CN102723975A - Signal detection method and device of MIMO (multiple input multiple output) system - Google Patents

Abstract

The invention relates to the technical field of signal detection and discloses a signal detection method and device of an MIMO (multiple input multiple output) system, wherein the method comprises the following steps: S1. constructing a search tree by utilizing a known channel matrix; S2. searching the Nth layer of the search tree; S21. dividing K nodes into M groups; S22. expanding sub nodes of the Nth layer of code according to the principle that the number of expanding sub nodes in all group of nodes are equal, and the number of expanding sub nodes in different groups of nodes is decreased sequentially from M; S23. sequencing according to the Euclidean distance between partial receiving vectors and partial transmitting vectors corresponding to all expanding sub nodes, and reserving K sub nodes of which the Euclidean distance is less than the threshold for the search of next layer; and S3. searching all the layers completely according to the modes of the steps S21-S23, and searching for the path with the minimum Euclidean distance from the paths consisting of sub nodes as the search results. According to the invention, the signal detection complexity is lowered and the detection efficiency of data receiving is improved.

Description

The signal detecting method of mimo system and device

Technical field

The present invention relates to the signal detection technique field, particularly relate to a kind of signal detecting method and device of mimo system.

Background technology

Multiple-input and multiple-output (MIMO) technology can improve transmission rate exponentially under the prerequisite that does not increase frequency band, frequency resource growing tension now is so the MIMO technology is considered to one of of paramount importance physical-layer techniques in the NGBW communication technology.

In mimo system; In order to improve the reliability of information source information transmission, at transmitting terminal, signal to be transmitted is at first through providing the chnnel coding of error correcting capability; Carry out space-time/space-frequency/space-time frequency coding again, perhaps send simultaneously by several transmitting antennas then according to the regular hour order.At receiving terminal, come from the signal of transmitting terminal simultaneously or according to regular hour order reception by multi-amplitude receiver antenna, and carry out space-time/space-frequency/empty time-frequency decoding and channel decoding successively, thereby with the raw information of decode results as signal to be sent.

The channel decoding that receiving terminal carried out comes down to detection to received signal, promptly from receive signal, detects Optimal Signals, as decode results.Yet; The signal detection technique of MIMO technology but is faced with a huge difficult problem; Though maximum likelihood (ML) algorithm sees it is optimum from the meaning of minimum error probability, its computation complexity is big, is the exponential form of number of antennas and order of modulation; For example: adopt 16QAM (16 rank quadrature amplitude modulation) when 5 width of cloth antennas are modulated, had to mode, computation complexity is 16 ⁵=1048576.Real-time system is difficult to accept big like this computation complexity.

As a kind of approximate simplification of ML algorithm, (Sphere Decoding, SD) serial algorithm is because it approaches or equals the performance of ML and receive extensive concern day by day than the computation complexity that the ML algorithm reduces greatly globular decoding.Therefore, the globular decoding mode becomes the preferred option of current MIMO input.

Depth-first algorithm (Depth First SD is arranged in the globular decoding mode; DFSD), distance priority algorithm (Metric First SD; MFSD) and breadth-first globular decoding (Breadth First SD; BFSD) algorithm three seed algorithm, wherein the breadth-first algorithm is called the K-bestSD algorithm again, below adopts the general abbreviation K-best SD of industry.Wherein, the breadth-first algorithm is because computation complexity is fixed, and confirm that great application prospect is arranged computing time in real-time system.Yet the computation complexity of breadth-first algorithm is still very big, how further to reduce complexity, and performance is unaffected basically, is a hot issue during it is used.

At present more existing method for simplifying to K-best SD algorithm; People such as Luis G.Barbero propose limited FSD algorithm (the L.G.Barbero and J.S.Thompson of node number that each node launches; " A Fixed-Complexity MIMO Detector Based on the Complex Sphere Decoder; " 2006IEEE 7th Workshop on Signal Processing Advances in Wireless Communications, Cannes, France:2006; Pp.1-5.); Reduced the node of visiting in the decode procedure to a certain extent, but only when institute's surviving path number is more just relatively near the performance of K-best SD algorithm, and the complexity of calculating this moment is than higher.

