ABSTRACT
The main aim of the physical layer is to boost the data rates over wireless channels with better quality of services (QOS), thereby, increasing the efficiency and reliability of new-generation wireless communication systems, especially 4G LTE and 5G system. The work presented in this chapter will provide a comprehensive study of combining effects of spatial multiplexing and space time coding techniques under various fading channel constraints. Performance of various space time block codes like quasi orthogonal space time block codes and rotational quasi orthogonal space time block codes is investigated using various decoding algorithms like V-BLAST and sphere decoder. The sphere decoder has been modified in terms of new k and k1 algorithms based on spectral efficiency and computational complexity. Moreover, a detailed mathematical analysis has been done to justify the proposed system model for modified sphere decoder so as to support the cooperative transmission in the downlink channel. BER and SNR parameters are used to validate the analytic result over higher QAM modulation techniques. Simulations are performed in MATLAB software, and the result obtained shows the significant decrement in error rates and computational complexity with higher spectral efficiency.
