JP4105177B2 - Wireless communication apparatus and method - Google Patents

Description

In a wireless system that performs communication via a wireless line, the present invention provides channel tracking (transmission) corresponding to a change in transfer function over time in order to suppress a decrease in reception quality due to a change in transfer function when the packet length to be transmitted is long. The present invention relates to a technique for performing function tuning.
In particular, 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 based on a transfer function matrix between the transmission and reception antennas. The present invention relates to a receiving technique for realizing good transmission characteristics while suppressing a circuit scale in a high-speed wireless access system that realizes wireless communication by demodulating data on a receiving station side.
In addition, the present invention is used particularly for increasing the transmission speed of a high-speed wireless access system using the 2.4 GHz band or the 5 GHz band.

In recent years, the IEEE802.11g standard, the IEEE802.11a standard, etc. have been remarkably spread as high-speed wireless access systems using the 2.4 GHz band or the 5 GHz band.
In these systems, a maximum transmission rate of 54 Mbps is realized. However, with the widespread use of wireless LAN, further increase in transmission rate is required.
For this purpose, MIMO (Multiple-Input Multiple-Output) technology is promising. 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 on the transmitting station side is estimated using this matrix, and the data in the transmitted signal is reproduced.

Here, in the MIMO wireless transmission / reception system, a case is considered where N signals are transmitted using N transmitting antennas and the transmitted N signals are received using M antennas.
First, there are N × M transmission paths between the antennas of the transmitting station and the receiving station, 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 M rows and N columns having this as the (j, i) th component is denoted as H. Furthermore, the transmission signal from the i transmit antenna and _{t i (t 1, t 2} , t 3, ···, t N) column vector whose components T, a received signal at the j-th receive antenna r and _{j (r 1, r 2,} r 3, ···, r M) column vector whose components R, the thermal noise of the j receiving antennas and _{n j (n 1, n 2} , n 3, · ... A column vector whose component is n _M ) is expressed as n.
In this case, the following relationship (1) is established.
R = H × T + n (1)

Therefore, a technique for estimating the transmission signal T based on the signal R received on the receiving station side is required. As the most basic one of the MIMO technology, there is a method generally called a ZF (Zero Forcing) method. (See Non-Patent Document 1)
Here, an inverse matrix H ⁻¹ of the transfer function matrix is obtained for the above equation (1), and a process of multiplying this from the left of both sides of the equation is performed. As a result, the following expression (1a) is obtained.
^{H -1 × R = T + H} -1 × n ... (1a)
That is, when the signals received by the respective receiving antennas are combined and processing for removing interference due to signals from other than the desired transmitting antenna is performed, a minute thermal noise H ⁻¹ × n is added to the actual transmitted signal vector T. A signal point is obtained.
Here, when a signal subjected to multilevel modulation such as BPSK, QPSK, 16QAM, or 64QAM is used as a transmission signal, possible signal points (signals obtained by mapping a digital signal by multilevel modulation) are discontinuous. It is.

Therefore, a hard decision process for searching for a signal point with the shortest Euclidean distance on the transmission constellation for H ⁻¹ × R is performed, and a true transmission signal is estimated.
In the above ZF method, when the thermal noise term H ⁻¹ × n is sufficiently small and the components for each transmitting antenna can be assumed to be uniform among the transmitting antennas, good signal reproduction characteristics are expected. it can.
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 reception antenna is different for a certain transfer function matrix (transmission characteristics between the transmission antennas are different).
Furthermore, if the transfer function matrix H is a matrix that does not have an inverse matrix (or the determinant of the inverse matrix is very small), the estimation of the transmission signal becomes very unstable.
In the situation described above, there is a possibility that the reception characteristics of the receiving antenna at the receiving station are significantly degraded.
As a method for solving such problems, a method having the most excellent characteristics is a method called an MLD method. (See Non-Patent Document 2)

In this MLD method, first, when the modulation method of a transmission signal from each transmitting 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.
Further, in the MLD method, prediction of received signals when the signals are transmitted is performed on all possible candidates (total of N _max ^N types) as transmission signals, and the most actual reception among them is performed. The one that is close to the signal is selected as the highest signal point of the estimation system. That is, if an arbitrarily selected transmission signal candidate T, for example, the kth transmission signal candidate is represented by T ^[k] , the Euclidean distance E defined by the following equation (2) is minimized. Select a value for k.
E = (R−H × T ^[k] ) ^H × (R−H × T ^[k] ) (2)
Note that ^{MH with} respect to the matrix M indicates a matrix that is Hermitian conjugate of the matrix M. With the above processing, the MLD method can perform stable reception processing for any matrix H, and reception characteristics are greatly improved compared to the ZF method.

Here, FIG. 2 shows a configuration of a transmission section of a transmission station to which the MIMO technique in the prior art is applied. In this figure, the transmission unit of the transmission station includes a data division circuit 101, a preamble assignment circuit 102-1, modulation circuits 103-1 to 103-N, radio units 104-1 to 104-N, and transmission antennas 105-1 to 105. -N.
As an example, a case where a transmitting station transmits N systems of data using N transmitting antennas will be described as an example.

When data to be transmitted is input from the external circuit, the data dividing circuit 101 divides this data into N systems and outputs each to different preamble circuits.
For example, the data division circuit 101 outputs the first system data to the preamble provision circuit 102-1. As a result, the preamble circuit 102-1 is input to the modulation circuit 103-1 (Chl) with the preamble signal applied.
In the modulation circuit 103-1, predetermined modulation (multilevel modulation such as BPSK, QPSK, 16QAM, 64QAM, etc.) is performed on the data to which the input preamble signal is added, and the modulated transmission signal is wirelessly transmitted. Output to unit 104-1.

The radio unit 104-1 converts the transmission signal into a radio frequency and transmits the radio signal to the reception station via the transmission antenna 105-1 (radiated as a radio wave).
Similarly to the “Ch1” system described above, the data of the second system output from the data dividing circuit 101 is converted into the preamble assigning circuit 102-2, the modulation circuit 103-2 (Ch2), and the radio unit 104-2. And transmitted from the antenna 105-2.
Similarly, similarly to the above-described “Ch1” and “Ch2” systems, the N-th system data output from the data dividing circuit 101 is converted into a preamble assigning circuit 102-N, a modulation circuit 103-N (ChN), and a radio. Processed by the unit 104-N and transmitted from the antenna 105-N.
Thereby, the data to be transmitted divided by the data dividing circuit 101 is individually transmitted from different antennas (105-1 to 105-N).

