Index modulation for next generation radio communications.

Abstract

Man’s insatiable desire for swift and more efficient internet service, a wide range of connectivity and increased data rate of transmission necessitated the need for further research to improve the efficiency of the existing systems. The development and evolution of the next-generation communication systems can be ascribed to the multiple-input multiple-output (MIMO) techniques implemented. The fundamental founding block of the MIMO systems is the spatial modulation (SM) which interestingly was able to attain high spectral efficiency as the receiver maintained significantly lower complexity. However, even with the feat achieved by the SM scheme, there was still a need improve on the performance of the SM scheme which meant an increase in the spectral efficiency was required, this prompted further research and a new scheme was introduced. The quadrature SM (QSM) scheme was introduced to better the performance of the conventional SM. QSM retains all the good benefits the SM scheme offers, while still enhancing the spectral efficiency and improving overall throughput. However, the demand for increased reliability, i.e., improving the QSM scheme’s error performance led to a new scheme being introduced. Space-time QSM (ST-QSM) improves the QSM scheme’s error performance by achieving second-order diversity gain for QSM. This scheme combines both the spatial dimension and diversity to the QSM scheme, bringing about a new and improved scheme. In this dissertation, a scheme was introduced to fix the high computational complexity (CC) that affects MIMO systems transmitting at high data rates. Signal orthogonal projection (OP) was employed to decrease the CC of the space-time block coded spatial modulation (STBC-SM). The proposed scheme is called STBC-SM-OP and its results were investigated by comparing it with the STBC-SM with maximum likelihood detection (STBC-SM-ML). The proposed STBC-SM-OP scheme’s error performance matched that of STBC-SM-ML tightly down to low BER whilst maintaining a low CC.