1 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony Introduction to Packet Voice Technologies Cisco Networking Academy Program.

14 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP 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

19 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP 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.

39 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP 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

43 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 E&M Signaling Separate signaling leads for each direction E-lead (inbound direction) M-lead (outbound direction) Allows independent signaling

52 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP 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.

57 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP 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.

58 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP 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.

61 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP 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

72 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 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

1 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony Introduction to Packet Voice Technologies Cisco Networking Academy Program.

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1 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony Introduction to Packet Voice Technologies Cisco Networking Academy Program.

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Presentation on theme: "1 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony Introduction to Packet Voice Technologies Cisco Networking Academy Program."— Presentation transcript:

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