Next, FIG. 3 shows the configuration of the receiving unit of the receiving station in the prior art.
The reception unit of the reception station includes reception antennas 111-1 to 111 -M, radio units 112-1 to 112 -M, a channel estimation circuit 113, a reception signal management unit 114, a transfer function matrix management circuit 115, a signal detection circuit 116, The data composition circuit 117 is configured.
Also, each of the first reception antenna 111-1 to the Mth reception antenna 111-M individually receives a reception signal.

The channel estimation circuit 113 inputs the signal (packet) transmitted from the transmission unit via the radio units 112-1 to 112-M.
Then, the channel estimation circuit 113 determines the transfer function between each of the transmission antennas 105-1 to 105-N and the reception antennas 111-1 to 111-M based on the reception status of the predetermined preamble signal given on the transmission side in the packet. (Pilot data in the preamble signal is determined in advance by both the transmission and reception units, and a transfer function is obtained from the reception status of this pilot data).
The channel estimation circuit 113 outputs the acquired information h _{j, i} of each transfer function to the transfer function matrix management circuit 115 and outputs the data signal subsequent to the preamble signal to the reception signal management circuit 114 one symbol at a time. .
Here, the transfer function matrix management circuit 115 manages a matrix composed of h _{j, i} input from the channel estimation circuit 113 as a transfer function matrix H.

Then, the received signal management circuit 114 receives the data signal input in symbol units using the received signals (r ₁ , r ₂ ,..., R _M ) of the receiving antennas 111-1 and 111 _-M as components. The signal vector R is once managed by an internal storage unit.

The signal detection circuit 116 estimates the most likely transmission signal from the relationship between the transfer function matrix managed by the transfer function matrix management circuit 115 and the reception signal managed by the reception signal management circuit 114. As the method used at this time, other methods including the methods defined in Non-Patent Document 1, Non-Patent Document 2, and the like may be used. Here, it will be generalized and will be described as the signal detection circuit 116.
The data as the estimated transmission signal output from the signal detection circuit 116 is processed in time series continuously over a plurality of symbols. However, after receiving a series of data, the data synthesis circuit 117 synthesizes the symbols to generate data. Is reconstructed and output as
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. 2003 A.van Zelst et.al., “Space Division Multiplexing (SDM) for OFDM Systems”, Proc, VTC2000 Spring, Vol. 2, pp.1070 -1074

  In the above reception processing, when the data length of the input packet is long, the transfer function matrix H extracted by the preamble at the beginning of the packet changes with time, and the symbol positioned at the back of the packet is reproduced with high accuracy. May not be possible. In the prior art, it was assumed that the transfer function information used for signal detection was acquired at the beginning of the packet and the value did not fluctuate within the packet. This assumption is broken when expanding and sending long packets. In particular, IEEE802.11n, which has been standardized to improve the transmission speed by expanding IEEE802.11a, 802.11g, etc., which are high-speed wireless access systems, is actually being studied in this way. In order to be able to receive a long packet stably even under various operating conditions, there has been a demand for it.

An example of a countermeasure for this is the method described in “Asai et al.,“ Simplified Blind Channel Tracking Method for MIMO-OFDM ”, IEICE Technical Report, RCS2004-290”. The principle is briefly shown below. The transfer function information is obtained by comparing the known transmission signal with the actual reception state of the signal. For the data portion other than the preamble, there is no reason to know the true transmission signal on the reception side, but it is possible to estimate it in the process of signal detection processing at reception.
For example, the case where the number of transmission / reception antennas is 3 and the number of MIMO multiplexing is also 3 will be described as an example. A column vector of 3 rows and 1 column having signals transmitted from three transmission antennas as components at a certain time (symbol) is defined as T ₁ . In addition, a column vector whose components are reception signals at three reception antennas for this signal is R ₁ . Similarly, it is assumed that T ₂ and R ₂ , and T ₃ and R ₃ are obtained as combinations of transmission signals and reception signals at different times. It is assumed that the transfer function matrix (3 rows and 3 columns) at this time is H. A replica matrix of a 3 × 3 transmission signal in which transmission signal vectors T ₁ , T ₂ , and T ₃ are arranged in each column is represented as T _rep, and further, received signal vectors R ₁ , R ₂ , and R ₃ are represented as When a matrix of 3 _× 3 received signals arranged in columns is expressed as R _rep , the following equation (3) is given.
R _rep = H · T _rep + N (3)
Here, the last term is a matrix related to thermal noise. Therefore, if this term is ignored, the transfer function matrix can be estimated by the following equation (4).
H ≒ R _rep · T _rep ^-1 (4)
Therefore, it is possible to estimate the transfer function matrix at that moment from the multiplication of the reception signal matrix configured based on the reception signal and the inverse matrix of the replica matrix of the transmission signal.

In this case, in FIG. 3, the transfer function matrix management circuit 115 needs to calibrate the transfer function at predetermined intervals, and re-encodes and re-modulates the decoded information signal sequence. Thus, a replica matrix of the transmission signal is generated.
Further, the transfer function matrix management circuit 115 reads the reception signal matrix at the time corresponding to this replica matrix from the reception signal matrix group stored in the reception signal management circuit 14.
Then, the transfer function matrix management circuit 115 obtains a transfer function estimation matrix by multiplying the inverse matrix of the replica matrix from the right of the received signal matrix.
In this way, the transfer function matrix management circuit 115 replaces the transfer function estimation matrix thus obtained with the transfer function matrix H stored at that time for each predetermined time, so that the transfer function matrix (that is, the channel) Tracking can be performed.

Since the above-described channel tracking method is MIMO, it is necessary to improve estimation accuracy. A replica signal of a transmission signal is generated for information of a plurality of symbols, and a transfer function is generated using the inverse matrix and the reception signal matrix. The estimation matrix is estimated.
However, in this channel tracking method, the estimation accuracy depends on the characteristics of the replica matrix to be used, a plurality of symbols are required to obtain the replica matrix, and the update period is also required to be more than a plurality of symbol periods. There is a drawback that it cannot support tracking. Furthermore, when a transmission signal vector at a certain time is represented by a linear combination of one or a plurality of transmission signal vectors at other times, the replica matrix of the transmission signal does not have an inverse matrix. In this case, the transfer function matrix cannot be obtained, and the update process cannot be performed.

