 seen, both temporal and angular, when deviation or more [Hans03]. comparing both bands. The largest difference, between In contrast to the approach of Hansen, Fügen et al. two environments and between both bands, was found turned to advanced simulation tools as most of the re- for the (azimuthal) angular spread, with strong decorre- alistic environments are too complex to use analytical lation between the two frequency bands. The decorre- channel models [FMDW03]. They used the proprietary lation is strongest in urban environment, which has 3D RT tool of Karlsruhe University in an urban macro- a richer scattering than the suburbs, as measured from cellular environment without high-rise buildings, Karls- the larger angular spreads. The authors conclude from ruhe, over an area of approx. 500 X 700 m². The their findings that downlink beamforming based on simulation incorporates multiple reflections, multiple uplink measurements in scattering-rich environments is diffractions, and combinations of both. The BS was vir- sub-optimal [FBKE02]. tually placed at 25.5 m height, well above the average Propagation modelling and channel characterisation CHAPTER 4.7 Excess delay (ns) DoA (°) (a) Digital power spectral density. (b) Azimuthal power spectral density. Figure 4.7-41 Intracluster marginal power density distributions for LoS, measured (solid line) VS. modelled (dashed) (after [CTLM02]). building height of 12.5 m and the carrier frequency was were clustered by a 2D Gaussian kernel density estima- 2 GHz. The results show that the angular spreads at the tor; a cluster was defined as a set of multipath compo- MT are higher on street crossings than in street canyons. nents with similar excess delays and AoAs. Chong et al. Also, the authors model both delay and angular spread, at propose a cluster model, to be discussed in the chapter on BS and MT, with an offset negative exponential function MIMO modelling, in which the temporal and spatial of distance between BS and MT. A disadvantage is that domain are independent for O