Mid-Band Spectrum Coexistence in the U.S.: How the DoD and Mobile Operators Will Align on a Dynamic Spectrum Sharing Framework

In my previous blog, I discussed the current state of the mobile industry, the economic pressures associated with it, and how Spectrum Effect is helping operators leverage the power of AI to maximize capacity and improve end-user quality of experience with their existing Spectrum and Radio Access Network (RAN) investments.

Now that the Biden administration has released the National Spectrum Research and Development Plan (https://www.whitehouse.gov/wp-content/uploads/2024/10/National-Spectrum-RD-Plan-2024.pdf), it seems like the right time to share some details about Spectrum Effect’s work in the area of Spectrum Coexistence. That is, helping incumbent users and future entrants utilize shared bandwidths in a harmonized, secure, and trusted manner. Let’s start with the problem we are facing here in the U.S., which may help contextualize why our government is aggressively investing in related R&D efforts.

Spectrum is the backbone of today’s economy. Many of the most successful and influential U.S. companies are built around the devices we carry in our pockets, the applications they host, and the services and experiences enabled by mobile connectivity. In the public sector, secure spectrum access underpins a broad range of critical infrastructure and public safety capabilities that similarly impact the lives of all Americans. As a global technology leader, the United States must ensure a robust spectrum pipeline to sustain its leadership in the digital age and ensure access to critical services.

Spectrum is a finite resource, and there are no clean and available spectrum bands in today’s pipeline. Many U.S. mobile industry and government organizations have expressed concerns about this shortage of spectrum, warning that we are lagging behind global competitors. The next likely tranche of spectrum to be made available for U.S. mobile operators falls within the lower 3GHz range, which is currently occupied by the Department of Defense (DoD). One option is for the DoD to vacate this spectrum, but studies indicate that this approach could cost up to $120 billion and take 20 years to implement. That cost, by the way, is one that taxpayers would assume if the DoD were forced to relocate.

Clearly, a more practical solution is needed—one that involves sharing the lower 3GHz spectrum between mobile operators and DoD through a Dynamic Spectrum Sharing (DSS) framework. For DSS to be viable, the framework must be both efficient and effective. Operators have made it clear that current spectrum-sharing methods fall short of meeting their requirements.

We have deepened our understanding of this challenge through our collaborative work with partners like MITRE and AT&T and believe there are two fundamental keys to solving this problem:

1. First, using the Radio Access Network as a Sensor (RaaS) to detect usage by the incumbents.
2. Second, using a wide area, multi-site, intelligent analysis software platform that allows the RAN to dynamically maneuver around incumbent users.

Based on our work with the U.S. Tier-1 operators and MITRE Corporation, a leader in federal research and development, Spectrum Effect has formed a unique perspective in this space, and we believe we are uniquely positioned to deliver a win-win solution for both MNOs and federal users.

Let me give a quick recap of what Spectrum Effect does in U.S. Tier-1 mobile operator networks to illustrate how we can extend our current solution to deliver a DSS framework using the RAN as a Sensor. The Spectrum Effect team utilized RAN performance management data from 50 mobile operator networks across the globe to train AI models that can detect various signatures created by interference present in a mobile network. We employed over 7 million hours — that’s around 800 years of data — to train our AI models. We did this because interference is a major factor impacting throughput and end-user QoE in mobile networks. If an operator can detect and remove or mitigate the interference in their network, they recover significant CAPEX investments and reduce churn, thereby increasing revenues.

When a mobile operator deploys the Spectrum-NET platform, it pulls data from the RAN every 15 minutes. This data is then analyzed using AI models to identify and map out interference in the network, identifying the interference type, location, and even the root cause. While helpful, improving the network requires one more step: removing the interference or configuring the network to avoid it. The Spectrum-NET platform does just that. We use closed-loop AI-driven automation to push configuration changes back into the network, optimizing throughput for the operator and improving QoE. This process is ongoing, as the system continuously detects and optimizes the network in response to changes in interference types and levels.

So, what does this have to do with dynamic spectrum sharing? The goal of the DSS framework is to permit operators to fully utilize the lower 3GHz spectrum, but only when incumbent systems are not active. If they are active, mobile operators are required to cease use of the spectrum until the incumbent system is no longer active.

The various radar systems the DoD uses have unique signatures that will show up as interference in RAN networks. Spectrum Effect is currently partnered with MITRE to train its ML models to recognize representative types of incumbent radar signatures. Spectrum Effect is researching the exact type and reporting frequency of the data from the network needed to align both the detection and mitigation strategies with incumbent protection requirements. This will solve the detection issue.

Next, we must ensure that mobile operators aren’t using the spectrum when the incumbent is present. Spectrum-NET can already push configuration changes in the RAN network to mitigate RF interference and improve network performance. Spectrum-NET will apply the same concept to dynamically push parameters on the grouping of cells to optimally maneuver around incumbent systems.

We are investing in this work because we believe this concept of using the RAN as a Sensor is the key to maximizing the U.S. mobile operators’ access to shared spectrum bands and to helping the U.S. maintain its global competitiveness while safeguarding U.S. economic and national security.