CN101867553A - LTE system using time domain precoder and precoding method thereof - Google Patents

Abstract

The invention requests to protect a technology for improving bandwidth efficiency of an LTE system by utilizing a time domain precoder (TDP), relating to an LTE wireless communication technology which utilizes a matrix modulation and time domain precoding technology. The precoder utilizes the characteristic that a sending end of a TD-LTE system has known channel information to send a modulated matrix according to a channel information construction, and introduces a memory characteristic and symbol feedback on the basis to design a TDP precoding module. After the TDP precoding module is added in a TD-LTE link, CP is not needed to be sent in the system; and since the CP signal is not needed to be sent, the redundancy is eliminated, and the bandwidth efficiency is greatly improved. After a feedback channel is added, the precoder also can be applied in an FDD-LTE system to improve the bandwidth efficiency.

Description

A kind of LTE system and method for precoding that utilizes time domain precoder

Technical field

The present invention relates generally to wireless communication field, especially about the problem of the bandwidth efficiency of 3GPP LTE system.

Background technology

The LTE of 3GPP (Long Term Evolution, Long Term Evolution) project is the evolution of 3G, new technologies such as OFDM and MIMO have been adopted, improve and strengthened the aerial access technology of 3G such as comprising WCDMA and TD-SCDMA, the peak rate of descending 100Mbps, up 50Mbps can be provided under the 20MHz spectral bandwidth, improved the performance of Cell Edge User, improved cell capacity and reduce system delay.

For mobile communication system, when all being multipath usually, its employed wireless channel becomes fading channel, wireless multipath channel can make the signal by it multidiameter delay occur, if this multidiameter delay expands to next symbol, will cause intersymbol interference ISI, have a strong impact on the transmission quality of digital signal.At present, in the third generation mobile communication system (as the LTE system) based on OFDM, its solution is by inserting protection interval, i.e. Cyclic Prefix (CP) at input.Like this, both can effectively reduce intersymbol interference, linear convolution can be converted to circular convolution again, simplify the convolution algorithm of channel, can use simple single tap (1-Tap) equilibrium at receiving terminal.

In using Cyclic Prefix in OFDM System system (CP-OFDM), comprise IDFT, added cyclic prefix CP and string and changed three processes,

As everyone knows, wireless channel in the mobile communication is a time varying channel, insert at the ofdm system input that Cyclic Prefix (CP) effectively reduces intersymbol interference ISI and interchannel interference ICI is common way, the while can also be converted to circular convolution with linear convolution.But the length of CP generally all is greater than the maximum delay expansion of wireless channel, and this just means the sampling of having introduced L time domain, bandwidth efficiency just drops to (N)/(N+L), when L was big, the decline of bandwidth efficiency only was 80% such as the LTE system bandwidth efficient that adopts long CP clearly.

Problem for the bandwidth efficiency that solves the above-mentioned ofdm system that has used CP, the present invention is a kind of new precoding for ofdm system designs, utilize this precoding to replace CP, linear convolution can be transformed into the purpose of circular convolution, only need a simple single order (1-tap) equalizer at receiving terminal, just can eliminate ICI and ISI completely.Like this, do not need to send the CP signal, eliminated redundancy, bandwidth efficiency improves greatly.

Summary of the invention

Technical problem to be solved by this invention is, at existing OFDM wireless communication system when suppressing intersymbol interference, need the long Cyclic Prefix (CP) of transmission, cause the problem that reduces bandwidth efficiency, design a kind of LTE system that utilizes time domain precoder to improve bandwidth efficiency.

The technical scheme that the present invention solves the problems of the technologies described above is, increase precoding module at the ofdm system transmitting terminal, linear convolution is transformed into circular convolution, only needs a simple single order (1-tap) equalizer, just can eliminate ICI and ISI completely at receiving terminal.Like this, do not need to send the CP signal, eliminated redundancy, bandwidth efficiency improves greatly.Specifically comprise, utilize TD-LTE system transmitting terminal known channel information, make up the transmitting terminal modulation matrix, according to memory characteristic and symbol feedback, design TDP precoding module.In the TD-LTE link, increase the TDP precoding module, eliminate ICI and ISI, greatly improved the bandwidth usage efficient of TD-LTE system.

