We’ve set up stands at fixed distances and are working out a few basic parameters, moving the motes a distance of 1 or 2 m at different power levels. The radios are positioned battery down with radios facing, on top of the 2.5″ PVC pipe stands. Channel 25.
Power level:
Power 1 m 2m 0.5m
Level mean std dev mean std dev mean std dev
15 46 1.8 52 1.8
10 45 2.5 46 2.5
20 55 4.0 52 3.0 54 7.0
25
We are now using a WI-SPY to monitor the signals operating around our lab in order to minimize interference with our experiment. Our motes are operating on channel 25, which has a frequency of 2485 MHz. Since the WI-SPY is showing a lot of noise on channel 25 and minor noise on channel 1, we are going to change our motes to operate on channel 1 which has a frequency of 2405 MHz.
Once again, the radios are positioned battery down with radios facing, on top of the 2.5" PVC pipe stands. This time, new batteries are being employed.
For our next experiment we are going to vary the orientation of the motes atop the PVC pipe at a constant distance of 1.5m and power level 20
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[...] Face to Face at 0.5, 1.0 and 2m, power 10, 15 and 20. Conclusion – Things are going to be complicated.Rotating motes at 1.5m, power 20. Conclusion – Orientation matters.Pairwise compatibility (redo) (best)- facing, 2m, power 20. Comparison of signal strength of seven different motes. Conclusion – the motes are effectively interchangeable. The best test used 14 motes, 24″ apart and measured a between standard deviation of 3.7 and within of 0.64 RSSI value.Mote orientation – horizontal motes, 2m apart, 30-degree increments, power 10 and 20. Conclusions – Large variation (30-60, 25-50 RSSI) in signal strength as a function of orientation.Mote Power level – vertical orientation, 2 rotations, 2 heights, 0.5, 1.0 and 2.0m apart, power levels 1-31. Conclusion – the power level can be tweaked to separate various regions of the RSSI, such as providing greater separation between distances or orientations.Obstacle Interferance (inside puck) – one horizontal, one vertical, distance .55m. various obstacles: person, wire, roomba (like a laptop). Conclusion — these obstacles didn’t have much impact on the signal strength (< 1 or 2), except for the roomba, when put close to the mote. In the inside versus outside puck conditions, we find that the plastic of the puck makes a small, but insignificant difference in the signal.Second orientation test – one mote horizontal, the other vertical, .55m separation, vertical mote rotated in 30 degree increments about 360 degrees. Conclusion – in this configuration, the broadcast pattern is fairly reliable and smooth across a variety of power levels. Angle of approach test – A worn mote versus the Purell. The mote is worn in front at distances of .2 and .5 m and behind at a distance of .2. Conclusion: When behind at extreme angles, it was difficult to separate the signals.Full angle-height test (repeat with vertical transmitter) – Puck and badge orientation. The first test with full statistics at 2 heights, 4 distances and 10 angles between 0 and 180. The results indicate that it will be very difficult, if not impossible, to determine mote distance from the puck or vertical mote with a single RSSI reading at power level 3. Perhaps .25m at the high level can be distinguished from others, but that is it. [...]
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