Remarks on Fourier multipliers and applications to the Wave equation
  Exploiting continuity properties of Fourier multipliers on modulation spaces and Wiener amalgam spaces, we study the   Cauchy problem for the NLW equation. Local wellposedness for rough data in modulation spaces and Wiener amalgam spaces is shown. The results formulated in the framework of modulation spaces refine those in [3]. The same arguments may apply to obtain local wellposedness for the NLKG equation. 
Elena Cordero and Fabio Nicola