After increasing feedback channel, this precoding module also can be applied to the FDD-LTE system and improve bandwidth efficiency.

A kind of LTE system that utilizes time domain precoder to improve bandwidth efficiency, the element of resource mapping block is mapped to transmitting terminal data X (k) in each element of resource of Resource Block, inverse transform module is carried out inverse discrete Fourier transform to mapping (enum) data, obtain time-domain signal x (k), precoding module is carried out the time domain precoding to x (k), generate precoded signal q (k), parallel/serial modular converter is done parallel/serial conversion to signal q (k), obtain serial data stream, send to receiving terminal by channel, receiving terminal receives that data are that r (k) does serial/parallel conversion, the single order equalizer carries out the single order equilibrium to the parallel data stream y (k) that receives and obtains equalizing signal Y (k), and Fourier transformer recovers initial data to equalizing signal Y (k) as discrete Fourier transform (DFT)

Described precoding module q (k) comprises linear matrix modulating unit M _tWith delay cell, subtracter subtracts each other time-domain signal x (k) and the time domain precoded signal q (k) that is produced by the same moment by the resulting signal q of delay cell (k-1), by linear matrix modulating unit M _tModulate, obtain modulation signal M _t* (x (k)-q (k-1)) sends into adder with this modulation signal with time-domain signal x (k) and combines, and obtains precoded signal q (k).For a single aerial system, described linear matrix modulating unit M _tBe specially, according to the vectorial h=[h (0) of channel impulse response CIR, h (1) ..., h (L)] ^T, the vector matrix of setting up channel impulse response is C _hAnd C _t, according to vector matrix C _hAnd C _tMake up modulation matrix For multiaerial system, channel coefficient matrix is: H=[h ₁₁, h ₁₂h ₂₁, h ₂₂], decompose vector matrix C according to channel coefficient matrix _{H_ij}And C _{T_ij}, according to C _{H_ij}And C _{T_ij}Make up modulation matrix M _{T_ij}For:

The TDP precoding module satisfies: q _{_ ij}(k)=x _-j(k)+M _T-ij(x _{_ j}(k)-q _{_ ij}(k-1)),

Wherein, x _-j(k) signal on the expression transmitting antenna j.

The present invention also proposes to utilize in the LTE system time domain precoder to improve the method for bandwidth efficiency, specifically comprise, the element of resource mapping block is mapped to transmitting terminal data X (k) in each element of resource of Resource Block, inverse transform module is carried out inverse discrete Fourier transform to mapping (enum) data, obtain time-domain signal x (k), precoding module is carried out the time domain precoding to x (k), generate precoded signal q (k), parallel/serial modular converter is done parallel/serial conversion to signal q (k), obtain serial data stream, send to receiving terminal by channel, receiving terminal receives that data are that r (k) does serial/parallel conversion, the single order equalizer carries out the single order equilibrium to the parallel data stream y (k) that receives and obtains equalizing signal Y (k), and Fourier transformer recovers initial data to equalizing signal Y (k) as discrete Fourier transform (DFT)

A kind of TDP precoding module, q (k) comprises linear matrix modulating unit M _t, delay cell, subtracter, adder, time-domain signal x (k) and the time domain precoded signal q (k) that is produced by the same moment are subtracted each other by the resulting signal q of delay cell (k-1), by linear matrix modulating unit M _tModulate, obtain modulation signal M _t* (x (k)-q (k-1)) sends into adder with this modulation signal with time-domain signal x (k) and combines, and obtains precoded signal.

After increasing feedback channel, this precoding also can be applied to FDD-LTE system enhancement bandwidth efficiency.

