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Line of sight (LoS) propagation from an antenna. Line-of-sight propagation is a characteristic of electromagnetic radiation or acoustic wave propagation which means waves can only travel in a direct visual path from the source to the receiver without obstacles. [1] Electromagnetic transmission includes light emissions traveling in a straight line.
Line-of-sight propagation, electro-magnetic waves travelling in a straight line Non-line-of-sight propagation; Line-of-sight velocity, an object's speed straight towards or away from an observer; Line-of-sight double star, one in which two stars are only coincidentally close together as seen from Earth; Beyond visual line of sight
From the figure the received line of sight component may be written as = {() /}and the ground reflected component may be written as = {() (+ ′) / + ′}where () is the transmitted signal, is the length of the direct line-of-sight (LOS) ray, + ′ is the length of the ground-reflected ray, is the combined antenna gain along the LOS path, is the combined antenna gain along the ground-reflected ...
Satellite communication uses longer line-of-sight paths; for example home satellite dishes receive signals from communication satellites 22,000 miles (35,000 km) above the Earth, and ground stations can communicate with spacecraft billions of miles from Earth. Ground plane reflection effects are an important factor in VHF line-of-sight propagation.
Normally, signals in the microwave frequency range travel in straight lines, and so are limited to line-of-sight applications, in which the receiver can be 'seen' by the transmitter. Communication distances are limited by the visual horizon to around 48–64 kilometres (30–40 mi). Troposcatter allows microwave communication beyond the horizon.
UHF radio waves propagate mainly by line of sight; they are blocked by hills and large buildings although the transmission through building walls is strong enough for indoor reception. They are used for television broadcasting , cell phones , satellite communication including GPS , personal radio services including Wi-Fi and Bluetooth , walkie ...
Optical communication, also known as optical telecommunication, is communication at a distance using light to carry information. It can be performed visually or by using electronic devices . The earliest basic forms of optical communication date back several millennia, while the earliest electrical device created to do so was the photophone ...
Link 22 provides beyond line-of-sight (BLOS) communications. It interconnects air, surface, subsurface, and ground-based tactical data systems, and it is used for the exchange of tactical data among the military units of the participating nations. Link 22 will be deployed in peacetime, crisis, and war to support NATO and Allied warfare taskings.