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Energy-Efficient, Application-Aware Medium Access for Sensor Networks

Energy-Efficient, Application-Aware Medium Access for Sensor Networks. Venkatesh Rajenfran, J. J. Garcia-Luna-Aceves, and Katia Obraczka Computer Engineering Department University of California at Santa Cruz The IEEE International Conference on Mobile Ad-hoc and Sensor Systems (MASS 2005).

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Energy-Efficient, Application-Aware Medium Access for Sensor Networks

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  1. Energy-Efficient, Application-Aware Medium Access for Sensor Networks Venkatesh Rajenfran, J. J. Garcia-Luna-Aceves, and Katia Obraczka Computer Engineering Department University of California at Santa Cruz The IEEE International Conference on Mobile Ad-hoc and Sensor Systems (MASS 2005) Wang, Sheng-Shih September 29, 2005

  2. Outline • Introduction • FLow-Aware Medium Access (FLAMA) • Simulation • Test-bed Experiment • Conclusions

  3. Introduction --- MAC protocols for WSNs • Main goal • Energy efficiency • Category • Contention-based • S-MAC, T-MAC, BMAC, DSMAC, WiseMAC, … • Collision increases with the traffic load • Degrade channel utilization and waste energy • Schedule-based • TRAMA, LMAC, E-MAC, … • Requirement of time synchronization • Longer delay

  4. FLAMA --- Overview • Main goal • Energy efficiency • Features • Data gathering application • Collision-free • Low transmission delay

  5. FLAMA --- Time Organization … Schedule access period (time-slotted channel access) Random access period (contention-based channel access) • neighbor discovery • time synchronization • traffic information exchange • data transmission

  6. Query dissemination FLAMA --- Application sink

  7. FLAMA --- Application (cont’d) sink Forwarding Tree Formation  Each node knows the incoming and outgoing flow

  8. FLAMA --- Flow Model c, d, and e respectively denote the fractions of the flows that are forwarded C Fc D Fd B Fb Fe E A Node weights are directly proportional to the outgoing flow rate

  9. FLAMA --- Random Access Period • Main tasks • Time synchronization • Data forwarding tree formation • Traffic flow information exchange and weight computation • Two-hop neighborhood information and corresponding node weight exchange

  10. FLAMA --- Random Access Period • Length • Based on the time required to complete synchronization and tree formation • SYNC_INTERVAL Random access period … SYNC_INTERVAL

  11. FLAMA --- Time Synchronization • The sink initiates the time synchronization • A node synchronizes with its parent receiver clock drift sender T1 SYNC T2 = T1 +  +  T2 T3 SYNC_REQ T4 propagation delay T4 = T3 -  +  SYNC Calculate  = (T2 – T1 + T3 – T4)/2

  12. FLAMA --- Scheduled-Access Period • Goal • Collision-free transmission scheduling • Solution • Distributed election algorithm • Decide the state of each node at every slot • Priority n: node id t: slot id C: constant multiplier

  13. FLAMA --- Distributed Election Algorithm Calculate my priority. if((I have the highest two-hop priority) AND (I have data to send)) thenTransmit the data.elseif(the node with the highest one-hop priority is my child)then Keep in the receivedmode.endif Go to sleep.end if C Tx 25 D Sl 5 B Rx 10 A Tx 20

  14. Simulation Setup • Simulation platform: Qualnet • Physical layer model: Mica2 motes’ Chipcon CC1000 • Number of nodes: 16 • Grid topology: Node distance=75m • Radio data rate: 19.2 Kbps • Radio range: 300 feet  90m • Simulation time: 2000 secs • Data packet size: 128 bytes

  15. S-MAC Duty cycle=10% Adaptive listening is allowed Contention window for synchronization packets: 15 slots Contention window for data packets: 31 slots Topology for S-MAC and TRAMA Comparison

  16. Simulation Results --- Average Delivery Ratio FLAMA • FLAMA/TRAMA vs. S-MAC • Collision • Contention TRAMA • FLAMA vs. TRAMA • Less overhead (no schedule packets) S-MAC

  17. Simulation Results --- Energy Saving FLAMA • FLAMA vs. TRAMA • Less overhead (no schedule packets) • S-MAC • Fixed duty cycle S-MAC TRAMA

  18. Simulation Results --- Average Queuing Delay • TRAMA vs. others • Schedule announcement • Random schedule TRAMA FLAMA S-MAC

  19. Test-Bed Experiments --- Setup • Platform: TinyOS for Mica2 motes • No MAC buffer for frame queuing • All sensors are directed to the sink • Data payload: 128 bytes • S-MAC duty cycle: 10%

  20. Test-Bed Experiments --- Results • average delivery ratio RTS/CTS failure • percentage sleep time • average drops • No buffer • Collision

  21. Conclusions • FLAMA: An energy-efficient, schedule-based, MAC protocol • Simple • Application-aware (data gathering) • Collision-free • Outperform TRAMA and S-MAC in terms of reliability and energy saving

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