Open source speech codec designed for communications quality speech between 700 and 3200 bit/s. The main application is low bandwidth HF/VHF digital radio.
FreeDV development is performed using simulated channel that assume an "ideal" HF radio with flat frequency response and a linear PA. In practice radios and how they are connected to FreeDV varies widely. In this WP we will work out how to maximize the Tx and Rx performance of FreeDV signals using a selection of COTS radios.
We have some general guidelines that we have developed over the years (e.g. just tickle AGC). We are not sure if additional Tx or RX filtering helps of hinders FreeDV. Should AGC be on or off? What is the effect of over driving the Tx, is more better or worse? Can we damage radios with over driving FreeDV, or do they shut down gracefully? Do common radios have a flat Tx spectrum so power is allocated evenly over all carriers?
[ ] Write a test plan for evaluating freedv-gui with COTS radios, for example how will radio be tested and how we will measure performance? Maximum RMS power and min PER for a given noise of channel. Can we simulate a HF channel in the Rx, e.g. the effect of impulse noise of AGC? Consider separate Tx and Rx tests, e.g. optimise Tx for best RMS power/spectral flatness.
[ ] Select a range of radios to test (5?).
[ ] Build test bench (hardware/software) required to test a radio with freedv-gui, for example dummy loads, power sampler/ Can we simulate a HF channel in the Rx, for example using a SDR to generate a simulated HF signal for Rx testing.
[ ] Is this something we could collaborate on with other test labs, e.g. ARRL?
[ ] Acquire radios for test. Evaluate performance of selected radios.
[ ] Debug and improve performance if possible by adjusting radio. Log any issues that could be improved by FreeDV work.
[ ] Document how best to configure radio for maximum performance
[ ] Share results e.g. blog posts/conference presentation
FreeDV development is performed using simulated channel that assume an "ideal" HF radio with flat frequency response and a linear PA. In practice radios and how they are connected to FreeDV varies widely. In this WP we will work out how to maximize the Tx and Rx performance of FreeDV signals using a selection of COTS radios.
We have some general guidelines that we have developed over the years (e.g. just tickle AGC). We are not sure if additional Tx or RX filtering helps of hinders FreeDV. Should AGC be on or off? What is the effect of over driving the Tx, is more better or worse? Can we damage radios with over driving FreeDV, or do they shut down gracefully? Do common radios have a flat Tx spectrum so power is allocated evenly over all carriers?