CN101163121B - Communication system and character code selecting method thereof - Google Patents

Abstract

The invention provides a code selection method. The code selection method can be applied to a multiple-input and multiple-output communication system. The method consists of the following steps. First, a transmitter provides plural code form. Then a receiver receives the code form, calculates or looks up tables to obtain corresponding bit error rate for each code form according to a coding mode. Second, the receiver selects a group code format with the smallest bit error rate, and returns to the transmitter. Finally, the transmitter decides the group code used for transmitting data according to the code form with the smallest bit error rate.

Description

Communication system and character code selecting method thereof

Technical field

The present invention relates to a kind of multiple-input and multiple-output communication system with and Space-Time character code (space-time (ST) codeword) system of selection, particularly relate to a kind of use group-wise Space-Time block sign indicating number (groupedspace-time block code, G-STBC) coded system design, and the group's Space-Time character code under limited back information (group-wise ST codeword) system of selection and related system.

Background technology

Wireless telecommunication system needs more and more a large amount of data circulations, therefore how to do efficient coding, modulation and quality and the usefulness of signal processing to improve wireless telecommunications, all is that the problem that utmost point desire solves is gone up in research.In order effectively to promote data transmission rate and communication link quality, more and more many wireless telecommunication systems adopt the multiple antenna system design of multiple-input and multiple-output (MIMO), that is, in the transmission end and receiving terminal use many antennas, to realize down the powerful service quality demand of generation wireless telecommunication system.The coding of multiple antenna system, generally adopt the Space-Time sign indicating number (space-time code, STC).This coding is a kind of transmission design that is across the time and space, utilizes the relation of transmit antenna and delivery time to reach maximum diversity (full diversity), even coding gain (coding gain) can be provided.The main operating mode of Space-Time sign indicating number can be divided into the space various (spatial diversity, SD) and spatial multiplexing (spatialmultiplexing, SM).High link quality can be obtained via the various mode in space transmits redundancy (redundant) on different transmission antennas signal, Space-Time block coding (space-time block code for example, STBC) and the Space-Time trellis coding (ST trellis code, STTC).The high spectrum benefit then can transmit different data simultaneously via the spatial multiplexing mode and obtain on different transmission antennas, and for example multi-level Space-Time sign indicating number (layered STC, LSTC) or Bell Labs layered ST (BLAST) technology of knowing.

Fig. 1 is the system schematic of an existing Space-Time block coding, and clearly, two code elements of transmission are across space and time (Space-Time sign indicating number).Fig. 2 show another in conjunction with Q=2Alamouti ' s Space-Time sign indicating number in the existing coding techniques of transmission end, this is called two Space-Times and transmits diversity (double ST transmitdiversity, DSTTD) technology.Its Space-Time character code is

$X:=\left[\frac{\begin{array}{cc}{S}_{\mathrm{1,1}}& -{\mathrm{<figure-callout\; id="2"\; label="S"\; filenames="H061D1798920061020E000072.png,H061D1798920061020E000091.png"\; state="\{\{state\}\}">S</figure-callout>}}_{\mathrm{1,2}}^{*}\\ S_{\mathrm{1,2}}& S_{\mathrm{1,1}}^{*}\end{array}}{\begin{array}{cc}{\mathrm{<figure-callout\; id="2"\; label="S"\; filenames="H061D1798920061020E000072.png,H061D1798920061020E000091.png"\; state="\{\{state\}\}">S</figure-callout>}}_{\mathrm{2,1}}& {\mathrm{<figure-callout\; id="2"\; label="S"\; filenames="H061D1798920061020E000072.png,H061D1798920061020E000091.png"\; state="\{\{state\}\}">\; <figure-callout\; id="2"\; label="S"\; filenames="H061D1798920061020E000072.png,H061D1798920061020E000091.png"\; state="\{\{state\}\}">S</figure-callout>\; </figure-callout>}}_{\mathrm{2,2}}^{*}\\ {\mathrm{<figure-callout\; id="2"\; label="S"\; filenames="H061D1798920061020E000072.png,H061D1798920061020E000091.png"\; state="\{\{state\}\}">S</figure-callout>}}_{\mathrm{2,2}}& {\mathrm{<figure-callout\; id="2"\; label="S"\; filenames="H061D1798920061020E000072.png,H061D1798920061020E000091.png"\; state="\{\{state\}\}">S</figure-callout>}}_{\mathrm{2,1}}^{*}\end{array}}\right]$

The encoding rate of this moment is R=2, and can to obtain diversity gain be 2.Yet though the coded system of this coding techniques is simpler, its decoded mode is than the STBC complexity, and word code structure suffers many restrictions, make code Design more not have elasticity, so usefulness is relatively poor.

Yet to improve its frequency spectrum utilization benefit of communication link quality low though the space is various; On the contrary, though spatial multiplexing can promote data transmission rate, its docking adapter decline ability is relatively poor.Therefore, in order to obtain maximum benefit, must be in the space obtain the breakeven point an of the best between the various and spatial multiplexing.

In addition, the computing of receiver must be healed simply better, to reach decoding fast, also can simplify the design of receiver.With respect to the empty time-code of transmission end, receiver also must have the decoding capability of Space-Time sign indicating number, need make interference eliminated and signal simultaneously and detect.The optimal decoding method that a kind of receiver is commonly used adopts joint maximum likelihood, and (it adopts the mode of probability statistics that the signal that receives is deciphered for maximum likelihood, ML) detection method.Yet though joint maximum likelihood estimation method has preferable performance, required computational complexity is really also higher.Another kind of decoded mode adopts the gradual interference eliminated of ordering (ordered successive interference cancellation, hereinafter to be referred as OSIC) detect, be to utilize sortord and utilize previous interative computation result, the elimination that the signal that receives is disturbed and the detection of signal one by one.For instance, suppose that receiver receives the signal from action user 1 and action user 2, then the OSIC detection method can be earlier be carried out signal at action user 1 and be detected, and deduct (eliminations) user 1 the interference of taking action again, and the user's 2 that obtains taking action signal.The OSIC detection method is a kind of than associating ML method operand is lower but the technology that usefulness is suitable, yet, but further do not utilize the orthogonal property simplification signal detector of Space-Time sign indicating number.

In addition, become response when wireless communication environments is one, transmitting with receiving terminal needs suitably adaptive transmission mechanism, to handle the distortion of signal, reaches best service quality.Therefore, also need good adaptive transmission mechanism to adjust scheme for mimo system.

