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Reliable and Energy-Efficient Data Collection in Wireless Sensor Networks
Feng Wang Department of Computer and Information Science
University of Mississippi
January 2014
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January 2014 Reliable and Energy-Efficient Data Collection in Wireless Sensor Networks
About Myself
2/18
Feng Wang
Assistant Professor (Aug 2012- )
Department of Computer and Information Science
University of Mississippi
Email: [email protected]
Webpage: www.cs.olemiss.edu/~fwang
Research interest: computer networking Wireless mesh network, Wireless sensor network
Peer-to-peer network, Socialized content sharing
Cloud computing, Big data
mailto:[email protected]://www.cs.olemiss.edu/~fwang
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January 2014 Reliable and Energy-Efficient Data Collection in Wireless Sensor Networks
Research Work
3/18
Peer-to-peer overlay networks
Live video streaming: exploit stable peers to improve QoS Partly adopted by PPTV (one major video streaming company in China)
File sharing (e.g. BitTorrent) Tracker: balance resource availability and traffic locality
Peer: apply fountain codes to speed up sharing performance
Socialized content sharing
UGC video (e.g., YouTube/Twitter Vine video) sharing Adaptively prioritize data requests with collaborations
Popularity prediction of videos shared in online social networks
Instant video clip sharing over mobile social network platforms
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January 2014 Reliable and Energy-Efficient Data Collection in Wireless Sensor Networks
Research Work (cont.)
4/18
Cloud computing
Service migration/optimization Cloud assisted live video streaming for diversified/globalized demands
Optimization of cloud-based distributed interactive applications
Architecture design/performance analysis Utilization of customer-provided resources for cloud computing
Virtualization in cloud storage/synchronization services (e.g., Dropbox)
Network performance in virtual machine based cloud
Big data
Network-aware load balance and data locality in MapReduce
Crowdsourced live media streaming
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January 2014 Reliable and Energy-Efficient Data Collection in Wireless Sensor Networks
Research Work (cont.)
5/18
Wireless mesh networks
Path capacity estimation and optimization Analyze available additional capacity without violating QoS
Path diversified multi-QoS optimization in multi-channel networks
Wireless sensor networks
Local calibration assisted time synchronization Calibrate by local crystal oscillator’s properties to reduce messages
Data collection/diffusion Location-oblivious: hybrid push-pull and adaptive ultra-node selection
Error-bounded: filter goes along paths to suppress unnecessary report
Reliable and energy-efficient: to be discussed in this talk
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January 2014 Reliable and Energy-Efficient Data Collection in Wireless Sensor Networks
Outline
6/18
Reliable and energy-efficient data collection
Background and overview Wireless sensor network
Data collection service
Issues, challenges and solutions Wireless sensor deployment
Control message dissemination
Sensing data gathering
Case study: Guangzhou New TV Tower
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January 2014 Reliable and Energy-Efficient Data Collection in Wireless Sensor Networks
Wireless Sensor Network (WSN)
Network of collaborative wireless sensor nodes Computing, sensing, communication and storage
Often powered by battery and expected to work for long time Relatively small and deployed in great number
Need careful design to be energy-efficient
Nowadays widely used in many applications, such as
Habitat monitoring
Battlefield surveillance
Building control
Volcano monitoring
Water monitoring
Structure health monitoring
7/18
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January 2014 Reliable and Energy-Efficient Data Collection in Wireless Sensor Networks
Data Collection
8/18
Data collection service
Sensor nodes deployed at specific locations
Sensing ambient environment
Data forwarded to base station for further processing
Traditional (wired) approach More impact to ambient environment
Need extra efforts and costs Line protection
Find and repair a broken line
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January 2014 Reliable and Energy-Efficient Data Collection in Wireless Sensor Networks
Challenges and Issues in Data Collection WSN
9/18
From WSNs
Limited hardware capacity and energy budgets
Wireless communication Major source of energy consumption
Loss due to interference and collision
From data collection Various application and networking requirements
Reduce/balance energy costs to extend network lifetime Heterogeneous data rate (temperature, acceleration, ...)
Hard to apply aggregation: “many-to-one” traffic pattern
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January 2014 Reliable and Energy-Efficient Data Collection in Wireless Sensor Networks
How Data Collection WSNs Work ?
