when space division multiplexing transmission is applied to OFDM, it is necessary to transmit the transmission timing of the OFDM symbol in synchronization.

  In space division multiplex transmission, the transmission rate can be increased according to the number of antennas without increasing the frequency bandwidth. For example, when the transmission rate is doubled, simultaneous transmission is performed from two antennas. The number of antennas on the receiving side is usually the same as the number of antennas used on the transmitting side. However, the signal detection method used in the demodulation circuit (Zero-forcing (ZF) method, Minimum mean square error (MMSE) method, Ordered successive detection (OSD) method, Maximum Likelihood detection (MLD) method, etc.)) However, for example, when an MLD system that realizes an excellent error rate is used, demodulation is possible even if reception is performed with one receiving antenna. On the other hand, when the number of reception antennas is larger than the number of transmission antennas, a reception diversity effect can be obtained.

  Here, these signal detection methods used in the demodulation circuit are also called signal separation or interference canceller, and the essence is to detect a transmission signal for each data series from the multiplexed signal. In order to receive this multiplexed OFDM signal, it is essential to demodulate the received signal in synchronism with the received signal and correct various distortions etc. from the received signal.

  FIG. 13 shows a configuration example of a conventional multicarrier signal demodulation circuit (Non-Patent Document 1). Here, a case where two multiplexed received signals for processing two data series are input is shown.

  In the figure, a reception signal level detection circuit 81 receives a reception OFDM signal S81 from each reception antenna, performs detection comparison of the reception signal level, and outputs a detection comparison result signal S82. The synchronization processing path selection circuit 82 receives the reception OFDM signal S81 from each reception antenna, and selects one reception system having a high reception level according to the detection comparison result signal S82. The selected received OFDM signal S83 is input to the delay circuit 83, the delay circuit output signal S84 is input to the complex conjugate circuit 84, and the complex conjugate signal S85 is output. The multiplication circuit 85 performs a multiplication process that is an autocorrelation operation between the selected received OFDM signal S83 and the complex conjugate signal S85, and outputs a multiplication result signal S86. The coarse timing detection circuit 86 receives the multiplication result signal S86 and performs coarse timing detection based on the autocorrelation calculation.

  On the other hand, the matched filter circuit 87 receives the selected received OFDM signal S83 and performs timing detection based on the autocorrelation calculation result within the search range corresponding to the coarse timing signal S77. The precision timing detection circuit 88 receives the matched filter output signal S88, performs precision timing determination, and outputs the obtained timing signal S89.

As described above, the conventional multicarrier signal demodulating circuit first detects the received signal level of each receiving system in order to detect the timing signal of the space division multiplexed signal, and performs timing detection according to the received signal level. The timing detection process is performed by limiting to one system. In addition, timing detection in two stages, coarse timing detection and fine timing detection, is performed.
Hiraaki, et al., “Timing / Frequency Synchronization Method in MIMO-OFDM System”, IEICE, IEICE Technical Report RCS2003-21

  In a conventional wireless LAN system (IEEE802.11a, IEEE802.11g, etc.), signal transmission / reception is performed in a completely independent packet mode for each packet. In such a packet mode, it is necessary to detect and correct the carrier frequency error only from the preamble signal at the head of the received packet. Furthermore, it is necessary to detect and correct phase rotation such as control error in carrier frequency error correction using the pilot signal and pilot subcarrier signal.

  FIG. 14 shows a packet format using an OFDM signal defined by IEEE802.11a. The leading PLCP preamble is a known fixed pattern signal of 16 μsec required for the reception synchronization processing of the radio packet signal. A short preamble (8 μsec) composed of 10 short training symbols is defined as a signal obtained by thinning the number of subcarriers to 12, and is mainly used for AFC coarse adjustment, timing detection, and the like. A long preamble (8 μsec) composed of two OFDM symbols is defined as a signal in which a known pattern is assigned to all 52 subcarriers, and is mainly used for AFC fine adjustment and channel estimation. Next, a header signal called SIGNAL that transmits the transmission speed and packet length of the data part is transmitted. The header signal is composed of one OFDM symbol.

  FIG. 15 shows the IEEE802.11a packet format in a two-dimensional representation of the frequency axis / time axis. The shaded portion is a known training signal. Four pilot subcarriers, which are known training signals, are also inserted into the OFDM symbol of the data part. On the receiving side, phase tracking processing is performed to detect phase rotation common to all subcarriers by observing the pilot subcarriers and correct the rotation of the reference phase.

  By the way, a wireless LAN system using space division multiplex transmission that realizes high-speed transmission of wireless packets while realizing backward compatibility with conventional wireless LAN systems (IEEE802.11a, IEEE802.11g, etc.) is desired. ing. In a wireless LAN using this space division multiplex transmission, a signal conforming to IEEE802.11a is an OFDM signal before being multiplexed.

  Thus, for example, in order to demodulate a space division multiplexed signal while ensuring backward compatibility with the IEEE802.11a system, a packet signal having a common part with the IEEE802.11a signal shown in FIG. A function for demodulating the signal is required. FIG. 17 shows a packet format having a common part with the IEEE802.11a signal in a two-dimensional representation of the frequency domain and the time domain. However, although the number of MIMO preambles is shown as 2, it varies depending on system requirements and the number of multiplexed data. In order to establish synchronization from a space-division multiplexed signal and perform demodulation, it is necessary to perform timing detection using this leading preamble signal.

