Wireless networks use radio frequencies within the microwave spectrum to transmit signals. The frequency determines how often the signal cycles per second, while the wavelength is the distance between points in the signal cycle. As the signal spreads from the transmitter, it loses energy through free path loss. Absorption and reflection can also weaken the signal as it passes through obstacles, and multipath issues can occur when multiple reflected signals reach the receiver at different times. Maintaining line of sight and keeping the first Fresnel zone clear of obstacles helps ensure good signal quality for outdoor wireless links.

1. Wireless Fundamentals Introducing WLAN RF Principles