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/