Exploiting Time and Frequency Diversity by Iterative Decoding in OFDM-CDMA Systems

This paper examines iterative decoding of a serial concatenated coding scheme consisting of an outer convolutional and an inner Walsh-Hadamard block code, and the scheme is applied for an OFDM-CDMA uplink transmission. New aspects arise because OFDM enables the iterative decoding structure to exploit time as well as frequency diversity of a mobile radio channel. To the authors knowledge, this is the first time that iterative decoding is performed in both time and frequency domain. Besides the derivation of basic decoding algorithms, simulation results are shown for differently interleaved indoor channels. The results confirm that the iterative decoding scheme benefits from the selectivity in time as well as in frequency direction.