CN102723975B - 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 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 not increase under the prerequisite of frequency band, improve exponentially transmission rate, frequency resource growing tension now, so 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 first through providing the chnnel coding of error correcting capability, carry out again space-time/space-frequency/space-time frequency coding, then by several transmitting antennas simultaneously or send according to regular hour order.At receiving terminal, by multi-amplitude receiver antenna, receive and come from the signal of transmitting terminal simultaneously or according to regular hour order, and carry out successively space-time/space-frequency/empty time-frequency decoding and channel decoding, thus the raw information using decode results as signal to be sent.

The channel decoding that receiving terminal carries out is in fact detection to received signal, from receive signal, detects Optimal Signals, as decode results.Yet, the signal detection technique of MIMO technology is but faced with a huge difficult problem, although maximum likelihood (ML) algorithm is optimum from the meaning of minimum error probability, but its computation complexity is large, it is the exponential form of number of antennas and order of modulation, for example: while adopting 16QAM (16 rank quadrature amplitude modulation) mode to modulate, have 5 width antenna, computation complexity is 16 ⁵=1048576.Real-time system is difficult to accept large like this computation complexity.

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

In globular decoding mode, there is depth-first algorithm (Depth First SD, DFSD), distance priority algorithm (Metric First SD, MFSD) and breadth-first globular decoding (Breadth First SD, BFSD) algorithm three seed algorithm, wherein breadth-first algorithm is called again K-bestSD algorithm, below adopts the abbreviation K-best SD that industry is general.Wherein, breadth-first algorithm, because computation complexity is fixed, is determined, is had great application prospect in real-time system computing time.Yet the computation complexity of breadth-first algorithm is still very large, how further to reduce complexity, and performance is substantially unaffected, be a hot issue in its application.

Have at present some method for simplifying to K-best SD algorithm, the people such as Luis G.Barbero propose limited FSD algorithm (the L.G.Barbero and J.S.Thompson of nodes 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 to a certain extent the node of accessing in decode procedure, but only when institute's surviving path number is more, just relatively approach the performance of K-best SD algorithm, and the complexity of now calculating is higher.

The people such as Cong Xiong propose algorithm (the Cong Xiong that reserve section in FSD algorithm is counted and reduced with the increase of searching for the number of plies, Xin Zhang, Kai Wu, 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

(1) technical problem that will solve

The technical problem to be solved in the present invention is: how a kind of input scheme of mimo system is provided, with substantially not reducing 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 invention provides a kind of signal detecting method of mimo system, comprise the following steps:

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

S2, according to step S21～S23, the N layer of described search tree is searched for total number of plies that N is described 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 forms sends vector, and described transmission symbol table is shown the form that sends vector;

S22, according to the expansion son node number of every group of interior nodes equates, the expansion son node number of interior nodes does not start to successively decrease successively from M on the same group principle, launch the child node of N node layer, launch the mode of child node for add new element after the corresponding part transmission of described node vector, until form whole transmission vector, the corresponding described new element of described child node;

S23, the part of Euclidean distance receiving between vector according to part transmission vector corresponding to the child node of all expansion and part sort, K child node of reserve part Euclidean distance minimum is for the search of lower one deck, described part reception vector is comprised of a part of element of the receiving symbol corresponding with described transmission symbol, described receiving symbol is expressed as the form that receives vector, and N, K, M are positive integer;

S3, according to the mode of step S21～S23 search for described search tree other layer, in the path being formed by child node, find the path of Euclidean distance minimum as Search Results.

Preferably, step S1 is specially: by each line ordering of advancing of described channel matrix, then utilize described possible transmission symbol trigonometric ratio to form described search tree the channel matrix obtaining after sequence.

Preferably, the described possible transmission symbol choosing set that freely all permutation and combination of each antenna possibility transmitted signal form.

Preferably, described by the mode of channel matrix trigonometric ratio for channel matrix is carried out to QR decomposition.

