Research On Interferences Suppression Techniques For Cognitive UWB Wireless Communication Systems

Nowadays cognitive ultra wideband (CUWB), which is emerged to improve UWB coexistence with narrowband systems, is becoming the research focus. The subject selection of this dissertation is originated from the national high technology research and development program of china (863program), etc. Interferences suppression techniques for CUWB are mainly discussed, which is quite significant to theoretic research and has a wide application prospect.Based on the deep research of the UWB pulse design for multi-user interference (MUI) suppression based on UWB spectral mask in China, the CUWB adaptive pulse design for narrow band interference (NBI) suppression and the game theory for interferences suppression in the cognitive radio network, the following innovative results are achieved:Aiming at suppressing the MUI for the UWB systems, a design algorithm to generate orthogonal UWB pulses is proposed based on the eigenvector of Hermite matrix and Polycycle signal. The shaped pulses have many characteristics in favor of multi-access detection, such as high spectral occupation rate, high auto-correlation and weak cross-correlation. Furthermore, through the analyses and simulation of suppressing MUI in2PPM-THMA UWB systems, the proposed pulses are proved to have stronger anti-interference ability than that of Scholtz pulse.Aiming at suppressing the frequency band interference locating at4.2-4.8GHz for the UWB systems, a frequency adaptive detect and avoid (DAA) design method is proposed based on direct sequence spread spectrum-carrier modulation method. Simulation results show that the proposed DAA method can provide stable UWB normal transmit power and have high transmission efficiency.Aiming at suppressing NBI for the UWB systems, two cognitive UWB adaptive pulse design methods are proposed based on the idea of transform domain communication system,namely,the NBI suppressions based on Rayleigh signal and combined bipolar Gaussian signal. Simulation results show that the power spectral density (PSD) of the proposed pulses produces arbitrary spectral notches with flexible cognitive avoid ability and meets with the UWB spectral mask in China. Moreover, the proposed pulses are proved to have stronger anti-interference performance.Aiming at solving the distribution optimization problems in the cognitive radio network, a interference avoidance algorithm based on non-cooperative game theory in cognitve Ad Hoc network is proposed. The net utility function based on interference pricing function is constructed, and the existence and existence of the Nash equilibrium are proved by mathematics derivation. The analysis and simulation results show that the proposed algorithm is at the premise of guaranteeing the primary user interference temperature constraints, can realize the best compromise between net utility and convergence rate.Furthermore,the proposed algorithm, compared with the SINR balancing algorithm,has faster convergence rate and lower average transmit power.In addition, the proposed algorithm can satisfy the CR user demand for real-time communication,and has the advantages of insensitivity to user number and moderate algorithm complexity.The final chapter summarizes the content of the whole dissertation and forecasts valuable research directions.