“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/

Even if the 6G standardization is just beginning, the last five years of intensive research have illuminated the contours of the next-generation technology. In this episode, Emil Björnson and Erik G. Larsson discuss the recent paper “6G takes shape” written by leading researchers at UT Austin and Qualcomm. The conversation covers lessons learned from 5G, the potential role of new frequency bands and waveforms, and new coding schemes and forms of MIMO. The roles of machine learning and generative AI, as well as satellite integration and Open RAN, are also discussed. The original paper by Jeffrey G. Andrews, Todd E. Humphreys, and Tingfang Ji will appear in the IEEE BITS magazine, and the preprint is openly available: https://arxiv.org/abs/2411.18435 Music: On the Verge by Joseph McDade. Visit Erik’s website https://liu.se/en/employee/erila39 and Emil’s website https://ebjornson.com/

New cellular network deployments are often associated with new frequency bands. 6G will likely use the upper mid-band from 7-24 GHz. It is called the “golden band” since it provides more spectrum than in current 5G networks and features decent propagation conditions. In this episode, Erik G. Larsson and Emil Björnson discuss the coexistence issues that must be overcome when operating in this band and how much spectrum we can expect to utilize. The future role of multi-antenna technology and its associated challenges are detailed, including the emerging “Gigantic MIMO” term. The prospects of exploiting near-field propagation effects in 6G and the road towards distributed cell-free MIMO are also covered. You can read Emil’s paper about Gigantic MIMO here: https://arxiv.org/pdf/2407.05630 Nokia has a white paper about coverage evaluation: https://onestore.nokia.com/asset/213702 Music: On the Verge by Joseph McDade. Visit Erik’s website https://liu.se/en/employee/erila39 and Emil’s website https://ebjornson.com/

Many textbook models of communication systems assume that the transmitter and receiver are synchronized in time, frequency, and phase. Achieving and maintaining such synchronization is an often-overlooked practical challenge. However, the importance of synchronization grows as we plan to use larger antenna arrays and distributed MIMO in 6G. In this episode, Emil Björnson and Erik G. Larsson discuss some fundamental principles of synchronization, including the underlying physical phenomena, pilot signaling for phase synchronization, and reciprocity calibration. We especially discuss how the seemingly simplest angular beamforming can be among the hardest features to support from a synchronization perspective, with a digital array. More technical details in the papers https://arxiv.org/abs/2304.05144 and https://arxiv.org/abs/2401.11730 Music: On the Verge by Joseph McDade. Visit Erik’s website https://liu.se/en/employee/erila39 and Emil’s website https://ebjornson.com/

Massive bandwidths are available in the sub-terahertz bands, but the coverage of a cellular network exploiting those frequencies will be spotty. The 6GTandem project tries to circumvent this issue by developing a dual-frequency system architecture that jointly uses the sub-6 GHz and sub-THz bands. In this episode, Erik G. Larsson and Emil Björnson are visited by Dr. Parisa Aghdam, Technical Lead of 6GTandem and Research Manager at Ericsson. The discussion starts with potential use cases, such as extended reality services in stadiums and connected factories. The conversation then focuses on hardware aspects, such as how to build a distributed antenna system using plastic microwave fibers and amplifiers so that sub-THz signals can be transmitted from many different locations. You can read more about the EU-funded project and its partners at https://horizon-6gtandem.eu/ Music: On the Verge by Joseph McDade. Visit Erik’s website https://liu.se/en/employee/erila39 and Emil’s website https://ebjornson.com/

Many topics are studied within the 6G research community, from hardware design to algorithms, protocols, and services. Erik G. Larsson and Emil Björnson recently attended the ELLIIT 6G Symposium in Lund, Sweden. In this episode, they discuss ten things that they learned from listening to the keynote speeches. The topics span from integrated sensing, positioning, and localization via machine-learning applications in communications to fundamental communication theory, such as circuits for universal channel decoding and jamming protection. The expected 6G spectrum ranges, energy efficiency in base stations, and new use cases for electromagnetic materials are also covered. You can find slides from the symposium at https://elliit.se/news-and-events/focus-period-lund-2023/ Music: On the Verge by Joseph McDade. Visit Erik’s website https://liu.se/en/employee/erila39 and Emil’s website https://ebjornson.com/

We celebrate the three-year anniversary of the podcast with a live recording from the Wireless Future Symposium that was held in September 2023. A panel of experts answered questions that we received on social media. Liesbet Van der Perre (KU Leuven) discusses the future of wireless Internet-of-Things, Fredrik Tufvesson (Lund University) explains new channel properties at higher frequencies, Jakob Hoydis (NVIDIA) describes differentiable ray-tracing and its connection to machine learning, Deniz Gündüz (Imperial College London) presents his vision for how artificial intelligence will affect future wireless networks, Henk Wymeersch (Chalmers University of Technology) elaborates on the similarities and differences between communication and positioning, and Luca Sanguinetti (University of Pisa) demystifies holographic MIMO and its relation to near-field communications. Music: On the Verge by Joseph McDade. Visit Erik’s website https://liu.se/en/employee/erila39 and Emil’s website https://ebjornson.com/

