1. A method performed by a user equipment device (UE), comprising:receiving a dedicated notification message from a base station, wherein the dedicated notification message indicates an establishment of at least one Signaling Radio Bearer (SRB) using a Packet Data Convergence Protocol (PDCP) layer in a transparent mode; and
establishing the at least one SRB using the PDCP layer in a transparent mode prior to an establishment of Access Stratum (AS) security, wherein the at least one SRB is utilized in a first communication between the UE and the base station prior to establishment of the AS security and a second SRB including PDCP layer information is utilized in a second communication between the UE and the base station after establishment of the AS security.