CN103227768B - The application in OFDM modulates of a kind of new ICI self elimination method - Google Patents

Abstract

The present invention is applied in OFDM modulating system, carries out allied signal process at frequency domain and time domain, is made up of OFDM manipulator and transmitting terminal and ofdm demodulator and receiving terminal.Before transmitting terminal carries out iFFT, transmitting information in even subcarriers, odd subcarriers fills out 0；Or transmit information in odd subcarriers, odd subcarriers fills out 0, or extension said method, and at the subcarrier transmitting data can divided exactly by 4, its remaining sub-carriers fills out 0 so that it is further eliminate the impact of ICI.Carry out the time domain waveform after above-mentioned process and there is symmetry, it is possible to waveform is compressed；Carry out contrary process at receiving terminal, according to symmetry, waveform is reduced and FFT.Under the premise not reducing channel transport efficiency, significantly reducing the impact of ICI, channel utilization is basically unchanged simultaneously.The core concept of the present invention is: compressed by adjacent sub-carrier item on frequency domain, to eliminate the impact of ICI；In time domain, utilize symmetry compression time domain waveform, to improve channel transport efficiency.

Description

The application in OFDM modulates of a kind of new ICI self elimination method

Technical field

The method that the present invention proposes, can be applicable to, in OFDM (OrthogonalFrequencyDivisionMultiplexing, OFDM) modulation, belong to mobile communication technology field.

Technical background

At OFDM/QAM(QAM, QuadratureAmplitudeModulation, quadrature amplitude modulation) in transmission system, frequency selective fading that mobile multipath channel causes and the Doppler frequency displacement that high-speed mobile causes are two principal elements affecting transmission reliability.The mobile Doppler (Doppler) caused reference frequency difference between frequency displacement and transceiver, all can produce frequency deviation, and frequency deviation can cause the inter-sub-carrier interference (ICI) in OFDM symbol；The thinking reducing ICI impact is, various algorithm is adopted to estimate Doppler frequency shift value, then manage to calculate ICI size, and manage to eliminate, but when channel conditions deteriorate, accurately estimate frequency deviation value very difficult, especially in a mobile environment, the impact of Doppler frequency shift effect is dynamically change, it is difficult to accurately follow the tracks of, the combined effect of multipath and interchannel noise, can substantially reduce algorithm effect, especially to high order modulation (such as 16QAM, 64QAM), when signal to noise ratio (snr) is not high, improvement effect is poor.

Another thinking reducing ICI impact is, OFDM modulation is improved, is inherently eliminated the frequency deviation impact on ICI, and this kind of method is called ICI self elimination method, and its essence is that OFDM modulation is improved, and eliminates the basic reason producing ICI.The most classical a kind of ICI self elimination method is, before carrying out iFFT, makes adjacent odd even subcarrier opposite number each other, namely by the information that a pair odd even subcarrier transmission is identical, repeats (AdjacentSub-carrierRepeat, ASR) method also known as adjacent sub-carriers.ICI based on ASR eliminates OFDM modulating system certainly, can substantially reduce ICI impact, but can cause that modulation efficiency (or channel utilization) reduces to original 50%, lose more than gain.

Summary of the invention

The goal of the invention of the present invention: when carrying out OFDM modulation, processed by the allied signal of frequency domain and time domain, be inherently eliminated the ICI impact on transmission performance, and do not reduce bandwidth availability ratio.

The technical scheme is that and make discovery from observation, odd subcarriers fills out the time domain waveform of the OFDM symbol after 0, its first half is identical with latter half, utilize this characteristic, have only to send the first half of OFDM symbol at transmitting terminal, utilize above characteristic to recover the time domain waveform compressed at receiving terminal.Can also transmitting data in odd subcarriers, even subcarriers fills out 0；Or extension is scheme herein, and at the subcarrier transmitting data can divided exactly by 4, its remaining sub-carriers fills out 0 so that it is further eliminate the impact of ICI.

