Doppler channel emulation of high-bandwidth signals

Abstract

The Airborne Networks Group at MIT Lincoln Laboratory has funded the construction of a channel emulator capable of applying, in real-time, environmental models to communications equipment in order to test the robustness of new wireless communications algorithms in development. Specific design goals for the new emulator included support for higher bandwidth capabilities than commercial channel emulators and the creation of a flexible framework for future implementation of more complex channel models. Following construction of the emulator's framework, a module capable of applying Doppler shifting to the input signal was created and tested using DVB-S2 satellite modems. Testing not only verified the functionality of the emulator but also showed that DVB-S2 modems are unequipped to handle the continuous spectral frequency shifts due to the Doppler effect. The emulator framework has considerable room for growth, both in terms of implementing new channel transformation models as well as the re-implementation of the emulator on custom hardware for emulation of channels with wider bandwidths, more complex noise sources, or platform-dependent spatial blockage effects.