INFLUENCE OF MULTIPATH PROPAGATION ON BIT ERROR RATE

Conventional wave propagation models for transmitter networks predict fieldstrength levels only. Wideband wave propagation models however, i nclude algorithms to characterize the radio channel. For digital radio systems the BER of the unprotected radio channel is an important para meter. In the approach presented in this paper, the influence of multi path propagation on different digital modulation schemes is investigat ed. The calculations are based on a 3D wave propagation model, which y ields a Fieldstrength-Delay-Spectrum (FDS). The FDS is defined by ampl itudes and delays of all incident waves, from which information about intersymbol interference due to multipath propagation is derived. Two algorithms to derive the BER from the FDS for both linear and non-line ar digital modulation schemes are presented. The emphasis is on GMSK a nd PSK-modulation schemes, which are used in digital mobile radio syst ems (DCS 1800, GSM, DECT) as well as in digital audio broadcast system s (DAB). An analysis of the performance of the different modulation sc hemes in difficult terrain is shown.