open telephony software, hardware, critical thinking
It’s been a few years since FreeDV 2020 was released. On-air experience suggests FreeDV 2020 is less robust to low SNR and fading than the 700x modes, which means it can only be used on benign HF channels, with slow fading and a relatively high SNR. Factors include the high bit rate required for the codec [3], and the modem waveform design.
The goal of this project is to improve the robustness of 2020, and provide intelligible speech at the same operating point SNR as FreeDV 700E. In numerical terms, this can be expressed as the SNR where 700E achieves a coded bit error rate of 0.01, and a packet error rate (PER) of 0.1.
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