Summary of the invention

The invention provides a kind of MIMO communication system and character code selecting method thereof, can utilize quadrature formula Space-Time block sign indicating number (orthogonal STBC, to call O-STBC in the following text) algebraic property, carry out the G-STBC code Design, and under limited back information, based on the condition of minimum bit error rate (bit error rate is to call BER in the following text), select an optimum character code structure in order to transmission.

The invention provides a kind of character code (codeword) system of selection.This group's character code selecting method is applicable to the communication system with multiple transmission antenna and multiple receive antennas.The method comprises the following steps.At first, reflector provides plural character code form.Then, receiver receives described character code form, and according to a decoded mode, calculates or the bit error rate (BER) of the correspondence that obtains each described character code of tabling look-up.Secondly, receiver is selected one and is had the character code form of minimum bit error rate, and returns to reflector.At last, reflector is according to the character code form with minimum bit error rate, and decision is in order to carry out the Space-Time character code of transfer of data.

The present invention also provides a kind of MIMO communication system.Reflector at first provides plural character code form.Receiver receives the character code form, and according to a decoded mode, calculates or the bit error rate of the correspondence that obtains each character code form of tabling look-up.Wherein, receiver is selected one and is had the character code form of minimum bit error rate, and returns to reflector, and reflector is again according to the character code form with minimum bit error rate, and decision is in order to carry out the Space-Time character code of transfer of data.

For above and other objects of the present invention, feature and advantage can be become apparent, cited below particularlyly go out preferred embodiment, and be described with reference to the accompanying drawings as follows.

Description of drawings

Fig. 1 shows an existing Space-Time block coding system schematic.

Fig. 2 shows another existing Space-Time block coding system schematic.

Fig. 3 shows a communication system schematic diagram according to the embodiment of the invention.

Fig. 4 shows a character code selection flow chart according to the embodiment of the invention.

Fig. 5 and Fig. 6 show that respectively character code selecting method according to Fig. 4 is in the transmission end and the schematic flow sheet of receiving terminal.

Fig. 7 shows matched filtering access matrix (MFCM) schematic diagram according to the embodiment of the invention.

Fig. 8 a-8e shows that respectively be 5 kinds of possible group-wise Space-Time character code schematic diagrames of 10 o'clock according to the embodiment of the invention in total antenna number that transmits.

The reference numeral explanation

300～communication system;

310～reflector;

312～separate the multitask module;

314～modulation module;

316～G-STBC encoder;

318～controller;

320～receiver;

322～Space-Time sign indicating number matched filter;

324～group-wise OSIC detector;

326～multiplexer;

328～selection signal;

T1-TN～transmission antenna;

R1-RM～reception antenna;

S410-S460～step;

S510-S550～step;

S610-S650～step;

(K)～orthogonal matrix;

N～always transmit antenna number;

K～symbol time.

Embodiment

Fig. 3 shows a communication system schematic diagram according to the embodiment of the invention.At least one reflector 310 and a receiver 320 have been comprised in the communication system 300.Note that communication system of the present invention is a transceiver architecture that comprises receiver and emitter design, can be used for mimo system.Having comprised one in the reflector 310 separates multitask module 312, modulation module 314, group-wise Space-Time block sign indicating number (group-wise STBC, G-STBC) encoder 316, controller 318 and N root transmits antenna T1～TN.Wherein, the N root transmits antenna T1～TN and is divided into Q antenna groups, and each antenna groups is made up of 2～4 antennas.A Space-Time sign indicating number passage matched filter (matched filter, MF) 322, group-wise OSIC detectors 324, a multiplexer 326 and a M root reception antenna R1～RN, and M 〉=Q have then been comprised in the receiver 320.

At first, in the transmission end, the input serial data produces several subdata strings through separating multitask module 312, be modulated into data symbols (symbol) via modulator 314, carry out the Space-Time coding via group-wise Space-Time block code coder 316 according to selected word code structure again, be sent to receiver 328 by antenna T1～TN at last.Wherein, in this embodiment, word code structure comprises the number of antennas of use and required transmission symbol time.

So in receiving terminal, receiver 320 receives the signal of this transmission, carries out the signal demodulation via Space-Time channel matched filter 322.Wherein, Space-Time passage matched filter 322 is a matched filtering access matrix MFCM, and Space-Time sign indicating number passage matched filter 322 MFCM in view of the above reduces the Spatial Dimension that receives signal, further deciphers for follow-up group-wise OSIC detector 324.Decoding principle and form about matched filtering channel matrix MFCM will be described in detail as follows.Then, the signal that group-wise OSIC detector 324 receives behind Space-Time sign indicating number passage matched filter 322 detects rule according to OSIC again, and it is carried out interference eliminated and signal detection.Above-mentioned detection mode corresponds to the used modulation system in transmission end, for instance, when the BPSK modulation was used in the transmission end, the detection mode of receiving terminal just was the detection at BPSK, when the QPSK modulation was used in the transmission end, the detection mode of receiving terminal just was to detect at QPSK.In other words, different modulation systems, the detection method that correspondence is different.Because, the decoding of BPSK and QPSK belongs to the detection of real number and complex symbol respectively, thus below also will discuss at the detection mode of real number and complex symbol respectively.For instance,, can directly use antenna groups formula OSIC detection method to detect, that is can detect whole symbol datas of a certain antenna groups in each interative computation simultaneously for the detection of real number code element.For the detection of complex symbol, then must cooperate the antenna groups formula detect rule, second order segmentation detection method then and recurrence (recursive) mode detect.This is because for the detection of complex symbol, only by 2L _qIndividual real number code element is a half code element (i.e., the L of unit block _qIndividual) can in certain iterative processing of OSIC, can be detected simultaneously, and these code elements are if not to belong to the real part (Re) of the complex symbol in a certain antenna groups be exactly its imaginary part (Im).Antenna groups formula for complex symbol detects rule, be meant the real part (Re) of same antenna group and the result of imaginary part (Im) are averaged, produce the matrix structure of similar real number code element, just can utilize above-mentioned antenna groups formula OSIC detection method to detect.The second order segmentation detection method then practice detects the antenna groups (N with higher link ability for elder generation _q=4 or N _q=3), detect antenna groups (N again with low link ability _q=2), to reduce its computational complexity.Recursive fashion then is in conjunction with second order segmentation detection method then, utilizes previous operation result to obtain the detected symbol of next stage, can effectively reduce its computational complexity.In conjunction with above-mentioned decoded mode, will the computational complexity of receiver be reduced, also the design complexities of the receiver of Jian Huaing.

