Adaptive Quadrature Spatial Modulation And Detection Algorithm

Multiple Input Multiple Output(MIMO)technology is developed when the traditional Single Input Single Output(SISO)technology cannot meet the increasing demands of mobile communication systems.MIMO system has multiple antennas at both the receiving end and the transmitting end,which can improve the multiplexing and diversity gain of the system by establishing multiple communication links while ensuring system transmission reliability.But inevitably,it also brings a series of problems such as Inter Channel Interference(ICI)?requirement for Inter Antenna Synchronization(IAS).In order to avoid the above problems,Spatial Modulation(SM)technology with only one active transmit antenna at each time slot emerged.Quadrature Spatial Modulation(QSM)technology is an extension of SM technology,which decomposes signals into two components,orthogonal and in-phase,and selects one active antenna to transmit separately.This allows QSM technology to further improve the spectral efficiency of the system while maintaining the advantages of SM technology.This paper proposes a MIMO transmission scheme with higher spectral efficiency-Adaptive Quadrature Spatial Modulation(AQSM)system.Compared with the traditional QSM system,the AQSM system combines Adaptive Modulation(AM)technology and QSM technology.The proposed AQSM system improves the spectral efficiency(SE)of the QSM system by adaptively adjusting the modulation order of the transmitter.In a QSM system,the transmission information is mapped to a spatial symbol and a constellation symbol of constant modulation order but in proposed AQSM system,the receiving end feeds back the channel information to the transmitting end through a feedback link.The spectral efficiency of the system is improved by increasing the size of the transmitted signal constellation as the channel condition improves keeping the bit error rate(BER)below the target BER.In addition,this paper deeply studies the algorithm principle of Sphere Decoding(SD)detection algorithm.Starting from the problems of slow convergence of search radius and redundant calculations of SD detection algorithm,this paper studies low complexity detection algorithms suitable for AQSM system,aiming at the case that the modulation order of AQSM system will increase to a higher order.Based on the SD detection algorithm,this paper proposes two low-complexity detection algorithms with optimal bit error performance:AQSM-Sorted-SD detection algorithm which based on the sorting of the first-level Euclidean distance of the candidate solution vectors and AQSM-Ordered-SD detection algorithm which based on the sorting of the active antenna combinations.Simulation results show that the proposed AQSM system can effectively improve the spectral efficiency of the QSM system under the condition that the system BER below the target BER,and the two proposed algorithms can effectively reduce the computational complexity without losing any bit error performance.