CN102238126B - Method for reducing peak-to-average power ratio of OFDM (orthogonal frequency division multiplexing)/OQAM system based on selective sequence - Google Patents

Abstract

The invention discloses a method for reducing a peak-to-average power ratio of an OFDM (orthogonal frequency division multiplexing)/OQAM (orthogonally multiplexed QAM) system based on a selective sequence. The method comprises the following steps of: coding, interleaving and modulating an input data stream, performing up-sampling on the obtained information source data packets, and then, enablingthe information source data packets to respectively pass through a filter bank; respectively selecting an optimized phase rotation sequence for a time domain signal of each obtained data block in order; and finally, selecting a signal, of which the peak-to-average power ratio is lowest, for transmission, and transmitting information of the phase rotation sequence as sideband information. The method provided by the invention can effectively lower the peak-to-average power ratio of the OFDM/OQAM system without influencing the power spectral density and the error rate performance of the system, improve work efficiency an HPA (high-power amplifier) and reduce energy consumption.

Description

Reduce the method for the peak-to-average power ratio of OFDM/OQAM system based on the selectivity sequence

Technical field

The invention belongs to the wireless and cable communicating technology field based on OFDM (OFDM/OQAM) system of offset quadrature amplitude modulation(PAM), be specifically related to adopt the selectivity sequence to reduce the method for the peak-to-average power ratio of OFDM/OQAM system.

Background technology

OFDM (OFDM/OQAM) technology based on the offset quadrature amplitude modulation(PAM) is a kind of promising multi-carrier modulation technology, because it has advantages such as high spectrum resolution and Large Volume Data transfer rate, has obtained extensive concern.Compare with traditional ofdm system, the part technical advantage of OFDM/OQAM system may be summarized as follows: 1) when the user is asynchronous, can carry out the distribution of subcarrier well; 2) meet the prototype filter pulse that condition is reinvented in (being similar to) perfection by design, under the prerequisite that does not need Cyclic Prefix, still can obtain littler intersymbol interference and interchannel interference; 3) by being combined with the OQAM modulated filter bank, can obtain maximized message transmission rate; 4) can finish high performance frequency spectrum perception; 5) can make the secondary lobe of frequency spectrum lower by the original shape Filter Design, the interference of the system that makes between can successive bands is lower; 6) frequency spectrum perception and transfer of data can be carried out synchronously.Therefore, for LTE-advanced and IMT-advanced etc., OFDM/OQAM is suggested as a good candidate scheme.For example, insert and cognitive radio for dynamic spectrum, OFDM/OQAM has been chosen as the up-and-coming technology of physical layer, wherein frequency spectrum perception and transfer of data can be carried out simultaneously, that is to say, same bank of filters not only can be used for frequency spectrum perception also can be used for transfer of data, and this has guaranteed the compatible performance of system.This is a key facility for opportunistic communication system efficiently.

But in the OFDM/OQAM system, some challenging problems still do not solve.Wherein one of problem of most critical is exactly the design of its high power amplifier (HPA), because the peak-to-average power ratio of OFDM/OQAM signal (PAPR) is too big.Generally, HPA is operated in the zone of saturation or near its power output efficient maximum of zone of saturation.Therefore, because the high PAPR of input signal, memoryless nonlinear distortion will be introduced in communication channel, cause out of band spectrum regeneration.Therefore, in the OFDM/OQAM wireless communication system, the high PAPR that reduces signal is extremely important.

People have proposed the PAPR that a lot of technology reduce traditional ofdm system.For example: coding techniques, multitone is reserved, companding technology etc.But all methods that reduce the PAPR of ofdm signal all can not directly apply in the OFDM/OQAM system.Because in traditional ofdm system, each OFDM symbol is independently in time domain, does not exist overlapping between the adjacent OFDM symbol.Therefore, the reduction of the PAPR of symbol before or after the reduction of the PAPR of an OFDM symbol can not influence.But in the OFDM/OQAM system, time-domain symbol exists overlapping.Therefore, the PAPR that we reduce each OFDM/OQAM symbol independently can impact other symbols, thereby the effect that causes final PAPR to reduce is bad.

Summary of the invention

Higher at signal peak-to-average power power ratio in the OFDM/OQAM system, and the method for existing control and reduction ofdm signal peak-to-average power ratio can not directly apply in the OFDM/OQAM system, the present invention proposes the method that reduces the peak-to-average power ratio of OFDM/OQAM system based on the selectivity sequence, this method is in the peak-to-average power ratio that reduces the OFDM/OQAM system, power spectral density and the bit error rate performance that can guarantee system are unaffected, and the operating efficiency of raising HPA, save power consumption.

