Wireless Mesh Network

in Wireless
History



Main article: History of wireless mesh networking



Network structure



Architecture



Wireless mesh architecture is a first step towards providing high-bandwidth network over a specific coverage area. Wireless mesh architecture infrastructure is, in effect, a router network minus the cabling between nodes. It's built of peer radio devices that don't have to be cabled to a wired port like traditional WLAN access points (AP) do. Mesh architecture sustains signal strength by breaking long distances into a series of shorter hops. Intermediate nodes not only boost the signal, but cooperatively make forwarding decisions based on their knowledge of the network, i.e. performs routing. Such an architecture may with careful design provide high bandwidth, spectral efficiency, and economic advantage over the coverage area.



Example of three types of wireless mesh network:



Infrastructure wireless mesh networks: Mesh routers form an infrastructure for clients.



Client wireless mesh networks: Client nodes constitute the actual network to perform routing and configuration functionalities.



Hybrid wireless mesh networks: Mesh clients can perform mesh functions with other mesh clients as well as accessing the network.



Wireless mesh network have a relatively stable topology except for the occasional failure of nodes or addition of new nodes. The traffic, being aggregated from a large number of end users, changes infrequently. Practically all the traffic in an infrastructure mesh network is either forwarded to or from a gateway, while in ad hoc networks or client mesh networks the traffic flows between arbitrary pairs of nodes.



Management



This type of infrastructure can be decentralized (with no central server) or centrally managed (with a central server), both are relatively inexpensive, and very reliable and resilient, as each node needs only transmit as far as the next node. Nodes act as routers to transmit data from nearby nodes to peers that are too far away to reach in a single hop, resulting in a network that can span larger distances. The topology of a mesh network is also more reliable, as each node is connected to several other nodes. If one node drops out of the network, due to hardware failure or any other reason, its neighbors can find another route using a routing protocol.



Applications



Mesh networks may involve either fixed or mobile devices. The solutions are as diverse as communication needs, for example in difficult environments such as emergency situations, tunnels and oil rigs to battlefield surveillance and high speed mobile video applications on board public transport or real time racing car telemetry. A significant application for wireless mesh networks is VoIP. By using a Quality of Service scheme, the wireless mesh may support local telephone calls to be routed through the mesh. For example, miner safety has improved with VOIP phones communicating over a mesh network.



Some current applications:



U.S. military forces are now using wireless mesh networking to connect their computers, mainly ruggedized laptops, in field operations. It enables troops to know the locations and status of every soldier or marine, and to coordinate their activities without much direction from central command. Video Clip



Electric meters now being deployed on residences transfer their readings from one to another and eventually to the central office for billing without the need for human meter readers or the need to connect the meters with cables.



The laptops in the one laptop per child program use wireless mesh networking to enable students to exchange files and get on the Internet even though they lack wired or cell phone or other physical connections in their area.



The 66-satellite Iridium constellation operates as a mesh network, with wireless links between adjacent satellites. Calls between two satellite phones are routed through the mesh, from one satellite to another across the constellation, without having to go through an earth station. This makes for a smaller travel distance for the signal, reducing latency, and also allows for the constellation to operate with far fewer earth stations that would be required for 66 traditional communications satellites.



Operation



The principle is similar to the way packets travel around the wired Internet data will hop from one device to another until it reaches its destination. Dynamic routing algorithms implemented in each device allow this to happen. To implement such dynamic routing protocols, each device needs to communicate routing information to other devices in the network. Each device then determines what to do with the data it receives either pass it on to the next device or keep it, depending on the protocol. The routing algorithm used should attempt to always ensure that the data takes the most appropriate (fastest) route to its destination.



Multi-radio mesh



Multi-radio mesh refers to a unique pair of dedicated radios on each end of the link. This means there is a unique frequency used for each wireless hop and thus a dedicated CSMA collision domain. This is a true mesh link where you can achieve maximum performance without bandwidth degradation in the mesh and without adding latency. Thus voice and video applications work just as they would on a wired Ethernet network. In true 802.11 networks, there is no concept of a mesh. There are only Access Points (AP's) and Stations. So a Multi-radio wireless mesh node will dedicate one of the radios to act as a station, and connect to a neighbor node AP radio. Single and dual-radio mesh use proprietary means to repeat the signal which means that more than two nodes are in the same collision domain and frequency.Animation. That is what causes bandwidth degradation and high latency. Detailed explanation Here.



