[Tinyos-help] Outdoor Range with Tmote sky

[Philip Levis]

On Feb 20, 2007, at 10:42 AM, Jacob Sorber wrote:

> You are asking for a simple answer where none exists.  Wireless  
> channels are tricky.  While line-of-sight is straightforward, "not  
> in line of sight" could mean a lot of things.  What is obstructing  
> the signal?  A building?  A person?  A hill of dirt and rock?  Is  
> it raining?  What is the humidity?  I have yet to find a radio that  
> is immune to obstructions.  If you find one, I would love to see  
> it.  My experience has been that the 2.5Ghz radios are usually more  
> robust to obstructions than the CC1000 radios on the Mica2/Mica2Dot  
> motes, but not always.  When one mote is a meter under water the  
> CC1000 seems to do much better than the CC2420, though neither work  
> very well in that situation.  Also a rain storm can reduce the  
> range some.  The best thing to do is to program two motes and take  
> them outside and see.  It will only take a few minutes.  If you  
> need a more technical explanation for why node A can't hear node B,  
> then you need to do some reading in the wireless comm literature.   
> This might be a good place to start ( www.eecs.berkeley.edu/~dtse/ 
> cu_day1.ppt).
>

My understanding is that the waves which are really resistant to  
obstructions are extremely low frequency (ELF) ones: think < 100Hz.  
That's what submarines use to communicate when submerged, for example 
[1].

Phil


[1] http://en.wikipedia.org/wiki/Communication_with_submarines