frequency assignment process

A Strategy for Active Remote Sensing Amid Increased Demand for Radio Spectrum (2015)

Chapter: 7 spectrum access: allocation policies and the assignment process.

Spectrum Access: Allocation Policies and the Assignment Process

INTRODUCTION

The radio frequency (RF) spectrum has many uses beyond the popular mobile communications and TV broadcasting. The onset of smart phones, tablets, and machine-to-machine communications has created great demand for wireless broadband and digital data to support numerous mobile applications. This increased demand for mobile broadband creates a derived demand for additional RF spectrum for mobile broadband. Some of the many examples include smart phone applications, as well as wireless broadband deployed in support of applications in agriculture, automotive, education, energy efficiency, health, commerce, and smart cities. The largest increase in mobile broadband use has been in video. By the end of 2013 it was estimated that greater than 50 percent of wireless broadband use was for video. 1 This is expected to continue to be the greatest driver of additional wireless broadband demand.

___________

1 Sandvine, Global Internet Phenomena Report , 2013, https://www.sandvine.com/downloads/general/global-internet-phenomena/2013/2h-2013-global-internet-phenomena-report.pdf .

RADIO SPECTRUM POLICIES

U.S. Radio Spectrum Policies

U.S. spectrum policy is driven by its broader broadband policy, which can be summarized as “more is better.” In 2010, the U.S. Federal Communications Commission (FCC) issued a National Broadband Plan (NBP). 2 This plan set a goal of allocating an additional 500 MHz of RF spectrum to mobile broadband uses over the next 10 years. Two significant reallocations meet a portion of this goal and will be available in the next few years:

• Advanced Wireless Services, Band 3 (AWS-3) . This will extend the existing wireless broadband AWS band and make 65 MHz of spectrum available through a combination of reallocating and sharing with federal users.
• TV Incentive Auction . This will simultaneously buy out TV broadcasters and sell the reclaimed RF spectrum to mobile broadband providers. The amount of spectrum reallocated will be determined in the auction by a combination of what mobile wireless providers are willing to pay and how much TV broadcasters demand for their licenses. If properly designed and executed, this auction should reallocate up to 120 MHz from TV to mobile broadband uses.

These two allocations, however, comprise less than 200 MHz of new spectrum for mobile broadband. Meeting the remainder of the NBP’s goal of 500 MHz of spectrum will be difficult because it will involve significant transfers of spectrum currently dedicated to various uses by federal government agencies. 3 Much of this spectrum is likely to be made available to the private sector only on a shared basis.

International Radio Spectrum Policies

The United States is not alone in its desire to have more RF spectrum available for commercial uses. Table 7.1 is a snapshot across the world indicating the amount of spectrum in the pipeline for mobile broadband, and Figure 7.1 depicts the large and growing global use of mobile phones. Finding this additional spectrum is a challenge for policy makers and may be unattainable. The tools available to policy makers to meet these goals consist of reallocation, spectrum sharing, and developing higher spectral efficiencies.

2 FCC, “National Broadband Plan,” https://www.fcc.gov/national-broadband-plan , accessed June 4, 2015.

3 It is also possible that spectrum allocated to satellite uses that could be used terrestrially could go toward this 500 MHz.

TABLE 7.1 Summary of Total Available Licensed Spectrum Available for Mobile Broadband (in megahertz)

NOTE: U.S. Pipeline numbers do not include the significant amount of spectrum that will be made available for mobile broadband from incentive auctions and federal repurposing.

SOURCE: Federal Communications Commission, “The Mobile Broadband Spectrum Challenge: International Comparisons,” FCC White Paper, Wireless Telecommunications Bureau, Office of Engineering and Technology, Washington, D.C., February 26, 2013.

