Multiuser Capacity Enhancement using Hybrid CDMA-NOMA Scheme

Abstract

The increasing demands for high throughput in the fifth generation (5G) are posing different challenges for the design of access schemes. To meet these challenges, new multiple access (MA) schemes are being developed. Non-orthogonal multiple access (NOMA) is considered as one of the outperformance multiple access technique to deal with the heterogeneous wireless networks. This feature makes NOMA capable of increasing spectral efficiency gain over the conventional multiple access schemes. Non-Orthogonal Multiple Access (NOMA), which will resolve power distribution issues, high data rate requirements, design challenges and limitations of all generations. NOMA uses the power domain to separate signals from each other. It is an additional form for providing a multi-user access scheme. It gives a new dimension in which signals can be separated and given access to a base station. NOMA uses the power domain to separate signals. Code domain multiple access (CDMA) has been adopted as the multiple access scheme for the third generation cellular mobile systems because of it’s flexibility in cell planning, support for different rate traffics, user capacity and robustness to multipath fading channel conditions. One of the advantage of CDMA is to increase the number of simultaneous users (user capacity) with acceptable error performance. In this thesis power allocation issue will be discussed. For previous work in NOMA power allocation to multiple users is a big challenge. For multiple users the power allocation strategy is under investigation. In our research we will reduce this issue by assigning different codes to all users in the cell. We are going to combine CDMA with NOMA for multiuser capacity enhancement and better utilizing of power allocation scheme, for designing hybrid technique BER performance of CDMA under different channels is analyzed, BER performance of SISO-NOMA is analyzed in different channels as AWGN, Rician, Rayleigh and NYUSIM channel models. We designed a hybrid CDMA-NOMA scheme and BER is analyzed under different fading channels specially in NYUSIM channel model, the 5G channel model.