Multipath Triangulation Decimeterlevel Wi Fi Localization and Orientation

Multipath Triangulation: Decimeter-level Wi. Fi Localization and Orientation with a Single Unaided Receiver Elahe Soltanaghaei Avinash Kalyanaraman Kamin Whitehouse

Unaided Localization: 2

Unaided Localization: Unilaterally determine another node’s position and orientation by receiving one or more packets with no assistance from any other node …not even the transmitter 3

Unaided Localization: Can we achieve unaided decimeter-level accuracy with commodity Wi. Fi radios? 4

State of the Art: triangulation Spot. Fi [18] and Array. Track [47] Eliminate multipath to achieve decimeter accuracy Requires multiple receivers 5

State of the Art: Trilateration Emulated bandwidth Chronos [40] and Tone. Track [49] Eliminate multipath interference Requires coordination with transmitter to estimate To. F 6

Multipath Triangulation Use reflections to create multipath triangles Constrain triangle with Ao. A, Ao. D, and r. To. F b Angle of Departure Angle of Arrival c a Relative Time of Flight 7

Outline • 3 D Multipath Resolution • Multipath Geometry • Evaluation 8

3 D Multipath Resolution Given: measurement of mixed signals at the receiver Goal: estimate Ao. A, Ao. D, and Tof of multiple paths b a 9

3 D Multipath Resolution Subcarrier Frequency 1 Subcarrier Frequency 2. . . Subcarrier Frequency 30 Txr 1 2 3 A Rxr B C 1 . 7+3 i . 4+. 3 i . 6+. 4 i 2 2+. 1 i . 1+5 i . 2+2 i 3 1+. 4 i . 3+7 i . 9+1 i A B C 1 . 7+3 i . 4+. 3 i . 6+. 4 i 2 2+. 1 i . 1+5 i . 2+2 i 3 1+. 4 i . 3+7 i . 9+1 i 3 x 3 x 30=270 CSI values 10

3 D Multipath Resolution Angle of Departure (Ao. D): phase shift across transmitting antennas: Angle of Arrival (Ao. A): phase shift across receiving antennas: Time of Flight (To. F): phase shift across frequencies: 11

3 D Multipath Resolution subcarrier 1 subcarrier 2 TX antenna 1 Path 1 RX antenna 2 Path 2 RX antenna 3 . . .

3 D Multipath Resolution subcarrier 1 RX antenna 3 . . . subcarrier 1 subcarrier 2 RX antenna 2 Path 2 RX antenna 1 subcarrier 2 TX antenna 1 Path 1 Known

3 D Multipath Resolution subcarrier 1 subcarrier 2 subcarrier 1 RX antenna 1 RX antenna 2 Path 2 RX antenna 3 . . . subcarrier 2 TX antenna 1 Path 1 Parameters - Unknown

Multipath Geometry α Target b - a c α 3 2 1 0 + 15

Outline • 3 D Multipath Resolution • Multipath Geometry • Evaluation 16

Mono. Loco • • Implemented using commodity Wi. Fi chips • Intel 5300 • 802. 11 n • 40 Mhz bandwidth • 5 Ghz band Linear antenna array • 3 -elements • 2. 7 cm antenna spacing 17

Experimental Setup 18

Results 0. 5 m 0. 2 m 1. 3 m 19

Sensitivity Analysis 20

Sensitivity Analysis Ao. A Ao. D 21

Conclusion • Multipath triangulation: the first technique for unaided localization with only relative To. F values • This method is general and can be applied beyond Wi. Fi. • 3 D multipath super-resolution: more parameters and higher accuracy than existing approaches • Mono. Loco: the first Wi. Fi localization system that simultaneously provides decimeter -level localization and degree-level orientation • by only using CSI measurements from a single receiver, with no coordination, and handful of packets. 22