Preferably, in step S1, by the mode of each line ordering of advancing of described channel matrix, be: if all nodes of this row are less than or equal to K, according to gain order from small to large, sort, otherwise sort according to gain order from big to small.

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

Preferably, the mode that forms path by child node in step S4 is: from every one deck, select a child node to be connected in turn and form 2 ^{n * m}paths, and the child node of selected j layer is all to launch from the selected child node of last layer, j=2 ..., N, m is for sending the order of modulation of symbol.

Preferably, step by K child node of reserve part Euclidean distance minimum in step S23 for the search of lower one deck replaces with: K child node of reserve part Euclidean distance minimum, and delete the child node that Euclidean distance value is greater than distance threshold from a described K child node, remaining child node is for the search of lower one deck.

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, for receiving symbol;

Detecting signal unit, for first utilizing known channel matrix and possible transmission symbol to process symbol that described signal receiving unit receives to form search tree, and in such a way the N layer of described search tree is searched for:

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

According to the principle that the expansion son node number of every group of interior nodes equates, the expansion son node number of interior nodes does not start to successively decrease successively from M on the same group, launch the child node of N node layer, launch the mode of child node for add new element after the corresponding part transmission of described node vector, until form whole transmission vector, the corresponding described new element of described child node, total number of plies that N is described search tree;

Secondly the part of Euclidean distance that sends vector according to part corresponding to the child node of all expansion and partly receive between vector sorts, K child node of reserve part Euclidean distance minimum is for the search of lower one deck, described part reception vector is comprised of a part of element of the receiving symbol corresponding with described transmission symbol, described receiving symbol is expressed as the form that receives vector, and N, K, M are positive integer;

Again search for other layer of described search tree, in the path being formed by child node, find the path of Euclidean distance minimum as Search Results;

Signal output unit, for the Search Results output that described detecting signal unit is obtained.

(3) beneficial effect

Technique scheme tool has the following advantages: the method that expanding node number limits when to the search of every layer of search tree reduces the nodes of search, substantially 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 less, power consumption is lower.Method of the present invention also can be applicable to multiuser signal detection and other input.

Accompanying drawing explanation

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

Fig. 2 receives structural representation according to the transmission of embodiment of the present invention mimo system;

Fig. 3 is the schematic diagram of the search tree of maximum likelihood searching;

Fig. 4 is the schematic diagram of the search tree of formation after the signal receiving being processed according to the embodiment of the present invention;

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

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

Embodiment

Below in conjunction with drawings and Examples, the specific embodiment of the present invention is described in further detail.Following examples are used for illustrating the present invention, but are not used for limiting the scope of the invention.

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

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

Be specially: by each line ordering of advancing of described channel matrix, then the channel matrix after sequence is utilized described possible transmission symbol trigonometric ratio to form search tree, sort method is (if this layer of all possible nodes is not more than K)/gain from small to large (if this layer of all possible nodes is greater than K) from big to small, sequence can be played acceleration to search, further improves the speed of input.The described possible transmission symbol choosing set that freely all permutation and combination of each antenna possibility transmitted signal form.

S2, in accordance with the following steps the N layer of described search tree is searched for total number of plies that N is described search tree;

S21, K current reservation node is divided into M group, the corresponding part that sends a part of element composition of symbol of each node sends vector, described transmission symbol table is shown the form that sends vector, the initial value of M can be set as counting of modulation constellation, the number of the signal of namely all transmissions; It is unequal that the group of every layer is counted M, and the number of M being along with search increasing of the number of plies and reducing, reduce can be linear (as every layer of M number reduces fixing number), also can nonlinear (as constant in front which floor M, which floor M be directly reduced to 1 afterwards); The group number of every layer is different, and each layer comprises 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 equates, the expansion son node number of interior nodes does not start to successively decrease successively from M on the same group principle, launch the child node of N node layer, launch the mode of child node for add new element after the corresponding part transmission of described node vector, until form whole transmission vector, the corresponding described new element of described child node;

