Re: Help plz!
Hi friend
====================
4.2 GSM Control Channels:-
These are:
1. Broadcast Control Channel (BCCH).
2. Common Control Channel (CCCH).
3. Dedicated Control Channel (DCCH).
4.2.1 BCCH Group:-
The Broadcast Control Channels (BCCH) is downlink only (BSS to MS) and comprises the following:
1. BCCH system information broadcasts allow the MS to correctly camp onto a cell’s transmission. These messages also contain information concerning idle neighbors.
2. The Synchronization Channel (SCH) carries information for frame synchronization and includes the BSIC.
3. The Frequency Control Channel (FCCH) provides information for carrier synchronization.
4.2.2 CCCH Group:-
The Common Control Channel Group is bi-directional i.e., it works in both uplink and downlink directions.
1. Random Access Channel (RACH) is the “uplink” used by MSs to gain access to the system.
2. Paging Channel (PCH) and Access Granted Channel (AGCH) operate in the “downlink” direction. The AGCH is used to assign resources to the MS, usually a Standalone Dedicated Control Channel (SDCCH), although a TCH can be assigned in this way. The PCH is used by the system to page a MS. The PCH and AGCH are never used at the same time.
4.2.3 DCCH Group:-
Dedicated Control Channels (DCCH) is assigned to a single MS to allow point to point signaling transactions.
1. Standalone Dedicated Control Channel (SDCCH) which supports the transfer of Data to and from the MS during call setup, location updating and Short Message Service (SMS).
2. Associated Control Channel (ACCH). This consists of slow ACCH which is used for system information, radio link measurements and power control messages. Fast ACCH is used to pass “event” type messages e.g. handover and disconnect commands. Both FACCH and SACCH operate in uplink and downlink directions.
enjoy