CN101867553B - 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, the 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, can provide the peak rate of descending 100Mbps, up 50Mbps 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 wireless channel used becomes fading channel, wireless multipath channel can make multidiameter delay to occur by its signal, 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 based on OFDM (as the LTE system), its solution is to protect interval at input by insertion, i.e. Cyclic Prefix (CP).Like this, both can effectively reduce intersymbol interference, linear convolution can be converted to circular convolution again, simplify the convolution algorithm of channel, at receiving terminal, can use simple single tap (1-Tap) equilibrium.

In the ofdm system (CP-OFDM) that uses Cyclic Prefix, comprise IDFT, added cyclic prefix CP and string and changed three processes,

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

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 to the purpose of circular convolution, only need a simple single order (1-tap) equalizer at receiving terminal, just can eliminate completely ICI and ISI.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, for existing OFDM wireless communication system when suppressing intersymbol interference, need the longer Cyclic Prefix (CP) of transmission, cause the problem that reduces bandwidth efficiency, design a kind of LTE system of utilizing 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 to circular convolution, at receiving terminal, only needs a simple single order (1-tap) equalizer, just can eliminate completely ICI and ISI.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, build the transmitting terminal modulation matrix, according to memory characteristic and symbol feedback, design TDP precoding module.Increase the TDP precoding module in the TD-LTE link, eliminate ICI and ISI, greatly improved the bandwidth usage efficiency 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 of utilizing 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) received and obtains equalizing signal Y (k), 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) produced by the same moment by the resulting signal q of delay cell (k-1), by linear matrix modulating unit M _tmodulated, obtained modulation signal M _t* (x (k)-q (k-1)), send into adder by this modulation signal with time-domain signal x (k) and combine, 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 _tbuild modulation matrix

for multiaerial system, channel coefficient matrix is: H=[h ₁₁, h ₁₂; h 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}build modulation matrix M _{t_ij}for:

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

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

The present invention also proposes in the LTE system to utilize 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) received and obtains equalizing signal Y (k), 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) 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 _tmodulated, obtained modulation signal M _t* (x (k)-q (k-1)), send into adder by this modulation signal with time-domain signal x (k) and combine, 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 to 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 to the purpose of circular convolution, by increase the TDP precoding module in the TD-LTE link, eliminate ICI and ISI, only need a simple single order (1-tap) equalizer at receiving terminal, just can eliminate completely ICI and ISI.Like this, do not need to send the CP signal, eliminated redundancy, bandwidth efficiency improves greatly.

The accompanying drawing explanation

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

generate, prepare the frequency domain symbol constantly transmitted at k after resource unit mapping, through after 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 at transmitting terminal for the TDD system channel impulse response coefficient (CIR) that uses the principle of reciprocity, the CIR representative be the decline that signal produces during through channel, embodiment be the effect that channel produces signal.

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

The symbol that carries CP is transmitted in channel, and the signal received, after a front L sampled signal is banned, can be expressed as:

y(k)＝C _px(k)+n(k) (4)

Here, n (k) is white Gaussian noise, and C _p=C _t+ C _h.C _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 obtained 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)) the conjugation symmetric extension, H (1), H (2) ..., the channel frequency response that H (N) representative is estimated on sub-carrier frequencies.In (6) generation, entered to (5), in 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 adjacent OFDM symbol is more than or equal to the length of channel impulse response, just can overcome ISI fully.

Because the signal that does not have CP, receiving terminal constantly to receive at k in native system 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 received, and is difficult to eliminate.For ICI and the ISI produced in erasure signal, and linear convolution is transformed into to circular convolution, in ofdm system (brief note is Precoded-OFDM, i.e. NCP-OFDM), adopts the time domain precoding.

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

Transmitting terminal data X (k) through the element of resource mapping block by data-mapping in each element of resource of Resource Block (frequency pilot sign occupied element of resource except), by 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 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 to parallel data stream y (k), the single order equalizer carries out the single order equilibrium to the parallel data stream y (k) received 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 _t.ISI based on offsetting to greatest extent the channel introducing and the principle of ICI, according to the vector matrix C of CIR _hand C _tbuild 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, * means C _tthe Moore-Penrose pseudoinverse, the conjugate transpose that subscript H is matrix.

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

The time-domain signal x (k) produced by fast discrete inverse Fourier transform IDFT, this time-domain signal x (k) and the time domain precoded signal q (k) produced by its same moment subtract each other by the resulting signal q of delay cell (k-1), then will subtract each other the gained signal by linear matrix modulating unit M _tmodulated, obtained modulation signal M _t* (x (k)-q (k-1)), the time-domain signal x (k) that this modulation signal is produced with original IDFT sends into adder and combines, and can obtain the signal q (k) 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) is the data of two adjacent moment through generating after the time domain precoding.

Through the signal q (k) of time domain precoder TDP through transmission after receiving terminal, the reception signal of Precoded-OFDM system receiving terminal is:

y(k)＝C _tq(k)+C _hq(k-1)+n(k) (11)

Wherein, the white Gaussian noise that n (k) produces for channel.

Formula (9) and (10) generation are advanced to (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 above formula, the signal of time domain precoding will have been carried out

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

Can adopt linear predictive coding and nonlinear precoding to carry out precoding processing to modulation signal, as adopted ZF preequalization (TxZF) and the least mean-square error preequalization (TxMMSE) in linear predictive coding

The ZF preequalization is in the ZF situation, and it is emitted as accordingly: x=Fc, and F=β H is arranged ^-1.At receiving terminal, obtain

β, according to formula (3.4), meets transmit power constraint.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.More severe H for some, 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 while determining modulation matrix, transmitting filter meets certain power constraint condition:

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

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

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

The THP precoding is a kind of method for precoding for the equalization problem of the intersymbol interference (ISI) in the SISO channel of serious linear distortion.Before signal transmits, it is carried out to equilibrium.But the TH precoding needs transmitting terminal to know the characteristic of channel.Trellis precoding carries out albefaction at the equalizer output to noise, and this pattern combines coding, precoding, and coding shaping and grid pattern, but the trellis precoding technology equally not too is applicable 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 illustrated, this system is the MIMO-Precoded-OFDM system.

