Research Article
An Optimization Method Combining RSSI and PDR Data to Estimate Distance between Smart Devices for COVID-19 Contact Tracing
Table 1
The results of the outdoor experiments.
| | Path index | Designed scenario | Designed path and distance symbol (#1 location-#2 location) | Real distance (m) | Estimation error of RSSI-onlymethod (m) | Estimation error of proposed method (m) |
| | 1 | Two people walk side by side in the same direction | #1 A⟶B⟶C⟶D⟶E
#2 F⟶G⟶H⟶I⟶J | d1 (A-F) | 1.01 | −0.08 | −0.16 | | d2 (B-G) | 0.51 | 0.02 | −0.27 | | d3 (C-H) | 1.01 | 0.06 | −0.18 | | d4 (D-I) | 0.51 | 0.02 | −0.09 | | d5 (E-J) | 0.51 | 0.06 | −0.11 |
| | 2 | Two people walk forward in the same direction, the one in front is fast, while the one behind is slow | #1 E⟶D⟶C
#2 I⟶H⟶F | d1 (E-I) | 2.10 | 0.05 | −0.05 | | d2 (D-H) | 2.28 | 0.38 | 0.09 | | d3 (C-F) | 4.21 | 1.13 | 0.23 |
| | 3 | Two people walk forward in the same direction, and the one behind exceeds the one in front | #1 B⟶C⟶D
#2 F⟶H⟶J | d1 (B-F) | 2.28 | 0.20 | 0.20 | | d2 (C-H) | 1.01 | 0.06 | −0.31 | | d3 (D-J) | 2.10 | 0.05 | 0.03 |
| | 4 | Two people face each other, pass by, continue walking in the opposite direction | #1 E⟶D⟶C⟶B⟶A
#2 F⟶G⟶H⟶I⟶J | d1 (E-F) | 8.22 | −0.11 | −0.98 | | d2 (D-G) | 4.11 | −0.84 | −0.91 | | d3 (C-H) | 1.01 | 1.47 | 0.97 | | d4 (B-I) | 4.11 | 3.45 | 2.19 | | d5 (A-J) | 8.18 | 1.82 | 2.23 |
| | 5 | Two people meet vertically at an intersection | #1 A⟶B⟶C⟶D
#2 K⟶L⟶M⟶I | d1 (A-K) | 8.65 | 0.05 | −0.22 | | d2 (B-L) | 5.77 | 0.37 | −0.34 | | d3 (C-M) | 2.88 | −0.03 | −0.43 | | d4 (D-I) | 0.51 | 0.02 | −0.12 |
| | 6 | Two people walk to an intersection, one goes on, and the other turns | #1 B⟶C⟶D⟶E
#2 G⟶H⟶M⟶L | d1 (B-G) | 0.51 | 0.64 | 0.76 | | d2 (C-H) | 1.01 | 0.86 | 0.84 | | d3 (D-M) | 2.04 | 2.00 | 0.98 | | d4 (E-L) | 4.56 | 1.58 | 0.90 |
| | 7 | Two people meet at an intersection, and then go forward in the same direction | #1 E⟶D⟶C⟶B
#2 L⟶M⟶H⟶G | d1 (E-L) | 4.56 | 0.42 | −0.06 | | d2 (D-M) | 2.04 | 0.11 | −0.22 | | d3 (C-H) | 1.01 | −0.01 | −0.32 | | d4 (B-G) | 0.51 | 0.02 | −0.12 |
| | 8 | Two people facing each other at an intersection, one turns after the other, and then walk forward in the same direction | #1 E⟶D⟶M⟶L
#2 B⟶C⟶I⟶M | d1 (E-B) | 6.12 | −1.48 | −1.79 | | d2 (D-C) | 2.04 | −0.03 | −0.40 | | d3 (M-I) | 1.53 | 1.74 | 1.00 | | d4 (L-M) | 2.04 | 0.44 | 0.50 |
| | 9 | One sits on a chair on the side of the road, and the other walks in front of him | #1 I⟶I⟶I⟶I
#2 B⟶C⟶D⟶E | d1 (I-B) | 4.11 | 0.53 | 0.01 | | d2 (I-C) | 2.10 | 0.05 | −0.06 | | d3 (I-D) | 0.51 | 0.06 | −0.18 | | d4 (I-E) | 2.10 | 0.21 | 0.08 |
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