Selecting the right SATCOM-On-The Move (SOTM) terminal is a process far more complex than an analysis of cost vs. data rate.

The wide variety of SOTM terminals available to commercial and military users today are as diverse as the platforms that carry them and differ widely depending upon requirements for upload and download speeds, transmission quality and vehicle selection.

In his MILCOM 2012 paper and presentation entitled "SATCOM-On-The Move: Why One Size Doesn't Fit All," SATCOM Technologies' Chief Technology Officer, Tim Shroyer, considers several factors that drive the selection of a specific SOTM earth terminal configuration.

"While the ultimate goal is to use satellite earth stations which are as small and light as possible, several trade-offs affect the ultimate coverage areas and communications data rates these systems can provide," Shroyer said. "SOTM system designers must optimize terminal size to satisfy the 'best' balance between performance, size, weight and power. Just as there is no single SOTM communications requirement, there is no single optimal SOTM terminal configuration."

"The MILCOM 2012 conference was cancelled this year due to Hurricane Sandy's arrival off the east coast," Shroyer said. "But the papers prepared for the conference will be included in the published proceedings."

"The fundamental problem facing all satellite communications systems is to provide suitable performance on the RF link through the desired satellite while minimizing interference energy towards adjacent satellites," Shroyer said. "Large, fixed earth stations do this very well. However, SOTM earth terminal antennas have the opposite effect. The small aperture size offers relatively low gain towards the satellite of interest and simultaneously radiates a significant amount of energy towards adjacent satellites. The problem is compounded when these SOTM terminals move over uneven terrain."

"Adjacent Satellite Interference, or ASI, is a real problem with SATCOM-On-The Move terminals," Shroyer added. "In fact, when designing and selecting the right SOTM terminal for specific military or commercial applications, ASI is often the chief consideration driving further decisions on antenna size, pointing accuracy, frequency used and link performance."

"The usual considerations of 'cost' and 'data rate' are only part of the equation," Shroyer said. "Vehicle constraints including size, weight and power all come into play when striking a balance between 'the smallest possible' terminal delivering 'the highest data rate'."

A complete PDF copy of Shroyer's MILCOM paper is available for downloading. Click here. The PowerPoint presentation is also available for downloading. Click here to download the PowerPoint presentation.


For more information on General Dynamics SATCOM Technologies' SATCOM-on-the-Move capabilities, contact Jimene Conn at +770-689-2052 or via e-mail at

General Dynamics SATCOM Technologies offers a family of satellite and wireless communications products and services. Visit our web site at

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