This July, SpectrumX, the U.S. National Science Foundation Spectrum Innovation Center, organized and conducted a large-scale field experiment at the NSF National Radio Astronomy Observatory (NSF NRAO) Very Large Array (VLA) in the Plains of San Agustin, New Mexico.
This week-long experiment brought together students, staff, and faculty from five NSF SpectrumX institutions and representatives from three other organizations: the NSF NRAO, the National Telecommunications and Information Administration’s (NTIA) Institute for Telecommunication Sciences (ITS), and MITRE. The participating NSF SpectrumX institutions were the Massachusetts Institute of Technology Haystack Observatory (MIT Haystack), Northwestern University, the University of Colorado Boulder, the University of Notre Dame, and the University of Wisconsin-Madison. A total of 25 individuals participated in this experiment, including 10 students.
“NSF has long funded foundational research into more efficient use of the spectrum, which is limited and yet instrumental for science, private industry and our national security,” says Jonathan Williams, a program director in the NSF Astronomical Sciences Division which supports SpectrumX and NSF NRAO. “This field experiment is helping us ensure continued U.S. leadership in the scientific exploration of the universe while opening new opportunities for mobile broadband, satellite communications and advanced wireless technologies.”
The experiment consisted of both passive sensing and active transmitting activities to assess spectrum usage and occupancy at radio frequencies in the 7.125 to 7.4 GHz band within the context of radio astronomy facilities. This band is of particular relevance and interest as it is currently under consideration to be used for the development and deployment of sixth-generation (6G) wireless mobile communications. In conducting this study, the Center aimed to collect real-world data that would enable members to provide objective expertise to decision makers on this matter.
“Allocating a band for 6G will require careful coordination to avoid interference with existing users,” said Mary Knapp, SpectrumX researcher and research scientist at MIT Haystack. “Regulatory bodies and industry stakeholders will need to conduct studies to assess the feasibility of sharing or reallocating this spectrum. Many of these studies will be proprietary and are unlikely to focus on the needs of passive users of the radio spectrum or on potential coexistence techniques. As a result, we intend to study the impact of 6G communication on radio astronomy, the most sensitive application in this band.”
To best assess these elements and collect the most relevant data, it was necessary for researchers to complete these studies at or near a major radio astronomy facility.
When this experiment was being organized, “the NRAO identified the VLA as the preferred site, perhaps because it is not in an official radio quiet zone like other facilities, so it is more vulnerable to interference from commercial devices like cell phones and cell towers in the local area,” said Knapp, who coordinated with the NSF NRAO to plan and execute this field experiment.
The VLA is one of the country’s most prominent astronomical radio observatories, comprising 27 radio antennas, each measuring 25 feet in diameter, and arranged in a Y-shape. The benefit of having multiple large antennas in this configuration is their combined data-collecting capacity, which far exceeds the capacity of each individual antenna, allowing for extremely sensitive, high-resolution images.
Additionally, conducting these studies at the remote VLA site enabled researchers to complete their experiments without excessive external wireless signal interference. The experiment was scheduled to take place during the VLA’s regular maintenance cycle so as not to interfere with the NRAO’s routine data collection and scientific studies.
Throughout the experiment, SpectrumX researchers utilized their own Mobile Experiment Platforms (MEPs) to both receive and transmit signals. Concurrently, the NSF NRAO, ITS, and MITRE gathered data using their own equipment. By collecting data through multiple receivers, including the VLA antennas and MEPs, researchers were able to increase the volume, as well as ensure the efficacy, of the data collected during the experiment.
Researchers began to arrive in New Mexico on Sunday, July 6. During the first few days on the ground, researchers attended training sessions, tested and recalibrated equipment, and conducted preliminary sensing experiments.
On Wednesday, July 9, the group was divided into teams of three to five, and each group comprised a mix of scientists and engineers, as well as undergraduate and graduate students, faculty, and professional staff. Each team was responsible for positioning the MEP at an assigned location, ensuring the MEP was running properly, and collecting data required for each experiment. Data collection locations were spread out, with some on the VLA site and some just outside. Two separate passive receiving activities were conducted that day.
