JP4188371B2 - Wireless communication apparatus and wireless communication method - Google Patents

Description

  The present invention uses the same frequency channel, transmits independent data from a plurality of different transmission antennas, receives signals using a plurality of reception antennas, and receives a reception station based on a transfer function matrix between the transmission and reception antennas. TECHNICAL FIELD The present invention relates to a wireless communication device and a wireless communication method in a high-speed wireless access system that realizes wireless communication by demodulating data on the side, and in particular, a high-speed wireless access system (or wireless LAN using 2.4 GHz band or 5 GHz band) The present invention relates to a wireless communication apparatus and a wireless communication method that are used to increase the transmission speed of a system and realize good transmission characteristics while suppressing the circuit scale.

  In recent years, the IEEE802.11g standard, the IEEE802.11a standard, and the like are remarkable as high-speed wireless access systems using the 2.4 GHz band or the 5 GHz band. In these systems, a transmission rate of 54 Mbps is realized at the maximum, but further increase in the transmission rate is required with the spread of wireless LAN.

  As a technology for that purpose, MIMO (Multiple-Input Multiple-Output) technology is prominent. This MIMO technology is such that different independent signals are transmitted on the same channel from a plurality of transmitting antennas on the transmitting station side, and signals are received using the same plurality of antennas on the receiving station side, between each transmitting antenna / receiving antenna. The transfer function matrix is obtained, the independent signal transmitted from each antenna is estimated on the transmitting station side using this matrix, and the data is reproduced.

Here, consider a case in which N signals are transmitted using N transmission antennas and signals are received using M antennas. First, there are N × M transmission paths between the antennas of the transmitting and receiving stations, and the transfer function when the signal is transmitted from the i-th transmitting antenna and received by the j-th receiving antenna is defined as h _{j and i.} A matrix of N rows and M columns as the (j, i) -th component is denoted as H.

Further, let t _{i be} a transmission signal from the i-th transmission antenna, Tx be a column vector whose components are (t ₁ , t ₂ , t ₃ ,... T _N ), and r _{j be} a reception signal at the j-th reception antenna. (R ₁ , r ₂ , r ₃ ,... R _M ) as a column vector, Rx, and the thermal noise of the j-th receiving antenna as n _j (n ₁ , n ₂ , n ₃ ,. A column vector having n _M ) as a component is denoted as n.

  In this case, the following relational expression holds.

Rx = H × Tx + n (Formula 1)
Here, Rx is a received signal vector, H is a transfer function matrix, Tx is a transmitted signal column vector, and n is a thermal noise column vector.

  Therefore, there is a need for a technique for estimating the transmission signal Tx based on the signal Rx received on the receiving station side. As the most basic one of the MIMO techniques, there is a method generally called a ZF (Zero Forcing) method (for example, see Non-Patent Document 1).

Here, an inverse matrix H ⁻¹ of the transfer function matrix is obtained for (Equation 1) above, and a process of multiplying it from the left of both sides of the equation is performed. As a result, the following expression is obtained.

^{H -1 × Rx = Tx + H} -1 × n ··· ( Equation 2)
Here, H ⁻¹ is an inverse matrix of a transfer function matrix, Rx is a vector of a received signal, H is a transfer function matrix, Tx is a column vector of a transmission signal, and n is a column vector of thermal noise.

That is, when the signals received by the respective receiving antennas are combined and processing for removing interference caused by signals other than those from the desired transmitting antenna is performed, a minute thermal noise term H ⁻¹ × n is added to the actual transmission signal vector Tx. Signal points are obtained. Here, when a signal subjected to multilevel modulation such as BPSK, QPSK, 16QAM, and 64QAM is used as a transmission signal, signal points that can be taken as the transmission signal are discontinuous. Therefore, a hard decision process is performed to search the point on the transmission constellation where H ⁻¹ × Rx is the closest to the Euclidean distance, and a true transmission signal is estimated.

In the above ZF method, good characteristics can be expected when the thermal noise term H ⁻¹ × n is sufficiently small and the components for each transmitting antenna can be assumed to be equal. However, in general, this assumption does not hold, and the expected value of the absolute value of the thermal noise H ⁻¹ × n for each transmission antenna differs for a certain transfer function matrix. Furthermore, if the transfer function matrix H is a matrix that does not have an inverse matrix (or its determinant is very small), the estimation of the transmission signal becomes very unstable. In such a situation, there is a possibility that the reception characteristic is greatly deteriorated. As a method for solving such a problem, a method having the most excellent characteristic is a method called an MLD (Maximum Likelihood Detection) method (for example, see Non-Patent Document 2).

First, when the modulation method of the transmission signal from each antenna is determined, the number of signal points that can be taken by a signal transmitted from one antenna (hereinafter referred to as N _max ) is determined. There are N _max ^N types of variations of signal vectors transmitted across the N antennas. In the MLD method, prediction of a reception signal when the signal is transmitted is performed for all candidates (total of N _{max and} ^N types) that can be taken as a transmission signal, and the most actual reception signal among them is predicted. Is selected as the signal point with the highest estimation accuracy. In other words, if the kth transmission signal candidate is represented by Tx ^[k] , the value of k that minimizes the Euclidean distance E defined by the following equation is selected.

^{E = (Rx-H × Tx} [k]) H × (Rx-H × Tx [k]) ··· ( Equation 3)

Note that ^MH refers to a matrix that is Hermitian conjugate of the matrix M with respect to the matrix M (which may be a vector M). With the above processing, it is possible to perform stable reception processing for any matrix H, and the characteristics are greatly improved with respect to the ZF method.

  Here, FIG. 7 shows the configuration of the transmission unit of the first radio station (transmission-side radio communication apparatus) in the prior art. 7, reference numeral 100 denotes a data division circuit, 101-1 to 101-4 denote preamble assignment circuits, 102-1 to 102-4 denote modulation circuits, 103-1 to 103-4 denote radio units, and 104-1 to 104- Reference numeral 4 denotes a transmission antenna. As an example, a case where the transmitting station transmits four systems of data using four transmitting antennas will be described as an example.

  When data is input, the data dividing circuit 100 separates the data into four systems. For example, the first system data is input to the preamble applying circuit 101-1, and is input to the modulation circuit (Ch1) 102-1 with the preamble signal applied. The modulation circuit performs predetermined modulation, and the modulated signal is converted into a radio frequency by the radio unit 103-1, and transmitted from the transmission antenna 104-1. Similarly, the second system data is 101-2 to 104-2, the third system data is 101-3 to 104-3, and the fourth system data is 101-4 to 104-4, respectively. Sent individually.

  FIG. 8 shows a configuration of a receiving unit of a wireless communication apparatus using the MLD method in the prior art. In the figure, 111-1 to 111-4 are receiving antennas, 112-1 to 112-4 are radio units, 113 is a channel estimation circuit, 114 is a received signal management unit, 115 is a transfer function matrix management circuit, and 116 is a replica signal. A generation circuit, 117 is a transmission signal generation circuit, 118 is a Euclidean distance calculation circuit, 119 is a selection circuit, and 120 is a data synthesis circuit.

The first reception antenna 111-1 to the fourth reception antenna 111-4 individually receive the reception signals. The received signal is input to the channel estimation circuit 113 via the radio units 112-1 to 112-4. From the reception status of a predetermined preamble signal given on the transmission side, the channel estimation circuit 113 obtains the transfer function between each transmission antenna and the reception antenna here. The acquired information h _{j, i} of each transfer function is managed as a transfer function matrix H by the transfer function matrix management circuit 115.

The data signal following the preamble signal is input to the received signal management circuit 114 for each symbol. In the reception signal management circuit 114, a reception signal vector Rx having the reception signals (r ₁ , r ₂ , r ₃ , r ₄ ) of each antenna as components is once managed.

On the other hand, the transmission signal generation circuit 117 generates N _max ^N types of transmission signal candidates {S [k]} (1 ≦ k ≦ N _max ^N ) as all signal patterns that can be output from the transmission antenna. The replica signal generation circuit 116 calculates the product of the signal S [k] input from the transmission signal generation circuit 117 and the transfer function matrix H managed by the transfer function matrix management circuit 115, H × S [k], and the Euclidean distance. The arithmetic circuit 118 calculates the Euclidean distance between this result and the received signal vector Rx managed by the received signal management circuit 114. The above Euclidean distance calculation processing is performed for all k values (total N _max ^N times). The selection circuit 119 selects a signal having the shortest Euclidean distance from these, and determines that the transmission signal has the highest estimation accuracy. These data are continuously processed over a plurality of symbols, but after receiving a series of data, the data is reconstructed by the data synthesis circuit 120 and output.

