JP3846356B2 - Orthogonal frequency division multiplexing receiver and reception method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an Orthogonal Frequency Division Multiplexing (OFDM) receiving apparatus and receiving method.
[0002]
[Prior art]
In recent years, the demand for multimedia communication services has increased rapidly, and studies on multimedia mobile communication systems using digital wireless communication have been actively conducted. As a transmission method effective for high-speed transmission and multipath, the OFDM method is employed in multimedia mobile communication systems and high-speed wireless LANs.
[0003]
The OFDM scheme is characterized in that, by transmitting a wideband signal with a large number of carrier waves (hereinafter referred to as “subcarriers”) orthogonal to each other, it is possible to improve resistance to delay interference in a multipath propagation path in digital wireless communication. In addition, since this OFDM method transmits transmission data distributed over a plurality of subcarriers, combining it with error correction provides excellent transmission characteristics against frequency selective transmission line distortion such as multipath distortion. It is known to show.
[0004]
By the way, in digital wireless communication, it has been proposed to perform diversity reception in units of OFDM subcarriers as a method for further improving transmission characteristics under severe reception conditions such as reception during movement. A typical diversity reception method includes combining diversity or selection diversity.
[0005]
FIG. 1 is a configuration diagram of a conventional receiving apparatus using combining diversity. FIG. 2 is a configuration diagram of a conventional receiving apparatus using selection diversity.
[0006]
According to the conventional receiving apparatus shown in FIG. 1 and FIG. 2, the demodulated data obtained by the two OFDM demodulating apparatuses are selected or combined according to the received power in units of OFDM subcarriers. In this case, since the transmission path responses of the two systems are different, frequency selective transmission path distortion can be improved.
[0007]
[Problems to be solved by the invention]
However, according to a conventional general OFDM diversity receiver, the magnitude of received power is used as an evaluation index when combining or selecting demodulated data of a plurality of systems. At this time, when receiving a co-channel interference wave in digital wireless communication, a system with high reception power does not necessarily have good reception quality. Furthermore, when the reception power of the co-channel interference wave is large, the OFDM reception signal may not be demodulated.
[0008]
Therefore, the present invention can combine subcarriers in a multipath propagation environment in which co-channel interference waves exist (even if the interference wave is stronger than the desired wave), without being disturbed by co-channel interference waves. An object of the present invention is to provide an OFDM reception apparatus and reception method that can perform selection diversity and improve reception quality.
[0009]
[Means for Solving the Problems]
According to the orthogonal frequency division multiplexing receiver of the present invention,
For each subarray divided into a plurality of groups, a plurality of antennas that receive orthogonal frequency division multiplexing received signals, and a weighting factor calculation that calculates weighting factors for the plurality of received signals based on the plurality of received signals and reference signals Means, multiplying means for multiplying each received signal by a weighting factor, adding means for adding the received signals of the multiplied products, and converting the sum of the received signals from the time domain to the frequency domain to subcarriers A fast Fourier transform means for deriving a unit carrier reception signal, a diversity processing means for spatially diversity-subdividing the subcarrier reception signal obtained for each subarray, and a diversity-processed subcarrier reception signal Correction means for correcting the amplitude and phase.
[0010]
According to the configuration of the present invention, the co-channel interference wave is suppressed in each subarray, and the output signal of each subarray in which the interference wave is suppressed is converted from the time domain to the frequency domain by the FFT circuit, respectively. Is a two-stage reception method in which diversity processing is performed in units of subcarriers. As a result, even in an environment where co-channel interference waves exist, diversity reception can be performed by removing the co-channel interference waves, and reception quality can be improved.
[0011]
According to another embodiment of the present invention, N (≧ 3) antennas are also preferably divided into K (≧ 2) sub-arrays.
[0012]
According to another embodiment of the present invention, it is also preferable that the plurality of antennas be arranged so that the correlation between output signals for each sub-array is minimized.
[0013]
According to another embodiment of the present invention, the weighting factor calculation means is configured so that the signal interference noise ratio is maximized by the correlation matrix estimation means for deriving each correlation matrix of the received signal, and each correlation matrix and the reference signal. It is also preferable to comprise weighting factor calculation means for calculating the weighting factor.
