The Study Of CMMB Signal Spectrum Sensing Techniques

There will be a substantial need for more spectral resources as wireless applications become more and more sophisticated. Today's wireless networks are characterized by a fixed spectrum assignment policy. However, a large portion of the assigned spectrum is used sporadically and geographical variations in the utilization of assigned spectrum ranges from 15%to 85%. The limited available spectrum and the inefficiency in the spectrum usage necessitate a new communication paradigm to improving the utilization of assigned spectrum. As a novel approach for improving the utilization of spectral resources, Cognitive radio techniques provide the capability to share or use the spectrum in an opportunistic manner.Cognitive radio is an intelligent wireless communication system that is aware of its surrounding environment (i.e., outside world), and uses the methodology of understanding-by-building to learn from the environment and adapt its internal states to statistical variations in the incoming RF stimuli by making corresponding changes in certain operating parameters (e.g., transmit-power, carrier-frequency, and modulation strategy) in real-time. As one of the most important technologies of cognitive radio, Spectrum sensing is able to detect the spectrum holes and cause no harm to licensed users. The spectrum sensing function enables the cognitive radio to further share or use the spectrum by detecting spectrum holes.In this dissertation, the basic principles of cognitive radio and spectrum sensing are introduced, spectrum sensing techniques are classified, performance metrics for assessing spectrum sensing techniques are established, and also the inputs and outputs of the spectrum sensor are specified. The spectrum sensing techniques simulation of China Multimedia Mobile Broadcasting (CMMB) signals is finished with MATLAB. During the simulation of spectrum sensing techniques, base band CMMB signals are transmitted, local sensing techniques like Energy Detection and Correlation Detection and cooperative sensing techniques like OR and AND rule are simulated, and also Missed Detection Probability vs. False Alarm Probability curves are plotted.