JP4290657B2 - Spatial division multiplexed signal detection circuit and spatial division multiplexed signal detection method - Google Patents

Description

  The present invention relates to a space division multiplex signal detection circuit and method for performing signal detection from a signal transmitted by space division multiplex transmission in a digital wireless communication system. In particular, the present invention relates to a space division multiplexing signal detection circuit and method applied to an OFDM (Orthogonal Frequency Division Multiplexing) modulation method among multicarrier modulation methods.

  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. 6 shows a configuration example of a space division multiplex transmission system. In the figure, a transmitter transmits a transmission signal of each transmission system (data series) subjected to serial / parallel conversion (S / P) from a transmission antenna (here, four) via an encoder, an interleaver, and an OFDM modulator. It is a configuration. The receiver processes the received signals of the receiving antennas (here, four) with an OFDM-MIMO demodulator, and outputs each data series through parallel-serial conversion (P / S) via a deinterleaver and 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. Of course, it is also possible to transmit from one transmission antenna without multiplexing. Usually, the number of antennas on the receiving side is the same as the number of antennas used on the transmitting side.

Here, when the number of transmission antennas (the number of transmission systems) is L and the number of reception antennas (the number of reception systems) is N, the received signal R is expressed by using a matrix expression in the frequency domain and using the transfer function H of the propagation path. It can be expressed as:

  In the demodulator, the zero-forcing (ZF) method, minimum mean square error (MMSE) method, ordered successive detection are used to detect the transmission signal of each transmission system from the space-division multiplexed signal shown in Equation (1). There are (OSD) method, maximum likelihood detection (MLD) method and the like. Among them, the error rate characteristic of the MLD method is the best. The excellent error rate characteristic means that communication with a low CNR is possible, and the MLD method can also contribute to the expansion of the communication area. Further, the MLD scheme can be demodulated even if it is received by one receiving antenna. Further, when the number of reception antennas is larger than the number of transmission antennas, a reception diversity effect can be obtained.

  Here, the signal detection method for performing signal detection from a space division multiplexed signal is also called signal separation or interference canceller, but the essence is that a signal transmitted from the multiplexed signal for each transmission system (data series) is used. Is to detect. In order to perform signal detection using the MLD method, as shown in FIG. 7, synchronization processing is performed before signal detection, multicarrier demodulation processing is performed for each reception system by an FFT circuit, and a channel estimation circuit is performed by a signal detection circuit. The signal of each transmission system (data series) is detected using the channel estimation result output from. The MLD scheme is not a scheme that can be applied only to the multicarrier modulation scheme, but is a technique that can be generally applied to single carrier transmission. Here, a case where the MLD scheme is applied to a subcarrier signal after multicarrier demodulation will be described.

The signal detection principle of the MLD method is shown in the following equation.

However,
T _{L, k} = [t ₁ , t ₂ ,…, t _L ] _k ^T
Indicates the kth signal point candidate,
h ′ _i = [h _i1 , h _i2 ,…, h _iL ]
Indicates the i-row vector of the channel-estimated N × L-MIMO matrix.

  In Equation (2), maximum likelihood estimation is performed using a metric μ which is one scale. In the MLD method, the distance between signal points of the replica signal and the reception signal is calculated for each reception system. Thereafter, the distance between signal points obtained in each receiving system is added. It should be noted that signal detection by the MLD method is possible even with one receiving system, and in this case, only the result of one receiving system is used. Among the added signal point distances, the one with the shortest signal point distance is selected as the most likely combination of transmission signals. Then, the transmission signal of this combination is output as a signal detection estimation result. As described above, the MLD scheme performs all searches for all combinations of replicas of transmission signals, so that the error rate characteristics are improved and excellent communication can be realized.

  FIG. 8 shows a configuration example of a conventional space division multiplex signal detection circuit (Non-Patent Document 1). Here, a case where N reception systems are used for L transmission systems (data series) is shown.

