A 6G bottleneck breakthrough  

Imagine gaming with next-to-zero lag, transferring massive files in a blink or joining lifelike holographic-style meetings from the comfort of your couch. These offer just a glimpse of the promise of the ultra-high data speeds of sixth generation (6G) wireless networks. But realizing this vision depends on solving a stubborn challenge: signal interference.  

Shimaa Naser, Sami Muhaidat and Zhiguo Ding, from the KU 6G Research Center and the Department of Computer and Information Engineering, are focusing on two particularly disruptive forms of interference that limit performance, including for the Internet of Things (IoT) and Vehicle-to-Everything (V2X) networks, where cars communicate with other vehicles, pedestrians and road infrastructure.  

One of the challenges the team is tackling is called intersymbol interference (ISI). This happens when units of data, or symbols, overlap, making it hard for receivers in cell phones or cars to distinguish them accurately. This is a particular problem at high data rates, when symbols are very close in time. The second major challenge is inter-user interference (IUI), which is common in dense networks, where multiple users or devices transmit data simultaneously on overlapping frequencies, causing signals to collide, degrading the receiver’s performance.

“Our research has potential for practical implementation, and real-world relevance for Internet of Things and Vehicle-to-Everything communications.”

Sami Muhaidat 

To counter these challenges, the team developed a receiver that combines two advanced techniques. The first is time-reversal (TR) waveforms, which focus energy in space and time. The second is non-orthogonal multiple access (NOMA), which allows multiple users to share the same channel by encoding each user’s data at a different power level. The combination significantly enhances spectral efficiency, a key indicator of how effectively a network uses its bandwidth.

“Integrating TR with NOMA enables higher spectral efficiency and more reliable connectivity by leveraging TR’s spatial-temporal focusing and NOMA’s power-domain multiplexing,” Muhaidat explains.  

What sets the approach apart is its simplicity and efficiency. Unlike conventional methods, it does not require the transmitter to do complex processing, called precoding, and it would work with low cost, less sophisticated receivers.  

“It achieves up to 98.13% average error rate improvement and is a scalable solution suitable for 6G applications,” Naser says. The system would also enable more energy-efficient communication, critical for sustainability and battery life. 

Following the team’s numerical simulations of the TR-NOMA scheme, the next step is experimental testing at the 6G Research Center. “Our research has potential for practical implementation, and real-world relevance for IoT and V2X communications,” Muhaidat says.  

Meanwhile, the team plans to investigate the use of adaptive TR techniques that can dynamically adjust, to manage changing interference levels and overcome the challenges of implementing the system in real-world high-mobility and high-density V2X and IoT networks.  

Reference

S. Naser, S. Muhaidat & Z. Ding, Receiver architecture design and analysis for NOMA-based multi-user communication systems. IEEE Trans. Wirel. Commun. 24, 7, 5738-5751 (2025). | Article