Testing Echo Cancellers:
GL's Manual Test Suite for testing compliance of ECs with G.168 provides the ultimate flexibility for almost any type of
network environment and configuration including:
- Conventional Telephone Networks
- Networks With Satellite Connectivity
- Wireless Networks such as Cellular and PCS
- Wireless Networks such as Cellular and PCS
The system uses two of GL's PCI Ultra T1 or E1 Cards (or a Dual Ultra Card). One Card emulates the Far End circuit,
provides the stimulus to the Echo Canceller, and captures its response. The second Card emulates the Near End circuit,
i.e. models the echo path, and injects noise and voice signals. This PC based system also controls the Echo Canceller
modes (NLP on/off, freeze, disable, etc.) and provides a captured PCM stream for analysis.
Main Features:
- Far End emulation is performed with GL's GUI-based File Playback and File Record Software (part # XX020)
- Near End emulation of hybrids by using GL's GUI based Delay/Attenuate Software (part # XX062)
- Echo canceller control using standard terminal emulation software, e.g. Hyperterminal
- Millisecond-level visibility and Analysis using GL's GLCView software
- Additional analysis capability using Syntrillium's Adobe Audition Software or
Goldwave Software
- All T1/E1 framing formats, signaling modes, and receiver interface strategies supported.
- Complete set of G.168 echo path models for emulation of Near End echo paths.
- G.168 CSS Single- and Double-Talk files recorded at various power levels.
- Detailed procedures for conducting G.168 compliance tests and analyzing results.
- VF Input and Output available at telephone handset for subjective evaluation of echo canceller performance.
- GL's family of T1/E1 cards or Laptop units and its
T1/E1 Analyzer GUI Software and Windows Client Server Software are general-purpose products supporting a wide
range of T1/E1 testing requirements
Delay/Attenuate Software Supports Hybrid Simulation
This application allows you to apply delay, attenuation, and/or filtering to a received signal on any number of
timeslots. You may also mix in additional signals from a number of sources, including
- Speech and/or Noise signals from files
- Speech signals inserted via VF input
- Gaussian noise signals generated internally
Transmitted signaling bits may be Onhook/Offhook, user-specified, or passed through from received to transmitted
timeslots. To view the Delay/Attenuate Timeslots screen, please click
here, or details for the entire application are provided at
http://www.gl.com/GUI_echocancellertesting.html.
The Delay/Attenuate Timeslots application may receive and transmit on either one or two boards. While there are a
number of different operating configurations, the most common and useful are:
- Looping back a processed signal- Applying delay, attenuation, and filtering to a received signal and
retransmitting the processed signal on the same board on which it was received. Speech and/or noise may also be
mixed in. Click to view a diagram of this configuration.
Note that the layout of the Delay/Attenuate Timeslots Dialog closely matched this diagram
- Applying pure delay to a signal- A received signal is delayed before being retransmitted
- Inserting a Simulated Echo Loop- A two-board system is inserted into a T1 or E1 trunk and is used to
simulate an echo path having known characteristics. Click here
to view a diagram of this configuration.
The layout of the Delay/Attenuate Timeslots application has been designed to closely resemble the above block
diagrams. Click here to view an illustration of this
resemblence for one such configuration.
Total Visibility and Analysis with GLCView
GLCView is a GL Software tool developed especially for G.168 testing. Among this product's features:
- Displays files captured during G.168 testing.
- Linear and Power displays shown.
- Zoom in on power window down to millisecond-level time scale.
- User-settable power calculation window from 1 ms to 35 ms.
- Multiple files viewable in single window.
- Print out graphs.
Screen Shot of GLCView
Supported G.165 and G.168 Tests
| Tests |
G.165 |
G.168 |
| Test 1: Steady state residual and returned echo level test (G.168 version 04/2000 only) |
NLP On
NLP Off |
Yes
Yes |
Yes
Yes |
| Test 2: Convergence test |
Test 2A: NLP On
Test 2A Part b (G.168 version 01/2007): Re-convergence with NLP On
Test 2B: NLP Off
Test 2B Part b (G.168 version 01/2007): Re-convergence with NLP Off
Test 2C with NLP On: Convergence test in presence of background noise
Test 2C with NLP off: Convergence test in presence of background noise
Test 2C-c (G.168 version 01/2007) for noise level -55 dBmO: Convergence test with NLP Off and background noise |
No
No
Yes
No
No
No
No |
Yes
Yes
Yes
Yes
Yes
Yes
Yes |
| Test 3: Double talk test |
Test 3A: low cancelled-end level
Test 3B: high cancelled-end level
Test 3B Part b (G.168 version 01/2007): stability test with low cancelled-end levels
Test 3C: simulated conversation |
Yes
Yes
No
No |
Yes
Yes
Yes
Yes |
| Test 4: Leak rate test |
Yes |
Yes |
|
Test 5: Infinite return loss convergence test |
Yes |
Yes |
| Test 6: Non-Divergence on narrow-band signal test |
Optional |
Yes |
|
Test 7: Stability test |
Optional |
Yes |
| Test 8: Overload Test |
Yes |
No |
| Test 8: Non-convergence of EC on SS5/SS6/SS7 tones in-band signaling and continuity
check tones |
No |
Yes |
| Test 9: Comfort noise test |
Yes |
Yes |
| Test 10: Facsimile test |
Test 10A (with NLP On and NLP Off): Canceller operation on the calling station side
Test 10B (with NLP On and NLP Off): Canceller operation on the called station side |
No
No |
Yes
Yes |
| Test 14: Low speed modem test |
No |
Yes |
| Test 15: DC Off sets |
Test 15A:
Test 15B: |
No
No |
Yes
Yes |
Note: The G.165 and G.168 Tests differ in the time to perform the tests. For example, Test 1 steady state
residual test requires 180 seconds in G.168, but it does not specify the exact time in G.165. With small modifications of
the test procedures (mainly the times), we can use the G.168 test procedures to perform the G.165 tests. As per the
customer’s requirement the manual test procedures can be modified. Contact GL for further details
Buyer's Guide:
Please Note: The XX in the Item No. refers to the hardware platform, listed at the bottom of the Buyer's Guide,
which the software will be running on. Therefore, XX can either be HDT, HDE, HUT, HUE, UTA or UEA depending
upon the hardware.
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