  However, the conventional multicarrier signal demodulation circuit shown in FIG. 13 is premised on communication in a continuous mode in which data is continuously transmitted / received, not in a packet mode in which data is transmitted / received independently. Further, when establishing timing synchronization, two-stage signal processing of coarse timing detection and fine timing detection is required, and there is a problem that the circuit scale and the amount of signal processing are increased, resulting in an increase in power consumption. Further, since the detection timing of the carrier frequency error is not fixed before the precise timing is detected, it is necessary to delay the reception signal. Due to this delay time, the time for returning the response signal is delayed, and there is a problem that the throughput is lowered in the operation in the packet mode at the single frequency applied in the wireless LAN.

  In addition, the conventional multi-carrier signal demodulation circuit assumes a frame structure in a continuous mode based on a unique preamble, so backward compatibility with conventional wireless LAN systems (such as IEEE802.11a and IEEE802.11g) There is also a problem that cannot be secured.

  Further, in a wireless LAN, an inexpensive oscillator is often used as a demodulator for cost reduction. With this inexpensive oscillator, the carrier frequency error becomes large. However, when the carrier frequency error is large in the conventional multicarrier signal demodulation circuit, there is a problem that the timing detection accuracy in the timing detection circuit deteriorates.

  In the conventional multicarrier signal demodulation circuit, the reception system used for the reception process is narrowed down to one according to the reception level of the signals received from the plurality of reception antennas. However, a low reception level in timing detection does not necessarily lead to characteristic deterioration. Although the timing detection accuracy can be improved by effectively utilizing the information of a plurality of reception systems, the conventional configuration sometimes uses only one reception system, so that the timing detection accuracy may deteriorate.

  The present invention secures backward compatibility with the existing system for each of the above-mentioned problems, establishes timing synchronization with high accuracy from a signal transmitted independently for each packet, and performs space division multiplex transmission. An object of the present invention is to provide a multicarrier signal demodulating circuit and a multicarrier signal demodulating method capable of demodulating the received signal.

  According to a first aspect of the present invention, there is provided timing detection means for inputting a received signal that has been subjected to multi-carrier modulation from one of the plurality of reception antennas, and performing timing detection by autocorrelation calculation or cross-correlation calculation; Timing determination means for determining the reception timing from the received timing detection signal and multicarrier modulated reception signals from a plurality of reception antennas, and using the reception timing determination signal obtained by the timing determination means, A plurality of GI removal means for removing GI, a plurality of multicarrier demodulation means for performing multicarrier demodulation on the output signals of the plurality of GI removal means, and subcarrier signals output from the plurality of multicarrier demodulation means Input and detect transmission signal from space division multiplexed signal And a that signal detection means.

  In the present invention, when a multicarrier signal subjected to space division multiplexing is received by a plurality of reception systems, it is possible to perform symbol removal by performing GI removal using reception timing detected by any one reception system.

  The second invention is obtained by a plurality of timing detection means that inputs multicarrier-modulated reception signals from a plurality of reception antennas and performs timing detection by autocorrelation calculation or cross-correlation calculation, respectively, and a plurality of timing detection means A plurality of timing determination means for determining the reception timing from each of the timing detection signals and a multicarrier-modulated reception signal from a plurality of reception antennas, and using each reception timing determination signal obtained by the plurality of timing determination means, A plurality of GI removing means for removing GI from each received signal, a plurality of multicarrier demodulating means for performing multicarrier demodulation on the output signals of the plurality of GI removing means, and a plurality of multicarrier demodulating means, respectively. Sub-carrier signal to be input and space division multiplexed signal And a signal detecting means for detecting et transmission signal.

  In the present invention, when a multicarrier signal that has been subjected to space division multiplexing is received by a plurality of reception systems, it is possible to perform symbol removal by performing GI removal using reception timings independently detected by each reception system.

  The third invention is obtained by a plurality of timing detection means that inputs multicarrier-modulated reception signals from a plurality of reception antennas and performs timing detection by autocorrelation calculation or cross-correlation calculation, respectively, and a plurality of timing detection means. Each timing detection signal is input, among which timing determination means for determining the earliest reception timing in time, and reception timing determination obtained by inputting multi-carrier modulated reception signals from a plurality of reception antennas. A plurality of GI removal means for removing GI from each received signal using the signal, a plurality of multicarrier demodulation means for performing multicarrier demodulation on the output signals of the plurality of GI removal means, and a plurality of multicarriers, respectively. Input subcarrier signal output from demodulation means From division multiplexed signal and a signal detecting means for detecting a transmission signal.

  In the present invention, when a multicarrier signal that has been subjected to space division multiplexing is received by a plurality of reception systems, GI removal is performed using reception timing that precedes in time among the reception timings detected by each reception system. Symbol extraction can be performed.

  According to a fourth aspect of the present invention, the timing determination means in the third aspect of the present invention is configured to determine an average reception timing of each reception timing instead of determining the earliest reception timing among the reception timings.

  In the present invention, when a multicarrier signal that has been subjected to space division multiplexing is received by a plurality of receiving systems, GI removal is performed using the average reception timing of the reception timings detected by each receiving system, and symbol extraction is performed. Can do.

