【作者】 田冲；

【导师】 袁东风；

【作者基本信息】 山东大学 ， 通信与信息系统， 2009， 博士

【摘要】 随着无线网络的快速发展,移动通信用户数和因特网用户数急剧增加,有限的无线资源与多媒体业务不断提高的服务质量要求之间的矛盾日益尖锐。新一代无线通信系统不仅要求具有更大的系统容量,还要支持移动多媒体业务传输,即除了提供话音业务之外,还要支持低/高速数据、图象等非话音业务的传输,同时能够满足不同用户和不同业务的服务质量(QoS)要求。无线资源调度技术是无线网络对用户提供服务质量保障的关键所在。在很多应用场景下,无线信道具有明显的资源受限和时变衰落特性,传统的基于有线网络或无线静态信道的分组调度算法无法保证无线网络用户获得很好的QoS。针对无线网络环境中的无线信道时变传输特性,设计能够在保证用户QoS的同时提高无线网络容量的调度算法是当前无线通信领域的一个研究热点。本论文以新一代通信系统中最重要的两类无线网络形态为研究背景,分别对基于IEEE 802.16无线城域网和认知无线电网络的调度算法进行了系统研究,同时尝试将经济学中的相关理论引用到无线调度算法的设计中,以更好地提高系统性能和用户对服务质量的评价水平。本论文的研究成果可为下一代无线通信网络提供高效的跨层调度策略,还可为下一代无线通信系统的标准化提供参考依据。具体而言,本文的主要研究内容和创新之处在于:1.研究了IEEE 802.16无线城域网中的跨层资源调度问题。首先深入研究了IEEE 802.16协议对物理层和MAC层的详细规范。对物理层的自适应调制编码技术进行了深入探讨,使传输参数自适应地匹配时变的无线信道,在保证预先设定的误包率(PER)前提下实现对带宽的高效利用。IEEE 802.16协议在MAC层定义了四种业务类型,不同业务类型具有各自不同的QoS需求,也就是说,调度算法需要在多种业务类型共存的场景中运行。基于上述分析,提出了一种新颖的跨层调度算法。该调度算法综合考虑无线信道状态、QoS满意程度、业务优先级、用户公平因子、队列状态等多个跨层因素来做出用户选择的决策,在首先保证各用户最小QoS需求的基础上,尽力提高系统的整体性能。对于选择出来要接受服务的用户,设计高效的时隙分配算法,根据当前系统资源总量及用户需求为其分配恰当的时隙资源,避免资源浪费,更好地提高系统性能。2.研究了认知无线电网络中的跨层资源调度问题。认知无线电技术的出现,为解决频谱资源不足、实现频谱动态管理及提高频谱利用率提供了强有力的技术支撑,是未来通信领域的热点技术之一。在认知无线电网络中设计调度算法,必须充分考虑认知用户对主要用户的功率干扰,以保证主要用户的QoS性能不因与次要用户工作在同一区域而受损害。论文采用了机会调度算法的设计理念,同时对信道状态信息和干扰功率信息进行机会的利用,使对主要用户干扰功率较大的用户在信道条件较好的情况下进行数据传输。在此基础上,提出了两种跨层调度算法:基于系统性能联合优化的调度算法和基于最小性能保证的两步调度算法,实现了在认知用户QoS性能没有明显退化的同时显著地降低了认知网络对主要用户的平均功率干扰。3.研究了基于投资管理理论的跨层资源调度问题。系统地研究了经济学中的投资管理理论,并找到了无线资源调度与投资管理理论相结合的结合点,研究了基于投资管理理论的无线调度算法的应用及性能,并基于无线接入网络和认知无线电网络分别设计了新颖的跨层调度准则,综合考虑网络性能与用户需求,为用户提供鲁棒的服务质量保证。4.研究了基于用户感知服务质量的跨层资源调度问题。将经济学理论中的容忍区域QoS模型以及感知服务质量分析理论应用到无线网络调度算法设计中。对无线网络环境中的用户感知服务质量进行了具体的理论分析并给出了恰当的管理策略。定义了用户感知服务质量的量化表达式,把用户感知服务质量当作一个新颖的QoS参数,并将其作为优化目标来设计高效的跨层调度算法,有效提高了用户对服务水平的满意度,同时实现了对系统资源的合理利用。更多还原

