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Reliable and Energy-Efficient Communication in Wireless Sensor Networks
 

Reliable and Energy-Efficient Communication in Wireless Sensor Networks

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CS Colloquium Western Michigan University

CS Colloquium Western Michigan University

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    Reliable and Energy-Efficient Communication in Wireless Sensor Networks Reliable and Energy-Efficient Communication in Wireless Sensor Networks Presentation Transcript

    • Computer Science ColloquiumWestern Michigan UniversityReliable and Energy-EfficientCommunication inWireless Sensor NetworksTorsten Braun, Universität Bern, Switzerlandbraun@iam.unibe.ch, cds.unibe.chjoint work with Philipp Hurni
    • Torsten Braun: Reliable and Energy-Efficient Communication in Wireless Sensor Networks Overview > Introduction — Wireless Sensor Network Applications and Application Requirements — Design, Implementation, Evaluation of WSN Protocols > Experimentation Platform for WSN Research — Wireless Sensor Network Testbed — Software-Based Estimation of Energy Consumption > WSN Research Experiments — Traffic-Adaptive and Energy-Efficient WSN MAC Protocol — Adaptive Forward Error Control in WSNs — TCP Performance Optimizations for WSNs > Conclusions Kalamazoo, June 13, 2012 2
    • Torsten Braun: Reliable and Energy-Efficient Communication in Wireless Sensor Networks Wireless Sensor Network Applications > Monitoring and control of buildings using sensor nodes and artificial neural networks Markus Wälchli, Torsten Braun: Building Intrusion Detection with a Wireless Sensor Network, ICST AdHocNets, Niagara Falls, 2009 Kalamazoo, June 13, 2012 3
    • Torsten Braun: Reliable and Energy-Efficient Communication in Wireless Sensor Networks Wireless Sensor Network Applications > Environmental monitoring (A4-Mesh, a4-mesh.unibe.ch) Plaine Morte glacier Tseuzier storage lake Sierre SionAlmerima Jamakovic, Torsten Braun,Thomas Staub, Markus Anwander:Authorisation and AuthenticationMechanisms in Support of SecureAccess to WMN Resources,IEEE HotMesh, San Francisco,June 2012 Kalamazoo, June 13, 2012 4
    • Torsten Braun: Reliable and Energy-Efficient Communication in Wireless Sensor Networks Application Requirements > Energy-efficient operation > Low delays > Reliability > Adaptivity to varying link characteristics and traffic load Kalamazoo, June 13, 2012 5
    • Torsten Braun: Reliable and Energy-Efficient Communication in Wireless Sensor Networks Design, Implementation, and Evaluation of Wireless Sensor Network Protocols > Simulations are only meaningful with accurate calibration of parameters, e.g., energy consumption, transmission characteristics, traffic models. > Experiments in testbeds give insights about protocol behaviour in more realistic scenarios and system-related issues, but face several problems — Experiment control — Scalability — Reproducability — Energy measurements — Mobility Kalamazoo, June 13, 2012 6
    • Wireless Sensor Network Testbed
    • Torsten Braun: Reliable and Energy-Efficient Communication in Wireless Sensor Networks Wisebed WSN Testbed @ Universität Bern> Wisebed: EU FP7 project, 2008 - 2011> Approx. 50 TelosB/MSB430 nodes connected to portal via Ethernet USB Mesh Node Internet LAN wireless Ethernet Portal Sensor Node Kalamazoo, June 13, 2012 8
    • Torsten Braun: Reliable and Energy-Efficient Communication in Wireless Sensor Networks TARWIS Experiment Configuration Kalamazoo, June 13, 2012 9
    • Torsten Braun: Reliable and Energy-Efficient Communication in Wireless Sensor Networks TARWIS Experiment Monitoring Kalamazoo, June 13, 2012 10
    • Torsten Braun: Reliable and Energy-Efficient Communication in Wireless Sensor Networks TARIWS-Generated Experiment Trace Kalamazoo, June 13, 2012 11
    • Software-Based Estimation ofEnergy Consumption
