On the Performance of Iterative Demapping and Decoding Techniques over Quasi-Static Fading Channels

In this paper, we investigate in detail the performance of iterative demapping and decoding techniques over quasi-static fading channels both with and without antenna diversity. In particular, we consider the effect on the system performance of various mapping schemes, different coding schemes, the inter- leaver size as well as space diversity. Results demonstrate that over quasi-static fading channels characterized by significant antenna diversity, mappings traditionally optimized for iterative receivers (e.g., Boronka mapping) outperform mappings more appropriate for non-iterative receivers (e.g., Gray mapping). In contrast, over quasi-static fading channels characterized by limited antenna diversity, Gray mapping always outperform Boronka mapping for all E_b/N₀ and all iterations. Strikingly, this situation is in sharp contrast to that in the AWGN case. We note that we can further improve the performance of non-iterative systems (e.g., Gray mapping) having limited antenna diversity by increasing the memory size and removing the interleaving.