Foreword in "RF imperfections in high-rate wireless systems: impact and digital compensation"

Foreword This book takes a modern, multidisciplinary view on radio system design: the advantages of digital signal processing are exploited to satisfy the ever increasing demands on better performing, flexible radio frequency (RF) circuits. By accepting that analog circuits are inherently imperfect, but by searching for methods to mitigate and compensate for this, significant steps can be made to improve the overall system solution. This is in contrast to the more traditional approach of designing RF circuits themselves to satisfy the demanding specifications set by current standards. Wireless communication has progressed dramatically in past years. Yet, the main research challenges changed focus to sustain this growth over many decades. In the early days, the main challenge of radio communications was to cover large distances. When in late 1980s, digital mobile communication emerged as a precursor to today’s mass-market cell phones, the priority shifted to achieving reliable communication over a difficult, i.e., time-varying and frequency-selective mobile channel. About a decade or research in many institutes around the world has been devoted to this challenge, exploiting the opportunities given by increasing computational power in digital circuits. Today we face a different paradigm: the technology for analog front-ends progress significantly slower than that of digital processors. So the imperfections of the RF have increasingly become the major bottleneck in our drive towards faster, yet more power-efficient radio circuits. Since digital signal processing can mitigate the design constraints for analog RF circuits, it allows more cost-effective and lower power consuming designs for the analog part. At the time of writing this book, algorithms for digital compensation,or digitally controlled calibration of the RF circuits start to be used in chipsets in the market. But the concepts addressed in this book xii Foreword may not be limited to only offering a proprietary advantage to smart implementers. It is not unlikely that future standards will increasingly be designed to anticipate for digital RF compensation, for instance by defining new preambles or pilots that also allow receivers to track phase drifts, or to estimate I-Q imbalance. An important step made in this book is to bring together models describing analog circuits with insights of digital signal processing. Tractable but realistic models to evaluate the effect of compensation measures are essential to support the design of effective practical solutions. Right from the start the book follows a timely approach that coincides with clear direction taken in many modern systems, namely the use of multiple antennas to accommodate more radio traffic, to offer better link throughput, and to reduce interference. Prof. Dr. Ir. Jean-Paul M.G. Linnartz Senior Director, Connectivity Systems and Networks, Philips Research Professor, Eindhoven University of Technology