  In a fifth aspect, the timing determination means in the third aspect is configured to determine the latest reception timing in time among the reception timings instead of determining the earliest reception timing in time among the reception timings. And

  In this invention, when receiving a multi-carrier signal that is space-division multiplexed by a plurality of reception systems, GI removal is performed using a reception timing that is delayed in time among the reception timings detected by each reception system, Symbol extraction can be performed.

  According to a sixth invention, in the third to fifth inventions, there is provided signal level detection means for detecting signal levels of a plurality of reception signals inputted from a plurality of reception antennas, and the timing judgment means is outputted from the signal level detection means. In accordance with the signal level information of each received signal, a part of the timing detection signal obtained by the plurality of timing detection means is selected, and reception timing determination processing is performed for the selected timing detection signal.

  In this invention, it is possible to select a reception system for performing timing detection according to the reception signal level of each reception system and perform timing determination.

  According to a seventh invention, in the third to fifth inventions, there is provided signal level detection means for detecting signal levels of a plurality of reception signals inputted from a plurality of reception antennas, and the timing judgment means is outputted from the signal level detection means. In accordance with the signal level information of each received signal, the timing detection signals obtained by a plurality of timing detection means are weighted, and reception timing determination processing is performed for each weighted timing detection signal.

  In the present invention, the reception timing can be determined using the timing detection signal weighted according to the reception signal level of each reception system.

  According to an eighth invention, in the first to seventh inventions, as the timing detection means, an automatic frequency control means for detecting and correcting a carrier frequency error added to the received signal, and a cross-correlation calculation for the output signal of the automatic frequency control means And a correlation calculation means for detecting timing by the GI removal means, and the output signal of the automatic frequency control means is inputted to the GI removal means.

  In the present invention, when a multicarrier signal that has been subjected to space division multiplexing is received by a plurality of receiving systems, a carrier frequency error added to each received signal is detected and corrected, and further, a cross-correlation operation is performed. Timing detection can be performed.

  In a ninth aspect based on the eighth aspect, the correlation calculation means includes a plurality of correlation calculation means for performing timing detection by different cross-correlation calculations for each reception system, and the timing determination means includes a plurality of timing detection signals to be input. It is the structure which performs the determination process of reception timing about.

  In the present invention, when receiving a multi-carrier signal multiplexed in space division by a plurality of receiving systems, it is possible to detect a more accurate reception timing by providing a plurality of correlation calculation means for each receiving system. .

  According to a tenth aspect of the present invention, in the eighth and ninth aspects, as the correlation calculation means, the output signal of the automatic frequency control means is input, the correlation means for performing the cross-correlation calculation, and the cross-correlation signal output from the correlation means. Input complex filter means for performing filter processing on complex signal, scalar signal conversion means for converting output signal of complex filter means to scalar signal, and output signal of scalar signal conversion means, and filter processing on scalar signal A scalar filter means for performing timing detection processing means for performing timing detection based on a scalar signal output from the scalar filter means;

  In an eleventh aspect based on the third to fifth aspects, the present invention includes a delay circuit that gives different delay amounts to reception signals of a plurality of reception antennas.

  In the present invention, the timing detection can be performed after intentionally spreading the reception signals of the respective reception systems.

  Also in the multicarrier signal demodulating method of the present invention, the processing procedure of each means of the multicarrier signal demodulating circuit of the present invention is similarly executed.

  The multicarrier signal demodulating circuit and the multicarrier signal demodulating method of the present invention can ensure backward compatibility with an existing system and can detect timing from a signal transmitted independently for each packet. In addition, highly accurate timing detection using received signals of a plurality of receiving systems can be performed. As a result, the delay time required for the demodulation process can be shortened, and a decrease in throughput can be avoided. Further, highly accurate timing detection can be performed even in an environment where a carrier frequency error having a large error amount exists.

(First embodiment)
FIG. 1 shows a first embodiment of a multicarrier signal demodulation circuit of the present invention. Here, the case where both the number of reception antennas and the number of data series are two is shown, but when both are three or more, the present invention can be similarly applied to the case where the number of reception antennas is the number of data series or more (in the embodiments described below). The same).

  In the figure, multicarrier-modulated reception signals S11-1 and S11-2 received by two reception antennas are input to GI removal circuits 11-1 and 11-2. One received signal (here, S11-1) is input to the timing detection circuit 12, and timing detection is performed by autocorrelation calculation or cross-correlation calculation. The timing detection signal S12 is input to the timing determination circuit 13, and the reception timing is determined. The GI removal circuits 11-1 and 11-2 remove the GI from the reception signals S11-1 and S11-2 based on the reception timing determination signal S13, respectively, and extract OFDM symbols. The OFDM symbol signals S14-1 and S14-2 output from the GI removal circuits 11-1 and 11-2 are input to the FFT circuits 14-1 and 14-2, respectively, where multicarrier demodulation is performed, and subcarrier signals are output. S15-1 and S15-2 are output. The signal detection circuit 15 performs signal detection on the spatial division multiplexed subcarrier signals S15-1 and S15-2 and outputs data symbol signals S16-1 and S16-2 for each data series.

  Here, when the timing detection circuit 12 performs timing detection using autocorrelation calculation, the timing determination circuit 13 is configured to determine the reception timing when the timing detection signal S12 exceeds a predetermined threshold, or the timing The detection timing can be continuously searched until the detection signal S13 exceeds a predetermined threshold and the maximum value is detected, and when the maximum value is detected, the position can be determined as the reception timing.

