Research Of Cognitive Spectrum Sencing And Application In Wireless Network

Because of rapid development of technology of wireless networks, spectrum resources become very scarce and people pay much attention on cognitive radio technology for it shows great potential to solve this problem. The CR technology can detect the existing users and monitor the usage of spectrum. It adjusts the transmitting parameters accordingly which improves the efficiencies of spectrum usage. And the key technology of CR is spectrum detection.In this paper, we research on the cognitive radio spectrum detection technology alone with the characteristics and trends of wireless networks based on OFDM. We design a detecting system based on chaos theory in accordance with the spectrum features of amateur radio and public television service frequency bands. This detecting system uses the same array which is cascaded multiplexing and splits the spectrum band into two parts by adjusting system parameters. After that, system can detect exact usage condition of spectrums and provide the spectrum pool for OFDM transmission. A new algorithm called TICTACTOEMIDLET algorithm is proposed for status determination in this model, determining whether the system is in a chaotic state according to frequency appearance of the signal phase sample in the phase diagram, and thus to determine whether the band is occupied. The simulation results show that the weak signal can be detected from the AWGN noise by using this model, and detecting speed is fast and need no manual operation. This paper also improves the classic Schmidl& Cox OFDM synchronization algorithm. Simulation results show a higher performance at high SNR cases using this algorithm.