autocorrelation depends only on the distance shift. their two independent means and variances. Therefore, Considering the case in which a series of propagation the performed measurements indicate that the assump- maps that account for shadowing needs to be generated, tion of a Gaussian distributed signal magnitude is not it involves producing a shadowing sample for each loca- valid, when the measured statistics are dominated by tion in every map. Since maps are two dimensional, it is a particular scenario, which has for instance much higher not possible to establish an order among its locations; amplitudes than all the other parts of the investigated consequently, the second approach cannot be adopted. In environment. Globally, it is observed that the log-nor- this situation, instead, the first one should be used; mality of the path loss is not valid for arbitrary scenarios; nevertheless, its application is not straightforward. CHAPTER 4.7 Propagation modelling and channel characterisation A two-dimensional modelling technique, which allows component (if it exists) plus several reflected and/or MTs in the vicinity of the simulated environment to diffracted ones, being usually described by a Rayleigh or undergo related shadowing effects, is presented in Rice distribution, depending on the existence of a LoS [FrLC03], [FGLM04] component [Pars92]. Under LoS (Rice case), the ratio between the power 2 + Ay2 of the LoS component and the power of the reflected/ R(Ax,Ay) = 2dcorr (4.7.8) diffracted ones is usually named the Rice or Ricean factor, K. It should be noted that the value of K is a useful where Ax and Ay are the MT shift in horizontal and measure of the communications link performance, its vertical coordinates, respectively, and dcorr is the decor- proper estimation being of practical importance for an relation distance. accurate channel characterisation [Corr01]. Assuming that a set of n shadowing maps corre- When the long-term fading effect is modelled by a log- sponding to n BSs covering the same area must 