Study On Utilization And Transmission Efficiency Of Energy In Wireless Networks

The rapid development of information and communication technology has led to the rapid popularization of intelligent terminals,which also bring the explosive growth of mobile data services.The increase energy consumption of equipment in mobile networks has become an important limiting factor for sustainable development strategies.Corresponding standards and technologies have been proposed in the fifth generation mobile communications(5G)to improve utilization and transmission efficiency of energy in wireless networks.In terms of energy utilization,energy storage at the user terminals(UTs)can be achieved by harvesting energy from the surrounding environment.However,how to reasonably design the parameters in the network to enable the information transmission,and as much as energy storage at UTs is a problem to be solved.In terms of transmission efficiency of energy,firstly,energy consumption and interference of the network will increase when the base station without associated user still keeps on,and unfairness problem will occur when the resource scheduling is unreasonable.Therefore,the affection of user association and resource scheduling of the base station to the energy efficiency of the network is worthy of researching.Secondly,the deployment of dense small cells brings serious interference among different cells.Therefore,how to coordinate small base stations(SBSs)to serve the deployed users,and how to allocate the transmission power of SBSs to reduce interference and improve energy efficiency of the network,are problems to be solved.Thirdly,how to assist the source node complete the information transmission through an energy-limited relay node has attracted much attention.According to the above discussions,this thesis focuses on the study of utilization and transmission efficiency of energy in wireless networks.The innovations of this thesis are summarized as follows:1.For user terminal(UT)energy-constrained dense small cell scenarios,a radio frequency energy harvesting method that considering the popularity caching scheme of small cell base stations(SBSs)is proposed,which is applicable to the UTs that are inconvenient to connect a charger.The proposed method is based on simultaneous wireless information and power transfer(SWIPT)system,reducing the delay of UTs that fetch contents through backhaul link by adopting popularity caching method in SBSs.Thereby harvesting energy of UTs is improved,and the resource and energy consumption of the backhaul link from core network to SBSs are reduced.Firstly,the corresponding network model,content request and popularity cache scheme are given in the system model.Secondly,popularity cache-based user association scheme and resource allocation method are designed.Further,the harvested energy maximization problem of SWIPT system with popularity cache scheme in dense small cell networks is established,where the transmit power of SBSs,minimum rate requirement,i.e.,quality of service(Qo S)of UTs,and power splitting ratio of SWIPT system are considered.Finally,an iterative power splitting ratio and power allocation optimization(IPSPA)algorithm is proposed to solve the formulated problem.Moreover,better energy harvesting performance of the proposed method is verified by comparing with uniform cache scheme and no caching scheme in the simulation.In addition,this work can be extended to the study of SBSs coordinated to provide services to users,and hybrid energy supply.2.For a two-tier heterogeneous network(Het Net)composed of one macrocell base station(MBS)and several SBSs.Due to the non-deterministic polynomial(NP)hardness of joint user association and resource scheduling,successive user association and resource scheduling algorithms that based on the sleep mode of SBSs are proposed to analyze the downlink energy efficiency of the two-tier Het Net.Firstly,the association relationship between the base stations and users is determined according to three user association algorithms.In the processes of user association,the SBSs without associated users will go to sleep mode to save energy and reduce the interference of the network.Secondly,the macrocell base station and small cell base stations resource blocks(RBs)are scheduled to users based on three scheduling algorithms.Moreover,fairness among users is also analyzed in the process of resource scheduling.Finally,analysis and discussion about reasonable algorithms in different network environments are given.In addition,the scenario that this work can be extended to the study of several MBSs and SBSs Het Net is discussed.Moreover,better power allocation,user association and resource scheduling methods can also be considered based on this work.3.For dense small cell network and relay energy-limited internet of things.Traditional method does not consider dynamic coordination of SBSs,or full-duplex relay-assisted coordinated communication with linear network coding scheme.On the one hand,the dynamic coordinated multi-point joint transmission(Co MP-JT)method is pro-posed to improve the energy efficiency of the network.Firstly,the problem of joint user association and power allocation of SBSs is established.Secondly,the dynamic Co MP-JT user association algorithm and dynamic Co MP-JT power allocation are adopted to solve the formulated problem.Simulations show that the proposed method has better energy efficiency compared with the second near coordinated multi-point(Co MP)transmission? transmission without Co MP and random Co MP methods.On the other hand,the full-duplex relay coordinated transmission model and method of SWIPT system is established to improve the spectral efficiency of the system.Further,an information decoding scheme consists of linear network coding and maximal ratio combining scheme is proposed to decode the information of the destination node.Finally,the iterative power splitting ratio(IPSR)algorithm is proposed to solve the formulated problem.Simulation results show that the proposed full-duplex relay coordinated transmission coordinated transmission technique has better spectrum efficiency compared with half-duplex relay coordinated transmission considering the direct link and full-duplex relay coordinated transmission not considering the direct link.In addition,the extended work of multi-antenna,new multiple access technology and multi-relay study is discussed.