VCE

The Voice Channel Emulator (VCE) is a computer based emulation of an air/ground voice channel which has the ability to manipulate many of the channel parameters that characterize real-life conditions. The VCE can support up to a maximum of sixteen positions, i.e. one air traffic controller and fifteen pseudo-pilots. The VCE was utilized by the Human Factors Laboratory to make recordings for voice quality and performance acceptability.

The VCE was also used to support the testing of various candidate vocoders in a multi-user air-traffic environment that can introduce controlled channel impairments such as background noise, bit and symbol errors, system delays, and RF fading. This testing not only allowed evaluation of the vocoders, but also served to validate NEXCOM requirements related to voice communication characteristics.

The key to keeping the architecture as flexible as possible was the allocation of most functionality to software rather than hardware using a number of custom digital signal processing (DSP) modules. The Microsoft Windows compatible graphical user interface was implemented in Visual Basic 4.0. The control and digital signal processing software were implemented in a combination of assembly language and C. Use of application specific hardware which might impair upgrades or enhancements was avoided. The control and user interface software runs on a Pentium class notebook computer. Notebook size was selected to enhance portability for anticipated field evaluation.

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