We present a wireless link budget analysis for impulse-radio ultrawideband (IR-UWB) systems with different pulse-shaping techniques using a realistic path loss model. Simulation results confirm that a proper pulse design technique is crucial for satisfying Federal Communications Commission mask requirements and performance enhancement of IR-UWB systems. We present a novel pulse design technique, based on a linear combination of modified doublets pulses and compare it with conventional pulses such as monocycle, doublet and fifth-order derivative of Gaussian pulses. The proposed pulse outperforms the conventional pulses in terms of spectral power efficiency and achievable reach using an M-ary pulse-amplitude modulation format and a fixed data...