  When the timing detection circuit 12 performs timing detection using cross-correlation calculation, the timing determination circuit 13 is configured to determine when the timing detection signal S12 exceeds a predetermined threshold as reception timing, or repeatedly transmit A threshold can be set for a signal obtained by adding the peak values of the cross-correlation calculation obtained from the preamble signal to be received, and the reception timing can be determined when the threshold is exceeded.

  Further, when the FFT window is opened from the reception timing obtained from each result of the autocorrelation calculation or the cross correlation calculation, in order to prevent characteristic deterioration in the multipath environment, the FFT is performed forward in time from the determined reception timing. You may make it open a window.

(Second Embodiment)
FIG. 2 shows a second embodiment of the multicarrier signal demodulation circuit of the present invention. In the figure, multicarrier-modulated reception signals S11-1 and S11-2 received by two reception antennas are input to GI removal circuits 11-1 and 11-2. The received signals S11-1 and S11-2 are input to timing detection circuits 12-1 and 12-2, and timing detection is performed by autocorrelation calculation or crosscorrelation calculation, respectively. The detected timing detection signals S12-1 and S12-2 are input to the timing determination circuits 13-1 and 13-2, respectively, and the reception timing is determined. The GI removal circuits 11-1 and 11-2 remove the GI from the reception signals S11-1 and S11-2 based on the reception timing determination signals S13-1 and S13-2, respectively, and extract OFDM symbols. . The OFDM symbol signals S14-1 and S14-2 output from the GI removal circuits 11-1 and 11-2 are input to the FFT circuits 14-1 and 14-2, respectively, where multicarrier demodulation is performed, and subcarrier signals are output. S15-1 and S15-2 are output. The signal detection circuit 15 performs signal detection on the spatial division multiplexed subcarrier signals S15-1 and S15-2 and outputs data symbol signals S16-1 and S16-2 for each data series.

  The timing detection circuits 12-1 and 12-2 and the timing determination circuits 13-1 and 13-2 in the present embodiment are configured to operate independently for each reception system, but the configuration is the same as in the first embodiment. The same as described.

(Third embodiment)
FIG. 3 shows a third embodiment of the multicarrier signal demodulation circuit of the present invention. In the figure, multicarrier-modulated reception signals S11-1 and S11-2 received by two reception antennas are input to GI removal circuits 11-1 and 11-2. The received signals S11-1 and S11-2 are input to timing detection circuits 12-1 and 12-2, and timing detection is performed by autocorrelation calculation or crosscorrelation calculation, respectively. The detected timing detection signals S12-1 and S12-2 are input to the preceding timing determination circuit 21, and the reception timing is determined. The GI removal circuits 11-1 and 11-2 remove the GI from the reception signals S11-1 and S11-2 based on the reception timing determination signal S21, respectively, and extract OFDM symbols. The OFDM symbol signals S14-1 and S14-2 output from the GI removal circuits 11-1 and 11-2 are input to the FFT circuits 14-1 and 14-2, respectively, where multicarrier demodulation is performed, and subcarrier signals are output. S15-1 and S15-2 are output. The signal detection circuit 15 performs signal detection on the spatial division multiplexed subcarrier signals S15-1 and S15-2 and outputs data symbol signals S16-1 and S16-2 for each data series.

  The preceding timing determination circuit 21 receives the timing detection signals S12-1 and S12-2 and determines the earliest reception timing among them. For example, the timing at which one of the timing detection signals S12-1 and S12-2 exceeds a predetermined threshold is determined as the reception timing, and the FFT window is opened. Other configurations and operations are the same as those in the first embodiment.

(Fourth embodiment)
FIG. 4 shows a fourth embodiment of the multicarrier signal demodulation circuit of the present invention. In the figure, multicarrier-modulated reception signals S11-1 and S11-2 received by two reception antennas are input to GI removal circuits 11-1 and 11-2. The received signals S11-1 and S11-2 are input to timing detection circuits 12-1 and 12-2, and timing detection is performed by autocorrelation calculation or crosscorrelation calculation, respectively. The detected timing detection signals S12-1 and S12-2 are input to the average timing determination circuit 22 to determine the reception timing. The GI removal circuits 11-1 and 11-2 remove the GI from the reception signals S11-1 and S11-2 based on the reception timing determination signal S22, respectively, and extract OFDM symbols. The OFDM symbol signals S14-1 and S14-2 output from the GI removal circuits 11-1 and 11-2 are input to the FFT circuits 14-1 and 14-2, respectively, where multicarrier demodulation is performed, and subcarrier signals are output. S15-1 and S15-2 are output. The signal detection circuit 15 performs signal detection on the spatial division multiplexed subcarrier signals S15-1 and S15-2 and outputs data symbol signals S16-1 and S16-2 for each data series.

  The average timing determination circuit 12 receives the timing detection signals S12-1 and S12-2 and determines a reception timing that is a temporal average value of each reception timing. Other configurations and operations are the same as those in the first embodiment.

