Reseaches On The Interference Management Of Small Cell Based On System Level Simulation Of LTE Networks

With the development of broadband mobile communications, network capacity is continuously enlarging, while the demands of the mobile terminal users for a high-rate wireless mobile communication services are also increasing the challenge for a larger network coverage and capacity. The new technologies at non-network level only has a limited improvement in system performance and user experience. Therefore, the definition of Heterogeneous Network is proposed to introduce small cells with low transmit power into the traditional network, which mainly includes femtocell, picocell and microcell. Regarded as an effective technology to improve system coverage and capacity and the performance of the network, but small cell technique also brings negative effects such as more complex inter-cell interference by overlapping with macrocell.This thesis first analyzes the LTE Inter-Cell interference coordination technique, such as fractional frequency reuse (FFR) and soft frequency reuse (SFR). Based on LTE system-level simulation platform,we simulates the FFR and SFR interference coordination algorithm, and analyzes the cell performance under different brand and power ratios, to provides an optimal brand and power ratio setting recommendations. The simulation result suggests that the system spectrum allocation based on FFR and SFR can alleviate the inter-cell interference and improve cell-edge throughput significantly.In order to solve the interference problem between small cell and macrocell, the thesis focus on achieving the goal of interference management by allocate spectrum and power reasonably. Interference analysis between different small cells and macrocells are conduced here. In Macro-Femto heterogeneous network,as for the condition of close access mode that with serious interference from the femtocell to the macrocell interference management based on FFR, SFR and cognitive spectrum allocation algorithm are studied. Then an LTE-based heterogeneous system level simulation platform is implemented to simulate interference management algorithms. The research results shows that FFR and SFR can reduce the interference from femtocell to macrocell users effectively to ensure both femtocell and macrocell users can get higher signal to noise ratio (SINR).The cognitive spectrum allocation algorithm can improve macrocell and femtocell throughput at the same time.At last, to solve the problems of load imbalance between picocell and macrocell, the cell range extension (CRE) technology has been proposed by 3GPP.Because more and more users began to choose picocell to access because of its extending coverage, it can effectively improve the system throughput, while the picocell CRE UEs may suffer serious interference from macrocell. To protect the service quality of CRE UEs, the thesis has studies an interference management approach that macrocell divides the system spectrum resources into two parts,one part with normal power and the other one with low power,and only the latter is used in CRE UEs to provide a better protection. On this basis, we simulates user access selection with various CRE bias setting on LTE heterogeneous system level platform.Then the thesis analyzes the system performance with the interference management approach under different power ratios of the normal power to low power and different CRE bias values, Finally an optimal relation of power ratio with CRE bias value is acquired. The simulation results show that the approach can effectively improve the cell-edge throughput and the whole system throughput.