DARPA developing collaborative intelligent Wireless Networks and Adaptive Radios to cooperatively share or dominate increasingly congested spectrum
Ongoing wireless revolution is fueling a voracious demand for access to the radio frequency (RF) spectrum around the world. In the civilian sector, consumer devices from smartphones to wearable fitness recorders to smart kitchen appliances are competing for bandwidth. Around 50 billion wireless devices are projected to be vying for access to mobile communications networks within the next few years and by 2030, the demand for wireless access could be 250 times what it is today. However, as the use of wireless technology proliferates, radios and communication devices often interfere with and disrupt other wireless devices.
Military spectrum requirements are also increasing exponentially as military operations increasingly rely on access to the wireless spectrum in order to assess the tactical environment and coordinate and execute their critical missions. The demand for more and timely information at every echelon is driving an increase in DoD’s need for spectrum.“Increasingly lower echelons, including individual soldiers, require situational awareness information resulting in more spectrum-enabled network links.” Managing this increasing demand, while combating what appears to be a looming scarcity of RF spectrum is a serious problem for our nation, both militarily and economically, says DARPA.
However, spectrum is a finite resource and additionally DOD has to free up 500 MHz of the spectrum it has for commercial use by 2020 leading to scarcity of spectrum for DOD use. Spectrum congestion is a growing problem, DARPA officials explain. It increasingly limits operational capabilities due to the increasing deployment and bandwidth of wireless communications, the use of network-centric and unmanned systems, and the need for increased flexibility in radar and communications spectrum to improve performance and overcome sophisticated countermeasures.
In March 2016, DARPA launched the Spectrum Collaboration Challenge (SC2), an initiative designed to ensure that the exponentially growing number of military and civilian wireless devices will have full access to the increasingly crowded electromagnetic spectrum. These networks will be capable of intelligently optimizing the spectrum by collaborating with, and learning from, the other systems that occupy the spectrum with them.
A Vanderbilt team of researchers and alumni – dubbed MarmotE – won the Round 1 in mid-December of the U.S. Defense Advanced Research Projects Agency’s Spectrum Collaboration Challenge (SC2), leading the top 10 teams, each awarded $750,000 in prize money. This was the first event of the three-year long tournament. Round 2 is set for December 2018. The ultimate SC2 winners will walk away in 2019 with $2 million in prize money.
Spectrum Collaboration Challenge administrator Paul Tilghman said: “SC2 sets out to bring the software defined radio and artificial intelligence communities together to fundamentally rethink 100 years of spectrum practise, and tackle the original and enduring spectrum grand challenge: efficient coexistence of all wireless communications.
DARPA Spectrum Challenge
Defense Advanced Research Projects Agency (DARPA) Spectrum Collaboration Challenge (SC2) will use a series of tournament events to spur development of next-generation wireless networks which make more effective use of the RF spectrum. Currently the spectrum is managed by nearly a century old technique, by isolating wireless systems by dividing the spectrum into exclusively licensed bands, which are allocated over large, geographically defined regions. This approach rations access to the spectrum in exchange for the guarantee of interference-free communication. However, allocation is human-driven and not adaptive to the dynamics of supply and demand. At any given time, many allocated bands are unused by licensees while other bands are overwhelmed, thus squandering the spectrum’s enormous capacity and unnecessarily creating conditions of scarcity.
The current situation also poses potential security risks for the military, creating the impression of reliable and unfettered access to the spectrum while in actuality creating a well-defined target for adversaries that may wish to disrupt wireless operations. First responder radios need to be able to communicate reliably in such congested and contested environments and to share radio spectrum without direct coordination or spectrum preplanning. SC2 competitors will reimagine spectrum access strategies and develop a new wireless paradigm in which radio networks, will autonomously collaborate and reason about how to share the RF spectrum, avoid interference, and jointly exploit opportunities to achieve the most efficient use of the available spectrum.
The competition will unfold in three year-long phases beginning in 2017 and finishing, for those teams that survive the two Preliminary Events, in a high-profile Championship Event in late 2019. All 30 teams will have to meet several requirements throughout the year to prepare for the Preliminary Event #1 Competition in December 2017. Top performers during phase 1 will proceed to phase 2 next year, which culminates in another event competition in December 2018. The DARPA has selected 30 teams for Phase I of the Spectrum Collaboration Challenge.
