（毕业设计论文）Adhoc网络论文：基于忙音的Adhoc网络MAC协议研究.docVIP

w Ad hoc网络论文：基于忙音的Ad hoc网络MAC协议研究 【中文摘要】Ad hoc网络,又称无线自组网,是由一组带有无线收发装置的节点组成的可快速搭建的网络,具有多跳、动态网络拓扑、分布式控制以及不依赖基站等特点,应用前景广泛,一直受到学术界和工业界的重视。MAC协议用来协调各个节点对信道的共享访问、减少通信冲突,是Ad hoc网络的一个关键技术。现有的IEEE 802.11 MAC协议广泛应用于Ad hoc网络,但该协议会带来信道接入不公平性、隐终端和暴露终端等问题。当前很多研究都试图提高Ad hoc网络的性能,但这些协议只考虑了较为理想的网络环境,即接收节点的干扰范围等于其传输范围,无法解决大干扰域问题。由于忙音可以在载波侦听范围内被成功接收,应用到MAC协议中,可以有效解决大干扰域下的隐终端和暴露终端问题,因此基于忙音的MAC协议是当前的一个研究热点。本文从以下方面对MAC协议进行研究:(1)分析了802.11协议中二进制指数退避算法的不足,提出一种改进的退避算法,通过增大初始竞争窗口值,降低报文冲突概率,并在节点成功访问信道多次后主动退让,保证所有节点公平使用信道资源。(2)通过分析大干扰域问题,提出一种可变频率的双忙音MAC协议,利用忙音的频率和持续时间携带节点id信息,其它欲发送分组的节点根据当前通信双方的id,判断自身是否在其干扰范围之内,从而决定是否发送分组。分析和仿真表明,该方法可以抑制隐终端并能同时缓解暴露终端问题。(3)对Ad hoc网络中的干扰积累现象进行了分析,并提出一种基于Hexagon模型的MAC协议,该协议根据数据分组的冲突情况来调节接收端忙音的发射功率,当来自某一发送节点的分组传输失败时,接收节点将提高忙音的发射功率以扩大干扰控制半径,直至成功接收数据分组。分析和仿真表明,该协议可以提高接收端在多源干扰下正确收到数据的概率,更好的缓解了大干扰域下的隐终端问题。 【英文摘要】Ad hoc network, also known as MANET, is a kind of network which consists of a set of nodes with wireless device for transmitting and receiving and can be quickly set up. As it has the features such as multi-hop, dynamic network topology, distributed control, and does not rely on base stations, it has a broad application prospect and has been subject to academic and industrial attention.Media access control protocol is used to coordinate nodes to access the shared channel and reduces conflicts, so it is a key technology to ad hoc network. Existing MAC protocols like IEEE 802.11 is widely used in ad hoc network, however, 802.11 will bring about the unfairness of channel access, hidden terminal and exposed terminal problems. Many studies have tried to improve the performance of ad hoc network, whereas, these MAC protocols usually consider only an ideal network environment, namely, the receiver’s interference range is equal to its transmission range, thus can not solve the large interference area problem.As busy tone can be successfully received in the carrier sensing range, it will effectively solve hidden terminal and exposed terminal problems in the large inte