    • Torsten Braun: Reliable and Energy-Efficient Communication in Wireless Sensor Networks Software-Based Estimation of Energy Consumption > Problem: Equipment of sensor nodes with measurement hardware is — very expensive. — difficult in out-door environments / real-world deployments. — not sufficient to support energy awareness. – Energy awareness: Application / system adapts operation to meet energy consumption constraints. > Solution: Software-based energy measurement (calibration of software-based model using measurement hardware) Kalamazoo, June 13, 2012 13
    • Torsten Braun: Reliable and Energy-Efficient Communication in Wireless Sensor Networks Hardware-Based Energy Measurements > Measurement of current draw and voltage using Sensor Network Management Devices (SNMD) from KIT Kalamazoo, June 13, 2012 14
    • Torsten Braun: Reliable and Energy-Efficient Communication in Wireless Sensor Networks Simple 3-State-Model A. Dunkels, F. Osterlind, N. Tsiftes, Z. He: Software-based On-line Energy Estimation for Sensor Nodes. IEEE EmNets, 2007 Kalamazoo, June 13, 2012 15
    • Torsten Braun: Reliable and Energy-Efficient Communication in Wireless Sensor Networks Measured vs. Estimated Energy ConsumptionApproach: Measurement of current draw in different states and energy estimation by Kalamazoo, June 13, 2012 16
    • Torsten Braun: Reliable and Energy-Efficient Communication in Wireless Sensor Networks 3-State-Model with State Transitions Revised estimation: Kalamazoo, June 13, 2012 17
    • Torsten Braun: Reliable and Energy-Efficient Communication in Wireless Sensor Networks Estimation Accuracy OLS: Ordinary Least Squares Regression AnalysisOn the Accuracy of Software-based Energy Estimation Techniques. Philipp Hurni, Torsten Braun, Benjamin Nyffenegger,Anton Hergenroeder: 8th European Conference on Wireless Sensor Networks (EWSN), Bonn, Germany, February 2011. Kalamazoo, June 13, 2012 18
    • MaxMAC: Maximally Traffic-Adaptive andEnergy-Efficient WSN MAC Protocol
    • Torsten Braun: Reliable and Energy-Efficient Communication in Wireless Sensor Networks WiseMAC > Very energy-efficient MAC protocol, but adaptivity to traffic variation is very limited. > Unsynchronized nodes wakeup for a short time > Tpreamble = min {4θL,T} — θ: clock drift, L: time since last update, T: duration of a cycle > „Piggybacking― of wakeup times Enz et al.: WiseNET: An Ultralow-Power Wireless Sensor Network Solution, IEEE Computer, Vol. 37, No. 8; August 2004 Kalamazoo, June 13, 2012 20
    • Torsten Braun: Reliable and Energy-Efficient Communication in Wireless Sensor Networks MaxMAC: a Maximally Traffic-Adaptive and Energy-Efficient WSN MAC Protocol > is based on sampling of preambles, cf. WiseMAC > Additional wakeups for higher rates of received packets (measurement by sliding window) — Periodic reports in acknowledgements from receiver to sender — State transitions if thresholds T1,T2,TCSMA are exceeded. packet rate ≥ T1 packet rate ≥ T2 packet rate ≥ TCSMA S1 S2 Base CSMA 2* 4* state duty duty RECV cycle cycle packet rate < T1 packet rate < T2 packet rate < TCSMA Lease expired Lease expired Lease expired Kalamazoo, June 13, 2012 21
    • Torsten Braun: Reliable and Energy-Efficient Communication in Wireless Sensor Networks MaxMAC CSMA Philipp Hurni and Torsten Braun. MaxMAC: a maximally traffic-adaptive MAC protocol for wireless sensor networks. 7th European Conference on Wireless Sensor Networks (EWSN), Coimbra, Portugal, February 2010. Kalamazoo, June 13, 2012 22
    • Torsten Braun: Reliable and Energy-Efficient Communication in Wireless Sensor Networks MaxMAC Implementation on MSB430 > Threshold parameters: T1 = 1, T2 = 2, TCSMA = 3 packets / s > Base duty cycle: 0.6 % (3 ms) for a base interval of 500 ms > Frame size: 40 bytes including header > Lease times: 3 s > Bit rate: 19.2 kbps > Implementation of packet burst mode Kalamazoo, June 13, 2012 23
    • Torsten Braun: Reliable and Energy-Efficient Communication in Wireless Sensor Networks Experiments with Intruder Scenario I WiseMAC MaxMAC CSMA Kalamazoo, June 13, 2012 24
    • Torsten Braun: Reliable and Energy-Efficient Communication in Wireless Sensor Networks Experiments with Intruder Scenario II Kalamazoo, June 13, 2012 25
