Modeling and design for future wireless cellular networks: coverage, rate, and security
Creators: name: Wang, He
Publisher: name: The Australian National University
Year: 2013
Subjects: cellular networks
network modeling
performance analysis
physical layer security
heterogenous network
femtocell

description: Accompanied by the wide penetration of smartphones and other personal mobile devices in recent years, the foremost demand for cellular communications has been transformed from offering subscribers a way to communicate through low data rate voice call connections initially, into providing connectivity with good coverage, high data rate, as well as strong security for sensitive data transmission. To satisfy the demands for improved coverage and data rate, the cellular network is undergoing a significant transition from conventional macrocell-only deployment to heterogeneous network (HetNet), in which a multitude of radio access technologies can be co-deployed intelligently and flexibly. However, the small cells newly introduced in HetNet, such as picocells and femtocells, have complicated the network topology and the interference environment, thus presenting new challenges in network modeling and design. In recent studies, performance analyses were carried out accurately and tractably with the help of Poisson point process (PPP)-based base station (BS) model. This PPP-based model is extended in this work with the impact of directional antennas taken into account. The significance of this extension is emphasized by the wide usage of directional antennas in sectorized macrocell cells. Moreover, studies showed that little coverage improvement can be achieved if small cells are randomly deployed in a uniform-distributed way. This fact inspires us to explore the effect of the non-uniform BS deployment. We propose a non-uniform femtocell deployment scheme, in which femtocell BSs are not utilized if they are located close to any macrocell BSs. Based upon our analytical framework, this scheme can provide remarkable improvements on both coverage and data rate, thus stressing the importance of selectively deploying femtocell BSs by considering their relative locations with macrocell BSs. To alleviate the severe interference problem, the uplink attenuation technique is frequently employed in femtocell receivers to reduce the impact of interference from unattached terminals such that femtocell communication can take place. In order to analyze and optimize the femtocell system performance with this technique, we propose an analytical framework and demonstrate the performance tradeoff resulted from higher and lower uplink attenuation levels. Furthermore, we provide two improved uplink attenuation algorithms, which adaptively adjust to the information of the scheduled traffic, data rate requirement, and interference condition. Apart from the cellular coverage and data rate, communication security has been an important issue to be addressed due to the increasing demand for transmitting private and sensitive information over wireless networks. In the last part of the thesis, physical layer security, as a new way to improve wireless secrecy, is studied for cellular networks. By highlighting the unique cellular features offered by the carrier-operated high-speed backhaul, we investigate the probabilistic characterization of the secrecy rate, and identify the performance impacts of cell association and location information exchange between BSs. These results provide necessary network design guidelines for selecting the appropriate cell association method and information exchange range.