CN100362773C - Broad band receiver of multiple input and multiple output system - Google Patents
Broad band receiver of multiple input and multiple output system Download PDFInfo
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Abstract
The present invention discloses a wideband receiver of a multiple-input multiple-output (MIMO) system, which comprises a first-stage parallel interference cancellation (PIC) structure and a final-stage PIC structure, wherein the first-stage PIC structure is used for the first-stage PIC processing for the vector of a receiving signal to obtain the corrected received signal vector of all data flow; the corrected received signal vector of all the data flow is transmitted to a next-stage PIC structure, wherein the first-stage PIC processing cancels the interference of symbols of the same data flow, and besides, the interference of other data flow is cancelled; the final-stage PIC structure is used for the last-grade PIC processing of the corrected received signal vector of all the data flow of the upper stage PIC structure to obtain the estimation value of symbols of all the data flow. The wideband receiver greatly reduces processing time delay, the estimating performance of the symbols of data flow is remarkably improved, and the structure of the receiver is simplified.
Description
Technical Field
The invention relates to the technical field of wireless communication, in particular to a broadband receiver of a multiple-input multiple-output (MIMO) system.
Background
The MIMO technology is a major technological breakthrough in the field of wireless communication, and can improve the capacity and spectrum utilization rate of a communication system by times without increasing the bandwidth. The MIMO technology simultaneously transmits and receives signals using multiple antennas at a transmitting end and a receiving end. Because the signals transmitted by the transmitting antennas simultaneously occupy the same frequency band, the communication bandwidth is not increased. There is one spatial channel between each transmit antenna and each receive antenna. The MIMO system can create a plurality of parallel independent spatial channels between a transmitting end and a receiving end through a plurality of transmitting antennas and a plurality of receiving antennas if channel impulse responses of each spatial channel are independent. By independently transmitting information through these parallel spatial channels, the transmission data rate of the MIMO system is multiplied.
At present, a D-BLAST (diagnostic Bell Laboratories layerspaced-time Architecture) method and a V-BLAST (Vertical Bell Laboratories layerspaced-time Architecture) method can realize the demodulation of the MIMO system. However, the complexity of the D-BLAST method is very high, and it is not easy to implement in real time, while the V-BLAST method is only suitable for demodulation of the MIMO system in the narrow band channel, and cannot implement demodulation of the MIMO system in the wide band channel.
The V-BLAST method based on the MISO-DFE can achieve demodulation of the MIMO system under a wideband channel, but the demodulation performance of the V-BLAST method based on the MISO-DFE is not ideal. The V-BLAST method based on MIMO-DFE can further improve the demodulation performance of the MIMO system under the broadband channel, the method improves the symbol estimation performance of the data stream to a certain extent, and reduces the series of serial interference cancellation and the processing delay to a certain extent. However, the V-BLAST method based on MIMO-DFE adopts serial interference cancellation, the processing delay is still large, and the hard decision performance of the symbol is low.
Disclosure of Invention
It is therefore a primary objective of the claimed invention to provide a wideband receiver for MIMO system to reduce the processing delay.
In order to achieve the purpose, the technical scheme of the invention is as follows:
a wideband receiver of a MIMO system, the wideband receiver comprising:
a first stage Parallel Interference Cancellation (PIC) structure, which performs multiple-input multiple-output decision feedback estimation on the unmodified received signal vector to obtain a signal estimation and a total signal estimation of each data stream, cancels interference between symbols in each data stream and interference between data streams by the signal estimation, the total signal estimation and the unmodified received signal vector of all the data streams to obtain a modified received signal vector of all the data streams, and sends the modified received signal vector of all the data streams to a next stage PIC structure;
and the final-stage PIC structure is used for calculating decision statistics of corrected receiving signal vectors of all data streams sent by the previous-stage PIC structure, and obtaining a symbol estimation value of each data stream according to the decision statistics of each data stream.
The wideband receiver further comprises at least one intermediate-level PIC structure, the intermediate-level PIC structure is located between the first-level PIC structure and the last-level PIC structure, each intermediate-level PIC structure is connected in series, each intermediate-level PIC structure calculates decision statistics of corrected received signal vectors of all data streams sent by the previous-level PIC structure, a symbol estimation value of each data stream is obtained from the decision statistics of each data stream, signal estimation and total signal estimation of all data streams are obtained from the symbol estimation values of all data streams, interference among symbols in each data stream and interference among the data streams are eliminated by the signal estimation, the total signal estimation and the uncorrected received signal vectors of all the data streams, further corrected received signal vectors of all the data streams are obtained, and the further corrected received signal vectors of all the data streams are sent to the next-level PIC structure.
