CN106254292B

CN106254292B - Reduction PAPR algorithm based on the distribution of stochastic filtering device in GFDM system

Info

Publication number: CN106254292B
Application number: CN201610585096.1A
Authority: CN
Inventors: 谢显中; 张苗; 吴垒; 姚鑫凌
Original assignee: Chongqing University of Post and Telecommunications
Current assignee: Chongqing University of Post and Telecommunications
Priority date: 2016-07-22
Filing date: 2016-07-22
Publication date: 2019-03-08
Anticipated expiration: 2036-07-22
Also published as: CN106254292A

Abstract

The reduction PAPR algorithm based on the distribution of stochastic filtering device in a kind of GFDM system is claimed in the present invention, is related to wireless communication system.As all multicarrier system, since output signal is superimposed, GFDM system still has high PAPR.Although the method for reducing PAPR in ofdm system has very much, the characteristics of due to GFDM system, directly borrowing the method for reduction PAPR in ofdm system, the effect is unsatisfactory.Current research there are aiming at the problem that, it can be with the design feature of flexible choice filter according to GFDM system, a kind of method for proposing new reduction system PAPR, by the way that every subcarriers are randomly assigned with different filters, phase equalization when being intended to destroy Signal averaging is to effectively inhibit PAPR, and will not cause the distortion of signal.Theory analysis and simulation result confirm the superiority of the algorithm.

Description

Reduction PAPR algorithm based on the distribution of stochastic filtering device in GFDM system

Technical field

The present invention relates to the skills of the reduction PAR peak to average ratio in wireless communication field more particularly to filter bank multi-carrier technology Art.

Background technique

Currently, the standard much wirelessly communicated all relies on OFDM, it, will high speed as a kind of important multi-transceiver technology Data flow is divided into several parallel low rate data streams transmitted on different subcarriers, is effective against intersymbol interference (ISI), but OFDM still has limitation, for this purpose, the novel multi-carrier modulation technology such as GFDM comes into being.GFDM is as 5G Alternative waveform, have the advantages that many OFDM are no: data symbol can be by the two-dimentional modular structure across time domain and frequency domain It propagates, adjustable pulse shaping filter has been used to make system that there is very high flexibility etc..

But as OFDM multicarrier system, since transmitting terminal output signal is overlapped mutually, may at a time it produce Raw biggish peak power, thus GFDM system can bring higher papr, abbreviation peak-to-average force ratio (PAPR).It is theoretical The upper quantity for reducing carrier wave can largely reduce the PAPR of system, and infeasible in practical applications, so The PAPR that high degree reduces system under conditions of multicarrier is only the key solved the problems, such as.Although reducing PAPR in ofdm system Method have very much, still, due to the design feature of GFDM system, the method effect of PAPR is directly reduced in borrow ofdm system It is unsatisfactory.

Document [Sendrei L, S,Michailow N,et al.Iterative receiver for clipped GFDM signals[C]//IEEE 24th International Conference Radioelektronika.2014, pp.1-4.] using iterative receiver to GFDM receive signal handled (Clipped- GFDM), this will lead to signal distortion, although successive ignition can effectively eliminate the nonlinear noise due to caused by clipping, The number of iterations is more, and operand is also more complicated；Document [Sharifian, Z, Omidi, M.J, Farhang, A, et al.Polynomial-based compressing and iterative expanding for PAPR reduction in GFDM [C] //IEEE 23rd Conference on Electrical Engineering, 2015, pp.518-523.] it provides A kind of to be based on multinomial companding algorithm (PCT-GFDM), it is one-to-one mapping, and pass through iterative receiver mode in receiving end Restore to send end signal, however this algorithm also will increase operand while reducing PAPR and sacrifice BER performance.

GFDM multicarrier system model is as shown in Figure 1.Binary sequence b completes corresponding constellation mapping by QAM modulation, A sequence d for complex data symbol composition is obtained, after going here and there and simultaneously (S/P) converting and up-sample (Upsampling), forms the road K packet Parallel data stream d containing M symbol_k={ d_0,k,d_1,k……d_M-1,k}^T, (k=0,1 ..., K-1), every road signal is with respectively The Pulse shaped filter of self-loopaIt is filtered, filter period MN, then by the centre frequency of respective subcarrier Modulation, which is superimposed to obtain again, sends signal x [n], is eventually adding cyclic prefix, is sent into signal.

