JP4198606B2 - Wireless communication system and transmission mode selection method - Google Patents

Description

  The present invention uses an orthogonal frequency division multiplexing (OFDM) modulation scheme, and uses a plurality of transmission modes that realize different transmission rates as combinations of modulation schemes and coding rates in error correction. In a wireless communication system capable of performing wireless communication by superimposing signals of one or a plurality of signal sequences on the same frequency band using one or a plurality of antennas in one antenna group, transmission quality and The present invention relates to an adaptive modulation system that performs communication while achieving both transmission efficiencies, and particularly to a technique for quickly estimating the communication state of a transmission path.

As a system that implements multiple transmission modes and performs communication by changing the transmission mode adaptively according to the communication situation, HiSWANa system compliant with ARIB STD-T70 standard, mainly based on 5 GHz band, ARIB STD-T71 standard compliant IEEE802.11a system.
These systems use a coded OFDM modulation scheme as a modulation scheme and support a plurality of transmission modes from 6 Mbps (BPSK R = 1/2) to 54 Mbps (64QAM R = 3/4).
As a method for selecting these transmission modes, the following OFDM modulation / demodulation circuit (see Patent Document 1) has been proposed.

FIG. 5 shows a flowchart of the receiving operation of the first and second radio stations in the conventional system. In FIG. 5, when a radio signal is received (S101), a preamble signal of the received signal is extracted (S102), and an FFT process is performed on the preamble signal (S103).
Then, it is separated into signals for each subcarrier in the frequency space by FFT processing, and a transfer function is obtained using a known preamble signal as a reference signal (S104).
Using this acquired transfer function, demodulation processing is performed by subsequent synchronous detection of data (S105). If the data continues (S106), the above processing S105 is continued, the user data is reproduced after the data is completed (S107), the reproduced user data is output, and the processing is terminated (S113).

  In the process of obtaining the transfer function in step S104, when the number of OFDM symbols of the preamble signal for performing channel estimation is M and the number of subcarriers of the OFDM signal is N, n collected in the mth OFDM symbol Assuming that the channel estimation signal of the th subcarrier is S (n, m) (S108), the signals collected in the M symbol preamble section are averaged as shown in Equation (1), and the noise component is removed to obtain n. The channel estimation signal C (n) of the th subcarrier is calculated (S109).

  Furthermore, using the obtained S (n, m) and C (n), information p shown in Equation (2) and information f shown in Equation (3) are calculated (S110).

The optimum transmission mode is obtained from the optimum transmission mode conversion table by referring to the optimum transmission mode conversion table that gives the optimum transmission mode for the combination of information f and p obtained by the equations (2) and (3). (S111).
The optimum transmission mode acquired from the optimum transmission mode conversion table is recorded and set as a recommended value for the transmission mode for the next transmission (S112).

In addition, in order to have the function of a 1st radio station and a 2nd radio station in a normal radio | wireless terminal, in FIG. 5, although the receiving flow was shown collectively, the 1st radio station and the 2nd radio station of FIG. When the functions are separated, processing S105 to processing S107 are not necessary for the first wireless station that transmits user data.
Similarly, the second wireless station that receives user data does not require processing S108 to processing S112.
Next, FIG. 6 shows a transmission flow of the first radio station in the conventional example. When user data to be transmitted is input (S121), a preamble signal is added to this signal (S122), the optimum transmission mode is referred to (S123), and data is transmitted using this optimum transmission mode (S124). .

In addition, in a wireless LAN system that assumes an office environment or the like, communication is efficiently performed with a plurality of users while adaptively switching a plurality of transmission modes.
The advantages of using multiple transmission modes adaptively can be broadly classified as follows:
(a) Response to the attenuation of received power depending on the distance between radio stations
(b) Response to transmission quality that varies with time due to fading, shadowing, etc.

Since the correspondence (a) hardly changes with time, it can be operated on the basis of a measurement result over a long period of time.
However, even in the optimum transmission mode obtained here, there is a possibility that the transmission quality is instantaneously deteriorated due to the effect of the correspondence (b).
The instantaneous degradation of transmission quality as shown in (b) can be guaranteed by retransmission control, but usually the number of retransmissions is finite and retransmission before the transmission mode can be optimized in response to instantaneous fluctuations. The upper limit of the number of times may be reached and retransmission may be aborted.

Since the resending of the retransmission is greatly reflected in the quality of service for the user, it may be fatal depending on the application to be used.
In consideration of this point, it is possible to operate on the safe side by setting a target transmission quality to be high by expecting a certain amount of instantaneous deterioration of quality.
However, this means that the transmission efficiency in the transmission mode is lowered, so that there is a problem that the throughput that can be provided decreases.

In this way, in a wireless LAN system where the transmission quality may fluctuate greatly instantaneously, in order to adaptively change the transmission mode, the instantaneous PER (Packet Error Rate) characteristics are estimated with higher accuracy. It is necessary to select a transmission mode that reflects the instantaneous PER characteristics.
The selection method of the optimum transmission mode in the conventional method can be used as an existing wireless LAN system, for example, in a system conforming to HiSWANa or IEEE802.11a in the 5 GHz band.
However, in recent years, the application of a technique called MIMO (Multiple-Input Multiple-Output) that attempts to improve transmission speed and frequency utilization efficiency by superimposing a plurality of different signal sequences on the same frequency band has been studied. .

  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 transmission signals are transmitted using N transmission antennas on the transmission side, and signals are received using N antennas on the reception side.
First, there are N × N transmission paths between the antennas of the transmitting and receiving stations, and the transfer function when transmitted from the i-th transmitting antenna and received by the j-th receiving antenna is h _{j, i.} A matrix of N rows and N columns as the (j, i) component is denoted as H. Further, a transmission signal from the i-th transmission antenna is denoted by t _i , a column vector having components (t ₁ , t ₂ , t ₃ ,..., T _N ) as Tx, and a reception signal at the j-th reception antenna as r _j. A column vector whose components are (r ₁ , r ₂ , r ₃ ,..., r _N ) is Rx, and the thermal noise of the jth receiving antenna is n _j (n ₁ , n ₂ , n ₃ ,..., n _N ). A column vector whose component is is denoted by n. In this case, the following relational expression (4) is established.

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 technology, there is a method generally called ZF (Zero Forcing) method (see Non-Patent Document 1).
Here, an inverse matrix H ⁻¹ of the transfer function matrix is obtained with respect to the above equation (4), and this is multiplied from the left of both sides of the equation. As a result, the following equation (5) is obtained.

That is, by synthesizing the signals received by the respective receiving antennas and performing processing for removing interference caused by signals from other than the desired transmitting antenna, a small thermal noise term H ⁻¹ × n is added to the actual transmitted signal vector Tx. An added signal point is 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 a point on the transmission constellation where H ⁻¹ × Rx is the closest to the Euclidean distance, and a true transmission signal (ie, transmitted by the transmitting station) is estimated.
JP 2001-103032 A 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.E86 B. No.1, January, 2003

However, when applying the above-described MIMO technique, instead of selecting the optimum one of the transmission modes represented as a combination of only the modulation scheme and the error correction coding rate as in the conventional scheme, It is necessary to select an optimal transmission mode as all combinations of the number of superpositions when superimposing the sequences, the modulation scheme, and the error correction coding rate.
Until now, there has been no technique for selecting an optimal transmission mode among such MIMO techniques. Furthermore, for example, when estimating a transmission signal using Equation (5), the basic policy is to eliminate interference from other signal sequences in the estimation of the transmission signal, and the S / N of each signal sequence is not necessarily used. The maximum ratio combining process that maximizes the ratio is not performed.

For this reason, even if the absolute value of each component of the transfer function matrix H is the same value, if the phase is different, the characteristics are greatly different from each other. It was impossible to grasp.
Therefore, the object of the present invention is made in view of such circumstances, and when performing the extension by applying the MIMO technology to the wireless LAN system, the instantaneous PER characteristic is changed to a small region (or less) such as a preamble. It is an object of the present invention to provide a system and method for quickly estimating from a sample) and selecting an optimum transmission mode in consideration of the MIMO technology based on the result.