Algorithm (Cong Xiong, Xin Zhang, Kai Wu that people such as Cong Xiong proposition is counted reserve section in the FSD algorithm to reduce with the increase of searching for the number of plies; And Dacheng Yang, " A simplified fixed-complexity sphere decoder for V-BLAST systems, " Communications Letters; IEEE; Vo1.13,2009, pp.582-584.); The theoretical foundation that this algorithm does not have the enough minimizing reserve sections of FSD to count out, the access node number of minimizing is relatively limited.

Summary of the invention

The technical problem that (one) will solve

The technical problem that the present invention will solve is: how a kind of input scheme of mimo system is provided, with not reducing basically under the prerequisite that detects performance, reduces the complexity of signal detection algorithm, improve the detection efficiency that receives data.

(2) technical scheme

In order to solve the problems of the technologies described above, the present invention provides a kind of signal detecting method of mimo system, may further comprise the steps:

S1, utilize known channel matrix and possible transmission symbol construction search tree;

S2, according to step S21～S23 the N layer of said search tree is searched for, N is total number of plies of said search tree:

S21, current reservation node is divided into M group, the part that the corresponding a part of element that sends symbol of each node is formed is sent vector, and said transmission symbolic representation is for sending the form of vector;

S22, according to the expansion son node number of every group of interior nodes equate, the expansion son node number of the interior nodes principle that begins to successively decrease successively from M on the same group not; Launch the child node of N node layer; Launch the mode of child node and add new element at the back for sending vector in the pairing part of said node; Up to forming whole transmission vector, the corresponding said new element of said child node;

S23, send vector according to the corresponding part of the child node of all expansion and sort with the part of Euclidean distance that partly receives between the vector; The minimum K node of reserve part Euclidean distance is used for the search of one deck down; Said part receives vector and is made up of a part of element of the receiving symbol corresponding with said transmission symbol; Said receiving symbol is expressed as the form that receives vector, and N, K, M are positive integer;

S3, search for other layer of said search tree according to the mode of step S21～S23, the path of in the path of being made up of child node, seeking the Euclidean distance minimum is as Search Results.

Preferably, step S1 is specially: with each line ordering of advancing of said channel matrix, the channel matrix that will obtain after will sorting then utilizes said possible transmission symbol trigonometric ratio to constitute said search tree.

Preferably, said possible transmission symbol is selected from the set that all permutation and combination constituted that possibly sent signal by each antenna.

Preferably, said mode with the channel matrix trigonometric ratio is decomposed for channel matrix being carried out QR.

Preferably, among the step S1, with the mode of each line ordering of advancing of said channel matrix be: if all node numbers of this row are less than or equal to K, then sort, otherwise sort according to gain order from big to small according to gain order from small to large.

Preferably, the initial value of M is the number of transmission symbol, and the value of M reduces along with increasing of the number of plies of search.

Preferably, the mode of forming the path by child node among the step S4 is: from each layer, select a node to be connected in turn and form 2 ^{N * m}Paths, and the child node of selected j layer all is to be selected child node from last layer to launch, j=2 ..., N, m is for sending the order of modulation of symbol.

Preferably; The step that the K node that reserve part Euclidean distance among the step S23 is minimum is used for the search of one deck down replaces with: the K node that the reserve part Euclidean distance is minimum; And deletion Euclidean distance value is greater than the child node of distance threshold from said K node, and remaining child node is used for the search of one deck down.

Preferably, the number of K reduces along with increasing of the number of plies of search.

