Path-Searching-based Signal Detection Algorithms For Quadrature Spatial Modulation

In recent years,with the popularization of mobile internet business,there is an increasing request for people to develop the mobile communication system.The traditional SISO(Single Input Single Output,SISO)techniques were unable to meet the need of the growing demand of mobile communications.By setting multiple antennas on the transmit side and the receive side,MIMO(Multiple Input Multiple Output,MIMO)techniques could both guarantee reliable transmissions as well as increase channel capacity and spectral efficiency in communication systems.Nevertheless,there still exist problems such as severe ICI(Inter Channel Interference,ICI),excessive detection complexity on the receive side,the difficulty of IAS(Inter Antenna Synchronization,IAS)and so on.SM(Spatial Modulation,SM)technique takes antenna indices into account to bring more transmit information,in which way spectral efficiency is increased.Since only one RF(Radio Frequency,RF)chain is used,the cost is reduced,too.During the transmission,for only one transmit antenna is activated,ICI and IAS could be avoided.However,SM marks time for low antenna utilization and high cost to increase spectral efficiency.In order to improve the spectral efficiency of conventional SM,QSM(Quadrature Spatial Modulation,QSM)technique comes into being.By mapping the modulated information into the in-phase and quadrature dimension,and being transmitted through one transmit antenna,respectively,QSM is able to both improve the antenna utilization as well as the spectral efficiency.In this way,QSM becomes one of the most promising MIMO transmission schemes.This thesis aims at exploiting low-complexity detection algorithms while maintaining near-optimal performance in QSM system.First of all,by detailedly analyzing the searching process of ML(Maximum Likelihood,ML)and traditional SD(Sphere Decoding,SD)algorithms,a fundamental cause of massive calculating redundancy is found out.To solve this problem,a novel detection algorithm,titled PS-SD(Path-Searching-based Sphere Decoding,PS-SD),is proposed.Subsequently,on the basis of PS-SD,this thesis further proposes an improved algorithm named IPS-SD(Improved Path-Searching-based Sphere Decoding,IPS-SD).By taking antenna combinations into consideration and setting a referenced threshold,IPS-SD achieves lower computational complexity than PS-SD with acceptable performance loss.Finally,performance and a substantial reduction in computational comple xity of the new SD detections above are carried out in QSM system,and being compared with ML and traditional SD on Matlab.Simulation results show that PS-SD is capable of reducing massive computational complexity on receive side while maintaining the performance of optimal ML detector.On the other hand,IPS-SD could achieve lower computational complexity than PS-SD with negligible performance loss.