[Tinyos-help] TOSSIM Gain and RSSI

[Philip Levis]

On Jul 1, 2007, at 1:21 AM, Tal Rusak wrote:

> Hi,
>      I have read the TOSSIM tutorial (11) at the following site:
> http://www.tinyos.net/tinyos-2.x/doc/html/tutorial/lesson11.html
>
>      This tutorial describes the "add" command, used to create network
> topologies, as follows:
> "add(src, dest, gain): Add a link from src  to dest with gain. When  
> src
> transmits, dest  will receive a packet attenuated by the gain value."
>
>      I am interested in a precise physical definition for the "gain"
> referred to in the above definition and the units of measure in  
> which it
> should be specified. I am also interested in how the "gain" is
> related to the RSSI (in dBm), as measured by the mote "dest", and  
> if there
> is a way to predict the RSSI from the gain.
>
>      Is it necessary to know the transmit power to know the RSSI,  
> and if
> so, then how is the transmit power determined and controlled?
>
>      I would appreciate any explanations, as well as citations in the
> literature that explain this relationship.
>
>      Many thanks for any assistance in advance.

Gain is the attenuation of the signal between the two nodes. It is in  
dB.

Currently, TOSSIM assumes that nodes transmit at 0dBm. The idea is  
that one could include simulation support for changing the TX power  
level. Currently there isn't such support.

Therefore, if you have an attenuation of -85dB and a constant noise  
floor of -90dBm, your SNR will be 5dB.

Phil