1. A COOPERATIVE LOW POWER MAC PROTOCOL FOR WIRELESS SENSOR NETWORKS Ahmed Ben Nacef, Sidi-Mohamed Senoucik, Yacine Ghamri- Doudane and Andr´e-Luc Beylot IEEE ICC 2011 Speaker : Chuan-Heng, Chi

2. Outline Introduction Related works Motivation Goals CL-MAC CL-MAC(P) CL-MAC(R) Simulation Conclusion

3. Introduction WSNs are composed of small and cheap sensors that can sense, compute and communicate

4. Introduction How to design a MAC protocol Reduce energy consumption with LPL Improve network throughputs with cooperative communication

5. Related works B-MAC Low Power Listening (LPL) Sender Receiver Long Preamble awake sleep DATA Target address in data header S R others Receive DATA

6. Related works X-MAC Sender Receiver awake sleep DATA Receive DATA S R PR R wake up A A Short preambles with target address information

7. Motivation Unnecessary energy waste Bad channel conditions and packet retransmission Sender Receiver DATA Receive DATA PR R wake up A A

8. Goals This proposed protocol combine the X-MAC and cooperative communication Reduce the energy consumption Improve the radio resource usage

9. CL-MAC A Cooperative LPL MAC Protocol Proactive low power cooperative [CL-MAC(P)] Reactive low power cooperative [CL-MAC(R)]

10. CL-MAC(P) Source Destination Wake-up N1 (selected relay) N2 RDV PR packets: destination address and RDV BRS: Begin Relay Selection R-R: Relay reply R-A: Relay ACK BRS R-R R-A DATA PR ACK S D N1 N2 awake sleep Preamble packets

11. CL-MAC(P) ACK DATA S D N1 N2 Source Destination Wake-up N1 (selected relay) N2 RDV PR packets: destination address and RDV BRS: Begin Relay Selection R-R: Relay reply R-A: Relay ACK BRS R-R R-A DATA PR More than one source awake sleep

12. CL-MAC(P) Preamble collision avoidance Source 1 Source 2 Wake-up Inter-preamble RandomBack-off Preamble heard  delay the transmission PR S1 S2 awake sleep

13. CL-MAC(P) Relay selection – The potential relay deduces the state of the channel to the destination from the last received packets and read its own residual energy N1 N2 Destination Begin 20 10 0.05 units R-R R-A 0.1 units CSI: channel state information RE: residual energy S D N1 N2 RDV awake sleep

14. CL-MAC(R) Source Destination N1 (selected relay) N2 PR packets: destination address and RDV DATA ACK Wake-up PR S D N1 N2 RDV awake sleep

15. CL-MAC(R) Source Destination N1 (selected relay) N2 PR packets: destination address and RDV RFR: Request-For-Relay DATA ACK DATA RFR S D N1 N2 Wake-up PR RDV awake sleep

16. Simulation Simulation environment Opnet simulator Sleep period : 0.09s Wake up period : 0.01s Interpreamble length : 0.005s Sink : 1 Source : varying from 1to 5 Potential relays : varying from 0 to 4 Each source node sends a periodic traffic : 1 packet/s The size of data packet : 127bytes The size of BRS,ACK,PR,R-R,RFR and R-ACK : 2020bytes The current draws of the radios are : 17.4mA for transmission, 19.7mA for reception and 10 -3 mA when the node is sleep mode

17. Simulation

21. Conclusion The proposed protocol and its variants combine Low Power Listening and cooperative communication techniques enhance the channel use reduce the energy consumption