[0014]
According to another embodiment of the present invention, the correlation matrix estimation means calculates a complex conjugate calculation means for obtaining a complex conjugate of the received signal, and calculates a correlation value between the received signal and a value derived from the complex conjugate calculation means. And a correlation value calculating means.
[0015]
According to another embodiment of the present invention, the diversity processing means includes a calculating means for calculating a weighting factor from the amplitude value and phase of the subcarrier received signal, and a weighting factor is multiplied for each subcarrier received signal. It is also preferable to comprise a synthesis diversity means for synthesizing with.
[0016]
According to another embodiment of the present invention, the diversity processing means includes a calculating means for calculating an amplitude value of the subcarrier received signal, and a selecting means for selecting a subarray corresponding to the subcarrier received signal that has obtained the maximum received amplitude. It is also preferable to comprise.
[0017]
According to another embodiment of the present invention, the correction unit performs propagation channel estimation using the pilot signal in the subcarrier reception signal selected or combined by the diversity processing unit, and stores the estimated value. Calculation for calculating, for each subcarrier, the ratio of the received data signal for each subcarrier received signal selected or combined by the storage means and the diversity processing means and the propagation path estimated value of the same subcarrier stored by the storage means And means.
[0018]
According to the orthogonal frequency division multiplexing reception method of the present invention,
For each subarray divided into a plurality of groups, a step of receiving an orthogonal frequency division multiplexing reception signal using a plurality of antennas and a weighting factor for the plurality of reception signals are calculated based on the plurality of reception signals and reference signals A step of multiplying each received signal by a weighting factor, a step of adding the received signals of the multiplied products, and converting the sum of the received signals from the time domain to the frequency domain by fast Fourier transform. Deriving a subcarrier reception signal in units of subcarriers, and performing a spatial diversity process on the subcarrier reception signal obtained for each subarray in units of subcarriers, and an amplitude in the diversity-processed subcarrier reception signal And correcting the phase.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0020]
FIG. 3 is a configuration diagram of the receiving apparatus of the present invention using the combining diversity. FIG. 3 has a Fast Fourier Transform (FFT) circuit 2 for each sub-array that receives an OFDM signal, as compared with FIG. Then, in the preceding stage of the FFT circuit 2, for each sub-array divided into a plurality of groups, a plurality of antennas 10, a weighting factor calculation unit 80 for calculating a weighting factor from a reception signal by the antenna 10, and each reception signal A multiplication unit 81 that multiplies the weight coefficient and an addition unit 82 that adds reception signals of the multiplied products.
[0021]
At this time, the weighting factor calculator 80 maximizes the signal interference noise ratio (SINR) of the output signal of the subarray from the received signal and the reference signal. To derive.
[0022]
FIG. 4 is a functional configuration diagram of the weighting coefficient calculation unit 80 of the present invention. The weighting factor calculation unit 80 is a correlation matrix estimation unit 801 that derives each correlation matrix of the received signal, and a weighting factor calculation unit that calculates the weighting factor so that the signal interference noise ratio is maximized by each correlation matrix and the reference signal. 802. The correlation matrix estimation unit 801 includes a complex conjugate calculation unit 8011 that calculates a complex conjugate of the received signal, and a correlation value calculation unit 8012 that calculates a correlation value between the received signal and a value derived from the complex conjugate calculation unit. .
[0023]
Further, other components of FIG. 3 will be described. The FFT circuit 2 converts the OFDM modulated wave on the time axis into data on the frequency axis, and derives subcarrier reception signals (baseband I and Q channel signals) indicating the amplitude and phase in subcarrier units. The plurality of subcarrier reception signals are input to the weighting factor calculation unit 30. The weighting factor calculation unit 30 calculates a correlation matrix of the subcarrier reception signal for each subcarrier, and calculates an eigenvector for the maximum eigenvalue of this correlation matrix. Let this eigenvector be the weighting coefficient vector of the corresponding subcarrier. Then, the weighting coefficient calculation unit 30 outputs the weighting coefficient of each subcarrier to the multiplication unit 31. The multiplication unit 31 multiplies each subcarrier received signal by a weighting coefficient, and the addition unit 32 synthesizes it in units of subcarriers.
[0024]
Next, the correcting unit 4 corrects the amplitude and phase in the subcarrier reception signal combined by the combining diversity circuit for each subcarrier by estimating the propagation path response for each subcarrier. This propagation path estimation is performed using a known pilot signal of each subcarrier stored in advance.