  FIG. 9 shows a transmission flow of the first wireless station (transmission side wireless communication apparatus) in the prior art. When data is input (step S100), the transmitting station divides the data into N data series (step S101), and a preamble signal is assigned to each of these signals (step S102). Then, the modulation process is performed (step S103). The modulated signal is converted into a radio frequency by the radio unit, and the signal is transmitted (step S104).

  FIG. 10 shows a reception flow of the wireless communication apparatus using the MLD method in the prior art. When the receiving station receives a radio packet (step S110), it detects a preamble (step S111) and performs channel estimation (step S112). Here, all transfer functions between the transmission antennas and the reception antennas are acquired.

A signal received subsequent to the preamble signal is managed as a received signal vector Rx having the received signal r _j at each receiving antenna as a component for each symbol (step S113). On the other hand, N _max ^N types of transmission signal candidates {S [k]} (1 ≦ k ≦ N _max ^N ) are generated as all signal patterns that can be output from the transmission antenna, and the transfer function matrix H is generated. (Step S115, the Euclidean distance with the received signal Rx is calculated (step S116). In this process S114 to S116, in actuality, N _max ^N processes in total. That is, N _max ^N processes S114 to S116 are processed in parallel, or N _max ^N times in series as S114 → S115 → S116 → S114 → S115 → S116 → S114 → S115 → S116 →. It may be processed automatically or a combination thereof.

In any case, when the calculated E _max distance for each of the N _max ^N transmission signal vectors is obtained, the whole is compared and a transmission signal vector S [k _best ] that gives the minimum Euclidean distance is searched (step S117). With this S [k _best ], the signal estimation transmitted from each transmitting antenna of the corresponding symbol is determined (step S118). Further, when the received data continues, the process returns to the processing step S113, and the processing steps S113 to S119 are repeated. When the received data is finished (step S119), the series of received data of each system is reconstructed, the data on the transmission side is reproduced, and the data is output (step S120).

The biggest problem of this MLD method is that the calculation process for _obtaining the Euclidean distance must be performed N _max ^N times. For example, when 64QAM is used as the modulation method, N _max = 64. Using this example, the number of Euclidean distance calculations is 64 ² (= 4096) when N = ² , 64 ³ (= 262144) times when N = 3, and 64 ⁴ (= 166777216 when N = 4. ) Diversify exponentially with times.

When this is realized as a circuit, there are a method of sequentially performing the processing steps S114 to S116 in FIG. 10 in series and a method of processing in parallel, that is, simultaneously. However, in the case of performing serially, it is necessary to perform N _max ^N times of loop processing to determine one symbol of transmission data, resulting in a huge processing delay. On the other hand, even when executed in parallel, N _max ^N similar circuits must be mounted, and when N is 3 or more, the circuit scale increases explosively, so mounting on LSI is completely impossible. It becomes. An intermediate combination is also conceivable, but it is difficult to achieve both circuit scale and calculation time.

All the problems are caused by the fact that the processing amount of calculation becomes a value proportional to N _max ^N , and it is a problem to suppress this calculation amount.
S. Kurosaki et. Al., “A SDM-COFDM Scheme Employing a Simple Feed-Forward Inter-Channel Interference Canceller for MIMO Based Broadband Wireless LANs”, IEICE TRANS. COMMUN., Vol. E86B. No. 1, January, 2003 A.van Zelst et. Al., “Space Division Multiplexing (SDM) forOFDM Systems”, Proc. VTC2000 Spring, Vol.2, pp.1070-1074

  Accordingly, an object of the present invention is to provide a wireless communication apparatus and a wireless communication that can be realized with a realistic circuit scale and calculation amount while realizing good characteristics when performing wireless communication using MIMO technology. It is to provide a method.

In order to solve the above-described problem, a wireless communication device of the present invention includes a first wireless station including N (N is an integer greater than 1) or more first antenna groups, and M (M is greater than 1). (Integer) constituted by a second radio station having a second group of antennas, and the first radio station is divided into N systems and means for dividing input user data into N systems Means for generating a first signal sequence of N systems by assigning signals of individual known patterns to the obtained data, and the first signal simultaneously at the same frequency using N first antenna groups A wireless communication apparatus in a wireless communication system comprising means for transmitting a superimposed sequence,
Means for individually receiving radio signals using the M second antenna groups;
The transfer function h _j between the i-th antenna in the first antenna group and the j-th antenna in the second antenna group, using the signal of the known pattern given to the received signal as a reference signal. _{, i} for obtaining,
Means for obtaining a first approximate column vector Tx of an estimated value of a transmission signal based on a transfer function matrix H of M rows and N columns with the transfer function h _{j, i} as the (j, i) element;
Means for obtaining a column vector Tx ′ obtained by performing hard decision processing on each transmission signal point given by each element of the column vector Tx;
A predetermined number of signal points are selected from the values of each component of the column vector Tx ′ and signal points that can be taken as transmission signals in the vicinity thereof, and these are combined, and transmission signal candidates transmitted from the first antenna group are combined. Means for generating a plurality of types of signals,
Based on the generated transmission signal candidate signal and the transfer function matrix H, one of the candidate signals is selected and transmitted from the first radio station based on the selected signal. Means for reproducing and outputting user data ,
Determining the value of the number of transmission signal candidates (N _t1 , N _t2 , N _t3 ..., N _tN ) according to the estimated value of the signal-to-noise ratio for each antenna;
It is characterized by that.
In addition, the wireless communication apparatus of the present invention includes a first wireless station including N (N is an integer greater than 1) or more first antenna groups and M (M is an integer greater than 1) second. A second wireless station having a plurality of antenna groups, wherein the first wireless station is configured to divide input user data into N systems, and the known data individually divided into the N systems. Means for generating a first signal sequence of N systems by assigning a signal of the pattern of N, and transmitting the first signal sequence simultaneously superimposed at the same frequency using N first antenna groups A wireless communication device in a wireless communication system comprising:
Means for individually receiving radio signals using the M second antenna groups;
The transfer function h _j between the i-th antenna in the first antenna group and the j-th antenna in the second antenna group, using the signal of the known pattern given to the received signal as a reference signal. _{, i} for obtaining,
Means for obtaining a first approximate column vector Tx of an estimated value of a transmission signal based on a transfer function matrix H of M rows and N columns with the transfer function h _{j, i} as the (j, i) element;
Means for obtaining a column vector Tx ′ obtained by performing hard decision processing on each transmission signal point given by each element of the column vector Tx;
A predetermined number of signal points are selected from the values of each component of the column vector Tx ′ and signal points that can be taken as transmission signals in the vicinity thereof, and these are combined, and transmission signal candidates transmitted from the first antenna group are combined. Means for generating a plurality of types of signals,
Based on the generated transmission signal candidate signal and the transfer function matrix H, one of the candidate signals is selected and transmitted from the first radio station based on the selected signal. Means for reproducing and outputting user data
With
The value of the number of transmission signal candidates (N _t1 , N _t2 , N _t3 ..., N _tN ) is determined according to eigenvalues for each antenna of the matrices H ^H and H.
It is characterized by that.

As a specific example, means for generating a plurality of types of signals that are candidates for transmission signals transmitted from the first antenna group includes:
When each component of the column vector Tx ′ is (t ₁ , t ₂ , t ₃ ,... T _N ), N _max pieces (N _max is an integer greater than 1) that can be taken as transmission signal points in each component. Among the signal points, N _t1 (N _t1 is an integer equal to or less than N _max ) signal points including t ₁ as signal points of the first component, and N _t2 including t ₂ as signal points of the second component (N _t2 is an integer less than or equal to N _max ) signal points,... N _tN (N _tN is an integer less than or equal to N _max ) signal points including t _N And a means for generating a plurality of types of signals that are candidates for the transmission signal in combination.