In addition, in this embodiment, group-wise OSIC detector 324 will be according to given environmental parameter, calculates one by one or table look-up to obtain the pairing bit error rate of each antenna groups (BER).Group-wise OSIC detector 324 finds that antenna groups that has minimum BER among all BER after calculating, and selects signal 328 passbacks to give reflector 310 this information utilization.

Group-wise OSIC based on above-mentioned low complex degree detects framework, and the present invention will develop a cover does not have total group-wise Space-Time coding that transmits the number of antennas restriction.Under delivering power that requires and data transmission rate restriction,, provide Space-Time character code selection criterion suitably to select best character code according to the Rule of judgment of minimum BER.

It should be noted that the back information that depends on receiver among the present invention in order to the best Space-Time word code structure of transmission.Therefore, when initial, can by reflector send earlier have the character code form training symbol (training symbol) to receiver, treat that receiver calculates the character code of minimum BER after, reflector and receiver carry out the transfer of data of reality again with the corresponding word code structure of this minimum BER.In addition, because the transmission end has the selection of different word code structures for transmission, therefore also can be designed in the design can be in the usefulness of transmission during lower or environment change, send a gravity treatment signal by the transmission end, transmit with the word code structure that requires receiver to select another group to have less BER value.Therefore, the present invention can provide the transmission of adaptive to adjust mechanism.

Fig. 4 shows a character code selection flow chart according to the embodiment of the invention.At first, reflector 310 is divided into Q antenna groups according to transmitting number of antennas N, and possible Space-Time character code form (step S410) is provided.Wherein, because signal adopts the O-STBC coding among the present invention, for meeting the characteristic of quadrature, each antenna groups internal antenna number is only being 2,3 or 4.This character code form has comprised different antenna configurations modes in selecting.For instance, supposing always to transmit antenna number N is 10, and the specified antenna configurations mode of then wherein a kind of character code form may be one group for 2 antennas, therefore, can be divided into 5 groups antenna groups altogether, with ∑ ₁=(2,2,2,2,2) expression.Similarly, suppose that another character code form is the antenna configurations mode of a group with 3,4, can ∑ ₂=(3,3,4) expression.Suppose total T1～T10 root antenna, according to ∑ ₁The character code form, T1 and T2 will be used for transmitting data simultaneously for one group, T3 and T4 will be used for transmitting data simultaneously for one group; If according to ∑ ₂The character code form, then T1, T2 and T3 will be used for transmitting data simultaneously for one group.Then, send this Q antenna groups form to receiver 320.Receiver 320 receives this character code (antenna groups form) (step S420), and the BER value (step S430) of calculating or tabling look-up and obtain each Space-Time character code correspondence.Above-mentioned calculating or the mode of tabling look-up will be described in detail as follows.Then, receiver 320 finds the character code with minimum BER, and the selection signal that will comprise this information returns to reflector 310 (step S440).So reflector 310 is just selected specified word code structure in the signal according to this, the word code structure (step S450) of decision transmission usefulness.At last, reflector and receiver are convenient carries out the transmission (step S460) of data with this word code structure.

See also Fig. 5 and Fig. 6, show that respectively character code selecting method according to Fig. 4 is in the transmission end and the schematic flow sheet of receiving terminal.As shown in Figure 5, reflector 310 is divided into Q antenna groups according to total antenna number N that transmits, and produces possible candidate's character code (step S510).The characteristic of Space-Time character code comprises encoding rate, various gain and receiver computational complexity, will be subjected to the influence of antenna groups structure (that is word code structure).For N total antenna number that transmits, both made to have under the identical antenna groups number, different antenna groups structures can provide different encoding rates.Moreover different antenna groups structures can provide different various gains, causes different communication link performances.In addition, detect rule based on group-wise OSIC, different antenna groups structures also will cause different receiver computational complexities.Therefore, the selection of Zui Jia Space-Time character code should be considered above-mentioned three characteristics simultaneously.Table three is listed when main aerial is counted N=2 to N=16 all possible empty character code and is selected L ^NThen represent and corresponding codes rate R ^NIn the table three, J ^NPossible character code number when being illustrated in main aerial and counting N, S ^NThe antenna configurations mode of representing each character code, L ^NRepresent that then OSIC detects needed interative computation number of times.Therefore, different total transmission antenna number N will have different possible word code structures.

N	J N	Possible sky Line Qun Group Group closes S N	Bian Code leads	Zui Da Stacked generation number
					2	1	(2)	1	?1
3	1	(3)	0.5	?1
					4	2	(4)，(2，2)	0.5，2	?1，2
5	1	(2，3)	1.5	?4
					6	3	(3，3)，(2，4)，(2，2，2)	1，1.5，3	?2，4，3
7	2	(3，4)，(2，2，3)	1，2.5	?2，6
					8	4	(4，4)，(2，3，3)，(2，2，4)，(2，2，2，2)	1，2，2.5，4	?2，6，6，4
9	3	(3，3，3)，(2，3，4)，(2，2，2，3)	1.5，2，3.5	?6，3，8
					10	5	(3，3，4)，(2，4，4)，(2，2，3，3)，(2，2，2，4)，(2，2，2，2，2)	1.5，2，3，3.5，5	?3，6，8，8.5
11	4	(3，4，4)，(2，3，3，3)，(2，2，3，4)，(2，2，2，2，4)	1.5，2.5，3，4.5	?3，8，8，10
					12	7	(4，4，4)，(3，3，3)，(2，3，3，4)，(2，2，4，4)，(2，2，2，3，3)，(2，2，2，2，4)，(2，2，2，2，2，2)	1.5，2，2.5，3，4， 4.5，6	?3，4，8，8，10?10，6
13	5	(3，3，3，4)，(2，3，4，4)，(2，2，3，3，3)，(2，2，2，3，4)，(2，2，2，2，2，3)	2，2.5，3.5，4，5.5	?4，8，10，10，12
					14	8	(3，3，3，4)，(2，4，4，4)，(2，3，3，3，3)，(2，2，3，3，4)，(2，2，2，4，4)，(2，2，2，2，3，3)，(2，2，2，2，2，4)，(2，2，2，2，2，2，2)	2，2.5，3，3.5， 4，5，5.5，7	?4，8，10，10，10?12，12，7
15	7	(3，4，4，4)，(3，3，3，3，3)，(2，3，3，3，4)，(2，2，3，4，4)，(2，2，2，3，3，3)，(2，2，2，2，3，4)，(2，2，2，2，2，2，3)	2，2.5，3，3.5， 4.5，5，6.5	?4，5，10，10，12?12，14

