Hi, > How is your work on LDPC going?
I've been plugging away for a few months on this, and am getting my head around the problem. I have a candidate waveform (i.e. modulation and coding combination) that has a 10dB improvement over the current FreeDV waveform. To develop this waveform I made a lot of assumptions in a simplified HF channel/modem simulation (for example perfect phase and fading magnitude estimation). So I now I'm working on replacing these assumptions with real world algorithms. The new waveform breaks a lot of "rules": + coherent rather than differential demodulation + 400ms (ish) of latency + partial protection of the vocoder payload + a relatively short LDPC codeword + no pilot tone So I need to get many ducks in a row before we see if these performance gains are real, or useful in the real world. I have got a good feel for the HF channel. A good approximation at our target SNRs is the bit error rate equals 0.1, almost independent of power. This explains why reliable HF data is so hard - you need tons of power to overcome those deep fades. Instead, I am using the natural tolerance of voice to errors (human FEC) and a powerful code. Cheers, David ------------------------------------------------------------------------------ Flow-based real-time traffic analytics software. Cisco certified tool. Monitor traffic, SLAs, QoS, Medianet, WAAS etc. with NetFlow Analyzer Customize your own dashboards, set traffic alerts and generate reports. Network behavioral analysis & security monitoring. All-in-one tool. http://pubads.g.doubleclick.net/gampad/clk?id=126839071&iu=/4140/ostg.clktrk _______________________________________________ Freetel-codec2 mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/freetel-codec2
