Milestone NRL/NASA Experiment Demonstrates Unprecedented Data Transmission Rates

During a record-breaking demonstration of a Ka-band, two-way satellite communications link, scientists from the Naval Research Laboratory (NRL), NASA's Lewis Research Center, and their industry partners achieved an unparalleled data rate transmission of 45 megabits per second (Mbps) between a moving vessel at sea and a fixed-earth station. Previously, the highest demonstrated ship-to-shore satellite data rate was 2 Mbps.

A series of tests conducted in October on southern Lake Michigan, near Chicago, using NASA's Advanced Communications Technology Satellite (ACTS), clearly illustrate the viability of high data rate (HDR) Ka-band systems for ship-to-shore communications. High data rates will open new applications for both Navy communications and civilian users of mobile satellite systems and services.

Using current technology, the Navy cannot link HDR shipboard local area networks (LANs) to terrestrial networks at comparable HDR speeds while ships are away from port. NRL now has programs underway to develop and demonstrate techniques to enable HDR wide area network satellite and wireless connectivity from ships, and HDR satellite communications are a critical component of many of these programs. The objectives of this experiment focused directly on significant elements of HDR mobile networking, in this particular case ship-to-shore, that address this current DoD requirement.

Ultimately, small-deck combatants such as destroyers and frigates outfitted with similar equipment could benefit from the same meteorological and oceanographic data currently received by carriers, cruisers and other large-deck combatants. The faster data transmission rate will also permit small-deck vessels to receive teletraining along with their large-deck counterparts and make teleconferencing technology available for interactive planning, crisis management and telemedicine.

The NRL-NASA Shipboard ACTS Ka-band Experiment (SHAKE) provided at least 20 times greater data rate than the current shipboard standard, demonstrating data rates of 45 Mbps and user applications (file transfers, video teleconferencing) data rates of above 40 Mbps, significantly higher than the current 1.5 Mbps or 64 Kbps standards. While future Navy systems may not require 45 Mbps to a single platform, it is likely data rates in the 1-2 Mbps range, with the ability to increase as required, will be required on a larger number of ships and combatants than is currently available today.

The NRL and NASA SHAKE researchers conducted other experiments concurrently with the data rate transmission trials, including:

· TCP/IP file transfers, which would permit the high speed transfer of imagery, strategic and tactical theater information to and from Navy ships. This data transfer technique is also applicable to a host of NASA spacecraft in near-Earth orbit that routinely transmit data from space to ground using Geostationary relay satellites. Data transfer tests were conducted in disk-to-disk, disk-to-tape, and tape-to-disk configurations.

· Video and voice technologies for real-time video and voice delivery. These technologies can be used for video conferencing, crisis response, telemedicine, mentoring, education, telephony, and entertainment.

· Tracking performance testing of the current system in a Ka-band with the satellite in an inclined-orbit environment was evaluated.

The final goal of this work, says NRL principal investigator Mike Rupar, is to support the use and understanding of emerging Ka-band satellites and services to fulfill emerging HDR Naval satellite based networking requirements. Understanding how emerging satellite services can best be used to meet Naval requirements and how the Navy can best be positioned to use these emerging services is a critical component of this work. Underlying networking, protocol, terminal, and bandwidth-on-demand issues, combined with variable bit rate service and HDR capabilities, present challenges not typically addressed in current Naval SATCOM systems, notes Rupar.

Louis R. Ignaczak, Chief, ACTS Experiments office notes, "With today's pressure of shrinking resources, rapid advancements in technology, and the pursuit of relevant communication architectures for one's mission, it is becoming extremely important to collaborate on synergistic endeavors and leverage unique opportunities - it seems to be a natural fit for NASA and NRL to jointly promote technology that benefits the Nation as a whole."

Supported by the Office of Naval Research, participating industry organizations included: Infinite Global Infrastructures, Chicago, IL; Sea-Tel, Inc., Concord, CA; Hill Mechanical Group, Chicago, IL; FORE Systems, Pittsburgh, PA; Xicom Technologies, Santa Clara, CA; Raytheon Marine Company, Manchester, NH; and Comsat Laboratories, Clarksburg, MD.

Background

The Advanced Communications Technology Satellite (ACTS) spacecraft was launched by NASA in September of 1993 to accelerate the advancement of satellite communications systems. ACTS is situated in geostationary orbit at 100 degrees West Longitude. The satellite and its associated ground systems are managed by the NASA Lewis Research Center in Cleveland, OH. System attributes once considered unique to ACTS that are now becoming common in modern satellite systems, include operation in the Ka-band, the use of high-gain spot beams, a high-gain steerable antenna, and a family of high data rate, very small aperture terminals.

To date, several mobile experiments have been performed through NASA's using a variety of different terminals supporting data rates ranging from 10 kilobits per second up to two megabits per second. These experiments have been performed on a variety of vehicles ranging from aircraft, land mobile vehicles, a commercial seismic acquisition vessel, and most recently, a US naval vessel (an Aegis cruiser). The highest ship-to-shore satellite data rate demonstrated during any of these experiments was a link operating at two megabits per second between the MV Geco Diamond and NASA's Jet Propulsion Laboratory using JPL's slotted waveguide mobile antenna system. This experiment was performed in conjunction with the American Petroleum Institute's ARIES project in February of 1996.

Experiment Overview

The NASA/NRL team performed a variety of application and technology verification experiments during the October trials. The shipboard station communicated via the satellite with the Cleveland ACTS High Data Rate station located at the NASA Lewis Research Center. The vessel used for the tests was the Entropy, a 45' Bayliner Motor Yacht based in Chicago, IL.

The fixed station consisted of a existing ACTS HDR station equipped with a NASA-developed custom Up/Downconverter and an EF Data SDM-9000 satellite modem with a DS-3 interface. The satellite link was optimized by the use of a COMSAT ALE-2000 ATM Link Enhancer using ATM Cell-Level Reed-Solomon Forward Error Correction. The COMSAT ALE was situated between the EF Data Modem and a FORE Systems ASX-200BX ATM switch. Connected to the ATM switch was a Sun Ultra2 workstation, as well as ATM video and audio adapters that were also provided by FORE Systems. The end-to-end communications system supported the transmission and reception of high-speed TCP/IP data transfers, interactive TCP/IP data, production-quality video, and CD-quality audio.

The shipboard station consisted of a 1.0 meter antenna with a tracking pedestal provided by Sea-Tel, Inc. This antenna system was integrated for Ka-band operation by a team of engineers and technicians from SeaTel, NASA and NRL, incorporating hardware contributions by all three organizations. The terminal included a NASA-designed primary Up/Downconverter, conscan tracking, a Xicom 120W Ka-band power amplifier, and the same modems as used by the fixed station. Heading stabilization was attained by a precision gyro compass manufactured by Raytheon Marine Company.

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