Multidimensional signals refer to signals that vary with respect to more than one independent variable. This can include signals that vary in space, time, frequency, or any other dimension. In multidimensional signal processing, researchers study how to analyze, manipulate, and process these signals effectively. This research area is important in fields such as image processing, communications, geophysics, and medical imaging, where data is often represented in multiple dimensions. Techniques in multidimensional signal processing include Fourier transforms, wavelet transforms, and other methods for representing and analyzing signals in multiple dimensions.