Joint Throughput and Blocklength Optimization for RIS-Aided Hybrid Multi-Access Short-Packet System

Hybrid multi-access that integrates non-orthogonal multiple access (NOMA) and orthogonal multiple access (OMA), provides greater flexibility in accessing a diverse range of device types and a vast number of devices. This letter investigates a reconfigurable intelligent surface (RIS) aided hybrid NOMA-OMA short-packet (RAHNOSP) system, where NOMA and OMA devices transmit messages to the access point aided by an RIS. Specifically, we focus on optimizing the throughput and the blocklength in the RAHNOSP system. To this end, we formulate a multi-objective optimization (MOO) problem that aims to maximize throughput and minimize blocklength simultaneously. To make the MOO problem tractable, the Chebyshev transformation is invoked to convert the MOO into a single-objective optimization problem, and then we decompose the transformed problem into two subproblems and solve them by using alternating optimization. Numerical results demonstrate that the proposed hybrid NOMA-OMA scheme outperforms the existing strategies in terms of throughput-blocklength tradeoff.