For this, the present invention proposes: transmitting data in even subcarriers, odd subcarriers fills out 0, that removes the impact that all odd subcarriers are brought, including affecting bigger adjacent sub-carrier.

In conventional ofdm communication system, it is assumed that owing to Doppler effect or the carrier deviation normalized value that causes due to crystal oscillator deviation are ε.In additive Gaussian channel situation, the demodulation signal of receiving terminal kth subcarrier can be described as:

$Z_k=X_k{S}_0+\underset{i=0,i\≠k}{\overset{N-1}{\mathrm{\Σ}}}{X}_i{S}_{k-i}+N_k,k=\mathrm{0,1},...,N-1---\left(1\right)$

Wherein N is total number subcarriers, X_kIt is the data of transmission, X on kth subcarrier_kS₀It is useful signal part, N_kIt it is additive Gaussian noise；S_k-iIt is the ICI influence value size brought to kth subcarrier of i-th subcarrier, it is possible to be expressed as:

$S_{k-i}=\frac{\sin \left[\mathrm{\π}(k-i+\mathrm{\ϵ})\right]}{N\sin \left[\frac{\mathrm{\π}}{N}(k-i+\mathrm{\ϵ})\right]}\·\exp \left[\mathrm{j\π}(1-1/N)(k-i+\mathrm{\ϵ})\right]---\left(2\right)$

Wherein ε=Δ f/fs is normalization carrier wave frequency deviation.When there is no carrier wave frequency deviation (ε=0), S₀=1, S_k-i=0, now there is no the impact of ICI.When there is frequency deviation, S_k-i≠ 0,For total ICI interference value.Observe S_k-iWaveform finds, distracter contribution is maximum is S_k-i=+1, item corresponding when-1, and these two adjacencies being exactly current kth subcarrier；If not sending the two adjacent sub-carrier item, i.e. X in modulated terminal_k-1=X_k+1=0, then two that to be inherently eliminated in ICI interference value maximum.In OFDM modulated terminal, if at k=0,2 ... 4, N-, subcarrier sends signal, at k=1,3,5 ..., N-3, N-1 subcarrier does not send signal (i.e. X_k=0, k=1,3,5 ..., N-3, N-1), just can reach basic ICI from the purpose eliminated.

But, at k=1,3,5 ..., N-1 subcarrier does not send signal, the data volume of transmission can be made to decrease half, namely channel utilization reduces half.But, ICI self elimination method (i.e. X presented above_k=0, k=1,3,5 ..., N-1) substitute in the output signal expression of OFDM manipulator, it has been found that a peculiar phenomenon: before and after the time domain waveform of output OFDM symbol, two parts are identical.The symmetry that we claim this phenomenon to be time domain waveform.Utilize symmetry, it is possible to waveform compression as another fallen in time domain, at demodulating end further according to Symmetry restoration.After above-mentioned process, channel utilization is identical with conventional OFDM system.

Can also transmitting data in odd subcarriers, even subcarriers fills out 0；Or extension said method, at the subcarrier transmitting data can divided exactly by 4, its remaining sub-carriers fills out 0 so that it is further eliminate the impact of ICI.Emulation and experiment test show, the program, under the premise not reducing channel transport efficiency, can significantly reduce the impact of ICI.

The core concept of the ICI self elimination method of suppression adjacent sub-carrier is: compressed by adjacent sub-carrier item on frequency domain, to eliminate the impact of ICI；In time domain, utilize symmetry compression time domain waveform, to improve channel transport efficiency.

The symmetry of time domain waveform is derived as follows.