In addition, the channel tracking method requires 4 × 4 inverse matrix calculation when there are a large number of multiplexed MIMOs, for example, if N transmission antennas, for example, 4 antennas are used and quadruplex multiplexing is performed. As a result, the scale of the arithmetic circuit for performing the calculation becomes large, which has been an obstacle to mounting all functions in one chip. Furthermore, a delay associated with this calculation process occurs, and more time is required for channel tracking.
Therefore, an object of the present invention is to perform channel tracking with high speed and high estimation accuracy in a short symbol period compared to the conventional example when performing wireless communication using the MIMO technology, with a realistic circuit scale and calculation amount. It is to provide a wireless communication apparatus that can be realized by the above.

In order to solve the above problems, a wireless communication apparatus of the present invention includes N (N ≧ 2, N is an integer) transmission antennas that multiplex and transmit a plurality of signal sequences on the same frequency channel in space. And a receiving station having M (M ≧ 1, M is an integer) receiving antennas that receive a transmitted radio signal and perform reception processing by separating the signal into a plurality of signal sequences. In a wireless communication apparatus capable of (Multiple Input Multiple Output) communication, the transmitting station includes user data dividing means for dividing user data into N systems, and signals of known patterns that are individually divided into the data divided into the N systems. And a signal transmission unit that simultaneously superimposes and transmits the signal sequence at the same frequency using the N transmission antennas, Station Signal receiving means for individually receiving radio signals using the M receiving antennas, and a signal having a known pattern given to the received signal as a reference signal, the i-th antenna of the transmitting antenna and the receiving Transfer function acquisition means for acquiring M × N sets of transfer functions h _{j, i} between the antenna and the j-th antenna, and M rows with the transfer function h _{j, i} as the (j, i) component An N-column matrix, that is, a transfer function matrix is H, an N-line signal sequence transmission signal is an N-row 1-column transmission signal column vector T, and a symbol-unit received signal received by M antennas is an M-row 1-column signal. When expressed as a received signal sequence vector R, an estimated transmission signal that is an estimated value of the transmission function sequence H transmitted by the transmitting station using the transfer function matrix H and the received signal sequence vector R for each symbol. Get column vector T ' A transmission signal estimation means; and the transfer function matrix H is decomposed into column vectors, expressed as H = (h ₁ , h ₂ ,..., H _N ), and the transmission signal sequence vector estimated for a predetermined symbol Is expressed as T ′ = (t ₁ , t ₂ ,..., T _N ) ^t ( ^{t on the} right shoulder indicates a transposed matrix), and is estimated from the k-th (1 ≦ k ≦ N, k is an integer) signal system From the received signal sequence vector R, replica received vector sequence means for generating a received signal replica sequence vector that estimates the received signal received by the antenna when the transmission signal t _k is transmitted, and k ′ (1 ≦ k ′ ≦ N, k ′ is an integer) interference signal removing means for subtracting the signal system of the received signal replica string vector other than the system to obtain an interference removing string vector, and the interference removing string vector obtained by the interference signal removing means Is divided by the estimated transmission signal of the k'th signal sequence. Then, an estimated transfer function sequence vector generating means for generating an estimated transfer function sequence vector of the k 'signal system, and the estimated transfer function sequence vector and the column vector of the k'th column of the transfer function matrix are linearly combined. Transfer function sequence vector synthesizing means for generating a new transfer function sequence vector, and a transfer function for updating the k'th row of the transfer function matrix stored in the transfer function obtaining means to the new transfer function sequence vector And a column vector updating means.
Thereby, when receiving a packet having a long packet length in a MIMO communication apparatus, the tracking process (channel tracking) of the variation of the transfer function estimated by the preamble over time is performed at the timing when one symbol is input. Compared to the processing using multiple symbols as in the conventional tracking method, channel tracking can be performed in a short period, so that the transfer function variation factor between multiple symbols can be reduced. It is possible to estimate a transfer function with higher accuracy without including it.

In the radio communication apparatus of the present invention, the interference signal removing means, the estimated transfer function sequence vector generating means, and the transfer function sequence vector combining means are provided for every signal system of the received signal replica sequence vector. It is characterized by.
In the wireless communication apparatus of the present invention, the interference signal removing unit, the estimated transfer function sequence vector generating unit, the transfer function sequence vector synthesizing unit, and the transfer function sequence vector updating unit are provided for one signal sequence. For each signal system of the signal replica sequence vector, a new transfer function sequence vector is sequentially generated and updated to the new transfer function sequence vector.
Thus, when the transfer function is estimated using the estimated transmission signal sequence vector T ′ obtained from the received symbol, each column vector in the estimated transmission signal matrix composed of the estimated transmission signal sequence vector T ′ is another column. Interference with the vector can be prevented, and the estimation accuracy of the transfer function can be improved.

In the wireless communication apparatus of the present invention, the transfer function sequence vector synthesizing means uses a forgetting factor μ (0 <μ ≦ 1: μ is a real number), and (1-μ) of the column vector h _k of the transfer function matrix. ) Times and μ times the estimated transfer function sequence vector h _k ′ of the k-th signal system, a new transfer function matrix is generated.
As a result, the wireless communication apparatus of the present invention suppresses a sudden change in the transfer function, that is, the newly estimated estimated transfer function sequence vector h _k ′ has low estimation accuracy due to the influence of noise or the like, and the actual transfer When the function is significantly different from the function, it is possible to prevent a significant decrease in communication efficiency due to complete replacement, and to adjust a transfer function having communication quality that can perform error correction, that is, channel tracking.

The radio communication apparatus of the present invention is characterized in that the forgetting factor μ is dynamically changed in proportion to the k-th component of the estimated transmission signal sequence vector T ′, that is, the absolute value of t _k .
Thus, the radio communication apparatus of the present invention, when the absolute value of the estimated transmission signal t _k of the k lines are estimated is large, the received signal strength received is high, the transfer function is more actual transfer estimated Since the function is close to the function, that is, the estimation accuracy is high, the forgetting factor μ is increased. On the other hand, when the estimated estimated transmission signal has a small absolute value, the received signal strength is low. It can be strongly received and the estimated transfer function is different from the actual transfer function, that is, the estimation accuracy may be low. Therefore, the channel tracking accuracy can be improved by reducing the forgetting factor μ. .

