Here’s the first test from our homemade spider antenna, which is supposed to be relatively angle independent. It looks like this (scale in cm):
The signal is on the central dipole. The four other blue protuberances are grounded.
We placed the motes at the two different vertical heights (.1m and .35m) at 4 distance from the vertical axis: .25, .50, .75 and 1.0. We used a power level of 3 on channel 26. A boxplot of results is here:
Ideally, the data would show 4 steps, one for each distance. In particular, we’d like to see a clear difference between .75 and 1.0m. That would mean that the angle and height of the mote was not very important compared to the distance. Unfortunately, this was not the case.
At the .25m distance, the extreme angles (near 0 and 180), the RSSI was very low, lower than some responses at the 1.0m distance, not a good sign.
Part of the problem may be that we used a power level of 3. At 1 m, the data seems much more sporadic (particularly before cleaning out the RSSI values collected with poor LQI values). However, there is little evidence that this configuration is worth pursuing.
For completion, I’ll through in the complete ANOVA table. Not surprisingly, with 38,000 data points, everything is significant.
General Linear Model: CleanRSSI versus Distance, Height, Angle
Factor Type Levels Values
Distance fixed 4 0.25, 0.50, 0.75, 1.00
Height fixed 2 0.10, 0.35
Angle fixed 19 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120,
130, 140, 150, 160, 170, 180
Analysis of Variance for CleanRSSI, using Adjusted SS for Tests
Source DF Seq SS Adj SS Adj MS F P
Distance 3 565573 528580 176193 138899.32 0.000
Height 1 0 348 348 274.27 0.000
Angle 18 142783 152032 8446 6658.44 0.000
Distance*Height 3 4669 4109 1370 1079.83 0.000
Distance*Angle 54 291034 294622 5456 4301.13 0.000
Height*Angle 18 73695 75701 4206 3315.43 0.000
Distance*Height*Angle 54 348568 348568 6455 5088.67 0.000
Error 38105 48336 48336 1
Total 38256 1474658
S = 1.12628 R-Sq = 96.72% R-Sq(adj) = 96.71%
[...] Antenna, HorizontalFull angle-height test – Fully crossed 2 heights, 4 distances, 10 angles. Power level 3. Conclusion: [...]
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