10/18
In practice, three stages
Deploy sensors to fulfill various application and
networking requirements
Disseminate messages (setup/management/
commands) to all sensors
Deliver sensing data from each sensor to base station
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January 2014 Reliable and Energy-Efficient Data Collection in Wireless Sensor Networks
Deployment Stage
11/18
How can we use min. # nodes to connect the network or max. network lifetime for given node #?
Previous work mainly focuses on network connectivity
For data collection Heterogeneous data rate
“Many-to-one” traffic pattern
Traffic-aware deployment Generalized Euclidian Steiner minimum
tree problem Hybrid algorithm to bypass local optima and
yield high quality results
Optimal discrete node assignment on topology
Topology adjustment to fit discrete node assignment
x x
x x
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January 2014 Reliable and Energy-Efficient Data Collection in Wireless Sensor Networks
Message Dissemination Stage
12/18
How to efficiently disseminate message to all nodes?
Most previous work: assume all nodes active all the time
Real world: nodes may work in low duty-cycles to save energy - Ratio between active and full active/dormant period
Topology of active nodes may change frequently and dramatically
Wireless losses further aggravate above issues
Duty-cycle-aware message dissemination
Transform the problem to a graph problem Min. cost/delay: find the shortest path
Centralized optimal solution: dynamic programming
Distributed implementation Scalability, reliability, efficiency
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January 2014 Reliable and Energy-Efficient Data Collection in Wireless Sensor Networks
Data Delivery Stage
13/18
New scenario: structural health monitoring for
high-rise structures
Much longer distance to base station
Much higher data concentration near base station
EleSense - base station on moving elevator
Optimal solution to min. delay and cost
Resolve practical issues Hardware constraint
Local search algorithm guided by evaluation function
Elevator operates in cycle pattern
Use known “short future” to further improve performance
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January 2014 Reliable and Energy-Efficient Data Collection in Wireless Sensor Networks
Guangzhou New TV Tower: A Case Study
14/18
World’s tallest TV tower (Nov 2010, 600m)
Hyperbolic shape
Uneven horizontal + extensive vertical dimension More variances in node capacity/wireless interference
System design (hierarchical architecture)
Close nodes as a cluster, sub-station as head Intra-cluster collection: traffic-aware deployment
Inter-cluster collection: EleSense framework
Stand-by mode: low duty-cycle Switch mode by command message dissemination
Collection mode: fully operate Back to stand-by mode if no new command
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January 2014 Reliable and Energy-Efficient Data Collection in Wireless Sensor Networks
Sensor Deployment for Civil Requirements
15/18
Sensor Type Monitoring Items Qty.
Weather station Temperature, humidity, rain, air pressure
1
Anemometer Wind speed and direction 2
Wind pressure sensor Wind pressure 4
Tiltmeter Inclination of tower 2
GPS Displacement 2
Vibrating wire gauge Strain, shrinkage and creep 60
Thermometer Temperature of structure 60
Digital video camera Displacement 3
Seismograph Earthquake motion 1
Corrosion sensor Corrosion of reinforcement 3
Accelerometer Acceleration 22
Fiber optical sensor Strain and temperature 120 Sensor Deployment on GNTVT
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January 2014 Reliable and Energy-Efficient Data Collection in Wireless Sensor Networks
System Deployment and Verification
16/18
Sensor node hardware
StanfordMote + Tokyo Sokushin AS-2000 (accelerometer)
Experiment results
Base station successfully receives all data packets while moving with elevator at both directions
Wireless transmissions could easily reach 55Kbps
Accelerometer Deployment Sub-station Base Station on Elevator
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January 2014 Reliable and Energy-Efficient Data Collection in Wireless Sensor Networks
Preliminary Evaluation for Full Tower
17/18
Due to limited time/area access
Emulation with real data/settings from
GNTVT to examine full tower performance
Results
Throughput gain: 212.7%
Communication cost reduction: 58.7%
Throughput Communication Cost
Example of Collected Acceleration Data
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January 2014 Reliable and Energy-Efficient Data Collection in Wireless Sensor Networks
Summary
18/18
Wireless sensor data collection
Greatly reduce deployment/maintenance costs
Pose new challenges such as reliability and energy-efficiency
Propose a full range of solutions across different stages
Traffic-aware deployment
Message dissemination with low duty-cycle
Elevator-assisted data delivery
Partially integrated in GNTVT’s new monitoring system
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January 2014 Reliable and Energy-Efficient Data Collection in Wireless Sensor Networks
Email: [email protected]
Thank you!
