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There are two types of multi frame:
1) 26 TDMA--frame of multiframe is used to carry TCH, SACCH and FACCH.
2) 50 TDMA--frame multiframe is used to carry BCCH, CCH, SDCCH AND SACCH.
Five types of bursts:
1. Normal Burst (NB):
. It is used to transmit both information and control bits
. T trail bits are used as guard time in achieving power level.-Training is used to estimate channel characteristics.
. SF stealing flags tells whether data or signalling is being transmitted.
. Normally for FACCH.
Access Burst: . It is used to send the Random Access Channel (RACH) information - RACh contains the first message from MS to BTS.
. It has a long guard period to allow BTS to calculate the Ms distance from the BTS and to provide timing advance information to MS.
3) Frequency Correction Burst (FCCH):
. It uses just to transmit Frequency Correction Channel (FCCH).
.142 bits are set to "0" in the known time slots.
4) Synchronization Burst (SCH):
. It is used to transmit synchronization information
. The training sequence includes a well-known sequence of bits
. Alos contains the running number of TDMA frame.
5) Dummy Burst:-
. It is transmitted when no other bursts are to be transmitted
. Uses same frequency channel which is used for BCCH to ensure if BCCH Transmits Burst in each time slot
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