Voice Quality Metrics in VoIP

Name: Faraj Ramadan Kassem ID: 415Supervisor : Mrs. Eman Elsahly

Spring 2012-2013

Applications

Video conferencing.

Remote video surveillance.

VoIP cell phones.

1/15

Aims

Objectives Objectives

Over View of VoIP Technology Over View of VoIP Technology

VoIP Quality VoIP Quality

VoIP Codecs VoIP Codecs

LOGO

Outline 2/15

10%

30%

35%

0.5%

0.5%

85%

Time Table

Project proposal submission

April May June July

Collection and study information

Analysis

Simulation

Write Report

3/15

Comparing to VoIP systems by simulation.

AimAim

4/15

Objective

VoIP voice quality

Bandwidth requirements

VoIP Equipment

Phone Frequencies

Codecs

Setup simulation

5/15

VoIP (Voice over Internet Protocol).Sometimes referred to as Internet telephony.  Sending voice information as digital form in discrete packets.

VoIP Technology6/15

RTP (Real Time Protocol).RTCP (Real Time Control Protocol).ISDN (Integrated Services Digital Network )

ISDN (Integrated Services Network).IETF (Internet Engineering Task Force ).MGCP(Media Gateway Control Protocol).SIP(Session Initiation Protocol )

Description VoIP Protocol

ITU standard protocol for interactive conference. H.323

(IETF ) standard for PSTN gateway control. MGCP IETF standard protocol for interactive and no interactive

conference. SIP

IETF standard protocol for media streaming. RTPIETF standard that provides out-of-band control information

for an RTP flow .RTCP

Major VoIP Protocols : 7/15

VoIP Protocols and the OSI Model:VoIP Protocols OSI Layer

Softphone/Call Manager/Human Speech ApplicationCodecs Presentation

H.323/SIP/MGCP SessionRTP/UDP (Media) ; TCP/UDP (Signal) Transport

Internet Protocol (IP) Network FR, ATM, MLPPP, PPP and HDLC link Data

.… Physical

FR (Frame Relay). PPP (Point to Point Protocol). MLPPP(Multi Link PPP).HDLC (High-Level Data Link Control).

RTP (Real Time Protocol) .ATM (Asynchronous Transfer Mode).Codecs (Coding decoding).

8/15

Advantages of VoIP:Low cost.Use existing infrastructure.Call forwarding.Voice mail and fax applications.Call waiting.Caller ID.Send documents and/or pictures while you

talk at the same time.

9/15

Disadvantages of VoIP:

Sound quality and reliability .Lack of continuous service during a power outage.Emergency calls (911) (Problem of locating call).Vulnerable to same attacks as IP data networksViruses, Worms and spams .Packet loss.

10/15

VoIP Voice Quality Factors Packet Loss.

Loss of packets severely degrades the voice application. Network packets loss (as a result of congestion or rerouting in the IP network). Late arrival loss (dropped at receiver). Link failures or system errors.

End-to-end Delay. Transmission and queuing delay. VoIP Typically tolerates delay up to 150ms before the quality of the call degrades . Codec processing delay . Packetizing/depacketizing delay.

Jitter (delay variation). Caused by queuing delay within the IP network. Instantaneous buffer use causes delay variation in the same voice stream .

11/15

End-to-end perceived voice quality (MOS)

IP Network

Receiver

Encoder

Sender

PacketizerJitter

buffer DecoderDe-

packetizer

packet loss

network delay

jitter

coding distortion

codec delaydelay delay buffer-delay

buffer-loss

codec impairment

delay

Other impairments: echo, sidetone, background noise

MOS (Mean Opinion Score).

12/15

VoIP Codecs:

Codec is a process of digitizing the voice sample , or converting digitized signal into an analog signal.

Each VoIP equipment must implement Codec in order to implement VoIP.

13/15

Common VoIP Codecs:Comments Bandwidth/kbps Codec

Delivers precise speech transmission. Very low processor requirements. Needs at least 128 kbps for two-way.

64 G.711

Adapts to varying compressions and bandwidth is conserved with network congestion.

48/56/94 G.722

High compression with high quality audio. Can use with dial-up. Lot of processor power.

5.3/6.3 G.723

An improved version of G.723. 16/24/32/40 G.726

Excellent bandwidth utilization. Error tolerant. License required.

8 G.729

High compression ratio. Free and available in many hardware and software platforms. Same encoding is used in GSM cellphones (improved versions are often used nowadays).

13 GSM

14/15

Reference:Books:

Olivier Hersent , “Deploying VoIP Protocols and IMS Infrastructure”, Second Edition (© 2011 John Wiley & Sons Ltd).

Whitepaper: Preparing for the Promise of Voice-over Internet Protocol (VoIP) – Cox

Communications

World wide web: http://www.nwfusion.com/research/voip.html

15/15

Any questi ons?

Thanks!