Improved outage performance with power optimization for URLLC using Cooperative NOMA

Ultra-reliable low latency communication (URLLC) is one of the key services offered by the 5G wireless networks. This service type is characterized by stringent high reliability and low latency criteria, thus require efficient multiple access techniques to facilitate various mission-critical services. Non-orthogonal multiple access (NOMA) effectively enhances spectral efficiency and ensures fairness by exploiting the power allocation at receivers compared to orthogonal multiple access (OMA). Therefore, it becomes suitable for facilitating URLLC service. The addition of the cooperative relaying technique to NOMA can enhance the reliability of the data transmission. This motivated us to analyze the performance of cooperative NOMA (C-NOMA) for short packet URLLC data transmission. Hence, we have proposed a C-NOMA based system using the decode and forward (DF) relaying technique and successive interference cancellation (SIC) at the receiver to minimize the overall error probability for URLLC. The minimization of overall outage probability has been achieved by optimizing power allocation at the receiver considering the decoding error and error due to queuing delay violation while ensuring fair throughput among users. The simulation study has shown that the proposed C-NOMA based short packet transmission improves overall outage probability, energy efficiency, and ensures fair throughput among users in comparison to only NOMA and OMA based techniques.