Outside the United States, it is common to allocate spectrum to a specific cellular technology (2G, 3G, or 4G). Reallocation, sometimes referred to as refarming, could involve moving from 3G to 4G services and enabling higher efficiencies, exploiting the digital dividend from more efficient TV broadcasting technology, or finding bands of low usage and thus reallocating them to a higher use. Exploiting the digital dividend by migrating from analog to digital TV, and freeing up spectrum for other uses in the process, is a primary means of providing additional spectrum. 4 The Mobile Satellite Services (MSS) spectrum is also under consideration for terrestrial uses.

The European Union (EU) has been addressing the potential for spectrum sharing through the TV Whitespace, as well as Licensed Shared Access (LSA) and Authorized Shared Access (ASA) for both the 2.3 GHz and the 3.5 GHz band.

With additional capital investments, higher spectral efficiencies can be obtained by waveform and network optimization as well as higher spatial reuse (cell splitting). Moving from waveforms for voice services to data services can provide sig-

4 Over the past decade, interest was expressed by both the private sector and government institutions in several countries, including the United States, to develop high-speed communication using the power grid instead of towers and repeaters. To date, the concept has not materialized, but should such an approach become feasible, its potential RFI effects on active sensing could be detrimental.

FIGURE 7.1 Top 13 mobile operators. SOURCE: Data from J. Groves and W. Croft, “Operator Group Ranking, Q1 2013: Chinese Carriers Continue Strong Growth; Egypt Deal Lifts Orange,” Research, GSMA Intelligence, July 4, 2013, https://gsmaintelligence.com/research/ .

significant improvements in spectral efficiency. Enabling greater use of femtocells 5 and tower access and thus higher spatial reuse can also have significant positive impacts.

SPECTRUM ALLOCATION AND ASSIGNMENT

The entire radio spectrum is divided into blocks or bands of frequencies that are used for specific types of services. The spectrum management process is broken up into two general areas: spectrum allocation and spectrum assignment.

Spectrum allocation determines what blocks of frequencies are used for what specific purpose under a set of technical and operational rules. For example, spectrum managers in some countries have allocated 698 to 793 MHz band (a.k.a. 700 MHz band) for mobile services that eventually became 4G/LTE mobile broadband. Spectrum can be allocated on a primary basis in which that service is given priority and is protected from other services that may come in at a later date and create interference to the operations of the primary allocated service. Spectrum can be allocated on a coprimary basis in which its use is also protected in the same manner as a primary service. Secondary allocations are for services that are allowed but must protect all primary (and co-primary) services. For example:

5 Femtocells are discussed in Chapter 9 .

• Primary allocation in the 3.1 to 3.3 GHz band is Radio Location Service (RLS), which includes S-band radars.
• Secondary allocation in the 3.1 to 3.3 GHz band is Earth Exploration Satellite Service (EESS) and Space Research Services (SRS).

Spectrum assignment determines who gets to access blocks of the spectrum over a specific geographic region in support of a specific service. This comes in the form of a license or an assignment. A typical example of this would be a major cellular service provider (e.g., Verizon Wireless, AT&T, T-Mobile) licensed to operate specific blocks of spectrum in the 700 MHz band, or the military being assigned a band for its exclusive use. In some cases, spectrum can be accessed through “license by rule” in which a specific entity is allowed to operate but does not have a license. This is also called unlicensed spectrum (United States) and license-free spectrum (EU). One well-known example is the Wi-Fi band at 2.4-2.483 GHz.

U.S. Framework

Radio regulation in the United States began in 1910 with the Wireless Ship Act requiring ocean going ships to have transmitting equipment. The sinking of the Titanic in 1912 precipitated international obligations in wireless communications and eventually in the Radio Act of 1912. The Radio Act provided regulation for licensing all transmitters for interstate and foreign commerce to be overseen by the Secretary of Commerce.

During the 1920s there was an explosion of requests for licenses and burgeoning interference concerns, which were addressed by then Secretary of Commerce Herbert Hoover. The Radio Act of 1927 established a new temporary independent agency, the Federal Radio Commission, with the stated purpose to resolve these numerous interference issues. 6 The commission was empowered to impose rules and regulations for both the licensing and operations of the radio spectrum.

