EXIT chart aided design of DS-CDMA UltraWideBand systems using iterative decoding

This paper presents a novel UltraWideBand (UWB), Direct Sequence Code Division Multiple Access (DS-CDMA) aided system designed for the IEEE 802.15.3a UWB channel specifications. Substantial performance improvements can be attained by serially concatenated channel encoding combined with a Unity Rate Code (URC). We compare the performance of the iterative aided decoding Correlation (Corr) and Minimum Mean Square Error (MMSE) detectors exchanging extrinsic information between the URC's decoder as well as the outer Recursive Systematic Convolutional (RSC) code's decoder. Moreover, the iterative decoding convergence analysis of the proposed system is carried out with the aid of Extrinsic Information Transfer (EXIT) charts. As expected, the iteratively decoded fully-loaded system employing MMSE detection outperforms its counterpart employing the equivalent Corr detection. Explicitly, UWB DS-CDMA using the MMSE detector attains a BER of 10^-5 at E_b/N_o = 2dB when supporting U = 32 users employing i = 12 decoding iterations, while the same system using the Corr detector operates at BER-10^-1.