【作者】 张翼德；

【导师】 李乐民；

【作者基本信息】 电子科技大学 ， 通信与信息系统， 2006， 博士

【摘要】 以无线蜂窝通信网为代表的移动通信系统是无线通信技术发展史上的一个里程碑。为了达到支持人们用任何形式互相交流任何信息资源的目标，蜂窝移动通信系统尚有许多关键的技术问题有待解决，其中为多业务的QoS(Quality of Service，服务质量)提供保障是最值得关注的问题之一。而为多业务提供QoS保障的关键是找到一种有效的无线资源管理策略。无线蜂窝通信网中由于无线资源的匮乏、底层恶劣的无线信号传播环境和信号衰落、用户的移动性、频繁的越区切换以及各种业务不同的业务特性，使得无线蜂窝通信网中多业务的QoS保障成为难以解决的问题。随着移动应用越来越普及，人们要求无线蜂窝网能够提供的服务也越来越多样化。下一代无线网络将能够承载多业务——话音、视频、图形图像和数据等，这些不同种类的业务具有不同的QoS要求和无线资源需求，这就要求多业务无线资源管理算法不仅能满足各种不同多业务应用的QoS要求，而且能充分利用无线蜂窝网中相对稀缺的无线资源(系统容量、带宽和功率等)。本文拟从系统设计的角度，针对多业务无线蜂窝通信系统的系统容量，以及多业务带宽分配方案和多业务呼叫接纳控制算法等几个重要的无线资源管理算法进行研究。本文第二章研究了在多业务无线蜂窝通信网中移动性对与系统容量有关的各种系统性能参数的显著影响。由于无线蜂窝通信网复杂的自然特性，移动性和系统容量之间不存在简单的线性关系。就现阶段研究来看，还没有针对无线蜂窝网在移动性和系统容量方面结论性的研究结论。针对无论是从移动终端(UE)还是基站(Node B)来说，接收到的信号都是源自不同发送源的合成信号，不容易得到其分布特性的解析公式，本文提出了用计算机仿真的方法来研究移动性对系统容量的显著影响。本文第二章建立了底层的无线传播模型、移动性模型，还综合考虑了保护信道(GC)机制和呼叫越区切换判据等因素，弥补了目前文献中一些假设条件过于简单或太理想化的不足，使之更符合无线蜂窝通信系统的实际情况。本文研究了移动性的变化对新呼叫阻塞概率(P_b)、切换呼叫中断概率(P_d)、呼叫强制中断概率(P_t)和系统整体的带宽利用率(BUR)等与系统容量有关的各种系统性能参数具体的显著影响。由于同时研究了移动性和保护信道(GC)机制，第二章的结论还适用于在无线蜂窝网中充分利用用户的移动性特性来调整系统提供QoS保障所涉及到的配置参数，以及动态地调整系统切换呼叫请求的保留门限，以提高系统的性能、容量和无线资源的使用效率。本文第三章提出了无线蜂窝通信网中的多业务带宽分配方案(BAS)。下一代无线蜂窝网中微微小区的系统设计导致更为频繁的越区切换，而各种业务不同的特性使得在越区切换过程中保障多业务必需的QoS更为困难。本文第三章提出了适合于自适应多媒体业务的多业务带宽分配方案(BAS)。虽然以可控的、受约束的方式降格(Degrade)系统中的自适应多媒体业务的QoS已经被证明是改良系统整体性能的一个有效方法，但是对被降格的呼叫进行补偿的机制很少在文献中被考虑。本文提出的多业务带宽分配方案(BAS)的特点之一是方案中兼顾了降格算法和补偿机制。针对文献中研究的一些QoS参数不能够完全反映出多业务带宽分配方案性能的各个方面，本文定义了四个新的与自适应带宽分配方案有关的QoS参数。本文还从理论上推导出BAS算法的理论上限性能，并且给出了数值计算结果。从获得的新呼叫阻塞概率(P_b)、切换呼叫中断概率(P_d)和系统整体的带宽利用率(BUR)等重要的系统性能参数来看，本文的BAS算法在理论上比文献中已有的一些经典算法有更好的性能，不仅能够满足各种不同应用的QoS要求，而且能充分利用无线蜂窝网中相对稀缺的无线资源。本文还使用计算机仿真的方法来分析与多业务自适应带宽分配方案有关的QoS参数的性能和对系统的影响，有利于深入理解影响自适应多媒体业务性能的各种参数，提高无线蜂窝网中无线资源的利用率。本文第四章提出了新的无线蜂窝通信网的多业务呼叫接纳控制算法(CAC)。当小区容量和无线资源的使用已处于饱和状态时，如果继续允许接纳新的用户进入到系统中来，将使已有用户的QoS无法得到必要的保障。对于多业务应用而言，接纳一个新到达的多业务呼叫对已有呼叫的QoS的影响更为明显。针对同时支持传统业务和自适应多媒体业务的多业务无线蜂窝通信网，本文第四章分别提出了对应的呼叫接纳控制算法，包括自适应多媒体业务基本层的CAC算法(CAC_B)，自适应多媒体业务增强层的CAC算法(CAC_E)，和非实时数据业务的CAC算法(CAC_D)。这些呼叫接纳控制算法之间可以配合运行，弥补了文献中呼叫接纳控制算法只能单独作用的不足。为了验证本文提出的多业务呼叫接纳控制算法的性能，本文针对支持自适应多媒体业务的无线蜂窝网的不同运行情形，进行了计算机仿真。本文的计算机仿真结果有利于无线蜂窝系统同时利用自适应多媒体业务特性和用户移动性特性来进行系统设计与规划，调整提供QoS保障所涉及的系统性能参数，提高无线资源的使用效率，平衡系统中的负载和确保在用户之间合理的公平性。本文采用计算机仿真的方法来验证以上所提出的各种算法理论分析的正确性以及各项性能指标。本文所有的无线资源管理算法和无线蜂窝网性能分析的仿真是在一个无线蜂窝网仿真平台上完成的。本文第五章对这些仿真工作进行了简要总结，介绍了这个无线蜂窝网仿真平台主要结构，并且给出了主要的流程图和仿真研究时所用的部分代码。本文第六章对全文的工作进行了简要的总结，提出了对未来进一步研究的建议。更多还原

