Introduction to Packet Voice Technologies
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Transcript of Introduction to Packet Voice Technologies
![Page 1: Introduction to Packet Voice Technologies](https://reader033.fdocuments.us/reader033/viewer/2022061605/56813356550346895d9a6872/html5/thumbnails/1.jpg)
1© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony
Introduction to Packet Voice Technologies
Cisco Networking Academy Program
![Page 2: Introduction to Packet Voice Technologies](https://reader033.fdocuments.us/reader033/viewer/2022061605/56813356550346895d9a6872/html5/thumbnails/2.jpg)
2© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Traditional Telephony
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3© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Basic Components of a Telephony Network
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4© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Central Office Switches
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5© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
What Is a PBX?
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6© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Basic Call Setup
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7© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Supervisory Signaling
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8© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Address Signaling
Tone telephone
DTMF dialing• Rotary telephone
– Pulse dialing
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9© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Informational Signaling
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10© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Digital vs. Analog Connections
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11© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Time-Division Multiplexing
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12© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Frequency-Division Multiplexing
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13© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Packetized Telephony Networks
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14© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Packet Telephony vs. Circuit-Switched Telephony
• More efficient use of bandwidth and equipment
• Lower transmission costs
• Consolidated network expenses
• Increased revenue from new services
• Service innovation
• Access to new communications devices
• Flexible new pricing structures
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15© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Call Control
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16© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Distributed Call Control
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17© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Centralized Call Control
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18© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Packet Telephony Components
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19© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Real-Time vs. Best-Effort Traffic
• Real-time traffic needs guaranteed delay and timing.
• IP networks are best-effort with no guarantees of delivery, delay, or timing.
• Solution is quality of service end-to-end.
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20© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Foreign Exchange Station Interface
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21© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Foreign Exchange Office Interface
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22© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
E&M Interface
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23© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
T1 Interface
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24© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
E1 Interface
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25© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
BRI
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26© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Physical Connectivity Options
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27© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Cisco IP Phone
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28© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Analog Voice Basics
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29© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Local Loops
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30© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Types of Local-Loop Signaling
• Supervisory signaling
• Address signaling
• Informational Signaling
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31© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
On Hook
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32© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Off Hook
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33© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Ringing
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34© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Ringing (Cont.)
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35© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Pulse Dialing
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36© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Dual Tone Multifrequency
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37© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Informational Signaling with Call-Progress Indicators
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38© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Trunks
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39© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Foreign Exchange Trunks
• Foreign Exchange Office
Connects directly to office equipment
Used to extend connections to another location
• Foreign Exchange Station
Connects directly to station equipment
Used to provision local service
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40© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Types of Trunk Signaling
• Loop start
• Ground start
• E&M Wink Start
• E&M immediate start
• E&M delay start
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41© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Loop-Start Signaling
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42© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Ground-Start Signaling
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43© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
E&M Signaling
• Separate signaling leads for each direction
• E-lead (inbound direction)
• M-lead (outbound direction)
• Allows independent signaling
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44© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
E&M Type I
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45© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
E&M Type V
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46© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
E&M Type II
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47© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
E&M Type III
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48© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
E&M Type IV
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49© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Trunk Supervisory Signaling—Wink Start
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50© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Trunk Supervisory Signaling—Immediate Start
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51© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Trunk Supervisory Signaling—Delay Start
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52© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
2-Wire to 4-Wire Conversion and Echo
• Echo is due to a reflection.
• Impedance mismatch at the 2-wire to 4-wire hybrid is the most common reason for echo.
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53© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Echo Is Always Present
• Echo as a problem is a function of the echo delay and the loudness of the echo.
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54© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Echo Suppression
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55© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Echo Cancellation
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56© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Analog-to-Digital Voice Encoding
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57© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Digitizing Analog Signals
1. Sample the analog signal regularly.
2. Quantize the sample.
3. Encode the value into a binary expression.
4. Compress the samples to reduce bandwidth, optional step.
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58© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Basic Voice Encoding: Converting Digital to Analog
1. Decompress the samples, if compressed.
2. Decode the samples into voltage amplitudes, rebuilding the PAM signal.
3. Filter the signal to remove any noise.
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59© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Nyquist Theorem
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60© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Voice Compression Techniques
• Waveform algorithms
PCM
ADPCM
• Source algorithms
LDCELP
CS-ACELP
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61© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Example: Waveform Compression
• PCM
Waveform coding scheme
• ADPCM
Waveform coding scheme
Adaptive: automatic companding
Differential: encode changes between samples only
• ITU standards:
G.711 rate: 64 kbps = (2 * 4 kHz) * 8 bits/sample
G.726 rate: 32 kbps = (2 * 4 kHz) * 4 bits/sample
G.726 rate: 24 kbps = (2 * 4 kHz) * 3 bits/sample
G.726 rate: 16 kbps = (2 * 4 kHz) * 2 bits/sample
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62© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Compression Bandwidth Requirements
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64© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Perceptual Speech Quality Measurement
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65© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Signaling Systems
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66© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
T1 Digital Signal Format
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67© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Robbed-Bit Signaling
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68© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Channel Associated Signaling—T1
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69© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
E1 Framing and Signaling
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70© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Channel Associated Signaling—E1
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71© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Common Channel Signaling
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72© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
ISDN
• ISDN
Part of network architecture
Definition for access to the network
Allows access to multiple services through a single access
Used for data, voice, or video
• Standards-based
ITU recommendations
Proprietary implementations
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73© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
ISDN Network Architecture
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74© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0
Layer 3 (Q.930/931) Messages
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75© 2005 Cisco Systems, Inc. All rights reserved. Cisco PublicIP Telephony v1.0