In order to execute, as a function of a received signal (r), a procedure of channel estimation in a transmission channel with memory in a telecommunications system, there is envisaged an operation of estimation of a delay spread associated to said channel, said operation of estimation comprising calculation of a root mean square value (τrms) of delay spread by means of a step of evaluation of crossings with a threshold level of a quantity associated to a transfer function of said channel. Said step of evaluation of crossings comprises evaluating a mean number of crossings (λ0) of the real and imaginary parts of said channel transfer function with a threshold level corresponding to the zero level. Example application is to OFDM telecommunications systems and in particular wireless systems according to the IEEE 802.11a WLAN standard or the HyperlanII WLAN standard.