Radio Resource Control

The Radio Resource Control (RRC) protocol belongs to the UMTS WCDMA protocol stack and handles the control plane signalling of Layer 3 between the UEs (User Equipment) and the UTRAN. It includes:

• Functions for connection establishment and release,
• Broadcast of system information,
• Radio bearer establishment/reconfiguration and release,
• RRC connection mobility procedures,
• Paging notification and release,
• Outer loop power control.

There can only be one RRC connection open to a UE at any one time.

RRC inactivity timers

The configuration of RRC inactivity timers in a W-CDMA network has considerable impact on the battery life of a phone when a packet data connection is open.

The RRC idle mode (no connection) has the lowest energy consumption. The states in the RRC connected mode, in order of decreasing power consumption, are CELL_DCH (Dedicated Channel), CELL_FACH (Forward access channel), CELL_PCH (Cell Paging channel) and URA_PCH (URA Paging channel). The power consumption in the CELL_FACH is roughly 50 percent of that in CELL_DCH, and the PCH states use about 1-2 percent of the power consumption of the CELL_DCH state.

The transitions to lower energy consuming states occur when inactivity timers trigger. The T1 timer controls transition from DCH to FACH, the T2 timer controls transition from FACH to PCH, and the T3 timer controls transition from PCH to idle.

Different operators have different configurations for the inactivity timers, which leads to differences in energy consumption. Another factor is that not all operators use the PCH states.

See also

• Radio Resource Management
• Mobility management
• Radio Network Controller
• UMTS
• WCDMA

References

3GPP 25.331 specification - Radio Resource Control.

This article is based on material taken from the Free On-line Dictionary of Computing prior to 1 November 2008 and incorporated under the "relicensing" terms of the GFDL, version 1.3 or later.