Research On The Interference Coordination Technologies Of Small Cell In LTE-A

Currently, Long Time Evolution-Advanced (LTE-A), which is proposed and driven by the3rd Generation Partnership Project (3GPP), has become a widely used standard of4th generation mobile communication in the global. A series of key technologies have been applied to the LTE-A system, such as Carrier Aggregation, Coordinated Multi-Points, Enhanced Multiple-Input Multiple-Output, Relay, etc. Compared to the former mobile communication systems, LTE-A system has significantly improved the frequency efficiency, system bandwidth, peak data rate, system throughput, etc. With the rapidly growing demand of mobile data traffic, dense deployment of Small Cell has become the first choice to satisfy the users’demands. The related technologies of Small Cell Enhancements (SCE) for E-UTRA and E-UTRAN in physical layer aspects have become the most important direction during the Release12period, and it is expected to be written into3GPP specification by the end of2014.Due to the dense and random deployment of Small cell, it may bring some difficulty in network planning and optimization. The main challenges of Small Cell deployment are the more and more intense inter-cell interference (ICI). In order to maximize the utilization of spectrum resource, LTE usually share the same frequency band between the Macro Cell and Small Cells. So new technologies should be introduced to reduce and avoid the co-layer interference among Small Cells and the cross-layer interference between Macro Cells and Small Cells. In order to reduce the ICI, some mature technologies have been adopted into LTE already, such as fractional frequency reuse, soft frequency reuse, etc. But when these technologies are applied to the Small Cell scenario, there is no significant gain observed, and what’s more, they are very difficult to be successfully deployed. LTE-A has introduced a new interference coordination technique which is called enhanced Inter-Cell Interference Coordination (eICIC) in Release10. The eICIC technique is a time domain solution to offload users from Macro Cell to Small Cell. The paper has proposed an algorithm that adjusts the Almost Blank Subframe (ABS) ratio on a fast basis, aiming at balancing the instantaneous load between Macro Cell and Small Cell. With this dynamic solution, the work can bring significant system throughput gain and improve user performance. For the co-layer interference among Small Cells, the thesis introduced a Small Cell fast on/off mechanism by introducing the reasonable judgment and switching process to achieve a fast activation and dormancy scheme of Small Cell. In this way, the Small Cell fast on/off mechanism can not only reduce the interference among Small Cells, but also bring down the energy consumption and improve the system performance.In order to accurately assess the performance of new technical solutions, the thesis adopted a LTE-A system-level simulation platform according to3GPP SCE scenario. Finally, the thesis validated the system performance gain from the dynamic ABS algorithm-based eICIC and the Small Cell fast on/off mechanism through the LTE-A system-level simulation platform. The simulation results and conclusions can provide theorectical reference to the dense deployment of Small Cells in the future.