  In the figure, N FFT (Fast Fourier Transform) circuits 81 receive a reception signal S80 of each reception system and output a subcarrier signal S81 subjected to multicarrier demodulation. The subcarrier signal S81 is a subcarrier signal that is spatially multiplexed on the propagation path when attention is paid to each data series. The space-division multiplexed subcarrier signal S81 is input to the subcarrier signal storage circuit 82 and stored for the time required for signal processing in the MLD system. Channel estimation circuit 83 estimates channel distortion of the propagation path from subcarrier signal S81, and outputs channel estimation signals S83 corresponding to L transmission systems.

On the other hand, the L transmission signal generation circuits 84 corresponding to the number of transmission systems output a transmission signal (M-value signal) S84 having a modulation multi-level number M that may be transmitted. The complex multiplier 85 performs complex multiplication of the channel estimation signal S83 and the M-value signal S84 to generate a received signal replica signal S85 corresponding to each transmission system. At this time, L complex multiplications of the same number as the L transmission systems are performed, and replica signals are respectively generated. The replica signal addition circuit 86 performs vector addition of L replica signals, and generates an addition replica signal S86 corresponding to each reception system. From this complex multiplier 85 to the replica signal adding circuit 86 is required M ^L number of combinations, the combination of the M ^L number is needed the N content is a number of received lines. In other words, the complex multiplier 85, it is necessary only ^L × M L × N.

  The signal point distance calculation circuit 87 for N reception systems calculates the signal point distance between the subcarrier signal S82 of each reception system stored in the subcarrier signal storage circuit 82 and the added replica signal S86 corresponding to each reception system. The signal point distance signal S87 is added by the calculation result adding circuit 88. This added signal S88 is inputted to the maximum likelihood estimation circuit 89 and is estimated maximum likelihood, and the signal detection is performed on the assumption that the combination of replica signals having the shortest signal point distance among the input signals is the most probable transmission signal combination. L transmission signals S89 corresponding to this are output.

As described above, the conventional space division multiplex signal detection circuit first calculates the distance between the signal points of the received signal and the replica signal for each reception system, and obtains the replica signal having the smallest distance between the signal points for the result. By selecting and outputting a signal constituting the replica signal, signal detection is performed by maximum likelihood estimation of the space division multiplexed signal.
A.van Zelst, R.van Nee and GAAwater, "Space division multiplexing (SDM) for OFDM systems", Proc. Of VTC2000-Spring, pp.1070-1074

  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 (for example, IEEE802.11a and IEEE802.11g) is studied. Has been.

  In a wireless LAN that realizes this backward compatibility and uses space division multiplexing transmission, the signal conforming to IEEE802.11a becomes an OFDM signal before being multiplexed and corresponds to an existing system. In consideration of this backward compatibility, an example of a packet format having a common part with the IEEE802.11a signal is shown in FIG. FIG. 10 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. In these packets, in order to realize backward compatibility, a preamble signal that can be demodulated by the existing system is transmitted at the beginning of the packet.

  However, since the data portion is space-division multiplexed and transmitted, the application of a high-performance signal detection method is very important for improving communication quality. Furthermore, high-performance signal detection is naturally important even when all transmitted packets are transmitted as a space-division multiplexed signal. Even in this case, it is desirable to apply the MLD method as a technique for realizing high-performance signal detection. Also, in order to realize a further increase in transmission speed, a signal having a large modulation multi-value number (for example, 64QAM) is often applied to subcarrier modulation of a signal before multiplexing.

In the conventional space division multiplexing signal detection circuit, as shown in the equation (2), all searches for the replica signal and the received signal are performed. Assuming that the number of transmission systems (the number of data series) L, the number of reception systems N, and the modulation multi-level number M of the transmission signal, the number of complex multipliers required at the time of replica signal generation is only L × M ^L × N. The circuit scale increases. In particular, when a modulation scheme having a large modulation multi-level number is applied to increase the speed, the circuit scale increases exponentially, and the influence is more serious.

  For example, the complex multiplier includes four real multipliers having a large circuit scale and an adder 2. Therefore, using many complex multipliers means that the circuit scale increases. In particular, in a wireless LAN in which a PCMCIA card or the like is frequently used, the circuit scale allowed for the PCMCIA card is limited. Furthermore, power consumption increases in proportion to the circuit scale. In particular, when considering use in a wireless LAN or the like where it is difficult to use an external power supply, an increase in power consumption accelerates battery consumption.