S23, according to part corresponding to the child node of all expansion, send vector and sort with the part of Euclidean distance that part receives between vector (corresponding with described part reception vector), reserve part Euclidean distance is less than K child node of threshold value for the search of lower one deck, described part reception vector is comprised of a part of element of the receiving symbol corresponding with described transmission symbol, described 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; K child node of reserve part Euclidean distance minimum in step S23 can be replaced with the step for the search of lower one deck: K child node of reserve part Euclidean distance minimum, and delete the child node that Euclidean distance value is greater than distance threshold from a described K child node, remaining child node is for the search of lower one deck.

S3, according to the mode of step S21～S23, all layers has all been searched for, in the path being formed by child node, found the path of Euclidean distance minimum as Search Results.

Below the present invention will be described in more detail.

1, receive the mathematical notation of signal

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

y＝Hs+n (1)

Be that in MIMO, a transmission symbol (vector s) contains a plurality of transmitted signals (scalar).

If adopt Maximum Likelihood Detection (ML) algorithm to carry out input, maximum likelihood solution is chosen one group exactly meet:

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

Wherein, set for all possible transmitted signal.When the order of modulation of signal is m, obtain need limit 2 ^{m * N}plant and may arrange.When number of antennas is large, order of modulation is higher time, the complexity of ML algorithm is very high, to such an extent as to cannot apply, so in fact generally adopt the algorithm of suboptimum, for example, the present invention based on the breadth-first algorithm (BFSD algorithm) of globular decoding (Sphere Decoding, SD), be often called in the industry K-best SD algorithm.

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

Matrix H is carried out to QR decomposition, H=QR, wherein Q is the unitary matrice on N * N rank, Q ^hq=E, E is unit matrix, R is the upper triangular matrix on N * N rank, is expressed as:

Formula (1) can further be expressed as:

ρ＝Rs+η (3)

Wherein: ρ=Q ^hy, η=Q ^hn.

Or 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.From formula (4), can see the reception data ρ of N layer _nonly by this layer, send data s _idetermine, be not subject to the interference of other layer; And the reception data ρ of N-1 layer _n-1except the transmission data s with N-1 layer _n-1outside the Pass having, be also subject to N layer and send data s _nimpact.Generally, the reception data ρ of i layer _inot only with the transmission data s of i layer _irelevant, be also subject to i+1 layer to send data (s to N layer _i+1s _n) impact, so in the situation that known i+1 layer to the transmission data 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 be the estimated value that i layer sends vector, T represents transposition., by i layer, the estimated value of the transmission vector of test section and the Euclidean distance between reception value (can be understood as transmitted 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 N layer _nrelevant, so input can be first since N layer, order is to ground floor.If consider all values of transmitted signal modulation system, the N layer that starts most to detect has 2 ^mplant and select, the selection of each value is regarded as to a node, each node is a kind of possible solution.Such N layer just has 2 ^mindividual node; Secondly the N-1 layer detecting is equivalent on the basis of N layer, by each node unfolding calculation 2 of N layer ^mindividual node, therefore has 2 ^m* 2 ^mindividual node; Every layer is all multiplied by 2 on the basis of the nodes of anterior layer afterwards ^m, last one deck total (2 ^m) ⁿ=2 ^{n * m}individual node.These nodes are coupled together according to their accessed order, just form 2 ^{n * m}paths, these paths from same node, each node one deck separate 2 ^mindividual node, is similar to the tree of a handstand, as shown in Figure 4.The search procedure of SD serial algorithm just can be described with this Fig. 4, and each node is a kind of possible solution.

If sending the estimated value of vector is formula (5), tree-shaped part Euclidean distance when searching i layer is just (6), then the part Euclidean distance of all nodes of search in this layer is arranged according to order from small to large, only retained a minimum K node (or can be understood as certain count destination node) for new search.

