CN101499834B - Feedback quantity control method, communication system and related apparatus - Google Patents

Abstract

The embodiment of the invention discloses a feedback quantity control method and a communication system and relevant equipment, which are used for reducing feedback quantity. The method comprises the following steps of: receiving data frames sent by a sender; determining a precoding matrix of subcarriers in each pilot frequency position in the data frames; obtaining transferring code word information corresponding to the precoding matrix according to a preset classification code book of code word state; and feedbacking the transferring code word information to the sender. The embodiment of the invention also provides a communication system and relevant equipment and can effectively reduce feedback quantity.

Description

A kind of feedback quantity control method and communication system and relevant device

Technical field

The present invention relates to communication field, relate in particular to a kind of feedback quantity control method and communication system and relevant device.

Background technology

Along with the user is day by day ardent for the demand of fast wireless network, the data transmission rate that the mobile communication system of a new generation is expected to provide higher, more reliable and stable communication and wider signal cover are also supported to use mobility, so that allow in the near future the user obtain and the identical even better service quality of wired broadband network now by wireless network transmissions.

Can improve transmission rate after adopting multiple-input and multiple-output (MIMO, Multiple In and Multiple Out) in present global inserting of microwave interoperability (WiMAX, the World Interoperability for MicrowaveAccess) system.

Mimo system utilizes the antenna array of transmitting-receiving two-end, can obtain a compromise between spatial reuse and space diversity, thereby provides larger power system capacity and the service quality of Geng Gao for wireless communication system.If know the state information (CSI) of channel at transmit leg, namely closed-loop system just can be taked certain preliminary treatment at transmit leg to transmitting, and offsets wireless channel to the impact of signal transmission, obtains better systematic function than open cycle system.

At closed-loop MIMO-OFDM (OFDM, Orthogonal Frequency DivisionMultiplexing) in the system, transmit leg is according to CSI, multiply by a preconditioning matrix transmitting, so that transmitted signal is transmitted at the larger subchannel of gain, but because Frequency Division Duplexing (FDD) (FDD, Frequency Division Duplexing) system does not have channel symmetry, need the recipient by feedback channel CSI to be passed to transmit leg, in this case, pre-coding matrix can design the recipient, then transmit leg feeds back to transmit leg, so in the MIMO-OFDM system, need to be known the pre-coding matrix on all subcarriers, if feedback algorithm is not effectively designed, feedback quantity bears large being difficult to.

Some feedback quantity control methods namely have very large correlation mostly according to the frequency domain correlation on the channel in the prior art between adjacent sub-carrier, thereby utilize this correlation, and the codeword information that the recipient feeds back pilot tone place pre-coding matrix reduces feedback quantity.

Feedback quantity control method in the above-mentioned scheme is owing to be based on frequency domain correlation, so this scheme is subject to the restriction of frequency dependence, the carrier number that each block of sub-carriers comprises can not be too large, otherwise may be so that the distortion of the pre-coding matrix of the pre-coding matrix of the non-pilot tone virgin's carrier wave that calculates and pilot tone virgin carrier wave be very large, affect systematic function, if but carrier block choosing is little, the feedback quantity of system just can not effectively reduce.

Summary of the invention

The embodiment of the invention provides a kind of feedback quantity control method and communication system and relevant device, can effectively reduce the system feedback amount.

The feedback quantity control method that the embodiment of the invention provides comprises: receive the Frame that transmit leg sends; Determine the pre-coding matrix of each pilot tone virgin carrier wave in the described Frame; Obtain transfer codeword information corresponding to described pre-coding matrix according to the code word state classification code book that presets; Feed back described transfer codeword information to described transmit leg.

The communication system that the embodiment of the invention provides comprises: transmit leg and recipient, and described transmit leg is used for sending Frame to described recipient, receives the transfer codeword information of feedback; Described recipient is used for receiving the Frame that described transmit leg sends, determine the pre-coding matrix of each pilot tone virgin carrier wave in the described Frame, obtain transfer codeword information corresponding to described pre-coding matrix according to the code word state classification code book that presets, feed back described transfer codeword information to described transmit leg.

The transfer of data network element that the embodiment of the invention provides comprises: transmitting element is used for sending Frame and OFDM symbol; The codeword information receiving element is used for receiving codeword information; Query unit is used for pre-coding matrix corresponding to code word state classification code book inquiry that is presetting according to the described codeword information that receives; The pre-coding matrix processing unit is used for going out pre-coding matrix on the non-pilot sub-carrier to know the pre-coding matrix of all subcarriers according to the described pre-coding matrix interpolation that inquires.

The transfer of data network element that the embodiment of the invention provides, comprise: the frequency domain feedback control unit, be used for receiving the OFDM symbol, obtain the channel estimation value at pilot tone place according to the pilot frequency sequence in the described OFDM symbol, obtain the pre-coding matrix of described pilot tone virgin's carrier wave according to described estimated value, the codeword information of the described pre-coding matrix of inquiry in described code word state classification code book; The time domain feedback control unit is used for receiving data frames, determines the pre-coding matrix of each pilot tone virgin carrier wave in the described Frame, obtains transfer codeword information corresponding to described pre-coding matrix according to the code word state classification code book that presets; Feedback unit is used for feeding back the transfer codeword information that codeword information that described frequency domain feedback control unit obtains and described time domain feedback control unit obtain to transmit leg.

