Ern Worthman,
Editorial Director
First generation WLANs were traditionally designed for cable replacement - quite simply, to clean up some of the rat's nest of wires commonly found in home offices or entertainment systems. However, with the rapid evolution of wireless technologies, subsequent iterations of WLANs have taken on a much more central role in networking, especially with wireless Internet.

Glossary of Acronyms

AP - Access Point-
ISP - Internet Service Provider
Wi-Fi - Wireless High Fidelity-
WLAN - Wireless Local Area Network

In a traditional WLAN, multiple clients access the network through a direct wireless link to an AP. This is often referred to as a one to many (or many to one) application. This is also referred to as single-hop network. The most common model is the familiar public Wi-Fi network typically found in airports, coffee shops and hundreds of other locations.

However, such a system has a number of limitations, mainly that all of the clients must be within the AP's receiving footprint and this single access point must handle all of the data, no matter how busy the network gets.

Enter Mesh Networks
Mesh networks raise the bar a notch for wireless network access. Mesh networks are multi-hop networks. It is a flexible architecture that removes the access point as the single direct connection to the network. In mesh networks, essentially any node can be a radio link and serve as a router or AP. Its most significant feature is that if a particular AP is congested, data is re-routed to the nearest available node. Data will continue to hop from one node to the next until it reaches its final destination.

Mesh Advantages
Obviously, mesh networks have advantages over their single-hop counterparts. Loading is a network's Achilles' heel. Traditional single-hop networks are fairly susceptable to loading limitations. Mesh networks, however, because they are not dependent on the performance of a single node for their operation, are significantly less susceptible, if not, theoretically, impervious, to loading issues. The first significant advantage to mesh networks is spatial reuse. Spatial reuse is the technology of mesh networks that doesn't share the AP (as single-hop networks do). For example, as multiple devices attempt to access the network simultaneously, it's possible a virtual traffic jam could occur, with the net result being system slowdown. In mesh network topology, these same devices connect to the network at the same time but likely through different nodes. This technique reduces or, in most cases, eliminates the degradation within the system's performance. The shorter transmission ranges in a mesh network reduce interference, by supporting simultaneous, spatially separated, data flows.

The next advantage is robustness. In a single-hop network, if the sole access point goes down, so does the network. In the mesh network architecture, if the nearest AP is down or there is localized interference, the network will continue to operate - data will simply be routed along an alternate path. The third significant advantage mesh networks have is higher bandwidth. Bandwidth is a function of a number of variables including signal strength, loading, interference and other signal degradation factors. In single-hop networks, all the data is routed along the single channel. In mesh networks, data is transmitted across multiple short hops. Two obvious benefits of this are that the bandwidth isn't so tapped (data spread across multiple frequencies), and mesh networks offer shorter data paths, requiring less power.

A Quick Technology Primer
The operation of a mesh network is fairly straightforward. A mesh network offers multiple paths from source to destination. Intelligent routing algorithms allow decision making at each node, on which path to forward packets through the network in order to improve performance. If the link between a pair of nodes along one of the paths is bottlenecked, then the algorithms establish another path that avoids the congested link. Also, if a node goes down, an alternate route is chosen based on the routing algorithms. For example, a user enters the mesh network using Wi-Fi protocols and, when sending data, hops from one node to the other until it reaches the node that connects to the ISP. One of the few, and generally acceptable, downsides here is the time it takes for the corresponding web page to return to the user. If a lot of hops are involved, the user will notice it in download speeds.

An Emerging Application
Mesh networks are rapidly being implemented for anytime, city- or muni-wide Wi-Fi networks. Simply drop in the backhaul nodes where coverage is necessary, and automatic mechanisms connect the node into the network. Theoretically, mesh networks can be expanded indefinitely so the footprint of the network is unlimited (although practical limitations do exist).

As well, mesh networks can be implemented as temporary wireless networks. The backhaul nodes are quick and easy to install and remove. A common scenario would be, for example, emergency crews establishing a mesh network when working at a disaster site. Construction sites, stadiums, concerts and many other enterprises can benefit from mesh networks when needing network connectivity in temporary work areas. Mesh networks are a growing and popular way to provide anytime, anywhere wireless Internet access. Many cities are using mesh networks to provide a ubiquitous wireless network throughout the city, benefiting citizens, businesses and tourists alike. Expect mesh networks to be a major player in the drive to connect anything to anyone at any time.