The 3G Iub interface is the terrestrial interface between NodeB and RNC. The Radio Network Layer defines procedures related to the operation of the WCDMA NodeB. The Transport Network Layer defines procedures for establishing physical connections between the 3G NodeB and the 3G RNC.
The 3G Iub application protocol, WCDMA NodeB application part (NBAP) initiates the establishment of a signaling connection over 3G Iub. It is divided into two essential components, CCP and NCP.
NCP is used for signaling that initiates a 3G UE context for a dedicated WCDMA UE or signals that are not related to specific WCDMA UE. Examples of NBAP-C procedure are 3G cell configuration, handling of common channels and radio link setup
CCP is used for signaling relating to a specific WCDMA UE context.
SAAL is an ATM Adaptation Layer that supports communication between signaling entities over an ATM link.
The user plane 3G Iub Frame Protocol (FP), defined the structure of the WCDMA frames and the basic in band control procedure for every type of WCDMA transport channel. There are DCH-FP, RACH-FP, FACH-FP, HS-DSCH FP and PCH FP.