As can be seen from the above technical solutions, the embodiment of the invention has the following advantages:

In the embodiment of the invention, the recipient is after receiving Frame, determine the pre-coding matrix of each pilot tone virgin carrier wave in the described Frame, obtain transfer codeword information corresponding to described pre-coding matrix according to the code word state classification code book that presets, feed back described transfer codeword information to transmit leg, therefore do not need to feed back the codeword information of all transfering states, thereby can reduce the system feedback amount, therefore, the embodiment of the invention provides another to reduce the method for feedback quantity in terms of existing technologies.

Description of drawings

Fig. 1 is MIMO-OFDM system schematic in the embodiment of the invention;

Fig. 2 is feedback quantity control method the first embodiment flow chart in the embodiment of the invention;

Fig. 3 is precoding interpolation algorithm schematic diagram in the embodiment of the invention;

Fig. 4 is feedback quantity control method the second embodiment flow chart in the embodiment of the invention;

Fig. 5 is markov Codebook Model schematic diagram in the embodiment of the invention;

Fig. 6 is communication system embodiment schematic diagram in the embodiment of the invention;

Fig. 7 is transfer of data network element the first embodiment schematic diagram in the embodiment of the invention;

Fig. 8 is transfer of data network element the second embodiment schematic diagram in the embodiment of the invention.

Embodiment

The embodiment of the invention provides a kind of feedback quantity control method and communication system and relevant device, is used for reducing the system feedback amount.

In the embodiment of the invention because channel has correlation in time domain, so code word when time domain is carried out state transitions from a state transitions to fixing several states, rather than all states.The recipient is after receiving Frame in the embodiment of the invention, determine the pre-coding matrix of each pilot tone virgin carrier wave in the described Frame, obtain transfer codeword information corresponding to described pre-coding matrix according to the code word state classification code book that presets, feed back described transfer codeword information to transmit leg, therefore do not need to feed back the codeword information of all transfering states, thereby can reduce the system feedback amount.

On above-mentioned basis, can also adopt simultaneously the minimizing feedback algorithm on the frequency-domain and time-domain in the embodiment of the invention, namely the time-frequency two dimension is united the minimizing feedback algorithm.

See also Fig. 1, the MIMO-OFDM system configuration in the paper embodiment of the invention, whole system is comprised of four parts: transmit leg, forward direction wireless channel, recipient and feedback channel.

Supposing the system has the T transmit antennas, a R root reception antenna and C subcarrier, and feedback algorithm adopts the method for designing based on code book, and then the codeword information number is N _B(=2 ^B), namely each codeword information represents with B bit, if do not adopt any feedback algorithm, the each feedback quantity of recipient is C*B.

According to the type that reduces feedback the feedback quantity control method in the embodiment of the invention is divided into: time-frequency combination reduces feedback system and time domain reduces feedback system, and lower mask body is introduced:

One, time-frequency combination reduces feedback system:

In actual applications, the coherence bandwidth of channel can be smaller sometimes, and then this moment, wideband MIMO-ofdm system need to be modulated on the corresponding more subcarrier, and the channel of each subcarrier of guarantee all is flat fading.

Transmitting-receiving two-end in the manner all transmits take Frame as unit, each Frame is divided into three parts: pilot frequency sequence, and use the Chu sequence as pilot tone, be understandable that, can with other similar sequences as pilot frequency sequence, be used for frame synchronization, channel estimating equally; The signaling territory comprises the OFDM symbol adopts in the current frame data territory number of sub carrier wave size, also comprises the fields such as the frequency domain interval Δ F of frame length Δ T, pilot tone of present frame and modulation coding mode; Data field, i.e. the present frame data load that will transmit.

Wherein, fixing number of sub carrier wave, reliable modulation system (two-phase PSK (BPSK are for example all adopted in pilot frequency sequence and signaling territory, Binary Phase Shift Keying)) transmit, suitable coding can also be carried out in the signaling territory, to guarantee the accuracy of its reception.

Utilize the time-frequency two-dimensional correlation of channel in the manner, transmit leg is determined pilot frequency sequence according to the performance requirement of system, and utilizes time-frequency two-dimensional to unite and reduce the pre-coding matrix that feedback algorithm calculates each subcarrier of current data block; Correspondingly, the recipient utilizes pilot frequency information, estimate the channel information on the pilot tone virgin carrier wave, then calculate the pre-coding matrix on these pilot tones virgin carrier wave, the codeword information of these pre-coding matrixes in the code word state classification code book that presets fed back to transmit leg.

For ease of understanding, the below is elaborated, and sees also Fig. 2, and feedback quantity control method the first embodiment comprises in the embodiment of the invention:

201, transmit leg arranges pilot frequency sequence;

In the present embodiment, during system initialization, transmit leg need to arrange some pilot tone places according to performance requirements and form pilot frequency sequence, namely because channel exists correlation in time and frequency, so can on time domain and frequency domain, select some subcarriers uniformly, insert pilot tone at these subcarriers, this pilot tone is used to indicate the recipient codeword information of the pre-coding matrix of these subcarriers on code book is feedbacked.Arranging of concrete performance requirement and pilot frequency sequence can be determined according to practical application, do not do restriction herein, only describe with an example, precoding interpolation in the present embodiment as shown in Figure 3, black block among Fig. 3 represents pilot tone, namely suppose on frequency domain, to insert a pilot tone every Δ F=K subcarrier, insert a pilot tone every Δ T=L OFDM symbol on the time domain, as shown in Figure 3, F (n, t) pre-coding matrix on n the subcarrier of t OFDM symbol of expression, it is obtained by recipient's feedback;

Pre-coding matrix on n the subcarrier of t the OFDM symbol that expression obtains by interpolation, namely transmit leg obtains the pre-coding matrix of other non-pilot tone virgin's carrier waves according to the pre-coding matrix interpolation of pilot tone virgin's carrier wave of recipient's feedback.

