lec19_rtwlcom - Real-time Communications over Wireless...

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1 Real-time Communications over Wireless Sensor Networks Instructor: Chang-Gun Lee Forest Monitoring Sensor Networks •Periodic monitoring of forest •Fast delivery of emergency event
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2 Rescue Supporting Sensor Networks Periodic messages Æ message delivery meeting deadlines Aperiodic messages Æ message delivery ASAP Wireless Sensor Networks • Delivering sensory data to the sink in time is important • Most existing wireless protocols make the underlying assumption that the network traffic is intrinsically random and work in a contention-based way – No-deterministic guarantee of message delivery
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3 CSMA/CA MAC Protocol (802.11) Problems 1. Random arbitration: collisions Æ waste of channel 2. No overload prevention: Miss all deadlines Can Real-Time Techniques solve the problems? I-EDF • Motivation: Can we leverage on the “Periodic” nature of sensor messages? – Collision-free deterministic MAC protocol •Id e a s – Cellular Architecture – Implicit EDF for collision free scheduling – Frame reclaiming of unused reserved slots for serving Aperiodic messages ASAP
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4 Network Architecture Cell structure: 7 channels messages are broadcasted inside the cell a router node at cell center router Intra-cell broadcast • Medium Access for intra-cell communication
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This note was uploaded on 07/02/2008 for the course COMPUTER S 664 taught by Professor Leechangkyu during the Spring '08 term at Korea University.

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lec19_rtwlcom - Real-time Communications over Wireless...

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