Iterative joint channel estimation and detection combined with pilot-tone symbols in convolutionally coded OFDM systems

This paper presents a maximum a posteriori (MAP) joint channel estimator and detector for convolutionally coded OFDM systems over mobile radio communication channels, which is suitable for turbo principles. To the purpose of the synchronization, the several papers where a known pilot-tone symbol [T.P. Holden and K. Feher, 1990], [P. Hoeher and F. Tufvesson, 1999] is transmitted simultaneously, were proposed. This pilot-tone symbol technique is applied to the channel estimation for OFDM systems, so that it gives the use of decision-directed algorithm based on the symbol-by-symbol MAP algorithm, which is optimal detection algorithm [L.R. Bahl et al., 1974] in terms of bit error rate (BER). However, in the presence of unknown quantities, since the symbol MAP algorithm is not optimal, the MAP algorithm, which is jointly linked with per-survivor processing (PSP) algorithm [R. Raheli, et al., 1995], is required. Instead of one 2-dimensional channel estimation scheme [P. Hoeher et al., 1997], two 1-dimensional channel estimation techniques with convolutional codes are presented in an iterative receiver structure. Hence, the proposed iterative joint estimation and detection algorithm gives the reliability values to the component decoder for convolutional codes, which is combined with pilot-tone technique, to obtain the better performance in the iterative way. Simulations demonstrate the performance of the proposed iterative joint channel estimator and detector.