Short-Packet Transmission in NOMA-ISAC Systems

To facilitate low-latency communication and reliable sensing capabilities for wireless networks, a short-packet transmission framework is proposed in an uplink non-orthogonal multiple access (NOMA)-based integrated sensing and communication (ISAC) system. Three schemes are considered, namely, orthogonal multiple access (OMA)-ISAC, NOMA-ISAC, and Semi-NOMA-ISAC, where communication-centric (C-C) successive interference cancellation (SIC) design and sensing-centric (S-C) SIC design are introduced for the latter two schemes. The achievable short-packet transmission rate and the achievable sensing rate are developed for measuring the communication performance and the sensing performance, respectively. To strike a balance between communication and sensing capabilities, a weighted sum communication rate and sensing rate maximization problem is formulated. A key challenge arises from the fact that short-packet transmission introduces performance loss terms, which makes the optimization problem highly coupled and strictly non-convex. To conquer this difficulty, an alternating optimization based approach is developed for each considered scheme to carry out the joint optimization in an alternative manner. The convergence and effectiveness of the proposed designs are evaluated via simulations, which demonstrate that i) NOMA-ISAC and Semi-NOMA-ISAC achieve higher overall performance compared to OMA-ISAC scheme; ii) the C-C SIC design outperforms the S-C SIC design at a large communication weight.