CN100539483C - Utilize sequence of pilot symbols to reduce the method and apparatus of ofdm system peak-to-average force ratio - Google Patents
Utilize sequence of pilot symbols to reduce the method and apparatus of ofdm system peak-to-average force ratio Download PDFInfo
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- CN100539483C CN100539483C CNB031475337A CN03147533A CN100539483C CN 100539483 C CN100539483 C CN 100539483C CN B031475337 A CNB031475337 A CN B031475337A CN 03147533 A CN03147533 A CN 03147533A CN 100539483 C CN100539483 C CN 100539483C
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Abstract
A kind of method of utilizing sequence of pilot symbols to reduce the peak-to-average force ratio of ofdm system comprises step: change the polarity and the power of the original pilot frequency sequence in the OFDM symbol, obtain one group of all possible sequence; Each sequence in this group sequence is carried out inverse Fourier transform; To carry out inverse Fourier transform through coding and the data sequence that interweaves, and each sequence in the one group of sequence that obtains after result of calculation and the front pilot tone conversion will be carried out add operation, obtain another group sequence; Calculate the peak-to-average force ratio of each sequence in this group sequence respectively, select sequence corresponding to minimum peak-to-average force ratio as transmitting sequence.The present invention adopts low complex degree, high efficiency algorithm by changing the polarity and the transmitting power of pilot frequency sequence in the ofdm system, not needing additional information transmission and not increasing under the prerequisite of receiver complexity, has reduced the peak-to-average force ratio of ofdm system.
Description
Technical field
The present invention relates to OFDM communications (OFDM) technical field, specifically, the present invention relates generally to the method and apparatus that reduces peak-to-average force ratio in the ofdm communication system.
Background technology
Owing to have the very high availability of frequency spectrum, be convenient to the data rate that provides higher, OFDM (OFDM) technology has become the mainstream technology of next generation communication system.But this technology has an intrinsic shortcoming, promptly has very high peak-to-average force ratio.Peak-to-average force ratio (brief note is PAPR) is meant the ratio of peak power and average power.Avoid distortion and frequency spectrum diffusion, high peak-to-average force ratio needs the emission amplifier of the big range of linearity and high-output power.In order to address this problem current existing several different methods.
These methods can be divided three classes: block encoding, cutting method and probabilistic method.The method of block encoding be with an OFDM symbol by certain rule encoding, this sign indicating number has less peak-to-average force ratio, thereby reaches the purpose that reduces peak-to-average force ratio.So the method for cutting down is exactly that the bigger carrier wave of amplitude or carrier wave are cut down or compressed a kind of method that reduces peak-to-average force ratio.The thinking of probabilistic method is to reach the purpose that obtains less peak-to-average force ratio by the probability of occurrence that reduces peak value.Be part transmitting sequence (PTS) and select mapping (SLM) two kinds of methods in these class methods according to representational.
In three current class methods, the method for block encoding only is applicable to the system that carrier number is very little, and application limit is very big.The method of cutting down is too big to the influence of systematic function.Probability method has application promise in clinical practice.Mainly contain part transmitting sequence (PTS) in these class methods and select mapping (SLM) two kinds of methods.
In SLM, the information sequence after the modulation need multiply by one group of fixing random sequence that certain feature is arranged.This random sequence is long more, and performance is good more.At receiving terminal, also need corresponding division process.In PTS, the sub-piece sequence of information after each modulation will multiply by one group of signal of determining phase place deflection, and the results added after transmitter is taken advantage of each sub-piece be the phase place deflection of an optimization of the sub-piece selection of each information with the principle of minimum peak-to-average force ratio.Equally, also need corresponding inverse operation at receiving terminal.The operand of multiply operation is bigger.As seen, the operand of these two kinds of methods is big especially, and needs additional information transmission, and this will reduce the availability of frequency spectrum.
Summary of the invention
The objective of the invention is to propose a kind of by changing the polarity and the transmitting power of pilot frequency sequence in the ofdm system, adopt low complex degree, high efficiency algorithm, do not need additional information transmission and do not increasing under the prerequisite of receiver complexity, reducing the method and the device of the peak-to-average force ratio of ofdm system.
