Research On Rake Receiver Technology Of IR-UWB System

Ultra-wideband (UWB) wireless transmission is a novel short-distance wireless communication technique, in which data are transferred by using non-sinusoidal pulses with very short duration. It has many advantages, such as high transmission rate, low power consumption, good security, and high robustness to multi-path and low cost. Especially, it does not need extra frequency spectrum, and can coexist with the existing wireless communication systems at the same frequency bands, which makes it much attractive nowadays when the frequency spectrum resource has become more and more precious.In wide band wireless communication, multi-path propagation can make received signals produce selective fading and influence signal detection. Rake and antenna diversity are techniques used widely in wide band wireless systems to combat multi-path fading. It can compensate channel fading loss, increase the security of channel land improve the performance of the system but not increasing the transmission power after diversity and combination by using fading independence of the same receive antenna in different transmission path and fading in dependence of different receive antennas while they receive signals in large enough space distance. Antenna diversity can resist multi-path fading, increase the security of channel by compensating channel fading loss and improve the performance of the system but not increasing the transmission power.This dissertation considers performance analysis of Rake receiver in Impulse radio (IR) Ultra Wideband (UWB) systems. First, a detailed performance analysis of Rake receiver in IR-UWB systems is performed in asynchronous environments, considering the effects of both Multiple-access Interference (MAI) and Inter-symbol Interference (ISI), and approximate expressions for the bit error probability (BEP) of Rake receivers with various combining schemes are derived. We research, simulate and compare the performance of Rake receivers with different reception schemes, combination modes and channel models. Finally, considering the tradeoff between the performance and complexity of Rake receiver ,we put forward a MMSE-Rake receiver with low complexity ,of which can estimate the combining coefficient with less fingers; The results of simulation prove that it can improve system BER performance obviously in seriously fading channel.