(Fifth embodiment)
FIG. 5 shows a fifth embodiment of the multicarrier signal demodulation circuit of the present invention. In the figure, multicarrier-modulated reception signals S11-1 and S11-2 received by two reception antennas are input to GI removal circuits 11-1 and 11-2. The received signals S11-1 and S11-2 are input to timing detection circuits 12-1 and 12-2, and timing detection is performed by autocorrelation calculation or crosscorrelation calculation, respectively. The detected timing detection signals S12-1 and S12-2 are input to the backward timing determination circuit 23, and the reception timing is determined. The GI removal circuits 11-1 and 11-2 remove the GI from the reception signals S11-1 and S11-2 based on the reception timing determination signal S23, respectively, and extract OFDM symbols. The OFDM symbol signals S14-1 and S14-2 output from the GI removal circuits 11-1 and 11-2 are input to the FFT circuits 14-1 and 14-2, respectively, where multicarrier demodulation is performed, and subcarrier signals are output. S15-1 and S15-2 are output. The signal detection circuit 15 performs signal detection on the spatial division multiplexed subcarrier signals S15-1 and S15-2 and outputs data symbol signals S16-1 and S16-2 for each data series.

  The backward timing determination circuit 23 receives the timing detection signals S12-1 and S12-2 and determines the latest reception timing in time. Other configurations and operations are the same as those in the first embodiment.

(Sixth embodiment)
FIG. 6 shows a sixth embodiment of the multicarrier signal demodulation circuit of the present invention. The feature of this embodiment is that in the third embodiment, a signal level detection circuit 31 for detecting the signal level of each received signal S11-1, S11-2 is provided, and signal level information having signal level information of each received signal. The signal S31 is input to the preceding timing determination circuit 21.

  The timing determination circuit 21 selects the timing detection signals S12-1 and S12-2 in each reception system according to the signal level information signal S31, and performs reception timing determination processing based on the selected timing detection signals. For example, when there are four reception systems, two systems are selected from the one with the higher signal level of each reception signal, and reception timing determination processing is performed based on the timing detection signals of the two systems. The preceding timing determination circuit 21 performs weighting by multiplying the timing detection signals S12-1 and S12-2 in each reception system by a coefficient corresponding to the signal level of each reception system, and each weighted timing detection. You may make it perform the determination process of a reception timing about a signal.

  The configuration using the signal level detection circuit 31 of the present embodiment can be similarly applied to the fourth embodiment using the average timing determination circuit 22 and the fifth embodiment using the rear timing determination circuit 23. .

(Seventh embodiment)
FIG. 7 shows a seventh embodiment of the multicarrier signal demodulation circuit of the present invention. The feature of this embodiment is that the timing detection circuits 12-1 and 12-2 of the third embodiment automatically detect and correct the carrier frequency error added to the reception signals S11-1 and S11-2 of each reception system. The frequency control circuits 41-1 and 41-2 and the correlation calculation circuits 42-1 and 42-2 for detecting timing by the cross-correlation calculation for the output signals S41-1 and S41-2 are provided. The correlation calculation circuit 42-1 , 42-2, the timing detection signals S42-1 and S42-2 output from the preceding timing determination circuit 21 are input. The output signals S41-1 and S41-2 of the automatic frequency control circuits 41-1 and 41-2 are input to the GI removal circuits 11-1 and 11-2, respectively.

  By providing such automatic frequency control circuits 41-1 and 41-2, timing detection correction can be performed even when a large carrier frequency error is added to the reception signals S11-1 and S11-2 of each reception system. Furthermore, highly accurate timing detection can be performed by the cross-correlation calculation in the correlation calculation circuits 42-1 and 42-2. When the correlation calculation circuits 42-1 and 42-2 are configured to detect timing by autocorrelation calculation that can be realized with a simple circuit scale, the automatic frequency control circuits 41-1 and 41-2 are not necessarily provided. It does not have to be.

  The configuration including the automatic frequency control circuits 41-1 and 41-2 of the present embodiment includes the first and second embodiments, the fourth embodiment using the average timing determination circuit 22, and the rear timing. The present invention can be similarly applied to the fifth embodiment using the determination circuit 23 and the sixth embodiment including the signal level detection circuit 31.

(Eighth embodiment)
FIG. 8 shows an example of an eighth embodiment of the multicarrier signal demodulation circuit of the present invention. This embodiment is an example applied to the seventh embodiment, and is characterized in that a plurality of correlation operation circuits 42-1 and 42-2 are provided for each reception system. The correlation calculation circuits 41-11 and 41-12 receive the output signal S41-1 of the automatic frequency control circuit 41-1, and detect timing by mutually different correlation calculations. The correlation calculation circuits 41-21 and 41-22 receive the output signal S41-2 of the automatic frequency control circuit 41-2 and detect timing by mutually different correlation calculations. The preceding timing determination circuit 21 includes timing detection signals S42-11, S42-12, S42-21, and S42-22 output from the correlation calculation circuits 41-11 and 41-12 and the correlation calculation circuits 41-21 and 41-22. And the reception timing is determined according to the algorithm shown in the third embodiment.

  The configuration including a plurality of correlation operation circuits for each reception system of the present embodiment is the same as that of the fourth embodiment using the average timing determination circuit 22 and the fifth embodiment using the rear timing determination circuit 23, and further the signal level. The present invention can be similarly applied to the sixth embodiment including the detection circuit 31.

