Wireless Future

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 [https://arxiv.org/abs/2406.00142]). Technical details can be found in: https://arxiv.org/pdf/2405.01074 [https://arxiv.org/pdf/2405.01074] and https://arxiv.org/pdf/2403.17908 [https://arxiv.org/pdf/2403.17908]  Music: On the Verge by Joseph McDade. Visit Erik’s website https://liu.se/en/employee/erila39 [https://liu.se/en/employee/erila39] and Emil’s website https://ebjornson.com/ [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 [https://www.nowpublishers.com/NowOpen] Music: On the Verge by Joseph McDade. Visit Erik’s website https://liu.se/en/employee/erila39 [https://liu.se/en/employee/erila39] and Emil’s website https://ebjornson.com/ [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 [https://arxiv.org/abs/2411.18435] Music: On the Verge by Joseph McDade. Visit Erik’s website https://liu.se/en/employee/erila39 [https://liu.se/en/employee/erila39] and Emil’s website https://ebjornson.com/ [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 [https://arxiv.org/pdf/2407.05630] Nokia has a white paper about coverage evaluation: https://onestore.nokia.com/asset/213702 [https://onestore.nokia.com/asset/213702] Music: On the Verge by Joseph McDade. Visit Erik’s website https://liu.se/en/employee/erila39 [https://liu.se/en/employee/erila39] and Emil’s website https://ebjornson.com/ [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 [https://arxiv.org/abs/2304.05144] and https://arxiv.org/abs/2401.11730 [https://arxiv.org/abs/2401.11730] Music: On the Verge by Joseph McDade. Visit Erik’s website https://liu.se/en/employee/erila39 [https://liu.se/en/employee/erila39] and Emil’s website https://ebjornson.com/ [https://ebjornson.com/]