The present paper proposes and studies an algorithm to estimate chan- nels with a sparse common support (SCS). It is a generalization of the classical sampling of signals with Finite Rate of Innovation (FRI) and thus called SCS-FRI. It is applicable to OFDM and Walsh- Hadamard coded (CDMA downlink) communications since SCS-FRI is shown to work not only on contiguous DFT pilots but also uniformly scattered ones. The support estimation performances compare favorably to theoretical lower-bounds, and importantly this translates into a sub- stantial equalization gain at the receiver compared to the widely used spectrum lowpass interpolation method.