An Empirical Study on Radio Propagation in Heterogeneous Networks: with Focus on Mobile Broadband Networks and Small Cell Deployment

The growing demand for mobile services represents a challenge for the existing networks. In order to cope with the increasing coverage and capacity requirements, operators have shifted the focus of their network evolution strategies from the densification and optimization of the macro layer to the deployment of heterogeneous networks (HetNets), where multiple radio access technologies and cell deployment options will coexist. These networks may be enhanced in the future by the use of higher frequency bands, which can help in supporting larger data rates as well as in coping with capacity problems in ultra-dense deployments. In order to plan and deploy such networks, radio propagation must be studied and properly modeled. The combination of different cell types and new frequencies have shaped a large set of yet unexplored propagation scenarios, which is further enlarged by the atypical use cases that will exist in the future cellular networks. With the aim of providing insight into some of these unexplored propagation scenarios, this thesis investigates, through experimental work and simulation analysis, different deployment configurations. The evaluation of the empirical data, together with the simulation results, is used to provide deployment guidelines and simple models useful for both radio planning and optimization; as well as for standardization purposes. The first part of the work addresses outdoor propagation. In the initial part of the analysis, the applicability of existing large-scale path loss models is validated, based on measurements, for selected frequencies, distances ranges and base station configurations outside of their original range of application. A lower accuracy of the models in the short range is observed, caused by the difficulty in predicting the antenna patterns effects in the close vicinity of the base station antenna. A geometrical extension of the models is proposed and the base station antenna pattern distortion effects are further analyzed in detail by means of simulations. With particular focus on relay node scenarios, a set of deployment guidelines is given based on empirical observations and performance evaluations. The propagation at higher frequencies is explored through several dedicated measurement campaigns for both the urban macro and micro cell scenarios with different base station