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High-Speed Digital Device Prods Battlefield Bandwidth Efficiency

June 2000
By Clarence A. Robinson, Jr.

Canadian-built transmitter uses narrow spectrum slices, avoids interference, establishes clear links.

As the U.S. Army scrambles to digitize the battlefield, an important element in the warfighter’s information network is a new high-capacity line-of-sight radio. Operating with an extremely efficient waveform in minimally occupied portions of the electromagnetic spectrum, this multiband software-reprogrammable radio system significantly enhances the ability to meet burgeoning theater bandwidth requirements.

Delivering a common operational picture to the maneuver commander requires extensive bandwidth to move digital data around the battlefield to where it is needed most. Much of the current-inventory technology can only push data at a meager 16 kilobits per second to a brigade tactical operations center. The warfighter information network-terrestrial, or WIN-T, program is using military and commercial technology to expand bandwidth and expedite the movement of data to the deployed warfighter.

Between the end of the Gulf War and U.S. involvement in the Balkans, Army bandwidth requirements increased by an estimated 200 percent for tactical command, control, communications and intelligence functions. The service is addressing its growing bandwidth needs by developing and deploying an architecture to achieve and maintain information superiority.

Technology applications provide situational awareness to commanders at all levels, David W. Keetley explains. He is the director for space and terrestrial communications at the Army Communications-Electronics Command’s (CECOM’s) Research and Development Center, Fort Monmouth, New Jersey. The center is developing the technologies for an emerging digital force structure.

Behind the Army’s increased bandwidth use are automated tools that assist commanders in executing all aspects of military operations. These tools, for example, include videoconferences for collaborative planning and networks for seamless connectivity, Keetley observes. This increase in data communications requires extensive bandwidth to move information, especially from supporting installations to tactical warfighting units.

The high-capacity line-of-sight (HCLOS) radio is part of the Army’s area common user system program, the first phase of the WIN-T program, and meets the requirements of both efforts. The HCLOS radio supports the current trend of increasing throughput to support voice, data and video on the digital battlefield. The addition of extremely fast asynchronous transfer mode (ATM) switches places extra requirements on line-of-sight radios, which the HCLOS system meets, Keetley says.

“High bandwidth capacity provides high-quality and near-real-time imagery down to brigade level. However, this cannot be accomplished over narrow bandwidth pipes,” Keetley states. He points out that Army research and development is being keyed toward the force objective of the 2010 time frame, which is for on-the-move, self-agile, self-organizing, higher-bandwidth and beyond-line-of sight communications, all integrated seamlessly and leveraging off the digital cellular industry’s concepts.

Built by BAE (British Aerospace Engineering) Systems Canada Incorporated, Quebec, the HCLOS radio opens up bandwidth by communicating at more than 8 megabits per second over a 40-kilometer (25-mile) path with 99.9 percent reliability. Responding to the clamor for bandwidth expansion, the Army is procuring the HCLOS radio to provide a factor-of-eight capacity increase above the highest throughput of existing radio systems, according to Keetley.

A BAE Systems contract calls for delivery this summer of HCLOS, also known by its military nomenclature as the AN/GRC-245(V). The radio provides the high-speed backbone for the Army’s top priority of digitizing tactical forces with modern computers and data transport networks that will shorten the commander’s decision cycle. HCLOS bridges the mobile subscriber equipment (MSE) system with other nodes, such as the triservice tactical radio (TRITAC), to bring higher capacity to the subscriber, Keetley maintains.

“The present AN/GRC-226 radio that operates with MSE provides a maximum of 2-megabits-per-second capacity; however, the multiplexers inside the radio limit bandwidth to approximately 1 megabit per second,” Keetley offers. “HCLOS technology takes the radios, multiplexers and switches associated with them up to more than 8 megabits per second, providing bandwidth increases in the backbone.

“The new radio also expands frequency operations well above the North Atlantic Treaty Organization’s Band III, which is 1350 to 1850 megahertz. This feature enables the Army to maintain communications in regions where the electromagnetic spectrum is crowded, especially in Europe where lower frequencies are congested,” Keetley continues. The HCLOS radio supports the Army’s requirement for increasing traffic by providing up to 8,192 kilobits (8.2 megabits) per second. Another requirement is for a low-traffic bit error rate, since ATM technology is less tolerant to errors than other switches.

