Further Improvement of NR RRC Inactive for Small Data Transmission

Currently the typical applications which are common to both smart phones and C-IoT equipment have periodic and infrequent small packet transmissions. RRC INACTIVE state as a new type of UE state targets to reduce signaling overhead and UE power consumption for infrequent data transmission. Since the RRC inactive State state had not supported data transmission until 3GPP Release 16, the UE has to resume the connection to transmit small data and be released to INACTIVE state subsequently. This results in unnecessary power consumption and signaling overhead. On this point, the small data transmission (SDT) during the INACTIVE state has been studied in 3GPP Release 17. In this paper, the performance of SDT is evaluated. The detailed design of SDT are analyzed in terms of subsequent transmission, cell reselection, timers and anchor relocation.