In 1934 Congress passed the Communications Act, which put both wired and wireless communications under the regulatory control of a permanent agency called the Federal Communications Commission. Ever since, the FCC has been directed by five commissioners appointed by the President and confirmed by the

6 Some argue that its ulterior purpose was to protect incumbent interests and limit competition. See T. Hazlett, The wireless craze, the unlimited bandwidth myth, the spectrum auction faux pas, and the punchline to Ronald Coase’s big joke—An essay on airwave allocation policy, Harvard Journal of Law and Technology 14(2), 2001.

Senate for 5-year terms. The President designates one commissioner to serve as chairman. Today the Commission has 7 bureaus and 11 staff offices. 7

The United States has a separate administrative office that manages federal use of the RF spectrum. The Office of Spectrum Management within the NTIA of the Department of Commerce provides this function. Therefore the United States has two separate organizations providing spectrum management: an independent agency, the FCC, for all nonfederal uses and the executive branch office of NTIA for federal uses. In addition to the two regulatory agencies, the U.S. Congress also intervenes in spectrum policy—for example, by directing the reallocation of a band of spectrum and then mandating that the reallocated frequencies be auctioned.

International Framework

Spectrum policy and management at the international scale is broken into cooperative activities across borders in the shape of treaties and regulatory activities within a sovereign nation. The use of RF spectrum is very different than use of other national resources. First of all, RF transmissions cannot be contained at the borders, and thus border agreements between nations to address potential interference scenarios must be addressed. Secondly, uses of the RF spectrum in space (for example, satellite systems) need to be coordinated because the actual transmitters cross international borders.

Cooperation at the international scale for spectrum management occurs both at the global level, in the form of agreements made at the International Telecommunications Union (ITU), and at the regional level, such as the European Conference of Postal and Telecommunications (CEPT) Administration.

The ITU is a specialized agency within the United Nations. It specializes in promoting cooperation for spectrum allocation and global regulation of the radio spectrum. Individual countries sometimes deviate from ITU rules and spectrum allocations, however, because the organization does not have an effective enforcement mechanism for its rules and allocations and thus largely depends on countries to abide by the rules because it is in their own long-term self-interest to do so. The ITU has divided the world into three regions to enable specific rules and spectrum allocations customized to those geographies (see Figure 7.2 ). This methodology may no longer be appropriate because of the global nature of the telecommunication marketplace.

One division of the ITU, the ITU-R (Radio Communication Sector), holds

7 The seven bureaus are Consumer and Government Affairs, Enforcement, International, Media, Public Safety and Homeland Security, Wireless Telecommunications, and Wireline Communications (see Federal Communications Commission, “Bureaus and Offices,” http://www.fcc.gov/bureaus-offices , accessed June 4, 2015).

FIGURE 7.2 International Telecommunication Union geographic regions. SOURCE: NASA, NASA Radio Frequency (RF) Spectrum Management Manual , NASA Procedural Requirement (NPR) 2570.1B, effective date December 5, 2008, Figure 1-1 , http://nodis3.gsfc.nasa.gov/npg_img/N_PR_2570_001B_/N_PR_2570_001B_.pdf .

the World Radiocommunication Conference (WRC), where it proposes intergovernmental treaties on spectrum allocations. The most recent WRC was held in 2012, and the next conference is scheduled for 2015. The U.S. delegation is led by a term-limited ambassador specifically appointed for the WRC. The results of a conference are sets of treaties on spectrum allocations and equipment rules. Any such treaties need to be ratified by the U.S. Senate if they are to become binding within the U.S. regulatory framework. There have been multiple occasions where only a limited number of the treaties from a specific WRC are ratified. Therefore the rules and allocations adopted by either the FCC or NTIA are not always in agreement with those of the ITU.

Regional organizations, such as CEPT, are voluntary associations across the member communities. They attempt to develop common policies and regulations across their community and are a focal point for information on spectrum use among its members. An example of regulations would be a series of recommendations for the technical rules for specific services and/or recommendations for how to perform interference analysis on specific systems. Many of the technical rules that are implemented by regulators across the world are based, at least in a small part, on these analyses and recommendations.