In this case, the means for reproducing and outputting the user data transmitted from the first radio station includes:
N _mld types (N _mld = N _t1 × N _t2 ×... × N _tN : N _mld is an integer) of column vectors (1 ≦ k ≦ N _mld : k) that are candidates for the transmission signal. An integer) means for calculating a column vector given by the product of the transfer function matrix H and the column vector, that is, H × S [k], when S [k] is the column vector;
Means for calculating a signal point distance between the column vector H × S [k] and the actual received signal vector Rx for each column vector S [k];
Means for selecting a transmission signal point S [k _best ] that minimizes the distance between the signal points from among all k;
Means for combining the elements of the selected column vector and reproducing the user data transmitted from the first wireless station.

The means for obtaining the first approximate column vector Tx is:
Means for generating an N-row M-column matrix H ^H that is Hermitian conjugate of the transfer function matrix H;
Means for calculating a product of these matrices, that is, a matrix H ^H × H of N rows and N columns, and calculating a matrix (H ^H × H) ⁻¹ of N rows and N columns of an inverse matrix of the matrix;
Means for calculating a product of the inverse matrix and the matrix H ^H , that is, a matrix of N rows and M columns (H ^H × H) ⁻¹ × H ^H ;
Wherein the second of the m antenna reception signals actually received by the antenna group and r _m, column vector of M rows each component given by _{(r 1, r 2, r} 3, ··· r M) , Rx may be used to calculate a column vector Tx of N rows given by (H ^H × H) ⁻¹ × H ^H × Rx.
As a result, in the conventional MLD method, the circuit scale for calculating the Euclidean distance is exponentially divergent in proportion to the signal type N _max ^N with respect to the number N of superposed transmission signals. Therefore, it is possible to provide a simple method for realizing characteristics equivalent to the MLD method while suppressing the circuit scale.

The means for obtaining the first approximate column vector Tx is as follows when N = M:
Means for calculating an inverse matrix of the transfer function matrix H, that is, a matrix H ⁻¹ having N rows and N columns;
Wherein the second m-th received signal actually received by the antenna of the antenna group and r _m, column vector of N rows each component given by _{(r 1, r 2, r} 3, ··· r M) , Rx, means for calculating a column vector Tx of N rows given by H ⁻¹ × Rx;
You may make it have.
Thereby, when the number of antennas on the transmission / reception side is the same (N = M), the arithmetic processing can be further simplified.

The means for obtaining the first approximate column vector Tx is:
Means for generating an N-row M-column matrix H ^H that is Hermitian conjugate of the transfer function matrix H;
Means for obtaining a column vector y having each signal as a component when a preamble signal transmitted by the first radio station is received by the second antenna group;
Means for generating a Hermite conjugate row vector y ^H of the column vector;
The product of these vectors is a matrix of M rows and M columns, ie Y = y × and means for calculating the y ^H,
Means for averaging the values of each component of the matrix Y over a plurality of symbols and replacing them when the preamble signal covers a plurality of symbols;
Means for calculating an inverse matrix of the matrix Y, ie, Y ⁻¹ ;
Means for generating a matrix product of the matrices H ^H and Y ⁻¹ , that is, a matrix H ^H × Y ⁻¹ of N rows and M columns;
Wherein the second of the m antenna reception signals actually received by the antenna group and r _m, column vector of M rows each component given by _{(r 1, r 2, r} 3, ··· r M) , Rx, means for calculating a column vector Tx of N rows given by H ^H × Y ⁻¹ × Rx;
You may make it have.
This makes it possible to apply the MMSE method, which has better characteristics than the ZF method, when providing the initial information of the transmission signal point search, and to provide a simple implementation method for improving the characteristics.

In this wireless communication apparatus, an orthogonal frequency division multiplexing (OFDM) modulation scheme using a plurality of subcarriers between the wireless stations may be used.
As a result, the expansion of high-speed wireless LAN systems using the 5 GHz band and the 2.4 GHz band is currently attracting attention as an application area of the MIMO technology, and the present invention can be applied to these wireless LAN systems.

The present invention also provides
A first radio station having N (N is an integer greater than 1) or more first antenna groups, and a second radio station having M (M is an integer greater than 1) second antenna groups. A wireless communication method in a wireless communication system configured with a station,
By the first radio station,
Dividing the input user data into N systems;
Providing a signal of an individual known pattern to the data divided into the N systems to generate a first signal sequence of the N systems;
Performing the process of superimposing and transmitting the first signal sequence simultaneously at the same frequency using N first antenna groups,
By the second radio station,
Individually receiving radio signals using the M second antenna groups;
A transfer function h _j, between the i-th antenna of the first antenna group and the j-th antenna of the second antenna group, with a known pattern signal given to the received signal as a reference signal obtaining _i ;
Obtaining a first approximate column vector Tx of the estimated value of the transmission signal based on a transfer function matrix H of M rows and N columns with the transfer function h _{j, i} as the (j, i) element;
Obtaining a column vector Tx ′ obtained by performing hard decision processing on each transmission signal point given by each element of the column vector Tx;
A predetermined number of signal points are selected from the values of each component of the column vector Tx ′ and signal points that can be taken as transmission signals in the vicinity thereof, and these are combined, and transmission signal candidates transmitted from the first antenna group are combined. Generating a plurality of types of signals
Based on the generated transmission signal candidate signal and the transfer function matrix H, one of the candidate signals is selected and transmitted from the first radio station based on the selected signal. And reproducing and outputting the user data ,
Determining the value of the number of transmission signal candidates (N _t1 , N _t2 , N _t3 ..., N _tN ) according to the estimated value of the signal-to-noise ratio for each antenna;
A wireless communication method is provided.
The present invention also provides
A first radio station having N (N is an integer greater than 1) or more first antenna groups, and a second radio station having M (M is an integer greater than 1) second antenna groups. A wireless communication method in a wireless communication system configured with a station,
By the first radio station,
Dividing the input user data into N systems;
Providing a signal of an individual known pattern to the data divided into the N systems to generate a first signal sequence of the N systems;
Simultaneously superimposing and transmitting the first signal sequence at the same frequency using N first antenna groups;
Is implemented,
By the second radio station,
Individually receiving radio signals using the M second antenna groups;
A transfer function h _j, between the i-th antenna of the first antenna group and the j-th antenna of the second antenna group, with a known pattern signal given to the received signal as a reference signal obtaining _i ;
Obtaining a first approximate column vector Tx of the estimated value of the transmission signal based on a transfer function matrix H of M rows and N columns with the transfer function h _{j, i} as the (j, i) element;
Obtaining a column vector Tx ′ obtained by performing hard decision processing on each transmission signal point given by each element of the column vector Tx;
A predetermined number of signal points are selected from the values of each component of the column vector Tx ′ and signal points that can be taken as transmission signals in the vicinity thereof, and these are combined, and transmission signal candidates transmitted from the first antenna group are combined. Generating a plurality of types of signals
Based on the generated transmission signal candidate signal and the transfer function matrix H, one of the candidate signals is selected and transmitted from the first radio station based on the selected signal. Playing and outputting the user data
Is implemented,
The value of the number of transmission signal candidates (N _t1 , N _t2 , N _t3 ..., N _tN ) is determined according to eigenvalues for each antenna of the matrices H ^H and H.
A wireless communication method is provided.

As a specific example, the step of generating a plurality of types of signals that are candidates for transmission signals transmitted from the first antenna group includes:
When each component of the column vector Tx ′ is (t ₁ , t ₂ , t ₃ ,... T _N ), N _max pieces (N _max is an integer greater than 1) that can be taken as transmission signal points in each component. Among the signal points, N _t1 (N _t1 is an integer equal to or less than N _max ) signal points including t ₁ as signal points of the first component, and N _t2 including t ₂ as signal points of the second component (N _t2 is an integer less than or equal to N _max ) signal points,... N _tN (N _tN is an integer less than or equal to N _max ) signal points including t _N Combining and generating a plurality of types of signals as candidates for the transmission signal.

In this case, the step of reproducing and outputting the user data transmitted from the first wireless station includes:
N _mld types (N _mld = N _t1 × N _t2 ×... × N _tN : N _mld is an integer) of column vectors (1 ≦ k ≦ N _mld : k) that are candidates for the transmission signal. A step of calculating a column vector given by the product of the transfer function matrix H and the column vector, that is, H × S [k], where S (k) is the (integer) th column vector;
Calculating a distance between signal points of the column vector H × S [k] and the actual received signal vector Rx for each column vector S [k];
Selecting a transmission signal point S [k _best ] that minimizes the distance between the signal points from among all k;
And combining the elements of the selected column vector to reproduce user data transmitted from the first radio station.

