CN101605119B - Method for reducing peak-to-average power ratio by chaotically coding time-domain OFDM signals - Google Patents
Method for reducing peak-to-average power ratio by chaotically coding time-domain OFDM signals Download PDFInfo
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Abstract
本发明公开了无线通信技术领域中的一种对时域的OFDM信号进行混沌编码降低峰均比的方法。技术方案是，所述方法基于传统的OFDM系统，在IFFT之后加入混沌编码器对时域的信号进行编码，在FFT之前加入混沌解码器对时域的信号进行解码；在IFFT之后加入混沌编码器对时域的信号进行编码用于使时域信号混沌化，避免出现高均峰比；在FFT之前加入混沌解码器对时域的信号进行解码用于将混沌化的时域信号恢复为正常的时域信号；混沌编码器和混沌解码器的初始状态相同。本发明将时域的信号进行混沌编码使得时域信号的分布混沌化，从而避免了高峰均比的出现，其适用于各种调制方式，而且对时域信号进行处理的过程中没有降低码率。
The invention discloses a method for performing chaotic coding on OFDM signals in the time domain to reduce the peak-to-average ratio in the technical field of wireless communication. The technical solution is that the method is based on a traditional OFDM system, adding a chaotic coder after the IFFT to encode the signal in the time domain, adding a chaotic decoder before the FFT to decode the signal in the time domain; adding a chaotic coder after the IFFT Encoding the time-domain signal is used to make the time-domain signal chaotic and avoid high peak-to-average ratio; adding a chaotic decoder before FFT to decode the time-domain signal is used to restore the chaotic time-domain signal to the normal time domain Signal; the initial state of the chaotic encoder and the chaotic decoder are the same. The present invention performs chaotic coding on the time-domain signal to make the distribution of the time-domain signal chaotic, thereby avoiding the appearance of the peak-to-average ratio, which is applicable to various modulation methods, and does not reduce the code rate in the process of processing the time-domain signal .
Description
Technical field
The invention belongs to wireless communication technology field, relate in particular to a kind of ofdm signal and carry out the method that chaotically coding reduces peak-to-average force ratio time domain.
Background technology
OFDM (Orthogonal Frequency Division Multiplexing, OFDM) technology has anti-multipath interference performance, high spectrum efficiency and the good property that overcomes frequency selective fading, can be used widely in a lot of fields.A main shortcoming of OFDM radio communication is exactly that its time-domain signal possibly have high peak-to-average force ratio (PAR), and the ratio maximum of peak power and average power can reach the number of subcarrier, so along with this problem of sub-carrier number purpose increase is serious all the more.High PAR needs the high power amplifier (HPA) that linear dynamic range is big, but utilizing of its power is insufficient.If the linear dynamic range of high power amplifier is big inadequately, high PAR can cause distortion in the band, thereby causes the rising and the out-of-band radiation of the error rate, disturbs the communication of adjacent frequency.
Various methods are suggested the problem that solves high peak-to-average force ratio, comprise Methods for Coding, amplitude limit and filtering, selectivity mapping, partial sequence transmission or the like.Methods for Coding has a lot, like Golay complementary series etc., can realize very low peak-to-average force ratio, but code check can descend a lot, and the situation efficient big to number of sub carrier wave is lower.And the truncation noise in the band that the method for amplitude limit meeting and filtering causes can't be eliminated, so this method can cause the increase of the error rate.And selectivity mapping and partial sequence transmission need to transmit the extra correct decoding of information ability.
Judge to reducing the technological quality of PAR comprises a lot of aspects, like the effect of PAR reduction, increase, complexity and the throughput of the error rate.Main consideration is to reduce the cost of PAR will be lower than booster output and utilize inadequate cost.So the method for the reduction PAR of low-complexity has better prospect.
Summary of the invention
The objective of the invention is to, the problem to the method for the equal peak of the reduction OFDM time-domain signal ratio commonly used of above-mentioned proposition exists proposes the method that a kind of ofdm signal to time domain carries out chaotically coding reduction peak-to-average force ratio, in order to address the above problem.
Technical scheme of the present invention is; A kind of ofdm signal to time domain carries out the method that chaotically coding reduces peak-to-average force ratio; Based on traditional ofdm system; It is characterized in that said method adds the chaotically coding device signal of time domain is encoded after IFFT, before FFT, add chaotic decoder the signal of time domain is decoded;
The said chaotically coding device that after IFFT, adds is encoded to the signal of time domain and is used to make time-domain signal chaotization, avoids occurring high all peak ratios;
The said chaotic decoder that adds before the FFT is decoded to the signal of time domain and is used for chaotization time-domain signal is reverted to normal time-domain signal.