The broadband receiver further comprises a despreading unit connected with the first-stage PIC structure, wherein the despreading unit is used for despreading the unmodified received signal vector after spreading to obtain a received signal vector, and sending the received signal vector to the first-stage PIC structure.
The wideband receiver further comprises a despreading unit connected with the first-stage PIC structure, wherein the despreading unit is used for despreading the unmodified received signal vector after spreading to obtain the unmodified received signal vector, and sending the received signal vector to the first-stage PIC structure and the intermediate-stage PIC structure.
The first level PIC fabric comprises:
the first-stage detection unit is used for obtaining signal estimation and total signal estimation of all data streams from the unmodified received signal vector and sending the signal estimation and the total signal estimation of all the data streams to the first-stage interference cancellation and received signal vector correction unit;
and the first-stage interference cancellation and received signal vector correction unit cancels the interference between symbols in each data stream and the interference between the data streams by the signal estimation, the total signal estimation and the unmodified received signal vectors of all the data streams to obtain the corrected received signal vectors of all the data streams, and sends the corrected received signal vectors of all the data streams to the next-stage PIC structure.
The last stage PIC structure comprises M symbol estimation units, wherein M is the number of transmitting antennas, each symbol estimation unit corresponds to one data stream, each symbol estimation unit is used for calculating decision statistics of the data stream according to the corrected received signal vector of the corresponding data stream, and the decision statistics are used for obtaining a symbol estimation value of the data stream.
Each intermediate stage PIC fabric comprises:
the intermediate stage detection unit is used for obtaining signal estimation and total signal estimation of all data streams by corrected received signal vectors of all data streams from the PIC structure of the upper stage, and sending the signal estimation and the total signal estimation of all the data streams to the intermediate stage interference cancellation and received signal vector correction unit;
and the intermediate-stage interference cancellation and received signal vector correction unit cancels the interference between the symbols of each data stream and the interference between the data streams according to the signal estimation, the total signal estimation and the unmodified received signal vector of all the data streams to obtain the further corrected received signal vectors of all the data streams, and sends the further corrected received signal vectors of all the data streams to the next-stage PIC structure.
The first stage detection unit includes:
a multiple-input multiple-output feedforward filter (MIMO FFF) unit, which completes the forward filtering of the received signal vector by the input forward filtering weight matrix and sends the signal vector obtained by filtering to the adder;
an adder for calculating a difference between a signal vector output from the MIMO FFF unit and a signal vector output from a multiple-input multiple-output feedback filter (MIMO FBF) unit, and sending the calculated difference to the soft decision unit;
the soft decision unit is used for carrying out soft decision on each component of the difference sent by the adder to obtain the symbol estimation of each data stream and sending the symbol estimation of all the data streams to the signal estimation unit and the MIMO FBF unit;
the weight matrix calculation unit is used for calculating a forward filtering weight matrix and a feedback filtering weight matrix from the input received signal vector, sending the forward filtering weight matrix to the MIMO FFF unit and sending the feedback filtering weight matrix to the MIMO FBF unit;
the MIMO FBF unit completes the feedback filtering of the vectors which are input by the soft decision unit and comprise the symbol estimation of the M data streams through the feedback filtering weight matrix and sends the signal vectors obtained by the filtering to the adder;
and the signal estimation unit is used for obtaining the signal estimation of each data stream and the total signal estimation of all the data streams according to the symbol estimation of all the data streams, and sending the signal estimation result of each data stream and the total signal estimation of all the data streams to the first-stage interference cancellation and received signal vector correction unit.
The intermediate stage detection unit includes:
m middle-stage symbol estimation units, which are used for respectively finishing symbol estimation of M data streams, wherein M is the number of transmitting antennas, and sending the symbol estimation of the M data streams to a middle-stage signal estimation unit;
and the intermediate-stage signal estimation unit is used for finishing the signal estimation and the total signal estimation of each data stream.
Through the technical scheme, the broadband receiver of the MIMO system adopts parallel interference cancellation reception, obtains larger performance improvement through fewer stages, and greatly reduces the processing time delay. Meanwhile, in the first-stage parallel interference cancellation and the intermediate-stage parallel interference cancellation, not only the interference of other data streams is cancelled, but also the interference between symbols of the same data stream is cancelled, the processing mode not only improves the performance of each-stage parallel interference cancellation, but also enables the detection of each data stream to be detected according to the detection method of a flat fading channel when the next-stage parallel interference cancellation is processed, thereby greatly simplifying the internal structure of the subsequent parallel interference cancellation structure of each stage, reducing the calculation amount and reducing the realization complexity. Moreover, the broadband receiver of the invention adopts the soft decision method to improve the performance of symbol estimation, solves the problem of lower performance of hard decision of the symbol in the broadband demodulation method of the existing MIMO system, and obviously improves the performance of symbol estimation of the data stream.
