LAN case, a similar spatial separation can be achieved using a new class of device called an access point array, described below in the Section "Wireless LAN Arrays, p. 52", which combines a wireless LAN controller with an array of sector antennas to multiply network capacity. The general technique of multiplying network throughput by addressing separate spatial zones or propagation paths is known as space division multiplexing (Section "Space Division Multiple Access, p. 94"), and finds its most remarkable application in MIMO radio, described in the Section "MIMO Radio, p. 124". Mesh Networks Mesh networks, also known as mobile ad hoc networks (MANETs), are local or metropolitan area networks in which nodes are mobile and communicate directly with adjacent nodes without the need for central controlling devices. The topology of a mesh, shown generically in Figure 3-8, can be constantly changing, as nodes enter and leave the network, and data packets are forwarded from node-to-node towards their destination in a process called hopping. The data routing function is distributed throughout the entire mesh rather than being under the control of one or more dedicated devices. This is similar to the way that data travels around the Internet, with a packet hopping from one device to another until it reaches its destination, although in mesh networks, the routing capabilities are included in every node rather than just in dedicated routers. This dynamic routing capability requires each device to communicate its routing information to every device it connects with, and to update this as nodes move within, join and leave the mesh. This distributed control and continuous reconfiguration allows for rapid re-routing around overloaded, unreliable or broken paths, allowing mesh networks to be self-healing and very reliable, provided that the density of nodes is sufficiently high to allow alternative paths. A key challenge in the design of the routing protocol is to achieve this continuous re-configuration capability with a manag