The step of obtaining the first approximate column vector Tx includes:
Generating an N-row M-column matrix H ^H that is Hermitian conjugate of the transfer function matrix H;
Calculating the product of these matrices, i.e. the matrix H ^H × H of N rows and N columns;
Calculating an inverse matrix of the matrix, that is, an N × N matrix (H ^H × H) ⁻¹ ;
Calculating the product of the inverse matrix and the matrix H ^H , that is, a matrix of N rows and M columns (H ^H × H) ⁻¹ × H ^H ;
Wherein the second of the m antenna reception signals actually received by the antenna group and r _m, column vector of M rows each component given by _{(r 1, r 2, r} 3, ··· r M) Is a column vector Tx of N rows given by (H ^H × H) ⁻¹ × H ^H × Rx,
May be included.
As a result, in the conventional MLD method, the circuit scale for calculating the Euclidean distance is exponentially divergent in proportion to the signal type N _max ^N with respect to the number N of superposed transmission signals. Therefore, it is possible to provide a simple method for realizing characteristics equivalent to the MLD method while suppressing the circuit scale.

Further, the step of obtaining the first approximate column vector Tx may be performed when N = M.
Calculating an inverse matrix of the transfer function matrix H, that is, a matrix H ⁻¹ having N rows and N columns;
Wherein the second m-th received signal actually received by the antenna of the antenna group and r _m, column vector of N rows each component given by _{(r 1, r 2, r} 3, ··· r M) Is a column vector Tx of N rows given by H ⁻¹ × Rx,
May be included.
Thereby, when the number of antennas on the transmission / reception side is the same (N = M), the arithmetic processing can be further simplified.

The step of obtaining the first approximate column vector Tx includes:
Generating an N-row M-column matrix H ^H that is Hermitian conjugate of the transfer function matrix H;
Obtaining a column vector y having each signal as a component when a preamble signal transmitted by the first radio station is received by the second antenna group;
Generating a Hermite conjugate row vector y ^H of the column vector;
The product of these vectors is a matrix of M rows and M columns, ie Y = y × calculating y ^H ;
If the preamble signal spans multiple symbols, averaging the values of each component of the matrix Y over multiple symbols and replacing it with
Calculating an inverse matrix of the matrix Y, ie Y ⁻¹ ;
Generating a matrix product of the matrices H ^H and Y ⁻¹ , that is, a matrix H ^H × Y ⁻¹ with N rows and M columns;
Wherein the second of the m antenna reception signals actually received by the antenna group and r _m, column vector of M rows each component given by _{(r 1, r 2, r} 3, ··· r M) Where Rx is a step of calculating a column vector Tx of N rows given by H ^H × Y ⁻¹ × Rx;
May be included.
This makes it possible to apply the MMSE method, which has better characteristics than the ZF method, when providing the initial information of the transmission signal point search, and to provide a simple implementation method for improving the characteristics.

In the wireless communication device or wireless communication methods, depending on the number of candidates of the transmitted signal _{(N t1, N t2, N} t3 ···, N tN) the value of the estimated value of the signal-to-noise ratio for each antenna Has been decided. Alternatively, the value of the number of transmission signal candidates (N _t1 , N _t2 , N _t3 ..., N _tN ) is determined according to the eigenvalues for each antenna of the matrices H ^H and H.
Accordingly, it is possible to provide a simple implementation method for selecting the optimum number of candidates (N _t1 , N _t2 , N _t3 ..., N _tN ) in order to improve the characteristics while suppressing the circuit scale.
In this wireless communication method, an orthogonal frequency division multiplexing (OFDM) modulation method using a plurality of subcarriers between the wireless stations may be used.

  The present invention also provides a wireless communication system having the above-described wireless communication apparatus on the receiving side and performing wireless transmission / reception.

In the wireless communication apparatus of the present invention, in the conventional method, the candidate group of transmission signals {S [k]} to be generated is all signals that can be taken as transmission signals, and the first approximation Tx ′ of the estimated value of the transmission signals. In the present invention, the first approximate column vector Tx ′ of the estimated value of the transmission signal is obtained based on the transfer function matrix H after the channel estimation processing, and the candidate group {S The range of [k]} is limited.
Thus, it is possible to provide a wireless communication apparatus and a wireless communication method that can be realized with a realistic circuit scale and calculation amount while realizing good characteristics when performing wireless communication using MIMO technology. Can do.
As a specific example, based on the transfer function matrix H after channel estimation processing, H ^H , H ^H × H, (H ^H × H) ⁻¹ , (H ^H × H) ⁻¹ × H ^H are sequentially calculated. Do. When a received signal of a certain symbol is a vector Rx, the calculation of (H ^H × H) ⁻¹ × H ^H × Rx is performed to obtain a first approximate Tx of the estimated value of the transmission signal, and further by a hard decision circuit Tx ′ closest to Tx is obtained, and transmission signal candidates are generated only in the vicinity of Tx ′.
As a result, in the conventional MLD method, the circuit scale for calculating the Euclidean distance is exponentially divergent in proportion to the signal type N _max ^N with respect to the number N of superposed transmission signals. Therefore, it is possible to provide a simple method for realizing characteristics equivalent to the MLD method while suppressing the circuit scale.
Here, when the number of antennas on the transmission / reception side is the same (N = M), the inverse matrix H ⁻¹ of the transfer function matrix H is calculated, and when the reception signal vector Rx is used, the transmission signal is expressed by H ⁻¹ × Rx. A first approximation Tx of the estimated value is obtained.
Thereby, when the number of antennas on the transmission / reception side is the same (N = M), the arithmetic processing can be further simplified.

Also, a column vector y having a preamble signal received by each antenna as a signal component is obtained, and a Hermite conjugate row vector y ^H of the column vector is generated, and Y = y × y ^H and inverse matrix Y ⁻¹ are calculated, and further, matrix H ^H × Y ⁻¹ is generated, and the first estimated value of the transmission signal given by H ^H × Y ⁻¹ × Rx is obtained from received signal vector Rx. It is also possible to obtain the approximate Tx. Further, Tx ′ closest to Tx is obtained by the hard decision circuit, and transmission signal candidates are generated only in the vicinity of Tx ′.
This makes it possible to apply the MMSE method, which has better characteristics than the ZF method, when providing the initial information of the transmission signal point search, and to provide a simple implementation method for improving the characteristics.

  In addition, when an orthogonal frequency division multiplexing (OFDM) modulation scheme using a plurality of subcarriers between radio stations is used, the 5 GHz band and the 2.4 GHz band are currently used as the application area of the MIMO technology. The expansion of the high-speed wireless LAN system which has been attracting attention is applicable, and the present invention can be applied to these wireless LAN systems.

Further, the value of the vector of transmission signal candidates (N _t1 , N _t2 , N _t3 ..., N _tN ) is set according to the estimated value of the signal-to-noise ratio for each antenna, or the eigenvalue for each antenna. Can be determined according to This can provide a simple implementation method for selecting the optimum number of candidates (N _t1 , N _t2 , N _t3 ..., N _tN ) in order to improve the characteristics while suppressing the circuit scale.

The figure which shows the structural example of the receiving part of the radio | wireless communication apparatus in the 1st Embodiment of this invention. The figure which shows the structural example of the receiving part of the radio | wireless communication apparatus in the 2nd Embodiment of this invention. The figure which shows the structural example of the receiving part of the radio | wireless communication apparatus in the 3rd Embodiment of this invention. The figure which shows the reception flow of the radio | wireless communication apparatus in the 1st Embodiment of this invention. The figure which shows the reception flow of the radio | wireless communication apparatus in the 2nd Embodiment of this invention. The figure which shows the reception flow of the radio | wireless communication apparatus in the 3rd Embodiment of this invention. The figure which shows the transmission part structure of the 1st radio station in a prior art. The figure which shows the structure of the receiving part of the radio | wireless communication apparatus using the MLD method in a prior art. The figure which shows the transmission flow of the 1st radio station in a prior art. The figure which shows the reception flow of the radio | wireless communication apparatus using the MLD method in a prior art.