  The present invention makes it possible to reduce the circuit scale and realize excellent error rate characteristics even when the number of modulation multilevels becomes large, when detecting signals by receiving a space division multiplexed signal. An object of the present invention is to provide a space division multiplexed signal detection circuit and a space division multiplexed signal detection method.

The present invention is characterized in that the number of complex multipliers in the replica signal generation unit in the conventional space division multiplex signal detection circuit is reduced. In the present invention, the replica signal is considered divided into each term as shown in the equation (3).

In the conventional configuration, replica signals corresponding to all combinations to be searched are generated. That is, in order to calculate M ^L × N combinations of h ′ _i T _{L, k} , L × M ^L × N complex multipliers are required. On the other hand, in the present invention, a replica signal, which is a result of complex multiplication corresponding to each term of Expression (3), is stored in a readable / writable storage circuit such as a RAM. Specifically, the replica signal of the portion h _i1 t _1k is stored in the storage circuit. At this time, since the transmission signal of t _1k takes different values of M values, M complex multipliers are used, and the obtained replica signals are stored in M storage circuits. Similarly, M replica multipliers are used for the replica signal of h _i2 t _2k , and the obtained replica signals are stored in M storage circuits. Thereafter, the same processing is performed up to h _iL t _Lk . As a result, when a replica signal added with h ′ _i T _{L, k} is calculated, it can be realized with L × M × N complex multipliers and L × M × N storage circuits. Then, an added replica signal can be derived from a combination of replica signals corresponding to each transmission signal stored in the storage circuit.

In addition, a readable / writable storage circuit is significantly smaller in circuit scale than a complex multiplier. Therefore, by using L × M × N storage circuits, the effect of reducing the circuit scale by reducing the number of complex multipliers from L × M ^L × N, which was conventionally required, to L × M × N is as follows. large. In particular, even when the modulation level M of the transmission signal, which was a problem in the conventional circuit, is large, the number of complex multipliers does not increase exponentially, and the circuit scale can be greatly reduced.

  Furthermore, in the present invention, the same value as that of the added replica signal derived by the conventional method can be obtained, so that an exceptional effect can be obtained in which there is no characteristic deterioration of the signal detection portion while reducing the circuit scale.

  In the first invention and the second invention, after generating a replica signal corresponding to each transmission signal (M-value signal corresponding to each transmission sequence), each replica signal is stored in the replica signal storage means, and the combination is considered. Then, reading is performed while generating an added replica signal. As a result, it is possible to realize excellent error rate characteristics while greatly reducing the required number of complex multipliers in the replica signal generating means as described above.

  The third invention is characterized in that the replica signal read from the replica signal storage means is selected in accordance with the replica control signal output from the replica signal generation control means. Specifically, replica signal candidates to be read from the replica signal storage means when information such as few signal point candidates to be searched is known in advance on the demodulator side or becomes clear in the process of received signal processing On the other hand, the number of readouts is controlled in accordance with the replica control signal based on the information. As a result, not only can the required number of complex multipliers in the replica signal generating means be reduced, but also the number of complex multiplications performed by the signal point distance calculating means can be reduced by reducing the number of combinations of replica signals. .

  In the fourth invention, the transmission signal temporary estimation means performs temporary estimation of each transmission signal, the replica signal generation control means generates a replica control signal corresponding to the temporary estimation information signal, and reads the replica signal from the replica signal storage means It is characterized by selecting. As this transmission signal temporary estimation means, the ZF method, the MMSE method, the OSD method, or the MLD method can be applied. Moreover, it is also possible to apply the combination system of each system or each system partially. For example, when several transmission signal point candidates are narrowed down according to the temporary estimation information signal based on the ZF method, it is also possible to generate an added replica signal by a combination of replica signals with respect to the narrowed value.

  Further, the transmission signal temporary estimation means can use signal point information when narrowed down to several transmission signal point candidates using the ZF method. Various methods can be considered as signal detection methods and signal separation methods, and combinations of these methods are also conceivable. However, the effective method at this time is to estimate the final transmission signal point by a single calculation process. Instead, a method of estimating a final transmission signal point with respect to a limited signal point obtained by temporary estimation may be used. In this case, it is not necessary to provide replica signals for all possible transmission signal point candidates on the transmission side. By performing control to output a replica signal for the limited transmission signal point candidates, an effect of reducing the calculation of the signal point distance performed by the signal point distance calculation means in the subsequent stage can be obtained.

