Research On Interference Control And Identification In Cognitive Radio Network

Along with the development of wireless communication systems, it makes people more convenient to contact with others than before. More wireless communication de-vices will bring a significant increase with demand of data transmission. The shortage problem of spectrum resource is now being more serious. The cognitive radio technology can be seen as a promising way to enhance the spectrum efficiency, which provides a flex-ible way to utilize the spectrum resource. And the researches on the interference control and interference identification are insufficient, which will be the important directions in the future.The dissertation discusses the interference control problem, interference identifica-tion problem and coverage problem. The details are as follows:interference control in mobility environment, multi-subchannel interference control, interference signal identi-fication and coverage enhancement with transmission power limitation. The research methodology includes the convex optimization theory, stochastic theory, statistical hy-pothesis testing theory, transformation electromagnetic theory, etc.The main contributions of this dissertation are summarized as follows.1. Since the interference control is rely on the channel state information, the inaccu-racy of channel state information may cause failed interference control. The out-dated process and channel estimation error in channel state information are sum-marized as two main reasons which make it difficult for interference control in mo-bility environment. To cope with the outdate process in channel state information, the Clark-Jakes'model has been used to describe the time-varying channel. The short frame structure and the average interference power limitation are designed for interference control. To further improve the interference control performance, a spherical error model is proposed to deal with channel estimation error.2. To cope with the multi-subchannel interference problem, the bandwidth-interference power product (BIP) metric is proposed to evaluate the multi-subchannel interference. The multi-subchannel interference control optimization problem can be converted into a BIP minimizing problem. Solve by the decompo-sition theory and convex optimization theory, the interference power is controlled in secondary user which uses the optimized results in channel selection and power control.3. To solve the interference identification problem, the modulation feature can be used to identify whether the received signal from primary user. Based on Kolmogorov-Smirnov test and cumulant test, a hybrid modulation classification method which has two steps is proposed. The interference from the unauthorized user can be identified quickly.4. Due to the interference constraints, the secondary user cannot increase the transmis-sion power to ensure the coverage quality. A novel transformation electromagnetic theory-based coverage optimization method is proposed. To improve the coverage quality in shadow area, a special cloak is designed for obstacle. The Fourier ap-proximated boundary functions are used to solve the calculation problem in rectan-gular cloak. It provides a novel method to improve the coverage quality, especially suitable for cognitive radio system.