[aprssig] ALOHA Circle Calculation
Alex Carver kf4lvz at yahoo.comTue Aug 3 20:07:09 UTC 2010
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> From: "Bob Bruninga " > > ... [the ALOHA circle] is the circle that contians > > a FULL [APRS channel]. > > Ah, now the fun begins. You want to know how many > packets each of those stations puts on the network per 30 > minutes. So we assume 2 for a home station, 6 for WX, > 3 per digi and so on (this is from memory so I may not have > exact numbers here). > > Then we need to know how many copies each of those > generates. So we start at own-station and go > outward. Multiply each station's number by 1 until you > get to the first digi. From then on, multiply each > stations numbers by 2, and so on until the third digi, > multiply by 3 and so on. Once this total number > reaches 1800, (30 minutes of seconds), then the channel is > 100% saturated. > > That range defines the aloha circle. How did you ever come up with the 1800 number? Are you assuming a packet fits in a one-second window or are you using some other metric? I always had a problem calling APRS an ALOHA network because the real ALOHANet used two frequencies rather than one. Acknowledgments came back to the sender over a second channel which kept the first channel free for the next transmission.
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