The Federal Circuit held that the patent owner had waived the argument that an inter partes review is time-barred under 35 U.S.C. 315(b) because it failed to raise the argument before the Patent Trial and Appeal Board.
Had the argument been raised, the IPR would have been time-barred because, a few days after institution, Silver Spring Networks completed its merger with Itron Networked Solutions which was sued by Acoustic Technology years ago regarding the same patent.
Read the case here.