[Tinyos-help] LQI Correlation Function

[Philip Levis]

On Apr 2, 2007, at 10:47 AM, Francis Simoneau wrote:

> I am looking for any papers on the Internet that
> describe the derivation of the MultiHopLQIM.nc
> correlation function.
>
>
>   uint16_t correlation(uint8_t v) {
>     uint16_t c = (80 - (v - 40));
>     c = (((c * c) >> 3) * c) >> 3;
>     return c;
>   }
>
>
> My interest is in how it works in a sparse
> network (ie tmotes 30 - 80 meters apart).
> What is the link quality where a hop is
> better than a straight connection of a poorer
> LQI valued link, for a CC2420 radio.

This is the Boomerang function, right? I think the TinyOS one uses a  
-50.

As far as I understand it, it's something Gil cooked up. Prabal Dutta  
has done some simple examination of its behavior. Basically, the  
steepness of the function causes you to greatly prefer perfect links,  
such that you have stable routes of short hops.

Phil