In OFDM modulates, the output signal after N point inverse discrete Fourier transform/inverse fast fourier transform (iDFT/iFFT) module is represented by:

$x\left(n\right)=\frac{1}{N}\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}X\left(k\right)\exp \left(j\frac{2\mathrm{\π}}{N}\mathrm{nk}\right),n=\mathrm{0,1},...,N-1---\left(3\right)$

Wherein N is even number, because odd subcarriers is filled with 0, X (1)=X (3)=...=X (2n+1)=...=X (N-3)=X (N-1)=0, substitute into (3) formula:

$x\left(n\right)=\frac{1}{N}\underset{i=0}{\overset{N/2-1}{\mathrm{\Σ}}}X\left(2i\right)\exp \left(j\frac{2\mathrm{\π}}{N}\left(2i\right)n\right),n=0,1,...,N-1$

$=\frac{1}{N}\underset{i=0}{\overset{N/2-1}{\mathrm{\Σ}}}X\left(2i\right)\exp \left(j\frac{2\mathrm{\π}}{N}\left(2i\right)n\right),n=\mathrm{0,1},...,N/2-1$

$=\frac{1}{N}\underset{i=0}{\overset{N/2-1}{\mathrm{\Σ}}}X\left(2i\right)\exp \left(j\frac{2\mathrm{\π}}{N}\left(2i\right)n\right)\exp \left(j2\mathrm{\πi}\right),n=\mathrm{0,1},...,N/2-1$

$=\frac{1}{N}\underset{i=0}{\overset{N/2-1}{\mathrm{\Σ}}}X\left(2i\right)\exp \left(j\frac{2\mathrm{\π}}{N}\left(2i\right)(n+N/2)\right),n=\mathrm{0,1},...,N/2-1---\left(4\right)$

$=x(n+N/2)$

X (n)=x (n+N/2), represents that front and back two parts of time domain waveform x (n) are identical.

The ICI self elimination method of suppression adjacent sub-carrier application principle in OFDM modulates is as shown in Figure 1；It is the OFDM transmission system of a kind of improvement, is made up of the OFDM manipulator (transmitting terminal) improved and the ofdm demodulator (receiving terminal) improved.

At transmitting terminal, data stream is first admitted to nQAM mapper (Mapper) and carries out planisphere mapping, and N/2 is to data in output, is then fed into 2 times of up-samplers, and N is to data in output；Data are met the condition suppressing adjacent sub-carrier by this N:

X_K≠0,k=0,2,...,4N-,X_k≠0,k=0,2,...,4N-,

X_k=0,k=1,3,...,5N-,X_k=0,k=1,3,...,5N-,

Parallel data is transfused to N point inverse discrete Fourier transform/inverse fast fourier transform (iDFT/iFFT) module by this N, and output duration is T_SOFDM symbol, after parallel serial conversion, become the time domain waveform of front and back two parts identical (symmetry)；This waveform is after waveform compression device compresses, and output duration is T_SThe time-domain signal of/2；This signal processes through prefixing (CP) and after orthogonal modulation module, exports a brand-new OFDM modulated signal.

The processing procedure of demodulator is substantially the inverse process of said process.

The invention have the benefit that compared with conventional OFDM modulation system, the present invention can reduce the inter-sub-carrier interference (ICI) impact on receptivity significantly, especially moving, under multipath scenario, and channel utilization is basic and conventional OFDM modulation systems compliant；Compared with typical ICI self elimination method, channel utilization improves nearly one times, and at ICI on the eradicating efficacy receiving performance impact, two kinds of methods are equally matched.

Accompanying drawing explanation

Fig. 1 is the OFDM modulation demodulation system theory diagram adopting the present invention program corresponding

Fig. 2 is 2 rank ICI contrast of ICI distracter in the ofdm system that cancellation scheme is corresponding of conventional OFDM system and the present invention

Fig. 3 is that under different schemes, Fig. 3 is ofdm signal spectral decomposition schematic diagram, and under frequency domain, useful signal disturbs signal situation of change under different frequency deviations from ICI as can be seen from Fig.

Fig. 4 is single footpath, the lower 4 kinds of option b ER performance comparison of Gaussian channel

Fig. 5 is the rural area lower 3 kinds of option b ER performance comparison of multipath (RAX) channel

Fig. 6 is the lower 2 kinds of option b ER performance comparison of city multipath (TUX) channel.

