【作者】 李文璟；

【导师】 孟洛明；

【作者基本信息】 北京邮电大学 ， 通信与信息系统， 2016， 博士

【摘要】 自组织网络(Self-Organizing Networks: SON)是移动通信网络长期演进(Long Term Evolution: LTE )系统中引入的概念。SON主要目的是通过无线网络的自配置、自优化和自治愈功能来提高网络的自管理能力,取代高成本的网络运营人员的人工介入,从而达到减少人力投入、降低网络运营成本、提高网络运营效率和质量的目的。小区中断补偿是自治愈中的一个功能,属于SON研究中的重要内容。在移动通信网中,有多种原因会引起小区通信中断现象,如基站出现软件或硬件故障、配置错误、停电等。小区中断补偿是通过对相关监测数据进行分析,触发相应的修复补偿功能,使得中断小区可以自主补偿故障造成的系统性能下降,从而达到保证网络服务质量的目的。小区中断补偿管理机制的研究对实现无线接入网自治愈具有重要作用,是无线通信网络领域和管理领域的关注热点。本文从小区中断补偿自主管理架构、面向多目标的小区中断补偿机制和优化算法两方面展开研究,主要研究内容包括:(1)为适应无线接入网自主小区中断补偿需求,本文对通用的自主管理控制环进行了增强,增加了“评估”环节,通过该环节对自主管理效果进行评估,再根据评估结果来调整自主管理策略和自主管理功能,使得小区中断补偿实现无人工干预的全自主闭环管理,为实现小区中断补偿机制和算法奠定了理论基础。(2)针对LTE/LTE-A网络和自组织网络发展初期,网元数量少、SON功能少的场景,研究了集中式自组织网络管理架构和相应的集中式小区中断补偿管理机制,并提出了基于参考信号(Reference Signal: RS)调整的集中式补偿方案生成算法。仿真实验验证了该算法在补偿小区中断引起的覆盖问题方面是有效的,同时对原有用户所带来的性能劣化处于可接受状态。(3)随着LTE/LTE-A网络规模的扩大,网元数量和SON功能的不断增加,集中式网络管理架构存在效率低、扩展性差、存在失效瓶颈等问题,为解决上述问题,研究了分布式自组织网络管理架构和相应的分布式小区中断补偿管理机制,并提出了基于RS调整的分布式补偿方案生成算法。仿真实验验证了该算法在实现中断补偿方面效果明显,确保了区域覆盖保持在较高的水平,并降低了覆盖交叠的产生概率,同时信号质量、吞吐量等性能指标也保持在可接受的水平,保障了区域的服务质量。(4)参考信号发射功率的调整是受限的,受到基站最大发射功率要求的限制,若无法再调整,则补偿效果难以达到,尤其是在广阔的农村区域,由于基站数量少、间距长、覆盖面积大,一般已经按照最大发射功率来进行初始设定,此时基于RS调整的覆盖补偿方案则不再可行,需要考虑采用其他方式来实现中断补偿。因此,本文研究了基于天线倾角调整的小区中断补偿管理机制及相应算法。仿真结果表明所提算法能够有效解决小区中断引起的弱覆盖和覆盖漏洞问题,同时用户的服务质量能够得到保证。在郊区场景中,基于倾角调整的补偿方案比基于功率调整的补偿方案更有优势。(5)小区中断补偿可以通过调整单个控制参数或联合调整多个控制参数来实现。对于大规模的复杂网络场景,可以根据需求和场景的不同,应用多种管理机制,即采用混合式自组织网络管理架构,因此本文研究了混合式自组织网络管理架构。同时,还研究了通过联合调节基站功率及倾角对中断小区进行补偿的机制与算法,仿真结果表明,功率和倾角联合调整方案可以满足补偿覆盖漏洞的要求,并达到了各项优化目标。更多还原

【Abstract】 The concept of Self-Organizing Network (SON) is introduced in Long Term Evolution (LTE) system. Main purpose of SON is to improve the self organizing ability of the network by the self-configuration, self-optimization and self-healing functions, to replace the high cost man-powered network operations, so as to reduce the manpower and operating costs, while enhance the efficiency and quality of the network. Cell Outage Compensation (COC) is one of the important functions of the self-healing. Cell outage is the total loss of radio services in the coverage area of a cell. There are diverse reasons for the cell outage in mobile communication network,including system hardware or software failures, power supply outage or configuration error etc. The aim of COC is to mitigate the performance degradation induced by the outage to the utmost extent by automatically analyzing the corresponding measurement data and adjusting the related radio parameters of the neighboring cells. The research of COC management mechanism plays an important role in the self-healing of the system, and becomes the hot spot in the wireless communication filed and network management field.The research of paper includes two aspects: autonomous COC management architecture and multiple objectives oriented COC algorithm. The main content of the paper are depicted as follows:(1) To satisfy the requirements of autonomous COC management, an evaluation step is added to the general autonomous management control loop. In the evaluation step,the effect of autonomous management is evaluated and management policies can be adjusted. Thus a closed control loop without human intervention is designed, which becames the theoretical base to realize the COC mechanisms and algorithms.(2) For the early development scenario of LTE/LTE-A network, where network elements and SON functions are few,the paper studies the centralized autonomous management architecture and corresponding centralized COC management mechanism, and proposes the Reference Signal (RS) adjustment based COC scheme generation algorithm. Simulation results show that the algorithm is effective in compensating the coverage problem induced by cell outage while the performance degradation of the compensating cells can be kept on the accepted levels.(3) With the development of LTE/LTE-A network, the number of network elements and SON functions is increased, in this case, the problems of centralized management architecture are emerged, such as low efficiency and bad expandability.To resolve the problems, the paper studies the distributed autonomous management architecture and corresponding distributed COC management mechanism, and proposes the Reference Signal (RS) adjustment based COC scheme generation algorithm. Simulation results show that the algorithm is effective to achieve outage compensation, ensuring regional coverage at a higher level, and reducing the emergence of coverage overlap. Meanwhile the performance is kept on the accepted levels guaranteeing the quality of services.(4) The adjustment of reference signal transmission power is limited. When the transmission power of base stations reaches the adjustment limitation, the coverage gap could not be compensated effectively, especially in the suburb area where transmission power has already been at its maximum because of the less stations and long distances. Thus the paper proposes the automated cell outage compensation mechanism and algorithm based on downtilt adjustments. The simulation results prove that the proposed optimization scheme can effectively solve the weak coverage problems caused by cell outage while the service quality can be maintained, and the performance of downtile based scheme is better than that of RS based scheme, especially in the suburb area.(5) COC can be realized by adjusting the single parameter or multiple parameters. In the scenario of large scale and complicated networks, the hybric autonomous network management architecture can be adopted. The paper studies the hybric autonomous network management architecture and proposes the COC mechanism based on joint optimization of power and tilt. The simulation results show that the joint adjustment scheme can reach the requirements of gap compensation, while the optimization objectives are realized well.更多还原