Abstract
The objective of this thesis is to evaluate the performance of block codes that are designed to be rotationally invariant, in a multilevel coding scheme, over a channel modelled to be white gaussian noise. Also, the use of non-binary codes for rotational invariance is studied, and one such code is designed and studied for its performance on the gaussian channel, for a 4 Quadrature Amplitude Modulation (QAM) signal constellation. The different types of constellations used include the 4 QAM, 8 Amplitude Modulation-Phase Modulation (AM-PM), and the 16 QAM constellations. Bose Chaudhuri-Hocquengham (BCH), Reed-Muller (RM), non-binary codes are used for simulation of the designed systems. Decoding of these codes using both hard and soft decisions is done. Simulations are carried out to study the performance of the designed codes. Soft decisions perform better than hard decision decoding, though they tend to be very slow. Hard decisions are better suited to block codes, since they are simpler to implement and take less time for decoding. The multilevel coding scheme allows ease and flexibility in the design of codes, and simplifies the construction of rotationally invariant codes. Non-binary codes are in particular very well suited to construction of rotationally invariant codes. They allow multiple partitioning and this improves the performance of multilevel schemes, by reducing multiplicity loss.
Kulandaivelu, Anita (1993). Rotationally invariant multilevel block codes. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -1993 -THESIS -K963.