Communication Efficiency Comparison of Several Communication Systems

Of increasing importance in communication systems, particularly those required for data transmission from space craft, is the minimization of the total transmitted energy required to transmit a given amount of data. Modulation systems can be compared on the basis of a figure of merit defined as the ratio of energy required per bit transmitted in the presence of a given noise spectral density. Using this criterion, several families of communication systems are compared in this article, including AM, FM, FM/FM, and orthogonal matched filter communication systems. It is found that the orthogonal systems uniformly require less power to transmit at a given information rate than other systems and approach closely the theoretical limit established by Shannon´s channel capacity theorem.