CN109787669A - Joint inhibits the method for precoding of OFDMA system spectral sidelobes and peak-to-average force ratio - Google Patents
Joint inhibits the method for precoding of OFDMA system spectral sidelobes and peak-to-average force ratio Download PDFInfo
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Abstract
The invention discloses the method for precoding that a kind of joint inhibits OFDMA system spectral sidelobes and peak-to-average force ratio.This method changes the correlation of OFDMA system transmitting terminal input data by matrix multiplication, to OFDMA system spectral sidelobes and papr model on the basis of, establish Model for Multi-Objective Optimization, follow that power before and after precoding is constant and the constant design principle of data error rate, optimal precoding column vector combination is found by the algorithm of column circulation and column exchange, to solve multi-objective optimization question, spectral sidelobes and peak-to-average force ratio are simultaneously effective reduced.
Description
Technical field
The invention belongs to wireless communication fields, specifically, being that a kind of joint inhibits OFDMA system spectral sidelobes and peak value
The method for precoding of average power ratio.
Background technique
Highspeed serial data stream is the parallel subnumber of multiple low bit speed rates by serioparallel exchange by multi-carrier communications systems
According to stream, to constitute the multi-carrier communications systems of multiple parallel low-rate symbols, conventional single carrier communication system, only meeting are compared
There is small part sub-channel signal by the influence to decline, therefore is highly resistant to frequency selective fading.OFDM is a kind of multicarrier
Modulation technique is effective against frequency selective fading, and each subcarrier is mutually orthogonal, and intercarrier is overlapped without mutual
Interference, to save spectral bandwidth, improves frequency spectrum resource utilization rate to greatest extent.
OFDMA is a kind of multiple access technique based on OFDM, and OFDMA technology inherits the anti-complicated time-varying letter of OFDM technology
The advantages of road declines, but also inherit two intrinsic deficiencies of OFDM technology: outer (OOB, the Out-of-band) secondary lobe of spectral band
(out-of-band power radiation) is big and papr (PAPR, Peak-to-Average-Power-Ratio) is high.
In OFDMA system, the outer secondary lobe of spectral band shows as a certain user's corresponding data sub-carrier section to adjacent sub-carrier
Out-of-band power radiation in frequency band, leads to multi-access users Communication Jamming.The radiation of sub-band out-of-band power is defined as working band
Interior sub-band out-of-band power radiates (IBOSB, In-Band Out-Of-SubBand).Neighboring user channel is interfered in IBOSB conference；
PAPR greatly then signal exceed power amplifier (HPA, High Power Amplifier) linear working range, cause signal non-
Linear distortion.IBOSB and PAPR problem will affect the performance of communication system, and limitation even hinders the reality of OFDMA technology to answer
With.
At present for OOB inhibit and PAPR reduce research it is more, but for OOB and PAPR joint inhibit research compared with
Few, there has been no the researchs of comparison system jointly controlled for OOB and PAPR problem at this stage, and combine the big portion of research inhibited
It is divided into the simple combination for individually inhibiting OOB method and reduction PAPR method.Research only solves the problems, such as OOB (or PAPR) and ignores
PAPR (OOB) problem, PAPR (OOB) problem can still have or even even worse；PAPR problem is only studied, OOB problem can be interfered
Adjacent channel；OOB problem is only studied, PAPR problem will lead to the Linear Amplifer range that signal exceeds power amplifier, cause
Signal non-linear distortion, spectral sidelobes regeneration；Therefore, really there are problems that the necessity that research joint inhibits OOB and PAPR.
The methods of time-domain windowed, pulse shaping, correlative coding, Subcarrier's weight and the inhibition queue that OOB inhibits are studied, with
And it reduces the peak value window of PAPR, cyclic prefix, retain adjustment, best selective mapping, partial transmission sequence, grid auxiliary star
The methods of the selection of stand collection and related precoding, or sacrifice communication system bit error rate and (receive data error rate, Bit
Error rate) performance is cost, or increasing the complexity of ofdm system is cost, or the calculating of increase ofdm system is answered
Miscellaneous degree is cost, or increases receiving end decoding complex degree.