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

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

The channel impulse response coefficient CIR known at transmitting terminal arranged according to matrix (2) and matrix (3), then built modulation matrix according to formula (9): for by modulation matrix, do not eliminate because channel carries out to signal ISI and the ICI that linear convolution brings, according to memory characteristic and symbol feedback, build time domain precoding TDP module.Then, by channel, owing to having adopted time domain precoding algorithm, make the former linear convolution carried out of channel convert circular convolution to coded signal 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 illustrates, H _ij(j=1,2 represent transmitting antenna; I=1,2 represent reception antenna) what mean is the 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 ₁₂; h ₂₁, h ₂₂].Each footnote i j means that the transmitting antenna j that is is to the channel status between 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 according to formula (2) and formula (3), constructed Matrix C _{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}build 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 meets:

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) what (j=1,2) meaned is the signal on 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).

What each root reception antenna received is all the data from two transmitting antennas, by formula (11), knows that the data on 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) what mean is transmitting antenna 1 to the signal of two adjacent moment of having carried out the time domain precoding on reception antenna 1,

Q _{_ 12}(k-1), q _{_ 12}(k) what mean is transmitting antenna 2 to the signal of two adjacent moment of having carried out the time domain precoding on reception antenna 1, n _{_ 1}(k) mean the noise of reception antenna 1.

The parameter of correspondence 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 reception 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}and x (k) _-2(k).

That is, shown in (16), by signal received on 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, be multiplied by respectively Matrix C _{p_11}and C _{p_21}contrary, the signal that can obtain on 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)。

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

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

We relatively analyze implementation result by the emulation of performance and bandwidth efficiency.

Utilize the LTE system constructing of time domain precoder as shown in Figure 5, at first the transmitting terminal code word passes through scrambling module, and code word is combined with specific scramble sequence, produces new scrambling bit stream, then passes through modulation module.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 every two bits in sequence of binary digits, has four kinds of combinations, 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 judges according to the phase place of planisphere and the carrier signal that receives the information bit that transmitting terminal sends.After having modulated, through layer mapping, the symbol of odd number all is mapped on 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), then obtain time-domain signal x (k) through fast discrete inverse Fourier transform IDFT, by x (k) is carried out to the time domain precoding, produce q (k) signal.

Newly increase the TDP precoding module in the TD-LTE down link, 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 system, in 7 sampling intervals of circulating prefix-length, binary data stream is adopted to the QPSK modulation system.Utilize block pilot frequency mode, and the channel response of hypothesis pilot frame accurately estimates, carry out channel estimating in time domain employing linear interpolation mode, and the error bit ability of system is compared.

The Main Function process of time domain precoding module is as follows:

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

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

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

Use the CP (being designated as normal CP) of normal length and the CP of extension length (be designated as and expand CP) in the TD-LTE system, and do not use CP and use the MIMO-Precoded-OFDM system of TDP precoding, system bandwidth efficiency is compared.Although 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 of using normal length CP and the system of using TDP Comparatively speaking bandwidth efficiency, has larger decline, is only 80%.Because it does not need to use CP, the TDP system can realize the maximization of bandwidth efficiency, uses the system bandwidth efficiency of normal length CP between between the two, but 10% the loss of also having an appointment.

Claims (3)

1. a LTE system of utilizing 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 comprises the linear matrix modulating unit, delay cell, subtracter, subtracter passes through the resulting signal subtraction of delay cell by time-domain signal x (k) with the time domain precoded signal produced by the same moment, by linear matrix modulating unit modulation matrix, modulated, obtain modulation signal, this modulation signal and time-domain signal are sent into to adder to combine, obtain 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 do serial/parallel conversion, the single order equalizer carries out the single order equilibrium to the parallel data stream y (k) received and obtains equalizing signal Y (k), Fourier transformer recovers initial data to equalizing signal Y (k) as discrete Fourier transform (DFT)

described modulation matrix is specially, as CIR length is L+1, and according to the vectorial h=[h (0) of channel impulse response coefficient CIR, h (1) ..., h (L)] ^t, the vector matrix of setting up channel impulse response is

with

according to vector matrix C _hand C _tbuild modulation matrix

wherein, * means C _tthe Moore-Penrose pseudoinverse, the conjugate transpose that subscript H is matrix.

2.LTE utilize time domain precoder to improve the method for bandwidth efficiency in 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 comprises the linear matrix modulating unit, delay cell, subtracter, subtracter passes through the resulting signal subtraction of delay cell by time-domain signal x (k) with the time domain precoded signal produced by the same moment, by linear matrix modulating unit modulation matrix, modulated, obtain modulation signal, this modulation signal is sent into to adder with time-domain signal x (k) to combine, obtain 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) received and obtains equalizing signal Y (k), Fourier transformer recovers initial data to equalizing signal Y (k) as discrete Fourier transform (DFT)

described modulation matrix is specially, as CIR length is L+1, and 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

with

according to vector matrix C _hand C _tbuild modulation matrix wherein, * means C _tthe Moore-Penrose pseudoinverse, the conjugate transpose that subscript H is matrix.

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

with

according to vector matrix C _hand C _tbuild modulation matrix wherein, * means C _tthe Moore-Penrose pseudoinverse, the conjugate transpose that subscript H is matrix.

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