  One of the most promising approaches to overcome the uncertainty and dynamic
channel variations of millimeter wave (mmW) communications is to deploy
dual-mode base stations that integrate both mmW and microwave ($\mu$W)
frequencies. In particular, if properly designed, such dual-mode base stations
can enhance mobility and handover in highly mobile wireless environments. In
this paper, a novel approach for analyzing and managing mobility in joint
$\mu$W-mmW networks is proposed. The proposed approach leverages device-level
caching along with the capabilities of dual-mode base stations to minimize
handover failures and provide seamless mobility. First, fundamental results on
the caching capabilities, including caching probability and cache duration, are
derived for the proposed dual-mode network scenario. Second, the average
achievable rate of caching is derived for mobile users. Then, the impact of
caching on the number of handovers (HOs) and the average handover failure (HOF)
is analyzed. The derived analytical results suggest that content caching will
reduce the HOF and enhance the mobility management in heterogeneous wireless
networks with mmW capabilities. Numerical results corroborate the analytical
derivations and show that the proposed solution provides significant reductions
in the average HOF, reaching up to 45%, for mobile users moving with relatively
high speeds.
