Bit error distribution in digital mobile radiocommunication¿comparison between field measurements and fading simulation

It is proposed to test the performance of mobile radio equipment by use of a fading simulator. This procedure has the advantages that the measurements can be made in laboratories, and that the random fading is reproducible in its statistical charcter. It is essential, however, to compare the results of fading simulation with field measurements. The fading simulator used is non-frequency-selective, and produces the two main random processes, Rayleigh and log-normal superimposed. The mobile measurements were made near Darmstadt, F.R.Germany. In most cases the results corresponded well with the simulation. The expected dependences of the signal/noise ratio and speed of the mobile on the bit error rates(BERs) were confirmed. Some measurements, however, revealed higher BERs than expected. Moreover, losses of data synchronism occurred. These irregularities are caused by heavy obstructions of the direct radio path and extremely low obstructions of the waves scattered from mountains, which were so far away that the excess delay can be of the order of magnitude of the clock period of the digital signal.