202, send the OFDM symbol that comprises pilot frequency sequence;

When system initialization, data are that unit transmits by piece, insert uniformly pilot frequency sequence at each certain interval of first OFDM symbol of first data block, and send the data block that this comprises pilot frequency sequence to the recipient.

203, the recipient obtains pilot tone place channel estimation value according to pilot frequency sequence;

In the present embodiment, after the recipient gets access to data block, read pilot frequency sequence from first OFDM symbol of this data block, and according to this pilot frequency sequence, obtain the channel estimation value at pilot tone place, concrete acquisition process is prior art, repeats no more herein.

Above-mentioned recipient gets access to after two pilot frequency sequences at least, obtain channel information at least two corresponding time points according to described pilot frequency sequence, described channel information added up obtain transition probability matrix, and make up code word state classification code book according to described transition probability matrix, simultaneously send described transition probability matrix to described transmit leg, and transmit leg makes up code word state classification code book according to this transition probability matrix equally.

204, the recipient chooses pilot tone virgin carrier wave pre-coding matrix and feedback matrix codeword information; After the recipient gets access to the channel estimation value at pilot tone place, choose the pre-coding matrix of pilot tone virgin carrier wave according to the pre-coding matrix selection rule that presets, and selected pre-coding matrix corresponding codeword information in code word state classification code book is fed back to transmit leg.

At first the precoding strategy in the embodiment of the invention is described, what adopt in the embodiment of the invention is Grassmann precoding strategy, particularly, in the MIMO-OFDM system, when the length of Cyclic Prefix during greater than channel length, the impact of intersymbol interference can be eliminated fully, and then the input/output relation on n carrier wave is Y _n=H _nX _n+ N _n, wherein, N _nThat each element is obeyed CN (0, N ₀) N that distributes _rDimensional vector, X _nN _tThe column vector that transmits of dimension, total transmitting power is ε _s, namely $E\left[X_n^H{X}_n\right]\≤{\mathrm{\ϵ}}_s,$ Y _nBe N _rThe reception signal train vector of dimension, H _nBe N _r* N _tThe frequency domain channel matrix.In linear pre-coding system, X _nCan be expressed as X _n=F _nS _n, wherein, F _nBe the N on the subcarrier n _tThe pre-coding matrix of * M, S _nBe the pre-signal transmission column vector of M dimension, because the maximum multiplexing tuple of mimo system is minimum transmit receive antenna number, so M≤min{N _t, N _r.Because transmit power limited, precoding must be satisfied $F_n^H{F}_n=I_M,$ So F _nBe chosen as a N _tThe para-unitary matrix of * M.If the recipient adopts minimum mean square error detector, recipient Y to the received signal then _nMultiply by one and detect matrix G _n, this moment $G_n=[F_n^H{H}_n^H{H}_n{F}_n+({\mathrm{MN}}_0/{\mathrm{\ϵ}}_s)I_M{]}^{-1}{F}_n^H{H}_n^H,$ Signal after then detecting is ${\hat{X}}_n=G_n{Y}_n.$

The above has introduced the precoding strategy in the present embodiment, is understandable that, above-mentioned introduction only is for the ease of understanding, can adopt equally in actual applications the precoding strategy of other modes, not doing restriction herein.

The below describes the rule of choosing pre-coding matrix in the present embodiment, concrete pre-coding matrix selection rule can have multiple, do not do restriction herein, only describe with two examples, all describe as an example of the pre-coding matrix chosen by minimization system error rate rule and/or maximized system capacity rule example among two examples and the follow-up embodiment below:

(1) minimization system error rate rule:

When system adopted different modulation systems, the error rate of system can be write as the function of snr of received signal, therefore can be with the maximization snr of received signal as the standard of selecting pre-coding matrix.The snr of received signal that least mean-square error detects receiver can be expressed as

${\mathrm{SNR}}_n\left(F_n\right)=\frac{{\mathrm{\ϵ}}_s}{{\mathrm{MN}}_0|F_n^H{H}_n^H{H}_n{F}_n+({\mathrm{MN}}_0/{\mathrm{\ϵ}}_s)I_M{|}^{-1}}-1$

Then maximizing the snr of received signal standard namely is to select a pre-coding matrix F _n, so that

$F_n=\underset{\underset{f}{F_{n,i}}\∈\mathrm{fF}}{\arg \max }\mathrm{SN}{R}_n\left(F_{n,i}\right)$

By formula ${\hat{X}}_n=G_n{Y}_n$ Can find out, be not unique based on the pre-coding matrix that maximizes the snr of received signal standard, for any U ∈ U (M, M), SNR _n(F _n)=SNR _n(F _nU), after namely the unitary matrice on M rank was taken advantage of on the pre-coding matrix right side, the signal to noise ratio that receives signal was constant, that is to say brightly can obtain several pre-coding matrixes on the pilot tone virgin carrier wave.

(2) maximized system capacity rule:

For given H _nAnd F _n, the power system capacity of incoherent multiple Gaussian source is

$C_n\left(F_n\right)=\mathrm{lo}{g}_2\det (I_M+\frac{{\mathrm{\ϵ}}_s}{{\mathrm{MN}}_0}{F}_n^H{H}_n^H{H}_n{F}_n)$

The maximized system capacity standard namely is to select a pre-coding matrix F _n, so that

$F_n=\underset{F_{n,i}\∈F}{\arg \max }{C}_n\left(F_{n,i}\right)$

Equally, neither be unique based on the pre-coding matrix of maximized system capacity standard, it also has consistency, for U ∈ U (M, M) arbitrarily, C _n(F _n)=C _n(F _nU) all there are several pre-coding matrixes.

