Abstract
This paper studies a new amplify-and-forward cooperative overlay cognitive radio (CR) non-orthogonal multiple access (AFCO-NOMA) system, where a primary network shares its license spectrum with a secondary network by using NOMA principles. An approximate closed-form expression for the outage probability of the proposed system is analyzed. Asymptotic expressions for the outage probability in high signal-to-noise ratio (SNR) regime of both secondary and primary destinations are derived assuming channel estimation error (CEE) and imperfect successive interference cancellation (SIC). Further, the optimal power allocation coefficients to maximize the system throughput for different target rates are determined to ensure priority to the primary user. The diversity order at the primary and secondary destinations are also derived. Moreover, the AFCO-NOMA system is compared with the OMA-based cooperative overlay system in terms of outage probability. The paper also studies the impact of various parameters such as power allocation coefficients, CEE, and detection threshold, on the outage performance of the proposed system. Monte Carlo simulations are used to confirm the correctness of the derived analytical results.
Highlights
Non-orthogonal multiple access (NOMA) has been identified as a key multiple access technology for efficient utilization of spectrum resources in the fifth-generation (5G) mobile networks [1]- [3]
The approximate closed-form expressions for the outage probabilities of both the primary and secondary symbols are derived under the imperfect channel state information (CSI) and successive interference cancellation (SIC) conditions at the relay and destination
The paper analyzed the effect of various parameters on the outage performance of the proposed AFCONOMA system
Summary
Non-orthogonal multiple access (NOMA) has been identified as a key multiple access technology for efficient utilization of spectrum resources in the fifth-generation (5G) mobile networks [1]- [3]. In [6], a cooperative relaying system using NOMA (CRS-NOMA) has been proposed, where multiplexed symbols are transmitted and received in two-time phases using NOMA and a transceiver works as a relay to improve the performance. In [9], the performance of a NOMA based CRS was studied, where two sources transmit symbols to their corresponding destinations over the same frequency band simultaneously with the help of an AF relay. In [10], a NOMA system with a relaying concept has been proposed, in which the multiplexed symbols received in the consecutive time phases over the direct and through relay link are decoded at the destination using maximum-ratio-combining (MRC). A NOMA based system with an AF dedicated relay has been proposed in [11], where both MRC diversity and SIC schemes were applied twice at the destination to decode both the symbols
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