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secondary surveillance and communication system, which supports Air Traffic Control.
CHALLENGES
Impediments to Networked UA Communications
As the Services and industry work to make the ubiquitous network a reality, individual programs will
have to address a number of complex issues. While the solutions to these issues may be highly tailored to
individual program requirements, they must draw on GIG standards to assure seamless connectivity and
broad based information sharing. Current data link systems focus on aircraft and sensor technology rather
than network based interfaces, and often use unique formats for data transfer. The resultant, tightly
coupled interfaces preclude broad interoperability.
Traditional circuit based systems have enjoyed success over the years. Many users expect circuit
functionality and performance to be emulated in an IP environment. While dedicated circuits offer
performance precisely tailored to the operational requirement, they represent single points of failure and
often have limited interoperability/flexibility due to optimization for specialized applications. Sized for
peak demand, point-to-point circuits are not always required to operate at full capacity. Due to being
closed circuits, however, their surplus bandwidth is not available to external users.
Frequency Spectrum Considerations and Bandwidth Constraints
Many UAS use COTS data link equipment that offers the developers reduced costs for the equipment and
shorter development periods. Problems associated with using commercial RF for military applications
include being designed within the U.S. authorized spectrum, which means that they are given the “lowest”
priority within the United States and its Possessions (US&P). As a result, use of these frequencies may
be prohibited in some countries. The use of COTS usage for proof of concept is OKaccpetable on a
temporary basis, but the strong consideration must be given system must be replaced withselecting a
material solution that truly takes spectrum supportability into account. equipment that operates in theThis
includes considering equipment designed to operate in properly allocated band before field testing and
especially before entering formal development or large numbers are procured. Such replacement efforts
need to be programmed into the transition plan from ACTDs into a normal acquisition program.
RF spectrum challenges for UAS
􀂾 Spectrum use is controlled internationally by treaties and within the US&P by laws and regulations.
􀂾 Those treaties, laws, and regulations have divided the spectrum by type of service use, (e.g., radio
navigation, aeronautical mobile, fixed-satellite, and mobile satellite), by user (e.g., Government and
non-government), and by region (1) Europe, Africa, Former Soviet Union, and Near East; (2)
Western Hemisphere; and (3) Far East and Western Pacific.
UAS ROADMAP 2005
APPENDIX C - COMMUNICATIONS
Page C-17
􀂾 Any new federal government system that seeks to use a portion of the spectrum must seek both a
frequency allocation and a frequency assignment. Normally, new systems can not interfere with older
systems with prior equal or higher status (e.g., primary or secondary) assignment.
If a new system does not conform with the existing treaties, laws and regulations, it can only operate on a
“not to interfere basis” (NIB) with other approved systems.
The DoD Policy on Electromagnetic Spectrum – Management and Use (DoDD 4650.1) provides specific
requirements that program offices must meet when developing and using RF systems. It states,
“Spectrum-dependent equipment or systems shall not be developed or procured without reasonable
assurance that required electromagnetic spectrum is, or shall be, available to support the development,
testing, and operation of that equipment or system.”
DoDD 4650.1 further states that “No spectrum-dependent ‘off-the-shelf” system shall be purchased or
procured without the assurance that spectrum supportability has been, or can be obtained.”
Finally, DoDD 4650.1 requires the acquisition community to insure compliance with supportability
requirements and to provide oversight to the process prior to and through the development, test and
evaluation phases of a system. Since systems are designed within the U.S., they must meet U.S.
requirements, and since there is no way of predicting where they may be used “outside the U.S.,” it is
necessary to consider the potential limitations of International Law/International Treaties on the
development of unmanned aircraft systems. Spectrum flexibility in development must be a consideration,
or International Law must accommodate use of military systems regardless of the country of origin.
　
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