GSM uses a combination of Control and dedicated channels.
Below are GSM channels that an RF engineer should understand:-
-Broadcast Control Channel (BCCH)
-Frequency Correction Channel (FCCH)
-Synchronisation Channel (SCH)
-Random Access Channel (RACH)
-Paging Channel (PCH)
-Access Grant Control Channel (AGCH)
-Cell Broadcast Channel (CBCH)
-TCH (Traffic Channel)
You will also need to look at Full Rate, Half Rate, RF planning, Frequency Hopping, etc..
VBR/ Wallis Dudhnath