The wireless communication method of the present invention includes a first wireless station having a first antenna group of N _tx (N _tx > 1: integer) or more and a second radio station of N _rx (N _rx ≧ 1: integer). And an orthogonal frequency division multiplex modulation method using N _SC (N _SC > 1: integer) subcarriers for user information transmission, and a modulation method and Signals of one or a plurality of signal sequences using a plurality of transmission modes realizing different transmission rates as combinations of coding rates in error correction, and further using one or a plurality of antennas in the first antenna group In the wireless communication system capable of performing wireless communication by superimposing on the same frequency band, the first wireless station receives a wireless signal using the first antenna group, and FFT (Fast Subtract received signal by Fourier Transform processing The step of converting into a signal on each carrier axis, and using a known pattern signal given to the received signal as a reference signal, the i-th antenna in the first antenna group and the second antenna group A transfer function h _{j, i} ^[k] for the k-th (1 ≦ k ≦ N _SC : k is an integer) subcarrier to the j-th antenna, and the transfer function h _{j, i} ^[k] the first (j, i) with respect to the transfer function matrix H _k regarding the k-th subcarrier of the N _rx rows N _tx columns having elements, a predetermined evaluation defined the components of the matrix H _k as a variable function F (H _k ), a step of calculating a total F _total for all subcarriers of the evaluation function F (H _k ) by calculation, and a modulation scheme, a coding rate, and a signal sequence for the value of F _total Refer to the conversion table that gives the combination of the number of superimpositions and select the optimal transmission mode When the optimum transmission mode selection step to be selected and the number of superpositions of the transmission mode last selected in the optimum transmission mode selection step is N ′ (1 ≦ N ′ ≦ N _tx : N ′ is an integer), the user A step of dividing user data into N ′ systems when data is input, and a first known signal sequence of the N ′ system by adding signals of individual known patterns to the data divided into the N ′ systems. And transmitting the first signal sequence superimposed on the same frequency band using the transmission mode selected in the optimum transmission mode selection step using the first antenna group. The second radio station individually receives a radio signal using the N _rx second antenna group, and a signal of a known pattern added to the received signal as a reference signal. The signals of each of the above signal sequences are A step of releasing demodulating, by combining all of the signal sequence demodulated, characterized in that a step of outputting as user data.

The wireless communication method of the present invention includes a first wireless station having a first antenna group of N _tx (N _tx > 1: integer) or more and a second radio station of N _rx (N _rx ≧ 1: integer). And an orthogonal frequency division multiplex modulation method using N _SC (N _SC > 1: integer) subcarriers for user information transmission, and a modulation method and Signals of one or a plurality of signal sequences using a plurality of transmission modes realizing different transmission rates as combinations of coding rates in error correction, and further using one or a plurality of antennas in the first antenna group In the wireless communication system capable of performing wireless communication by superimposing on the same frequency band, the first wireless station receives a wireless signal using the first antenna group, and FFT (Fast Subtract received signal by Fourier Transform processing The step of converting into a signal on each carrier axis, and using a known pattern signal given to the received signal as a reference signal, the i-th antenna in the first antenna group and the second antenna group A transfer function h _{j, i} ^[k] for the k-th (1 ≦ k ≦ N _SC : k is an integer) subcarrier to the j-th antenna, and the transfer function h _{j, i} ^[k] the first (j, i) to N _rx × N transfer function matrix H _k regarding the k-th subcarrier of _tx columns whose elements, determining a Hermitian conjugate matrix H _k ^H of the matrix H _k, the matrix H _determining the product of _k and H _k ^H , ie, either H _k × H _k ^H or H _k ^H × H _k , and the matrix H _k × H _k ^H or H _k ^H × H _k A predetermined evaluation function F (H _k × H _k ^H ) or F (H _k ^H × H _k ) defined with each component as a variable is calculated. A step, a step of calculating the total F _total for all subcarriers of the evaluation function F (H _k × H _k ^H ) or F (H _k ^H × H _k ) by calculation, and modulating the value of the F _total An optimum transmission mode selection step for selecting an optimum transmission mode with reference to a conversion table that gives a combination of a scheme, a coding rate, and the number of superimpositions of a signal sequence, and a transmission mode last selected in the optimum transmission mode selection step. When the number of superpositions is N ′ (1 ≦ N ′ ≦ N _tx : N ′ is an integer), the step of dividing the user data into N ′ systems when the user data is input; A step of generating a first signal sequence of N ′ system by giving a signal of an individual known pattern to the divided data, and selecting in the optimum transmission mode selection step using the first antenna group Using the same transmission mode And sending by superimposing said first signal sequence at the frequency band, the second radio station receives radio signals individually using the second antenna group of N _rx present A step, a step of separating and demodulating the signals of each signal sequence using a known pattern signal given to the received signal as a reference signal, and synthesizing all the demodulated signal sequences and outputting them as user data And a step.

  The wireless communication method of the present invention uses the determinant Det (M) of the matrix M or its absolute value | Det (M) | as the evaluation function F (M) for the matrix M in the wireless communication method described above. Characteristic (corresponding to equation (6)).

  The wireless communication method of the present invention uses the logarithm value Log (| Det (M) |) of the absolute value of the determinant of the matrix M as the evaluation function F (M) for the matrix M in the wireless communication method described above. (Corresponding to equation (7)).

  The wireless communication method of the present invention is characterized in that, in the wireless communication method described above, the sum of absolute values of each component of the matrix M is used as the evaluation function F (M) for the matrix M (Formula (8)). Correspondence).

  The wireless communication method of the present invention is characterized in that, in the wireless communication method described above, the sum of the squares of the absolute values of the components of the matrix M is used as the evaluation function F (M) for the matrix M (Equation ( 10)).

  The wireless communication method of the present invention is characterized in that, in the above-described wireless communication method, a logarithmic value of the sum of absolute values of each component of the matrix M is used as the evaluation function F (M) for the matrix M (formula ( 9)).

In the wireless communication method of the present invention, in the wireless communication method described above, as the evaluation function F (M) for the square matrix M of N rows and N columns, the inverse matrix of the matrix M is G, and the inverse matrix G is further configured. When the column vectors are V ₁ , V ₂ , V ₃ ,..., V _N , the reciprocal of the value obtained by calculating the square root of the sum of the squares of the absolute values of the respective components for each column vector is obtained. A value obtained by taking the sum of the values for all column vectors is used (corresponding to equation (22)).

In the wireless communication method of the present invention, in the wireless communication method described above, an inverse matrix of a square matrix M of N rows and N columns is G, and column vectors constituting the inverse matrix G are V ₁ , V ₂ , V ₃ , respectively. ,..., V _N , the square root of the sum of the squares of the absolute values of the respective components is obtained for each column vector, the logarithmic value of the reciprocal of the square root value is obtained, and the logarithmic values are further calculated for all columns. A value obtained by summing up the vectors is used (corresponding to equation (23)).

The wireless communication method of the present invention is the above-described wireless communication method, wherein the eigenvalues λ ₁ , λ ₂ , λ ₃ ,..., Λ _N of the matrix M are used as the evaluation function F (M) for the square matrix M of N rows and N columns. And a value obtained by taking the sum of absolute values of the eigenvalues is used (corresponding to equation (11)).

The wireless communication method of the present invention is the above-described wireless communication method, wherein the eigenvalues λ ₁ , λ ₂ , λ ₃ ,..., Λ _N of the matrix M are used as the evaluation function F (M) for the square matrix M of N rows and N columns. And a value obtained by taking the sum of the squares of the absolute values of the eigenvalues is used (corresponding to equation (12)).

