Antenna Selection and Bit Allocation Strategies for Generalized Spatial Modulation

Abstract: Spatial Modulation (SM) is a novel transmission technique for Multiple InputMultiple Output (MIMO) systems. In SM, a block of information bits is dividedinto two, and mapped to constellation symbols and spatial symbols. Spatialinformation is carried by the active transmit antenna index for each transmittedblock. Generalized Spatial Modulation (GSM) overcomes the single activetransmit antenna constraint of SM, and lets multiples of transmit antennas tobe activated at the same time. This allows GSM to increase the amount ofspatial symbols and the spectral efficiency with respect to SM despite of havingthe same number of transmit antennas. However, since the receiver needs thechannel information to detect the transmitted symbols, performance of GSM isaffected significantly under unfavorable channel conditions. In this thesis, antennaselection and bit allocation strategies are presented to improve the errorperformance of GSM systems with the Channel State Information (CSI) knownat the receiver.Since there can be more possible antenna combinations than the amountthat can be utilized, employing an antenna selection strategy is necessary inGSM systems. In order to improve average Bit Error Rate (BER) of GSMsystems, a novel antenna selection method is proposed. The proposed methodmaximizes the Euclidean distance of the selected antenna combinations with theChannel State Information at the Receiver (CSIR). By making use of statisticalproperties of the channel, a heuristic which decreases the search domain for theantenna selection method is presented.Another factor translating into bit error performance of communication systemsis bit allocation. The proposed bit allocation strategies aim at minimizingthe Hamming distance for the symbols that are neighboring in Euclidean spacewith the given CSI. The first approach for bit allocation utilizes set partitioningof the signal constellation, the second is based on the Delaunay tessellation ofthe signal constellation.The strategies presented in this thesis for both antenna selection and bit allocationare analyzed in terms of performance and in computational complexity.The algorithms for the implementation of each proposed strategy are describedin detail. The BER performance of the proposed algorithms is demonstrated byMonte Carlo simulations. They are compared in error performance and computationalcomplexity to each other and to the conventional approaches in theliterature.