Said chaotically coding device comprises the chaos filter.
Said chaotic decoder comprises the inverse filter of chaos filter.
The initial condition of said chaotically coding device and said chaotic decoder is identical.
Effect of the present invention is, the signal of time domain carried out chaotically coding make that the distribution of time-domain signal is chaotization, thereby avoided the appearance of high peak-to-average force ratio; Simultaneously, this method is that time-domain signal is handled, so code check does not reduce; And this method is transparent to modulation system, is applicable to various modulation systems.
Description of drawings
Fig. 1 is traditional ofdm system schematic diagram;
Fig. 2 adopts the chaotically coding device to reduce the ofdm system schematic diagram of peak-to-average force ratio;
Fig. 3 is basic chaotically coding device and decoder schematic diagram, wherein: (a) be basic chaotically coding device schematic diagram, (b) be basic chaotic decoder schematic diagram;
Fig. 4 is the time-domain signal figure that does not carry out chaotically coding that the embodiment of the invention provides, and wherein: (a) being time-domain signal real part figure, (b) is time-domain signal imaginary part figure;
Fig. 5 is the time-domain signal figure through chaotically coding that the embodiment of the invention provides, and wherein: (a) being time-domain signal real part figure, (b) is time-domain signal imaginary part figure;
Fig. 6 is the PAR value figure through the time-domain signal after the chaotically coding; (a) be that sub-carrier number is the PAR value figure of 8 time-domain signal; (b) be that sub-carrier number is the PAR value figure of 64 time-domain signal; (c) be that sub-carrier number is the PAR value figure of 256 time-domain signal; (d) be that sub-carrier number is the PAR value figure of 512 time-domain signal.
Embodiment
Below in conjunction with accompanying drawing, preferred embodiment is elaborated.Should be emphasized that following explanation only is exemplary, rather than in order to limit scope of the present invention and application thereof.
Fig. 1 is traditional ofdm system schematic diagram.Among Fig. 1, in traditional ofdm system, the original data sequence { S that send
kThrough after sign map, string and variation and the FFT (IFFT), obtain original discrete time signal { x
n, the original time-domain signal { x that obtains simulating through digital-to-analogue conversion again
t, with { x
tAdd carrier modulation after, send to receiving terminal through channel.Obtain the time-domain signal { y of the simulation of OFDM base band after the receiving terminal demodulation
t, at discrete time-domain signal { y through obtaining after the analog-to-digital conversion
n, pass through successively more at last invert fast fourier transformation (FFT), and string changes and the symbol inverse mapping after, obtain final data sequence { R
k.
In above-mentioned process, behind original time-domain signal process serial to parallel conversion, parallel data are carried out the modulation that FFT (IFFT) realizes multicarrier.The signal of an OFDM is to be formed through addition after independently modulating by a plurality of sub-carrier signals.At some constantly, if a plurality of subcarriers will produce very big peak-to-average power ratio when adding up with same direction.The present invention is directed to this problem that exists in traditional ofdm system, proposed the ofdm signal of time domain is carried out the method that chaotically coding reduces peak-to-average force ratio.
Fig. 2 adopts the chaotically coding device to reduce the ofdm system schematic diagram of peak-to-average force ratio.Among Fig. 2, the present invention adds the chaotically coding device signal of time domain is encoded in traditional ofdm system after IFFT, before FFT, adds chaotic decoder the signal of time domain is decoded.Adding after IFFT that the chaotically coding device encodes to the signal of time domain is in order to make time-domain signal chaotization, avoids occurring high all peak ratios.Because after IFFT, add the chaotically coding device, the probability of small-signal homophase is reduced, the possibility that produces very big instantaneous peak value amplitude that on amplitude, is superimposed so also decreases, thereby has avoided the excessive problem of peak-to-average force ratio well.Correspondingly, before FFT, add chaotic decoder the signal of time domain is decoded, be used for chaotization time-domain signal is reverted to normal time-domain signal.
