irical-statistical models such as Hata-like models, frequency is. multiwall models for indoors, etc. can provide a nearly A wide range of comparisons between measurements similar level of accuracy in most cases with a lower and RT simulations has been carried out [TLVD01]. Part computing time. Ray models are therefore worthwhile if of the measurement campaign was carried out in the 5th a higher insight into the multipath process is needed. floor of the Communications Engineering Department of This is the case of fading statistics assessments, wide- the University of Cantabria, a very complex environ- band assessments, multidimensional (space, time, fre- ment. Three RX trajectories, T1, T2 and T3, are analysed quency, Doppler frequency) channel characterisation, and here. Both the data obtained from the measurements and any other problem involving these aspects. In [Bert02] those resulting from the simulations were processed in and [ChBe01] a VPL RT model is used to perform radio order to obtain the Rician probability distribution channel characterisation. Channel statistics are needed function that best fitted the curve in each case, according for advanced system design, but measurements are costly. to the criterion of the minimum root mean square Moreover, measurements carried out in one environment error. Figure 4.7-19 shows the Rice K-factor of the local may not apply to a different environment. The use of ray fast fading estimated for these three trajectories. models is a relatively inexpensive substitute for mea- Figure 4.7-20 presents the normalised level crossing rate surements, with the advantage of allowing the simulation for the trajectory T1, this case being representative of all of a large number of cases in a very short time. In [Bert02] the others. It can be observed that the results obtained, it is shown how it is possible to derive channel statistics on from both the measurements and the simulations, closely the base of the output of a large number of RT runs by approximate the theoretical ones si