CN100362772C - Receiver of multiple input and multiple output system - Google Patents
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Abstract
The present invention discloses a receiver of a multi-input and multi-output system which comprises a grouping perpendicular layered time-space detection unit (101) used for receiving signal vector; symbols of all the received signal vector, which are to be detected are divided into a plurality of groups to complete grouping perpendicular layered time-space detection; the corrected received signal vector of all the symbols is output to a parallel perpendicular layered time-space detection unit (102) which is used for receiving the received signal vector of all the symbols corrected by the grouping perpendicular layered time-space detection unit (101). after the parallel perpendicular layered time-space detection is carried out by the received signal vector of all the symbols, the estimation of each symbol is output. The demodulation performance of the receiver can be greatly improved under the condition that the time delay is lowered or increased slightly.
Description
Technical Field
The present invention relates to the field of wireless communication technologies, and in particular, to a 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. MIMO technology employs multiple antennas (antenna arrays) at the transmitting end and the receiving end to simultaneously transmit and receive signals. 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. If the channel impulse response of each spatial channel is independent, the MIMO system can create a plurality of parallel independent spatial channels between the transmitting end and the receiving end through a plurality of transmitting antennas and a plurality of receiving antennas. By transmitting information independently through these parallel spatial channels, the transmission data rate of the MIMO system must be multiplied. The above conclusions were fully demonstrated by g.j.fosschini and m.j.gans in 1998 and quantitatively indicated: assuming that the MIMO system has M transmitting antennas and N receiving antennas, an NxM order channel matrix can be established under a narrow-band slow fading channel. The elements of the matrix are complex Gaussian random variables which are independently and identically distributed. The channel capacity that can be obtained by a MIMO system will be min (m, n) times that of a Single Input Single Output (SISO) system, where min (m, n) represents taking the minimum of m and n, and the total transmit power remains unchanged.
J. Foshini, G.J. 1996, has proposed a D-BLAST Bell laborator Diagonal Layered Space-time Architecture (Diagnonal D-BLAST, BLAST: diagnonal Bell Laboratories layred Space-time Architecture) method for MIMO systems, which can achieve demodulation of MIMO systems and can achieve a capacity close to 90% of the theoretical capacity. However, the D-BLAST method is relatively complex and not easily implemented in real time.
In 1999, g.d. golden, g.j.foshini, r.a.valenzuela and p.w.wolfiansky proposed a simplified BLAST method-bell labs Vertical layered space-time structure (V-BLAST, vertical BLAST). The method has been implemented in real time in the laboratory. The experimental results show that: the MIMO system with 8 antennas and 12 antennas at the transmitting end and the receiving end respectively can obtain the spectral efficiency of 20-40bps/Hz in the indoor environment when the average SNR is changed in the range of 24 dB-34 dB. Although this spectral efficiency is achieved in an indoor environment, spectral efficiency of this order is unprecedented.
In the V-BLAST method, assuming that M is the number of transmit antennas, the receiver correspondingly receives using N antennas, and the transmitted symbol vector is: a = [ a ] 1 ，a 2 ，…，a M ] T The received signal vector is:
r 1 ＝Ha+v (1)
where H is an N × M dimensional channel matrix, v denotes an N dimensional noise vector whose components are white Gaussian noise, σ, which is independently equally distributed 2 For the power, σ, of each noise component in the received signal vector s 2 Is the power of the transmitted symbol, r 1 Is an N-dimensional received signal vector.
s≡[k 1 ，k 2 ，…，k M ] T Is an permutation of integers 1,2, … …, M that represents the order in which the symbol components in symbol vector a are detected. The V-BLAST detection algorithm consists of 1 According to s ≡ [ k ] 1 ，k 2 ，…，k M ] T Given order computation decision statistic y k1 ，y k2 ，…，y kM . By decision statistic y k1 ，y k2 ，…，y kM Can form an estimate of the data symbol k1 ， k2 ，…， kM 。
S ≡ k can be calculated according to some optimal criterion 1 ，k 2 ，…，k M ] T Here, the optimal arrangement calculated according to some optimal criterion is denoted as S OPT ≡[k 1 ，k 2 ，…，k M ] T . The following is set forth at a given s ≡ [ k ] 1 ，k 2 ，…，k M ] T The following V-BLAST algorithm testing procedure.
The V-BLAST algorithm calculates the decision statistics serially using a linear zero-forcing and sign-cancellation method.
The method comprises the following steps:
step 1: using an N-dimensional zero-forcing weight vector w k1 By calculating r 1 Linear combination of the components to obtain decision statistic y k1 ：
Step 2: by y k1 To quantify k1 ：
Where Q (-) is a quantization function, which corresponds to the transmit-end modulation method. a = [ a ] 1 ，a 2 ，…，a M ] T Where each symbol is a result of modulation of an information bit.
And step 3: suppose that
From the received signal vector r 1 In eliminating a k1 Obtaining a corrected received signal vector r 2 ：
Here (H) k1 K-th of the expression matrix H 1 And (4) columns.
