In the wireless networks, the power saving is highly important. The way of power saving by resource allocation and scheduling is attached more attention on recently. This paper explores optimal and suboptimal scheduling strategy for a multicarrier system over fading channels. The scheduling objective is to minimize the average system power under the delay constraint. Specifically, we study the trade-offs between the total transmit power of an orthogonal frequency division multiplexing (OFDM) system and the buffering delay of the packets in a transmission buffer. We formulate this optimization problem as a MDP and use dynamic programming techniques to obtain the optimal solution. Since finding the optimal policies becomes complex and practically un-realizable for large number of carriers in the system, we offer a suboptimal power allocation and bit loading algorithm using the results of the single carrier system and a greedy approach. Simulations show that the sub-optimal algorithm, which has reduced complexity, has performance close to the optimal one.