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ECE/MAE 7750: Distributed Control Systems FISP: Focused Independent Study and Presentation

ECE/MAE 7750: Distributed Control Systems FISP: Focused Independent Study and Presentation. SMAC Protocol With Coordinate Sleeping for Ad-hoc Wireless Sensor Networks. Presenter: Abhishek Gupta Dept. of Electrical and Computer Engineering Utah State University Email: abhishek@cc.usu.edu

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ECE/MAE 7750: Distributed Control Systems FISP: Focused Independent Study and Presentation

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  1. ECE/MAE 7750: Distributed Control SystemsFISP: Focused Independent Study and Presentation SMAC Protocol With Coordinate Sleeping for Ad-hoc Wireless Sensor Networks Presenter: Abhishek Gupta Dept. of Electrical and Computer Engineering Utah State University Email: abhishek@cc.usu.edu Date: February 02, 2005

  2. Outline • Introduction to Ad-hoc Wireless Sensor Networks • The problem and existing solutions • Introduction to S-MAC protocol • S-MAC design • Performance • Conclusion

  3. Introduction to Ad-hoc Wireless Sensor Networks • An Ad Hoc wireless sensor network is a network of sensor devices that are deployed in an ad hoc fashion and coordinate for sensing a physical phenomenon. • Each wireless sensing node typically includes • A Sensor • A processor • A radio • A battery

  4. Ad-hoc Wireless Sensor NetworkApplications Applications include • Traffic Surveillance • Military Applications • Fire Detection • Agricultural management • Structure and Earthquake monitoring • Industrial Control • Rescue Operations

  5. Attributes of Ad hoc Wireless Sensor Networks • Extremely power efficient • Batteries die over time • Cost of recharging nodes may exceed the cost of node itself. • Insensitive to change in network topology and node density. • New nodes can be added • Existing nodes can be relocated • Efficient use of bandwidth. • Fairness can be compromised for energy efficiency. • Inter-network data processing • Sending raw data to some end node for processing consume more energy.

  6. Energy Efficiency in Ad hoc Wireless Sensor Networks • Energy efficiency is the primary concern in a wireless sensor networks. • Causes of energy waste • Collisions • Takes place at the receiver • Increases Latency • Overhearing • Happens when the nodes pick up data destined to other nodes • Idle Listening • Listening to traffic that is not sent

  7. Energy Efficiency in Ad hoc Wireless Sensor Networks • Motes, which are used as nodes in wireless sensor networks, work on extremely low energy !!! Source: http://www.intel.com/research/exploratory/motes.htm

  8. MAC ProtocolsExisting Solution • Stands for Medium Access Control. • Determine when and how nodes should access the shared medium. • Two broad categories • Contention based protocols e.g. IEEE 802.11, CSMA etc. • Scheduled based protocols e.g. TDMA, FDMA etc

  9. MAC ProtocolsLimitations of Existing Solution • TDMA (Scheduled protocol) • Each node gets full bandwidth for a pre-allocated time in turns • Major drawback: Not suitable for networks whose node density changes. • FDMA (Scheduled protocol) • Each node gets a permanent share of bandwidth • Major drawback: Poor bandwidth utilization • IEEE 802.11 (Contention based protocol) • Each node contends for the medium as necessary • Major drawback: Wastes a lot of energy in idle listening

  10. SMAC ProtocolIntroduction • Stands for Sensors Medium Access Control • Specifically designed for Ad hoc wireless sensor networks • Primary goal: Energy Efficiency

  11. Latency Fairness Energy SMAC designFeatures Main features of SMAC include • Periodic Listen • Collision Avoidance • Overhearing Avoidance • Message Passing Tradeoffs

  12. Energy Latency SMAC DesignPeriodic Listen and Sleep • Problem: Idle listening consumes significant energy • Solution: Put all the nodes to sleep periodically Turn off radio when sleeping Reduce duty cycle to ~10% Preferable, neighboring nodes follow same schedule

  13. Schedule 1 Schedule 2 SMAC DesignChoosing and Maintaining Schedule • Nodes exchange their schedule by periodically broadcasting SYNC packet • Nodes take following 2 steps to choose their schedule • Listen for SYNC packets for a fixed amount of time • Case 1: No SYNC packets are received • Case 2: SYNC packet is received. • Case 3: Multiple SYNC packets are received. Border nodes with 2 schedule broadcast twice • Broadcast the chosen schedule by sending out SYNC packet.

  14. SMAC DesignListen and Sleep - Maintaining Synchronization • The listen time is divided into two parts: • For sending/receiving SYNC signal. • For sending/receiving Data.

  15. RTS CTS CTS SMAC DesignAdaptive listening • Used to reduces multi-hop latency due to periodic sleep. • Neighboring nodes wake up for a short period of time at the end of each transmission. 2 4 1 3

  16. SMAC DesignOverhearing Avoidance • All immediate neighbors of sender and receiver are put to sleep upon receiving RTS/CTS. • Neighbors do not overhear data packets and following ACKS. • The duration field in the packet indicates how long to sleep.

  17. DATA/ACK DATA/ACK DATA/ACK DATA/ACK DATA Unfairness Contention for medium SMAC designMessage Passing • SMAC reintroduces the concept of Message Passing • Long messages are converted into small fragment and are transmitted in bursts. • Receiver acknowledges each received fragment. Hidden terminal problem solved by ACK C SYNC A B corrupt

  18. SMAC DesignImplementation • To demonstrate the effectiveness of SMAC protocol compared to conventional protocols, they were implemented and tested on Motes. • Operating System used was TinyOS. • Three MAC modules were implemented on Rene Motes • An 802.11 like protocol without sleep • SMAC without periodic sleep • SMAC with period sleep UCB mote with whip Antenna

  19. SMAC DesignImplementation • Tests on a two hop network • Measures total energy overtime to send messages Idle listening rarely happens Periodic sleep for Idle listening The graph shows the mean energy on radios of source nodes

  20. SMAC DesignImplementation • Tests on a ten hop network The graph shows aggregate energy consumption in a 10-hop network

  21. SMAC DesignConclusion • SMAC offers significant energy efficiency over always listening MAC protocols. • SMAC is able to greatly prolong the network life, which is critical for real-world network applications.

  22. References: • Medium Access Control With Coordinated Adaptive Sleeping for Wireless Sensor Networks, by Wei Ye, John Heidemann, and Deborah Estrin (IEEE/ACM TRANSACTIONS ON NETWORKING, VOL. 12, NO. 3, JUNE 2004 ) • Presentation by Wei Ye on MAC Layer Design for Wireless Sensor Networks • Presentation by Ranjith Udayshankar on Medium Access Control With Coordinated Adaptive Sleeping for Wireless Sensor Networks • Figure of motes power spectrum obtained from http://www.intel.com/research/exploratory/motes.htm

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