U.S. Federal Assignments

Federal frequency assignments are provided by the Office of Spectrum Management within NTIA. NTIA has a formal process in which all federal spectrum users provide advisory support through the Interdepartmental Radio Advisory Committee (IRAC). The following two examples demonstrate how federal departments provide support in securing frequency assignments:

• National Science Foundation (NSF) . The Electromagnetic Spectrum Management (ESM) unit at NSF is responsible for assisting projects and systems to gain access to the radio spectrum for research. ESM is represented in IRAC and participates in ITU committees. Spectrum uses that come under its rubric include radio telescopes and radio astronomy, radar astronomy, incoherent scatter radar arrays, HF radars, micro- and nanosatellites, S-band radars, and telecom systems for polar programs.
• National Oceanic and Atmospheric Administration (NOAA). The Radio Frequency Management Division is responsible for assisting users within the entire Department of Commerce in obtaining access to the RF spectrum. It is represented in IRAC and participates in the ITU, the Organization of American States Commission for Inter-American Telecommunications, the Space Frequency Coordination Group, and a steering group on radio frequency coordination of the World Meteorological Organization.

The federal government maintains software and informational resources to assist in applying for spectrum assignments for federal use. The Spectrum XXI (SXXI) software was developed to fulfill a need to automate many processes and to standardize spectrum management processes throughout the federal government. 8 SXXI assists in the process of obtaining a frequency assignment and also carries out other support functions, including interference analysis. NTIA also keeps current a Government Master File that catalogs the frequencies assigned to all U.S. federal government agencies in the United States. 9 Nevertheless, security and other concerns obscure how some spectral bands are used.

8 See DISA, SPECTRUM XXI: Spectrum Management in the 21st Century , ITT Advanced Engineering and Sciences, http://www.disa.mil/mission-support/spectrum/jsc-joint-spectrum-center/~/media/files/disa/services/jsc/spectrumxxi_jsc.pdf , accessed June 4, 2015.

9 See “National Telecommunications and Information Administration,” http://www.ntia.doc.gov/ , accessed June 4, 2015.

U.S. Nonfederal Assignments

Nonfederal spectrum use licenses are obtained through the FCC via multiple mechanisms: by rule, direct assignment, auction, or acquisition. There also are means of obtaining experimental and Special Temporary Authority (STA) licenses.

• License by rule (unlicensed access). This is commonly used for accessing the spectrum by unlicensed devices such as those used in Wi-Fi local area networks. The ability to access the spectrum is defined by the technical rules stipulating that any piece of equipment that follows technical rules may access that portion of the spectrum. The 2.4-2.483 GHz band for Wi-Fi is an example of where such an approach is applied. A variant of license by rule are the nonexclusive licenses now proposed in the 3.5 GHz band.
• Direct assignment. This is used for systems in which an auction may not be applicable or desirable, such as when there are no competing commercial demands for the band. In this case, the FCC directly provides a license based on requirements that are specific to the band and service type. For example, the mobile satellite service (MSS) spectrum was licensed in this manner.
• Auction. Since the mid-1990s when Congress first directed the FCC to use auctions, this has been the most commonly understood mechanism for obtaining a commercial RF spectrum license. Since 1994 the FCC has held approximately 100 auctions for spectrum licenses. Each auction has specific rules such as who can participate, bidding mechanisms, and credits for small businesses or new entrants. Almost $100 billion has been generated through auctions in the United States. 10
• Acquisition. Licenses are often traded between companies. Furthermore, the spectrum holdings of a company that is being acquired is transferred to the parent entity. In both cases, this requires FCC approval. There are cases in which the FCC may not approve such an acquisition if it believes that harm will be done to the consumer. An example of this is when an acquisition would reduce competition and thus increase the potential for monopolistic or duopolistic behavior. 11
• Experimental license . The FCC allows for scientific research and technical

10 See FCC,“FCC Auctions: Band Plans,” http://wireless.fcc.gov/auctions/default.htm?job=bandplans , accessed June 4, 2015.