Used the ofdm system of TDP precoding module, linear convolution can be transformed into circular convolution, the present invention is a kind of new precoding for ofdm system designs, utilize this precoding to replace CP, linear convolution can be transformed into the purpose of circular convolution,, eliminate ICI and ISI by in the TD-LTE link, increasing the TDP precoding module, only need a simple single order (1-tap) equalizer at receiving terminal, just can eliminate ICI and ISI completely.Like this, do not need to send the CP signal, eliminated redundancy, bandwidth efficiency improves greatly.

Description of drawings

Fig. 1 carries the ofdm system model (CP-OFDM) of CP

Fig. 2 adopts the Precoded-OFDM system model of TDP module

Fig. 3 TDP precoding module

Figure 42 * 2MIMO channel

Increase TDP precoding module schematic diagram in Fig. 5 TD-LTE link

Embodiment

Below by the drawings and specific embodiments enforcement of the present invention is further described in detail.

Carry the ofdm system model (CP-OFDM) of CP as shown in Figure 1.Suppose

The frequency domain symbol that after the Resource Unit mapping, generate, preparation is transmitted constantly at k, through after the IFFT, its length becomes N, and corresponding time-domain symbol is defined as:

$x\left(K\right)=F^H\stackrel{\‾}{X}\left(k\right)---\left(1\right)$

Wherein, F is the DFT matrix of N * N, and F is arranged ^H=F ^-1Represent the IDFT conversion.

Known for the TDD system channel impulse response coefficient (CIR) that uses the principle of reciprocity at transmitting terminal, the CIR representative be the decline that signal is produced during through channel, embodiment be channel to effect that signal produced.

Suppose that CIR length is L+1, and N＞L+1.After the IDFT, add CP in each symbol front, CP is the repetition of the last L of this symbol sampling.If h=[h (0), h (1) ..., h (L)] ^TBe the vector of CIR, define the Matrix C of two N * N according to the vector of CIR _hAnd C _tFor:

The symbol that carries CP transmits in channel, and the signal that receives can be expressed as after a preceding L sampled signal is banned:

y(k)＝C _px(k)+n(k) (4)

Here, n (k) is a white Gaussian noise, and C _p=C _t+ C _hC _pBe the circular matrix of a N * N, what this means that signal and channel carry out is circular convolution rather than linear convolution.When carried out the DFT operation at receiving terminal after, the frequency domain symbol that obtains is:

$\stackrel{\‾}{Y}\left(k\right)=\mathrm{Fy}\left(k\right)=F{C}_p{F}^H\stackrel{\‾}{X}\left(k\right)+\mathrm{Fn}\left(k\right)---\left(5\right)$

Can obtain: ${\mathrm{FC}}_p{F}^H=\stackrel{\‾}{S}---\left(6\right)$

Wherein, Be S=diag (H (1), H (2) ..., H (N)) conjugation symmetry expansion, H (1), H (2) ..., H (N) represents estimated channel frequency response on sub-carrier frequencies.In (6) generation, entered (5), under muting situation:

X(k)＝S ^-1Y(k) (7)

Only need a simple single order (1-tap) equalizer at receiving terminal, just can eliminate ICI fully, and as long as the length of the cyclic prefix CP between the adjacent OFDM symbol more than or equal to the length of channel impulse response, just can overcome ISI fully.

Because do not have CP in the native system, receiving terminal at the signal that k receives constantly is:

y(k)＝C _tx(k)+C _hx(k-1)+n(k) (8)

Like this, signal and channel be actual, and what carry out is linear convolution, and linear convolution will produce ICI and ISI in the signal that receives, and is difficult to eliminate.For ICI and the ISI that produces in the erasure signal, and linear convolution is transformed into circular convolution, adopts the time domain precoding in the ofdm system (brief note is Precoded-OFDM, i.e. NCP-OFDM).

Signal after the conversion of overfrequency-time is carried out precoding processing, precoding module (brief note is TDP) promptly is set after the IDFT of ofdm system module and before the serial to parallel conversion, belong to the precoding of time domain.Be illustrated in figure 2 as the Precoded-OFDM system model that adopts the TDP module.

