Study On OFDM With Index Modulation

Orthogonal frequency division multiplexing(OFDM)with index modulation(IM)is a novel multi-carrier modulation.Compared with OFDM,OFDM-IM has stronger robustness to the inter-carrier interference(ICI)in rapidly time-varying(RTV)channels.Besides,in some scenarios,OFDM-IM can achieve higher spectral efficiency and better error performance than OFDM.In this thesis,firstly,to address this problem that OFDM-IM can not provide transmit diversity(TD),the OFDM-IM-TD is proposed.Both theoretical analysis and simulation results show that the OFDM-IM-TD can achieve TD.Next,to increase information rate(IR)of OFDM-IM,OFDM-IM-IR is proposed.Theoretical performance of the OFDM-IM-IR is analyzed in terms of the minimum mean square Euclidean distance(MSED).Simulation results show that OFDM-IM-IR can increase IR effectively.Furthermore,to reduce the detection complexities of OFDM-IM-TD and OFDM-IM-IR,log-likelihood ratio(LLR)-based detection is proposed.Secondly,note that,due to the ICI,the performance of OFDM-IM is seriously degraded especially in RTV channels.To address this problem,linear precoding method is proposed.The optimal precoding matrix is designed to maximize the lower bound of system capacity,and particle swarm optimization(PSO)is employed to solve the matrix optimization problem.Simulation results show that proposed linear precoding method can improve effectively the performance in RTV channels.Finally,the extention of OFDM-IM in multiple antenna systems is studied,and generalized joint space-frequency index modulation(G-JSFIM)and Kronecker product-based joint space-frequency index modulation(KP-JSFIM)schemes are proposed.In G-JSFIM,IM is applied directly in joint space-frequency resources.However,KP-JSFIM first chooses the frequency active patterns and antenna active patterns,and then,obtains the final active pattern by the Kronecker product of the two patterns.In general,the proposed G-JSFIM features flexible transmit rate adjustment and KP-JSFIM features low complexity.Furthermore,to improve the perfromance of G-JSFIM and KP-JSFIM in RTV channels,the linear precoding scheme of single antenna OFDM-IM is extended to G-JSFIM and KP-JSFIM.