This paper considers the design of a cross-layer medium access control (MAC) protocol for wireless ad hoc cooperative networks. Specifically, we redesign the message exchange process of the MAC protocol previously proposed by Shan et al. By using a HRP signal with shorter length the proposed protocol can reduce the protocol overhead and thus improve the transmission reliability. We also propose to use only one HRP signal to resolve the collision among the helpers with the same cooperative rate. The proposed protocol achieves higher path throughput and lower end-to-end packet latency compared with that by Shan et al. and the traditional IEEE 802.11 MAC protocol.