Research On Resource Allocation For Energy Harvesting Systems

With the development of communication technology,the demands of high-data-rate transfer and multi-media offering are rising rapidly.And as consciousness for environment protections is increasing,energy conservation has become a hot issue in both industry and academia.Contributing to both energy-deficiency alleviation and carbon footprint reduction,energy harvesting(EH)is deemed to be a promising technique recently.By investigating and classifying the literatures,this paper summarizes the conclusions of resource allocation schemes for energy harvesting systems and finds out that most of the researches are focus on the two-hop relay systems.,Based on these conclusions,this paper expands the system model and proposes optimal resource allocation algorithms,including power allocation algorithms,relay selection scheme and so on.Numerical simulation validates that the algorithms can effectively improve the system performance when different system conditions are chosen.The main contents and innovations of this paper are shown as following:Firstly,this paper researches on resource allocation for a multi-user energy harvesting relay system.Different from existing researches,this paper considers uplink multi-user relay systems which adopt both energy harvesting and sleep mode.After establishing the system model,a heuristic algorithm which includes the power allocation scheme and time slot assignment scheme is proposed.The relay in our system is an EH node with random charging rate while the base station(BS)is supplied by power grid and users work with traditional rechargeable batteries.We propose a novel power allocation scheme with which the system can minimize the total energy consumption.After formulating a joint optimization problem,we put forward a heuristic algorithm and successfully decrease the computational complexity.Firstly,by fixing the transmission time,we modify the problem into a convex optimization problem.Secondly,the shortest transmission time can be obtained by the method of bisection.The simulation results show that the proposed scheme can effectively bring a lower energy consumption,and we further validate that a combination of EH and SM plays a significant role in energy saving.Secondly,uplink joint relay selection and power allocation in an energy harvesting multi-relays multi-users system is studied.By further expanding the system model,this paper take multi-relay in to consideration and relay selection algorithm becomes more and more important.The problem is formulated as a non-convex optimization that maximize the system throughput,while random energy harvesting ratio and limited total transmit power in users are considered.To solve this non-convex optimization problem,we propose a heuristic algorithm to obtain a suboptimal solution,in which high system throughput can be achieved while computational complexity is kept relatively low.Numerical simulation reveals how the system throughput varies with the energy harvesting ratio,the total transmit power maximum and the relay number.These prove the effectiveness of the proposed scheme.