Presented by Jehn-Ruey Jiang Department of Computer Science and Information Engineering

1. A Hybrid Power-Saving Protocol byDual-Channel and Dual-Transmission-Range Clustering for IEEE 802.11-Based MANETs Presented by Jehn-Ruey Jiang Department of Computer Science and Information Engineering National Central University

2. To Rest, to Go Far!!

3. Outline • IEEE 802.11 MANETs • Power Saving Problem • Hybrid Power Saving Protocols • Simulation Results • Conclusion

4. Outline • IEEE 802.11 MANETs • Power Saving Problem • Hybrid Power Saving Protocols • Simulation Results • Conclusion

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

6. WLAN Market Source:wireless.industrial-networking.com

7. IEEE 802.11 Family(1/2) • 802.11 (1997) • 2 Mbps in the 2.4 GHz band • 802.11b (1999) (WiFi, Wireless Fidelity) • 5.5 and 11 Mbps in the 2.4 GHz band • 802.11a (1999) (WiFi5) • 6 to 54 Mbps in the 5 GHz band • 802.11g (2001) • 54 Mbps in the 2.4 GHz band • 802.11n (2005) (MIMO) • 108 Mbps in the 2.4 and the 5 GHz bands

8. 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

9. Infrastructure vs. Ad-hoc Modes Infrastructure Network Wired Network AP AP AP Multi-hop Ad Hoc Network Ad-Hoc network Ad-Hoc network

10. Ad Hoc Network (1/3) • A collection of wireless mobile hosts forming a temporary network without the aid of established infrastructure or centralized administration • by D. B. Johnson et al. • Also called MANET(Mobile Ad hoc Network) • by Internet Society IETF

11. Ad Hoc Network (2/3) • Single-Hop • Each node is within each other’s transmission range • Fully connected • Multi-Hop • A node reaches another node via a chain of intermediate nodes • Networks may partition and/or merge

12. Ad Hoc Network (3/3) • Application • Battlefields • Disaster Rescue • Spontaneous Meetings • Outdoor Activities

13. Outline • IEEE 802.11 MANETs • Power Saving Problem • Hybrid Power Saving Protocols • Simulation Results • Conclusion

14. Power Saving Problem • Battery is a limited resource for portable devices • Battery technology does not progress fast enough • Power saving becomes a critical issue in MANETs, in which devices are all supported by batteries

15. Solutions to Power Saving Problems • PHY Layer: transmission power control • Huang (ICCCN’01), Ramanathan (INFOCOM’00) • MAC Layer: power mode management • Tseng (INFOCOM’02), Chiasserini (WCNC’00) • Network Layer: power-aware routing • Singh (ICMCN’98), Ryu (ICC’00)

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? No! Yes! B C D A E F

17. Power Mode Management • Doze mode vs. Active mode • Example: • A is sending to B • Does C need to stay awake? No! It can turn off its radio to save energy! B But it should turn on its radio periodiclally for possible data comm. A C

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

19. Our Focus • Among the three solutions: • PHY Layer: transmission power control • MAC Layer: power mode management • Network Layer: power-aware routing

20. IEEE 802.11 PS Mode • An IEEE 802.11 Card is allowed to turn off its radio to be in the PS mode to save energy • PowerConsumption:(ORiNOCO IEEE 802.11b PC Gold Card) Vcc:5V, Speed:11Mbps

21. MAC Layer Power-Saving Protocol • Two types of MAC layer PS protocol for IEEE 802.11-based MANETs • Synchronous (IEEE 802.11 PS Protocol) • Synchronous Beacon Intervals • For sending beacons and ATIM (Ad hoc Traffic Indication Map) • Asynchronous [Tseng et. al. 2002][Jiang et. al. 2003] • Asynchronous Beacon Intervals • For sending beacons and MTIM (Multi-Hop Traffic Indication Map)

22. Beacon: • For a device to notify its existence to others • For devices to synchronize their clocks

23. BeaconFrame Data Frame ACK IEEE 802.11 PS Protocol Target Beacon Transmission Time(TBTT) Beacon Interval Beacon Interval ATIM Window ATIM Window Active mode Power saving Mode Host A No ATIM means no data to send or to receive with each other ATIM Power saving Mode ATIM Window ATIM Window Active mode Host B ACK Clock Synchronized by TSF (Time Synchronization Function)

24. IEEE 802.11 PS Protocol (cont.) • Suitable for Single-hop environment • Advantages • More power efficiency • Low active ratio (less duty cycle) • Drawbacks • Clock synchronization for multi-hop networks is costly and even impossible • Network partitioning • Not Scalable

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

26. D ╳ F Network Partition ╳ E ╳ ╳ Network-Partitioning Example The red ones do not know the existence of the blue ones, not to mention the time when they are awake. The blue ones do not know the existence of the red ones, not to mention the time when they are awake. C A B Host A ATIM window Host B Host C Host D Host E Host F

