The radio resource management (RRM) functionality with HSDPA and HSUPA has experienced changes compared with Release 99.

In Release 99 the scheduling control was purely based in the radio network controller (RNC) while in the base station (BTS or Node B in 3GPP terminology) there was mainly a power control related functionality (fast closed loop power control).

In Release 99 if there were two RNCs involved for connection, the scheduling was distributed.The serving RNC (SRNC) – the one being connected to the core network for that connection – would handle the scheduling for dedicated channels (DCHs) and the one actually being connected to the base transceiver station (BTS) would handle the common channel (like FACH).

As scheduling has been moved to the BTS, there is now a change in the overall RRM architecture.

The SRNC will still retain control of handovers and is the one which will decide the suitable mapping for quality of service (QoS) parameters.

With HSDPA the situation is simplified in the sense that as there are no soft handovers for HSDPA data,then there is no need to run user data over multiple Iub and Iur interfaces and, even

though HSDPA is supported over Iur in the specifications, the utilization of the Iur interface can be completely avoided by performing SRNC relocation, when the serving high-speed downlink shared channel (HS-DSCH) cell is under a different controlling RNC (CRNC).

With Release 99 this cannot be avoided at RNC area boundaries when soft handover is used between two base stations under different RNCs. Thus, the typical HSDPA scenario could be presented by just showing a single RNC.