The present invention also provides a kind of signal supervisory instrument of mimo system, comprising:

Signal receiving unit is used for receiving symbol;

Detecting signal unit is used at first utilizing known channel matrix and possible transmission symbol to handle symbol that said signal receiving unit receives constituting search tree, and in such a way the N layer of said search tree is searched for:

Current reservation node is divided into M group, and the part that the corresponding a part of element that sends symbol of each node is formed is sent vector, and said transmission symbol number is expressed as the form of sending vector;

According to the expansion son node number of every group of interior nodes equate, the expansion son node number of the interior nodes principle that begins to successively decrease successively from M on the same group not; Launch the child node of N node layer; Launch the mode of child node and add new element at the back for sending vector in the pairing part of said node; Up to the whole transmission vector of formation, the corresponding said new element of said child node, N is total number of plies of said search tree;

The part of Euclidean distance of secondly sending vector according to the corresponding part of the child node of all expansion and partly receiving between the vector sorts; The minimum K node of reserve part Euclidean distance is used for the search of one deck down; Said part receives vector and is made up of a part of element of the receiving symbol corresponding with said transmission symbol; Said receiving symbol is expressed as the form that receives vector, and N, K, M are positive integer;

Search for other layer of said search tree once more, in the path of forming by child node, seek the minimum path of Euclidean distance as Search Results;

Signal output unit is used for the Search Results output that said detecting signal unit is obtained.

(3) beneficial effect

Technique scheme has following advantage: the expanding node number carries out the node number that limiting method reduces search through to the search of every layer of search tree the time; Basically do not reducing on the basis of detecting performance; Reduced the complexity of input; Improved the detection efficiency that receives data, and its hardware circuit implementation is simpler, circuit area is littler, power consumption is lower.Method of the present invention also can be applicable to multiple user signals and detects and other input.

Description of drawings

Fig. 1 is the flow chart according to the signal detecting method of the embodiment of the invention;

Fig. 2 is the transmission reception structural representation according to embodiment of the invention mimo system;

Fig. 3 is the sketch map of the search tree of maximum likelihood searching;

Fig. 4 is the sketch map of the search tree that constitutes after to the signal processing that receives according to the embodiment of the invention;

Fig. 5 is first figure as a result of emulation experiment according to an embodiment of the invention;

Fig. 6 is second figure as a result of emulation experiment according to an embodiment of the invention.

Embodiment

Below in conjunction with accompanying drawing and embodiment, specific embodiments of the invention describes in further detail.Following examples are used to explain the present invention, but are not used for limiting scope of the present invention.

Shown in Figure 1 is the flow chart of the signal detecting method of embodiment of the invention mimo system, as shown in Figure 1, said method comprising the steps of:

S1, handle the signal receive and utilize known channel matrix and possible transmission symbol to constitute search tree;

Be specially: with each line ordering of advancing of said channel matrix; Channel matrix after will sorting then utilizes said possible transmission symbol trigonometric ratio to constitute search tree; Sort method is (if all possible node number of this layer is not more than K)/gain from small to large (if all possible node number of this layer is greater than K) from big to small; Ordering can be played acceleration to search, further improves the speed of input.Said possible transmission symbol is selected from the set that all permutation and combination constituted that possibly sent signal by each antenna.

S2, according to following steps the N layer of said search tree is searched for, N is total number of plies of said search tree;

S21, K current reservation node is divided into the M group; The corresponding part of sending a part of element composition of symbol of each node is sent vector; Said transmission symbolic representation is for sending the form of vector; The initial value of M can be set at counting of modulation constellation, the number of the signal of all transmissions just; It is unequal that every layer group is counted M, and the number of M being along with search increasing of the number of plies and reducing, reduce can be linear (number that reduces to fix like every layer of M number), also can nonlinear (constant like preceding which floor M, which floor M the back directly be reduced to 1); Every layer group number is different, comprises in each layer that the number of the child node of the group that child node is maximum also can be different, can do to accept or reject compromise according to the requirement of performance and complexity.