Specific embodiments

1 basic scheme

The ICI self elimination method of suppression adjacent sub-carrier application principle in OFDM modulates is as shown in Figure 1, at transmitting terminal, data stream is first admitted to nQAM mapper (Mapper) and carries out planisphere mapping, N/2 is to data in output, then 2 times of up-samplings, and through N point inverse discrete Fourier transform/inverse fast fourier transform (iDFT/iFFT) module.Data are after up-sampling, and what even subcarriers was corresponding is data, and odd subcarriers is filled with 0, and after iDFT/iFFT module, output length is T_SOFDM symbol, front and back two parts of this symbol time domain waveform are identical (symmetry).

After IDFT, the expression formula of output signal is:

$x\left(n\right)=\frac{1}{N}\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}X\left(k\right)\exp \left(j\frac{2\mathrm{\π}}{N}\mathrm{nk}\right),n=\mathrm{0,1},...,N-1---\left(5\right)$

Wherein N is even number, because odd subcarriers is filled with 0, X (1)=X (3)=...=X (2n+1)=...=X (N-3)=X (N-1)=0, substitute into (1) formula:

$x\left(n\right)=\frac{1}{N}\underset{i=0}{\overset{N/2-1}{\mathrm{\Σ}}}X\left(2i\right)\exp \left(j\frac{2\mathrm{\π}}{N}\left(2i\right)n\right),n=0,1,...,N-1$

$=\frac{1}{N}\underset{i=0}{\overset{N/2-1}{\mathrm{\Σ}}}X\left(2i\right)\exp \left(j\frac{2\mathrm{\π}}{N}\left(2i\right)n\right),n=\mathrm{0,1},...,N/2-1$

$=\frac{1}{N}\underset{i=0}{\overset{N/2-1}{\mathrm{\Σ}}}X\left(2i\right)\exp \left(j\frac{2\mathrm{\π}}{N}\left(2i\right)n\right)\exp \left(j2\mathrm{\πi}\right),n=\mathrm{0,1},...,N/2-1$

$=\frac{1}{N}\underset{i=0}{\overset{N/2-1}{\mathrm{\Σ}}}X\left(2i\right)\exp \left(j\frac{2\mathrm{\π}}{N}\left(2i\right)(n+N/2)\right),n=\mathrm{0,1},...,N/2-1---\left(6\right)$

$=x(n+N/2)$

X (n)=x (n+N/2), represents that front and back two parts of time domain waveform x (n) are identical, thus, it is possible to x (n) sequence is carried out time domain data compression.

What can also adopt that odd subcarriers transmits is the scheme filled by 0 of data, even subcarriers, and at this moment after iDFT/iFFT, the OFDM symbol of output is the negative symmetries of front and back two parts.

Utilizing two parts before and after OFDM symbol identical or this characteristic on the contrary, can only transmit the half of OFDM symbol waveform in data compressing module, second half is compressed.Before carrying out iFFT, owing to adjacent sub-carrier is filled out 0, make channel utilization have dropped half, but in time domain, OFDM meets and is compressed by half, makes channel utilization identical with conventional OFDM transmission system.But after adjacent sub-carrier is removed, it is possible to eliminate the impact of the ICI that frequency deviation causes.

