Since the actual distribution of the received signals in multi-hop amplify-and- forward (AF) relaying transmission is no longer Gaussian, which is caused by the multiplication of fading gains and noise, a new fitted distribution named as logistic distribution is used to derive a novel noncoherent detector based on the maximum likelihood (ML) method. In order to get better performance of the receiver, one or more multi-hop AF links are added to form a multi- branch cooperative diversity system. Therefore, at the destination, combining method is applied to combine several signals together to obtain better diversity gains. Numerical results show that the new detector based on the logistic distribution outperforms the conventional energy detector. Also, it is shown that the performance of receiver is significantly improved when combining method is applied in the multi-branch cooperative diversity system especially when the number of branches increases.