⚡ electrical engineering

Over-the-Air Successive Interference Cancellation for Efficient 5G NR and Wi-Fi Spectrum Reuse

This paper presents an over-the-air experimental evaluation demonstrating that sample-domain successive interference cancellation (SIC) can effectively suppress dominant 5G NR signals to recover concurrent Wi-Fi transmissions, achieving significant cancellation depth and channel suppression in a controlled shielded environment.

Original authors: Mir Lodro, Francesco Raimondo, Geoffrey S. Hilton, Mark A. Beach, Andrew C. M. Austin

Published 2026-05-27

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CC BY 4.0

Original authors: Mir Lodro, Francesco Raimondo, Geoffrey S. Hilton, Mark A. Beach, Andrew C. M. Austin

Original paper licensed under CC BY 4.0 (http://creativecommons.org/licenses/by/4.0/). ✨ This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer

Imagine you are trying to have a quiet conversation with a friend in a crowded room, but right next to you, a rock band is playing at full volume. Normally, you can't hear your friend at all; the music drowns them out completely.

This paper describes a clever experiment where researchers figured out how to "turn down" the rock band in real-time so your friend's voice becomes clear again, even though both are happening at the exact same time and in the same space.

Here is a breakdown of what they did, using simple analogies:

The Problem: Two Voices, One Channel

In the world of wireless internet, we have two main technologies: 5G (the fast, powerful cellular network) and Wi-Fi (the network in your home or office). Usually, they try to take turns talking so they don't crash into each other.

However, the researchers wanted to see if they could make them talk at the same time on the same frequency. The problem is that 5G is like a giant truck, and Wi-Fi is like a bicycle. If they drive on the same road, the truck's noise completely drowns out the bicycle. In a normal setup, the bicycle (Wi-Fi) would just give up and wait for the truck to pass.

The Solution: The "Noise-Canceling" Trick

The researchers built a special "listening box" (a shielded room) to test a new trick called Successive Interference Cancellation (SIC). Think of this like a high-tech noise-canceling headphone, but for a radio receiver.

Here is how their "magic receiver" works, step-by-step:

The Mixed Soup: The receiver catches a messy signal that is a blend of the loud 5G truck and the quiet Wi-Fi bicycle.
Reconstructing the Loud Voice: First, the receiver focuses entirely on the loud 5G signal. It figures out exactly what the 5G signal sounds like, including how it bounced off the walls and changed shape.
Creating a "Negative" Copy: The receiver then creates a perfect, mirror-image copy of that 5G signal.
Subtracting the Noise: It plays this "negative" copy against the original messy signal. Just like noise-canceling headphones cancel out background hum, this subtraction removes the 5G truck from the mix.
The Result: Once the loud truck is subtracted, the quiet bicycle (the Wi-Fi signal) is left behind in the "residual" signal, finally loud enough to be heard and understood.

The Experiment: A Controlled Test

To prove this works, the team didn't just guess; they built a laboratory setup:

The Room: They used a giant metal box (a shielded enclosure) that blocks out all outside radio waves, ensuring no one else was interfering with their test.
The Actors: They used two radios (called USRPs). One acted as the 5G transmitter, and the other as the Wi-Fi transmitter.
The Volume Knob: They used a precise "attenuator" (a volume knob) to control how loud the Wi-Fi signal was compared to the 5G signal. They tested scenarios where the Wi-Fi was much quieter than the 5G.

What They Found

The results were promising. When they turned up the volume on the 5G signal so much that the Wi-Fi was completely impossible to hear on its own, they applied their "subtraction trick."

Before the trick: The Wi-Fi was lost in the noise.
After the trick: The 5G signal was successfully "silenced" (suppressed by about 11 to 27 decibels, depending on the test conditions), and the Wi-Fi signal popped back into existence, allowing the receiver to decode the data.

They measured this using standard quality checks (like checking for errors in the message), and they found that even when the 5G signal was very strong, the Wi-Fi could still be recovered after the cancellation.

The Bottom Line

This paper doesn't claim this technology is ready for your phone tomorrow. Instead, it proves a concept: We don't always have to make 5G and Wi-Fi take turns. If we have a smart receiver that can identify and subtract the loud 5G signal, both technologies can share the same airwaves at the same time, potentially making our wireless spectrum much more efficient.

In short: They proved you can hear the whisper (Wi-Fi) even when the shout (5G) is right next to you, as long as you have a smart enough ear to cancel out the shout first.

Technical Summary: Over-the-Air Successive Interference Cancellation for Efficient 5G NR and Wi-Fi Spectrum Reuse

Problem Statement
The paper addresses the challenge of efficient spectrum reuse between 5G New Radio (5G NR) and Wi-Fi systems operating in shared or adjacent bands, particularly in unlicensed spectrum. Current coexistence strategies primarily rely on Medium Access Control (MAC) layer mechanisms, such as Listen-Before-Talk (LBT), random backoff, and energy detection. The authors argue that these approaches are limited by the collision domain observed by transmitters, leading to issues like asymmetric sensing, hidden nodes, and inefficient airtime use in heterogeneous deployments. The paper posits that moving beyond collision avoidance to physical-layer separation of overlapping waveforms could allow for more aggressive spectral reuse. Specifically, if a receiver can estimate and suppress a dominant interfering waveform, concurrent transmissions need not be strictly separated in time or frequency.

