Research On Interference Mitigation In LTE And LTE-Advanced System

In mobile communication, interference control is always the basis for system to keep steady and high-efficiency. Different from 3G system which uses CDMA, LTE and LTE-Advanced system use OFDM technology. Due to the orthogonality of the multiple sub-carriers, the intra-cell interference in LTE system can be ignored, while the inter-cell interference becomes the main interference source. This dissertation focuses on IDMA interference cancellation technology and inter-cell interference coordination (ICIC) technology.Interference cancellation based on IDMA is the best and the most complex technology to mitigate inter-cell interference. Instead of avoiding or randomizing interference, it can really eliminate the strong interference, which plays an important role in the performance enhancement. But if the IDMA interference cancellation technology is used, there are a lot of preconditions needed to satisfy. As for this problem, this dissertation proposes a new IDMA receiver of lower complexity. According to the simulation results and analysis, the appropriate length of spreading coding and the iteration number for data services are given.It is known that ICIC technology enhances the performance of cell-edge users by sacrificing the throughput of the whole cell to some extent. It can mitigate the inter-cell interference with a lower complexity. The basis of this technology is to judge the users'position status, which means whether users exist in cell center or cell edge. In order to solve this problem, RSRP double-thresholds reporting mechanism is proposed, where different thresholds are used according to the different position status. This method can solve the Ping-pong problem in wireless channels, therefore decreases the air interface signaling and leases the burden on UE consumption. Simulation analysis is also given to verify the advantage of this mechanism.