I started the month by adding Word Error Rate (WER) curves to the draft RADE V2 paper, returning to the use of Automatic Speech Recognition (ASR) to evaluate the performance of RADE V2. Two hundred samples (25 minutes) from the Librispeech dataset were passed through SSB, RADE V1 and V2 at a range of SNRs, then post processed by the Whisper ASR system, and the Word Error Rate (WER) measured (Fig. 6 – lifted from a draft RADE V2 paper). The “MPP” curves simulate a fading HF channel.

These curves support the roughly 3 dB increase in performance of V2 over RADE V1 indicated by previous tests. Quite remarkably, they also suggest a 10 dB improvement of RADE V2 over SSB. This feels a bit too good to be true – it would be nice to devise a controlled experiment to test this over the air.

I completed writing up the Phase C stored file test results in the V2 test report, and drafted the Phase D (OTA PTT) test design.

Returning to the V2 C Port, I added an API, and build on Peter’s fine work to edit and extend the API documentation. We discovered automatic gain control (AGC) was missing from the original agentic AI port, so that was added and tested. I removed the RADE V1 C API from the reference Python repo, as we now have a native C port that has been verified. The wave demonstration utilities were tuned to remove unnecessary code and provide a clean, minimal examples for users of the API. In particular, I provided float to 16 bit integer scaling documentation, to ensure the signals would not be clipped on transmission, and would remain in the middle of the AGC range on receive.

Peter, Mooneer, and I worked on the RADE V2 verification procedure, performing test integrations of two applications with the RADE V2 C library. This experience allowed us to fine tune the verification procedure, and track down some issues in the applications and V2 C Port.

We noticed some RADE V2 signals on air (other projects using code from the partially finished work in our repository), and posted a status notice to indicate RADE V2 is a work in progress on not ready for on air use.

Quite some time was spent migrating the V2 C repo out of personal accounts, and into a project wide freedv account. Finally, I worked on a budget update. As our ARDC grant is drawing to a close, we need to keep careful track of the remaining funds.