Efficient Handling of Small Data Transmission for RRC Inactive UEs in 5G Networks

Small Data Transmission (SDT) in RRC Inactive state is one of the new features being introduced in 3GPP Release 17 for 5G NR. It enables UEs in RRC Inactive state to transmit infrequent and small data without requiring an RRC state transition. In this paper, we study the envisioned SDT solutions, namely RACH-based SDT and CG-based SDT. We evaluate their performance in terms of packet delay, UE power consumption, signaling overhead and physical resource efficiency. Results show that all SDT solutions bring attractive gains as compared to the conventional data transfer after the RRC connection resume. Particularly, CG-based SDT solution achieves the highest gains with 73% in UE power efficiency and 85% in latency reduction. It enables to reduce the signaling overhead and to save the physical resource usage by 78%. We further analyse the performance sensitivity to the payload size, the traffic arrival rate and the UE mobility pattern.