Research Of The ICI Mitigation In OFDM Cooperative Communication Systems

OFDM cooperative communication systems have attracted great attention in wireless communications recently. However, the carrier frequency offset (CFO) can lead to inter-carrier interference (ICI), which destroys the performance of the OFDM system. For the conventional OFDM system there is only one CFO between source and destination. But in the OFDM cooperative communication system, the CFO exists between each relay and destination. These multiple CFOs make the system suffer from serious ICI. This paper mainly focuses on how to mitigate the ICI in an OFDM cooperative communication system.Firstly, the radio channel, OFDM and cooperative communication are introduced in this paper. Then this paper models the OFDM cooperative communication system, makes the analysis and simulations of the impact on the system which is caused by the CFOs.Secondly, for the problem of the ICI in an OFDM cooperative communication system, many methods have been analyzed both in advantages and disadvantages. In this paper, a method by using frequency-domain correlative coding has been proposed to mitigate the ICI in OFDM cooperative communication system. The Carrier to Interference ratio is taken to prove that the system performance is improved by using the correlative coding. The results of simulations show that correlative coding in the OFDM cooperative communication system can mitigate the ICI.Finally, on the basis of frequency-domain correlative coding, this paper proposes a joint time-frequency scheme, in which frequency-domain correlative coding and time-domain windowing technologies are combined to mitigate the ICI in the OFDM cooperative communication system. Simulations show that the proposed scheme accelerates the attenuation of the spectrum tails, increases the CIR, improves the system performance and mitigates the ICI efficiently.