Data Transmission for Military Communication; Parameters and Capabilities

The transmission of high-speed digital data over long-haul military and commercial communication facilities has been a difficult problem for system designers because there are so many different types of communications facilities with widely differing characteristics which must be considered. Additionally, the system designer must consider the type of digital data modulation which best serves his purposes, the economics of the various approaches and a host of related problems such as clocking,, synchronization, standardization, etc. The major obstacle to progress in this area has been the reluctance of individuals to assign numerical values to telephone circuit parameters. It is the purpose of this paper to assign numerical values to all the parameters that are of concern in the data transmission problem and to show how the various parameters are interrelated and how the information can be usefully applied towards a system design. The paper is concerned with data transmission over voice channels having a nominal bandwidth of 3 kc and over the 48-kc group allocations found in most frequency division multiplex systems. The first portion of the paper is devoted to a discussion of the many factors that must be considered. This includes delay distortion, noise, multipath distortion, bandwidth and amplitude response, transmit level, level variations, frequency translation errors, synchronization, standardization, cost considerations and facilities characteristics. The latter portion of the paper shows how these factors can be used to solve problems related to the transmission of high-speed digital data over military and commercial communications facilities.