Analysis Of MBS Offloading Through CoMP In Heterogeneous Cellular Networks

To meet the ever-growing demand for a higher communicating rate and better communication quality,macro base station(MBS)only model is unsustainable.More and more Small Cells are overlaid under the macro base station tier,thus forming the so-called heterogeneous cellular networks(HetNets).Heterogeneity is expected to be a key feature of future cellular networks,and an essential means for providing higher end-user throughput as well as expanding its indoor and cell edge coverage.In HetNets,one of the Small Cells' goal is to ease the load pressure of MBS.However,the random deployment of Small Cells and their uncoordinated densification raise important concerns about interferences and energy efficiency.On the other hand,cooperation has been proved as an effective method to dress the problems arose.Meanwhile the trend of Small Cell densification will show the advantages of cooperative communication.In this paper,in a typical 2-tier HetNets,we propose a novel method to offload users from MBSs through Small Cell cooperation.In the traditional offloading strategy,the typical user will access to its nearest MBS or Small Cell based on its maximum received signal strength.In the proposed cooperative strategy,the cooperative Small Cell cluster will take the place of the single Small Cell.Here,we use the association probability to measure the offloading performance of different strategies.By using the tools from stochastic geometry,we then obtain the expression of the association probabilities.Then under different offload strategies,we propose the dynamic power consumption model,where the power consumption of the base station is related to its current load.Based on the models,we analyze coverage performance under different offloading strategies and obtain the expressions of the coverage probabilities and mean achievable rate for the typical user.Then on this basis,the energy efficiency of the system is obtained.Numerical results show that Small Cell cooperation can offload more users from MBS tier compare to a single Small Cell.And it can also increase the system's coverage performance.As Small Cells become denser,user's mean achievable rate increase.Based on the dynamic power consumption model,the energy efficiency increases as well.It shows the great importance of cooperation and Small Cell densification.