Research Of Simultaneous Wireless Information And Power Transfer

Recently, the rapid expansion of Mobile Internet and the Internet of Things has brought huge opportunities for wireless communication industry. Especially, the short-distance communication represented by the wireless sensor network shows vast potential for future development in the fields of smart city, smart home, intelligent transportation system and so on. The wireless sensor networks are usually energy constrained, and the sensors are always placed in the inaccessible environments. So the wireless sensor networks will reach the end of their lifetime when the energy of batteries is exhausted. To solve the problem, energy harvesting via wireless power transfer is a potential solution.Electromagnetic wave could be utilized not only to transmit information, but also to transmit power wirelessly, so the concept of simultaneous wireless information and power transfer (SWIPT) was proposed. The main concerned issue of this thesis is to design the overall architecture of SWIPT, and the major contributions are the proposed capacity optimization algorithm and the energy efficiency optimization algorithm for SWIPT.In the first part, the overall architecture has been designed for the SWIPT of short-distance communications represented by the wireless sensor network. The system is modeled based on the narrowband MI SO scenario, and the upper bound performance in theory is derived for SWIPT. Besides, the receiver architecture is discussed; the time switching and the power splitting receivers, the separated and the integrated receivers are compared.In the second part, the capacity optimization problem has been studied for SWIPT. Firstly, based on the scenario of narrowband MISO link and the application of power splitting separated receiver, the mathematical model is established for capacity optimization problem constrained by the minimum requested harvested power. Secondly, the Lagrangian dual method is adopted to solve the optimization problem with continuous power splitting ratios, and the closed solution is deduced. However, the exhaustion method is employed to solve the optimization problem with the discrete power splitting ratios. Finally, simulation is conducted to analyze the feasibility and performance of the algorithms, and related influencing factors are also discussed. The obtained simulation results reveal that with15KHz bandwidth,2.4GHz carrier frequency and43dBm transmission power, the transmission distance is about1-2meters meeting the demands of some short-distance communications, and the date rate meets the demand of medium speed transmission with level of hundreds of Kbps.In the third part, the energy efficiency optimization problem has been studied for SWIPT. Firstly, based on the scenario of narrowband MISO link and the application of power splitting separated receiver, the mathematical model is established for energy efficiency optimization problem constrained by the minimum requested harvested power and the minimum QoS requirement. Secondly, nonlinear fractional programming, one dimension searching and the convex optimization are involved to resolve the problem. Finally, simulation is conducted to analyze the feasibility and performance of the algorithm, and related influencing factors are discussed. The simulation results show that the proposed algorithm would improve the energy efficiency of the system significantly compared with the capacity optimization algorithm.