System information delivery for layer-2-based sidelink relay

Abstract

Apparatus and methods are provided for system information delivery through a sidelink relay in a NR network. In one novel aspect, on-demand system information is delivered to a remote UE through a PC5-RRC message. In one embodiment, the relay UE aggregates SI requests from one or more UEs in the SI Request destined to the gNB. In one embodiment, the PC5-RRC message is a PC5 unicast message based on an Uu-RRC broadcast SI Update message from the gNB. In another embodiment, the PC5-RRC message is a PC5 broadcast message, which includes a version number in a MAC header indicating an SI update broadcast. In yet another embodiment, the PC5-RRC message is a PC5 groupcast message. In one embodiment, the remote UE is in an RRC-IDLE state, and wherein the UE sends the SI Request message destined to the gNB through the sidelink in a PC5-RRC SI Request message.