11 See, for example, Federal Communications Commission, “Order Dismissing Applications and Staff Report: Staff Analysis and Findings,” https://apps.fcc.gov/edocs_public/attachmatch/DA-11-1955A2.pdf , accessed January 26, 2015.

development without an explicit long-term license. An STA is an experimental license that is not expected to last more than 6 months. 12 , 13

The FCC maintains software and information resources to assist users in applying for spectrum licenses and to understand the current state of licenses across the country. Two resources are particularly useful: the Universal Licensing System 14 (ULS) and the Spectrum Dashboard. 15 The ULS allows a user to search for all of the licenses that have been assigned for a specific frequency band, geographic area, and/or service type. The Spectrum Dashboard allows a user to look at specific frequency bands and to determine which services are allowed, which technical rules are enforced, and which licenses have been assigned.

Challenges of New Allocations

Gaining access to the spectrum for new uses can be a difficult and time-consuming process. As noted, uses of RF spectrum that cross country borders require international coordination. The WRC process, required for new international allocations, can take years if not decades. 16 Even for purely domestic allocations, finding spectrum for new uses is very difficult. Virtually all readily usable RF spectrum has some incumbent user with an interest in maintaining current allocations. Consequently, any new allocation and subsequent assignment will displace the rights of some existing entity, generating opposition to change. As a result, spectrum allocation tends to be an inherently political process with many competing interests. For example, the digital TV transition that ultimately led to the 700 MHz allocation was begun in the 1980s and took two laws—one in 1997 and another in 2006—before the reallocation could be consummated in 2009, with services beginning to be deployed a couple of years later.

12 See Part 5 of the FCC rules governing the usage of the experimental radio service (47 CFR Part 5, available at_ http://ecfr.gpoaccess.gov/ ).

13 The committee is aware of possible changes to the rules regarding FCC experimental licenses, but the impact on remote sensing systems is unclear at present.

14 FCC, “Universal Licensing System,” http://wireless.fcc.gov/uls , accessed June 4, 2015.

15 FCC, “Spectrum Dashboard: Exploring America’s Spectrum,” http://reboot.fcc.gov/reform/systems/spectrum-dashboard , accessed June 4, 2015.

16 An example of this process would be the allocation of spectrum for mobile satellite services (MSS). Initial work in ITU-R in the 1980’s precipitated the WRC-1992 to allocate 1980-2010 MHz and 2170-2200 MHz for MSS worldwide. FCC completed the allocation of the sub-band 1990-2025 MHz and 2165-2200 MHz for MSS in 1997. The technical rules were completed by the FCC in 2000. In 2001 the FCC assigned eight licenses. By 2010 six licenses had been revoked and the remaining two license holders had filed for bankruptcy. By 2012 the band had be reduced to 30 MHz and reallocated to allow mobile terrestrial service and now called AWS-4 (Advanced Wireless Services, Band 4).

SPECTRUM ALLOCATION ISSUES FOR CUBESATS

One of the most important advances in educating the future science and aerospace workforces has been the introduction of the CubeSat program by NSF. In this program, students under faculty supervision design, build, launch, and analyze data from a small satellite, usually a 10 cm cube, with a mass of no more than 1.33 kg. The sounding rocket and balloon programs of NASA were for many generations the vehicles by which future experimentalists were trained. With the advent of CubeSats, that educational experience, for both scientists and engineers, has been extended to actual satellites.

The introduction of CubeSats has also led to a burst of creativity from which it is now being recognized that CubeSats in larger versions, either individually or through constellations, can make important scientific measurements, particularly of Earth and geospace. For example, the 2013 National Research Council report Solar and Space Physics: A Science for a Technological Society 17 anticipates and promotes the concept that constellations of CubeSats will be essential to understanding the space environment of Earth.

