Research On Interference Suppression In Two-tier Cognitive Femtocell Networks

According to some investigation, the Macrocell network is in poor performance in indoor communications, most of which exists a problem of poor signal cover. In order to solve this problem, a Femtocell technology with great advantages in indoor communications could be introduced. Cognitive Radio, which is skilled in spectrum resources detection, can be incorporated with Femtocell. Thus it may construct a two-tier Femtocell networks with cognitive ability, which possesses more advantages. Even though the two-tier Femtocell networks can effectively solve the problem of indoor coverage, it will also lead to serious interference. Therefore, how to find out strategies for interference suppression is one of the key technologies in the two-tier Femtocell networks.In order to study interference suppression in the two-tier cognitive Femtocell networks, this thesis tries to set up a cognitive empowered Femtocell network. With the analysis of interferences based on different sources and characteristics, a stochastic dual control strategy is introduced, which can effectivity reduce interference suppression. In this study, the strategy is improved by adding a second-order interference to work together with the first-order interference, whose purpose is to make the interference mitigation enhanced and then to optimize the algorithm. What’s more, this study creates a multi-user cooperative spectrum detection model. With the energy detection algorithm, the system can make a judgement of polymerization interference. Then with the known false alarm probability, the probability of system detection is deduced which can calculate the optimal solution by particle swarm algorithm based on simulated annealing(SAPSO). Simulation result shows that the abovementioned theory can improve the spectrum utilization and achieve the purpose of interference suppression.