Study Of Narrowband Interference Suppression In UWB Systems

The ultra-wideband (UWB) technology has become a candidate for short-range and high speed wireless personal area net (WPAN) and has a wide applied prospect in radio communication areas. The performance of the narrowband interference (NBI) resistance in UWB systems is studied in this thesis. The primary contents of the thesis are as following:Over the additive white Gaussian noise (AWGN) channel, the conventional formula of the bit error rate in a traditional wideband system is modified in the presence of the narrowband interference. The calculation is made simple by using the modified formula, which is also suitable for the UWB systems. Under the partial band interference, tone and multi-tone interferences, the performance of the direct spread ultra-wideband (DS-UWB) system is analyzed in detail and the simulation and comparison are carried out. The simulation results show that the results obtained by utilizing the modified formula are in accordance with the ones from the system simulation.Through using the UWB indoor channel model proposed by IEEE 802.15.3a study group and the maximum ratio combining Rake (MRC-Rake) receiver, the impact of the alterable chip duty factor on the DS-UWB system performance is investigated in the presence of the different narrowband interferences. The simulation results reveal that by adjusting the chip duty factor reasonably, the DS-UWB signals are got without the loss of the process gain. The narrowband interference and multi-path fading have less effect on the acquired DS-UWB signals, and then the characteristics of the bit error rate in the UWB system are improved significantly.The performances of both the basic transmitted reference (TR) receiver and the modified transmitted reference (MTR) receiver are analyzed and simulated. The simulation results indicate that the MTR receiver has better characteristics than the TR receiver, including the bit error rate and the data rate. The notch filter is added in the basic TR to resist the NBI. Based on the UWB channel model presented by IEEE study group, the performance simulation of the bit error rate for the TR autocorrelation receiver is conducted through setting various system parameters. The simulation results show that the TR-UWB system with a notch filter has stable performance of the bit error rate, and is able to mitigate the NBI effectively. The proposed receiver, which has a simple structure, does not need the channel estimation and therefore, the system complexity is lowered greatly.