空天信息网络中QoS保障的可靠传输策略研究

发布时间：2018-05-06 09:41

本文选题：空天信息网络 + H-ARQ　；参考：《哈尔滨工业大学》2015年硕士论文

【摘要】：空天信息网络是一种综合网络,其涵盖了多种空基和天基通信系统,包括的网络节点有各种通信平台、飞行器以及不同轨道、不同种类的卫星。空天信息网络环境十分复杂,由于具有时延长、误码率高、信道非对称、带宽资源有限、高动态特性等特征,以及承载的业务类型具有多样性,给信息可靠传输带来挑战,因此保障信息的可靠传输是空天信息网络的关键问题之一。本文针对空天信息网络的特点,从点对点链路传输和端到端网络传输两方面研究空天信息网络的可靠传输问题,提出基于链路层和传输层跨层优化的可靠传输方案,在保障信息可靠传输的基础上提高传输效率。本文主要研究空天信息网络应用于大数据量、传输类型多样化的通信业务,针对空天信息网络的特点和传输的业务需求,研究基于QoS(Quality of Service,服务质量)保障的可靠传输策略。在数据链路层提出一种基于业务类型、网络状况自适应调整的H-ARQ(Hybrid Automatic Repeat Request,混合自动重传请求)策略,将前向纠错方法和自动重传请求技术结合起来,保障点到点的可靠传输。研究确定了适用于空天网络的前向纠错编码方案,选择合适的自动重传请求协议,并且分析推导出延时、吞吐量的表达式,确定对其具有影响的因素,然后根据业务类型、网络状况调整传输业务的重传次数、前向纠错编码参数来满足不同业务类型对延时、吞吐量的要求。在传输层提出对现有的TCP(Transmission Control Protocol,传输控制协议)协议进行优化的方案,用以适应空天网络的特殊环境,保障端到端的可靠传输。分别设计了基于优先级的慢启动算法以及基于业务类型自适应调整的算法。本文设计基于优先级的慢启动算法的原理是定义一个新的慢启动临界值应用于慢启动阶段,开始时采用较大的发送窗口和增长速度,当发送窗口大于新的临界值时改变发送窗口的增长方式,引入一个与往返时延有关的限制窗口增长速度的因子,使其增长速度减缓,直至平滑的进入拥塞避免阶段。此外,本文采用显示拥塞通知方法来区分丢包原因,如果是链路错误丢包,则立即重传丢失的数据包而发送窗口cwnd按原来的方式增加,不减小发送窗口。如果是拥塞丢包,则根据不同的业务类型,决定cwnd的窗口减小方式,以及快速恢复方式,这即是基于业务类型自适应调整发送窗口的设计思想。最后,利用NS-2构建了网络仿真环境,验证了提出的算法能够很好的应用在空天信息网络中,获得较高的传输效率且满足不同业务类型的QoS要求。
[Abstract]:Space-space information network is a kind of integrated network, which covers a variety of space-based and space-based communication systems, including a variety of communication platforms, aircraft and different orbits, different types of satellites. The space-space information network environment is very complex, because of the characteristics of extended time, high bit error rate, asymmetric channel, limited bandwidth resources, high dynamic characteristics, and the diversity of service types, it brings challenges to the reliable transmission of information. Therefore, ensuring the reliable transmission of information is one of the key problems in space-space information network. According to the characteristics of space-space information network, this paper studies the reliable transmission of space-space information network from two aspects of point-to-point link transmission and end-to-end network transmission, and puts forward a reliable transmission scheme based on link layer and cross-layer optimization of transmission layer. The transmission efficiency is improved on the basis of ensuring reliable transmission of information. This paper mainly studies the application of space-space information network to large amount of data and diversified types of communication services. According to the characteristics of space-space information network and the service requirements of transmission, the reliable transmission strategy based on QoS(Quality of Service (QoS) guarantee is studied. In the data link layer, a hybrid automatic retransmission request (H-ARQ(Hybrid Automatic Repeat Request,) strategy based on service type and adaptive network condition adjustment is proposed, which combines forward error correction method with automatic retransmission request technology to ensure reliable point-to-point transmission. In this paper, the forward error correction coding scheme suitable for space-space network is determined, the appropriate automatic retransmission request protocol is selected, the expressions of delay and throughput are deduced, and the factors affecting it are determined. Network conditions adjust the number of retransmissions and forward error correction coding parameters to meet the requirements of delay and throughput for different traffic types. In the transport layer, a scheme of optimizing the existing TCP(Transmission Control protocol is proposed to adapt to the special environment of the space-space network and to ensure the end-to-end reliable transmission. Slow start algorithm based on priority and adaptive adjustment algorithm based on service type are designed respectively. In this paper, the principle of designing a priority-based slow start algorithm is to define a new slow start threshold to be applied to the slow start phase. When the transmission window is larger than the new critical value, the growth mode of the transmission window is changed, and a factor related to round-trip delay is introduced to limit the growth rate of the window, which slows down the growth rate until it smoothly enters the stage of congestion avoidance. In addition, this paper uses the method of displaying congestion notification to distinguish the cause of packet loss. If it is a link error, the lost packet is retransmitted immediately and the transmission window cwnd is increased in the same way without decreasing the transmission window. In case of congestion loss, the window reduction mode and fast recovery mode of cwnd are determined according to different traffic types, which is the design idea of adaptively adjusting the sending window based on traffic type. Finally, the network simulation environment is constructed by using NS-2, which verifies that the proposed algorithm can be well applied in space-space information networks, and achieve higher transmission efficiency and meet the requirements of different traffic types of QoS.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN915.0

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