Concatenated coding schemes and interleaving techniques over Rayleigh fading ionospheric channels

In this paper the performance of a concatenated coding scheme is evaluated over a slow Rayleigh fading HF ionospheric link with additive white Gaussian noise (AWGN). Well‐known Ungerboeck TCM techniques onto an 8‐PSK signal set are used as inner codes and Reed–Solomon block codes as outer codes. The coded/modulated signal is further differentially encoded before transmission to combat random phase changes. Block interleaving techniques are necessary to randomise long bursts of errors caused by the fading channel. The performance of the proposed concatenated coding system is investigated for various Doppler spreads. Significant coding gains are achieved over uncoded, diversity or other conventionally coded systems with a small bandwidth expansion. Finally the interesting effects of interleaving on the behaviour of the proposed systems are analysed. Copyright © 2001 John Wiley & Sons, Ltd.     

Turbo Trellis Coded Modulation with Enhanced Transition Metric over Rayleigh Fading Channels

This paper investigates the performance of a new Turbo Trellis Coded Modulation scheme over correlated flat fading channels with channel interleaving. The novelty of the scheme is based on the application of a new modified transition metric incorporated in the symbol-by-symbol MAP algorithm. We consider frequency non-selective, slow Rayleigh fading channels. Extensive simulation results together with EXIT chart analysis show that the proposed scheme achieves better performance compared to the conventional transition metric when channel state information is not available at the decoder. Kostas V. Koutsouvelis was born in Thessaloniki, Greece, on July 16,1970. He received the degree Diploma in Electrical Engineering from Aristotle University of Thessaloniki, Greece in 1996 and the Master degree in Satellite Communications Engineering from University of Surrey in 1997. From 1998 to 2003 he was involved in the development of V5.2 interface as a senior software designer in Intracom plc. In 2004 joined the research and development division of Hellenic Telecommunication Organization (OTE) and his also PhD candidate at Aristotle University of Thessaloniki working with Turbo codes and Turbo Coded Modulation. Christos E. Dimakiswasborn in Serres, Greece, on July 27, 1955.He received the degree Diploma in Electrical Engineering from the Aristotle University of Thessaloniki, Greece, in 1980. Working in the satellite communications and in the error correcting coding area he received his PhD degree in digital telecommunications from the Aristotle University of Thessaloniki, Greece, in 1994. In 1980 he joined the Department of Electrical Engineering, Telecommunications Division of the Aristotle University of Thessaloniki as a research fellow. Since 1997 he is a lecturer of digital communications at the same University. Presently, his research interests include digital modulations, coding theory, satellite and mobile communications and system simulation. Stamatis S. Kouris was born in Corfu, Greece. He received the degree of Doctor Engineer in Electrical Engineering from the University of Rome, Italy and the Diploma of Specialization in Telecommunications of the Instituto Superiore, University of Rome, in 1960 and 1963 respectively. In 1971 he was awarded the PhD Degree of the University of Edinburgh, UK. In the 1974 he was awarded a specialization Diploma in administration from the University of Pomona CA, USA. He is a member of the Technical Chamber of Greece, URSI, IRI and other organizations. Since 1964 he has been involved in research on radio-propagation, antennas and microwaves, working mainly at the Fondazione Bordoni, Italy, University of Edinburgh, UK and University of Thessaloniki, Greece. He has published several papers on radio-propagation, antennas, communication transmission and microwaves and millimeter-waves devices. In 1976 he joined with the Department of Electrical Engineering, School of Engineering Science, Aristotle University of Thessaloniki. He served as professor of telecommunications from 1978 to 2002. Since 2002 he is an emeritus professor.     

Theoretical and experimental infrared spectra of hydrated and dehydrated sulfonated poly(ether ether ketone)

Time-dependent FT-IR spectra of sulfonated poly(ether ether ketone) during dehydration show diminishing 1081 cm⁻¹ and 1023 cm⁻¹ band intensities concurrent with the emergence and shifting of bands at 1362 cm⁻¹ and 898 cm⁻¹. Animations of density functional theory calculated normal modes enable assignment of the 1081 cm⁻¹ and 1023 cm⁻¹ bands as group modes that include a sulfonate exchange site with C_3v local symmetry, while the 1362 cm⁻¹ and 898 cm⁻¹ bands are assigned as group modes that include an associated sulfonic acid with no local symmetry (C₁). In contrast to analogously assigned Nafion group mode bands, the SPEEK C_3v and C₁ bands coexist throughout the entire dehydration–hydration cycle, suggesting the presence of associated and dissociated exchange sites in SPEEK at all states-of-hydration. This supports a morphological model for SPEEK featuring branched hydrophilic domains and dead-end aqueous confines.