The third and final phase, to be held until the final competition at the end of 2019, will award $2 million, $1 million, and $750,000 prizes, respectively, to the top three finishers. The team whose advanced, software-defined radios collaborate most effectively with a diversity of simultaneously operating radios in a manner that optimizes spectrum usage for the entire communicating ensemble will walk away with a grand prize of $2 million.
The DARPA Spectrum Challenge aims to stimulate the development of innovative approaches to adaptive, software-based radio communications in such multi-user environments. Teams will compete to create protocols for software-defined radios that best use communication channels in the presence of other dynamic users and interfering signals. The Challenge is not focused on developing new radio hardware, but instead seeks algorithmic strategies for guaranteeing successful communication in the presence of other radios without explicit coordination.
To host the new Challenge, DARPA aims to construct the largest-of-its-kind wireless testbed, which will serve during and after the SC2 as a national asset for evaluating spectrum-sharing strategies, tactics, and algorithms for next-generation radio systems.
This new breed of collaborative intelligent radio networks could give rise to a rich spectral ecosystem able to accommodate an enormous diversity of communicating devices while operating 100 to 1,000 times more efficiently than today’s wireless networks
New DARPA Grand Challenge to Focus on Spectrum Collaboration
The win is especially significant for Peter Volgyesi, a research scientist and Miklos Maroti, a research associate professor at Vanderbilt’s Institute for Software Integrated Systems. For the preliminary event, 475 fully autonomous matches were run with the 19 qualified teams’ radio designs in SC2’s custom testbed environment, known as Colosseum. The final matches for the first event were carried out across six different communications scenarios designed to mirror real-world congested environments, but with more complexity than existing commercial radios are equipped to handle.
The competing teams faced fluctuating bandwidths and interference from other competitors as well as DARPA designed bots that tested and challenged their radio designs. Each team’s radio performance was scored based on its collaborative spectrum sharing abilities.
“Central management of the spectrum is simply not scalable and pretty wasteful, but ad-hoc sharing as implemented in WiFi is not working either,” said Maroti. “The best solution to spectrum management would be a combination of distributed cooperation and adaptation driven by the latest advances of machine learning.”
The Round 1 competition found that when two radio networks were asked to share the spectrum, the top performing teams were successful at adapting their spectrum usage so that both networks could successfully transmit with minimal interference.
Fully autonomous sharing of the spectrum with three simultaneous wireless technologies however, remains a difficult challenge. When three different technologies attempt to coexist simultaneously there is a smaller set of overlapping strategies that will fulfill each individual radio network’s needs. This causes conflict and requires a higher degree of agility and reasoning, which will be required to be successful in the next phase.
The next preliminary event will further challenge competitors with an interference environment beyond what existing commercial and military radios can handle—upping the number of simultaneous wireless network types from three to five, and raising the total number of radios from 15 to 50.
SC2 teams will take advantage of recent advances in artificial intelligence and machine learning and the expanding capacities of software-defined radios to develop breakthrough capabilities that can help bring about spectrum abundance.
After two intense days of competition, teams from Tennessee Technological University and Georgia Tech Research Institute and an independent team of individuals emerged as the overall winners, earning a total of $150,000 in prize money. The agency’s Spectrum Collaboration Challenge (SC2) will reward teams for developing smart systems that collaboratively, rather than competitively, adapt in real time to today’s fast-changing, congested spectrum environment—redefining the conventional spectrum management roles of humans and machines in order to maximize the flow of radio frequency (RF) signals.
The challenge is expected to both take advantage of recent significant progress in the fields of artificial intelligence and machine learning and also spur new developments in those research domains, with potential applications in other fields where collaborative decision-making is critical.
Both the preliminary and final events included two separate tournaments, each with its own goals:
In each match, three teams attempted to effectively share the spectrum while transmitting random data files from their source radio to their destination radio over the same 5 MHz UHF band. A team’s match score was its total packets delivered plus the higher of the two other teams’ delivered packets—thus motivating cooperative behavior.
