Efficient multi-antenna expansion method for Vandermonde-subspace frequency division multiplexing for 5G new waveform

This paper proposes a new efficient multi-antenna expansion method for Vandermonde-subspace frequency division multiplexing (VFDM). VFDM is a technique for interference cancellation in overlay networks that allows a secondary network to operate simultaneously with a primary network on the same frequency band; however, conventional VFDM is not applicable to multi-antenna systems in general, such as the multiple-input multiple-output system. Our proposed method expands on conventional VFDM without losing its advantage of computational efficiency by adopting an expanded Vandermonde matrix for a multi-antenna system. In the new method, the null-space precoder can be obtained directly from the solution matrices of the “matrix coefficient matrix polynomial” equation, and the solution matrices are obtained by Newton´s method for a nonlinear system of equations. Moreover, we also show the particular characteristics of solutions of the matrix polynomial, which are important for the efficient implementation of the multi-antenna VFDM.