Modeling and performance analysis of wirelessly powered backscatter communication networks

In wireless-powered communication networks, the users need to harvest enough energy from the dedicated power station or existing radio frequency signal in order to actively transmit data. This requires the user to dedicate longer time for energy harvesting. The performance of the system is affected since the user cannot transmit data to the receiver in the network during the energy harvesting time. Therefore, in the technical literature, wirelessly powered backscatter communication network model has been proposed. In the backscatter communication method, the user modulates the incoming signal and sends it to the receiver. Since the incoming signal is used to transmit data during the backscatter period, the user does not need a radio frequency signal generator which consumes a certain amount of power in the internal circuitry. Receivers and transmitters in the backscatter communication system do not have components such as amplifiers and frequency mixers that consume a significant amount of energy. Therefore, especially in scenarious such as low power wireless communication, sensor networks and radio frequency identification, wirelessly powered transmission backscatter communication is important. In this thesis, first, wireless-powered communication network architecture is explained and basic information about energy harvesting scenarios are given. Then, backscatter communication techniques are explained. Next, studies on wirelessly powered backscatter communication networks with one or more users are examined in the technical literature. First, overlay and underlay cognitive radio based backscatter communication systems with single transmitter are discussed. Then, the case with multiple transmitters is considered. Employing the total amount of data that reaches the receiver per unit time as the performance criterion, resulting mathematical models are constructed optimization problems are formulated. The models are compared with communication systems that employs either backscatter communication or wirelessly-powered communication. It has been observed that the former provides better results in terms of the total amount of data that reaches the receiver. Different from the cognitive radio based network model, a wirelessly powered backscatter communication network consisting of a dedicated power station, information receiver and two users is also considered. In this scenario, one user works in backscatter communication mode while the other user employs in energy harvest-then-transmit mode. The cases where the battery capacity of the user operating in energy harvest-then-transmit mode is assumed to be finite and infinite are discussed. Backscattering, energy harvesting and transmission times are derived analytically and the effect of battery capacity and backscattering rate on the total amount of data transmitted per unit time are demonstrated via simulations.