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    Performance of multilevel-turbo codes with blind/non-blind equalization over WSSUS multipath channels
    (2006) Uçan, Osman N.; Buyukatak, Kenan; Göse, Ersin; Osman, Onur; Odabaşıoğlu, Niyazi
    In this paper, in order to improve error performance, we introduce a new type of turbo codes, called 'multilevel-turbo codes (ML-TC)' and we evaluate their performance over wide-sense stationary uncorrelated scattering (WSSUS) multipath channels. The basic idea of ML-TC scheme is to partition a signal set into several levels and to encode each level separately by a proper component of the turbo encoder. In the considered structure, the parallel input data sequences are encoded by our multilevel scheme and mapped to any modulation type such as MPSK, MQAM, etc. Since WSSUS channels are very severe fading environments, it is needed to pass the received noisy signals through non-blind or blind equalizers before turbo decoders. In ML-TC schemes, noisy WSSUS corrupted signal sequence is first processed in equalizer block, then fed into the first level of turbo decoder and the first sequence is estimated from this first Turbo decoder. Subsequently, the other following input sequences of the frame are computed by using the estimated input bit streams of previous levels. Here, as a ML-TC example, 4PSK 2 level-turbo codes (2L-TC) is chosen and its error performance is evaluated in WSSUS channel modelled by COST 207 (Cooperation in the field of Science & Technology, Project #207). It is shown that 2L-TC signals with equalizer blocks exhibit considerable performance gains even at lower SNR values compared to 8PSK-turbo trellis coded modulation (TTCM). The simulation results of the proposed scheme have up to 5.5 dB coding gain compared to 8PSK-TTCM for all cases. It is interesting that after a constant SNR value, 2L-TC with blind equalizer has better error performance than non-blind filtered schemes. We conclude that our proposed scheme has promising results compared to classical schemes for all SNR values in WSSUS channels. Copyright © 2005 John Wiley & Sons, Ltd.
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    Performance of transmit diversity-Turbo Trellis Coded Modulation (TD-TTCM) over genetically estimated WSSUS mimo channels
    (Fachverlag Schiele und Sohn GmbH, 2004) Göse, Ersin; Pastacı, Halit; Uçan, Osman N.; Buyukatak, Kenan; Osman, Onur
    This paper presents the performance of Transmit Diversity-Turbo Trellis Coded Modulation (TD-TTCM) over Wide Sense Stationary Uncorrelated Scattering (WSSUS), Multiple-lnput-Multiple-Output (MIMO) channels. To achieve high bandwidth efficiency and/or high power efficiency, in TD-TTCM, binary input sequence is passed through a turbo trellis encoder, mapped to 8-PSK and then fed into a new transmit diversity (TD) scheme for high data transmission over wireless fading channels. At the receiver side, the distorted multi-path signals are received by multiple receive antennas. WSSUS MIMO channel parameters and modulated signals are estimated by using Genetic Algorithm (GA) and an iterative combiner, respectively. Then they are taken as an input to Turbo trellis decoder. Here, TD-TTCM and its efficient implementations are discussed and simulation results are presented.