The impact of channel estimation errors on the performance of cooperative nonorthogonal multiple access 5G systems under Nakagami‐m fading

Abstract

AbstractNonorthogonal multiple access (NOMA), which can provide high data rates and spectral efficiency in wireless communication, is a promising multiple access technique for the fifth‐generation systems. In this paper, a cooperative NOMA downlink network is investigated over Nakagami‐m fading channels with channel estimation errors taken into consideration. We assume that the direct links between the base station and the users are available and selection combining is conducted at the receiver of the users. First, the closed‐form expressions for the exact and lower bounds of the outage probability are obtained, respectively. Furthermore, due to the presence of the imperfect channel state information, an error floor exists by approximating the outage probability at the high‐signal‐to‐noise‐ratio regime. Next, the ergodic sum rate for the proposed network is analyzed, and the closed‐form expressions for the upper bound of the ergodic sum rate are attained. Finally, extensive numerical results are presented to confirm the correctness of our analysis and to show the superiority of NOMA over conventional cooperative orthogonal multiple access.