UMTS Channels (Logical, Transport and Physical)

Edited by Zahid Ghadialy (

Last Updated: 01/10/2005

Why do we need BCCH over FACH and under what scenarios would it become applicable. Is it a handset related feature or a network related activity that comes in place due to service demands?

It is mandatory for UE to support BCCH mapped onto FACH. UE has to read System Information from BCCH mapped on BCH in IDLE, CELL_FACH, CELL_PCH and URA_PCH state. When the System Information gets changed MIB value tag is updated and Paging message is transmitted indicating that System Information has changed. The UE's in IDLE, CELL_PCH and URA_PCH will be able to read the updated System Information. To tell the UE's in CELL_FACH to read the new System Information SYSTEM INFORMATION CHANGE INDICATION message is sent on BCCH mapped to FACH.

Also when DRAC procedures are applicable, Sib 10 is transmitted over FACH. System Information Block type 10 shall be acquired on the FACH and only by UEs with support for simultaneous reception of one SCCPCH and one DPCH. If System Information Block type 10 is not broadcast in a cell, the DRAC procedures do not apply in this cell. Note that the UE has to be in CELL_DCH to read Sib 10.

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