The wireless communication method of the present invention is the above-described wireless communication method, wherein the eigenvalues λ ₁ , λ ₂ , λ ₃ ,..., Λ _N of the matrix M are used as the evaluation function F (M) for the square matrix M of N rows and N columns. And a value obtained by taking the sum of the reciprocal of the absolute value of the eigenvalue is used (corresponding to equation (13)).

The wireless communication method of the present invention is the above-described wireless communication method, wherein the eigenvalues λ ₁ , λ ₂ , λ ₃ ,..., Λ _N of the matrix M are used as the evaluation function F (M) for the square matrix M of N rows and N columns. And a value obtained by taking the sum of the squares of the reciprocals of the absolute values of the eigenvalues is used (corresponding to equation (14)).

The wireless communication method of the present invention is the above-described wireless communication method, wherein the eigenvalues λ ₁ , λ ₂ , λ ₃ ,..., Λ _N of the matrix M are used as the evaluation function F (M) for the square matrix M of N rows and N columns. And a value obtained by taking the sum of the logarithm of the absolute value of the eigenvalue is used (corresponding to equation (15)).

The wireless communication method of the present invention is the above-described wireless communication method, wherein the eigenvalues λ ₁ , λ ₂ , λ ₃ ,..., Λ _N of the matrix M are used as the evaluation function F (M) for the square matrix M of N rows and N columns. And the eigenvalue having the maximum absolute value among the eigenvalues is represented by λ _max , and the eigenvalue having the minimum absolute value is represented by λ _mini, and the absolute value of λ _mini / λ _max is used. (Corresponding to equation (16)).

The wireless communication method of the present invention is the above-described wireless communication method, wherein the eigenvalues λ ₁ , λ ₂ , λ ₃ ,..., Λ _N of the matrix M are used as the evaluation function F (M) for the square matrix M of N rows and N columns. look, further eigenvalues absolute value is maximized lambda _max in the eigenvalues, when the absolute value is represented eigenvalues become minimum lambda _mini, and characterized by using the absolute value of the λ _max / λ _mini (Corresponding to equation (17)).

The wireless communication method of the present invention is the above-described wireless communication method, wherein the eigenvalues λ ₁ , λ ₂ , λ ₃ ,..., Λ _N of the matrix M are used as the evaluation function F (M) for the square matrix M of N rows and N columns. Further, when the eigenvalue having the maximum absolute value among the eigenvalues is expressed as λ _max and the eigenvalue having the minimum absolute value as λ _mini , the square value of the absolute value of λ _mini / λ _max is used. (Corresponding to equation (18)).

The wireless communication method of the present invention is the above-described wireless communication method, wherein the eigenvalues λ ₁ , λ ₂ , λ ₃ ,..., Λ _N of the matrix M are used as the evaluation function F (M) for the square matrix M of N rows and N columns. Further, when the eigenvalue having the maximum absolute value among the eigenvalues is expressed as λ _max , and the eigenvalue having the minimum absolute value as λ _mini , the square value of the absolute value of λ _max / λ _mini is used. (Corresponding to equation (19)).

The wireless communication method of the present invention is the above-described wireless communication method, wherein the eigenvalues λ ₁ , λ ₂ , λ ₃ ,..., Λ _N of the matrix M are used as the evaluation function F (M) for the square matrix M of N rows and N columns. look, further absolute eigenvalues is maximized lambda _max in the eigenvalues, eigenvalues absolute value is minimum when expressed as lambda _mini, using the logarithm of the absolute value of the λ _max / λ _mini (Corresponding to equation (24)).

The wireless communication method of the present invention obtains eigenvalues λ ₁ , λ ₂ , λ ₃ ,..., Λ _N of the matrix M as the evaluation function F (M) for the square matrix M of N rows and N columns, absolute value of the eigenvalue of maximum lambda _max in the eigenvalues absolute value is minimum when expressed as lambda _mini, characterized by using the square of the sum of the absolute values of λ _mini / λ _max.

The wireless communication method of the present invention obtains eigenvalues λ ₁ , λ ₂ , λ ₃ ,..., Λ _N of the matrix M as the evaluation function F (M) for the square matrix M of N rows and N columns, The sum of the squares of the absolute values of λ _max / λ _mini is used, where λ _{max is} the eigenvalue having the _maximum absolute value and λ _mini is the eigenvalue having the minimum absolute value.

  In the wireless communication method of the present invention, in the wireless communication method described above, as the evaluation function F (M) for the matrix M, the determinant of the matrix M is the square root of the sum of the squares of the absolute values of the components of the matrix M. A value obtained by dividing the taken value is used (corresponding to Expression (20)).

  In the wireless communication method of the present invention, in the wireless communication method described above, as the evaluation function F (M) for the matrix M, the determinant of the matrix M is the square root of the sum of the squares of the absolute values of the components of the matrix M. The logarithmic value of the value divided by the taken value is used (corresponding to equation (21)).

The radio communication system of the present invention includes a first radio station having a first antenna group of N _tx (N _tx > 1: integer) or more and a second radio station of N _rx (N _rx ≧ 1: integer). And an orthogonal frequency division multiplex modulation method using N _SC (N _SC > 1: integer) subcarriers for user information transmission, and a modulation method and Signals of one or a plurality of signal sequences using a plurality of transmission modes realizing different transmission rates as combinations of coding rates in error correction, and further using one or a plurality of antennas in the first antenna group Is a wireless communication system capable of performing wireless communication by superimposing them on the same frequency band, wherein the first wireless station includes a receiving means for receiving a wireless signal using the first antenna group, and an FFT (Fast Fourier Transform) process A reception signal conversion means for converting the signal into a signal on each axis of the carrier, and a signal having a known pattern given to the reception signal as a reference signal, the i-th antenna and the second antenna in the first antenna group Transfer function acquisition means for acquiring a transfer function h _{j, i} ^[k] related to a kth (1 ≦ k ≦ N _SC : k is an integer) subcarrier between the jth antenna of the group and the transfer function h _With respect to the transfer function matrix H _k related to the k th subcarrier of N _rx rows and N _tx columns, ^where _{j, i} ^[k] is the (j, i) element, a predetermined value defined with each component of the matrix H _k as a variable and evaluation function calculation means for calculating the evaluation function F (H _k), and summation means for obtaining by calculation the total sum F _total for all subcarriers of the evaluation function F (H _k), for values of the F _total , A conversion table that gives a combination of modulation scheme and coding rate and the number of superimposed signal sequences. The transmission mode selection means for selecting the optimum transmission mode with reference to the table, and the superposition number of the transmission mode last selected in the optimum transmission mode selection step is N ′ (1 ≦ N ′ ≦ N _tx : N ′ When the user data is input, the user data dividing means for dividing the user data into N ′ systems, and a signal of an individual known pattern is given to the data divided into the N ′ systems. Using the transmission mode selected in the optimal transmission mode selection step using the first antenna group and the signal sequence generation means for generating the first signal sequence of the N ′ system, and on the same frequency band And transmitting means for superimposing and transmitting the first signal sequence, wherein the second radio station individually receives radio signals using the N _rx second antenna groups. And a signal with a known pattern attached to the received signal As a reference signal, demodulating means for demodulating to separate the signals of the respective signal sequences, were synthesized all signal sequences obtained by demodulating, and having a signal sequence combining means for outputting as a user data.

