DoD Faces a Fight for Spectrum
By Barry Manz Editor
Spectrum management sounds innocuous enough until all of the activities that a spectrum manager must perform are spelled out. It’s somewhat akin to those of an air traffic controller in slow motion.
The job has become increasingly difficult as the most appealing region of the spectrum below about 3 GHz is already at capacity, forcing national and international regulatory agencies to propose a variety of ways to cram more services into a finite space. The one likely to generate the most resources is spectrum sharing, which while universally loathed (by DoD in particular), appears likely to be implemented as there are no alternatives that can free-up as many resources.
Spectrum management functions in an environment in which national and international politics and regulations and agreements are accompanied by national security interests as well as the revenue-generating interest of the private sector. It is an extraordinarily complex set of tasks that globally requires thousands of people whose mission is to continually sort out signal activity at frequencies from ELF through about 100 GHz.
They must continuously monitor “known” signals, and look for signals of interest, determine their type, where they come from, who and what is generating them, whether they belong there, and what to do about them if they don’t. Spectrum managers today find themselves at the epicenter of the “search for bandwidth”, whether they reside in the offices of wireless carriers or the Pentagon, Army, Air Force, Marine Corps, or Navy. Their job is only going to get more difficult because spectrum is no longer a commodity but rather a precious resource whose quantity is known, finite, and thus extraordinarily valuable. How spectral resources are allocated and managed holds the key to the health of entire industries and the ability of governments and militaries to do their jobs.
Playing Nicely Together
Spectrum sharing has been universally resisted not just by DoD but by wireless carriers as well, even though they are its likely beneficiaries, as they fear it will subject them to uncertainty and interference problems. DoD has fiercely protected its substantial resources by repeatedly playing the “national security” card, which may still work in some cases. However, the federal government “owns” more spectrum than any other entity and DoD owns more of that than anyone else, although it reportedly uses only about 10% of what it’s been allocated. This makes it vulnerable to spectrum sharing and the potential for some of its resources to be reallocated to commercial services. Nevertheless, as DoD has outlined in its own spectrum management plans (Figure 1), it will be in need of not less but more spectrum at frequencies below 3 GHz, between 4.2 and 4.4 GHz, and in the millimeter-wave region, the latter being of little problem as it is not densely inhabited. DoD will thus have to justify its frequency allocations, share them, or lose them and will soon have the opportunity to make its case.
In June, President Obama issued a memorandum directing federal agencies to enhance spectral efficiency and release spectrum for use by consumer and business broadband users. The edict notes that appropriate safeguards will be created to ensure that government systems can remain secure. Its goal is to ensure that there will be spectrum available to meet the future demands for high-speed connectivity not just in major “metro” areas but in rural areas as well. Figure 2 shows that this is not the case today.
Specifically, it authorizes the government to spend $100 million to foster spectrum sharing and advanced communications. The National Science Foundation will award $23 million in spectrum-sharing R&D grants and DARPA will announce the first of $60 million in spectrum-sharing contracts that will be doled out within the next 5 years. The NTIA and National Institute of Standards and Technology (NIST) will devote another $17.5 million for spectrum and advanced communications research and accelerate public-private collaboration at federal laboratories.
The memorandum further requires NTIA to publish a list of federal test facilities that commercial operators can use to research and test spectrum-sharing technologies. Service relocations will be on top of 500 MHz the FCC is already trying pry away from its existing users.
However, the FCC has authority only over commercial entities, thus sparing DoD from this initiative. A push toward spectrum sharing between commercial and government users has also come from NTIA as well as in a report from the President’s Council of Advisors on Science and Technology (PCAST). The council, using NTIA data, projected that it would cost $18 billion to clear the 1755 to 1855 MHz band, which is now used by DoD and other agencies but is targeted by the NTIA for commercial use. The PCAST report also estimated that agencies could share up to 1 GHz of spectrum.
The Obama administration has been consistently promoting its broadband initiative by various means since 2010, and the latest memorandum puts more teeth in the effort by essentially saying that as spectrum is finite, is fully allocated at the most appealing frequencies, that some of what’s been allocated isn’t fully utilized, and since only below 6 GHz or thereabouts is of commercial interest, the only ways to accommodate the growth in commercial wireless traffic is to use it more efficiently and share it between government and private industry.
According to the report issued with the President’s June announcement, there is currently quite a bit of spectrum available now, and that through its initiative and that of the FCC, more should be available in some bands in the future (Table 1).
DoD arguably requires considerable flexibility in its use of spectrum, unlike a wireless carrier or broadcaster that uses a fixed frequency or frequencies only in a single country. DoD obviously needs a broad range of dedicated frequencies so that its suppliers have a specification to build to and must be able to operate in many regions of spectrum as frequencies are better suited for some applications than others and because the military operates all over the world not just in North America.
Even more vexing is the challenge of actually operating in other countries, whose frequency allocations are in many cases different than those of the U.S. and it must deftly wend its way around commercial services as well as those used by enemy forces. The technological capabilities of non-state enemies are increasingly sophisticated and the U.S. must comply with internationally-binding frequency assignments (that the enemy ignores), and potentially disastrous interference is as much a national as international problem.
Picking the Best Fruit
That the spectrum up to 3 GHz is full to capacity is hardly surprising to anyone in the RF and microwave industry. However, in addition to the region’s superior propagation characteristics, it is also the result of technological development and the emergence of new services beginning with the first use of radiotelegraphy in the early 20th Century. As new services were created, agencies were formed to find a home for them first nationally and then internationally, and as technology enabled the use of higher frequencies more services were added to the spectral mix. Services were placed according to what the technology could achieve and which frequencies offered the propagation characteristics that best suited them based on the current knowledge of the day. Some of the key regulatory events are detailed in “Spectrum Management: How We Got Here,” on page 20.
