The Communications Theory and Systems (CTS) group at UCSD has long been one of the largest and most visible communications groups in the world. Faculty research spans the full spectrum from fundamental theory to deployable systems and real-world applications. The group is well known for foundational contributions in information theory, error-control coding, signal processing, image and video compression, statistical learning, and control and optimization. On the system side, CTS faculty pioneer next generation wireless technologies, including MIMO and millimeter-wave communications, AI-native wireless communications, edge computing, ubiquitous computing, wireless sensing and health, AR/VR systems, non-terrestrial and satellite networks, underwater acoustic communications, and large-scale distributed systems such as sensor networks, social networks, and the internet of Things. CTS faculty are closely affiliated with the Center for Wireless Communications (CWC). Through close collaboration with industry partners, the group continues to shape future communication standards, AI-driven network architectures, mobile applications and wireless hardware design.