19/40
Question and Comments?
mailto:[email protected]
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January 2014 Reliable and Energy-Efficient Data Collection in Wireless Sensor Networks
Deployment Stage
20/-
• Bai et al. “Complete Optimal Deployment Patterns for Full-Coverage and k-Connectivity (k
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January 2014 Reliable and Energy-Efficient Data Collection in Wireless Sensor Networks
System Model and Problem Statement
21/-
System model
M source nodes (S-nodes) with location S={s1,…,sM} and data rate
Location of base station: s0
Traffic-aware deployment problem
Given N relay nodes (R-nodes), find their locations {f1,…,fN} with communication ranges R={r1,…,rN} and data paths for S-nodes P={p1,…,pM} to
Communication range:
Forwarding path connectivity:
S-nodes and sink connectivity:
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January 2014 Reliable and Energy-Efficient Data Collection in Wireless Sensor Networks
Our Solution
22/-
Optimal solution for single source case
Single traffic flow: deploy nodes from source with distance of
L/N (Theorem 1)
Multi traffic flow: merge all
flows into one and apply Theorem 1 (Theorem 2)
Transform general case into directed graph G=(V,E)
V={v0,v1,...,vM,vM+1,...} vi=si, for ; vj: merge vertices, for j>M
E={e1,e2,…}, for edge ei with length : total data rate of flows through edge
: number of assigned R-nodes
: maximum R-node energy cost
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January 2014 Reliable and Energy-Efficient Data Collection in Wireless Sensor Networks
Our Solution (cont.)
23/-
Solution for general case
Theoretical solution in continuous space To , we need and have ([Olariu06])
Find topology (merge vertices) to minimize total weighted edge length
Generalized Euclidian Steiner Minimum Tree problem (NP-hard, [Xue99])
Hybrid algorithm: bypass local optima and yield high quality results
Practical solution on discrete R-node deployment Fractional node number: up to 40% degradation by simply rounding
Discrete R-node assignment algorithm: optimal assignment on topology
Merge vertex adjustment algorithm: fit discrete node assignment
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• Olariu et al. “Design guidelines for maximizing lifetime and avoiding energy holes in sensor networks with uniform distribution and uniform reporting”, IEEE INFOCOM 2006
• Xue et al. “Computing the minimum cost pipe network interconnecting one sink and many sources”, SIAM J. Optimiz., 1999
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January 2014 Reliable and Energy-Efficient Data Collection in Wireless Sensor Networks
Performance Evaluation
24/-
Our solution: significantly extend network lifetime
Up to 7 times of Connectivity-Only and 15 times of Direct-Connection
Close to theoretical upper bound (difference 13.5%) Upper bound of optimal solution with small M ( 15 in our evaluation)
Network Lifetime by Numerical Analysis Network Lifetime by ns-2 simulations
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January 2014 Reliable and Energy-Efficient Data Collection in Wireless Sensor Networks
Message Dissemination Stage
25/-
Efficiently deliver messages to all nodes at low costs
Conventional assumption in previous works
All nodes active all the time ([Stann2006, Kyasanur2006])
Real world
Nodes may work in low duty-cycles to save energy - Ratio between active and full active/dormant period
Topology of active nodes may change frequently and dramatically
Active/dormant pattern is often application-specific
May not be determined before node deployment
Should not be disturbed by message dissemination
Wireless losses further aggravate above issues • Kyasanur et al. “Smart Gossip: An Adaptive Gossip-based Broadcasting Service for Sensor Networks,” IEEE MASS, 2006 • Stann et al. “RBP: Robust Broadcast Propagation in Wireless Networks,” ACM SenSys, 2006
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January 2014 Reliable and Energy-Efficient Data Collection in Wireless Sensor Networks
Problem Formulation
26/-
Duty-cycle-aware message dissemination problem:
Notations Active/dormant state of node i at t: (1: active; 0: dormant)
Neighbor set of node i:
Forwarding Sequence (FS):
Node set covered by i-th forwarding:
For message dissemination starting from s at t0, find
s.t. Duty-cycle constraint:
Forwarding order constraint:
Coverage constraint:
To minimize , a function of message and time costs A common linear combination form:
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January 2014 Reliable and Energy-Efficient Data Collection in Wireless Sensor Networks
Centralized Optimal Solution
27/-
Transform to time-space graph
Vertex : nodes in R have message at t
Edge : Time edge: no forwarding at t
Forwarding edge: forward to nodes in at t
Weight W Time edge:
Forwarding edge: (p: forwardings at t)
