SwissQual®Call QualityApplication Sheet13.0.1

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The firmware of the instrument makes use of several valuable open source software packages. For information, see the "Open SourceAcknowledgement" on the user documentation CD-ROM (included in delivery).Rohde & Schwarz would like to thank the open source community for their valuable contribution to embedded computing.

© SwissQual AGAllmendweg 8, 4528 Zuchwil, SwitzerlandPhone: +41 32 686 65 65Fax:+41 32 686 65 66E-mail: info@swissqual.comInternet: http://www.swissqual.com/Printed in Germany – Subject to change – Data without tolerance limits is not binding.R&S® is a registered trademark of Rohde & Schwarz GmbH & Co. KG.Trade names are trademarks of the owners.SwissQual has made every effort to ensure that eventual instructions contained in the document are adequate and free of errors andomissions. SwissQual will, if necessary, explain issues which may not be covered by the documents. SwissQual’s liability for any errorsin the documents is limited to the correction of errors and the aforementioned advisory services.Copyright 2000 - 2013 SwissQual AG. All rights reserved.No part of this publication may be copied, distributed, transmitted, transcribed, stored in a retrieval system, or translated into any humanor computer language without the prior written permission of SwissQual AG.Confidential materials.All information in this document is regarded as commercial valuable, protected and privileged intellectual property, and is providedunder the terms of existing Non-Disclosure Agreements or as commercial-in-confidence material.When you refer to a SwissQual technology or product, you must acknowledge the respective text or logo trademark somewhere in yourtext.SwissQual®, Seven.Five®, SQuad®, QualiPoc®, NetQual®, VQuad®, Diversity® as well as the following logos are registered trade-marks of SwissQual AG.Diversity ExplorerTM, Diversity RangerTM, Diversity UnattendedTM, NiNA+TM, NiNATM, NQAgentTM, NQCommTM, NQDITM, NQTMTM,NQViewTM, NQWebTM, QPControlTM, QPViewTM, QualiPoc FreeriderTM, QualiPoc iQTM, QualiPoc MobileTM, QualiPoc StaticTM, Quali-Watch-MTM, QualiWatch-STM, SystemInspectorTM, TestManagerTM, VMonTM, VQuad-HDTM are trademarks of SwissQual AG.

The following abbreviations are used throughout this manual: R&S®___ is abbreviated as R&S ___.

ContentsSwissQual®

3Application Sheet Call Quality ─ 13.0.1

Contents1 Call Quality.............................................................................................5

1.1 Defining Call Quality.....................................................................................................5

1.2 3 Viewing the Results...................................................................................................6

ContentsSwissQual®

4Application Sheet Call Quality ─ 13.0.1

Call QualitySwissQual®

5Application Sheet Call Quality ─ 13.0.1

1 Call QualityThe following sections describe Call Quality, which rates a complete call according tosubscriber experience.

The goal is to model how a subscriber would rate the call when the call is over. The mainquality determination is provided by the so-called "recency effect", that is, recent per-ceived quality degradations have a greater influence on the score, and a weighted aver-age procedure, in which a strong quality drop has a strong influence on the overall callquality.

To create the Call Quality prediction model, an auditory investigation was performed witha simulated conversation in a fixed temporal structure [Neusinger, Berger: ETSI-STQ04/2202]. This model can also be applied to test calls that consist of a series of testsamples that have been scored by P.862.1 or SQuad-LQ, so long as the defined temporalstructure has been met. The corresponding ETSI recommendation is [ETSI-STQ TR 102506].

The Call Quality model contains the following steps:

● Recency effect scores from the fist samples in the call are weighted less in the aver-aging process

● To model impacts on call quality by drops of quality during the call, non-linear aver-aging is applied, which weights single MOS drops stronger than when the commonquality in the call is high.

1.1 Defining Call Quality

The Call Quality model can be applied to each call that fulfils the required temporal struc-ture. To use the Call Quality model, you need to create and run a Speech measurementjob, for example, Job_CallQuality.ini, that matches the following requirements:

● "Job type": "Intrusive"● 10 x Speech and Speech-P.862 tests, that alternate between 5 x A->B and 5 x B->A● Sample length + Record hangover = 11.5 s

NQDI can calculate Call Quality during post-processing or during the database importprocedure, that is, the VoiceEngine does not calculate Call Quality. NQDI calculates theCall Quality of calls that meet the following requirements:

● "Job type": "Intrusive"● Only 5 Speech or Speech-P.862 tests in UL or DL per call● 5 x A->B or 5 x B->A tests (alternating)● Time from the beginning of the first sample in the call to the beginning of the last (fifth)

sample in this direction is within the 100 and 115 s range

The Call Quality is calculated separately for the A->B and B->A directions as well for P.862.1 and SQuad-LQ. As a result, four Call Quality values are calculated for Speech-P.862 and UL/DL tests and two values for SQuad-LQ Speech UL and DL tests. For Qual-

Defining Call Quality

Call QualitySwissQual®

6Application Sheet Call Quality ─ 13.0.1

iPoc or special applications that involve a DL or UL test, only one Call Quality value iscalculated for the test direction.

If you use a default SwissQual audio file, for example, AM_FM_IRS.wav, to evaluate theCall Quality, you need to specify a "Record HO" value of 5500 ms. If you use theAM_CallQual_IRS.wav audio file, which is a special Call Quality speech sample, youneed to specify a "Record HO" value of 1000 ms.

Due to the short hangover time, do not use the AM_CallQual_IRS.wav audio file forVideo Calls.

1.2 3 Viewing the Results

If a job NQDI meets the requirements for a Call Quality calculation, the Call Quality valuesappears on the "CallQuality" tab in NQDI.

Fig. 1-1: CallQuality tab in NQDI window

3 Viewing the Results