In addition, the receiving apparatus of the present invention receives a MIMO (N MIMO (N ≧ 2, N is an integer)) transmission station having N (N ≧ 2, N is an integer) transmitting a plurality of signal sequences on the same frequency channel. A receiving apparatus having M (M ≧ 1, M is an integer) receiving antennas that receive a radio signal transmitted by a multiple input (Multiple Input Multiple Output) communication method and perform reception processing by separating the signal into a plurality of signal sequences. A signal receiving means for individually receiving radio signals using the M receiving antennas, a signal having a known pattern given to the received signal as a reference signal, and the i-th antenna among the transmitting antennas; Transfer function acquisition means for acquiring M × N sets of transfer functions h _{j, i} with respect to the j-th antenna among the receiving antennas, and the transfer function h _{j, i} as the (j, i) component M-by-N matrix, ie transfer function The number matrix is H, the transmission signal of the N signal series is the transmission signal sequence vector T of N rows and 1 column, and the reception signal in units of symbols received by the M antennas is the reception signal sequence vector R of M rows and 1 column. When notated, an estimated transmission signal sequence vector T ′, which is an estimated value of the transmission signal sequence vector T transmitted by the transmitting station using the transfer function matrix H and the received signal sequence vector R, is obtained for each symbol. Transmitting signal estimation means for decomposing the transfer function matrix H into column vectors, expressed as H = (h ₁ , h ₂ ,..., H _N ), and the transmission signal sequence estimated for a predetermined symbol When the vector is expressed as T ′ = (t ₁ , t ₂ ,..., T _N ) ^t ( ^{t on the} right shoulder indicates a transposed matrix), from the k-th (1 ≦ k ≦ N, k is an integer) signal system when transmitting estimated transmission signal t _k, reception is received by the antenna Received signal replica string other than the k ′ (1 ≦ k ′ ≦ N, k ′ is an integer) system from the received signal string vector R; An interference signal removing unit that subtracts the signal system of the vector to obtain an interference removal column vector; and the interference cancellation column vector obtained by the interference signal removal unit is divided by the estimated transmission signal of the k'th signal sequence, 'Estimated transfer function sequence vector generating means for generating an estimated transfer function sequence vector of a signal system; and a new transfer function by linearly combining the estimated transfer function sequence vector and the column vector of the k'th column of the transfer function matrix A transfer function that generates a column vector; a transfer function that updates the k′th row of the transfer function matrix stored in the transfer function acquisition means to the new transfer function column vector; And having a vector updating means.

In addition, the reception method of the present invention provides a MIMO (N MIMO (N ≧ 2, N is an integer)) transmission station equipped with MIMO (N ≧ 2, N is an integer) transmitting a plurality of signal sequences on the same frequency channel. A reception method for receiving wireless signals transmitted by a multiple input (Multiple Input Multiple Output) communication method using M reception antennas (M ≧ 1, M is an integer) that performs reception processing by separating the signal into a plurality of signal sequences. A signal reception process for individually receiving radio signals using the M reception antennas, and a signal having a known pattern added to the reception signal as a reference signal, and the i-th antenna of the transmission antenna and the reception A transfer function acquisition process for acquiring M × N sets of transfer functions h _{j, i} with respect to the j-th antenna among the antennas, and M rows with the transfer function h _{j, i} as the (j, i) component N-column matrix or transfer function The number matrix is H, the transmission signal of the N signal series is the transmission signal sequence vector T of N rows and 1 column, and the reception signal in units of symbols received by the M antennas is the reception signal sequence vector R of M rows and 1 column. When notated, an estimated transmission signal sequence vector T ′, which is an estimated value of the transmission signal sequence vector T transmitted by the transmitting station using the transfer function matrix H and the received signal sequence vector R, is obtained for each symbol. Transmitting signal estimation process, the transfer function matrix H is decomposed into column vectors, expressed as H = (h ₁ , h ₂ ,..., H _N ), and the transmission signal sequence estimated for a predetermined symbol When the vector is expressed as T ′ = (t ₁ , t ₂ ,..., T _N ) ^t ( ^{t on the} right shoulder indicates a transposed matrix), from the k-th (1 ≦ k ≦ N, k is an integer) signal system when transmitting estimated transmission signal t _k, reception is received by the antenna A received signal replica sequence vector other than the k ′ (1 ≦ k ′ ≦ N, k ′ is an integer) system from the received signal sequence vector R An interference signal removal process for subtracting the signal system of the signal to obtain an interference removal column vector, and the interference removal column vector obtained by the interference signal removal unit is divided by the estimated transmission signal of the k'th signal sequence to obtain the k'th An estimated transfer function sequence vector generation process for generating an estimated transfer function sequence vector of a signal system, and a new transfer function sequence by linearly combining the estimated transfer function sequence vector and the k'th column vector of the transfer function matrix Transfer function sequence vector synthesis process for generating vectors, and a transfer function sequence vector for updating the k'th row of the transfer function matrix stored in the transfer function acquisition means to the new transfer function sequence vector Characterized in that it has an update process.

Note that it is also preferable to apply the above method to a radio communication system using an orthogonal frequency division multiplexing (OFDM) modulation scheme using a plurality of subcarriers.
Especially when MIMO processing and OFDM technology are applied and reception processing is performed on the receiving side using the MLD method or a method equivalent thereto, when performing channel tracking processing, it is necessary to perform a large number of matrix calculations. By performing the approximation process using a circuit that is simple and has a small circuit scale, the circuit scale can be reduced and the power consumption can be reduced.

As described above in detail, according to the present invention, when performing highly efficient wireless communication using MIMO technology, the channel tracking process is performed with one symbol, so that it is compared with the conventional channel tracking system. An effect of greatly reducing the circuit scale and the amount of calculation can be obtained.
As a result, according to the present invention, the circuit scale can be greatly reduced, so that the receiving circuit can be mounted in a one-chip LSI. Further, the above-described reduction in circuit scale and reduction in the amount of calculation can also be expected to have a secondary effect of directly reducing power consumption.

The wireless communication apparatus (system) of the present invention estimates a transmission signal sequence vector T from a reception signal sequence vector R of one symbol in tracking of a transfer function in MIMO communication, decomposes the transfer function matrix into column vectors, Each component of the column vector h _k of one transfer function matrix is set as an unknown, and the column vector h _k is multiplied from the received signal vector R by subtracting the term of the column vector other than the column vector h _k and the estimated transmission signal. by dividing by the estimated transmission signal t _k and is, it performs tracking processing by obtaining a column vector h _{k 'of} estimated transfer function matrix.

Hereinafter, a wireless communication apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the embodiment.
Hereinafter, embodiments of the present invention will be described with reference to the drawings. The difference between the present invention and the prior art is in the configuration of the receiving unit, and the configuration on the transmission side of the present invention is the same as the conventional example already described.
Therefore, only the receiving station will be described below. Similar to the conventional method, a case where the transmitting station transmits N systems of data using N transmitting antennas is used as an example.