Summary of the invention
The purpose of the present invention is to provide the precoding sides that a kind of joint inhibits OFDMA system spectral sidelobes and peak-to-average force ratio
Method, design precoding realize that the joint of OFDMA system spectral sidelobes and papr inhibits.
The technical solution for realizing the aim of the invention is as follows: a kind of joint inhibits OFDMA system spectral sidelobes and peak-to-average force ratio
Method for precoding, pass through to input OFDMA system initial data symbol in advance multiplied by one by optimization matrix carry out
Precoding realizes that the joint of OFDMA system spectral sidelobes and papr inhibits；By being built to OFDMA system signal
Mould simultaneously solves the matrix that multi-objective optimization question calculates the optimization.
Compared with prior art, the present invention its remarkable advantage: (1) power that is followed of present invention design pre-coding matrix is not
Change principle and data error rate principle of invariance can significantly reduce whole under the premise of not influencing the communication performance of point-to-point transmission
The interference of a system；(2) it is modeled, is had using the frequency spectrum and peak-to-average power ratio that the form that matrix vector is multiplied is OFDMA system
Description is simple, is easy to the advantages of optimizing；(3) matrix of multi-objective optimization question is solved by column exchange and the search of column round-robin method
Solution, has the advantages that simple and easy, computation complexity is small.
Detailed description of the invention
Fig. 1 is the transmitter architecture of precode OFDM A k-th of user of system.
Specific embodiment
The present invention is directed to two deficiencies of OFDMA system: spectral sidelobes are big and papr is high, and joint is inhibited
The Method Modeling of the two is a multi-objective optimization question.The multi-objective optimization question of spectral sidelobes and papr is very
Not there is while meeting the optimal solution of multiple targets in solution hard to find, therefore design precoding first inhibits spectral sidelobes,
And provide the design method of precoding；Then under conditions of keeping precoding to inhibit spectral sidelobes performance constant, followed using column
Ring and column exchange algorithm, seek the pre-coding matrix for reducing papr, inhibit to realize and be combined using precoding
The spectral sidelobes and papr of OFDMA system.
A kind of joint of the present invention inhibits the method for precoding of OFDMA system spectral sidelobes and peak-to-average force ratio, comprising the following steps:
The first step, it is a multiple-objection optimization that joint, which is inhibited the Method Modeling of OFDMA system spectral sidelobes and peak-to-average force ratio,
Problem；
Second step, design precoding inhibits OFDMA system spectral sidelobes, and provides the design method of precoding；
Third step is recycled using column under conditions of keeping precoding to inhibit spectral sidelobes performance constant and column exchange is calculated
Method calculates the pre-coding matrix for reducing papr, realizes and is inhibited by the frequency spectrum of OFDMA system using precoding joint
Valve and papr.
