Research On Downlink Interference Mitigation For Wireless Heterogeneous Networks

Wireless communications are developed greatly in recent years. Femtocell, alsoknown as home base station, has attracted a lot of attention of telecom operators as acost-effective approach for improving the indoor coverage and average throughput. Inwireless heterogeneous networks, contrasts to well-planned macrocell networks,femtocells are densely and randomly deployed within the coverage area of macrocell.Femtocell technology, which is adopted in two-tier wireless heterogeneousnetworks, brings severe cross-tier and co-tier interference as an interference source. APseudo-Random Subchannel Selection (PRSS) scheme for downlink interferencemitigation is proposed to suppress the cross-tier and co-tier interference. Firstly, thehybrid frequency allocation scheme is adopted, which divides the whole band intothree sub-bands, such as macrocell dedicated, femtocell dedicated, andmacrocell-femtocell shared frequency bands. On the shared frequency band, the PRSSscheme is performed to randomize the cross-tier interference by aggressor femtocellsselecting subchannels pseudo-randomly under the control of pseudo-random sequence.With the help of the Neighbor Relation Matrix, the maximal number of sequences thateach femtocell picks can be calculated. The co-tier interference can be suppressed byfemtocell selecting different pseudo-random sequences.A system-level simulation platform is established to evaluate the interferencemitigation effect of the PRSS scheme. Firstly the general structure of the simulationplatform is introduced. Then new snapshot can be created after the initialization ofsimulation parameters. After that, the femtocells and User Equipments (UEs) aredropped in random distributed locations in this platform, as well as the femtocellblocks. And then the path loss, log-normal shadowing and antenna gain are calculatedfor obtaining the received power of each UE. Femtocells can select the subchannelfollowing the PRSS scheme, and then resource scheduling can be established. Finallythe system-level simulation platform can complete the performance calculation andstatistics.The simulation results show that the PRSS can suppress the cross-tier and co-tierinterference, and get better SINR performance than other four traditional interference suppression schemes. Meanwhile, the average throughput of macrocell and femtocellsare increased obviously.