  We design a lightweight beam-searching algorithm for mobile millimeter-wave
systems. We construct and maintain a set of path skeletons, i.e., potential
paths between a user and the serving base station to substantially expedite the
beam-searching process. To exploit the spatial correlations of the channels, we
propose an efficient algorithm that measures the similarity of the skeletons
and re-executes the beam-searching procedure only when the old one becomes
obsolete. We identify and optimize several tradeoffs between: i) the
beam-searching overhead and the instantaneous rate of the users, and ii) the
number of users and the update overhead of the path skeletons. Simulation
results in an outdoor environment with real building map data show that the
proposed method can significantly improve the performance of beam-searching in
terms of latency, energy consumption and achievable throughout.
