Theories And Methods Of Energy-efficient Resource Allocation For Heterogeneous Cloud Radio Access Networks

With the ability of fiully exploring the potential of both heterogeneous networks and cloud radio access networks,the architecture of Heterogeneous Cloud Radio Access Networks(H-CRANs)is proposed to improve the energy efficiency of the system,However,due to the absence of the relevant basic theories and some key supporting technologies,the development and application of H-CRANs are restricted.This dissertation mainly involves around the networking theory and key technologies of H-CRANs.The major research works and the contribution can be summarized as follows:1.The definition of the enhanced-energy-efficiency metric and the networking performance of H-CRANsSince traditional spectrum efficiency and energy efficiency metrics cannot characterize the impacts of some key factors like the transmission via fronthaul and the node density in H-CRANs,the cost coefficient is introduced to energy efficiency metrics to reflect the cost impacts of these factors,and the enhanced metric named Economical Energy Efficiency(E3)is proposed,with the definition detail included in this dissertation.The overall impacts of these factors are analyzed according to the simulation results.2.The energy-efficient resource allocation for H-CRANs based on cooperative node selection.While choosing cooperative nodes,it is difficult for existing cooperative transmission schemes to jointly consider the cost and the cooperative gain.Accordingly,this dissertation proposes a joint scheme for both cooperative node selection and resource allocation to optimize the E3 performance of the H-CRANs system,with the constraints of fronthaul capacity and maximum transmitting power both considered.With the help of fractional programming theory,the original non-convex optimization problem is transformed into an equivalent form so as to be effectively solved using the proposed iterative algorithm.Simulation results indicate that the proposed algorithm converges quickly,and the E3 performance of H-CRANs can be improved by more than 20%through selecting the cooperative nodes properly.3.The energy-efficient resource allocation for H-CRANs based on transmitting method selection.While using edge cache to ease the pressure on fronthaul transmission,it is difficult for current schemes to comprehensively consider the impacts on system cost and the cooperative gain.Accordingly,this dissertation proposes a joint scheme for both transmitting method selection and resource allocation to optimize the E3 performance of the H-CRANs system,considering the constraints of fronthaul capacity,maximum transmitting power,and cache size.By decoupling the optimization variables,the original optimization problems is divided into two sub problems on power allocation and transmitting method selection respectively,and the final solution can be obtained by solving the two sub problems iteratively.Simulation results indicate that the proposed algorithm converges quickly,and the E3 performance of H-CRANs can be improved by more than 10%through supporting the proper services with edge cache.4.The energy-efficient resource allocation for H-CRANs based on serving node selection.Since different access points have diversified working style,it is difficult for current schemes to properly balance the throughput,the energy consumption,and the cost of the H-CRANs.Accordingly,using E3 metric,this dissertation studies and designs a joint optimization scheme of H-CRANs serving node selection and resource allocation,under the constraints of fronthaul capacity,maximum transmitting power,the size of both centralized cache and edge cache,the serving node selection,and the transmitting method selection.By decoupling the optimization variables,the original optimization problems is divided into two sub problems on power allocation and serving node selection respectively,and the final solution can be obtained by solving the two sub problems iteratively.Simulation results indicate that the proposed algorithm converges quickly and can improve the E3 performance of H-CRANs by more than 20%.The E3 metric helps to evaluate the energy efficiency performance of the system with a more comprehensive consideration on some key factors like fronthaul transmission and content caching.The corresponding optimization schemes significantly improve the E3 performance of the H-CRANs,and the analysis of how these key factors affecting H-CRAN system is also included in this dissertation.