Online Journal of Space Communication


A fully articulated steerable shipboard satellite antenna system operating at Ka-band was developed by engineers from the Naval Research Laboratory (NRL), NASA's Glenn Research Center, and a number of industry partners. A series of tests conducted in October of 1998 on Lake Michigan achieved an unparalleled data rate transmission of 45 megabits per second (Mbps) between a moving vessel at sea and a fixed-earth station using NASA's Advanced Communications Technology Satellite (ACTS). Network and application layer tests ran concurrently with the data rate transmission trials, examining TCP/IP file transfers, video and voice transfer technologies, and Asynchronous Transfer Mode (ATM) techniques.

This experiment, called the Shipboard ACTS Ka-band Experiment (SHAKE), collected a data set of time-correlated measurements. The samples, collected at one-second (or faster) intervals, included vessel motion, RF and IF (modem) measurements. DS-3 layer port statistics, ATM layer statistics, TCP/IP statistics, and application performance. This data set (discussed herein) represents the one of the most comprehensive collections of its type ever recorded on a vessel. Tracking was measured at various sea states and weather conditions, including seas that generated peak pitch variations on the vessel of + 12 degrees, and peak roll variations of + 24 degrees.

The SHAKE experiment, utilizing a combination of commercial-off-the-shelf (COTS) and government hardware, clearly illustrated the viability of high data rate (HDR) Ka-band systems for ship-to-shore communications. The system, which was developed over a period of four months, was tested during a two-week period on Lake Michigane on a 45-foot Bayliner Motor Yacht. Entropy.

Underlying networking, protocol, terminal, and bandwidth-on-demand issues, combined with variable bit rate servive and HDR capabilities, present challenges not typically addressed in current Naval SATCOM systems. Through this study, numerous system optimizations were documented, which are presented as work remaining in order to realize reliable services that would support Naval HDR shipboard SATCOM requirements using commercially-available Ka-Band satellite systems.



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