FIG. 1 is a diagram illustrating a configuration of a receiving unit of a receiving station in the embodiment of the present invention. In the figure, the receiving unit of the present invention includes receiving antennas 111-1 to 111 -M, radio units 112-1 to 112 -M, channel estimation circuit 113, received signal management circuit 114, transfer function matrix management circuit 115, signal detection. The circuit 116 and the data synthesis circuit 117 are provided as in the conventional example.
The difference between the prior art shown in the present invention and FIG. 3 shown in FIG. 1, a replica received vector generating circuit 1, h ₁ generating circuit 2-1, h ₂ generating circuit 2-2, ..., h _N generation circuit 2-N , A transfer function vector synthesis circuit 3 and a transfer function matrix update control circuit 4 are newly provided. Hereinafter, the reception unit including the newly provided circuit will be described.

The first reception antenna 111-1, the second reception antenna 111-2,..., And the Mth reception antenna 111-M individually receive reception signals.
The radio units 112-1 to 112 -M receive the received signals individually received by the first receiving antenna 111-1, the second receiving antenna 111-2, and the M-th receiving antenna 111 -M, respectively. Then, signal processing such as amplification and noise removal is performed and output to the channel estimation circuit 113.
The channel estimation circuit 113 uses, as a reference signal, a preamble signal composed of known pattern data given on the transmission side, and, as described above, N transmission antennas i (1 ≦ i ≦). N) and M × N sets of transfer functions (h _{j, i} ) between the receiving antennas j (1 ≦ j ≦ M) are acquired and output to the transfer function matrix management circuit 115.
The transfer function matrix management circuit 115 manages the input transfer function (h _{j, i} ) as a transfer function matrix H that is a matrix of M rows and N columns, with the matrix components as components.

The received signal management circuit 114 receives a data signal subsequent to the preamble signal one symbol at a time from the channel estimation circuit 113 and receives the received signal (r ₁ , r ₂ ,..., R _M ) of each antenna as a component. Once managed as a vector R.
In the signal detection circuit 116, the estimated transmission signal T (N lines) that seems to be most likely from the relationship between the transfer function matrix managed by the transfer function matrix management circuit 115 and the received signal vector R managed by the received signal management circuit 114. N-row 1-column estimated transmission signal sequence vector) transmitted by the antenna of (1) is obtained and output to the replica reception vector generation circuit 1. As the transmission signal estimation method at this time, other methods may be used including the methods defined in Non-Patent Document 1, Non-Patent Document 2, and the like as described in the related art.

The replica reception vector generation circuit 1 decomposes the transfer function matrix H stored in the transfer function matrix management circuit 115 into column vectors, that is, H = (h ₁ , h ₂ ,..., H _N ). A received signal corresponding to a transmission signal t _k from a certain transmission antenna by multiplying one component of the function matrix (column vector) and the estimated transmission signal sequence vector T = (t ₁ , t ₂ ,..., T _N ). A replica column vector R ′ (t _k ) is calculated. (1 ≦ k ≦ N, k is an integer)

As described above, the replica reception vector generation circuit 1 calculates the reception signal replica sequence vector R ′ (t _k ) according to the following (5).
R ′ (t _k ) = t _k · h _k (5)
The received signal replica column vector R '(t _k), when transmitting the estimated transmitted signal t _k from the k signal lines, each receive antenna, i.e., a first reception antenna 111-1, a second reception antenna 111 -2,..., A column vector having elements of estimated values of received signals that will be received by the Mth receiving antenna 111-M.

Here, when tracking is performed at a predetermined period, the transfer function matrix H = (h ₁ , h ₂ ,..., H _N ) is transferred to the transfer function matrix H ′ = (h ₁ ′, h ₂ ′,. , H _N ′), since the amount of change is fine, the following approximate expression holds between the estimated transmission signal vector T, the actual reception signal vector R, and the transfer function matrices H and H ′. It will be.
Here, the received signal string vector is R = (r ₁ , r ₂ ,..., R _N ) ^t , and the description of “ ^t ” on the right shoulder of “(t ₁ , t ₂ ,..., R _N )” is , “(R ₁ , r ₂ ,..., R _N ) ^t ” is a transposed matrix (that is, a column vector) of the row vector “(r ₁ , r ₂ ,..., R _N )”.

R ≒ t ₁・ h ₁ '+ t ₂・ h ₁ + ... + t _N・ h _N
≒ t ₁・ h ₁ + t ₂・ h ₂ '+… + t _N・ h _N
・
・
・
≒ t ₁・ h ₁ + t ₂・ h ₂ + ... + t _N・ h _N '... (6)
Substituting equation (5) into equation (6), the following (6-a) is generated.
R≈t ₁ · h ₁ '+ R' (t ₂ ) + ... + R '(t _N )
≒ t ₂・ h ₂ '+ R' (t ₁ ) + R '(t ₃ ) + ... + R' (t _N )
・
・
・
_{≒ t N · h N '+} R' (t 1) + ... + R '(t N-1) ... (6-a)
Each row of the equation (6-a) is a linear equation in which each component of h _k ′ is an unconstant value, and can be easily obtained by modification as the following equation (7).
h ₁ '≈ {R−R ′ (t ₂ ) −... −R ′ (t _N )} / t ₁
h ₂ '≈ {R−R ′ (t ₁ ) −R ′ (t ₃ ) −... −R ′ (t _N )} / t ₂
・
h _k '≈ {R−R ′ (t ₁ ) −... −R ′ (t _k−1 ) −R ′ (t _{k + 1} ) −... −R ′ (t _N )} / t _k
・
h _N '≈ {R−R ′ (t ₁ ) −... −R ′ (t _N−1 )} / t _N (7)

The h ₁ generation circuit 2-1 receives the received signal for the k ′ signal sequence (2 ≦ k ′ ≦ N, k ′ is an integer) other than the first signal sequence, as shown in the first row of the above equation (7). Each replica column vector R ′ (t _{k ′} ) is subtracted from the actual received signal column vector R to calculate a column vector h ₁ ′ as an estimated transfer function column vector.
Similarly, as shown in the second row of the above equation (7), the h ₂ generation circuit 2-2 is the k ′ signal sequence (1 ≦ k ′ ≦ N and k ′ ≠ 2) other than the second signal sequence. , k 'is the received signal replica column vector R on integer)'_'subtracted) from the actual received signal column vector R each column vector h _2' (t _k is calculated as the estimated transfer function column vector h ₂ '.
Similarly, as shown in the Nth row of the above equation (7), the h _N generation circuit 2-N has a k ′ signal sequence (1 ≦ k ′ ≦ N−1, k ′ other than the first signal sequence). The received signal replica column vector R ′ (t _{k ′} ) for (integer) is subtracted from the actual received signal column vector R, and the column vector h _N ′ is calculated as an estimated transfer function column vector.

