【作者】 李昕；

【导师】 刘文予；

【作者基本信息】 华中科技大学 ， 通信与信息系统， 2005， 硕士

【摘要】 q无线通信的发展以及宽带技术的应用使宽带无线通信网络成为个人通信及各种无线业务的首选,在宽带无线通信系统中,无线信道环境非常恶劣,信号能量不仅随着传输距离的增加迅速衰减,而且还会受到诸如多径衰落和多普勒频移等因素的影响,这些对数据传输,特别是高速数据传输提出了挑战。在提高数据传输可靠性方面,ARQ(Automatic-Repeat-reQuest)技术发挥了巨大的作用。多拒绝自动请求重传技术结合了多拒绝MR 自动请求重传机制和HIPERLAN 标准的优点,仿真和原理机系统都验证了该算法能有效的提高无线链路层的吞吐率。多ARQ技术提供具有不同发送与确认机制的RLC 实体,由此形成了无线链路层QoS 的基础框架。用户希望无线网络和有线网络一样提供丰富的QoS 支持。本文讨论了IP QoS 的区分服务体系结构,分析了GPS、WFQ、WF~2Q、DRR 和CBQ 等调度算法。结合IP QoS中的区分服务体系结构和多ARQ 技术,本文提出了一个适用于无线数据链路层的QoS模块框架。该模块将不同服务质量要求的业务映射到相应的RLC 实体,结合无线链路层传输技术,与RLC 子层向上层提供多用户、多业务的QoS 控制。拥塞控制是QoS 一个重要的功能。本文讨论了TCP 协议的慢启动、拥塞避免、快速重传和恢复算法,通过分析RED 算法与ARQ 算法,提出了一种适用于无线网络的基于多拒绝ARQ 算法的拥塞控制方法。该方法结合RED 算法,通过ARQ 发送窗口和分割队列长度以及重传率进行拥塞控制。仿真表明,这种方法能预测链路拥塞,反馈链路拥塞程度,能提高链路吞吐率。更多还原

【Abstract】 The development of wireless communication and broadband technologies makes broadband wireless communication network the first choice in the filed of personal communication and wireless services. The wireless channel places fundamental limitations on the performance of wireless communication systems. This makes high speed data transmission a big challenge in wireless network. ARQ(Automatic-Repeat-reQuest) can greatly improve the reliability of data transmission. Multi-rejects ARQ which combines the strong points of MR ARQ and HIPERLAN can effectively improve the throughput in the wireless datalink layer. Multi-ARQ supplies us several RLC entities which are different in the mechanisms of data sending and acknowledge and forms the basic frame of wireless datalink layer QoS. A wireless datalink layer QoS framework is developed based on diffserv architecture of IP QoS and Multi-ARQ technology. This QoS module together with RLC sub layer provides upper layer multi-user and multi-service QoS control. Congestion control is an important function of QoS. This paper discusses TCP’s slow start, congestion avoidance, fast retransmission and fast recovery algorithms, develops a congestion control method for wireless networks based on multi-rejects ARQ algorithm. According to RED algorithm, this method controls the congestion through the ARQ send window, the length of segmentation queue and the link-layer retransmission rate. The simulation proves this method can improve the link throughput.更多还原