Research On Narrowband Interference Suppression For CS Based IR-UWB Systems

Ultra-wideband (UWB) is a promising technology for short-distance wireless communications. It has advantages such as high data rate and low-power consumpthion. Due to the extremely wide bandwidth, UWB shares some parts of spectrum resources with the existing narrowband wireless communication systems. In order to ensure that the existing narrowband communication systems can work normally, the Federal Communications Commission (FCC) defines some regulation for UWB systems to limit their maxmum effective isotropic radiated power. However, the radiated power of narrowband wireless communication systems is usually much greater than that of UWB systems. Thus, narrowband wireless communication systems interfere with UWB systems badly. Traditional UWB narrowband inference (NBI) suppression techniques are based on the Discrete Fourier Transformation (DFT). Due to the fact that the bandwidth of UWB signals is on the order of Gigahertz, according to the Nyquist sampling theory, the sampling rate must be extremely high. This can increase the difficulty of system implementation and the computational complexity of sigrnal processing. Evidently, it is an urgent issue to realize NBI detection and suppression with low rate sampling.Different from Nyquist sampling theorem, the emerging compressed sensing theory (CS) can reconstruct or approximate the original signal with high probability using few measurements. This undoubtedly provides a feasible way to resolve the sampling problem of UWB signals. The main purpose of this study is to adopt the CS theory into the narrowband interference detection and suppression for UWB systems so as to avoid the sampling problem faced by the traditional NBI suppression schemes. The main contributions of this thesis include the following aspects:1. A method is proposed for narrowband interference sensing and reconstruction. WLAN signals are typical interference for UWB systems. For the purpose of simplification, we model the WLAN interference as multi-frequency cosine signals. For noiseless scenarios, we adopt the CS theory to measure and reconstruct different narrowband interferences. Simulation results show that, we can reconstruct typical narrowband interference precisely. This can make a solid foundation for the CS-based UWB NBI detection and suppression. 2. We propose a CS-based NBI detection and suppression method for IR-UWB. This method can be used to detect and suppress the NBI involved in the pilots and load signals effectively. We reconstruct the signal correlation template using the NBI-suppressed pilot signals. The NBI-supressed load signals are demodulated with a correlation receiver. Simulation results show that, the IR-UWB system can get better bit error rate (BER) performance by using this proposed NBI detection and suppression method.