This paper investigates the optimal call admission control (CAC) policy for non-priority scheme (NPS) and reserved channel scheme (RCS) in wireless networks, respectively. Both new call and handoff call arrival processes are assumed to be Poisson processes, and the call holding times are exponentially distributed with different rate for new call and handoff calls. Admitting each call would bring a reward to the network provider but holding each call in the system would also incur some expenses (or cost) to the provider. We concentrate on the optimization problems of when to admit or reject a call in order to achieve the maximum total expected discounted reward. By establishing a discounted semi Markov decision process (SMDP) model, we verify that the optimal policies are state-related control limit policies for both NPS and RCS. Our numerical results explained in both tables and diagrams are consistent with our theoretic results.