The recent book Radar & Communication Spectrum Sharing, co-edited by KU EECS Professors Shannon Blunt and Erik Perrins is the first comprehensive coverage of this rapidly growing problem space, the book is published by the Institution of Engineering and Technology (IET) in London. The radio frequency (RF) spectrum has arguably become the most expensive “real estate” on the planet, with the 2015 auction of a measly 65 MHz garnering over $40 billion in revenue for the government. The primary driver of this demand is the incredible connectivity provided by Fourth Generation (4G) communications, with the promise of even greater prospects on the horizon with 5G. The paradigm shift arising from this tremendous connectivity is leading to altogether new capabilities like the Internet of Things (also known as Machine-to-Machine Communications) that will transform the way we live in ways that are scarcely even imaginable today.
However, the RF spectrum is also home to myriad other important applications including radar, navigation, broadcast television and radio, and others. It has only been in very recent years that the notion of sharing spectrum with radar has even been considered due to the extreme sensitivity radar requires and the tremendous breadth of different forms it may take. Radar modes predominantly comprise moving target indication (MTI), various forms of imaging, and tracking and arise in a wide array of uses including national defense, scientific missions, weather monitoring, automotive blind spot and collision avoidance detection, and more. Moreover, of all the different applications within the RF spectrum, radar requires the largest uninterrupted swaths that are free from interference by other users. That radar/communication spectrum sharing is now being explored speaks to the incredible economic pressure created by the revenue generating juggernaut of commercial cellular that has ultimately lead to this point where we must consider how these extremely different systems can interact without completely jamming one another.
In 2013, the Defense Advanced Research Projects Agency (DARPA) addressed this problem head-on with the Shared Spectrum Access for Radar and Communications (SSPARC) program which has funded research into a variety of radically new spectrum sharing approaches. The 2015 spectrum auction also led to the establishment of the National Spectrum Consortium whose purpose is to use money the government collected from this spectrum sale to support the Spectrum Access Research & Development Program (SAR&DP), which is still ongoing. Of course, while the demand for spectrum usage is growing exponentially, the amount available remains finite. Consequently, the research community is stepping up to explore this extremely important problem space that will have an impact on our lives in many ways we see and in others we never even realize.
Within this setting, the book that Blunt and Perrins have produced draws from an international team of highly respected researchers and touches on the extremely diverse attributes of spectrum sharing that have a particular impact on the operation of radar and communication systems. Specifically, topics in electromagnetics, systems engineering, signal processing, and interference management are individually addressed. Moreover, when the many different forms of radar are crossed with the variety of different communication modes, new symbiotic operating paradigms can also begin to emerge (some already have). Far from being the final word on the matter, this book sets the stage for an explosion in spectrum sharing research that is still in its infancy. As Prof. Hugh Griffiths of University College London, a prominent researcher and contributor to the book, has stated on multiple occasions, “the only definitive thing that we can say about spectral congestion is that it will continue to get worse.” From the standpoint of current and future electrical engineers, this kind of statement can be directly translated to mean “job security” for a long time to come.