CN106209716B - A method of reducing extensive MU-MIMO-OFDM system peak-to-average power ratio - Google Patents

A method of reducing extensive MU-MIMO-OFDM system peak-to-average power ratio Download PDF

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CN106209716B
CN106209716B CN201610514411.1A CN201610514411A CN106209716B CN 106209716 B CN106209716 B CN 106209716B CN 201610514411 A CN201610514411 A CN 201610514411A CN 106209716 B CN106209716 B CN 106209716B
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signal
mimo
interference signal
papr
extensive
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CN106209716A (en
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方俊
崔星星
包恒耀
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University of Electronic Science and Technology of China
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2614—Peak power aspects
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/0001—Arrangements for dividing the transmission path
    • H04L5/0003—Two-dimensional division
    • H04L5/0005—Time-frequency
    • H04L5/0007—Time-frequency the frequencies being orthogonal, e.g. OFDM(A), DMT

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  • Computer Networks & Wireless Communication (AREA)
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Abstract

The invention belongs to wirelessly communicate (wireless communication) technical field, more particularly to a kind of algorithm that the peak-to-average power ratio (peak-to-average power ratio, PAPR) of extensive MU-MIMO-OFDM downlink is reduced using alternately update (alternating direction method of multiplier) algorithm.The present invention provides a kind of method for not needing side information and can reducing extensive MU-MIMO-OFDM system PAPR, and provides higher system performance.By the present invention in that interference signal is located in channel kernel, make the interference signal of superposition on system performance almost without what influence, by using alternative and iterative algorithm, each parameter of alternating iteration finally obtains the interference signal.

