Voice FundamentalsReference Guide

© 2002 Nortel Networks Corporation.

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Foreword

Power Networks

Best in class

Voice communication

Intended Audience

1 Introduction

1.1 Short History of the Telephone

2 The Telephone

2.1 Key Voice Fundamentals

2.1.1 Frequency

2.1.2 Levels

2.2 Basic Operation of the Telephone

2.2.1 Basic Telephone - Signalling

2.2.2 Basic Telephone - The Speech Path

2.3 Other Types of Telephone

2.3.1 “Two wire” Vs. “Four wire”

3 The PBX

3.1 Introduction to the PBX

3.2 Call Routing in a PBX

3.3 Voice Interfaces on a PBX

4 Introduction to Digital Voice

4.1 The Channel Bank

4.2 Digital Voice - Pulse Code Modulation (PCM) - G.711

4.2.1 A-law and µ- PCM

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4.2.2 Power of a Digital Signal

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4.2.3 Distortion Resulting from the Digitisation Process

4.3 The Digital 1.544Mbit/s PBX Interface (DS-1)

4.3.1 Physical Interface

4.3.2 Framing - D4

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4.3.3 Framing - Extended Superframe (ESF)

4.3.4 Channel Associated Signalling (CAS) on DS-1

4.3.5 Common Channel Signalling on DS-1

4.3.6 DS-1 Alarms

4.4 The Digital 2.048Mbit/s PBX Interface (E1)

4.4.1 Physical Interface - G.703

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4.4.2 Framing Structure - G.704

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4.4.3 Channel Associated Signalling (CAS) on E1

4.4.4 Common Channel Signalling (CCS) on E1

4.4.5 E1 Alarms

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4.5 The Need for PBX Synchronisation

4.5.1 PBXs With No Synchronisation

4.5.2 PBXs With Synchronisation

5 Speech Compression

5.1 Different Coding Types

5.2 Adaptive Differential Pulse Code Modulation (ADPCM)

5.3 Code Excited Linear Prediction (CELP)

5.4 Low Delay Code Excited Linear Prediction (LD-CELP) - ITU-T G.728

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5.5 Conjugate-Structure Algebraic Code Excited Linear Prediction CS-ACELP - ITU-T G.729

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5.6 Other Compression Techniques

5.7 Speech Compression Impairments

5.7.1 Mean Opinion Score (MOS)

5.7.2 Quantisation Distortion Units (QDUs)

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5.7.3 Speech Compression and Voice-band Data

5.8 Fax Relay

6 Echo and Echo Control

6.1 What is Echo

6.1.1 Causes of Echo

6.2 Echo Control Devices

6.2.1 When Do We Need Echo Control

6.2.2 Echo Control Devices

6.3 Echo Suppressors

6.4 Echo Cancellers

6.4.1 Nonlinear Processor

6.4.2 Tail Circuit Considerations

6.4.3 Types of Echo Canceller

6.4.4 Tone Disabling of Echo Cancellers and Echo Suppressors

6.4.5 G.168 (Improved Echo Canceller)

7 Introduction to Signalling Systems

7.1 Analogue Signalling Systems

7.1.1 Ground Start: 2 Way PBX to Public Exchange Trunk Circuit

Outgoing Call From PBX:

Incoming Call to PBX:

7.1.2 E&M Trunk

7.1.3 AC Signalling Schemes

7.1.4 Manual Signalling

7.2 Digital Signalling Systems

7.2.1 Channel Associated Signalling (CAS)

7.2.2 Common Channel Signalling (CCS)

7.2.2.1 Private to Public Networking Protocols

7.2.2.2 Public to Public Networking Protocol

7.2.2.3 Private Networking Protocols

7.2.2.4 How Does CCS Work

Layer 2

Layer 3

8 Voice Within the Enterprise Network

8.1 What is an Enterprise Network

8.1.1 Different Types of Enterprise Networks

8.2 Time Division Multiplexers (TDM)

8.2.1 TDM Synchronisation

9 Voice Over Asynchronous Transfer Mode (ATM)

9.1 Introduction to ATM

9.1.1 The ATM Cell

9.1.2 The ATM Adaptation Layers

9.1.3 ATM Service Categories

9.1.4 Statistical Multiplexing with ATM

9.2 Voice and Telephony Over ATM (VTOA)

9.2.1 Voice Sample Cellification

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9.2.2 Speech Activity Detection

9.3 PBX Synchronisation Across an ATM Network

9.3.1 Synchronous Residual Time Stamp (SRTS)

9.3.2 Adaptive Clock Recovery (ACR)

9.3.3 Independent Timing

10 Voice Over Frame Relay

10.1 Introduction to Frame Relay

10.2 Voice Over Frame Relay (VoFR)

10.2.1 Delay on Frame Relay Networks

10.2.2 VoFR Standards

10.3 Benefits and Issues of VoFR

10.3.1 Benefits

10.3.2 Issues

11 Voice Over IP

11.1 What is IP

11.1.1 How Voice Over IP Works

11.1.2 Benefits and Issues of Voice Over IP

11.1.3 Standards

12 Voice Switching in the Enterprise Network

12.1 The Evolution of Voice Networks

12.2 What is Voice Switching

12.3 Why Perform Voice Switching

Appendix A - Company and Product Overview

Nortel's History

Nortel

Power Networks

Wide Area Networking

Passport

Passport Voice Networking

Vector

Concorde

Management Systems

Internet and Intranet

Digital Switching

Meridian 1

Meridian SL-100

Multi-Media Carrier Switch (MMCS)

Mercator

Norstar

Multi-media Communications

Mobility

APPENDIX B - Introduction to Decibels

APPENDIX C - Glossary of Terms

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APPENDIX D - References

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Acknowledgments:

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