The emergence of this new satellite technology, with its unique and in some ways challenging needs for spectrum, has been difficult to accommodate within the deliberative and cumbersome spectrum allocation process. The issue is particularly acute for CubeSats that are for educational purposes, which are, by definition, extremely low-cost and run by students. A complicated bureaucracy for getting a communication license runs counter to the education intent and is a serious impediment to the success of the educational CubeSat program.

There is also confusion about what license to seek. If the educational CubeSat is deemed a government satellite, which most are not, one must download to government ground stations, for which the cost normally exceeds the budget of a low-cost CubeSat. Alternatively, if the CubeSat is not considered to be a government satellite, a license can be sought in the amateur radio band. However, this has become more difficult, since the VHF band for CubeSats has been eliminated, leaving only the UHF band as a possibility.

ESTIMATING THE VALUE OF ACTIVE SENSING

This report offers a number of different ways in which the value of active sensing for research can be estimated. Table 2.5 provides the estimated financial savings to the U.S. economy to which active atmospheric sensing contributes, according to NOAA. Finding 3.2 says, “Active microwave sensors provide unique ocean measure-

17 National Research Council (NRC), Solar and Space Physics: A Science for a Technological Society , The National Academies Press, Washington, D.C., 2013.

ments for scientific and operational applications that are vital to the interests of the United States.” Chapter 4 adds that active microwave remote sensing of the land has proven valuable across a number of science disciplines and practical applications, including geology, urban planning, agriculture and crop management, forestry and biomass assessment, hydrology and water resource management, weather forecasting, generation of topographic maps, sea ice mapping and glacier studies, earthquake and volcano studies, and postdisaster assessment. Chapters 5 and 6 also state that active sensing of the near-Earth environment is essential to understanding space weather and identifying near-Earth objects.

Other benefits certainly flow from this research. Basic research begets advanced research; technologies spin off from research; and training the next generation of scientists and engineers spurs society’s technological progress.

However, many of these benefits are not easy to fully internalize in a market system, so the value of active sensing is very difficult to compare with commercial systems. For example, benefits from advances in weather prediction might be hard to internalize such that private entities would not invest sufficiently in the prediction systems. Also, basic research such as this develops knowledge, which is a public good that is again hard to fully internalize in a market system. Early scientific discoveries can also lead to many different paths of social benefits.

When considering the relative values of various potential services for a given spectrum band, regulators should take into account that the value of the scientific uses of the spectrum is not easy to establish and thus difficult to compare against the value of the commercial uses.

DECADAL SURVEYS OF SCIENTIFIC FIELDS

The National Academies of Scineces, Engineering, and Medicine conducts large surveys of each of the space science disciplines, called decadal surveys, about every 10 years. The surveys, executed by members of the research community, set science and mission priorities for the coming decade. The effort results in a report that provides guidance to the federal agencies supporting the discipline, and the agencies typically set about executing the priorities to the extent possible. The two disciplinary surveys most relevant to this report are the solar and space physics survey and the Earth science and applications from space survey. 18 To date, neither decadal survey has addressed spectrum needs for these communities, although it would be beneficial to do so in the future.

18 The most recent survey of solar and space physics is Solar and Space Physics , 2013. The most recent survey of Earth science is NRC, Earth Science and Applications from Space: National Imperatives for the Next Decade and Beyond , The National Academies Press, Washington, D.C., 2007.

FINDINGS AND RECOMMENDATIONS

Finding 7.1: The U.S. approval process for transmit assignment for environmental radar is too cumbersome, lengthy, and inefficient. The U.S. Interagency Radio Advisory Committee operates by consensus of its members and thus provides numerous opportunities to table or veto applications. Specifically, the allocation for P-band radar allocations is ineffective and encourages only voluntary self-compliance by the applicant.

Finding 7.2: Merit alone will not assure that the spectrum required is available for the scientific community. Scientific interests must be actively engaged in the spectrum allocation and assignment process to assure that science needs are met.

