User's Manual Part 1

Nomad User’s Manual Chapter 7 – Monitoring a Test in Progress

L. Voice Quality Task Status Window

 Status for the current Voice Quality cycle is noted here as one of the following options:

o Waiting – This state indicates that the call has been placed midway through one of

the Sourcing/Recording cycles. Nomad will remain idle until the start of the next

full Sourcing/Recording cycle, at which point data capture will begin.

o Recording – In this state, Nomad is currently recording the .WAV file that the

mobile receives from the Audio Server to be using for downlink MOS scoring.

o Sourcing – In this state, Nomad is sourcing the reference audio file to the mobile to

be transmitted to the Audio Server and used for uplink MOS scoring. Note that the

waveform and audio playing during this state represent the downlink audio recorded

in the previous 10 second window. In parallel with the audio playback, Nomad sources

a ‘perfect’ audio clip for uplink transmission that is inaudible to the user.

 The waveform playback seen here represents the audio recorded by Nomad in the previous

10 second time window. This playback occurs in parallel with audio clip sourcing. Audio

sourcing is not audible to the user, but is noted as Sourcing in this window.

 MOS represents the score of the current speech waveform being displayed. A MOS value of

3.500 or higher generally indicates good voice quality. The color of the MOS area

represents the MOS Thresholds configured on the Settings → Voice Quality tab. Below

the MOS score is a label of either ‘HD’ or ‘NB’ that is based on the spectral energy measured

within the downlink wav file. If the ratio of spectral energy above 4k in the wav file is

greater than or equal to .09, this is labeled as ‘HD’, otherwise it is labeled as ‘NB’.

 Ins Gain (PESQ) or Attenuation (POLQA)

o Insertion Gain provides the amplitude of the current waveform when the PESQ

scoring algorithm is in use. Ins Gain measures the gain that Nomad has applied to

the downlink voice signal. For the best results, Spirent Communications

recommends maintaining downlink insertion gain between -7 and 0 dB, ideally as

close to 0 dB as possible. Increase Input Level to increase Ins Gain toward 0 dB.

o Attenuation provides the amplitude of the current waveform when the POLQA

scoring algorithm is in use. Attenuation measures the downlink signal gain

reduced by Nomad. For the best results, Spirent Communications recommends

maintaining downlink attenuation between 0 and 7 dB, ideally as close to 0 dB as

possible. Increase Input Level to decrease Attenuation toward 0 dB. Note that

compared to PESQ, POLQA is more forgiving when it comes to attenuation

adjustment.

 Avg MOS indicates the average of all MOS values collected during the current test session.

 Std Dev indicates the spread of the MOS values about the average.

 Algorithm displays the scoring algorithm as PESQ or POLQA. See Appendix E for an

introduction to POLQA including a comparison between PESQ and POLQA.

 Select Monitor Audio to listen to waveform playback for the current test channel. Audio

may be monitored for one test channel at a time.