ATOLS A WSN-based, RSS-driven, Real-time Location Tracking System - - PowerPoint PPT Presentation

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ATOLS A WSN-based, RSS-driven, Real-time Location Tracking System - - PowerPoint PPT Presentation

ATOLS A WSN-based, RSS-driven, Real-time Location Tracking System for Independent Living Facilities Pawel Gburzynski, Wlodek Olesinski Jasmien Van Vooren Olsonet Communications, Ottawa, Canada Alphatronics, Belgium University of Alberta,


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SLIDE 1

ATOLS

A WSN-based, RSS-driven, Real-time Location Tracking System

for Independent Living Facilities

Pawel Gburzynski, Wlodek Olesinski Jasmien Van Vooren

1 August 2016

Olsonet Communications, Ottawa, Canada Alphatronics, Belgium University of Alberta, Computing Science, Edmonton, Canada Vistula University, Warsaw, Poland

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SLIDE 2

Indoor Location Tracking

2 August 2016

Radio-based: TOA / TOF, TDOA / TDOF, AOA Phase Difference RSS Non-radio-based: Ultrasound, infrared, pressure sensors, active floor

considered passé these days

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SLIDE 3

Problem definition

August 2016 3

Estimate the location of people (and possibly other objects) wearing RF Tags. Coordinates in 3D Named places (within a building) A practical project: a system was already deployed, and we wanted to extend it with the new functionality … … in some preferably minimalistic way

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SLIDE 4

Militza (Brugges)

August 2016 4

an Independent Living facility

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SLIDE 5

Annonciaden (Antwerp)

August 2016 5

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SLIDE 6

August 2016 6

What is a “location”?

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SLIDE 7

August 2016 7

The WSN: Tags & Pegs

Tags implement some end functionality, e.g., sensing; a Tag can be mobile Pegs act as semi-infrastructure (e.g., static, devoid of sensors/actuators, used solely for communication) Pegs can be used as reference, e.g., for location tracking (if they do not move) Power considerations: Pegs can be powered from external sources, while Tags are battery powered The hierarchy is natural in many applications

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SLIDE 8

August 2016 8

Devices

7cm

CC430F6137 (MSP430 + CC1100)

4 KB RAM 32KB flash

BMA250 (accelerometer)

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SLIDE 9

August 2016 9

Devices

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SLIDE 10

August 2016 10

Devices: MSP430/CC1100

Small footprint, 4KB of RAM, 32KB for program (this is not a Java-friendly platform) Radio is ISM, highly configurable, (can be) integrated with the microcontroller, not BT Adjustable transmit power level, RSS measurable by the receiver

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SLIDE 11

August 2016 11

Software

PicOS: Olsonet’s OS for tiny devices TARP/VNETI: Olsonet’s ad-hoc mesh networking scheme (no ZigBee) VUEE: Olsonet’s virtual development and testing platform for complete applications (praxes)

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SLIDE 12

August 2016 12

RSS is a crude attribute

  • high power
  • longer distance
  • fewer Pegs
  • cruder estimates
  • low power
  • shorter distance
  • more Pegs
  • finer resolution
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SLIDE 13

August 2016 13

Profiling / surveying

Attempts at correlating RSS with distance via blanket functions don’t work too well We can afford (relatively) many Pegs (say, tricky areas can be better covered, if that helps) Profile Sample: a vector of readings collected from a known location Tracking Sample: a vector of readings collected from a tracked device

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SLIDE 14

August 2016 14

A floor in Annonciaden

2 1 3 4 5 6 7 8 9 10 11 12 13 1 2 3 4 5

Peg sample tricky locations can be split internally

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SLIDE 15

August 2016 15

Location bursts

Tags emit “bursts” of 32 short packets transmitted at increasing power levels [in groups of 4]: . . .

PL 0 PL 1 PL 7

Pegs receive what they can and forward the corresponding RSS vectors to the master.

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SLIDE 16

August 2016 16

A profile sample

# loc 1'0'2, att 5 "23-Jul-2016 19:59:03” 3 0 61 68 77 90 95 4 0 57 66 76 85 94 105 112 5 0 60 70 79 88 96 108 115 6 74 83 92 102 111 119 131 138 7 82 89 99 109 118 125 137 145 8 75 84 93 102 111 119 132 138 9 82 91 100 109 119 126 139 145 11 0 69 77 85 97 104 12 0 60 73 80 P0 P7

Peg power level

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SLIDE 17

August 2016 17

A tracking sample ...

... looks similar, except that the location isn’t known

Vectors arrive individually, the estimator can use any set of three or more vectors to attempt an estimation Given a set of tracking vectors:

)} ,..., , {(

7 i i i

RSS RSS P

... and a set of profile samples, guess at the most likely location

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SLIDE 18

August 2016 18

The algorithm (a rough idea)

Iterations by power levels, from low to high Maintain the set of ranked candidate locations; each iteration can trim the set and update the ranks of whatever locations remain in the set If after trimming the set becomes empty, the last nonempty set (with its ranks) is returned (the highest ranked location is the simple result)

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SLIDE 19

August 2016 19

Like RFID/ranging combo

Low power levels have priority; this way, closeness to a Peg always translates in a good estimate Allows for sparse coverage in areas where some tolerance can be afforded; no need to be close to a Peg for a decent estimate

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August 2016 20

Some options

History option? In the underlying application, the tracking events tend to be sparse; can be adapted to periodic (non-triggered) tracking Area geometry info can be provided (a measure of effort to cross locations) and is relevant jointly with the history option Integrated into the event (sensor data) passing network; some events can act as (potentially strong) location hints

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SLIDE 21

August 2016 21

Accuracy?

Difficult to quantify in a global and meaningful way An error may be more tolerable if the locations are easy to reach from one another

90% (absolute) success rate in some accidental and rather poorly devised setup

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SLIDE 22

August 2016 22

Range, density?

100m ballpark range in open air [minimal antennas]; 10-50m in a building, depending on wall type, etc. Recommended (?) (at least) one Peg for every formal location Different types of walls (obstacles) affect the range, sometimes drastically Easy to throw in extra Pegs if there are problems (the network is a true (I mean TRUE) mesh (ad-hoc)

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SLIDE 23

August 2016 23

Energy budget

Location burst: 32 x 80 @ 38400 + overhead → 0.2s @ ca. 20 mA Idle Tag current drain: 3uA 10s → 5+ months (1000 mAh battery) 20s → 9+ months 1m → 2+ years 1h → practically forever variable interval, e.g., triggered by accelerometer

can be reduced to 16 or so

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August 2016 24

That’s it