A Study On Narrowband Interference Suppression In Ultra-Wideband Communications

The Ultra-wideband is a promising new communication technology for high data rate, short range communications. However, according to the FCC’s regulation, due to the wideband of the UWB systems,.many narrowband signals reside within the UWB frequency band, and the transmitted power of UWB systems is far lower than the transmitted power of narrowband systems, so we must consider the impact of narrowband systems interference on the performance of UWB systems.This thesis concentrates on the narrowband interference suppression in the UWB systems. The major contributions of the thesis are as follows:We derived closed-form expressions for the BER of a general binary coherent UWB system, based on MF reception with tone interferers in different scenarios. The scenarios considered include additive white Gaussian noise channels, flat-fading channels, and frequency-selective multipath fading channels. In the frequency-selective multipath fading scenario, Rake reception was considered, and an approximation based on perturbation theory was derived. Simulations results for NBI are in good agreement with our analytical results in different scenarios, showing the approach is useful for investigating the coexistence of ultra-wide bandwidth systems with existing wireless systems.Finally, owing to the coexistence problem between ultra-wide bandwidth(UWB) systems and narrowband systems, a TH sequence design which can adapt to current channel conditions has been proposed for DS-IR-UWB systems to cope with the coexistence problem. The TH design shapes the DS-IR-UWB signal spectrum and creates a spectral null at the frequency region where the NB interferer operates. Therefore, mutual interference between DS-IR-UWB and NB systems can be highly reduced. Also this sequence design has low computational complexity and can be easily implemented in practical systems. In Nakagami fading channel, Numerical results are provided to show that the BER performances of the DS-IR-UWB system can be significantly enchanced by using this TH sequence design.