For achieving the above object, according to an aspect of of the present present invention, a kind of method of utilizing sequence of pilot symbols to reduce the peak-to-average force ratio of ofdm system is characterized in that comprising step:
Change the polarity and the power of the original pilot frequency sequence in the OFDM symbol, obtain one group of all possible sequence, wherein, comprise the frequency pilot sign of similar number in the described OFDM symbol, and the position of described pilot frequency sequence does not need any change;
Each sequence in this group sequence is carried out inverse Fourier transform;
To carry out inverse Fourier transform through coding and the data sequence that interweaves, and each sequence in the one group of sequence that obtains after transformation results and the front inverse Fourier transform will be carried out add operation, obtain another group sequence;
Calculate the peak-to-average force ratio of each sequence in this another group sequence respectively, select sequence corresponding to minimum peak-to-average force ratio as transmitting sequence.
According to another aspect of the present invention, a kind of device that utilizes sequence of pilot symbols to reduce the peak-to-average force ratio of ofdm system is characterized in that comprising:
Change the polarity and the power model of pilot tone, the output of input termination pilot frequency sequence module, the input of output termination matrix IDFT module, the polarity of described change pilot tone and power model change the polarity and the power of the symbol of pilot frequency sequence;
Matrix IDFT module, the input termination changes the polarity and the power model of pilot tone, output termination add operation module, described matrix IDFT module is done output matrix behind the inverse Fourier transform with the matrix of input
The IDFT module, the output of input termination data sequence module, the vector that described IDFT module will be imported is made inverse Fourier transform, output vector
The add operation module, the output of receiving matrix IDFT module and IDFT module is with vector
And matrix
Every row carry out addition respectively and obtain new matrix c
μ, and operation result exported to sequence selection module;
Sequence selection module selects to have the sequence of minimum peak-to-average force ratio as output sequence.
The present invention adopts low complex degree, high efficiency algorithm by changing the polarity and the transmitting power of pilot frequency sequence in the ofdm system, not needing additional information transmission and not increasing under the prerequisite of receiver complexity, has reduced the peak-to-average force ratio of ofdm system.
Description of drawings
Fig. 1 utilizes sequence of pilot symbols to reduce the device schematic diagram of the peak-to-average force ratio of ofdm system;
Fig. 2 is the frame structure of a typical ofdm system;
Fig. 3 is the distribution map of pilot tone and data in the typical OFDM symbol;
Peak-to-average force ratio when Fig. 4 is the down different pilot power of QPSK modulation〉constant (χ
0) probability distribution graph;
Peak-to-average force ratio when Fig. 5 is the down different pilot power of 16QAM modulation〉constant (χ
0) probability distribution graph;
Peak-to-average force ratio when Fig. 6 is the down different pilot power of 64QAM modulation〉constant (χ
0) probability distribution graph;
Fig. 7 is the peak-to-average force ratio of PRPC and SLM〉constant (χ
0) the probability distribution comparison diagram;
Fig. 8 is the peak-to-average force ratio of PRPC and PTS〉constant (χ
0) the probability distribution comparison diagram.
Embodiment
The present invention utilizes the method for sequence of pilot symbols reduction ofdm system peak-to-average force ratio, at first changes the polarity and the power of the original pilot frequency sequence in the OFDM symbol, obtains one group of all possible sequence; Secondly, each sequence in this group sequence is carried out inverse Fourier transform (IDFT); Then, will also carry out inverse Fourier transform through coding and the data sequence that interweaves, and each sequence in the one group of sequence that obtains after result of calculation and the front pilot tone conversion will be carried out add operation, obtain another group sequence.At last, calculate the peak-to-average force ratio of each sequence in this group sequence respectively, select sequence corresponding to minimum peak-to-average force ratio as transmitting sequence.Change the polarity and the power of the original pilot frequency sequence in the OFDM symbol, allow each pilot tone can get+1 or-1 two value exactly, so just can obtain one group of possible sequence; In these possible sequences, except that pilot frequency sequence, other parts are zero.If necessary, adjust the amplitude of pilot frequency sequence again, to change the power of pilot tone.Be meant result behind the block interleaving that information source carries out through chnnel coding with by certain rule through coding and the data sequence that interweaves.In this sequence, the position of corresponding pilot frequency sequence part is entirely by zero setting.The peak-to-average force ratio of each sequence is meant the power ratio of the peak value and the mean value of this sequence.Transmitting sequence is meant and will gives the sequence of radio frequency part.
