Abstract
In mobile communication systems such as a wireless cellular system, there have been continuously growing demands for higher capacity in recent decades. In the development of mobile communications systems, the orthogonalization and non-orthogonalization of wireless resources such as carrier, space, time, frequency, and spreading code elements have occurred in turn, in accordance with the progress of semiconductor integration, and nonlinear signal processing has been increasing utilized in wireless communications. In this paper, we introduce several nonlinear signal processing schemes in wireless communications to support the evolution of wireless access systems. First, the requirement of higher frequency efficiency and higher capacity in mobile communication systems is described, and the non-orthogonalization utilized in recent wireless access system is explained. As an example, multiple-input multiple-output (MIMO) transmission and faster than Nyquist (FTN) signaling are briefly reviewed. The non-orthogonal multiple access (NOMA) is currently considered as an advanced access technique in fifth-generation mobile communications system (5G). Then, the architecture of NOMA using nonlinear signal processing and its performance are introduced. In addition, the utilization of non-orthogonal mapping using chaos in modulation is introduced, and its performance is shown through numerical simulations. With these examples, we try to highlight the importance of nonlinear signal processing in next-generation wireless communication systems.
