Research On Several Key Technologies In Spatial Modulation Systems

Spatial modulation (SM) technology is a promising multiple antenna transmission technology. It simplifies the traditional MIMO system structure, reduces the system cost, and improves the energy consumption efficiency and flexibility of the communication system. As a key technology of the future 5G communications, SM has a good application prospect in indoor optical communications and large-scale MIMO communications, which has been a hot topic in the current wireless communications filed. Spatial modulation technology is also a novel hybrid modulation, and expands the signal constellation to the spatial-and-signal constellations, which make the system design more flexible. However, some new challenges are presented. Hence, we in-depth studied the antenna selection issue at transmitter, the signal detection problem at the receiver, and the multi-user interference suppression problem in the SM system. The main works include:First of all, we deeply studied the existing detection algorithms for the SM system, and from the point of view of a two-dimensional vector quantization, analyzed the existing low complexity and optimal detection algorithm for SM systems with QAM modulation. Then, the inherent properties of digital modulation symbols are exploited to propose a low complexity and optimal ML detection algorithm specialized for PSK, whose computational complexity has nothing to do with the order of modulation symbols. The proposed algorithm makes the existing low complexity and optimal detection algorithm for SM perfect. The simulation results, which are the performance comparison of the proposed algorithm with existing detection algorithms, show the advantages and disadvantages of the proposed method. Moreover, the low complexity and the optimality are confirmed from two aspects of theory and simulations.Secondly, for the high complexity and performance loss problem of antenna selection techniques in SM systems, this thesis puts forward two kinds of antenna selection algorithms with low complexity and optimal BER performance based on maximization-minimum Euclidean Distance Antenna Selection (EDAS) criterion, EAQ-EDAS (Equal Amplitude and Quantization based EDAS) algorithm and the RS-EDAS (Rotational Symmetry based EDAS) algorithm. EAQ-EDAS algorithm is proposed for the SM systems with MPSK modulation, and employs the equal amplitude features of MPSK modulation as well as the two-dimensional quantization principle to implement the complexity free of the modulation order, while maintaining the BER optimality. RS-EDAS algorithm exploits the rotational symmetry of modulation symbols to reduce the size of the symbol search space. Thus, the computational complexity of the algorithm is also reduced. Then, from different point of views, we proved the RS-EDAS algorithm that has low computational complexity and optimal BER performance. Moreover, compared with the existing optimal antenna selection algorithms, the proposed algorithms has extremely low computational complexity, and at the same time, compared with the existing sub-optimal antenna selection algorithms, they are perfect in BER performance, especially in the correlated channel.Finally, interference alignment technology is introduced into the GSM networks and GSM based cognitive radio networks to eliminate the interferences among users. In the GSM interference network, we directly use of the existing interference alignment classic algorithms to eliminate interferences within the network. The simulations verifies that the new transmission scheme based on interference alignment technology can eliminate the interference between the users, at the same time improve each user's average transmission rate and network capacity. For the interference problem in GSM-CR network, we first studied the interference problem in the traditional CR network, and proposed a optimal transceiver design scheme based on interference alignment. After the feasibility and the features such as low complexity and low feedback of the scheme are verified, the basic idea of the scheme is applied in GSM-CR network. New algorithm utlizes the particularity of the conditions to realize IA in GSM network to simply the optimal transceiver design algorithm from the original iteration algorithm to the non-iterative algorithm, which greatly reduces the complexity of the algorithm. Moreover, the algorithm eliminates the interferences among users in GSM-CR network, and optimizes the transmission performance of each user. The simulations show that the IA scheme for the two networks can eliminate the interference between the users, and increase the total capacity of the networks.