On outage analysis of cooperative overlay NOMA system with CEE and imperfect SIC

This paper studies a new decode-and-forward cooperative overlay cognitive radio non-orthogonal multiple access (DFCO-NOMA) system, where a secondary network shares the license spectrum of a primary network by using NOMA principles. Asymptotic expressions for the outage probability in high signal-to-noise ratio regime of both secondary and primary destinations are derived assuming channel estimation error (CEE) and imperfect successive interference cancellation. The diversity order for the primary and secondary symbols are also derived. Further, the optimal power allocation coefficients to maximize the system throughput are determined to ensure priority to the primary network. The paper also investigates the impact of various parameters such as power allocation coefficients, CEE, and detection threshold, on the outage performance of the proposed system. The accuracy of derived analytical results are verified through the Monte Carlo simulations.