1. A Power Saving MAC Protocol for Wireless Networks Technical Report July 2002 Eun-Sun Jung Texas A&M University, College Station Nitin H. Vaidya University of Illinois at Urbana-Champaign

2. Richie.Lin2 Outline Introduction Related Work New Power Saving Mechanism (NPSM) Performance Evaluation Conclusion

3. Richie.Lin3 Introduction Battery power in one of the critical resources in wireless networks Battery management Power control Energy-efficient protocols using directional antennas Power saving mode

4. Richie.Lin4 Introduction Power saving mode Awake states Transmit Receive idle Doze states Transition delay ( 250uS ->800uS ) Additional energy consumption when changes state from doe to awake

5. Richie.Lin5 Introduction 802.11 PCF Power saving mechanism DCF Power saving mechanism

6. Richie.Lin6 Introduction Significantly affected by ATIM window size Optimal ATIM window size Network load Beacon interval size

7. Richie.Lin7 Related Work [ 3] B. Chen, K. Jamieson, H. Balakrishnan, and R. Morris, “Span: An Energy-Efficient Coordination Algorithm for Topology Maintenance in Ad Hoc Wireless Networks,” in MOBICOM 2001 Elects coordinators which periodically rotate their roles Coordinators stay awake and forward traffic for active connections Non-coordinators follow the power saving mechanism of IEEE 8012.11 DCF [15] S. Singh, M. Woo, and C. S. Raghavendra, “Power-aware Routing in Mobile Ad Hoc Networks,” in MOBICOM 1998. Using control channel determines when and for how long to power off

8. Richie.Lin8 Related Work [20] Y.-C. Tseng, C.-S. Hsu, and T.-Y. Hsieh, “Power-Saving Proto-cols for IEEE 802.11-Based Multi-Hop Ad Hoc Networks,” in INFOCOM 2002, Multi-hop synchronization of beacon intervals solutions [22] H. Woesner, J.-P. Ebert, M. Schlager, and A. Wolisz, “Power-Saving Mechanisms in Emerging Standards for Wireless LANs: The MAC Level Perspective,” IEEE Personal Communications, 1998. A mechanism to choose the ATIM window size dynamically Allows nodes to power off whenever they finish packet transmission

9. Richie.Lin9 Related Work [23] Y. Xu, J. Heidemann, and D. Estrin, “Geography-informed En-ergy Conservation for Ad Hoc Routing,” in MOBICOM 2001, Uses location information All nodes in the same grid are equivalent in terms of traffic forwarding Guarantees that one node in each grid stays awake in order to forward traffic [24] W. Ye, J. Heidemann, and D. Estrin, “An Energy-Efficient MAC Protocol for Wireless Sensor Networks,” in INFOCOM 2002, Allows nodes to sleep during neighbors’ transmissions

10. Richie.Lin10 Related Work [25] R. Zheng and R. Kravets, “On-demand Power Management for Ad Hoc Network,” Tech. Rep. UIUCDCS- R-2002-2280, Depart-ment of Computer Science, University of Illinois at Urbana-Champaign, 2002. Routing node stay awake reduce end-to-end delay

11. Richie.Lin11 New Power Saving Mechanism (NPSM) Removing the ATIM window In order to reduce control overhead Start of a beacon interval, every node enters an awake state for a specified duration called DATA window Node transmits a packet to a destination it includes the number of pending packets in the packet

12. Richie.Lin12 Proposed Power Saving Mechanism Announcing pending packets T(i) : number of packet transmits for node i R(i) : number of packet receiver for node ii Up(i) : number of packets that neighbor node I needs to transmit or receive R total : sum of R over all neighbors

13. Richie.Lin13 Proposed Power Saving Mechanism Extend Data window Has not finished receiving all the packets Infer the neighbors node i in awake and need to transmit to node I 20ms < DATA window size < 100ms, step 5ms

14. Richie.Lin14 Performance Evaluation Metrics are used to evaluate Aggregate throughput over all flows in the network Total data delivered per unit of energy consumption (K bits delivered per joule) Average packet delay over all flows in the network Simulation model Used ns-2 11 Mbps bit rate, transmission range 250m Transmit 1.65W, Receive 1.4W, Idle 1.15W, Doze 0.045W 800uS as the doze-to-awake transition time

15. Richie.Lin15 Simulation Results One hop : varying the network load

16. Richie.Lin16 Simulation Results One hop : varying the network load

17. Richie.Lin17 Simulation Results One hop : varying packet size

18. Richie.Lin18 Simulation Results Multi-hop : varying the network load

19. Richie.Lin19 Simulation Results Multi-hop : varying the network load

20. Richie.Lin20 Conclusion Removing the ATIM window makes more bandwidth Better aggregate throughput and energy savings as compared to PSM NPSM saves energy at the cost of increasing the packet delay Trade-off between energy savings and packet delay

21. Richie.Lin21 Thank You !!