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DS-UWB pulse design in IEEE802.15.3a multipath fading channel for cognitive radio applications

This paper presents a novel spectrum shaping technique in direct sequence ultra-wideband (DS-UWB) communication systems. This proposed pulse introduces spectral nulls to limit the interference impact of high power coexisting narrowband signals and to elevate the applications of cognitive radio. The idea depends on the addition and subtraction of several UWB Gaussian derivative pulses in order to design a new pulse that has spectral null at the operating frequency of the narrowband interference (NBI) signal. The use of the Gaussian derivative ensures that the UWB spectrum mask established by the Federal Communications Commission (FCC) is met. The NBI signals are modelled as either the wireless local area network (WLAN) IEEE802.11n which operates in the 5 GHz frequency band or multi tone signals. The power spectral density of the proposed transmitted UWB pulse is derived analytically. The bit error rate performance of the proposed pulse is derived in the multi-path IEEE802.15.3a UWB fading channel models and validated with simulations. Results show that the impact of either the IEEE802.11n interference signal or the multi tone interference signals can be effectively suppressed by transmitting and matched filtering the new pulse with a single or multiple spectral nulls at the interference operating frequencies.