Research On The Methods Of ICI Analysis And Suppression In OFDM

OFDM is an attractive multi-carrier modulation technique which has some advantages with anti-multipath fading, make full use of spectrum resources, simple structure, easy to implement and so on, so it has been widely used in many areas. However, the one of main drawbacks of OFDM systems is sensitive to the carrier frequency offset. Any transmission synchronization error generated in the process, the wireless fading channel multi-path effects, send and receive side of the oscillator, job insecurity, as well as the Doppler effect causes such as carrier frequency offset, the carrier frequency offset can damage the orthogonality between data sub-carrier symbols, thus resulting in inter-carrier interference.At first, the capacity of OFDM systems was analyzed that restrains ICI, In order to reduce the impact of ICI on OFDM systems'performance, some new technologies have been introduced in the OFDM systems to be ensure that the data sub-carrier symbols'orthogonality can be maintained in the transmission process, and the introduction of these technologies has laid a theoretical foundation for studying ways to eliminate ICI. Then the ICI of OFDM systems has been a detailed analysis that caused by frequency offset. ICI will not only result in loss of signal to noise ratio and bit error rate performance degradation for OFDM systems, it will bring serious floor effect. Finally three kinds of effective methods were proposed to eliminate ICI on the impact of OFDM systems. Optimal self-cancellation method not only can compensate for the elimination method of self-cancellation of defects, but also has significant effect in improving the performance of CIR in OFDM systems. Based on matrix transformation to eliminate the ICI method can not only improve the system contains CIR, to improve the system BER performance, but also saves the bandwidth of the system. Offset based on virtual carriers is estimated to eliminate ICI method both in the carrier frequency offset larger, or the number of higher order modulation, can effectively improve the BER performance of OFDM systems. Thus it provides effective solution to eliminate the ICI in OFDM systems under different conditions.