S22, according to the expansion son node number of every group of interior nodes equate, the expansion son node number of the interior nodes principle that begins to successively decrease successively from M on the same group not; Launch the child node of N node layer; Launch the mode of child node and add new element at the back for sending vector in the pairing part of said node; Up to forming whole transmission vector, the corresponding said new element of said child node;

S23, send vector according to the corresponding part of the child node of all expansion and sort with the part of Euclidean distance that part receives between the vector (corresponding with said part reception vector); The reserve part Euclidean distance is used for the search of one deck down less than the K node of threshold value; Said part receives vector and is made up of a part of element of the receiving symbol corresponding with said transmission symbol; Said receiving symbol is expressed as the form that receives vector, and N, K, M are positive integer; The number of K reduces along with increasing of the number of plies of search; Threshold value can obtain according to noise profile; The step that can the K node of reserve part Euclidean distance minimum among the step S23 be used for the search of one deck down replaces with: the K node that the reserve part Euclidean distance is minimum; And deletion Euclidean distance value is greater than the child node of distance threshold from said K node, and remaining child node is used for the search of one deck down.

S3, according to the mode of step S21～S23 all layers all search for, the path of searching Euclidean distance minimum is as Search Results in the path of being made up of child node.

Below the present invention will be described in more detail.

1, receives the mathematical notation of signal

For mimo system, have under the condition of enriching scattering path, suppose that number of transmit antennas is Nt, the reception antenna number is Nr, satisfies Nt >=Nr, system model is as shown in Figure 3.In order to express easily, get Nt=Nr=N.S=(s ₁s ₂S _N) ^TBe the transmission vector of plural number, y=(y ₁y ₂Y _N) ^TBe the reception vector of plural number, n=(n ₁n ₂N _N) ^TBe the noise vector of plural number, satisfying real part imaginary part variance is σ, and H is the complex channel matrix on N * N rank, and wherein each element all is independent identically distributed multiple Gaussian random variable, satisfy E (| h _{I, j}| ²)=1.Then receiving signal can be expressed as:

y＝Hs+n (1)

Be that a transmission symbol (vector s) contains a plurality of transmission signals (scalar) among the MIMO.

If adopt Maximum Likelihood Detection (ML) algorithm to carry out input, it is exactly to choose one group

to satisfy that maximum likelihood is separated:

$\hat{s}=\underset{\ℵ}{\arg \min }{\left|\right|y-\mathrm{Hs}\left|\right|}^2---\left(2\right)$

Wherein,

is the set of all possible transmission signal.When the order of modulation of signal is m, obtain

Need limit 2 ^{M * N}Plant and to arrange.Big when the antenna number, when order of modulation is higher; The complexity of ML algorithm is very high, to such an extent as to can't use, so in fact generally adopt the algorithm of suboptimum; For example; The present invention based on globular decoding (Sphere Decoding, breadth-first algorithm SD) (BFSD algorithm) often is called K-best SD algorithm in the industry.

2, the trigonometric ratio of matrix and tree-shaped search

Matrix H is carried out QR decompose, H=QR, wherein Q is the unitary matrice on N * N rank, Q ^HQ=E, E are unit matrix, and R is the upper triangular matrix on N * N rank, is expressed as:

Then formula (1) can further be expressed as:

ρ＝Rs+η (3)

Wherein: ρ=Q ^HY, η=Q ^HN.

Perhaps, formula (3) can also be expressed as:

Further formula (3.a) is launched, can be obtained:

${\mathrm{\ρ}}_i=r_{i,i}{s}_i+\underset{j=i+1}{\overset{N}{\mathrm{\Σ}}}\left(r_{i,j}{s}_j\right)+{\mathrm{\η}}_i,i=\mathrm{1,2},...N---\left(4\right)$

The ρ that each calculates _iCan regard a layer data as.Can see the reception data ρ of N layer from formula (4) _NOnly send data s by this layer _iDecision does not receive the interference of other layer; And the reception data ρ of N-1 layer _N-1Except with the transmission data s of N-1 layer _N-1Outside the Pass having, also receive the N layer and send data s _NInfluence.Generally, the reception data ρ of i layer _iNot only with the transmission data s of i layer _iRelevant, also receive the i+1 layer to send data (s to the N layer _I+1S _N) influence, so at known i+1 layer under the transmission data conditions of N layer, can be in the hope of the transmission data of i layer.

