On the performance of TH-PPM and TH-PAM as transmission formats for UWB communications

We aim to clarify some aspects of ultra wide band impulse radio system performances with respect to the choice of the modulation format, in conjunction with a time hopping (TH) CDMA scheme. We show that when long TH codes are used, the ability to reduce multiple access interference is nearly the same for both PAM and PPM. The amount of interference critically influences both channel estimation and data detection, thereby essentially determining the performance of the system. In a realistic scenario for packet transmission, with channel estimation partly based on a short training preamble and partly on the data modulated signal, the two modulation formats yield comparable performances, as is revealed by the results of our simulations, carried out under plausible assumptions on signal format and channel structure.