  Furthermore, in the transmission signal temporary estimation means, specifically, the signal separation and signal detection methods described in the references (Electronic Information and Communication Society, IEICE Technical Report, RCS2003-303) can be applied. In the technique described in this reference, the number of transmission signal point candidates is reduced once using the ZF method. By inputting the reduced transmission signal point candidate information to the replica signal generation control unit, a replica control signal for narrowing the output signal of the replica signal storage unit is generated.

  In the fifth invention, not only the output signal of the replica signal storage means is narrowed down based on the temporary estimation information signal (limited transmission signal point candidates) output from the transmission signal temporary estimation means, but also the transmission signal generation means It is also characterized by narrowing down the M-value signal output from. For example, when several transmission signal point candidates are narrowed down using a value based on the ZF method, a transmission signal related to a combination of transmission signals corresponding to the narrowed value is generated. Specifically, when the number of transmission signal points as candidates is narrowed down from M to M ′ by the transmission signal temporary estimation means, the number of complex multipliers used for replica signal generation is L × M ′ × N. Thus, the number of readable / writable storage circuits can be set to L × M ′ × N.

  With the above-described features of the present invention, it is possible to apply a signal detection method having excellent error rate characteristics even in a wireless LAN or the like in which the circuit scale or power consumption is severely limited. That is, from the viewpoint of circuit scale and power consumption, conventionally, even when a signal detection method having a small circuit scale but a poor error rate characteristic has to be used, by using the present invention, the error rate characteristic is excellent. By applying the signal detection method, a high quality wireless system can be realized. Further, communication with a low CNR is possible while reducing the circuit scale, and the communication area can be expanded.

  In addition, the signal point distance calculation means in the present invention can perform distance calculation based on the Euclidean distance, the Manhattan distance, and the like, and can also use each square distance and the like.

  The storage means in the present invention can be a circuit using, for example, a RAM or the like as a rewritable circuit for each received packet. However, if the transmission signal point does not fluctuate, a ROM may be used.

  Furthermore, the present invention is not only effective for the MLD scheme that performs full search, but performs a difference calculation between a received signal and a replica signal, and performs a signal search that estimates the maximum likelihood of the transmission signal from the result. It is applicable to all cases of signal detection circuits. For example, the present invention can also be applied to a case where processing by the MLD method is performed after the provisional signal estimation by the ZF method or the like.

  Furthermore, the present invention is applied to a subcarrier signal after multicarrier demodulation in the multicarrier modulation scheme, but can also be applied to the case of using a single carrier modulation scheme. When applied to subcarrier signals, the configuration of the present invention can be provided in parallel for the total number of subcarriers in correspondence with the number of subcarriers of the multicarrier signal to be demodulated. Furthermore, it is also possible to provide only for a plurality of subcarriers or one subcarrier, and use by switching the subcarriers to be sequentially input. The number provided in parallel is normally determined from the requirements of the system, and the present invention can cope with the requirements of the parallel number.

  Further, as an M-value signal generated by the transmission signal generation means in the present invention, an M-value QAM signal, an M-value PSK signal, an M-value ASK signal, an M-value FSK signal, an M-value CCK (Complementary Code Keying) signal, and M-multiplexed signals. The present invention can also be applied to general modulation schemes applied to wireless communication schemes such as SS (Spread Spectrum) signals. Further, in the present invention, it is important to reduce the number of complex multipliers used for calculating the combination, and it can be applied to a transmission signal using a modulation multi-level number of 2 or more or a code multiplexing number corresponding to the modulation multi-level number. It is.

  Further, the multicarrier demodulation means may perform multicarrier demodulation after removing a repetitive signal section called a guard interval.

  The channel estimation means may have a plurality of configurations depending on the signal format in which the channel estimation preamble signal for the space-division multiplexed signal on the transmission side is transmitted. Simply, various configurations can be applied, such as when synchronous detection is performed using a preamble signal at a receiver to obtain a channel estimation result, or when inverse matrix calculation is performed.

