Transmission and detection techniques for MIMO systems

It is well-known that Multiple-Input Multiple-Output (MIMO) wireless systems are disposed by two conclusive goals: high data rate and high performance. This thesis is concerned with transmission and detection techniques of MIMO systems, particularly on Spatial Modulation (SM). SM is a lately developed transmission technique for multiple antenna systems. The idea behind SM is to map a block of information bits into two parts, carried separately by the index of the active transmitter and the symbol chosen from constellation points. All four transmission techniques presented in this thesis are based on the SM principle. The first system, called spatial phase shift keying (SPSK) modulation, follows the idea of SM but uses multiple active transmitters and it shows a gain of 2 dB over a transmission technique based on SM. Antenna beam pattern modulation (ABPM) is the second proposed technique. In this technique, the antenna beam patterns are utilised to transmit information. The contribution of this scheme is to improve the data rate utilizing different beam patterns in order to generate another dimension to the constellation diagram. Optimization of the beam pattern design results in improved system performance. In addition to all the benefits of ABPM at the transmission design, a sub-optimal detection method based on lattice reduction (LR) is used to reduce the computational complexity in comparison to the optimal maximum likelihood (ML) method. The aim of this proposed sub-optimal detection method (LR) is to achieve performance similar to that of the ML scheme at affordable complexity. ABPM shows a gain of more than 2 dB over transmission techniques based on SM. The third scheme is called antenna pattern shift keying (APSK) modulation. This scheme combines the idea of SPSK and ABPM because the antenna beam patterns and the indices of the active transmitters carry the symbol chosen from a constellation diagram. APSK improves the data rate and the overall system performance. APSK has similar performance as a spatial multiplexing scheme but APSK reduces the number of RF chains and it has a gain of 3.5 dB in comparison to that of a technique based on SM. The last scheme included in this thesis, is a precoder technique based on LR. This novel LR pre-coder is applied to the generalised pre-coding aided spatial modulation (GPSM) scheme to improve the system’s performance and it shows a gain of more than 1 dB over the traditional GPSM. Additionally, a suboptimal detector scheme is proposed to achieve performance similar to that of the ML detector but with lower complexity. Using that in combination with the LR pre-coding technique means that the performance of the GPSM scheme is preserved with a much lower detection complexity.