Description

A method of reducing extensive MU-MIMO-OFDM system peak-to-average power ratio
Technical field
The invention belongs to wirelessly communicate (wireless communication) technical field more particularly to a kind of utilize to hand over Extensive MU-MIMO- is reduced for update (alternating direction method of multiplier) algorithm The algorithm of the peak-to-average power ratio (peak-to-average power ratio, PAPR) of OFDM downlink.
Background technique
OFDM technology is that present wireless communication is conducive to one of most widely used technology, has been included into the bases such as LTE WiMax In this all emerging wireless communication standard, it has mitigating frequency-selective fading ability strong, frequency efficiency height and anti-intersymbol The advantages that interference performance is strong can greatly improve the transmission rate of system.However, due between its each subcarrier of OFDM phase it is mutual Independent, the fluctuation range of signal may be very big after superposition, when emitting signal has biggish PAPR, the radio frequency mould of base station Block needs to be equipped with linear power amplifier, this will increase the hardware cost of radio-frequency module, while can also reduce the power of system Efficiency.When base station is equipped with large-scale transmitting antenna, hardware cost and power efficiency problem can become more serious.Cause This, in extensive MIMO-OFDM system, the effective PAPR Restrain measurement of design high speed is particularly important.
For the PAPR problem of ofdm system, existing research work is concentrated mainly on the two kinds of fields SISO and point-to-point MIMO Scape.And for the scene of MU-MIMO, relevant research work is simultaneously few.At MU-MIMO, the collaborative work between user is very Difficulty, therefore inhibiting processing in the PAPR of transmitting terminal is preferably transparent (such as without side information) for user terminal.This also makes MU-MIMO system can not be extended at existing most of algorithms.It, will be under extensive MU-MIMO-OFDM system in the present invention The problem of reducing PAPR, is modeled as an optimization problem, by increasing an interference signal on transmitting signal, and utilizes ADMM Algorithm alternately updates parameters, since interference letter is located in channel kernel by the present invention, can disappear in this way after transmitting Except the interference signal, receiving end is had little effect, hardly influences the performance of system, and does not need any side letter Breath.
Summary of the invention
Extensive MU-MIMO-OFDM system can be reduced by not needing side information the purpose of the present invention is to provide one kind The method of PAPR, and higher system performance is provided.By the present invention in that interference signal is located in channel kernel, make the dry of superposition Signal is disturbed on system performance almost without what influence, by using alternative and iterative algorithm, each parameter of alternating iteration is finally obtained The interference signal.
Based on the method for the extensive MU-MIMO-OFDM system peak-to-average power ratio of reduction alternately updated, including walk as follows It is rapid:
S1, an extensive MU-MIMO-OFDM downlink frequency domain signal X is given, the frequency domain signal X row is reduced PAPR processing, wherein the reduction PAPR processing are as follows: be superimposed an interference signal Δ X repeatedly in the frequency domain signal X；
S2, setting initial parameter: the multiplication for enabling penalty factor ρ=0 in DMM iteration, order are truncated using dichotomy Factor lambda=0 enables the number of iterations t=0, enables initial superposition interference signal Δ X(0)=0, calculate X and mapping matrix described in S1Wherein, HnFor channel；
S3, outer loop is carried out, the time-domain signal Y after superposition interference signal is truncated using dichotomy, thus more New Y, to m=1 ..., M:Wherein, xm,Table respectively Show X and Δ X(t)M column,For L × N point Fourier transformation, PROXINF is to utilize dichotomy pairIt is truncated, λ is Penalty factor in dichotomy, to obtain Y(t+1)M column；
S4, ADMM interior loop is carried out, the specific steps are as follows:
S41, D is enabled(0)=Δ X(t), U(0)=0, calculate A(t+1)=FLNY(t+1)- X, wherein A(t+1)For the frequency after truncation Difference between domain signal and original signal X, FLNFor L × N point inverse Fourier transform, U is that the Lagrange in ADMM iteration multiplies Son, D are the Δ X in ADMM iteration(t), the D that final iteration generates is Δ X(t+1)；
S42, for i=1 ..., Imax- 1, repeat following recursion cycle:
U(i+1)=U(i)+ρ(D(i+1)-Z(i+1)), whereinD, the line n of Z, U are respectively indicated, n isIn Some value,Certain subcarriers to choose from W subcarrier at random are used for transmission, W be total subcarrier number, 1 ≤n≤W；
S5, interference signal is finally returned thatAnd t=t+1 is enabled, if t < Tmax, then return step S2, otherwise End loop.
The beneficial effects of the present invention are:
Even if can still effectively reduce system PAPR by the iteration of seldom number, only need not influence system simultaneously Performance.Compared to the algorithm of traditional super reduction system PAPR, the present invention has stronger actual operation.
Detailed description of the invention
Fig. 1 is to be applied to reduce the flow chart of PAPR using the method for the present invention.
Fig. 2 is extensive MIMO-OFDM system down link block diagram
Fig. 3 is the amplitude of each algorithm under time-domain sampling, subcarrier in frequency domain.
Fig. 4 is relationship, the relationship of SNR and BER of PAPR and CCDF.
Specific embodiment
With reference to the accompanying drawing, the present invention is described in further detail.
The PAPR that the present invention is implemented for reducing ofdm signal, for convenience of description, following embodiments will establish following system Model is illustrated.
