Tijs van Dam, Koen Langendoen SenSys’03 Ku Dara Network & Security LAB at KAISTĢ Contents Introduction S- MAC drawbacks T- MAC Experiments Conclusionsĭesign to maximize packet throughput, minimize latency and provide fairness Protocol design for wireless sensor networks Focuses on minimizing energy consumption What was the most wasted energy in traditional MAC protocol? Idle listening A node does not know when it will be the receiver of a message from one of its neighbors It must keep its radio in receive mode at all times Ex) sensor application : 1/sec, messages fairly short, transmit(5ms), receive(5ms), 990ms on listening while nothing happens(99%) T-MACĤ S-MAC Idle listening problem solution S-MAC in sensor networkĭuty cycle is involved, each node sleep periodically S-MAC in sensor network Single-frequency contention-based protocol Time is divided into –fairly large-frame (frame: 1sec) Every frame has two parts : active part (200ms) /sleep part (800ms) duty cycle = listen interval / frame length (20%) All messages are packed into the active part Tradeoff Energy efficiency ↑, throughput ↓, latency↑ T-MACĥ Drawbacks of S-MAC Active (Listen) interval – long enough to handle to the highest expected load If message rate is less – energy is still wasted in idle-listening S-MAC’ fixed duty cycle is NOT OPTIMAL T-MACīasic idea To utilize an active and a sleep cycle, similar to S-MAC To introduce an adaptive duty cycle by dynamically ending the active part An active period ends when no activation event has occurred for a time TA Activation event The reception of any data on the radio (RTS, CTS, DATA, ACK) The sensing of communication on the radio (overhearing) Difference in the duty cycle S-MAC - fixed duty cycle T-MAC – Dynamic duty cycle T-MAC
1 An Adaptive Energy-Efficient MAC Protocol for Wireless Sensor Network
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