Wherein,Indicate the cyclic convolution about n, n ∈ [0, MN-1], d_m,kIt indicates m-th transmitted on k-th of carrier wave Complex data symbol.

According to document [Michailow N, Gaspar I, Krone S, et al.Generalized frequency division multiplexing:Analysis of an alternative multi-carrier technique for next generation cellular systems[C]//International Symposium on Wireless Communication Systems.IEEE, 2012:171-175.] GFDM module can realize with IFFT/FFT, time domain is grasped Frequency-domain operations are converted to, as shown in Fig. 2, then formula (1) can indicate are as follows:

Wherein, W_Md_kIndicate the FFT of M point；In a frequency domain, up-sampling treatment shows as signal replication, replicates matrix R^(L)It is By L I_MIt is connected in series, i.e. R^(L)={ I_M,I_M,......,I_M}^T, I_MFor the unit matrix of M × M；Electric-wave filter matrix Γ=diag (W_LMG), g is the time sample vector of filter pulse；Up-conversion is signal multiplied by a permutation matrix P in frequency domain representation^(k), P^(k)According to P⁽¹⁾={ I_LM,0_LM,0_LM,...}^T, P⁽²⁾={ 0_LM,I_LM,0_LM,...}^TRule analogize, wherein 0_LMFor LM × The null matrix of LM.

Further, sending signal can be indicated with linear matrix are as follows:

X=Ad (3)

Here, A indicates the modulation matrix of a MN × KM.

After removing cyclic prefix (CP), the vector being made of reception sample of signal can be write as:

Y=Hx+n (4)

Wherein, H is the impulse response function of channel,Indicate that mean value is 0 and variance isAdditivity it is high This white noise vector ,~indicate equivalent；

In receiving end, channel distortion is compensated to obtain by frequency domain equalization (FDE)In order to eliminate or inhibit due to In the nonopiate caused inter-carrier interference (ICI) of intercarrier, matched-filter receiver (MF), zero-forcing receiver are usually utilized (ZF), three kinds of least mean-square error receiver (MMSE) etc. linear GFDM receivers rebuild GFDM system and send data, use I_MNIt is The unit matrix of MN × MN, then has respectively:

The PAPR of GFDM system may be expressed as:

Wherein E { } indicates operation of averaging.It for convenience, can be with according to the signal after modulated on k-th of the carrier wave of formula (1) It indicates are as follows:

Since intersymbol is mutually indepedent, so x_kIt is also mutually indepedent between [n], to have:

E{x_k[n] }=0

X as can be seen from the above equation_kThe mean value and variance of [n] are unrelated with k, according to central-limit theorem it is found that when K is enough When big, x [n] obedience mean value is 0 and variance is 2 σ_n ²=K σ²Multiple Gauss distribution, wherein σ_n ²Indicate the side of x [n] real and imaginary parts Difference.

The performance of system PAPR can with complementary error cumulative function (CCDF) indicate, it can calculate PAPR be more than to The probability of threshold value γ out.By the analysis of front, the envelope of x [n] | x [n] | Rayleigh distributed, power | x [n] |²It obeys The χ that freedom degree is 2²Distribution.Enable S=| x [n] |², then the probability density function of S are as follows:

It enablesThe then probability density function of T are as follows:

f_T(t)=K σ²f_S(Kσ²T)=e^-t, t > 0 (12)

Then have

Since each T is independent, so the cumulative function (CDF) of PAPR can indicate are as follows:

Therefore, the complimentary cumulative function (CCDF) of the PAPR of GFDM system are as follows:

P (PAPR > γ)=1- (1-e^-γ)^MN (15)

The reason of high PAPR can have been generated in conjunction with GFDM system with the design feature of flexible choice filter, invent one kind The new algorithm that system PAPR is reduced based on filter is randomly assigned.