Minimize : find shortest path from to last row
Dynamic programming solution
Recurrence relation: : total weights of shortest path from to
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January 2014 Reliable and Energy-Efficient Data Collection in Wireless Sensor Networks
Distributed Implementation
28/-
Scalable forwarding sequence generating
CovSet: nodes being covered within 2-hop
Compute 2-hop optimal FS from current CovSet Re-compute if CovSet update does not match computed FS
Accommodate wireless loss
RcvSet: nodes having received message within 2-hop RcvSet may NOT be equal to CovSet due to wireless loss
Set CovSet to RcvSet periodically
Expedite information updating
Piggy-back RcvSet with messages
Overhearing during active mode
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January 2014 Reliable and Energy-Efficient Data Collection in Wireless Sensor Networks
Performance Evaluation
29/-
RBP ([Stann06]): unacceptable when duty-cycle
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January 2014 Reliable and Energy-Efficient Data Collection in Wireless Sensor Networks
Data Delivery Stage
30/-
Diverse application-specific QoS requirements
Reliability [Xu04], delay [Song06], throughput
[Ahn06], energy consumption [Burri07], …
New scenario: Structural health monitoring
(SHM) for high-rise structures
High-rise structure: normal horizontal dimension
but extensive vertical dimension
New challenges Much longer distance to base station
Much higher data concentration near base station
• Xu et al. “A Wireless Sensor Network For Structural Monitoring,” ACM SenSys, 2004 • Song et al. “Time-Optimum Packet Scheduling for Many-to-One Routing in Wireless Sensor Networks,” IEEE MASS, 2006 • Ahn et al. “Funneling-MAC: A Localized, Sink-Oriented MAC For Boosting Fidelity in Sensor Networks,” ACM SenSys, 2006 • Burri et al. “Dozer: Ultra-Low Power Data Gathering in Sensor Networks,” ACM/IEEE IPSN, 2007
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January 2014 Reliable and Energy-Efficient Data Collection in Wireless Sensor Networks
Elevator-Assisted Data Delivery
31/-
EleSense - elevator-assisted data collection
Base station on elevator Collect data when serving passenger
Reduce distances between nodes and base station
Effectively balance traffic relaying among sensor nodes
Still a series of issues to address
Elevator not controlled by base station Various node capacity to transmit data to base station
Relay by neighbour or wait for base station arrival?
Limited queuing buffer: rate control and fairness
Interference/collision at both nodes and moving base station
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January 2014 Reliable and Energy-Efficient Data Collection in Wireless Sensor Networks
Solution Design
32/-
Elevator-assisted data delivery problem
Assumption: elevator movement known a priori
Modeled as a cross-layer optimization problem Link scheduling, packet routing, end-to-end delivery
Theoretical solution
Transform into a graph problem
Solve optimally by dynamic programming
Good for analysis but hard to apply to WSNs Intensive computation/memory requirement
Base on a priori information
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January 2014 Reliable and Energy-Efficient Data Collection in Wireless Sensor Networks
Resolve Practical Issues
33/-
Accommodate hardware constraint
Local search algorithm Explore vertices by order based on evaluation function
Limit search range to finish in one time unit
Work without a priori information
Naive approach Use current elevator location
An observation Elevator operates in cycle pattern
Use known “short future” movements
to further improve performance
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January 2014 Reliable and Energy-Efficient Data Collection in Wireless Sensor Networks
Performance Evaluation
34/-
EleSense achieves good reliability and fairness
Throughput gain: 30.7% to 159.6% over StaticSense and 40.9% to 423.2% over Ele802.11
Communication cost: 58.9% to73.1% of the runner-up
Communication Cost Throughput
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January 2014 Reliable and Energy-Efficient Data Collection in Wireless Sensor Networks
Guangzhou New TV Tower: A Case Study
35/-
Guangzhou New TV Tower (GNTVT)
World’s tallest TV tower (600m) Locate in Guangzhou, China
Fully operate in Nov 2010 and broadcast
16th Asia Games
Hyperbolic shape: more challenges Uneven horizontal dimension
60mX80m at ground, minimum of 20.65mX
27.5m at 280m, 40.5mX54m at top (454m)
Extensive vertical dimension Main tower: 454m, antennary mask: 146m
Cause more variances in node capacity
and wireless interference/collision
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January 2014 Reliable and Energy-Efficient Data Collection in Wireless Sensor Networks
Sensor Deployment for Civil Requirements
36/-
Sensor Type Monitoring Items Qty.
