Research On Network Energy Efficiency Optimization In Dense Small Cell Networks

In recent years,with the explosive growth of mobile data traffic,a cellular communication system is faced with enormous challenges.On the one hand,in order to meet the increasing demand of mobile data traffic and improve the data rate of the communication network,the characteristic of the heterogeneous cellular network become extremely complicated,and many technologies need to be reconsidered.On the other hand,the rapid deployment of small cell base stations result in increasing of the extra energy consumption.Based on the concept of green communication,wireless communication technologies pay more attentions to the network energy efficiency while guaranteeing the users' quality of service.This thesis focus on the energy efficiency optimization,in dense heterogeneous cellular network,which combines the networks cell association,base station on/off strategy and resource allocation technology.The main contents are as follows:Firstly,based on the characteristic of dense heterogeneous cellular network,this thesis discussed the current research works on cell association,base station on/off strategy and resource allocation technology.Meanwhile,the advantages and disadvantages of those schemes are also pointed out.Secondly,considering the difference between the transmission power and the maximum available traffic load of various base stations in the dense heterogeneous cellular network,an energy efficiency based jointly optimizing cell association and femtocell base station on/off strategy algorithm is proposed,including the users' minimum target SINR,traffic load balancing and maximum outage probability constraints.The proposed optimization problem is transformed in to two sub-optimization problems,namely,the optimal cell association load balancing based scheme and the optimal femtocell base station on/off strategy.Additionally,in order to improve the network performance and ensure the shut femtocell base station can be quickly awakened to serve the dynamic data traffic,the multi-level sleep strategy is proposed,which considers the minimum coverage probability and maximum average delay constraints.Furthermore,by solving the probability of the sleep state will decide the optimal sleep strategy of the femtocell base station.Finally,in order to further improve the network energy efficiency,multi-level sleep strategy based resource allocation algorithm is proposed.The optimization problem is a nonconvex problem,which could be transformed into an equal convex form and solved by an iterative algorithm based on energy efficiency optimization.Simulation results indicate that the proposed joint femtocell base station sleep strategy and resource allocation algorithm could achieve significant improvement of the network energy efficiency while guaranteeing the minimum rate requirement and the maximum transmission power constraints.