1. A Hybrid Power-Saving Protocol by Dual-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. 2/74 To Rest, to Go Far!!

3. 3/74 Outline  IEEE 802.11 MANETs  Power Saving Problem  Hybrid Power Saving Protocols  Simulation Results  Conclusion

4. 4/74 Outline  IEEE 802.11 MANETs  Power Saving Problem  Hybrid Power Saving Protocols  Simulation Results  Conclusion

5. 5/74 IEEE 802.11 Overview  Approved by IEEE in 1997  Extensions approved in 1999 (High Rate)  Standard for Wireless Local Area Networks (WLAN)

6. 6/74 WLAN Market Source: wireless.industrial-networking.comwireless.industrial-networking.com

7. 7/74 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. 8/74 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. 9/74 Infrastructure vs. Ad-hoc Modes Infrastructure Network Ad-Hoc network AP Wired Network Ad-Hoc network Multi-hop Ad Hoc Network

10. 10/74 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. 11/74 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. 12/74 Ad Hoc Network (3/3)  Application Battlefields Disaster Rescue Spontaneous Meetings Outdoor Activities

13. 13/74 Outline  IEEE 802.11 MANETs  Power Saving Problem  Hybrid Power Saving Protocols  Simulation Results  Conclusion

14. 14/74 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. 15/74 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. 16/74 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? A B C D F E No!Yes!

17. 17/74 Power Mode Management  Doze mode vs. Active mode  Example: A is sending to B Does C need to stay awake? A B C No! It can turn off its radio to save energy! But it should turn on its radio periodiclally for possible data comm.

18. 18/74 Power-Aware Routing  Routing in an ad hoc network with energy- saving (prolonging network lifetime) in mind  Example: +–+– +–+– +–+– +–+– +–+– +–+– SRC N1 N2 DES T N4 N3 Better!!

19. 19/74 Our Focus  Among the three solutions: PHY Layer: transmission power control MAC Layer: power mode management Network Layer: power-aware routing

20. 20/74 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  Power Consumption: (ORiNOCO IEEE 802.11b PC Gold Card) Vcc:5V, Speed:11Mbps

21. 21/74 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. 22/74 Beacon: 1.For a device to notify its existence to others 2.For devices to synchronize their clocks

23. 23/74 IEEE 802.11 PS Protocol Beacon Interval Host A Host B ATIM Window Beacon Frame Target Beacon Transmission Time(TBTT) No ATIM means no data to send or to receive with each other ATIM Window Clock Synchronized by TSF (Time Synchronization Function) ATIM Window ATIM ACK Data Frame ACK Active mode Power saving Mode

24. 24/74 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. 25/74 Clock Drift Example Max. clock drift for IEEE 802.11 TSF (200 DSSS nodes, 11Mbps, aBP=0.1s) 200  s Maximum Tolerance

26. 26/74 Network-Partitioning Example Host A Host B A B C DE F Host C Host D Host E Host F ╳ ╳ ATIM window ╳ ╳ Network Partition The blue ones do not know the existence of the red ones, not to mention the time when they are awake. The red ones do not know the existence of the blue ones, not to mention the time when they are awake.

27. 27/74 Asynchronous PS Protocols (1/2)  Try to solve the network partitioning problem to achieve Neighbor discovery Wakeup prediction  Without synchronizing hosts’ clocks

28. 28/74 Asynchronous PS Protocols (2/2)  Three existent asynchronous PS protocols Dominating-Awake-Interval Periodical-Fully-Awake-Interval Quorum-Based

29. 29/74 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

30. 30/74

31. 31/74 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. 32/74 Numbering Beacon Intervals 0123 4567 891011 12131415 And they are organized as a  n   n array n consecutive beacon intervals are numbered as 0 to n-1 101514131211109876543210 … Beacon interval

33. 33/74 Quorum Intervals (1/4) Intervals from one row and one column are called Quorum Intervals 0123 4567 891011 12131415 Example: Quorum intervals are numbered by 2, 6, 8, 9, 10, 11, 14

34. 34/74 Quorum Intervals (2/4) Intervals from one row and one column are called Quorum Intervals 0123 4567 891011 12131415 Example: Quorum intervals are numbered by 0, 1, 2, 3, 5, 9, 13

35. 35/74 Quorum Intervals (3/4) Any two sets of quorum intervals have two common 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 15141312 111098 7654 3210

36. 36/74 Quorum Intervals (4/4) 1514131211109876543210 2151413121110987654310 2 overlapping quorum intervals Host D Host C 2151413121110987654310 Host D 1514131211109876543210 Host C Even when the beacon interval numbers are not aligned (they are rotated), there are always at least two overlapping quorum intervals

37. 37/74 Structure of Quorum Intervals

38. 38/74 Networks Merge Properly Host A Host B A B C DE F Host C Host D Host E Host F ATIM window Beacon window Monitor window

