The relationship between fading and bandwidth for multipath channels

A signal transmitted over a multipath channel experiences fading, the variability of which is a function of: 1) signal bandwidth; and 2) power delay profiles of the channel´s specular and diffuse components. We analyze this general relationship and, for several important classes of multipath channel, we derive simple, closed-form approximations for what we call the stability bandwidth, W₀. For signal bandwidths greater than W₀, the local area variation in the received signal power is acceptably small, e.g., less than 1 dB standard deviation of decibel power. We demonstrate the accuracy of our W₀ approximations for some representative cases. Moreover, we show that the root mean square delay spread-a statistic commonly used to characterize multipath channels-has limited utility in estimating W₀.