The transfer function sequence vector synthesizing circuit 3 linearly combines the k-th column of the transfer function matrix that has been used so far, that is, h _k and the estimated transfer function sequence vector h _k ′, to generate a new transfer function sequence vector h. _k ^(new) is obtained.
Here, the transfer function sequence vector synthesizing circuit 3 reads out h _k in the transfer function matrix H = (h ₁ , h ₂ ,..., H _N ) currently stored in the transfer function matrix management circuit 115 and performs a predetermined forgetting. Using the coefficient μ (0 <μ ≦ 1), a new transfer function column vector h _k ^(new) to be newly stored in the transfer function matrix management circuit 115 is calculated by the following equation (4).
h _k ^(new) = (1−μ) · h _k + μ · h _k ′ (8)
According to the above equation (8), the estimated transfer function sequence vector h _k ′ multiplied by a predetermined forgetting factor μ and the transfer function matrix vector h _k multiplied by “1−μ” are linearly combined and estimated. Instead of abruptly replacing the estimated transfer function sequence vector h _k ′, the adjustment is performed while leaving the immediately preceding component.

The transfer function matrix update control circuit 4 converts the obtained transfer function sequence vector h _k ^(new) into a transfer function matrix H = (h ₁ , h ₂ ,..., H _k stored in the transfer function matrix management circuit 115. ,..., H _N ) are overwritten on the corresponding column vectors to form a new transfer function matrix H.
In addition, the transfer function matrix update control circuit 4 includes estimated transfer function sequence vectors h ₁ ′, h ₁ generation circuit 2-1, h ₂ generation circuit 2-2, h _N generation circuit 2-N, respectively. Similarly to the above-described processing, h ₂ ′,..., h _N ′ is also a transfer function matrix H = (h ₁ , h ₂ ,..., h _k ,... h _N ) stored in the transfer function matrix management circuit 115. Overwrite each corresponding column vector of. At this time, at the periodic tracking timing, the transfer function matrix update control circuit 4 replaces the first column of the transfer function matrix with a new transfer function sequence vector for a certain symbol and the second row for the symbol with the next timing. It is also possible to control so that the columns are sequentially replaced in time series so as to replace.

In the configuration described above, a circuit for calculating N estimated transfer function sequence vectors of the h ₁ generation circuit 2-1 to h _N generation circuit 2-N corresponding to each signal system of the transmission signal of the transmission unit. It was provided separately.
However, a configuration may be adopted in which one h _k generation circuit 2-k is provided and the estimated transfer function sequence vectors h ₁ ′ to h _k ′ are sequentially _obtained in time series by a sequential circuit. For example, using one h _k generation circuit 2-k, at a periodic tracking timing, a certain symbol is used as the h ₁ generation circuit 2-1 to obtain the first column of the transfer function matrix, and the following The timing symbol is used as the h ₂ generation circuit 2-2 to obtain the second column of the transfer function matrix, and the N th timing symbol is used as the h _N generation circuit 2- to obtain the Nth column of the transfer function matrix. It can also be used as N.

Next, with reference to FIG.1 and FIG.2, operation | movement of the radio | wireless communications system which has a transmission part and a receiving part in embodiment mentioned above is demonstrated.
Here, in order to simplify the description, for example, the configuration of the wireless communication system in the case of 4 × 4 (M = 4, N = 4) MIMO will be described.
That is, with four transmission antennas and four reception antennas, that is, the transmission unit has transmission antennas 105-1 to 105-4, and the reception unit has reception antennas 111-1 to 111-4. Other configurations are also configured corresponding to the number of antennas.
The transmission unit individually transmits data from the transmission antennas 105-1 to 105-4.

And the 1st receiving antenna 111-1-the 4th receiving antenna 111-4 each receive a received signal individually.
As a result, the radio units 112-1 to 112-4 receive the received signals R {r ₁ , r ₂ , r ₃ , r ₁ , received individually by the first receiving antenna 111-1 to the fourth receiving antenna 111-4, respectively. r ₄ } is input, signal processing such as amplification and noise removal is performed, and the result is output to the channel estimation circuit 113.
Next, the channel estimation circuit 113 uses a preamble signal composed of known pattern data given on the transmission side as a reference signal, and from the reception status of this reference signal, as described above, each of the four transmission antennas i ( 1 × i ≦ 4) and each of the four receiving antennas j (1 ≦ j ≦ 4), 4 × 4 sets of transfer functions (h _{j, i} ) are obtained, decomposed into column vectors, and H = {H ₁ , h ₂ , h ₃ , h ₄ } is output to the transfer function matrix management circuit 115 for management.

Then, the received signal management circuit 114 is a component of the received signals (r ₁ , r ₂ , r ₃ , r ₄ ) of the respective antennas, each of which receives the data signal subsequent to the preamble signal from the channel estimation circuit 113 one symbol at a time. The received signal sequence vector R = {r ₁ , r ₂ , r ₃ , r ₄ } ^t is stored.
Next, the signal detection circuit 116 reads the reception signal vector R from the reception signal management circuit 114 and reads the transfer function matrix from the transfer function matrix management circuit 115 to obtain an estimated value of the transmission signal. The estimated transmission signal sequence vector T = {t ₁ , t ₂ , t ₃ , t ₄ } ^t is output.

Next, the replica reception vector generation circuit 1 calculates the reception signal replica column vector R ′ (t _k ) by the equation (1).
The replica reception vector generation circuit 1 outputs the reception signal replica string vector R ′ (t _k ) to each of the h ₁ generation circuits 2-1 to h ₄ generation circuits 2-4.
At this time, each of the h ₁ generation circuit 2-1 to h ₄ generation circuit 2-4 includes an actually received reception signal sequence used when calculating the estimated transmission signal sequence vector T from the reception signal management circuit 114. A vector R = {r ₁ , r ₂ , r ₃ , r ₄ } ^t is input.

