CN102238128B - Method for self-elimination of inter-subcarrier interference of differential OFDM (orthogonal frequency division multiplexing) system - Google Patents
Method for self-elimination of inter-subcarrier interference of differential OFDM (orthogonal frequency division multiplexing) system Download PDFInfo
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Abstract
The invention discloses a method for self-elimination of inter-subcarrier interference of a differential OFDM (orthogonal frequency division multiplexing) system. In comparison with a primal differential OFDM system, a zero insertion algorithm and a displacement offsetting algorithm are added, wherein the zero insertion algorithm enables adjacent carriers of a subcarrier carrying information to return to zero, so that, the interference of the adjacent carriers on the information carrying carrier is effectively reduced. In a process of transmitting the information to a receiving terminal through a wireless channel, orthogonality cannot be completely formed under influence of Doppler frequency shift caused by carrier synchronous error and movement, and the subcarriers generate mutual interference; and by the displacement offsetting algorithm, the subcarriers carrying the information are amplified, a signal-to-noise ratio of the subcarrier to the adjacent subcarriers is increased, and the adjacent subcarriers are further subtracted, so that the inter-subcarrier interference is effectively eliminated.
Description
Technical field
The present invention relates to difference ofdm system, particularly a sub-carrier is eliminated the method for disturbing.
Background technology
OFDM technology is used widely in wideband wireless mobile communication system because having good antagonism selectivity of channel frequency decline ability.But ofdm system requires strict orthogonal between subcarrier, frequency shift (FS) is proposed to very strict requirement.The generation of frequency shift (FS) comprises carrier synchronization error and kinetic Doppler frequency shift, frequency synchronization error can reduce impact by well-designed Carrier Synchronization Algorithm, and Doppler frequency shift causes the time selective fading of channel, particularly, in high-speed motion situation, the ICI that channel rapid fading causes will cause systematic function fast-descending.
The method that reduces at present ICI impact includes frequency-domain equilibrium method, time-domain windowed method, frequency deviation estimation and compensation method and iteration elimination method, and its deficiency is:
Although wherein frequency-domain equilibrium method and time-domain windowed method have some improvement on the impact of ICI, be with outward leakage the increase of output power, and significantly reduced the utilance of system; Frequency deviation estimation and compensation method are under fast-fading environment, and it is large that the error of estimation becomes, the DeGrain that improves to ICI; Iteration elimination method realizes too complicated, and time delay is also larger, need to after receiving one or more OFDM symbols, by complicated matrix operation or FFT, convert, and its amount of calculation is very large, is unfavorable for practical application.
Summary of the invention
Object of the present invention be just to provide a kind of for difference ofdm system from eliminating the method for disturbing between subcarrier, it effectively eliminates the interference between subcarrier by zero insertion algorithm and displacement cancellation algorithms, and has reduced the complexity that system realizes.
The object of the invention is to realize by such technical scheme, its step is as follows:
1) at transmitting terminal, the information of required transmission is modulated, differential coding is gone here and there and is changed;
2) to the data after step 1) processing, utilize zero insertion algorithm to process;
3) by step 2) carrying after processing the subcarrier of information carry out Fourier transform, parallel-serial conversion is inserted Cyclic Prefix again;
4) by wireless antenna, to receiving terminal, send information;
5) receiving terminal carries out timing synchronization to information, and carrier synchronization is gone here and there and changing, then carries out Fourier transform to having carried the subcarrier of information;
6) the information utilization displacement cancellation algorithms after step 5) processing is processed, eliminated the interference between subcarrier;
7) information after step 6) processing is carried out to parallel-serial conversion, Differential Detection and demodulation.
Further, step 2) the zero insertion algorithm described in is, the information of required transmission is carried on the subcarrier of odd number or even number, at even number or odd subcarriers, makes zero.
Further, the displacement cancellation algorithms in step 6) is the subcarrier of carrying signal to be amplified, then deduct adjacent two subcarriers that do not carry raw information.
Owing to having adopted technique scheme, the present invention has advantages of as follows:
Show with contrast simulation by analysis, under the identical prerequisite of spectrum efficiency, when signal to noise ratio is greater than 34dB, the present invention is lower than the iteration elimination method error rate, and complexity significantly reduces.
Other advantages of the present invention, target and feature will be set forth to a certain extent in the following description, and to a certain extent, very in will be apparent to those skilled in the art to investigating below, or can be instructed from the practice of the present invention.Target of the present invention and other advantages can be realized and be obtained by specification and claims below.
Accompanying drawing explanation
Accompanying drawing of the present invention is described as follows.
Fig. 1 is principle flow chart of the present invention.
Fig. 2 is the first analogous diagram of the present invention.
Fig. 3 is the second analogous diagram of the present invention.
Embodiment
Below in conjunction with drawings and Examples, the invention will be further described.