In the first step:
OFDMA system communication scenes are communication uplink, are made of a communication base station and K transmitting node, are emitted
Node is user, user index k=1,2 ... K, spectral bandwidth B are formed by N number of subband is wide, and subband width is subcarrier,
Each sub-carrier indices are n=0,1...N-1；There is K user in OFDMA system, each subcarrier is divided into K according to indexed sequential
Group subcarrier collection is distributed to each user and is used, therefore each subcarrier integrates the number of sub carrier wave for including as P=N/K, and kth user distributes
Sub-carrier indices be Bk∈ [(k-1) P, kP-1], the roll-off factor of time domain window are β；The OFDMA symbol data period is T, then respectively
Δ f=1/T, protection interval duration T are divided between sub-carrier frequenciesg, practical OFDMA symbol cycle TuFor Tu=T+Tg (1)
If the sampling interval is Ts(N Δ f), then time domain discrete signal sequence and protection interval sequence length divide=T/N=1/
Not Wei N and v, OFDMA symbol sequence total length be L=N+v (2)
One OFDMA symbol is closed by multiple by the sub-carrier signal of phase-shift keying (PSK) PSK or quadrature amplitude modulation QAM
At the data to be modulated for defining each subcarrier of kth user areWherein, M≤P；Assuming that be modulated
DataIn elementIt is stochastic variable mutually indepedent and with distribution, is the star of phase-shift keying (PSK)
Seat mapping point meets expectation E [c(k)]=0M×1, covariance E [c(k)(c(k))H]=IM；Wherein, IMIndicate that size is the list of M × M
Bit matrix；
One pre-coding matrix G of premultiplication before data symbol IDFT to be modulated modulation(k)；Define G(k)Indicate kth user
Size be P × M pre-coding matrix, (i, n) element isInput data symbol c(k)Pass through premultiplication precoding square
Battle array G(k)Realize precoding processing after data be
Matrix vector expression formula are as follows:
d(k)=G(k)c(k) (4)
Data d after precoding processing(k)It is (long by subcarrier maps, IDFT modulation (size N), insertion cyclic prefix
For degree for v), time domain adds rectangular window and digital-to-analogue conversion, and the power spectrum of final output signal is,
Wherein,And whereinIt is the Fourier transform matrix that size is N × N, (m, i) a element isB(k)It indicates
Size is the subcarrier maps matrix of the kth user of N × P:
B(k)=[0P×[(k-1)P] IP 0P×(N-kP)]T (6)
C indicates that the cyclic prefix that size is (1+ β) L × N and cyclic suffix are inserted into matrix:
In second step:
Define working band Ξ=[- 1/2T of OFDMA signals,1/2Ts], the sub- working band of kth user isThe sub-band external power of kth user is inhibited to radiate the smallest code optimization mesh that prelists
Scalar functions are as follows:
Objective optimisation problems (8) can be expressed as:
Define three Hermitian complex conjugate symmetry matrixes:
Under conditions of signal power is certain, meet
Objective optimisation problems (8) can be expressed as:
Wherein
The design of precoding should follow following principle:
Principle 1: the mean power of OFDMA symbol is consistent before and after precoding；
Principle 2: whether there is or not the OFDMA system of precoding reception data error rate performance is consistent.
Using column circulation and column exchange algorithm in third step, the pre-coding matrix for reducing papr is calculated, it is real
Now inhibit the spectral sidelobes of OFDMA system and the concrete methods of realizing of papr using precoding joint are as follows:
For the PAPR for k-th of user for inhibiting OFDMA system, establishes and the objective optimization of the precoding of PAPR is inhibited to ask
Topic:
Wherein,And
Joint inhibits the precoding objective optimisation problems (13) of IBOSB and inhibits the precoding objective optimisation problems of PAPR
(14), the multi-objective optimization question that precoding joint inhibits the two is established:
The solution of multi-objective optimization question (15) is calculated using " two steps are walked " strategy.
Above-mentioned method for precoding uses the solution of " two steps are walked " policy calculation multi-objective optimization question (15) specific
Are as follows:
The first step, the first optimal solution of one of single-object problem in solution multi-objective optimization question；
Second step finds other objective optimizations under conditions of guaranteeing that single-object problem obtains optimal solution in the first step
The optimal solution of problem.
In described " two steps are walked " strategy, firstly, objective optimisation problemsPre-coding matrix solution G(k)By matrixFeature vector constitute；Secondly, being based on pre-coding matrix solution G(k)It is exchanged using column circulation with column
Algorithm.
The column circulation is as follows with column exchange algorithm process:
Define two kinds of rank transformation matrixesColumn circular matrix
With column switching matrix
Pass through rank transformation matrixThe right side multiplies pre-coding matrix G(k), realize pre-coding matrix G(k)Column rearrangement, target
Optimization problem function f2(G(k)) value again；Rank transformation matrixOptimum column search area be reduced into search reduce PAPR arrive
Threshold values optimum column circular matrix belowOr column switching matrix
The present invention will be further explained below with reference to the attached drawings.
