  Inspired by the paper of Groenewald, Kaashoek and Ran (Wiener-Hopf indices of
unitary functions on the unit circle in terms of realizations and related
results on Toeplitz operators. \emph{Indag. Math.} 28, (2017), 649-710), we
present an operator-theoretic approach to provide further insight and simpler
computational formulas for the Wiener-Hopf indices of a rational matrix valued
function taking unimodular values on the unit circle.