The corrected received signal vector r is processed according to the above steps 1 to 3 2 The same calculation is performed, namely: from w k2 To obtain y k2 Then by y k2 To obtain a k2 A from k2 And r 3 . According to the sequence k 3 ，k 4 ，…，k M Following calculation, the estimate of the other transmitted symbol can be derived k3 ， k4 ，…， kM 。
Weight vector w k1 ，w k2 ，…，w kM Is the key to the algorithm. The specific calculation method of the weight vector is dependent on the calculation criterion used. The calculation of the weight vectors is usually done using the ZF criterion and the MMSE criterion. Vector w under ZF criterion k1 ，w k2 ，…，w kM Called zero-forcing vector, satisfies the following relationship:
thus, with the ZF criterion, the V-BLAST algorithm can be implemented by the following recursive procedure:
initialization:
G 1 ＝H + (6a)
i＝1 (6b)
the following calculations were performed:
i＝i+1 (6i)
equations (6 c) to (6 i) are recursively calculated, and calculation is not stopped until i = M + 1. Estimates of all transmitted symbols have now been obtained by the V-BLAST method: a k1 ， k2 ，…， kM
In the above formula, + represents Moore-Penrose pseudo-inverse; let k be in the matrix H 1 ，k 2 ，…，k i The column is a 0 column vector, and other column vectors are kept unchanged to obtain a matrix
(G i ) ki Representation matrix G i Kth of (1) i And (6) rows.
In the recursive implementation of the above V-BLAST method, equations (6 a) and (6 h) are the calculation equations of the zero-forcing vector under the ZF criterion. If the weight vectors are calculated using the MMSE criterion, equations (6 a) and (6 h) need to be modified accordingly. Regardless of the criterion used to calculate the weight vector, the recursive implementation of the V-BLAST method is as described above, except that the expressions of the weight vector calculation formulas (6 a) and (6 h) under different criteria are transformed accordingly, and are consistent with the adopted criterion.
From the recursive implementation of the above V-BLAST method, it can be seen that: the V-BLAST method adopts the idea of serial interference cancellation. Namely: detecting a symbol and then carrying out interference cancellation; correcting the received signal vector once through interference cancellation to ensure that the corrected received signal vector no longer contains the information of the detected symbol; the detection of the rest symbols is based on the corrected received signal vector, thereby eliminating the influence of the detected symbols on the detection of other symbols and improving the detection performance of the rest symbols.
In the recursive implementation of the V-BLAST method described above, equation (6 c) is to calculate S according to the SNR maximization criterion OPT ≡[k 1 ，k 2 ，…，k M ] T The formula (2). The formula is adopted to show that: the V-BLAST algorithm first calculates an estimate of the symbol with the highest SNR, then removes the effect of the symbol on the detection of other symbols from the received signal vector, then detects the symbol with the second highest SNR from the modified received signal vector, and then removes the effect of the symbol on the detection of the remaining symbols. By analogy, the symbol with the smallest SNR is finally detected. This detection order maximizes the benefit of symbol detection with minimum SNR, thereby optimizing the performance of the overall successive interference cancellation method.
From the above analysis, the conventional receiver has a complexity lower than that of the receiver using the V-BLAST method than that of the receiver using the D-BLAST method, but the receiver using the V-BLAST method has disadvantages:
the existing receiver adopts serial interference cancellation, and the processing time delay is larger. In general, in MIMO communication, a receiving end needs to feed back ACK/NACK information, and whether to perform symbol retransmission is determined by the ACK/NACK information. Therefore, the smaller the processing delay of the receiver, the smaller the delay of the ACK/NACK feedback, and accordingly the larger the capacity and throughput of the system. Therefore, the serial cancellation scheme of V-BLAST needs to be improved.
Disclosure of Invention
Accordingly, an object of the present invention is to provide a receiver that can effectively reduce the processing delay of the V-BLAST method and improve the symbol detection performance.
In order to achieve the above object, the present invention provides a receiver of a mimo system, the receiver comprising:
the grouped vertical layered space-time detection unit 101 is used for receiving signal vectors, dividing symbols to be detected in all the received signal vectors into a plurality of groups, completing grouped vertical layered space-time detection, and outputting corrected received signal vectors of all the symbols to the parallel vertical layered space-time detection unit 102;
a parallel vertical layered space-time detecting unit 102, configured to receive the received signal vectors of all symbols corrected by the grouped vertical layered space-time detecting unit 101, perform parallel vertical layered space-time detection on the received signal vectors of all symbols, and output an estimate of each symbol.
