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Newsletter: GL Announces Echo, Delay, and Voice Quality Analysis of Voice Calls in VoIP, TDM, 2Wire, and Mobile Networks

Welcome to another February 2011 issue of GL Communications’ Newsletter providing information and insight into our new Echo Measurement Utility Software (EMU) that measures Echo Path Delay (EPD) and Echo Return Loss (ERL) of voice calls. Echo can be as simple as sidetone, or more complex such as line, and acoustic echo. The EMU when combined with GL’s VQuad™, Dual UTA, T1 E1 Analyzers, or Voiceband Analyzer, additional voice quality metrics such as round trip delay (RTD), voice quality, and noise can also be measured.


A voice call may transit a variety of networks – Mobile, VoIP, TDM, and others.

A typical call can have many of the following characteristics that can affect quality:

  • narrowband (8 kbps) or wideband call (> 64 kbps)
  • end-to-end digital but with D/D conversions (codec conversions)
  • many D/A and A/D conversions
  • additive noise and/or background noise,
  • speech level variations
  • variable delay,
  • echo in the form of sidetone, line echo, or acoustic echo,
  • signaling and voiceband conversions that affect DTMF, FAX, and MODEM transmissions
  • packet delay, loss, sequencing, and duplications

To provide a comprehensive assessment of voice quality irrespective of network type, GL has combined various tools together into one platform consisting of VQuad™, Dual UTA, USB T1 E1, and WEBViewer. This platform provides the ability to make VoIP, TDM, and Mobile calls from any fixed or mobile location. All interface flexibility is provided (2Wire, 4Wire, VoIP, TDM, and Mobile) within the Dual UTA and USB T1 E1 Analyzer. In addition, VQuad™ provides algorithms for signaling, voice transmission, and voice quality assessment. WEBViewer™ provides the central point where voice metrics are stored and displayed through a WEB interface.

Recently, GL introduced Echo Measurement Utility (EMU) software within this architecture to assess sidetone, line, and acoustic echo and corresponding delays. EMU is an offline adjunct analysis application (under control of VQuad™) that compares the source and received files to determine echoes and delay of echoes.

As shown above, the EMU provides delay and ERL measurements for all detected echoes, along with an ‘ERL vs Delay’ plot where each echo is depicted within the plot. One can zoom-in on a particular echo to gauge overall echo impairments. In addition, the application includes signal graphs for source signal, received signal, error signal, and adaptive filter coefficients.

GL’s EMU can seamlessly work with other GL intrusive capture tools such as RTP Toolbox™ and T1/E1 Analyzers.

Main Features:

  • Measures EPD in msec and ERL in dB
  • Compares source and received files to determine maximum of 4 echoes
  • Ability to automate the entire test process using VQuad™ scripting including sending the results to the central database for access via GL’s WebViewer™
  • Detailed offline analysis
  • Supports Line and Acoustic Echo Modes
  • Graphically displays source signal, received signal, error signal, and adaptive filter coefficients
  • Allows zoom-in on each graph, and exporting snapshot of these graphs to a file for later analysis
  • Calculates adaptive filter coefficients and echo characteristics for the error signal
  • Speaker option to play the audio files (intrusive and non-intrusive)
  • Option to zoom-in on any particular echo to investigate further

Echo Measurement Utility (EMU) with GL Tools

The EMU requires only two files to function – the sending file and simultaneously recorded received file. Any tool that achieves this can be used with the EMU.

GL provides various emulation and capture tools that can be used with the EMU:

  • For VoIP – VQuad™ or RTP Toolbox™
  • For Mobile Phones – VQuad™ with Dual UTA
  • For TDM – VQuad™ with USB T1 E1 unit, or tProbe™ T1 E1 unit alone, or USB T1 E1 unit alone, Universal T1 E1 Card alone
  • For 2Wire – VQuad™ with Dual UTA
  • For 4Wire – VQuad™ with Dual UTA

VQuad™ with Dual UTA

The EMU can be used effectively with VQuad™ software and different hardware to support nearly any network interface. The figure below depicts EMU working with VQuad™/ Dual UTA intrusive tool. VQuad™ software along with the Dual UTA hardware supports transmitting and receiving files across the following interfaces: RJ11 2-wire analog, 3.5 mm jack for mobile headset connection, Handset phones and balanced I/O for VoIP soft phones.

In addition, VQuad™ provides the capability to remotely control the EMU through scripting, thus, automating the entire testing process including sending results to the central database for access via GL’s WebViewer™.

RTP ToolBox™ or VQuad™ with VoIP option

GL’s RTP Toolbox™ or VQuad™ with VoIP option can be used with EMU to assess line or acoustic echo.

T1/E1 Analysis or VQuad™ with T1/E1 Option

GL’s T1/E1 Analysis application (requires hardware) is used with EMU to detect possible echoes through a T1/E1 channel. Through T1/E1 WCS scripting or VQuad™ with T1/E1 option, it is possible to automate the entire testing process including sending and receiving files. The intrusive files and the received files are fed as input to EMU for further analysis.

For comprehensive information on the each of the above testing scenario, you can visit Testing Scenarios section.  Back to Latest News Page
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