2 high-order extensions

Above-mentioned basic scheme can also carry out the extension of higher order, for instance, the subcarrier transmitting data symbol only can divided exactly by 4 in carrier number, other aspect fills 0, OFDM symbol waveform after iFFT is identical with Ts/4 for the cycle, it is possible to by all the other 3/4 waveform compression.Such high-order extension can bring better impact for ICI from elimination aspect than basic scheme before, when being left out CP and affecting, because waveform having been compressed in time domain, will not reduce band efficiency；But, owing to meeting after each compression will add CP, to eliminate intersymbol interference (ISI), when extending too many, will produce to significantly affect to channel utilization.Meanwhile, when realizing, high-order extension can consume more hardware resource.But, in this programme, on a lot of subcarriers, transmission is all 0, it is possible to use this characteristic, improves IDFT algorithm, reduces the requirement to resource with this.In actual applications, it is possible to use can by 2 or the subcarrier divided exactly by 4 to transmit information, other subcarriers fill out 0, so can take into account the contradiction between ICI eradicating efficacy, resource consumption and channel utilization.

The 3ICI impact on performance of BER

In conventional ofdm communication system, it is assumed that owing to Doppler effect or the carrier deviation normalized value that causes due to crystal oscillator deviation are ε.In additive Gaussian channel situation, the demodulation signal at receiving terminal kth subcarrier can be described as:

$Z_k=X_k{S}_0+\underset{i=0,i\≠k}{\overset{N-1}{\mathrm{\Σ}}}{X}_i{S}_{k-i}+N_k,k=\mathrm{0,1},...,N-1---\left(7\right)$

Wherein N is total number subcarriers, and Xk is the data of transmission, N on kth subcarrier_kIt is corresponding additive Gaussian noise, S_k-iIt is the ICI influence value size brought to kth subcarrier of i-th subcarrier, it is possible to be expressed as:

$S_{k-i}=\frac{\sin \left[\mathrm{\π}(k-i+\mathrm{\ϵ})\right]}{N\sin \left[\frac{\mathrm{\π}}{N}(k-i+\mathrm{\ϵ})\right]}\·\exp \left[\mathrm{j\π}(1-1/N)(k-i+\mathrm{\ϵ})\right]---\left(8\right)$

Wherein ε=Δ f/fs is normalization carrier wave frequency deviation.Formula (7) right half part first term is required useful signal, when there is no carrier wave frequency deviation (ε=0), and S₀=1, S_i-k=0, now there is no the impact of ICI.

The basic ICI proposed for the present invention eliminates system (2 rank scheme) certainly, and the demodulation signal of receiving terminal kth subcarrier can be described as:

$Z_k^{\′}=X_k{S}_0+\underset{i=0,i\≠k/2}{\overset{N/2-1}{\mathrm{\Σ}}}{X}_{2i}{S}_{k-2i}+N_k,k=\mathrm{0,2,4},...,N-2---\left(9\right)$

Z'_k=0, k=1,3,5 ..., N-3, N-1

Wherein N is total number subcarriers, X_kIt is the data of transmission, N on kth subcarrier_kIt is corresponding additive Gaussian noise, S_k-2iIt it is the ICI interference value that brings to kth subcarrier of the 2i subcarrier.

Fig. 2 is conventional system and 2 rank ICI elimination system S certainly_i-kModulus value compare, in figure, total sub-carrier number N=16, frequency deviation ε are taken as 0.15 and 0.3,7 sub carriers is useful signal S₀；2 rank ICI eliminate the S of system_k-2iThe S of modulus value and conventional system_k-iModulus value is compared, and quantity decreases 1 times, and maximum 2 points (adjacent sub-carriers of 7 sub carriers) of modulus value without.

In formula (7), Section 1 is useful signal, and Section 2 is total distracter；Fig. 3 is ofdm signal spectral decomposition schematic diagram, and solid line is the frequency spectrum of 7 sub carriers, and chain-dotted line is the frequency spectrum of interfering sub-carrier in conventional system, and void is scribed ss the present invention 2 rank ICI from the frequency spectrum eliminating system interference subcarrier.Situation when imaginary point vertical line is do not have frequency deviation, now the interference value of two kinds of systems is all 0；Solid vertical line is situation during frequency deviation ε=0.3, and now the present invention 2 rank ICI is significantly less than the interference value of conventional system from the interference value of the system of elimination.