The block vertical layered space-time detection unit 101 includes: symbol grouping and reordering unit 201 one or more modified intra-group symbol detection and interference cancellation units 202 and preprocessing units 203, wherein,
a symbol grouping and rearranging unit 201, configured to receive a signal vector, group all symbols to be detected in the received signal vector, rearrange a transmitted symbol vector and a channel matrix, and output the received signal vector to a first modified intra-group symbol detection and interference cancellation unit 202;
each corrected intra-group symbol detection and interference cancellation unit 202 detects corresponding intra-group symbols in the input received signal vector to obtain estimated values of all symbols in the group and signal estimation of all symbols, and performs interference cancellation on all detected symbols to obtain a corrected received signal vector which is used as a received signal vector to be detected of the next corrected intra-group symbol detection and interference cancellation unit or as a received signal vector processed by the symbol of the preprocessing unit 203, and the signal estimation of all symbols in the group is sent to the preprocessing unit 203;
a preprocessing unit 203 for receiving all the symbol signal estimates of all the modified intra-group symbol detection and interference cancellation unit 202 and the modified received signal vector of the last modified intra-group symbol detection and interference cancellation unit to obtain a modified received signal vector of all the symbols, wherein the modified received signal vector of symbols is formed by the sum of the modified received signal vector of the last modified intra-group symbol detection and interference cancellation unit and the signal estimates of the symbols received from the modified intra-group symbol detection and interference cancellation unit 202.
The modified intra-group symbol detection and interference cancellation unit 202 may comprise:
a weight vector calculation unit 301, configured to calculate more than one weight vector according to the estimation of the channel matrix, and output each weight vector to a corresponding decision statistic calculation unit 302;
more than one decision statistic calculation unit 302, configured to receive the signal vector, determine a decision statistic according to the received weight vector, and output the decision statistic to the transmit symbol estimation unit 303;
more than one transmitted symbol estimation unit 303, which estimates the transmitted symbol according to the received decision statistic and outputs the estimated value of the transmitted symbol to the signal estimation and interference cancellation unit 304;
the signal estimation and interference cancellation unit 304 receives the signal vector and the estimated values of all the transmitted symbols in the group, obtains the signal estimation of the transmitted symbol according to the estimated values of the transmitted symbol, performs interference cancellation on the received signal vector to obtain a corrected received signal vector, outputs the corrected received signal vector to the next symbol detection and interference cancellation unit in the group or the preprocessing unit 203, and sends the signal estimation of the transmitted symbol to the preprocessing unit 203, where the signal estimation of the transmitted symbol is the product of the estimated value of the symbol and a column vector formed by columns corresponding to the symbol in a corresponding channel estimation matrix.
The parallel vertical layered space-time detection unit 102 may include:
a signal modification unit 401, configured to detect modified received signal vectors of all symbols, calculate more than one weight vector according to the estimation of the channel matrix and the modified received signal vectors of all symbols, calculate decision statistics of corresponding symbols according to each calculated weight vector, calculate an estimated value of the symbol according to the decision statistics of the symbol, perform at least one stage of parallel interference cancellation on the received signal vectors, and send the more than one modified received signal vectors obtained through the interference cancellation to the signal detection unit;
The signal modification unit may include:
at least one stage of parallel interference cancellation units, each stage of parallel interference cancellation units are connected in series, the last stage of parallel interference cancellation unit is connected with the signal detection unit,
the parallel interference cancellation unit is used for receiving signal vectors and calculating more than one weight vector; according to each weight vector, parallelly calculating decision statistic corresponding to the symbols; estimating symbols by utilizing each decision statistic to obtain more than one symbol estimation value; then, the more than one symbol estimated value and the received signal vector are subjected to interference cancellation; and outputting more than one corrected received signal vector obtained by interference cancellation to a next-stage parallel interference cancellation unit or a signal detection unit.
The parallel interference cancellation unit may include:
a weight vector calculation unit 501 for calculating one or more weight vectors from the estimation of the channel matrix and outputting the weight vectors to each decision statistic calculation unit 502;
more than one decision statistic calculation unit 502, configured to receive the signal vector, determine a decision statistic according to the received weight vector, and output the decision statistic to the transmit symbol estimation unit 503;
more than one transmitted symbol estimation unit 503, estimating the transmitted symbol according to the received decision statistic, and outputting it to the interference cancellation unit 504;
the interference cancellation unit 504 receives the signal vectors and the estimated values of all the transmitted symbols, performs interference cancellation on the received signal vectors according to the estimated values of the transmitted symbols, obtains more than one corrected received signal vectors, and outputs the corrected received signal vectors to the next-stage parallel interference cancellation unit or the signal detection unit.
The signal detection unit may include:
a weight vector calculation unit 501 for calculating one or more weight vectors from the estimation of the channel matrix and outputting the weight vectors to each decision statistic calculation unit 502;
more than one decision statistic calculation unit 502, configured to receive the modified received signal vector, determine a decision statistic according to each weight vector calculated by the weight vector calculation unit 501, and output the decision statistic to the transmission symbol estimation unit 503;
more than one transmitted symbol estimation unit 503 estimates the transmitted symbols according to the received decision statistic, and obtains the estimated values of more than one transmitted symbols.