39. 39/74 Quorum Systems Help with the Proof  What is a quorum system? A collection of mutually intersecting subsets of an universal set U, where each subset is called a quorum. E.G. {{1, 2},{2, 3},{1,3}} is a quorum system under U={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. 40/74 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. 41/74 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. 42/74 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. 43/74 Outline  IEEE 802.11 MANETs  Power Saving Problem  Hybrid Power Saving Protocols  Simulation Results  Conclusion

44. 44/74 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. 45/74 Cluster Forming

46. 46/74 Dual transmission ranges  Cluster head uses Range R A for inter-cluster transmission Range R B for intra-cluster transmission E F RARA RBRB E, F: cluster heads

47. 47/74 Dual channels  Two non-interfering comm. channels are used Channel A for inter-cluster transmission Channel B for Intra-cluster transmission E F RARA RBRB E, F: cluster heads Channel A Channel B

48. 48/74 Two types of beacon frames  Intra-cluster beacon Send in channel B with transmission range R B For cluster forming For clock synchronization  Inter-cluster beacon Send in channel A with transmission range R A For neighboring cluster heads discovery For wakeup prediction

49. 49/74 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. 50/74 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.

51. 51/74 State Transition Listening State Cluster Member State Cluster Head State Do not receive intra-cluster beacon in channel B over ( q +1 beacon intervals + a random backoff time) A host enters the network initially Receive an intra-cluster beacon in channel B from the cluster head Do not receive intra-cluster beacon in channel B from cluster head over q+1 beacon intervals Broadcast intra- cluster beacon every non-quorum interval Receive an intra-cluster beacon in channel B during ( q +1 beacon intervals + a random backoff time) Dismissal mechanism is invoked

52. 52/74 xy RBRB R A v.s. R B One extreme case for infinite host density: R A = R B +

53. 53/74 x y RBRB RBRB R A v.s. R B One extreme case for infinite host density: R A = 2R B -

54. 54/74 xy RBRB RBRB RBRB z R A v.s. R B

55. 55/74 Structure of Beacon Intervals BMBMB’M’ Active period Active period in channel A quorum Intervalnon-quorum Interval B B’M’ Cluster Head Cluster members M B’M’ ： Beacon window and MTIM window in channel A ： Beacon window and MTIM window in channel B ： Monitor mode in channel A ： PS mode Active period in channel B quorum Interval non-quorum Interval Active period in channel B

56. 56/74 Dismissal Mechanism (1/2)  To keep the fraction of cluster heads ASAP when network topology changes  To balance the load of cluster heads  But how? ： Cluster heads High priority Dismissal (back to listening state) Low priority Dismissal Mechanism is invoked To detect if hosts are moving too close. To take service time and residual engergy into consideration.

57. 57/74  Distance Default Dismissal Range = 1/5 R B By RSSI estimation  Priority (exchanged in inter-cluster beacons) Cluster head service time Short service time Low priority Remaining battery energy High remaining battery energy Low priority Cluster head ID Small cluster head ID Low priority Dismissal Mechanism (2/2)

58. 58/74 Cluster Forming (1/2) 100 hosts 33 cluster heads 67 cluster members RBRB

59. 59/74 Cluster Forming (2/2) 500 hosts 45 cluster heads 455 cluster members RBRB

60. 60/74 Routing (1/5)  Based on AODV RREQ (Route request) ONLY rebroadcast by cluster heads Intra-RREQ ： within a cluster using channel B Inter-RREQ ： between cluster heads using channel A RREP (Route reply) Intra-RREP ： within a cluster using channel B Inter-RREP ： between cluster heads using channel A

61. 61/74 1.If the source host is a member, it undergoes MTIM-ACK-RREQ-RREQ message exchange with the cluster head using channel B with transmission range R B. 2.If the cluster head receives no RREP in the same beacon interval, it will rebroadcast the RREQ to all its neighboring cluster heads using channel A with transmission range R A. 3.If a host originates or receives a RREP, it will remains in active mode in channel A. This is prepared for the upcoming data transmission. Routing (2/5)

62. 62/74 Routing (3/5) Non-Quorum Interval RREQ ATIM Window ATIM ACK Active mode Cluster member X Cluster head ATIM Window Active mode Cluster member Y RREP RREQ

63. 63/74 MTIMRREQ Routing (4/5) RBRB Cluster member Cluster head A Cluster head C Cluster head B RARA ACK RREQ X Y RREP

64. 64/74 Routing (5/5) Source Destination R B = Intra-cluster broadcast R A = Inter-cluster broadcast

65. 65/74 Outline  IEEE 802.11 MANETs  Power Saving Problem  Hybrid Power Saving Protocols  Simulation Results  Conclusion

66. 66/74 Simulation Results  Parameters Area size ： 1000mx1000m R A ： 250m R B ： 125m Mobility ： 0~10m/sec with pause time 20 seconds Traffic load ： 1~4 routes/sec Number of hosts ： 100~1000 hosts  Performance metrics Cluster head ratio Survival ratio Throughput