Unlike the AN/GRC-226 with a 10-5 forward error rate, the HCLOS radio also meets a residual forward error correction rate requirement of 10-8, making it suitable for passing ATM traffic. A programmable digital modem is used with a bandwidth efficient Trellis coded modulation scheme. Spectrum efficiency is at 3 bits per hertz, Army and BAE Systems officials claim. They also add that the mean-time-between-failure reliability rate is more than 5,000 hours.

The HCLOS radio operates in three configurations: Band I, from 225 to 400 megahertz; and Band III+, from 1350 to 2690 megahertz. Channel spacing is 125 kilohertz. One radio configuration provides only Band I, another is only for Band III+, and the third combines Band I and Band III+, depending on where the Army plans to place the radio within the information infrastructure. As production models are delivered, the AN/GRC-245(V) will replace the AN/GRC-226 radio in one of four versions of MSE’s AN/TRC-190 shelter.

HCLOS, with more than four times the throughput of the AN/GRC-226, provides more than twice the frequency coverage in Band III+ using three times less frequency spectrum. The efficiency of the AN/GRC-245(V) also allows a greater number of radios to be deployed in a given frequency. In addition, HCLOS provides backward compatibility with existing legacy equipment and over-the-air compatibility with the AN/GRC-226, Keetley points out.

This new radio provides an open-standard simple network management protocol remote control capability that allows it to be fully controlled by the network management system. Electronic protection measures within the HCLOS radio are intended to effectively integrate radio performance with the planning and monitoring functions of the network control system. The AN/GRC-245 (V) also has the capability to assess the bit-error-rate activity at its frequency of operation and dynamically provide feedback to the network management system.

This bit-error-rate assessment feature enables characterization of the electronic battlefield based on sources of interference, friendly or otherwise. The radio offers automatic power control in increments of 3 decibels (dB) over a range of 20 dB, supporting low-probability-of-intercept electronic support measures strategy and minimizing the occurrence of self-interference. As a further security measure against spoofing, the radio incorporates a hidden frame structure. HCLOS also is capable of automatically coordinating changes to a designated alternate frequency if the radio detects interference.

Having delivered an initial five HCLOS units for the Army’s Joint Contingency Force exercise, BAE Systems may remain under contract for 10 option years. The company will deliver the first production quantities of the radio to Fort Hood, Texas, this summer. The basic first-year contract for $14 million calls for delivery of 231 radios. An additional $12 million is for another batch of 170 radios, integration into 216 AN/TRC-190 communications shelters, kits, spares, support and fielding.

In winning the radio contract in June 1998, BAE Systems, then known as Canadian Marconi, competed against GTE, the MSE and original AN/GRC-226 contractor, and Raytheon.

Keetley insists that the very narrow spectrum needed for transmissions makes HCLOS effective for sharing. Otherwise, he maintains, the new radio might well be restricted to only a fraction of its bandwidth capacity by interference. HCLOS also provides a fully programmable digital modem to support multiple waveforms. The radio supports a wide range of traffic rates, including commercial standards, and has the potential for growth to a 16-megabit-per-second capacity.

Donald L. Keller, chief of the technical management division, program manager, WIN-T, explains that HCLOS uses very sophisticated modulation techniques to achieve the high-capacity bandwidth. Also located at Fort Monmouth, WIN-T is a subordinate element of the program executive office, command, control and communications systems. Keller stresses that the Army wanted a nondevelopmental product and a system that was already close to what was being marketed.

“Everything appears to this radio as a data stream, even when voice is transmitted. Switches that interconnect with the radio digitize voice traffic,” Keller offers. He believes the radio is in a different class. “This is a point-to-point radio system, and a major advantage is that it does not handle routing. The switches and the routers that feed the radio handle the routing of traffic.”

The Army also anticipates using the HCLOS radio with MSE equipment configured for a brigade subscriber node for initial brigade combat teams. Although it is still taking shape, the node will consist of commercial switching technology and two HCLOS radios to connect the brigade’s nodes. Cisco routers and Lucent post branch exchanges are expected to be in the node packages, Keller confirms.

He verifies that “modifications are being made to switches that will allow them to handle a lot more data. But unless you can open the pipe and interconnect the switches, that data cannot get to the next switch. HCLOS allows a lot more bandwidth for data communications on the battlefield and interconnects the switches.”

In the Army’s transitional phase, HCLOS will be totally backward compatible with the current inventory of radios. Although the ultimate goal is to use HCLOS to replace the AN/GRC-226 radio, it can be placed into a mode that allows it to operate just as would the AN/GRC-226 with the flip of a switch. “This feature avoids interoperability issues during the transition phase,” Keller emphasizes.