Two kinds of pre-coding matrix selection criterions that the above introduces can obtain several pre-coding matrixes, and these pre-coding matrixes have identical column space, and therefore, the choice criteria of pre-coding matrix depends on F _nColumn space.

By all at U (N _r, the set of the M n-dimensional subspace n that the matrix on M) is opened is exactly Grassmann stream shape, and note is G (N _r, M).Because Grassmann stream shape is a quotient space, any point F ∈ G (N in the space _r, M) N of expression _rThe equivalet class of * M orthogonal matrix, if two matrix column spaces are identical, then these two matrixes are equivalent, can be expressed as [F]={ FU:U ∈ U (M, M) } such as the equivalet class of F.Therefore, pre-coding matrix is exactly a point on the Grassmann stream shape.

When given codeword information number N _BAfter, based on the Codebook Design method of Grassmann stream shape, be exactly so that the maximization of minimum code word information distance.In Grassmann stream shape, the definition of the distance between the subspace has a lot, and topmost three sub spaces distance definitions are: string distance, norm projection distance and Fubini-Study distance.Subspace P _F1And P _F2String apart from being defined as

Subspace P _F1And P _F2Norm projection distance be

$d_{\mathrm{proj}}(F_1,F_2)={\left|\right|F_1{F}_1^{*}-F_2{F}_2^{*}\left|\right|}_2=\sqrt{1-l_{\min }^2\left\{F_1^{*}{F}_2\right\}}$

And subspace P _F1And P _F2The Fubini-Study distance definition be

$d_{\mathrm{FS}}(F_1,F_2)=\arccos \left|\det \left(F_1^{*}{F}_2\right)\right|$

Order $S=\{P_{F_1},P_{F_2},K,P_{F_{N_B}}\}$ Be the subspace set of codeword information, wherein P _FiBe codeword information F _iColumn space, then the Codebook Design criterion based on Grassmann stream shape is

Namely by different distance definitions, can obtain different code books.

Behind the above-mentioned pre-coding matrix of determining pilot tone virgin's carrier wave, in the code word state classification code book that gets access to before, inquire about codeword information corresponding to this pre-coding matrix, and this codeword information is fed back to transmit leg.

Be understandable that above-mentioned two pre-coding matrix selection rules can also be combined with, concrete mode is not done restriction herein.

205, transmit leg goes out the pre-coding matrix of all subcarriers according to the codeword information interpolation;

Transmit leg gets access to by feedback channel after the codeword information of pre-coding matrix of pilot tone virgin's carrier wave of recipient feedback, in code book, find out corresponding pre-coding matrix according to this codeword information, reduce feedback algorithm according to frequency domain, interpolation goes out the pre-coding matrix on other carrier waves of this OFDM symbol, because channel is the piece decline, pre-coding matrix on the corresponding subcarrier with frequency pilot sign of pre-coding matrix in this data block on other OFDM symbols is identical, so transmit leg can obtain according to the codeword information of recipient's feedback the pre-coding matrix of all subcarriers.

In the present embodiment, transmit leg goes out the process of the pre-coding matrix on other carrier waves of OFDM symbol according to the codeword information interpolation that receives similar with process in the prior art frequency domain minimizing feedback system, repeats no more herein.

206, the recipient calculates the pre-coding matrix of each pilot tone virgin carrier wave;

In the present embodiment, when the recipient receives next symbol, calculate the pre-coding matrix of each pilot tone virgin carrier wave in this symbol, and reduce feedback algorithm according to time domain, corresponding codeword information is fed back to transmit leg.

In the present embodiment, if the symbol that the recipient receives is not first symbol, then can calculate pre-coding matrix to each the pilot tone virgin carrier wave in this symbol, the method for the pre-coding matrix of concrete computational methods and aforementioned calculating pilot tone virgin carrier wave is similar.

Lower mask body is introduced the time domain of describing in the present embodiment and is reduced feedback algorithm:

In whole system, the variation of the pre-coding matrix on each subcarrier on time domain is modeled as the discrete time Markov chain of a finite state, its state J _nWith each the codeword information F in the code book _nCorresponding one by one.

An important parameter of Discrete Time Finite state Markov chain is exactly its transition probability matrix Pr (J _n=i|J _n=j), because code book is a quantification to pre-coding matrix, therefore is difficult to provide the closed expression of transition probability matrix, but can passes through Monte Carlo simulation, obtain the transition probability matrix of code book.Code word is when state transitions, from a state transitions to fixing several states, rather than all states.Therefore, when time domain is fed back, only need to send the codeword information of the state that previous code word state may shift because transmit leg is known the pre-coding matrix at previous pilot tone place, recipient, can reduce feedback quantity.

Idiographic flow can be determined for the transition probability matrix that: recipient obtains according to statistics before all transfering states corresponding to pre-coding matrix of pilot tone virgin carrier wave, and inquire about codeword information corresponding to described transfering state according to described code word state classification code book, namely determine the codeword information that this codeword information may be transferred to, and these codeword information are fed back to transmit leg.

Be understandable that, do not affecting under the prerequisite of systematic function as far as possible, for further improving the effect that reduces feedback, can also obtain concrete codeword information transition probability, and just this codeword information is fed back to transmit leg when only having the probability that shifts when codeword information greater than certain threshold value, namely the little codeword information of metastatic potential is not fed back, then can further be improved the effect that reduces feedback.

