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NET 3710

This article explores the process of analog to digital conversion using Pulse Code Modulation (PCM) in the .NET framework. It covers topics such as T-Carrier, digital multiplexing, and the hierarchy of SONET/SDH.

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NET 3710

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  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 • + 8,000 Framing Bits/Second • = 1.544 Megabits/Second

  11. Digital Multiplex Using Time Division • DS-0: 1 Channel, 64 Kb/s • DS-1: 24 Channels, 1.544 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

  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)

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