Adaptive Energy-Efficient Group Communication Support in Wireless Ad hoc Networks*

1. PhD Dissertation Defense Adaptive Energy-Efficient Group Communication Support in Wireless Ad hoc Networks* PhD Dissertation Defense Bin Wang Committee Prof. Sandeep K. S. Gupta (Chair) Prof. Hasan Çam Prof. Rida Bazzi/Prof. Yann-Hang Lee Prof. Stephen S. Yau *Supported by NSF

2. Outline Outline • Group Communication Service (GCS) • Wireless Ad hoc Networks • Group Management and Multicasting • GCS Requirements • Context-Awareness Group Management – Group Model • Energy-Efficient Multicast – Local Refinement • Mobility Tolerant – Two-Tier Model • Thesis Work • Context-Awareness Ephemeral Group Management • Refining Energy-efficient Multicast Tree (REMiT) Framework

3. Wireless Ad hoc Networks Wireless Ad hoc Networks • All Wireless Media - No Infrastructure • Ad hoc Networking • Limited Resources: Energy, Bandwidth, Memory and CPU • Dynamic Connectivity - Node Mobility and Interference • Large Scale Distributed Network • Context-Awareness Collaboration

4. Group Communication Service Group Membership Management and Multicasting • Group Management • Using contextual information to facilitate social group identification • Minimize user distraction – Automating group formation • Ephemeral Group Interaction Session • Group Communication Primitive – Multicast • Limited Battery Energy • Mobility-Tolerant Slides Distribution =

5. GCS Requirements GCS Requirements • Context-Awareness Group Management • Context Toolkit [Abowd01] : Context Widget for application development • View Maintenance [Hommel02]: Simple Beacon • Our approach – Group Model to construct a bridge between social group and device group • Energy-Efficient Multicasting • BIP/MIP [Wieselthier01]: add node one by one • EWMA [Enz02]: Reduce downstream node transmission (not fair to same level nodes) • Our approach – REMiT Framework – conceptual algorithmic structure for building distributed protocols by adapting multicast tree and make it energy-efficient (e.g. multicasting traffic distribution and interference) • Mobility Tolerant • ODMRP [Gerla02] : mesh-based on demand Multicast Routing • Two-Tier Unicast [Zhang02] : Grid approach for mobile sinks • Our approach - Two-Tier Model in REMiT Framework • Distributed and Light-weight: local knowledge, low overhead, scalability and adaptability

6. Thesis Contributions • Context Awareness Ephemeral Group Managementa • Group Model – mapping social group to device group • CAEG Service – use context to form device group automatically and efficiently • Energy-Efficient Multicastingb • Local Refinement – parent/branch swapping • Min. Energy and Max. Lifetime • REMiT Framework • Optimum Solution to Max. Lifetime Problem – Pruned Prim Tree • REMiT Protocols a: Percom’04, IEEE Pervasive Computing Magazine 2002, ASEE’03, WCRS’02 b: Journal of Information Science and Engineering 2004, Resource Management in Wireless Networking Book Chapter 2005, NCA’03, ICPP’03, GlobleCom’03

7. Energy-Efficient Multicasting Thesis Work

8. Energy Efficiency j m pi,m pi,j pi,k k i Energy Efficient Multicasting • Source of Energy Consumption • Communication vs. Computation • Energy Saving Techniques • Turn-off transceivers • Scheduling and defer transmission when channel conditions are poor • Transmission Power Control • Energy-Efficient Routes Wireless Multicast Advantage

9. REMiT Framework Energy Cost Model Energy-Efficient Multicasting Application Specified Requirement Reliability & Optimization goals Optimization goals,Sources distribution, Expected traffic pattern Initial Tree Adaptive Refinement EE Multicast Tree EE Multicasting Protocol Tree Cost Computation Node Cost Computation Network Parameters feedback (multicast traffic distribution, mobility, link error rate)

10. Refinement Energy Efficient Multicasting • Why Refinement? • Improve energy-efficiency among two hops neighbors with one hop knowledge • Fairness to all nodes • Distributed and low overhead • Free Lunch? NO! Performance is affected by initial tree x j i …

11. Basic Results of Refinement x j i Energy Efficient Multicasting • Refinement Process: One-by-one and Simultaneity • Determined by Optimization Goal • Positive Gain – Who are affected? How affected? • Source-based • Group-shared: tree path (i,j) • Disconnection Free • Tree remains connected after , if and only if node x is on the tree path i,j • Explore tree path i,j in distributed manner Lemma: Nodes j and x are the only nodes in the whose node cost may be affected by .