On the basis of the above, can also improve the process of codeword information coding, namely according to the size of transition probability codeword information is divided, for the large codeword information of transition probability according to the Huffman mode, adopt less bit to encode, for the little codeword information of transition probability according to the Huffman mode, adopt more bit to encode, then when transfering state is more, can also further improve the effect that reduces feedback, above-mentioned huffman coding mode is a kind of possibility, can choose different encoding schemes according to actual conditions in concrete application.

207, reduce feedback algorithm according to time domain and feed back corresponding pre-coding matrix.

After having carried out time domain minimizing feedback algorithm, the transfer codeword information that gets access to is fed back to transmit leg.

After the step 207, transmit leg can be known the pre-coding matrix on all subcarriers, after the data field data in these pre-coding matrixes and the Frame are multiplied each other, the data after these precodings is sent to the recipient.

The recipient receives after the data, because the recipient knows the channel information on each subcarrier, the recipient also utilizes frequency domain to reduce feedback algorithm simultaneously, interpolation goes out the pre-coding matrix on all subcarriers, so just can carry out ZF or least mean-square error detection to receiving data, thereby recover initial data.

The below reduces feedback system to time-frequency combination and carries out integral body introduction:

In the manner, during system initialization, transmit leg is a plurality of pilot frequency sequences of emission continuously, the recipient obtains channel information on a plurality of time points according to these pilot frequency sequences, these information are carried out statistical analysis, can obtain the transition probability matrix of code book, and this transition probability matrix is passed through to transmit leg, after knowing probability transfer matrix, transmitting-receiving two-end constructs the code book by the state classification of previous moment code word.

When beginning to transmit data, transmit leg consists of bit rate to be sent the Frame that comprises pilot frequency sequence, signaling territory and data field, each Frame is comprised of Δ T OFDM symbol, and first OFDM of Frame inserts pilot frequency sequence uniformly every a Δ F subcarrier.

After the recipient receives frequency pilot sign, the use channel estimation methods estimates the channel information on the carrier wave of pilot tone place, if current transmission is first Frame, owing to there is not the codeword information of previous moment, then do not adopt time domain to reduce feedback algorithm, and need to feed back to transmit leg to the pre-coding matrix of these carrier waves sequence number in traditional code book; If current time transmission is not first Frame, then the recipient calculates the pre-coding matrix codeword information on the subcarrier of pilot tone place according to code word state classification code book, and the codeword information of these pre-coding matrixes is fed back to transmit leg.

If feedback channel is zero defect and undelayed, after then transmit leg is received feedback information, from code book, find out the pre-coding matrix on these subcarriers, then reduce feedback algorithm according to frequency domain, interpolation goes out the pre-coding matrix on the non-pilot sub-carrier, can obtain like this pre-coding matrix on all subcarriers, after the data field data in these pre-coding matrixes and the Frame are multiplied each other, the data after these precodings are sent to the recipient.

Because the recipient knows the channel information on each subcarrier, also utilize simultaneously frequency domain to reduce feedback algorithm, interpolation goes out the pre-coding matrix on the non-pilot sub-carrier, therefore can carry out ZF or least mean-square error detection to receiving data, recovers initial data.

In above-described embodiment, when the Cyclic Prefix of ofdm system during greater than channel length, exist correlation between adjacent sub-carrier, the correlation between subcarrier can be weighed with the frequency coherence coefficient, and it is nearer that subcarrier leans on, and coherence factor is larger, and correlation is also just larger.Because pre-coding matrix is the function of channel response, therefore pre-coding matrix exists correlation at frequency domain, transmit leg can utilize the pre-coding matrix that feeds back on the parton carrier wave, according to certain algorithm, calculates the pre-coding matrix on all the other subcarriers.Equally, channel also exists correlation on time domain, the Doppler of the correlation cochannel of time domain expands relevant frequently, Doppler expands larger frequently, the time variation of channel is faster, channel is only relevant in a short period of time, otherwise the variation of channel is very slow, keeps relevant in for a long time, because channel exists correlation in time domain, the pre-coding matrix of two adjacent data blocks also exists correlation, has known the pre-coding matrix of previous data block, and the scope of the pre-coding matrix that a rear data block is possible can be dwindled greatly, like this, just can reduce the feedback quantity of system.

The above-mentioned time-frequency combination of having introduced reduces feedback system, is mainly used in the situation that need to be modulated on a lot of subcarriers, if when the number of sub carrier wave of OFDM modulation is fewer, then can adopt time domain to reduce feedback system:

Two, time domain reduces feedback system:

When the sub-carrier number of OFDM modulation is less with respect to the number of sub carrier wave in the aforementioned time-frequency combination minimizing feedback system, can only adopt time domain to reduce feedback algorithm, at this moment can obtain and the approximately uniform performance of time-frequency unity feedback algorithm.

Adopt the transmitting-receiving two-end of the manner to transmit take Frame as unit, each Frame is divided into three parts: pilot frequency sequence, and use the Chu sequence as pilot tone, be understandable that, can with other similar sequences as pilot frequency sequence, be used for frame synchronization, channel estimating equally; The signaling territory comprises the OFDM symbol adopts in the current frame data territory number of sub carrier wave size, also comprises the fields such as the frequency domain interval Δ F of frame length Δ T, pilot tone of present frame and modulation coding mode; Data field, i.e. the present frame data load that will transmit.

Wherein, fixing number of sub carrier wave is all adopted in pilot frequency sequence and signaling territory, modulation system (for example BPSK) is transmitted reliably, and suitable coding can also be carried out in the signaling territory, to guarantee the accuracy of its reception.