BAE was already building AN/GRC-226 radios under contract for the Army and was exporting similar types of radios to the armies of other nations. The HCLOS design is based on an Army performance specification, Keller asserts. BAE’s previous radio designs and the evolution of the technology, through corporate developmental funding, met the nondevelopment requirement, he maintains. A similar radio, although one that employs frequency hopping, is the AN/GRC-512(V), a BAE Systems product fielded with South Korea’s army.

The company’s extensive investment in electronic counter countermeasures technology for the AN/GRC-512 radio, where issues of spectrum management and radio control are vital, brings significant technical enhancements to the HCLOS radio program. These enhancements are in two domains—system planning tools and electronic protection measures.

System planning tools for the radio are intended primarily to increase the radio operator’s level of confidence that an established link is solid, and in case of difficulty, provide for dynamic troubleshooting. Features include an antenna alignment tool at the base of the mast that can be remotely controlled. This tool provides an audible indication of alignment while alignment is in progress. Prior to establishing a link on the assigned frequency, the operator can validate, through the radio’s spectrum scan mode, that the frequency is free of interference. Once a link is established, the operator can invoke the transmission-quality test mode to verify that the link has acceptable bit-error-rate quality.

If necessary, a user can adjust the remote end of the radio link through operator control. The process provides the operator with confidence that the radio link has been properly engineered and that any inconsistencies observed are not related to deployment.

The two-module HCLOS ties together all of the networks, running from a tactical operations center to the backbone. A baseband module handles traffic out of a router or a switch at baseband levels. The radio frequency module is designed for use in the MSE shelter, replacing the AN/GRC-226 in the same slot and rack. The antennas for the AN/GRC-226 can be used with HCLOS; however, some new antennas will be provided for the Band III+ application along with modifications to the shelter for this slightly heavier new antenna.

The radio frequency unit is completely weatherproof and can be deployed outside the shelter. Using only the existing radio frequency cable, the unit can be placed at the base of a mast antenna to increase the range capability of the transmission system. HCLOS supports multiple traffic rates. Duplex digital traffic travels at data rates of 256, 512, 768, 1,024, 1,536, 1,544, 2,048, 4,096 and 8,192 kilobits per second.

A digital voice orderwire is provided for link engineering. As a link alignment aid, an emergency high-sensitivity orderwire-only mode allows link establishment with misaligned antennas. For on-the-move and range-extension communications, the HCLOS system can use an optional smart antenna through an airborne relay. The programmable modem allows the HCLOS waveform to be optimized for this application, providing reliable communications for a mobile tactical operations center.

Keller reports that HCLOS radios coming off the production line will be fielded with the 4th Infantry Division as part of the Army’s digitization program. The division, located at Fort Hood, Texas, is being equipped as the Army’s first digital division, and will operate with ATM switches and the HCLOS radio to provide more dynamic bandwidth allocation, he notes. This arrangement opens up more video applications and allows movement of imagery for collaborative planning. Battlefield videoconferencing is considered the commander’s single most important warfighting tool.

The radio also will be delivered to units of the III Corps, the initial digital corps, and then migrate into the 1st Cavalry Division. Keller explains that there are enough options in the BAE contract to allow for procurement of up to 500 radios a year over the next eight years if required.

As III Corps systems are fielded at Fort Hood, the Army will begin with the 124th Signal Battalion, which supports the 4th Infantry Division. A corps-level unit, the 16th Signal Battalion, will follow. After this, the Army will field equipment for the 13th Signal Battalion for the 1st Cavalry Division, Keller reveals, followed by the 57th Signal battalion, another III Corps unit. Reserve and National Guard components for the III Corps, such as the 136th and 212th Signal Battalions, will then receive HCLOS radios. By the end of 2004, the equipment for the III Corps will be fielded, including its Reserve and National Guard components, he discloses

As the Army gives priority to the first digitized division and digitized corps at Fort Hood, it also will begin to equip a new interim brigade combat team at Fort Lewis, Washington. The same digital systems, including HCLOS radios, will be used with the brigade as those being used at Fort Hood, Keller details.

Army officials are convinced that information technology will enable dominance on future battlefields. Consequently, it is building and sustaining robust digital networks to provide commanders at all echelons with situational awareness through a common operational picture. This is where the HCLOS radio plays an important role, Keller concludes.