Summary of the invention

Present invention seek to address that the above problem of the prior art.Propose a kind of method.Technical scheme is as follows:

A kind of reduction PAPR algorithm based on the distribution of stochastic filtering device in GFDM system comprising following steps:

Step 1, GFDM system initialization generate the sequence C containing a K element={ c at random₀, c₁......c_k,......c_K-1, wherein c_k∈{0,1}；Wherein the size of K is the sub-carrier number size of system；

Step 2, the K subcarriers signal for obtaining GFDM system select filter to be filtered simultaneously K subcarriers signal Number, works as c_kWhen=0, indicates that and first filter is selected to be filtered K subcarriers signal；Work as c_kWhen=1, the is selected Two filters are filtered K subcarriers signal, and wherein first filter is different from second filter type；

Step 3 obtains GFDM signal to by the filtered K subcarriers Signal averaging of step 2, calculates GFDM signal PAPR is simultaneously stored.

Further, work as c in the step 2_kWhen=0, first filter selects raised cosine filter RC；Work as c_kWhen=1, Second filter selects root raised cosine filter RRC.

Further, the K subcarriers signal of GFDM system described in the step 2 includes the parallel data stream of M symbol d_k={ d_0,k,d_1,k……d_M-1,k}^T, (k=0,1 ..., K-1).

Further, step 3 calculates the step of PAPR of GFDM signal specifically: firstly, calculating separately this N number of data symbols Number power, maximum value power therein is selected, secondly, the mean power of GFDM signal is calculated, finally, by maximum value power The PAPR for obtaining GFDM is compared with mean power.

It advantages of the present invention and has the beneficial effect that:

The basic reason for leading to PAPR in multi-carrier systems is that sub-carrier signal is continuously superimposed, when sub-carrier phase is consistent When just will appear higher peak power.In traditional GFDM system, every subcarriers with identical filter to signal into Row processing, this will increase the consistent probability of sub-carrier phase.For this purpose, herein according to different filters phase-frequency characteristic it is different this Feature proposes a kind of new method for reducing PAPR.By being randomly assigned different filters to each subcarrier, between subcarrier Complex data symbol introduce out of phase offset vector, high degree destroy sub-carrier phase it is consistent, thus effectively inhibit PAPR, The program is known as being based on stochastic filtering device allocation algorithm (RAF-GFDM).Two kinds of raised cosine filters common and that effect is good are selected herein Wave device (RC) and root raised cosine filter (RRC) can share in this way when system is realized with other modules.

Compared by the complexity of several different drop PAPR algorithms, it can be seen that margining amplitude technique does not increase additional complexity Degree, but PAPR is reduced with the bit error rate performance of sacrificial system；The computation complexity of PCT algorithm is increased slightly, but its same limit Width method is the same, will increase the bit error rate of system.SLM algorithm is a linear process, will not bring signal distortion, complexity It is moderate, but the effect for reducing PAPR does not protrude；And algorithm proposed in this paper is equally linear process, though reducing PAPR's There is no that margining amplitude technique and PCT algorithm are prominent in effect, but win and increase additional calculating cost no, and to the bit error rate almost without It influences, there is higher practical application value.

Detailed description of the invention

Fig. 1 is that the present invention provides preferred embodiment GFDM transmitting terminal system model.

Fig. 2 GFDM signal sending end frequency domain handles model

Fig. 3 RAF-GFDM process flow diagram

PAPR performance under Fig. 4 difference rolloff-factor

Fig. 5 PAPR reducing effect comparison diagram

BER performance compares under MF in Fig. 6 Gaussian channel

BER performance compares under ZF in Fig. 7 Gaussian channel

BER performance compares under MMSE in Fig. 8 Gaussian channel

BER performance in Fig. 9 walking multipath channel under MF compares

BER performance in Figure 10 walking multipath channel under ZF compares

BER performance in Figure 11 walking multipath channel under MMSE compares

The BER performance of algorithms of different in Figure 12 Gaussian channel

The BER performance of algorithms of different in Figure 13 walking multipath channel

1 transmitting terminal computational complexity of table compares

2 simulation parameter of table

Specific embodiment

Following will be combined with the drawings in the embodiments of the present invention, and technical solution in the embodiment of the present invention carries out clear, detailed Carefully describe.Described embodiment is only a part of the embodiments of the present invention.