27. Asynchronous PS Protocols (1/2) • Try to solve the network partitioning problem to achieve • Neighbor discovery • Wakeup prediction • Without synchronizing hosts’ clocks

28. Asynchronous PS Protocols (2/2) • Three existent asynchronous PS protocols • Dominating-Awake-Interval • Periodical-Fully-Awake-Interval • Quorum-Based

29. What is a quorum? • minimum number of people who must be present at a meeting (of a committee, etc) before it can proceed and its decisions, etc can be considered valid-- Oxford Dictionary

31. What is a quorum again? • From Math.quorums:mutually intersecting subsets of a universal set U • E.G.{1, 2}, {2, 3} and {1,3} are quorums under U={1,2,3}

32. … 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 0 1 Beacon interval Numbering Beacon Intervals n consecutive beacon intervals are numbered as 0 to n-1 And they are organized as an n array

33. Quorum Intervals (1/4) Intervals from one row and one column are called Quorum Intervals Example: Quorum intervals arenumbered by 2, 6, 8, 9, 10, 11, 14

34. Quorum Intervals (2/4) Intervals from one row and one column are called Quorum Intervals Example: Quorum intervals arenumbered by 0, 1, 2, 3, 5, 9, 13

35. 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Quorum Intervals (3/4) Any two sets of quorum intervals havetwocommon members For example: The set of quorum intervals {0, 1, 2, 3, 5, 9, 13} and the set of quorum intervals {2, 6, 8, 9, 10, 11, 14} have two common members: 2 and 9

36. Host D 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Host C 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Quorum Intervals (4/4) Host D 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Host C 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 2 overlapping quorum intervals Even when the beacon interval numbers are not aligned (they are rotated), there are always at least two overlapping quorum intervals

37. Structure of Quorum Intervals

38. D F E Networks Merge Properly C A B Host A ATIM window Host B Beacon window Host C Monitor window Host D Host E Host F

39. Quorum Systems Help with the Proof • What is a quorum system?A collection of mutually intersectingsubsets of an universal set U, where each subset is called a quorum.E.G. {{1, 2},{2, 3},{1,3}} is a quorum system underU={1,2,3}, where {1, 2}, {2, 3} and {1,3} are quorums. • Not all quorum systems are applicable to QAPS • Only those quorum systems with the rotation closure property are applicable.

40. Optimal Quorum System (1/2) • Quorum Size Lower Bound for quorum systems satisfying the rotation closure property:k, where k(k-1)+1=n, the cardinality of the universal set,and k-1 is a prime power(k n )

41. Optimal Quorum System (2/2) • Optimal quorum system • FPP quorum system • Near optimal quorum systems • Grid quorum system • Torus quorum system • Cyclic (difference set) quorum system • E-Torus quorum system

42. QAPS: Quorum-based Asynchronous Power Saving Protocols • Advantages • Do not need synchronized clocks • Suitable for multi-hop MANETs • Asynchronous neighbor discovery and wakeup prediction • Drawbacks • Higher active ratio than the synchronous PS protocol • Not suitable for high host density environment

43. Outline • IEEE 802.11 MANETs • Power Saving Problem • Hybrid Power Saving Protocols • Simulation Results • Conclusion

44. HPS Overview • A Hybrid PS protocol • Synchronous – IEEE 802.11 PS protocol • Asynchronous – QAPS • Forming clustering networks • Utilizing the concepts of dual-channel and dual-transmission-range • Taking advantages of two types of PS protocols • To reduce the active ratio • Suitable for multi-hop MANETs

45. Cluster Forming

46. Dual transmission ranges • Cluster head uses • Range RA for inter-cluster transmission • Range RB for intra-cluster transmission F RA E RB E, F: cluster heads

47. Dual channels • Two non-interfering comm. channels are used • Channel A for inter-cluster transmission • Channel B for Intra-cluster transmission F E RA RB Channel A Channel B E, F: cluster heads

48. Two types of beacon frames • Intra-cluster beacon • Send in channel B with transmission range RB • For cluster forming • For clock synchronization • Inter-cluster beacon • Send in channel A with transmission range RA • For neighboring cluster heads discovery • For wakeup prediction

49. Practical Considerations • Dual transmission ranges • Practical for IEEE 802.11 Standard • More power efficiency • Dual channels • Practical for IEEE 802.11 Standard • Non-interfering channels (such as 1, 6, 11) • Inter-cluster and Intra-cluster comm. can take place simultaneously

50. Clustering Who is Boss? • If somebody near me says that he/she is Boss, then I am his/her employee. • If nobody is Boss, then I am Boss. • Boss should keep whistling periodically to summon employees. He/She should relay messages for employees and thus spend more energy. • An employee just keep watching if Boss is there.