SESAM: A Semi -Synchronous, Energy Savvy, Application-Aware MAC

1. Networking Group University of Trento http://networking.disi.unitn.it SESAM: A Semi -Synchronous, Energy Savvy, Application-Aware MAC Renato Lo Cigno, Matteo Nardelli DISI, University of Trento Trento, Italy Michael Welzl Institute of Computer Science, University of Innsbruck Innsbruck, Austria

2. Outline • TRITon Project • Energy consumption • Mac Protocol in WSN • SESAM • Future work • Conclusion

3. TRITon is a research and innovation project funded by the project members and the Autonomous Province of Trento (Provincia Autonoma di Trento, PAT) aimed at advancing the state of the art in the management of road tunnels, specifically to improve safety and reduce energy costs. An example application, central in TRITon, is adaptive lighting. In current deployments, the light intensity inside the tunnel is typically regulated based on design parameters and the current date and time, and regardless of the actual environmental conditions. Web Site: http://triton.disi.unitn.it/

4. In TRITon, the light intensity inside the tunnel will instead be regulated through a wireless sensor network (WSN). To bring state-of-the-art research and technology like WSN into road tunnel management, the traditional lab-centered research is not sufficient. Indeed, TRITon will transfer its results in real test-sites, four operational tunnels on road SS 45bis near Trento. This will provide not only the ultimate test for the project outcomes, but also a direct and measurable benefit to the local population.

5. Outline • TRITon Project • Energy consumption • Mac Protocol in WSN • SESAM • Future work • Conclusion

6. 600 500 400 300 200 100 0 2 4 6 8 10 12 14 16 18 20 Energy consumption Energy efficiency is one of the primary concern in a wireless sensor network expecially if the sensors are located in unfriendly environment like a road tunnel In Table we report the typical consumption value of a WSN node Total energy consumption per node per day Bench-MAC 0.2 pck/min Bench-MAC 1.0 pck/min Bench-MAC 5.0 pck/min Graph rappresent the energy consumption with different transmission rate Energy [J] No. of stations

7. Energy consumption Energy consumption per day for each function; 1 pck/min 100 Bench-MAC Tx Bench-MAC Rx Bench-MAC Sense 80 60 Energy [J] 40 20 0 2 4 6 8 10 12 14 16 18 20 No. of stations

8. Energy consumption

9. Outline • TRITon Project • Energy consumption • Mac Protocol in WSN • SESAM • Future work

10. Mac Protocol An extensive amount of work has been done on energy conserving MAC protocols. Existing approaches can be categorized as synchronous and asynchronous, although there are some hybrids. • Synchronous: SMAC • PROS • periodic listening; • collision avoidance; • overhearing avoidance. • CONS • Nighbors synchronization • Sleep and listen period is predefined and constant • Complex implementation • Asynchronous: BMAC • PROS • Low Power Listening (LPL) • Scalability • CONS • preamble is longer than sleep period; • overhearing.

11. Outline • TRITon Project • Energy consumption • Mac Protocol in WSN • SESAM • Future work • Conclusion

12. SESAM SESAM is a distributed MAC protocol, which, making use of application level information to predict future transmission instants between nodes. Our goal is: • Useless (re)-trasmissions; • receiving packets which are not for the node; • sensing the channel without need. Constraints are: • No global coordination, but only pairwise (i,j) implicit signaling; • Self-bootstrapping properties for new nodes entering the system and for the activation of a new traffic relation.

13. SESAM The system is based on low-level real time MAC functions able to do CSMA and generate acknowledgments. Elementary coordination for a single relation:

14. SESAM Housekeeping periods:

15. Result We compared SESAM with two version of a B-MAC like protocol. For all protocol we consider acknowelged transmission and absence of collision avoidance procedures BenchMAC-0: Upon plain CDMA we insert a low power listening (LPL) functionality which enables nodes to sleep most of the time, and wake up periodically to sample the channel status; BenchMac-1: This is the 1-persistant version of the protocol. The different with the BenchMAC-0 are: if the channel is sensed busy the node wait until the trasmission ends and immediatly transmits the packet and all other nodes must keep sensing the channel after the end of a packet trasmission.

16. 600 500 400 300 200 100 0 2 4 6 8 10 12 14 16 18 20 Result Total energy consumption per node per day SESAM BanchMAC 1-P BanchMAC 0-P rate: 2pck/min rate: 1pck/min rate: 0,5pck/min Energy [J] No. of Station

17. Result Packet Lost for 10 station 100 τlp = 500ms 80 60 BanchMAC 0-P BanchMAC 1-P % Packet lost SESAM τlp = 50ms 40 20 0 10 20 30 60 90 120 150 180 210 240 Packet/min

18. Outline • TRITon Project • Energy consumption • Mac Protocol in WSN • SESAM • Future work • Conclusion

19. Multi-housekeeping domain The most critical working conditions for a CSMA base WSN are with a wide area coverage using the same frequency channel

20. Multi-housekeeping domain - bootstrapping Power on Packet format: Sensing channel NEW HK = (ID node, HK domain, τ, NEW) ACK HK = (ID node, ID node sender, HK, τ, ACK) Y rx msg? Send msg. ACK to HK N end sense? N Y Send msg. NEW HK Syncro. to one or multi HK

21. Outline • TRITon Project • Energy consumption • Mac Protocol in WSN • SESAM • Future work • Conclusion

22. Conclusion