voice quality metrics in voip
DESCRIPTION
TRANSCRIPT
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.
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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
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Comparing to VoIP systems by simulation.
AimAim
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Objective
VoIP voice quality
Bandwidth requirements
VoIP Equipment
Phone Frequencies
Codecs
Setup simulation
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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).
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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.
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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.
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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 .
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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).
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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.
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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
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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
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Any questi ons?
Thanks!