  FIG. 9 shows a configuration example of the correlation calculation circuit 42. In the figure, a correlation circuit 51 is composed of, for example, a matched filter, and receives an output signal S41 of an automatic frequency control circuit 41 to perform a cross correlation calculation. The complex filter circuit 52 uses, for example, an IIR (Infinite impulse response) filter, receives the cross-correlation signal S51 repeatedly output from the correlation circuit 51, and performs filter processing for each IQ channel that is a complex signal. By using the IIR filter, it is possible to use the highly reliable rear portion of the short preamble signal that is repeatedly transmitted. The scalar signal conversion circuit 53 converts the output signal S52 of the complex filter circuit 52 into a scalar signal S53. As the scalar signal S53, an amplitude signal and a power signal converted from a complex signal can be considered.

  The scalar filter circuit 54 uses, for example, an FIR (Finite impulse response) filter, receives the scalar signal S53 output from the scalar signal conversion circuit 53, and performs filter processing on the scalar signal. By using the FIR filter, it is possible to collect delayed waves that arrive with a time delay due to multipath interference and improve the reception level. The timing detection processing circuit 55 performs timing detection based on the scalar signal S54 output from the scalar filter circuit 54.

  FIG. 10 shows a configuration example of the timing detection processing circuit 55. In the figure, the scalar signal S54 output from the scalar filter circuit 54 is input to the delay circuit 61, the output signal S61 is input to the delay circuit 62, and the output signal S62 is input to the level determination circuit 63-1. 11 is compared with a predetermined threshold value (for example, the threshold value of the scalar signal itself) shown in FIG. The delay time of the delay circuits 61 and 62 is set to the repetition time of the short preamble signal. Further, the output signal S61 of the delay circuit 61 is input to the level determination circuit 63-2 and compared with a predetermined threshold value shown in FIG.

  On the other hand, the scalar signal S54 and the output signal S61 of the delay circuit 61 are input to the division circuit 64, and the division operation of S61 / S54 is performed. The output signal S64 of the division circuit 64 is input to the level determination circuit 63-3 and is compared with a predetermined threshold value corresponding to the ratio obtained from the division result. For example, the level determination signal is output when the value of S61 / S54 indicating how much the delay circuit 61 has fallen from the scalar signal S54 is smaller than the threshold value. The condition determination circuit 65 receives the output signals S63-1 to S63-3 of the level determination circuits 63-1 to 63-3, and outputs the timing detection signal S42 when the AND conditions of all the input signals are satisfied.

  The determination operation shown in FIG. 11 utilizes the fact that the output decreases when moving from the short preamble signal to the long preamble signal. Here, the threshold value is exceeded twice in succession, and the ratio obtained from the division result falls below the threshold value. It is assumed that the timing is detected only when

(Ninth embodiment)
FIG. 12 shows a ninth embodiment of the multicarrier signal demodulation circuit of the present invention. The feature of the present embodiment is that, in the third embodiment, there is provided a delay circuit 71 that gives different delays to the received signals S11-1 and S11-2. Here, the delay circuit 71 is arranged to give a delay to the received signal S11-2. As a result, the delays of the received signals S11-1 and S11-2 are intentionally spread and can be used for timing determination in the preceding timing determination circuit 21.

  In each of the embodiments described above, the automatic frequency control circuits 41-1 and 41-2 and the timing detection circuits 12-1 and 12-2 (correlation calculation circuits 42-1 and 42-2) use a short preamble signal. By performing carrier frequency error detection correction and timing detection, the delay time can be shortened. Note that timing detection may be performed using a long preamble signal.

  The timing detection circuits 12-1 and 12-2 (correlation calculation circuits 42-1 and 42-2) are based on timing detection by autocorrelation calculation giving priority to circuit scale reduction and cross-correlation calculation giving priority to timing detection accuracy. It corresponds to both timing detection. In either case, a short preamble signal and a long preamble signal can be used. In addition, when a cross-correlation operation is performed, a matched filter is generally applied, but the tap coefficient is not a signal waveform itself but a +1, -1 tap coefficient obtained by hard decision of the signal waveform. It is also possible to reduce the circuit scale.

  In the signal detection circuit 15 in each embodiment, simple synchronous detection is performed in the case of single transmission (the SISO signal portion in FIGS. 16 and 17). Furthermore, the ZF system, MMSE system, MLD system, OSD system, or a combination thereof, and a system in which the circuit scale of the MLD system is simplified can be applied to the space division multiplexed signal portion. In particular, signal detection based on the MLD method is also applicable to signal detection during single transmission.

  In addition, each circuit described above does not always operate, but can be operated only when necessary, so that power consumption can be reduced.

