> From: Matthew Kaufman [mailto:matt...@matthew.at] > Sent: Tuesday, February 08, 2011 12:23 PM > To: theory and practice of decentralized computer networks > Cc: Llew Roberts > Subject: Re: [p2p-hackers] What we should build for the Egyptian (and other) > protesters > > On 2/8/2011 12:15 PM, Llew Roberts wrote: > > > > As a side note, I've learned one interesting thing that may seem > > obvious when you take a moment to think about it: one of the main > > factors that limits data transfer rate over long distances using HF > > frequencies is propagation delay. > > It doesn't seem obvious to me, largely because it isn't true.
You're right. I left out that atmospheric conditions have a random, unpredictable and variable effect on propagation delay. One of my sources ["Practical Packet Radio" by Stan Horzepa] mentioned that these propagation delays needed to be taken into account when configuring your system(s) and could cause unpredictable data loss. I mistakenly (?) identified this as a potential limit on transfer rate for these systems. > There's lots of OFDM (and other) modes that can go much faster than > this, they're just not in common use by folks who have legal limits on > occupied bandwidth. That's true, but I specifically mentioned the modes in use on HF where there isn't much experimentation with those modes. There doesn't even seem to be much perceived need for experimentation on HF. Most experimentation with the new modes is happening on UHF, where there are the fewest restrictions. Llew _______________________________________________ p2p-hackers mailing list p2p-hackers@lists.zooko.com http://lists.zooko.com/mailman/listinfo/p2p-hackers