The radio communication system of the present invention includes a first radio station having a first antenna group of N _tx (N _tx > 1: integer) or more and a second radio station of N _rx (N _rx ≧ 1: integer). And an orthogonal frequency division multiplex modulation method using N _SC (N _SC > 1: integer) subcarriers for user information transmission, and a modulation method and Signals of one or a plurality of signal sequences using a plurality of transmission modes realizing different transmission rates as combinations of coding rates in error correction, and further using one or a plurality of antennas in the first antenna group Is a wireless communication system capable of performing wireless communication by superimposing them on the same frequency band, wherein the first wireless station includes a receiving means for receiving a wireless signal using the first antenna group, and an FFT (Fast Fourier Transform) process A reception signal conversion means for converting the signal into a signal on each axis of the carrier, and a signal having a known pattern given to the reception signal as a reference signal, the i-th antenna and the second antenna in the first antenna group Transfer function obtaining means for obtaining a transfer function h _{j, i} ^[k] related to a k-th (1 ≦ k ≦ N _SC : k is an integer) sub-carrier between the j-th antenna and the transfer function h. _{j, i} ^[k] the first (j, i) with respect to the transfer function matrix H _k regarding the k-th subcarrier of the N _rx rows N _tx columns whose elements, obtaining the Hermitian conjugate matrix H _k ^H of the matrix H _k a Hermitian conjugate operation means, a product calculation means for calculating either the product i.e. _{H k} × _{H k} ^H or _{H k} ^H × _{H k} of the matrix _{H k} and _{H k} ^H, the matrix _{H k} × _{H k} ^H or H A predetermined evaluation function F (H _k × H _k) defined with each component of any matrix of _k ^H × H _k as a variable ^H ) or F (H _k ^H × H _k ), and a sum F for all subcarriers of the evaluation function F (H _k × H _k ^H ) or F (H _k ^H × H _k ) a summation means for obtaining by calculation the _total, with respect to the value of the F _total, with reference to the conversion table that gives the combination of superimposed number of modulation scheme and coding rate and signal sequences, transmission mode selection for selecting the optimum transmission mode And when the superimposition number of the transmission mode last selected in the optimum transmission mode selection step is N ′ (1 ≦ N ′ ≦ N _tx : N ′ is an integer), when user data is input And a user data dividing means for dividing the user data into N ′ systems, and generating a first signal sequence of N ′ systems by giving individual known pattern signals to the data divided into the N ′ systems. Signal sequence generation means and the first antenna group, Using the transmission mode selected by suitable transmission mode selecting step, and transmitting means for transmitting by superimposing said first signal sequence at the same frequency band, the second radio station, N _rx present Receiving means for individually receiving a radio signal using the second antenna group, and using a known pattern signal given to the received signal as a reference signal, the signals of each signal series are separated and demodulated A demodulating means and a signal series synthesizing means for synthesizing all demodulated signal sequences and outputting them as user data are provided.

As described above, the wireless communication method of the present invention is different from the conventional system in that the i-th antenna in the first antenna group and the first antenna are used as a reference signal with a known pattern signal added to the received signal. Obtaining a transfer function h _{j, i} ^[k] for the k-th (1 ≦ k ≦ N _SC : k is an integer) subcarrier between the j-th antenna of the two antenna groups, and the transfer function h _{j, i} ^[k] the first (j, i) with respect to the transfer function matrix H _k regarding the k-th subcarrier of the N _rx rows N _tx columns whose elements are defined the components of the transfer function matrix H _k as a variable And a step of calculating a predetermined evaluation function F (H _k ) and a step (or configuration) of calculating a total F _total for all subcarriers of the evaluation function F (H _k ) by calculation.

  Here, it is also preferable to use the determinant Det (M) of the matrix M or its absolute value | Det (M) | as the evaluation function F (M). It is also preferable to use the logarithm value Log (| Det (M) |) of the absolute value of the determinant of the matrix M as the evaluation function F (M). It is also preferable to use the sum of absolute values of each component of the matrix M as the evaluation function F (M). It is also preferable to use the sum of the squares of the absolute values of the components of the matrix M as the evaluation function F (M). It is also preferable to use a logarithmic value of the sum of absolute values of the components of the matrix M as the evaluation function F (M).

Further, when the inverse matrix of the matrix M is G and the column vectors constituting the inverse matrix G are V ₁ , V ₂ , V ₃ ,..., V _N , respectively, the evaluation function F (M) It is also preferable to use a value obtained by calculating the reciprocal of the value obtained by calculating the square root of the sum of the squares of the absolute values of the respective components for each column vector, and further calculating the sum of the values for all the column vectors. Further, as the evaluation function F (M), each column vector _{V 1, V 2, V 3} , ..., a pair of the reciprocal of the value of the square root for each V _N for square value of the sum of the absolute values of the components It is also preferable to obtain a numerical value and use a value obtained by summing the values with respect to all column vectors.

Furthermore, when the eigenvalues of the matrix M are λ ₁ , λ ₂ , λ ₃ ,..., Λ _N , it is preferable to use a value obtained by summing up the absolute values of the eigenvalues as the evaluation function F (M). It is also preferable to use a value obtained by taking the sum of the squares of the absolute values of the eigenvalues as the evaluation function F (M). It is also preferable to use a value obtained by summing the reciprocal of the absolute value of the eigenvalue as the evaluation function F (M). As the evaluation function F (M), it is also preferable to use a value obtained by summing the squares of the reciprocals of the absolute values of the eigenvalues. It is also preferable to use a value obtained by summing the logarithmic values of the absolute values of the eigenvalues as the evaluation function F (M).

Further, when the eigenvalue having the maximum absolute value among the eigenvalues is expressed as λ _max and the eigenvalue having the minimum absolute value as λ _mini , the evaluation function F (M) is expressed as λ _max / λ _mini. It is also preferable to use the absolute value of. It is also preferable to use an absolute value of λ _mini / λ _max as the evaluation function F (M). It is also preferable to use the square value of the absolute value of λ _max / λ _mini as the evaluation function F (M). Furthermore, it is also preferable to use the square value of the absolute value of λ _mini / λ _max as the evaluation function F (M). It is also preferable to use a logarithmic value of the absolute value of λ _max / λ _mini as the evaluation function F (M). Further, as the evaluation function F (M), it is also preferable to use a value obtained by dividing the determinant of the matrix M by a value obtained by taking the square root of the sum of the squares of the absolute values of the components of the matrix M.

It is also preferable to use a logarithmic value obtained by dividing the determinant of the matrix M by the value obtained by taking the square root of the sum of the squares of the absolute values of the components of the matrix M as the evaluation function F (M). Furthermore, when the matrix M of the evaluation function F (M) is a non-square matrix, a matrix that is the product of the matrix M and the Hermitian conjugate matrix ^MH of the matrix instead of the matrix M described above. , M ^H × M, or M × M ^H is preferably replaced with the matrix M.
The above is a specific example for giving the previous evaluation function F (M).

As described above, according to the present invention, in the wireless LAN system to which the MIMO technology is applied, the preamble added to the received signal received and the signal of the known pattern stored in advance (the pattern used for the preamble) By comparing / calculating a reference signal that is the same), the kth (1) between the i-th antenna of the first antenna group and the j-th antenna of the second antenna group. ≦ k ≦ N _SC : k is an integer) Acquires a transfer function h _{j, i} ^[k] related to a subcarrier and generates an evaluation function F (H _k ) based on the transfer function H _k , that is, an instantaneous PER characteristic as a preamble, etc. Thus, it is possible to provide a method for quickly estimating from a small region (or a small number of samples) and selecting an optimum transmission mode in consideration of the MIMO technique.

Hereinafter, a wireless communication system according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 (first embodiment) and FIG. 2 (second embodiment) are block diagrams showing the configuration of the embodiment.
The wireless communication system of the present invention includes a first wireless station (transmission) including N _tx (N _tx > 1: integer) or more first antenna groups (antennas 100 ₁ to 100 _p , p = N _tx ). Station T1 or T2) and a second radio station (receiving station R) having N _rx (N _rx ≧ 1: integer) second antenna group (antenna 101 ₁ to antenna 101 _q , q = N _rx ). ), And uses an Orthogonal Frequency Division Multiplexing (OFDM) modulation scheme that uses N _SC subcarriers for user information transmission, and differs as a combination of modulation scheme and coding rate in error correction. A plurality of transmission modes for realizing a transmission rate are used, and further, one or a plurality of antennas in the first antenna group are used to superimpose signals of one or a plurality of signal sequences on the same frequency band and are wireless. To communicate It has a possible configuration.