The receiver of the invention carries out grouping vertical layering space-time detection and parallel vertical layering space-time detection on the received signal vector, not only can greatly reduce the processing time delay through the grouping vertical layering space-time detection, but also can provide the corrected received signal vector of all symbols after the grouping space-time detection, and then carries out a plurality of levels of parallel vertical layering space-time detection on the corrected received signal vector of all symbols, thus greatly improving the detection performance of all symbols. Therefore, as long as the group number of the groups and the number of parallel vertical layered space-time detection stages are well controlled, the processing delay can be reduced, and the performance of symbol detection is improved. Therefore, the receiver provided by the invention can greatly improve the demodulation performance under the condition that the time delay is reduced or slightly increased.
Drawings
FIG. 1 is a schematic diagram of the structure of an apparatus for carrying out the present invention;
FIG. 2 is a schematic structural diagram of a grouped vertical layered space-time detection unit according to the present invention;
FIG. 3 is a schematic diagram of the structure of the ith modified intra-group symbol detection and interference cancellation unit shown in FIG. 2;
FIG. 4 is a schematic structural diagram of a parallel vertical layered space-time detection unit according to the present invention;
fig. 5 is a schematic structural diagram of an i-th stage PIC unit in the signal modification unit shown in fig. 4;
fig. 6 is a schematic structural diagram of an S-th stage PIC unit in the signal detection unit shown in fig. 4.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the accompanying drawings.
Fig. 1 is a schematic diagram of a MIMO receiver according to the present invention. As shown in fig. 1, the receiver of the present invention includes a grouped vertical layered space-time detection unit 101 and a parallel vertical layered space-time detection unit 102. The grouped vertical layered space-time detection unit 101 receives signal vectors, divides symbols to be detected in all received signal vectors into Z groups, completes grouped vertical layered space-time detection, outputs corrected received signal vectors of all symbols to the parallel vertical layered space-time detection unit 102, and the parallel vertical layered space-time detection unit 102 receives the received signal vectors of all symbols corrected by the grouped vertical layered space-time detection unit 101, performs parallel vertical layered space-time detection on the received signal vectors, and outputs estimation of each symbol.
The working principle of the invention is as follows: the grouped vertical layered space-time detection unit 101 divides symbols to be detected in all received signal vectors into Z groups, performs detection of all symbols in parallel in a first group to obtain estimation of all symbols and signal estimation of all symbols, and eliminates interference of all symbols in the first group from the received signal vectors to obtain corrected received signal vectors, which are used as input signals of the first group to a second group for detection of the second group of symbols, so that detection of the second group of symbols is not interfered by the first group of symbols; and taking the received signal vector output by the first group as the received signal vector adopted in the detection of each symbol in the second group, carrying out the detection of all symbols in parallel to obtain the estimation of each symbol in the second group and the signal estimation of all symbols, eliminating the interference of all symbols in the second group from the received signal vector output by the first group to obtain a further corrected received signal vector, and taking the received signal vector as the input signal vector of the second group to the third group for the detection of the third group of symbols. And detecting other subsequent groups of symbols by analogy. After the detection of the Z groups of symbols is finished, the signal estimation of each group of symbols in the Z groups and the received signal vector corrected by the Z group are respectively obtained, and then the corrected received signal vectors of all the symbols are obtained through the signal estimation of each group of symbols and the received signal vector corrected by the Z group. Finally, the corrected received signal vectors of all symbols are output and sent in parallel to the parallel vertical layered space-time detection unit 102.
Parallel vertical layered space-time detection section 102 receives the corrected received signal vectors of all symbols outputted from packet vertical layered space-time detection section 101, and performs multistage parallel interference cancellation. When each stage of parallel interference cancellation processing is carried out, receiving signal vectors of all symbols are detected, more than one weight vector is calculated, and estimation values of all symbols are estimated according to the weight vectors; and then carrying out interference cancellation on the estimated symbols to obtain corrected received signal vectors of all the symbols, and then estimating the symbols again. The corrected received signal vector of the mth symbol is obtained by excluding the mth symbol and removing the interference of the rest M-1 symbols from the received signal vector, wherein M is the total number of symbols to be detected in the received signal vector, and the signal vector is used as the received signal vector adopted during the detection of the mth symbol in the next stage of parallel interference cancellation processing; in the last stage of parallel interference cancellation processing, M symbols are detected by M corrected received signal vectors provided by the previous stage at the same time, and M symbols are estimated, wherein the M estimated values are the detection results of the multistage parallel interference cancellation structure. The received signal vector detected in the first stage of parallel interference cancellation processing is the corrected received signal vector of all symbols from the block space-time detection unit 101, and in other stages of parallel interference processing, the received signal vector is obtained after the previous stage of parallel interference cancellation.
