User-centric Joint Interference Rejection Method in Ultra Dense Network

As one of the key technologies of 5G, ultra dense network (UDN) increases the system capacity of local hotspot areas by deploying wireless network infrastructure more densely. Aiming at the handover and interference of edge users, this paper adopts a user-centric transmission scheme and proposes a user-centric joint interference rejection method. In order to simplify the complicate network topology and reduce the computational complexity of the interference rejection method, a dynamic clustering algorithm based on graph theory is proposed in which a virtual cell cluster of different sizes is formed to achieve joint transmission of all micro-base stations to users in the cluster by introducing a reasonable threshold to divide the network. Besides, for intra-cluster and inter-cluster interference, a joint interference rejection algorithm that uses ZF and MMSE precoding to reject intra-cluster interference and inter-cluster MMSE precoding to further reject inter-cluster interference is proposed. The simulation results show that the proposed virtual small clustering algorithm can greatly increase the system capacity and reduce the system bit error rate (BER) and the spectrum efficiency of the system has been further improved after the interference rejection between clusters.