Research On Interference Coordination Schemes For Relay-Based LTE-A System

In order to maintain remarkable superiority at the mobile communication domain,3rd Generation Partner Project (3GPP) proposes LTE technology standard to compete with WiMAX. At the end of 2008, 3GPP puts forwards smooth evolution technology of LTE, LTE-A.In order to solve the capacity and coverage problems in LTE, relay has been adopted in 3GPP LTE-A system, as it can enhance cell capacity and expand the cell coverage efficiently and effectively. Relay is useful in many scenarios, such as enhancing the capacity of hotspot, overcoming the coverage of dead spot, temporary deployment for conferences and group handover for vehicles. However, Relay destroys frequency orthogonal characteristic at the same cell and brings in intra-cell interference.Firstly, the paper outlines the key technologies in LTE-A. Secondly, the three types of common interference suppression technologies, such as interference randomization, interference cancellation and interference coordination, are introduced in detail. Interference randomization only turns the interference into white noise, the effect is not obvious and it is often used as an assistant method to suppress the interference between control channels. The effect of interference cancellation is most obvious, however it need reconstruct the interference signal and demands complex equipment, so it is not widely adopted. Interference coordination has advantages in remarkable effect on interference suppression and easy realization. Finally, according to relay pattern, different interference coordination schemes are proposed to solve the interference between access link and direct link respectively.The paper's main contribution includes two aspects. Firstly, system-level simulation on average throughput of the backhaul link is made, and the result demonstrates that SDMA (Space Division Multiple Address) extract the potential capacity of the backhaul link, the link between BS and relay. Secondly in view of LTE-A system based on type I and type II relay, novel interference coordination schemes are proposed and confirmed by system-level simulation respectively. The simulation results show that the two proposed schemes have achieved prominent gain on cell average throughput and Cumulative Distribution Function (CDF) of SINR (Signal to Interference plus Noise Ratio).