If send the estimated value of vector be:

$\hat{s}={\left(\begin{array}{cccc}{\hat{s}}_1& {\hat{s}}_2& \·\·\·& {\hat{s}}_N\end{array}\right)}^T---\left(5\right)$

Wherein

is the estimated value that the i layer sends vector, and T representes transposition.Then by the i layer, the estimated value of the transmission vector of test section and the Euclidean distance between the reception value (be appreciated that and be transmission signal and the distance that receives signal through channel) are:

$d_i=\underset{j=i}{\overset{N}{\mathrm{\Σ}}}{({\mathrm{\ρ}}_j-\underset{k=j}{\overset{N}{\mathrm{\Σ}}}{r}_{j,k}{\hat{s}}_k)}^2---\left(6\right)$

Because the reception data ρ of N layer _NOnly send data s with the N layer _NRelevant, so input can be earlier since the N layer, order is to ground floor.If consider to send all values of signal modulation system, the N layer that begins to detect most has 2 ^mPlant and select, regard the selection of each value as a node, each node all is a kind of possible separating.Such N layer just has 2 ^mIndividual node; Secondly the N-1 layer that detects is equivalent on the basis of N layer, with each node of N layer unfolding calculation 2 all ^mTherefore individual node has 2 ^m* 2 ^mIndividual node; Every layer all multiply by 2 on the basis of the node number of anterior layer afterwards ^m, last one deck total (2 ^m) ^N=2 ^{N * m}Individual node.The order that these nodes are visited according to them couples together, and just forms 2 ^{N * m}Paths, these paths tell 2 from same node, each node at following one deck ^mIndividual node is similar to the tree of a handstand, and is as shown in Figure 4.The search procedure of SD serial algorithm is described with regard to available this Fig. 4, and each node all is a kind of possible separating.

If sending the estimated value of vector is formula (5); Then tree-shaped part Euclidean distance when searching the i layer just is (6); Then the part Euclidean distance of all nodes of search in this layer is arranged according to order from small to large, only kept minimum K node (perhaps being appreciated that node) and be used for new search for certain number.

The calculating of new one deck then is on the basis of preceding one deck reserve section point, to launch new value to select, and utilizes these values just can obtain part and sends vector and partly receive the part Euclidean distance between the vector.These part Euclidean distances are pressed from small to large or rank order from big to small, and the reserve part Euclidean distance is less than the fixed number destination node of threshold value, and then this new one deck detects and finishes.

In an example of the present invention, Fig. 3 provides the sketch map of four layers of maximum likelihood searching.

Fig. 4 shows a tree-shaped search sketch map of the present invention, supposes that wherein every layer keeps 8 nodes at most, and each node possible child node number at most is 4.8 nodes are from left to right arranged according to order from small to large, and they are divided into 4 groups, and every group has two nodes, and the number of the child node of two nodes is 4 in first group, second and third, the number of four groups child node is respectively 3,2,1.But among Fig. 4, the circle that the straight line of solid line is corresponding is represented the node that launches, and is that the circle that the straight line of dotted line is corresponding expresses possibility not have the node of expansion.The circle of solid line representes that the node that keeps, the circle of dotted line represent the node that does not keep.

