  Dynamic spectrum sharing is a promising technology for improving the spectrum
utilization. In this paper, we study how secondary users can share the spectrum
in a distributed fashion based on social imitations. The imitation-based
mechanism leverages the social intelligence of the secondary user crowd and
only requires a low computational power for each individual user. We introduce
the information sharing graph to model the social information sharing
relationship among the secondary users. We propose an imitative spectrum access
mechanism on a general information sharing graph such that each secondary user
first estimates its expected throughput based on local observations, and then
imitates the channel selection of another neighboring user who achieves a
higher throughput. We show that the imitative spectrum access mechanism
converges to an imitation equilibrium, where no beneficial imitation can be
further carried out on the time average. Numerical results show that the
imitative spectrum access mechanism can achieve efficient spectrum utilization
and meanwhile provide good fairness across secondary users.
