TriopusNet Ted Tsung-Te Lai Automating Wireless Sensor Network Deployment and Replacement in Pipeline Monitoring Ted Tsung-Te Lai Albert Wei-Ju Chen Kuei-Han Li Polly Huang Hao-Hua Chu National Taiwan University

Outline Motivation TriopusNet System Design Evaluation Limitations Related Work Conclusion

Water pipelines are everywhere people live

Pipelines carry important resources (gas, oil…etc.)

Pipelines carry very important resources (beer pipeline!)

Pipeline monitoring is essential Motivation leaking leaking

Water contamination (Boston, 2010)

Difficult sensor deployment

WSN challenges (Deployment and maintenance) Deployment challenges Difficult to access pipelines to place sensors (often hidden inside walls or underground) May need to break pipes to install sensors inside Maintenance challenge Difficult to replace out-of-battery sensors Real pipeline environment Difficult to ensure network connectivity during sensor placement and replacement

Research question Can we automate WSN sensor placement and replacement in pipeline? While minimize the number of sensor nodes Good sensing and networking coverage Reduce the human effort bottleneck for long-term, large-scale WSN deployment & maintenance.

Single-Release Point the enabling concept Place sensors at a single release point Sensors automatically place themselves in the pipes

How to realize single-release point? Sensor placement Mobile sensors Sensor latch mechanism Sensor placement algorithm Sensor localization Sensor replacement Sensor replacement algorithm

Outline Motivation TriopusNet System Design Evaluation Limitations Related Work Conclusion

TriopusNet automate WSN deployment in pipeline Triopus node three arms for latching Single-release point Gateway node Gateway node Gateway node

TriopusNet automate WSN deployment in pipeline Sensor placement Mobile sensors Sensor latch mechanism Sensor placement algorithm Sensor localization Sensor replacement Sensor replacement algorithm

Mobile sensor (components) Sensor mote Actuator pull/push a mechanical arm Localization sensors (SenSys’ 10) water pressure + gyro

Mobile sensor (kmote) = + Kmote CPU board USB board (data processing) (program uploading) A Telosb-like platform, TinyOS compatible Smaller form-factor, only CPU board is needed

Mobile sensor (latch & delatch mechanism) Linear actuator, off-the-shelf from market A motor with gear inside to control the arm Spec: Stroke: 2cm Weight: 15gram Arm extending speed: 2cm/sec 2cm 1cm 0cm

Prototype #1 (8cm diameter)

Prototype #2 (one motor, three arms)

Prototype #2 (6cm diameter)

Sensor placement algorithm Where are the optimal locations to place sensors in pipes (after releasing them from the single-release point)? Networking coverage Interconnectivity among all nodes Sensing coverage Each pipe segment has at least one sensor Minimize # of sensor nodes for deployment

Sensor placement algorithm root water inlet branch 2 branch 1 faucet 1 branch 3 faucet 4 faucet 3 faucet 2

Sensor placement algorithm root water inlet branch 2 n7 branch 1 faucet 1 branch 3 n1 n6 faucet 4 faucet 3 n4 n5 faucet 2 n2 n3

Sensor placement algorithm root water inlet branch 2 n7 branch 1 faucet 1 branch 3 n1 n6 faucet 4 faucet 3 n4 n5 faucet 2 n2 n3

Sensor placement algorithm root water inlet branch 2 branch 1 faucet 1 branch 3 faucet 4 faucet 3 faucet 2

Sensor placement algorithm root Post-order traversal : n1 -> n2 -> … n7 n7 n1 n6 n4 n5 n2 n3

Sensor placement algorithm root Post-order traversal : n1 -> n2 -> … n7 n7 1st n1 n6 n4 n5 n2 n3

Sensor placement algorithm root Post-order traversal : n1 -> n2 -> … n7 n7 1st n1 n6 n4 n5 2nd n2 n3

Sensor placement algorithm root Post-order traversal : n1 -> n2 -> … n7 n7 1st n1 n6 n4 n5 2nd 3rd n2 n3

Sensor placement algorithm root Post-order traversal : n1 -> n2 -> … n7 n7 1st n1 n6 4th n4 n5 2nd 3rd n2 n3

Sensor placement algorithm root Post-order traversal : n1 -> n2 -> … n7 n7 1st n1 n6 4th 5th n4 n5 2nd 3rd n2 n3

