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CHIPS Articles: Electromagnetic Spectrum Management

Electromagnetic Spectrum Management
By John J. Lussier and Stephen A. Ward - April-June 2002
Background

The ability of Naval forces to support diverse operations and crises is largely dependent on their ability to communicate. Uniquely, the Navy's SEAL Teams, submarines, and Battle Groups, along with various Marine Corps' units deployed aboard Amphibious Ready Groups, are often first to arrive in a theater and must rely on the wireless electromagnetic spectrum to remain highly maneuverable, flexible, and tactically effective.

In the last few years, the rapid adoption of commercial communication technologies has taxed spectrum resources. Domestic and international companies and even civil agencies are putting pressure on their governments to allocate more spectrum to commercial applications. In the United States, much of the spectrum under discussion is dedicated to U.S. military missions.

Worldwide, many governments interested in promoting their telecommunication services consider this reallocation of spectrum simply as a way to generate revenue. Most are not fully aware of the impact on joint military operations and international security. As the civilian sector moves forward with faster, more convenient, and less expensive communication platforms, the military services are under increasing pressure to vacate more spectrum and modify operational military systems.

Our notions of warfare are undergoing radical change. Industrial Age warfare, historically based on massive forces and attrition, is rapidly giving way to the understanding that forces best able to effectively employ information technologies have the advantage. Our forces must achieve and maintain a level of information superiority never before attained. They must have the capability to collect, process, and disseminate an uninterrupted flow of information while exploiting or denying an adversary's ability to do the same.

To meet this challenge, the DON has developed the Network Centric Warfare concept. It outlines the way the DON will organize and fight in the Information Age. As an information superiority-enabled concept of operations, Network Centric Warfare increases combat power by networking together sensors, weapon systems, decision-makers, and warfighters. The advantage is enhanced and shared awareness, increased speed of command, higher tempo of operations, greater lethality, increased survivability, and a high degree of self-synchronization. The electromagnetic spectrum is the key enabler of Network Centric Warfare.

Increasingly, "speed of command" will decide engagements where the precise placement and timing of both forces and effects are substituted for traditional notions of combat mass. In such an information rich and highly mobile environment, spectrum emerges as the lifeblood of the battlefield.

What is ELECTROMAGNETIC SPECTRUM?

The electromagnetic spectrum is a term used to describe the entire range of light radiation, from gamma rays to radio waves. It is a convenient aggregation of types of radiation, which include visible light; radio waves; microwaves, infrared and ultraviolet light; X-rays; gamma rays and cosmic rays. The electromagnetic spectrum can be expressed in terms of energy, wavelength, or frequency.

Electromagnetic waves can be generated in frequency ranges from 1Hz to Gamma rays (1025 Hz). The preponderance of the Navy-Marine Corps use of spectrum falls within the radio frequency range from 10s of Hz to 300 GHz. A valuable advantage exists in this frequency range; atmospheric interaction with electromagnetic waves provides propagation characteristics that can be exploited to transfer information. The physics of waveform performance drives spectrum desirability. Within the current realm of technology, 6 GHz and below is considered prime spectrum "real estate" due to its propagation characteristics.

DON Strategic Vision

The DON Strategic Vision for Spectrum Management (Strategic Vision) was developed in light of the changes in the way warfare is conducted, the tremendous increase in the demand for spectrum access throughout the world, and the emerging threats from terrorism. Assured spectrum access is vital to maintaining our national security and military superiority and our responsiveness to events that challenge our interests at home and abroad.

As a Department, acting in the best interests of the American people, we must conscientiously apportion this limited resource between spectrum wants and actual warfighting spectrum needs. In order to accomplish this, the DON must demonstrate the efficient use of current spectrum assignments as well as effectively engage new technologies that will improve the use of the spectrum or reduce the amount of spectrum required. The overriding objective to develop a proactive, time phased spectrum management strategy based on Naval warfare requirements will allow the DON to make spectrum transparent to its warfighters. Then our forces will be able to operate any time, any place with impunity.

"Information dominance is key to our success, spectrum access is indispensable in achieving that dominance."--Defense Science Board, "Coping with Change" November 2000

The DON Strategic Vision was developed to identify and proactively manage spectrum issues crucial to operational capabilities, and to outline the leadership roles within the Navy and Marine Corps. The Department of the Navy Chief Information Officer (DON CIO), the Assistant Secretary of the Navy for Research, Development, and Acquisition (ASN (RD&A)), and the Navy and Marine Corps CIOs together will evaluate current and future operational and acquisition requirements.

