Research On Polarization Spectrum Sensing Algorithms In Cognitive Radios

To meet the increasing demand for wireless communication, Cognitive Ra-dio (CR) is proposed to enhance the spectrum utilization by sensing and reusing unoccupied spectrum holes. Currently, spectrum sensing technology detects the available spectrum by utilizing the time-frequency-space domain information. It is significant to bear in mind that polarization characteristics is another es-sential information of signals. However, the research on polarization spectrum sensing of signals is limited. Hence, polarization spectrum sensing technology is a promising solution to the dilemma of frequency scarcity.The dissertation is focused on the polarization spectrum sensing algorithms which is supported by the National Science Foundation Project "Research and Application of Polarization Spectrum Sensing". The main contents are:(1)The dissertation surveys the existed research on sensing algorithms and their advantages and disadvantages. The polarization theories and applications are included. Based on the existed research, the limitation in traditional spec-trum sensing is pointed in Chapter2.(2)To fully exploit the potential polarization characteristics of signals, a De-gree of Polarization (DoP) sensing algorithm is proposed in Chapter3. First, the paper researches on the depolarization effect systematically and the correlation polarization channel model is established. Second, we analyze the statistical polarization information of signals and noise. Based on the statistical polar-ization characteristics, the DoP sensing algorithm is proposed. The theoretical detection performance and the threshold of DoP is given by Random Matrix Theory (RMT). As evaluated in simulation, DoP needs no prior information for detection and overcomes the noise uncertainty problem. It is shown that3dB performance gain is achieved by DoP compared with traditional methods.(3)To solve the Polarization Mode Dispersion (PMD) in depolarization channel, in Chapter4, a Variance of Polarization Distance (VoPD) sensing al-gorithm is proposed. By analyzing the polarization characteristics of broadband signals in frequency domain, the dual-polarized broadband channel model and broadband polarization detection model are constructed. The theoretical de-tection performance and the threshold of VoPD is given based on curve fitting and beta distribution. Finally, the detection performance is evaluated by the simulation which shows a significant detection performance improvement.