Techniques are provided for efficient allocation of frequency spectrum blocks. In one example, there is provided a method, operable by one or more network entities, for reallocating a portion of a first frequency band allocated to a first radio access technology (RAT) to a second RAT. The method may involve determining a migration block granularity for reallocating the portion of the first frequency band to the second RAT. The method may involve identifying spectrum block(s) of the determined granularity in the first frequency band. The method may involve aggregating the identified spectrum block(s) with a native carrier in a second frequency band allocated to the second RAT. The method may involve controlling of the aggregated spectrum block(s) via the native carrier for the second RAT.