[4rgento]

To describe electromagnetic waves, or to write a solution to the wave equation, you need to use a system of coordinates. The most common by far is the rectangular system (x,y,z), but there are other ones: cylindrical coordinates, elliptical, spherical, and more. This is like choosing a base in a vector space. If you choose rectangular coordinates then your solutions are expressed as a linear combination of plane waves ( Cos(k*x-wt), k is wave vector, x is position, w is frequency and t is time ). If you choose cylindrical coordinates, then your solution will be spanned as a combination of bessel functions( more exactly cylindrical waves) whose parameters are called: OAM, spin, and momentum (in z axis). As nature doesn't care which coordinate system we choose and neither the wave equation, a solution in one system of coordinates y also a solution in another. In this case, a cylindrical wave can be expressed as an infinite combination of plane waves. So what this people seems to be saying is more or less: "Instead of emitting waves and, in the receiver, just measure the frequency; let's emit more complex patterns and, in the receiver, measure enough features of the wave ( not just the frequency) so that we can tell it apart from other signals.

I hope this helps.