Research On Energy-saving Optimization In Dense Heterogeneous Networks

The increasing of users and required data rates has triggered extended size of wireless cellular networks.Vast network size and massive wireless devices have put forward higher requirements for network capacity and energy efficiency.Therefore,the dense deployment of low-cost and high-capacity small BSs(SBSs)in the coverage of macro BSs(MBSs)has been introduced as a promising solution to reduce the energy consumption of the whole networks while satisfying the quality of service(QoS)requirements of the users.Furthermore,the uneven distribution of user traffic in the networks has brought more opportunities to the dense heterogeneous networks in reducing energy consumption.The main work of this paper is to design the energy-saving strategies in dense heterogeneous networks based on the on/off strategies,whose premise is ensuring the QoS for users.The main research work and innovations of the paper are summarized as follows:1.An Energy-Saving Scheme With Joint User Association,Clustering,and On/Off Strategies in Dense Heterogeneous NetworksThis paper proposes an energy saving algorithm with joint user association,clustering and on/off strategies for the down-link transmission of the dense heterogeneous networks.Firstly,this algorithm proposes a distributed optimal association policy proportional to energy efficiency for new arriving users and re-associated users.Then,based on distance and load,the clustering problem is modeled as an integer linear programming,and the near-optimal clustering results are obtained by using the semi-definite programming.In the end,this paper proposes a low-complexity clustering-based energy-saving algorithm based on the load effect of switching off base stations on others.The simulation results demonstrate that,the proposed clustering-based energy saving algorithm can reduce the average network cost largely for different network load conditions compared with traditional algorithms.2.A DTMDP-based Asynchronous On/Off Strategy in Green Heterogeneous NetworksTo dynamically adjust the on/off states of the SBS based on the traffic level of the networks,the DTMDP model is developed to match up the BS switching operations with the traffic load variations.Then,an asynchronous decision-making algorithm,which is based on the Bellman equation and the on/off priorities of the BSs,is firstly put forward and proved to be optimal in this paper.Through reducing the state and action space during one decision,the proposed asynchronous algorithm can avoid the “curse of dimensionality” occurred in DTMDP frequently.Finally,numerical simulations are conducted to validate the effectiveness and advantages of the proposed asynchronous on/off strategies.