1 Research Highlights Power-Saving Issues

2 Outline E. S. Jung and N. Vaidya, “ An Energy Efficient MAC Protocol for Wireless LANs ”, INFOCOM E. S. Jung and N. Vaidya, “ An Energy Efficient MAC Protocol for Wireless LANs ”, INFOCOM Eun-Sun Jung and Nitin Vaidya, “ A Power Control MAC Protocol for Ad Hoc Networks, ” ACM International Conference on Mobile Computing and Networking (MobiCom), September Eun-Sun Jung and Nitin Vaidya, “ A Power Control MAC Protocol for Ad Hoc Networks, ” ACM International Conference on Mobile Computing and Networking (MobiCom), September Y.-C. Tseng, C.-S. Hsu, and T.-Y. Hsieh, “ Power-Saving Protocols for IEEE Based Multi-Hop Ad Hoc Networks, ” IEEE INFOCOM, Y.-C. Tseng, C.-S. Hsu, and T.-Y. Hsieh, “ Power-Saving Protocols for IEEE Based Multi-Hop Ad Hoc Networks, ” IEEE INFOCOM, 2002.

3 Research Highlight: ATIM window length adjustment ATIM window length has performance impact on an ad hoc network. ATIM window length has performance impact on an ad hoc network. How to choose a proper size of ATIM window? How to choose a proper size of ATIM window? Ref: E. S. Jung and N. Vaidya, “ An Energy Efficient MAC Protocol for Wireless LANs ”, INFOCOM Ref: E. S. Jung and N. Vaidya, “ An Energy Efficient MAC Protocol for Wireless LANs ”, INFOCOM 2002.

4 Research Highlight: Asynchronous PS for multi-hop MANET Y.-C. Tseng, C.-S. Hsu, and T.-Y. Hsieh, “ Power- Saving Protocols for IEEE Based Multi-Hop Ad Hoc Networks, ” IEEE INFOCOM, Y.-C. Tseng, C.-S. Hsu, and T.-Y. Hsieh, “ Power- Saving Protocols for IEEE Based Multi-Hop Ad Hoc Networks, ” IEEE INFOCOM, Problem statement: Problem statement: –clock drift (asynchronous) –network partitioning Example: Example: Proposed solutions: Proposed solutions: –dominating: over ½ of awake time –periodical: wake up fully from time to time –quorum: from quorum concept in distributed systems

5 Research Highlight: Soft handover by PS mode for soft handover: for soft handover: – only allows hard handover searching for new AP only after a STA loses its previous AP searching for new AP only after a STA loses its previous AP thus, causing long delay (e.g., VoIP services are delay-sensitive) thus, causing long delay (e.g., VoIP services are delay-sensitive) –to support soft handover, a STA must frequently scan new AP ’ s approach: approach: –using PS mode as an excuse to search for neighboring APs (through such as an full frame with PS bit = 1) –the old AP will buffer frames during the PS period.