In the method that the present invention proposes, the chaotically coding device comprises the chaos filter, and chaotic decoder comprises the inverse filter of chaos filter.The chaos filter has a lot of implementations, adopts 2 the most basic rank chaos filters to get final product.The good autocorrelation and the cross correlation of the sequence after a lot of complicated chaos filters are devoted to encode.Focusing on the signal of time domain of this method is chaotization, and the cross correlation of the sequence after need not encoding is so adopt the most basic chaos filter to get final product.Fig. 3 is basic chaotically coding device and decoder schematic diagram, wherein: (a) be basic chaotically coding device schematic diagram, (b) be basic chaotic decoder schematic diagram.Among Fig. 3, Z
-1Be delay unit, LCIRC is left circulative shift operation.Chaotically coding device shown in Figure 3 and the pairing equation of chaotic decoder are:
Coding: y (n)=x (n)+{ y (n-1)+f (y (n-2)) };
Decoding: x (n)=y (n)-{ y (n-1)+f (y (n-2)) };
Wherein, f () is left cyclic shift function, promptly multiply by 2 and adds carry digit afterwards.Be noted that in order to make chaotic decoder correctly chaotization time-domain signal reverted to normal time-domain signal, should adopt and the identical chaotic decoder of chaotically coding device initial condition.
Fig. 4 is the time-domain signal figure that does not carry out chaotically coding that the embodiment of the invention provides, and wherein: (a) being time-domain signal real part figure, (b) is time-domain signal imaginary part figure.To some input { S
k, time-domain signal { x
nAnd { x
tPossibly have very high peak-to-average force ratio, at this moment the signal distributions of time domain is concentrated relatively.Fig. 4 is that sub-carrier number is 8, { S
kBe the time-domain signal under the situation of complete ' 1 ' input, and can find out that therefrom the distribution of signal is more extreme, the real part of time-domain signal only gets 8 and 0.
Fig. 5 is the time-domain signal figure through chaotically coding that the embodiment of the invention provides, and wherein: (a) being time-domain signal real part figure, (b) is time-domain signal imaginary part figure.Sub-carrier number to Fig. 4 is 8, { S
kBe the time-domain signal under the situation of complete ' 1 ' input, it is chaotization to make that through chaotically coding time-domain signal distributes, the relative homogenizing of distribution of time-domain signal, thereby reduced peak-to-average force ratio.
Fig. 6 is the PAR value figure through the time-domain signal after the chaotically coding; (a) be that sub-carrier number is the PAR value figure of 8 time-domain signal; (b) be that sub-carrier number is the PAR value figure of 64 time-domain signal; (c) be that sub-carrier number is the PAR value figure of 256 time-domain signal; (d) be that sub-carrier number is the PAR value figure of 512 time-domain signal.The modulation system that emulation is adopted is BPSK, but this method all is suitable for various modulation systems, because the time-domain signal that chaotically coding is handled is transparent to modulation system.N among the figure representes the input of different initial data, under the situation like 8 number of sub-carrier, has input possible in 256, all calculates here.And be 64,256 and 512 situation for sub-carrier number, also only calculated 256 kinds of situation, because in these cases, the amount of calculation that the whole circumstances are all calculated is too big.Peak-to-average force ratio from figure sees that difference is little under the situation of different carrier number, and at this moment peak-to-average force ratio depends on the distribution situation of chaotic signal, and this is determined by the chaos filter characteristic.So the situation big to sub-carrier number, the reduction of peak-to-average force ratio is big more.
The present invention adopts the chaos filter as encoder the signal of the time domain of OFDM to be encoded to reduce the peak-to-average force ratio of ofdm signal, realizes simply, and complexity is low, and is transparent to modulation system, is applicable to various modulation systems.Adopt the inverse filter of encoder to decode at receiving terminal, can accurately recover original information as long as the initial condition of encoder is identical.
The above; Be merely the preferable embodiment of the present invention, but protection scope of the present invention is not limited thereto, any technical staff who is familiar with the present technique field is in the technical scope that the present invention discloses; The variation that can expect easily or replacement all should be encompassed within protection scope of the present invention.Therefore, protection scope of the present invention should be as the criterion with the protection range of claim.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| WO2006070299A1 (en) * | 2004-12-28 | 2006-07-06 | Koninklijke Philips Electronics N.V. | Method and apparatus for synchronization control of digital signals |
| CN101394391A (en) * | 2008-11-03 | 2009-03-25 | 华北电力大学 | OFDM Synchronization Method Based on Four-dimensional Chaotic System |
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| WO2006070299A1 (en) * | 2004-12-28 | 2006-07-06 | Koninklijke Philips Electronics N.V. | Method and apparatus for synchronization control of digital signals |
| CN101394391A (en) * | 2008-11-03 | 2009-03-25 | 华北电力大学 | OFDM Synchronization Method Based on Four-dimensional Chaotic System |
Non-Patent Citations (1)
| Title |
|---|
| 刘晓胜，等.《基于混沌跳频的电力线交织编码技术》.《电力系统自动化》.2008,第32卷(第14期),第55-58页. * |
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