摘要
在802.11协议中,DCF(Distributed Coordination Function)机制是节点共享无线信道进行数据传输的基本接入方式,为了解决无线网络中隐藏节点问题,使用RTS/CTS机制减少冲突,然而当网络节点数增加时,节点传输的冲突次数亦增加,从而使网络性能明显下降。因此,需要设计新的MAC协议,以适应当前Ad Hoc网络应用的快速发展。在IEEE 802.11的分布式协调功能访问机制(DCF)基础上,本文设计新的节点合作式的网络协议(C-MAC)。C-MAC节点通过控制帧获得本节点2跳内的邻接节点信息,并且根据邻接节点的信息设计调度算法,使节点以轮询的合作方式传输数据,有效地避免冲突。仿真实验表明,在改变节点速率、帧长度、网络节点数等参数情况下,分别以吞吐量、单帧传输时间和公平性为指标,对DCF和C-MAC协议进行性能比较。在节点传输速率为11Mbps时,C-MAC协议吞吐量比标准DCF最多可增加50%。
DCF （Distributed Coordination Function） is a compulsory medium access control （MAC） scheme in IEEE 802. 11 protocol. In order to avoid the performance degradation due to hidden nodes, DCF adopts RTS/CTS mechanism to decrease colli- sions. However, hidden node problem degrades system performance sharply when the number of wireless nodes increases. There- fore, it is necessary to design a novel MAC protocol to satisfy the requirements of Ad Hoe networks. Based on the Distributed Co- ordination Function （DCF） of IEEE 802.11, we design a cooperative MAC protocol （C-MAC）. C-MAC node achieves the infor- mation of two-hop neighbor nodes from control frames, and according to the information of two-hop neighbor nodes, we design a scheduling algorithm to schedule each node to transmit at a particular time slot. We build a simulator to evaluate the performance of C-MAC in terms of throughput, transmission time per bop and fairness index. When the transmission rate is 11Mbps, the throughput of C-MAC increases 50% at most compared with the one of DCF.
出处
《计算机与现代化》
2014年第3期145-150,共6页
Computer and Modernization