It is easy to get carried away by futuristic 6G visions, but what matters in the end is what technology and services the telecom operators will deploy. In this episode, Erik G. Larsson and Emil Björnson discuss a new white paper from SK Telecom that describes the lessons learned from 5G and how these experiences can be utilized to make 6G more successful. The paper and conversation cover network evolution, commercial use cases, virtualization, artificial intelligence, and frequency spectrum. The latest developments in defining official 6G requirements are also discussed. The white paper can be found here:https://www.sktelecom.com/en/press/press_detail.do?idx=1575 The following news article about mmWave licenses is mentioned: https://telecoms.com/521670/south-korea-cancels-skts-28-ghz-5g-licence/ The IMT-2030 Framework for 6G can be found here: https://www.itu.int/en/ITU-R/study-groups/rsg5/rwp5d/imt-2030/Pages/default.aspx Music: On the Verge by Joseph McDade. Visit Erik’s website https://liu.se/en/employee/erila39 and Emil’s website https://ebjornson.com/

The main directions for 6G research have been established and include pushing the communication to higher frequency bands, creating smart radio environments, and removing the conventional cell structure. There are many engineering issues to address on the way to realizing these visions. In this episode, Emil Björnson and Erik G. Larsson discuss the article “The Road to 6G: Ten Physical Layer Challenges for Communications Engineers” from 2021. What specific research challenges did the authors identify, and what remains to be done? The conversation covers system modeling complexity, hardware implementation issues, and signal processing scalability. The article can be found here: https://arxiv.org/pdf/2004.07130 The following papers were also mentioned: https://arxiv.org/pdf/2111.15568 and https://arxiv.org/pdf/2104.15027 Music: On the Verge by Joseph McDade. Visit Erik’s website https://liu.se/en/employee/erila39 and Emil’s website https://ebjornson.com/

The speed of wired optical fiber technology is soon reaching 1 million megabits per second, also known as 1 terabit/s. Wireless technology is improving at the same pace but is 10 years behind in speed, thus we can expect to reach 1 terabit/s over wireless during the next decade. In this episode, Erik G. Larsson and Emil Björnson discuss these expected developments with a focus on the potential use cases and how to reach these immense speeds in different frequency bands – from 1 GHz to 200 GHz. Their own thoughts are mixed with insights gathered at a recent workshop at TU Berlin. Major research challenges remain, particularly related to algorithms, transceiver hardware, and decoding complexity. Music: On the Verge by Joseph McDade. Visit Erik’s website https://liu.se/en/employee/erila39 and Emil’s website https://ebjornson.com/

Research is carried out to obtain new knowledge, find solutions to pertinent problems, and challenge the researchers’ abilities. Two key aspects of the scientific process are reproducibility and replicability, which sound similar but are distinctly different. In this episode, Erik G. Larsson and Emil Björnson discuss these principles and their impact on wireless communication research. The conversation covers the replication crisis, Monte Carlo simulations, best practices, pitfalls that new researchers should avoid, and what the community can become better at. The following article is mentioned: “Reproducible Research: Best Practices and Potential Misuse” (https://arxiv.org/pdf/1905.00645.pdf). Music: On the Verge by Joseph McDade. Visit Erik’s website https://liu.se/en/employee/erila39 and Emil’s website https://ebjornson.com/

Information theory is the research discipline that establishes the fundamental limits for information transfer, storage, and processing. Major advances in wireless communications have often been a combination of information-theoretic predictions and engineering efforts that turn them into mainstream technology. Erik G. Larsson and Emil Björnson invited the information-theorist Giuseppe Caire, Professor at TU Berlin, to discuss how the discipline is shaping current and future wireless networks. The conversation first covers the journey from classical multiuser information theory to Massive MIMO technology in 5G. The rest of the episode goes through potential future developments that can be assessed through information theory: distributed MIMO, orthogonal time-frequency-space (OTFS) modulation, coded caching, reconfigurable intelligent surfaces, terahertz bands, and the use of ever larger numbers of antennas. The following papers are mentioned: “OTFS vs. OFDM in the Presence of Sparsity: A Fair Comparison” (https://doi.org/10.1109/TWC.2021.3129975) , “Joint Spatial Division and Multiplexing”(https://arxiv.org/pdf/1209.1402.pdf), and “Massive MIMO has Unlimited Capacity” (https://arxiv.org/pdf/1705.00538.pdf). Music: On the Verge by Joseph McDade. Visit Erik’s website https://liu.se/en/employee/erila39 and Emil’s website https://ebjornson.com/