Transmitting terminal data X (k) through the element of resource mapping block with data map (frequency pilot sign occupied element of resource except) in each element of resource of Resource Block, with mapping (enum) data process fast discrete inverse Fourier transform IDFT, obtain time-domain signal x (k), precoding module is carried out the time domain precoding to x (k), generate precoded signal q (k), parallel/serial modular converter is done parallel/serial conversion to signal q (k), data after precoding in the Resource Block can be become the data flow of one row serial, data flow is through channel, increase noise n (k), receiving terminal receives that data are r (k).

Serial/parallel modular converter is done serial/parallel conversion to the data that receive.Serial data stream r (k) is become parallel data stream y (k), the single order equalizer carries out the single order equilibrium to the parallel data stream y (k) that receives and obtains equalizing signal Y (k), and discrete Fourier transformer is made discrete Fourier transform (DFT) DFT to equalizing signal Y (k) can recover original data

For a single aerial system, suppose the channel of the TDD system of the known TD-LTE of transmitting terminal, the vector that obtains channel impulse response CIR is h=[h (0), h (1) ..., h (L)] ^T, the vector matrix of calling formula (2) and (3) acquisition channel impulse response coefficient CIR is C _hAnd C _tBased on ISI that offsets the channel introducing to greatest extent and the principle of ICI, according to the vector matrix C of CIR _hAnd C _tMake up modulation matrix M as follows _t,

$M_t=C_t^{*}{C}_h=C_t^H{\left(C_t{C}_t^H\right)}^{-1}{C}_h---\left(9\right)$

This M _tBe N * N matrix, * represents C _tThe Moore-Penrose pseudoinverse, subscript H is the conjugate transpose of matrix.

Be illustrated in figure 3 as one of mode of structure TDP precoding module of the present invention, based on the principle of simplifying most, this TDP precoding module comprises a linear matrix modulation M _tUnit and delay cell constitute by the linear matrix modulating unit is in parallel with delay cell.

Time-domain signal x (k) by fast discrete inverse Fourier transform IDFT generation, this time-domain signal x (k) and the time domain precoded signal q (k) that is produced by its same moment subtract each other by the resulting signal q of delay cell (k-1), will subtract each other the gained signal then by linear matrix modulating unit M _tModulate, obtain modulation signal M _t* (x (k)-q (k-1)) sends into adder with this modulation signal with time-domain signal x (k) that original IDFT is produced and combines, and can obtain the signal q (k) that generated by time domain precoder TDP,

That is: q (k)=x (k)+M _t* (x (k)-q (k-1)) (10)

Wherein, x (k) is the signal of transmitting terminal, M _tFor sending modulation matrix, q (k-1), q (k) are the data through two adjacent moment that generate after the time domain precoding.

Behind receiving terminal, the received signal of Precoded-OFDM system receiving terminal is the signal q (k) of process time domain precoder TDP through Channel Transmission:

y(k)＝C _tq(k)+C _hq(k-1)+n(k) (11)

Wherein, n (k) is the white Gaussian noise of channel generation.

Formula (9) and (10) generation are advanced (11) formula, can obtain:

$y\left(k\right)=C_t*\{x\left(k\right)+C_t^H{\left(C_t{C}_t^H\right)}^{-1}{C}_h*(x\left(k\right)-q(k-1))\}+C_h*q(k-1)+n\left(k\right)$

$=C_t*x\left(k\right)+C_h*x\left(k\right)-C_h*q(k-1)+C_h*q(k-1)+n\left(k\right)---\left(12\right)$

$=C_p*x\left(k\right)+n\left(k\right)$

From following formula as can be known, the signal of time domain precoding will have been carried out

Transmit by channel, this moment, channel signal was:

Be channel to the effect of signal be linear convolution.But, using after the time domain precoding, linear convolution has been transformed into circular convolution, i.e. y (k)=C _p* x (k)+n (k) is because C _p=C _t+ C _hBe the circular matrix of a N * N, can learn by formula (2) and formula (3) addition.This means with after the TDP module replacement CP module, eliminated the ICI and the ISI that produce in the signal fully, only need use a simple single order equilibrium (1-Tap) just original signal can be recovered out at receiving terminal.Owing in this time domain pre-coding scheme, do not use CP, thus in the system without any redundancy, also just without any bandwidth loss, thereby improved bandwidth usage efficient.

