What is LOS and NLOS?

Answer 1

Line-of-sight (LOS) is a condition where a signal travels over the air directly from a wireless transmitter to a wireless receiver without passing an obstruction. LOS is an ideal condition for a wireless transmission because the propagation challenge only comes from weather or atmospheric parameters and the characteristic of its operating frequency. In LOS environment, signal can reach longer distance with better signal strength and higher throughput.

Conversely, non-line-of-sight (NLOS) is a condition where a signal from a wireless transmitter passes several obstructions before arriving at a wireless receiver. The signal may be reflected, refracted, diffracted, absorbed or scattered. These create multiple signals that will arrive at a receiver at different times, from different paths, and with different strength. Consequently, wireless systems developed for NLOS environment have to incorporate a number of techniques to overcome this problem and that make the systems more complex than those for LOS. But NLOS capable systems simplify network planning and site acquisition.