The figure which shows 1st Embodiment of the multicarrier signal demodulation circuit of this invention. The figure which shows 2nd Embodiment of the multicarrier signal demodulation circuit of this invention. The figure which shows 3rd Embodiment of the multicarrier signal demodulation circuit of this invention. The figure which shows 4th Embodiment of the multicarrier signal demodulation circuit of this invention. The figure which shows 5th Embodiment of the multicarrier signal demodulation circuit of this invention. The figure which shows 6th Embodiment of the multicarrier signal demodulation circuit of this invention. The figure which shows 7th Embodiment of the multicarrier signal demodulation circuit of this invention. The figure which shows 8th Embodiment of the multicarrier signal demodulation circuit of this invention. The figure which shows the structural example of the correlation calculating circuit. The figure which shows the structural example of the timing detection process circuit. The figure explaining the operation example of the timing detection process circuit 55. FIG. The figure which shows 9th Embodiment of the multicarrier signal demodulation circuit of this invention. The figure which shows the structural example of a space division multiplex transmission system. The figure which shows the structural example of the conventional multicarrier signal demodulation circuit. The figure which shows the packet format using the OFDM signal prescribed | regulated by IEEE802.11a. The figure which shows the packet format of IEEE802.11a by two-dimensional expression. The figure which shows the packet format used by this invention. The figure which shows the two-dimensional expression of the packet format used by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 GI removal circuit 12 Timing detection circuit 13 Timing determination circuit 14 FFT circuit 15 Signal detection circuit 21 Leading timing determination circuit 22 Average timing determination circuit 23 Backward timing determination circuit 31 Signal level detection circuit 41 Automatic frequency control circuit 42 Correlation calculation circuit 51 Correlation Circuit 52 Complex filter circuit 53 Scalar signal conversion circuit 54 Scalar filter circuit 55 Timing detection processing circuit 61 Delay circuit 62 Delay circuit 63 Level determination circuit 64 Division circuit 65 Condition determination circuit 71 Delay circuit

Claims (22)

