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WIRELESS MESH NETWORKS
Abstract
As various wireless networks evolve into the next generation to provide better services, a key technology, Wireless Mesh Networks (WMNs), has emerged recently. In WMNs, nodes are comprised of mesh routers and mesh clients. Each node operates not only as a host but also as a router, forwarding packets on behalf of other nodes that may not be within direct wireless transmission range of their destinations. A node can send and receive messages, and in a mesh network, a node also functions as a router and can relay messages for its neighbors. Through the relaying process, a packet of wireless data will find its way to its destination, passing through intermediate nodes with reliable communication links. A mesh network offers multiple redundant communications paths throughout the network. If one page link fails for any reason, the network automatically routes messages through alternate paths. A WMN is dynamically self-organized and self-configured, with the nodes in the network automatically establishing and maintaining mesh connectivity among themselves (creating, in effect, an ad hoc network). This feature brings many advantages to WMNs such as low up-front cost, easy network maintenance, robustness, reliable service coverage and also provides a flexible architecture.
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Wireless Mesh NetworksChallenges and Opportunities
Overview
Gateways
Multiple interfaces (wired & wireless)
Mobility
Stationary (e.g. rooftop) – most common case
Mobile (e.g., airplane, busses/subway)
Serve as (multi-hop) “access points” to user nodes
Relatively few are needed, (can be expensive)
Wireless Routers
Users
Typically one interface.
Mobility
Stationary
Mobile
Connected to the mesh network through wireless routers (or directly to gateways)
The only sources/destinations for data traffic flows in the network.
User – Wireless Router Links
Wired
Bus (PCI, PCMCIA, USB)
Ethernet, Firewire, etc.
Wireless
802.11x
Bluetooth
Proprietary
Point-to-Point or Point-to-Multipoint
If properly designed is not a bottleneck.
If different from router-to-router links we’ll call them access links
Router to Router Links
Wireless
802.11x
Proprietary
Usually multipoint to multipoint
Sometimes a collection of point to point
Often the bottleneck
If different from router-to-user links we’ll call them backbone links
Gateway to Internet Links
Wired
Ethernet, TV Cable, Power Lines
Wireless
802.16
Proprietary
Point to Point or Point-to-Multipoint
We’ll call them backhaul links
If properly designed, not the bottleneck
How it Works
User-Internet Data Flows
In most applications the main data flows
User-User Data Flows
In most applications a small percentage of data flows
Taxonomy
Mesh vs. Ad-Hoc Networks
Multihop
Nodes are wireless, possibly mobil
May rely on infrastructure
Most traffic is user-to-user
Broadband Internet Access
Extend WLAN Coverage
Mobile Internet Access
Direct competition with G2.5 and G3 cellular systems.
Emergency Response
Layer 2 Connectivity
The entire wireless mesh cloud becomes one (giant) Ethernet switch
Simple, fast installation
Short-term events (e.g., conferences, conventions, shows)
Where wires are not desired (e.g., hotels, airports)
Where wires are impossible (e.g., historic buildings)
Military Communications
Community Networks
Many Other Applications
Remote monitoring and control
Public transportation Internet access
Multimedia home networking
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A node can send and receive messages, and in a mesh network, a node also functions as a router and can relay messages for its neighbors. Through the relaying process, a packet of wireless data will find its way to its destination, passing through intermediate nodes with reliable communication links. A mesh network offers multiple redundant communications paths throughout the network.
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