Research topics



One of the most often cited papers on Wireless Mesh Networks identified the following areas as open research problems in 2005 :



New modulation scheme



In order to achieve higher transmission rate, new wideband transmission schemes other than OFDM and UWB are needed.



Advanced antenna processing



Advanced antenna processing including directional, smart and multiple antenna technologies is further investigated, since their complexity and cost are still too high for wide commercialization.



Flexible spectrum management



Tremendous efforts on research of frequency-agile techniques are being performed for increased efficiency.



Cross-layer design



Cross-layer research is a popular current research topic where information is shared between different communications layers in order to increase the knowledge and current state of the network. This could enable new and more efficient protocols to be developed. It is important to note that careless cross-layer design could lead to code which is difficult to maintain and extend.



Protocols



Routing protocols



There are more than 70 competing schemes for routing packets across mesh networks. Some of these include:



AODV (Ad hoc On-Demand Distance Vector)



OLSR (Optimized Link State Routing protocol)



DSR (Dynamic Source Routing)



OSPF (Open Shortest Path First Routing)



DSDV (Destination-Sequenced Distance-Vector Routing)



B.A.T.M.A.N. (Better Approach To Mobile Adhoc Networking)



PWRP (Predictive Wireless Routing Protocol)



OORP (OrderOne Routing Protocol) (OrderOne Networks Routing Protocol)



TORA (Temporally-Ordered Routing Algorithm)



HSLS (Hazy-Sighted Link State)



IWMP (Infrastructure Wireless Mesh Protocol) for Infrastructure Mesh Networks by GRECO UFPB-Brazil



The IEEE is developing a set of standards under the title 802.11s to define an architecture and protocol for ESS Mesh Networking.



A more thorough list can be found at Ad hoc routing protocol list.



Autoconfiguration protocols



Standard autoconfiguration protocols, such as DHCP or IPv6 stateless autoconfiguration may be used over mesh networks.



Mesh network specific autoconfiguration protocols include:



The Ad-Hoc Configuration Protocol (AHCP)



Proactive Autoconfiguration (Proactive Autoconfiguration Protocol)



Dynamic WMN Configuration Protocol (DWCP)



See also



Wikimedia Commons has media related to: Mesh network



Mesh networking



INSTEON



IEEE 802.11s



Smart antenna



Mobile ad-hoc network



Wireless ad-hoc network



Wireless Distribution System



Wireless LAN



Peer to peer



EnOcean



MICAz



ZigBee



Ant colony optimization



ANT (network)



Wireless community network



Shared mesh



Meraki



CUWiN



Optimized Link State Routing protocol



DASH7



roofnet



MeshBox



Firetide



Switched mesh



Netsukuku



TinyOS



Public Safety Network



Dust Networks



comparison of wireless data standards



References



^ a b c Ian F. Akyildiz, Xudong Wang, Weilin Wang: "Wireless mesh networks: a survey", "Computer Networks and ISDN Systems", v.47 n.4,p.445-487, 15 March 2005



^ J. Jun, M.L. Sichitiu, "The nominal capacity of wireless mesh networks", in IEEE Wireless Communications, vol 10, 5 pp 8-14. October 2003



^ S.M. Chen, P, Lin, D-W Huang, S-R Yang, "A study on distributed/centralized scheduling for wireless mesh network" in Proceedings of the 2006 International Conference on Wireless Communications and Mobile Computing, pp 599 - 604. Vancouver, British Columbia, Canada. 2006



^ V. Kawadia, P.R. Kumar, "A Cautionary Perspective on Cross-Layer Design," in IEEE Wireless Communications, pp 3-11, February 2005.



External links



How Wireless Mesh Networks Work at HowStuffWorks



IET From hotspots to blankets



Mesh Network serves three California Communities



Using Mesh Networks for Video Surveillance



LastMile Wireless Mesh Networks An Industry Overview



Ian. F. Akyildiz and Xudong Wang, "A Survey on Wireless Mesh Networks," IEEE Communications Magazine, vol. 43, no. 9, s23-s30, Sept. 2005



Iamatechie , "Wifi Mesh Network" Post Series regarding Wifi Mesh Networking



Mesh Networks Research Group Projects and tutorials' compilation related to the Wireless Mesh Networks



Victor Pierobon, "The first concept of wireless mesh" The 1994 beginning of wireless mesh.



Building a Rural Wireless Mesh Network Guide



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This article was published on 2010/10/10