1. A Survey on Wireless Mesh Networks Sih-Han Chen 陳思翰 Department of Computer Science and Information Engineering National Taipei University of Technology 2006.04.11

2. 2006/4/112 Outlines Introduction Network Architecture and characteristics WMNs VS ad hoc networks Critical Design Factors Advances and Research Challenges Conclusion

3. 2006/4/113 Overview WMNs Similar to ad-hoc network dynamically self-organized and self- configured Two types of nodes Mesh router, Mesh client Intrgration - ( eg. cellular,Wi-Fi,WiMAX …) Flexibility -Mesh router equipped with multiple wireless interfaces

4. 2006/4/114 Outlines Introduction Network Architecture and characteristics The characteristics of WMNs WMNs VS ad hoc networks Advances and Research Challenges Conclusion

5. 2006/4/115 Mesh router and Mesh client Mesh router on embedded system Mesh client Much simpler than mesh router(no gateway or bridge functions)

6. 2006/4/116 Architecture of WMNs (type1) Infrastructure/Backbone WMNs

7. 2006/4/117 Client WMNs (type2) In the same network or cluster Provide peer to peer networks among client devices

8. 2006/4/118 Hybrid WMNs (type3)

9. 2006/4/119 Hybrid WMNs Combine infrastructure and client meshing Mesh client access the mesh router directly with other mesh clients This type will be the most applicable case in our opinion

10. 2006/4/1110 Characteristics WMNs support ad hoc networking - Self-forming, self-healing, self- organization WMNs are multi-hop wireless networks Extend the coverage range without sacrificing the channel capacity Provide NLOS connectivity Mobility and power-consumption depend on the type of mesh nodes

11. 2006/4/1111 Characteristics (cont ’ d) Mobility of end nodes is supported easily Mesh router integrate heterogeneous networks Compatibility and interoperability Hybrid WMNs has all the advantages

12. 2006/4/1112 Outlines Introduction Network Architecture and characteristics WMNs VS ad hoc networks Critical Design Factors Advances and Research Challenges Conclusion

13. 2006/4/1113 WMNs VS ad hoc network WMNs are generally considered as a type of ad hoc networks WMNs aim to diversify the capabilities of ad hoc net work Consequently, ad hoc net work can be a subset of WMNs

14. 2006/4/1114 WMNs VS ad hoc network Wireless infrastructure/backbone WMNs consist of wireless backbone with mesh router Ad hoc network depends on the individual contribution of end-user Ad hoc network may not be reliable

15. 2006/4/1115 WMNs VS ad hoc network Dedicated routing and configuration In ad hoc, end-user must self perform In WMNs, mesh router do this work -the end-user device ’ s loading is significantly decreased (saving energy)

16. 2006/4/1116 WMNs VS ad hoc network Multiple radio In WMNs, all traffic functionalities separate into different radio In ad hoc, performed in the same channel Multiple radio, improves the capacity of network

17. 2006/4/1117 WMNs VS ad hoc network Mobility Additional challenges on routing protocol Integration Enable integration of various existing network or use the same radio network

18. 2006/4/1118 Outlines Introduction Network Architecture and characteristics WMNs VS ad hoc networks Critical Design Factors Advances and Research Challenges Conclusion

19. 2006/4/1119 Critical Design Factors Radio Techniques Scalability Mesh connectivity Broadband and QoS Security Ease of Use Compatibility and Inter- operability

20. 2006/4/1120 Outlines Introduction Network Architecture and characteristics WMNs VS ad hoc networks Critical Design Factors Advances and Research Challenges Conclusion

21. 2006/4/1121 Advances and Research Challenges Network Capacity Method I The Guideline to improve capacity A node should only communicate with nearby nodes Two major schemes : deploy relaying node Group into clusters challenging task

22. 2006/4/1122 Advances and Research Challenges Network Capacity (cond ’ t) Method II Increase capacity by the node mobility Not Send,until des_Node get closer to it Limitation Transmission delay rather large Require buffer may be

23. 2006/4/1123 Advances and Research Challenges MAC Layer communication The feather of MAC for WMNs More than one-hop communication Distributed, need to collaboration Network self-organization Mobility affects the performance of MAC (exchange network)

24. 2006/4/1124 Advances and Research Challenges MAC Layer communication A MAC protocol for WMNs can be design in two way Single-channel MAC Multi-channel MAC Open search issue

25. 2006/4/1125 Single-channel MAC Three approaches Modifying Existing MAC Protocols - only low end-to-end throughput Cross-Layer Design Directional antennas-based MACs MACs with power control -adv: eliminate expose node -dis : more hidden nodes are produced Proposing Innovative MAC Protocol

26. 2006/4/1126 Multi-channel MAC Multi-Channel Single-Transceiver -concern with cost and compability -only one channel active at a time in each node Multi-Channel Multi-Transceiver -so far no this MAC protocol Multi-Radio -each has its own MAC layer, indep. -Multi-radio Unification protocol(MUP)

27. 2006/4/1127 MAC Open search issue Scalable MAC MAC/Physical Cross-Layer Design Network Integration in MAC layer (bridge function )

28. 2006/4/1128 Advances and Research Challenges Routing Layer communication An optimal routing protocol for WMNs must have following feather: Multiple Performance Metrics Scalability Robustness Efficient Routing with Mesh Infrastructure

29. 2006/4/1129 Advances and Research Challenges Routing Layer communication Common routing 1) Multi-Radio Routing 2) Multi-Path Routing 3) Geographic Routing 4) Hierarchical Routing

30. 2006/4/1130 Geographic Routing Use physical location info. By like GPS Less impact when topology change Usually use greedy method i.e. Single path greedy (in early) Dis : delivery is not guaranteed even if a path exit between src and des

31. 2006/4/1131 Hierarchical Routing Group network node into cluster Each cluster has one or more cluster head (leader) Node may be one or more hops away from cluster head Some node work as gateway More Scalable

32. 2006/4/1132 Hierarchical Routing Becomes a cluster leader.

33. 2006/4/1133 Logical structure of a cluster hierarchy. Multi-level

34. 2006/4/1134 Logical structure of a cluster hierarchy. Multi-level node A wishes to send a message to node I by a flat routing A →B →C →D → E →F →G → H →I. by hierarchical route A →B →D →H →I.

35. 2006/4/1135 Outlines Introduction Network Architecture and characteristics WMNs VS ad hoc networks Critical Design Factors Advances and Research Challenges Conclusion

36. 2006/4/1136 Conclusion The most important and urgent problem: 1) Scalability 2) Security WMNs will be one of the most promising technologies for next-generation wireless networking.

37. 2006/4/1137 References [1]XUDONG WANG, KIYON, INC., “ A Survey on Wireless Mesh Networks ” IEEE Communications Magazine, Volume 43, Issue 9, Sept. 2005 Page(s):S23 - S30 [2]E. M. Belding-Royer, “ Multi-level Hierarchies for Scalable ad hoc Routing, ” ACM/Kluwer Wireless Networks (WINET), vol. 9, no. 5, Sept. 2003,pp. 461 – 78. [3]H. Frey, “ Scalable Geographic Routing Algorithms for Wireless Ad HocNetworks, ” IEEE Network Mag., July/Aug. 2004, pp. 18 – 22.