The calculating of new one deck is on the basis of front 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 vector.These part Euclidean distances are pressed to order sequence from small to large or from big to small, and reserve part Euclidean distance is less than the fixed number destination node of threshold value, and this new one deck detects and finishes.

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

Fig. 4 shows a tree-shaped search schematic diagram of the present invention, wherein supposes that every layer retains at most 8 nodes, and each node at most possible child node number 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 the child node of four groups is respectively 3,2,1.But in Fig. 4, the circle that the straight line of solid line is corresponding represents the node launching, that the circle corresponding to straight line of dotted line expresses possibility there is no the node of expansion.The circle of solid line represents the node retaining, and the circle of dotted line represents the node not retaining.

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).In Fig. 5 and Fig. 6, there is the Performance Ratio of three kinds of algorithms, traditional K-best SD algorithm (representing with KSD in figure), algorithm of the present invention (representing with SRKSD in figure) and the fixedly Sphere Decoding Algorithm of complexity (representing with FSD in figure).Fig. 5 is illustrated in the performance curve in not sequence situation, and Fig. 6 is illustrated in the performance curve in sequence situation, all adds " O " to show sequence before all algorithms.The transverse axis of figure represents that signal to noise ratio snr, the longitudinal axis represent bit error rate BER performance.Wherein the K value of traditional K-best SD algorithm is the same with algorithm of the present invention, so computation complexity is greater than this algorithm, fixedly the computation complexity of the globular decoding of complexity is the same with this algorithm.From Fig. 5, Fig. 6, all can find out, method performance of the present invention is substantially the same with K-best SD algorithm performance, difference that cannot resolution performance from figure.Fig. 5 can find out that the performance of method of the present invention will be better than FSD algorithm greatly, at BER=10 in the situation that not sorting ^-3situation under, the performance of method of the present invention under three kinds of modulation systems is better than FSD algorithm and is greater than 5dB.In the situation that having sequence, the performance of method of the present invention is better than FSD algorithm as can be seen from Figure 6.At BER=10 ^-3, when modulation system is got 16-QAM, method of the present invention is than the good 0.5dB of the FSD algorithm of same complexity left and right.

Thereby can find out, embodiments of the invention realized with in the situation that width is the same with the performance of breadth-first Sphere Decoding Algorithm substantially, in the situation that computation complexity is the same, performance is better than the fixedly Sphere Decoding Algorithm of complexity.

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

Signal receiving unit, for receiving symbol;

Detecting signal unit, for first utilizing known channel matrix and possible transmission symbol to process symbol that described signal receiving unit receives to form search tree, and in such a way the N layer of described search tree is searched for:

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

According to the principle that the expansion son node number of every group of interior nodes equates, the expansion son node number of interior nodes does not start to successively decrease successively from M on the same group, launch the child node of N node layer, launch the mode of child node for add new element after the corresponding part transmission of described node vector, until form whole transmission vector, the corresponding described new element of described child node, total number of plies that N is described search tree;

Secondly the part of Euclidean distance that sends vector according to part corresponding to the child node of all expansion and partly receive between vector sorts, K child node of reserve part Euclidean distance minimum is for the search of lower one deck, described part reception vector is comprised of a part of element of the receiving symbol corresponding with described transmission symbol, described receiving symbol is expressed as the form that receives vector, and N, K, M are positive integer;

Again search for other layer of described search tree, in the path being formed by child node, find the path of Euclidean distance minimum as Search Results;

Signal output unit, for the Search Results output that described detecting signal unit is obtained.

As can be seen from the above embodiments, the present invention's method that expanding node number limits when to the search of every layer of search tree reduces the nodes of search, substantially 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 less, power consumption is lower.Method of the present invention also can be applicable to multiuser signal detection and other input.

The above is only the preferred embodiment of the present invention; it should be pointed out that for those skilled in the art, do not departing under the prerequisite of the technology of the present invention principle; can also make some improvement and replacement, these improvement and replacement also should be considered as protection scope of the present invention.

