This document discusses digital telecommunications hierarchies and transmission modes. It describes: - Digital signal hierarchies including DS0, T1, E1, OC-1, STS-1, and STM-1. - Transmission modes like parallel, serial, synchronous, and asynchronous. - How digital voice is encoded by sampling at 8 kHz and using 8 bits per sample. - The framing structures of T1 and E1 interfaces, including how they are composed of DS0 channels and use timeslots like TS0 for framing and TS16 for signaling.

1. Digital Hierarchy
T1 STS4
OC1 DS3
DS0
STM 16 OC 256 T4

2. Parallel Transmission
Serial Transmission
Transmission Modes

3. Data Transmission
Data Transmission
Synchronous
SerialParallel
Asynchronous

4. Parallel Transmission

5. Serial Transmission
The 8 bits are sent
one after another

6. Synchronous Transmission

7. Asynchronous Transmission

8. Voice Digitalization
Digital Telephony
-Sample
8 bits per sample
8 khz (8000 Samples/Sec)
Voice Bandwidth =
200 Hz to 3000 Hz

9. T1 is made up of 24 DS0 Lines
T1 speed is 1.544 Mbps
T1 Hierarchy
1
0
1
2
22
23
DS0s
T1 Frame 2 10101010 01010101 1111000
0
0
T1 Frame 12 10101010 01010101 11110000 0
T1 Framing bits 100011011100
T1 Frame 1 10101010 01010101 1111000
0
0 1 23

10. T1 Hierarchy
T1 frame is made up of 192 (Voice) + 1 (parity) bits
T1 frame is transmitted in a time of 0.125 milli seconds
giving a total speed of 193/0.125 = 1544 kbps
or 1.544 Mbps

11. T1 Hierarchy
T1 is made up of 24 DS0 Lines
T1 speed is 1.544 Mbps
0
1
2
22
23
T1
T1T1C
T1CT2
T2
T2
T2
T2
T2
T2
T3
T3
T3
T3
T3
T3
T4
DS0s
T1
1.544
Mbps
T1C
3.152
MbpsT2
6.312
Mbps
T3
44.736
Mbps
T4
274.76
Mbps
DS0 – 64kbps
T2
T3
T1 = 24
DS0sT1C = 48
DS0sT2 = 96
DS0s
T3 = 672
DS0s
T4 = 4032
DSOs

12. E1 Interface
• Supports 32 user channels( each of 64 kbps access
rate)
• Provides 2.048 Mbps access rate
• Mostly only 30 are dedicated channels
E1 supports 3 different bit structures
1. Frame
2. Multi frame
3. Unframed
The mode of operation dictates how the bits are
structured

13. E1 is made up of 32 DS0 Lines
E1 speed is 2.048 Mbps
E1 Hierarchy
0
1
2
30
31
DS0s
E1 Frame 2 10011011 01010101 11110000
E1 Frame1610011011 01010101 11110000
E1 Frame 1 10011011 01010101 11110000
0 1 31

14. TS 0 TS 1 TS 31
E1 Frame 256 bits
Multiframe
E1 basic frame consists of 256
bits
32 time slots
Each time slot contain 8 bits
And provides 64kbps
throughput
E1 TIME SLOTS FUNCTIONS:
TS0 - Synchronization
- alarms
- messages
TS16 - for Signaling
- can carry data as well
(TS1-TS15) & (TS17-TS31)
Structure of E1 Frame
011011 (bits 2 – 7)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 150

15. E1 Hierarchy
TS0 TS1 TS30 TS31
E1 takes 32 DS0 Channels
30 Slots for Voice
Two Special Timeslots
TS0 is used for Framing and Synchronization
TS16 is used for signaling
Speed of an E1 line is 32 @ 64 kbps = 2.048 Mbps
TS2 TS16