16

10

(4，4，4，4)，(3，3，3，3，4)，(2，3，3，4，4)，(2，2，4，4，4)，(2，2，3，3，3，3)，(2，2，2，3，3，4)，(2，2，2，2，4，4)，(2，2，2，2，2，3，3)，(2，2，2，2，2，2，4)(2，2，2，2，2，2，2，2)

2，2.5，3，3.5，4， 4.5，5，6，6.5，8

?4，5，10，10，12?12，12，14，14，8

Table three

It is 10 o'clock 5 kinds of possible character codes (3,3,4), (2,4,4), (2,2,3,3), the schematic diagram of (2,2,2,4) and (2,2,2,2,2) in total antenna number that transmits that Fig. 8 a-8e is respectively according to the embodiment of the invention.For instance, with 8c figure is example, be illustrated in total transmission antenna number N=10, be divided into Q=4 antenna groups and character code (antenna groups structure) structure is (2,2,3,3) the G-STBC word code structure schematic diagram the time, wherein, the part of 2 antennas is the STBC of use 2 * 2, and the part of 3 antennas is then used 3 * 8 STBC, and employed STBC is quadrature formula STBC (O-STBC) in each group, and this word code structure is a unit with symbol time length N=8.By 8a-8e figure as can be known, the Space-Time sign indicating number in each group is necessary under the condition of quadrature, and decision antenna groups structure also will determine word code structure.

Then, transmit these possible Space-Time character code forms to receiver 320 (step S520).Then, wait for receiver 320 passbacks one information.So, judge whether back information (step S530) of receiver 320.If receiver 320 is back information (step S530 not) not as yet, then return step S530, continue to judge.If receiver 320 is back information (step S530 is), then reflector 310 is according to the optimum character code that is had in this back information, and decision is the Space-Time character code (step S540) of transmission usefulness with this optimum character code.At last, pass to receiving terminal with this best Space-Time character code after with digital coding again, carry out the transmission (step S550) of data.

In receiving terminal, as shown in Figure 6, receiver 320 receives the Space-Time character code form (step S610) that reflector 310 is sent.Comprised different antenna configurations modes in this character code form.For instance, supposing always to transmit antenna number N is 10, and then as shown in Table 3, it has comprised 5 kinds of possible word code structures.Then, according to decoded mode, calculate the BER value (step S620) that (tabling look-up) obtains each Space-Time character code correspondence.Reference table three is 10 o'clock in total transmission antenna number N as can be known, will obtain 5 BER value BER1～BER5 behind the execution in step S620, more than the example, the character code ∑ ₁(2,2,2,2,2) will have the BER value BER1 of a correspondence, character code ∑ ₂(3,3,4) have the BER value BER2 of a correspondence, by that analogy.Then, find character code form (step S630) with minimum BER value.Frequency spectrum benefit h (M to system requirements _j ^N), if given bit transfer rate R _b(being modulation format) then will define its pairing Space-Time character code.Therefore, at given total delivering power P _TAnd required data transmission rate R _bRestriction under, if select j character code, then need satisfy

$j=\arg \underset{\&ForAll;j}{\min }{P}_e\left(S_j^N\right|\{P_T,R_b\}).$

P wherein _eRepresent the whole BER value of j character code, it can be calculated as follows:

$P_e\left(j\right)=\frac{1}{\mathrm{\&eta;}\left(M_j^N\right)}{\mathrm{\&Sigma;}}_{q=1}^Q\left(R_q^N\left(j\right)R_{b,q}\left(j\right)\right)P_{e,q}\left(j\right)=\frac{1}{R^N\left(j\right)}{\mathrm{\&Sigma;}}_{q=1}^Q{R}_q^N\left(j\right)P_{e,q}\left(j\right)$

In the following formula, P _{E, q}(j) be the BER of q antenna groups under j the pattern (mode), and mode-definition is the combination of a specific Space-Time character code modulation format employed with it.Suppose in the interative computation process of OSIC, to ignore its error propagation effect (error propagation effect), P _{E, q}(j) can be approximately signal after the detection to disturbing and noise ratio (signal-to-interference-plus-noise ratio, SINR) γ _qAnd transmission data rate R _{B, q}Function

$P_{e,q}\&ap;g_{\mathrm{\&gamma;}},R_b({\mathrm{\&gamma;}}_q,R_{b,q}),$

Wherein

And

${\mathrm{\&sigma;}}_{v,q}^2\left(j\right)=\frac{{\mathrm{\&sigma;}}_{\mathrm{<figure-callout\; id="2"\; label="v"\; filenames="H061D1798920061020E000072.png,H061D1798920061020E000091.png"\; state="\{\{state\}\}">v</figure-callout>}}^2}{2}{e}_{q_i}^T{\left[H_{c,q_i}^T\left(j\right)H_{c,q_i}\left(j\right)\right]}^{-1}{e}_{q_i}$

${\mathrm{\&epsiv;}}_q\left(j\right)=e_{q_i}^T{[\frac{2}{{\mathrm{\&sigma;}}_v^2}{H}_{c,q_i}^T\left(j\right)H_{c,q_i}\left(j\right)+I]}^{-1}{e}_{q_i}$

Respectively be noise power and the code element mean square error after the detection of q antenna groups.Wherein

Definition is as H _{C, i}(H _{C, i}To introduce in the back), e _lThen be

In l unit standard vector (unit standardvector).The present invention supposes to use M-ary QAM modulation, and then the BER of q antenna groups can be similar to as follows

$g_{\mathrm{\&gamma;}},R_b({\mathrm{\&gamma;}}_q,R_b)\&ap;\frac{2}{R_{b,q}}(1-\frac{1}{\sqrt{2^{R_{b,q}}}})\mathrm{erfc}\left(\sqrt{\frac{1.5{\mathrm{\&gamma;}}_q}{2^{R_{b,q}}-1}}\right)$

Wherein, $2^{R_{b,q}}=\stackrel{\&OverBar;}{M},$ Erfc () is a complementary error function (complementary errorfunction).