For difference ofdm system, from eliminating a method of disturbing between subcarrier, its step is as follows:
1) at transmitting terminal, the information of required transmission is modulated, differential coding is gone here and there and is changed;
2) to the data after step 1) processing, utilize zero insertion algorithm to process;
3) by step 2) carrying after processing the subcarrier of information carry out Fourier transform, parallel-serial conversion is inserted Cyclic Prefix again;
4) by wireless antenna, to receiving terminal, send information;
5) receiving terminal carries out timing synchronization to information, and carrier synchronization is gone here and there and changing, then carries out Fourier transform to having carried the subcarrier of information;
6) the information utilization displacement cancellation algorithms after step 5) processing is processed, eliminated the interference between subcarrier;
7) information after step 6) processing is carried out to parallel-serial conversion, Differential Detection and demodulation.
The relatively original difference ofdm system of the present invention has increased step 2) and step 6), step 2) zero insertion algorithm adjacent carrier that the subcarrier of beared information is subject to be zero, effectively reduce the interference that beared information carrier wave is subject to adjacent carrier.Information exchange is crossed in the process that wireless channel is sent to receiving terminal, be subject to the impact of carrier synchronization error and kinetic Doppler frequency shift, cannot be completed into quadrature, between subcarrier, mutually there is to disturb the displacement cancellation algorithms by being afraid of in step 6) to state, the subcarrier that has carried information is amplified, subtract the signal to noise ratio that adds this subcarrier and adjacent sub-carrier, then deduct adjacent sub-carrier, effectively eliminated the interference between subcarrier.
Step 2) the zero insertion algorithm described in is, the information of required transmission is carried on the subcarrier of odd number or even number, at even number or odd subcarriers, makes zero.
Displacement cancellation algorithms in step 6) is the subcarrier of carrying signal to be amplified, then deduct adjacent two subcarriers that do not carry raw information.
Fig. 1 is the ofdm system model of ASIZ-SSC-FDD, and establishing sub-carrier number is N, first binary bits information is mapped as to symbol
,
the mapping symbols that represents n participation differential coding in i OFDM symbol, wherein
.Then will
carry out differential coding, rule is
,
initial value be chosen as any point in modulation constellation, then by serial to parallel conversion be
individual one group,
(
)
individual allocation of symbols is to even number or odd number road, and nil symbol is assigned to odd number road or even number road, then just as conventional ofdm system transmission.At receiving terminal, finish synchronous after, the cancellation algorithms of taking to be shifted suppresses the interference of ICI, when Doppler is larger, by ASIZ-SSC, from the system of eliminating ICI algorithm, can effectively improve the performance of system.Carrier to interference power ratio has improved at least 15dB than conventional system, and the error rate is obviously improved systematic function.Through the signal of FFT, through displacement, offset and process again.Entered after Differential Detection, gave demodulator.
Its error rate analyzer is as follows:
Signal by ICI after eliminating
send into differential levels detector, the judgement amount of output is:
（1）
Wherein
represent the value of information after n oneself elimination of subcarrier in i OFDM symbol,
represent conjugate operation, without loss of generality, suppose
, judgment variables
can be expressed as:
(2)
A=B=0 wherein, C=1, X=
, Y=
.By eigenfunction method, try to achieve the error rate as expression formula (3)
From formula (3), the error rate is only relevant with the correlation function of detection variable, and the calculating of the error rate is the calculating of the correlation function of detection variable.
In formula,
represent the interval between subcarrier,
represent noise,
represent in i OFDM symbol
the mapping symbols of individual participation differential coding.
Abbreviation obtains:
(7)
Wherein
represent white Gaussian noise power.
Through calculating:
In formula,
represent maximum Doppler frequency domain,
the symbol duration that represents OFDM.
Same thinking, tries to achieve
(9)
The present invention is carried out to emulation, and simulation parameter is set to: OFDM symbol time
=200us, guard time interval
=50us, number of sub carrier wave is 1024, without chnnel coding.On the synchronous basis of transmitting-receiving, to rayleigh fading channel, the bit error rate performance of frequency domain differential detection has been carried out to emulation, channel model has adopted SUI4 channel model, analyzes with simulation result as Fig. 2 Fig. 3.
Fig. 2 is under SUI4 channel, the radio frequency 300M of supposing the system, and the speed of motion is respectively 1000km/h, 800km/h, 600km/h, maximum doppler frequency is to be respectively set to 278Hz, 222Hz, 167Hz.As can be seen from the figure, simulation result and theory analysis are very approaching.Ber curve from three kinds of conditions can find out, along with the increase of maximum doppler frequency, error performance decreases, but adds after error correction coding, can proper communication.
Fig. 3 is under SUI4 channel, maximum doppler frequency is set to 222Hz, by frequency domain differential demodulation scheme with based on iteration elimination ICI scheme, contrast, the same for guaranteeing two schemes spectrum efficiency, the OFDM scheme of ASIZ-SSC-FDD adopts 16DAPSK, iteration elimination ICI scheme adopts QPSK, simulation result to show when Eb/N0 is greater than 34dB, and this scheme is better than iterative scheme.
