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A Survey on Wireless Mesh Networks

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A Survey on Wireless Mesh Networks Powered By Docstoc
					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
 Outlines
             Introduction
             Network   Architecture and
              characteristics
             WMNs VS ad hoc networks
             Critical Design Factors
             Advances and Research
              Challenges
             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
              characteristics
             The characteristics of WMNs
             WMNs VS ad hoc networks
             Advances and Research
              Challenges
             Conclusion
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            Mesh router and Mesh client
               Mesh router on
                embedded 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
                  sacrificing 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
                easily

               Mesh router integrate heterogeneous
                networks

               Compatibility and interoperability

               Hybrid WMNs has all the advantages
2006/4/11                                            11
 Outlines
             Introduction
             Network   Architecture and
              characteristics
             WMNs VS ad hoc networks
             Critical Design Factors
             Advances and Research
              Challenges
             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
             configuration

                 ad hoc, end-user must self
               In
               perform

               InWMNs, 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

                 WMNs, all traffic functionalities
               In
               separate into different radio

                 ad hoc, performed in the same
               In
               channel

               Multipleradio, improves the
2006/4/11
               capacity of network              16
            WMNs      VS   ad hoc network
             Mobility
               Additional challenges on routing
                protocol


             Integration
               Enable integration of various
                existing network or use the same
                radio network
2006/4/11                                          17
 Outlines
             Introduction
             Network   Architecture and
              characteristics
             WMNs VS ad hoc networks
             Critical Design Factors
             Advances and Research
              Challenges
             Conclusion
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            Critical Design Factors
             Radio Techniques
             Scalability
             Mesh connectivity
             Broadband and QoS
             Security
             Ease of Use
             Compatibility and Inter-

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              operability                19
 Outlines
             Introduction
             Network   Architecture and
              characteristics
             WMNs VS ad hoc networks
             Critical Design Factors
             Advances and Research
              Challenges
             Conclusion
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Advances and Research Challenges

            Network Capacity
               Method I
                 The Guideline to improve capacity
                   A node should only communicate
                    with nearby nodes

                 Twomajor schemes :
                  deploy relaying node
                  Group 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 closer
                to it
               Limitation
                 Transmission  delay rather large
                 Require 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

                       affects the performance of
                Mobility
 2006/4/11      MAC (exchange network)          23
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
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            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
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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.
2006/4/11
              -Multi-radio Unification protocol(MUP)
                                                   26
            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 Metrics
                   Scalability
                   Robustness
                   Efficient Routing with Mesh
                    Infrastructure
 2006/4/11                                          28
Advances and Research Challenges

             Routing Layer communication
                 Common routing
                  1)   Multi-Radio Routing
                  2)   Multi-Path Routing
                  3)   Geographic Routing
                  4)   Hierarchical Routing



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            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
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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
by hierarchical route
         wishes
node Arouting to send a
by→B →D →H →I.
A a flat
message to → E I
A →B →C →Dnode →F →G
→ H →I.




 2006/4/11                       34
 Outlines
             Introduction
             Network   Architecture and
              characteristics
             WMNs VS ad hoc networks
             Critical Design Factors
             Advances and Research
              Challenges
             Conclusion
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            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.

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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.


2006/4/11                                                    37

				
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