By following formula as can be known, the delivering power P that is requiring _TAnd data transmission rate R _bRestriction according to the BER performance, can select to have provided the pairing character code of minimum BER performance down.Suppose that in the BER value that all calculate BER2 is minimum BER value.This has the pairing character code form of minimum BER value will be regarded as best Space-Time character code form, so the optimum character code form is its pairing character code form ∑ ₂, that is (3,3,4) will be the character code form of the best.So receiver 320 produces selects signal, having comprised the optimum character code form in this signal is ∑ ₂Information, select signal to return this to reflector 310 (step S640).At last, reflector 310 can be according to this optimum character code form (∑ ₂) encode, carry out the transmission (step S650) of data then with receiver.

To sum up state as can be known, can improve the link quality and increase data transfer rate, and also can make balance point is preferably arranged between the two according to transmission system of the present invention and transmission method thereof.In addition, because the O-STBC coded system is used in the transmission end, can effectively reduce the computational complexity of receiver.

For deciding means that above-mentioned antenna groups is described and relation and the influence between the various related operation, below will describe with mathematical formulae.Please note, below quote thesis for the doctorate " Space-time signal processing for MIMO wireless communications:Space-time signaling and interference suppression " (hereinafter to be referred as document one) partial results of the same inventor of the present invention, the detailed inference process can be with reference to inventor's paper, below only take passages its partial results, and improved with aid illustration.

At first the form of definition of data is considered the G-STBC system under Rayleigh flat-fading environment, and as shown in Figure 3, wherein N antenna placed in the transmission end, and receiving terminal is placed M antenna.N transmission antenna will be divided into Q antenna groups (N ₁..., N _Q), each antenna groups is then used 2～4 antennas, makes N ₁+ ...+N _Q=N.For q group, with continuous B _qIndividual data code element is encoded with the O-STBC coded system, and at K _qIndividual symbol time is interior by N _qIndividual antenna sends out.

If definition K=max{K ₁..., K _Q, K=k then _qK _q, k wherein _q=K/K _qEach antenna groups can be sent out L in K symbol time _q=k _qB _qTherefore individual independent code element, is transmitted altogether by Q antenna groups in K symbol time

$L_T:=\underset{q=1}{\overset{Q}{\mathrm{\&Sigma;}}}{L}_q=K\underset{q=1}{\overset{Q}{\mathrm{\&Sigma;}}}\frac{B_q}{K_q}$

Individual data code element.The character code of each antenna groups is called group's character code (group code), can be by N _qSpace-Time character code matrix (codeword matrix) X of * K _qDescribe fully.With q group data code element s _q(k) be divided into the serial data block as

$s_{q,l}\left(k\right)=s_q(L_{q}k+\tilde{l}1),l=1,...,L_q$

Then the Space-Time character code of q group can be written as

$X_q\left(k\right):=\underset{l=1}{\overset{2L_q}{\mathrm{\&Sigma;}}}{A}_{q,l}{\tilde{s}}_{q,l}\left(k\right)---\left(1\right)$

A wherein _{Q, l}Be Space-Time modulation matrix (modulation matrix).For the subsequent analysis convenience, to give a definition ${\tilde{s}}_{q,l}\left(k\right)=\mathrm{Re}\left\{s_{q,l}\left(k\right)\right\},l=1,...,L_q,$ And ${\tilde{s}}_{q,l}\left(k\right)=\mathrm{Im}\left\{s_{q,l-L_q}\left(k\right)\right\},1=L_q+1,...,2L_q.$

(〉=Q) individual antenna, then the signal of being received on M antenna in K symbol time is to suppose to use M at receiving terminal

$Y\left(k\right):=[y\left(k\right),y(k+1),...,y(k+K-1)]=\underset{q=1}{\overset{Q}{\mathrm{\&Sigma;}}}\sqrt{\frac{P_q}{N}}{H}_q{X}_q\left(k\right)+V\left(k\right)---\left(2\right)$

Wherein $H_q=\sqrt{P_q}{C}_q,$ P _qBe the delivering power of q group, and satisfy P ₁+ ...+P _Q=P _T, and P _TBe total delivering power; In addition, C _qBe the MIMO access matrix of q group to receiver, last V (k) ∈ C ^{M * K}Be noise matrix.Following hypothesis will be used in the discussion of back:

(a1) data symbols s _q(k), q=1 ..., Q is i.i.d., and its mean value is 0 (zero-mean), and variance is 1 (unit-variance), and adopts identical modulation technique.

(a2) each antenna groups transmits identical power, i.e. P ₁=...=P _Q=P _T/ Q.

(a3) C _q, q=1 ..., Q, each element in the matrix are that i.i.d. plural number Gaussian random variable and its mean value are 0, variance is 1, and hypothesis remains unchanged in K symbol time.

(a4) V (k) is the Space-Time white noise, and its mean value is 0, and variance is s _v ²

(a5) according to O-STBC, when using real number code element and 2≤N _q≤ 4, or use complex symbol and N _qUnder=2 situations, adopting encoding rate is orthogonal space-time zone block code of 1 (unit-rate); And when using complex symbol and 3≤N _qUnder≤4 situations, adopting encoding rate is orthogonal space-time zone block code of 1/2 (half-rate).

The real number vector model

For easy analysis, (2) are rewritten into following 2KM * 1 linear vector model

$y_c\left(k\right):={[{\tilde{y}}^T\left(k\right),{\tilde{y}}^T(k+1),...,{\tilde{y}}^T(k+K-1)]}^T=H_c{s}_c\left(k\right)+v_c\left(k\right)$

(3)

Wherein

$\tilde{y}\left(k\right):={\left[\mathrm{Re}\right\{y^T\left(k\right)\left\}\mathrm{Im}\right\{y^T\left(k\right)\left\}\right]}^T\&Element;R^{2M}$

${\tilde{s}}_q\left(k\right):={\left[\mathrm{Re}\right\{s_q^T\left(k\right)\left\}\mathrm{Im}\right\{s_q^T\left(k\right)\left\}\right]}^T\&Element;R^{2L_q}$

$s_q\left(k\right):={[s_{q,1}\left(k\right),s_{q,2}\left(k\right),...,s_{q,L_q}\left(k\right)]}^T$

H _c∈R ^2KM×2LT

Be equivalent access matrix, and

$s_c\left(k\right):={[{\tilde{s}}_1^T\left(k\right),{\tilde{s}}_2^T\left(k\right),...{\tilde{s}}_Q^T\left(k\right)]}^T\&Element;R^{2L_T},$

v _c(k) ∈ ^R2KMBe noise vector.With y _c(k) respectively be multiplied by H about equation _cTo produce matched filtering (matched-filtered, MF) data vector

$z\left(k\right):=H_c^T{y}_c\left(k\right)=F{s}_c\left(k\right)+v\left(k\right)---\left(4\right)$

Wherein $F:=H_c^T{H}_c\&Element;R^{2L_T\&times;{2L}_T}$ For the matched filtering access matrix (matched-filtered channelmatrix, MFCM), $v\left(k\right):=H_c^T{v}_c\left(k\right).$ Below will detect signal based on model (4).