  Further, the demodulator including the space division multiplex signal detection circuit of the present invention may be provided with a plurality of means for demodulating the existing system. In this case, in order not to increase the circuit scale more than necessary, the circuit of the present invention and the circuit for the existing system may be shared.

  Further, the present invention can naturally be expanded when the number of transmission systems (number of data series) L is two or more multiplexed, and can naturally be expanded when the number of reception systems N is two or more. Further, in a configuration in which the number of transmission systems (number of data series) L is two or more multiplexes, it is not necessary to provide as many reception systems as the number of transmission systems, and the number of transmission systems and the number of reception systems are the same according to the system requirements. Alternatively, the number of reception systems may be smaller than the number of transmission systems. For example, the MLD scheme can be applied even with a minimum configuration with two transmission systems and one reception system.

  In addition, each means in the present invention may not be operated constantly, but may be operated only when necessary to reduce power consumption.

  In the present invention, when signal detection is performed by receiving a signal subjected to space division multiplex transmission, especially when the number of modulation multi-values is increased, the circuit scale can be reduced, and the characteristic degradation accompanying the circuit scale reduction can be reduced. Excellent error rate characteristics can be realized.

(First embodiment)
FIG. 1 shows a first embodiment of the space division multiplex signal detection circuit of the present invention. Here, a case where one reception system is used for two transmission systems (data series) is shown.

  In the figure, an FFT circuit 81 receives a received signal S80 and outputs a multicarrier demodulated subcarrier signal S81. The subcarrier signal S81 is input to the subcarrier signal storage circuit 82, and is stored for MLD signal processing required time (for example, 10 FDM symbol time). The channel estimation circuit 83 estimates channel distortion of the propagation path from the subcarrier signal S81 and outputs a channel estimation signal S83 corresponding to each transmission system.

  On the other hand, the transmission signal generation circuit 84 according to the number of transmission systems outputs a transmission signal (M-value signal) S84 having a modulation multi-level number M that may be transmitted. The complex multiplier 85 performs complex multiplication of the channel estimation signal S83 and the M-value signal S84, and generates a replica signal S85 of the received signal corresponding to each transmission system. The replica signal storage circuit 11 stores the replica signal S85 corresponding to each transmission system for a signal detection time (for example, 10 FDM symbol time). The replica signal addition circuit 86 performs vector addition of the replica signal S11 read from the replica signal storage circuit 11, and generates an addition replica signal S86. The complex multiplier 85, the replica signal storage circuit 11, and the replica signal addition circuit 86 need M combinations.

  The signal point distance calculation circuit 87 calculates a signal point distance between the subcarrier signal S82 stored in the subcarrier signal storage circuit 82 and the added replica signal S86. This signal point distance signal S87 is input to the maximum likelihood estimation circuit 89 and maximum likelihood estimation is performed, and the combination of replica signals having the shortest signal point distance among the input signals is assumed to be the most probable transmission signal combination. A transmission signal S89 corresponding to the detected signal is output.

(Second Embodiment)
FIG. 2 shows a second embodiment of the space division multiplex signal detection circuit of the present invention. Here, a case where N reception systems are used for L transmission systems (data series) is shown.

  In the figure, N FFT circuits 81 receive a reception signal S80 of each reception system, and output a subcarrier signal S81 subjected to multicarrier demodulation. The subcarrier signal S81 is input to the subcarrier signal storage circuit 82, and is stored for MLD signal processing required time (for example, 10 FDM symbol time). Note that when the clock frequency of the demodulator is increased, the memory circuit can be reduced. Channel estimation circuit 83 estimates channel distortion of the propagation path from subcarrier signal S81, and outputs channel estimation signals S83 corresponding to L transmission systems.

