A Survey on Wireless Mesh Networks

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. Outlines • Introduction • Network Architecture and characteristics • WMNs VS ad hoc networks • Critical Design Factors • Advances and Research Challenges • Conclusion

3. 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. Outlines • Introduction • Network Architecture and characteristics • The characteristics of WMNs • WMNs VS ad hoc networks • Advances and Research Challenges • Conclusion

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

6. Architecture of WMNs (type1) • Infrastructure/Backbone WMNs

7. Client WMNs (type2) • In the same network or cluster • Providepeer to peernetworks among client devices

8. Hybrid WMNs (type3)

9. Hybrid WMNs • Combineinfrastructure and client meshing • Mesh client access the mesh routerdirectlywith other mesh clients • This type will be the mostapplicablecase in our opinion

10. 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. 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. Outlines • Introduction • Network Architecture and characteristics • WMNs VS ad hoc networks • Critical Design Factors • Advances and Research Challenges • Conclusion

13. 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 asubsetof WMNs

14. WMNs VS ad hoc network • Wireless infrastructure/backbone • WMNs consist of wireless backbone withmesh router • Ad hoc network depends on theindividualcontribution of end-user • Ad hoc network maynotbe reliable

15. 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. 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. 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. Outlines • Introduction • Network Architecture and characteristics • WMNs VS ad hoc networks • Critical Design Factors • Advances and Research Challenges • Conclusion

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

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

21. 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. Advances and Research Challenges Network Capacity(cond’t) • Method II • Increase capacity by the node mobility • Not Send ,untildes_Node getcloserto it • Limitation • Transmission delay rather large • Require buffer may be

23. 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. 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. 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. 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. MAC Open search issue • Scalable MAC • MAC/Physical Cross-Layer Design • Network Integration in MAC layer (bridge function )

28. 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. Advances and Research Challenges Routing Layer communication • Common routing • Multi-Radio Routing • Multi-Path Routing • Geographic Routing • Hierarchical Routing

30. Geographic Routing • Usephysicallocation info. By like GPS • Less impactwhen topology change • Usually usegreedymethod • i.e. Single path greedy (in early) • Dis :delivery is not guaranteedeven if a path exit between src and des

31. 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. Hierarchical RoutingBecomes a cluster leader.

33. Logical structure of a cluster hierarchy. Multi-level

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

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

36. Conclusion • The most important and urgent problem: • Scalability • Security • WMNs will be one of the most promising technologies for next-generation wireless networking.

37. 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.