【作者】 李欢欢；

【导师】 吴迪；

【作者基本信息】 大连理工大学 ， 计算机应用技术， 2009， 硕士

【摘要】 随着人类社会信息化的高速发展,多媒体传输已经成为当代网络研究的热点之一。视频作为一种生动直观且信息量丰富的媒体备受人们青睐,但是其巨大的信息量使得其在转发传输方面制约了其传输范围。随着无线终端的增多和无线技术的发展,在ad hoc网络中传输实时多媒体成了现代的热门应用。经过压缩后的多媒体数据对于ad hoc网络传输信道的要求依然苛刻。严格按照协议层针对一个协议层的优化不但有可能不会提高网络的整体性能,反而有可能造成其他层的失调。因此,为了使ad hoc传输信道能够提供可靠的通信保障,我们将利用跨层设计的思想,对影响ad hoc网络传输视频质量的各个因素进行综合调整。本文对移动ad hoc网络和多媒体的特性进行了研究,设计了一套有效的多媒体传输方案。首先在多媒体压缩编码方面,选择目前压缩效率最高的H.264视频压缩标准,并使用MDC、FEC等技术增强视频码流的容错性。然后设计了一套移动ad hoc网络多媒体传输方案。使用改进的AOMDV路由进行路由选择,并引入了优先级调度、拥塞控制、等手段增强移动ad hoc网络传输的可靠性。为了验证设计的合理性,在NS2仿真工具上建立实验平台。然后设计场景进行仿真实验,对得到的数据进行分析。结果显示,本文的设计提高了ad hoc网络的吞吐量,降低了时延,虽然为了保证视频流的通畅在一定程度上牺牲了视频的质量,但是仍然使质量保证在了可感知的范围之内。更多还原

【Abstract】 As the human society gets more and more informationized, multimedia transmission becomes one of the hotspots in the concurrent network research. As a vivid and visual media with rich information, videos are one of the most favorite media, however, due to the huge information it carries, the transmission range is limited in terms of forward transmissions. As the use of wireless terminals increase and wireless technology develops, transmission of real-time multimedia content in ad hoc networks is becoming a popular application nowadays.The compressed multimedia data still has demanding requirements for the transmission channel of ad hoc networks. In stead of improving the global performance of the network, the optimization of a specific protocol layer which is strictly based on protocol layers could possibly cause disorders in other layers. Therefore, to enable ad hoc transmission channels to provide reliable communication guarantees, we employed the idea of cross-layer design and make composite adjustments in various factors that may affect the quality of video transmission in ad hoc networks.This paper addresses in the properties of mobile ad hoc network and multimedia communication, and proposes a communication scheme. At first, multimedia data is compressed by H.264 which has the highest compression ratio. MDC and FEC technologies are introduced to improve the tolerance of compressed multimedia data flows. We also design a robust transmission scheme for error-sensitive multimedia data flows. Improved AOMDV routing protocol is used for routing selection, and priority schedule combining with congestion control and cross-layer design are also used to improve the reliability of the error-prone mobile ad hoc network.To testify the rationality of our design, we build an experiment platform on NS2 simulation tool, scenarios are designed for the simulation experiments, and the data collected in the previous process are analyzed. The result shows that designs in this paper improve the throughput and reduce the delays of ad hoc networks. Though the quality of videos is sacrificed to some extent to guarantee smooth video streams, the quality is still within the sensible range.更多还原