Performance evaluation for multi-antenna UWOC-RF NOMA systems with imperfect CSI and SIC

Information transmission is easily affected by obstacles or other factors, which makes it challenging to achieve perfect channel state information (CSI) and successive interference cancellation (SIC) in practical applications. Therefore, in this paper, a dual-hop underwater wireless optical communication-radio frequency (UWOC-RF) system with non-orthogonal multiple access (NOMA) in the presence of both imprecise CSI and imperfect SIC is investigated. In particular, the underwater source sends a superimposed optical NOMA signal to a pair of land-based users via a decode-and-forward relay on the surface, which decodes the received signal and encodes it into the RF one before broadcasting it to the terrestrial users. Considering a scenario that both the land-based users are equipped with multiple antennas and adopt a maximal-ratio combining technique to deal with those multiple copies of received signals, we first format the expressions of probability density function, cumulative distribution function, and the p-th moment of the imperfect channel gain in the UWOC link. And then the analytical and asymptotic expressions for outage probability as well as the closed-form expression for average achievable rate of each user are obtained by utilizing the Meijer's-G and the Fox's-H functions. Finally, Monte-Carlo simulations are performed to validate the accuracy of those analytical expressions.