Can adopt linear predictive coding and nonlinear precoding that modulation signal is carried out precoding processing, as adopting ZF preequalization (TxZF) and the least mean-square error preequalization (TxMMSE) in the linear predictive coding

The ZF preequalization is under the ZF situation, and it is emitted as accordingly: x=Fc, and F=β H is arranged ^-1Obtain at receiving terminal

β satisfies transmit power constraint according to formula (3.4).That is: $\mathrm{\β}=\sqrt{\frac{1}{\mathrm{Tr}\left(H^{-1}{H}^{-H}\right)}}$

This β value realizes by automatic gain control mechanism at receiver end.For some more abominable H, it is very little that the β value can be selected, and this is equivalent to lower SNR.

Least mean-square error preequalization (TxMMSE)

Adopted least mean-square error (MMSE) criterion when determining modulation matrix, transmitting filter satisfies certain power constraints:

$\mathrm{\β}=\sqrt{\frac{1}{\mathrm{trace}\left(\stackrel{\‾}{F}{\stackrel{\‾}{F}}^H\right)}}$

The MMSE preequalization can reduce transmitted power with respect to the ZF preequalization.

Nonlinear precoding can adopt THP precoding and grid precoding (Trellis precoding).

The THP precoding is a kind of method for precoding at the equalization problem of the intersymbol interference (ISI) in the SISO channel of serious linear distortion.Before signal transmits, it is carried out equilibrium.But the TH precoding needs transmitting terminal to know the characteristic of channel.The grid precoding is carried out albefaction at the equalizer output to noise, and this pattern combines coding, precoding, and coding shaping and grid pattern, but the grid precoding technique equally not too is fit to frequency selective fading channels.

In order to adapt to the LTE system, for multiaerial system, below in conjunction with at mimo channel enforcement of the present invention being further specified, this system is the MIMO-Precoded-OFDM system.

For general LTE system, the TDP precoding module is placed fast discrete Fourier transform module (IDFT module) afterwards usually, the time-domain signal that produces after the IDFT is operated.

As shown in Figure 3, the TDP precoding module only needs a linear matrix modulation M _tUnit and delay cell.

Arranging according to matrix (2) and matrix (3), make up modulation matrix according to formula (9) again at the known channel impulse response coefficient CIR of transmitting terminal:

For do not eliminate by modulation matrix because channel carries out ISI and the ICI that linear convolution brought to signal, according to memory characteristic and symbol feedback, make up time domain precoding TDP module.Then, by channel,, make the former linear convolution that carries out of channel convert circular convolution to coded signal owing to adopted time domain precoding algorithm because there is not any redundancy, so the bandwidth efficiency of system without any loss.

Simple for describing, selecting 2 * 2MIMO channel as shown in Figure 4 is that example further specifies H _Ij(j=1,2 represent transmitting antenna; I=1,2 represent reception antenna) expression be channel status between a pair of dual-mode antenna.As everyone knows, the mimo channel for 2 * 2, its channel coefficient matrix can be expressed as: H=[h ₁₁, h ₁₂h ₂₁, h ₂₂].The transmitting antenna j that each footnote i j represents to be is to the channel status between the reception antenna i.Therefore, according to channel coefficient matrix H, can decomposite four similar matrix: C _{T_11}, C _{T_12}, C _{T_21}, C _{T_22}, C _{H_11}, C _{H_12}, C _{H_21}, C _{H_22}Each Matrix C _{H_ij}And C _{T_ij}(i=1,2; J=1,2) all construct Matrix C according to formula (2) and formula (3) _{H_ij}And C _{T_ij}In each element all take from the corresponding element h of channel coefficient matrix H _Ij

