In episode fifty, Erik G. Larsson and Emil Björnson leave Earth to take a closer look at the new advancements in satellite communications. Constellations with thousands of low-Earth-orbit satellites are now orbiting the sky to deliver fast Internet connectivity to infrastructure, homes, and maybe even directly to 6G mobile phones. How can we reach such distant satellites, and how do the satellite constellations connect back to Earth? What are the intended use cases? How can the massive Doppler effect be overcome? What is the role of multi-antenna technology? All the answers are provided in this massive episode. To learn more about Distributed MIMO in space, we recommend the paper https://arxiv.org/pdf/2603.12914 The Swedish SMART 6GSAT research center has the website https://cos.eecs.kth.seMusic: On the Verge by Joseph McDade. Visit Erik’s website https://liu.se/en/employee/erila39 and Emil’s website https://ebjornson.com/

The NYU Wireless Workshop this year was a lively scientific event, where the future of wireless technology was debated. Erik G. Larsson was among the invited speakers, and the main theme was “Twenty Years of Massive MIMO: What’s Next?”. In this episode, he discusses the main insights with Emil Björnson. They first dissect the practical challenges that still hinder multi-antenna technology from reaching its full potential. It ranges from unfavorable traffic patterns to channel characteristics and channel state information, and how to circumvent these issues. The conversation also covers wireless sensing, AI data aggregation over the air, near-field communications, and common misconceptions around mutual coupling. The most thought-provoking question is: Is the demand for wireless connectivity saturating, or is there still a wireless future ahead? Music: On the Verge by Joseph McDade. Visit Erik’s website https://liu.se/en/employee/erila39and Emil’s website https://ebjornson.com/

Antenna arrays are used everywhere to enhance the wireless signal quality through beamforming and aperture gains. A common practice is to arrange antennas uniformly along a line or in a rectangle, but this is not necessarily the preferred arrangement. In this episode, Emil Björnson and Erik G. Larsson discuss how the geometry of an antenna array affects the shape of the beams it can transmit and the ability to spatially multiplex many users. They uncover how uniform arrays excel at packing many antennas into a compact space, while adjacent antennas collect redundant information about the world around us. In future systems operating above 6 GHz, we might not be able to afford to fill the aperture with antennas and can instead place them in a sparse non-uniform pattern. The vision is to optimize the arrangement at each base station site to maximize its communication and/or sensing performance. The conversation covers grating lobes, minimum redundancy arrays, preoptimized irregular arrays, and movable/fluid antenna systems. Further details can be found in “From Antenna Abundance to Antenna Intelligence in 6G Gigantic MIMO Systems”, https://arxiv.org/abs/2601.08326 Music: On the Verge by Joseph McDade. Visit Erik’s website https://liu.se/en/employee/erila39 and Emil’s website https://ebjornson.com/

Almost every 6G-related keynote speech at scientific conferences focuses on ISAC: Integrated sensing and communications. In this episode, Erik G. Larsson and Emil Björnson discuss how sensing and communication technologies have been developed separately in the past but are built on similar yet distinctly different principles. The conversation covers different integration levels, beamforming implementations, fundamental tradeoffs, alternative waveforms, and the most important question: What would ISAC be used for if it becomes widely available in 6G networks? Music: On the Verge by Joseph McDade. Visit Erik’s website https://liu.se/en/employee/erila39 and Emil’s website https://ebjornson.com/

One of the first topics covered in this podcast was reconfigurable intelligent surfaces (RIS). Five years later, Erik G. Larsson and Emil Björnson return to this topic to reflect on what has happened since then. The conversation covers how these surfaces can improve wave propagation between transmitters and receivers, and identifies the most convincing practical use cases. Core challenges overcome in recent years are discussed, and Emil describes the RIS used in his lab and the lessons learned from his measurements. They also go through new forms of RIS, known as Beyond-Diagonal RIS, STAR-RIS, and Stacked Intelligent Metasurfaces. To learn more, you can read the paper “Reconfigurable Intelligent Surfaces in Upper Mid-Band 6G Networks: Gain or Pain?” (https://doi.org/10.1109/MWC.2025.3616979). Music: On the Verge by Joseph McDade. Visit Erik’s website https://liu.se/en/employee/erila39 and Emil’s website https://ebjornson.com/

“6G should be for the many, not the few” is the final sentence of a recent book by William Webb. In this episode, Erik G. Larsson and Emil Björnson use this book as the starting point for a conversation on why and how wireless technology can improve its coverage. The end goal is to deliver ubiquitous connectivity, so we can use any wirelessly connected application anywhere at any time. The discussion starts at the conceptual level: Why do cellular networks have generations? How are visions for future generations created, and can they be trusted? Different ways to enhance future networks are then covered, from making optimal use of existing network resources to adding different kinds of new infrastructure where it is most needed. The episode was inspired by the book “The 6G Manifesto”, ISBN 9798338481936. Music: On the Verge by Joseph McDade. Visit Erik’s website https://liu.se/en/employee/erila39 and Emil’s website https://ebjornson.com/

Coverage holes exist in cellular networks despite decades of wireless technology evolution, but new potential solutions are on the horizon. In this episode, Emil Björnson and Erik G. Larsson discuss network-controlled repeaters, reconfigurable intelligent surfaces, and half-duplex relays. Network-controlled repeaters have attracted particular attention from 3GPP in recent years; the conversation focuses on how these can create strong propagation paths through signal amplification. Implementation challenges related to synchronization, band selectivity, and stability are also covered. A detailed overview is provided in “Achieving Distributed MIMO Performance with Repeater-Assisted Cellular Massive MIMO” (https://arxiv.org/abs/2406.00142). Technical details can be found in: https://arxiv.org/pdf/2405.01074 and https://arxiv.org/pdf/2403.17908 Music: On the Verge by Joseph McDade. Visit Erik’s website https://liu.se/en/employee/erila39 and Emil’s website https://ebjornson.com/

There are many textbooks to choose between when learning the basics of wireless communications. In this episode, Erik G. Larsson and Emil Björnson discuss the recent book “Introduction to Multiple Antenna Communications and Reconfigurable Surfaces” that Emil has written together with Özlem Tugfe Demir. The conversation focuses on ten subtopics that are covered by the book and differentiates it from many previous textbooks. These are related to the dimensionality of physical constants, the choice of performance metrics, and the motivation behind OFDM signaling. Various system modeling characteristics are discussed, including how the antenna array geometry impacts the channel, dual-polarized signals, carrier frequency dependencies, and the connection between models for small-scale fading and radar cross-sections. The role of non-orthogonal multiple access, hybrid beamforming, and reconfigurable intelligent surfaces are also covered. The textbook is meant for teaching an introductory course on the topic and can be freely downloaded from https://www.nowpublishers.com/NowOpen

Music: On the Verge by Joseph McDade. Visit Erik’s website https://liu.se/en/employee/erila39 and Emil’s website https://ebjornson.com/