【Abstract】 With the development of mobile communications, mobile users and Internet users are increasing dramatically, and the conflict between the limited wireless resource and the increasing Quality of Service (QoS) requirement of multimedia traffics is becoming more and more serious. People expect that next generation mobile communication systems can provide larger capacity and support mobile multimedia services. Besides providing real-time speech service, next generation mobile communication systems are required to support other services such as low/high rate data, pictures etc. Heterogeneous services have different QoS requirements, for example, the requirements of time delay, error bit rate, and transmitting rate for heterogeneous services are differentiated. In many circumstances, packet scheduling policies designed for wired networks and wireless static channels are inadequate for wireless networks because of the limited and time-varying wireless channel capacity. As a result, it is a hot topic in the area of wireless communications to design the packet scheduling algorithms by considering the characteristics of wireless time-varying channels with the objectives of providing QoS guarantees to users as well as increasing the capacities of the wireless networks.In this dissertation, the cross-layer resource scheduling techniques in the typical two emerging types of wireless networks, IEEE 802.16 based Wireless Metropolitan Area Networks(WMAN) and Cognitive Radio Networks, are intensively studied. Economics theories are introduced into the design of wireless scheduling algorithms in order to improve the system performance and user perceived QoS. The research results provide next generation wireless communication networks reference cross-layer optimization strategies and are helpful for the standardization studied. The contents of this work are listed as follows:1. Based on the careful research of IEEE 802.16 protocol, we propose a novel cross-layer scheduling algorithm at the IEEE 802.16 WMAN MAC layer for multiple connections with diverse QoS requirements, where each connection employs AMC scheme at the PHY layer. Based on the specified QoS parameters, our scheduler will first satisfy all the QoS requirements; at the same time, it uses the wireless bandwidth efficiently by exploiting multiuser diversity among connections with different kinds of services and finally makes an optimum trade off between throughput and fairness.2. For cross layer resource scheduling in cognitive radio networks. In cognitive radio systems, one more aspect should be considered to protect the primary user from harmful interference when cognitive users are working in the vicinity of the primary user. Providing individual QoS guarantees and hybrid fairness for multimedia services is also a challenging issue, especially exploiting the synergy between the PHY layer and the MAC layer. The design essence of opportunistic scheduling are exploited here. The scheduler can use the channel state information and interference power information opportunistically. As a result, the user whose interference power is larger will be scheduled when its channel condition is in good state. Our scheduler can decrease the average interference to the primary user with efficient bandwidth utilization and without significantly dropping the QoS.3. We present novel cross-Layer scheduling strategies based on portfolio optimization for multiple connections in wireless access networks and cognitive radio networks, find the way to incorporate the portfolio theory in the design of wireless resource scheduling, and investigate the application and performance of portfolio optimization based scheduling algorithm. Each connection admitted in the system is assigned a priority, which is updated dynamically based on its channel quality, QoS status, system specific considerations and user preferences. The proposed schemes can achieve a desired QoS level and provide flexibility in setting user preference levels.4. For cross layer resource scheduling base on user perceived quality of service, we incorporate the tolerance region based QoS model and the analysis theory of user perceived quality of service into the design of wireless resource scheduling. User perceived QoS in wireless environment is well investigated, and the corresponding policy is given. We regard user perceived QoS as a novel QoS parameter, and make it as the optimize objective to design the cross layer scheduling algorithm. The proposed schemes can clearly improve the degree of user satisfaction, and at the same time use the wireless resource efficiently.更多还原