Space-Time Turbo Coded Modulation: Design and Applications
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Space-Time Turbo Coded Modulation: Design and Applications Djordje Tujkovic Centre for Wireless Communications (CWC), University of Oulu, P.O. Box 4500, Tutkijantie 2E, FIN-90014 Oulu, Finland Email: [email protected]
Markku Juntti Centre for Wireless Communications (CWC), University of Oulu, P.O. Box 4500, Tutkijantie 2E, FIN-90014 Oulu, Finland Email: [email protected]
Matti Latva-aho Centre for Wireless Communications (CWC), University of Oulu, P.O. Box 4500, Tutkijantie 2E, FIN-90014 Oulu, Finland Email: [email protected] Received 1 June 2001 and in revised form 14 January 2002 A design method for recursive space-time trellis codes and parallel-concatenated space-time turbo coded modulation is proposed that can be applied to an arbitrary existing space-time trellis code. The method enables a large, systematic increase in coding gain while preserving the maximum transmit diversity gain and bandwidth efficiency property of the considered spacetime trellis code. Applying the above method to Tarokh et al. space-time trellis codes, significant performance improvements can be obtained even with extremely short input information frames. The application of space-time turbo coded modulation to the space-frequency domain is also proposed in this paper. Exploiting the bandwidth efficient orthogonal frequency division modulation (OFDM), multiple transmit antennas and large frequency selectivity offered by typical low mobility indoor environments, the proposed space-frequency turbo coded modulation performs within 2.5 dB of the outage capacity for a variety of practical wideband multiple-input multiple-output (MIMO) radio channels. Keywords and phrases: space-time coding, turbo coded modulation, OFDM modulation.
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INTRODUCTION
The knowledge of the fact that increasing the codeword length of block codes or constraint length of convolutional codes leads to better performance dates back to Shannon theory [1]. It is also well known that in case of maximumlikelihood (ML) decoding the drawback of such a performance gain is the increased decoding complexity up to the point where decoding becomes physically unrealizable. Thus, the research in coding theory over the years has seen many proposals aiming at constructing powerful codes with large equivalent codeword or constraint lengths structured so to permit breaking the ML decoding into simpler partial decoding steps. Turbo codes [2] are the most recent of such an attempt, already accepted to be the result of a clever intuition built upon several concepts already established, rather than just a sudden apparition. Turbo codes were originally introduced as binary errorcorrecting codes built from the parallel concatenation of two recursive systematic convolutional codes (RSC) exploiting a
suboptimal but very powerful iterative decoding algorithm, the so-called turbo decoding algorithm. However, it turned out that the method applied for this parallel concatenation is more general. The turbo principle is nowadays successfully applied in many detection/decoding p
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