  On the transmitting station side, it is necessary to acquire a transfer function matrix. One method for that purpose will be described first. For example, a control unit (not shown) of the transmitting station (T1 or T2), when starting transmission processing of actual transmission data to the receiving station R, sends a normal communication method from the transmitting / receiving means 1 without using the MIMO method as a transmission method. In order to perform a process of obtaining a transfer function matrix (a matrix composed of transfer functions of subcarriers between the antennas in the first and second antenna groups) from any one antenna of the first antenna group, A predetermined control signal is transmitted to the receiving station R.

In this case, for example, the control signal instructs the receiving station R to transmit a response signal to which a preamble (a signal of a known pattern) is added according to the MIMO scheme. At this time, the signal of this known pattern needs to be set in advance as common between the transmitting station T1 (or T2) and the receiving station R.
On the transmitting station side, the preamble is separated from the received response signal (received signal) from the receiving station, and the transfer function h _{j, i} ^[k] and a transfer function matrix H _k are obtained, and an evaluation function is calculated based on the transfer function matrix H _k (or transfer function h _{j, i} ).

  As described above, the control unit of the transmitting station (T1 or T2) can obtain a transfer function matrix with the receiving station before actually transmitting data in the transmission process. Since this transfer function changes from moment to moment depending on time and surrounding conditions, it is necessary to update information at a certain period. For this purpose, the time elapsed from the time when the currently used transfer function matrix is obtained is measured, and whether or not the elapsed time measured periodically exceeds a predetermined time threshold is detected. When it is detected that the elapsed time has exceeded the time threshold, the transmission / reception means 1 again transmits a control signal to the receiving station R to obtain a new transfer function matrix and select the optimum transmission mode each time. Then, data transmission is continued.

On the transmitting station side, the value of the total F _total indicating the reception state between the transmitting station and the receiving station is obtained from this evaluation function, and the optimum transmission mode is selected from the conversion table 8 based on the total F _total. In this transmission mode, the desired data is transmitted to the corresponding receiving station R.

As a result, data transmission processing can be performed in a stable state from the transmitting station to the receiving station.
The above description is one example for acquiring the transfer function matrix on the transmitting station side, and the transfer function matrix may be estimated using any other method.

<First Embodiment>
In the transmission station T1 of FIG. 1, the transmission / reception means 1 transmits / receives a radio signal to / from another station, that is, the reception station R via the antennas 100 ₁ to 100 _q . The received signal converting means 2 converts the radio signal (received signal) received by the FFT processing into an on-axis signal (IQ vector) for each subcarrier. Here, on-axis indicates a position coordinate table of an orthogonal coordinate system formed by the I (carrier in-phase component) axis and the Q (carrier orthogonal component) axis. The transfer function acquisition means 3 compares a known pattern signal given to the received signal as a preamble signal with the same reference signal as the known pattern signal stored therein, and performs a predetermined calculation. Thus, the transfer function for the kth (1 ≦ k ≦ N _SC : k is an integer) subcarrier between the i-th antenna in the first antenna group and the j-th antenna in the second antenna group. Get h _{j, i} ^[k] . In the predetermined calculation, since the corresponding pattern is known in advance by the reference signal, the reception strength of the received preamble is obtained while corresponding to the pattern of the reference signal, and between the antennas of the first and second antenna groups. Shows an operation for _obtaining the transfer function h _{j, i} ^[k] . The evaluation function calculation means 4 obtains this for the transfer function matrix H _k related to the k th subcarrier of N _rx rows and N _tx columns with the transfer function h _{j, i} ^[k] as the (j, i) element. A predetermined evaluation function F (H _k ) defined by using each component of the transfer function matrix H _k as a variable is calculated.

The sum calculation means 5 calculates the sum F _total for all subcarriers of the evaluation function F (H _k ) in N _rx rows and N _tx columns by calculation. Transmission mode selection means 5, to the value of the total sum F _total, with reference to the conversion table 8 that gives the combination of the superposition number of the modulation scheme and coding rate and signal sequences, the value of the sum F _total from the conversion table 8 Select the optimal transmission mode corresponding to. In the conversion table 8, a combination of a modulation scheme, a coding rate, and the number of superimposed signal sequences is stored as an optimum transmission mode in correspondence with a plurality of total F _total values.

The user data dividing means 9 transmits the user to be transmitted when the number of superimposed transmission modes selected last in the transmission mode selection means 5 is N ′ (1 ≦ N ′ ≦ N _tx : N ′ is an integer). When data is input, this user data is divided into N ′ systems. The signal sequence generation means 6 assigns an individual known pattern signal to the data divided into N ′ systems as a preamble, and generates a first signal sequence of the N ′ system. The transmission / reception means 1 uses the first antenna group, uses the transmission mode selected by the transmission mode selection means 5, and superimposes the first signal sequence on the same frequency band and transmits it as a radio signal. To do.

Next, in the receiving station R of FIG. 1, the transmission / reception means 12 individually receives radio signals using N _rx antenna groups (antennas 101 ₁ to 101 _q ). The demodulating unit 11 separates and demodulates the signals of each signal series, using the received radio signal, that is, a known pattern signal added to the received signal as a reference signal. The signal sequence synthesizing unit 10 synthesizes all the demodulated signal sequences and outputs the synthesis result as user data.
Further, although not shown as a normal transceiver, the transmitting station T1 is provided with a demodulating means 11 and a signal sequence synthesizing means 10 in the receiving station R. Similarly, although not shown as a normal transceiver, the receiving station R includes a received signal converting means 2, a transfer function acquiring means 3, an evaluation function calculating means 4, a sum calculating means 5, a transmission at the transmitting station T1. Mode selection means 7, conversion table 8, user data division means 9 and signal sequence generation means 6 are provided. The transmission / reception means 1 and 12 have the same configuration.

Next, the operation of the first embodiment of the present invention will be described with reference to FIGS. 3 and 4 are flowcharts for explaining an operation example of the first embodiment of the present invention.
FIG. 3 is a flowchart in the reception process of the transmitting station T1 (or receiving station R) in the first embodiment of the present invention.
When the transmission / reception means 1 receives a radio signal using the plurality of antennas 101 ₁ to 101 _p and outputs it as a reception signal (step S1), the reception signal conversion means 2 receives the preamble of the reception signal input from the transmission means 1 A signal is extracted (step S2).

Then, the received signal conversion means 2 performs an FFT (Fast Fourier Transform) process on the preamble signal for each antenna in the antennas 101 ₁ to 101 _p (step S3).
Next, after the received signal conversion means 2 separates the signal for each subcarrier in the frequency space by FFT processing, the transfer function obtaining means 3 compares the received preamble signal with the known preamble signal as a reference signal. Thus, the transfer function h _{j, i} ^[k] for the k-th subcarrier between the i-th antenna of the first antenna group of the transmitting station T1 and the j-th antenna of the second antenna group of the receiving station R Is acquired (step S4).

Then, the demodulating means 11 uses the transfer function matrix H _k for each subcarrier constituted by the transfer function h _{j, i} ^[k] , and in the received signals input from the antennas 101 ₁ to 101 _p , the counterpart station Is separated for each signal series transmitted from the receiver, that is, interference is removed from other signal series (step S5), and subsequent demodulation processing is performed by synchronous detection of data (step S6).
In addition, when the signal series synthesizing unit 10 detects that the data continues (step S7), the signal series synthesizing unit 10 continues to perform steps S5 and S6 until the end of the data is detected. A plurality of data (signal series) are combined to reproduce user data (step S8), the user data is output, and the process is terminated (step S13).

The transfer function acquisition unit 3 acquires the transfer function matrix H _k for each subcarrier in step S4, and the evaluation function calculation unit 4 evaluates the evaluation function F (H _k using each component of the transfer function matrix H _k as a variable. ) Is obtained by calculation (step S9).
Then, the sum calculating means 5 adds the value of the input evaluation function F (H _k ) to all the subcarriers to obtain the sum F _total (step S10).
Next, the transmission mode selection means 7 refers to the conversion table 8 in order to select the optimal transmission mode based on this total F _total value, searches for and selects the optimal transmission mode corresponding to the total F _total value, Record (step S11). The transmission mode selection means 7 records and sets the optimum transmission mode acquired in step S11 in the internal storage unit as a recommended value for the transmission mode for the next transmission (step S12).