Next, the h ₁ generation circuit 2-1 solves the equation using the transfer function h ₁ ′ as an unknown in the above equation (3).
That is, the h ₁ generation circuit 2-1 determines the term “t ₂ · h ₂ + t ₃ · h ₃ + t ₄ · h ₄ ” other than the signal system “t ₁ · h ₁ ′” defined as an unknown from the received signal vector R. Is subtracted and divided by the transmission signal t _1, which is a coefficient of h ₁ ′ defined as an unknown, to obtain the following equation (9) for calculating the unknown h ₁ ′.
h ₁ '≈ {Rt ₂ · h ₂ -t ₃ · h ₃ -t ₄ · h ₄ } / t ₁ (9)
As a result, the h ₁ generation circuit 2-1 calculates the estimated transfer function sequence vector h ₁ ′.
Similarly, the h ₂ generation circuit 2-2, the h ₃ generation circuit 2-3, and the h ₄ generation circuit 2-4 also correspond to the set transfer function sequence vectors as the unknowns, and the h ₁ generation circuit 2. The estimated transfer function sequence vectors h ₂ ′, h ₃ ′, and h ₄ ′ are calculated by the same processing as −1, respectively.

Next, the transfer function sequence vector synthesizing circuit 3 receives an estimated transfer function from each of the h ₁ generation circuit 2-1, the h ₂ generation circuit 2-2, the h ₃ generation circuit 2-3, and the h ₄ generation circuit 2-4. Input column vectors h ₁ ', h ₂ ', h ₃ ', h ₄ '.
The transfer function column vector synthesis circuit 3 reads each column vector h ₁ , h ₂ , h ₃ , h ₄ of the current transfer function matrix Hnow from the transfer function matrix management circuit 115 and uses the above equation (8). Thus, new transfer function sequence vectors h ₁ ^(new) , h ₂ ^(new) , h ₃ ^(new) , h ₄ ^(new) corresponding to each signal system are calculated.
Then, the transfer function sequence vector synthesis circuit 3 sends the calculated new transfer function sequence vectors h ₁ ^(new) , h ₂ ^(new) , h ₃ ^(new) , h ₄ ^(new) to the transfer function matrix update control circuit 4. Output to.

Next, the transfer function matrix update control circuit 4 converts each transfer function column vector h _{1 to} h _{4 of the} transfer function matrix H stored in the transfer function matrix management circuit 115 into a new input transfer function column vector. Overwrite and replace with h ₁ ^(new) , h ₂ ^(new) , h ₃ ^(new) , h ₄ ^(new) .
At this time, as described above, the transfer function matrix update control circuit 4 does not replace the transfer function matrix all at once, but sequentially replaces the existing transfer functions stored in the transfer function matrix management circuit 115 in the tracking period. The rows of the function matrix may be replaced by the obtained new transfer function column vectors h ₁ ^(new) , h ₂ ^(new) , h ₃ ^(new) , h ₄ ^(new) .
Here, if the obtained transfer function matrix h _k ^(new) is insufficient as the estimation accuracy, it is possible to control the replacement as necessary, such as deferring the transfer function matrix replacement. is there.

  Note that a program for realizing the function of the receiving unit in FIG. 1 is recorded on a computer-readable recording medium, and the program recorded on the recording medium is read into a computer system and executed, whereby data of the received data is received. Regeneration may be performed. 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 example of 1 structure of the receiving part of the receiving station by one Embodiment of this invention. It is a block diagram which shows the structure of the transmission part of the transmission station to which a MIMO technique is applied. It is a block diagram which shows the structure of the receiving part of the receiving station in a prior art.

Explanation of symbols

1 ... replica reception vector generator 2-1 ... h ₁ generating circuit 2-2 ... h ₂ generating circuit 2-N ... h _N generation circuit 3 ... transfer function column vector synthesizing circuit 4 ... Transfer function matrix update control circuit 101 ... Data division circuits 102-1, 102-2, 102-N ... Preamble applying circuits 103-1, 103-2, 103-N ... Modulation circuit 104 -1, 104-2, 104-N: wireless units 105-1, 105-2, 105-M ... transmitting antennas 111-1, 111-2, 111-M ... receiving antennas 112-1 , 112-2, 112 -M ... wireless unit 113 ... channel estimation circuit 114 ... received signal management circuit 115 ... transfer function matrix management circuit 116 ... signal detection circuit 117 ... data synthesis circuit

Claims (7)

