Design of Block-Coded Communication Systems

Abstract

The design and performance of frequency multiplexed, phase-modulated communication systems is presented. In particular, the transmitter is assumed to be an ideal phase modulator which modulates a RF carrier with <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</tex> phase-modulated, sinusoidal data subcarriers, and in general, <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M</tex> binary-valued composite signals. The receiver is a superheterodyne phase-locked loop (PLL) whose output is applied to one of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</tex> subcarrier extractors. Each subcarrier extractor consists of a subcarrier tracking loop, a timing loop, and a data detector which operates as a cross-correlator. The paper presents results which allow the design engineer to allocate the total power between <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</tex> modulated data subcarriers, <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M</tex> binary-valued signals, and the carrier signal. The total power in the distortion component is computed. Finally, a method is given which allows the communications engineer to select the data rate and the modulation factor of each data subcarrier which will minimize the probability that the data detector will err in the decision process. The results are sufficiently general so that they may be used in designing block-coded systems. Such systems have application in various branches of aerospace communication engineering, e.g., channelized communication satellites and deep-space probes.