2-Wire and 4-Wire Voiceband Measurements

Welcome to the latest issue of GL Communications' Newsletter providing information and insight into our MAPS™ APS emulator for performing voiceband measurements of legacy 2-wire and 4-wire voice grade circuits.

GL’s test tools can be configured to simulate 2-wire calls with FXO and FXS ports and 4-wire calls with VF ports to provide various voiceband measurements. The voiceband measurement tests supported are - Voice Quality Test (VQT) using PESQ or POLQA algorithms, Signal-to-Noise Ratio and Level, Three Tone Slope (Gain Slope), C Notch Noise, 1004 Hz Net Loss, Attenuation Distortion, Intermodulation Distortion, and Impulse Noise.

Overview

As depicted in the below image of end-to-end voiceband measurement test scenario, the application is connected to the real network’s device under test. In this case MAPS™ APS acts as FXO to generate analog calls to a Teltone telephone line simulator through a MPLS network. After successful connection, different traffic options can be verified. It works in conjunction with GL’s Voice Band Analyzer (VBA) and Voice Quality Testing (VQT) applications to provide various voiceband measurements. In addition, Remote MAPS™ application facilitates remote control of multiple MAPS server nodes running at different locations using a single remote client instance.

These test reports can then be analyzed within MAPS™ APS or via NetSurveyorWebLite™ - an integrated and simplified web-based system that is distributed at the probe level.

The voiceband measurement tests using 2-wire/4-wire includes the following:

  • Voice Quality Test (VQT) - This test involves the transmission of reference voice file and recording of degraded file in both directions. The VQT software calculates a PESQ or POLQA score by comparing and analyzing the reference and degraded files.
  • Signal-to-Noise Ratio and Level - This test involves transmission of 1004 Hz reference tone and increasing the tone level at every iteration (example, by 5 dBm). The reception side measures each level and calculates a S/N ratio. This is done in both the directions in a single test.
  • Three Tone Slope (Gain Slope) - The specific term gain-slope refers to the measurement of received level at 404 Hz, 1004 Hz, and 2804 Hz and calculation of the difference between levels at 404 Hz and 1004 Hz for 404 Hz gain-slope and the difference between levels at 2804 Hz and 1004 Hz for 2804 Hz gain-slope.
  • C Notch Noise Test - This test measures power by applying C-Message and notch filters to get dBrnC0 value.
  • 1004Hz Net Loss - This test is used to test 1004 Hz net loss and periodically report the received tone level of a continuous 1004 Hz tone.
  • Attenuation Distortion Test - This is a measure of the change in net loss as the frequency of a signal on the line varies across the Voice Frequency (VF) bandwidth.
  • Intermodulation Distortion - This is a measure of distortion resulting from the line having output characteristic that is not a perfectly linear reproduction of the input signal. The test transmits a composite four-tone test signal and measures the second and third order intermodulation products relative to the level of the test signal.
  • Impulse Noise – This is a measure of any momentary occurrence of the noise on a line significantly exceeding the normal noise peaks. It is analyzed by counting the number of noise bursts that exceed a threshold during a specified period.

Main Features

  • Perform voiceband measurement tests for Central Office, PBX, Gateway, Analog/Digital/VoIP Networks
  • Manual and automated bulk analog call simulation
  • Call monitoring and call recording
  • Multiple users and tests per system
  • Up to 96 independent FXO ports per MAPS™ APS system
  • Fully automated and remotely accessible with Remote MAPS™ client
  • APIs for Python and Java

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