Provided by the inventionly a kind ofly reduce the method for the peak-to-average power ratio of OFDM/OQAM system based on the selectivity sequence, the information source packet of establishing an OFDM/OQAM system comprises M data block, and each data block comprises N q system symbol; Wherein, q=2 ^l, l, M and N are positive integer, it is characterized in that, and this method comprises the steps:

(1) data flow of input obtains an information source packet X=[X through after encoding, interweaving, modulate ₀, X ₁..., X _M-1], X wherein _mBe m data block among the X, be expressed as X _m=[X _m(0), X _m(1) ..., X _m(N-1)] ^T, X wherein _m(n) n data symbol of m data block of expression, and X _m(n)=a _m(n)+jb _m(n), n=0,1 ..., N-1, wherein a _m(n) and b _m(n) be X respectively _m(n) real part and imaginary part, j is the imaginary part of symbol, the transposition of T representing matrix;

(2) the input data symbol is carried out N times of up-sampling, X _mIn the up-sampling that obtains of n data symbol after signal

Be designated as $x_m^n\left(t\right)=X_m\left(n\right)\mathrm{\δ}(t-\mathrm{mT}),$ Wherein T is a data symbol duration, and t is time variable, t 〉=0, impulse function $\mathrm{\δ}\left(t\right)=\left\{\begin{array}{cc}1,& t=0\\ 0,& \mathrm{else}\end{array}\right.,$ Then the signal that obtains is passed through prototype filter h (t), and will

Imaginary part time-delay

X then _mIn n data symbol by filter after and be modulated to mark signal on the carrier wave

Be expressed as

$s_m^n\left(t\right)=\{a_m\left(n\right)h(t-\mathrm{mT})+j{b}_m\left(n\right)h(t-\frac{T}{2}-\mathrm{mT})\}{e}^{\mathrm{jn}(\frac{2\mathrm{\π}}{T}t+\frac{T}{2})}$

Wherein $e^{\mathrm{jn}(\frac{2\mathrm{\π}}{T}t+\frac{T}{2})}=\sin \left(n(\frac{2\mathrm{\π}}{T}t+\frac{T}{2})\right)+j\cos \left(n(\frac{2\mathrm{\π}}{T}t+\frac{T}{2})\right);$

(3) adopt the selectivity sequence to reduce peak-to-average power ratio:

(3.1) produce U phase place rotatable sequence, wherein each phase rotation coefficient is selected from and defaultly gathers that { 1 ,-1} remembers that U phase place rotatable sequence is

U=0,1 ..., U-1, wherein

N=0,1 ..., N-1, note Expression acts on the phase place rotatable sequence of m data block, and makes P _{M, u}=P _u

(3.2) initialization m=0 multiply by U phase place rotatable sequence respectively to m data block and obtains U candidate signal

${\tilde{s}}_{0,u}\left(t\right)=\underset{n=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{s}_0^n\left(t\right){\mathrm{<figure-callout\; id="0"\; label="P"\; filenames="HDA0000070294060000021.png"\; state="\{\{state\}\}">P</figure-callout>}}_{0,u}^n,u=\mathrm{0,1},...,U-1$

And calculate this U candidate signal

${\mathrm{PAPR}}_0^u={10\log }_{10}\frac{\underset{0\&le;t\&le;(K-1)T}{\max }\left[{\left|{\tilde{s}}_{0,u}\left(t\right)\right|}^2\right]}{E\left[{\left|{\tilde{s}}_{0,u}\left(t\right)\right|}^2\right]},u=\mathrm{0,1},...,U-1$

E[ wherein] expression averages;

(3.3) note is minimum

For

Its corresponding block is

Corresponding phase place rotatable sequence sequence number note is S ₀, and make m=m+1;

(3.4) m data block be multiply by U phase place rotatable sequence respectively and obtain U candidate signal

${\tilde{s}}_{m,u}\left(t\right)=\underset{n=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{s}_m^n\left(t\right)P_{m,u}^n,u=\mathrm{0,1},...,U-1$

And calculate this U candidate signal

${\mathrm{PAPR}}_m^u={10\log }_{10}\frac{\underset{\mathrm{mT}\&le;t\&le;(m+K-1)T}{\max }\left[{|\underset{p=0}{\overset{m-1}{\mathrm{\&Sigma;}}}{\tilde{s}}_p^{*}\left(t\right)+{\tilde{s}}_{m,u}\left(t\right)|}^2\right]}{E\left[{|\underset{p=0}{\overset{m-1}{\mathrm{\&Sigma;}}}{\tilde{s}}_p^{*}\left(t\right)+{\tilde{s}}_{m,u}\left(t\right)|}^2\right]},u=\mathrm{0,1},...,U-1;$

(3.5) note is minimum

For

Its corresponding block is

Corresponding phase place rotatable sequence sequence number note is S _m, and make m=m+1;

(3.6) if m＜M forwards step (3.4) to; Otherwise, calculate final output signal

$\tilde{s}\left(t\right)=\underset{m=0}{\overset{M-1}{\mathrm{\&Sigma;}}}{\tilde{s}}_m^{*}\left(t\right)$

Forward step (4) to;

(4) the phase place rotatable sequence sequence number of establishing optimization is S=[S ₀, S ₁..., S _M-1], with the signal of output

Send into channel, and sequence S is sent into channel as side information.