[0025]
The correction unit 4 includes a storage unit and a calculation unit. The storage unit performs propagation channel estimation using the pilot signal in the subcarrier reception signal selected or combined by the diversity processing unit, and stores the estimated value. Further, the calculation unit calculates, for each subcarrier, a ratio between the reception data signal for each subcarrier reception signal selected or combined by the diversity processing unit and the propagation path estimated value of the same subcarrier stored in the storage unit. calculate.
[0026]
Further, the corrected subcarrier received signal is demodulated by the demodulator 5, converted back to a serial signal by the parallel-serial converter 6, and the serial signal is decoded by the decoder 7. The decoding unit 7 performs reverse processing of the interleave circuit encoded on the transmission side by the deinterleave circuit. The processed data is transferred to the subsequent Viterbi decoder circuit and Viterbi-decoded. Further, the output data of the Viterbi decoding circuit is input to the error correction circuit, and the reverse processing of the encoder on the transmission side is performed. The processed data is output as a TS (Transport Stream) signal from the output terminal.
[0027]
FIG. 5 is a configuration diagram of a receiving apparatus of the present invention using selection diversity. FIG. 4 shows a circuit similar to that shown in FIGS. 3 and 4 in the preceding stage of the FFT circuit 2 as compared with FIG.
[0028]
According to FIG. 5, subcarrier reception signals in units of subcarriers are derived by the FFT circuit 2 provided for each antenna 1. The plurality of subcarrier reception signals are input to the comparison unit 33. The comparison unit 33 compares the reception signal amplitude of each subarray for each subcarrier, and outputs a control signal for selecting a subarray having a large reception signal amplitude to the selector 34. The selector 34 selects an antenna reception signal corresponding to the subcarrier reception signal for which the maximum reception amplitude is obtained. The subsequent processing is the same as in FIG.
[0029]
FIG. 6 is a layout view of the first array antenna according to the present invention as viewed from above. According to the present invention, the number of antenna elements for each subarray and its arrangement are set so that the correlation between output signals for each subarray is minimized. According to FIG. 6, twelve antenna elements are divided into three subarrays every four. Each subarray is arranged at a position of 120 ° from the center of the antenna system.
[0030]
FIG. 7 is a layout view of the second array antenna according to the present invention as viewed from above. According to FIG. 7, 16 antenna elements are arranged in a square shape of 4 rows and 4 columns. However, in the receiving apparatus, every four lines are divided into four subarrays.
[0031]
FIG. 8 is a layout view of the third array antenna according to the present invention as viewed from above. According to FIG. 8, six antenna elements are arranged in a rectangular shape with 2 rows and 3 columns. However, in the receiving apparatus, one central column is shared by two subarrays. That is, N (≧ 3) antennas can be divided into K (≧ 2) subarrays.
[0032]
FIG. 9 is a layout view of the fourth array antenna according to the present invention as viewed from above. According to FIG. 9, as in FIG. 7, 16 antenna elements are arranged in a square shape of 4 rows and 4 columns. However, in the receiving apparatus, it is divided into a first subarray by the first row and the second row, a second subarray by the second row and the third row, and a third subarray by the third row and the fourth row. Has been.
[0033]
According to the above-described various embodiments of the present invention, various changes, modifications, and omissions of the technical idea and scope of the present invention can be easily made by those skilled in the art. In particular, in the above description, the device configuration has been described in detail, but it can be easily conceived by those skilled in the art that it can be realized as a method. The above description is merely an example, and is not intended to be restrictive. The invention is limited only as defined in the following claims and the equivalents thereto.
[0034]
【The invention's effect】
As described above in detail, according to the receiving apparatus and reception method of the OFDM system of the present invention, even in a multipath propagation environment where co-channel interference waves exist, sub-channels are not affected by co-channel interference waves. Carrier unit combining or selection diversity can be performed, and reception quality can be improved.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a conventional receiving apparatus using combining diversity.
FIG. 2 is a configuration diagram of a conventional receiving apparatus using selection diversity.
FIG. 3 is a configuration diagram of a receiving apparatus according to the present invention that uses combining diversity;
FIG. 4 is a functional configuration diagram of a weight coefficient calculation unit 80 according to the present invention.
