CN103248602B - A kind of based on Linear block coding reduction ofdm signal peak-to-average ratio SLM method - Google Patents

Abstract

The invention discloses a kind of based on Linear block coding reduction ofdm signal peak-to-average ratio SLM method, the problem solving current ofdm system signal height PAPR.In order to obtain side information accurately at receiving terminal, correctly recovering downhole data signal, it is proposed that side information is carried out Linear block coding by one, this coded method is simple, and easily decodes.In order to save side information transmission, the side information after coding is superimposed upon on underground signal, recovers side information at receiving terminal by channel estimation methods.Theory analysis and simulation result show: when not reducing system PAPR performance, and linear block codes is improved SLM algorithm and can be obtained than the better PAPR of traditional SLM algorithm and bit error rate performance.The present invention realizes easily, can be used in all kinds of employing OFDM communication system being modulated.

Description

A kind of based on Linear block coding reduction ofdm signal peak-to-average ratio SLM method

Technical field

The present invention relates to OFDM (OrthogonalFrequencyDivisionMultiplexing, OFDM) technical field in mobile communication system, ofdm signal improved, particularly relates to a kind of based on Linear block coding reduction ofdm signal peak-to-average ratio SLM method.

Background technology

OFDM (OFDM) technology, with the feature such as its efficient availability of frequency spectrum, good Effect of Carrier Frequency Offset, power system capacity be big, becomes one of core technology of forth generation mobile communication system.But owing to ofdm signal shows as multiple orthogonal sub-carriers Signal averaging in time domain, therefore its signal has high peak power and average power ratio (Peak-to-AveragePowerRatio, PAPR), this feature just requires that the high power amplifier of the transmitter in mobile communication system has the significantly high linearity, otherwise producing non-linear distortion, harmonic wave produced by non-linear distortion can have a strong impact on systematic function.But the power device of large dynamic range, it is meant that the equipment cost of transmitter is higher.

Solve distorted signals problem in ofdm communication system, will the PAPR of signal in reduction system, the reduction PAPR method proposed at present has a lot, mainly have: pre-distortion signal technology, signal redundancy techniques, coding techniques three kinds, wherein pre-distortion signal technology includes amplitude limit, companding transform and preserved sub-carrier etc., such as document " Jeng, Shiann-Shiun-Shiun, Chen, Jia-Ming-M..EfficientPAPRReductioninOFDMSystemsBasedonaC ompandingTechniqueWithTrapeziumDistribution [J] .IEEETransactionsonBroadcasting.2011.Vol.57 (2), Part:1:291-298 "；Signal redundancy techniques includes selective mapping (SLM) and partial transmission sequence method (PTS), " EomSeung-Sik; NamHaewoon; KoYoung-ChaiChai; Low-ComplexityPAPRReductionSchemewithoutSideInformationf orOFDMSystems.SignalIEEETransactionsonProcessing; Vol.60 (7), 2012:3657 3669 "；Coding techniques includes Reed-Muller coding and Golay complementary series etc., such as " SabbaghianMaryam; Kwak; Yongjun, SmidaBesma, TarokhVahid; NearShannonLimitandLowPeaktoAveragePowerRatioTurboBlockC odedOFDM; IEEETransactionsonCommunications, Vol.59 (8), 2011:2042 2045 ".The algorithm reducing PAPR at present both at home and abroad is a lot, and various algorithms have advantage and limitation thereof.Generally speaking, these algorithms are generally with sacrificial system performance for cost, if signal distortion techniques is to reduce system BER performance for dominant cost to obtain low PAPR performance.For signal redundancy techniques, there is good PAPR and reduce performance, but it is to obtain good PAPR performance with higher system-computed complexity for cost.Coding techniques class technology makes system information speed be greatly lowered owing to needs send bulk redundancy information, and namely it obtains better PAPR performance to reduce system power performance for cost.Owing to SLM algorithm undistorted can reduce PAPR, therefore obtain in reduction ofdm signal PAPR field and pay close attention to widely.At receiving terminal, traditional SLM algorithm needs side information accurately to recover ofdm signal, if side information error of transmission, then can cause that whole signal sequence recovers unsuccessfully or loses, therefore, the wrong error detection probability of side information is most important to system errors performance.Side information individually transmission can take extra bandwidth, causes that efficiency of transmission reduces.The present invention proposes a kind of based on Linear block coding reduction ofdm signal peak-to-average ratio SLM method.

