User-Centric Resource Allocation in Downlink Multi-Carrier NOMA System With Coexistence of URLLC and eMBB Users

This article proposes user-centric resource allocation in a downlink multicarrier (MC)- non-orthogonal multiple access (NOMA) system in the presence of both ultra-reliable and low-latency (URLLC) and enhanced mobile broadband (eMBB) traffic. The NOMA scheme is applied to eMBB traffic to provide a higher data rate, while the orthogonal multiple access (OMA) scheme is employed by URLLC traffic to guarantee latency and reliability. The joint optimization problem is formulated as a sum-rate maximization of the system while considering the quality-of-service (QoS) requirements for each user. A two-stage algorithm is employed, where the resource allocation problem of eMBB users is first tackled using quadratic and Lagrangian dual transforms owing to the non-convexity nature of the problem. Then, the resource allocation of punctured URLLC users is solved, where a hyperparameter is introduced to control the trade-off between the sum-rate of eMBB and URLLC traffic. Simulation results reveal that the proposed user-centric resource allocation algorithm maximizes the sum-rate while fully ensuring the minimum QoS for all users compared to the conventional algorithms.