According to the theory diagram of Fig. 1, the present invention program is emulated.Simulation parameter is: N=1024, and available subcarrier is 880, and balanced way is the linear interpolation method based on Comb Pilot, selects QPSK mapping mode.

The scene description that emulation adopts is:

Scheme 1: conventional OFDM system, receiving terminal is provided without ICI removing method.

Scheme 2: the 2 rank ICI of the present invention are from eliminating system, and receiving terminal is provided without ICI removing method.

Scheme 3: the 4 rank ICI of the present invention are from eliminating system, and receiving terminal is provided without ICI removing method.

Scheme 4: the ICI of adjacent odd even subcarrier opposite number each other from sterilizing system, i.e. ASR(AdjacentSub-carrierRepeat) system.Namely two adjacent carriers transmit a pair data symbol, on odd point subcarrier transmission be even number point sub-carrier negate symbol.At receiving terminal, the demodulation value of two adjacent carriers of transmission same-sign adjudicates the data symbol transmitted jointly.Under same map mode, its channel efficiency have dropped 50%, in order to make channel efficiency consistent with above 3 kinds of situations, it is necessary to adopts 16QAM to map.

Fig. 4 represent above-mentioned four kinds of schemes under single footpath (relative to multipath) condition, the result of different carrier frequency deviation.Simulate single footpath ε=0(respectively and be equivalent to Gaussian channel), in the situation of ε=0.3, bit error rate (BER) performance of 4 kinds of schemes；During ε=0, the performance of BER of scheme 1,2,3 is almost identical, and the bit error rate of scheme 4 is higher than system 1,2,3, this is because under Gaussian channel, when signal to noise ratio is identical, the noise robustness of QPSK is better than 16QAM；During ε=0.3, have employed the BER of the ICI scheme 2,3,4 from cancellation scheme significantly lower than scheme 1, wherein, have employed the bit error rate of the present invention 4 rank ICI scheme 3 from cancellation scheme minimum, next to that the 2 rank ICI of the present invention are from cancellation scheme, the ICI of worst is adjacent odd even subcarrier opposite number each other is from disappearing scheme.

Simulation result shows, when not reducing band efficiency, the bit error rate rate performance of the present invention program can be become better and better along with the raising of exponent number.

Under mobile multi-path channel environment, simulated channel adopts 6 classical tap TUX channels (city multipath channel) and the RAX channel (rural area multipath channel) of definition in 3GPPTR25.943 consensus standard.In order to compare the size of the Doppler frequency deviation under different mobile channels, definition ε d is normalization maximum Doppler frequency offset herein, and ε d is the maximum Doppler frequency offset ratio with subcarrier spacing of channel.

Fig. 5 represents the scheme 1,2,4 bit error rate (BER) performance under RAX channel model, and simulated environment is ε d=0.01, ε d=0.2, the corresponding smaller and relatively larger two kinds of situations of Doppler frequency deviation.Simulation result shows that the present invention program BER performance under RAX channel model is better than scheme 1,4.

Fig. 6 represent scheme 2,4 under TUX channel model, the BER performance of ε d=0.01 and ε d=0.2, the respectively corresponding smaller and relatively larger two kinds of situations of Doppler frequency deviation.It is shown that the ICI that the present invention proposes under TUX channel model is better than scheme 4 from the BER performance of cancellation scheme.

4 band efficiency analyses

The band efficiency of conventional OFDM system is (impact ignoring CP):

${\mathrm{\η}}_b=\frac{N\·{\log }_{2}M}{T_s\·B}\mathrm{bit}/(s\·\mathrm{Hz})---\left(10\right)$

The L rank ICI of adjacent odd even subcarrier opposite number each other is from the band efficiency (ignoring the impact of CP) of cancellation scheme and L rank ASR scheme:

${\mathrm{\η}}_b=\frac{N/L\·{\log }_{2}M}{T_s\·B}\mathrm{bit}/(s\·\mathrm{Hz})---\left(11\right)$