1, precode OFDM A system modelling
OFDMA system communication scenes are communication uplink, by a communication base station and K transmitting node (user) group
At, user index k=1,2 ... K, spectral bandwidth B are made of N number of subband wide (subcarrier), and each sub-carrier indices are n
=0,1...N-1；There is K user in OFDMA system, each subcarrier is divided into K group subcarrier collection according to indexed sequential, distribution
It is used to each user, therefore each subcarrier integrates the number of sub carrier wave for including as P=N/K, the sub-carrier indices of kth user distribution are Bk
∈ [(k-1) P, kP-1], the roll-off factor of time domain window are β.The OFDMA symbol data period is T, then is divided between each sub-carrier frequencies
Δ f=1/T, protection interval duration Tg, practical OFDMA symbol cycle TuFor,
Tu=T+Tg (18)
If the sampling interval is Ts(N Δ f), then time domain discrete signal sequence and protection interval sequence length divide=T/N=1/
It is notNAnd v, OFDMA symbol sequence total length are
L=N+v (19)
One OFDMA symbol passes through phase-shift keying (PSK) (PSK, Phase-Shiftkeying) or quadrature amplitude tune by multiple
The sub-carrier signal synthesis for making (QAM, Quadrature Amplitude Modulation), defines each subcarrier of kth user
Data to be modulated areWherein, M≤P.Assuming that data to be modulated
In elementIt is stochastic variable mutually indepedent and with distribution, is the constellation mapping point of phase-shift keying (PSK), meets expectation E [c(k)]
=0M×1, covariance E [c(k)(c(k))H]=IM.Wherein, IMIndicate that size is the unit matrix of M × M.
Combine the transmitting terminal system block diagram for inhibiting IBOSB and PAPR Fig. 1 shows precoding, basic principle is in number to be modulated
According to one pre-coding matrix G of premultiplication before symbol IDFT modulation(k).Define G(k)The size for indicating kth user is prelisting for P × M
Code matrix, (i, n) element areInput data symbol c(k)Pass through premultiplication pre-coding matrix G(k)Realize precoding processing
Data afterwards are
Matrix vector expression formula are as follows:
d(k)=G(k)c(k) (21)
Data d after precoding processing(k)It is (long by subcarrier maps, IDFT modulation (size N), insertion cyclic prefix
For degree for v), time domain adds rectangular window and digital-to-analogue conversion, and the power spectrum of final output signal is,
Wherein,And whereinIt is the Fourier transform matrix that size is N × N, (m, i) a element isB(k)It indicates
Size is the subcarrier maps matrix of the kth user of N × P:
B(k)=[0P×[(k-1)P] IP 0P×(N-kP)]T (23)
C indicate size be (1+ β (cyclic prefix and cyclic suffix of L × N are inserted into matrix:
2, precoding inhibits OFDMA system spectral sidelobes
Define working band Ξ=[- 1/2T of OFDMA signals,1/2Ts], the sub- working band of kth user isTherefore the sub-band external power of kth user is inhibited to radiate the smallest precoding excellent
Change objective function are as follows:
Pay attention to inhibiting the precoding objective optimization function (8) of IBOSB, only and the element of only column vector matrix α (f) is frequency
The function of rate f, therefore objective optimisation problems (8) can be expressed as:
Now define three Hermitian (complex conjugate symmetry) matrixes:
Under conditions of signal power is certain, meet
Objective optimisation problems (8) can be expressed as:
Wherein
Precoding Design principle: precoding is reducing the same of sub-band out-of-band power as a kind of method for inhibiting IBOSB
When, it should ensure that the performance for not influencing OFDMA system, or bring additional cost, should keep as far as possible with OFDMA when no precoding
The consistency of system, therefore the design of precoding should follow following principle:
Principle 1: the mean power of OFDMA symbol is consistent before and after precoding；
Principle 2: whether there is or not the OFDMA system of precoding reception data error rate performance is consistent.
