Research On Downlink Interference Management Technology In Heterogeneous Networks

With spectral efficiency of point-to-point link in cellular network approaches to the Shannon limit, the deployment of pico base stations in macro base station network becomes an effective means to meet the explosive demand of the coming data traffic. Through the reuse of spectral resource in the existing system, heterogeneous network (HetNet) not only can improve the spectral efficiency but also make it more flexible for site deployment with lower network maintenance price and wide spreader coverage. For co-channel HetNet with single radio access technology, the severe downlink intercell interference restricts the cell split gain, and in order to overcome it, the corresponding measure, such as cell range expansion (CRE), worsens the link quality of cell edge users. It makes the interference management of HetNet more complicate and needs effective interference control to improve the performance of cell users. Form the perspectives of network and user equipments, focusing on severe intercell from neighbor macro base stations suffer by users in range expansion region, the thesis conducted research on downlink interference management technology in HetNet, in order to mitigate the interference from macro base stations.To overcome the intercell interference received by CRE users, as an the widely used interference coordination method, the time domain almost blank subframes (ABS) technique suffers from inherited shortcoming, that is, macro base stations mute on ABS subframes and the waste of precious time-frequency resource often restricts the performance of macro base stations. Aiming at the problem, when the transmitter with multi-antennas, the thesis proposed a novel spatial interference coordination based on ABS scheme and designed corresponding coordination beamforming strategy through incorporating time and spatial domain interference coordination. Macro base stations send data to macro users and mitigate the intercell interference according to the indication of interference control feedback from range expansion region users on ABS subframes. The thesis designed the detailed algorithm and procedure, and evaluate the performance of the proposed algorithm by system level simulation.For receivers, advanced receivers in user equipment (UE) to resist intercell interference are getting significant attention from the3rd Generation Partnership Project (3GPP), such as successive interference cancellation (SIC) receivers. Unlike the traditional receiver dealing with the interference as noise, SIC receivers in UEs need to detect the interference signal and subtract the reconstructed interference before detecting the desired signal. Without the condition of correct interference signal data detection, the residual interference resulted from imperfect interference cancelation will worsen the performance of SIC receivers. Since HSDPA transmit signal with full power and cannot reduce intercell interference by power adaption, in order to improve the performance of RE UEs, the thesis proposed a successive interference cancellation algorithm based on rate adaptation. The thesis analyzed the relationship between residual interference from imperfect cancelation and the rate of interference signal, then established the sum rate maximum optimization problem based on rate adaptation. Based on the optimization result obtained by analyzing the characteristic of the problem, the thesis designed the detailed procedure of the algorithm and verify the system performance of the algorithm through simulation.