This mode transmit leg and recipient assist to finish, transmit leg is responsible for sending the preliminary treatment of Frame, comprise pilot tone insertion, signaling territory formation and select pre-coding matrix according to feedback information, the recipient mainly realizes channel estimating, reduce feedback algorithm according to time domain calculates the needs feedack and transmits precoding information to transmit leg.

For ease of understanding, the below is elaborated, and sees also Fig. 4, and feedback quantity control method the second embodiment comprises in the embodiment of the invention:

401, receive the Frame that transmit leg sends;

Consistent in the process of concrete system initialization and the previous embodiment, repeat no more in the present embodiment, namely in the present embodiment directly the step with receiving data frames begin.

402, calculate the pre-coding matrix of each pilot tone virgin carrier wave;

The recipient calculates the pre-coding matrix of each subcarrier in this Frame after receiving the Frame that transmit leg sends, the process of the calculating pre-coding matrix of describing in concrete computational process and above-described embodiment is consistent, repeats no more herein.

403, obtain transfering state corresponding to pre-coding matrix;

In the system initialization process, the recipient calculates transition probability matrix, namely can know the possible transfering state of codeword information of the pre-coding matrix of current subcarrier, and namely which codeword information is current codeword information may be transferred to.

In the residing system of present embodiment, the variation of the pre-coding matrix on each subcarrier on time domain is modeled as the discrete time Markov chain of a finite state, its state J _nWith each the codeword information F in the code book _nCorresponding one by one.

An important parameter of Discrete Time Finite state Markov chain is exactly its transition probability matrix Pr (J _n=i|J _n=j), because code book is a quantification to pre-coding matrix, therefore is difficult to provide the closed expression of transition probability matrix, but can passes through Monte Carlo simulation, obtain the transition probability matrix of code book.See also Fig. 5, S1 to S6 is respectively different codeword information in the code book among Fig. 5, and as shown in Figure 5, codeword information only can be from a state transitions to fixing several states when state transitions, rather than all states.The S4 among Fig. 5 for example, namely might be transferred to S6 or S3, and can not be transferred to other codeword information, therefore, when time domain is fed back, because transmit leg is known the pre-coding matrix at previous pilot tone place, recipient and only need to be sent the codeword information of the state that previous code word state may shift, can reduce feedback quantity.

Be N such as the numeral number _BNamely 2 ^B, the possible transfering state number of a certain codeword information is T, reduces feedback algorithm as not adopting time domain, then feedback quantity is N _c* log ₂And after adopting this algorithm, feedback quantity becomes N (B), _c* log ₂(T), when the code book number is a lot, can effectively reduce feedback quantity.

404, obtain transfer codeword information corresponding to transfering state according to presetting rule;

In the present embodiment, the recipient need to feed back to transmit leg with the codeword information that current code word information may be transferred to, being the recipient determines all transfering states corresponding to pre-coding matrix of pilot tone virgin carrier wave according to described transition probability matrix, and inquires about codeword information corresponding to described transfering state according to described code word state classification code book.

The codeword information that the recipient can inquire these feeds back to transmit leg, be understandable that, in order further to reduce feedback quantity, can will obtain the codeword information transition probability, and a threshold value is set, only transition probability is fed back to transmit leg greater than the codeword information of this threshold value;

When transfering state is many, in order further to reduce feedback quantity, can also classify to codeword information, for the large codeword information of transition probability according to the Huffman mode, adopt less bit to encode, according to the Huffman mode, adopt more bit to encode for the little codeword information of transition probability, then when transfering state is more, can also further improve the effect that reduces feedback.

405, described transfer codeword information is fed back to transmit leg;

The recipient feeds back to transmit leg with the transfer codeword information of determining after having determined the transfer codeword information.

406, transmit leg carry out that data are processed and transmission processing after data.

After the step 406, because the recipient has calculated the pre-coding matrix of all subcarriers, then transmit leg can be known the pre-coding matrix on all subcarriers, after the data field data in these pre-coding matrixes and the Frame are multiplied each other, the data after these precodings is sent to the recipient.

The recipient receives after the data, owing to calculated the pre-coding matrix of all subcarriers, thus can data be carried out ZF or least mean-square error detects to receiving, thus recover initial data.

The below reduces feedback system to time domain and carries out integral body introduction:

During system initialization, transmit leg sends a plurality of pilot frequency sequences continuously, the recipient obtains channel information on a plurality of time points according to these pilot frequency sequences, these information are carried out statistical analysis, can obtain the transition probability matrix of code book, and this transition probability matrix by to transmit leg, know probability transfer matrix after, transmitting-receiving two-end constructs the code book by the state classification of previous moment code word.

When beginning to transmit data, transmit leg consists of the Frame that comprises pilot frequency sequence, signaling territory and data field with bit rate to be sent, and each Frame is comprised of Δ T OFDM symbol.

After the recipient receives frequency pilot sign and signaling information, estimate the channel information of each subcarrier by channel estimating, if current transmission is first Frame, because it does not have the codeword information of previous moment, then do not adopt time domain to reduce feedback algorithm, and adopt traditional time-frequency unity feedback algorithm; If the current time transmission is not first Frame, the recipient is according to code word state classification code book, calculate the pre-coding matrix codeword information on each subcarrier, and obtain the transfer codeword information of these codeword information, will shift codeword information and feed back to transmit leg.

If feedback channel is zero defect and delay, after transmit leg is received feedback information, from code book, find out the pre-coding matrix on each subcarrier, after multiplying each other with data field data in the Frame, send data after these precodings to the recipient.

