  We address a centralized caching problem with unequal cache sizes. We
consider a system with a server of files connected through a shared error-free
link to a group of cache-enabled users where one subgroup has a larger cache
size than the other. We propose an explicit caching scheme for the considered
system aimed at minimizing the load of worst-case demands over the shared link.
As suggested by numerical evaluations, our scheme improves upon the best
existing explicit scheme by having a lower worst-case load; also, our scheme
performs within a multiplicative factor of 1.11 from the scheme that can be
obtained by solving an optimisation problem in which the number of parameters
grows exponentially with the number of users.
