Research On Interference Management In Ultra Dense Networks

The development of high-definition video,augmented reality,wearable devices and other technologies has promoted the sustainable development of the communications industry,but it has also brought an exponential growth in the demand for communications traffic.In order to meet this demand,mobile communication networks have evolved from traditional single-layer cellular networks to today's dense heterogeneous networks.In the future,the formation of ultra-dense networks(UDN)by deploying denser low-power nodes is expected to achieve 1000 times magnitude of the system capacity.In UDN,with the coverage areas of each base station are overlapping,serious inter cell interference restricts the increase of the data rate for the edge users.Based on this,this thesis focuses on the downlink interference management in UDN.The main work points are as follows:This thesis analyzes the characteristics and types of interference in UDN,and summarizes the existing classical interference management methods in cellular networks.At the same time,the advantages and defects of each interference management scheme are briefly analyzed.In order to reduce the cross-tier interference between macro base station and small base station due to the overlapping coverage and large transmission power difference,this paper proposes a low-power almost blank subframe(LP-ABS)scheme,which can achieve independent power adjustment for each macro base station on the LP-ABS.Firstly,the scheme classifies all users into four categories and selects their corresponding associated base station.Then,the LP-ABS ratio reserved by the macro base station for the lowpower nodes is determined according to the load.Finally,a maximized system throughput model based on the macro base station LP-ABS power setting is established.Gradient descent method is used to obtain the optimal solution of the power on LP-ABS for each macro base station.The simulation results show that compared with the traditional zero power almost blank subframe(ZP-ABS)and all macro base stations using the same low power transmission data in the ABS timeslot,the proposed scheme can obtain better system throughput gain.With the increasing of lower power access nodes,the co-tier interference between low power nodes can not be ignored.In the traditional base station centric clustering scheme in the CoMP,cluster edge users are still suffer inter-cluster interference Therefore,this thesis put forward a user-centric coordinated multi-point joint transmission(CoMP JT)interference management scheme.Firstly,a user-centric base station cluster is established based on the received SINR of users,and then in order to obtain the maximum of the sum logarithm of user rate,this thesis construct a joint optimization problem,which decomposed into two sub-problems,namely resource scheduling and power allocation.At the same time,this paper considers the difference of user's business and gives users different priorities when allocating resources.The simulation results show that the proposed algorithm based on user priority resource allocation can meet the requirements of different user rates.Compared with the traditional non-overlapping cooperative clusters,the user-centered overlapping clustering scheme improves the user's rate very well.