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New book by Qualcomm experts explains the fundamentals of 5G communications

Jul 29, 2021

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Building technology for the greater good — that’s at Qualcomm’s core. It’s why we invent the breakthroughs that take on the world’s greatest challenges. For over 30 years, our foundational expertise in mobile has changed the way we connect, communicate, and compute. And now, with 5G connectivity, we’re helping enrich lives and transform industries.

But what exactly is 5G? How was it defined and by whom? Why does it look like it does? For the answers to those questions and more, check out the new book “Fundamentals of 5G Communications: Connectivity for Enhanced Mobile Broadband and Beyond” authored by four Qualcomm innovators:

  • Wanshi Chen, senior director of Technology, Qualcomm Technologies, Inc.
  • Peter Gaal, vice president of Technical Standards, Qualcomm Technologies, Inc.
  • Juan Montojo, vice president of Technical Standards, Qualcomm Technologies, Inc.
  • Haris Zisimopoulos, senior director of Technical Standards, Qualcomm Technologies International, Ltd.

We recently spoke with the authors about the impetus for writing the book, what sets it apart, and how their work helped inform the narrative:

Tell us a bit about your backgrounds and your work at Qualcomm.

Juan Montojo: I joined Qualcomm in January 1997 as an engineering intern and became a full-time employee shortly after. I’ve worked on satellite communications as well as the cellular (2G) mode of the user terminal, HDR (cdma2000 EvDO) when 3G was getting designed and standardized, UMTS (WCDMA and TD-SCDMA), and later on LTE (4G). I spent almost four years in Germany, leading our research center in Nuremberg, and returned to San Diego in 2015 when 5G started to heat up. Currently, I’m the technologies lead for 3GPP – the industry organization that defines specifications for 3G, 4G, and now 5G.

Peter Gaal: I joined Qualcomm a couple years after Juan. Initially, I worked on the position location project. Later, I was involved in cdma2000 standardization, including physical layer and position location aspects. Since 2007, I’ve been attending 3GPP meetings, first in the RAN4 group and then in the RAN1 group (RAN stands for Radio Access Network) and have been standards lead for my company in each group. Besides participating in the standards work, I contributed to the design and development of LTE and, more recently, 5G NR.

Wanshi Chen: In May 2006, I joined Qualcomm where I have been contributing to the design, development, and specification of LTE and 5G NR standardization through active participation in 3GPP RAN1 and 3GPP RAN. In April 2021, I was appointed 3GPP TSG (Technical Specification Group) RAN plenary chair.

Haris Zisimopoulos: I’ve been with the company for about nine years. I participate in 3GPP System Architecture Working Group 2 (WG2) — the 3GPP group related to 3GPP system architecture. I was rapporteur of various 3GPP projects namely the Proximity Services/D2D (device-to-device), Next Generation eCall, Unlicensed Spectrum System optimizations, and Radio Capabilities Signaling optimization. And since 2015, I’ve been Qualcomm Technologies’ 3GPP Service and System Aspects (SA) plenary and SA WG2 lead, and an active contributor in a variety of technical architecture designs of the Non-Standalone and Standalone 5G in 3GPP rel.15, 16, and 17. 

What was the impetus for writing the book?

Wanshi: The fifth generation (5G) of wireless communications in 3GPP provides a platform that not only accommodates traditional evolved mobile broadband services, but also expands into new deployments and new verticals (e.g., automotive with cellular vehicle-to-everything (C-V2X), unlicensed spectrum, manufacturing with ultra-reliable low-latency communication (URLLC), and machine type communications). Such a comprehensive system is a result of close collaborations within the mobile ecosystem (network operators, device makers, infrastructure vendors) players around the world, with extensive performance evaluations, link-level and system-level analysis, meticulous comparison of various schemes for best tradeoff, and consolidated examinations across various areas. As a result, we feel that it’s critical to understand the stories behind the standardization, so that together we can do even better for future evolutions of the standardization, including moving toward 6G. This motivated us to write the book.

Haris: We hope that the book provides info not only on the “what” i.e., how specific features are defined, but also on the “why” i.e., what is the background that led the design decisions of 3GPP. Also, we aspired to cover as much as possible — the entire system architecture, which, in my view at least, is one of the top selling points of 5G compared to other wireless access technologies.

Why now?

Juan: We knew that we could write a book, but we also knew it would take time to do it. A few of us have been involved in writing chapters for other books, but it was time to change that and write our own. Wanshi got the invitation to write a 5G book when he was 3GPP RAN1 Chairman, and it was the perfect excuse to find time to write the book together.

Peter: [Laughs] It was mostly peer pressure for me.

How is this book different from other books on 5G?

Wanshi: While there are numerous books on 5G in the market, our book is NOT intended to describe what the 5G standardization is. Rather, our focus is on the ‘how’ and ‘why’ of 5G standardization – in the context of an end-to-end system setting. In other words, we wanted to tell the insiders’ stories about 5G standardization. We want to motivate our readers to contribute, either for the first time or with more effort, to 5G or future generations of standardization for wireless communications.