Explanation of symbols

  1-1 to 1-4 Transmitting antenna 2-1 to 2-4 Radio unit 3 Channel estimation circuit 4 Received signal management circuit 5 Transfer function matrix management circuit 6 Matrix operation circuit # 1 7 Matrix operation circuit # 2 8 Hard decision circuit 9 Transmission signal candidate generation circuit 10 Replica generation circuit 11 Euclidean distance operation circuit 12 Selection circuit 13 Data synthesis circuit 21 Matrix operation circuit # 1 22 Matrix operation circuit # 2 31 Matrix operation circuit # 1 32 Matrix operation circuit # 2 33 Reception signal management circuit DESCRIPTION OF SYMBOLS 100 Data division | segmentation circuit 101-1 to 101-4 Preamble provision circuit 102-1 to 102-4 Modulation circuit 103-1 to 103-4 Radio | wireless part 104-1 to 104-4 Transmission antenna 111-1 to 111-4 Reception antenna 112-1 to 112-4 Radio unit 113 Channel estimation circuit 114 Reception signal management circuit 115 Transfer function matrix management circuit 116 Replica generation circuit 117 Transmission signal generation circuit 118 Euclidean distance calculation circuit 119 Selection circuit 120 Data synthesis circuit

  The difference between the present invention and the prior art lies in the configuration and processing contents of the receiving unit of the wireless communication apparatus. The configuration and processing contents of the transmitting unit of the transmitting side wireless communication apparatus, that is, the conventional examples shown in FIGS. This is also common in the present invention. Therefore, a description will be given below of the receiving unit of the receiving-side wireless communication device.

  Hereinafter, various embodiments of the present invention will be described with reference to the drawings. In each figure, the product of the matrix is indicated by “·”.

[First Embodiment]
FIG. 1 is a diagram illustrating a first exemplary embodiment of a wireless communication device according to the present invention, and is a diagram illustrating a configuration example of a receiving unit of the wireless communication device. Here, as an example, a case where the number of receiving antennas M = 4 will be described as an example. In FIG. 1, 1-1 to 1-4 are receiving antennas, 2-1 to 2-4 are radio units, 3 is a channel estimation circuit, 4 is a received signal management circuit, 5 is a transfer function matrix management circuit, and 6 is a matrix. Arithmetic circuits # 1, 7 are matrix arithmetic circuits # 2, 8 are hard decision circuits, 9 is a transmission signal candidate generation circuit, 10 is a replica generation circuit, 11 is a Euclidean distance calculation circuit, 12 is a selection circuit, and 13 is a data synthesis circuit. Is shown.

The first receiving antenna 1-1 to the fourth receiving antenna 1-4 individually receive the received signals. The received signal is input to the channel estimation circuit 3 via the radio units 2-1 to 2-4. From the reception status of a predetermined preamble signal given on the transmission side, the transfer function between each transmission antenna and the reception antenna is acquired here by the channel estimation circuit 3. The acquired information h _{j, i} of each transfer function is managed as a transfer function matrix H by the transfer function matrix management circuit 5.

The data signal following the preamble signal is input to the received signal management circuit 4 for each symbol. In the received signal management circuit 4, the received signal vector Rx having the received signals (r ₁ , r ₂ , r ₃ , r ₄ ) of each antenna as components is once managed. In the matrix operation circuit # 1 (6), the acquired transfer function matrix H to H ^H (H Hermitian matrix), H ^H × H, (H ^H × H) ⁻¹ , (H ^H × H) ⁻¹ × H Sequential calculation with ^H.

The (H ^H × H) ⁻¹ × H ^H obtained here and the received signal vector Rx managed by the received signal management circuit 4 are subjected to integration processing by the matrix operation circuit # 2 (7). The signal point Tx = (H ^H × H) ⁻¹ × H ^H × Rx obtained here is a first approximation of the estimated value of the transmission signal, but transmission generally takes a discontinuous value due to the thermal noise term. It does not coincide with a point on the signal constellation. Therefore, the hard decision circuit 8 determines the transmission signal point Tx ′ closest to Tx.

The transmission signal candidate generation circuit 9 generates a transmission signal candidate group {S [k]} close to Tx ′ including the transmission signal point Tx ′ obtained previously. In the conventional MLD method, this transmission signal candidate group {S [k]} has all N _max ^N possible signal points as candidates, irrespective of the transmission signal point Tx ′ that is hard-decided. However, here, the transmission signal point Tx ′ is used as a reference, and the signal point is close to this signal point.

For example, when each component of the column vector Tx ′ of transmission signal points is (t ₁ , t ₂ , t ₃ ,... T _N ), N _max pieces (N _max can be taken as transmission signal points in each component). N _t1 (N _t1 is an integer less than or equal to N _max ) signal points including t ₁ as signal points of the first component, and t as signal points of the second component _N t2 _{(N t2} is _{N max} following integer) signal points including _{2, N} tN including _{t N} as signal points ... N-th component _{(N tN} is _{N max} following integer) signal By selecting points and combining them, a plurality of types of signals that are candidates for transmission signals transmitted from the first antenna group are generated, and N _mld types (N _mld = N _t1 × N _t2 ×.・ × N _tN : N _mld is an integer) column vector. The k-th (1 ≦ k ≦ N _mld : k is an integer) -th column vector in S is assumed to be S [k].
The values of some elements in (N _t1 , N _t2 ,..., N _tN ) may coincide with N _max , but at least one element takes a value smaller than N _max. As a result, N _mld <N _max ^N.

Also, the column vector S [k] generated by the transmission signal candidate generation circuit 9 is integrated by the replica generation circuit 10 with the transfer function matrix H managed by the transfer function matrix management circuit 5, and the transmission signal is S. The estimated value of the received signal when [k] is obtained. The distance between this value and the actual received signal managed by the received signal management circuit 4, that is, the Euclidean distance is obtained by the Euclidean distance calculation circuit 11. After performing the same processing for all the transmission signal candidate groups {S [k]}, the selection circuit 12 selects the signal S [k _best ] with the shortest Euclidean distance.
The reception signal determined for each symbol in this way is synthesized for each symbol by the data synthesis circuit 13, and the N series signals are combined into one series, and finally the data on the transmission side is reproduced. Output.

  In the description, the processing to be performed on all of the plurality of transmission signal candidate groups {S [k]} is grouped into one function block, the transmission signal candidate generation circuit 9, the replica generation circuit 10, and the Euclidean distance calculation circuit 11. However, a function for performing a predetermined number of operations is required in each functional block. For example, in order to shorten the processing delay, a similar circuit is mounted in parallel by the number of times of calculation. In order to suppress the circuit scale, the transmission signal candidate generation circuit 9 → the replica generation circuit 10 → the Euclidean distance calculation circuit 11 → the transmission signal candidate generation circuit 9 → the replica generation circuit 10 → the Euclidean distance calculation circuit 11 → the transmission signal candidate. It is also possible to adopt a configuration in which processing is performed on the generation circuit 9 →... And the loop.

  The above description shows an example in which the number of antennas of the first antenna group (transmission side) and the second antenna group (reception side) is generally different between N and M. On the other hand, when it is limited to N = M, the processing is slightly simplified.

[Second Embodiment]
FIG. 2 is a diagram illustrating a second exemplary embodiment of the wireless communication device of the present invention, and is a diagram illustrating a configuration example of a receiving unit of the wireless communication device. In FIG. 2, the contents of the process are the same as those shown in FIG. 1 except for the matrix operation circuit # 2 indicated by the matrix operation circuit # 1, 2 indicated by 21. Also, the matrix operation circuit # 1 (6) in FIG. 1 and the matrix operation circuit # 1 (21) in FIG. 2, the matrix operation circuit # 2 (7) in FIG. 1, and the matrix operation circuit # 2 (22) in FIG. The only difference is the content of processing performed internally.

In general, the values of N and M are different, and the transfer function matrix H is a non-square matrix. For this reason, the matrix is converted into a square matrix by using the product of Hermitian matrices H ^H and H of the transfer function matrix H. However, if the original matrix is a square matrix, such processing is not necessary, and the matrix calculation circuit # 1 (21) obtains an inverse matrix H- ¹ of the transfer function matrix H, and the matrix calculation circuit # 2 (22 ), The product of this inverse matrix and the received signal vector Rx may be taken.

