O-MAC: A Receiver Centric Power Management Protocol

1. O-MAC: A Receiver CentricPower Management Protocol Hui Cao, *Kenneth W. Parker, Anish Arora The Ohio State University, *The Samraksh Company

2. Outline 1. Receiver centric design 2. Energy efficiency comparison 3. O-MAC protocol design

3. Part I: Receiver Centric Design

4. Dominant Receiver Power Consumption Large portion of energy is consumed in receiver radio One typical surveillance application: Receiver Radio ~2100 J/day Signal processing ~60 J/day Everything else ~8 J/day

5. Rx becomes higher than Tx! with evolution of Berkeley motes Other popular radio chips also have higher Rx power consumption Increasing Rx Power Consumption

6. Receiver Centric vs. Transmitter Centric Transmitter Centric MAC design: • Transmitter implicitly knows receiver will wakeup during transmission • Collision avoidance is transmitter driven (i.e., RTS-CTS, CCA) Receiver Centric MAC design: • Receiver explicitly communicates its wakeup schedule to transmitter • Collision avoidance is receiver driven (i.e., receivers use TDMA) Transmitter Receiver Transmitter Receiver Transmitter Receiver

7. Receiver Efficiency≈ Total Energy Efficiency ≠ Transmitter Efficiency Why Receiver Centric Design? • Historically, MAC design has focused on Transmitter Efficiency • However, dominant cost of receiver radio has implied that • We claim: Receiver Centric approach yields substantially higherReceiver Efficiency Goodput Receiver Efficiency = Receiver Power Consumption Goodput Transmitter Efficiency = Transmitter Power Consumption Goodput Total Energy Efficiency = Transmitter + Receiver Power Consumption

8. Part II:Energy Efficiency Comparison

9. Assumptions and Notations • Traffic model • Uniform random traffic • Notations: • E: energy efficiency Goodput (Msgs Sent + Receive) Total (Msgs Sent + Receive)

10. Theoretical Energy Efficiency • We’ll consider: • Synchronous Blinking (S-MAC, T-MAC) • Long Preamble (B-MAC, WiseMAC) • Asynchronous Wake-up • Random Time-Spreading • Staggered On • Pseudo-randomStaggered On

11. Synchronous Blinking (e.g. S-MAC & T-MAC) • : number of interfering nodes

12. 2) Long Preamble (e.g. B-MAC, WiseMAC) : duty cycle

13. 3) Asynchronous Wakeup : duty cycle

14. 4) Random Time Spreading • In each time slot, each node wakes up randomly • No time sync • Power efficiency: • : number of interfering nodes : duty cycle

15. 5) Staggered On • Only one receiver wakes up in the interference region at one time • Scheduled globally to avoid receiver collision

16. 6)Pseudo-randomStaggered On ris a factor near 1

17. 0.45 0.4 0.35 Staggered On 0.3 Pseudo-random Staggered On Long Preamble 0.25 The energy efficiency Synchronous Blinking Asynchronous Wake-up 0.2 Random Time Spreading 0.15 0.1 0.05 0 10 15 20 25 30 35 40 45 50 The average number of nodes that interfere Energy efficiency comparison

18. Part III: O-MAC Protocol Design

19. O-MAC Protocol Design • Based on: Pseudo-random Staggered On • The Core Protocol • Interfaces • Neighbor list • Send • Receive • Synchronous ACK • Pseudo-random Scheduler

20. O-MAC Analysis and Simulation • Simulation confirms theoretical analysis • Maximal energy efficiency for particular traffic load! • Adaptive duty cycle

21. O-MAC Key Implementation Issues • Time Synchronization • Current technique: • < 10 PPM • Every 2 minutes, to guarantee 1ms accuracy • Cost: 0.001% duty cycle Sender Centric Application Receiver Centric Communication • Adaptive Duty Cycle • A cross layer design issue

22. Conclusion and Future work • Conclusion: • Receiver Centric has substantial impact on power management • Receiver vs. Transmitter Collision Avoidance • OMAC has been implemented and is being integrated for mobile sensor network experiments on Dec.7 at OSU • Future work: • Receiver Centric higher layer protocol (Network, Transport, Application) • Adaptive duty cycle scheme