Research On LDPC-coded Spatial Modulation Techniques

The fifth-generation mobile communication(5G)will cover a variety of scenarios,providing high-efficiency,high-efficiency communication services.To meet the communication services in various scenarios,key performance parameters such as data transmission rate and spectrum efficiency need to be improved in 5G and future communications.Therefore,wireless key technologies in 5G and future communication systems have become an important research topic.Low-density parity-check(LDPC)codes are used in various communication scenarios such as optical fiber communication,deep space communication,and wireless communication due to its excellent performance.At present,binary LDPC codes have become the coding scheme of the data channel in the 5G Enhanced Mobile Broadband(e MBB)scene.For short and medium code lengths,nonbinary LDPC codes have better error correction performance than binary LDPC codes,and are suitable for combination with high order modulation.Therefore,this thesis has conducted in-depth research on nonbinary LDPC coded modulation,constellation shaping,and spatial modulation techniques.The content and main results are as follows:For nonbinary LDPC coded modulation systems,a construction method of quasi-cyclic nonbinary LDPC codes is proposed based on ”optimal” cycle distributions.Besides,the constellation shaping is studied.Combined probability shaping methods with geometric shaping methods,a constellation shaping method is designed based on traditional signal constellations to obtain a certain shaping gain.In coded spatial modulation systems,the transmit signal set is considered as the Cartesian product of the spatial constellation and signal constellation.Based on that,nonbinary LDPC coded spatial modulation system is proposed.To further improve system performance,the constellation shaping technique is applied to the signal constellation of coded spatial modulation systems.In addition,a two-layer nonbinary LDPC coded spatial modulation system is proposed to reduce the decoding complexity of one-layer nonbinary LDPC coded spatial modulation system.And then,in order to solve the problem that the number of transmit antennas in the spatial modulation system is limited to the powers of two,we combine the spatial modulation with Gallager mapping to propose a scheme(named GM-SM)that can provide an acceptable performance for spatial modulation transmission with an arbitrary number of transmit antennas.To improve the system's reachable information rate,the optimal transmit antenna active distribution can be obtained by using a designed search algorithm.In addition,we study the index mapping rules to optimize the transmit antenna index labelling and validated by using EXIT Charts.Finally,for the generalized spatial modulation(GSM)system,Gallager mapping is combined with the system for spatial constellation mapping.A GM-GSM system is designed to reduce the number of transmit antennas and increase the flexibility of GSM systems.In addition,we study to use quadrature spatial modulation(QSM)to transmit high-dimensional constellation symbols.And then,a method for designing high-dimensional constellation is proposed.Gallager mapping is applied to the spatial constellation of QSM system to ensure that the system will extend the spatial constelltiaon for high-dimensional constellation symbol transmission at each time slot.