Drawings
Fig. 1 is a schematic diagram of a wideband receiver of a MIMO system according to an embodiment of the present invention.
Fig. 2 is a schematic diagram of a first-stage PIC structure of a wideband receiver of a MIMO system according to an embodiment of the present invention.
Fig. 3 is a schematic diagram of an intermediate-level PIC structure of a wideband receiver of a MIMO system according to an embodiment of the present invention.
Fig. 4 is a diagram illustrating a last stage PIC structure of a MIMO system according to an embodiment of the present invention.
Fig. 5 is a schematic diagram of a first-stage detection unit of a first-stage PIC structure of a MIMO system according to an embodiment of the present invention.
Fig. 6 is a schematic diagram of an intermediate level detection unit of an intermediate level PIC structure of a MIMO system according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described in detail with reference to the accompanying drawings and specific embodiments.
Assuming that M is the number of transmit antennas, the receiver uses N antennas for reception. The N-dimensional chip-level received signal vector is X (t). The transmitting end adopts OVSF code c to transmit M data streams.
Fig. 1 is a schematic diagram of a wideband receiver of a MIMO system according to an embodiment of the present invention. As shown in FIG. 1, the wideband receiver consists of a despreading unit 101 and an S-stage PIC architecture (S ≧ 2). The S-level PIC fabric includes a first level PIC fabric 102, (S-2) intermediate level PIC fabrics 103, and a last level PIC fabric 104.
Despreading section 101 first receives a spread received signal vector and performs despreading on the spread received signal vectorEach component of the vector is despread to obtain a received signal vector. Wherein, the despreading unit 101 completes despreading of each component in the input N-dimensional baseband received signal vector X (t) by using the product of the OVSF code c and the scrambling code to obtain an N-dimensional received signal vector X c (k)。
The first stage PIC structure 102 performs a first stage PIC process on the received signal vector obtained by the despreading unit 101, where the first stage PIC process includes: the multiple-input multiple-output decision feedback estimation is performed on the received signal vector from the despreading unit 101 to obtain symbol estimates of all M data streams, and the signal estimates and the total signal estimates of the M data streams are obtained by the symbol estimates of the M data streams, and parallel interference cancellation is performed according to the signal estimates and the total signal estimates of the M data streams and the received signal vector to obtain a corrected received signal vector of the M data streams. In the first stage PIC processing, not only the interference of other data streams but also the interference between symbols of the data stream is to be eliminated, so that the modified received signal vector of each data stream is not only reduced by the signal estimates of other data streams, but also reduced by the estimate of the interference between symbols of the data stream.
Second level PIC structure 103 (i.e., the first intermediate level PIC structure) performs a first intermediate level PIC process on the modified received signal vectors for the M data streams from first level PIC structure 102 to obtain further updated modified received signal vectors for the M data streams. The first intermediate stage PIC process includes: symbol estimation of the M data streams is performed on the corrected received signal vectors of the M data streams from the first-stage PIC structure 102, so as to obtain symbol estimation values of the M data streams, signal estimation and total signal estimation of the M data streams are obtained from the symbol estimation values of the M data streams, and first intermediate-stage parallel interference cancellation processing is performed on the signal estimation and total signal estimation of the M data streams and the received signal vectors from the despreading unit 101, so as to obtain further updated M corrected received signal vectors of the M data streams. In the first intermediate stage PIC processing, not only the interference of other data streams but also the interference between symbols of the data stream should be eliminated, so that the modified received signal vector of each data stream not only subtracts the signal estimates of other data streams, but also subtracts the estimate of the interference between symbols of the data stream.
The processing of the remaining intermediate-level PIC fabric 103 is identical. The process by which all intermediate-level PIC fabric 103 can be obtained is:
when the ith (i =2, …, S-1) stage PIC structure performs the ith stage parallel interference cancellation processing, the ith stage PIC processing is performed on the M corrected received signal vectors from the (i-1) stage PIC structure to obtain further updated corrected received signal vectors of the M data streams. Which comprises the following steps: symbol estimation of M data streams is performed by M modified received signal vectors from the (i-1) th level PIC structure, to obtain symbol estimation values of the M data streams, signal estimation and total signal estimation of the M data streams are obtained by the symbol estimation values of the M data streams, and ith parallel interference cancellation processing is performed by the signal estimation and total signal estimation of the M data streams and the received signal vector from the despreading unit 101, to obtain further updated M modified received signal vectors of the M data streams. In the interference cancellation process, not only the interference of other data streams but also the interference between symbols of the current data stream are to be cancelled, so that the corrected received signal vector of each data stream is subtracted not only the signal estimation of the other data streams but also the estimation of the interference between symbols of the current data stream.