The goal of the Strategic Vision is to create the foundation for development of an innovative, entrepreneurial, long-term spectrum management strategy based on evolving naval warfare requirements. This will allow the DON to support the development of the overall DoD Spectrum Strategy, foster sharing and compatibility with commercial entities, recognize creative approaches to warfighting requirements, and establish professional relationships with industry groups, research laboratories, academics, and the operational DON components.

The Navy has a unique challenge among the Military Services, because Navy Command and Control centers are afloat assets with no direct access to commercial or military communications systems via landline. The only access to these vital communication resources by commanders at sea is via wireless links. A broad range of the spectrum may be required to support the functions of even a small collection of these communication networks. Spectrum management becomes more complex as the number of systems using it increases.

Our command, control, communications, computer, intelligence, surveillance and reconnaissance (C4ISR) capabilities are structured to provide Naval forces with a seamless transfer of information that allows freedom of action and limits vulnerability during both combat and non-combat operations. The capabilities of the DON's significant inventory of radio frequency-spectrum-dependent systems can be loosely categorized as those that communicate information in the form of audio, video or digital data; weapon systems sensors such as radar; electronic warfare systems; and navigation systems.

Technologically superior and precise equipment has been critical to our combat successes — the act of dropping a bomb has spectrum implications. The Joint Direct Attack Munition (JDAM) program upgrades general purpose and penetrator bombs. Installed as a tail kit, it provides each weapon with an all-weather, autonomous, high accuracy, conventional bombing capability. On-target delivery of a JDAM can involve 30 events of spectrum consumption. We must strive to maintain our technical warfighting advantage as we face a wider and asymmetrical range of threats from our savvy adversaries.

DON Dependence on Spectrum

The DON's dependence on spectrum systems are selectively integrated aboard Navy/Marine Corp platforms and within military units to provide the capabilities needed to accomplish the various assigned missions. For example, a Navy aircraft typically hosts many spectrum-related devices. First, voice communications and digital data links are supported by one or more radios. Next, guidance and navigation systems include a radar altimeter, tactical air navigation, Global Positioning Systems (GPS), and an instrument landing system. Also, weapon systems, with associated fire control radar, may include radio- or laser-guided bombs and missiles.

Finally, sophisticated electronic warfare systems exist to detect and suppress enemy radar and communication sites. Similar functions are integrated into surface ships, ground vehicles, and personnel units. Each of these platforms provides a set of capabilities that can be further combined for progressively larger and more complex operations.

Technology advances have created expanding demands for spectrum. New spectrum has become available as reliable, inexpensive microwave and millimeter wave devices — capable of operating at higher frequencies. However, frequencies above 3 GHz are highly susceptible to atmospheric interference and environmental losses caused by rain or foliage. Based on current technology, the upper range of the spectrum has reached its practical limit because of propagation limits.

Because the propagation of electromagnetic waves is a physical phenomenon not limited by political or social boundaries, avoiding unintentional interference with wireless information systems in other countries is mutually beneficial. International, then national, regulatory processes control access to spectrum. Spectrum is a national asset governed by civil authority. Although standards for spectrum use vary among nations and regions of the world, economic and commercial markets, which are boundary neutral, are often the top considerations in determining spectrum policy and use.

In the past, the prime drivers in military system design and procurement were technical capability and operational requirements. In that era, as new systems were designed, spectrum use and availability were assumed. Those are no longer safe assumptions. Both military technology transfer and industry research have accelerated the expansion of commercial/private sector wireless technology. Every product, device, and system under development must now be open to locating in any spectrum band. The specific portion of the spectrum used determines performance capability, and the equipment and systems using it.

The challenge in today's spectrum environment is to maintain an appropriate balance of priorities in providing for the needs of all spectrum users. The explosion of spectrum-dependent technologies will no doubt continue, even in the face of a finite spectrum resource. As technology innovations occur, DON dependence on spectrum access will also increase.

Implementation

Within the DON, the responsibility for spectrum management is vested at multiple organizational levels and in several operational, research, and acquisition areas. Of the entire radio frequency range, the U.S. Government has exclusive use of just 1.4 percent. That represents a very small commitment of spectrum resources to provide for national security and critical public services. The DON, to accomplish its warfighting mission, seeks specific allotments through DoD assignment within that 1.4 percent. The DON shares 93.1 percent of the spectrum with non-government users. The DON remains an accountable steward for this national asset; it maintains its own spectrum management organization and provides a representative to the Interdepartment Radio Advisory Committee.