Use the OSIC detection method under the real number code element

The algorithm that below adopts document one to be proposed detects and transmits signal.By the special construction that utilizes matched filtering access matrix F to be had, the OSIC detector can detect whole L of some antenna groups simultaneously in interative computation each time _q=K symbol data is referred to as " antenna groups OSIC detection " method.

A. matched filtering access matrix

In order to make the OSIC rule can effectively detect the transmission signal, must analyze the structure of F.Because it detects rule by proposing in the document one and complete analysis being arranged, and applicable to this real number code element situation, therefore only states its result herein.

Definition O (K) is the set of real number orthogonal matrix of the K * K of one group of all tool K independent variable; (K L) is the set of real number orthogonal matrix of the K * K of one group of all tool L independent variable.

II.1 as a result: consider the real number code element, and 2≤N _p, N _q≤ 4.According to O-STBC, as can be known K ∈ 2,4}.Definition F _{P, q}For F (wherein F is defined in (4) for p, q) individual K * K block matrices.Then can learn F _{Q, q}=α _qI _KAnd F _{P, q}∈ (K) is if p ≠ q.，

The result of II.1 is as a result put in order in table one, wherein, F _{P, q} ^{(s, t)}Be F _{Q, q}(s, t) individual block matrices.The structure chart of F then is shown in Fig. 7.

Table one

B. group-wise OSIC detection algorithm

Next will find F ^-1,, will have the structure identical with F with rough.At first define Φ _KL(L) but be the set of real number symmetry (symmetric) matrix of the KL * KL of one group of all regurgitation (invertible), make for X ∈ Φ _KL(L), X wherein _{K, l}For X (k, the l) submatrix of individual K * K can get X _{L, l}=β _qI _KAnd X _{K, l}∈ O (K) is as k ≠ l.

True II.1: if F ∈ Φ _KL(L), F then ^-1Identical result (can referring to document one) is also arranged.，

According to true II.1, can obtain following II.2 as a result:

II.2 as a result: consider the real number code element, and 2≤N _p, N _q≤ 4, as can be known K ∈ 2,4}.F ∈ R ^{LT * LT}Be defined in (4).Each F then ^-1Block diagonal angle (diagonal) submatrix of K * K be a constant unit matrix; Each F ^-1Non-diagonal angle (off-diagonal) K * K block submatrix belong to O (K).Hence one can see that F ^-1The online element in all KL diagonal angle have L=Q different levels (level) β _l, l=1 ..., L, that is

diag(F ^-1)＝{β ₁，...，β ₁，β ₂，...，β ₂，...，β _L，...，β _L}(5)，

Wherein, each level in (5) β _lNumber K is all arranged.By (5) as can be known, (zero-forcing, ZF) (or least mean-square error (minimum mean square error, MMSE) criterion), the OSIC detector can detect K code element to criterion simultaneously in the primary iteration computing based on zero forcing.

Based on detection-deduction program of OSIC, can learn in the i time interative computation of OSIC, i=1 ..., L-1, noise covariance (covariance) matrix is F _i ^-1, wherein

$F_i=H_{c,i}^T{H}_{c,i}---\left(6\right)$

Be the matched filtering access matrix in the i time interative computation of OSIC, can be by from H _cMiddle deletion is i block (that is H of unit by K row (columns) _{C, i}) (corresponding to detected signal in the preceding interative computation).Hence one can see that F _i∈ F (L-i).

II.3 as a result: according to true II.1, as can be known

And

$\mathrm{diag}\left(F_i^{-1}\right)=\{{\mathrm{\&beta;}}_1,...,{\mathrm{\&beta;}}_1,{\mathrm{\&beta;}}_2,...,{\mathrm{\&beta;}}_2,...,{\mathrm{\&beta;}}_L,...,{\mathrm{\&beta;}}_L\}---\left(7\right)$

Wherein β _{I, l}For being distributed in F _i ^-1The level that diagonal angle the online the 1st is different, each β _lRespectively there be K.，

By above analysis as can be known, above-mentioned algorithm can be carried out antenna groups OSIC detection.

Use the OSIC detection method under the complex symbol

Though using under the real number code element, detecting can carry out antenna groups formula OSIC.Yet, under complex symbol is used, can't carry out antenna groups formula OSIC and detect.Only by 2L _qIndividual real number code element is a half code element (i.e., the L of unit block _qIndividual) can in certain iterative processing of OSIC, can be detected simultaneously, and these code elements are if not to belong to the real part of the complex symbol in a certain antenna groups be exactly its imaginary part.

A. matched filtering access matrix

Under complex symbol, the following result of II.1 as a result that is different from is arranged.

III.1 as a result: consider complex symbol, and 2≤N _p, N _q≤ 4.According to O-STBC, as can be known K ∈ 2,8}.Definition F _{P, q}(p, q) individual 2L for F _q* 2L _qBlock matrices, wherein F is defined in (4).Then can obtain result as table two.

Table two

B. group-wise OSIC detection algorithm

According to III.1 as a result, can infer F _i ^-1To no longer have similar F _iStructure.Analyzing F _i ^-1Structure before, need the definition following parameters.At first being defined in the i time interative computation of OSIC, is a decision-making Γ of group (decision group) at half real number code element of a certain antenna groups _{I, g}, g=1 ..., G _i, wherein, G _iBe the i time total decision-making group number in the interative computation.Therefore, each antenna groups will have two decision-making groups, and each decision-making group has L _qIndividual real number code element.Further define I _{I, 1}And I _{I, 1/2}Be respectively encoding rate in the i time interative computation and be 1 and encoding rate be the set of Decision Making Unit's deck label (index) of 1/2 Space-Time sign indicating number, so G _{I, 1}=| I _{I, 1}| and G _{I, 2}=| I _{I, 2}|, be the number of parameters that is comprised in each set.Define I at last _i:=I _{I, 1}∪ I _{I, 1/2}Be the set of the i time total Decision Making Unit deck label in the interative computation, so G _i=| I _i|.According to above-mentioned definition, as can be known

(8)

In addition, if with F _iThe online element in diagonal angle be divided into G _iIndividual decision-making group, and each decision-making group has the numerical value of identical non-zero, that is

