GSM Traffic and Control Channels
There are two types of channles in a GSM Network
Traffic Channels(TCH) and Control Channels (CCH)
Traffic Channels
Traffic Channels are used to take encoded speech and user data over the network the are two types of traffic Channels
Full Rate Traffic Channels (TCH/F) at a net bit rate of 22.8kbps
Half Rate Traffic Channels (TCH/H) at a net bit rate of 11.4Kbps
Control Channels
Control Channels can be one of the following type
- Broadcasting Control Channels (these are for downlink only)
Frequency Correction Channels (FCCH)
These are used for the correction of the mobile terminal frequency
Broadcast Control Channels (BCCHs)
these are used for broadcasting information to the mobiles about the
cell in which they are located and also about neighboring cells
Synchronization Channels (SCHs)
These are used for the frame synchronization of the mobiles and
identification of the Base Station
- Common Control Channels (CCCHs)
Access Grant Channels (AGCH)
These are used for the assignment of a dedicated channel
Paging Channels (PCH)
These are used for paging to the mobiles, these are used on downlink
Random Access Channels ( RCHs)
these are used on the uplink for the random access attempts made by the
mobile
- Dedicated Control Channels (DCCHs)
DCCHs are used on both uplink and downlink
Stand alone Dedicated Control Channels (SDCCHs)
SDCCHs are major channels used for location updation, registration and
for SMS
Fast Associated Control Channels (FACCH)
FACCH carry the same information as the SDCCH, the only difference is
that they are used in case when very fast exchange on information is
needed
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