67. 67/74 Cluster Head Ratio

68. 68/74 Survival Ratio

69. 69/74 Throughput Comparison with QAPS

70. 70/74 Outline  IEEE 802.11 MANETs  Power Saving Problem  Hybrid Power Saving Protocols  Simulation Results  Conclusion

71. 71/74 Conclusion (1/2)  Taking advantages of both the sync. and async. PS protocol, and utilizing the concepts of dual-channel and dual-transmission-range To save more energy To accommodate more hosts Without clock synchronization No network partitioning

72. 72/74 Conclusion (2/2)  Adopting cluster-based routing to reduce the number of routing request rebroadcasts dramatically  Using dismissal mechanism to void the ever-increasing of cluster heads to make the protocol adaptive to topology changing  Practical for IEEE 802.11-based MANETs

73. 73/74 References: 1. Yu-Chee Tseng, Chih-Shun Hsu and Ten-Yueng Hsieh, “Power-Saving Protocols for IEEE 802.11-Based Multi-Hop Ad Hoc Networks,” InfoCom’2002, 2002 2. Jehn-Ruey Jiang, Yu-Chee Tseng, Chih-Shun Hsu and Ten-Hwang Lai, “Quorum-based asynchronous power- saving protocols for IEEE 802.11 ad hoc networks,” ACM Journal on Mobile Networks and Applications, Feb. 2005. (ICPP 2003 Best Paper Award) 3. Jehn-Ruey Jiang, Chau-Yuan Yang, Ting-Yao Chiou and Shing-Tsaan Huang, "A Hybrid Power-Saving Protocol by Dual-Channel and Dual-Transmission-Range Clustering for IEEE 802.11-Based MANETs," International Journal of Pervasive Computing and Communications, to appear.

74. 74/74 Q&A

75. 75/74 The States (1/3)  Listening State Listen in channel B for intra-cluster beacons for a period of (q+1 beacon intervals plus a random back-off time) 0-15 time slots with each time slot occupying 20 μs

76. 76/74 The States (2/3)  Cluster Head state Running async PS protocol for inter-cluster comm. Running sync PS protocol for inter-cluster comm.

77. 77/74 The States (3/3)  Cluster Member State Synchronizing its clock with the cluster head’s Running sync PS protocol Adopting cluster head’s quorum information

78. 78/74 Rotation Closure Property (1/3)  Definition. Given a non-negative integer i and a quorum H in a quorum system Q under U = {0,…, n  1}, we define rotate(H, i) = {j+i  j  H} (mod n).  E.G. Let H={0,3} be a subset of U={0,…,3}. We have rotate(H, 0)={0, 3}, rotate(H, 1)={1,0}, rotate(H, 2)={2, 1}, rotate(H, 3)={3, 2}

79. 79/74 Rotation Closure Property (2/3) DDefinition. A quorum system Q under U = {0,…, n  1} is said to have the rotation closure property if  G,H  Q, i  {0,…, n  1}: G  rotate(H, i)  .

80. 80/74 Rotation Closure Property (3/3)  For example, Q 1 ={{0,1},{0,2},{1,2}} under U={0,1,2}} Q 2 ={{0,1},{0,2},{0,3},{1,2,3}} under U={0,1,2,3}  Because {0,1}  rotate({0,3},3) = {0,1}  {3, 2} =  Closure

81. 81/74 Examples of quorum systems  Majority quorum system  Tree quorum system  Hierarchical quorum system  Cohorts quorum system  ………  

82. 82/74 FPP quorum system  Proposed by Maekawa in 1985  For solving distributed mutual exclusion  Constructed with a hypergraph An edge can connect more than 2 vertices  FPP:Finite Projective Plane A hypergraph with each pair of edges having exactly one common vertex  Also a Singer difference set quorum system

83. 83/74 FPP quorum system Example 01 2 34 5 6 A FPP quorum system: { {0,1,2}, {1,5,6}, {2,3,6}, {0,4,6}, {1,3,4}, {2,4,5}, {0,3,5} } 0 3 5

84. 84/74 Torus quorum system For a t  w torus, a quorum contains all elements from some column c, plus  w/2  elements, each of which comes from column c+i, i=1..  w/2  171615141312 11109876 543210 One full column One half column cover in a wrap around manner { {1,7,13,8,3,10}, {5,11,17,12,1,14},…}

85. 85/74 Cyclic (difference set) quorum system  Def: A subset D={d 1,…,d k } of Z n is called a difference set if for every e  0 (mod n), there exist elements d i and d j  D such that d i -d j =e.  {0,1,2,4} is a difference set under Z 8  { {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 C(8)

86. 86/74 E-Torus quorum system Trunk Branch cyclic E(t x w, k)