Hi all.
Sorry about the delay in replying. I shall reply in more detail very soon. The basis of the system relies on trellis encoding, with multiple carriers, and a form of forward error correction and interleaving code that spreads errors both across the carriers and in the time domain, so you can either have a pulse that blanks out all carriers for a short time, or you can lose some of your carriers all the time, and no degradation will result. Only severe interference or Gaussian noise will blank out the transmission enough to degrade the resolved DataStream. The potential use that I can see is video, but it may well be of interest to the packet community. I will get the protocol written up that I have been using in my tests shortly. It was really just a few evenings I had spare, and it needs someone with better programming skills than me to take it on further. But I think a semi-lossless video system using this technique would be extremely interesting. The other interesting thing about this system is that when errors are detected and cannot be corrected, some data bits are more resistant to going through the noise than others. So with a semi-lossless system, you could detect a poor signal and produce a lower resolution/lower number of bit depth image. That would be interesting. The most significant bits will produce a bitrate of around 5.5kbits/sec in around 6dB C:N (or that's the theory!), which would be enough for GSM compression anyway. Taking this on then, with an audio signal, you could have GSM quality at poor C:N ratios, then as the C:N goes up, you start to get more audio bandwidth and less compression artefacts until at 30dB C:N you end up with near CD-quality audio. All food for thought, but I'll publish the spec first. Sam ----- Original Message ----- From: "Jon Maguire" <[EMAIL PROTECTED]> To: <digitalradio@yahoogroups.com> Sent: Saturday, June 10, 2006 1:05 AM Subject: [digitalradio] Re: Digital Video on 12.5khz channel http://groups.yahoo.com/group/digitalradio/message/15125 Paul, I believe you are correct. According to http://www.arrl.org/FandES/field/regulations/news/part97/Part97.pdf 97.305 Note 5, the authorized bandwidth at 144.1-148.0 is 20Khz 73... Jon W1MNK ------------------------ Yahoo! Groups Need a Digital mode QSO? Connect to Telnet://cluster.dynalias.org Other areas of interest: The MixW Reflector : http://groups.yahoo.com/group/themixwgroup/ DigiPol: http://groups.yahoo.com/group/Digipol (band plan policy discussion) Yahoo! Groups Links ------------------------ Yahoo! Groups Sponsor --------------------~--> You can search right from your browser? It's easy and it's free. See how. http://us.click.yahoo.com/_7bhrC/NGxNAA/yQLSAA/ELTolB/TM --------------------------------------------------------------------~-> Need a Digital mode QSO? Connect to Telnet://cluster.dynalias.org Other areas of interest: The MixW Reflector : http://groups.yahoo.com/group/themixwgroup/ DigiPol: http://groups.yahoo.com/group/Digipol (band plan policy discussion) Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/digitalradio/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
