Research On Inte-Cell Interference Controlling Technologies For Broadband Mobile Communication System

Orthogonal frequency division multiplexing (OFDM) is selected as the main access technique in almost all the possible evolution technologies targeting to 4G The main advantages are easy to implement the lager bandwidth from 5M to 100M, and the high bandwidth efficiency, the ability to combat multi-path fading, the compatible to MIMO. In 3GPP LTE, OFDM is an ordinary single carrier network. It provides the attractive property of intra-cell orthogonality. But OFDM is different from CDMA. Just like GSM, it cannot average the inter-cell interference by spreading processing and cause the strong inter-cell interference in OFDM system. In order to improve spectrum efficiency and reduce the interference, the flexible interference mitigation techniques including the coordination, cancellation and randomization are used, but in practices, these solutions can not improve the cell edge uses throughput and system throughput much more to target the operator's requirements. So in 3GPP LTE-Advanced, current research, inter-cell interference controlling technology is also in hot debates. In this thesis, extensive research on key technology of inter-cell interference controlling is studied.The frequency hopping is an important technique in interference randomization. It can bring the frequency diversity gain and interference diversity gain. A new predefined pattern combinated with inter/intra TTI band hopping and mirror hopping based on the study of frequency hopping design principal is presented. The method can keep single carrier transmission and avoid collisions at the same time is suitable for various RBs transmission bandwidths. The solution for scheduled users and frequency hopping users coexisting is presented. For frequency hopping resource fragments caused by HARQ, a solution is gived according to this qucstion.The conclusion is verified by computer analyses and simulation. This method is suitable for most of low and all high moving speed scenarios and has a good prospect of application.LTE doesn't use the uplink joint receiver just like the CDMA soft handover, as the flat network requirement. But as the BBU-RRU is widely used, the backhaul limit between base stations is broken, and in LTE-Advanced, the joint receiving is re-considered as a basic technique for improving the cell edge users'throughput. In this thesis, the system of uplink CoMP (Coordinated MultiPoint transmission/reception) is studied, the Shannon capacity is analyzed based on the property of interference is approximate log-normal distribution. From the analysis and simulation, the uplink CoMP is very important to improve the cell edge users'throughput and system performance. In the same time, a comprehensive solution is proposed in the combination with ICIC, frequency hopping and CoMP to avoid the resource collision of the three techniques.LTE-Advanced need the obvious improvement at cell edge, it is important for seamless quality requirement. The base model of downlink CoMP is founded, and I analyze the main two factors for CoMP gain. The key to the CoMP gain controlling are the CoMP geography area controlling and multi user CoMP. In the thesis, the gain curve of SINR for CoMP and non-CoMP is compared, and illuminates how to find the suitable CoMP geography area. From the system performance and cell edge performance, both single user CoMP and multi user CoMP improve the performance, and the multi-user CoMP has more potential gain for the throughput.