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Asynchronous Power-Saving Protocols via Quorum Systems for IEEE 802.11 Ad Hoc Networks

Asynchronous Power-Saving Protocols via Quorum Systems for IEEE 802.11 Ad Hoc Networks. Jehn-Ruey Jiang Hsuan-Chuang University. To Rest, to Go Far!. Outline. IEEE 802.11 Overview Power Saving Issues Asynchronous Quorum-based PS Protocols Optimal AQPS Protocols Analysis and Simulation

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Asynchronous Power-Saving Protocols via Quorum Systems for IEEE 802.11 Ad Hoc Networks

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  1. Asynchronous Power-Saving Protocols via Quorum Systems forIEEE 802.11 Ad Hoc Networks Jehn-Ruey Jiang Hsuan-Chuang University

  2. To Rest, to Go Far!

  3. Outline IEEE 802.11 Overview Power Saving Issues Asynchronous Quorum-based PS Protocols Optimal AQPS Protocols Analysis and Simulation Conclusion

  4. Outline IEEE 802.11 Overview Power Saving Issues Asynchronous Quorum-based PS Protocols Optimal AQPS Protocols Analysis and Simulation Conclusion

  5. IEEE 802.11 • Approved by IEEE in 1997 • Extensions approved in 1999 • Standard for Wireless Local Area Networks ( WLAN )

  6. IEEE 802.11 Family(1/2) • 802.11a:6 to 54 Mbps in the 5 GHz band • 802.11b (WiFi, Wireless Fidelity):5.5 and 11 Mbps in the 2.4 GHz band • 802.11g:54 Mbps in the 2.4 GHz band

  7. IEEE 802.11 Family(2/2) • 802.11c: support for 802.11 frames • 802.11d: new support for 802.11 frames • 802.11e: QoS enhancement in MAC • 802.11f: Inter Access Point Protocol • 802.11h: channel selection and power control • 802.11i: security enhancement in MAC • 802.11j: 5 GHz globalization

  8. IEEE 802.11 Market Source: Cahners In-Stat ($ Million)

  9. IEEE 802.11 Components • Station (STA) - Mobile host • Access Point (AP) - Stations are connected to access points. • Basic Service Set (BSS) - Stations and the AP within the same radio coverage form a BSS. • Extended Service Set (ESS) - Several BSSs connected through APs form an ESS.

  10. Infrastructure vs Ad-hoc Modes infrastructure network AP AP wired network AP Multi-hop ad hoc network ad-hoc network ad-hoc network

  11. Ad hoc Networks • Ad hoc: formed, arranged, or done (often temporarily) for a particular purpose only • Mobile Ad Hoc Network (MANET):A collection of wireless mobile hosts forming a temporary network without the aid of established infrastructure or centralized administration

  12. Applications of MANETs • Battlefields • Disaster rescue • Spontaneous meetings • Outdoor activities

  13. Single-Hop vs Multi-Hop • Single-Hop • Each node is within each other’s transmission range • Fully connected • Multi-Hop • A node reaches other nodes via a chain of intermediate nodes • Networks may partition and/or merge

  14. Outline IEEE 802.11 Overview Power Saving Issues Asynchronous Quorum-based PS Protocols Optimal AQPS Protocols Analysis and Simulation Conclusion

  15. Power Saving - Overview • Battery is a limited resource for portable devices • Power saving becoming a very hot topic is wireless communication • Solutions: • PHY: transmission power control • MAC: power mode management • Network Layer: power-aware routing

  16. Transmission Power Control • Tuning transmission energy for higher channel reuse • Example: • A is sending to B (based on IEEE 802.11) • Can (C, D) and (E, F) join? Source: Prof. Tseng

  17. Power Mode Management • doze mode vs. active mode • example: • A is sending to B • Does C need to stay awake? Source: Prof. Tseng

  18. N2 N1 SRC DEST + – + – + – + – + – + – N3 N4 Power-Aware Routing • Routing in an ad hoc network with energy-saving (prolonging network lifetime) in mind • Example: Source: Prof. Tseng

  19. IEEE 802.11 PS Mode(1/2) • PowerConsumption: (ORiNOCO IEEE 802.11b PC Gold Card) Vcc:5V, Speed:11Mbps

  20. IEEE 802.11 PS Mode(2/2) • Environments: • Infrastructure • Ad hoc (infrastructureless) • Single-hop • Multi-hop

  21. PS: Infrastructure (1/3) • Clock synchronization is required (via TSF) • The AP is responsible for generating beacons each of which contains a valid time stamp • If the channel is in use, defer beacon transmission until it is free

  22. PS: Infrastructure (2/3) • A host always notifies AP its mode • A PS host periodically wakes up to listen to beacons • AP keeps a PS host awake by sending”traffic indication map (TIM)”in a beacon for unicast data • AP keeps all PS hosts awake by sending”delivery traffic indication map (DTIM)”in a beacon for broadcast data