A wave of digitalization is sweeping over the world, but not everything benefits from a transformation from analog to digital methods. In this episode, Emil Björnson and Erik G. Larsson discuss the fundamentals of analog modulation techniques to pinpoint their key advantages. Particular attention is given to how analog modulation enables over-the-air aggregation of data, which can be used for computations, efficient federated training of machine learning models, and distributed hypothesis testing. The conversation covers the need for coherent operation and power control and outlines the challenges that researchers are now facing when extending the methods to multi-antenna systems. Towards the end, the following paper is mentioned: “Optimal MIMO Combining for Blind Federated Edge Learning with Gradient Sparsification” (https://arxiv.org/pdf/2203.12957.pdf). Music: On the Verge by Joseph McDade. Visit Erik’s website https://liu.se/en/employee/erila39 and Emil’s website https://ebjornson.com/

Many assumptions must be made when simulating a communication link, including the modulation format, channel coding, multi-antenna transmission scheme, receiver processing, and channel modeling. In this episode, Emil Björnson and Erik G. Larsson are visited by Jakob Hoydis, Principal Research Scientist at NVIDIA, to discuss the fundamentals of link-level simulations. Jakob has led the development of the new open-source simulator Sionna, which is particularly well suited for machine learning research. The conversation covers the needs and means for making accurate simulations, channel modeling, reproducibility, and how machine learning can be used to improve standard algorithms. Other topics that are discussed are MIMO decoding and technical debt. Sionna can be downloaded from https://nvlabs.github.io/sionna/ and the white paper that is mentioned in the episode is found here: https://arxiv.org/pdf/2203.11854.pdf Music: On the Verge by Joseph McDade. Visit Erik’s website https://liu.se/en/employee/erila39 and Emil’s website https://ebjornson.com/

The research towards 6G is intense and many new technology components are being proposed by academia and industry. In this episode, Erik G. Larsson and Emil Björnson identify the key selling points of six of these 6G technologies. They discuss the potential for major breakthroughs and what the main challenges are. The episode covers: 1) Semantic communications; 2) Distributed/cell-free Massive MIMO; 3) Reconfigurable intelligent surfaces; 4) Full-duplex radios; 5) Joint communication and sensing; and 6) Orbital Angular Momentum (OAM). The following paper is mentioned: “Is Orbital Angular Momentum (OAM) Based Radio Communication an Unexploited Area?” by Edfors and Johansson (https://lup.lub.lu.se/search/ws/files/4023050/2339120.pdf). Music: On the Verge by Joseph McDade. Visit Erik’s website https://liu.se/en/employee/erila39 and Emil’s website https://ebjornson.com/

The reliability of an application is determined by its weakest link, which often is the wireless link. Channel coding and retransmissions are traditionally used to enhance reliability but at the cost of extra latency. 5G promises to enhance both reliability and latency in a new operational mode called ultra-reliable low-latency communication (URLLC). In this episode, Erik G. Larsson and Emil Björnson discuss URLLC with Petar Popovski, Professor at Aalborg University, Denmark. The conversation pinpoints the physical reasons for latency and unreliability, and viable solutions related to network deployment, diversity, digital vs. analog communications, non-orthogonal network slicing, and machine learning. Further details can be found in the article “Wireless Access in Ultra-Reliable Low-Latency Communication (URLLC)” (https://doi.org/10.1109/TCOMM.2019.2914652) and its companion video (https://youtu.be/XGbe_ckKKpE). Music: On the Verge by Joseph McDade. Visit Erik’s website https://liu.se/en/employee/erila39 and Emil’s website https://ebjornson.com/

Mobile network technology builds on open standards, but it is nevertheless a major effort to implement the required software protocols and interface them with actual hardware. Many algorithmic choices must also be made in the implementation, leading to each vendor having its proprietary solution. The OpenAirInterface Alliance wants to change the game by providing open-source software implementations of the wireless air interface and core network. In this episode, Emil Björnson and Erik G. Larsson are discussing these prospects with a Board Member of the Alliance: Florian Kaltenberger, Associate Professor at EURECOM, France. The conversation covers the fundamentals of air interfaces, how anyone can build a 5G network using their open-source software and off-the-shelf hardware, and the pros and cons of implementing everything in software. The connections to Open RAN, functional splits, and patent licenses are also discussed. Further details can be found at https://openairinterface.org and in the paper “OpenAirInterface: Democratizing innovation in the 5G Era” (https://doi.org/10.1016/j.comnet.2020.107284). Music: On the Verge by Joseph McDade. Visit Erik’s website https://liu.se/en/employee/erila39 and Emil’s website https://ebjornson.com/

In the near future, we will be able to deploy new wireless networks without installing new physical infrastructure. The networks will instead be virtualized on shared hardware using the new concept of network slicing. This will enable tailored wireless services for businesses, entertainment, and devices with special demands. In this episode, Erik G. Larsson and Emil Björnson discuss why we need multiple virtual networks, what the practical services might be, who will pay for it, and whether the concept might break net neutrality. The episode starts with a continued discussion on the usefulness of models, based on feedback from listeners regarding Episode 25. The network slicing topic starts after 10 minutes. Music: On the Verge by Joseph McDade. Visit Erik’s website https://liu.se/en/employee/erila39 and Emil’s website https://ebjornson.com/