A transmitting station having N (N ≧ 2, N is an integer) transmitting antennas that multiplex and transmit a plurality of signal sequences in space on the same frequency channel; In a wireless communication apparatus capable of MIMO (Multiple Input Multiple Output) communication configured by a receiving station provided with M receiving antennas (M ≧ 1, M is an integer) that performs reception processing by separating into signal sequences,
The transmitting station is
User data dividing means for dividing user data into N systems;
A signal sequence generation means for generating a signal sequence of N systems by giving individual known pattern signals to the data divided into the N systems;
Signal transmitting means for simultaneously superimposing and transmitting the signal sequence at the same frequency using N transmitting antennas,
The receiving station is
Signal receiving means for individually receiving radio signals using the M receiving antennas;
M × N sets of transfer functions h _j, between the i-th antenna of the transmission antennas and the j-th antenna of the reception antennas, using a signal of a known pattern given to the reception signal as a reference signal _. transfer function acquisition means for acquiring _i ;
A matrix of M rows and N columns having the transfer function h _{j, i} as the (j, i) component, that is, a transfer function matrix H, a transmission signal of N signal sequences, a transmission signal sequence vector T of N rows and 1 column, When a received signal in units of symbols received by M antennas is expressed as a received signal column vector R of M rows and 1 column,
Transmission signal estimation means for obtaining an estimated transmission signal sequence vector T ′ which is an estimated value of the transmission signal sequence vector T transmitted by the transmission station using the transfer function matrix H and the received signal sequence vector R for each symbol. When,
The transfer function matrix H is decomposed into column vectors, expressed as H = (h ₁ , h ₂ ,..., H _N ), and the transmission signal column vector estimated for a predetermined symbol is expressed as T ′ = (t ₁ , t ₂ ,..., T _N ) ^t ( ^{t on the} right shoulder indicates a transposed matrix)
The k (1 ≦ k ≦ N, k is an integer) replica received vector in transmission of estimated transmitted signal t _k from the signal line, and generates a received signal replica column vector estimating the signal received by the antenna Generating means;
Interference signal removing means for subtracting received signal replica string vectors other than the k ′ (1 ≦ k ′ ≦ N, k ′ is an integer) system from the received signal string vector R to obtain an interference removed string vector;
Estimated transfer function sequence vector generation means for generating an estimated transfer function sequence vector of the k 'signal system by dividing the interference cancellation sequence vector obtained by the interference signal cancellation means by the estimated transmission signal of the k' signal sequence; ,
Transfer function sequence vector combining means for linearly combining the estimated transfer function sequence vector and the k'th column vector of the transfer function matrix to generate a new transfer function sequence vector;
A wireless communication apparatus comprising: transfer function sequence vector updating means for updating the k′th row of the transfer function matrix stored in the transfer function acquisition means to the new transfer function sequence vector. The wireless communication device according to claim 1,
2. The radio communication apparatus according to claim 1, wherein the interference signal removing unit, the estimated transfer function sequence vector generating unit, and the transfer function sequence vector combining unit are provided for each of all the signal systems. The wireless communication device according to claim 1,
The interference signal removing means, the estimated transfer function sequence vector generating means, the transfer function sequence vector synthesizing unit and the transfer function sequence vector updating means are provided for one signal sequence, and a new transfer function is sequentially added to each signal system. A wireless communication apparatus, wherein a column vector is generated and updated to the new transfer function column vector. In the wireless communication apparatus according to any one of claims 1 to 3,
The transfer function column vector synthesizing means uses a forgetting factor μ (0 <μ ≦ 1: μ is a real number), (1-μ) times the column vector h _k of the transfer function matrix, and the k-th signal system. A wireless communication apparatus characterized by generating a new transfer function matrix by linearly synthesizing μ times the estimated transfer function sequence vector h _k ′. The wireless communication device according to claim 4, wherein
The forgetting factor μ is the radio communication apparatus characterized by dynamically changing in proportion to the absolute value of the k component i.e. t _k of the estimated transmission signal column vector T '. Transmitted by a MIMO (Multiple Input Multiple Output) communication system from a transmission station equipped with N (N ≧ 2, N is an integer) transmission antennas that multiplex and transmit a plurality of signal sequences on the same frequency channel. A receiving apparatus including M (M ≧ 1, M is an integer) receiving antennas that receive received radio signals and perform reception processing by separating them into a plurality of signal sequences;
Signal receiving means for individually receiving radio signals using the M receiving antennas;
M × N sets of transfer functions h _j, between the i-th antenna of the transmission antennas and the j-th antenna of the reception antennas, using a signal of a known pattern given to the reception signal as a reference signal _. transfer function acquisition means for acquiring _i ;
A matrix of M rows and N columns having the transfer function h _{j, i} as the (j, i) component, that is, a transfer function matrix H, a transmission signal of N signal sequences, a transmission signal sequence vector T of N rows and 1 column, When a received signal in units of symbols received by M antennas is expressed as a received signal column vector R of M rows and 1 column,
Transmission signal estimation means for obtaining an estimated transmission signal sequence vector T ′ which is an estimated value of the transmission signal sequence vector T transmitted by the transmission station using the transfer function matrix H and the received signal sequence vector R for each symbol. When,
The transfer function matrix H is decomposed into column vectors, expressed as H = (h ₁ , h ₂ ,..., H _N ), and the transmission signal column vector estimated for a predetermined symbol is expressed as T ′ = (t ₁ , t ₂ ,..., T _N ) ^t ( ^{t on the} right shoulder indicates a transposed matrix)
The k (1 ≦ k ≦ N, k is an integer) replica received vector in transmission of estimated transmitted signal t _k from the signal line, and generates a received signal replica column vector estimating the signal received by the antenna Generating means;
Interference signal removing means for subtracting received signal replica string vectors other than the k ′ (1 ≦ k ′ ≦ N, k ′ is an integer) system from the received signal string vector R to obtain an interference removed string vector;
Estimated transfer function sequence vector generation means for generating an estimated transfer function sequence vector of the k 'signal system by dividing the interference cancellation sequence vector obtained by the interference signal cancellation means by the estimated transmission signal of the k' signal sequence; ,
Transfer function sequence vector combining means for linearly combining the estimated transfer function sequence vector and the k'th column vector of the transfer function matrix to generate a new transfer function sequence vector;
A receiving apparatus comprising: transfer function sequence vector updating means for updating the k′th row of the transfer function matrix stored in the transfer function obtaining means to the new transfer function sequence vector. Transmitted by a MIMO (Multiple Input Multiple Output) communication system from a transmission station equipped with N (N ≧ 2, N is an integer) transmission antennas that multiplex and transmit a plurality of signal sequences on the same frequency channel. A reception method of receiving the received radio signal by M reception antennas (M ≧ 1, M is an integer) that performs reception processing by separating the signal into a plurality of signal sequences,
A signal receiving process of individually receiving radio signals using the M receiving antennas;
M × N sets of transfer functions h _j, between the i-th antenna of the transmission antennas and the j-th antenna of the reception antennas, using a signal of a known pattern given to the reception signal as a reference signal _. a transfer function acquisition process for acquiring _i ;
A matrix of M rows and N columns having the transfer function h _{j, i} as the (j, i) component, that is, a transfer function matrix H, a transmission signal of N signal sequences, a transmission signal sequence vector T of N rows and 1 column, When a received signal in units of symbols received by M antennas is expressed as a received signal column vector R of M rows and 1 column,
A transmission signal estimation process for obtaining an estimated transmission signal sequence vector T ′ that is an estimated value of the transmission signal sequence vector T transmitted by the transmission station using the transfer function matrix H and the received signal sequence vector R for each symbol. When,
The transfer function matrix H is decomposed into column vectors, expressed as H = (h ₁ , h ₂ ,..., H _N ), and the transmission signal column vector estimated for a predetermined symbol is expressed as T ′ = (t ₁ , t ₂ ,..., T _N ) ^t ( ^{t on the} right shoulder indicates a transposed matrix)
The k (1 ≦ k ≦ N, k is an integer) in the case of transmitting the estimated transmission signal t _k from the signal system, generating a replica matrix to generate a received signal replica column vector estimating the signal received by the antenna Process,
An interference signal removal step of subtracting received signal replica sequence vectors other than the k ′ (1 ≦ k ′ ≦ N, k ′ is an integer) system from the received signal sequence vector R to obtain an interference elimination sequence vector;
An estimated transfer function sequence vector generation step of generating an estimated transfer function sequence vector of the k 'signal system by dividing the interference cancellation sequence vector obtained by the interference signal cancellation means by the estimated transmission signal of the k'th signal sequence; ,
A transfer function sequence vector synthesis process for generating a new transfer function sequence vector by linearly combining the estimated transfer function sequence vector and the k'th column vector of the transfer function matrix;
A receiving method comprising: a transfer function sequence vector updating step of updating the k'th row of the transfer function matrix stored in the transfer function obtaining means to the new transfer function sequence vector.

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