CN105187354A - Method for suppressing OFDM communication signal peak-to-average power ratio based on PTS technology - Google Patents

Abstract

The invention discloses a method for suppressing an OFDM communication signal Peak-to-Average Power Ratio (PAR) based on a PTS technology. A transmitting end generates an OFDM signal with a low PAR, and encoding and modulating steps include: (1) after performing scrambling processing on an information bit stream to be transmitted, feeding into a convolutional code encoder, and completing PSK phase mapping of a bit output by the encoder; (2) feeding a code element phase sequence into K*V-dimensional row-column interleaver to complete interleaving, and building a K*V-dimensional matrix, wherein K=N/(V+1), and N is the number of subcarriers of OFDM symbols; and (3) taking out code element phases of the K*V-dimensional matrix to form V subblocks of a size K, multiplying by exp(j(phi<h>)) to perform phase correction, performing OFDM modulation, and using optimal phase grouping to generate an OFDM signal with a minimum PAR again as a transmitting signal, thereby realizing PAR suppression. The method for suppressing the OFDM communication signal PAR based on the PTS technology has the beneficial effect that original information can be restored without using side information.

Description

A kind of method suppressing ofdm communication signal peak-to-average ratio based on PTS technology

Technical field

The present invention relates to the communications field, or rather, is a kind of method suppressing ofdm communication signal peak-to-average ratio based on PTS technology.

Background technology

It is reduce communication performance principal element that multi-path effect causes channel selectivity to decline, and ofdm communication technology adopts orthogonal multiple carrier parallel transmission information, fading channel is divided into multiple near flat channel, has good anti-many ways performance.But, when signal on certain moment multiple subcarrier is with larger amplitude cophase stacking, just may there is very large peak value, bring larger peak power and average power ratio (Peak-to-AveragePowerRatio, PAR) thus.OFDM sub-carrier number is more, and PAR is larger, and too high PAR is a major defect of ofdm system, and it is very high to some components and parts dynamic range requirement of system, such as power amplifier, A/D, D/A converter etc.Otherwise the non-linear of these components and parts also can produce nonlinear distortion to ofdm signal, the harmonic wave produced can cause the mutual interference between subchannel, thus affects the performance of ofdm system.

Ofdm signal PAR suppression technology has multiple, partial transmission sequence PTS (PartialTransmitSequence wherein, PTS) be a kind of method of effective reduction ofdm signal PAR, the core concept of PTS finds the PAR characteristic that ofdm signal is optimized in optimum phase grouping, found optimum phase grouping is mapped as side information and is sent to receiving terminal, first receiving terminal has needed edge information decoding, and another mistake maps the phase place grouping obtaining transmitting terminal, thus recovers raw information.Obviously, when utilizing PTS technology to produce the OFDM symbol decoding of low PAR, could recover raw information when only having edge information decoding correct, otherwise will cause whole OFDM symbol error code, side information takies the bandwidth efficiency that frequency spectrum resource also reduces OFDM in addition.

Summary of the invention

Object of the present invention is exactly to overcome above-mentioned problems of the prior art, and a kind of method suppressing OFDM (OFDM) signal of communication peak-to-average ratio based on PTS technology is provided, for the PAR heavy dependence side information shortcoming suppressing OFDM based on PTS technology, a kind of PTS combining convolution code is provided to suppress the PAR method of OFDM, the method does not need transmitting terminal side information to map, avoid and cause by side information the risk that bandwidth efficiency declines and the error rate increases, there is good practicality.

The object of the invention is to have come by following technical solution, the coded modulation step that transmitting terminal produces the ofdm signal of low PAR is as follows:

(1) to after information bit sts-stream scrambling sts waiting for transmission process, send into encoder for convolution codes, bit is exported to encoder and completes PSK phase mapping.

(2) send into K*V dimension row-column interleaver to the acquisition symbol phases sequence of step 1 and complete intertexture, structure K*V ties up matrix, and wherein K=N/ (V+1), N are the sub-carrier number of OFDM symbol.