The last stage PIC structure 104 performs S-stage PIC processing on the modified received signal vectors of the M data streams from the (S-1) -th stage PIC structure (i.e., the (S-2) -th intermediate stage PIC structure) to obtain symbol estimation values of the M data streams, which are the final detection results of the M data streams. Wherein the S-th stage PIC processing comprises: and respectively carrying out symbol estimation on the M corrected received signal vectors from the (S-1) th-level PIC structure to obtain symbol estimation values of the M data streams.
The wideband receiver removes the despreading unit 101 if the spreading process is not performed at the time of signal transmission. At this time, the symbol-level received signal vector is input to the first-level PIC structure 102, the first-level PIC structure 102 performs mimo decision feedback estimation on the symbol-level received signal vector to obtain symbol estimates of all M data streams, and obtains signal estimates and total signal estimates of the M data streams from the symbol estimates of the M data streams, and performs parallel interference cancellation according to the signal estimates and the total signal estimates of the M data streams and the symbol-level received signal vector to obtain a modified received signal vector of the M data streams. In the first stage PIC processing, not only the interference of other data streams but also the interference between symbols of the data stream is to be eliminated, so that the corrected received signal vector of each data stream not only subtracts the signal estimates of other data streams, but also subtracts the estimate of the interference between symbols of the data stream. Similarly, second-level PIC structure 103 (i.e., the first intermediate-level PIC structure) performs a first intermediate-level PIC process on the modified received signal vectors for the M data streams from first-level PIC structure 102 to obtain further updated modified received signal vectors for the M data streams. The first intermediate stage PIC processing includes: the symbol estimation of the M data streams is performed on the modified received signal vectors of the M data streams from the first-stage PIC structure 102, to obtain symbol estimation values of the M data streams, the signal estimation and the total signal estimation of the M data streams are obtained from the symbol estimation values of the M data streams, and the first intermediate-stage parallel interference cancellation processing is performed on the signal estimation and the total signal estimation of the M data streams and the symbol-stage received signal vectors, to obtain further updated M modified received signal vectors of the M data streams. In the first intermediate stage PIC processing, not only the interference of other data streams but also the interference between symbols of the data stream should be eliminated, so that the modified received signal vector of each data stream is not only reduced by the signal estimates of other data streams, but also reduced by the estimate of the interference between symbols of the data stream. Similarly, the processing of the remaining intermediate level PIC fabric 103 is now still exactly the same. At this time, the last stage PIC structure 104 performs S-stage PIC processing on the modified received signal vectors of M data streams from the (S-1) -th stage PIC structure (i.e., the (S-2) -th intermediate stage PIC structure) to obtain symbol estimation values of the M data streams, where the symbol estimation values of the M data streams are the final detection results of the M data streams. Wherein the S-th stage PIC processing comprises: and respectively carrying out symbol estimation on the M corrected received signal vectors from the (S-1) th-level PIC structure to obtain symbol estimation values of the M data streams.
Fig. 2 is a schematic diagram of a first-stage PIC structure of a wideband receiver of a MIMO system according to an embodiment of the present invention. As shown in fig. 2, the first stage PIC structure is composed of a first stage detection unit 201 and a first stage interference cancellation and received signal vector modification unit 202. First-stage detecting section 201 obtains signal estimates and total signal estimates for M data streams from the received signal vectors from despreading section 101, and sends the signal estimates and total signal estimates for M data streams to first-stage interference cancellation and received signal vector correcting section 202. The input signal of the first stage interference cancellation and received signal vector modification unit 202 is the signal estimate and total signal estimate and received signal vector for the M data streams. First stage interference cancellation received signal vector modification unit 202 obtains M modified received signal vectors from the input signal and sends the M modified received signal vectors to second stage PIC structure 103 (i.e., the first intermediate stage PIC structure).
