基于Netgraph的CMMB协议栈的研究与实现

【作者】 余佳；

【导师】 罗蕾；

【作者基本信息】 电子科技大学 ， 计算机应用技术， 2010， 硕士

【摘要】 随着手机的日益普及和智能化,人们对于移动终端的各种应用的热情也越来越高。越来越多的移动终端及其相关的产品极大的丰富和改善了人们的生活。CMMB多媒体广播电视正式在这种情况下产生并走向成熟的。CMMB (China Mobile Multimedia Broadcasting)标准是国家广播电影电视总局推出的自主研发、具有自主知识产权的移动广播电视标准。国外主流广播电视标准还有美国高通公司提出的MediaFLO,欧洲的DVB-H和韩国的T-DMB等。本文实现的CMMB协议栈是CMMB MTV手机电视播放器的一部分。该协议栈采用了在FreeBSD操作系统中用于PPP等协议栈构建的Netgraph机制。Netgraph中的内存管理部分是用Mbuf机制实现的。鉴于国内外对于Netgraph和Mbuf机制进行详细介绍的资料甚少,本文通过深入分析,详细阐述了Netgraph机制和Mbuf机制的实现原理,然后提出了这两种机制使用的方法。并结合实际的项目,提出了把Netgraph从ECOS操作系统上移植到Windows Mobile上的具体做法。移植工作主要涉及到Netgraph的软中断机制,SPL互斥机制,以及对于Mbuf长度的修改方法。根据CMMB协议标准,本文给出了一种在Netgraph机制的基础上构建CMMB协议栈的设计和实现方案,并结合Netgraph的特点设计和实现了协议栈底层的驱动适配层。实际测试和产品应用的结果表明,基于Netgraph构建的CMMB协议栈很好地适应了嵌入式设备的要求,具有稳定可靠、内存利用率高、结构清晰、高内聚低耦合的特点,实现了预期的目标。更多还原

【Abstract】 As mobile phones become more and more prevailed and intelligent, people become more and more passionate about various applications for mobile terminals. Increasing number of mobile terminals and related products have enormously enriched and improved people’s everyday life. CMMB has grown and become mature right under the circumstances.CMMB(China Mobile Multimedia Broadcasting) standard is a mobile broadcasting television standard self developed by The State Broadcasting Film and Television Administration(SARFT), and SARFT owns its independent intellectual property rights. The main standards abroad include:MediaFLO developed by American company Qualcomm, DVB-H in Europe and T-DMB in Korea.The CMMB protocol stack developed in this thesis is a part of the CMMB MTV mobile phone TV player software. The protocol stack has utilized the Netgraph mechanism in FreeBSD OS. The memory management in Netgraph is controlled by Mbuf mechanism. As very few documents has give detailed introduction about Netgraph and Mbuf, this thesis try to give more comprehensive description for Netgraph and Mbuf mechanism after thorough study, and also gives the specific procedure for transplanting Netgraph from ECOS to Windows Mobile combining the project. The transplanting procedure mainly includes the SWI mechanism and SPL mutex mechanism in Netgraph, and also some modification to the Mbuf. According to CMMB standard, this thesis provides a scheme to design and implement CMMB protocol based on Netgraph, and also designed and implemented the driver adaptor layer at the bottom of the protocol stack layer.The testing and application of the software indicates that:the CMMB protocol stack based on Netgraph satisfied the requirements of embedded devices, and its feature includes:stable, high memory usage ratio, clear structure, high cohesion and low coupling.更多还原