Two-dimensional iterative processing for dab receivers based on trellis-decomposition

We investigate iterative trellis decoding techniques for dab,with the objective of gaining from processing 2d-blocks in an ofdm scheme,that is,blocks based on the time and frequency dimension,and from trellis decomposition. trellis-decomposition methods allow us to estimate the unknown channel phase since this phase relates to the sub-trellises. we will determine a-posteriori sub-trellis probabilities,and use these probabilities for weighting the a-posteriori symbol probabilities resulting from all the sub-trellises. alternatively we can determine a dominant sub-trellis and use the a-posteriori symbol probabilities corresponding to this dominant sub-trellis. this dominant sub-trellis approach results in a significant complexity reduction. we will investigate both iterative and non-iterative methods. the advantage of non-iterative methods is that their forwardbackward procedures are extremely simple; however,also their gain of 0.7db,relative to two-symbol differential detection (2sdd) at a ber of 10-4,is modest. iterative procedures lead to the significantly larger gain of 3.7db at a ber of 10-4 for five iterations,where a part of this gain comes from 2d processing. simulations of our iterative approach applied to the tu-6 (cost207) channel show that we get an improvement of 2.4db at a doppler frequency of 10hz. copyright © 2012 wim j. van houtum and frans m. j. willems.