| Space-time block coding (STBC) is a diversity proving technique in presence of multiple transmit antennas. One of the major challenges of STBC design is to have full-diversity/good error-rate performance with low decoding complexity. We proposed the lowest known complexity maximum-likelihood decoding of full-diversity quasi-orthogonal STBC (QO-STBC) for QAM signal constellations. Next, we provided a high performing 4 x 4 QO-STBC with linear decoding.;Automatic-Repeat-reQuest (ARQ) is an error control protocol and is part of most wireless systems design. We for the first time combined opportunistic spectrum access with ARQ protocol, then found optimal power allocation for the protocol.;Recently, there has been a growing interest in the field of physical layer security. In that effort, we proposed two works (i) we showed ARQ can provide reliability and security simultaneously, and (ii) waveform and energy designs can exploit the multi-path channels to provide security.;With recent research interests on dimensionality reduction and outlier resistant signal processing, we focussed on L1 signal processing as the final research topic. Specifically, we proposed two low-complexity algorithms to compute the L1 principal component vector. |
