انگلیسی: Nowadays with the extension and the advancement of communications, the number of electronic devices has been increased. Moreover, with the development of the Internet of Things (IoT) in the next generation of communication networks, it is expected that a large number of devices will be connected simultaneously. Establishing such a large scale of communications requires mechanisms to improve efficiency in energy consumption leading to the advent of a new branch in communications called green communications. There are two general approaches to realize green communications. First is to use energy efficient methods to achieve the desired quality of service (QoS) by consuming the least possible amount of energy. Second is to harvest energy from different ambient and dedicated sources such as radio frequency (RF) signals. In addition to information transmission, an RF signal can carry energy. Hence, in addition to decoding the information bits, part of the received signal energy can be extracted using appropriate methods. This capability of RF signals has led to the appearance of a new approach in RF-based energy harvesting networks named simultaneous wireless information and power transfer (SWIPT). In this thesis, a multi-user SWIPT-based relay system consisting one multiple-antenna source and one multiple-antenna relay is studied, where each user is considered battery limited and has capability of harvesting energy from received signal using power splitting method. To characterize the system performance, two optimization problems for both the sum throughput maximization and the minimum throughput maximization are formulated. Our aim is to design the source precoder matrix, the relay amplification matrix and the power splitting ratio at each user. The resulting non-convex optimization problems are divided into three sub-problems which are then solved via alternating optimization (AO) approach. To tackle the non-convexity of the resulting sub-problems, a method based on the minorization-maximization (MaMi) technique is proposed. Finally, the simulation results are presented to evaluate the performance and convergence of the proposed scheme. Moreover, the throughput performance of the proposed system is compared with an equivalent system that uses the time switching architecture in the receiver of each user. کلمات کلیدی انگلیسی: (Simultaneous Wireless Information and Power Transfer (SWIPT Energy Harvesting Cooperative Communications Beamforming