The system block diagram of MU-MIMO-OFDM system down link is as shown in Figure 2.Wherein, base station emits day equipped with M root Line, the single-antenna subscriber number of synchronization service is K, and the sub-carrier number of K < < M, OFDM modulation is N.At the both ends of frequency band Usually there are portion subcarriers to be used as protection interval, therefore N number of subcarrier is divided into two parts: being located at setLoad Wave is transmitted for data, is located at setSubcarrier be used as protect bandwidth.In Fig. 1, Sn∈OK×1It is carried for n-th of son The transmission information of K user, X on wavem∈CN×1For the frequency domain information after precoding, Δ Xm∈CN×1For the frequency for reducing PAPR Domain superposed signal, Ym∈CN×1For time-domain signal corresponding after superposed signal.
Under extensive MU-MIMO-OFDM system reduce PAPR the problem of be modeled as
Wherein, ym∈CLN×1For Y ∈ CLN×MM column, indicate m root antenna on after L times of over-sampling time domain letter Number；X∈CN×MSignal is sent for known frequency domain,For Δ X ∈ CN×MLine n, indicate on n-th of subcarrier for reducing (frequency domain) signal that PAPR is superimposed.Want the direct solution problem extremely difficult, therefore, using the method alternately updated, successively Δ X and Y are updated, to obtain the solution of the problem
In emulation, if there is M=128 root transmitting antenna in the base station of the mimo system, K=16 single-antenna subscriber is serviced.It examines Consider the OFDM and modulates the frequency spectrum mapping for sharing N=128 subcarrier, usingThe 40MHz being appointed as in WI-FI model, and setA subcarrier is transmitted for signal.Initial transmissions signal X is set simultaneously (to generate as original bit by convolutional encoding Multinomial [5o 7o])), the modulated modulated signal of 64QAM, wireless channel is frequency selectivity, channel multi-path number 8, Time domain channel response matrixThe Gaussian Profile that d=1 ..., D obeys zero-mean, variance is 1, and its n-th equivalent of son carries Frequency response H on wavenIt can be expressed asIt is detected in receiving end using Viterbi decoding Information flow.The initial value of each parameter is respectively T in algorithmmax=200, Imax=2, λ=1, ρ=0.5.Furthermore to frequency-region signal L=4 times of over-sampling is carried out to calculate PAPR.
Based on above-mentioned constructed model and definition, parameter is carried out based on the algorithm of alternating iteration the present invention provides a kind of Alternating iteration, so that disturbing signal is acquired, to reduce the PAPR of system.
Include the following steps:
S1, an extensive MU-MIMO-OFDM downlink frequency domain signal X is given.It is superimposed one repeatedly on this signal Interference signal Δ X can reduce the PAPR of signal；
S2, setting initial parameter ρ, λ, t=0, Δ X(0)=0, and calculate initial transmissions signal X and mapping matrix
S3, outer loop:
Y is updated, to m=1 ..., M
WhereinFor LN point frequency domain over-sampling, PROXINF is to utilize dichotomy pairIt is truncated.
S4, ADMM interior loop:
Enable D(0)=Δ X(t), U(0)=0, it calculates
A(t+1)=FLNY(t+1)-X
For i=1 ..., Imax- 1, repeat following recursion cycle
U(i+1)=U(i)+ρ(D(i+1)-Z(i+1))
WhereinRespectively indicate D, the line n of Z, U.
S5, interference signal is finally returned thatAnd t=t+1 is enabled, if t < Tmax, then return step S2, otherwise End loop.
By aforesaid operations, the estimation to Δ X and Y is just completed.
Algorithm performance comparative analysis of the related algorithm for reducing PAPR with the method for the present invention will be utilized, below with further Verify performance of the invention.
Using two kinds of measurement indexs come the performance of metric algorithm.One is PAPR performance for measuring time-domain signal, is cried Do complementary cumulative distribution function (complementary cumulative distribution function, abbreviation CCDF)； One is the correctness restored for measuring receiving end bit stream, is called the bit error rate (Bit Error Rate, BER).Assuming that m Time-domain signal on root transmitting antenna is ym, then the definition of PAPR is on the transmitting antenna
Bit error rate be in data communication, in the digital signal received within a certain period of time occur mistake bit number with Received the ratio between the total bit number of digital signal in the same time.
Fig. 3 (a), (c), (e) and (g) describes the width of time-domain sampling signal on first transmitting antenna in each algorithm Degree.From these figures can be seen that it is proposed that the obtained solution of algorithm in each element more integrated distribution near the upper bound, from And there is lower PAPR.(d), (b), (f) and (h) be each algorithm equivalent transmitting frequency-region signal amplitude.It can from figure Out, ZF, FITRA and
It is proposed that algorithm all without out-of-band interference, and clipping algorithm can cause in protection bandwidth it is seriously dry It disturbs.Illustrate that this method all shows more preferably on RSNR and success rate than other algorithms.Institute after Fig. 4 (a) tests for 1000 times There is the average result of the CCDF of antenna.Algorithm proposed by the invention can reduce the PAPR (CCDF of 7dB compared to ZF algorithm (PAPR)=10-2).And FITRA algorithm can only reduce 3dB.But algorithm above can all lead to the deterioration of BER performance.Fig. 4 (b) In it can be seen that the present invention there are about the performance loss of 1dB, this is mainly due to the present invention will increase average emitted power.Total comes It says, PAPR can be both greatly reduced with respect to other algorithms in the present invention, and does not lead to the significantly sacrificing of BER performance, compared to other calculations Method has apparent performance advantage.
To sum up told, it is proposed that invention be based on alternately update the extensive MU-MIMO-OFDM downlink of reduction The algorithm of PAPR, is superimposed an interference signal on initial transmissions frequency-region signal, which is located at the kernel of channel It is interior, the signal can be eliminated after through dissemination channel.Pass through well-designed iterative algorithm, each ginseng of alternating more new algorithm Number, to obtain the estimated value of interference signal, the PAPR of system can be reduced after superposition and will not have to system BER performance too big Influence.The number of iterations is more, and the PAPR performance of system is better, and transmitting antenna is more, and the performance of system is also better.

