A Low-rate Code-spread and Chip-interleaved Time-hopping UWB System

We consider a code-spread and chip-interleaved time-hopping (TH) multiple-access scheme for multiuser UWB communications. In such a system, each user´s chip sequence is interleaved by a user-specific distinct random interleaver, and the receiver is a low-complexity chip-level iterative multiuser detector (MUD) which performs simple Rake-type combining to collect the energy dispersed in multipath UWB channels. To further reduce the receiver complexity, time reversal (TR)-a transmitter preprocessing technique, is also considered. Furthermore, the zigzag Hadamard (ZH) code is proposed as the low-rate code for the code-spread TH-UWB system.