12. Basic Results of Refinement Cont. Energy Efficient Multicasting • Refinement Threshold – (over head)/(duration of two consecutive refinement) • Refinement Frequency • Determined by multicast traffic distribution and interference • Simultaneous refinement • Positive Gain and Disconnection Free • Lock node i’s one hop neighbors • Non-block lock to avoid dead lock • Randomization to avoid live lock S 5 2 6 1 4 3

13. Min Energy vs. Max Lifetime Energy-Efficient Multicasting 1 Initial battery energy at nodes 1, 2 and 3 are 200 EU 10 EU/pck 6 EU/pck 2 3 8 EU/pck Minimum Energy Tree Maximum Lifetime Tree 1 1 2 2 3 3

14. Source-based Trees vs. Group-shared Energy-Efficient Multicasting

15. Node Cost Energy-Efficient Multicasting • Energy consumed (per bit) at node i in source-based multicast tree T: • Node i’s lifetime: maximum number of bits in multicasting that may be processed by the node i: LTi = Ri / Eiwhere Ri is the residual battery energy at node i

16. Metrics of Multicast Tree x j i Energy-Efficient Multicasting • Total Energy Cost (TEC): Sum of node energy cost • NP-hard for source-based and group-shared trees • Simultaneous refinement • Lifetime of Multicast tree: Duration until first node fails due to energy exhaustion • P problem (Pruned Prim Tree) • Asymmetric Graph and Non-zero reception cost • One-by-One refinement

17. S-REMiT and G-REMiT Protocols REMiT Protocols • Minimizing TEC of source-based/group-shared multicast tree Construct Initial Tree Node i obtains locks from neighbors Selects new parent /tree neighbor with the highest positive Gain Y Switch parent/tree neighbor and Prune Neighbor made refinement ? N Wait for time t Unlock all the neighbors

18. Node Cost in Group-shared Tree REMiT Protocols e e Subtree Bi d d Ei[1] Ei[1] Ei[2] Ei[2] a a b Subtree Ai b i i c c

19. NS-2 Performance Results REMiT Protocols Using 802.11 and Free Space Propagation50% nodes are in the group Using 802.11 and Free Space Propagation 100% nodes are in the group

20. L-REMiT Algorithm REMiT Protocols • Maximizing Lifetime of source-based multicast tree Construct Initial Tree and Initial Bottleneck Election Source s selects bottleneck node x Refine bottleneck node and Prune Positive Gain? N Y Bottleneck node Re-election Terminate L-REMiT

21. Bottleneck Election in L-REMiT REMiT Protocols S Bottleneck is E S Bottleneck is F {E} {C} {B} {G} B B C C {I} {E} {F} {G} {E} {F} D E F G D G E F {H} {J} {I} {L} {K} H I K H I J K L J L Initial Bottleneck Election Bottleneck Re-election

22. NS-2 Performance Results REMiT Protocols Using 802.11 and Free Space Propagation Model and 100% nodes are multicast group nodes

23. Two-Tier Multicasting Model REMiT Protocols Logical View Physical View Group-shared Tree Higher Tier Lower Tier Stationary and Low Mobility Node High Mobility Node

24. Dynamic Multicast Traffic Distribution Due to Mobility T-REMiT at higher tier x B x B 15 12 15 C Group Node C Non-Group Node 1 D 1 13 D A 13 y A y y Group-shared Tree is not energy-efficient any more! Adapt to New Traffic Distribution E’A=50*12=600 EU/sec E’B=50*13=650 EU/sec E’C=150*13+50*12=2550 EU/sec EA=150*12+50*15=2550 EU/sec EB=50*15=750 EU/sec EC=50*12+150=750 EU/sec

25. NS-2 Performance Results REMiT Protocols Using 802.11 and Free Space Propagation Model and 50% nodes are multicast group nodes with dynamic traffic distribution.