The device that utilizes sequence of pilot symbols to reduce the ofdm system peak-to-average force ratio of the present invention comprises changing pilot tone polarity and 5 modules such as power model, matrix IDFT module, IDFT module, add operation module and sequence selection module.Wherein, change the input that pilot tone polarity and power model receive the pilot frequency sequence module, generate an output matrix and give matrix IDFT module.IDFT module receiving data sequence is exported to the add operation module with the sequence after the IDFT conversion.The output of add operation module receiving matrix IDFT module and IDFT module is exported to sequence selection module with the result after the computing.Sequence selection module receives the output of addition module, and the sequence of selecting to have minimum peak-to-average force ratio outputs to radio frequency.
Below in conjunction with accompanying drawing in detail the present invention is described in detail.As depicted in figs. 1 and 2, an OFDM frame is made up of a Preamble and a plurality of OFDM symbol, and each OFDM symbol comprises the frequency pilot sign and the data sequence of some.Method of the present invention just is based on the ofdm system of this structure.Suppose in each OFDM symbol, comprise the frequency pilot sign of similar number.We come mark with μ OFDM symbol with vectorial A μ, then have
In the following formula, A
μ,
With
Be 3 vectors that length is identical.
Represent sequence of pilot symbols in μ the OFDM symbol.In this sequence, all fill with 0 the position corresponding with data.
Represent data sequence in μ the OFDM symbol.In this sequence, all fill with 0 the position corresponding with pilot tone.
The present invention is described in further detail below in conjunction with accompanying drawing.Following elder generation is discussed respectively each composition module in the invention.
1, the polarity and the power model (M100) of change pilot tone
Pilot frequency sequence
Be that a value is+1 or-1 given sequence.Changing the polarity of pilot tone and the value of each symbol that power model makes pilot frequency sequence can get+1 or-1 two value.Suppose that each OFDM symbol occupies M carrier wave, wherein have n to give frequency pilot sign.After changing the polarity of each frequency pilot sign so, can obtain 2
n(N=2
n) individual possible sequence
For convenience, we remember N=2
nSo, change the polarity of pilot tone and the output of power model
Can be expressed as
The size of this matrix is N * M, a kind of possible pilot frequency sequence value of every line display.
2, matrix IDFT module (M101)
This module is with the matrix of input
Make inverse Fourier transform by row, obtain a new matrix
Each row sequence of this matrix is exactly the result of the inverse Fourier transform of a possible pilot frequency sequence.
3, IDFT module (M102)
The vector that this module will be imported
Make inverse Fourier transform, obtain a new vector
4, add operation module (M103)
This module is with vector
And matrix
Every row carry out addition respectively and obtain new matrix c
μ
5, sequence selection (M104) module
This module compute matrix c
μThe peak-to-average force ratio of each row vector selects to have that sequence of minimum peak-to-average force ratio as output sequence.
It is 4 parts that concrete signal processing is divided into, and is described in detail as follows respectively:
1, at first, determine that frequency pilot sign occupies the number and the position of carrier number, the structure vector
This vectorial length is a carrier number that the OFDM symbol is occupied, and the position except that frequency pilot sign all is changed to zero entirely.Polarity and power model (M100) by changing each frequency pilot sign obtain matrix as shown in Equation (2)
Utilize matrix IDFT module (M101) to finish to matrix
Make inverse Fourier transform by row, obtain a new matrix
Because this matrix has comprised the result of the IDFT of the possible pilot frequency sequence of institute, so for data sequence all fix, so this matrix only needs to calculate once when just beginning, and just can be saved in the memory, uses for the data sequence in each OFDM symbol.In addition, because IDFT is a linear operation, the power that increases pilot tone just is equivalent to matrix
Multiply by a normal real number.