FIG. 5 is a configuration diagram of a receiving apparatus of the present invention using selection diversity.
FIG. 6 is a layout view of a first array antenna according to the present invention as viewed from above.
FIG. 7 is a layout view of a second array antenna according to the present invention as viewed from above.
FIG. 8 is a layout view of a third array antenna according to the present invention as viewed from above.
FIG. 9 is a layout view of a fourth array antenna according to the present invention as viewed from above.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Antenna element 10 and 11 Antenna element 2 FFT grouped, Fast Fourier transform part 30 Weight coefficient calculation part 31 Multiplication part 32 Addition part 33 Comparison part, Diversity control part 34 Selector 4 Correction part 5 Demodulation part 6 Parallel / Serial conversion unit 7 Decoding unit 80 Weight coefficient calculation unit 801 Correlation matrix estimation unit 8011 Complex conjugate calculation unit 8012 Correlation value calculation unit 802 Weight coefficient calculation unit 803 Reference signal generation unit 81 Multiplication unit 82 Addition unit

Claims (9)

In the orthogonal frequency division multiplexing receiver,
For each subarray divided into multiple groups,
A plurality of antennas for receiving the reception signal of the orthogonal frequency division multiplexing system;
Weighting factor calculating means for calculating weighting factors for the plurality of received signals based on the plurality of received signals and the reference signal ;
Multiplying means for multiplying each received signal by the weighting factor;
Adding means for adding received signals of the multiplied products;
Fast Fourier transform means for deriving a subcarrier received signal in subcarrier units by converting the summed received signal from the time domain to the frequency domain;
Diversity processing means for performing spatial diversity processing on a subcarrier basis for the subcarrier received signal obtained for each subarray ;
A receiving apparatus comprising: correction means for correcting an amplitude and a phase in the diversity-processed subcarrier reception signal. The receiving apparatus according to claim 1, wherein the N (≧ 3) antennas are divided into K (≧ 2) subarrays. The receiving apparatus according to claim 1, wherein the plurality of antennas are arranged so that a correlation between output signals of the subarrays is minimized. The weight coefficient calculation means includes:
Correlation matrix estimation means for deriving each correlation matrix of the received signal;
The weight coefficient calculation means for calculating a weight coefficient so that a signal interference noise ratio is maximized by each correlation matrix and the reference signal is provided. Receiver device. The correlation matrix estimation means includes
Complex conjugate calculation means for obtaining a complex conjugate of the received signal;
Correlation value calculation means for calculating a correlation value between the received signal and a value derived from the complex conjugate calculation means;
The receiving apparatus according to claim 4, further comprising: The diversity processing means includes:
Calculating means for calculating a weighting factor from the amplitude value and phase of the subcarrier received signal;
6. The receiving apparatus according to claim 1, further comprising combining diversity means for multiplying the subcarrier received signal by the weighting coefficient and combining the signals in units of subcarriers. The diversity processing means includes:
Calculating means for calculating an amplitude value of the subcarrier received signal;
6. The receiving apparatus according to claim 1, further comprising selection means for selecting the sub-array corresponding to the sub-carrier received signal that has obtained the maximum reception amplitude. The correction means performs a channel estimation using a pilot signal in a subcarrier reception signal selected or combined by the diversity processing means, and stores an estimated value,
Calculation means for calculating, for each subcarrier, a ratio between a reception data signal for each subcarrier reception signal selected or combined by the diversity processing means and a propagation path estimation value of the same subcarrier stored by the storage means; The receiving apparatus according to claim 6 or 7, further comprising: In the reception method of the orthogonal frequency division multiplexing system,
For each subarray divided into multiple groups,
Receiving the orthogonal frequency division multiplexing received signal using a plurality of antennas;
Calculating a weighting factor for the plurality of received signals based on the plurality of received signals and a reference signal ;
Multiplying each received signal by the weighting factor;
Adding received signals of the multiplied products;
Transforming the summed received signal from the time domain to the frequency domain by fast Fourier transform to derive a subcarrier received signal in subcarrier units,
Spatial diversity processing of the subcarrier received signal obtained for each subarray in units of subcarriers ;
Correcting the amplitude and phase of the diversity-processed subcarrier received signal.

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