Virtual Sectorization in Future Mobile Networks

Abstract

Virtual Sectorization (ViS) is proposed as a solution to cope with the exponential growth of data traffic in mobile networks. Through the use of an Active Antenna System (AAS), two vertically separated beams (serving two distinct cells) are created within the original coverage area of a macro-cell. One of these cells, referred to as virtual cell, can be flexibly placed anywhere within the original coverage area because the large antenna array is capable of producing very narrow beams. The position of the virtual cell is done by choosing an electrical azimuth and downtilt such that the virtual cell’s footprint is as much as possible steered towards an area of relatively heavy traffic (a traffic hotspot). The key advantage of the approach is that, depending on the choice for deployment, either the spectrum or the transmit power is reused in the same geographical region, which provides an increase of traffic handling capacity. With an antenna beam directed to a specific area of high user density, more users can potentially benefit from better antenna gain and hence experience higher Signal-to-Interference-plus-Noise Ratio (SINR) values compared to the non-ViS case. However, the involved trade-offs make the deployment of ViS non-trivial. Using ViS implies a reduction of either transmit power or bandwidth for the macro-cell, and one additional interferer in the network, both of which can have a negative effect on performance if not addressed correctly. In order to cope with the complexity of these trade-offs, SON algorithms capable of dynamically share the spectrum or power resources between virtual and macro-cells, as the ones presented in this thesis work, are needed. The key functionality of these algorithms is to find an optimum configuration for the given resource sharing scheme which is able to maximize the network capacity while minimizing the aforementioned negative effects.