  As described above, in the description of FIGS. 1 and 2, the conventional ZF method is used as the first approximation of the estimated value of the transmission signal. On the other hand, it is possible to select another method as the first approximation of the estimated value of the transmission signal. For example, the MMSE (Minimum Mean Square Error) method is an example.

[Third Embodiment]
FIG. 3 is a diagram illustrating a third exemplary embodiment of the present invention, and is a diagram illustrating a configuration example of a receiving unit of a wireless communication device. In FIG. 3, except for the reception signal management circuit indicated by matrix operation circuits # 2 and 33 indicated by matrix operation circuits # 1 and 32 indicated by 31, the processing contents are the same as those described in FIG. Also, the matrix operation circuit # 1 (6) in FIG. 1 and the matrix operation circuit # 1 (31) in FIG. 3, the matrix operation circuit # 2 (7) in FIG. 1, and the matrix operation circuit # 2 (31) in FIG. The reception signal management circuit 4 of FIG. 1 and the reception signal management circuit 33 of FIG.

In addition to the conventional function, the reception signal management circuit 33 has a function of extracting the preamble signal y from the received signal and inputting it to the matrix operation circuit # 1 (31). In the matrix operation circuit # 1 (31), H ^H is obtained from the transfer function matrix H acquired by the transfer function matrix management circuit 5, and the Hermitian conjugate vector is obtained for the preamble signal y input from the reception signal management circuit 33. It generates y ^H, and further executing calculation of y × ^{y H.} When the preamble signal is a plurality of symbols, the matrix Y is acquired as an average value of y × y ^{H as} an average value of a plurality of symbols, or when the preamble signal is one symbol, as it is. Further, the inverse matrix Y ⁻¹ and the matrix H ^H × Y ⁻¹ are sequentially calculated. The above is the function of the matrix operation circuit # 1 (31). On the other hand, the matrix operation circuit # 2 (32) calculates the matrix product of H ^H × Y ⁻¹ acquired from the matrix operation circuit # 1 (31) and the reception signal Rx input from the reception signal management circuit 33. To do. This H ^H × Y ⁻¹ × Rx is the first approximation of the estimated value of the transmission signal in this embodiment.

Then, similarly to the case shown in FIG. 1, the received signal is actually received by the second antenna group of the m antenna and r _m, each component _{(r 1, r 2, r} 3, ··· r _M ) column vector vector Mx) is Rx, N row column vector Tx given by H ^H × Y ⁻¹ × Rx is calculated, and transmission signal points given by each element of the column vector Tx Then, a column vector Tx ′ that has been subjected to hard decision processing is obtained.

When each component of the column vector Tx ′ is (t ₁ , t ₂ , t ₃ ,... T _N ), N _max pieces that can be taken as transmission signal points in each component (N _max is an integer greater than 1) Among the signal points, N _t1 (N _t1 is an integer equal to or less than N _max ) signal points including t ₁ as signal points of the first component, and N _t2 including t ₂ as signal points of the second component (N _t2 is an integer less than or equal to N _max ) signal points,... N _tN (N _tN is an integer less than or equal to N _max ) signal points including t _N In combination, a plurality of types of signals that are transmission signal candidates transmitted from the first antenna group are generated.

Then, N _mld types (N _mld = N _t1 × N _t2 ×... × N _tN : N _mld is an integer) column vectors (1 ≦ k ≦ N _mld : k) that are transmission signal candidates. Is an integer) When the Sth column vector is S [k], the product of the transfer function matrix H and the column vector, that is, the column vector given by H × S [k] is calculated. Further, the distance between signal points between the column vector H × S [k] and the actual received signal vector Rx for each column vector S [k] is calculated, and the distance between the signal points is minimized among all k. The transmission signal point S [k _best ] to be selected is selected, the elements of the selected column vector are combined, and the user data transmitted from the first radio station is reproduced and output.
In the above description, the matrix (H ^H × H) ⁻¹ × H ^H or H ⁻¹ is used as the estimated value (primary approximation) of the transmission signal. Other means may be used as long as the solution (or approximate solution) of the equation without the thermal noise term in the equation can be obtained.

  Note that, as an application area of the MIMO technology, expansion of a high-speed wireless LAN system using a 5 GHz band, a 2.4 GHz band, or the like is currently attracting attention. In these wireless LAN systems, an orthogonal frequency division multiplexing (OFDM) modulation scheme using a plurality of subcarriers is used. When the present invention is applied to these systems, each subcarrier is The above-described processing is performed.

[Explanation by reception flow]
FIG. 4 shows a reception flow in the wireless communication apparatus according to the first embodiment (see FIG. 1) of the present invention. In the conventional method shown in FIG. 10, the transmission signal candidate group {S [k]} generated in the processing step S114 is all signals that can be taken as the transmission signal, and the first approximation Tx of the estimated value of the transmission signal. In the present invention, H ^H , H ^H × H, (H ^H × H) ⁻¹ , (H ^H ) based on the transfer function matrix H after the channel estimation process (step S3). × H) performs sequential calculation and ^-1 × ^{H H} (step S4).

When the received signal of a certain symbol is Rx (step S5), (H ^H × H) ⁻¹ × H ^H × Rx is calculated (step S6), and the first approximation of the estimated value of the transmission signal is performed by hard decision processing. Tx ′ is obtained (step S7). The transmission signal candidate generation processing is limited to the vicinity of the first approximation Tx ′ of the estimated value of the transmission signal (step S8). The subsequent processing steps S10 to S15 are the same as the processing steps S116 to S121 of the conventional method shown in FIG.

  FIG. 5 is a diagram showing a reception flow in the wireless communication apparatus according to the second embodiment (see FIG. 2) of the present invention. The only difference from the reception flow shown in FIG. 4 is that the contents of the matrix calculation processing in processing step S4 and processing step S6 shown in FIG. 4 are replaced with processing step S24 and processing step S26 in FIG.

  FIG. 6 is a diagram showing a reception flow of the wireless communication apparatus in the third embodiment (see FIG. 3) of the present invention. The difference from the reception flow shown in FIG. 4 is that processing step S4 in FIG. 4 is replaced with processing steps S45 to S47 in FIG. 6, and processing step S6 is replaced with processing S49. Each content in each processing step corresponds to the processing described in FIG.

As described above, the method of obtaining the first approximation of the estimated value of the transmission signal is different, but the range for searching for the signal point with the minimum Euclidean distance is limited in the vicinity of the obtained transmission signal point of the first approximation. This is a feature of the present invention. As an example, assuming 64QAM, N _max = 64. However, if only the candidates for each transmit antenna to 5 points of the point of each component and to its first proximity Tx ', the computation amount is suppressed to 5 ^N. Furthermore, when limited to 9 points including up to the second proximity, the operation amount is suppressed to 9 ^N.
Further, it is not always necessary to be isotropic with respect to each component of Tx ′. When the transmission signal points are arranged in a grid, candidates may be selected so as to include each component of Tx ′ as the four corner points of the lattice including each component of Tx. In this case, the calculation amount is ^4N .
Taking the case of N = 4 as an example, the amount of calculation in the conventional method is 16,777,216 times, 6,561 times for 9 ^N , 625 times for 5 ^N , 256 times for 4 ^N It becomes. In this way, it is possible to dramatically reduce the calculation amount.

Here, the number of transmission signal candidates for each transmission antenna (N _t1 , N _t2 , N _t3 ..., N _tN ) is the same, but a different value may be used for each antenna. For example, if N = M, an estimated value of the signal-to-noise ratio of the signal corresponding to the i-th transmitting antenna can be obtained by the following equation.

Here, g _{j, i} represents the j-th, i-th component of the inverse matrix of the transfer function matrix H. In general, since the error is small due to thermal noise in the large good condition of the signal-to-noise ratio, and a small value of N _ti for such antennas, N _ti for small poor antenna signal-to-noise ratio Is set as a large value.
Note that a similar signal-to-noise ratio can be obtained by an operation different from the equation used here, and such a similar physical quantity can also be used.