Methodology
The authors propose and evaluate an Over-the-Air (OTA) Successive Interference Cancellation (SIC) framework designed for a scenario where a strong 5G NR signal acts as a dominant interferer to a weaker co-channel Wi-Fi signal.

System Model: The received composite waveform is modeled as the sum of the 5G NR signal, the Wi-Fi signal, and noise. The SIC receiver aims to reconstruct the dominant 5G component and subtract it from the composite signal to recover the residual Wi-Fi waveform.
Cancellation Algorithm: The proposed receiver operates in the sample domain. The process involves:
1. Demodulation and Reconstruction: The receiver demodulates the strong 5G signal to reconstruct an estimate of the transmitted waveform.
2. Alignment and Estimation: The reconstructed 5G reference is aligned with the captured composite waveform. A complex scalar gain ( $\hat{\alpha}$ ) is fitted to correct amplitude and phase, followed by a regularized Finite Impulse Response (FIR) channel estimation ( $\hat{h}_{NR}$ ) to model the coupling response.
3. Subtraction: The estimated 5G waveform is subtracted from the composite signal to produce a residual waveform, which ideally contains only the Wi-Fi signal and noise.
Experimental Setup: The evaluation was conducted in a controlled, high-performance RF shielding box (R&S TS7124M) to ensure repeatability and isolation from external interference.
- Hardware: Two USRP-2953R radios were used. USRP 1 transmitted the 5G NR waveform and captured the composite signal, while USRP 2 transmitted the Wi-Fi waveform.
- Waveforms: The 5G NR signal used 64-QAM modulation with 15 kHz subcarrier spacing over 66 PRBs. The Wi-Fi signal utilized IEEE 802.11ac VHT configuration (20 MHz bandwidth, MCS 2).
- Channel Conditions: To simulate realistic propagation, quasi-static baseband channel models (TDL-B, TDL-C for NR; TGn Model-B, Model-D for Wi-Fi) were applied before transmission. A precision RF attenuator in the Wi-Fi path allowed for controlled variation of the relative signal strength between the two technologies.

Key Contributions
The paper outlines four primary contributions:

Controlled Testbed: The presentation of a controlled OTA coexistence testbed for concurrent 5G NR and Wi-Fi transmission within a shielded environment.
SIC Implementation: The implementation of a sample-domain SIC receiver utilizing waveform alignment, complex-gain fitting, and FIR channel estimation to suppress dominant 5G interference.
Evaluation Methodology: The definition of a comprehensive evaluation framework that jointly reports 5G and Wi-Fi Error Vector Magnitude (EVM), Bit Error Rate (BER), sample-domain cancellation depth, and channel-estimate suppression.
Experimental Validation: The demonstration, via OTA measurements, that receiver-side cancellation can effectively suppress the dominant 5G component, enabling the recovery of the weaker Wi-Fi waveform from the residual signal.

Results
The study focused on a representative operating point with 18 dB attenuation in the Wi-Fi path, where the 5G signal dominated the composite waveform.

Cancellation Performance: At the 18 dB attenuation point, the system achieved a sample-domain cancellation depth of 11.88 dB and a 5G channel suppression of 26.96 dB.
Recovery Metrics:
- 5G Performance: The 5G composite signal maintained stable performance across channel conditions, with EVM ranging from 10.35% to 11.23% and BER between $2 \times 10^{-2}$ and $5 \times 10^{-2}$ .
- Wi-Fi Performance: Without SIC, Wi-Fi decoding failed on the composite waveform. After SIC, Wi-Fi recovery was successful on the residual signal. The residual Wi-Fi EVM ranged from 26.80% (no-fading case) to 43.69% (filtered channel cases), with BER ranging from $7 \times 10^{-3}$ to $8 \times 10^{-2}$ .
Channel Sensitivity: The results indicated that while cancellation depth was relatively consistent across different channel models, the quality of the residual Wi-Fi recovery was highly sensitive to channel conditions. The "no-fading" case yielded the best recovery, while filtered channel cases resulted in higher residual distortion and error rates.

Significance and Claims
The paper claims that the proposed methodology provides a practical basis for assessing cross-technology coexistence and receiver-side interference suppression under controlled OTA conditions. The authors assert that their results demonstrate that receiver-side cancellation can sufficiently suppress the dominant 5G interference to enable the recovery of weaker co-channel Wi-Fi transmissions. This suggests that spectral resources could be reused more aggressively without relying solely on time or frequency separation, provided the residual waveform remains decodable. The work is framed as a validation of the feasibility of such physical-layer approaches, moving beyond traditional MAC-layer collision avoidance.

The Problem: Two Voices, One Channel

The Solution: The "Noise-Canceling" Trick

The Experiment: A Controlled Test

What They Found

The Bottom Line

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