Fig. 5, Fig. 6 show the result of emulation experiment according to an embodiment of the invention.Wherein experimental situation is 8 transmitting antennas, 8 reception antennas, 16-/64-/256-QAM modulation system (representing with m=4, m=8, m=16 respectively).The performance that three kinds of algorithms are arranged among Fig. 5 and Fig. 6 relatively, traditional K-best SD algorithm (representing with KSD among the figure), algorithm of the present invention (representing with SRKSD among the figure) and the fixing globular decoding algorithm (representing with FSD among the figure) of complexity.Fig. 5 is illustrated in the performance curve under the not ordering situation, and Fig. 6 is illustrated in the performance curve under the ordering situation, all adds " O " before all algorithms to show ordering.The transverse axis of figure representes that signal to noise ratio snr, the longitudinal axis represent bit error rate BER performance.The K value of wherein traditional K-best SD algorithm is the same with algorithm of the present invention, thus computation complexity greater than this algorithm, fixedly the computation complexity of the globular decoding of complexity is the same with this algorithm.Can find out all that from Fig. 5, Fig. 6 method performance of the present invention is the same basically with K-best SD algorithm performance, difference that can't resolution performance from figure.Fig. 5 can find out that the performance of method of the present invention will be superior to the FSD algorithm greatly, at BER=10 under the situation that does not have ordering ^-3Situation under, the performance of method of the present invention under three kinds of modulation systems is better than the FSD algorithm greater than 5dB.As can beappreciated from fig. 6 having under the situation of ordering, the performance of method of the present invention is better than the FSD algorithm.At BER=10 ^-3, when modulation system is got 16-QAM, about the FSD algorithm good 0.5dB of method of the present invention than same complexity.

Thereby can find out that it is the same basically with the performance with breadth-first globular decoding algorithm under the same situation of width that embodiments of the invention have been realized, under the same situation of computation complexity, performance is superior to the fixedly globular decoding algorithm of complexity.

The present invention also provides a kind of signal supervisory instrument of mimo system, comprising:

Signal receiving unit is used for receiving symbol;

Detecting signal unit is used at first utilizing known channel matrix and possible transmission symbol to handle symbol that said signal receiving unit receives constituting search tree, and in such a way the N layer of said search tree is searched for:

Current reservation node is divided into M group, and the part that the corresponding a part of element that sends symbol of each node is formed is sent vector, and said transmission symbol number is expressed as the form of sending vector;

According to the expansion son node number of every group of interior nodes equate, the expansion son node number of the interior nodes principle that begins to successively decrease successively from M on the same group not; Launch the child node of N node layer; Launch the mode of child node and add new element at the back for sending vector in the pairing part of said node; Up to the whole transmission vector of formation, the corresponding said new element of said child node, N is total number of plies of said search tree;

The part of Euclidean distance of secondly sending vector according to the corresponding part of the child node of all expansion and partly receiving between the vector sorts; The minimum K node of reserve part Euclidean distance is used for the search of one deck down; Said part receives vector and is made up of a part of element of the receiving symbol corresponding with said transmission symbol; Said receiving symbol is expressed as the form that receives vector, and N, K, M are positive integer;

Search for other layer of said search tree once more, in the path of forming by child node, seek the minimum path of Euclidean distance as Search Results;

Signal output unit is used for the Search Results output that said detecting signal unit is obtained.

Can find out by above embodiment; The present invention's expanding node number through to the search of every layer of search tree the time carries out the node number that limiting method reduces search; Basically do not reducing on the basis of detecting performance, reducing the complexity of input, improving the detection efficiency that receives data; And its hardware circuit implementation is simpler, and circuit area is littler, power consumption is lower.Method of the present invention also can be applicable to multiple user signals and detects and other input.

The above only is a preferred implementation of the present invention; Should be pointed out that for those skilled in the art, under the prerequisite that does not break away from know-why of the present invention; Can also make some improvement and replacement, these improvement and replacement also should be regarded as protection scope of the present invention.

