Signal Processing for the 5G Revolution [From the Guest Editors]

C ellular communication systems are continuing to incorporate advanced signal processing techniques. Third-generation cellular systems are already widely deployed and are being followed by fourth-generation (4G) systems. Since 4G cellular technology development is considered to have concluded in 2011, the attention of the research community is shifting toward what will be the next set of innovations in wireless communication technologies that are now broadly known as fifth-generation (5G) technologies. Given a historical ten-year cycle for every generation of cellular advancement, it is expected that networks with 5G technologies will be deployed around 2020. While 4G standards were designed to meet requirements issued by the International Telecommunication Union-Radio, no definition for 5G is currently available. Experts vary in opinion whether the next generation of cellular networks will continue to enhance (peak) service rates further, focus on spectral efficiency enhancements, or move to newer metrics such as energy efficiency, costand utilization-efficiency, or even define new metrics around service quality experience. There is also the possibility that 5G will enable digital sensing, communication, and processing capabilities to be ubiquitously embedded into everyday objects, turning them into the Internet of Things (IoT) or machine-to-machine (M2M). In this new paradigm, smart devices will collect data, relay the information or context to each other, and process the information collaboratively over the 5G cellular networks. No matter what the eventual metric or system, it is certain that signal processing will play an important role in the features that define 5G. This issue of IEEE Signal Processing Magazine (SPM) provides an overview of recent advances in signal processing for communication with an emphasis on signal processing techniques that will be relevant for 5G cellular systems. It covers a wide range of topics including modulation, beamforming, cross-layer optimization based on different performance metrics, location-aware communication, cloud computing, and cloud radio access networks. The articles provide a diverse perspective on the potential challenges in 5G cellular systems.