around the point where the Doppler spectrum has been T1_1800 T2_1800 T2_2400 calculated are obtained by suitably sampling the curve r(l) Simulations VS. measurements r(l==t) = |r(t)| = (4.7.3) Figure 4.7-19 Measured and simulated Rice K-factor for the three routes. CHAPTER 4.7 Propagation modelling and channel characterisation Envelope level crossing rate, LR/fm at a central RX point (15 m, 15 m)in an arbitrary indoor environment of 30 m X 30 m. The procedure is described as follows. During each computer run, all the walls are moved simultaneously and randomly to give uncorrelated wall movements and the phasor sum of all the rays ar- riving at the receiver is obtained. An optional additional random variable with a 10% standard deviation (selected arbitrarily) is added to the values of the electromagnetic measurements properties of the walls (permittivity and conductivity) to method 1 account for uncertainties in these values. The values of n method 3 computer runs are then averaged to obtain an estimate of the local mean field strength at the RX point. The esti- mated level is compared with the value obtained by av- Level (dB) eraging a block of points around the receiver separated by Figure 4.7-20 Measured and simulated Rice K-factor for the less than N/4. The obtained averaged field value is com- three routes. pared for different computer runs (for the wall imper- fection model) and different number of points forming resources. An alternative approach to estimating the the averaging block (for the spatial sampling approach). expected local mean level, based on artificially modu- The results are summarised in Table 4.7.3. The results lating the wall surfaces to cover all the possible signal from averaging blocks of points following the spatial phases, is the proposed wall imperfection model. The sampling approach suggest that averaging 400 points (5x proposed model is implemented by randomly varying the X 5%) seems to be enough for indoor environments to position of each wall using a uniformly distributed reach 