The Spectrum Collaboration Challenge (SC2) developed two sets of innovative technologies:

SC2 visualization tool

Collaborative Intelligent Radio Networks(CIRNs)

SC2 competitors each developed a Collaborative Intelligent Radio Network, which is a radio network capable of autonomous collaboration with other competitors’ CIRNs. CIRNs reason and collaborate in order to automate the currently inefficient, labor-intensive process of spectrum management. Specifically, CIRNs figure out the best way to share congested radio frequencies between independent systems that don’t use the same radio communications standard, and dynamically adapt as the situation changes.

SC2 Competitor Technologies

Radio networks have become more and more self-controlled in recent years. The most advanced of these are called Cognitive Radio networks. CIRN technology is a type of Cognitive Radio that goes beyond previous designs. In prior approaches, each independent network operates standalone using only the implicit information gained by sensing other spectrum users. With CIRN technology, independent radio networks exchange explicit information and make agreements to solve joint problems for mutual benefit.

Past Grand Challenges sponsored by DARPA focused on autonomous control of a single system such as an automobile. The Spectrum Collaboration Challenge broke new ground by requiring independent, separately-developed systems to collaborate to solve joint problems. The independent radio networks cooperated to minimize interference to each other, for example by agreeing which network will transmit on which channel. They also cooperated to provide more spectrum to networks with high-priority data, and to prevent interference to nearby protected receivers.

CIRNs don’t have to be able to talk to each other over the air. They exchange the necessary information and cooperation messages over any available data link, such as a satellite or the public Internet. To understand each other, the CIRNs are programmed to communicate over the data link using a common protocol. At the end of SC2, DARPA released its protocol called the CIRN Interaction Language (CIL) as a basis for further development and standardization.

Tools for R&D on Spectrum Collaboration

DARPA developed various innovative tools to enable the competitors’ CIRN technology development and the hosting of the SC2 competition. 

Colosseum:  DARPA built the world’s largest testbed for doing repeatable radio experiments. The testbed is called Colosseum. It’s like a holodeck for radios. Experimenters can connect up to 256 radios which transmit, receive and interfere with each other just as they would in the real world. Except their movements and the world around them are totally controlled by the test script.

Colosseum was commissioned at Johns Hopkins University Applied Physics Laboratory, where SC2 competitors were able to login from anywhere on the Internet to conduct their experiments during the three year build up to the SC2 Championship Event.  In October 2019, Colosseum was moved to the show floor of Mobile World Congress – Los Angeles, where it was on public display during the live final competition of SC2.  With the SC2 competition now completed, Colosseum has transitioned to a national research asset supporting academic, industry and defense exploration of wireless networks.  Colosseum is now being operated by the Institute for the Wireless Internet of Things at Northeastern University in support of the National Science Foundations-sponsored Platforms for Advanced Wireless Research (PAWR) program. 

Colosseum is so big, its input and output data streams are also massive. DARPA had to build new tools to automate input generation and to make the output data understandable.

Learn more about Colosseum here.


RF Scenarios: DARPA tested SC2 teams’ radio designs over a series of RF scenarios designed to mimic the challenges that collaborative, autonomous radios will face in the real world.  These custom RF scenarios consisted of 3-dimensional models of the environment and the motion of all the radios. From this, a toolchain automatically generated the terabytes of data that describe the changing characteristics of radio wave propagation between each pair of radios as they move. This data was streamed into Colosseum in real-time to drive the experiment.

Here are some of the RF scenarios developed specifically for the SC2 Championship Event:

Visualization: DARPA also developed new visualization tools for SC2 to enable analysis and commentary on CIRN performance.  For the first time ever, these tools made it possible to comprehend the RF spectrum and complex behaviors such as how the CIRNs were using the radio spectrum and how they interfered with each other. Researchers could quickly scrub back and forth through time in RF scenarios while focusing on different 3D views of the radios and their interactions both spatially and in the RF spectrum. The visualizations also provided a valuable way for spectators of the SC2 competition to understand what was happening so they could engage with the new CIRN technology.