Fig. 3 is a schematic diagram of an intermediate-level PIC structure of a wideband receiver of a MIMO system according to an embodiment of the present invention. The second-level PIC structure through the (S-1) -th level PIC structure are all intermediate-level PIC structures and have identical structures. As shown in fig. 3, the i (i =2, …, S-1) th stage PIC structure 103 is composed of an intermediate stage detection unit 301 and an intermediate stage interference cancellation and received signal vector modification unit 302. The mid-stage detection unit 301 obtains signal estimates and total signal estimates for the M data streams from the M modified received signal vectors from the (i-1) th-stage PIC structure, and sends the signal estimates and the total signal estimates for the M data streams to the mid-stage interference cancellation and received signal vector modification unit 302. The input signal of the inter-stage interference cancellation and received signal vector modification unit 302 is the received signal vector sent from the inter-stage detection unit 301 and the total signal estimation and despreading unit 101 for the M data streams. The inter-stage interference cancellation and received signal vector modification unit 302 obtains M modified received signal vectors from the input signal, and sends the M modified received signal vectors to the (i + 1) th stage PIC architecture.
Fig. 4 is a schematic diagram of a last stage PIC structure of the MIMO system according to an embodiment of the present invention. As shown in fig. 4, the last stage PIC structure 104 is composed of M symbol estimation units 401. A symbol estimation unit M (M =1,2, …, M) obtains a symbol estimation of the mth data stream from the corrected received signal vector of the mth data stream. The symbol estimates for the M data streams are the final detection results for the M data streams.
The following describes the first-stage detection unit 201 in fig. 2, the first-stage interference cancellation and received signal vector modification unit 202 in fig. 2, the intermediate-stage detection unit 301 in fig. 3, and the symbol estimation unit 401 in the S-stage PIC structure 104 in fig. 4 in detail.
Let OVSF code c be o c And (t) the scrambling code is s (t). The input of despreading section 101 is an N-dimensional chip-level received signal vector x (t) = [ x ] 1 (t)，x 2 (t)，…，x N (t)] T Then the output x of the despreading unit 101 c (t)＝[x c1 (t)，x c2 (t)，…，x cN (t)] T Calculated according to the following formula:
n＝1，2，…，N， (1)
wherein, T s Is the symbol period.
Signal model for MIMO systems:
x c (k)＝[x c1 (k)，x c2 (k)，…，x cN (k)] T is to x c (t) at time kT s The result of sampling can be written as follows:
here, the
s c，m [k]＝[s c，m [k+L a ]…s c，m [k-L c ]] T ，s c，m [k]Is the kth symbol sent by the mth antenna;
n c [k]＝[n C，1 [k]…n c，N [k]] T Is an N-dimensional noise vector whose components each obey N (0, σ) n 2 ) Are distributed, and
I N is an identity matrix of order N.
The first stage detection unit 201 of the first stage PIC architecture 102 is described below.
Referring to fig. 5, the first-stage detection unit 201 of the first-stage PIC structure 102 is composed of a MIMO DFE demodulation unit 501 and a signal estimation unit 502, which are multiple-input multiple-output decision feedback equalizers.
MIMO DFE demodulation section 501 is composed of weight matrix calculation section 503, MIM0 FFF section 504, MIM0 FBF section 505, adder section 506, and soft decision section 507. Wherein, the weight matrix calculation unit 503 completes the calculation of the forward filtering weight matrix and the feedback filtering weight matrix by the input received signal vector, and sends the forward filtering weight matrix to the MIMO FFF unit 504, and sends the feedback filtering weight matrix to the MIMO FBF unit 505; the MIMO FFF unit 504 performs forward filtering on the received signal vector from the input forward filtering weight matrix, and sends the signal vector obtained by filtering to the adder 506; the MIMO FBF unit 505 performs feedback filtering on a vector formed by symbol estimates of the M data streams input by the soft decision unit 507 by using a feedback filtering weight matrix, and sends a signal vector obtained by filtering to the adder 506; adder 506 obtains the difference between the signal vector output from MIMO FFF section 504 and the signal vector output from MIMO FBF section 505, and sends the obtained difference to soft decision section 507; soft decision section 507 performs soft decision on each component of the difference sent from adder 506 to obtain a symbol estimate for each data stream, and sends the symbol estimates for M data streams to signal estimation section 502 and MIMO FBF section 505.
The signal estimation unit 502 obtains the signal estimation of each data stream and the total signal estimation of all data streams from the symbol estimation of M data streams, and sends the signal estimation result of each data stream and the total signal estimation of all data streams to the interference cancellation and received signal vector correction unit 202 of the first stage PIC.
