Electrical and Electronic Engineering - Theses
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ItemEnergy efficiency of wireless network using coordinated gated narrow beams( 2019)With the ever-increasing demand for wireless service and higher data rate, the wireless network has experienced an unprecedented growth worldwide in the past decade and it is expected to grow continuously. Energy efficiency of the wireless network has become a growing concern for network operators and standardization authorities, not only to reduce the overall electric energy usage but also to reduce its environmental footprint. This has triggered research work to explore future, green wireless technologies and strategies in order to bring energy efficiency improvements in the entire network. In this thesis, we investigate the opportunity of improving energy efficiency through the use of coordinated gated narrow beams for downlink transmission of data. This is a class of Coordinated Multipoint (CoMP) transmission technique which is originally proposed in LTE standards for enhancing cell-edge throughput. The principle is that multiple base stations are coordinated with each other so that potential interfering source from the adjacent base station can be steered away by appropriate beamforming and scheduling. The thesis is divided into three parts. In the first part, we develop a realistic coordinated beamforming strategy using gated narrow beams and estimate the network throughput and base station power consumption based on network level simulation. In the simulator, we apply a practical traffic model in which users entering at a rate consistent with time of day dependent traffic level, and a proportional fair resource scheduling scheme to ensure fairness between users. Then, we analyse the required channel state information to support the beam coordination and resource scheduling, and develop a low-overhead signalling and control framework that provides sufficient signalling information. The signalling design and its implementation leverage signalling functionality and protocol in current standards. We develop methodologies for quantifying the signalling overheads introduced in terms of the percentage of downlink resource occupied by additional coordination reference signals. Finally, we develop energy consumption models of the functional components and processes in the coordinated network architecture, including backhaul switches and interfaces, and a central coordination unit. We quantify the additional energy costs associated with the coordination and signalling functions, and perform a comprehensive evaluation on the energy efficiency of an LTE network employing the proposed coordinated gated narrow beams. Our results show that significant energy savings can be achieved compared with a conventional network with no coordination.