Statistical properties of the RMS delay-spread of mobile radio channels with independent Rayleigh-fading paths

The statistical properties of the RMS delay-spread for mobile radio channels with independent Rayleigh-fading paths are investigated. We give analytical formulas for the statistical distribution of the local RMS delay-spread for two independent paths (two-delay model). We show that there is a considerable difference between the mean RMS delay-spread and the expected value of the local RMS delay-spread if the number of paths is small; however, this difference vanishes for a large number of paths.