jhaynesatalumni writes: > I'm willing to believe that the timing tolerances in -tor modes > are so tight that ordinary PC operating systems cannot cope with > them the way a dedicated processor can. What I don't understand > is why the tolerances need to be so tight. The transmitter sends > a packet and then listens for an ACK or NAK. Why can't it wait > arbitrarily long?
The ACK time could be made as long as you like, but the throughput would suffer accordingly. For example, with Pactor I, (according to p. 9-24 of the 2005 ARRL Handbook), the sender sends the packet in 0.96 seconds, then propagation delays and receipt of the ACK takes 0.29 seconds, for a total of 1.25 seconds per packet. If we increase the ACK delay to be the same as the transmit time, the total time per packet would be 1.92 seconds for the same amount of data as Pactor I sends in 1.25 second, and the throughput would be 1.25/1.96 or approximately 0.65 times what the present protocol delivers. Is it doable? Yes. Would most hams want it? I have my doubts. To get the same throughput with a longer ACK time, you have to make the transmit time longer too, so it bears the same relationship to the total time as it does now. That means either a much longer data packet, or a pipelined group of packets covered by a single ACK. The longer the packet, the greater chance that a static crash or other event will corrupt the packet, so we're back to talking about pipelined packets. -- 73 DE AE6VW Chris Jewell Gualala CA USA 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/