    • Adaptive Forward Error Correction
    • Torsten Braun: Reliable and Energy-Efficient Communication in Wireless Sensor Networks Error Control in Wireless Sensor Networks > Wireless channels in sensor networks have varying bit error rates, sometimes up to 20 %. > Options — Automatic Repeat Request (ARQ) – Retransmission adds delay. – Original transmission was useless, but consumed bandwidth and energy. — Forward Error Correction (FEC) – Relatively small delay (due to encoding and decoding) compared to ARQ for error correction – En-/decoding can be costly (several 100 ms for decoding). – Too strong codes consume computing resources and bandwidth. – Too weak codes might not be able to correct errors. > Proposed Approach: Adaptive FEC Kalamazoo, June 13, 2012 27
    • Torsten Braun: Reliable and Energy-Efficient Communication in Wireless Sensor Networks Implementation of FEC Library > Repetition Code > Hamming Code > Double Error Correction Triple Error Detection (DECTED) > Bose-Chaudhuri-Hocquengham (BCH) Kalamazoo, June 13, 2012 28
    • Torsten Braun: Reliable and Energy-Efficient Communication in Wireless Sensor Networks Adaptive FEC > Stateful Adaptive FEC (SA) — Selection of current code dependent on success of previous transmission (next higher / lower level) — Quick adaptation > Stateful History Adaptive (SHA) — History of last transmissions (here: 5) — For successful/failed transmissions: storage of next lower/higher level — Selection of level with majority in history — Reacts less quickly than SA-FEC Philipp Hurni, Sebastian > Stateful Sender Receiver Adaptive (SSRA) Barthlomé, Torsten Braun: — Consideration of number of corrected bit errors Link-Quality Aware Run-Time Adaptive Forward Error Correction by receiver (to be reported in acknowledgement) Strategies in Wireless Sensor Networks, submitted (63,36) Kalamazoo, June 13, 2012 29
    • Torsten Braun: Reliable and Energy-Efficient Communication in Wireless Sensor Networks Energy Consumption by FEC and ARQ > Additional power consumption by FEC > In case of no FEC, MSB430 node can enter lower power mode with Idefault > Energy for encoding/decoding 32 bytes (30/100 ms): 0.95 mJ > Energy for retransmission Kalamazoo, June 13, 2012 30
    • Torsten Braun: Reliable and Energy-Efficient Communication in Wireless Sensor Networks Wisebed Experiments > Different link characteristics → Deployment of a single FEC scheme would not be most efficient. Kalamazoo, June 13, 2012 31
    • Torsten Braun: Reliable and Energy-Efficient Communication in Wireless Sensor Networks Static vs. Adaptive FEC > Better error correction performance of adaptive FEC schemes than for static ones. > Adaptive FEC advantages — Lower processing and energy costs — Lower bandwidth and lower interference in multi-hop scenarios — Higher packet delivery rate — Adapt automatically to different link characteristics Kalamazoo, June 13, 2012 32
    • TCP Performance Optimizations forWireless Sensor Networks
    • Torsten Braun: Reliable and Energy-Efficient Communication in Wireless Sensor Networks Reasons for Poor TCP Performance in Wireless Multi-Hop Networks > Higher bit error rates and packet loss > Underlying MAC protocols (exponential back-off, hidden / exposed nodes) > TCP end-to-end error and congestion control mechanisms TCP data segment loss TCP acknowledgement loss Kalamazoo, June 13, 2012 34
    • Torsten Braun: Reliable and Energy-Efficient Communication in Wireless Sensor Networks Optimization of TCP in WSNs > Distributed TCP Caching (Dunkels et al., 2004) Adam Dunkels, Thiemo Voigt, and Juan Alonso. Making TCP/IP Viable for Wireless Sensor Networks. 1st European Workshop on Wireless Sensor Networks (EWSN 2004) > TCP Support for Sensor Networks (Braun et al., 2007) Torsten Braun, Thiemo Voigt, Adam Dunkels. RCP Support for Sensor networks. IEEE/IFIP WONS 2007. Kalamazoo, June 13, 2012 35
