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Energy-Efficient, Collision-Free Medium Access Control for Wireless Sensor Networks

Energy-Efficient, Collision-Free Medium Access Control for Wireless Sensor Networks. Venkatesh Rajendran , Katia Obraczka , J.J. Garcia-Luna- Aceves Wireless Networks 2006 JY Hong 2008. 10. 30. Contents. Introduction Related Works TRAMA Protocol Overview Neighbor Protocol

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Energy-Efficient, Collision-Free Medium Access Control for Wireless Sensor Networks

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  1. Energy-Efficient, Collision-Free Medium Access Control for Wireless Sensor Networks VenkateshRajendran, KatiaObraczka, J.J. Garcia-Luna-Aceves Wireless Networks 2006 JY Hong 2008. 10. 30

  2. Contents • Introduction • Related Works • TRAMA • Protocol Overview • Neighbor Protocol • Schedule Exchange Protocol • Adaptive Election Algorithm • Simulation Results • Conclusion TRAMA

  3. Introduction • Wireless Sensor Network (WSN) • Large ensembles of interconnected nodes • Self-organize into a multi-hop wireless network • The scheduling of transmissions among nodes is major challenge • Prolongs the battery life of each node • Self adaptive to changes in traffic, node state, connectivity TRAMA

  4. Related Works - 1 • Research Categories of MAC • Contention-based • DCF 802.11b (Distributed Coordination Function) • PAMAS (Power Aware Multi Access Protocol with Signaling for ad hoc networks) • S-MAC (Sensor MAC) • Schedule-based, Contention-free • TDMA, FDMA, CDMA • NAMA (Node Activation Multiple Access) TRAMA

  5. Related Works - 2 • S-MAC : Basic Mechanism TRAMA

  6. TRafficAdaptive Multiple Access • TRAMA Characteristics • Energy-Efficient • No collision, No idle listening, No idle sender • Schedule-based • Fair • Transmitter-Election Algorithm • Identify of nodes one and two hop away • Traffic information • Adaptive scheduling TRAMA

  7. Protocol Overview • Three components of TRAMA • Neighbor Protocol (NP) • Gather 2-hop neighborhood information • Schedule Exchange Protocol (SEP) • Gather 1-hop traffic information for Scheduling • Adaptive Election Algorithm (AEA) • Select transmitters TRAMA

  8. Protocol Overview • Access mode • Random Access • Node can join the network • All nodes must be in transmit or receive state  Collision • Significant role in energy consumption • Scheduled Access • Collision-free data exchange and schedule propagation Time slot Organization TRAMA

  9. NP • NP • Gather neighborhood information by exchanging small signaling packets in random access period TRAMA

  10. SEP - 1 • Transmission slots • Collision-free data exchange and schedule propagation • SEP • Traffic-based information (Schedules) with neighbors • Traffic coming from a node • The set of receiver for the traffic originating at the node • A node has to announce its schedule using SEP before starting actual transmissions TRAMA

  11. SEP - 2 • Schedule packet format TRAMA

  12. SEP - 3 Schedule packet of node u (if winning slot are 2, 10, 20, 30, 35, 50, 58, 60) • Example u 14 7 2 7 14 15 2 7 14 15 2 7 14 15 2 7 14 15 …….. 2 30 2 10 20 15 Changeover Slot Schedule packet of node 14 (if winning slot are 5, 15, 38, 42) 2 7 14 15 60 u u u u 15 38 5 42 TRAMA

  13. AEA - 1 • Original NCR algorithm • Contending set • All nodes that are in two-hop neighborhood • No sleep state, not adaptive with traffic • TRAMA’s AEA • Possible state of a node • TX(Transmit), RX(Receive), SL(Sleep) TRAMA

  14. AEA - 2 • U is a TX state • Highest priority among its contending set • U has data to send • U is a RX state • Intended receiver of the current transmitter • By consulting the schedule sent out by the selected transmitter • U is a SL state • No transmitter, No intended receiver • Each node executes AEA to decide its current state • Current node priorities in two-hop neighborhood • Based on the announced schedules form one-hop neighbors TRAMA

  15. AEA - 3 • When a node becomes an Absolute Winner for a particular timeslot and has announced a non-zero bitmap for this slot, it know that no other node in its two-hop neighborhood will be transmitting in this slot Absolute Winner Intended Receiver TRAMA

  16. AEA - 4 • To avoid wasting slots when the Winner has no data to send • Possible Transmitter Set in the one-hop neighborhood • Highest priority in two-hop neighbor  No collision • PTX(u) Absolute Winner TRAMA

  17. Simulation Parameters • Simulation platform • QUALNET • 500m X 500m area • 50 nodes are uniformly distributed • 6 one-hop neighbors on average • 17 two-hop neighbors on average • Node traffic • Statistically generated based on a exponentially distributed inter-arrival time TRAMA

  18. Simulation Results - 1 Percentage received TRAMA

  19. Simulation Results - 2 Average Delay TRAMA

  20. Simulation Results - 3 Percentage Sleep time TRAMA

  21. Conclusion • TRAMA achieves • Energy-savings comparable to S-MAC • Delivery guarantees comparable to NAMA • TRAMA Limitations • Complex election algorithm and data structure • Overhead due to explicit schedule propagation • Higher Queueingdelay  Long delay • TRAMA has higher delay • It Suited for • Not delay sensitive • High delivery guarantees • Energy efficiency WSAN : Research Challenges

  22. Questions or Comments WSAN : Research Challenges

  23. Appendix - Alternate Winner Absolute Winner Alternate Winner TRAMA

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