Interference Management In Heterogeneous Networks

The deployment of Heterogeneous Networks(HetNets)can improve the coverage of users in door and the capacity of the HetNets and attracts many attentions.However,the interference in HetNets is serious,which limits the capacity of HetNets to a large extent.To reduce the interference and improve the capacity,we focus on interference management(IM)in HetNets.The main innovations and contributions of the paper are as follows.1)Firstly,we introduce the conventional opportunistic interference align-ment(OIA)into HetNets and it indeed reduces the CI from the MUs effectively.Then,based on the unique characteristic in HetNets,the novel opportunistic in-terference mitigation(OIM)schemes based on adaptive reference signal spaces(A-RSSs)are proposed.However,broadcasting the A-RSS constantly makes the system more complicated,so a complexity-performance tradeoff is consid-ered.To decrease the complexity of the system,the quantization codebook is introduced and the quantized A-RSS based OIM is proposed.2)A joint femtocell clustering and selective beamforming scheme is pro-posed to mitigate the severe interference at femtocell base stations(FBSs)caused by the uplink transmissions of MUs in HetNets.Firstly,a number of adjacent FBSs are clustered.Then,both beamforming at the in-cluster femtocell users and MUs are designed with a strategy to minimize the generated interference(MinGI)toward some selected interference-vulnerable FBSs within each clus-ter.By employing such low-complexity selective beamforming,the in-cluster interference is significantly mitigated.3)The CA is introduced to HetNets,so that the BS can schedule all the discrete component carrier(CC)and transmit different data in different CCs.To decrease the interference at MU or pico users(PUs),the MUs and PUs are allocated to different CCs.For the MUs,an improved simulated annealing(SA)algorithm is proposed to maximize the sum rate of the MUs.However,the sys-tem overhead of applying improved SA to PUs is too heavy,a novel maximize minimum distance(MMD)based PUs allocation algorithm is proposed.In the proposed MMD,the minimum distance from a given PU to the PBSs trans-mitting data in each CC is calculated,and the CC correspond to the maximum minimum distance is selected.