As in the conventional system, a normal wireless terminal has the functions of the transmitting station T1 and the receiving station R. Therefore, FIG. 3 shows a flowchart of the receiving process.
However, if the functions of the transmitting station T1 and the receiving station R are separated as shown in FIG. 1, the processing in steps S5 to S8 is not necessary for the transmitting station T1 that transmits user data. Similarly, steps S9 to S12 are not required for a receiving station that receives user data.

Next, the transmission operation of the transmission station T1 in the first embodiment of the present invention will be described using the flowchart of FIG.
When user data to be transmitted is input (step S21), the user data dividing unit 9 refers to the optimum transmission mode stored and set in the storage unit in the transmission mode selection unit 7, and multiplexes the signal sequences in MIMO. The number N ′ is acquired (step S23).
Then, the user data dividing means 9 divides the input user data into N′-sequence signal sequences in accordance with the multiplexing number N ′ (step S23).

Next, the signal sequence generating means 6 gives a preamble signal to each of the divided signal sequences (step S24).
Then, the transmission / reception means 1 transmits the signal sequence signals as radio signals from the N ′ antennas (antennas 100 ₁ to 100 _p ) that are input using the optimal transmission mode (step S25).
Here, as the form of the function of the evaluation function F (H _k ) for the matrix H, there are options using the following functions. For example, when the transfer function matrix H _k is a square matrix, the following is given as an example.

Here, when the inverse matrix of the transfer function matrix H _k is G and the (j, i) component of the inverse matrix G is expressed as g _{j, i} , the following evaluation function may be used.

  Here, each of the formulas (6) to (24) corresponds to each of claims 3 to 21 of the present invention and defines this point.

<Second Embodiment>
Note that when the transfer function matrix H _k is a non-square matrix, instead of the transfer function matrix H _k of the above equation, and the transfer function matrix H _k, and the matrix H _k ^H Hermitian conjugate of the transfer function matrix The matrix H _k ^H × H _k or the matrix H _k × H _k ^H can be used in place of the transfer function matrix H _k . Claim 2 of the present invention defines this point.
FIG. 2 shows a configuration example of a wireless communication system according to the second embodiment of the present invention. The difference from the first embodiment is that, as described above, the matrix H _k ^H × H _k or the matrix H _k × H _k ^H is used instead of the transfer function matrix H _k .

For this reason, as a configuration of the second embodiment, in addition to the first embodiment, the Hermitian conjugate computing means 13 for computing the Hermitian conjugate of the transfer function matrix H _k and the matrix H _k ^H × H _k or the matrix H Product calculation means 14 for calculating _k × H _k ^H is provided.
Hereinafter, as shown in FIG. 2, in each configuration of the second embodiment, the same reference numerals are given to the same configurations as those of the first embodiment, the description thereof will be omitted, and only different configurations and operations will be described. .
In FIG. 2, Hermitian conjugate calculation means 13 relates to the k th subcarrier of N _rx rows and N _tx columns having the transfer function h _{j, i} ^[k] obtained by transfer function acquisition means 3 as the (j, i) element. against the transfer function matrix H _k, determined by calculating a Hermitian conjugate matrix H _k ^H of the transfer function matrix H _k.

Product calculation unit 14 is obtained by calculating any of the above product of the transfer function matrix _{H k} and Hermitian conjugate matrix _{H k} ^H, i.e. matrix _{H k} × _{H k} ^H or matrix _{H k} ^H × _{H k.}
The evaluation function calculation means 4 uses each component of the matrix H _k × H _k ^H or matrix H _k ^H × H _k as a variable instead of the transfer function matrix H _k in the first embodiment. A predetermined evaluation function F (H _k × H _k ^H ) or F (H _k ^H × H _k ) defined by the variable is calculated.
The sum calculation means 5 calculates the sum F _total for all subcarriers of the evaluation function F (H _k × H _k ^H ) or F (H _k ^H × H _k ) by calculation. Regarding other configurations, the first and second embodiments have the same configuration.

In step S9 of the flowchart of FIG. 3, the Hermitian conjugate calculating means 13 calculates a Hermitian conjugate matrix H _k ^H of the transfer function matrix H _k , and the product calculating means 14 is a matrix H _k × H _k ^H or a matrix H _k ^H. XH _k is calculated by calculating one of them.
Then, in step S9 of the flowchart of FIG. 3, the sum calculation means 5 calculates the sum F _total for all subcarriers of the evaluation function F (H _k × H _k ^H ) or F (H _k ^H × H _k ) by calculation. . For the processes other than step S9 and step S10, the same operation is performed in the second embodiment and the first embodiment.
The above-described first and second embodiments are all illustrative and do not limit the present invention, and the present invention can be implemented in various other modifications and changes. . Therefore, the scope of the present invention is defined only by the claims and their equivalents.

  3 and 4 is recorded on a computer-readable recording medium, and the program recorded on the recording medium is read into a computer system and executed, thereby executing the MIMO technique. The wireless signal transmission / reception processing may be performed using Here, the “computer system” includes an OS and hardware such as peripheral devices. The “computer system” includes a WWW system having a homepage providing environment (or display environment). The “computer-readable recording medium” refers to a portable medium such as a flexible disk, a magneto-optical disk, a ROM, and a CD-ROM, and a storage device such as a hard disk built in the computer system. Further, the “computer-readable recording medium” refers to a volatile memory (RAM) in a computer system that becomes a server or a client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. In addition, those holding programs for a certain period of time are also included.

  The program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the “transmission medium” for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line. The program may be for realizing a part of the functions described above. Furthermore, what can implement | achieve the function mentioned above in combination with the program already recorded on the computer system, and what is called a difference file (difference program) may be sufficient.

It is a block diagram which shows the structural example of the 1st Embodiment of this invention. It is a block diagram which shows the structural example of the 2nd Embodiment of this invention. It is a flowchart which shows the operation example of reception of the 1st and 2nd radio station in embodiment of this invention. It is a flowchart which shows the operation example of transmission of the 1st radio station in embodiment of this invention. It is a flowchart which shows the reception operation | movement of the 1st and 2nd radio station in a conventional system. It is a flowchart which shows the transmission operation | movement of the 1st radio station in a conventional system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,12 ... Transmission / reception means 2 ... Reception signal conversion means 3 ... Transfer function acquisition means 4 ... Evaluation function calculation means 5 ... Summation calculation means 6 ... Signal sequence generation means 7 ... Transmission mode selection means 8 ... Conversion table 9 ... User data division | segmentation Means 10 ... Signal sequence synthesis means 11 ... Demodulation means 13 ... Hermitian conjugate computation means 14 ... Product computation means 100 ₁ , 100 ₂ , 100 _p , 101 ₁ , 101 ₂ , 101 _q ... Antenna T1, T2 ... Transmitting station R ... Reception Station

Claims (23)

