A Survey on Wireless Mesh Networks
Sih-Han Chen 陳思翰Department of Computer Science and Information EngineeringNational Taipei University of Technology2006.04.11
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Outlines
Introduction Network Architecture and chara
cteristics WMNs VS ad hoc networks Critical Design Factors Advances and Research Challen
ges Conclusion
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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
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Outlines
Introduction Network Architecture and chara
cteristics The characteristics of WMNs WMNs VS ad hoc networks Advances and Research Challen
ges Conclusion
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Mesh router and Mesh client Mesh router on e
mbedded system
Mesh client Much simpler than
mesh router(no gateway or bridge functions)
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Architecture of WMNs (type1)
Infrastructure/Backbone WMNs
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Client WMNs (type2)
In the same network or cluster Provide peer to peer networks
among client devices
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Hybrid WMNs (type3)
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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
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Characteristics WMNs support ad hoc networking
- Self-forming, self-healing, self-organization
WMNs are multi-hop wireless networks Extend the coverage range without sacr
ificing the channel capacity Provide NLOS connectivity
Mobility and power-consumption depend on the type of mesh nodes
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Characteristics (cont’d) Mobility of end nodes is supported e
asily
Mesh router integrate heterogeneous networks
Compatibility and interoperability
Hybrid WMNs has all the advantages
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Outlines
Introduction Network Architecture and chara
cteristics WMNs VS ad hoc networks Critical Design Factors Advances and Research Challen
ges Conclusion
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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
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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
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WMNs VS ad hoc network Dedicated routing and configurat
ion
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)
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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
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WMNs VS ad hoc networkMobility
Additional challenges on routing protocol
IntegrationEnable integration of various
existing network or use the same radio network
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Outlines
Introduction Network Architecture and chara
cteristics WMNs VS ad hoc networks Critical Design Factors Advances and Research Challen
ges Conclusion
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Critical Design Factors
Radio Techniques Scalability Mesh connectivity Broadband and QoS Security Ease of Use Compatibility and Inter-operabil
ity
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Outlines
Introduction Network Architecture and chara
cteristics WMNs VS ad hoc networks Critical Design Factors Advances and Research Challen
ges Conclusion
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Advances and Research Challenges
Network Capacity Method I
The Guideline to improve capacityA node should only communicate with nearby nodes
Two major schemes :deploy relaying nodeGroup into clusters
challenging task
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Advances and Research Challenges
Network Capacity (cond’t)
Method II Increase capacity by the node mobility Not Send ,until des_Node get clos
er to it Limitation
Transmission delay rather largeRequire buffer may be
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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)
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Advances and Research Challenges
MAC Layer communication
A MAC protocol for WMNs can be design in two way
Single-channel MACMulti-channel MAC
Open search issue
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Single-channel MAC Three approaches
Modifying Existing MAC Protocols-only low end-to-end throughput
Cross-Layer DesignDirectional antennas-based MACsMACs with power control-adv: eliminate expose node-dis : more hidden nodes are produced
Proposing Innovative MAC Protocol
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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)
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MAC Open search issue
Scalable MAC
MAC/Physical Cross-Layer Design
Network Integration in MAC layer (bridge function )
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Advances and Research Challenges
Routing Layer communication
An optimal routing protocol for WMNs must have following feather:
Multiple Performance MetricsScalabilityRobustnessEfficient Routing with Mesh Inf
rastructure
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Advances and Research Challenges
Routing Layer communication
Common routing1) Multi-Radio Routing2) Multi-Path Routing3) Geographic Routing4) Hierarchical Routing
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Geographic Routing Use physical location info. By like GP
S
Less impact when topology change
Usually use greedy method i.e. Single path greedy (in early) Dis : delivery is not guaranteed eve
n if a path exit between src and des
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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
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Hierarchical Routing
Becomes a cluster leader.
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Logical structure of a cluster hierarchy. Multi-level
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Logical structure of a cluster hierarchy. Multi-level
node A wishes to send amessage to node I
by a flat routingA →B →C →D → E →F →G → H →I.
by hierarchical routeA →B →D →H →I.
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Outlines
Introduction Network Architecture and chara
cteristics WMNs VS ad hoc networks Critical Design Factors Advances and Research Challen
ges Conclusion
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Conclusion The most important and urgent pr
oblem:1) Scalability2) Security
WMNs will be one of the most promising technologies fornext-generation wireless networking.
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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.