High-speed Wireless access
An article in IEEE Spectrum on Non Line of Sight Wireless Systems:
Line Of Sight (LOS) systems rely on a high-power transmitter at the base station, an unimpeded line of sight between transmitter and customer, and a highly directional outdoor antenna at the customer premises, all of which add up to a technology too expensive for the residential market.
NLOS attacks the problem with smart antennas, advanced modulation techniques, and, in some cases, a mesh architecture in which nodes–the individual routers on the customer’s premises–are connected by multiple links. The mesh architecture helps keep signal strength up by replacing single, long radio links with multiple short ones.