Data Communication & Computer Network

Unguided medium transport electromagnetic waves without using a physical conductor. This type of communication is often referred to as wireless communication. Signals are normally broadcast through free space and thus are available to anyone who has a device capable of receiving them. The below figure shows the part of the electromagnetic spectrum, ranging from 3 kHz to 900 THz, used for wireless communication. Unguided signals can travel from the source to the destination in several ways:  Gound propagation ,  Sky propagation  and  Line-of-sight propagation  as shown in below figure. Propagation Modes Ground Propagation:  In this, radio waves travel through the lowest portion of the atmosphere, hugging the Earth. These low-frequency signals emanate in all directions from the transmitting antenna and follow the curvature of the planet. Sky Propagation:  In this, higher-frequency radio waves radiate upward into the ionosphere where they are reflected back to Earth. This type of transmis