The first-stage detection unit 201 of the first-stage PIC structure completes demodulation of the input signal vector, and obtains a signal estimate and a total signal estimate for each data stream, which are specifically described as follows:
the MIMO DFE demodulation unit 501 performs the following functions:
let the input signal vector of MIMO DFE demodulation unit 501 be:
wherein the content of the first and second substances,
the weight matrix of the MIMOFFF unit 504 is W c Is N (K) f A + 1) x M matrix, the weight matrix of the MIMOFBF block 505 is V c Is K b M x M order matrix, K b Is the feedback filter length.
The weight matrix calculation unit 503 calculates the weight matrix W according to the following formula c And V c ：
Wherein the content of the first and second substances,
H 1，c，m is H c，m The estimation of (2) is obtained by the first channel estimation; h if the channel estimation is perfect 1，c，m ＝H c，m 。
Is that
Is estimated.
the MIMOFBF unit 505 is configured by a feedback filtering weight matrix V c Completing the filtering of the input vector and converting the filtering result delta y c [k]To adder 506:
wherein the content of the first and second substances,
s c，m [k]is estimated as
in the ith PIC architecture, the signal estimation unit performs the following functions:
the signal estimation for the mth data stream is as follows:
H i，c，m is H c，m Is obtained from the ith channel estimate, (H) l Column l representing the matrix H;for symbols s in the ith level PIC structure c，m [k]Is estimated.
The total signal estimate for the mth signal stream is obtained according to equation (4 f):
wherein the content of the first and second substances,
for symbols s in the ith level PIC structure c，m [k]Is estimated.
The total signal estimate for the M data streams is as follows:
in the i (i =1,2, …, S-1) stage PIC structure, the first stage interference cancellation and received signal vector modification unit 202 and the intermediate stage interference cancellation and received signal vector modification unit 302 calculate M modified received signal vectors according to the following two formulas:
X i+1，c，m [k]＝X i+1，c [k]+U i，c，m [k]，m＝1，2，…，M (5b)
the intermediate-level detection unit 30l of the intermediate-level PIC architecture l03 is described below.
Fig. 6 is a schematic diagram of an intermediate level detection unit of an intermediate level PIC structure of a MIMO system according to an embodiment of the present invention. As shown in fig. 6, the inter-stage detection unit 301 is composed of M inter-stage symbol estimation units 601 and an inter-stage signal estimation unit 602. The M symbol estimation units 601 respectively perform symbol estimation for the M data streams. The intermediate-stage signal estimation unit 602 performs signal estimation and total signal estimation for each data stream, which is the same as the signal estimation unit 502 in the first-stage detection unit 201 of the first-stage PIC structure 102. The function of the mid-stage symbol estimation unit 601 is exactly the same as the symbol estimation unit 401 in the S-th stage PIC architecture.
The input signal of the symbol estimation unit m in the level i (i > 1) PIC structure is X i，c，m [k]The unit performs the following functions:
(1) First, a weight vector W is calculated i，c，m
Calculating W according to formula (6 a) under ZF criterion i，c，m W is calculated according to the formula (6 b) under the MMSE criterion i，c，m ：
Wherein σ 2 For receiving the power of the noise component in the signal vector, σ s 2 Is the power of the transmitted symbol.
(2) Calculating a statistical decision quantity y i，c，m
y i，c，m [k]＝W i，c，m x i，c，m [k]，m＝1，2，…，M (6c)
(3) Symbol estimation: soft decision function is composed of statistical decision quantity y i，c，m [k]Obtaining an estimate of a symbol
Taking the parameters:
K f 、K b the value of (A) can be obtained by simulation optimization, and can also be determined according to the requirements on detection performance and complexity;
d 1 can be in the interval of 0,d MAX ]Internal optimizationThe process can be carried out in such a way that, among others,
definition of soft decision function:
is provided with
y＝a+v
Wherein a is ∈ { A ∈ [ ] 1 ，A 2 ，…；A K }，{A 1 ，A 2 ，…，A K Is the set of all possible transmitted symbols; v is white gaussian noise.
Then a soft decision for y = a + v is calculated as:
wherein, β is called correction factor, which is used to correct the deviation of symbol estimation and the deviation of interference cancellation caused by non-ideal channel estimation; f (y | A) k ) Denotes that the transmitted symbol is A k The probability density function of y is received. Beta and f (y | A) k ) The calculation method of (2) is as follows:
(1) If the transmitted symbol is complex, then
Wherein, AR k 、AI k Are respectively A k The real and imaginary parts of (c); YR and YI are respectively a real part and an imaginary part of y; VR and VI are respectively the real part and the imaginary part of v, and respectively obey N (0, sigma) 2 ) And (4) distribution. And β is a complex number.
