  This paper studies how to maximize a spectrum database operator's expected
revenue in sharing spectrum to secondary users, through joint pricing and
admission control of spectrum resources. A unique feature of our model is the
consideration of the stochastic and heterogeneous nature of secondary users'
demands. We formulate the problem as a stochastic dynamic programming problem,
and present the optimal solutions under both static and dynamic pricing
schemes. In the case of static pricing, the prices do not change with time,
although the admission control policy can still be time-dependent. In this
case, we show that a stationary (time-independent) admission policy is in fact
optimal under a wide range of system parameters. In the case of dynamic
pricing, we allow both prices and admission control policies to be
time-dependent. We show that the optimal dynamic pricing can improve the
operator's revenue by more than 30% over the optimal static pricing, when
secondary users' demands for spectrum opportunities are highly elastic.
