Applications of turbo principle to broadband communications

One of main challenges in the design of a broadband communication system is to provide bandwidth and power efficient data transmission techniques overcoming deleterious effects such as noise, intersymbol interference (ISI), and multiple assess interference (MAI). Recently, turbo principle has been widely investigated to suppress these impairments, and promising results have been reported.; This thesis deals with the application of turbo principle to broadband communications. We first introduce basic ideas of turbo principle employed in turbo codes, turbo trellis-coded modulation (TTCM), turbo equalization, and turbo multiuser detection.; In order to mitigate ISI in transmissions over dispersive channels, we apply turbo equalization approaches to broadband transmission over both wired and wireless channels. We study various turbo equalization methods applicable to a broadband transmission over a category 6 (CAT-6) copper cable up to 100 meters. Computer simulation results with a rate 1/2 recursive systematic convolutional (RCS) code and BPSK modulation show that the turbo process, employing iterative equalization and decoding, offers iterative gain over conventional non-iterative schemes.; A multiple input multiple output (MIMO) system using layered space-time architecture is known to offer a capacity far exceeding that of a single-antenna system in rich scattering; channels. For transmission from multiple transmit antennas employing layered space-time architecture, inter-channel interference (ICI) between different antenna elements needs to be suppressed. When the MIMO system is used in multiuser environments, MAI also needs to be suppressed. In order to overcome ICI and MAI simultaneously, we apply an iterative signal process approach. We consider a coded MIMO DS-CDMA system using layered space-time transmission in multipath wireless channels, where space-time signals from multiple antennas of multiple users propagate through rich scattering multipath fading. We propose a receiver employing iterative joint detection and decoding with a low-complexity detector using linear MMSE filtering with a-priori information and parallel soft-input soft-output (SISO) decoders. Computer simulation results show that the proposed receiver for multiuser MIMO transmission provides high spectral efficiency and performance approaching to single-user bound. Furthermore, the low-complexity receiver outperforms an iterative soft decision-directed maximal ratio combining (DD-MRC) receiver, RAKE receiver as well as a conventional non-iterative receiver. (Abstract shortened by UMI.)...