L rank ICI of the present invention is from the band efficiency (ignoring the impact of CP) of cancellation scheme:

${\mathrm{\η}}_b=\frac{N/L\·{\log }_{2}M}{T_s/L\·B}=\frac{N\·{\log }_{2}M}{T_s\·B}\mathrm{bit}/(s\·\mathrm{Hz})---\left(12\right)$

Wherein, N is variable number, and Ts is the OFDM symbol length after IDFT/IFFT, and M is the system number of qam mode adopted, B be can channel width.Wherein L refers to the exponent number that high-order extends, for instance L=4, is every 4 same data of sub-carrier-wave transmission, is the subcarrier transmitting data of carrier number aliquot 4 in the present invention program in ASR scheme, and all the other fill 0.

Comparison expression (10), (11), (12), it can be seen that under same map mode (namely nQAM is identical), the band efficiency of the present invention program is identical with conventional OFDM system, are L times of band efficiency of ASR scheme.

When considering when affecting of CP, the bandwidth availability ratio of the present invention program slightly reduces, and factor of influence β is:

$\mathrm{\β}=\frac{T_s}{T_s+L\·T_{\mathrm{CP}}}---\left(13\right)$

Conventional OFDM system can regard the system of L=1 as；Consider that CP duration is the situation of the 1/16 of OFDM symbol duration, then the 2 rank ICI of the present invention are the 94.4% of conventional OFDM system from the bandwidth availability ratio of cancellation scheme, and 4 rank ICI are the 85% of conventional OFDM system from the bandwidth availability ratio of cancellation scheme.

Take into account bandwidth availability ratio and ICI from eradicating efficacy, the 2 rank ICI of the present invention are best from the combination property of cancellation scheme.

The ultimate principle of the present invention and principal character and advantages of the present invention have more than been shown and described.Skill will appreciate that of the industry; the present invention is not restricted to the described embodiments; described in above-described embodiment and description is that principles of the invention is described; without departing from the spirit and scope of the present invention; the present invention also has various changes and modifications; these changes and improvements both fall within the claimed scope of the invention, and claimed scope is defined by its equivalent of appending claims.

Claims (5)

1. inter-carrier interference (Inter-CarrierInterference one kind new, ICI) self elimination method application in OFDM modulates, the OFDM modulating system that new ICI self elimination method is suitable for is made up of OFDM manipulator and transmitting terminal and ofdm demodulator and receiving terminal, it is characterized in that, at transmitting terminal, N number of subcarrier is divided into even subcarriers and odd subcarriers, wherein N is total number subcarriers and N is even number, only send information in even subcarriers, odd subcarriers fills out 0, then utilizes symmetry that time domain waveform is compressed:

Uploading transmission information in even subcarriers, odd subcarriers fills out 0, and its process is as follows, and at transmitting terminal, data stream is first admitted to nQAM mapper (Mapper) and carries out planisphere mapping, and N/2 is to data in output, is then fed into 2 times of up-samplers, and N is to data in output；Data are met the condition suppressing adjacent sub-carrier by this N:

X_k≠ 0, k=0,2,4 ..., N-2

X_k=0, k=1,3,5 ..., N-1

Parallel data is transfused to N point inverse discrete Fourier transform/inverse fast fourier transform (iDFT/iFFT) module by this N, and output duration is T_SOFDM symbol, after parallel serial conversion, become the time domain waveform that front and back two parts are identical；Latter half identical for waveform, after waveform compression device compresses, is reduce by this waveform, and output duration is T_SThe time-domain signal of/2；This signal processes through prefixing (CP) and after orthogonal modulation module, exports a brand-new OFDM modulated signal, and the processing procedure of demodulator is then the inverse process of said process.

