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Application of novel ICI self-eliminating method in OFDM modulation

A self-cancelling, modulator technology, applied in transmission noise suppression, electrical components, transmission systems, etc., can solve the problem of more than the loss.

Inactive Publication Date: 2013-07-31
NANJING UNIV OF POSTS & TELECOMM
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The ASR-based ICI self-cancellation OFDM modulation system can significantly reduce the impact of ICI, but it will cause the modulation efficiency (or channel utilization) to drop to 50% of the original, which is not worth the candle.

Method used

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  • Application of novel ICI self-eliminating method in OFDM modulation
  • Application of novel ICI self-eliminating method in OFDM modulation
  • Application of novel ICI self-eliminating method in OFDM modulation

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Embodiment Construction

[0038] Specific implementation plan

[0039] 1 basic plan

[0040] The application principle of ICI self-cancellation method to suppress adjacent subcarriers in OFDM modulation is as follows figure 1 As shown, at the sending end, the data stream is first sent to the nQAM mapper (Mapper) for constellation mapping, output N / 2 pairs of data, then 2 times upsampling, and undergoes N-point inverse discrete Fourier transform / inverse fast Fourier transform (iDFT / iFFT) module. After the data is up-sampled, the even-numbered sub-carrier corresponds to the data, and the odd-numbered sub-carrier is filled with 0. After passing through the iDFT / iFFT module, the output length is T S OFDM symbol, the front and back parts of the time-domain waveform of the symbol are the same (symmetry).

[0041] After IDFT, the expression of the output signal is:

[0042] x ( n ) = 1 N X k = 0 N - 1 X ( k ) exp ( j 2 π N nk ) , n = 0,1...

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Abstract

The invention discloses a method applied to an OFDM (Orthogonal Frequency Division Multiplexing) modulation system. Combination signal processing is performed in a frequency domain and a time domain. The system consists of an OFDM modulator, namely a sending end, and an OFDM demodulator, namely a receiving end. The method comprises the steps that before the sending end performs iFFT (Inverse Fast Fourier Transform), information is transmitted at even subcarriers, and 0 is filled in odd subcarriers; or the information is transmitted at the odd subcarriers, and 0 is filled in the odd subcarriers; or data is transmitted at the subcarriers capable of being divided exactly by 4, and 0 is filled in the rest of subcarriers to ensure that an effect of ICI (Inter-Carrier Interference) is further eliminated. A time domain waveform subjected to the processing has symmetry, and can be compressed; an opposite course is performed at the receiving end, and the waveform is subjected to reduction and FFT (Fast Fourier Transform) according to the symmetry; on the premise that the channel transmission efficiency is not reduced, the effect of the ICI can be reduced significantly, and a channel utilization ratio is not changed basically; and a core concept of the method is that adjacent subcarrier terms are compressed in the frequency domain in order to eliminate the effect of the ICI, and the time domain waveform is compressed in the time domain according to the symmetry in order to improve the channel transmission efficiency.

Description

Technical field [0001] The method proposed by the present invention can be applied to Orthogonal Frequency Division Multiplexing (OFDM) modulation, and belongs to the field of mobile communication technology. technical background [0002] In an OFDM / QAM (QAM, Quadrature Amplitude Modulation, Quadrature Amplitude Modulation) transmission system, frequency selective fading caused by mobile multipath channels and Doppler frequency shift caused by high-speed movement are the two main factors affecting transmission reliability. The Doppler frequency shift caused by movement and the reference frequency difference between the transceivers will cause frequency offset, which will cause inter-subcarrier interference (ICI) in the OFDM symbol; one idea to reduce the impact of ICI is , Using various algorithms to estimate the Doppler frequency shift value, and then try to calculate the ICI size, and try to eliminate it, but when the channel conditions deteriorate, it is very difficult to accu...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H04L27/26H04B15/00
Inventor 曾桂根季叶一
Owner NANJING UNIV OF POSTS & TELECOMM
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