3, column circulation and column exchange algorithm
The PAPR for considering k-th of user of inhibition OFDMA system now, establishes the objective optimization for inhibiting the precoding of PAPR
Problem:
Wherein,And
To realize that precoding joint inhibits IBOSB and PAPR, joint inhibits the precoding objective optimisation problems (13) of IBOSB
With the precoding objective optimisation problems (14) for inhibiting PAPR, the multi-objective optimization question that precoding joint inhibits the two is established:
The solution computation complexity of multi-objective optimization question (15) is very high, and be likely to be not present so that multiple target simultaneously
Optimal scheme.In response to this problem, seek the solution of multi-objective optimization question (15) using " two steps are walked " strategy.First
Step: the optimal solution of one of single-object problem first in solution multi-objective optimization question；Step 2: guaranteeing the first step
Under conditions of middle single-object problem obtains optimal solution, the optimal solution of other objective optimisation problems is found.Obviously, in second step
The optimal solution of target is only the optimal solution under the conditions of meeting the first step, is not the optimal solution of multi-objective optimization question, is target
Suboptimal solution.
For multi-objective optimization question, based on " two steps are walked " strategy, firstly, objective optimisation problemsPrelist
Code matrix solution G(k)By matrixFeature vector constitute；Secondly, being based on pre-coding matrix solution G(k)Make
With column circulation and column exchange algorithm.
Column circulation and column exchange algorithm:
Define two kinds of rank transformation matrixesColumn circular matrix
With column switching matrix
Pass through rank transformation matrixThe right side multiplies pre-coding matrix G(k), realize pre-coding matrix G(k)Column rearrangement, target
Optimization problem function f2(G(k)) value again.Therefore, rank transformation matrixOptimum column search area be reduced into search reduce
PAPR is to threshold values optimum column circular matrix belowOr column switching matrix
Fig. 1 illustrates the transmitting terminal block diagram of precode OFDM A system.From the figure, it can be seen that precoding processing is initial
Before data modulation, then the data after precoding processing are modulated using subcarrier maps, IDFT, insertion cyclic prefix,
After windowing process, then output OFDM A time domain discrete signal.
Pseudocode in column circulation and column exchange algorithm depicts the realization step of column circulation and column exchange, and algorithm is divided into two
Step is traversed:
The first step traverses column circular matrixFinding reduces OFDMA signal PAPR to threshold values column circular matrix belowAnd rank rear circular matrixThe right side multiplies initial pre-coding matrix G(k), to constitute joint precoding.If first step search success,
Then algorithm terminates, and otherwise algorithm enters second step；
Second step traverses column switching matrixFinding reduces OFDMA signal PAPR to threshold values column switching matrix belowAnd rank rear switching matrixThe right side multiplies initial pre-coding matrix G(k), to constitute joint precoding, algorithm terminates.If algorithm
Second step still fails, and the operation of two step of algorithm does not traverse so that PAPR meets threshold values rank transformation matrix belowIt is (this
Situation probability is very low), then rank transformation matrixThe column circular matrix for making PAPR minimum in the operation of two step of selection algorithmOr column
Switching matrixComposition.
If the optimum column transformation matrix of arithmetic result is column circular matrixThen defining side information is [t, 0], wherein t
Indicate total step-length of column ring shift right；If the optimum column transformation matrix of arithmetic result is column switching matrixThen define sideband
Information is [t, m], wherein t, and m indicates to carry out the column index of column exchange.Therefore, can be according to side information end in receiving end
No is integer 0, judges optimum column transformation matrixIt is column circular matrixForm or column switching matrixForm, thus into
The corresponding inverse rank transformation operation recovery of row goes out primary data.
Precoding joint inhibits sub-band out-of-band radiation and reduces the puppet of the column circulation of PAPR and the main flow of column exchange
Code is as follows.
Algorithm starts
Algorithm initialization:
Step 1: program initialization is made by spectral model (formula 5) the constitution optimization problem (formula 13) of OFDMA system
Feature vector, which is obtained, with the Eigenvalues Decomposition of matrix constructs initial pre-coding matrix；
Step 2: it definition column swap block: indicates precoding G(k)M column exchange position with t column；
Step 3: definition circulation column move function: indicating precoding G(k)All column ring shift right t column；
Algorithm is step 1: circulation column move search
Calculate G(k)c(k)Peak-to-average power ratio value；
The column ring shift right 1 of pre-coding matrix is arranged, the letter that the pre-coding matrix after column move acts on system generation is calculated
Number peak-to-average power ratio.
