  Graph signal processing (GSP) is an important methodology for studying data
residing on irregular structures. As acquired data is increasingly taking the
form of multi-way tensors, new signal processing tools are needed to maximally
utilize the multi-way structure within the data. In this paper, we review
modern signal processing frameworks generalizing GSP to multi-way data,
starting from graph signals coupled to familiar regular axes such as time in
sensor networks, and then extending to general graphs across all tensor modes.
This widely applicable paradigm motivates reformulating and improving upon
classical problems and approaches to creatively address the challenges in
tensor-based data. We synthesize common themes arising from current efforts to
combine GSP with tensor analysis and highlight future directions in extending
GSP to the multi-way paradigm.
