It is the next frontier of networking—a frontier where communication nodes may move at Mach speeds, wireless line of sight covers hundreds of miles, and weather affects communications capabilities such as chat and e-mail. It is the airborne network (AN). In the coming years, the military services and commercial aviation enterprises will internetwork their respective fleets of airborne assets. For the military, these assets range from unmanned aircraft, smart munitions, and fast-moving fighter aircraft to "air stationary" tankers and slow-moving cargo planes. This fast-paced, ever-changing environment presents challenges across all network layers—from basic connectivity and linking/routing challenges to management of the proposed global network. Accordingly, military entities define the AN as the sum total of all capabilities required for conducting airborne network-centric operations to shorten the kill chain and facilitate the synchronized flow of relevant information by extending the Global Information Grid (GIG) to the airborne domain (see figure).

Artist’s depiction of the various nodes served by extending the GIG to the airborne domain

With administrative support from the Armed Forces Communications and Electronics Association's Erie Canal Chapter, AFRL recently hosted the first annual Airborne Network Technology Review Days—a landmark event comprising the Air Force's first-ever public forum for outlining its goals associated with connecting airborne assets to the GIG. This forum served as the public's introduction to the AN technologies of the National Aeronautics and Space Administration, Federal Aviation Administration, and Defense Advanced Research Projects Agency, all of which presented straightforward, detailed AN deployment challenges to event participants from industry and academia. The event's final discussion forum consisted of a technology panel focused on the challenges confronting the successful deployment of an AN and on the related research areas needing more emphasis.

Many of the identified challenges mirror the problems associated with nodes joining and leaving any network environment and thus include such issues as topology, routing, and addressing. Certain network protocols are simply not amenable to environments that are defined by intermittent connections and delayed acknowledgments—typical occurrences in tactical military networks. During the Review Days forum, technology panel members advocated research in network theory that would aid system designers in determining, in advance, the limitations that certain environments impose on specific protocols. Lacking advanced understanding in network theory, researchers must rigorously examine both existing and emerging protocols to determine if they demonstrate the essential characteristics, including security, that an AN requires—a daunting challenge given the number of potential protocols. Essentially, for every protocol that meets an AN requirement, that same protocol fails at two others. Furthermore, both the tasks of formulating improved network theory and those associated with performing exhaustive testing require researchers to define metrics for qualifying and quantifying required performance.

The Review Days event helped to highlight the need for a robust AN modeling and simulation (M&S) capability. Model validation, a necessity for verifying simulation results, has become increasingly difficult given both the recent decrease in the inventory of research and development aircraft and the general unavailability of platforms due to their use in Operations ENDURING FREEDOM and IRAQI FREEDOM. Fortunately, current AN M&S is more technologically advanced than its embryonic state might imply. For instance, researchers can employ models of air assets, antenna propagation patterns, platform mobility performance characteristics, terrain interference maps, weather effects, communications models, satellite parameters, and urban considerations in their constructs, and use comprehensive, user-friendly visual displays for information input and output. While researchers will continue to refine these models in the coming years, widespread acceptance of their work among operational leaders will rely on their development of more realistic mission models. This dichotomy illustrates the paradox at hand: warfighters want to know how they can exploit the AN; network engineers want to know how the warfighter intends to use the AN so that they can design it correctly. It is essential that the two groups collaborate on the development of more realistic, mission-oriented themes so that network engineers can test their proposed methods and demonstrate new capabilities in real-world scenarios. This challenge is unique to creating the AN, because although there is extensive understanding of how similar aircraft collaborate during traditional air missions, there is no such knowledge regarding the collaboration of dissimilar, non-peer platforms. Without the benefit of the warfighter's wealth of mission experience, M&S designers will continue to guesstimate real-world mission impact. For the AN to succeed, these collaborative efforts must overcome man-made impediments such as bureaucracy, the "not invented here" syndrome, and the classic cultural differences between engineers and warfighters.

The AN's intricacy continues to grow as joint force considerations increasingly mandate that domain-specific solutions be designed for seamless integration into the GIG, as well as communication with allied and coalition assets. This inherent complexity will require the knowledge and skill of experienced systems engineers in creating and pushing new paradigms, since activities involving the AN's optimization and verification may require "peering into the code" or "opening the black box." Furthermore, ensuring a complete, integrated solution—one sufficiently capable and modular enough to evolve with technology—will require strong engineering leadership. Any new system deployment presents three onerous challenges. The first and foremost issue stems from installation costs. Installation of even the simplest hardware device on the largest platform comes at an extremely high expense— estimates of $1 million per airframe are not uncommon. Secondly, every platform presents a unique combination of electrical power, space, and weight constraints. Finally, each platform harbors legacy systems, and any new system must not only coexist with these antiquated systems, but also share limited onboard bandwidth. The combined effect of these challenges can create significant fielding delays, as evidenced by such experiences as the Link-16 deployment—this 1970s technology will be completely installed on 1970s platforms by the end of 2009.

AN designers must also address the necessary implementation of information assurance safeguards and their integration with network management (NM) tools, and these considerations differ significantly with respect to the AN versus traditional ground-based networks. The internet worked AN requires an interdisciplinary approach to developing creative threat assessments so that network engineers can determine workable security overlays, both for existing functional systems and for the integrated security demands of next-generation systems. Additional network design concerns include capabilities such as scalable key management, cross-domain security, timely authentication, network access control, and intrusion detection, and this functionality will require the AN's tight coupling with associated NM capabilities. Highly mobile, high-speed, and ad hoc NM entails a number of aspects that warrant investigation, such as the volume and flow of NM traffic; AN policy-based networking; manageable end-to-end, mission-based quality of service; predictive network planning; dynamic bandwidth management; and usable, onboard NM graphical user interfaces for airborne operators.

Inarguably, the airborne extension of the GIG presents unique networking problems that are further complicated by a variety of nontechnical constraints, and it may thus take many years for industry, academia, and government scientists to find applicable solutions. Fortunately, time is not currently a factor, as the goal for achieving a comprehensive AN deployment extends well into the next decade. As a means of advancing the technology needed to cultivate this next networking frontier, AFRL plans to continue hosting the annual Airborne Network Technology Review Days event, which attracted 230 attendees from more than 25 companies in its first year. The ultimate goal is to build a seamless, airborne, network-centric environment that brings relevant and timely information—and therefore, battlefield dominance—directly to the tip of the spear.

Capt Eugene D. Turnbaugh, of the Air Force Research Laboratory's Information Directorate, wrote this article. For more information, contact TECH CONNECT at (800) 203-6451 or place a request at . Reference document IF-H-05-19.