GSM Um Interface -- Burst Formats

57

Encrypted

BURST

3

T

3

T

1

S

26

Training

1

S

57

Encrypted

8.25

GP

41

Syn. Sequence

8

T

36

Encrypted

68.25

Guard Period

Normal Burst

RACH Burst : Access

3

T

3

T

3

T

142

Fixed Bits of All Zeros

8.25

GP

FCCH Burst : Frequency Correction

3

T

3

T

8.25

GP

SCH Burst : Synchronization

3

T

3

T

26

Training

58

Mixed Bits

8.25

GP

Dummy Burst

58

Mixed Bits

Transmit

Direction

MS BTS

577 usec

156.25 bits (577 usec)

3.693 usec per bit

156.25/0.576923=270.833 kbps

T: Tail bits (start bits

or stop bits)

0 usec

250

50

100

200

150

577 usec

0 km

75

15

30

60

45

One way distance

173 km

39

Encrypted

39

Encrypted

64 Extended

Training Training

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