The DON is responsible for granting frequency allocation for equipment and coordinating its use both in the U.S. and in foreign countries. This involves obtaining frequency certifications and assignments from the National Telecommunications and Information Administration for operations in the U.S., and coordinating with host nations through the Joint Staff Military Communications Electronics Board for operations outside of the U.S. The DON CIO's role is to ensure compliance with the DoD spectrum policies, and develop the DON policy and strategic planning for spectrum use.

The DON CIO is the DON point of contact for spectrum policy issues and works with industry as the Navy/Marine Corps liaison. The DON CIO supports spectrum analyses and studies with organizations such as the Center for Naval Analyses, the Naval Postgraduate School, the Office of Naval Research, the Joint Spectrum Center, and the Navy Studies Board. The DON CIO collaborates with the ASN (RD&A) and the Navy and Marine Corps CIOs to develop strategy planning for efficient spectrum use and development.

ASN (RD&A) monitors compliance with spectrum policy in all phases of the acquisition process. It ensures that spectrum use and availability is considered in normal programmatic activities. As the DON's lead in research and development, the Assistant Secretary is actively engaged with government research agencies, industry, and private research institutes seeking to leverage new technologies to improve spectrum efficiency.

The Chief of Naval Operations (CNO), Space, Information Warfare, Command and Control and the Marine Corps Assistant Chief of Staff have primary responsibility for identifying requirements that support the Navy and Marine Corps operational missions. In their dual role as their respective Service's CIO, they are responsible for implementing spectrum policy guidance. They issue updates to Secretary of the Navy Instructions in support of spectrum identification and certification policies for all DON programs and DON-controlled/managed joint programs.

The CNO and the Commandant of the Marine Corps issue operational guidance for the management of DON specific and shared spectrum, control of electromagnetic interference, and resolve operational issues. As Naval forces deploy, Joint and Service frequency managers negotiate spectrum access with host and surrounding nations. The differing spectrum allocations abroad place a premium on frequency agility in Navy and Marine Corps operational systems to adapt to foreign environments. Active collaboration with other military services, DoD, Federal Government, international spectrum groups, and foreign governments is paramount.

The DON's global electronic networking architecture, Information Technology for the 21st Century (IT-21), provides seamless, interoperable transfer of voice, video, and data between afloat and ashore forces. Spectrum remains the key to exploit IT-21 capabilities like the exchange and distribution of wideband information, reliable, jam-resistant communications, and information warfare protection.

DON Spectrum Management Action Areas

The DON has identified five spectrum management action areas: 1) Policy, 2) Strategic Planning, 3) Operations, 4) Acquisition, 5) Research & Development.

Policy

The DON is developing technical, business, and operational guidance for proactive spectrum management. The DON goal is to develop a realistic and dynamic Strategic Spectrum Plan that defines spectrum requirements consistent with emerging technologies, commercial trends, and increasing market demands. Development and implementation of the plan will require participation by all Navy spectrum management organizations and activities. The DON must continue to ensure that the Navy has the most effective representation possible in international spectrum negotiations.

The DON will provide ongoing spectrum guidance for program development. Primarily, the DON must continue to ensure all spectrum dependent systems complete certification reviews at development and acquisition stages to identify and assign required frequencies prior to expenditure of funds. The DON will establish a process by which the Navy and Marine Corps can seek the most efficient use of spectrum allocations. This activity will include identification of inefficient systems for transition or planned obsolescence. [See infobox below on Improving Spectrum Efficiency]

In order to provide qualified Navy and Marine Corps spectrum managers, the DON will establish Standard Operating Procedures for spectrum management and support military and civilian personnel assignment qualifications.

Strategic Planning

The DON's information needs and its spectrum requirements have exceeded current DON spectrum allocations. In addition, the DON is a major user of commercial satellite communications, cellular telephone, and mobile services. As advanced capabilities are developed to counter emerging threats, spectrum requirements are projected to grow as well.

Faced with these challenges, the DON spectrum strategy will identify and proactively manage spectrum issues crucial to DON operational capabilities of today and requirements for tomorrow: 1) Develop and implement a short-, mid-term, and long-range spectrum vision and strategy; 2) Track industry developments in spectrum research and implementation of techniques for more efficient use of spectrum; 3) Conduct national/international spectrum outreach to promote access to the spectrum needed for Navy and Marine Corps operations, and; 4) Identify both potential spectrum conflicts and opportunities for spectrum sharing.

These strategies must embrace and foster innovation and business partnerships with industry to encourage the development of new public and private technologies.

