I Welcome you to the fourth issue of the IEEE Communications Surveys and Tutorials in 2017. This issue includes 35 papers covering different aspects of communication networks. In particular, these articles survey and tutor various issues in “Wireless, Sensor, and Cognitive Radio Networks,” “Software-Defined Networking, Mobile Edge Computing, and Intelligent Networks,” “Internet of Things and Vehicular Networks,” “Security, High-Performance Computing, Positioning, and Localization Techniques,” and “Internet, Multimedia, Social Network, Molecular Network, and Optical Communication.” A brief account for each of these papers is given below.