I am assuming that you are asking about TOSSIM? Gain is the
attenuation between the communication of two motes. Since TOSSIM
assumes that packets are sent at 0 dBm, it is also an approximation
to the signal power of successfully received packets.
To answer the specific questions:
> - what implies increasing the gain value ?
Increasing the gain value implies that the connection is becoming
stronger.
> - what implies decreasing the gain value ?
Decreasing the gain values means the connection is becoming weaker.
> - what implies the gain value ?
The gain value can be estimated by the RSSI of received packets.
> - can I have a positive gain value and what is the difference between a
> negative and a pisitive gain value?
A positive gain value will imply that the signal is stronger at
reception than when it is transmitted, which does not correspond to
what happens in reality.
> -if a -4 as gain value sensors communicate correctly or not?
There is no specific gain value at which motes can or cannot
communication. Instead, packet reception is calculated from the SNR
curve, as explained in
HyungJune Lee, Alberto Cerpa, and Philip Levis
"Improving Wireless Simulation Through Noise Modeling." In Proceedings of
the Sixth International Conference on Information Processing in Wireless
Sensor Networks (IPSN), 2007.
SNR = power - noise, so depending on noise value packet reception may
or may not be successful.
> - if a want to improve the channel (2 mote can better communicate) I
> need to increase or decrease the gain value?
Increasing the gain value implies a better link.
> - which impact have the gain under the noise trace readings?
Noise and gain are not directly related but both are used through the
equation above to determine SNR, which can be used to determine PRR.
> - why do I choose -20 for the gain value instead of -8?
At -8 dBm there will be a higher probability of packet reception than
with -20 dBm.
Thanks,
Tal
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