(2) If the transmitted symbol is real, then
Wherein YR is the real part of y; VR is the real part of v, obeying N (0, σ) 2 ) And (4) distribution. And β is a real number.
(3) The value of β is closely related to the SNR of the symbol and is a function of the SNR of the symbol.
To simplify the calculation, it is also possible to directly let β =1, i.e.: the effect of the deviation of the channel estimate on the symbol estimation and interference cancellation is not considered.
Generally, the SNR (signaltonoisereratio) of a symbol at a receiving end needs to reach a certain value, so that the performance of a bit BLER (blockaerrorrate) after demapping and decoding can meet the requirement of service quality. For a given BLER value, it can be determined by simulation: minimum SNR value S that a symbol needs to reach in order to achieve the required BLER performance after decoding MIN . And get T 1 ＝S MIN -δ 1 ， T 2 ＝S MIN -δ 2 . Wherein, delta 1 ＞0，δ 2 ＞δ 1 。
If the SNR of the symbol is greater than the threshold T 1 ＝S MIN -δ 1 The channel estimate for the symbol is considered to be relatively accurate and can be approximated as β =1.
If the SNR of the symbol is less than or equal to the threshold T 2 ＝S MIN -δ 2 The SNR of the symbol is considered to be too low, making the channel estimation very poor, and can be approximated as β =0.
If the SNR of the symbol is greater than the threshold T 2 ＝S MIN -δ 2 And is less than or equal to threshold T 1 ＝S MIN -δ 1 The determination can be optimized by cossa simulation or MATLAB simulation: when SNR is in (T) 2 ，T 1 ) The specific value of beta in the case of internal variation.
δ 1 、δ 2 The precision and SNR optimization interval (T) of correction of beta on symbol estimation deviation is directly influenced by value 2 ，T 1 ) The size of (2). δ can be determined according to the need for correction accuracy and optimization of the amount of computation 1 And delta 2 The numerical value of (c). In summary, the values of β are as follows:
in the above formula, α i Is taken by taking the value of i-1 ，SNR i ]And performing COSSAP simulation or MATLAB simulation optimization. Where I is the optimization interval (T) for SNR 2 ，T 1 ) And quantifying the obtained number of the cells, and determining according to needs.
In the MIMO receiver, the value range of the series S is that S is more than or equal to 2 and less than M. Generally, the value of S may be determined according to specific performance and latency requirements. In general, the performance is already good when S =2 or 3.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (9)
1. A wideband receiver for a multiple-input multiple-output system, the wideband receiver comprising:
the first-stage parallel interference cancellation PIC structure is used for carrying out multi-input multi-output decision feedback estimation on the unmodified received signal vectors to obtain signal estimation and total signal estimation of each data stream, canceling interference among symbols in each data stream and interference among the data streams by the signal estimation, the total signal estimation and the unmodified received signal vectors of all the data streams to obtain modified received signal vectors of all the data streams, and sending the modified received signal vectors of all the data streams to the next-stage PIC structure;
and the final-stage PIC structure is used for calculating decision statistics of corrected receiving signal vectors of all data streams sent by the previous-stage PIC structure, and obtaining a symbol estimation value of each data stream according to the decision statistics of each data stream.
2. The wideband receiver of claim 1, further comprising at least one intermediate stage PIC structure, where the intermediate stage PIC structure is located between the first stage PIC structure and the last stage PIC structure, each intermediate stage PIC structure is connected in series, each intermediate stage PIC structure performs decision statistic calculation on the modified received signal vectors of all data streams sent by the previous stage PIC structure, obtains a symbol estimation value of each data stream from the decision statistic of each data stream, obtains a signal estimation value and a total signal estimation value of all data streams from the symbol estimation values of all data streams, cancels interference between symbols in each data stream and interference between data streams from the signal estimation values, the total signal estimation value and the unmodified received signal vectors of all data streams, obtains further modified received signal vectors of all data streams, and sends the further modified received signal vectors of all data streams to the next stage PIC structure.
3. The wideband receiver of claim 1, further comprising a despreading unit coupled to the first stage PIC fabric, wherein the despreading unit is configured to despread the spread received signal vectors to obtain uncorrected received signal vectors, and to send the uncorrected received signal vectors to the first stage PIC fabric.
4. The wideband receiver of claim 2, further comprising a despreading unit coupled to the first stage PIC architecture, wherein the despreading unit is configured to despread the spread received signal vectors to obtain uncorrected received signal vectors, and to send the uncorrected received signal vectors to the first stage PIC architecture and the intermediate stage PIC architecture.