According to C _{T_ij}Make up modulation matrix M _{T_ij}As follows:

$M_{t\_\mathrm{ij}}=C_{t\_\mathrm{ij}}^H{\left(C_{t\_\mathrm{ij}}{C}_{t\_\mathrm{ij}}^H\right)}^{-1}{C}_{h\_\mathrm{ij}},(i=\mathrm{1,2};j=\mathrm{1,2})---\left(13\right)$

Corresponding TDP precoding module satisfies:

q _{_ij}(k)＝x _-j(k)+M _t-ij(x _{_j}(k)-q _{_ij}(k-1)) (i＝1，2；j＝1，2) (14)

Wherein, x _-j(k) (j=1,2) expression is signal on the transmitting antenna j.

The TDP precoding module is modulated to the data of reception antenna i transmitting antenna j according to formula (14), generates precoded signal q _{_ ij}(k).

Each root reception antenna receives all is data from two transmitting antennas, knows that by formula (11) data on the reception antenna 1 are:

y _{_1}(k)＝C _{t_11}q _-11(k)+C _{h_11}q _-11(k-1)+C _{t_12}q _-12(k)+C _{h_12}q _-12(k-1)+n _{_1}(k) (15)

Wherein, q _{_ 11}(k-1), q _{_ 11}(k) signal of two adjacent moment of having carried out the time domain precoding that are transmitting antenna 1 to the reception antenna 1 of expression,

q _{_ 12}(k-1), q _{_ 12}(k) signal of two adjacent moment of having carried out the time domain precoding that are transmitting antenna 2 to the reception antenna 1 of expression, n _{_ 1}(k) noise of expression reception antenna 1.

Corresponding parameters in substitution (13) and (14) formula:

y _{_1}(k)＝C _{t_11}x _-1(k)+C _{h_11}x _-1(k)+C _{t_12}x _-2(k)+C _{h_12}x _-2(k)+n _{_1}(k)

y _{_1}(k)＝(C _{p_11}) ^-1*C _{p_11}x _-1(k)+(C _{p_12}) ^-1C _{p_12}x _-2(k)+n _{_1}(k)＝x _-1(k)+x _-2(k)+n _{_1}(k)

(16)

Wherein, C _{P_11}=C _{T_11}+ C _{H_11}, C _{P_12}=C _{T_12}+ C _{H_12}

For the MIMO-Precoded-OFDM system, the received signal of receiving terminal is equivalent to the Precoded-OFDM system and has carried out vertical demixing time space, utilizes serial interference feedback canceller method, can recover original signal x _{_ 1}(k) and x _-2(k).

That is, as the formula (16), with signal received on the reception antenna

y _{_ 1}(k)=C _{P_11}x _-1(k)+C _{P_21}x _-2(k)+n _{_ 1}(k) by the single order equilibrium, multiply by Matrix C respectively _{P_11}And C _{P_21}Contrary, the signal that can obtain on the reception antenna 1 is:

y _{_1}(k)＝(C _{p_11}) ^-1*C _{p_11}x _-1(k)+(C _{p_21}) ^-1C _{p_21}x _-2(k)+n _{_1}(k)＝x _-1(k)+x _-2(k)+n _{_1}(k)。

Under muting situation, the data on the reception antenna 1 can be recovered completely.

Data on the reception antenna 2 and reception antenna 1 are identical, repeat no more here.

Implementation result is relatively analyzed in the emulation of our through performance and bandwidth efficiency.

