Iterative demodulation of zero-padded OFDM with MMSE equalization using a priori information

In this paper, we describe a novel scheme for iterative demapping, also known as turbo demodulation, of zero-padded (ZP) OFDM. Our scheme includes an MMSE equalizer which accepts a priori information delivered by an outer channel decoder. By enabling the equalizer to process independent reliability information about the encoded bits, the equalization stage can be included in the iterative decoding process, yielding superior performance when compared to iterative demapping. We derive an MMSE equalizer that accepts a priori information stemming from the outer decoder for several mappings and incorporate an additional rate-one inner code which removes the error floor, which is otherwise present in iterative demapping.