5. The wideband receiver of claim 1 or 2, wherein the first stage PIC fabric comprises:
the first-stage detection unit is used for obtaining signal estimation and total signal estimation of all data streams from the unmodified received signal vector and sending the signal estimation and the total signal estimation of all the data streams to the first-stage interference cancellation and received signal vector correction unit;
and the first-stage interference cancellation and received signal vector correction unit cancels the interference between symbols in each data stream and the interference between the data streams by the signal estimation, the total signal estimation and the unmodified received signal vectors of all the data streams to obtain the corrected received signal vectors of all the data streams, and sends the corrected received signal vectors of all the data streams to the next-stage PIC structure.
6. A wideband receiver as claimed in claim 1 or 2, characterised in that the last stage PIC architecture includes M symbol estimation units, where M is the number of transmit antennas, each symbol estimation unit corresponding to a data stream, each symbol estimation unit being arranged to perform a calculation of decision statistics for the data stream based on the modified received signal vector for the respective data stream, from which decision statistics symbol estimates for the data stream are derived.
7. The wideband receiver of claim 2, wherein each intermediate-level PIC fabric comprises:
the intermediate stage detection unit is used for obtaining signal estimation and total signal estimation of all data streams by corrected received signal vectors of all data streams from the PIC structure of the upper stage, and sending the signal estimation and the total signal estimation of all the data streams to the intermediate stage interference cancellation and received signal vector correction unit;
and the intermediate-stage interference cancellation and received signal vector correction unit cancels the interference between the symbols of each data stream and the interference between the data streams according to the signal estimation, the total signal estimation and the uncorrected received signal vector of all the data streams to obtain a further corrected received signal vector of all the data streams, and sends the further corrected received signal vector of all the data streams to a next-stage PIC structure.
8. The wideband receiver of claim 5, wherein the first stage detection unit comprises:
the MIMO FFF unit completes the forward filtering of the received signal vector by the input forward filtering weight matrix and sends the signal vector obtained by filtering to the adder;
the adder is used for calculating the difference between the signal vector output by the MIMO FFF unit and the signal vector output by the MIMO FBF unit of the multi-input multi-output feedback filter and sending the calculated difference to the soft decision unit;
the soft decision unit is used for carrying out soft decision on each component of the difference sent by the adder to obtain the symbol estimation of each data stream and sending the symbol estimation of all the data streams to the signal estimation unit and the MIMO FBF unit;
the weight matrix calculation unit is used for calculating a forward filtering weight matrix and a feedback filtering weight matrix from the input received signal vector, sending the forward filtering weight matrix to the MIMO FFF unit and sending the feedback filtering weight matrix to the MIMO FBF unit;
the MIMO FBF unit completes the feedback filtering of the vectors which are input by the soft decision unit and comprise the symbol estimation of the M data streams through the feedback filtering weight matrix and sends the signal vectors obtained by the filtering to the adder;
and the signal estimation unit is used for obtaining the signal estimation of each data stream and the total signal estimation of all the data streams according to the symbol estimation of all the data streams, and sending the signal estimation result of each data stream and the total signal estimation of all the data streams to the first-stage interference cancellation and received signal vector correction unit.
9. The wideband receiver of claim 7, wherein the mid-stage detection unit comprises:
m middle-stage symbol estimation units, which are used for respectively finishing symbol estimation of M data streams, wherein M is the number of transmitting antennas, and sending the symbol estimation of the M data streams to a middle-stage signal estimation unit;
and the intermediate-stage signal estimation unit is used for finishing the signal estimation and the total signal estimation of each data stream.
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| WO2002093784A1 (en) * | 2001-05-11 | 2002-11-21 | Qualcomm Incorporated | Method and apparatus for processing data in a multiple-input multiple-output (mimo) communication system utilizing channel state information |
| WO2003073609A1 (en) * | 2002-02-22 | 2003-09-04 | Nokia Corporation | Apparatus, and associated method, for a multiple-input, multiple-output communication system |
| CN1463100A (en) * | 2002-05-30 | 2003-12-24 | 华为技术有限公司 | Method and device for eliminating interference in parallel |
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| WO2002093784A1 (en) * | 2001-05-11 | 2002-11-21 | Qualcomm Incorporated | Method and apparatus for processing data in a multiple-input multiple-output (mimo) communication system utilizing channel state information |
| WO2003073609A1 (en) * | 2002-02-22 | 2003-09-04 | Nokia Corporation | Apparatus, and associated method, for a multiple-input, multiple-output communication system |
| CN1463100A (en) * | 2002-05-30 | 2003-12-24 | 华为技术有限公司 | Method and device for eliminating interference in parallel |
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