Claims (1)

1. a kind of method for reducing extensive MU-MIMO-OFDM system peak-to-average power ratio, which comprises the steps of:
S1, an extensive MU-MIMO-OFDM downlink frequency domain signal X is given, the frequency domain signal X is reduced PAPR processing, wherein the reduction PAPR processing are as follows: be superimposed an interference signal Δ X repeatedly in the frequency domain signal X；
S2, setting initial parameter: enable penalty factor ρ=0.5 in ADMM iteration, enable the multiplication that is truncated using dichotomy because Sub- λ=1 enables the number of iterations t=0, enables initial superposition interference signal Δ X(0)=0, calculate X and mapping matrix described in S1Wherein, HnFor channel matrix；
S3, outer loop is carried out, the time-domain signal Y after superposition interference signal is truncated using dichotomy, so that Y is updated, To m=1 ..., M:Wherein, M is transmitting antenna number, xm,Respectively indicate X and Δ X(t)M column,For L × N point Fourier transformation, PROXINF is to utilize dichotomy pairInto Row truncation, λ is the multiplication factor in dichotomy, to obtain Y(t+1)M column；
S4, ADMM interior loop is carried out, the specific steps are as follows:
S41, D is enabled(0)=Δ X(t), U(0)=0, calculate A(t+1)=FLNY(t+1)- X, wherein A(t+1)For the frequency domain letter after truncation Difference number between original signal X, FLNFor L × N point inverse Fourier transform, U is the Lagrange multiplier in ADMM iteration, D For the Δ X in ADMM iteration(t), the D that final iteration generates is Δ X(t+1)；
S42, for i=1 ..., Imax- 1, repeat following recursion cycle:
U(i+1)=U(i)+ρ(D(i+1)-Z(i+1)), whereinD, the line n of Z, U are respectively indicated, n isIn certain One value,For the certain subcarriers being used for transmission chosen from W subcarrier at random, W is total subcarrier number, 1≤n ≤W；
S5, interference signal is finally returned thatAnd t=t+1 is enabled, if t < Tmax, then return step S2, otherwise terminates to follow Ring.
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CN107222446B (en) * 2017-06-28 2019-12-17 电子科技大学 Large-scale MIMO-OFDM peak-to-average power ratio reduction system and method thereof
CN108366035B (en) * 2018-05-21 2020-09-22 东南大学 Precoding method for reducing ADMA system signal peak-to-average power ratio
CN109818633B (en) * 2018-12-19 2021-03-02 武汉船舶通信研究所（中国船舶重工集团公司第七二二研究所） Signal transmitting method and device based on SCPC array and symbol space synthesis
CN113872912A (en) * 2021-10-18 2021-12-31 江苏科技大学 Low-complexity reduction method for peak-to-average power ratio of MIMO-OFDM system
CN114124637B (en) * 2021-11-25 2024-02-27 江苏科技大学 Low-complexity method suitable for reducing peak-to-average ratio of OFDM (orthogonal frequency division multiplexing) system

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