Robert J. Baxley, G. Tong Zhou
This tutorial will address the problem of high peak-to-average-power ratio (PAR) communications signals. Signals with high PAR are becoming more prevalent as modern communications systems are increasingly drifting toward high bandwidth multi-carrier (MC) modulations like OFDM, but even single-carrier (SC) modulated signals can exhibit high PAR after filtering or when multiple SC signals are modulated on different carrier frequencies and transmitted simultaneously through a single power amplifier (PA). It is challenging for nonlinear system components to accommodate high-PAR signals while meeting system specifications (e.g. spectral mask, EVM, BER, etc. ) and maintain high power efficiencies. In fact, with rising energy costs, base station power consumption is costly. In [John Walko, “Green issues challenge base station power,” EE Times Europe, Sept. 19, 2007.], it is estimated that a typical European cellular operator spends $62M/year just to power base stations. This cost is expected to rise with the deployment of more MC waveforms. PAR reduction can help reduce this cost by creating more power-efficient waveforms.
In this tutorial we will outline the PAR reduction problem and provide a comprehensive review of all viable PAR-reduction methods. This includes distortion methods, distortionless methods and synergistic methods that combine with other components of the signal to achieve PAR reduction. For the different methods we will delve into the details of the pertinent algorithms and parameter optimization. We will review performance bounds and compare existing practical methods to these bounds and we will review PAR reduction in MIMO systems and discuss the features unique to multiple antenna systems. Finally, we will conclude the session with open research questions in PAR reduction.
Robert J. Baxley is a Research Engineer with the Georgia Tech Research Institute (GTRI) Information Technology and Telecommunications Lab (ITTL). He received the B.S. degree in 2003, the M.S. degree in 2005, and the Ph.D. degree in 2008, all in Electrical Engineering from Georgia Tech. In 2005, Dr. Baxley received the institute-wide Sigma Xi award for best M.S. thesis and he is a recipient of the National Science Foundation Graduate Research Fellowship. He has authored more than 20 peer-reviewed technical papers on the topic of peak-to-average power ratio (PAR) reduction. His current research interests include communications theory, signal processing, and statistics.
G. Tong Zhou received the B.Sc. degree in biomedical engineering and instrumentation from the Tianjin University, China, in 1989 and the M.Sc. degree in biophysics, the M.Sc. degree in electrical engineering, and the Ph.D. degree in electrical engineering, all from the University of Virginia (UVA), Charlottesville, in 1992, 1993, and 1995, respectively. Since September 1995, she has been with the School of Electrical and Computer Engineering at Georgia Tech, Atlanta, where she is now a Professor. Her research interests are in the general areas of statistical signal processing and communications applications. Dr. Zhou received the National Science Foundation Faculty Early Career Development (CAREER) Award in 1997. She served as Chair of the IEEE Signal Processing Society Signal Processing Theory and Methods Technical Committee during 2006 and 2007.