(3) the symbol phases formation size of taking out the K*V dimension matrix of step 2 by row is the sub-block of K, V altogether, is multiplied by carry out phase only pupil filter, it is one group of phase factor.The Comb Pilot block revising rear V sub-block and a long K has V+1 sub-block altogether and carries out OFDM modulation, and each symbol phases of sub-block is that interval is evenly distributed on OFDM symbol frequency axis with V+1, carries out IFFT conversion, forms V ^hindividual OFDM symbol, and calculate each symbol PAR, the optimum phase grouping that wherein minimum PAR is corresponding, utilize optimum phase divide into groups to regenerate there is minimum PAR ofdm signal as transmitting, realize PAR and suppress.

The demodulating and decoding treatment step of receiving terminal is as follows:

(1) take out pilot frequency sequence and complete channel estimating and correction.

(2) symbol phases after compensating step 1, with the extraction of V+1 interval, obtains K*V and ties up matrix, takes out matrix symbol phases and forms a sub-block, be total to V, be all multiplied by the symbol phases of the 1st sub-block by row and calculate likelihood ratio tolerance acquisition soft decoding information, input state metric matrix is initialized as full 0, Soft Inform ation is sent into H decoder and carry out the calculating of Viterbi Maximum Likelihood path metric, preserve output state metric matrix corresponding to wherein maximum likelihood ratio path metric and survivor path.

(3) using the output state metric matrix of step 2 as decoder input state metric matrix next time, the survivor path of residue sub-block is obtained according to the method for step 1.

(4) utilize step 2 and step 3 to obtain all survivor paths and carry out backtracking process, output bit flow carries out descrambling again, recovers transmitting terminal raw information.

Beneficial effect of the present invention is: the present invention adopts the grouping of PTS technology optimum phase, intertexture and convolution code combined coding modulation to produce the ofdm signal of low PAR, viterbi algorithm is adopted to find maximum survivor path relevant with receiving sequence and the uniqueness utilizing survivor path in grid, do not need to use side information, raw information can be recovered, avoid and cause by side information the risk that bandwidth efficiency declines and the error rate increases, there is good practicality.

Accompanying drawing explanation

Fig. 1 is the OFDM coded modulation block diagram that PAR suppresses.

Fig. 2 is the PTS packet map mode of OFDM symbol.

Fig. 3 is OFDM maker (i-th PTS grouping).

Fig. 4 is that PTS optimum phase divides group selector.

Fig. 5 is OFDM demodulation and decoding block diagram.

Fig. 6 is Viterbi decoding and PTS Combined Treatment.

Embodiment

Below in conjunction with drawings and Examples, the present invention will be further described:

Fig. 1 is the OFDM coded modulation block diagram that PAR suppresses.First to after information bit scrambling process waiting for transmission, send into encoder for convolution codes, bit is exported to encoder and carries out PSK phase mapping.The row-column interleaver again symbol phases after mapping being sent into K*V completes intertexture, and structure K*V ties up matrix, and wherein K=N/ (V+1), N are the sub-carrier number of OFDM symbol.Each row formation sub-block { d' of matrix _v(k) }, V altogether, be multiplied by carry out phase only pupil filter and obtain d _vh(k), such as formula (1), wherein it is one group of phase factor.Then according to the mode of Fig. 2, be that interval is evenly distributed on OFDM symbol frequency axis by each symbol of Comb Pilot block and coded message sub-block with V+1, carry out IFFT conversion, obtain OFDM symbol, altogether V ^hindividual OFDM symbol, such as formula (2) and Fig. 3, wherein u (k) is pilot frequency sequence.The PAR of each symbol is calculated, the optimum phase grouping finding minimum PAR corresponding according to formula (3) as Fig. 4.Finally will again substitute into formula (1) and formula (2), produce the ofdm signal with minimum PAR.

