N-fold sectorization in the light of intra-site coordinated multi-point transmission

Mobile data communication has become ubiquitous during the last few years. To meet the exponential growth of mobile data traffic, mobile network operators face the challenge of significantly increasing their network capacity. Furthermore, the spatial distribution of the available user data rates has to become more homogeneous to improve the user experience. An increase in the number of base stations and coordinated multi-point transmit and receive techniques are among the most promising concepts to accommodate both objectives in sectorized cellular networks. This thesis focuses on the degrees-offreedom in the design of sectorized cellular networks using so-called intra-site coordinated multi-point transmission. In order to investigate the degrees-of-freedom available, a generalized concept of modeling such networks is proposed that can be used to analyze networks with arbitrary extents of sectorization and overlapping coverage areas. Furthermore, an advanced threedimensional base station antenna model is developed that allows tuning major antenna radiation characteristics, and also incorporates an antenna gain formulation. To assess the potential performance of sectorized cellular networks, transmission concepts with and without intra-site base station cooperation are selected for a detailed analysis. Based on this, the impact of the extent of sectorization and the impact of major antenna radiation characteristics are evaluated through a system level analysis. The sensitivity to non-full load and the impact of the degree of cooperation are analyzed as well. Moreover, the results are extended to consider multi-antenna base stations. Thus, it is shown that higher extents of sectorization can, indeed, improve the network performance. However, for conventional non-cooperative transmission, this gain has to be compensated by a user performance degradation. One of the key results is that the application of joint Wiener filtering at 6-sector sites with 35° antennas already achieves 77% of the average network throughput gain that can be obtained while switching from these 6-sector to 12-sector sites with 17.5° antennas. The last part of this thesis discusses practical implications of the theoretical results obtained. One of these is the fact that intra-site cooperation renders 70° antennas, i. e., typical antennas for 3-sector sites, attractive even for cellular network designs with higher extents of sectorization. In general, it is found that intra-site cooperation in conjunction with higher extents of sectorization is a suitable means to improve network and user throughput as well as the spatial homogeneity of user data rates.