Research On Subcarrier Index Modulation Technology

OFDM is one of the most popular multi-carrier transmission technology in wireless communications.OFDM has the advantages of low system complexity,high frequency band utilization,and strong ability to resist narrow-band interference.However,it also has some shortcomings such as sensitivity to carrier frequency offset and high PAPR.Under this background,Index Modulation(IM)technology is proposed.This thesis studies the OFDM-IM technology which based on the index modulation in frequency domain,and presents the WFRFT-IM system which based on the WFRFT.The performance of the two models was compared and analyzed,and the influence of system parameters on the system performance was explored.This thesis first introduces the background of the emergence of IM technology and its technical characteristics,then introduces the OFDM-IM technology.After that,it gives the appearance and development process of OFDM-IM technology,briefly describes its development status,and explains the advantages of OFDM-IM compared to OFDM according to the principle.Finally,the performance of OFDM-IM system is theoretically analyzed.Next,this thesis gives the basic principles of the OFDM-IM system firstly,and accordingly establishes the mathematical model of the OFDM-IM system.For the transmission and reception process,two index mapping schemes are given: look-up table method and combinatorial method.Three demodulation algorithms : ML algorithm,LLR algorithm,and re ML algorithm are followed.At last,a theoretical analysis of the performance of the OFDM-IM system is made.After theoretical analysis,this thesis combines the simulation results to analyze the transmission performance of OFDM-IM.According to the simulation results,the relationship between the spectral efficiency improvement and the modulation order is given.After that,the performance of different modulation combinations is discussed through simulation,and the parameter selection strategy under different modulation combinations is given.Then the bit error rate performance and the complexity of the three demodulation algorithms are studied,and their respective advantages are analyzed.The system performance of OFDM-IM system under Rayleigh fading channel with/without carrier frequency offset is given later,and the reasons for the difference in performance are explained.WFRFT is a mathematical tool that can jointly analyze and process signals in the time and frequency domains.It belongs to a hybrid carrier system that includes a single-carrier and multi-carrier system,and has the advantages of both systems.Especially in the time-frequency dual-select channel,the modulation order can be changed to combat inter-channel interference.Based on this feature,this thesis further improves the OFDM-IM system,uses WFRFT to replace the traditional fourier transform module,and proposes WFRFT-IM.It has achieved better performance than OFDM-IM under proper modulation order.