The result is what appears in the spectrum chart adorning engineers’ walls, which is so densely populated in some spectral regions as to be unreadable without terrific eyesight or magnification. Like a hard drive in need of defragmenting, a specific service is not contiguously allocated but in many cases is separated in different bands. There remain some slivers of spectrum in the “sweet spot” between VHF and 3 GHz that could be reallocated to serve wireless applications. Their current owners would obviously have to move elsewhere, sometimes at enormous cost and always with difficulty. DoD is one of those owners.
One might assume that DoD would receive preferential treatment in retaining its spectrum and although it usually doesn’t, if it can prove that national security is at stake it’s been a tough argument to quash. DoD has played this Ace so many times that it is wearing thin and as it uses so little of its allocations in the current environment something will have to give. DoD has fended off many challenges over the years, the most recent being the sad case of LightSquared, which embodies all of the onerous elements that make effective spectrum management essential.
The company created by Harbinger Capital Partners founder Philip Falcone had a plan to bring high-speed, LTE-based broadband service to rural areas where it might never be available – a great solution for “bridging the digital divide”. It would have combined high-power terrestrial base stations with satellite-delivered L-band signals to provide a service that LightSquared could sell on a wholesale basis to retailers that would brand it as their own.
The problem, which should have been obvious to anyone with even a smattering of knowledge about RF technology, was the close proximity of the LightSquared allocation to GPS services. After a long, contentious, politically-charged war of words between the GPS industry, DoD, the FAA, and industrial and agricultural interests on one side and LightSquared on the other, the plan fell apart and took much of Falcone’s wealth with it. The opponents said LightSquared was either a threat to national security or would destroy the GPS industry and make consumer GPS devices useless.
LightSquared said GPS manufacturers were too cheap to add “five-cent filters” to their receivers, which it claimed would have eliminated the potential for interference. But no filter in a GPS receiver could reasonably be expected to attenuate the strong signals generated by LightSquared, even it if it moved slightly further away from its original allocation (as it proposed). The world and national security depend on GPS and there are hundreds of millions of existing GPS-enabled devices that could not be modified. This time, national security was a real concern and DoD ruled the day.
There are other examples of the potential encroachment of commercial services on DoD’s “space”, such as the threat from Digital Audio Broadcast (DAB). In 1992 the World Administrative Radio Conference (WARC) allocated 1452 to 1492 MHz for satellite and terrestrial services, which is in the middle of a band used in the U.S. for aeronautical flight test telemetry. Users objected to losing the band and the U.S. then chose 2310 to 2360 MHz for DAB instead. The telemetry users lost half the band, which was reallocated for non-government use.
In 1979, the WARC suggested that governments move their radar systems operating between 3400 to 3700 MHz to different frequencies so fixed wireless access applications could be accommodated. This is one of the bands used by AWACS so DoD ignored the ruling, although other countries adopted it. When the WARC suggested around 2000 that certain bands be allocated for the third generation of wireless services, its recommendations were at frequencies used by DoD systems. DoD successfully demonstrated that spectrum band-sharing would not work and it ultimately lost no allocations.
Even Wi-Fi once appeared to be a potential threat as WRC 2003, the word “administrative” having by this time been dropped from the name, globally allocated the spectrum between 5 and 6 GHz for Wi-Fi (IEEE 802.11a). This was in direct conflict with DoD antiaircraft and missile defense systems as well as instrumentation used at radar test ranges. As IEEE 802.11b at 2.4 GHz soon followed and essentially replaced the “a” version (offering greater range at less cost), this threat more or less disappeared.
While losing spectrum allocations may be in DoD’s future, it faces the threat of terrorists operating in its bands not in far-flung countries but at home. As these groups are becoming more sophisticated, can use encryption, and have ability to hide their weaker signals under stronger ones to avoid detection, they are becoming increasingly dangerous. The initial problem is not how they can be dealt with but how they can be found.
This is a major and increasingly difficult task. It requires the use of advanced spectrum capture and recording systems that must monitor the spectrum continuously along with an army of analysts to find signals of interest and evaluate them within the massive amounts of generated spectrum data captured at numerous points throughout the U.S.
As the nation has learned, the National Security Agency and other intelligence services already do this. But whether or not anyone actually knows what signal activity is present at all points below a certain reasonable frequency limit, what it is, and whether it poses a threat, remains an open question.
Mapping the RF Domain
In the hope of finding an answer to this question, DARPA, best known for teaming up with industry partners to accomplish what no technology or technologist has achieved before, is working on a program called Advanced RF Mapping (RadioMap).
Its goal is to provide real-time awareness of radio spectrum use across frequency, geography, and time by creating a map that dynamically depicts spectrum usage to simplify the task of spectrum managers and allow them to reduce spectrum congestion and interference. RadioMap uses data and voice communications systems as input when they are not communicating. DARPA likens RadioMap to traffic cameras that show traffic flow at different times of the day, providing real-time situational awareness. It may actually be more like a Google Earth for RF.
Seemingly clairvoyant (the broad agency announcement was issued in 2012), DARPA takes pains to point out that it’s not interested in what people are communicating, just frequency usage. For DoD, RadioMap is designed to provide better situational awareness to small tactical units such as platoons or companies, their radios performing not just their traditional function but providing information about nearby threats and opportunities as well.
As if massive budget cuts were not enough, DoD also faces increased pressure to reduce its spectrum allocations or either lose some of them or share them with the commercial world, while also attempting to create a net-centric environment that depends on the electromagnetic spectrum and combatting threats to its security in the U.S. It’s a tall order.