We chatted with Erik Dahlman, Stefan Parkvall, and Johan Skold, the three authors of the second edition of 5G NR: The Next Generation Wireless Access Technology, about the new edition updates and the evolution of 5G NR.

The new edition of your book 5G NR: The Next Generation of Wireless Access Technology has been extensively updated to reflect the latest Release 16 and its new features. Can we go through the importance of these and explain why they were brought in, and the benefits they provide? Let’s take these in turn, starting with IAB.

Integrated Access Backhaul is one of the major enhancements in Release 16 where the NR radio technology is used not only to connect terminals to base stations but also for wireless backhaul, that is, to connect base stations to each other. This can speed up deployment of small base stations compared to deploying an optical fiber for the base station interconnect. The new chapter on IAB in the second edition provides an extensive description of the overall IAB architecture as well as the enhancements introduced on the physical layer.

Thank you. The next key area is NR Unlicensed.

Spectrum availability is essential to wireless communication and the large amount of spectrum available in unlicensed bands is attractive for increasing data rates and capacity. In Release 16, NR is enhanced to enable operation in unlicensed spectrum, both with and without assistance from a licensed carrier. License-assisted operation, where a complementary  NR carrier (or LTE carrier) in licensed spectra handles connection setup and mobility, can be an attractive choice for existing operators to access more spectrum.  Operation without assistance from a carrier in licensed spectrum, on the other hand, is highly relevant for use cases and scenarios where no licensed spectrum lis available and greatly adds to the deployment flexibility.  To support operation in unlicensed spectrum, Release 16 introduces channel-access mechanisms based on listen-before-talk as well as various enhancements to scheduling, hybrid-ARQ, and physical layers. These enhancements are all described in great detail in one new chapter.

Let’s turn to V2X.

Intelligent transportation systems (ITS) are one example of a new vertical in focus for Release 16. ITS aims to improve traffic safety, and reduce traffic congestion and fuel consumption. To facilitate ITS, communication is required not only between vehicles and the fixed infrastructure but also between vehicles. Release 16 therefore extends NR to provide advanced vehicle-to-anything (V2X) communications, in particular a sidelink for direct communication between vehicles. Although the sidelink is developed with V2X as the main use case, the design is flexible and can be used also for general device-to-device communication. A whole chapter is devoted to the Release 16 sidelink design with in-depth description of the use cases, sidelink radio-resource management, and physical-layer design.

Let’s turn now to Industrial IoT.

Industrial internet-of-things (IIoT) is another example of a major vertical in focus for Release 16 enhancements. While release 15 can provide very low air-interface latency and high reliability, further enhancements to latency and reliability are introduced in release 16. This is to enable a wider set of industrial IoT use cases and to address increased demand for new use cases, such as factory automation, electrical power distribution, and transport industry. Technically, there are several enhancements to scheduling, channel prioritization, uplink pre-emption, and physical channels. Individually, they may seem relatively small but used together they provide a significant performance improvement. Time-sensitive networking (TSN) is also supported by new mechanisms in Release 16 providing distribution of very accurate time reference over-the-air, a crucial aspect in many industrial automation scenarios. One of the new chapters in the second edition is devoted to IIoT and TSN.

Another key feature is CLI/RIM.

In TDD wide-area deployments, the set of slots used for uplink and downlink transmissions are typically defined a priori and coordinated between cells in order to avoid downlink transmissions in one cell interfering with uplink reception in another cell. This is particularly important given the large difference in transmission power between uplink and downlink and the above-rooftop location of base station antennas. However, under some (rare) weather conditions, (downlink) radio waves can propagate a very long distance and cause interference at a very remote base station. Release 16 therefore introduces mechanisms to detect these conditions, as well as tools to mitigate the interference problem. This is known as remote interference management (RIM) and is described in one of the new chapters together with another TDD-specific interference scenario, cross-link interference (CLI).

Thank you for that useful overview. 5G NR is still evolving and the next release will be Release 17. What aspects of Release 17 do you discuss in the book?

In the book we discuss some of the enhancements currently being worked upon in Release 17. Some examples are extension of NR to frequencies between 52.6 and 71 GHz, IAB enhancements to support changes in the network topology, and extensions of the sideling to better support public safety use cases. Broadcast/multicast support, where one data stream is simultaneously received by multiple devices, and support for NR in non-terrestrial networks including satellites are other examples of new functionality added in Release 17. RedCap, short for reduced capabilities, refers to work in Release 17 on NR devices targeting reduced-cost devices for industrial use cases and wearables where lower data rates are sufficient. Given the impact from COVID-19 work in 3GPP on Release 17 is delayed and many details remain to be settled.

Lastly, for those new to your previous books, can you summarize your approach to explaining 5G NR and why it will be beneficial to the reader?

The NR standard is a complex one. We have tried to describe the standard using words and figures rather than equations. More important, we also provide some reasoning why a certain feature is designed in a particular way, something that is not obvious when reading the official specifications. Hopefully this makes the NR more accessible to those outside 3GPP that are curious about the technology behind NR.

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