Suppose { a _{I, g}} _G=1 ^GiHas D _i(G _i) individual different level, then can learn

Next definition

But be the set of real number symmetrical matrix of the J * J of one group of all regurgitation, make for

, can get: each block diagonal angle submatrix of (1) X is a constant unit matrix

, g=1 ..., G, wherein M _g∈ 2,4,8}.(2) { a _g} _G=1 ^GHave D different level, wherein

(3) for i, j=1 ..., G, i ≠ j, the M of X _i* M _jEach 4 * 4 block submatrix in the non-diagonal angle of the block submatrix belong to (4) or null matrix.Wherein, work as D=G, then

To be rewritten as

III.2 as a result: consider complex symbol.Suppose encoding rate be 1 and encoding rate be that 1/2 Space-Time sign indicating number is present in i the interative computation of OSIC simultaneously, that is And

Definition i (g), g=1 ..., G _i, be the element of g among the i, and F _i∈ R ^{Ji * Ji}Be the matched filtering access matrix in the i time interative computation of OSIC, wherein

And L _g∈ 2,4,8}.，

Therefore, if Then By the F as can be known of III.2 as a result _i ^-1Has G _i(〉=D _i) individual different level { β _{I, g}} _G=1 ^Gi(F wherein _iHas only D _iIndividual different level), that is

By (11) as can be known, only with 2L _qIndividual real number code element is a half code element (i.e., the L of unit block _qIndividual) can in certain iterative processing of OSIC, be detected simultaneously, and these code elements are if not to belong to the real part of the complex symbol in a certain antenna groups be exactly its imaginary part.Therefore, so a detection characteristic will cause computational burden.For solving the above problems, will develop the technology that some reduce computational complexity subsequently.

In the realization subject under discussion of using the group-wise OSIC detection technique under the complex symbol situation

, the realization subject under discussion that some group-wise OSIC detect will be discussed herein, and comprise the antenna groups formula and detect rule, second order segmentation (two-stage) detection rule and recurrence (recursive) realization.Owing to, can finish, therefore, below only inquire into how to be implemented in the group-wise OSIC detection technique of using under the complex symbol by the method that document one is proposed in the realization that the group-wise OSIC that uses under the real number code element situation detects.

A. antenna groups formula detection method

As described in III.2 as a result, be distributed in F _i ^-1In the online a certain antenna groups in diagonal angle altogether

Individual element will have two different levels

And

For realizing that the antenna groups formula detects, the simplest a kind of method promptly is directly to search F _i ^-1The label of diagonal angle on-line decision group is checked the pairing level minimum of its which label.Though this method is simple but performance is also relatively poor.Therefore, will be corresponding to two levels of a certain antenna groups And

Average

${\mathrm{\&beta;}}_{i,q}=\frac{{\mathrm{\&beta;}}_{q_i,1}+{\mathrm{\&beta;}}_{q_i,2}}{2}---\left(12\right)$

And with F _i ^-1xThe diagonal angle online common

Individual element is rewritten as

Can be according to β _{I, 1}, β _{I, 2}..., β _{I, Q-i}, search its label, check the pairing level minimum of its which label.This method of searching label is not to be best method, so its performance also can decay to some extent, but shows this performance degradation and not serious in the Computer Simulation.

B. second order segmentation detection method

In theory, comparatively strong for the antenna groups with higher various gain (that is having more number of antennas or lower encoding rate) antagonism channel fading, performance is also more excellent.In view of this, the present invention proposes a kind of detection rule of second order segmentation.Its practice is for detecting the antenna groups (N with low encoding rate earlier _q=4 or N _q=3) detect the antenna groups (N that has than high code-rate again _q=2), to reduce its computational complexity.In the same manner, this method of searching label is not to be best method, so its performance also can decay to some extent, but shows this performance degradation and not serious in the Computer Simulation.

C. recursive form is realized

In order further to slow down the receiver amount of calculation, the recurrence rule that adopts similar document one to be proposed realizes group-wise OSIC detector.But the method that document one is proposed can't directly and fully be suitable in this invention, need make some modifications and just can be used.

By III.2 as a result as can be known, exist

In can form orthogonal matrix smallest dimension be 4 * 4, wherein, Be F _i ^-1(p, q) individual submatrix.Because this realization based on the recurrence rule once can only be handled a block orthogonal matrix, therefore work as F _iDimension when very big, directly its group-wise OSIC detector is realized needing more recurrence number of times with recursive fashion, cause bigger amount of calculation.But fortunately,, can assist and reduce its operand if then in conjunction with second order segmentation detection method.Suppose at F _i ^-1The online element that belongs to a certain antenna groups in diagonal angle has two different levels.If F _iIt is the matched filtering access matrix in i the interative computation.F then _I1 ^-Divisible as follows

(13)

Wherein $B_{i-1}\&Element;R^{2(L_T-{\mathrm{\&Sigma;}}_{j=1}^{i-1}{L}_{q_j})\&times;{2L}_{q_{i-1}},}$ $D_{i-1}=d_{i-1}{I}_{2L_{q_{i-1}}},$ And d _I-1Be constant.Further, if hypothesis $2(L_T-{\mathrm{\&Sigma;}}_{j=1}^{i-1}{L}_{q_j})\&times;2(L_T-{\mathrm{\&Sigma;}}_{j=1}^{i-1}{L}_{q_j})$ The F of dimension _I-1Be F _I-1 ^-1The principle submatrix, and $F_0^{-1}=F^{-1}.$ By (13) and utilize inversion lemma for block matrix, F _I-1Can be expressed as follows

${\stackrel{\&OverBar;}{F}}_{i-1}={(F_i-B_{i-1}{D}_{i-1}^{-1}{B}_{i-1}^T)}^{-1}---\left(14\right)$

Can learn by (14)

$F_i={\stackrel{\&OverBar;}{F}}_{i-1}^{-1}+B_{i-1}{D}_{i-1}^{-1}{B}_{i-1}^T---\left(15\right)$

Utilize matrix inversion lemma, and can obtain through deriving

$F_i^{-1}={\stackrel{\&OverBar;}{F}}_{i-1}-E_{i-1}{C}_{i-1}^{-1}{E}_{i-1}^T---\left(16\right)$

Wherein, $E_{i-1}:={\stackrel{\&OverBar;}{F}}_{i-1}{B}_{i-1}$ And

$C_{i-1}=B_{i-1}^T{\stackrel{\&OverBar;}{F}}_{i-1}{B}_{i-1}+D_{i-1}=\left[\begin{array}{cc}{c}_{1,i-1}{I}_{L_{q_{i-1}}}& 0_{L_{q_{i-1}}}\\ 0_{L_{q_{i-1}}}& {\mathrm{<figure-callout\; id="2"\; label="c"\; filenames="H061D1798920061020E000072.png,H061D1798920061020E000091.png"\; state="\{\{state\}\}">c</figure-callout>}}_{2,i-1}{I}_{L_{q_{i-1}}}\end{array}\right]$

Wherein, $c_{j,i-1},j=\mathrm{1,2},$ Be constant.

