  This paper introduces a new theoretical framework for optimal handover
procedures in heterogeneous networks by devising the novel fractional Gittins
indices, which are dynamical priorities whose values can be statically
associated to the decision states of evolving processes representing handover
alternatives. The simple policy of activating at any time the one process
currently at highest priority optimizes the bandwidth of a handover, if all
other inactive processes remain idle. However, numerical evidence shows that in
practice this condition can be relaxed for a wide range of handover models,
because the bandwidth actually achieved by the policy never deviates for more
than 12% from the optimally achievable bandwidth and remains in median within a
deviation of 2% from this optimum.