A first radio station having N _tx (N _tx > 1: integer) or more first antenna groups and a second radio station having N _rx (N _rx ≧ 1: integer) second antenna groups. Of orthogonal frequency division multiplex modulation using N _SC (N _SC > 1: integer) subcarriers for user information transmission, and a combination of modulation scheme and coding rate in error correction Using a plurality of transmission modes that realize different transmission rates, and further superimposing signals of one or more signal sequences on the same frequency band using one or more antennas in the first antenna group. In a wireless communication system capable of performing wireless communication,
The first radio station is
Receiving a radio signal using the first antenna group;
A step of converting a received signal into a signal on each subcarrier axis by FFT (Fast Fourier Transform) processing;
Using a known pattern signal given to the received signal as a reference signal, the kth (1 ≦ 1) between the i-th antenna of the first antenna group and the j-th antenna of the second antenna group. k ≦ N _SC : k is an integer) obtaining a transfer function h _{j, i} ^[k] for subcarriers;
With respect to the transfer function matrix H _k related to the k th subcarrier of N _rx rows and N _tx columns with the transfer function h _{j, i} ^[k] as the (j, i) element, each component of the matrix H _k is used as a variable. Calculating a prescribed predetermined evaluation function F (H _k );
Calculating a total F _total for all subcarriers of the evaluation function F (H _k ) by calculation;
An optimum transmission mode selection step of selecting an optimum transmission mode with reference to a conversion table that gives a combination of a modulation scheme, a coding rate, and a number of superimpositions of a signal sequence with respect to the value of F _total ;
When the number of superimposed transmission modes last selected in the optimum transmission mode selection step is N ′ (1 ≦ N ′ ≦ N _tx : N ′ is an integer), user data is input when user data is input. Dividing N ′ system into
Providing a signal of an individual known pattern to the data divided into the N ′ system to generate a first signal sequence of the N ′ system;
Using the first antenna group, using the transmission mode selected in the optimum transmission mode selection step, and superimposing and transmitting the first signal sequence on the same frequency band, and
The second radio station is
Individually receiving radio signals using the N _rx second antenna groups;
A step of separating and demodulating the signals of each of the signal series using a known pattern signal given to the received signal as a reference signal;
And a step of synthesizing all demodulated signal sequences and outputting them as user data. A first radio station having N _tx (N _tx > 1: integer) or more first antenna groups and a second radio station having N _rx (N _rx ≧ 1: integer) second antenna groups. Of orthogonal frequency division multiplex modulation using N _SC (N _SC > 1: integer) subcarriers for user information transmission, and a combination of modulation scheme and coding rate in error correction Using a plurality of transmission modes that realize different transmission rates, and further superimposing signals of one or more signal sequences on the same frequency band using one or more antennas in the first antenna group. In a wireless communication system capable of performing wireless communication,
The first radio station is
Receiving a radio signal using the first antenna group;
A step of converting a received signal into a signal on each subcarrier axis by FFT (Fast Fourier Transform) processing;
Using a known pattern signal given to the received signal as a reference signal, the kth (1 ≦ 1) between the i-th antenna of the first antenna group and the j-th antenna of the second antenna group. k ≦ N _SC : k is an integer) obtaining a transfer function h _{j, i} ^[k] for the subcarrier;
A Hermitian conjugate matrix H _k of the matrix H _k with respect to the transfer function matrix H _k related to the k th subcarrier of N _rx rows and N _tx columns, where the transfer function h _{j, i} ^[k] is the (j, i) element. determining _k ^H ;
And determining one of the product i.e. _{H k} × _{H k} ^H or _{H k} ^H × _{H k} of the matrix _{H k} and _{H k} ^H,
A predetermined evaluation function F (H _k × H _k ^H ) or F (H _k ^H × H) defined with each component of the matrix H _k × H _k ^H or H _k ^H × H _k as a variable. _k )), and
Calculating the total F _total for all subcarriers of the evaluation function F (H _k × H _k ^H ) or F (H _k ^H × H _k ) by calculation;
An optimum transmission mode selection step of selecting an optimum transmission mode with reference to a conversion table that gives a combination of a modulation scheme, a coding rate, and a number of superimpositions of a signal sequence with respect to the value of F _total ;
When the number of superimposed transmission modes last selected in the optimum transmission mode selection step is N ′ (1 ≦ N ′ ≦ N _tx : N ′ is an integer), user data is input when user data is input. Dividing N ′ system into
Providing a signal of an individual known pattern to the data divided into the N ′ system to generate a first signal sequence of the N ′ system;
Using the first antenna group, using the transmission mode selected in the optimum transmission mode selection step, and superimposing and transmitting the first signal sequence on the same frequency band, and
The second radio station is
Individually receiving radio signals using the N _rx second antenna groups;
A step of separating and demodulating the signals of each of the signal series using a known pattern signal given to the received signal as a reference signal;
And a step of synthesizing all demodulated signal sequences and outputting them as user data.   3. The wireless communication method according to claim 1, wherein a determinant Det (M) of the matrix M or an absolute value | Det (M) | thereof is used as the evaluation function F (M) for the matrix M. A wireless communication method.   3. The wireless communication method according to claim 1, wherein a logarithm value Log (| Det (M) |) of an absolute value of a determinant of the matrix M is used as the evaluation function F (M) for the matrix M. A wireless communication method characterized by being used.   3. The wireless communication method according to claim 1, wherein a sum of absolute values of components of the matrix M is used as the evaluation function F (M) for the matrix M.   The wireless communication method according to claim 1 or 2, wherein a sum of squares of absolute values of components of the matrix M is used as the evaluation function F (M) for the matrix M. Communication method.   The wireless communication method according to claim 1 or 2, wherein a logarithmic value of a sum of absolute values of components of the matrix M is used as the evaluation function F (M) for the matrix M. Communication method. The radio communication method according to claim 1 or 2, wherein the inverse function of the matrix M is G as the evaluation function F (M) for the square matrix M of N rows and N columns, and the inverse matrix G is When each column vector is V ₁ , V ₂ , V ₃ ,..., V _N , the reciprocal of the value obtained by calculating the square root of the sum of the squares of the absolute values of the respective components is obtained for each column vector. Further, a wireless communication method characterized by using a value obtained by summing the values with respect to all column vectors. The wireless communication method according to claim 1 or 2, wherein an inverse matrix of a square matrix M of N rows and N columns is G, and column vectors constituting the inverse matrix G are V ₁ , V ₂ , When V ₃ ,..., V _N are obtained, the square root of the sum of the squares of the absolute values of the respective components is obtained for each column vector, the logarithmic value of the reciprocal of the square root value is obtained, and the logarithmic value is further calculated. A wireless communication method characterized by using a value obtained by summing up all column vectors. 3. The wireless communication method according to claim 1, wherein the eigenvalues λ ₁ , λ ₂ , λ ₃ ,... Of the matrix M are used as the evaluation function F (M) for the square matrix M of N rows and N columns. A wireless communication method characterized in that λ _N is obtained and a value obtained by taking the sum of absolute values of the eigenvalues is used. 3. The wireless communication method according to claim 1, wherein the eigenvalues λ ₁ , λ ₂ , λ ₃ ,... Of the matrix M are used as the evaluation function F (M) for the square matrix M of N rows and N columns. A wireless communication method characterized in that λ _N is obtained and a value obtained by taking a sum of squares of absolute values of the eigenvalues is used. 3. The wireless communication method according to claim 1, wherein the eigenvalues λ ₁ , λ ₂ , λ ₃ ,... Of the matrix M are used as the evaluation function F (M) for the square matrix M of N rows and N columns. A wireless communication method characterized by obtaining λ _N and further using a value obtained by taking the sum of the reciprocals of the absolute values of the eigenvalues. 3. The wireless communication method according to claim 1, wherein the eigenvalues λ ₁ , λ ₂ , λ ₃ ,... Of the matrix M are used as the evaluation function F (M) for the square matrix M of N rows and N columns. A wireless communication method characterized in that λ _N is obtained and a value obtained by taking the sum of squares of reciprocals of absolute values of the eigenvalues is used. 3. The wireless communication method according to claim 1, wherein the eigenvalues λ ₁ , λ ₂ , λ ₃ ,... Of the matrix M are used as the evaluation function F (M) for the square matrix M of N rows and N columns. A wireless communication method characterized in that λ _N is obtained and a value obtained by taking a sum of logarithmic values of absolute values of the eigenvalues is used. 3. The wireless communication method according to claim 1, wherein the eigenvalues λ ₁ , λ ₂ , λ ₃ ,... Of the matrix M are used as the evaluation function F (M) for the square matrix M of N rows and N columns. When λ _N is obtained and the eigenvalue having the maximum absolute value among the eigenvalues is expressed as λ _max and the eigenvalue having the minimum absolute value is expressed as λ _mini , the absolute value of λ _mini / λ _max is used. A wireless communication method. 