Iur Interface

The interface between RNCs is the Iur interface.
The primary purpose of this interface is to support inter-RNC mobility
(SRNS relocation) and a soft handover between Node Bs connected to different
RNCs. The protocol architecture for the Iur interface is shown in Figure
6-22. The controlling application protocol is known as the Radio
Network System Application Part (RNSAP). Signaling between RNCs is
SS7-based, whereby RNSAP uses the services of SCCP. As is the case for
the Iu-PS interface, the signaling can be transported on a standard ATM
SS7 transport or can use an IP-based transport over ATM. The same
applies for the transport network control plane.
The user plane contains two frame protocols, one related to dedicated
transport channels, the DCH FP, and one related to common transport
channels, the CCH FP. These user protocols carry the actual user data and
signaling between the SRNC and DRNC.