Research Of Joint Transmission And Joint Resource Allocation In Ultra-dense Networks

As more and more user demand for the high rate,low latency services,such as the High Definition(HD)video and Virtual Reality(VR),it will be gradually unable for the fourth generation of mobile telecommunication(4G)to meet the future communication needs.Thus,the research on the fifth generation of mobile telecommunication(5G)is significant and forward-looking.Compare to 4G,5G will support higher user data rate,higher reliability,lower network latency,multiple devices and denser user equipment.In order to meet the high communication requirements in some specific scenarios,e.g.,the office building and large stadium,the Ultra-Dense Networks(UDNs)emerged.UDNs can improve the capacity of the system by deploying the multilevel,dense communication nodes.In hotspot and high capacity area,the deployment of UDNs has shown great potential on supporting multi services with high rate and high density.The application of UDNs can help to increase the efficient of frequency resource and realize the mass but high quality communications.The interference problem which exists in UDNs is severe and unavoidable.Because of the high density of the communication nodes,not only the distance between transmitter and receiver is diminished,but that between the receiver and interference source is also smaller.The close distance will lead to the increase of interference intensity and the larger amount of interference sources.Moreover,because the distribution of base stations in UDNs is multi-level and heterogeneous,the inter-layer interference cannot be ignored,and the system capacity is smaller than expectation.Hence,the research of UDNs should focus on the methods to mitigate the co-channel interference.In this paper,we use coordinated multi-point(CoMP)technology to manage interferences in UDNs.The reasons for the adoption of Co MP are as follow: first of all,due to the dense distribution of nodes,it is possible to meet the requirement of multi points cooperation in Co MP technology.Secondly,interference usually c omes from several neighboring nodes.There exist a large number of heterogeneous interference sources with strong interference intensity.Hence,it is infeasible to study single node without considering the interference from adjacent nodes.In Co MP,this paper mainly concentrates on the influence of the joint transmission(JT)in interference management.Starting with the selection of cooperative sets in joint transmission,we discuss the influence of different cooperative set selection methods on interference reduction and the improvement of system performance.Then,we consider the selection of cooperative sets with the restriction of backhaul capacity,and we also try to reduce the pressure of backhaul link by sleeping and waking up some base stations.In addition,as the traditional sub-channel allocation method is not appropriate to the scenario of JT,which means a few nodes transmit to one user on the same sub-channel simultaneously,the improvement of the conventional sub-channel allocation algorithm is studied in joint transmission scheme.By using the joint transmission technology and sub-channel allocation algorithm in UDNs,the intensity of interference is effectively reduced to improve the performance of system.