Iterative interference cancellation and decoding for a coded UWB-TH-CDMA system in AWGN channel

We consider a low-complexity iterative receiver for decoding multiuser information data in a bandwidth efficient convolutionally coded UWB-TH-CDMA (ultra-wide bandwidth time-hopping spread-spectrum code-division multiple-access) system introduced by R.A. Scholtz (see Proc. Military Commun. Conf., vol.2, p.447-50, 1993). The proposed receiver structure consists of a bank of soft interference canceller-likelihood calculators (SICLC), each followed by a soft-input soft-output (SISO) convolutional decoder. Information is fed back from the SISO decoders to the SICLCs for interference cancellation. Each SICLC then provides soft information about the coded symbols in the form of a log-likelihood ratio (LLR), which is used by the corresponding SISO decoder as a priori information about the coded symbols. We evaluate the performance of the proposed receiver in AWGN channels. Our numerical results show that the new receiver significantly improves the system performance. Moreover, at relatively high signal-to-noise ratios, after few iterations, multiple access interference (MAI) is efficiently suppressed, and single-user performance is achieved.