Distributed Spectrum’s Flexible Solution for Radiofrequency Spectrum Monitoring

The radiofrequency (RF) spectrum may be invisible, but it is a vital part of our lives. Radio, television, mobile phones, wireless internet, GPS, radar, baby monitors, even garage door openers—they all send out signals on the RF spectrum. As more technologies use the RF spectrum, it grows more congested, especially at certain frequency ranges.

Monitoring the RF spectrum is challenging, but necessary in industries like defense and security where situational awareness can be a life and death matter. The military uses RF spectrum monitoring to track personnel and adversaries on the ground, monitor the activity of aircraft and watercraft, and secure proving grounds and test areas.

These military applications overlap with security applications, such as detecting hidden signals along the spectrum and conducting counter-surveillance. RF signal detection has an important role to play in protecting water and land borders, as well as in monitoring drones, which use the spectrum. Monitoring can help ensure that drones operate as intended and are disabled if needed.

Meanwhile, telecom providers need to monitor the RF spectrum to detect interferences that can cause poor call quality, limited range, dropped calls, and slow download speeds, all of which can harm their bottom line.

For government regulators, RF spectrum monitoring is a core part of their mandate. Regulators must ensure the spectrum is available for legitimate beneficial uses and free of interference from unauthorized users. For example, radiofrequencies reserved for certain uses, such as airport traffic communications, are protected to prevent interference. However, people can mistakenly use these frequencies. Monitoring can help identify these cases before they threaten safety. Regulators also need to know who is using the RF spectrum so they can allocate the spectrum efficiently and plan for the future.

Building a New RF Monitoring Solution

Xfund portfolio company Distributed Spectrum has developed a flexible, yet powerful solution for RF spectrum monitoring. The company started as a senior thesis project by a trio of students at the Harvard School of Engineering and Applied Sciences; their initial idea was to connect several cheap, commercially produced radio frequency monitors and establish them as a network.

The ultimate goal of the Distributed Spectrum founders was to develop sensors capable of detecting communications across the full RF spectrum. Then, a software interface would be able to determine if that signal was disrupting communications in the local area and if the signal was expected to be there or not. Most importantly, the technology would be capable of tracing the signal back to its source to help identify who might be responsible for the disruption.

As the trio began to bring their ideas into reality, they received support from the National Security Innovation Network and later won a Small Business Innovation Research grant from the National Science Foundation before meeting their first investor, Patrick Chung of Xfund.

"I rarely meet a group so fully immersed and committed to a technology," says Chung. "[Distributed Spectrum co-founder] Alex [Wulff] even authored and published a book on the topic!"

Clock accuracy was one hurdle that Distributed Spectrum faced in the process of creating their product. Identifying the source of a jamming signal requires a network of at least two sensors. The sensors triangulate the position of the signal by using the difference between the times when each receives the signal. Radio waves travel so fast that a clock that is off by only a millisecond can cause the triangulation to be off by a million feet. Adding more sensors can help verify the location by allowing for other triangulations to confirm that the location is correct. This can help eliminate signal interference or, in some settings, figure out why an unexpected signal blockage is occurring.

The ability to detect signal interference has several military and industry applications. Interference detection could help save lives on the ground during periods of conflict. For example, the crew of a military tank will sometimes lose their ability to communicate. Often, the problem is a hardware malfunction. However, investigating a hardware issue is extremely dangerous since exiting the vehicle will put crew members at serious risk if it turns out they are under an attack.

With Distributed Spectrum’s system, the crew can detect in a matter of seconds if their signal is being purposely jammed and then exit the vehicle with confidence if it is not. Because of this and other potential applications, the company was approached by the Department of Defense and offered a subcontract with the Air Force.

Built-in Flexibility and Local Data Processing

Distributed Spectrum’s system allows users to get a full picture of the RF environment in a particular location. The software creates a live map of all existing sensors in relation to each other and allows the network to be configured to look for certain types of signals. This capability can be used to trace friendly signals or identify potentially malicious ones. Through the network, alerts can be set up to provide real-time feedback and updates, whether the goal is to keep an airport communication system free from disruption or monitor RF use by enemy forces in a combat zone.

The sensors themselves are low-cost and run on off-the-shelf hardware, so they are easy to deploy and replace. They are also small and light, so they can be placed almost anywhere, including on moving vehicles or in a backpack, to expand the network. They integrate with commonly used communications apps and protocols like Android Team Awareness Kit (ATAK) and Micro Air Vehicle Link (MAVLink). In addition, the product leverages advances in edge computing for faster processing. The system uses proprietary algorithms to analyze RF signals, and the data processing is performed on the sensors in the field, without the need for a high-bandwidth network link.

The flexibility and modular nature of the Distributed Spectrum solution are key parts of its value. RF spectrum monitoring has always been important in the defense industry, but has traditionally been accomplished via purpose-built systems that use expensive hardware. Distributed Spectrum’s solution offers a nimbler, yet powerful alternative.

"This is one of our highest-trajectory companies," reports Patrick Chung of Xfund. "An extraordinary match of the right team, technology, and market."