Teams could not coordinate in advance on how to share the spectrum; instead, they had to develop and implement algorithms to enable their assigned software-defined radios to dynamically communicate at a high rate while leaving spectrum available for the other two teams to do the same. This event tested conditions encountered during military operations involving multiple units and coalition partners, and also has possible future commercial applications.
In each match, two teams sought to dominate the spectrum, with the winner being the first to transmit all its files of random data (or to successfully transmit the most packets in three minutes) from a source radio to a destination radio. Teams had to develop and implement algorithms to enable their assigned software-defined radio to dynamically communicate at a high rate in the presence of competitors’ signals within the same 5 MHz UHF band. This event tested conditions directly applicable to military communications, where radios must deliver high-priority data in congested and often contested electromagnetic environments.
DARPA NEXT GENERATION COMMUNICATIONS PROGRAM
The XG Program is developing technology and system concepts for military radios to dynamically access spectrum in order to establish and maintain communications. The goal is to demonstrate the ability to access 10 times more spectrum with near-zero setup time; simplify RF spectrum planning, management and coordination; and automatically de-conflict operational spectrum usage.
XG technology assesses the spectrum environment and dynamically uses spectrum across frequency, space and time. XG is designed to be successful in the face of jammers and without harmful interference to commercial, public service, and military communications systems. XG is transitioning to the Army to solve spectrum challenges in-theater.
In 2005, Shared Spectrum Company was awarded the prime contract to for Phase III of the neXt Generation Communications (XG) program funded by the Department of Defense’s (DoD) Defense Advanced Research Projects Agency (DARPA) and managed by the Air Force Research Laboratory (AFRL).
DARPA’s Advanced RF Mapping (Radio Map)
For warfighters efficiently managing the congested RF spectrum has become critical to ensure effective communications and intelligence gathering.
DARPA’s Advanced RF Mapping (RadioMap) program seeks to provide real-time awareness of radio spectrum use across frequency, geography and time. The goal is to provide a map that gives an accurate picture of spectrum use in complex environments. With this information, spectrum managers and automatic spectrum allocation systems can operate much more efficiently, reducing the problems caused by spectrum congestion and enabling better mitigation of interference problems.
The program plans to provide this information in part by using radios deployed for other purposes, like data and voice communications systems. The program aims to develop ways to use the capabilities of modern radios to sense the spectrum when they are not communicating.
“RadioMap adds value to existing radios, jammers and other RF electronic equipment used by our military forces in the field,” said John Chapin, DARPA program manager. “This program doesn’t require purchasing new spectrum-sensing devices. Rather, it uses existing radios and jammers that do double-duty. In the ‘down’ time when they aren’t performing their primary function, the devices sense the spectrum around them and, through RadioMap technology, provide an accurate picture of what frequencies are currently in use and where.”
The map can be likened to traffic cams in busy cities that show the flow of traffic at different times of the day, giving real-time awareness of whether a section of road is jammed with traffic or clear, helping drivers plan their commute. Such systems aren’t designed to show specific licenses plates or vehicle types, but rather are designed to help see and avoid congestion, resulting in smoother traffic flow.
RadioMap isn’t designed to deal with specifics of transmissions, rather its purpose is to identify frequency usage—where and when the radio frequency “highway” is jammed or clear—allowing better planning and allocation of the spectrum to warfighters overseas operating in RF congested environments.
Another goal of the RadioMap program is to assist small tactical units such as platoons or companies that rarely carry equipment for monitoring radio emissions. With RadioMap, the radios already carried by these units would do double duty to inform the troops about nearby threats and opportunities that are visible in the RF spectrum.
Vencore, Inc. announced that its innovative research arm, Vencore Labs, received a$5.0 million award for phase three of the Advanced Radio Frequency (RF) Mapping (RadioMap) program, which is supported by the Air Force Research Lab (AFRL) and the Defense Advanced Research Projects Agency (DARPA). Vencore Labs will be responsible for developing software associated with (i) distributed command and control (C2), (ii) management of the RadioMap tasking, and (iii) software agents for C2 of RadioMap tasks on RF platforms. Vencore Labs performs as a subcontractor to Lockheed Martin on this program.
“Vencore Labs plans to continue expanding the capabilities and maturing the technology we developed for phases one and two of this effort. This third phase includes plans for testing RadioMap on RF-capable equipment that is typical in current forward-deployed environments, along with a field test and demonstration.”