$\begin{array}{c}{x}_i\left(n\right)=\underset{m=0}{\overset{N-1}{\&Sigma;}}\{\underset{k=0}{\overset{K-1}{\&Sigma;}}u(k+1)\mathrm{\&delta;}(m-1-Vk-k)\\ +\underset{v=1}{\overset{V}{\&Sigma;}}\underset{k=0}{\overset{K-1}{\&Sigma;}}{d}_{vh}(k+1)\mathrm{\&delta;}(m-1-v-kV-k)\}{e}^{-j\frac{2\mathrm{\&pi;}}{N}nm},i=1,2,\mathrm{...},V^H\\ \left(2\right){\mathrm{PAR}}_i\left(dB\right)=10{\log }_{10}\frac{\max \left\{\right|x\left(n\right){|}^2\}}{E\left\{\right|x\left(n\right){|}^2\}},i=1,2,\mathrm{...},V^H\end{array}---\left(3\right)$

Fig. 5 is receiving terminal demodulating and decoding block diagram.First to received signal through row FFT process, and with V+1 interval, pilot frequency sequence is extracted to FFT Output rusults, LS criterion or MMSE criterion can be adopted to carry out channel estimating, and utilize estimated result to revise information sequence.Again revised sequence is extracted with V+1 interval, obtain K*V and tie up matrix, each row formation sub-block { r of matrix _v' (k), be multiplied by carry out phase only pupil filter and obtain r _vhk (), such as formula (4).The Soft Inform ation tolerance of sub-block symbol phases is obtained, σ in formula (5) according to formula (5) ²for noise power, S ₀for being mapped as the some set in the PSK planisphere of bit " 0 ", S ₁for being mapped as the some set in the PSK planisphere of bit " 1 ", for getting real part, for getting imaginary part.The maximum-likelihood decoding of Viterbi is selected to maximize log-likelihood function M exactly _vh(R _vh| C _v) as decoding output codons, such as formula (6). for receiving sequence y _vhthe conditional probability density function of (k), such as formula (7), E in formula _sfor symbol energy.In formula (6) for the estimation of the survivor path to v sub-block, Y _vhfor the sequence of symhols received, D ₁=2E _s/ σ ²and D ₂=(K/2) ln (/ (π σ ²))-E _s/ σ ²(K+|Y _vh| ²) be independent of constant, then corresponding path metric can have provide, represent receive sequence of symhols and the inner product (being correlated with) of correspondence code metasequence, viterbi algorithm then finds out survivor path maximum with the calculation of correlation of receiving sequence in grid if phase place and the transmitting terminal of receiving terminal PTS inverse mapping are inconsistent, then M _vh(R _vh| C _v) calculation of correlation will reduce.Therefore, formula (4) is utilized to travel through all soft Inform ation tolerance under utilizing formula (5) to obtain out of phase, inputs H decoder respectively, as Fig. 6, preserves maximum M _vh(R _vh| C _v) corresponding decoder output state metric matrix and survivor path, thus avoid needing to use side information to obtain the optimum phase grouping of transmitting terminal.

$\begin{array}{c}{M}_{vh}\left(Y_{vh}\right|{\hat{C}}_v)=\underset{k=1}{\overset{K}{\&Sigma;}}\ln p\left(y_{vh}\right(k\left)\right|{\hat{c}}_v\left(k\right))=-\frac{E_s}{{\mathrm{\&sigma;}}^2}\underset{k=1}{\overset{K}{\&Sigma;}}{\left(y_{vh}\right(k)-{\hat{c}}_v(k\left)\right)}^2\\ +\frac{{\mathrm{\&sigma;}}^2}{2}\ln \frac{E_s}{{\mathrm{\&pi;\&sigma;}}^2}=2\frac{E_s}{{\mathrm{\&sigma;}}^2}\underset{k=1}{\overset{K}{\&Sigma;}}\left(y_{vh}\right(k\left){\hat{c}}_v\right(k\left)\right)-\frac{E_s}{{\mathrm{\&sigma;}}^2}\left(\right|Y_{vh}{|}^2+K)+\frac{K}{2}\ln \frac{E_s}{{\mathrm{\&pi;\&sigma;}}^2}\\ =D_1(Y_{vh}\&CenterDot;{\hat{C}}_v)+D_2\end{array}---\left(6\right)$

$p\left(y_{vh}\right(k\left)\right|{\hat{c}}_v\left(k\right))=\sqrt{\frac{E_s}{{\mathrm{\&sigma;}}^2}}{e}^{-(E_s/{\mathrm{\&sigma;}}^2){\left(y_{vh}\right(k)-{\hat{c}}_v(k\left)\right)}^2}---\left(7\right)$

