Functions in RNC

􀂾Admission Control (AC) decides whether a request to establish a radio access bearer (RAB) is

admitted in the RAN or not. Admission Control is used to maintain stability and to achieve high

traffic capacity of the RAN. The Admission Control algorithm is executed when radio access bearer is set up or the bearer is modified. AC is also involved in all kinds of handovers, cell update, location update requests.

􀂾Packet Scheduler (PS) allocates the instantaneous free capacity to non-real time packet data

users. This is done after circuit-switched real time services have been allocated capacity, and

within the limits of predefined load thresholds. Based on radio interface interference information,

traffic volume measurement reports from UE (uplink), and received data in the RNC buffers

(downlink), the Packet Scheduler will allocate radio resources for the RAB.

Basically PS will assign radio resources (radio channels) to non-rt traffic, like DCH, or HSDSCH.

􀂾Load Control (LC) guards the system against overload, that is, keeps it stable. In an overload

situation, RRM, or more specifically the Load Control algorithm, returns the system in a quick and controlled fashion back to the normal load state, which is defined by radio network planning. In a CDMA system, the most important obstacle to the efficient use of available radio resources is interference. Therefore, load control measures the interference both in the uplink and the

downlink directions periodically under one RNC. As regards the downlink direction, interference is the same as the transmission power of the cell in question. Load Control measurements are

performed on a cell-by-cell basis.

􀂾Resource Manager is located in the RNC and works in close co-operation with Admission Control and the Packet Scheduler. The main function of the Resource Manager is to allocate downlink spreading code(s) when Admission Control or the Packet Scheduler requests it. Admission Control and the Packet Scheduler provide the actual input for code allocation. The Resource Manager, in turn, informs the Packet Scheduler about the resource situation.

􀂾Power Control adjusts the transmission power of the UE in the uplink and of the BTS in the downlink. In order for a BTS receiver to be able to recover the signal emitted by a UE, there must be a difference in power between said signal and the interference level. In the context of Power Control a value called SIR is used to represent this power difference. Thus, the Power Control aims at using the minimum SIR required for the quality of the connection to remain sufficient. Power Control works on a connection basis.

􀂾Handover.

When reporting criteria are fulfilled the UE sends the RRC message “MEASUREMENT REPORT” to the RNC. The measurement report includes a reporting event and measurement results of active set cells and triggered cells (other cells that trigger a reporting event).

When the handover procedure is ended successfully, the RNC checks if the measurement control is needed. If measurement control parameters are changed then the RNC sends the RRC message MEASUREMENT CONTROL to the UE.

UE compares the measurement results of different sectors to HO thresholds provided by

the RNC and sends back measurements results to RNC, which triggers a SHO if needed. SHO

in a MEHO (mobile-evaluated handover), the final HO decision is made in the SRNC.

UTRAN may control a measurement in the UE by broadcast information (SIB 11 and 12) in

Idle mode and by transmitting a Measurement Control message in Connected mode.

Measurement control contains:

- measurement number;

- measurement command (setup/modify/release);

- measurement type (UE internal, intra/inter-frequency, inter-RAT);

- measurement objects (e.g. neighbour cell list);

- measurement quantity (e.g. RSCP, Ec/N0, TX power etc.);

- reporting quantity (e.g. RSCP, Ec/N0, TX power etc.);

- reporting criteria (Event triggered, Periodic mode).

A set of neighbour cells has to be defined for each cell in the radio network configuration

database in RNC. In the Connected mode, a mobile searches neighbouring cell

continuously. If it founds a new cell, it decodes its BCH and sends the measured CPICH

Ec/N0 to the SRNC. In RAS05.1, the neighbour list can be automatically generated in Nokia

NetAct and transmitted to the corresponding RNCs, as described earlier. If the active set is

updated (e.g., mobile handovers to another cell), a new neighbour list is sent to the UE.