PHASE COHERENT M-ARY TRANSMISSION WITH BINARY WAVEFORMS THROUGH A GAUSSIAN CHANNEL.
LITTON SYSTEMS INC WALTHAM MASS INFORMATION SCIENCES LAB
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A generic digital communication method, called q-M-ary transmission, is introduced and evaluated under the special conditions of phase coherent reception of signals transmitted through a non-fading medium. The basic feature of this method is the use of M-ary transmission alphabets, but employing only q different waveforms to synthesize the transmitted signals. Special attention is directed to the effect of bandwidth constraints on the performance attainable with this method, and to the value of high-order M-ary transmission alphabets, when implemented with this method. Comparison of a particular form of this method q 2 with conventional binary coding indicates that at least a few db improvement is provided by the 2-M-ary method with M large, even when bandwidth is severely limited. A variety of results have been obtained in an intermediate step toward evaluating q-M-ary systems, which may prove useful for evaluating a wide variety of M-ary systems. Of particular importance are general relations between the degree to which pairwise correlation between transmitted signals can be made small, and the degree to which bandwidth is constrained. Author