Accurate link quality estimation is a fundamental building block in quality aware multi hop routing. In an inherently lossy, unreliable and dynamic medium such as wireless, the task of accurate estimation becomes very...Accurate link quality estimation is a fundamental building block in quality aware multi hop routing. In an inherently lossy, unreliable and dynamic medium such as wireless, the task of accurate estimation becomes very challenging. Over the years ETX has been widely used as a reliable link quality estimation metric. However, more recently it has been established that under heavy traffic loads ETX performance gets significantly worse. We examine the ETX metric＇s behavior in detail with respect to the MAC layer and UDP data; and identify the causes of its unreliability. Motivated by the observations made in our analysis, we present the design and implementation of our link quality measurement metric xDDR - a variation of ETX. This article extends xDDR to support network mobility. Our experiments show that xDDR substantially outperforms minimum hop count, ETX and HETX in terms of end-to-end packet delivery ratio in static as well as mobile scenarios.展开更多
MANET 是独立的网络自治系统,不依赖于固定主干网络,可提供有效的数据和多媒体通信服务。它使用无线通信技术,所有主机均可以移动。但是众所周知,无线系统是带宽受限系统,信道分配算法至关重要。提高无线资源的使用效率,提高系统的容量...MANET 是独立的网络自治系统,不依赖于固定主干网络,可提供有效的数据和多媒体通信服务。它使用无线通信技术,所有主机均可以移动。但是众所周知,无线系统是带宽受限系统,信道分配算法至关重要。提高无线资源的使用效率,提高系统的容量和传输质量,一直是研究的重要课题。本文对移动 Ad hoc 网络 MAC 接入控制协议的研究现状进行了综述,揭示了它们的特点和功能,比较了各自的贡献和不足。这些协议涵盖了目前能见到的绝大部分类型的 MAC 协议。最后对 MAC 协议研究的发展方向进行了展望。展开更多
Ad Hoc网络中无线信道的时变特性和网络拓扑的不断变化导致了链路的频繁断续,使得数据包大量丢失。这就要求高层应用协议能够快速访问底层传输协议甚至信道的状态信息,各层协议之间能够根据需要互相交换信息,迅速作出决策,提高分组接收...Ad Hoc网络中无线信道的时变特性和网络拓扑的不断变化导致了链路的频繁断续,使得数据包大量丢失。这就要求高层应用协议能够快速访问底层传输协议甚至信道的状态信息,各层协议之间能够根据需要互相交换信息,迅速作出决策,提高分组接收成功率。基于QualNet网络仿真器设计并实现了一种网络协议栈跨层交互的机制。结果表明,利用该机制,能够快速建立跨层协议的交互,使得高层协议及时获取低层协议的有用信息,从而可根据信道的状况动态调节网络协议设置,提高分组发送成功率,优化网络传输的性能。展开更多
提出了一种TBPR(time-based broadcasting for power-aware routing)协议.TBPR采用路由请求报文延迟发送机制,并通过比较路径中的累计功率消耗,选择能量消耗较低的路由,以降低网络的能量消耗,延长网络的生存周期.计算机仿真实验表明,TBP...提出了一种TBPR(time-based broadcasting for power-aware routing)协议.TBPR采用路由请求报文延迟发送机制,并通过比较路径中的累计功率消耗,选择能量消耗较低的路由,以降低网络的能量消耗,延长网络的生存周期.计算机仿真实验表明,TBPR能够取得较好的节能效果,并降低无线AdHoc网络中的能量消耗.展开更多
提出了无线移动 Ad hoc 网中一种基于拓扑维护的自适应多信道路由协议:MOLSR-TM,该协议把拓扑维护状况感知和自适应控制算法引入 OLSR 以调整 HELLO 消息的发送频率和邻居记录表、拓扑记录表的刷新频率,从而增强节点掌握网络拓扑的能力...提出了无线移动 Ad hoc 网中一种基于拓扑维护的自适应多信道路由协议:MOLSR-TM,该协议把拓扑维护状况感知和自适应控制算法引入 OLSR 以调整 HELLO 消息的发送频率和邻居记录表、拓扑记录表的刷新频率,从而增强节点掌握网络拓扑的能力,改善路由表项不全导致的分组寻路失败问题。性能分析和仿真结果表明:MOLSR-TM 能改善节点的拓扑维护状况,增强动态拓扑适应能力,提高数据成功率、端到端时延和网络吞吐率等性能。展开更多
文摘Accurate link quality estimation is a fundamental building block in quality aware multi hop routing. In an inherently lossy, unreliable and dynamic medium such as wireless, the task of accurate estimation becomes very challenging. Over the years ETX has been widely used as a reliable link quality estimation metric. However, more recently it has been established that under heavy traffic loads ETX performance gets significantly worse. We examine the ETX metric＇s behavior in detail with respect to the MAC layer and UDP data; and identify the causes of its unreliability. Motivated by the observations made in our analysis, we present the design and implementation of our link quality measurement metric xDDR - a variation of ETX. This article extends xDDR to support network mobility. Our experiments show that xDDR substantially outperforms minimum hop count, ETX and HETX in terms of end-to-end packet delivery ratio in static as well as mobile scenarios.
文摘MANET 是独立的网络自治系统,不依赖于固定主干网络,可提供有效的数据和多媒体通信服务。它使用无线通信技术,所有主机均可以移动。但是众所周知,无线系统是带宽受限系统,信道分配算法至关重要。提高无线资源的使用效率,提高系统的容量和传输质量,一直是研究的重要课题。本文对移动 Ad hoc 网络 MAC 接入控制协议的研究现状进行了综述,揭示了它们的特点和功能,比较了各自的贡献和不足。这些协议涵盖了目前能见到的绝大部分类型的 MAC 协议。最后对 MAC 协议研究的发展方向进行了展望。
文摘提出了一种TBPR(time-based broadcasting for power-aware routing)协议.TBPR采用路由请求报文延迟发送机制,并通过比较路径中的累计功率消耗,选择能量消耗较低的路由,以降低网络的能量消耗,延长网络的生存周期.计算机仿真实验表明,TBPR能够取得较好的节能效果,并降低无线AdHoc网络中的能量消耗.
文摘提出了无线移动 Ad hoc 网中一种基于拓扑维护的自适应多信道路由协议:MOLSR-TM,该协议把拓扑维护状况感知和自适应控制算法引入 OLSR 以调整 HELLO 消息的发送频率和邻居记录表、拓扑记录表的刷新频率,从而增强节点掌握网络拓扑的能力,改善路由表项不全导致的分组寻路失败问题。性能分析和仿真结果表明:MOLSR-TM 能改善节点的拓扑维护状况,增强动态拓扑适应能力,提高数据成功率、端到端时延和网络吞吐率等性能。