If G(k)c(k)Peak-to-average power ratio become smaller, then record column move after pre-coding matrix and peak-to-average power ratio value；
Continue to arrange the column ring shift right 1 of pre-coding matrix, until the column of pre-coding matrix are circulated back to original position
It sets.
Algorithm is step 2: column exchange search
The a certain column of pre-coding matrix and another column are exchanged into position, the pre-coding matrix after calculating column exchange, which acts on, is
The peak-to-average power ratio for the signal that system generates.
If G(k)c(k)Peak-to-average power ratio become smaller, then the pre-coding matrix and peak-to-average power ratio after recording column exchange
Value；
Continue until by the combination of two column of pre-coding matrix to traverse two column exchange positions of pre-coding matrix one time.
Export the pre-coding matrix finally recorded.
Algorithm terminates.
Claims (3)
1. the method for precoding that a kind of joint inhibits OFDMA system spectral sidelobes and peak-to-average force ratio, it is characterised in that: by input
The initial data symbol of OFDMA system carries out precoding multiplied by a matrix by optimization in advance, realizes OFDMA system frequency spectrum
The joint of secondary lobe and papr inhibits；By to OFDMA system signal modeling and solving multi-objective optimization question meter
Calculate the matrix of the optimization.
2. method for precoding according to claim 1, it is characterised in that: in the Precoding Design, computing system first
Power spectral coefficient；
Wherein It is the Fourier transformation that size is N × N
Matrix, (m, i) a element areB(k)Indicate that size is the subcarrier of the kth user of N × P
Mapping matrix
B(k)=[0P×[(k-1)P] IP 0P×(N-kP)]T
C indicates that the cyclic prefix that size is (1+ β) L × N and cyclic suffix are inserted into matrix
3. method for precoding according to claim 1, it is characterised in that: in the Precoding Design, by rightThe Eigenvalues Decomposition for carrying out matrix obtains several feature vectors, these combination of eigenvectors rise
To form pre-coding matrix G(k)；By G(k)In column ring shift right, the peak-to-average power ratio of computing system, finding makes peak-to-average power ratio
Reduced pre-coding matrix；The G that will be obtained again(k)In it is any two column exchange, the peak-to-average power ratio of computing system, finding makes peak
The pre-coding matrix that equal power ratio reduces.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112702095A (en) * | 2020-12-28 | 2021-04-23 | 西安交通大学 | PAPR suppression method based on constructive interference precoding in MIMO-OFDM |
| CN113517916A (en) * | 2021-07-12 | 2021-10-19 | 北京通广龙电子科技有限公司 | Beam forming method of airborne phased array antenna |
| CN113691479A (en) * | 2021-07-15 | 2021-11-23 | 中国电子科技集团公司第二十九研究所 | Method and device for eliminating side lobe influence of signal and readable storage medium |
-
2018
- 2018-12-30 CN CN201811649718.8A patent/CN109787669A/en active Pending
Non-Patent Citations (1)
| Title |
|---|
| RENHUI XU: "A Unitary Precoder for Optimizing Spectrum and PAPR Characteristic of OFDMA Signal", 《IEEE TRANSACTIONS ON BROADCASTING》 * |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112702095A (en) * | 2020-12-28 | 2021-04-23 | 西安交通大学 | PAPR suppression method based on constructive interference precoding in MIMO-OFDM |
| CN113517916A (en) * | 2021-07-12 | 2021-10-19 | 北京通广龙电子科技有限公司 | Beam forming method of airborne phased array antenna |
| CN113517916B (en) * | 2021-07-12 | 2023-09-08 | 北京通广龙电子科技有限公司 | Beam forming method of airborne phased array antenna |
| CN113691479A (en) * | 2021-07-15 | 2021-11-23 | 中国电子科技集团公司第二十九研究所 | Method and device for eliminating side lobe influence of signal and readable storage medium |
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Application publication date: 20190521 |