Technical scheme is as follows:

Two kinds of raised cosine filters (RC) and root raised cosine filter (RRC) common and that effect is good are selected herein, in this way It can be shared with other modules when system is realized.Specific step is as follows:

(1) firstly, generating the binary sequence C comprising K element at random_k∈ { 0,1 }, k ∈ [0, K-1].

(2) then, filter is numbered, works as C_kWhen=1, RCC filter is selected to carry out kth subcarriers signal Otherwise filtering selects RC filter to be filtered kth subcarriers signal.

(3) finally, the road-load wave of K is superimposed to obtain GFDM signal, PAPR is calculated.

Next the complexity of RAF-GFDM above is analyzed, to compare, we also give OFDM and tradition The complexity of GFDM system, Clipped-GFDM system, PCT-GFDM, SLM-GFDM system etc..With reference to formula (2), GFDM is generated The step of signal needs is as follows:

(1) FFT of K M point；

(2) K filtering, primary filtering carry out LM plural multiplication；

(3) plural number of K MN point adds operation；

(4) IFFT of K MN point.

We use plural multiplication C^MThe complexity of measurement system, so the complexity of traditional GFDM system can indicate Are as follows:

It is proposed in this paper based on the algorithm for being randomly assigned filter, compared to traditional GFDM system, only in signal It is varied in filtering processing step, but there is no the operation costs for increasing system, so:

As shown in table 2, the complexity for giving several different drop PAPR algorithms compares, it can be seen that margining amplitude technique does not increase Add additional complexity, but PAPR is reduced with the bit error rate performance of sacrificial system；The computation complexity of PCT algorithm slightly increases Add, but it is the same with margining amplitude technique, will increase the bit error rate of system.SLM algorithm is a linear process, and signal will not be brought abnormal Become, complexity is also moderate, but the effect for reducing PAPR does not protrude；And algorithm proposed in this paper is equally linear process, though There is no margining amplitude technique and PCT algorithm prominent in the effect for reducing PAPR, but wins and increase additional calculating cost no, and is right The bit error rate has little effect, and has higher practical application value.

Herein by every subcarriers are randomly assigned with different filter RC and RRC, it is intended to destroy K subcarriers signal The consistency of phase, the probability for making each sub-carrier signal occur peak power when continuously superposition are reduced.In order to analyze herein The performance of method, we and tradition GFDM, the iteration margining amplitude technique (Clipped-GFDM) of document [15] proposition, multinomial companding method (PCT-GFDM) and Choose for user algorithm (SLM-GFDM) carries out emulation comparison.Channel includes Gaussian channel and walking multipath letter Road, is respectively adopted tri- kinds of reception modes of MF, ZF, MMSE, and other simulation parameters of this paper are as shown in table 2.

Fig. 3 is influence of the rolloff-factor of filter to RAF-GFDM system PAPR.It was noticed that RAF-GFDM system PAPR performance and institute's selecting filter rolloff-factor (roll-off) it is related, be not to be the bigger the better, nor the smaller the better, But general impacts are not too big.So the RAF- that we need that suitable rolloff-factor is selected to make system in practical applications The PAPR performance of GFDM system is optimal.

Fig. 4 compares the method for different reduction PAPR, it was noted that the PAPR of GFDM system is slightly above OFDM accelerates the attenuation outside a channel of system this is because GFDM has used more flexible filter, i.e. RRC, RC etc..Assuming that using Be normalized filter, then the mean power of GFDM signal will be less than ofdm signal, so the PAPR of GFDM is compared OFDM can increased.We can also be seen that method proposed in this paper can be effectively reduced compared with tradition GFDM simultaneously The PAPR of GFDM system.In addition, although Clipped-GFDM scheme and PCT-GFDM scheme reduce the performance of PAPR better than herein The algorithm of proposition, but both algorithms belong to nonlinear operation, not only complexity is higher, can also seriously affect system BER performance.Further, we also make comparisons with the Choose for user algorithm (SLM) for being all linear operation, the PAPR drop of context of methods Inefficient fruit is better than SLM algorithm.

