Study On OFDM Index Modulation Under High Mobility

Orthogonal frequency division multiplexing(OFDM)index modulation(IM)is a novel multi-carrier modulation technique.Compare with the conventional OFDM system,OFDM-IM has stronger robust to the inter-carrier interference(ICI)for rapidly time-varying(RTV)channels.Besides,the spectral efficiency of the OFDM-IM scheme can exceed that of conventional OFDM without increasing modulation order.In this thesis,we first study the system model of OFDM-IM and its conventional detectors in RTV channels under high mobility,i.e,block-cancellation(BC)-based detector,signal-power(SP)-based detection and minimum mean square error log-likelihood ratio(MMSE-LLR)-based detector.Note that,due to the ICI,the BC-based detector and SP-based detector suffer from error propagation especially in the high speed.To address this problem,the message passing(MP)algorithm-based detector is studied.Specially,a pattern-aware(PA)-MP detector is proposed by taking the activation pattern constraint into account in the MP iteration procedure.Simulation results show that the proposed PA-MP detector can overcome the error propagation with a cost of higher computational complexity than the BC and SP detectors.In addition,compare with MMSE-LLR,the proposed PA-MP algorithm has lower complexity and better bit error rate(BER)performance.Furthermore,in order to reduce the complexity of the PA-MP algorithm,a quasi-banded PA-MP algorithm is proposed.The quasi-banded PA-MP algorithm can provide a trade-off between the complexity and BER by selecting the band width.Secondly,note that the parallel MIMO-OFDM-IM and generalized IM space frequency(GSFIM)schemes cannot provide transmit diversity.Space-frequency shift keying(SFSK)is proposed to achieve transmit diversity.Moreover,to increase the spectral efficiency,the generalized SFSK(GSFSK)is also given.Then,the construction of the dispersion matrices of SFSK and GSFSK based on the circular shift of a sparse column vector is proposed.Since the dispersion matrices constructed are sparse in both antenna and sub-carrier dimensions,the proposed SFSK and GSFSK schemes can overcome the inter antenna interference and ICI effectively.Next,the asymptotic diversity order of this construction is derived.Finally,to reduce the ML detection complexity,the MMSE correlation-based detection and MMSE-LLR based detection for the proposed SFSK and GSFSK schemes are presented.