On the other hand, the L transmission signal generation circuits 84 corresponding to the number of transmission systems output a modulation multilevel number M transmission signal (M-value signal) S84. The complex multiplier 85 performs complex multiplication of the channel estimation signal S83 and the M-value signal S84 to generate a received signal replica signal S85 corresponding to each transmission system. At this time, L complex multiplications of the same number as the L transmission systems are performed, and replica signals are respectively generated. The L replica signal storage circuits 11 store the replica signal S85 corresponding to each transmission system over a signal detection time (for example, 10 FDM symbol time). Note that when the clock frequency of the demodulator is increased, the memory circuit can be reduced. The replica signal addition circuit 86 performs vector addition of the L replica signals S11 read from the replica signal storage circuit 11, and generates an addition replica signal S86 corresponding to each reception system. The complex multiplier 85, the replica signal storage circuit 11, and the replica signal addition circuit 86 require M sets, and the M sets are required for N reception systems. That is, the number of complex multipliers 85 is L × M × N, which is a significant reduction compared to the conventional L × M ^L × N.

  The signal point distance calculation circuit 87 for N reception systems calculates the signal point distance between the subcarrier signal S82 of each reception system stored in the subcarrier signal storage circuit 82 and the added replica signal S86 corresponding to each reception system. The signal point distance signal S87 is added by the calculation result adding circuit 88. This added signal S88 is input to the maximum likelihood estimation circuit 89 and is estimated maximum likelihood, and the signal detection is performed on the assumption that the combination of replica signals having the shortest signal point distance among the input signals is the most probable transmission signal combination. L transmission signals S89 corresponding to this are output.

(Third embodiment)
FIG. 3 shows a third embodiment of the space division multiplex signal detection circuit of the present invention. The present embodiment is characterized in that a replica signal generation control circuit 21 is added to the configuration of the second embodiment. The replica signal generation control circuit 21 outputs a replica control signal S21 that selects the replica signal S11 to be read from the replica signal storage circuit 11. Other configurations are the same as those of the second embodiment.

  As a result, not only can the required number of complex multipliers 85 be reduced as in the second embodiment, but also the number of combinations of replica signals is reduced, and the complex calculation performed by the signal point distance calculation circuit (87) at the subsequent stage is also performed. The number of multiplications can also be reduced.

(Fourth embodiment)
FIG. 4 shows a fourth embodiment of the space division multiplex signal detection circuit of the present invention. The present embodiment is characterized in that a replica signal generation control circuit 21 and a transmission signal temporary estimation circuit 22 are added to the configuration of the second embodiment. The transmission signal provisional estimation circuit 22 receives the N reception system subcarrier signals S81 output from the FFT circuit 81 and the channel estimation signal S83 output from the channel estimation circuit 83, and provisionally outputs L transmission signals. Make an estimate. The replica signal generation control circuit 21 generates a replica control signal S21 corresponding to the temporary estimation information signal (limited transmission signal point candidates) S22, and selects the replica signal S11 to be read from the replica signal storage circuit 11.

  The transmission signal temporary estimation circuit 22 can be applied with a ZF method, an MMSE method, an OSD method, or an MLD method. Moreover, it is also possible to apply the combination system of each system or each system partially. For example, when several transmission signal point candidates are narrowed down according to the temporary estimated information signal based on the ZF method, the replica signal adding circuit 86 generates an added replica signal S86 by combining the replica signal S11 with respect to the narrowed value. Is done. Other configurations are the same as those of the second embodiment.

  As a result, not only can the required number of complex multipliers 85 be reduced as in the second embodiment, but also the number of combinations of replica signals is reduced, and the complex calculation performed by the signal point distance calculation circuit (87) at the subsequent stage is also performed. The number of multiplications can also be reduced.

(Fifth embodiment)
FIG. 5 shows a fifth embodiment of the space division multiplex signal detection circuit of the present invention. In this embodiment, in the configuration of the fourth embodiment, the output signal of the replica signal storage circuit 11 is determined based on the temporary estimation information signal (limited transmission signal point candidates) S22 output from the transmission signal temporary estimation circuit 22. In addition to narrowing down, the M value signal S84 output from the transmission signal generation circuit 84 is narrowed down. For example, when several transmission signal point candidates are narrowed down using values based on the ZF method, the transmission signal generation circuit 84 generates an M-value signal S84 related to a combination of transmission signals with respect to the narrowed values. To do. Other configurations are the same as those of the second embodiment.

