The Digilock Orthogonal Modulation System

Publisher Summary This chapter discusses the digilock orthogonal modulation system. In applying orthogonal waveforms to practical communication systems, it is necessary to assign each waveform to a particular state of the information source to be transmitted. It is usual to assume that the message source produces completely random messages in the sense that no message is more likely to be transmitted than any other, so that the entropy of the source is a maximum from an information theory point of view. When this is the case, it is natural to proceed on the basis that each orthogonal signal must be receivable with the same probability of error in the presence of channel noise with specified statistical properties. For Gaussian noise with a constant spectral density, it is easy to see that this restriction implies that each waveform be transmitted using the same amount of energy. In the digital computer mechanization of the over-all synchronizing and data detection process, digitized equivalents of the subinterval matched filter outputs are used first to establish over-all waveform synchronization based on the comma-free property of the generated waveforms and to subsequently transform the detected 16 degrees of freedom back into 5-bit parallel data outputs.