Wireless Mesh Networks for Localization Dr Kristofer Pister

Wireless Mesh Networks for Localization Dr. Kristofer Pister Prof. EECS, UC Berkeley Founder & CTO, Dust Networks

Outline Goals Challenges Technical Approaches Real-world Deployments Future Technology Developments 1

First RFID myth “Now I’ll know where all of my stuff is, all of the time!” 2

First RFID myth “Now I’ll know where all of my stuff is, all of the time!” The reality: - RFID systems tell you where your stuff was the last time it went by a reader. Very useful if: - You have chokepoints in your supply chain - You can put a reader on ALL possible entries/exits - You can serialize your material flow 3

Second RFID myth “Now I’ll know where all of my stuff is, all of the time!” “And it will only cost ten cents per tag!” 4

Second RFID myth “Now I’ll know where all of my stuff is, all of the time!” “And it will only cost ten cents per tag!” The Reality: - Tags may get to $0. 10 or lower (probably $0. 25 today) and… - Readers may get to $100 but… - Installing power and comm to all of the readers will dominate the cost of tags for most deployments 5

Mesh to the rescue? Good news, bad news + Low cost of “reader” installation - Completely wireless - Self-configuring - 5 -10 year battery life for infrastructure + Sense state of items as well as location - Increased tag cost - Dollars, not pennies - Constraints on measurement accuracy 6

RSSI-based localization Received Signal Strength Indication - Used as a surrogate for range Use range to known locations to estimate position - Tri-lateration or - Multi-lateration - (not Triangulation) 7

Other localization approaches Acoustic - Sub-cm accuracy in unobstructed environments GPS - Need clear line of sight to satellites Pseudolites - Still doesn’t work well indoors - Rosum? 8

Distance vs. Received Signal Strength RSSI and distance for Consolidated network 1/R 2? 1/R 4? Distance [meters] 60 40 20 0 -100 -90 -80 -70 -60 RSSI [d. Bm] -50 -40 9

Distance vs. Received Signal Strength RSSI and distance for Consolidated network 1/R 2? 1/R 4? Distance [meters] 60 40 20 0 -100 -90 -80 -70 -60 RSSI [d. Bm] -50 -40 10

Distance vs. Received Signal Strength RSSI and distance for Consolidated network 1/R 2? 1/R 4? Distance [meters] 60 40 20 0 -100 -90 -80 -70 -60 RSSI [d. Bm] -50 -40 11

Be cautious of RSSI Chipcon CC 2341 802. 15. 4 datasheet: - 0. 5 m resolution - “Location error can be less than 3 m, depending on factors described below…” - Requires calibrated base stations 10 m accuracy reasonable, 1 m no way Maybe it’s perfect for you, but… - Get a demonstration in your environment - Run it for a while and move stuff around 12

Scalability: 32 acre Test Network 1, 100 m -1400 Motes - 32 Acres - ~3 m accuracy? 600 m 13

Technology to the rescue Accurate RF distance measurement UWB - 10 cm? RF Round-Trip Time of Flight - < 1 m 14

Outdoor Measurement Results Steven Lanzisera, UC Berkeley - slanzise@eecs. berkeley. edu - pister@eecs. berkeley. edu 15