Research On Multiple Antenna Transmission Technology Based On Spatial Modulation

Spatial Modulation(SM),as an emerging MIMO transmission technology,introduces the spatial dimension into traditional two-dimensional modulation by establishing the mapping relationship between information bits and transmit antenna index.Therefore,a three-dimensional constellation space is formed.Generalized Spatial Modulation(GSM)transmission technology are proposed by scholars to the problems of low spectral efficiency of the SM technology and insufficient utilization of antenna resources.These emerging MIMO transmission technologies can significantly reduce or even eliminate the influence that problems of inter-channel interference and high implementation costs of multiple RF links in traditional MIMO systems,which is forming an important research directions in wireless communication systems.This thesis,mainly studies and improves solutions to the problems existing in SM technology and its extension technology,aiming at reducing the complexity and improving system bit error rate(BER)performance.The work and innovations contained in this thesis are as follows:1.The bit mapping technology is studied to enhance the BER performance of SM system.Considering the problem that the current bit mapping algorithms cannot balance system BER performance and complexity,an improved bit mapping algorithm named Symbol Nearest Method(SNM)is proposed.This algorithm sorts SM symbols based on the distance between symbols,and assigns Gray-coded bit sequences to the ordered SM symbols.Simulation and analysis results show that the system performance of the new algorithm is close to BER lower bound under high signal-to-noise ratio,and the complexity of algorithm is()2O K,where K is the number of symbols and the value is relatively low.Thus,the algorithm can achieve a compromise between system BER performance and complexity.2.In the GSM system,multiple antennas at the transmitter are activated,which results in more complicated signal detection at the receiver.In order to reduce the detection complexity,an improved Sphere Decoding(SD)detection algorithm is proposed,which is called Reliable SD(R-SD)detection algorithm.The algorithm sorts the candidate transmit antenna combinations in descending order according to the set sorting criteria,searching the transmit antenna combinations in order by SD detection algorithm,setting a threshold value for the search results for reliability judgment.If the judgment is reliable,the detection is terminated.Otherwise,the search process will continue.If all the search results do not satisfy the reliability judgment conditions,the optimal result would be adopted as the final detection result.Simulation and analysis results show that the system BER performance of R-SD detection is approximately the same as that of Maximum Likelihood(ML)detection.When multiple antennas are configured at the transmitter and receiver,and the modulation order is high,the computational complexity of R-SD detection is about 88% lower than that of ML detection.Thus,R-SD detection is more practical in GSM system.