Ample medium access control (MAC) protocols for Ad hoc networks have been proposed. However, most oal (PHY) layer and the MAC layers. Therefore, their efficiencf them do not take into account the interactions between the physicy and feasibility are greatly limited. In this article, we present a novel MAC protocol for Ad hoc networks according to the idea of cross-layer design. The proposed protocol combines an MAC protocol termed dual busy tone multiple access (DBTMA) with Orthogonal frequency division multiplexing (OFDM) system in IEEE 802.1 la standard. The analysis showed that the proposed protocol provides higher throughput and is more flexible than previous MAC protocols. In addition, it can provide Quality of Service(QoS) guarantee to the packets with different delay requirements in the presence of hidden terminals.