2, secondly, determine that data in each OFDM symbol occupy the number and the position of carrier number, structure vector
This vectorial length is a carrier number that the OFDM symbol is occupied, and the position of frequency pilot sign all is changed to zero entirely.The vector that to import by IDFT module (M102)
Make inverse Fourier transform, obtain a new vector
3, then, with vector
Give add operation module (M103) with the matrix in the memory, this module is with vector
And matrix
Every row carry out addition respectively and obtain new matrix c
μ
4, last, sequence selection module (M104) compute matrix c
μThe peak-to-average force ratio of each row vector selects to have that sequence of minimum peak-to-average force ratio as output sequence.
The present invention compares with the algorithm of the peak-to-average force ratio of existing reduction ofdm system, and the PRPC method that the present invention proposes has following advantage:
1, good performance. The PRPC method reducing aspect the peak-to-average force ratio, can obtain than in the past The better performance of method. In order to prove this point, in the accompanying drawing 4,5,6,7,8 with the PRPC method and Carried out Performance Ratio according to representational two kinds of method SLM and PTS. Use the size of IDFT in the emulation Be 128, wherein pilot number is 8, lay respectively at ± 7, ± 21, ± 35, ± 49. Fig. 4,5,6 provides respectively Under QPSK, 16QAM, three kinds of modulation systems of 64QAM, different pilot powers are to PRPC method performance Impact. The value of dB is that pilot power is equivalent to data power. 0dB represents pilot power and number Identical according to power, 3dB represents that pilot power is a times of data power, and 3dB represents pilot power 4 times of data power. Can find out that under different modulation systems, the power of pilot tone is more big, PRPC Algorithm Performance is more good. Fig. 7 has provided respectively in identical IFFT length with Fig. 8, the side of QPSK modulation Under the formula, the Performance Ratio of PTS, SLM and PRPC. Can find out, under identical condition, PRPC Performance be better than the performance of other two kinds of methods.
2, low complex degree. In SLM, the information sequence after the modulation need to multiply by one group of fixing having The random sequence of certain feature. This random sequence is more long, and performance is more good. At receiving terminal, also need Corresponding division process. In PTS, the information sub-block sequence after each modulation will multiply by one group to be determined Results added after the signal of phase place deflection, emitter are taken advantage of each sub-block, former with minimum peak-to-average force ratio Then be the phase place deflection that each information sub-block is selected an optimization. Equally, also need corresponding at receiving terminal Inverse operation. The operand of multiply operation is bigger. The PRPC method does not need complicated multiplying, institute Very low with complexity.
3, availability of frequency spectrum height. Method in the past all needs to transmit additional information, and receiver Can restoring data. And the PRPC method does not need additional information transmission, so saved partial frequency spectrum, carries Supplied service efficiency.
4, implementation method is simple. The current method knot that all needs to change receiver more or less Structure, this will not utilize the operation of system, also increase the complexity of system simultaneously. PRPC among the present invention Method does not need to change any structure of receiver, and is very simple.
5, high reliability. In other method, the reliability of additional information transmission is extremely important, In case make mistakes the consequence of bringing on a disaster property. The PRPC method since without any need for additional information, institute Need not considering this problem, thereby has higher reliability.
Claims (2)
1. method of utilizing sequence of pilot symbols to reduce the peak-to-average force ratio of ofdm system is characterized in that comprising step:
Change the polarity and the power of the original pilot frequency sequence in the OFDM symbol, obtain one group of all possible sequence, wherein, comprise the frequency pilot sign of similar number in the described OFDM symbol, and the position of described pilot frequency sequence does not need any change;
Each sequence in this group sequence is carried out inverse Fourier transform;
To carry out inverse Fourier transform through coding and the data sequence that interweaves, and each sequence in the one group of sequence that obtains after transformation results and the front inverse Fourier transform will be carried out add operation, obtain another group sequence;
Calculate the peak-to-average force ratio of each sequence in this another group sequence respectively, select sequence corresponding to minimum peak-to-average force ratio as transmitting sequence.
