Research On Energy Efficiency Enhancement Scheme In 5G Heterogeneous Cellular Networks

The gradual popularization of smart devices has led to explosive growth of traffic demands in the network which has posed significant challenges to network performance.In order to provide larger transmission rate and higher quality of service,5G heterogeneous cellular networks(HCNs)deploy enormous small cell base stations(SBSs)in the coverage of the macrocell base station,which can greatly increase network capacity and meet the dramatically growing traffic demands.However,the large number of SBSs have brought the increase of energy consumption and intra-layer interference,resulting in degradation of network performance.According to the idea of green communication,the thesis proposes an energy efficiency(EE)resource allocation scheme to optimize network resource allocation and dynamically adjust base stations working mode in order to increase network EE with time varying traffic demands.The tidal effect in communication network is related to the time varying traffic demands.In this thesis,a dynamic small cell base stations on/off strategy in 5G HCNs is proposed to maximize the energy efficiency,which consists of the following three steps.Firstly,the loading balance based base stations and user equipments(UEs)association.Secondly,the Markov Chain based traffic load prediction.Finally,the dynamic SBSs on/off scheme to maximize network EE under the constraint of network outage probability and minimum signal to interference plus noise ratio(SINR)constraint,with the predicted traffic load.The proposed scheme could estimate the transmission performance and outage probability of the network in advance according to the predicted load,and make decisions for SBSs to reduce the interruption time while ensuring the transmission performance of UEs.Notice that,the proposed scheme can reduce network energy consumption and improve network EE with the price of transmission rate.In order to further improve EE of HCNs,the thesis jointly considers the small base station clustering,geometric approach based power allocation,dynamic SBSs on/off scheme,and proposes a clustering and geometric approach based resource allocation scheme to ensure the network outage probability,the minimum received SINR and loading balance.The intra-layer interference is increasing with the increasing number of SBSs,especially for edge UEs.In order to reduce the intra-layer interference,a semi-definite programming based correlation clustering scheme is proposed to cluster SBSs into different groups to guarantee the continuous service of UEs in the handover process.Moreover,an energy efficient and geometric approach based power allocation scheme is introduced to optimize transmission power allocation based on the geometric water-filling algorithm,which could improve network EE and reduce the computational complexity.Last but not least,to further improve network EE under communication tidal effect,a dynamic SBSs on/off scheme is discussed.Additionally,to ensure the transmission quality of UEs in the core area,the corresponding SBS will keep working mode.From simulation results,it can see that the proposed scheme can achieve considerable performance improvement in network EE and loading balance compared with the comparison schemes.