Cognitive Radio Cooperative Spectrum Sensing And Cross - Layer Optimization

The existing solution to spectrum allocation results in the inefficient use of the current radio spectrum. Cognitive Radio has been paid much attention as Cognitive Radio has the ability to identify an unoccupied spectrum band for temporarily and dynamically usage, and vacates the spectrum when it is necessary. Spectrum sensing and cross-layer designing are the key step in Cognitive Radio. Spectrum sensing could detect an unoccupied spectrum band so that cognitive user could make an opportunistic access. Due to the cognitive user’s low priority to use spectrum, cross-layer design focuses on improving quality of service by designing different layers’ parameters. Services based on transmission control protocol such as surfing online, shopping online, video online and online game become much more. So the wireless network throughput of cognitive user based on transmission control protocol is selected as the Quality of Service of cognitive user.This paper starts with cooperative spectrum sensing for Cognitive Radio. The method to use power spectral densities of every cognitive user related has been proposed. After removing the direct current component of spectrum of every cognitive user, we remove the relativity of every cognitive user by power spectral density integration algorithm, and then calculate the information vector which contains the features of the spectrum environment of these cognitive users. We perform the spectrum sensing by choosing spectrum sensing algorithms based on whether cognitive users need to know the boundary of primary user or not and make an analysis about complexity. After the spectrum sensing algorithm of the paper detecting the spectrum, we define the formulas of the probability of interference with primary user when cognitive user carries on services based on transmission control protocol and the probability of wasting unoccupied spectrum when cognitive user don’t carry on services based on transmission control protocol. And the relationship between these two formulas of the probability is analyzed. The simulations are given about the relationship between signals to noise ratio and probability of detection, complexity et al.After accessing to the licensed bands, Cognitive Radio needs to improve the Quality of Service, such as packet loss probability of cognitive radio based on transmission control protocol. In high-speed environment, Bit Error Rate has an influence on the wireless network throughput of cognitive user based on transmission control protocol. So adaptive channel estimation method based on Least Mean Square has been proposed to mitigate Bit Error Rate. We give the system diagram of channel estimation and cross-layer design, and evolve the application of Least Mean Square in the Basis Expansion Model. The relationships between the error of channel estimation and packet loss probability are analyzed. At the speed of 90km/h, 180km/h, 270km/h and 450km/h, the simulations and analysis are given about the relationships between cognitive user Bit Error Rate and signals to noise ratio in the cognitive receiver, the relationships between Normalized Mean Square Error and the number of iteration, the relationships between packet loss probability of cognitive radio based on transmission control protocol and noise ratio in the cognitive receiver and the relationships between Bit Error Rate and packet loss probability.After cognitive user opportunistic spectrum access to unoccupied spectrum band which is detected by spectrum sensing algorithm of Chapter 2 and cognitive user mitigates Bit Error Rate and packet loss probability by channel estimation algorithm of Chapter 3, we research on the relationships between the wireless network throughput of cognitive user based on transmission control protocol and the error of channel estimation at different speeds. Simulations show the wireless network throughput of cognitive user based on transmission control protocol has low speed to transmit data at the speed of 90km/h.