System Design On Simultaneous Wireless Information And Power Transfer In Heterogeneous Networks Based On Stochastic Geometry

As the number of base stations and terminals as well as the volume of data traffic continue to increase,consequently there comes a lack in energy and radio spectrum resource.Therefore,there exists an urgent need for the integration of existing study on communications and energy technologies,to meet the requirement of reliable communications and to effectively deal with the energy shortage issues at the same time.As a result,the introduction of new energy sources to wireless communication systems has caused widespread attention in the industry.On one hand,energy-limited wireless networks equipped with batteries of limited capacity may result in limited running time,while the battery replace-ment or recharging is inconvenient or even hazardous or impossible.On the other hand,the use of multiple-input multiple-output(MIMO)and other mod-ern communication technologies make far-field wireless power transmission(WPT)become possible.Therefore,a more convenient,safe and green choice is to harvest energy from radio frequency signals,which can provide a perma-nent supply of energy for wireless devices.Meanwhile,faced with hundreds of millions of wireless terminal devices,Internet of Things(IoT)and wireless sen-sor networks will serve as an important role in scenarios such as cargo tracking,landslides or forest fires forecasting,etc.Combined with wireless information transmission(WIT)and WPT,simultaneous wireless information and power transfer(SWIPT)becomes a promising novel technology.Future mobile communication network topology becomes more and more irregular.The introduction of small cell deployments and ultra-dense network-ing(UDN)architecture make the distribution of signal source more complex,and cell area and coverage also become more chaotic.Considering current SWIPT system under heterogeneous cellular networks lacks a systematic study and an effective evaluation methods,this thesis focuses on the analysis and sys-tem design for SWIPT under heterogeneous cellular network.Firstly,a reliable model of heterogeneous networks is established focusing on power splitting(PS)mechanism in SWIPT system,including base stations deployment model,channel model,user access model,etc.,and performance metrics such as cov-erage probability,user average harvested energy and the average cell through-put are defined.And then,theoretical expressions of these metrics are derived.Both Monte Carlo simulations and numerical simulations are given to verify the effectiveness of the theoretical analysis;Secondly,an optimization problem to maximize the average harvested energy under coverage probability constraints is formulated.Based on the stochastic geometry treatment,two PS schemes are proposed based on the solution of the optimization problem.The first one is the optimal fixed PS ration design for each tier,and further a dynamic location-based PS ratio design(DLPS)is proposed.A practical application flow of op-portunistically energy harvesting with proposed DLPS scheme is also provided.And simulation results demonstrate the average harvested energy is effectively increased by more than 30%when coverage probability requirement is greater than 0.7 by the proposed DLPS compared with the optimal fixed PS ratio design while maintaining the coverage performance.