  23. PS: Infrastructure (3/3)

  24. ATIM Window ATIM Window power saving state active state ATIM data frame Beacon BTA=2, BTB=5 power saving state ACK ACK Beacon PS : 1-hop Ad hoc Network (1/2) Beacon Interval Beacon Interval Host A Host B Source: Prof. Tseng

  25. Beacon Interval Beacon Interval Beacon Beacon Beacon PS: 1-hop Ad hoc Network (2/2) Target Beacon Transmission Time (TBTT) Beacon Interval Beacon Interval Power Saving Mode ATIM Window Beacon ATIM Data Frame Host A ATIM Data Frame Host B ACK ACK Host C ACK ACK

  26. PS: m-hop Ad hoc Network (1/3) • Problems: • Clock Synchronization is harddue to communication delays and mobility • Network Partitionunsynchronized hosts with different wakeup times may not recognize each other

  27. Clock Drift Example Max. clock drift for IEEE 802.11 TSF (200 DSSS nodes, 11Mbps, aBP=0.1s)

  28. A D C ╳ F Network Partition ╳ B E ╳ ╳ Network-Partitioning Example Host A ATIM window Host B Host C Host D Host E Host F Source: Prof. Tseng

  29. PS: m-hop Ad hoc Network (3/2) • Solution: • Not to synchronize hosts’ clocks • But to achieve • Wakeup prediction • Neighbor discovery

  30. PS: m-hop Ad hoc Network (3/3) • Three asyn. solutions: • Dominating-Awake-Interval • Periodical-Fully-Awake-Interval • Quorum-Based Ref:“Power-Saving Protocols for IEEE 802.11-BasedMulti-Hop Ad Hoc Networks,”Yu-Chee Tseng, Chih-Shun Hsu and Ten-Yueng HsiehInfoCom’2002

  31. Outline IEEE 802.11 Overview Power Saving Issues Asynchronous Quorum-based PS Protocols Optimal AQPS Protocols Analysis and Simulation Conclusion

  32. Quorum-based PS Protocol

  33. Quorum interval

  34. Touchdown • A PS host’s beacon can be heard twice or more for every n consecutive beacon intervals, which in turn solves • Wakeup prediction • Neighbor discovery

  35. Observation • A quorum system may be translated to a power-saving protocol, whose power-consumption is proportional to the quorum size.

  36. Questions • Can any quorum system be translated toan asyn. PS protocol? NO! • Which can be? Those with the Rotation Closure Property!!

  37. Outline IEEE 802.11 Overview Power Saving Issues Asynchronous Quorum-based PS Protocols Optimal AQPS Protocols Analysis and Simulation Conclusion

  38. Contributions • Propose the rotation closure property • Propose the lower bound of the quorum size • Propose a novel quorum systems to be translated to an adaptive PS protocol

  39. What are quorum systems? • Quorum: a subset of universal set U • E.G. q1={1, 2} and q2= {2, 3} are quorums under U={1,2,3} • Quorum system: a collection of mutually intersecting quorums • E.G. {{1, 2},{2, 3},{1,3}} is a quorum system under U={1,2,3}

  40. Rotation Closure Property • For example, • Q1={{0,1},{0,2},{1,2}} under U={0,1,2} • Q2={{0,1},{0,2},{0,3},{1,2,3}} under U={0,1,2,3}   Because {0,1} rotate({0,3},3) =

  41. Examples of quorum systems • Majority quorum system • Tree quorum system • Hierarchical quorum system • Cohorts quorum system • ………    

  42. Optimal Quorum Size • Optimal quorum size:k, where k(k-1)+1=n and k-1 is a prime power (K n)

  43. Optimal Quorum Systems • Near optimal quorum systems • Grid quorum system • Torus quorum system • Cyclic (difference set) quorum system • Optimal quorum system • FPP quorum system

  44. Torus quorum system

  45. Cyclic (difference set) quorum system • Def: A subset D={d1,…,dk} of Zn is called a difference set if for every e0 (mod n), thereexist elements di and djD such that di-dj=e. • {0,1,2,4} is a difference set under Z8 • { {0, 1, 2, 4}, {1, 2, 3, 5}, {2, 3, 4, 6}, {3, 4, 5, 7},{4, 5, 6, 0}, {5, 6, 7, 1}, {6, 7, 0, 2}, {7, 0, 1, 3} }is a cyclic (difference set) quorum system

  46. FPP quorum system • FPP:Finite Projective Plane • Proposed byMaekawa in 1985 • For solving distributed mutual exclusion • Constructed with a hypergraph • Also a Singer difference set quorum system

  47. E-Torus quorum system

  48. Outline IEEE 802.11 Overview Power Saving Issues Asynchronous Quorum-based PS Protocols Optimal AQPS Protocols Analysis and Simulation Conclusion

  49. Analysis (1/3) • Active Ratio:the number of quorum intervals over n,where n is cardinality of the universal set • neighbor sensibility (NS)the worst-case delay for a PS host to detect the existence of anewly approaching PS host in its neighborhood

  50. Analysis (2/3)

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