Operations

Sophisticated electronics systems operating in a constrained area (such as an aircraft carrier) place heavy demands on the spectrum to accommodate information flow without mutual electromagnetic interference. Navy and Marine Corps defensive and offensive detection, tracking, and weapon systems also place heavy demands on the management and use of the electromagnetic spectrum. Operational forces must continue to be educated and trained on the technical aspects of efficient spectrum use, (e.g., shared bandwidth, filter usage, and power usage).

The DON must identify technology to reduce bandwidth needed for control and instrumentation of test and evaluation. Additionally, the DON must seek spectrum consistent with increased instrumentation and test complexity for test and evaluation and training facilities. Improvements in modeling and simulation data to facilitate electromagnetic environmental effects analysis and deployment coordination are necessary. Additional automation to track host nation spectrum usage agreements is an administrative requisite.

Acquisition

The DON will ensure that the appropriate use of spectrum by new and upgraded systems is considered throughout the developmental process. Spectrum compatibility evaluation models developed early in the system development process will facilitate environmental analysis. Spectrum efficiency must be a priority in system development programs. Spectrum conservation and efficient use will be a metric for program managers. All new and upgraded systems (including commercial off-the-shelf (COTS) equipment) will account for their spectrum use and impacts based on military capabilities and spectrum efficiency.

Spectrum management requirements will be addressed throughout system life cycles. As a final check, test and evaluation will include ensuring that the system meets certification criteria. Coordination and certification rules must be enforced to avoid spectrum chaos, both within the United States and abroad. Spectrum management must be a conscious consideration from system conception through system deployment.

Research and Development

The DON should maintain its pre-eminence in identifying and evaluating new techniques for efficient spectrum use that could potentially benefit the Navy and/or the Marine Corps. Spectrum sharing and software programmability are compelling technologies whose research and development has benefited from DON sponsorship.

"Just as the existence of the U.S. Navy dissuades others from investing in competing navies — … — we must develop new capabilities that merely by our possessing them will dissuade adversaries from trying to compete."--Secretary of Defense Donald H. Rumsfeld, "21st Century Transformation of U.S. Armed Forces", National Defense University Jan. 31, 2002

Further investment is needed to fully evaluate and exploit emerging technologies such as coherent tracking, orthogonal concepts, and adaptive bandwidth management. ASN (RD&A) will continue to theorize the practical application of promising science to the warfighting needs of the DON. Technology advances are allowing us to use spectrum more efficiently and effectively in the areas of frequency, time, space, and modulation. Once fixed by hardware, operating frequencies are now becoming software programmable over wide frequency ranges. One example is the Joint Tactical Radio System, which can "sniff" for channels in use and change, in near-real time to unused channels eliminating interference. [See info box below on Promising Technologies]

Conclusions

Effectiveness in 21st Century warfare will depend heavily on how well the different branches of our military can communicate and coordinate their efforts on the battlefield. Joint operations no longer infer just inter-service and traditional treaty partner participation. Now our Navy and Marine Corps warfighters must operate effectively with ad-hoc coalition members and international partners for peace. Additionally, the DON must provide our forces the ability to support national security by active participation in Homeland Defense.

Demands for spectrum to handle the rapidly increasing information flow of modern, joint, dispersed forces are escalating rapidly. The DON recognizes that military capabilities must drive spectrum requirements. Spectrum management no longer exists just to prevent electromagnetic systems interference. To ensure uninterrupted, successful, and effective employment of U.S. Navy and Marine Corps operational capabilities, the DON will continue to transform its approach to spectrum management.

Information dominance is key to the success of future U.S. military operations. Spectrum access is the enabler for that information dominance. The measure of spectrum management success is simple — Navy and Marine Corps warfighters must have seamless and transparent access to spectrum.

John J. Lussier is the program manager for Department of the Navy Electromagnetic Spectrum Management. Stephen A. Ward is a wireless expert supporting the DON CIO.

Improving Spectrum Efficiency

Normally, the Navy/Marine Corps team might be skeptical if a contractor were offering to deliver Vietnam era ships, aircraft, or weapons systems. But today, a spectrum technology that has been around for about thirty years is promising to provide our warfighters with significant advances. Called Orthogonal Frequency Division Multiplexing (OFDM), this technology offers the Spectrum Management team higher effective bandwidth utilization and a promise to solve the problem of interference from signals bouncing off buildings, people, cars and the landscape. A prudent forecast also predicts increased range of operation.

After more than three decades in research, this RF science is ready for deployment because advances in radio and digital technology now make it cost effective for general application. Bell Labs patented the technology in 1970 and it was used in a (now abandoned) naval communications system with the code name Catherine.