Juan: We wanted to explain how 5G came about. We try to relate it to 4G design to put it in context. And we want to emphasize how 5G will serve multiple verticals (broadcast, automotive, Internet of Things, etc.).

Peter: We also wanted to provide a glimpse into the rationale behind design choices. In some cases, this was done by explaining why a particular feature was defined the way it was, and in others, it was done by mentioning what other alternatives, ultimately not chosen, were also considered. That means giving more information than what's needed just to implement the standard.

What unique perspective did you bring to the project?

Wanshi: Our first-hand experience and stories are unique. We are involved in research, design, standardization, product development, testing, and whatever necessary to bring these systems to fruition. We have been involved with 3GPP for many years, and together, we have about 70 years of experience designing cellular communications systems. We have the necessary knowledge to explain the reasons for the standardization, and our goal is to teach, enrich, and motivate current and future engineers.

Is there a particular part of the book that you’re most proud of? If so, why?

Peter: Obviously, I'm attached to the chapters I wrote — mainly the ones about downlink and uplink data operations. But I also think the intro written by Ed Tiedemann, senior vice president of engineering for Qualcomm Technologies and Qualcomm Fellow, is uniquely insightful.

Wanshi:  I am most proud of the book’s depth. We provide comprehensive coverage of various aspects of 5G, while diving into the details for each aspect. Besides the traditional enhanced mobile broadband aspects, we cover all major vertical domains, with a focus on practical and commercial applications. This book can serve both as an essential reference for telecom professionals and as a textbook for students learning about 5G.

Juan: Personally, I really like and enjoyed writing “Chapter 1 5G vs. 4G: What’s New?” It does put 5G in perspective of where we were with 4G and how we positioned it to serve the very diverse use cases it is designed for.

Haris: I am proud of how some of the radio features that are described in specific sections link and pave the way to the system architecture aspects and vice versa. For example, what was the motivation of specific radio features like URLLC in fulfilling certain system and service requirements. Also, the section about the migration from 4G to 5G for mobile network operators.

What do you think might surprise people about this book (without giving anything away)?

Juan: Perhaps how extensive it is. We cover Rel-15 and Rel-16 (the first two releases of 5G) extensively. We also provide a glimpse into the ongoing Rel-17 and present views on cellular deployment in specific areas that go beyond what most books do.

Wanshi: We share the reasoning behind some 5G design aspects, which may not be obvious to some audiences. As we are trying to optimize performance for every single design aspect, there is always a tradeoff in terms of standardization and implementation complexity. Careful tradeoffs are critical in designing a commercial system.

Haris: I hope some of the insights we provide on the motivation for the design decisions surprises them. I hope readers not only gain knowledge about the technical aspects but why certain decisions, sometimes even compromises, were made in 3GPP for specific features.

What’s next for 5G?

Haris: I hope expansion to more verticals that would lead to further enhancements driven by the real needs of new industries to fulfill their goals. In my 4G journey in standards so far, I had the pleasure to interact with colleagues from various industries that want to use 5G, and it helped expand my technical knowledge in areas I would never have imagined.

Wanshi: We successfully delivered the 1st release (Rel-15) and the 2nd release (Rel-16) 5G standards and are now in the process of completing the 3rd release (Rel-17) of 5G standards.

Peter: Work has already started on 5G Advanced (Rel-18 and beyond). There is an active discussion, including the 3GPP Workshop held a couple of weeks ago and chaired by Wanshi, on what features should be enhanced and what new features should be added.

Wanshi: The workshop is the first opportunity for companies and organizations around the world to share their views on future evolution of 5G, particularly focusing on the next release (Rel-18). Overall, it was observed that a balanced evolution is expected in terms of mobile broadband evolution versus further vertical domain expansion; immediate versus longer term commercial needs; and device evolution versus network evolution.

How  has your work at Qualcomm helped you in your work on 5G?


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Wanshi: I am deeply grateful to work at a company like Qualcomm. From the top levels to the less experienced engineers, the focus is always on technical excellence, promoting innovations through open, careful, and very involved discussion. We are not designing things just for the sake of doing it, but always with potential commercial applications in mind.

Peter: For me, being a standards delegate and the company’s RAN1 lead gave me the opportunity to participate in the standards discussions. And that resulted in being able to share the design choices described in the book.

Haris: Vastly. I have worked in quite a few companies before joining Qualcomm Technologies, more or less in the same area of system architecture standards in 3GPP. And I have to say, without a doubt, that being a standards engineer here, in this area, is by far the best place to work. Every day you work with committed colleagues that excel in their respective areas. We’re a top 5G innovator, so it’s pleasurable to interact and get info and help from the best in each individual technical area (radio, protocols, security, etc.).

Juan: This is the place to be to do communications systems design. One could be tempted to portray us as a silicon company only, but we are much more than that. Qualcomm companies have designed end-to-end communications systems from its inception and never stopped doing it. We are a reference for every other company in the field.


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