The present invention is a kind of method that reduces the peak-to-average power ratio of OFDM/OQAM signal based on the selectivity sequence, it not only can reduce the peak-to-average power ratio of OFDM/OQAM signal preferably, and can also keep the power spectral density of OFDM/OQAM signal constant, thereby obtain bit error rate performance preferably., through after encoding, interweaving, modulate the information source packet that obtains is carried out passing through bank of filters respectively after the up-sampling in data.Then, with the phase place rotatable sequence that the OFDM/OQAM signal that obtains is optimized according to the rule selection, finally select the signal of peak-to-average power ratio minimum to transmit, and the information of phase place rotatable sequence is sent to receiving terminal as side information.The present invention can reduce the peak-to-average power ratio of OFDM/OQAM signal effectively, simultaneously, can guarantee that the power spectral density of system and bit error rate performance are unaffected, improves the operating efficiency of HPA, saves power consumption.

Description of drawings

Fig. 1 is the system flow block diagram of the inventive method;

Fig. 2 adopts the selectivity sequence to reduce the FB(flow block) of peak-to-average power ratio among the present invention.

Embodiment

The present invention is further described below in conjunction with accompanying drawing and one group of concrete parameter:

Employing selectivity sequence provided by the invention reduce the OFDM/OQAM system peak-to-average power ratio method handling process as shown in Figure 1, wherein, adopt handling process that the selectivity sequence reduces peak-to-average power ratio as shown in Figure 2.

The duration of prototype filter h (t) is KT, and wherein K is a positive even numbers; General, K is more big, and secondary lobe is more little; But the K increase can cause higher computation complexity; Therefore, the K value of choosing in the reality is no more than 8 usually.

The step of the inventive method (1) and (2) are identical with the OFDM/OQAM system original treatment step of transmitting terminal.

Below by by embodiment the present invention being described in further detail, but following examples only are illustrative, and protection scope of the present invention is not subjected to the restriction of these embodiment.

Example:

Parameter declaration: adopt the QAM modulation of q=4, sub-carrier number N=64, the OFDM/OQAM system of prototype filter parameter K=4, the phase place rotatable sequence number that produces in the selectivity sequence is got U=16 and U=128 respectively.

Simulation result shows that the ability that the present invention reduces PAPR is better than the ability that traditional selectivity mapping method directly applies to the reduction PAPR of OFDM/OQAM system far away.Simultaneously, the present invention can not influence the power spectral density of OFDM/OQAM signal.And, owing to the reduction of PAPR, improved the operating efficiency of HPA, saved consumed power.

When U=128, at Pr{PAPR＞PAPR ₀}=10 ^-3The time, the reduction amount that the selectivity sequence method that adopts the present invention to propose can obtain PAPR is 4.7dB; The reduction amount that adopts original selectivity mapping method can obtain PAPR is 1.3dB.Obviously, when parameter was identical, the present invention had improved the ability that reduces PAPR greatly.Simultaneously, the present invention's power spectral density of reducing the OFDM/OQAM signal after the PAPR does not overlap fully with the ideal power spectrum density that the OFDM/OQAM primary signal is passed through under the HPA situation.When U=16, to compare with primary signal, the method for proposition has been saved 45% energy, and the energy that traditional selectivity mapping method is saved only is 10%.Simultaneously, the ability that the present invention reduces PAPR is better than the ability that traditional selectivity mapping method directly applies to the reduction PAPR of OFDM/OQAM system far away, has promoted the ability of saving energy simultaneously greatly.

The above is preferred embodiment of the present invention, but the present invention should not be confined to the disclosed content of this embodiment and accompanying drawing.So everyly do not break away from the equivalence of finishing under the spirit disclosed in this invention or revise, all fall into the scope of protection of the invention.