Improving this situation will require ongoing effort in two complementary areas.

Recommendation 7.1: The science community should increase its participation in the International Telecommunications Union, the National Telecommunications and Information Administration, and the Federal Communications Commission spectrum management processes. This includes close monitoring of all spectrum management issues to provide early warning for areas of concern. It also requires regular filings in regulatory proceedings and meetings with decision makers to build credibility for the science community and ensure a seat at the table for spectrum-related decision making that impacts the science community.

This increased participation could be encouraged by organizations such as the International Radio Science Society, the American Astronomical Society, the Institute of Electrical and Electronics Engineers, and the American Geophysical Union, and supported by the relevant funding agencies.

Recommendation 7.2: For participation in the spectrum management process to be effective, the science community, NASA, the National Oceanic and Atmospheric Administration, the National Science Foundation, and the Department of Defense should also articulate the value of the science-based uses of the radio frequency spectrum. Such value will include both economic value, by advancing commerce or reducing the adverse economic impact of natural phenomena, and noneconomic values that comes from scientific research.

Finding 7.3: CubeSats that are undertaken for education are essential for the training of the nation’s aerospace workforce. They are at the forefront of the revolution in small satellite technology that is becoming essential to understanding the envi-

ronment of Earth and geospace. However, the spectrum allocation process creates impediments to the success of the educational CubeSat program.

Recommendation 7.3: Given the importance of the educational CubeSat program for the development of the aerospace workforce and for the development of small satellite technology, the National Science Foundation, NASA, the Federal Communications Commission, and the National Telecommunications and Information Administration should undertake a concerted and coordinated effort to eliminate impediments in the spectrum allocation process that are currently inhibiting the success of educational CubeSats.

Recommendation 7.4: The next decadal surveys in solar and space physics (see Recommendation 5.2 ) and Earth science and applications from space should address the future spectrum needs of those communities.

Active remote sensing is the principal tool used to study and to predict short- and long-term changes in the environment of Earth - the atmosphere, the oceans and the land surfaces - as well as the near space environment of Earth. All of these measurements are essential to understanding terrestrial weather, climate change, space weather hazards, and threats from asteroids. Active remote sensing measurements are of inestimable benefit to society, as we pursue the development of a technological civilization that is economically viable, and seek to maintain the quality of our life.

A Strategy for Active Remote Sensing Amid Increased Demand for Spectrum describes the threats, both current and future, to the effective use of the electromagnetic spectrum required for active remote sensing. This report offers specific recommendations for protecting and making effective use of the spectrum required for active remote sensing.

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What is FA (Frequency Assignment)

• Frequency assignment refers to the process of allocating specific radio frequencies or channels to a set of transmitters or geographical areas.
• The primary goal of FA is to ensure efficient and interference-free utilization of the available electromagnetic spectrum.
• Quality of Service (QoS) : Each transmitter should provide a defined level of service within its coverage area.
• Interference Avoidance : Transmitters must not cause harmful interference to each other.
• Achieving these goals is intricate due to the complex interactions between transmitters and the limited available spectrum.
• Specify technical characteristics for each transmitter (e.g., geographical coordinates, Effective Radiated Power (ERP), antenna height, and pattern).
• Define the quality of service needed for each area.
• Evaluate mutual compatibility between transmitter requirements.
• Determine which requirements can share frequencies and which cannot.
• Estimate interference levels if incompatible requirements were to share the same frequency.
• Use the compatibility assessment results to create a frequency plan.
• Assign frequencies or channels to transmitters while minimizing interference.
• Consider factors like propagation conditions, terrain, and co-channel interference.
• An assignment represents the entry in a frequency plan, including a transmitter’s technical details and its assigned frequency.
• In traditional systems, each transmitter has a unique frequency.
• With digital broadcasting (e.g., COFDM-based systems), Single Frequency Networks (SFNs) allow multiple transmitters to broadcast the same content on the same frequency, improving spectral efficiency.

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