Article Figures & Data
Figures
- Figure 1.
Schematic of the experimental setup (plan view).
- Figure 2a.
“Clear condition,” AP visible (the white box with two aerials, on the horizontal arm next to the lamp; arrow).
- Figure 2b.
“Tree condition,” AP obscured by L. tulipifera (lower part of the light pole visible to the left of the tree trunk).
- Figure 3.
Effect of a single large broadleaf tree (Liriodendron tulipifera, tree shown in Figure 2); in-leaf (a), and defoliated (b), on signal and noise levels, at two AP-computer distances. Each boxplot summarizes ≈5 minutes of signal and noise data. Legend: light grey: signal - clear condition; dark grey: signal - tree condition; corresponding noise data in white boxes under each signal box. Extent of tree canopy shown by the thick line placed at about −88 dBm (black line: tree in leaf; grey line: tree defoliated). The minimum required signal strength (−75 dBm) shown by dotted line.
- Figure 4.
Effect of two large conifer trees in a park (Pinus pinea) on signal and noise levels in summer (a), and in winter (b). Legend as in Figure 3.
- Figure 5.
Effects of small street trees (Platanus x acerifolia) on signal and noise levels (3, 6, and 11 trees in signal path); in-leaf (a), and defoliated (b). Legend as in Figure 3.
- Figure 6.
Effects of medium-sized street trees (Liquidambar styraciflua), in-leaf (a), and defoliated (b), on signal & noise levels (1, 4, and 9 trees in signal path). Legend as in Figure 3.
- Figure 7.
The signal-attenuation increase with canopy depth. Dotted lines are 95% confidence bands for the fitted line. Note the high outliers at 5 m (16 ft) canopy depth: this is the large L. tulipifera, shown in Figure 2 and Figure 3.
Tables
- Table 1:
Tree characteristics and signal parameters (in dB) measured in a municipal Wi-Fi network in Mountain View, California.
Location Tree sp. Leaf size (mm × mm) # of trees in LOS Canopy depth (m) Dist. to AP (m) Δ Signalz, summer Clear - Tree in leaf Δ Signal, winter Clear - Tree defoliated Δ Noise, summer Clear - Tree in leaf Δ Noise, winter Clear - Tree defoliated Bernardo Street Platanus × acerifolia 100 × 100
to
160 × 18011 24.5 150 −0.3 3.5 0.2 0 6 14 90 −1 3.2 0.3 0.1 3 6.5 30 1.9 3.2 −0.1 0.7 Bernardo Street Prunus cerasifera 40 × 80 4 23 90 7.4 8.7 −0.3 −0.7 Cuesta Park Liriodendron tulipifera 120 × 120 1 3 30 13.1 11 0 −1 10 11.8 2.7 0.4 −1.7 Villa Street Pistacia chinensis 70 × 20
(240 × 170)4 41 54 -- -- -- -- 3 22 23 3.6 4.2 0.9 0.8 Glenborough Street Liquidambar styraciflua 100 × 120 9 52 100 7.6 3.9 0 −0.7 4 21 60 2.2 5.1 −0.4 −0.1 1 5 30 2.6 2.3 0.1 0.1 Cuesta Park Pinus radiata, Sequoia sempervirens 100 × 1.5,
18 × 40
(150 × 20)7 75 90 18.7 14 −0.1 1.1 3 35 45 5.1 5.6 −1.2 −0.3 1 10 20 2.1 2.2 −0.5 1.2 Cuesta Park Pinus pinea 140 × 1.5 2 25 60 4 9.4 0.3 −0.1 Average attenuation: (all trees: n = 7): 5.3y 5.6y −0.03x −0.04 (defoliated broadleaf: n = 5): 4.8y −0.20 - Table 2:
Results of general linear model (GLM) analysis describing the factors that influence the attenuation of Wi-Fi signal, noise, and signal-to-noise ratio (SNR).
Factors tested (coefficients for the factors retained in final model) Intercept Distance to AP (m) Tree count Tree size (S,M,L) Canopy depth (m) Broadleaf or conifer In-leaf or depth (m) Leaf area (cm2) Leaf dim ratio Metric Model r2 Fullz Finaly ΔSNR −7.836 – – − 4.77x 0.123w −4.89x – – – 0.62 0.58 ΔSignal −1.308 – – − 4.40x 0.124w −4.37x – – – 0.64 0.55 ΔNoise – – – – – – – – – 0.25 0.00
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