Above-mentioned derivation utilizes F _I-1And F _I-1 ^-1Information under, provide a simple recurrence formula to calculate F _i ^-1, and do not have any direct matrix inversion operation, therefore can reduce its computational complexity effectively.

Above-mentioned explanation provides several different embodiment or uses the embodiment of different qualities of the present invention.Specific device in the example and method the invention is not restricted to this certainly in order to help explaination main spirit of the present invention and purpose.

Therefore; though the present invention discloses as above with preferred embodiment; right its is not that those skilled in the art can do some changes and retouching under the premise without departing from the spirit and scope of the present invention, so protection scope of the present invention is as the criterion with claim of the present invention in order to qualification the present invention.

Claims (20)

1. a character code selecting method is applicable to a multiple-input and multiple-output communication system, and this communication system has multiple transmission antenna and multiple receive antennas, and this method comprises:

One reflector provides plural character code form;

One receiver receives described character code form, and according to a decoded mode, calculates or the bit error rate of the correspondence that obtains each described character code form of tabling look-up;

This receiver is selected one and is had the character code form of minimum bit error rate, and returns to this reflector; And

This reflector has the character code form of minimum bit error rate according to this, and decision is in order to carrying out the character code of transfer of data,

Wherein all adopt quadrature formula Space-Time sign indicating number coding in each described character code, and this decoded mode is an ordering gradual interference eliminated detection method and wherein under complex symbol, this receiver also adopts the different layers level that element had that belongs to an antenna groups on the diagonal with the inverse matrix of a matched filtering access matrix to carry out on average, detects to carry out this gradual interference eliminated that sorts.

2. character code selecting method as claimed in claim 1, wherein this reflector is carried out the following step:

Number according to described transmission antenna produces described character code form;

Receive a character code form of this receiver; And

According to this character code form that receives, determine character code, and transmit with the character code of this decision in order to transmission.

3. character code selecting method as claimed in claim 1, wherein this receiver is carried out the following step:

Receive the described character code form of this reflector;

According to this decoded mode, calculate this corresponding bit error rate of each described character code form; And

Transmit one and select signal, transmit the character code of usefulness in order to determine this reflector to this reflector,

The information that wherein comprises this character code in this selection signal with minimum bit error rate.

4. character code selecting method as claimed in claim 1, wherein this character code is chosen as Space-Time character code selection.

5. character code selecting method as claimed in claim 1 comprises N in wherein said each described character code _qRoot antenna, and N _qBe 2,3 or 4.

6. character code selecting method as claimed in claim 5, wherein the number of antennas N in each described character code _qDifferent.

7. character code selecting method as claimed in claim 1, wherein the gradual interference eliminated detection method of this ordering also is used two stage detection methods and detects.

8. character code selecting method as claimed in claim 7, wherein this two stage detection method comprises that detection earlier has the character code group of 3 or 4 antennas, detects the character code group with 2 antennas again.

9. character code selecting method as claimed in claim 8, wherein this two stage detection method comprises and utilizes the recursive detection mode to carry out two stage detections.

10. character code selecting method as claimed in claim 1, wherein under the detection of real number code element, receiver utilizes this gradual interference inversion that sorts to carry out the antenna groups formula and detects.

11. a communication system, it has multiple transmission antenna and multiple receive antennas, comprises at least:

One reflector is in order to provide plural character code form; And

One receiver receives described character code form, and according to a decoded mode, calculate or the bit error rate of the correspondence that obtains each described character code form of tabling look-up,

Wherein this receiver is selected a character code form with minimum bit error rate, and passback gives this reflector, and this reflector has the character code form of minimum bit error rate according to this, and decision is in order to carrying out the character code of transfer of data,

Wherein all adopt quadrature formula Space-Time sign indicating number coding in each described character code, and this decoded mode is for the gradual interference eliminated detection method of ordering and wherein under complex symbol, this receiver also adopts the different layers level that element had that belongs to an antenna groups on the diagonal with the inverse matrix of a matched filtering access matrix to carry out on average, detects to carry out this gradual interference eliminated that sorts.

12. communication system as claimed in claim 11, wherein this reflector also comprises:

One separates the multitask module, produces multiple subdata string in order to will import data;

One modulation module is in order to be modulated to complex modulation symbol with described subdata string;

One group-wise Space-Time block code coder carries out group-wise Space-Time block coding in order to the described modulated symbol after will modulating; And

One controller in order to described character code form to be provided, and has the character code form of minimum bit error rate according to this of this receiver passback, and decision is in order to carry out the character code of transfer of data.

13. communication system as claimed in claim 12, wherein this receiver also comprises:

One empty time-code passage matched filter is in order to reduce the coding signal Spatial Dimension that this reflector transmits;

One detector is in order to detect this coding signal; And

One multiplexer is reduced into original data in order to this signal after will detecting.

14. communication system as claimed in claim 13 wherein comprises N in each described character code _qRoot antenna, and N _qBe 2,3 or 4.

15. communication system as claimed in claim 14, wherein the number of antennas N in each described character code _qSystem is different.

16. communication system as claimed in claim 11, wherein the gradual interference eliminated detection method of this ordering also is used two stage detection methods and detects.

17. communication system as claimed in claim 16, wherein this two stage detection method comprises that decoding earlier has the character code group of 3 or 4 antennas, and decoding has the character code group of 2 antennas again.

18. communication system as claimed in claim 17, wherein this two stage detection method comprises and utilizes the recursive detection mode to detect.

19. communication system as claimed in claim 13, wherein under the decoding of real number code element, this detector is that the gradual interference eliminated of an execution ordering is carried out the detector that the antenna groups formula detects.

20. communication system as claimed in claim 13, wherein under complex symbol, this detector is that an execution averages a real part of each described character code and the signal of an imaginary part, to carry out the detector that the antenna groups formula detects.

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