Wifi Survey Not My

User-Perceived Quality Assessment
CERN-OPEN-2004-007

for VoIP Applications
24/01/2004

Technical Report

Razvan Beuran

Mihai Ivanovici

January 2004

The authors are currently Project Associates with CERN, 1211 Genève 23, Switzerland. They can be reached using their corresponding e-mail addresses: {Razvan.Beuran, Mihail.Ivanovici}@cern.ch.

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Table of ContentsAbstract.......................................................................................................................5 1 Introduction....................................................................................................................7 1.1 State of the art........................................................................................................8 1.2Report structure......................................................................................................9 2 Principles of VoIP........................................................................................................11 2.1 Basic facts............................................................................................................11 2.2 UPQ assessmentfor VoIP...................................................................................13 2.2.1 Mean Opinion Score (MOS).......................................................................13 2.2.2 Perceptual Speech Quality Measure (PSQM)............................................13 2.2.3 TheE-model.................................................................................................14 2.2.4 Perceptual Analysis/Measurement System (PAMS)..................................15 2.2.5 Perceptual Evaluation of Speech Quality (PESQ).....................................15 2.3 Delay issues..........................................................................................................16 2.3.1 Special jitterissues.......................................................................................17 2.3.2 Dejittering buffer.........................................................................................18 2.4 Packet loss issues.................................................................................................19 3 ExperimentalApparatus..............................................................................................21 3.1 Test setup..............................................................................................................21 3.2 NIST Net network emulator................................................................................22 3.2.1 Features........................................................................................................22 3.2.2Evaluation.....................................................................................................22 3.3 Speak Freely.........................................................................................................25 3.3.1 Features........................................................................................................26 3.3.2Evaluation.....................................................................................................27 3.4 Preliminary tests...................................................................................................29 3.4.1 Playback delay calibration...........................................................................29 3.4.2 Playback delay and jitterrelationship.........................................................32 3.4.3 Dejittering loss.............................................................................................34 3.4.4 Codec evaluation..........................................................................................34 3.5 Test configuration................................................................................................35 3.6 Result...