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Toward In-Band Self-Organization in Energy-Efficient MAC Protocols for Sensor Networks

Toward In-Band Self-Organization in Energy-Efficient MAC Protocols for Sensor Networks. Fan Yu, Tao Wu and Subir Biswas Michigan State University IEEE Transactions on Mobile Computing (TMC) February 2008. Outline. Introduction Related Work ISOMAC – I n-band S elf- O rganization MAC

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Toward In-Band Self-Organization in Energy-Efficient MAC Protocols for Sensor Networks

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  1. Toward In-Band Self-Organization in Energy-Efficient MAC Protocols for Sensor Networks Fan Yu, Tao Wu and Subir Biswas Michigan State University IEEE Transactions on Mobile Computing (TMC) February 2008

  2. Outline • Introduction • Related Work • ISOMAC – In-band Self-Organization MAC • Simulations • Conclusions

  3. Introduction • Wireless sensor networks are emerging enablers for a wide range of application paradigms. • The embedded sensor nodes are often critically constrained by their operating energy availability. • Motivation • Energy-efficient Medium Access Control (MAC) remains a key design challenge.

  4. Introduction • Challenges • For ad hoc deployed sensor networks, centralized infrastructure is not desirable.  Distributed scheme prefers. • Multihop sensor networks with unpredictable delay characteristics make time synchronization particular difficult. Asynchronous scheme prefers. • Goal • To develop a distributedTDMA-style scheduling protocol which does not depend on network time synchronization.

  5. Node 1 Send Sleep Sleep Sleep Sleep Sleep Wakeup Sleep Node 3 Sleep Sleep Send Sleep Sleep Sleep Sleep Wakeup Node 6 Sleep Sleep Sleep Wakeup Sleep Sleep Sleep Sleep Related Work • Zhihui Chen and Ashfaq Khokhar, “Self Organization and Energy Efficient TDMA Mac Protocol by Wake Up for Wireless Sensor Networks,” IEEE SECON, 2004 • TDMA-W • Each node broadcasts it Send slot number which doesn’t overlap in two-hop neighbors. And each node get receiving information in Wakeup slot. • Assumption • The Send slot number is the same as node’s id. • Nodes 1,4 and 6 wakeup at slot 7. • Nodes 2,3 and 7 wakeup at slot 8. Listen Shortcoming – Time synchronization & Must turn on at Wakeup slot even if no data transmission Chanel activities

  6. Time τ Interrupt sub-slot A Header-only Tx Header Data ISOMAC • ISOMAC includes • Asynchronous ISOMAC (ISOMAC-A) • Synchronous ISOMAC (ISOMAC-S) • Frame structure Header=data-present bit + Bitmap Vector

  7. D B E Time Timing constraint A B Tx-Slot D E Timing Constraint • Time Constraint • Each node chooses its transmission slot that does not overlap one-hop neighbor’s. • A and B, B and D, D and E are 1-hop neighbors separately. A τ

  8. τ A B Tx-Slot D Timing Constraint • A and B, B and D are 1-hop neighbors separately. A D B Time

  9. Bitmap Vector All Tx-slots allocated to P’s 1-hop neighbors. τ P’s Frame P’s Bitmap Vector (Length B=4) 1 0 1 1 Bitmap constraint Slot selected by the join node must be in its 1-hop neighbor Bitmap Vector.

  10. New joined C TDE<Bτ 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 1 0 1 1 0 Example • Node C joins. • The adjacent nodes are one-hop neighbors. A D B E 1 1 1 1 1 Length B=4

  11. State Machine Listen (Awake) ‘W’ frames are not over New node join Choose frame boundary points ‘W’ frames are over Choose a slot and Interrupt neighbors Timing constraint Bitmap constraint ‘W’ frames are over AND both the constraints are satisfied ‘W’ frames are not over All constraints are satisfied Stable (Sleep schedule) Evaluate (Awake) Interrupted by a Neighbor Bitmap constraints is not satisfied for W consecutive frames OR A collision is detected during a skipped slot ‘W’ frames are over AND at least one of the constraints is not satisfied Choose a slot and Interrupt neighbors Choose a slot and Interrupt neighbors

  12. Example • Node C joins. • Nodes A and B, D and E are one-hop neighbor A D B E TBD>Bτ Middle time of TBD A D B C E move move TCD>Bτ Middle time of TCE TCD<Bτ

  13. All Theader of node C’s neighbors. Awake state Sleep state Sleep-Wake Schedule A D B C E C’s Frame C’s Bitmap Vector (Length B=4) 1 0 1 1 Each frame for node C

  14. ISOMAC-S A D B C E C’s Frame C’s Bitmap Vector (Length B=4) 1 0 0 1

  15. Model for Energy Consumption Tframe=Fτ=1/ =100*0.005=1/2 τ All Theader of node C’s 1-hop neighbors. C’s Bitmap Vector (Length B=4) (Length B=24) 1 0 0 1 Each node at most transmits one data per frame.

  16. Simulation • Simulator: C-based simulator • Parameters The lower the frame occupancy, the better the spatial reuse.

  17. Conclusions • Present a self-organizing MAC protocol for distributed sensor networks. • ISOMAC can work without network time synchronization. • There is no contention-based operation in the protocol, it is virtually collision-free at the steady state.

  18. Thank you~

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