From implementation complexity, the amount of calculation of the OFDM scheme of ASIZ-SSC-FDD is directly proportional to N, and the amount of calculation of iteration elimination is directly proportional to N2.So scheme in this paper, implementation complexity is well below the ofdm system based on iteration elimination ICI scheme.
Compare with the ofdm system that ICI eliminates with complete channel estimating based on iterative algorithm, after being greater than 34dB, performance is better than the ofdm system of iteration, and along with signal to noise ratio increases, advantage is more obvious.This scheme is when realizing, and complexity is low, takies resource few.
Finally explanation is, above embodiment is only unrestricted in order to technical scheme of the present invention to be described, although the present invention is had been described in detail with reference to preferred embodiment, those of ordinary skill in the art is to be understood that, can modify or be equal to replacement technical scheme of the present invention, and not departing from aim and the scope of the technical program, it all should be encompassed in the middle of claim scope of the present invention.
Claims (3)
1. for difference ofdm system, certainly eliminate a method of disturbing between subcarrier, its step is as follows:
1) at transmitting terminal, the information of required transmission is modulated, differential coding is gone here and there and is changed;
2) to the data after step 1) processing, utilize zero insertion algorithm to process;
3) by step 2) carrying after processing the subcarrier of information carry out Fourier transform, parallel-serial conversion is inserted Cyclic Prefix again;
4) by wireless antenna, to receiving terminal, send information;
5) receiving terminal carries out timing synchronization to information, and carrier synchronization is gone here and there and changes, then carries out Fourier transform to having carried the subcarrier of information;
6) the information utilization displacement cancellation algorithms after step 5) processing is processed, eliminated the interference between subcarrier;
7) information after step 6) processing is carried out to parallel-serial conversion, Differential Detection and demodulation.
It is 2. as claimed in claim 1 that for difference ofdm system, oneself eliminates the method for disturbing between subcarrier, it is characterized in that: step 2) described in zero insertion algorithm be, the information of required transmission is carried on the subcarrier of odd number or even number, at even number or odd subcarriers, makes zero.
It is 3. as claimed in claim 1 that for difference ofdm system, oneself eliminates the method for disturbing between subcarrier, it is characterized in that: the displacement cancellation algorithms in step 6) is, the subcarrier of carrying signal is amplified, then deduct adjacent two subcarriers that do not carry raw information.
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| CN104022982A (en) * | 2014-05-09 | 2014-09-03 | 国家电网公司 | ICI self-elimination algorithm with variable coding efficiency |
| CN104836771B (en) * | 2015-05-29 | 2017-11-10 | 桂林电子科技大学 | Fading channel partially coherent detection method |
| CN106789808B (en) * | 2016-12-02 | 2019-10-01 | 上海微小卫星工程中心 | The ICI of high spectrum utilization eliminates communication means and system certainly |
| CN114838804B (en) * | 2022-05-09 | 2023-06-09 | 武汉理工大学 | Distributed vibration measuring device and method based on weak grating array and pulse coding |
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| CN101547170A (en) * | 2008-03-27 | 2009-09-30 | 电子科技大学 | Method for estimating time-varying channel parameter suitable for multi-carrier transmission of OFDM |
| US20100034302A1 (en) * | 2007-02-09 | 2010-02-11 | Nxp, B.V. | Method of synchronizing multi-carrier systems and multi-carrier system |
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| US20100034302A1 (en) * | 2007-02-09 | 2010-02-11 | Nxp, B.V. | Method of synchronizing multi-carrier systems and multi-carrier system |
| CN101547170A (en) * | 2008-03-27 | 2009-09-30 | 电子科技大学 | Method for estimating time-varying channel parameter suitable for multi-carrier transmission of OFDM |
Non-Patent Citations (1)
| Title |
|---|
| 李娟，赵利.《OFDM系统中子载波间干扰抑制算法的研究》.《计算机仿真》.2010, * |
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Address after: 518000 Guangdong city of Shenzhen province Qianhai Shenzhen Hong Kong cooperation zone before Bay Road No. 1 building 201 room A (located in Shenzhen Qianhai business secretary Co. Ltd.) Patentee after: Smart information service (Shenzhen) Co.,Ltd. Address before: 518000 Guangdong city of Shenzhen province Qianhai Shenzhen Hong Kong cooperation zone before Bay Road No. 1 building 201 room A (located in Shenzhen Qianhai business secretary Co. Ltd.) Patentee before: Lingzhi (Shenzhen) Information Service Co.,Ltd. Address after: 518000 Guangdong city of Shenzhen province Qianhai Shenzhen Hong Kong cooperation zone before Bay Road No. 1 building 201 room A (located in Shenzhen Qianhai business secretary Co. Ltd.) Patentee after: Lingzhi (Shenzhen) Information Service Co.,Ltd. Address before: 518000 Guangdong city of Shenzhen province Qianhai Shenzhen Hong Kong cooperation zone before Bay Road No. 1 building 201 room A (located in Shenzhen Qianhai business secretary Co. Ltd.) Patentee before: WEISHIBO INFORMATION SERVICE (SHENZHEN) Co.,Ltd. |
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