Weather station Temperature, humidity, rain, air pressure
1
Anemometer Wind speed and direction 2
Wind pressure sensor Wind pressure 4
Tiltmeter Inclination of tower 2
GPS Displacement 2
Vibrating wire gauge Strain, shrinkage and creep 60
Thermometer Temperature of structure 60
Digital video camera Displacement 3
Seismograph Earthquake motion 1
Corrosion sensor Corrosion of reinforcement 3
Accelerometer Acceleration 22
Fiber optical sensor Strain and temperature 120 Sensor Deployment on GNTVT
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January 2014 Reliable and Energy-Efficient Data Collection in Wireless Sensor Networks
Prototype System Design
37/-
Hierarchical architecture
Nodes close to each other form a cluster
Sub-station as cluster head Intra-cluster collection: traffic-aware deployment
Inter-cluster collection: EleSense framework
Two-mode working pattern
Stand-by mode All nodes in low duty-cycle to conserve energy
Switch mode by command message dissemination
Collection mode Nodes fully operate for data collection
Back to stand-by mode unless new command disseminated
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January 2014 Reliable and Energy-Efficient Data Collection in Wireless Sensor Networks
System Deployment and Verification
38/-
Sensor node hardware
Node: StanfordMote
Accelerometer: Tokyo Sokushin AS-2000
16-bit ADC with sample rate as 50Hz
Data traffic from each sensor
Total 50x60x2=6000 bytes
acceleration data per minute,
further divided into 20 packets
Accelerometer Deployment
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January 2014 Reliable and Energy-Efficient Data Collection in Wireless Sensor Networks
System Deployment and Verification (cont.)
39/-
GNTVT still in construction during our experiments
Only section below 240m allowed for temporary access 4 subsections, each for 60m
Experiments at both up/down directions for all subsections to fully understand wireless capacity
Sub-station Base Station on Elevator
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January 2014 Reliable and Energy-Efficient Data Collection in Wireless Sensor Networks
System Deployment and Verification (cont.)
40/-
Experiment results
Base station successfully receives all data packets while moving with elevator at both directions
Wireless transmissions could easily reach 55Kbps
Elevator Movement Start Height End Height Packet from Each Node Delivery Ratio
From bottom to top
0m 60m 20 100%
60m 120m 20 100%
120m 180m 20 100%
180m 240m 20 100%
From top to bottom
240m 180m 20 100%
180m 120m 20 100%
120m 60m 20 100%
60m 0m 20 100%
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January 2014 Reliable and Energy-Efficient Data Collection in Wireless Sensor Networks
Preliminary Evaluation for Full Tower
41/-
Limited time/area access due to construction phase
Emulation with real data/settings from
GNTVT to examine full tower performance
Results
Throughput gain: 212.7%
Communication cost reduction: 58.7%
Throughput Communication Cost
Example of Collected Acceleration Data
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January 2014 Reliable and Energy-Efficient Data Collection in Wireless Sensor Networks
Summary and Discussion
42/-
Wireless sensor data collection
Greatly reduce deployment/maintenance costs
Pose new challenges such as reliability and energy-efficiency
Propose a full range of solutions across different stages
Traffic-aware deployment
Message dissemination with low duty-cycle
Elevator-assisted data delivery
Partially integrated in GNTVT’s new monitoring system
Other issues worth further exploring
Learn/model elevator movement for further optimization
Multiple base stations for collaborative data collection