Claims (10)

1. a signal detecting method for mimo system, is characterized in that, comprises the following steps:

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

S2, according to step S21～S23, the N layer of described search tree is searched for total number of plies that N is described 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 forms sends vector, and described transmission symbol table is shown the form that sends vector;

S22, according to the expansion son node number of every group of interior nodes equates, the expansion son node number of interior nodes does not start to successively decrease successively from M on the same group principle, launch the child node of N node layer, launch the mode of child node for add new element after the corresponding part transmission of described node vector, until form whole transmission vector, the corresponding described new element of described child node;

S23, the part of Euclidean distance receiving between vector according to part transmission vector corresponding to the child node of all expansion and part sort, K child node of reserve part Euclidean distance minimum is for the search of lower one deck, described part reception vector is comprised of a part of element of the receiving symbol corresponding with described transmission symbol, described receiving symbol is expressed as the form that receives vector, and N, K, M are positive integer;

S3, according to the mode of step S21～S23 search for described search tree other layer, in the path being formed by child node, find the path of Euclidean distance minimum as Search Results.

2. the method for claim 1, is characterized in that, step S1 is specially: by each line ordering of advancing of described channel matrix, then utilize described possible transmission symbol trigonometric ratio to form described search tree the channel matrix obtaining after sequence.

3. the method for claim 1, is characterized in that, the described possible transmission symbol choosing set that freely all permutation and combination of each antenna possibility transmitted signal form.

4. method as claimed in claim 2, is characterized in that, described by the mode of channel matrix trigonometric ratio for channel matrix is carried out to QR decomposition.

5. method as claimed in claim 2, it is characterized in that, in step S1, by the mode of each line ordering of advancing of described channel matrix, be: if all nodes of this row are less than or equal to K, according to gain order from small to large, sort, otherwise sort according to gain order from big to small.

6. the method for claim 1, is characterized in that, the initial value of M is for sending the number of 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 that forms path by child node in step S3 is: from every one deck, select a child node to be connected in turn and form 2 ^{n * m}paths, and the child node of selected j layer is all to launch from the selected child node of last layer, j=2 ..., N, m is for sending the order of modulation of symbol.

8. the method for claim 1, it is characterized in that, step by K child node of reserve part Euclidean distance minimum in step S23 for the search of lower one deck replaces with: K child node of reserve part Euclidean distance minimum, and delete the child node that Euclidean distance value is greater than distance threshold from a described K child node, remaining child node is for the search of lower one deck.

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. a signal supervisory instrument for mimo system, is characterized in that, comprising:

Signal receiving unit, for receiving symbol;

Detecting signal unit, for first utilizing known channel matrix and possible transmission symbol to process symbol that described signal receiving unit receives to form search tree, and in such a way the N layer of described search tree is searched for:

Current reservation node is divided into M group, and the corresponding part that sends a part of element composition of symbol of each node sends vector, and described transmission symbol table is shown the form that sends vector;

According to the principle that the expansion son node number of every group of interior nodes equates, the expansion son node number of interior nodes does not start to successively decrease successively from M on the same group, launch the child node of N node layer, launch the mode of child node for add new element after the corresponding part transmission of described node vector, until form whole transmission vector, the corresponding described new element of described child node, total number of plies that N is described search tree;

Secondly the part of Euclidean distance that sends vector according to part corresponding to the child node of all expansion and partly receive between vector sorts, K child node of reserve part Euclidean distance minimum is for the search of lower one deck, described part reception vector is comprised of a part of element of the receiving symbol corresponding with described transmission symbol, described receiving symbol is expressed as the form that receives vector, and N, K, M are positive integer;

Again search for other layer of described search tree, in the path being formed by child node, find the path of Euclidean distance minimum as Search Results;

Signal output unit, for the Search Results output that described detecting signal unit is obtained.