Transmit Signal Design For Spatial Modulation Aided Millimeter-Wave Communication

Millimeter wave MIMO technology is one of the key technologies to meet high-speed communication of massive data.Unlike the existing microwave frequency band,millimeter wave signal has abundant spectral resources,but has poor diffraction ability and large attenuation in air.Therefore,combating severe path loss is a problem that must be solved by millimeter wave communication research.The existing MIMO technologies can bring performance gain in wireless communication systems,and millimeter wave antenna is small in size and easy to integrate,so the combination of millimeter wave transmission and MIMO technology can achieve better performance.In practical applications,wide-band signal processing requires high cost at millimeter-wave band,and multiple RF links used in MIMO systems can also result in extremely high power loss and hardware cost.Therefore,the popularization and application of millimeter wave MIMO technology faces both problem of cost and power consumption.As an emerging MIMO technology,spatial modulation activates only one transmit antenna in any time slot,and can implement MIMO transmission using fewer RF links.It has the advantages of low power consumption,low cost,and low complexity,so millimeter wave spatial modulation transmission has broad application prospects.In the classical spatial modulation transmission schemes,the two-dimensional modulated signals and the one-dimensional spatial constellations are independently and separately mapped,that is,the information bits are mapped to the corresponding modulation symbol and antenna index,respectively.Then the activated antenna transmits corresponding modulation symbols.Although the principle of independent mapping criteria is simple and feasible,there are some limitations of practical application.On one hand,the number of spatially modulated transmit antennas must be a power of two;on the other hand,the ability of carrying symbol for transmit antennas is different.Therefore,the performance of spatial modulation based on independent mapping is sub-optimal.In this thesis,the jointly mapped 3-dimensional signal design scheme is proposed to obtain better performance in mmWave SM-MIMO systems based on antenna switching or beam selection.Main contributions and innovations in this paper can be summarized as follows:1)Transmit signal design of mmWave SM based on antenna switching----In this thesis.3-D signal design scheme is proposed for spatial modulation transmission at mm Wave frequency based on the indoor mmWave line-of-sight channel scenarios.Firstly,the SM-MIMO system employing MRC detection is modeled.and the antenna switching design principle is analyzed.In order to improve the reliability of the millimeter-wave spatial modulation system,the joint mapping 3-D signal optimization design that satisfies the constraint of given spectral efficiency is proposed to minimize symbol error rate in this dissertation.Then exhaustive search algorithm and forward stepwise selection algorithm are proposed to solve the optimization problem.According to the comparative analysis,the proposed forward stepwise selection algorithm can achieve approximate optimal performance with minimal complexity.Simulation results show that the 3-D signal design can not only make the system configuration more flexible,but also obtain superior SER performance compared to the random selection scheme,the classical spatial modulation scheme and the adaptive precoding scheme.2)Transmit signal design of mmWave SM based on beam selection----Due to the limited rate of antenna switching,the spatial modulation system based on antenna switching is hardware constrained,and only part of the antennas are used in a certain time slot,which is disadvantageous for obtaining a higher beamforming gain.In contrast,beam selection carries spatial domain information by using different beam vectors in the analog phase-shifted network,which eliminates the need for high-speed antenna switching,and utilizes all transmit antennas in any time slot,facilitating the acquisition of millimeter-wave communication beamforming gain.In the millimeter-wave channel model of narrow-band cluster structure,this dissertation study three-dimensional signal optimization design aiming to improve transmission reliability.In this thesis,the modulation symbol set is generalized to the complex domain.and the modulation symbol satisfying the power constraint is obtained by solving the non-convex quadratic programming quadratic constrained optimization problem.Then the stepwise selection method is used to satisfy the dimensional constraint.Simulation results show that the proposed 3-D signal design scheme based on complex domain modulation improves the SER performance significantly.