Transforming radio communications

May 1, 2005
One of the most pressing issues of wireless communications is managing the finite radio frequency (RF) spectrum that is in such heavy and growing demand for cellular telephone, land-mobile radio, commercial broadcasting, and other RF applications.
John Keller, Editor in Chief
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One of the most pressing issues of wireless communications is managing the finite radio frequency (RF) spectrum that is in such heavy and growing demand for cellular telephone, land-mobile radio, commercial broadcasting, and other RF applications.

For their part, officials of the U.S. Department of Defense (DOD) and other federal agencies have been developing software-defined radios such as the Joint Tactical Radio System (JTRS) and the SPEAKeasy Radio system.

In the recent past, DOD has sponsored development of older radios such as the Single Channel Ground and Airborne Radio System (SINCGARS) and Have Quick radios primarily to safeguard communications from enemy jamming.

These systems also attempted to make efficient use of the RF spectrum, but only to a point. They were designed in the days when cell phones, pagers, Wi Fi Internet “hot spots,” and Bluetooth interconnects were in their infancy or only on the drawing board. New radio developments seek to deal with spectrum use head-on.

The next frontier of wireless radio communications is widely believed to be “cognitive radio,” or RF transceivers that use artificial intelligence, neural networks, or other advanced technologies to make informed decisions based on past usage.

These “smart” radios should be able determine their locations, sense spectrum use by neighboring devices, change frequency and output power automatically, and perhaps alter transmission parameters and characteristics, often without any human intervention at all.

In a civilian setting, these kinds of radios might be able to analyze current spectrum use and automatically use the clearest and most efficient frequencies available, based on the kinds of communications involved. For long-haul messages, these radios could choose between satellite and HF frequencies, for example.

In a military setting, cognitive radios might be able to detect enemy jamming or inadvertent RF interference and switch to frequencies unaffected by the problems. They also might determine the clearest frequencies for voice communications, as opposed to quick data messages. They also might be able to choose between military-only spectrum, or leased commercial bandwidth, for large data files such as imagery and video.

Cognitive radio, which could be as far in the future as five to ten years, may have capabilities such as analyzing RF spectrum use around its location and adapting its frequency use on the fly to use spectrum efficiently while keeping RF interference to a minimum, says Wayne Bonser, principal at the Air Force Research Laboratory (AFRL) Information Directorate in Rome, N.Y.

Bonser, who managed the SPEAKeasy radio program in the 1990s, made his comments at the Military Technologies Conference last March in Boston.

Cognitive radio could open fundamentally new ways for the government to manage the RF spectrum, Bonser says, such as short-term spectrum rentals, depending on usage load and emergency priorities, as well as automatic work-arounds to avoid congested frequencies.

At the same time, Bonser says, cognitive radio might complicate the already-difficult job of RF spectrum analysis, especially in this era of frequency-hopping radios, spread-spectrum use, and widespread encryption.

Bonser would not comment on how cognitive radio might influence electronic warfare and signals-intelligence technologies other than saying that experts like him are looking into these issues.

The technologies that could enable cognitive radio are evolutions of the technologies of SPEAKeasy and JTRS-blending computers and software with RF transceivers. SPEAKeasy and JTRS, after all, essentially are computers with antennas attached, Bonser points out.

This evolution can trace back to Guglielmo Marconi and the dawn of radio communications at the turn of the last century. Radio equipment in its earliest forms was application specific and proprietary technology built to operate only on a narrow set of frequencies for specific users.

That proprietary approach persisted throughout the 20th century as radios evolved, even through the SINCGARS and Have Quick anti-jam radios of the 1980s and 1990s.

It was SPEAKeasy and JTRS that flipped the paradigm from proprietary and application-specific equipment toward open-systems architectures and flexible spectrum use through employment of commercially developed computers and widely applicable software radio applications called waveforms.

Off-the-shelf computer microprocessors and other more-sophisticated digital technologies will continue to see widespread use in radio transceivers. Today, in fact, the most sophisticated receivers essentially are all-digital devices, except for the antennas.

The flexibility and new capabilities that digital technology provides also promise to get better and better as more-powerful processors, field-programmable gate arrays, and analog-to-digital converters come on the scene.

Bonser and his experts are wasting no time in investigating the future benefits of cognitive radio. AFRL scientists are able to test and validate their research using the Software Radio Development System (SoRDS)-a JTRS-compliant, software/hardware reconfigurable development platform that supports rapid technology coupling and prototyping.

SoRDS enables researchers to convert abstract models to portable software formats using mathematical analysis tools like MATLAB and move them to reconfigurable digital signal processing and field-programmable-gate-array emulation platforms for testing.

When it comes to radio communications transformation, we have seen only the beginning.

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