The recipient then can carry out ZF or least mean-square error detection to receiving data owing to channel information and the pre-coding matrix known on each subcarrier, recovers initial data.

In the embodiment of the invention because channel has correlation in time domain, so code word when time domain is carried out state transitions from a state transitions to fixing several states, rather than all states.The recipient is after receiving Frame in the embodiment of the invention, determine the pre-coding matrix of each pilot tone virgin carrier wave in the described Frame, obtain transfer codeword information corresponding to described pre-coding matrix according to the code word state classification code book that presets, feed back described transfer codeword information to transmit leg, therefore do not need to feed back the codeword information of all transfering states, thereby can reduce the system feedback amount.

See also Fig. 6, the communication system embodiment in the embodiment of the invention comprises:

Transmit leg 601 and recipient 602,

Described transmit leg 601 is used for sending Frame to described recipient 602, receives the transfer codeword information of feedback;

Described recipient 602 is used for receiving the Frame that described transmit leg 601 sends, determine the pre-coding matrix of each pilot tone virgin carrier wave in the described Frame, obtain transfer codeword information corresponding to described pre-coding matrix according to the code word state classification code book that presets, to the described transfer codeword information of described transmit leg 601 feedbacks.

In the present embodiment, described transmit leg 601 also is used for sending the OFDM symbol that comprises pilot frequency sequence to described recipient 602, codeword information according to feedback is inquired about corresponding pre-coding matrix at described code word state classification code book, go out pre-coding matrix on the non-pilot sub-carrier to know the pre-coding matrix of all subcarriers according to described pre-coding matrix interpolation, the pre-coding matrix of described all subcarriers and data in the data field that presets are multiplied each other obtains pre-code data, sends described pre-code data to recipient 602;

Described recipient 602 also is used for receiving the OFDM symbol that transmit leg 601 sends, obtain the channel estimation value at pilot tone place according to the pilot frequency sequence in the described OFDM symbol, obtain the pre-coding matrix of described pilot tone virgin's carrier wave according to described estimated value, the codeword information of the described pre-coding matrix of inquiry in described code word state classification code book is to the described codeword information of described transmit leg 601 feedbacks.

See also Fig. 7, transfer of data network element the first embodiment in the embodiment of the invention comprises:

Transmitting element 701 is used for sending Frame and OFDM symbol;

Codeword information receiving element 702 is used for receiving codeword information after transmitting element 701 has sent Frame or OFDM symbol;

Query unit 703 is used for pre-coding matrix corresponding to code word state classification code book inquiry that is presetting according to the described codeword information that receives;

Pre-coding matrix processing unit 704 is used for going out pre-coding matrix on the non-pilot sub-carrier to know the pre-coding matrix of all subcarriers according to the described pre-coding matrix interpolation that inquires.

Transfer of data network element in the present embodiment also comprises:

Data processing unit 705 is used for pre-coding matrix that will described all subcarriers and the data of the data field that presets multiply each other and obtain pre-code data, sends described pre-code data.

The transfer of data network element of describing in above-described embodiment can be used as the transmit leg among the preceding method embodiment.

See also Fig. 8, transfer of data network element the second embodiment comprises in the embodiment of the invention:

Frequency domain feedback control unit 801, be used for receiving the OFDM symbol, obtain the channel estimation value at pilot tone place according to the pilot frequency sequence in the described OFDM symbol, obtain the pre-coding matrix of described pilot tone virgin's carrier wave according to described estimated value, the codeword information of the described pre-coding matrix of inquiry in described code word state classification code book;

Time domain feedback control unit 803 is used for receiving data frames, determines the pre-coding matrix of each pilot tone virgin carrier wave in the described Frame, obtains transfer codeword information corresponding to described pre-coding matrix according to the code word state classification code book that presets;

Feedback unit 802 is used for feeding back the transfer codeword information that codeword information that described frequency domain feedback control unit 801 obtains and described time domain feedback control unit 803 obtain to transmit leg.

The transfer of data network element of describing in above-described embodiment can be used as the recipient among the preceding method embodiment.

One of ordinary skill in the art will appreciate that all or part of step that realizes in above-described embodiment method is to come the relevant hardware of instruction to finish by program, described program can be stored in a kind of computer-readable recording medium, this program comprises the steps: when carrying out

Receive the Frame that transmit leg sends;

Determine the pre-coding matrix of each pilot tone virgin carrier wave in the described Frame;

Obtain transfer codeword information corresponding to described pre-coding matrix according to the code word state classification code book that presets;

Feed back described transfer codeword information to described transmit leg.

The above-mentioned storage medium of mentioning can be read-only memory, disk or CD etc.

More than a kind of feedback quantity control method provided by the present invention and communication system and relevant device are described in detail, for one of ordinary skill in the art, thought according to the embodiment of the invention, all will change in specific embodiments and applications, in sum, this description should not be construed as limitation of the present invention.

Claims (11)

1. a feedback quantity control method is characterized in that, comprising:

Receive the Frame that transmit leg sends;

Determine the pre-coding matrix of each pilot tone virgin carrier wave in the described Frame;

Obtain transfer codeword information corresponding to described pre-coding matrix according to the code word state classification code book that presets;

Feed back described transfer codeword information to described transmit leg;

Comprise before the step of the Frame that described reception transmit leg sends:

Receive at least two pilot frequency sequences that transmit leg sends;

Obtain channel information at least two corresponding time points according to described pilot frequency sequence;

Described channel information added up obtain transition probability matrix;

Make up code word state classification code book according to described transition probability matrix, send described transition probability matrix to described transmit leg.

