Impulse Radio UWB Pulse Shaping for Cognitive Radio Applications

This paper introduces a method of shaping impulse radio Ultra Wideband (UWB) pulses in the context of using higher than normal power transmissions and cognitive radio to provide the ability for such systems to avoid interference with primary users in shared radio spectrum. Using multiple shaping frequencies and a standard Gaussian pulse shape, pulses are shaped in the time domain, according to the requirements of the frequency spectrum in use, and any limits on power spectral density. Simulation results are presented for an example scenario based on measured data, along with a more general approach applicable to a free spectrum scenario. We show that the introduced shaping technique ensures that up to 98.8% of capacity of the UWB bandwidth within the conventional spectrum mask can be achieved for a time scaling factor of 11 ns and shaping frequency of 30 MHz. Capacity well in excess of the 100% achievable with the spectral mask is possible when the transmit power is permitted to increase in areas of ‘white space’ spectrum.