【Abstract】 Wireless mobile communication system, represented by wireless cellular networks, is a milestone in the history of wireless communication technology. In order to support people to mutually communicate in any form of information resources, there are various issues have to be carefully examined in Wireless Cellular Networks, such as providing QoS guarantee for multi-service. One of the key elements in providing QoS guarantee for multi-service is an effective Resource Management Strategy. The lack of available radio resources, the scarcity and extreme fluctuation of available link bandwidth, the user mobility and frequent handoffs, and various characteristics of different services in the wireless cellular networks makes providing QoS guarantee for multi-service a very tough task. As the widely deploying of mobile applications, the demand for providing multi-service in wireless cellular networks becomes more imperative. The next generation of networks is expected to eventually carry multimedia traffic-voice, video, images, or data, or combinations of them. Since different traffic has diversified QoS and radio resource requirements, multi-service Resource Management Strategy not only has to ensure that the network meets the QoS requirements of different applications, but at the same time has to fully utilize the scarce wireless resources (system capacity, bandwidth, or power) available in the wireless cellular networks. This dissertation studies the capacity performance of the multi-service wireless cellular networks and other key radio resource management algorithms-bandwidth allocation scheme and call admission control algorithm.Chapter 2 of this dissertation reveals that the mobility influences on the capacity-related parameters in wireless cellular networks are conspicuous. Due to the complex nature, there does not seem to exist a simple linear relationship between mobility and capacity. To the best of the author’s knowledge, there has been so conclusive study on mobility and capacity for wireless cellular networks. As the statistics of the signals received by the mobile users from different base stations is hard to gain, whether to the user equipment (UE) or the basestation (Node B), computer simulation is used to study the mobility influences on capacity in wireless cellular network. The propagation model, the mobility model and traffic model are established in chapter 2, with concerns of guarded channel (GC) mechanism, handoff criterions and a simple power control algorithm, and some simplified or idealized assumptions adopted in current literatures are improved to better sketch the characterizations of practical system. The conclusion derived in this chapter could be utilized for dynamically adjusting the configuration parameters providing QoS guarantee and the reservation threshold of GC mechanism for handoff connections in wireless cellular network, which could improve the system performance, system capacity and the utilization of radio resource.Chapter 3 of this dissertation studies the multi-service Bandwidth Allocation Scheme algorithm (BAS). The system designing of next generation wireless cellular networks employing pico-cell will make handoff occurring much more frequently, which makes it more difficult to provide QoS guarantee for multi-service during handoff period, with concerning various characteristics of different services in the wireless cellular networks. The multi-service Bandwidth Allocation Scheme algorithm (BAS) for adaptive multimedia services is proposed in this chapter. In order to fully utilize the system resources, degrading the QoS of existing multimedia traffic in a controlled manner has been shown as an effective way to improve the overall system performance. However, compensation mechanisms are seldom considered in the literatures. One of the characteristic of the proposed multi-service BAS for adaptive multimedia services is the employment of the degradation policy and compensation mechanism. The performance analytical upper bounds of the proposed algorithm are also deduced in this section, with the numerical simulation results. In order to fully study the performance of multi-service BAS, four new QoS parameters related to multi-service BAS are defined. The numerical simulation results of the system performance parameters considered in this section-New Call Blocking Probability (P_b) and Handoff Call Dropping Probability (P_d) and system overall Bandwidth Utilization Rate (BUR)-show that the proposed algorithm outperforms other algorithms in the literature, in that it could not only fulfills the QoS requirement of different applications, but also efficiently utilizes the scarce radio resources in the system. Furthermore, this chapter also conducts computer simulation to demonstrate the performances of the new QoS parameters related to multi-service BAS and their impacts on the system performance, which will help us to better understand the nature of the performance of adaptive multimedia service, and improve the utilization of radio resources in wireless cellular networks.Chapter 4 of this dissertation studies the multi-service Call Admission Control algorithm (CAC). Admitting more users than the capacity into system will make the already admitted users suffer a loss of QoS, especially for the newly coming multi-service call, when the cell capacity and radio resources are depleted. Chapter 4 presents corresponding Call Admission Control (CAC) algorithms for different multi-service, including CAC algorithm for the basic layer (CAC_B), CAC algorithm for the enhancement layers (CAC_E), and CAC algorithm for non real-time data services (CAC_D). In order to valid the proposed multi-service CAC algorithms, computer simulations are carried out due to different scenario of the deployment phases of wireless cellular networks supporting adaptive multimedia service. The simulation results will benefit the system designing and planning of wireless cellular networks based on the characteristic of adaptive multimedia service and user mobility, as well as help dynamically adjusting the configuration parameters providing QoS guarantee, improving the utilization of radio resources, balancing the load of the system and ensuring the rational fairness among all users.Chapter 5 of this dissertation summarizes the simulation software. Simulation software is developed to verify and evaluate the proposed algorithms in this dissertation. All of the proposed radio resource management algorithms and the performance analysis are based on a wireless cellular network simulation platform. Chapter 5 presents the main frame of the simulation platform, the main parts of the software flow diagram and some of the selected codes. Chapter 6 of this dissertation concludes this dissertation, presents some suggestions for future research on some issues.更多还原