During to the 1st sub-block code metasequence decoding, decoder input state metric matrix is initialized as full 0, obtain Soft Inform ation tolerance feeding H decoder by formula (5) and carry out the calculating of Viterbi Maximum Likelihood path metric, preserve output state metric matrix and the survivor path of the wherein maximum correspondence of likelihood ratio path metric.Again using output state metric matrix as the input state metric matrix to the decoding of next sub-block sequence of symhols, same method obtains residue sub-block survivor path matrix.Finally backtracking process is carried out to all survivor paths, export decoding bit stream and carry out descrambling again, recover transmitting terminal raw information.

In addition to the implementation, the present invention can also have other execution modes, and all employings are equal to the technical scheme of replacement or equivalent transformation formation, all drop on the protection range of application claims.

Claims (1)

1. suppress a method for ofdm communication signal peak-to-average ratio based on PTS technology, it is characterized in that:

One, the ofdm communication signal producing low PAR at communications transmit end comprises the following steps:

(1) to after information bit sts-stream scrambling sts waiting for transmission process, send into encoder for convolution codes, bit is exported to encoder and completes PSK phase mapping;

(2) send into K*V dimension row-column interleaver to the acquisition symbol phases sequence of step (1) and complete intertexture, structure K*V ties up matrix, and wherein K=N/ (V+1), N are the sub-carrier number of OFDM symbol;

(3) symbol phases of taking out the K*V dimension matrix of step (2) by row forms the sub-block { d' that size is K _v(k) }, V altogether, be multiplied by carry out phase only pupil filter, such as formula (1), it is one group of phase factor; The Comb Pilot block revising rear V sub-block and a long K has V+1 sub-block altogether and carries out OFDM modulation, and each symbol phases of sub-block is that interval is evenly distributed on OFDM symbol frequency axis with V+1, carries out IFFT conversion, forms V according to formula (2) ^hindividual OFDM symbol, in formula (2), u (k) is pilot frequency sequence, and calculate each symbol PAR according to formula (4), the optimum phase grouping that wherein minimum PAR is corresponding, utilize optimum phase divide into groups regenerate there is minimum PAR ofdm signal as transmitting, realize PAR suppress;

$\begin{array}{c}{x}_i\left(n\right)=\underset{m=0}{\overset{N-1}{\&Sigma;}}\{\underset{k=0}{\overset{K-1}{\&Sigma;}}u(k+1)\mathrm{\&delta;}(m-1-Vk-k)\\ +\underset{v=0}{\overset{V}{\&Sigma;}}\underset{k=0}{\overset{K-1}{\&Sigma;}}{d}_{vh}(k+1)\mathrm{\&delta;}(m-1-v-kV-k)\}{e}^{-j\frac{2\mathrm{\&pi;}}{N}nm},i=1,2,\mathrm{...},V^H\end{array}---\left(2\right)$

${\mathrm{PAR}}_i\left(dB\right)=10{\log }_{10}\frac{max\left\{\right|x\left(n\right){|}^2\}}{E\left\{\right|x\left(n\right){|}^2\}},i=1,2,...,V^H---\left(4\right)$

Two, comprise the following steps in the process of communication receiver demodulating and decoding:

(1) take out pilot frequency sequence and complete channel estimating and correction;

(2) symbol phases after compensating step (1), with the extraction of V+1 interval, obtains K*V and ties up matrix, takes out matrix symbol phases and forms a sub-block, be total to V, be all multiplied by the symbol phases of the 1st sub-block by row and calculate likelihood ratio tolerance acquisition soft decoding information, input state metric matrix is initialized as full 0, Soft Inform ation is sent into H decoder and carry out the calculating of Viterbi Maximum Likelihood path metric, preserve output state metric matrix corresponding to wherein maximum likelihood ratio path metric and survivor path;

(3) using the output state metric matrix of step (2) as decoder input state metric matrix next time, the survivor path of residue sub-block is obtained according to the method for step (1);

(4) utilize step (2) and step (3) to obtain all survivor paths and carry out backtracking process, output bit flow carries out descrambling again, recovers transmitting terminal raw information.