ndovers and on the HOF. We use two different HetNet scenarios. The first scenario is 3GPP simulation model using static and random base station deployment models. The 3GPP HetNet model is a so-called generic model, which aims at capturing general effects that would typically occur if observing a large number of dense urban environments. The second model is based on site-specific use cases where a particular urban area is explicitly modelled using three-dimensional topography maps and ray-tracing propagation characteristics. We consider two dense metropolitan urban areas, based on data from Europe and Tokyo. LTE Small Cell Optimization Macro high load 95 percentile 50 percentile 5 percentile Without CA/DC CA with ideal DC with non-ideal backhaul backhaul Small cell - high load 95 percentile 50 percentile 5 percentile Without CA/DC CA with ideal DC with non-ideal backhaul backhaul Figure 8.12 Average PRB utilization in each cell with/without DC at high load (50 Mbps offered load) For the considered European city area, the macro sites are deployed at different heights, taking the local environment into account in order to have good wide area coverage. A total of 48 small cells are deployed at 5 m height in street canyons or at open squares. The small cells are deployed to further improve 5 percentile outage throughput of the network [6]. The former brings to a deployment where the small cells are clustered in certain areas, while other areas contain only few or no small cells. For the areas with small cells, there are on average two small cells per equivalent macro cell coverage area. The small cells are equipped with omni- directional antennas. The Tokyo area has more regular streets and buildings layout. Buildings have an average height of 24 m and a maximum of 150 m, and the streets are wider. A total of 20 macro sites (all with 3 sectors) are deployed per square kilometre. The macro antennas are placed 5 m above buildings in the local area. A total of 70 small cells are deployed at 5-m height. The small cells ar