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TECH TALK: City Wi-Fi Networks: Mesh Technology

April 13th, 2006 · No Comments

A technology overview of wireless mesh networks is provided by Wikipedia:

Wireless mesh networking is mesh networking implemented over a Wireless LAN.
This type of Internet infrastructure is decentralized, relatively inexpensive, and very reliable and resilient, as each node need only transmit as far as the next node. Nodes act as repeaters to transmit data from nearby nodes to peers that are too far away to reach, resulting in a network that can span large distances, especially over rough or difficult terrain. Mesh networks are also extremely 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 neighbours simply find another route. Extra capacity can be installed by simply adding more nodes. Mesh networks may involve either fixed or mobile devices. The solutions are as diverse as communications 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. The best mobile networks are those such as Motorola’s which provide a seamless handover between the mobile device and the fixed infrastructure points.

The principle is similar to the way packets travel around the wired Internet data will hop from one device to another until it reaches a given destination. Dynamic routing capabilities included in each device allow this to happen. To implement such dynamic routing capabilities, each device needs to communicate its routing information to every device it connects with, “almost in real time”. Each device then determines what to do with the data it receives either pass it on to the next device or keep it.

An article in Business Communications Review (January 2006) discussed the pros and cons of wireless mesh networks (WMNs). David Axner wrote: “A WMN is easier to install and is less expensive than wired networks, since it uses radio signals instead of cable to connect nodes. Resiliency is a key atrribute of WMNs…Mesh networks also have their down side. WMNs can suffer from bandwidth degradation, radio interference, and per-hop latency as networks grow. The BCR articles also discusses various technologies from companies like BelAir, Firetide, PacketHop, MeshDynamics, Motorola, Nortel, SkyPilot, Strix and Tropos. [Google and Earthlink are planning to deploy Tropos’ technology for San Francisco.]

MuniWireless is an excellent for additional information.

A useful resource is the book Wireless Networking in the Developing World .

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