Wireless Future

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/

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/

“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/

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/

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/

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/

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/

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/

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/

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/

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/

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/

The statistician George Box famously said that “All models are wrong, but some are useful”. In this episode, Emil Björnson and Erik G. Larsson discuss what models are useful in the context of wireless communications, and for what purposes. The conversation covers modeling of wireless propagation, noise, hardware, and wireless traffic. A key message is that the modeling requirements are different for algorithmic development and for performance evaluation. Music: On the Verge by Joseph McDade. Visit Erik’s website https://liu.se/en/employee/erila39 and Emil’s website https://ebjornson.com/