Signal propagation: path loss, fading, shadowing

How Signals Weaken Over Distance

Every radio signal loses strength as it travels from transmitter to receiver through a combination of predictable and unpredictable effects. Path loss is the dominant and most predictable factor, causing signal power to decrease with the square of the distance in free space, meaning doubling the distance reduces received power by 6 dB or one quarter. Real-world environments amplify this loss considerably beyond the free-space model because signals must contend with atmospheric absorption, terrain variations, and the complex geometry of urban landscapes filled with buildings, vehicles, and…