—Dynamic spectrum access (DSA) aims to improve spectrum efficiency via spectrum sensing and optimal spectrum access. An essential component in DSA is the joint design of sensing and access strategies. This paper focuses on dynamic spectrum access in the time domain. To maximize channel utilization while limiting interference to primary users, a framework of linear programming is presented based on the stationary distribution of the primary user channels. It is shown that the optimal tradeoff between sensing and transmitting is achieved with required limit on the interference to the primary users.