The LTE system constructing that utilizes time domain precoder as shown in Figure 5, the transmitting terminal code word is at first passed through scrambling module, and code word is combined with specific scramble sequence, produces new scrambling bit stream, passes through modulation module then.What the LTE down link adopted is the QPSK modulation.The data of modulation module input are the binary system Serial No.s of scrambling bit, and the QPSK modulation is divided into one group to per two bits in the sequence of binary digits, has four kinds of combinations, promptly 00,01,10,11, and wherein each group is called dibit elements.Each modulation can be transmitted 2 information bits, and these information bits are to transmit by four kinds of phase places of carrier wave.Demodulator is judged the information bit that transmitting terminal sends according to the phase place of planisphere and the carrier signal that receives.After modulation is finished, through layer mapping, the symbol of odd number all is mapped on the ground floor, the symbol of even number all is mapped on the second layer.Again through the element of resource mapping, transmitting terminal data X (k) is mapped in each element of resource of Resource Block (frequency pilot sign occupied element of resource except), obtain time-domain signal x (k) through fast discrete inverse Fourier transform IDFT then, by x (k) is carried out the time domain precoding, produce q (k) signal.

In the TD-LTE down link, increase the TDP precoding module newly, removed the functional module that increases cyclic prefix CP simultaneously, channel adopts 7 footpath channel models, and each footpath whose amplitude obeys rayleigh distributed, channel width is 1.6MHz, adopt 128 FFT in the system, in 7 sampling intervals of circulating prefix-length, binary data stream is adopted the QPSK modulation system.Utilize block pilot frequency mode, and the channel response of hypothesis pilot frame estimates accurately, carry out channel estimating in time domain employing linear interpolation mode, and the errored bit performance of system is compared.

The main mechanism of time domain precoding module is as follows:

Be ISI and the ICI that linear convolution is introduced in order to offset channel, the design modulation matrix

C wherein _hAnd C _tShown in (2) and formula (3), M _tBe N * N matrix, * represents C _tThe Moore-Penrose pseudoinverse, subscript H is the conjugate transpose of matrix.On this basis, introduce memory characteristic and symbol feedback, design TDP precoding module.Its input/output relation satisfies: q (k)=x (k)+M _t(x (k)-q (k-1)) so far realized the purpose that signal x (k) is carried out the time domain precoding.

Parallel/serial transducer becomes the data in the Resource Block data flow of one row serial.Then these data flow are launched from antenna separately.

In the TD-LTE system, use the CP (being designated as normal CP) of normal length and the CP of extension length (be designated as and expand CP), and do not use CP and use the MIMO-Precoded-OFDM system of TDP precoding, system bandwidth efficient is compared.Though use the system of extension length CP can obtain error performance preferably; but because the protection sampled signal of inserting is too many; with respect to the system that uses normal length CP and the system that uses TDP Comparatively speaking bandwidth efficiency has bigger decline, only is 80%.Because it does not need to use CP, the TDP system can realize the maximization of bandwidth efficiency, and the system bandwidth efficient of using normal length CP is between between the two, but 10% the loss of also having an appointment.

Claims (9)

1. LTE system that utilizes time domain precoder to improve bandwidth efficiency, it is characterized in that, the element of resource mapping block is mapped to transmitting terminal data X (k) in each element of resource of Resource Block, inverse transform module is carried out inverse discrete Fourier transform to mapping (enum) data, obtain time-domain signal x (k), precoding module is carried out the time domain precoding to x (k), generate precoded signal q (k), parallel/serial modular converter is done parallel/serial conversion to signal q (k), obtain serial data stream, send to receiving terminal by channel, receiving terminal receives that data are that r (k) does serial/parallel conversion, the single order equalizer carries out the single order equilibrium to the parallel data stream y (k) that receives and obtains equalizing signal Y (k), and Fourier transformer recovers initial data to equalizing signal Y (k) as discrete Fourier transform (DFT)

2. according to the described LTE of right 1 system, it is characterized in that described precoding module q (k) comprises linear matrix modulating unit M _tWith delay cell, subtracter subtracts each other time-domain signal x (k) and the time domain precoded signal q (k) that is produced by the same moment by the resulting signal q of delay cell (k-1), by linear matrix modulating unit M _tModulate, obtain modulation signal M _t* (x (k)-q (k-1)) sends into adder with this modulation signal with time-domain signal x (k) and combines, and obtains precoded signal q (k).