The same groups, with minimal adjustments, gathered again on Thursday, July 10, and Ali Abedi, SpectrumX researcher and assistant professor of computer sciences at the University of Wisconsin-Madison, led an active transmitting experiment. In this experiment, Abedi and his group used an MEP to transmit 6G-like waveforms centered at 7.130 GHz from multiple locations, both stationary and moving. The other groups aimed to capture this signal from the same locations at which they had been stationed the previous day.
The week concluded on Friday, July 11, with SpectrumX Research Deputy Director and MIT Haystack research engineer Frank Lind giving the NRAO a presentation on NSF SpectrumX and the VLA experiment, and researchers winding down final data collection activities.
Alisa Yurevich, a Tufts University student who participated in the VLA experiment as part of her Research Experience for Undergraduates (REU) program at MIT Haystack, stated that the most important lesson she learned from her experience in New Mexico was that “being adaptable is imperative. Nothing in the field goes exactly as planned, and it can be really difficult to accept that in the moment. Being able to recognize those challenges, trust the people around you, and keep pushing is a deeply useful skill I hope to carry with me throughout my career.”
“I was [also] able to see my mentors and fellow scientists in a completely new light. In the field, you witness a kind of passion that is really hard to replicate in the lab. Watching them push through challenges and pour themselves fully into this experiment moved me in a way I didn’t expect. It really solidified, once and for all, that this is the life I wish to pursue. I want to be out there, giving my all, just like they do,” Yurevich said.
The Center is pleased with the progress on developing and fielding the MEPs during these experiments as well as the potential for important research findings and impact. Analysis of the data collected during the VLA experiment is still ongoing, so full experiment results and outcomes are not yet available. At least four terabytes of data were collected by NSF SpectrumX MEPs in the field, all of which will be aggregated in the Center’s Spectrum Data System (SDS), a publicly available online resource. Further, the NSF SpectrumX team has identified multiple publication topics based on this experiment and its outcomes and plans to publish these at their earliest opportunity.
The organizational and inter-personal collaborations, which enabled researchers to share expertise, skills, and perspectives, enriched and strengthened the experiment as a whole. The extensive participation of student researchers both expanded the available on-ground support and provided these early career researchers with valuable technical experience and guidance from experts across a multitude of disciplines and organizations.
The successful completion of this collaborative experiment is an example of how NSF SpectrumX is driving multi-institutional, cross-sector spectrum research and workforce development. SpectrumX researchers are working to continue this momentum by identifying opportunities for future policy-relevant field research experiments that will allow them to help address spectrum challenges, provide student learning opportunities, and promote the coexistence of government, scientific, and commercial uses of the radio spectrum.
Acknowledgements and Notes
This field activity was supported by the U.S. National Science Foundation (NSF).
The Institute for Telecommunication Sciences (ITS) participated in this research activity as an independent and complementary investigator with the following goals: 1) provide subject matter expertise (SME) to NSF, SpectrumX, and others in the design and execution of tests/measurements, to ensure the experimental design supports the most accurate and useful data collection in accordance with best practices; 2) support ITS’s workforce development goals; and 3) obtain valuable, objective, real-world measurement data for spectrum frequency ranges of import to the research community and policymakers, particularly for upcoming band studies.
About SpectrumX
SpectrumX is funded by the NSF as part of its Spectrum Innovation Initiative, under grant number AST 21-32700. SpectrumX is the world’s largest academic hub where all radio spectrum stakeholders can innovate, collaborate, and contribute to maximizing social welfare of this precious resource.
To learn more about SpectrumX, please visit spectrumx.org.
Contact:
Stephanie Loney, Research Communications Specialist
NSF SpectrumX / Notre Dame Research / University of Notre Dame
sloney@nd.edu / 574.631.7804
spectrumx.org