26. Current State of Art REMiT Protocols

27. Context Awareness Ephemeral Group Management Thesis Work

28. Social Group Management Model Context Awareness Ephemeral Group Management Actual Mapping Logical Mapping Facilitate group membership and routines with minimum system set-up Social Context User User Group User Layer Group Session Profile Abstraction of social context User Group Profile Device Feedback Collaboration Tool Device Context Application Layer Device Device Group UserPerception

29. Context-Awareness Ephemeral Group Management in RCSM Context Awareness Ephemeral Group Management Smart Classroom Application (e.g. Group Chat) 1 6 CAEG Service on other devices 4 5 Group Activation/ Deactivation Group View Maintenance 4 3 Context Engine Context-Awareness Ephemeral Group (CAEG) Service 1. Group Profile Setup 2. Context Acquisition 3. Context Processing 4. Group Activation/Deactivation 5. Group View Exchanging 6. Group View Refresh Request 7. Group View Reply 2 R-ORB

30. Conclusions Conclusions • Three Challenges • Context-Awareness Group Management: Group Model • Energy-Efficient Multicast: Local Refinement • Mobility: Two-Tier Model • Energy-Efficient Multicasting • REMiT Framework • Min. Energy and Max. Lifetime • Optimum Solution for Max. Lifetime – Pruned Prim Tree • S-REMiT, L-REMiT, G-REMiT and T-REMiT • Social Group Management • Group Model - Map social group to device group • Context-Awareness Ephemeral Group Management

31. Future Work Conclusions • Distributed Scheduling Algorithm • Guarantee Energy Efficiency achieved at Routing Protocols • Reduce collision – packet lost ratio • Node goes to sleep – Idle energy • Energy-Efficient Multicasting • Saturation point between minimum energy and maximum lifetime trees • Using multiple trees to maximizing network lifetime • Directional Antenna • Social Group Management • Social context acquisition • Automatic group agreement formation

32. Publications Related to Thesis PhD Thesis Defense Journal Papers [1] Bin Wang and Sandeep K. S. Gupta, "Extending Lifetime of Multicast Trees in Wireless Ad hoc Networks", Journal of Information Science and Engineering, Special Issue on Mobile Computing, 20(3), May 2004, Institute of Information Science, Academia Sinica, Nankang, Taipei, Taiwan 115, Republic of China, pp. 425-447. [2] Stephen S. Yau, Fariaz Karim, Yu Wang, Bin Wang and Sandeep K. S. Gupta, "Reconfigurable Context-Sensitive Middleware for Pervasive Computing ", IEEE Pervasive Computing, joint special issue with IEEE Personal Communications on Context-Aware Pervasive Computing, 1(3), July-September 2002, IEEE Computer Society Press, Los Alamitos, USA, pp. 33-40. Book Chapters [1] Sandeep K. S. Gupta and Bin Wang, "Energy-efficient multicast protocols”, Resource Management in Wireless Networking, Mihaela Cardei, Ionut Cardei and Ding-Zhu Du (Eds.), Kluwer Academic Publishers, Dordrecht, The Netherlands (to apper). Conference Papers [1] Bin Wang, John Bodily, and Sandeep K. S. Gupta, "Supporting Persistent Social Groups in Ubiquitous Computing Environments Using Context-Aware Ephemeral Group Service", Proc. of Second IEEE International Conference on Pervasive Computing and Communications (PerCom), Orlando, FL, March 2004, pp. 287-296. [2] Bin Wang and Sandeep K. S. Gupta. “S-REMiT: A Distributed Algorithm for Source-based Energy Efficient Multicasting in Wireless Ad Hoc Networks ”, In Proceedings of IEEE GlobleCOM, San Francisco, CA, Dec. 2003, pp. 3519-3524. [3] Bin Wang and Sandeep K. S. Gupta,"On Maximizing Lifetime of Multicast Trees in Wireless Ad hoc Networks", In Proceedings of Thirty-Second International Conference on Parallel Processing (ICPP), Kaohsiung, Taiwan, China, October 2003, pp. 333-340. [4] Bin Wang and Sandeep K. S. Gupta, "G-REMiT: An Algorithm for Building Energy Efficient of Multicast Trees in Wireless Ad Hoc Networks", In Proceedings of IEEE International Symposium on Network Computing and Applications (NCA),Cambridge, MA, April 2003, pp. 265-272. [5] Stephen S. Yau, Sandeep K. S. Gupta, Fariaz Karim, Sheikh I. Ahamed, Yu Wang, and Bin Wang, "Smart Classroom: Enhancing Collaborative Learning Using Pervasive Computing Technology", Proc. of Sixth WFEO World Congress on Engineering Education & Second ASEE International Colloquium on Engineering Education (ASEE),June 2003, Nashville, Tennessee. [6] Bin Wang and Sandeep K. S. Gupta, “Situation-Aware Ephemeral Group Management", Workshop on Research in Computer Science (WRCS), Arizona State University, Tempe, AZ,March 2002.

