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.