(1) A network that relies on all nodes to propagate signals. Although the wireless signal may start at some base station (access point) attached to a wired network, a wireless mesh network extends the transmission distance by relaying the signal from one computer to another. Used on the battlefield to provide path diversity, it is also used for sensor networks and personal computers. See mobile ad hoc network, 802.11 and wireless LAN.|
When laptops are set up in a wireless mesh, it is called an "ad hoc" network.
(2) A network that provides Wi-Fi connectivity within an urban or suburban environment. It is comprised of "mesh routers," which are a combination base station (access point) and router in one device. Also called "mesh nodes," they are typically installed on street light poles, from which they obtain their power.
Access Point and Backhaul Router
Like any Wi-Fi access point, the access point in the mesh router communicates with the mobile users in the area. The backhaul side of the device relays the traffic from router to router wireless until it reaches a gateway that connects to the Internet or other private network via a wired or wireless connection.
A major benefit of wireless mesh networks is path diversity, which provides many routes to the central network in case one of the routers fails or its transmission path is temporarily blocked. The choice in routing algorithm is critical, and numerous mesh algorithms have been used over the years.
Number of Radios
Mesh routers can employ one, two or three radios. A single-radio router shares bandwidth between users and the backhaul. If two radios are used, one is dedicated to the frontside clients and the other to the backhaul. In three-radio routers, such as the systems from BelAir Networks (www.belairnetworks.com) and MeshDynamics (www.meshdynamics.com), two radios are used for the backhaul and can transmit and receive simultaneously over different Wi-Fi channels. See 802.11.
This simulated wireless mesh is overlaid onto an aerial view of a metropolitan area, showing how the mesh routers are situated in a typical environment. (Image courtesy of Tropos Networks, Inc., www.tropos.com)
Depending on foliage and topography, between 10 and 20 mesh routers are mounted on light poles or similar locations per square mile. In this image, the man is making a Wi-Fi voice call between his VoWi-Fi phone and a BelAir200 Wireless Multi-Service Switch Router. (Image courtesy of BelAir Networks Inc., www.belairnetworks.com)