Sensor placement algorithm root Post-order traversal : n1 -> n2 -> … n7 n7 6th 1st n1 n6 4th 5th n4 n5 2nd 3rd n2 n3

Sensor placement algorithm root Post-order traversal : n1 -> n2 -> … n7 7th n7 6th 1st n1 n6 4th 5th n4 n5 2nd 3rd n2 n3

Sensor placement algorithm Post-order traversal : n1 -> n2 -> … n7 Reasons: 1. Assure nodes cover all pipes 2. Allow blockage-free movement (bottom-up placement) root 7th n7 6th 1st n1 n6 4th 5th n4 n5 2nd 3rd n2 n3

Sensor placement algorithm Single-release point Gateway node Testing packet received ratio Bad link quality Good link quality, placement completed Gateway node Gateway node

Sensor localization Previous PipeProbe system [SenSys’10] Pressure graph Previous PipeProbe system [SenSys’10] cm-level positional accuracy Vertical pipe location Water pressure changes at different height levels Horizontal pipe location Node distance = node velocity * node flow time Pipe turn detection Gyroscope

Data Collection Collection Tree Protocol (CTP) in TinyOS Single-release point Collection Tree Protocol (CTP) in TinyOS Multi-sink tree to balance network load Gateway node Gateway node Gateway node

Sensor replacement algorithm Single-release point Gateway node Gateway node Low Battery… Gateway node

Outline Motivation TriopusNet System Design Evaluation Limitations Related Work Conclusion

Testbed

Testbed spatial layout Single-release point 150cm 200cm 200cm 200cm 200cm 200cm

Evaluation metrics Automated sensor placement # Nodes for pipeline deployment Data collection rate Energy consumption Automated sensor replacement

Experimental procedure (4 test scenarios) Single-release point 5 tests for each scenario gateway Scenario 3 Scenario 2 Scenario 4 Scenario 1 gateway gateway

# Deployed Nodes (Static v.s. TriopusNet deployment) Avg # of nodes deployed -Static: 7.5 -TriopusNet: 4.4 Avg. node-to-node distance: 173cm Std: 58cm Static (90cm) TriopusNetA TriopusNetB TriopusNetC

Avg. node-to-node distance

Avg. node-to-node distance

Avg. node-to-node distance

Avg. node-to-node distance

Data collection rate Each node sent 1000 packets to gateway -80% nodes achieve 99% packet receive rate -All nodes > 87% rate

Energy consumption (node placement) Each node requires 2.4 actuations on average (1 actuation consumes ~1J)

Evaluation metrics Automated sensor placement # nodes for sensing/networking coverage Data collection rate Energy consumption Automated sensor replacement

Test scenario and result for replacement Data collection rate Initial deployment After replacement Without replacement 0.99 0.98 0.80 Set these two nodes to low battery level and trigger replacement

Outline Motivation TriopusNet System Design Evaluation Limitations Related Work Conclusion

Limitation: Lack automatic faucets

Limitation: Node size

Limitation: Node size Single-release point Low Battery…

Outline Motivation TriopusNet System Design Evaluation Limitations Related Work Conclusion

PipeNet (IPSN’07, pipeline monitoring) Detect and localize leakage by pressure and ultrasonic sensors

NAWMS (SenSys’08, water flow sensing)

HydroSense (Ubicomp’09, water event sensing) Single-point pressure-based sensor of water usage toilet kitchen sink shower

Comparison to related work Multi-point sensing Single-point Single-release point NAWMS HydroSense TriopusNet PipeNet

Outline Motivation TriopusNet System Design Evaluation Limitations Related Work Conclusion

Conclusion TriopusNet: automating WSN deployment and replacement in pipeline monitoring Automated sensor placement and replacement to reduce human deployment and maintenance effort: mobile sensors with self-latching mechanism from a single-release point Results show smaller number of sensor nodes with good sensing/networking coverage

Thank shepherd (Prof. Gian Pietro Picco) & reviewers for valuable comments Questions & Answers TriopusNet: Automating WSN Deployement and Replacement in Pipeline Monitoring Ted Tsung-Te Lai, Albert Wei-Ju Chen, Kuei-Han Li Polly Huang, Hao-hua Chu Ubicomp lab http://mll.csie.ntu.edu.tw National Taiwan University