Research On Resource Allocation Based On Interference Coordination In Femtocell System

The introduction of femtocell can improve indoor coverage and enhance the performance ofsystem. But there still exists some technical problems, including interference coordination, accesscontrol, self optimization and so on. As an important measure to solve the above problem, theallocation of resources has become a research hotspot. The resources of femtocell system includepower, spectrum and so on. This thesis mainly studies resource allocation algorithm for femtocellsystem, including channel assignment algorithm, channel allocation algorithm, access controlalgorithm and so on.This thesis proposes a distributed power control algorithm in femtocell system based on Nashnon-cooperative game theory. It designs an utility function taking femtocell stations’ transmitpower as a variable and relates it to the requirements of macro users’ and femtocell users’ SINR.The utility also takes interference from femtocell stations’ distribution to users’ SINR into accountand improves the fairness of non-cooperative game. We prove the existence and uniqueness ofPareto Optimal point. The simulation results show that the algorithm improves the convergencespeed and system performance through improving users’ SINR.In the two-tier network comprised of macro cells and femtocells, cross-tier and co-tierinterference can be reduced by allocating resources reasonably. This thesis proposes a joint channelallocation and power control algorithm in which the objective is to maximize the whole networkcapacity with interference in control. Convex optimization method is introduced to combinechannel allocation and power control together in which subgradient method is used to solve theclose formula of power. In addition, the algorithm has connected the optimal of femtocells networkand macro network together, thus macro network’s throughput can be maximized by allocatingchannels basing on macro users’ location and channels’ condition. Simulation results prove that thethroughput of femtocells network and macro network are both improved significantly using theproposed algorithm.Finally, network performance is analyzed when use different resource allocation and accessschemes with stochastic geometry theory. Access factor is introduced and optimization algorithmfor users is proposed when macro cells and femtocells share spectrum, which can increase thesystem capacity and guarantee users’ communication probability. The simulation results show that femtocells’ permitted transmit power is increased based on the proposed access mechanism, andsystem capacity is optimized at the same time.