3. The wireless communication method according to claim 1, wherein the eigenvalues λ ₁ , λ ₂ , λ ₃ ,... Of the matrix M are used as the evaluation function F (M) for the square matrix M of N rows and N columns. seeking lambda _N, further eigenvalues absolute value among the eigenvalues is maximum lambda _max, eigenvalues absolute value is minimum when expressed as lambda _mini, the use of absolute values of λ _max / λ _mini A wireless communication method. 3. The wireless communication method according to claim 1, wherein the eigenvalues λ ₁ , λ ₂ , λ ₃ ,... Of the matrix M are used as the evaluation function F (M) for the square matrix M of N rows and N columns. When λ _N is obtained and the eigenvalue having the maximum absolute value among the eigenvalues is expressed as λ _max , and the eigenvalue having the minimum absolute value as λ _mini , the square of the absolute value of λ _mini / λ _max is calculated. A wireless communication method characterized by being used. 3. The wireless communication method according to claim 1, wherein the eigenvalues λ ₁ , λ ₂ , λ ₃ ,... Of the matrix M are used as the evaluation function F (M) for the square matrix M of N rows and N columns. When λ _N is obtained and the eigenvalue having the maximum absolute value among the eigenvalues is expressed as λ _max , and the eigenvalue having the minimum absolute value as λ _mini , the square of the absolute value of λ _max / λ _mini is calculated. A wireless communication method characterized by being used. 3. The wireless communication method according to claim 1, wherein the eigenvalues λ ₁ , λ ₂ , λ ₃ ,... Of the matrix M are used as the evaluation function F (M) for the square matrix M of N rows and N columns. seeking lambda _N, further absolute eigenvalues is maximized lambda _max in the eigenvalues, eigenvalues absolute value is minimum when expressed as lambda _mini, the logarithm of the absolute value of the λ _max / λ _mini A wireless communication method characterized by being used.   The wireless communication method according to claim 1 or 2, wherein the determinant of the matrix M is the sum of the squares of the absolute values of the components of the matrix M as the evaluation function F (M) for the matrix M. A wireless communication method using a value obtained by dividing a square root by a value.   The wireless communication method according to claim 1 or 2, wherein the determinant of the matrix M is the sum of the squares of the absolute values of the components of the matrix M as the evaluation function F (M) for the matrix M. A wireless communication method characterized by using a logarithmic value of a value obtained by dividing a square root by a value. A first radio station having N _tx (N _tx > 1: integer) or more first antenna groups and a second radio station having N _rx (N _rx ≧ 1: integer) second antenna groups. Of orthogonal frequency division multiplex modulation using N _SC (N _SC > 1: integer) subcarriers for user information transmission, and a combination of modulation scheme and coding rate in error correction Using a plurality of transmission modes that realize different transmission rates, and further superimposing signals of one or more signal sequences on the same frequency band using one or more antennas in the first antenna group. Wireless communication system capable of performing wireless communication,
The first radio station is
Receiving means for receiving a radio signal using the first antenna group;
A received signal converting means for converting a received signal into a signal on each subcarrier axis by FFT (Fast Fourier Transform) processing;
Using a known pattern signal given to the received signal as a reference signal, the kth (1 ≦ 1) between the i-th antenna of the first antenna group and the j-th antenna of the second antenna group. k ≦ N _SC : k is an integer) transfer function obtaining means for obtaining a transfer function h _{j, i} ^[k] related to subcarriers;
With respect to the transfer function matrix H _k related to the k th subcarrier of N _rx rows and N _tx columns with the transfer function h _{j, i} ^[k] as the (j, i) element, each component of the matrix H _k is used as a variable. An evaluation function calculating means for calculating a prescribed predetermined evaluation function F (H _k );
A sum calculating means for calculating a sum F _total for all subcarriers of the evaluation function F (H _k );
A transmission mode selection means for selecting an optimum transmission mode with reference to a conversion table that gives a combination of a modulation scheme, a coding rate, and the number of superimposed signal sequences with respect to the value of F _total ;
When the number of superimposed transmission modes last selected in the optimum transmission mode selection step is N ′ (1 ≦ N ′ ≦ N _tx : N ′ is an integer), user data is input when user data is input. Dividing user data into N ′ systems,
A signal sequence generating means for generating a first signal sequence of the N ′ system by giving a signal of an individual known pattern to the data divided into the N ′ system,
Using the first antenna group, using the transmission mode selected in the optimal transmission mode selection step, and comprising transmitting means for superimposing and transmitting the first signal sequence on the same frequency band,
The second radio station is
Receiving means for individually receiving radio signals using the N _rx second antenna groups;
Demodulating means for separating and demodulating the signals of each signal series, using a known pattern signal given to the received signal as a reference signal;
A radio communication system comprising: a signal sequence synthesizing unit that synthesizes all demodulated signal sequences and outputs them as user data. The radio communication system of the present invention includes a first radio station having a first antenna group of N _tx (N _tx > 1: integer) or more and a second radio station of N _rx (N _rx ≧ 1: integer). the combination of is constituted by a second radio station with the antenna group, using orthogonal frequency division multiplexing modulation scheme using N _SC present subcarriers for transmission user information and the coding rate in the modulation scheme and error correction Using a plurality of transmission modes that realize different transmission rates, and further superimposing signals of one or more signal sequences on the same frequency band using one or more antennas in the first antenna group. Wireless communication system capable of performing wireless communication,
The first radio station is
Receiving means for receiving a radio signal using the first antenna group;
A received signal converting means for converting a received signal into a signal on each subcarrier axis by FFT (Fast Fourier Transform) processing;
Using a known pattern signal given to the received signal as a reference signal, the kth (1 ≦ 1) between the i-th antenna of the first antenna group and the j-th antenna of the second antenna group. k ≦ N _SC : k is an integer) transfer function obtaining means for obtaining a transfer function h _{j, i} ^[k] related to subcarriers;
A Hermitian conjugate matrix H _k of the matrix H _k with respect to the transfer function matrix H _k related to the k th subcarrier of N _rx rows and N _tx columns, where the transfer function h _{j, i} ^[k] is the (j, i) element. Hermitian conjugate calculation means for obtaining _k ^H ;
A product calculating means for calculating either the product i.e. _{H k} × _{H k} ^H or _{H k} ^H × _{H k} of the matrix _{H k} and _{H k} ^H,
A predetermined evaluation function F (H _k × H _k ^H ) or F (H _k ^H × H) defined with each component of the matrix H _k × H _k ^H or H _k ^H × H _k as a variable. _k ), an evaluation function calculating means for calculating
A total calculation means for calculating a total F _total for all subcarriers of the evaluation function F (H _k × H _k ^H ) or F (H _k ^H × H _k ) by calculation;
A transmission mode selection means for selecting an optimum transmission mode with reference to a conversion table that gives a combination of a modulation scheme, a coding rate, and a superimposition number of a signal sequence with respect to the value of F _total ;
When the number of superimposed transmission modes last selected in the optimum transmission mode selection step is N ′ (1 ≦ N ′ ≦ N _tx : N ′ is an integer), user data is input when user data is input. Dividing user data into N ′ systems,
A signal sequence generation means for generating a first signal sequence of the N ′ system by giving a signal of an individual known pattern to the data divided into the N ′ system,
Using the first antenna group, and using the transmission mode selected in the optimum transmission mode selection step, and transmitting means for superimposing and transmitting the first signal sequence on the same frequency band, and
The second radio station is
Receiving means for individually receiving radio signals using the N _rx second antenna groups;
Demodulating means for separating and demodulating the signals of each signal series, using a known pattern signal given to the received signal as a reference signal;
A radio communication system comprising: a signal sequence synthesizing unit that synthesizes all demodulated signal sequences and outputs them as user data.

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