Gaussian systems refer to a class of linear systems where the noises and signals have a Gaussian probability distribution. In this research area, the focus is on analyzing and designing systems that are optimal for handling Gaussian signals and noise. Gaussian systems are commonly used in communication systems, signal processing, control systems, and many other applications where the noise can be modeled as Gaussian. Research in this area involves studying the statistical properties of Gaussian signals and noise, developing algorithms for optimal estimation and detection, and designing efficient communication and control systems that work well with Gaussian inputs.