Κωδικοποίηση χωροχρόνου (space-time) σε τηλεπικοινωνιακές ζεύξεις με διαλείψεις

Abstract

The object of this doctorate dissertation is the study of space-time coding. The appli- cation of this coding technique is investigated to the power line communications channel, while prior to this study, and for the better oversight of the channel behavior, it is in- vestigated the application of multiple access techniques, other modern coding techniques (one of which is Turbo coding) and various modulation techniques to the same channel, measuring the bit-error-rate and the throughput performance of the systems under study. After that, the e±ciency of the space-time coding technique is assessed when applied to the land mobile satellite channel, and the derived results are compared with the ones of the terrestrial wireless channel, which has comprehensively been studied in the literature. Next, the research is focused on the measurement of the channel capacity and the bit- error-rate, with two closed-form upper bounds presented, respectively, for the space-time coding system when applied to log-normal or Rician fading channel. The analytical results of these bounds are validated against both numerical methods and computer simulations. Afterwards, two hybrid automatic repeat request algorithms are proposed for multicast communications in the UMTS network, presenting interesting results outperforming all other algorithms proposed until today. Finally, these algorithms are combined with a proposed technique of packet level space-time coding, aiming at increasing the e±ciency of the system with regard to mean delay and throughput, while attaining even higher performance.