33. Thank You… …For Your Time and Interest!

34. Related Work References [1] J. E. Wieselthier, G. D. Nguyen, and A. Ephremides, Resource management in energy-limited, bandwidth-limited, transceiver-limited wireless networks for session-based multicasting. Computer Networks, 39(2):113–131, 2002. [2] J. E. Wieselthier, G. D. Nguyen, and A. Ephremides, Distributed algorithms for energy-efficient broadcasting in ad hoc networks, Proceedings of MilCom, Anaheim, CA, Oct. 2002. [3] M. Cagalj, J.P. Hubaux, and C. Enz. Minimum-energy broadcast in All-wireless networks: NP-completeness and distribution issues. In Proceedings of ACM MobiCom 2002, pages 172 – 182, Atlanta, Georgia, September 2002. [4] Suman Banerjee, Archan Misra, Jihwang Yeo, Ashok Agrawala, "Energy-efficient broadcast and multicast trees for reliable wireless communication", In Proceedings of IEEE Wireless Communications and Networking Conference WCNC, vol. 4, no. 1, Mar 2003 pp. 660-667 [5] P.-J. Wan, G. Calinescu, X.-Y. Li, O. Frieder, "Minimum-energy broadcast routing in static ad hoc wireless networks", IEEE INFOCOM 2001 - The Conference on Computer Communications, no. 1, April 2001 pp. 1162-1171 [6] A. K. Dey, D. Salber and G. D. Abowd, A Conceptual Framework and a Toolkit for Supporting the Rapid Prototyping of Context-Aware Applications . Human-Computer Interaction Journal, 16(2-4):97-166, 2001. [7] L. Briesemeister and G. Hommel, Localized Group Membership Service for Ad Hoc Networks. International Workshop on Ad Hoc Networking, pages 94-100, Vancouver, Canada, August 2002. [8] S. J. Lee, W. Su, and M. Gerla, On-demand Multicast Routing Protocol in Multihop Wireless Mobile Networks. Mobile Networks and Applications, 7(6):441-453, 2002. [9] F. Ye and H. Y. Luo and J. Cheng and S. W. Lu and L. X. Zhang. A Two-tier Data Dissemination Model for Large-scale Wireless Sensor Networks. In Proceedings of ACM MobiCom 2002, pages 148 – 159, Atlanta, Georgia, September 2002.

35. Node Cost in Reliable Multicasting Node Metric • Energy consumed (per bit) at node i in source-based multicast tree T for reliable multicasting: where is the link error rate between nodes i and its children, and is the link error rate between node i’s parent and corresponding children.

36. NS-2 Performance Results REMiT Protocols Using 802.11 and Free Space Propagation Model and 50% nodes are multicast group nodes

37. Multicast Tree Energy-Efficient Multicasting • What is a link? • Depends on power level • Using maximum transmission power results in too many links • link weight? 1. & 2.  Link-based view not appropriate! • Node-based view: construct tree with “minimum summation of node cost or maximum node cost”

38. Four Optimization Problems in EE Multicasting Optimization Problems

39. Group View Maintenance Context Awareness Ephemeral Group Management • Every node beacon its current local view • When a node hears other beacon: • New view? Combine the new view with the current view and reduce to small beacon interval • Same view? Increase to large beacon interval • Large beacon interval < device time-out value divided by # of hops • Small beacon interval < application required latency of view stable* Trade-off: # of messages and length of messages * View Stable is define as every node’s local is same as the correct global view

40. A Solution for Group View Maintenance Supporting Social Groups in Ubicomp Environments A B C {A} {B} {B} small {A,B} {A,B} {A,B} {B,C} big {A,B,C} {A,B,C} {A,B,C} {A,B,C} {A,B,C} {A,B,C} View Stable {A,B,C}

41. Performance Result of Group View Maintenance Protocol Context Awareness Ephemeral Group Management

42. Group Chat Application Prototype of CAEG and Chat Application • Uses the Services provided by the CAEG to implement a chat application for Windows CE. • Allows users to communicate via unicast/multicast text messages, and exchange files.

43. Three Networking Services Supporting Social Groups in Ubicomp Environments

44. Current Test Bed Test Bed