Terrestrial Radio Channels

Terrestrial Radio Channels

Radio channels carry signals in the electromagnetic spectrum. They are an attractive medium because they need no physical wire to be installed, can go through walls, provide connectivity to a mobile user, and can potentially carry a signal for long distances. The features of a radio channel depend considerably on the propagation environment and the distance over which a signal is to be carried. Environmental considerations decide path loss and shadow fading (which decrease the signal strength as the signal travels over a distance and around/through obstructing objects), multipath fading (due to signal reflection off of interfering objects), and interference (due to other transmissions and electromagnetic signals).

Terrestrial radio channels can be generally classified into two groups: those that operate in local areas, normally spanning from ten to a few hundred meters; and those that operate in the wide area, spanning tens of kilometers. The wireless LAN technologies explained in "Access Networks" use local-area radio channels; the cellular access technologies use wide-area radio channels. We'll discuss radio channels in detail in "Wireless and Mobile Networks".



Tags

lan, radio channels, electromagnetic signals

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