Nonlinear pulse combining in impulse radio UWB systems

Ultra-wideband (UWB) is a very promising wireless technology for short ranges, because of its many benefits. A common practice in UWB is time hopping (TH)-PAM impulse radio system, in which a number of extremely short pulses are transmitted for each bit and the polarity of pulses determines the bit. In multi-user environments, the interference from other users [multiple access interference (MAI)] may well dominate the Gaussian noise which makes the matched filter receiver be a suboptimal receiver. A model for the statistical structure of MAI in an additive white Gaussian noise channel is presented. Then, using this model, the authors propose a nonlinear pulse combining scheme for the receiver of TH-PAM systems. The bit error rate (BER) of our receiver is compared with that of matched filter receiver and blinking receiver, via simulations. The simulation results show that our receiver always outperforms the matched filter receiver. Blinking receiver performs better than our receiver only when the probability of collision is low and the energy of interfering users is high. In all other cases, our receiver has a lower BER than the blinking receiver. Furthermore, the blinking receiver needs to know the locations of all the interfering pulses, while in our method such information is not required.