In addition, as an index indicating the reception status of a signal corresponding to each transmission antenna, an eigenvalue of H ^H × H is often used for the transfer function matrix H. In general, the characteristic is better as the absolute value of the eigenvalue is larger, and the characteristic is worse when the absolute value of the eigenvalue is smaller. Therefore, _Nti is set to a small value when the absolute value of the eigenvalue is large, and _Nti is set to a large value when the absolute value of the eigenvalue is small.

  Furthermore, although the example using the Euclidean distance is shown here as the distance between the signal points of the actual received signal and the replica signal, other signal point distances (for example, approximate values for the Euclidean distance, etc.) may be used. I do not care.

As described above, according to the present invention, when performing high-efficiency wireless communication using MIMO technology, while achieving the good characteristics of the MLD method, the circuit is significantly larger than the conventional MLD method. It is possible to obtain an effect that the scale and the amount of calculation can be reduced. As a result, the receiving circuit can be mounted in a one-chip LSI. In addition, the reduction in the amount of computation can be expected to have a secondary effect of directly reducing power consumption.
Moreover, when realizing the above technology, it is preferable to implement it as hardware from the viewpoint of suppressing processing delay in a short time, but from the viewpoint of reducing the circuit scale, software processing with an equivalent processing flow can be used. It is also preferable to realize.

  In addition, all the embodiment described above shows this invention exemplarily, and does not show it limitedly, This invention can be implemented with another various deformation | transformation aspect and change aspect. Therefore, the scope of the present invention is defined only by the claims and their equivalents.

  In the present invention, when performing high-efficiency wireless communication using MIMO technology, the circuit scale and the amount of computation can be greatly reduced compared to the conventional MLD method while realizing the good characteristics of the MLD method. Thus, the present invention can be applied to a wireless communication device, a wireless communication method, a wireless communication system, and the like.

Claims (17)