Claims (1)

1. one kind is reduced the method for the peak-to-average power ratio of OFDM/OQAM system based on the selectivity sequence, and the information source packet of establishing an OFDM/OQAM system comprises M data block, and each data block comprises N q system symbol; Wherein, q=2 ^l, l, M and N are positive integer, it is characterized in that, and this method comprises the steps:

(1) data flow of input obtains an information source packet X=[X through after encoding, interweaving, modulate ₀, X ₁..., X _M-1], X wherein _mBe m data block among the X, be expressed as X _m=[X _m(0), X _m(1) ..., X _m(N-1)] ^T, X wherein _m(n) n data symbol of m data block of expression, and X _m(n)=a _m(n)+jb _m(n), n=0,1 ..., N-1, wherein a _m(n) and b _m(n) be X respectively _m(n) real part and imaginary part, j is the imaginary part of symbol, ^TThe transposition of representing matrix;

(2) the input data symbol is carried out N times of up-sampling, X _mIn the up-sampling that obtains of n data symbol after signal

Be designated as Wherein T ' is a data symbol duration, and t is time variable, t 〉=0, impulse function $\mathrm{\&delta;}\left(t\right)=\left\{\begin{array}{cc}1,& t=0\\ 0,& \mathrm{else}\end{array}\right.,$ Then the signal behind the up-sampling that obtains is passed through prototype filter h (t), and will Imaginary part time-delay

X then _mIn n data symbol by filter after and be modulated to mark signal on the carrier wave

Be expressed as

$s_m^n\left(t\right)=\{a_m\left(n\right)h(t-m{T}^{\&prime;})+j{b}_m\left(n\right)h(t-\frac{T^{\&prime;}}{2}-m{T}^{\&prime;})\}{e}^{\mathrm{jn}(\frac{2\mathrm{\&pi;}}{T^{\&prime;}}t+\frac{T^{\&prime;}}{2})}$

Wherein, $e^{\mathrm{jn}(\frac{2\mathrm{\&pi;}}{T^{\&prime;}}t+\frac{T^{\&prime;}}{2})}=\sin \left(n(\frac{2\mathrm{\&pi;}}{T^{\&prime;}}t+\frac{T^{\&prime;}}{2})\right)+j\cos \left(n(\frac{2\mathrm{\&pi;}}{T^{\&prime;}}t+\frac{T^{\&prime;}}{2})\right);$

(3) adopt the selectivity sequence to reduce peak-to-average power ratio:

(3.1) produce U phase place rotatable sequence, wherein each phase rotation coefficient is selected from and defaultly gathers that { 1 ,-1} remembers that U phase place rotatable sequence is

U=0,1 ..., U-1, wherein , n=0,1 ..., N-1, note

Expression acts on the phase place rotatable sequence of m data block, and makes P _{M, u}=P _u

(3.2) initialization m=0 is to m data block X _mIn n data symbol by filter after and be modulated to mark signal on the carrier wave

Multiply by U phase place rotatable sequence respectively and obtain U candidate signal

${\tilde{s}}_{m,u}\left(t\right)=\underset{n=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{s}_m^n\left(t\right)P_{m,u}^n,u=\mathrm{0,1},...,U-1$

And calculate this U candidate signal

${\mathrm{PAPR}}_m^u=10{\log }_{10}\frac{\underset{0\&le;t\&le;(K-1)T}{\max }\left[{\left|{\tilde{s}}_{m,u}\left(t\right)\right|}^2\right]}{E\left[{\left|{\tilde{s}}_{m,u}\left(t\right)\right|}^2\right]},u=\mathrm{0,1},...,U-1$

E[wherein] expression averages;

(3.3) obtain in the note step (3.2)

Middle minimum value is designated as

, its corresponding block is

, corresponding phase place rotatable sequence sequence number note is S ₀, and make m=m+1;

(3.4) m data block be multiply by U phase place rotatable sequence respectively and obtain U candidate signal

${\tilde{s}}_{m,u}\left(t\right)=\underset{n=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{s}_m^n\left(t\right)P_{m,u}^n,u=\mathrm{0,1},...,U-1$

And calculate this U candidate signal

${\mathrm{PAPR}}_m^u=10{\log }_{10}\frac{\underset{\mathrm{mT}\&le;t\&le;(m+K-1)T}{\max }\left[{|\underset{p=0}{\overset{m-1}{\mathrm{\&Sigma;}}}{\tilde{s}}_p^{*}\left(t\right)+{\tilde{s}}_{m,u}\left(t\right)|}^2\right]}{E\left[{\left|\underset{p=0}{\overset{m-1}{\mathrm{\&Sigma;}}}{\tilde{s}}_p^{*}\left(t\right){\tilde{s}}_{m,u}\left(t\right)\right|}^2\right]},u=\mathrm{0,1},...,U-1;$

(3.5) note is minimum

For

, its corresponding block is

, corresponding phase place rotatable sequence sequence number note is S _m, and make m=m+1;

(3.6) if m＜M forwards step (3.4) to; Otherwise, calculate final output signal

$\tilde{s}\left(t\right)=\underset{m=0}{\overset{M-1}{\mathrm{\&Sigma;}}}{\tilde{s}}_m^{*}\left(t\right)$

Forward step (4) to;

(4) the phase place rotatable sequence sequence number of establishing optimization is S=[S ₀, S ₁..., S _M-1], with the signal of output

Send into channel, and sequence S is sent into channel as side information.

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