 schemes in cheap tance, measured in hundred metres [KeBr05]. receivers where knowing the occurrences of fades be- In comparison, indoor environments at 60 GHz would forehand could be used to advantage [AJJF99]. Another be easier to model, as reported by Geng et al. [GKZV05]. envisaged use is that of transmit diversity in situations From the measured directional patterns at the campus of with insufficient knowledge of the channel or with too Helsinki University of Technology, they concluded that in low update rates of the channel state information LoS cases, the channel is well described by the direct [DuHH00]. Predicting the channel state could then path and first-order reflections. In NLoS cases, alleviate the need for frequent channel state updates. diffraction is the main propagation mechanism. This idea has been taken up by several authors. The A special case of non-stationary propagation conditions early publications mainly treat the narrowband case is encountered in tunnels, just behind the entrance. [EyDHH98], [HwWi98], [AJJF99] but later ones also Molina-García-Pardo et al. investigated this transitional address wideband aspects [SeKa02b]. A number of regime, called 'excitation zone' [MaLD94], using UTD publications showed a limited achievable prediction RT to examine path loss, delay spread, and angular spread range, normally fractions of a wavelength to about one over the first hundreds of metres in a rectangular straight wavelength under favourable conditions ([AJJF99], tunnel of cross-section 8.5 X 5.2 m 2 (w X h) [M0RJL03]. [Teal01], [Ekma02], [SeKa03]). The transmitter, at 2.1 GHz, was placed at the tunnel's centreline at 100 m distance from the entrance at three different heights, corresponding to elevations of 15°, 30°, Principle of fading prediction and 45°. In the excitation zone, delay spread, angular As an example of the principle of fading prediction, we spread and path loss change drastically. The angular will treat here the narrowband case. Extensions to the spread reaches it maximum trans