RECEPTION OF BROADCAST SYSTEM INFORMATION

RECEPTION OF BROADCAST SYSTEM INFORMATION

The RRC is provided with basic information about the network from the information
broadcast by each cell in the system. This information is called system information.

This broadcast information describes the common channels in the cell, measurement and cell selection/reselection related information for the transmitting cell and its neighbouring cells, someNAS-related information, information used in intersystem handovers and also location services related information.

Broadcast information is transmitted to the UE by UTRAN using the Broadcast Control Channel (BCCH) logical channel which is mapped onto the BCH transport channel in all states of UE except when in CELL DCH state. System information is also essential for the UE initially to establish the timing relationship with the network.

The system information is broadcast in small units called System Information Blocks (SIBs).
Each system information block encapsulates the same type of network information. This
is required so as to allow UEs to capture only the required system information. Moreover, different kinds of information have different requirements on scope (cell scope, PLMN scope), validity and frequency of updates.