This paper presents a general blind channel estimation algorithm for multicarrier transmission. The first stage is based on the classical Viterbi Viterbi approach with the estimation of the mean value of the 4 received estimated independently, phase ambiguities between frequencies have then to be fixed. This correction is done considering only an upper bound for the delay spread of the propagation channel. A projection algorithm is then introduced leading to the estimation of the channel impulse response. The proposed algorithm can be applied to all kinds of multicarrier waveforms. It leads to a communication capacity increase and it can also efficiently in a cognitive radio network context.