OFDM can be utilized in both mobile and fixed wireless networks. The standard Frequency Division Multiplexing (FDM) is a technology that transmits multiple signals simultaneously over a single transmission path, such as a cable or wireless system. Orthogonal spread spectrum technique distributes the data over a large number of carriers that are spaced apart at precise frequencies. This spacing prevents the demodulators from seeing frequencies other than their own. It is based on a mathematical formula, which ensures that individual channels maintain their distance. In simple terms, instead of sending all of the data on a very high-speed high-bandwidth channel, the data is separated into a number of separate sub-channels, each carrying a portion of the data, but at a much lower rate. It comes in many variants and proposed uses.

Some examples of specific functions:

WOFDM - Wideband OFDM, develops spacing between channels large enough so that any frequency errors between transmitter and receiver have no effect on performance

DAB - OFDM will form the basis for the European Digital Audio Broadcasting

VOFDM – Vector OFDM (also called MIMO-OFDM Multiple Input Multiple Output) has Non-Line-of-Sight (NLOS) functionality

ADSL - OFDM forms the basis for the global ADSL (asymmetric digital subscriber line)

Flash OFDM - fast-hopped OFDM, which uses multiple tones and fast hopping to spread signals over a given spectrum band

Unfortunately, OFDM has been divided into two primary technical factions: the Broadband Wireless Internet Forum (BWIF) and the OFDM Forum. While the industry groups compete for international recognition of their proposed standards, once again the DON stands to benefit by the simultaneous commercialization and application of this ‘updated' technology.

It appears that Vector OFDM (VOFDM) offers significant immediate opportunities for our warfighting forces. It uses base station antennas that do not rely upon line-of-sight (LOS). It solves the traditional problems of signals that echo as the transmissions bounce off structures arriving at the destination antenna at different times and in multiple forms creating interference. VOFDM deploys multiple antennas to simultaneously transmit data, in small pieces to the receiver; the data is easily reassembled at the destination. Since all data is transmitted both in the same frequency band and with separate spatial signatures, this technique utilizes spectrum very efficiently. To recap, OFDM benefits are high spectral efficiency and resilience to RF interference.

Promising Technologies

A revolutionary wireless technology, dubbed "ultra-wideband" (UWB) by the Department of Defense in the late 1980s, is actually an amalgam of technical areas such as: impulse, time domain, baseband, large-relative-bandwidth, nonsinusoidal, and orthogonal function radio/radar signals.

Best suited for transmitting digital data over a wide spectrum of frequency bands with very low power, the potential of UWB is clearly recognized by government, science, and business.

Studies since 1960 have produced steady refinement of this non-traditional approach to radio frequency science. Over 100 patents have been awarded for UWB and international standards groups have published extensively in this specialized field. The DON has been an early and ardent proponent of UWB technologies and plans to use UWB to advance the nation's defense systems. The scope of business and government applications for ultra-wideband technology is growing exponentially.

Business areas

UWB imaging devices could be used to improve the safety of the construction and home repair industries by locating steel reinforcement bars (i.e., re-bar) in concrete, or wall studs, electrical wiring and pipes hidden inside walls.

UWB devices could also improve automotive safety with collision avoidance systems and air bag proximity measurement for safe deployment.

Potential medical uses include the development of a mattress-installed breathing monitor to guard against Sudden Infant Death Syndrome and heart monitors that measure the heart's actual contractions.

In wireless networking systems, ultra-wideband offers bandwidth of about 100 megabits per second while consuming just 200 milliwatts.

Government and Military areas

UWB technology has been used for some time in Ground Penetrating Radar (GPR) applications and is now being developed for new types of imaging systems that would enable police, fire and rescue personnel to locate persons hidden behind a wall or under debris in crises or rescue situations.

UWB communication devices could be used to wirelessly distribute services such as phone and computer networking. These devices could provide covert, secure communication to military forces, police, fire, and rescue personnel.

Ultra wideband can be used for very high-resolution radars and precision (sub-centimeter) radio location systems.

UWB devices can locate hidden objects such as land mines and embedded explosives.

The DON realizes that it will benefit from the operational and cost improvements that will result from simultaneous commercial deployment. This ‘sharing' is jeopardized if the commercial adoption and expansion occurs as non-FCC licensed use of this technology. Without proper emission constraints, commercial applications could cause interference to existing licensed radio services, including public safety and critical national security systems such as the Global Positioning System (GPS).

The electromagnetic spectrum, left to right, ELF, VLF, LF, MF, HF, VHF, SHF, EHF, IR, UV, x-ray, gamma ray, cosmic-ray
The electromagnetic spectrum.
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