Summary of the invention

It is an object of the invention to the problems referred to above overcoming existing ofdm system to reduce Peak-to-Average Power Ratio method, it is provided that a kind of method reducing peak-to-average power ratio in orthogonal frequency division multiplex OFDM system.The method can obtain bit error rate performance more better than traditional SLM algorithm when not reducing system PAPR performance, eliminates the independent transmission of side information simultaneously, saves bandwidth.

For achieving the above object, the technical solution used in the present invention is as follows:

It is a kind of based on Linear block coding reduction ofdm signal peak-to-average ratio SLM method, it is characterised in that: comprise the steps of:

Step 1: the serial signal sequences collected becomes parallel transmission, is multiplied by different phase sequence S to each road signal_u=[S₁, S₂..., S_u], 1≤u≤U generates the U group alternative signal X containing identical information_u=[X₁, X₂..., X_u]；

Step 2: side information is done Linear block coding；

Step 3: if adopting the mode of energy supposition to be superimposed upon alternative signal X the information after coding_uOn obtain signal X '_u；

Step 4: to signal X '_uIt is IFFT, calculates the PAPR value often organizing signal and select the signal with minimum PAPR value to be transmitted.

At receiver, the method for channel estimating is adopted to recover the side information of superposition.The beneficial effects of the present invention is: the problem that the invention solves current ofdm system signal height PAPR.When not reducing system PAPR performance, linear block codes is improved SLM algorithm and can be obtained than the better PAPR of traditional SLM algorithm and bit error rate performance；In order to save side information transmission, the side information after coding is superimposed upon on underground signal, recovers side information at receiving terminal by channel estimation methods.

Accompanying drawing explanation

Fig. 1 is that one mainly realizes process schematic based on Linear block coding reduction ofdm signal peak-to-average ratio SLM method；

Fig. 2 is the PAPR simulation curve figure improving SLM embodiment of the method with tradition and contrast algorithm, " original OFDM " represents the CCDF curve of original OFDM signal PAPR, " tradition SLM " represents the CCDF curve of the ofdm signal PAPR adopting tradition SLM algorithm, " improvement SLM algorithm " represents the CCDF curve of the PAPR improving SLM method signal adopting the present invention to propose, and " Coded-SLM algorithm " represents documents " KyeongcheolYang；The CCDF curve of the PAPR of the SLM algorithm signal in Chang, S.-I.Peak-to-averagepowercontrolinOFDMusingstandardarray soflinearblockcodes.IEEECommunicationsLetters.2003.7 (4): 174-176 "；Abscissa represents the threshold value of PAPR, and vertical coordinate represents that PAPR exceedes the probability of a certain threshold value, i.e. complementary accumulated probability distribution function (CCDF).

Fig. 3 is the BER Simulation curve chart improving SLM embodiment of the method with tradition and contrast algorithm, " original OFDM " represents the ber curve of original OFDM signal, " tradition SLM " represents the ber curve of the ofdm signal adopting tradition SLM algorithm, " improving SLM algorithm " and represent the ber curve improving SLM method signal adopting the present invention to propose, " Coded-SLM algorithm " represents documents " KyeongcheolYang；The ber curve of the SLM algorithm signal in Chang, S.-I.Peak-to-averagepowercontrolinOFDMusingstandardarray soflinearblockcodes.IEEECommunicationsLetters.2003.7 (4): 174-176 ".

Detailed description of the invention

Below in conjunction with accompanying drawing, main principle, the detailed description of the invention etc. of realizing of technical scheme is described in detail.

It is as follows that one of the present invention reduces ofdm signal peak-to-average ratio SLM Method And Principle based on Linear block coding: in order to obtain side information accurately at receiving terminal, correctly recover downhole data signal, propose one and side information is carried out Linear block coding, this coded method is simple, and easily decodes.In order to save side information transmission, the side information after coding is superimposed upon on underground signal, recovers side information at receiving terminal by channel estimation methods.

