Akankshu,
It really depends on a lot of factors. An environment with lots of
obstacles(trees, cubicles, buildings, cars, etc) can cause severe
multipath effects which make estimation difficult. But as a start, you
can look at free space propagation loss models. These will give you a
*minimum* loss that any omnidirectional signal will experience as it
travels through free space (no obstacles near transmitter, receiver, or
anywhere inbetween). There are more complicated models that you can
look into but that would probably be my first start. The general
principle of Free Space Propagation is that each time the distance
doubles (goes from 1 meter to 2, 2 to 4, 4 to 8, etc) the signal
experiences a 3dB loss. This means that Received Signal Strength (RSS)
rapidly decrease as you first begin to move away from a transmitter,
then decrease more slowly as you get further and further away. The
signal strength loss between 1 meter and 2 meters is (approximately) the
same as the signal strength loss between 200 meters and 400 meters.
As for reliable reception, that depends on a lot of factors too (noise,
multipath signals arriving out of phase and at differing power levels,
etc). In a perfect world, as long as the RSS is above the radio
sensitivity, then you should be able to correctly detect and decode the
packet, but in reality, noise, interference and multipath effects lower
the effective sensitivity of the radio because it makes it harder to
decode the signal from the noisy environment.
Mathematical models can give you a basis to start your tests, but are
never going to be a replacement for actual experiments. Slight
differences in hardware between motes can also play a role in the
transmission range. Hope this helps.
-Paul
Akankshu Dhawan wrote:
Hi All
I know we can set the transmission power levels of different motes. I
want to know what is the correlation factor between the transmission
power level and distance that it can reliably propagate ?
I am using MICAZ motes and MTS310 sensorboard.
Thanks
Akankshu
--
First they ignore you, then they laugh at you, then they fight you,
then you win.
- Mahatma Gandhi
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