What does the term 'line of sight' refer to in wireless communication?

The term 'line of sight' in wireless communication refers specifically to a direct path between the transmitter and receiver without any obstructions intervening. This concept is crucial for many wireless communication technologies because when there is a clear line of sight, the signal can travel unimpeded, leading to a stronger and more reliable connection.

In scenarios where there are obstacles such as buildings, trees, or other structures, the signal may be absorbed, reflected, or diffracted, which can lead to degradation of the communication quality or even complete interruption. A clear line of sight is particularly important for high-frequency signals, such as those used in microwave communications and certain satellite communications, where the frequency's ability to penetrate obstacles is limited.

Other options presented do not relate to this concept. Encryption and modulation are important aspects of securing and processing signals, while measuring signal strength deals with assessing the quality of a received signal, rather than defining the physical pathway the signal takes between sender and receiver. Understanding the importance of line of sight helps in designing effective wireless communication systems.