Effects of bandwidth on microwave line-of-sight channel modelling and digital radio performance prediction

A technique of microwave line-of-sight channel transfer function measurements which makes a new approach to channel modeling possible is described. Propagation is divided into two parts: dispersive fading (DF, IBAD>1 dB) and wideband flat fading (FF, IBAD<1 dB), which are disjoint in time. The DF-part is modeled with the joint distribution of a four-parameter two-part channel representation with a constant delay, and the FF-part which includes signal enhancement is modeled with the fade depth distribution. Results for several measurement bandwidths up to 40 MHz clearly show that the DF-model depends on bandwidth while the FF-model depends only moderately on bandwidth. A new outage prediction method based on the actual channel models shows FF-outage to be insignificant. However, DF-outage depends strongly on the flat fade margin. A comparison with the conventional outage prediction method shows that, although quite different results are indicated for the DF- and FF-outage contributions, there is a rather good agreement between total outage predictions.<>