Using non-orthogonal multiple access with constant and multi envelope precoding for massive multiple input multiple output systems

Wireless communication plays key role to transmit information at the present time. In order to provide ever increasing data rate, power efficiency and spectral efficiency demands, multiple input multiple output systems are offered. However, number of antennas at the base stations of multiple input multiple output systems is not enough to meet these requirements. For this reason, massive multiple input multiple output systems which use a great number of antennas at the base stations have been proposed to solve this problem. Massive multiple input multiple output systems provide significant improvements for fifth generation wireless communication technologies. On the other hand, there are some problems need to be solved such as higher built cost and power consumption of these systems. Constant envelope precoding has been proposed to reduce base stations' building costs and hardware complexity. Constant evelope precoding is an effective and applicable technique that provides wireless communication with only one nonlinear power amplifier coupled with phase shifters in front of the each antennas at the base stations. Constant envelope precoding offers same level of multi user interference to each user and results in performance loss related to achievable data rates compared to conventional zero forcing precoding approaches. In order to recover performance loss, multi envelope precoding has recently been proposed. In multi envelope precoding, there are more than one but limited number of power amplifiers coupled with phase shifters in front of the each antennas at the base stations. Thus, different power levels can be provide to different group of antennas according to the power requirements. As a result of the multi envelope precoding, there is a considerable improvement in achievable data rates compared to constant envelope precoding, but still same level of multi user interference is observed on users. Non-orthogonal multiple access technique is an another prepared solution to meet new generation wireless communication demands. In non-orthogonal multiple access, users can be communicate at the same frequency band and time interval thanks to superposition coding and successive interference cancellation techniques. In this thesis, we proposed an idea that using non-orthogonal multiple access with constant and multi envelope precoding for massive multiple input multiple output systems with the objective of differentiate multi user interference observed on users according to their requirements. We pair users according to their channel conditions and examine the impact of the non-orthogonal multiple access multi user interference. Simulations for the independent and identically distributed Rayleigh fading channel show that different multi user interference levels are possible with non-orthogonal multiple access under both constant envelope and multi envelope precoding. Using multi envelope precoding provides better performance than constant envelope precoding.