o. Propagation modelling and channel characterisation CHAPTER 4.7 the MT, Nj is a randomly drawn path-loss exponent with mean = 2.33 and standard deviation = 0.3 and W is the main street (where the BS is located) width. In [HeKu05] several different deterministic simplified models are compared in a UMTS urban macrocellular environment with ultra-high sites, i.e. with BSs mounted at a height of at least 100 m. Namely, the models under comparison are COST-WI, flat edge, Maciel-Xia-Bertoni and a reference free-space formula. Since the elevation angle of the LoS path can be quite high, Maciel-Xia- Bertoni shows large prediction errors at small distances, where COST-WI performs well. A hybrid model is pro- posed which combines Maciel-Xia-Bertoni and COST- WI, switching from the former to the latter where the Figure 4.7-26 Example of dominant paths tracing in an outdoor elevation angle exceeds 0.15 degrees. scenario (Hong Kong city). The adoption of simplified models is almost mandatory parameters can automatically be calibrated with when general results must be derived which are not spe- measurements. The new model has been tested in cific to a particular topology. In [Fusc04] a simplified indoor and outdoor environments by comparing field Hata-like model is used to study innovative coverage so- strength predictions with measurements. Once cal- lutions for DVB systems. The capability of providing high ibration is done, the attainable accuracy is very good, quality reception by handheld terminals is a very impor- comparable with RT prediction (standard deviation tant target in digital video broadcasting. Unfortunately, of the error of about 4 dB indoors and 6-8 dB out- preliminary assessments and field trials indicate that this doors) with a very low computation time. The com- target cannot be satisfactory achieved by conventional putation time for the Munich COST 231 blind test network planning, based on the reuse of existing trans- scenario (2000 buildings, 10 m resolution, 8.7 km2 mission sites (in order to limit th