THE SCARCITY of spectral resources makes it challengingto satisfy the ever-growing demand for high-qualitywireless communication services, and increases the importanceto improve the spectrum utilization. Dynamic spectrum access,which enables users to proactively choose available channels,is one key approach to address this problem. However,dynamic spectrum access can be very challenging for instancein scenarios in which there is lack of prior informationon the channel conditions or especially when the channelconditions in different frequency bands vary over time andmultiple users dynamically access the channels simultaneously.Motivated by these considerations,