System Design Of Cooperative Relaying And Generalized Spatial Modulation Based Orthogonal Time Frequency Space Modulation

With the advent of the Internet of Things,wireless communication services and related applications have increased dramatically.Mobile communication networks have gradually carried massive data transmission and multimedia access.Existing networks require emerging communication technologies to achieve higher spectral efficiency,more reliable transmission quality,and larger system capacity.The widely researched Spatial Modulation(SM)technology can significantly improve the spectral efficiency of the system by mapping random input bits to the transmit antenna index and constellation symbol index,respectively.This technology can overcome the disadvantage of strong interference in the Multiple-Input and Multiple-Output system.It is studied that SM technology can avoid the problems of Inter-channel Interference and Inter-antenna Synchronization.Generalized SM(GSM)technology,which is extended from SM,completely inherits all the advantages of that,and can improve the system performance by activating more transmit antennas to make full use of the transmit diversity gain.In addition,this technology has more options for transmit antenna combinations,which can further improve the spectral efficiency.Orthogonal Time Frequency Space(OTFS)technology has been widely studied due to its unique performance advantages in dealing with time-varying channel fading.This technology can effectively overcome the problem of high Doppler frequency shift,and the system implementation is simple,which has good practical research significance.This paper focuses on GSM and OTFS technology,proposes a new modulation scheme that combines these two technologies,and studies the system design that combines it with the cooperative relaying technology.The main research work can be summarized as:1)This paper proposes a GSM based OTFS(GSM-OTFS)system.This scheme fully takes the advantages of OTFS and GSM,and can achieve higher spectral efficiency and better bit error rate(BER)performance.The GSM-OTFS system model and its signal processing have been presented.Furthermore,the theoretical average BER(ABER)of the GSM-OTFS system is derived with the union bound technique and the moment generating function(MGF).Numerical results show that the theoretical results of average BER performance of the GSMOTFS scheme match well with the simulation results,which proves the correctness of our theoretical analysis.The GSM-OTFS system can achieve better BER performance and spectral efficiency compared with the SM-OTFS system.2)Base on the GSM-OTFS system,this paper proposes a maximum ratio combining(MRC)based message passing(MP)joint detection algorithm.In this scheme,the MRC algorithm is used to recover the active antenna combination index,and on this basis,the MP detection is used to recover the modulation constellation symbol index.The detection process of the MRCMP algorithm is given in detail,and the computational complexity of the common detection schemes is analyzed.The simulation results show that MRC-MP scheme can effectively balance the BER performance and the computational complexity.3)According to the actual communication scenario,this paper proposes the decode and forward(DF)protocol based GSM-OTFS cooperative system,which fully combines the advantages of cooperative communication to improve the reliability of transmission and expand communication range.This system adds a multi-relay-mapping module to improve the spectral efficiency.At the same time,the application of DF protocol improves the transmission reliability.We give the signal processing of this system and derives the ABER performance expression.The numerical results demonstrate the effective combination of relay,which brings great performance gains to the GSM-OTFS system.4)In order to adapt to more changing communication scenarios,this paper studies the Incremental Hybrid Decode-Amplify-Forward(IHDAF)protocol based GSM-OTFS system.The improved scheme selects the specific forward protocol according to the instantaneous signal-to-noise ratio between each node.This paper introduces the working mechanism of the IHDAF protocol and the signal processing of the improved system,and derivers the outage probability expression.The simulation results prove that the system can fully improve the reliability of the communication,which has good research value.