1. NET 3710
PCM

2. Analog to Digital Conversion…
Voice sessions in analog format
Process to digitize analog signals is PCM
1938 Alec Reeves – England
1960s PCM becomes feasible
Why digital?

3. Digital Multiplex: How It’s Done....

4. T-Carrier Basic foundation for digital circuits
Bell system development
Circuit runs on twisted-pair copper cable
4 wires (2 pair – 1 Tx, 1 Rx)

5. 5 Steps in PCM process
Sampling
Quantizing
Encoding
Companding
Framing

6. Sample the Voice 8,000 Times Per Second

7. Encode the Sample as an 8-bit Word (Quantizing/Encoding)

8. Companding
Decoder expands the encoded signal back to its original form. This is Companding.
u law – U.S. standard 14 bit conversion to 8 bit compression
A law – European standard 13 bit conversion to 8 bits

9. Combine 24 Voice Channels.... Framing…..
T-1 Line
Multiplexer
Multiplexer
T-1 Framing = 24 time slots x 8 bits = 192 bits
1 Framing bit per frame = 193 total bits per frame
193 bit frame repeats 8000 times per second

10. The Arithmetic of T-1 8,000 Samples/Sec x 8 Bits/Sample
= 64,000 Bits/Second
x 24 Channels/T-1
= 1,536,000 Bits/Second
,000 Framing Bits/Second
= Megabits/Second

11. Digital Multiplex Using Time Division
DS-0: 1 Channel, 64 Kb/s
DS-1: 24 Channels, Mb/s
DS-2: 96 Channels, 6.3 Mb/s
DS-3: 672 Channels, 45 Mb/s

12. T-1 Components.... Channel Bank/T-1 Mux. Channel Service Unit
T-1 Line Repeaters
DSX-1 jack panel
RJ-48 Jack – pins 1,2 Rx; 4,5 Tx

13. Synchronous Optical Network (SONET)

14. Why SONET? DS Hierarchy is Limited
Self-Healing Fiber Ring is Supported
Add/Drop Capability is Enhanced
Interoperability Among Vendors
Seamless Interface Between Public and Private Networks
Merges North American and European Systems

15. SONET/SDH SONET used in U.S. and Canada
SDH (Synchronous Digital Hierarchy)
used by rest of world

16. SONET/SDH Hierarchy

17. SONET Line Rates SONET/SDH Circuit Line Rate in MB DS-1 Capacity
OC-3/STS-3/STM-1 84
OC-12/STS-12/STM-4
336
OC-48/STS-48/STM-16 2,
1,344
OC-192/STS-192/STM-64 9,
5,376
OC-768/STS-768/STM-256
39,
21,504

18. SONET Levels 4 levels Photonic – light, lasers, LEDs
Section – Regenerator to Regenerator
Line – ADM to ADM (maintenance span)
Path – End to end circuit

19. SONET Architecture SONET ring Spur or collapsed ring
UPSR (unidirectional path switched ring)
Redundant copies of signal, working and protect
Collector or edge rings
BLSR (bidirectional line switched ring)
Uses only capacity between nodes, share protection wavelengths
Core rings
DACS (Digital Access Cross-connect System)