Referring to fig. 2, the block vertical layered space-time detecting unit 101 includes: a symbol grouping and reordering unit 201, Z modified intra-group symbol detection and interference cancellation units 202, and a preprocessing unit 203. The symbol grouping and rearranging unit 201 divides M symbols to be detected in a received signal vector into Z groups according to a certain criterion, rearranges the M symbols according to a grouping sequence and a symbol sequence in the groups, and rearranges column vectors correspondingly forming a channel matrix to form a new channel matrix; the Z modified intra-group symbol detection and interference cancellation units perform detection and interference cancellation of the first to Z groups of symbols, respectively, and the received signal vector modified by one modified intra-group symbol detection and interference cancellation unit 202 is used for detection of symbols in the next modified intra-group symbol detection and interference cancellation unit. The modified intra-group symbol detection and interference cancellation unit 202 obtains signal estimates for all symbols, which are sent to a preprocessing unit 203. The pre-processing unit 203 obtains a modified received signal vector for all symbols from the signal estimates for all symbols from the Z modified intra-group symbol detection and interference cancellation units and the modified received signal vector from the Z modified intra-group symbol detection and interference cancellation unit. The modified received signal vectors of all symbols are sent in parallel to the parallel vertical layered space-time detection unit 102 for parallel detection of all symbols by the parallel vertical layered space-time detection unit 102. The modified received signal vector of symbols is formed by the sum of the modified received signal vector from the Z modified intra-group symbol detection and interference cancellation unit and the signal estimate for the symbol.
Fig. 3 is a schematic diagram of the structure of the i-th modified intra-group symbol detection and interference cancellation unit shown in fig. 2. Referring to fig. 3, each modified intra-group symbol detection and interference cancellation unit includes: weight vector calculation section 301, decision statistic calculation section 302, transmission symbol estimation section 303, and signal estimation and interference cancellation section 304. Wherein, the weight vector calculating unit 301 calculates more than one weight vector according to the estimation of the Q matrix, and inputs each weight vector to the decision statistic calculating unit 302 in sequence; each decision statistic calculation unit 302 calculates a decision statistic from the modified received signal vector ri and the weight vector output from the (i-1) th group, and transmits the calculated decision statistic to the transmission symbol estimation unit 303 connected thereto. Each transmitted symbol estimation unit 303 estimates the estimated value of the corresponding symbol in the group according to the received decision statistic and sends the estimated value to the signal estimation and interference cancellation unit 304, the signal estimation and interference cancellation unit 304 outputs the signal estimation of all symbols to the preprocessing unit 203 after the signal estimation and interference cancellation of all symbols in the group are completed by the estimated values of all symbols in the group and the corrected received signal vector ri, and sends the corrected received signal vector obtained by the interference cancellation to the (i + 1) th corrected symbol detection and interference cancellation unit/preprocessing unit in the group. The signal estimate for a symbol is the product of the estimated value for the symbol and a column vector formed by the column corresponding to the symbol in the corresponding channel estimation matrix.
Referring to fig. 4, the parallel vertical layered space-time detecting unit 102 includes a signal modifying unit 401, configured to detect modified received signal vectors of all symbols, calculate more than one weight vector according to the estimation of the channel matrix and the modified received signal vectors of all symbols, calculate an estimation value of a corresponding symbol according to each calculated weight vector, perform at least one level of parallel interference cancellation on the received signal vectors, and send the more than one modified received signal vectors obtained through the interference cancellation to the signal detecting unit; signal detection section 402 re-estimates symbol values from the received one or more corrected received signal vectors.
The signal modification unit 401 includes: first stage PIC unit to S-1 stage PIC unit. The first-stage PIC unit detects the corrected received signal vectors of all the symbols, estimates all the symbols respectively, performs interference cancellation on all the estimated symbols to obtain M corrected received signal vectors, and outputs the M corrected received signal vectors to the second-stage PIC unit; the second-stage PIC unit detects the received M received signal vectors corrected by the first-stage PIC unit, estimates M symbols again, performs interference cancellation on the estimated symbols to obtain M corrected received signal vectors, performs the same processing step by step, and then reaches the signal detection unit 402, namely the S-stage PIC unit; and the S-level PIC unit detects the corrected M received signal vectors provided by the S-1 level received by the S-level PIC unit and estimates M symbols, wherein the estimated values of the M symbols are the detection results of the multistage parallel interference cancellation structure.
Referring to fig. 5, the i (i < S) th stage PIC unit includes a weight vector calculation unit 501, 1 to M decision statistic calculation units 502, 1 to M transmit symbol estimation units 503, and an interference cancellation unit 504. Wherein, the weight vector calculating unit 501 calculates M weight vectors and outputs them to the 1-M decision statistic calculating units 502, each decision statistic calculating unit 502 calculates a decision statistic according to the received weight vector and the received modified received signal vector of the corresponding symbol, and then outputs the calculated decision statistic to the transmitting symbol estimating unit 503 connected thereto. Transmission symbol estimation section 503 estimates a symbol and transmits the symbol to interference cancellation section 504. Interference cancellation section 504 receives the estimated symbols transmitted by 1 to M transmit symbol estimation sections 503 and the received signal vectors that have not been subjected to any processing, and performs interference cancellation to obtain M corrected received signal vectors.
Referring to fig. 6, the S-th stage PIC unit includes a weight vector calculation unit 501, 1 to M decision statistic calculation units 502, and 1 to M transmit symbol estimation units 503. The S-th stage PIC unit is similar to the previous first to (S-1) -th stage PIC units. The difference is that the last stage PIC unit does not include an interference cancellation unit, that is, the last stage processing directly outputs the symbol estimation value as the final detection result, and interference cancellation is not performed after the symbol is estimated.