  Thus, for example, when the number of transmission signal points that are candidates in the transmission signal temporary estimation 84 is narrowed down from M to M ′, the number of complex multipliers 85 used for replica signal generation is L × M ′ × N. Thus, the number of replica signal storage circuits 11 is also L × M ′ × N.

The figure which shows the 1st Embodiment of this invention. The figure which shows the 2nd Embodiment of this invention. The figure which shows the 3rd Embodiment of this invention. The figure which shows the 4th Embodiment of this invention. The figure which shows the 5th Embodiment 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 a multicarrier signal demodulation circuit. The figure which shows the structural example of the conventional space division multiplex signal detection circuit. The figure which shows the example of the packet format used by this invention. The figure which shows the example of a two-dimensional display of the packet format used by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Replica signal memory | storage circuit 21 Replica signal production | generation control circuit 22 Transmission signal temporary estimation circuit 81 FFT circuit 82 Multicarrier signal memory circuit 83 Channel estimation circuit 84 Transmission signal generation circuit 85 Complex multiplier 86 Replica signal addition circuit 87 Signal point distance calculation Circuit 88 Calculation result addition circuit 89 Maximum likelihood estimation circuit

Claims (10)

Multicarrier demodulation means for inputting a multicarrier modulated reception signal, performing multicarrier demodulation, and outputting a subcarrier signal;
Subcarrier signal storage means for temporarily storing subcarrier signals output from the multicarrier demodulation means;
Channel estimation means for estimating channel distortion of the propagation path from the subcarrier signal output from the multicarrier demodulation means;
Transmission signal generating means for generating a signal of each transmission system that may be transmitted from a plurality of transmitters;
Replica signal generation means for performing complex multiplication of the output signal of the transmission signal generation means and the channel estimation signal output from the channel estimation means, and generating a replica signal of the reception signal corresponding to each transmission system;
Replica signal storage means for temporarily storing the replica signal generated for each transmission system by the replica signal generation means for each transmission system;
Replica signal addition means for reading a replica signal for each transmission system stored in the replica signal storage means and adding the vectors;
A signal point distance calculation means for calculating a signal point distance between the subcarrier signal stored in the subcarrier signal storage means and the output signal of the replica signal addition means;
And a maximum likelihood estimation means for estimating a replica signal indicating a minimum distance between signal points from an output signal of the signal point distance calculation means and detecting a transmission signal transmitted by space division multiplexing. Division multiplexed signal detection circuit. Multi-carrier demodulating means for receiving multi-carrier-modulated N (N is an integer of 1 or more) reception systems, performing multi-carrier demodulation, and outputting sub-carrier signals for each reception system;
Subcarrier signal storage means for temporarily storing subcarrier signals of N reception systems output from the multicarrier demodulation means;
Channel estimation means for estimating channel distortion of a channel from subcarrier signals of N reception systems output from the multicarrier demodulation means;
Transmission signal generating means for generating L M-value signals (M is an integer of 2 or more) that may be transmitted from L (L is an integer of 1 or more) transmitters;
Replica signal generation means for performing complex multiplication of the L output signals of the transmission signal generation means and the channel estimation signal output from the channel estimation means to generate replica signals of L reception signals corresponding to the respective transmission systems When,
Replica signal adding means for vector-adding the L replica signals generated for each transmission system by the replica signal generating means;
Input the subcarrier signals of N receiving systems stored in the subcarrier signal storage means and the output signal of the replica signal adding means, and calculate the distance between signal points of the N receiving systems. Computing means;
Adding means for adding distances between signal points of N receiving systems output from the signal point distance calculating means;
A maximum likelihood estimation means for estimating a replica signal indicating a minimum distance between signal points from the output of the addition means, and detecting L transmission signals subjected to space division multiplexing transmission;
In the space division multiplex signal detection circuit provided with a predetermined number of combinations for each of N reception systems from the replica signal generation means to the replica signal addition means,
Between the replica signal generating means for generating the L replica signals and the replica signal adding means, the L replica signals are temporarily stored for each transmission system, and the replica signals are read out in a predetermined procedure. A replica signal storing means for inputting to the replica signal adding means,
