Jim, Your analogy of the party line phone is quite correct. Packet suffers from not only time sharing, but also has a really bad modulation scheme for HF and should never have been used for this purpose.
While some of this technology can be used on VHF and above frequencies, it just does not seem appropriate for HF use due to the difficulty we have with throughput versus the need for bandwidth limitations due to the much narrower BW available and the long distance propagation which greatly increases the number of users of a given frequency. And not necessarily the users of that server either, but for other reasons, since no one owns an HF frequency. We are completely unlike a commercial or government channel. That is why BBS systems, ALE, or other Higher speeds require better conditions or wider bandwidths. I can see this useful for connecting to those limited resources, i.e., e-mail or BBS server, since there may be only one of those you can connect to at a given time from your QTH. Faster speeds means that operators can clear their traffic and let the next station connect. The other reason for higher speeds on HF would be for emergency use, but whatever design you have for emergencies, must be regularly exercised during normal times to insure it will be there when the emergency arrives. 73, Rick, KV9U jgorman01 wrote: >It is my understanding that all users CAN NOT share the frequency "at >the same time". Most high-speed connections are dedicated, I know >pactor is. I am not sure about ALE, but from a cursory view, I >believe it is also. Packet is the only protocol I know that is >designed to share a frequency, but it is also a lot slower because of >this. This is what I meant by a party line analogy. You have >sequential use, not concurrent use of a given frequency. > >This makes the analogy more like 10, 20, or 30 people sharing a PC or >phone. Using the example of 60 minutes versus 10 minutes, each person >has to wait 10 minutes multiplied by the number of people ahead of >them. Plus you need a way to assign people in the sequence. Are you >going to be willing to wait 10 minutes for your IM to be sent, even >iffile:///C:/Documents%20and%20Settings/Owner/Application%20Data/Microsoft/Internet%20Explorer/Quick%20Launch/Mozilla%20Firefox.lnk > <cid:part1.07040306.08070901@mwt.net> >it is sent quickly when you gain access? > >The original argument was that higher speeds allow faster sending >thereby clearing the frequency quicker. However, this only works if >people are willing to wait until their turn comes around. If they >need or just simply want immediate access, as IM implies, they will >use another frequency. This immediately reduces the spectrum >efficiency of the wider modes. In many cases and even perhaps most, >more narrow modes would work better to give instant access to more >people in the same bandwidth as a wider mode. In other words, they >can SHARE the same BANDWIDTH. > >My main point is that sharing spectrum is a complicated equation with >many variables. A simple argument doesn't always take into account >all the variables necessary to make an informed decision or it >contains several assumptions that may or may not be valid. One of >these assumptions implicit in the original argument is that people are >willing to wait until the frequency clears to use it. That wait time >may be seconds or even minutes (10 minutes in the example). It also >implies that there is a method of queuing requests for the frequency >or of collision avoidance. Neither of these assumptions were discussed >or proven. > >Jim >WA0LYK > > > 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/ <*> Your email settings: Individual Email | Traditional <*> To change settings online go to: http://groups.yahoo.com/group/digitalradio/join (Yahoo! ID required) <*> To change settings via email: mailto:[EMAIL PROTECTED] mailto:[EMAIL PROTECTED] <*> 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/
