中文摘要：

服务可用性分析是导航工程总体仿真验证与测试评估系统的核心模块之一，用于分析卫星导航系统提供的导航服务满足用户需求的时间百分比，能够直观地反映卫星导航系统服务能力。文章介绍了卫星导航系统服务可用性的相关概念，探讨了计算服务可用性的确定性算法和随机性算法，在此基础上提出了面向卫星导航系统的服务可用性仿真模型框架，并设计和实现了一个支持服务可用性分析的仿真系统。针对中国区域格网进行了服务可用性的仿真试验分析，验证了仿真模型框架和仿真系统的有效性。

英文摘要：

Service availability analysis is one of the key parts of analysis and evaluation of the navigation system, which is used to analyze whether the probability of the navigation service provided by the navigation system meets the users＇ need. The availability of service reflects the performance of the navigation system. In this article, the availability of service concept and feature of navigation system are introduced firstly, then the deterministic approach and random approach of availability of service determination are further studied. Based on these researches, the availabili ty of service-oriented simulation architecture is proposed, and meanwhile the simulation system supporting availability of service analysis is designed and implemented. Finally, simulation of the grid with 5° resolution is carried out, the related algorithms of service availability and the simulation architecture as well as the simulation system are testified.