A space-division multiplex signal detection circuit comprising M replicas from the replica signal generating means to the replica signal adding means for every N receiving systems. The space division multiplex signal detection circuit according to claim 2,
A space division multiplex signal detection circuit comprising: replica signal generation control means for outputting a replica control signal for selecting a replica signal to be read from the replica signal storage means. The space division multiplex signal detection circuit according to claim 3,
A transmission signal temporary estimation unit that receives a subcarrier signal of N reception systems output from the multicarrier demodulation unit and a channel estimation signal output from the channel estimation unit, and temporarily estimates L transmission signals. With
The replica signal generation control unit is configured to generate the replica control signal according to the temporary estimation information signal output from the transmission signal temporary estimation unit and to control reading of the replica signal. Division multiplexed signal detection circuit. In the space division multiplex signal detection circuit according to claim 4,
The transmission signal generating means for generating the L M-value signals is configured to output an M-value signal selected according to the temporary estimation information signal output from the transmission signal temporary estimation means. Spatial division multiplexed signal detection circuit. Step 1 of receiving a multicarrier modulated reception signal, performing multicarrier demodulation, and outputting a subcarrier signal;
Step 2 for temporarily storing the subcarrier signal output in Step 1;
Step 3 for estimating the channel distortion of the propagation path from the subcarrier signal output in Step 1;
Generating a signal for each transmission system that may be transmitted from a plurality of transmitters; and
Performing a complex multiplication of the signal generated in step 4 and the channel estimation signal estimated in step 3 to generate a replica signal of the received signal corresponding to each transmission system; and
Step 6 for temporarily storing the replica signal generated for each transmission system in Step 5 for each transmission system;
Step 7 of reading the replica signal for each transmission system stored in Step 6 and adding the vectors;
Calculating a distance between signal points of the subcarrier signal stored in step 2 and the output signal vector-added in step 7;
And a step 9 of estimating a replica signal indicating a minimum distance between signal points from the signal calculated in step 8 and detecting a transmission signal transmitted by space division multiplexing. . Step 1 of receiving multicarrier-modulated N reception signals (N is an integer equal to or greater than 1), performing multicarrier demodulation, and outputting subcarrier signals of each reception system;
Step 2 for temporarily storing the subcarrier signals of N reception systems output in Step 1;
Estimating a channel distortion of a propagation path from subcarrier signals of N reception systems output in step 1; and
Generating L M-value signals (M is an integer greater than or equal to 2) that may be transmitted from L (L is an integer greater than or equal to 1) transmitters;
Performing a complex multiplication of the L output signals generated in step 4 and the channel estimation signal estimated in step 3 to generate replica signals of L received signals corresponding to each transmission system; and
Step 6 for vector addition of the L replica signals generated for each transmission system in Step 5;
Inputting the subcarrier signals of the N reception systems stored in step 2 and the vector-added signal in step 6 to calculate the distance between the signal points of the N reception systems;
Step 8 of adding the distances between the signal points of the N receiving systems calculated in Step 7;
Estimating a replica signal indicating a minimum distance between signal points from the signal added in step 8, and detecting L transmission signals subjected to space division multiplex transmission; and
In the space division multiplex signal detection method in which the processing from step 5 to step 6 is performed by a predetermined number of combinations for each of N reception systems,
Between the step 5 and the step 6 for generating the L replica signals, the L replica signals are temporarily stored for each transmission system, and the replica signals are read out in a predetermined procedure. Step 10 is provided for the addition process,
The space division multiplex signal detection method characterized in that the processes of steps 5, 10, and 6 are performed in M combinations for each of N reception systems.
In the space division multiplex signal detection method according to claim 7,
A method of detecting a space division multiplex signal, comprising: selecting a replica signal to be read in step 10 in accordance with a replica control signal. The space division multiplex signal detection method according to claim 8,
Receiving the subcarrier signals of N reception systems output in step 1 and the channel estimation signal estimated in step 3, and performing step 12 for temporary estimation of L transmission signals;
The step 11 generates the replica control signal according to the temporary estimation information signal output in the step 12, and controls reading of the replica signal. The space division multiplex signal detection method according to claim 9,
The step 4 of generating the L M-value signals outputs the M-value signal selected according to the temporary estimation information signal output in the step 12.

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