Claims (10)

1. the signal detecting method of a mimo system is characterized in that, may further comprise the steps:

S1, utilize known channel matrix and possible transmission symbol construction search tree;

S2, according to step S21～S23 the N layer of said search tree is searched for, N is total number of plies of said search tree:

S21, current reservation node is divided into M group, the part that the corresponding a part of element that sends symbol of each node is formed is sent vector, and said transmission symbolic representation is for sending the form of vector;

S22, according to the expansion son node number of every group of interior nodes equate, the expansion son node number of the interior nodes principle that begins to successively decrease successively from M on the same group not; Launch the child node of N node layer; Launch the mode of child node and add new element at the back for sending vector in the pairing part of said node; Up to forming whole transmission vector, the corresponding said new element of said child node;

S23, send vector according to the corresponding part of the child node of all expansion and sort with the part of Euclidean distance that partly receives between the vector; The minimum K node of reserve part Euclidean distance is used for the search of one deck down; Said part receives vector and is made up of a part of element of the receiving symbol corresponding with said transmission symbol; Said receiving symbol is expressed as the form that receives vector, and N, K, M are positive integer;

S3, search for other layer of said search tree according to the mode of step S21～S23, the path of in the path of being made up of child node, seeking the Euclidean distance minimum is as Search Results.

2. the method for claim 1 is characterized in that, step S1 is specially: with each line ordering of advancing of said channel matrix, the channel matrix that will obtain after will sorting then utilizes said possible transmission symbol trigonometric ratio to constitute said search tree.

3. the method for claim 1 is characterized in that, said possible transmission symbol is selected from the set that all permutation and combination constituted that possibly sent signal by each antenna.

4. method as claimed in claim 2 is characterized in that, said mode with the channel matrix trigonometric ratio is decomposed for channel matrix being carried out QR.

5. method as claimed in claim 2; It is characterized in that; Among the step S1; With the mode of each line ordering of advancing of said channel matrix be: if all node numbers of this row are less than or equal to K, then sort, otherwise sort according to gain order from big to small according to gain order from small to large.

6. the method for claim 1 is characterized in that, the initial value of M is the number of transmission symbol, and the value of M reduces along with increasing of the number of plies of search.

7. the method for claim 1 is characterized in that, the mode of forming the path by child node among the step S4 is: from each layer, select a node to be connected in turn and form 2 ^{N * m}Paths, and the child node of selected j layer all is to be selected child node from last layer to launch, j=2 ..., N, m is for sending the order of modulation of symbol.

8. the method for claim 1; It is characterized in that; The step that the K node that reserve part Euclidean distance among the step S23 is minimum is used for the search of one deck down replaces with: the K node that the reserve part Euclidean distance is minimum; And deletion Euclidean distance value is greater than the child node of distance threshold from said K node, and remaining child node is used for the search of one deck down.

9. method as claimed in claim 7 is characterized in that, the number of K reduces along with increasing of the number of plies of search.

10. the signal supervisory instrument of a mimo system is characterized in that, comprising:

Signal receiving unit is used for receiving symbol;

Detecting signal unit is used at first utilizing known channel matrix and possible transmission symbol to handle symbol that said signal receiving unit receives constituting search tree, and in such a way the N layer of said search tree is searched for:

Current reservation node is divided into M group, and the part that the corresponding a part of element that sends symbol of each node is formed is sent vector, and said transmission symbol number is expressed as the form of sending vector;

According to the expansion son node number of every group of interior nodes equate, the expansion son node number of the interior nodes principle that begins to successively decrease successively from M on the same group not; Launch the child node of N node layer; Launch the mode of child node and add new element at the back for sending vector in the pairing part of said node; Up to the whole transmission vector of formation, the corresponding said new element of said child node, N is total number of plies of said search tree;

The part of Euclidean distance of secondly sending vector according to the corresponding part of the child node of all expansion and partly receiving between the vector sorts; The minimum K node of reserve part Euclidean distance is used for the search of one deck down; Said part receives vector and is made up of a part of element of the receiving symbol corresponding with said transmission symbol; Said receiving symbol is expressed as the form that receives vector, and N, K, M are positive integer;

Search for other layer of said search tree once more, in the path of forming by child node, seek the minimum path of Euclidean distance as Search Results;

Signal output unit is used for the Search Results output that said detecting signal unit is obtained.

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