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[aprssig] Fundamental APRS capacity

Rick Green rtg at aapsc.com
Mon Oct 4 11:15:24 UTC 2004


On Mon, 4 Oct 2004, Robert Bruninga wrote:

> Here is the algorithm to exactly (in real time) determine what
> the ALOHA circle range is for any user:
>
> * 1200 baud can handle about 60 packets per minute or 1800/30mins
> * Sort all stations heard on RF by range
> * Starting with closest, add these number of packets per 30 mins
>   - Mobile in motion = 15 per 30 mins
>   - Other Mobile      =  7 per 30 mins
>   - WX station         = 6 per 30 mins
>   - DIGIs                =  3 per 30 mins
>   - Home stations  =   2 per 30 mins
> * Multiply each of these by the number of copies (C).
> * C begins as 1, but as you encounter each digi, add 1 to C
> * When the total gets to 1800, STOP
> * The range of that last station is the limit of the local
>   network.  That is the ALOHA circle and should be plotted
>   on the map.
>
> Users should be encouraged to NOT routinely send any packets
> beyond their ALOHA circle because doing so is JAMMING other
> users with un-invited QRM.
>
 Great explanation, and the algorithm seems reasonable, but you stopped at
the most critical point.  How do you use this information to come up with
a reasonable path.  Should it be 'RELAY, WIDEC-C'?

-- 
Rick Green

"They that can give up essential liberty to obtain a little
 temporary safety, deserve neither liberty nor safety."
                                  -Benjamin Franklin





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