Repeat request ( ARQ) scheme is used to retransmit the data packets after unsuccessful transmission. However, this scheme may not be effective under a deep fading channel with correlated errors. Cooperative communications, which is the important technology in next wireless communications, can improve the reliabiliiy of wireless links, which can solve the problem above effectively.The paper proposes an adaptive cooperative MAC with priority for Ad Hoc networks. The protocol can dynamically select the relay which has better channel condition based on the instantaneous channel condition, and a high priority is given to the relay. Moreover, the protocol adds the new handshake scheme based on RTS/CTS to the protocol, which further improve the system performance. In addition,the proposed protocol is modeled by a modified Markov chain, in which considers the cooperative communications and the collision re8ulted from the relays. Furthermore, the throughput performance is evaluated by the model. The simulation results show the proposed protocol can highly improve the system performance compared with IEEE 802.11 DCF and general cooperative ARQ protocol.%ARQ(Auto Repeat reQuest)机制通常用来在传输失败后重传数据,但是在深衰落信道下,源节点多次重传有可能导致系统性能持续变坏,作为未来无线通信的重要技术,协同通信能够大大提高链路的可靠性,可以有效解决上述问题.本文针对Ad Hoc网络,提出了一种基于优先控制的自适应协同MAC(Media Access Contro1)协议.此协议采用ARQ机制,根据瞬时信道情况,自适应地选择信道质量更好的中继节点来重传数据,并且在优化的退避算法和中继选择算法的控制下,赋予中继节点相对源节点更高的优先级,协议中还在传统RTS/CTS分组交互基础上加入了新的握手交互机制,使得协议的性能进一步提升.本文还对经典二维Markov模型进行了改进,加入了协同机制并提出中继节点冲突模型,对所提协议进行了建模并推导出了吞吐量性能表达式.仿真结果表明,本文所提协议相对IEEE 802.11DCF协议和传统采用ARQ机制的协同MAC协议有着更好的性能.
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