http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
Monolithic implementation of turbo codes
xxii, 245 leaves : illustrations ; 28 cm.
Turbo codes were discovered in 1993; they consist of the parallel concatenation of recursive systematic convolutional coders separated by interleavers and use soft-input soft-output iterative decoders. Turbo codes have become a standard technique for channel coding due to their simplicity and performance. One of the key aspects of turbo codes is that they use soft-input and soft-output values in the decoding stage. Thus no information is discarded until the algorithm has iteratively converged to a solution, at which time a hard decision is taken. The soft-input soft-output concept refers to infinite quantized or analog values in a natural form. This research work proposes CMOS integrated circuit implementations of both the encoding and the decoding algorithms. In particular it explores an all-analog decoder implementation that will naturally exploit the continuous nature of the received signals. The proposed analog decoder is based on the additive soft-input soft-output algorithm that can be naturally mapped into a multiple input floating gate transistors implementation. By taking advantage of the symmetric structure of the trellis generated by convolutional codes, every node in the trellis can have a direct analog counterpart that will mathematically solve the decoding algorithm in the analog domain. A normalization circuitry is included to restore the signal levels at each stage; this block results in a large area compared to the area used by the algorithm computing cells. The normalization procedure utilizes negative feedback techniques to automatically restore the amplitude and offset levels required. In addition, a complete characterization and modeling methodology for multiple input floating gate transistors is presented. The multiple input floating gate devices used are based on a new structure that has an additional voltage input through an n-well. This input can be used for calibration, noise isolation or as an additional input. Complete design-flows for both digital and analog integrated circuit designs are presented. Theoretical results are validated by the fabrication and testing of digital and analog integrated circuits in CMOS technology.
"Major Subject: Electrical Engineering".
Issued also on microfiche from University Microfilm Inc.
Includes bibliographical references (leaves 226-242).