A very general fading scenario is considered for which exact, closed-form formulas for the correlation coefficient of the instantaneous power at the output of a Maximal Ratio Combining receiver is derived. The model includes the main fading environments as very particular cases. It is valid for both identically and non-identically distributed multipath clusters, and for both stationary and nonstationary environments. Most interestingly, the model allows for an uncountable number of combinations of novel fading scenarios. A further generalization is achieved with the angle as well as the time of arrival of the waves permitted to vary throughout the multipath clusters, as opposed to known models for which these parameters are fixed. Several particular examples illustrate the applicability of the general formulations.58924722479