Generations of mesh networks
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[[Category:Wikify from March 11, 2007]]
Wireless Mesh networks allow users to access data, video, and voice applications outdoors for a variety of applications. But earlier-generation mesh networking products perform poorly in the very multi-hop (node-to-node connection) environments in which they are being deployed. Here’s how third generation products compare with earlier generations of mesh.
First Generation- One-radio "Ad Hoc" Wireless Mesh. In single-generation mesh products, a single radio provides both service (connection to individual user devices) and backhaul (links across the mesh to the wired or fiber connection), so wireless congestion and contention takes place at every node. Users soon discovered that only one or two radio "hops" were possible between connections to the wired or fiber Ethernet. Support is also very poor for Video and Voice applications because of excessive and varying delay (latency) across the network.
Second Generation- Two-radio Wireless Mesh, shared Backhaul. To solve these contention and congestion issues, second-generation mesh was developed by placing two radios in each node, combining an 802.11b/g service radio with an 802.11a backhaul radio.While this offered a performance improvement in terms of bandwidth over first-generation mesh, problems remain. With heavy user demand, there is still significant contention and congestion on the backhaul links. This limits the number of radio hops before another costly wired or fiber Ethernet connection is needed.
Third Generation- Three Radio with Multi-radio Wireless Backhaul. Third generation mesh networking produucts add at least two physical radios for the backhaul. One backhaul radio is used to create a link to its upstream (nearer the wired source or "root") node. Another backhaul radio creates a link downstream to the next neighbor node. Unlike second-generation solution, these two radios may make use of different channels.
This increases the perfomance of the network in three ways:
Firstly, each node may be sending and receiving simultaneously to its upstream and downstream neighbors, unlike first-or second-generation nodes, which must continually "turn around" between sending and receiving upstream and downstream.
Secondly, because each link is managed independently, the available channels may be re-used across the network. This expands the available spectrum, increasing performance of the network 50 times or more compared to first- and second-generation solutions.
Thirdly, radio is a shared medium. Nearby radios not part of the mesh network are constantly competing for air space. In first and second generation technologies, the backhaul channel is effectively "locked" once selected. They have only one backhaul radio on each node and if the channel has to be changed it affects all nodes. In contrast, third generation mesh nodes have two backhaul radios. Those equipped with dynamic channel management software can proactively change channels within segments of the network when local RF interference is encountered.
[edit] See also
[edit] External links
- Performance Analysis of Mesh Architectures Why all mesh products are not created equal.
- Is Multi-radio mesh worthwhile? Cost considerations of multi-radio mesh.
