On Performance of Cooperative Transmission in Uplink Non-Orthogonal Multiple Access Wireless Sensor Networks

In this paper, we study the cooperative transmission of uplink non-orthogonal multiple access (NOMA) wireless sensor networks in terms of performance analysis. Specifically, two sensor nodes applying the NOMA scheme intent to transmit the messages to the sink with the cooperation of multiple amplify-and-forward (AF) relays. We propose a protocol that the best cooperative relay is selected to retransmit the messages from sensor nodes to sink based on channel state information. To evaluate the performance of this proposed system, the closed-form expressions of outage probability for two users are derived based on the signal-to-noise ratio (SNR) and signal-to-interference-plus-noise ratio (SINR) of transmission links. Furthermore, to look insight the behaviour of the proposed system, the numerical results are provided according to the operation key parameters, e.g., number of relay nodes, transmit power, and distances. Finally, to clarify the advantage of this proposed protocol, we provide a comparison of random relay selection and non-cooperative transmission. The Monte-Carlo simulation verifies the correctness of our analysis.