The grouping and reordering process of the symbol grouping and reordering unit 201 is as follows:
step 101: symbol grouping and reordering unit 201 from received signal vector and estimation of channel matrix HDividing M symbols a according to a certain criterion 1 ，a 2 ，…，a M Divided into Z groups, the number of symbols in the i (i =1,2, …, Z) th group is L i I th group L i A symbol is b i1 ，b i2 ，…，b iLi . Wherein,
indicating the ith group j symbol in the original symbol set with the sequence number M i，j (M i，j ∈[1，2，…，M])，j＝1，2，…，L i The value of j varies with the group number i.
Step 102: will sign a 1 ，a 2 ，…，a M Rearrangement is carried out, and the rearrangement result is: b 11 ，b 12 ，…，b 1L1 ，b 21 ，…，b 2L2 ，…，b Z1 ，…，b ZLZ . Thus, the corresponding transmitted symbol vector is converted to:
the channel matrix H in equation (1) can be written in the form of a column vector: h = [ H ] 1 ，H 2 ，…，H M ]。
Next, for sequence H 1 ，H 2 ，…，H M Is subjected to the sequence a 1 ，a 2 ，…，a M The same rearrangement gives a sequence Q 1 ，Q 2 ，…，Q M Let Q = [ Q ] 1 ，Q 2 ，…，Q M ]。
Thus, through the rearrangement of elements H and a, equation (1) can be updated as follows:
r 1 ＝Qb+v (1a)
step 103: the symbol grouping and reordering unit 201 estimates the updated channel matrix QTo Z modified intra-group symbol detection and interference cancellation units 202.
Can pass through
Is obtained by rearrangement.
It should be noted that, in the above embodiment, the weight vector may be calculated by using different optimization criteria, for example, the ZF criterion and the MMSE criterion. Furthermore, each transmit symbol estimation unit may use an existing hard decision function, such as a quantization function, or a soft decision function, to perform symbol estimation. When a soft decision function is used, each transmit symbol estimation unit may calculate an estimate of the corresponding transmit symbol from the received decision statistic according to equation (7).
j ＝D(y j )，j＝1，2，…，M (7)
In equation (7), the jth transmitted symbol estimation unit derives the jth decision statistic y j An estimate of the jth transmitted symbol is obtained.
In equation (7), the quantization function Q (-) in equations (3) and (6 f) is replaced with a soft decision function D (-).
The decision statistic in equation (7) can be expressed as follows:
y j ＝a j +v j ，j＝1，2，…，M (7-1)
wherein, a j ∈{A 1 ，A 2 ，…，A K }，{A 1 ，A 2 ，…，A K Is the set of all possible transmitted symbols; v. of j Is gaussian white noise.
Then (7) is specifically calculated according to the following formula:
wherein beta is j Called correction factor, to correct the deviation of symbol estimation and the deviation of interference cancellation caused by non-ideal channel estimation; f (y) j |A k ) Denotes that the transmitted symbol is A k Is received y j The probability density function of (a). Beta is a j And f (y) j |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 j 、YI j Are each y j The real and imaginary parts of (a); VR (virtual reality) j 、VI i Are each v j Subject to N (0, σ) respectively j 2 ) Distribution, and β j Is a complex number.
(2) If the transmitted symbol is real, then
Wherein, YR j Is y j The real part of (a); VR (virtual reality) j Is v is j Real part of, obey to N (0, σ) j 2 ) And (4) distribution. And beta is j Is a real number.
(3)β j Is closely related to the SNR of the symbol and is a function of the SNR of the symbol.
To simplify the calculation, β can also be directly made j =1, i.e.: biased pair regardless of channel estimatesNumber estimation and interference cancellation effects.
The method for calculating the weight vector in the grouped vertical layered space-time detection unit 101 is as follows:
under ZF criterion, in the first modified intra-group symbol detection and interference cancellation unit, the estimation of the channel matrix Q can be performed
The zero forcing weight vector is calculated according to the formula (8 a) and the formula (8 b):
wherein L is 1 Indicating the number of elements in group 1.
Under the ZF criterion, when the ith (1 < i ≦ Z) group symbol is detected, the channel matrix can be used
And (3) calculating a zero forcing weight vector according to the formula (8 c) and the formula (8 d):
wherein L is i Indicating the number of elements of the ith group.
Representing the estimate of the channel matrix Q at the time of the i-th set of detections.
Channel matrix without re-channel estimationFront of (2)
The columns are 0-column vectors, and the (J + 1) -th to Mth columns are
The (J + 1) th to M-th columns of (a).
In case of channel estimation anew, the channel matrix
Front of
The column is a 0-column vector, and the (J + 1) -th to mth columns are obtained by channel estimation. Wherein, the J ∈ [ J +1,M]Column pass through for J ∈ [ J +1,M of Q matrix]And the column is obtained by performing channel estimation again.
