Modified Generalised Quadrature Spatial Modulation

In this paper, we propose a Modified Generalised Quadrature Spatial Modulation (mGQSM) scheme with multiple RF chains. The proposed scheme, compared to GQSM, proposes a novel codebook design which provides one extra bit per channel use (bpcu) spectral efficiency with the constraint of $\{\log_{2}\begin{pmatrix} N_{t}\\ N_{r_{f}} \end{pmatrix}\}\geq0.5$, where $N_{t}$ denotes number of transmit antennas, and $N_{r_{f}}$ denotes number of RF chains, $1\leq N_{rf}\leq \lfloor\frac{N_{t}}{2}\rfloor$. Using the ML detection algorithm, we study the performance of mGQSM with and without imperfect channel state information, via numerical simulations. We compute the computational complexity of ML-decoding in terms of real valued multiplications and introduce a variant of mGQSM called Reduced Codebook mGQSM (RC-mGQSM) to reduce the complexity but resulting in a decrease in spectral efficiency.