Average Rate Analysis of Cooperative NOMA Aided Underwater Optical Wireless Systems

In this paper, we consider a cooperative non-orthogonal multiple access (NOMA) aided underwater optical wireless system in which the source transmits to two users where near user serves as relay node far user. Our proposed consists of narrow-angle light-emitting diode (LED)/photodiode (PD) elements at source, user, and order achieve communication, our selects single LED/PD each node. We propose several low complexity selection schemes that aim maximize link throughput addition optimal random for benchmarking. characterize performance scheme, bounds closed-form tight approximations on average achievable sum rates are presented. The use multi element nodes NOMA increase rate significantly over conventional orthogonal access. Moreover, near-optimal can be achieved using channel gain based line-of-sight medium-to-high transmit power regimes. derived expressions also useful investigate impact key parameters such power, allocation factor, placement, number