Performance analysis of time-hopping ultra-wideband systems in multipath fading channels (uncoded and coded schemes)

We evaluate the performance, in multipath Rayleigh fading channels, of both the uncoded and coded multiple access TH-UWB systems introduced by R.A. Scholtz (see Proc. Milcom 93, 1993), M.Z. Win (see Ph.D. dissertation, Electrical Engineering, University of Southern California, 1998) and A.R. Forouzan et al. (see Proc. PIAMC 2000, vol.2, p.1555-8, 2000). The receiver is a selective diversity combining receiver, known as SRAKE. Based on a Gaussian distribution assumption for multiple access interference at the output of the SRAKE receiver, and by using a virtual branch technique as introduced by M.Z. Win and J.H. Winters (see Proc. 49th Annual Int. Veh. Technol. Conf, vol.1, p.215-20, 1999; Proc. IEEE Int. Conf. on Commun., vol.1, p.6-10, 1999), the bit error rates for uncoded and coded schemes are derived. Our analysis shows that the effective order of diversity achieved by the coded scheme is the product of the number of branches of the SRAKE receiver and the Hamming distance of the code applied. Furthermore, it indicates that the coded scheme significantly outperforms the uncoded scheme.