Timing detection means for receiving a multicarrier-modulated reception signal from one of the plurality of reception antennas and performing timing detection by autocorrelation calculation or cross-correlation calculation;
Timing determination means for determining reception timing from a timing detection signal obtained by the timing detection means;
A plurality of GI removing means for inputting a reception signal subjected to multicarrier modulation from the plurality of receiving antennas and removing a guard interval (GI) from each received signal using the reception timing judgment signal obtained by the timing judgment means. When,
A plurality of multicarrier demodulation means for performing multicarrier demodulation on the output signals of the plurality of GI removal means;
A multicarrier signal demodulation circuit comprising: signal detection means for inputting a subcarrier signal output from the plurality of multicarrier demodulation means and detecting a transmission signal from the space division multiplexed signal. A plurality of timing detection means for inputting a reception signal modulated by multicarrier from a plurality of reception antennas and performing timing detection by autocorrelation calculation or cross-correlation calculation;
A plurality of timing judging means for judging the reception timing from the timing detection signals obtained by the plurality of timing detecting means;
A plurality of reception signals subjected to multi-carrier modulation are input from the plurality of reception antennas, and a plurality of reception interval determination signals obtained by the plurality of timing determination units are used to remove a guard interval (GI) from each reception signal. GI removal means;
A plurality of multicarrier demodulation means for performing multicarrier demodulation on the output signals of the plurality of GI removal means;
A multicarrier signal demodulation circuit comprising: signal detection means for inputting a subcarrier signal output from the plurality of multicarrier demodulation means and detecting a transmission signal from the space division multiplexed signal. A plurality of timing detection means for inputting a reception signal modulated by multicarrier from a plurality of reception antennas and performing timing detection by autocorrelation calculation or cross-correlation calculation;
Each timing detection signal obtained by the plurality of timing detection means is respectively input, timing determination means for determining the earliest reception timing among them,
A plurality of GI removing means for inputting a reception signal subjected to multicarrier modulation from the plurality of receiving antennas and removing a guard interval (GI) from each received signal using the reception timing judgment signal obtained by the timing judgment means. When,
A plurality of multicarrier demodulation means for performing multicarrier demodulation on the output signals of the plurality of GI removal means;
A multicarrier signal demodulation circuit comprising: signal detection means for inputting a subcarrier signal output from the plurality of multicarrier demodulation means and detecting a transmission signal from the space division multiplexed signal. The multicarrier signal demodulation circuit according to claim 3,
The multi-carrier signal demodulating circuit characterized in that the timing determination means is configured to determine an average reception timing of the reception timings instead of determining the earliest reception timing among the reception timings. . The multicarrier signal demodulation circuit according to claim 3,
The timing determination means is configured to determine the latest reception timing in time among the reception timings instead of determining the earliest reception timing in time among the reception timings. Carrier signal demodulation circuit. In the multicarrier signal demodulation circuit according to any one of claims 3 to 5,
Comprising signal level detection means for detecting signal levels of a plurality of received signals inputted from a plurality of receiving antennas;
The timing determination means selects a part of the timing detection signals obtained by the plurality of timing detection means according to the signal level information of each received signal output from the signal level detection means, and selects the selected timing detection A multicarrier signal demodulating circuit, characterized in that the receiving timing determination process is performed on a signal. In the multicarrier signal demodulation circuit according to any one of claims 3 to 5,
Comprising signal level detection means for detecting signal levels of a plurality of received signals inputted from a plurality of receiving antennas;
The timing determination unit weights the timing detection signals obtained by the plurality of timing detection units according to the signal level information of each reception signal output from the signal level detection unit, and each weighted timing detection signal A multicarrier signal demodulating circuit characterized in that the receiving timing determination process is performed on a multi-carrier signal demodulating circuit. In the multicarrier signal demodulation circuit according to any one of claims 1 to 7,
As the timing detection means,
Automatic frequency control means for detecting and correcting a carrier frequency error added to the received signal, and correlation calculation means for performing timing detection by cross-correlation calculation with respect to the output signal of the automatic frequency control means,
The multi-carrier signal demodulating circuit, wherein the output signal of the automatic frequency control means is input to the GI removal means. The multicarrier signal demodulation circuit according to claim 8,
As the correlation calculation means, comprising a plurality of correlation calculation means for performing timing detection by different cross-correlation calculation for each receiving system,
The multi-carrier signal demodulation circuit, wherein the timing determination means is configured to perform the reception timing determination process for a plurality of input timing detection signals. The multicarrier signal demodulation circuit according to claim 8 or 9,
As the correlation calculation means,
Correlation means for inputting the output signal of the automatic frequency control means and performing cross-correlation calculation;
Complex filter means for inputting a cross-correlation signal output from the correlation means and performing filter processing on a complex signal;
Scalar signal conversion means for converting the output signal of the complex filter means into a scalar signal;
A scalar filter means for inputting an output signal of the scalar signal converting means and performing a filtering process on the scalar signal;
A multi-carrier signal demodulation circuit comprising: timing detection processing means for performing timing detection based on a scalar signal output from the scalar filter means. In the multicarrier signal demodulation circuit according to any one of claims 3 to 5,
A multicarrier signal demodulation circuit comprising a delay circuit that gives different delay amounts to the reception signals of the plurality of reception antennas. Step 1 of receiving a multicarrier modulated reception signal from one of the plurality of reception antennas and detecting timing by autocorrelation calculation or cross-correlation calculation; and reception timing from the timing detection signal obtained in Step 1 Step 2 for determining
Step 3 of receiving multicarrier-modulated reception signals from the plurality of reception antennas and using the reception timing determination signal obtained in Step 2 to remove a guard interval (GI) from each reception signal;
Step 4 for performing multicarrier demodulation for each output signal obtained in Step 3;
A multi-carrier signal demodulation method comprising: inputting each subcarrier signal demodulated in step 4 and detecting a transmission signal from the space-division multiplexed signal. Step 6 of receiving multicarrier-modulated received signals from a plurality of receiving antennas and performing timing detection by autocorrelation calculation or cross-correlation calculation,
Step 7 for determining the reception timing from each timing detection signal obtained in Step 6;
Step 3 of receiving multicarrier-modulated reception signals from the plurality of reception antennas and using each reception timing determination signal obtained in Step 7 to remove a guard interval (GI) from each reception signal;
Step 4 for performing multicarrier demodulation for each output signal obtained in Step 3;
A multi-carrier signal demodulation method comprising: inputting each subcarrier signal demodulated in step 4 and detecting a transmission signal from the space-division multiplexed signal. Step 6 of receiving multicarrier-modulated received signals from a plurality of receiving antennas and performing timing detection by autocorrelation calculation or cross-correlation calculation,
Step 8 for receiving each timing detection signal obtained in Step 6 and determining the earliest reception timing among them;
Step 3 of receiving multicarrier-modulated reception signals from the plurality of reception antennas and using the reception timing determination signal obtained in Step 8 to remove a guard interval (GI) from each reception signal;
A plurality of steps 4 for performing multicarrier demodulation for each output signal obtained in step 3;
A multi-carrier signal demodulation method comprising: inputting each subcarrier signal demodulated in step 4 and detecting a transmission signal from the space-division multiplexed signal. The multicarrier signal demodulation method according to claim 14,
The step 8 determines the average reception timing of the reception timings instead of determining the earliest reception timing among the reception timings. The multicarrier signal demodulation method according to claim 14,
The step 8 determines the latest reception timing in time among the reception timings instead of determining the earliest reception timing in the reception timings. . The multicarrier signal demodulation method according to any one of claims 14 to 16,
Detecting a signal level of a plurality of reception signals input from a plurality of reception antennas;
The step 8 selects a part of the timing detection signal obtained in the step 6 according to the signal level information of each reception signal detected in the step 9, and the reception timing of the selected timing detection signal is selected. A multi-carrier signal demodulation method characterized by performing determination processing. The multicarrier signal demodulation method according to any one of claims 14 to 16,
Detecting a signal level of a plurality of reception signals input from a plurality of reception antennas;
In the step 8, the timing detection signal obtained in the step 6 is weighted according to the signal level information of each reception signal detected in the step 9, and the reception timing is determined for each weighted timing detection signal. A multicarrier signal demodulating method characterized by performing processing. The multicarrier signal demodulation method according to any one of claims 12 to 18,
As Step 6,
Performing step 61 of detecting and correcting a carrier frequency error added to the received signal;
A step 62 of performing timing detection by a cross-correlation operation on the signal corrected in the carrier frequency error in the step 61;
In the step 3, the signal after the carrier frequency error correction in the step 61 is input. The multicarrier signal demodulation method according to claim 19,
In step 62, timing detection is performed by a plurality of cross-correlation calculations that differ for each reception system,
In the step 8, the reception timing determination process is performed for a plurality of input timing detection signals. A multicarrier signal demodulation method, wherein: The multicarrier signal demodulation method according to claim 19 or 20,
The step 62 includes
Step 621 for inputting the output signal of the automatic frequency control means and performing cross-correlation calculation; Step 622 for inputting the cross-correlation signal obtained in Step 621 and performing filter processing on the complex signal;
Converting the signal obtained in step 622 into a scalar signal; 623;
Performing a filtering process on the scalar signal obtained in step 623;
And a step 625 for performing timing detection based on the scalar signal obtained in the step 624. The multicarrier signal demodulation method according to any one of claims 14 to 16,
The method of demodulating a multicarrier signal, comprising the step of giving different delay amounts to the reception signals of the plurality of reception antennas.

Images