3. according to the described LTE of right 2 system, it is characterized in that, for a single aerial system, described linear matrix modulating unit M _tBe specially, according to the vectorial h=[h (0) of channel impulse response CIR, h (1) ..., h (L)] ^T, the vector matrix of setting up channel impulse response is C _hAnd C _t, according to vector matrix C _hAnd C _tMake up modulation matrix $M_t=C_t^{*}{C}_h=C_t^H{\left(C_t{C}_t^H\right)}^{-1}{C}_h.$

4. according to the described LTE of right 2 system, it is characterized in that for multiaerial system, channel coefficient matrix is: H=[h ₁₁, h ₁₂h ₂₁, h ₂₂], decompose vector matrix C according to channel coefficient matrix _{H_ij}And C _{T_ij}, according to C _{H_ij}And C _{T_ij}Make up modulation matrix M _{T_ij}For:

The TDP precoding module satisfies: q _{_ ij}(k)=x _-j(k)+M _T-ij(x _{_ j}(k)-q _{_ ij}(k-1)),

Wherein, x _-j(k) signal on the expression transmitting antenna j.

5.LTE utilize time domain precoder to improve the method for bandwidth efficiency in the system, it is characterized in that, the element of resource mapping block is mapped to transmitting terminal data X (k) in each element of resource of Resource Block, inverse transform module is carried out inverse discrete Fourier transform to mapping (enum) data, obtain time-domain signal x (k), precoding module is carried out the time domain precoding to x (k), generate precoded signal q (k), parallel/serial modular converter is done parallel/serial conversion to signal q (k), obtain serial data stream, send to receiving terminal by channel, receiving terminal receives that data are that r (k) does serial/parallel conversion, the single order equalizer carries out the single order equilibrium to the parallel data stream y (k) that receives and obtains equalizing signal Y (k), and Fourier transformer recovers initial data to equalizing signal Y (k) as discrete Fourier transform (DFT)

6. method according to claim 5 is characterized in that, described precoding module q (k) comprises linear matrix modulating unit M _tWith delay cell, subtracter subtracts each other time-domain signal x (k) and the time domain precoded signal q (k) that is produced by the same moment by the resulting signal q of delay cell (k-1), by linear matrix modulating unit M _tModulate, obtain modulation signal M _t* (x (k)-q (k-1)) sends into adder with this modulation signal with time-domain signal x (k) and combines, and obtains precoded signal q (k).

7. method according to claim 6 is characterized in that, for a single aerial system, and described linear matrix modulating unit M _tBe specially, according to the vectorial h=[h (0) of channel impulse response CIR, h (1) ..., h (L)] ^T, the vector matrix of setting up channel impulse response is C _hAnd C _t, according to vector matrix C _hAnd C _tMake up modulation matrix $M_t=C_t^{*}{C}_h=C_t^H{\left(C_t{C}_t^H\right)}^{-1}{C}_h.$

8. method according to claim 6 is characterized in that, for a single aerial system, for multiaerial system, channel coefficient matrix is: H=[h ₁₁, h ₁₂h ₂₁, h ₂₂], decompose vector matrix C according to channel coefficient matrix _{H_ij}And C _{T_ij}, according to C _{H_ij}And C _{T_ij}Make up modulation matrix M _{T_ij}For:

Precoding module satisfies: q _{_ ij}(k)=x _-j(k)+M _T-ij(x _{_ j}(k)-q _{_ ij}(k-1)), wherein, x _-j(k) signal on the expression transmitting antenna j.

9. a TDP precoding module is characterized in that, described precoding module comprises linear matrix modulating unit M _t, delay cell, subtracter, adder, subtracter subtracts each other time-domain signal x (k) and the time domain precoded signal q (k) that is produced by the same moment by the resulting signal q of delay cell (k-1), the signal after subtracting each other passes through linear matrix modulating unit M _tModulate, obtain modulation signal M _t* (x (k)-q (k-1)) sends into adder with this modulation signal with time-domain signal x (k) and combines, and obtains precoded signal.

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