Fig. 6 and Fig. 7, study in Gaussian channel and walking multipath channel respectively RAF-GFDM system proposed in this paper MF, The BER performance of tri- kinds of ZF, MMSE reception modes, and make ratio with a kind of BER performance for the traditional GFDM system for only using filter Compared with.It was noticed that no matter the BER of the RAF-GFDM system under Gaussian channel or walking multipath channel, MF reception mode Performance curve is all between the BER performance curve of traditional GFDM system that RC or RRC is used alone.And it is worth noting that, Receive mode according to ZF and MMSE, when signal-to-noise ratio (SNR) is lower, the BER performance curve of RAF-GFDM system still between It is used alone between the BER performance curve of traditional GFDM system of RC or RRC；But the RAF-GFDM system in middle high s/n ratio BER performance can slightly nearly, this explanation when noise is relatively high, BER is bigger by the poor filters affect of performance.It is comprehensive It is upper described, it is proposed in this paper smaller on the influence of the BER performance of GFDM system based on the algorithm for being randomly assigned filter.

Fig. 8 and Fig. 9 is respectively to use different reduction PAPR methods in Gaussian channel and walking multipath channel in GFDM system BER performance compare.It can be seen from the figure that proposed in Clipped-GFDM method and document [16] that document [15] proposes The BER performance of PCT algorithm has obvious variation, because both algorithms belong to non-linear process, the PAPR for reducing system is To sacrifice BER performance as cost；RAF-GFDM algorithm proposed in this paper can but reduce system under the premise of ensureing BER performance The PAPR of system.

Table 1 is that transmitting terminal computational complexity compares

Table 1

Table 2 is simulation parameter

Table 2

The above embodiment is interpreted as being merely to illustrate the present invention rather than limit the scope of the invention.? After the content for having read record of the invention, technical staff can be made various changes or modifications the present invention, these equivalent changes Change and modification equally falls into the scope of the claims in the present invention.

Claims

1. the reduction PAPR algorithm based on the distribution of stochastic filtering device in a kind of GFDM system, which comprises the following steps:

Step 1, GFDM system initialization generate the sequence C containing a K element={ c at random₀,c₁......c_k, ......c_K-1, wherein c_k∈{0,1}；Wherein the size of K is the sub-carrier number size of system；

Step 2, the K subcarriers signal for obtaining GFDM system select filter to be filtered and compile K subcarriers signal Number, work as c_kWhen=0, indicates that and first filter is selected to be filtered K subcarriers signal；Work as c_kWhen=1, second is selected Filter is filtered K subcarriers signal, and wherein first filter is different from second filter type；

Step 3 obtains GFDM signal to by the filtered K subcarriers Signal averaging of step 2, calculates the PAPR of GFDM signal And it stores.

2. the reduction PAPR algorithm based on the distribution of stochastic filtering device in GFDM system according to claim 1, feature exist In working as c in the step 2_kWhen=0, first filter selects raised cosine filter RC；Work as c_kWhen=1, second filter is selected Root raised cosine filter RRC.

3. the reduction PAPR algorithm based on the distribution of stochastic filtering device in GFDM system according to claim 1 or 2, feature It is, the K subcarriers signal of GFDM system described in the step 2 includes the parallel data stream d of M symbol_k={ d_0,k, d_1,k......d_M-1,k}^T, k=0,1 ..., K-1.

4. the reduction PAPR algorithm based on the distribution of stochastic filtering device in GFDM system according to claim 1 or 2, feature It is a step of GFDM signal includes N number of data symbol, and step 3 calculates the PAPR of GFDM signal specifically: firstly, respectively The power for calculating this N number of data symbol selects maximum value power therein, secondly, calculating the mean power of GFDM signal, most Afterwards, maximum value power is compared to the PAPR for obtaining GFDM with mean power.