2. method according to claim 1 is characterized in that, describedly comprises after described transmit leg sends the step of described transition probability matrix:

Transmit leg makes up code word state classification code book according to the transition probability matrix that receives.

3. method according to claim 1 and 2 is characterized in that, the step of the pre-coding matrix of each pilot tone virgin carrier wave comprises in described definite described Frame:

The recipient determines the pre-coding matrix at each pilot tone place in the described Frame according to minimization system error rate criterion and/or maximized system capacity criterion.

4. method according to claim 1 and 2 is characterized in that, the step that the code word state classification code book that described basis presets obtains transfer codeword information corresponding to described pre-coding matrix comprises:

The recipient determines all transfering states corresponding to pre-coding matrix of pilot tone virgin carrier wave according to described transition probability matrix;

Inquire about codeword information corresponding to described transfering state according to described code word state classification code book;

With described codeword information as shifting codeword information.

5. method according to claim 4 is characterized in that, describedly comprises before inquiring about the step of codeword information corresponding to described transfering state according to described code word state classification code book:

Obtain the transition probability of described all transfering states according to described transition probability matrix;

Described step of inquiring about codeword information corresponding to described transfering state according to described code word state classification code book comprises:

Determine that described all transfering state transition probabilities are more than or equal to the selected transfering state of the threshold value that presets;

Inquire about codeword information corresponding to described selected transfering state according to described code word state classification code book.

6. method according to claim 4 is characterized in that, describedly comprises before inquiring about the step of codeword information corresponding to described transfering state according to described code word state classification code book:

Obtain the transition probability of described all transfering states according to described transition probability matrix;

Described step of inquiring about codeword information corresponding to described transfering state according to described code word state classification code book comprises:

According to described transition probability all transfering states are divided into the first state class and the second state class, the mean transferred probability of described the first state class is greater than the mean transferred probability of described the second state class;

Adopt the huffman coding mode that described the first state class and described the second state class are encoded, the bit number that described the first state class coding is adopted is less than the bit number that described the second state class coding is adopted.

7. method according to claim 1 and 2 is characterized in that, described method also comprises:

Receive first orthogonal frequency division multiplex OFDM symbol that transmit leg sends;

Obtain the channel estimation value at pilot tone place according to the pilot frequency sequence in described first OFDM symbol;

Obtain the pre-coding matrix of described pilot tone virgin's carrier wave according to described estimated value;

The codeword information of the described pre-coding matrix of inquiry in described code word state classification code book;

Feed back described codeword information to described transmit leg.

8. method according to claim 7 is characterized in that, describedly comprises after described transmit leg feeds back the step of described codeword information:

Transmit leg is according to the pre-coding matrix of described codeword information in described code word state classification code book inquiry correspondence;

Go out pre-coding matrix on the non-pilot sub-carrier to know the pre-coding matrix of all subcarriers according to described pre-coding matrix interpolation;

The pre-coding matrix of described all subcarriers and data in the data field that presets are multiplied each other obtain pre-code data;

Send described pre-code data to the recipient.

9. a communication system is characterized in that, comprising:

Transmit leg and recipient,

Described transmit leg is used for sending Frame to described recipient, receives the transfer codeword information of feedback;

Described recipient is used for receiving the Frame that described transmit leg sends, determine the pre-coding matrix of each pilot tone virgin carrier wave in the described Frame, obtain transfer codeword information corresponding to described pre-coding matrix according to the code word state classification code book that presets, feed back described transfer codeword information to described transmit leg;

Described recipient also is used for receiving at least two pilot frequency sequences that transmit leg sends, obtain channel information at least two corresponding time points according to described pilot frequency sequence, described channel information added up obtain transition probability matrix, make up code word state classification code book according to described transition probability matrix, send described transition probability matrix to described transmit leg.

10. communication system according to claim 9 is characterized in that,

Described transmit leg also is used for sending the OFDM symbol that comprises pilot frequency sequence to described recipient, codeword information according to feedback is inquired about corresponding pre-coding matrix at described code word state classification code book, go out pre-coding matrix on the non-pilot sub-carrier to know the pre-coding matrix of all subcarriers according to described pre-coding matrix interpolation, the pre-coding matrix of described all subcarriers and data in the data field that presets are multiplied each other obtains pre-code data, sends described pre-code data to the recipient;

Described recipient also is used for receiving the OFDM symbol that transmit leg sends, obtain the channel estimation value at pilot tone place according to the pilot frequency sequence in the described OFDM symbol, obtain the pre-coding matrix of described pilot tone virgin's carrier wave according to described estimated value, the codeword information of the described pre-coding matrix of inquiry is fed back described codeword information to described transmit leg in described code word state classification code book.

11. a transfer of data network element is characterized in that, comprising:

The frequency domain feedback control unit, be used for receiving the OFDM symbol, obtain the channel estimation value at pilot tone place according to the pilot frequency sequence in the described OFDM symbol, obtain the pre-coding matrix of described pilot tone virgin's carrier wave according to described estimated value, the codeword information of the described pre-coding matrix of inquiry in described code word state classification code book;

The time domain feedback control unit is used for receiving data frames, determines the pre-coding matrix of each pilot tone virgin carrier wave in the described Frame, obtains transfer codeword information corresponding to described pre-coding matrix according to the code word state classification code book that presets;

Feedback unit is used for feeding back the transfer codeword information that codeword information that described frequency domain feedback control unit obtains and described time domain feedback control unit obtain to transmit leg.

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