The main purpose that side information carries out Linear block coding is to ensure that the recovery that receiving terminal can be correct to signal, namely can reduce the bit error rate of system.As long as an original bit transfer mistake may result in the reception whole mistake of signal, linear block codes is improved SLM algorithm and is adopted (6,3) linear block codes, namely represents 3 original bits with 6 bits, it is possible to remedy a mistake.The probability of erroneous interpretations made by definition (6,3) Linear block coding decoder:

$P_M\≤\underset{j=t+1}{\overset{6}{\mathrm{\Σ}}}\left(\begin{array}{c}6\\ j\end{array}\right)p^j{(1-p)}^{6-j}---\left(1\right)$

Wherein, j=1 ... 2³, represent 2³Different code words；Each code word is made up of 6 bits；P represents the transfer error probability under binary symmetric channel (binarysymmetricalchannel, BSC)；The error correcting capability t of code is that the maximum error correction number guaranteed by each code word defines, it may be assumed that

D in formula_minRepresent the minimum range of liner code, which determine error correction and the error detecing capability of coding.

The minimum distance d of (6,3) uniform enconding_minIt is 3.

Modulating according to QPSK, the bit error rate of tradition SLM algorithm is P_QPSK, then the bit error rate P of linear block codes improvement SLM algorithm is expressed as:

$\begin{array}{c}P=P_{QPSK}{P}_M\\ P_{QPSK}=\frac{1}{2}erfc\[\sqrt{\frac{E}{2n_0}}\]\end{array}---\left(3\right)$

This shows that linear block codes is improved SLM algorithm and reduced the bit error rate of system, improve systematic function.

Build the performance doing embodiment emulation on what a ofdm system platform to verify method that the present invention proposes.Embodiment algorithm simulating parameter is:

The each ofdm signal of ■ comprises 128 subcarriers

■ ofdm signal number 1000

■ adopts BSPK modulator approach

Refer to Fig. 2 can be seen that, two kinds based on coding are improved SLM algorithm: include linear block codes and improve SLM algorithm and " Coded-SLM algorithm ", with tradition SLM algorithm, there is almost identical PAPR performance, but from details enlarged drawing, can be seen that performance is slightly better than tradition SLM algorithm." Coded-SLM algorithm " adopts and whole signal is encoded, and implies side information in supervision code bit, therefore code character structure complexity, and still can take extra bandwidth.And linear block codes is improved SLM algorithm and only is encoded and is superimposed upon on signal sequence sending in the lump to side information, the supervision code bit of redundancy will not take extra bandwidth.

Refer to Fig. 3 it can be seen that the BER performance that linear block codes improves SLM algorithm is better than tradition SLM algorithm, close and original OFDM signal, slightly worse than the BER performance of " Coded-SLM algorithm ".But " Coded-SLM algorithm " adopts and whole signal is encoded, produce redundancy, although side information is implicitly included in redundancy function, but still takies the information of extra these redundancies of bandwidth for transmission.Therefore the bit error rate performance that linear block codes improvement SLM algorithm sacrifice is certain exchanges low computation complexity for and high bandwidth utilization is worth.

Claims (2)

1. one kind is reduced ofdm signal peak-to-average ratio SLM method based on Linear block coding, it is characterised in that: comprise the steps of:

Step 1: the serial signal sequences collected becomes parallel transmission, is multiplied by different phase sequence S to each road signal_u=[S₁,S₂,…,S_U], 1≤u≤U generates the U group alternative signal X containing identical information_u=[X₁,X₂,…,X_U]；

Step 2: side information is done Linear block coding；

Step 3: adopt the mode of weak energy supposition to be superimposed upon alternative signal X the information after coding_uOn obtain signal X '_u；

Step 4: to signal X '_uIt is IFFT, calculates the PAPR value often organizing signal and select the signal with minimum PAPR value to be transmitted.

2. one according to claim 1 reduces ofdm signal peak-to-average ratio SLM method based on Linear block coding, it is characterised in that: at receiver, adopt the method for channel estimating to recover the side information of superposition.