2. inter-carrier interference (Inter-CarrierInterference one kind new, ICI) self elimination method application in OFDM modulates, the OFDM modulating system that new ICI self elimination method is suitable for is made up of OFDM manipulator and transmitting terminal and ofdm demodulator and receiving terminal, it is characterized in that, at transmitting terminal, N number of subcarrier being divided into even subcarriers and odd subcarriers, wherein N is total number subcarriers and N is even number, only uploading transmission information in odd subcarriers, even subcarriers fills out 0；Then utilize waveform symmetry that time domain waveform is compressed；It is as follows that it implements process:

Transmitting information in odd subcarriers, even subcarriers fills out 0, and its process is as follows, and at transmitting terminal, data stream is first admitted to nQAM mapper (Mapper) and carries out planisphere mapping, and N/2 is to data in output, is then fed into 2 times of up-samplers, and N is to data in output；Data are met the condition suppressing adjacent sub-carrier by this N:

X_k≠ 0, k=1,3,5 ..., N-1

X_k=0, k=0,2,4 ..., N-2

Parallel data is transfused to N point inverse discrete Fourier transform/inverse fast fourier transform (iDFT/iFFT) module by this N, and output duration is T_SOFDM symbol, after parallel serial conversion, become the time domain waveform that front and back two parts absolute value is identical, symbol is contrary；Latter half identical for absolute value in waveform, that symbol is contrary, after waveform compression device compresses, is reduce by this waveform, and output duration is T_SThe time-domain signal of/2；This signal processes through prefixing (CP) and after orthogonal modulation module, exports a brand-new OFDM modulated signal, and the processing procedure of demodulator is then the inverse process of said process.

3. a kind of new ICI self elimination method according to claim 1 and 2 application in OFDM modulates, it is characterised in that after inverse discrete Fourier transform (iDFT), the expression formula of output signal is:

$X\left(n\right)=\frac{1}{N}\underset{k=0}{\overset{N-1}{\Σ}}X\left(k\right)\exp \left(j\frac{2\mathrm{\π}}{N}nk\right),n=0,1,...,N-1---\left(1\right)$

Wherein N is total number subcarriers and N is even number, because odd subcarriers is filled with 0, X (1)=X (3)=...=X (2n+1)=...=X (N-3)=X (N-1)=0, substitute into (1) formula:

$X\left(n\right)=\frac{1}{N}\underset{i=0}{\overset{N/2-1}{\Σ}}X\left(2i\right)\exp \left(j\frac{2\mathrm{\π}}{N}\right(2i\left)n\right),n=0,1,...,N-1$

X (n)=x (n+N/2), represents that front and back two parts of time domain waveform x (n) are identical, thus, it is possible to x (n) sequence is carried out time domain data compression；

What can also adopt that odd subcarriers transmits is the scheme filled by 0 of data, even subcarriers, and at this moment after iDFT/iFFT, the OFDM symbol of output is the negative symmetries of front and back two parts.

4. a kind of new ICI self elimination method according to claim 1 and 2 application in OFDM modulates, it is characterised in that receiving terminal is after waveform extension, FFT module, and the demodulation signal of kth subcarrier can improve and be described as:

$\begin{array}{c}{Z}_k^{\′}=X_k{S}_0+\underset{i=0,i\≠k}{\overset{N-1}{\Σ}}{X}_{2i}{S}_{k-2i}+N_k,k=0,2,4,...,N-2\\ Z_k^{\′}=0,k=1,3,5,...,N-3,N-1\end{array}---\left(2\right)$

Wherein N is total number subcarriers, and N is even number, X_kIt is the data of transmission, N on kth subcarrier_kIt is corresponding additive Gaussian noise, S_k-2iIt it is the ICI interference value that brings to kth subcarrier of the 2i subcarrier.

5. a kind of new ICI self elimination method according to claim 1 and 2 application in OFDM modulates, it is characterised in that can carrying out higher order extension, at transmitting terminal, upload transmission information in the even subcarriers that can be divided exactly by 4, its remaining sub-carriers fills out 0；Then utilize symmetry that time domain waveform carries out 4 times of compressions.