Under the MMSE criterion, in the first modified symbol detection and interference cancellation unit in the group, the channel matrix can be selected
The weight vector is calculated according to equation (9 a) and equation (9 b):
under the MMSE criterion, when the symbol detection of the ith (1 < i ≦ Z) group is carried out, the channel matrix can be used
A weight vector is calculated according to equation (9 c) and equation (9 d):
channel matrix without re-channel estimationFront of (2)
The columns are 0-column vectors, and the (J + 1) -th to Mth columns are
The (J + 1) th to M-th columns of (a).
In case of channel estimation anew, the channel matrixFront of
Column is 0 column vectorAnd (J + 1) th to mth columns are obtained by channel estimation. Wherein, the J ∈ [ J +1,M]Column pass through for J ∈ [ J +1,M of Q matrix]And the column is obtained by performing channel estimation again.
The calculation method of the weight vector in the parallel vertical layered space-time detection unit 102 is as follows:
under the ZF criterion, in the parallel interference cancellation structure of the ith (i is more than or equal to 1 and less than or equal to S) level, the channel matrix can be used for estimating the channel again
A weight vector is calculated according to equation (10 a):
in the above formula, the first and second carbon atoms are,
to represent
Column j, | B |) 2 ＝B H B, B is a column vector,
is an estimate of the channel matrix H in the ith stage PIC structure.
Under the ZF criterion, in the parallel interference cancellation structure of the ith (i is more than or equal to 1 and less than or equal to S) stage, the estimation of the channel matrix in the PIC structure of the previous stage can be carried out without carrying out channel estimation againA weight vector is calculated according to equation (10 b):
under the MMSE criterion, in the parallel interference cancellation structure of the ith (i is more than or equal to 1 and less than or equal to S) stage, the estimation of the channel matrix can be carried out under the condition of carrying out channel estimation again
The weight vector is calculated according to equation (10 c):
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. Under the MMSE criterion, in the parallel interference cancellation structure of the ith (i is more than or equal to 1 and less than or equal to S) stage, the estimation of the channel matrix can be carried out without carrying out channel estimation again
Calculating according to the formula (10 d) to obtain a weight vector:
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.
In short, the above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention.
Claims (7)
1. A receiver for a multiple-input multiple-output system, the receiver comprising:
the grouped vertical layered space-time detection unit (101) is used for receiving signal vectors, dividing symbols to be detected in all the received signal vectors into a plurality of groups, completing grouped vertical layered space-time detection, and outputting corrected received signal vectors of all the symbols to the parallel vertical layered space-time detection unit (102);
and a parallel vertical layered space-time detection unit (102) for receiving the received signal vectors of all symbols corrected by the grouped vertical layered space-time detection unit (101), performing parallel vertical layered space-time detection on the corrected received signal vectors of all symbols, and outputting an estimate of each symbol.
2. The receiver according to claim 1, characterized in that said packet vertical layer space-time detection unit (101) comprises: a symbol grouping and reordering unit (201), one or more modified intra-group symbol detection and interference cancellation units (202), and a pre-processing unit (203),
a symbol grouping and rearranging unit (201) for receiving the signal vector, grouping all symbols to be detected in the received signal vector, rearranging the transmission symbol vector and the channel matrix formed by the symbols to be detected in all the received signal vectors, and outputting the received signal vector to a first modified intra-group symbol detection and interference cancellation unit (202);
each corrected intra-group symbol detection and interference cancellation unit (202) detects corresponding intra-group symbols in the input received signal vector to obtain estimated values of all symbols in the group and signal estimation of all symbols, and performs interference cancellation on all detected symbols to obtain a corrected received signal vector which is used as a to-be-detected received signal vector of the next corrected intra-group symbol detection and interference cancellation unit or used as a to-be-processed received signal vector of a preprocessing unit (203), and the signal estimation of all symbols in the group is sent to the preprocessing unit (203);
a preprocessing unit (203) for receiving all symbol signal estimates from all modified intra-group symbol detection and interference cancellation units (202) and a last modified received signal vector from a last modified intra-group symbol detection and interference cancellation unit to obtain a modified received signal vector for all symbols, said modified received signal vector for symbols being formed by the sum of the modified received signal vector for the last modified intra-group symbol detection and interference cancellation unit and the signal estimates for the symbols received from the modified intra-group symbol detection and interference cancellation unit (202).