A first radio station having N (N is an integer greater than 1) or more first antenna groups, and a second radio station having M (M is an integer greater than 1) second antenna groups. A first wireless station configured to divide input user data into N systems, and to add a signal of an individual known pattern to the data divided into the N systems. A wireless communication system comprising: means for generating the first signal sequence; and means for simultaneously superimposing and transmitting the first signal sequence at the same frequency using the N first antenna groups. A communication device,
Means for individually receiving radio signals using the M second antenna groups;
The transfer function h _j between the i-th antenna in the first antenna group and the j-th antenna in the second antenna group, using the signal of the known pattern given to the received signal as a reference signal. _{, i} to obtain,
Means for obtaining a first approximate column vector Tx of an estimated value of a transmission signal based on a transfer function matrix H of M rows and N columns with the transfer function h _{j , i} as the (j, i) element;
Means for obtaining a column vector Tx ′ obtained by performing hard decision processing on each transmission signal point given by each element of the column vector Tx;
A predetermined number of signal points are selected from the values of each component of the column vector Tx ′ and signal points that can be taken as transmission signals in the vicinity thereof, and these are combined, and transmission signal candidates transmitted from the first antenna group are combined. Means for generating a plurality of types of signals,
Based on the generated transmission signal candidate signal and the transfer function matrix H, one of the candidate signals is selected and transmitted from the first radio station based on the selected signal. Means for reproducing and outputting user data ,
Determining the value of the number of transmission signal candidates (N _t1 , N _t2 , N _t3 ... , N _tN ) according to the estimated value of the signal-to-noise ratio for each antenna;
A wireless communication apparatus.   A first radio station having N (N is an integer greater than 1) or more first antenna groups, and a second radio station having M (M is an integer greater than 1) second antenna groups. A first wireless station configured to divide input user data into N systems, and to add a signal of an individual known pattern to the data divided into the N systems. A wireless communication system comprising: means for generating the first signal sequence; and means for simultaneously superimposing and transmitting the first signal sequence at the same frequency using the N first antenna groups. A communication device,
  Means for individually receiving radio signals using the M second antenna groups;
  A transfer function h between the i-th antenna in the first antenna group and the j-th antenna in the second antenna group, using the signal of the known pattern added to the received signal as a reference signal. _{j , i} Means for obtaining
  The transfer function h _{j , i} The second ( j , i ) Means for obtaining a first approximate column vector Tx of the estimated value of the transmission signal based on the transfer function matrix H of M rows and N columns as elements;
  Means for obtaining a column vector Tx 'obtained by performing a hard decision process on each transmission signal point given by each element of the column vector Tx;
  A predetermined number of signal points are selected from the values of each component of the column vector Tx ′ and signal points that can be taken as transmission signals in the vicinity thereof, and these are combined, and transmission signal candidates transmitted from the first antenna group are combined. Means for generating a plurality of types of signals,
  Based on the generated transmission signal candidate signal and the transfer function matrix H, one of the candidate signals is selected and transmitted from the first radio station based on the selected signal. Means for reproducing and outputting user data
  With
  The number of transmission signal candidates (N _t1 , N _t2 , N _t3 ... , N _tN ) Is the matrix H ^H ・ Determined according to the eigenvalue of each antenna of H,
  A wireless communication apparatus. The wireless communication apparatus according to claim 1 or 2 ,
The means for obtaining the first approximate column vector Tx is:
Means for generating an N-row M-column matrix H ^H that is Hermitian conjugate of the transfer function matrix H;
Means for calculating a product of these matrices, that is, a matrix H ^H × H of N rows and N columns, and calculating a matrix (H ^H × H) ⁻¹ of N rows and N columns of an inverse matrix of the matrix;
Means for calculating a product of the inverse matrix and the matrix H ^H , that is, a matrix of N rows and M columns (H ^H × H) ⁻¹ × H ^H ;
Wherein the second of the m antenna reception signals actually received by the antenna group and r _m, column vector of M rows each component given by _{(r 1, r 2, r} 3, ··· r M) And Rx, a means for calculating a column vector Tx of N rows given by (H ^H × H) ⁻¹ × H ^H × Rx. The wireless communication apparatus according to claim 1 or 2 ,
The means for obtaining the first approximate column vector Tx is as follows when N = M:
Means for calculating an inverse matrix of the transfer function matrix H, that is, a matrix H ⁻¹ having N rows and N columns;
Wherein the second m-th received signal actually received by the antenna of the antenna group and r _m, column vector of N rows each component given by _{(r 1, r 2, r} 3, ··· r M) , Rx, means for calculating a column vector Tx of N rows given by H ⁻¹ × Rx;
A wireless communication apparatus comprising: The wireless communication apparatus according to claim 1 or 2 ,
The means for obtaining the first approximate column vector Tx is:
Means for generating an N-row M-column matrix H ^H that is Hermitian conjugate of the transfer function matrix H;
Means for obtaining a column vector y having each signal as a component when a preamble signal transmitted by the first radio station is received by the second antenna group;
Means for generating a Hermite conjugate row vector y ^H of the column vector;
Means for calculating a matrix of M rows and M columns, ie Y = y × y ^H , as the product of these vectors;
Means for averaging the values of each component of the matrix Y over a plurality of symbols and replacing them when the preamble signal covers a plurality of symbols;
Means for calculating an inverse matrix of the matrix Y, ie, Y ⁻¹ ;
Means for generating a matrix product of the matrices H ^H and Y ⁻¹ , that is, a matrix H ^H × Y ⁻¹ of N rows and M columns;
Wherein the second of the m antenna reception signals actually received by the antenna group and r _m, column vector of M rows each component given by _{(r 1, r 2, r} 3, ··· r M) , Rx, means for calculating a column vector Tx of N rows given by H ^H × Y ⁻¹ × Rx;
A wireless communication apparatus comprising: In the wireless communication device according to claim 1 or 2 ,
Means for generating a plurality of types of signals that are candidates for transmission signals transmitted from the first antenna group,
When each component of the column vector Tx ′ is (t ₁ , t ₂ , t ₃ ,... T _N ), N _max pieces (N _max is an integer greater than 1) that can be taken as transmission signal points in each component. Among the signal points, N _t1 (N _t1 is an integer equal to or less than N _max ) signal points including t ₁ as signal points of the first component, and N _t2 including t ₂ as signal points of the second component (N _t2 is an integer less than or equal to N _max ) signal points,... N _tN (N _tN is an integer less than or equal to N _max ) signal points including t _N A wireless communication apparatus comprising means for generating a plurality of types of signals that are candidates for the transmission signal in combination. The wireless communication device according to claim 6 , wherein
Means for reproducing and outputting user data transmitted from the first radio station;
N _mld types (N _mld = N _t1 × N _t2 ×... × N _tN : N _mld is an integer) of column vectors (1 ≦ k ≦ N _mld : k) that are candidates for the transmission signal. An integer) means for calculating a column vector given by the product of the transfer function matrix H and the column vector, that is, H × S [k], when S [k] is the column vector;
Means for calculating a signal point distance between the column vector H × S [k] and the actual received signal vector Rx for each column vector S [k];
Means for selecting a transmission signal point S [k _best ] that minimizes the distance between the signal points from among all k;
Means for combining the elements of the selected column vector and reproducing the user data transmitted from the first radio station. In the wireless communication device according to claim 1 or 2 ,
A radio communication apparatus using an orthogonal frequency division multiplexing (OFDM) modulation scheme using a plurality of subcarriers between the radio stations. A first radio station having N (N is an integer greater than 1) or more first antenna groups, and a second radio station having M (M is an integer greater than 1) second antenna groups. A wireless communication method in a wireless communication system configured with a station,
By the first radio station,
Dividing the input user data into N systems;
Providing a signal of an individual known pattern to the data divided into the N systems to generate a first signal sequence of the N systems;
Performing the process of superimposing and transmitting the first signal sequence simultaneously at the same frequency using N first antenna groups,
By the second radio station,
Individually receiving radio signals using the M second antenna groups;
A transfer function h _j between the i-th antenna in the first antenna group and the j-th antenna in the second antenna group, using a known pattern signal given to the received signal as a reference signal _. obtaining _i ;
Obtaining a first approximate column vector Tx of an estimated value of the transmission signal based on a transfer function matrix H of M rows and N columns with the transfer function h _{j , i} as the (j, i) element;
Obtaining a column vector Tx ′ obtained by performing hard decision processing on each transmission signal point given by each element of the column vector Tx;
A predetermined number of signal points are selected from the values of each component of the column vector Tx ′ and signal points that can be taken as transmission signals in the vicinity thereof, and these are combined, and transmission signal candidates transmitted from the first antenna group are combined. Generating a plurality of types of signals
Based on the generated transmission signal candidate signal and the transfer function matrix H, one of the candidate signals is selected and transmitted from the first radio station based on the selected signal. And reproducing and outputting the user data ,
Determining the value of the number of transmission signal candidates (N _t1 , N _t2 , N _t3 ... , N _tN ) according to the estimated value of the signal-to-noise ratio for each antenna;
A wireless communication method.   A first radio station having N (N is an integer greater than 1) or more first antenna groups, and a second radio station having M (M is an integer greater than 1) second antenna groups. A wireless communication method in a wireless communication system configured with a station,
  By the first radio station,
  Dividing the input user data into N systems;
  Providing a signal of an individual known pattern to the data divided into the N systems to generate a first signal sequence of the N systems;
  Superimposing the first signal series at the same frequency simultaneously using N first antenna groups And send and
  Is implemented,
  By the second radio station,
  Individually receiving radio signals using the M second antenna groups;
  A transfer function h between the i-th antenna in the first antenna group and the j-th antenna in the second antenna group using a signal of a known pattern added to the received signal as a reference signal. _{j , i} Step to get the
  The transfer function h _{j , i} The second ( j , i ) Obtaining a first approximate column vector Tx of the estimated value of the transmission signal based on the transfer function matrix H of M rows and N columns as elements;
  Obtaining a column vector Tx ′ obtained by performing hard decision processing on each transmission signal point given by each element of the column vector Tx;
  A predetermined number of signal points are selected from the values of each component of the column vector Tx ′ and signal points that can be taken as transmission signals in the vicinity thereof, and these are combined, and transmission signal candidates transmitted from the first antenna group are combined. Generating a plurality of types of signals
  Based on the generated transmission signal candidate signal and the transfer function matrix H, one of the candidate signals is selected and transmitted from the first radio station based on the selected signal. Playing and outputting the user data
  Is implemented,
  The number of transmission signal candidates (N _t1 , N _t2 , N _t3 ... , N _tN ) Is the matrix H ^H ・ Determined according to the eigenvalue of each antenna of H,
  A wireless communication method. The wireless communication method according to claim 9 or 10,
The step of obtaining the first approximate column vector Tx includes:
Generating an N-row M-column matrix H ^H that is Hermitian conjugate of the transfer function matrix H;
Calculating the product of these matrices, i.e. the matrix H ^H × H of N rows and N columns;
Calculating an inverse matrix of the matrix, that is, an N × N matrix (H ^H × H) ⁻¹ ;
Calculating the product of the inverse matrix and the matrix H ^H , that is, a matrix of N rows and M columns (H ^H × H) ⁻¹ × H ^H ;
Wherein the second of the m antenna reception signals actually received by the antenna group and r _m, column vector of M rows each component given by _{(r 1, r 2, r} 3, ··· r M) Is a column vector Tx of N rows given by (H ^H × H) ⁻¹ × H ^H × Rx,
A wireless communication method comprising: The wireless communication method according to claim 9 or 10,
The step of obtaining the first approximate column vector Tx is performed when N = M.
Calculating an inverse matrix of the transfer function matrix H, that is, a matrix H ⁻¹ having N rows and N columns;
Wherein the second m-th received signal actually received by the antenna of the antenna group and r _m, column vector of N rows each component given by _{(r 1, r 2, r} 3, ··· r M) Is a column vector Tx of N rows given by H ⁻¹ × Rx,
A wireless communication method comprising: The wireless communication method according to claim 9 or 10,
The step of obtaining the first approximate column vector Tx includes:
Generating an N-row M-column matrix H ^H that is Hermitian conjugate of the transfer function matrix H;
Obtaining a column vector y having each signal as a component when a preamble signal transmitted by the first radio station is received by the second antenna group;
Generating a Hermite conjugate row vector y ^H of the column vector;
Calculating an M × M matrix as the product of these vectors, ie Y = y × y ^H ;
If the preamble signal spans multiple symbols, averaging the values of each component of the matrix Y over multiple symbols and replacing it with
Calculating an inverse matrix of the matrix Y, ie Y ⁻¹ ;
Generating a matrix product of the matrices H ^H and Y ⁻¹ , that is, a matrix H ^H × Y ⁻¹ with N rows and M columns;
Wherein the second of the m antenna reception signals actually received by the antenna group and r _m, column vector of M rows each component given by _{(r 1, r 2, r} 3, ··· r M) Where Rx is a step of calculating a column vector Tx of N rows given by H ^H × Y ⁻¹ × Rx;
A wireless communication method comprising: In the wireless communication method according to claim 9 or 10,
The step of generating a plurality of types of transmission signal candidates transmitted from the first antenna group includes:
When each component of the column vector Tx ′ is (t ₁ , t ₂ , t ₃ ,... T _N ), N _max pieces (N _max is an integer greater than 1) that can be taken as transmission signal points in each component. Among the signal points, N _t1 (N _t1 is an integer equal to or less than N _max ) signal points including t ₁ as signal points of the first component, and N _t2 including t ₂ as signal points of the second component (N _t2 is an integer less than or equal to N _max ) signal points,... N _tN (N _tN is an integer less than or equal to N _max ) signal points including t _N And a step of generating a plurality of types of signals that are candidates for the transmission signal in combination. The wireless communication method according to claim 14, wherein
The step of reproducing and outputting user data transmitted from the first radio station includes:
N _mld types (N _mld = N _t1 × N _t2 ×... × N _tN : N _mld is an integer) of column vectors (1 ≦ k ≦ N _mld : k) that are candidates for the transmission signal. A step of calculating a column vector given by the product of the transfer function matrix H and the column vector, that is, H × S [k], where S (k) is the (integer) th column vector;
Calculating a distance between signal points of the column vector H × S [k] and the actual received signal vector Rx for each column vector S [k];
Selecting a transmission signal point S [k _best ] that minimizes the distance between the signal points from among all k;
Combining the elements of the selected column vector to reproduce the user data transmitted from the first radio station. In the wireless communication method according to claim 9 or 10,
A radio communication method using an orthogonal frequency division multiplexing (OFDM) modulation scheme using a plurality of subcarriers between the radio stations. A wireless communication system that has the wireless communication device according to claim 1 or 2 on a receiving side and performs wireless transmission / reception.