Transmission Scheduling And Energy Management For Energy Harvesting Wireless Network

With the explosive growth of mobile users and high-speed network applications,the energy consumption and carbon emission of ICT industry are growing rapidly.Driven by the energy efficiency and enviro nmental concerns,the energy harvesting(EH)technology,which can be used to collect clean energy from the surroundings and draw distributed renewable energy sources into wireless communication networks,has provided a new direction for the green communications.Therefore,the EH technology has recently attracted extensive attention of researchers in communication field.But due to the external various factors,the energy is always intermittent and random when it is harvested from the natural environment.Hence,with regard to the data transmission in a wireless network,how to use the energy efficiently is a quite significant project of practical meaning.In this paper,we structure the mathematical model of EH wireless communication system and formulate the optimization problem by using the stochastic optimization theory.We also develop the transmission scheduling and energy management optimization algorithms for EH wireless communications network under different scenarios.The purpose of aforementioned work is to maximize the performance of the system or the efficiency of the energy harvested and reduces the energy consumption of the network from the traditional power grid.The specific work is as follows:1.Firstly,the optimal transmission algorithms for EH wireless communication system in specific scenarios are summarized and studied intensively,which provides a comparison reference for the algorithms in general scenarios.Specifically,we consider the two scenarios: given the deterministic knowledge of the event(energy harvesting,channel fading),and given their information.The corresponding optimal off-line and on-line optimal transmission algorithms are given respectively.In the first offline scenario,the collection graphics method,convex optimization and directional water-filling method are utilized to maximize the throughput by a deadline,subjecting to the constraints of causal energy harvesting and rechargeable battery capacity.And the impact of the battery capacity(infinite and finite)on the offline optimal algorithm are analyzed theoretically in the wireless static channel and fading channel respectively.Then we prove that minimizing the transmission completion time of the communication session is equivalent to maximizing the throughput by a deadline.In the second statistical scenario,the optimal transmission problem is considered.The online optimal strategy is obtained based on the Markov model,using stochastic dynamic programming.Some other suboptimal algorithms are introduced in order to reduce the complexity of the optimal online algorithm,and their performances of the offline and online optimal and suboptimal policies are compared numerically under different configurations.2.The optimal transmission power algorithm for EH wireless communication system in general scenario is explored.The EH process as well as wireless channel fluctuation,are always intermittent and random,so it's hard to obtain the probability distribution information in practice.The study in this general scenario has more practical significance.Considering the limited battery capacity and leakage,the throughput maximization problem of EH wireless system is formulated into a stochastic optimization problem,and Lyapunov optimization is utilized to solve the problem in this paper.A dynamic power control algorithm with low complexity is developed and is easy to implement.What's more,theoretical analysis of the proposed algorithm is performed,which illustrates that the proposed algorithm performs arbitrarily close to the optimal objective value.The numerical simulations verify the effectiveness of the proposed algorithm,which has the same performance as the optimal one with given statistical knowledge of the stochastic processes.Therefore,the proposed algorithm is a universal algorithm without depending on the statistical knowledge of EH and the channel state.3.The transmission scheduling and power allocation optimization algorithm for wireless communication system powered by hybrid energy source is studied,specifically,the hybrid energy source consists of EH source and power grid,and two conditions of single user and multi-user are considered.For high-power wireless communication nodes,such as the base station(BS),a BS powered solely by an energy harvester may not be able to maintain a stable operation and to guarantee a certain quality of service(Qo S).To achieve the reliable and green communication,namely,a hybrid energy harvesting system is preferable in practice for providing uninterrupted service.First the mathematical model for single user wireless system with hybrid energy source is established under the condition that energy arriving,data incoming and wireless channel are all general stochastic processes,taking into account of limited battery capacity,data cache capacity and the battery leakage.The user's toleration of delay constraint is transferred into a virtual queue stability constraint,a dynamic power control and the energy source scheduling algorithm for single user,the system is put forward based on the Lyapunov optimization.Then multi-user under the same scenario and constraints is studied further,and the dynamic power allocation and scheduling algorithm for multi-user is developed to satisfy the requirement of each user tolerant delay,specifically,the scheduling includes multi-user transmission scheduling and energy scheduling of energy sources.The energy consumption from the power grid is minimized by using the proposed algorithm,meanwhile,it can ensure that the maximum delay of all data queues cannot exceed user's requirements.So the system can make full use of the collection of clean energy and reduce carbon dioxide emissions.The performance of the proposed algorithm is analyzed theoretically,and the validity of the algorithm is verified by the comparison with other algorithms.4.The energy cooperation schemes of BSs supplied by hybrid energy source in cellular network are researched.A mathematic model of energy cooperation between the BSs is proposed based on the fact that the BSs equipped with energy harvesters and the harvested energy can be shared by the power line,in addition,the energy harvested is stored in individual limited rechargeable batteries and a portion of energy will lose when energy transfers.We select linear programming,greedy algorithm and Lyapunov optimization to develop energy cooperation schemes under three different scenarios based on the proposed model,and provide the corresponding optimal offline algorithm and online algorithm.The goal in this work is to minimize the sum of the energy consumed by the BSs from the conventional power grid,that is,to improve the utilization efficiency of the energy harvested and reduce carbon emissions.We validate the effectiveness of the proposed algorithm through numerical simulation,at the same time,we analyze the impacts of the transfer efficiency and the capacity of the battery on the property of the BSs,which is conducive to the design and realization of green communication.