RadioMap intends to develop technology that visually overlays spectrum information on a map enabling rapid frequency deconfliction and maximizing use of available spectrum for communications and intelligence, surveillance and reconnaissance (ISR) systems.
DARPA gave Lockheed Martin an $11.8 million contract for Phase 3 of RadioMap, during which the contractor is to build on the work in phases 1 and 2 to develop a working system capable of transitioning to the military services. During Phase 2 of the program, DARPA conducted successful tests at Quantico Marine Base, and John Chapin, DARPA program manager Chapin said the Marines will likely participate in Phase 3. “The Marine Corps is an ideal transition partner for RadioMap,” he said. “They have in place the doctrine, organizational structure, and information systems framework that can effectively integrate RadioMap software.”
DOD’s Electromagnetic Spectrum Strategy
DoD’s growing requirements to gather, analyze, and share information rapidly; to control an increasing number of automated Intelligence, Surveillance, and Reconnaissance (ISR) assets; to command geographically dispersed and mobile forces to gain access into denied areas; and to “train as we fight” requires that DoD maintain sufficient spectrum access,” says DODS’s Electromagnetic Spectrum Strategy unveiled in February 2014
However, adversaries are aggressively developing and fielding electronic attack (EA) and cyberspace technologies that significantly reduce the ability of DoD to access the spectrum and conduct military operations. This requires development, fielding, and integration of complex EA, electronic support (ES), and electronic protection (EP) technologies to attack adversary’s command, control, communications, and computers; ISR; improvised explosive devices (IEDS); and area denial weapon systems, all of which require access to spectrum.
Concurrently, the unprecedented consumer demand for wireless mobility and data consumption has resulted in reduction and fragmentation of spectrum of defence. Only 1.4 percent of the RF spectrum from 0 to 300 GHz is available exclusively to the U.S. government. Additionally, the Defense Department also is under a mandate to give up 500 MHz of bandwidth for civilian use by 2020.
This has resulted in complex Defense, spectrum management within and between the armed services, and any errors in the spectrum management plan may result in the denial of critical strategic and tactical links. The second is relatively easy for adversaries to target such a small part of the RF spectrum allocated exclusively to the government through jamming or electronic attack.
DOD’s Electromagnetic Spectrum Strategy 2013 called for ensuring the access to the congested and contested electromagnetic environment of the future, by adopting new agile and opportunistic spectrum operations, and through systems which are more efficient, flexible and adaptable and adopting new technologies capable of more efficient use of the spectrum and reduced risk of interference.
The DoD EMS Strategy will focus on the following goals:
Advancing the spectrum-dependent technologies that are more efficient, flexible, and adaptable in their use of spectrum.
This will include:
- Expediting development of technologies that increase a spectrum-dependent system’s ability to access wider frequency ranges, exploit spectrum efficiency gains, utilize less congested bands, and adapt to changing electromagnetic environments;
- Pursuing spectrum sharing opportunities;
- Evaluating commercial service capabilities (such as smartphones) for mission use; and
- Improving DoD’s oversight of spectrum use.
Increasing the agility of DoD’s spectrum operations. This will include:
- Managing spectrum-dependent systems in near-real-time by developing tools and techniques to quantify spectrum requirements and identify and mitigate spectrum issues;
- Improving the ability to identify, predict, and mitigate harmful interference; and
- Pursuing access to spectrum allocated for non-federal use and spectrum sharing technologies.
Encouraging DoD participation in changing national and international spectrum policy and regulation. In particular, DoD will focus on:
- Developing innovative alternatives that consider both DoD and commercial interests; and
- Improving its ability to adapt and implement regulatory and policy changes while maintaining full military capability
Opportunistic use of the spectrum is one of the promising approaches being pursued by both DoD and the wireless community. Therefore DoD systems must become more spectrally efficient, flexible, and adaptable, and DoD spectrum operations must become more agile in their ability to access spectrum in order to increase the options available to mission planners.
“DoD will also continue to adopt new tools and techniques to manage the spectrum more effectively, making our spectrum operations more agile,” says DOD’s spectrum strategy. Cognitive radio systems, improved spectrum sensing, and geo-location databases are among new opportunistic use technologies being considered.
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