2. device that utilizes sequence of pilot symbols to reduce the peak-to-average force ratio of ofdm system is characterized in that comprising:
Change the polarity and the power model (M100) of pilot tone, the output of input termination pilot frequency sequence module, the input of output termination matrix IDFT module (M101), the polarity of described change pilot tone and power model (M100) change the polarity and the power of the symbol of pilot frequency sequence;
Matrix IDFT module (M101), the input termination changes the polarity and the power model (M100) of pilot tone, output termination add operation module (M103), described matrix IDFT module (M101) is done output matrix behind the inverse Fourier transform with the matrix of input
IDFT module (M102), the output of input termination data sequence module, the vector that described IDFT module (M102) will be imported is made inverse Fourier transform, output vector
Add operation module (M103), the output of receiving matrix IDFT module (M101) and IDFT module (M102) is with vector
And matrix
Every row carry out addition respectively and obtain new matrix c
μ, and operation result exported to sequence selection module (M104);
Sequence selection module (M104) selects to have the sequence of minimum peak-to-average force ratio as output sequence.
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| CN101374125B (en) * | 2007-08-24 | 2011-03-09 | 大唐移动通信设备有限公司 | Method and apparatus for reducing PAR |
| CN101110619B (en) * | 2007-08-27 | 2011-03-02 | 中兴通讯股份有限公司 | Method and device for reducing PAR in OFDMA system |
| CN101695062B (en) * | 2009-10-19 | 2011-12-21 | 中国电子科技集团公司第五十四研究所 | Self-adaptive bit allocation method based on grouping in orthogonal frequency division multiplexing system |
| CN102263765B (en) * | 2011-08-22 | 2013-07-10 | 宁波大学 | Robust transmission method of digital broadcast mobile signals |
| CN102263761B (en) * | 2011-08-22 | 2013-06-12 | 宁波大学 | Method for modulating framing of multimedia wireless broadcast signals |
| CN102271117B (en) * | 2011-08-22 | 2013-06-26 | 宁波大学 | Anti-interference multimedia wireless broadcast signal framing modulation method |
| CN102271115B (en) * | 2011-08-22 | 2013-07-10 | 宁波大学 | Anti-noise transmission method of digital broadcasting mobile signals |
| CN102271111B (en) * | 2011-08-22 | 2013-06-26 | 宁波大学 | Anti-fading mobile multimedia broadcasting signal framing modulation method |
| CN102271116A (en) * | 2011-08-22 | 2011-12-07 | 宁波大学 | Anti-fading multimedia wireless broadcast signal framing modulation method |
| CN102546516B (en) * | 2012-02-22 | 2014-09-10 | 江苏东南大学资产经营有限公司 | Low peak-to-average ratio multi-antenna pilot optimization and low-complexity transmission method |
| CN103763272A (en) * | 2014-01-13 | 2014-04-30 | 宁波大学 | Framing modulation method for wireless signals of multimedia broadcast |
| CN103763267A (en) * | 2014-01-13 | 2014-04-30 | 宁波大学 | Anti-noise mobile signal transmission method for digital broadcast |
| CN103763274A (en) * | 2014-01-13 | 2014-04-30 | 宁波大学 | Anti-fading framing modulation method for wireless signals of multimedia broadcast |
| CN103763237A (en) * | 2014-01-13 | 2014-04-30 | 宁波大学 | Framing modulation method for mobile signals of multimedia broadcast single frequency network |
| CN103763271A (en) * | 2014-01-13 | 2014-04-30 | 宁波大学 | Anti-fading mobile multimedia broadcast signal framing modulation method for single-frequency network |
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