    • Torsten Braun: Reliable and Energy-Efficient Communication in Wireless Sensor Networks Caching and Congestion Control (cctrl) Module > is aware of all TCP packets forwarded by a node by interception of outbound packets. > allocates buffer for 2 packets per TCP connection (1 for each direction, µIP has max. 1 unacknowledged TCP data segment per connection) Philipp Hurni, Ulrich Bürgi, Markus Anwander, Torsten Braun: TCP Performance Optimizations for Wireless Sensor Networks, 9th European Conference on Wireless Sensor Networks (EWSN), Trento, Italy, February 2012 Kalamazoo, June 13, 2012 36
    • Torsten Braun: Reliable and Energy-Efficient Communication in Wireless Sensor Networks cctrl Functions > Caching of — complete TCP data segments and scheduling of retransmission timer (RTO = 3 ∙ RTTestimated, RTTestimated = estimated RTT between intermediate node and destination) — TCP/IP header for TCP acknowledgements > Local retransmission of TCP data segment (max. 3 attempts), when RTO expires prior to TCP acknowledgement reception (a) > Removal of TCP data segments, if acknowledgement number of TCP acknowledgement > sequence number of cached TCP data segment > For retransmitted TCP data segments, for which a TCP acknowledgement has been received: discard TCP data segment; regenerate TCP acknowledgement (b) Kalamazoo, June 13, 2012 37
    • Torsten Braun: Reliable and Energy-Efficient Communication in Wireless Sensor Networks Channel Activity Monitoring > MAC proxy notifies cctrl upon reception of any packet and stores a timestamp in activity history. > cctrl continuously calculates channel activity level (= # overheard packets by MAC proxy during the last time period RTTestimated) > Observation: — Channel activity level of most nodes = 0 during long idle periods — Long idle periods by – TCP data segment loss at one of the first hops – TCP acknowledgement loss close to its destination (i.e. TCP data segment’s source). > Approach: — Split RTO into: – RTO1 = 3 ∙ RTTestimated ∙ 2/3 – RTO2 = 3 ∙ RTTestimated ∙ 1/3 — When RTO1 expires: early retransmission, if channel activity level = 0; otherwise: retransmission when RTO2 expires. — Triggers early local retransmissions close to destination Kalamazoo, June 13, 2012 38
    • Torsten Braun: Reliable and Energy-Efficient Communication in Wireless Sensor Networks Long Idle Periods Kalamazoo, June 13, 2012 39
    • Torsten Braun: Reliable and Energy-Efficient Communication in Wireless Sensor Networks Spatial Reuse by Multiple TCP Connections Kalamazoo, June 13, 2012 40
    • Torsten Braun: Reliable and Energy-Efficient Communication in Wireless Sensor Networks Testbed Experiments > 7 TelosB nodes in different rooms of a 3 floor building using U Bern’s Wisebed testbed > Receiver node 1 > Sender nodes 2-7 > Experiments with different MAC protocols for 10 minutes, 15 repetitions > 16 bytes payload > 79 bytes per TCP data segment > 63 bytes per TCP acknowledgement > Total: approx. 2500 experiments during > 400 hours Kalamazoo, June 13, 2012 41
    • Torsten Braun: Reliable and Energy-Efficient Communication in Wireless Sensor Networks Overall Comparison of Throughput Kalamazoo, June 13, 2012 42
    • Torsten Braun: Reliable and Energy-Efficient Communication in Wireless Sensor Networks Overall Comparison of Energy Consumption Kalamazoo, June 13, 2012 43
    • Torsten Braun: Reliable and Energy-Efficient Communication in Wireless Sensor Networks Conclusions > Contributions — Design and experimental evaluation of energy-efficient, reliable, and adaptive protocols > Experiences: Development and use of WSN testbed resulted in — More efficient use of hardware resources — Testbed experiments as easy as simulations — Repeatability and larger number of experiments (statistical significance) — Reproducability of experiments and results > Outlook — Integration of wireless mesh nodes into testbed architecture — Mobility support — Multimedia sensor networks — Radio sensor networks Kalamazoo, June 13, 2012 44
    • Torsten Braun: Reliable and Energy-Efficient Communication in Wireless Sensor Networks Thanks for your attention ! > braun@iam.unibe.ch > http://cds.unibe.ch Kalamazoo, June 13, 2012 45