16. ITU-T Rec. G.704
E1 CAS Transmission Format
• Time Slot 16 : Frames 2 through 15 are the same as frame 1
• Time Slot 0: Even number frames 2 through 14 are the same as frame 0
• Time Slot 0: Odd number frames 3 through 15 are the same as frame 1
1 = bit set to 1 0 = bit set to 0
1/0 = speech / signalling (varying data) X = unassigned bit (normally set to 1)
Fr. Ch. Ch.
1 1 16
2 2 17
3 3 18
: : :
15 15 30
10 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Multiframe (16 frames)
Frame 0 (32 Time Slots)
10 2 3 4 5 6 7 8 9 10 11 12 13 14 15 1716 18 19 20 21 22 23 24 25 26 27 28 29 30 31
Frame 1 (32 Time Slots)
10 2 3 4 5 6 7 8 9 10 11 12 13 14 15 1716 18 19 20 21 22 23 24 25 26 27 28 29 30 31
Time Slot 0
(8 bits)
0X 0 1 1 0 1 1
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
Time Slot 1
Speech (Ch. 1)
Time Slot 16
(8 bits)
00 0 0 X 0 X X
Time Slot 0
(8 bits)
1X 0 X X X X X
Time Slot 16
Signalling Bits
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
Speech
Ch. 1-15
Speech
Ch. 16-30
Speech
Ch. 1-15
Speech
Ch. 16-30
Frame
Time Slot
Frame
Alignment
Word
Multi-
Frame
Alignment
Word
Changes to 1 on
loss of distant
multiframe
Changes to 1 on
loss of distant frame
(remote alarm)
Not-Frame
alignment word
A B C D A B C D
LSB

17. I 1 A N N N N N
1 2 3 4 5 6 7 8
I 0 0 1 1 0 1 1
1 2 3 4 5 6 7 8Bit # - >
Bit # - >
Odd Frames
Even Frames
International Bit
International Bit
1 Indicates ODD Frame
0 Indicates EVEN Frame
National Bits
Yellow Alarm (Alarm = 1)
(Normal = 0)
Frame Alignment pattern
E1 Framing Format

18. 1 2 3 4 5 6 7 8
CI 0 0 1 1 0 1 1
Frame 0
4 Bit CRC 0 Indicates EVEN Frame
Frame Alignment pattern
1 2 3 4 5 6 7 8
C3 0 0 1 1 0 1 1
0 Indicates EVEN Frame
Frame Alignment pattern
1 2 3 4 5 6 7 8
C2 0 0 1 1 0 1 1
0 Indicates EVEN Frame
Frame Alignment pattern
1 2 3 4 5 6 7 8
C4 0 0 1 1 0 1 1
0 Indicates EVEN Frame
Frame Alignment pattern
Frame 2
Frame 4
Frame 6
4 Bit CRC
4 Bit CRC
4 Bit CRC
Timeslot 0 Optional Operation (With CRC-4)

19. OC – 1 51.840 Mbps
OC – 3 155.520 Mbps
OC – 9 466.560 Mbps
OC – 12 622.080 Mbps
OC – 18 933.120 Mbps
OC – 24 1244.160 Mbps
OC – 36 1866.240 Mbps
OC – 48 2488.320 Mbps
OC – 96 4976.640 Mbps
OC – 192 9953.280 Mbps
SONET
STS –1 51.840 Mbps
STM – 1 155.520 Mbps
STM – 3 466.560 Mbps
STM– 4 622.080 Mbps
STM – 6 933.120 Mbps
STM – 8 1244.160 Mbps
STM – 12 1866.240 Mbps
STM – 16 2488.32 Mbps
STM – 32 4976.640 Mbps
STM – 64 9953.240 Mbps
SDH
Optical Hierarchy

21. Thank You!

22. • Made up of 16 consecutive frames
• This frame structure is used for two purposes
1.signaling(CAS): here each channel has a
predetermined frame. Half of the TS16 is
dedicated for the channel signaling information
signaling (CCS): here one or more channels of
64kbps are dedicated for signaling
2. Error correcting code mechanism: CRC is carried
in TS0.
Multi Frame Structure

23. E1 Timeslot 16

24. E1 Timeslot 16