GSM Um Interface -- Logical Channels

57

Encrypted

BURST

3

T

3

T

1

S

26

Training

1

S

57

Encrypted

8.25

GP

Normal Burst

577 usec

156.25 bits (577 usec)

TS0

TS1

TS2

TS3

TS4

TS5

TS6

TS7

TDMA Frame:114 info. bits per TS

Logic Channel Type:

Traffic Channel

TDMA

Frame

TCH

Multiframe

TC0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

Idle

SACCH

26 TC x 4.616 ms = 120 ms

577 usec x 8 = 4.616 ms

Channel Bit Rate = 24 x 114bits/120msec = 456bits/20ms = 22.8 kbps

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

50

BCH

Multiframe

51 TC X 4.616 MS =235.4 ms

Logic Channel Type:

Control Channel

...

...............

48

49

• 1 Superframe=26 x 51 TDMA Frames=1.62 sec.

• 1 Hyperframe=2048 Superframes=3.482 hours.( the repeated period of ciphering key)

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