User Grouping and Imperfect CSI for Downlink NOMA over κ- µ Fading

The massive increase in the utilization of mobile devices and communication networks has increased the requirement of massive connectivity and efficient spectrum utilization. Non-Orthogonal Multiple Access (NOMA) technique has been a promising technology towards the present day requirements of the users. In NOMA, the signals are superimposed with different power levels for each user and then transmitted to the receiver. The receiver performs Successive Interference Cancellation (SIC) to distinguish and obtain the required signal. Till now, various researches have focused on SIC with perfect characteristics whereas only few research focused on imperfect SIC (ipSIC). While perfect SIC (pSIC) acts an ideal case of no loss of information and external noises, the ipSIC acts as practical scenario of data transmission in real-time environment. In this paper, we aim to obtain the performance metrics of the considered NOMA system in presence of ipSIC and compare to the performance of pSIC of the same user. More importantly, we characterize channels as κ - µ fading distribution. We derive closed-form expressions of outage probability for two destinations. Meanwhile, we also perform the Monte-Carlo simulations to check the authenticity of obtained mathematical expressions.