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Burst Modes

There are 5 types of bursts in a TDMA frame: normal, frequency correction, synchronization, access, and dummy. A normal burst is used to transmit both information and control bits. An access burst contains the first message from an MS to a BTS and has a long guard period. A frequency correction burst just transmits frequency correction information with fixed bits set to 0.

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akash kumar Singh
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49 views6 pages

Burst Modes

There are 5 types of bursts in a TDMA frame: normal, frequency correction, synchronization, access, and dummy. A normal burst is used to transmit both information and control bits. An access burst contains the first message from an MS to a BTS and has a long guard period. A frequency correction burst just transmits frequency correction information with fixed bits set to 0.

Uploaded by

akash kumar Singh
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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Burst and Frames

Ź The information contained in one time


slot on the TDMA frame is call a burst.
Ź Five types of burst
ƒ Normal Burst (NB)
ƒ Frequency Correction Burst (FB)
ƒ Synchronization Burst (SB)
ƒ Access Burst (AB)
ƒ Dummy Burst
5/20/2008
Normal Burst
- 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

5/20/2008 T Data SF Training SF Data T GP


Access Burst
• 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
Training
Tail Sequence Data Tail Guard Period

8 bits 41 synch bits 36 encrypted bits 3 bits 68.25 bits

156.25 bits (0.577 ms)

5/20/2008
Frequency Correction Burst
• used just to transmit Frequency Correction
Channel (FCCH)
• 142 bits are set to “0” in the known time
slots.

Frequency Correction Burst


(FCCH) Guard
Tail Data Tail Period
3 bits 142 fixed bits (0) 3 bits 8.25 bits

156.25 bits (0.577 ms)

5/20/2008
Synchronization Burst
• used to transmit synchronization information
• the training sequence includes a well known
sequence of bits
• Also contains the running number of TDMA
frame.
Synchronization Burst
(SCH) Guard
Tail Data Extended Training Sequence Data Tail Period
3 bits 39 encrypted bits 64 synchronization bits 39 bits 3 bits 8.25 bits

156.25 bits (0.577 ms)

5/20/2008
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
• Quality monitoring
Guard
Tail Dummy Sequence Training Sequence Dummy SequenceTail Period
3 bits 58 mixed bits 28 midamble bits 58 mixed bits 3 bits 8.25 bits

156.25 bits (0.577 ms)

5/20/2008

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