3. The receiver of claim 2, wherein the modified intra-group symbol detection and interference cancellation unit (202) comprises:
a weight vector calculation unit (301) for calculating more than one weight vector according to the estimation of the channel matrix and outputting each weight vector to a corresponding decision statistic calculation unit (302);
more than one decision statistic calculation unit (302) for receiving the signal vector, determining a decision statistic according to the received weight vector, and outputting the decision statistic to the transmission symbol estimation unit (303);
more than one sending symbol estimation unit (303), estimate the sending symbol according to the decision statistic received, and output the estimated value of the sending symbol to the signal estimation and interference cancellation unit (304);
and a signal estimation and interference cancellation unit (304) which receives the signal vector and the estimated values of all the transmitted symbols in the group, obtains the signal estimation of the transmitted symbols according to the estimated values of the transmitted symbols, performs interference cancellation on the received signal vector to obtain a corrected received signal vector, outputs the corrected received signal vector to the next corrected symbol detection and interference cancellation unit or a preprocessing unit (203), and transmits the signal estimation of the transmitted symbols to the preprocessing unit (203), wherein the signal estimation of the transmitted symbols is the product of the estimated values of the symbols and column vectors formed by columns corresponding to the symbols in a corresponding channel estimation matrix.
4. The receiver according to claim 1, characterized in that said parallel vertical layered space-time detection unit (102) comprises:
the signal correction unit (401) is used for detecting corrected received signal vectors of all symbols, calculating more than one weight vector according to the estimation of a channel matrix and the corrected received signal vectors of all symbols, calculating decision statistics of corresponding symbols according to each calculated weight vector, calculating an estimated value of the symbol according to the decision statistics of the symbol, performing at least one stage of parallel interference cancellation on the received signal vectors, and sending the more than one corrected received signal vectors obtained through the interference cancellation to the signal detection unit;
a signal detection unit (402) re-estimates symbol values from the received one or more modified received signal vectors.
5. The receiver of claim 4, wherein the signal modification unit comprises:
at least one stage of parallel interference cancellation units, each stage of parallel interference cancellation units are connected in series, the last stage of parallel interference cancellation unit is connected with the signal detection unit,
the parallel interference cancellation unit is used for receiving signal vectors and calculating more than one weight vector; according to each weight vector, calculating decision statistic corresponding to the symbol in parallel; estimating symbols by utilizing each decision statistic to obtain more than one symbol estimation value; then, the more than one symbol estimation values and the received signal vectors are subjected to interference cancellation; and outputting more than one corrected received signal vector obtained by interference cancellation to a next-stage parallel interference cancellation unit or a signal detection unit.
6. The receiver of claim 5, wherein the parallel interference cancellation unit comprises:
a weight vector calculation unit (501) for calculating one or more weight vectors from the estimation of the channel matrix and outputting the weight vectors to each decision statistic calculation unit (502);
more than one decision statistic calculation unit (502) for receiving the signal vector, determining a decision statistic according to the received weight vector, and outputting the decision statistic to a transmission symbol estimation unit (503);
more than one sending symbol estimation unit (503), according to the received decision statistic estimation sending symbol, and output it to the interference cancellation unit (504);
and an interference cancellation unit (504) which receives the signal vectors and the estimated values of all the transmitted symbols, performs interference cancellation on the received signal vectors according to the estimated values of all the transmitted symbols, obtains more than one corrected received signal vectors and outputs the corrected received signal vectors to a next-stage parallel interference cancellation unit or a signal detection unit.
7. The receiver of claim 4, wherein the signal detection unit comprises:
a weight vector calculation unit (501) for calculating one or more weight vectors from the estimation of the channel matrix and outputting the weight vectors to each decision statistic calculation unit (502);
more than one decision statistic calculation unit (502) for receiving the modified received signal vector, determining a decision statistic according to each weight vector calculated by the weight vector calculation unit (501), and outputting the decision statistic to a transmitted symbol estimation unit (503);
and one or more transmission symbol estimation units (503) for estimating the transmission symbol based on the received decision statistic to obtain an estimation value of the one or more transmission symbols.
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| CN1304218A (en) * | 2000-01-13 | 2001-07-18 | 朗迅科技公司 | Space-time processing of multi-input and-output radio system |
| EP1255369A1 (en) * | 2001-05-04 | 2002-11-06 | TELEFONAKTIEBOLAGET LM ERICSSON (publ) | Link adaptation for wireless MIMO transmission schemes |
| 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 |
| CN1411190A (en) * | 2001-10-09 | 2003-04-16 | 华为技术有限公司 | Vertical Bell laboratory ranked space and time code array linear detecting method |
| US20030076777A1 (en) * | 2001-09-17 | 2003-04-24 | Stuber Gordon L. | Apparatus and methods for providing efficient space-time structures for preambles, pilots and data for multi-input, multi-output communications systems |
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| CN1304218A (en) * | 2000-01-13 | 2001-07-18 | 朗迅科技公司 | Space-time processing of multi-input and-output radio system |
| EP1255369A1 (en) * | 2001-05-04 | 2002-11-06 | TELEFONAKTIEBOLAGET LM ERICSSON (publ) | Link adaptation for wireless MIMO transmission schemes |
| 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 |
| US20030076777A1 (en) * | 2001-09-17 | 2003-04-24 | Stuber Gordon L. | Apparatus and methods for providing efficient space-time structures for preambles, pilots and data for multi-input, multi-output communications systems |
| CN1411190A (en) * | 2001-10-09 | 2003-04-16 | 华为技术有限公司 | Vertical Bell laboratory ranked space and time code array linear detecting method |
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