Collaborative Research: QNATS - The Queueing Network Approximator for Time-Dependent Systems

该基金将为具有时变输入参数、特征和协议的一般到达/服务过程交换网络的数值分析和近似的算法和支持理论的开发提供资金。 其结果将是QNATS，时间依赖系统的网络逼近器- QNATS将包括分析系统的设施，在这些系统中，到达和服务机制随时间变化，以及节点容量和服务器数量的变化。 还将考虑作为时间的函数的实体从嵌入节点的确定性添加/删除。 QNATS将允许时间相关的到达间隔和服务时间分布是一般的形状，而不是教科书模型往往不切实际的时间相关的指数/泊松分布。 QNATS模型将很容易建立，QNATS分析将能够提供足够快的结果，通过Web服务交互式使用。QNATS模型是最广泛使用的技术之一，用于设计和提高制造业，服务业，数字电信和计算机系统的性能。 事实上，评估模型对于评估网络基础设施本身的性能非常有用。实际上，其中离散实体从一个或多个服务节点竞争资源的任何系统都可以表示为队列网络。 例如，时间相关的无限服务器集群网络已经成为分析蜂窝电信系统的标准模型。 其他应用来自各种各样的领域，包括生物学中的人口过程，迁移/移民过程和流行病学。QNATS将允许工程师和科学家在许多领域，以避免灾难性的后果时，随时间变化的系统特性被忽略或近似的时间平均值，导致严重低估系统拥塞。

This NSF grant will provide funding for the development of algorithms and supporting theory for numerical analysis and approximation of general arrival/service-process queueing networks having time-dependent input parameters, characteristics and protocols. The result will be QNATS, the Queueing Network Approximator for Time-Dependent Systems---an addition to the NSF Cyberinfrastructure of web-useable software that is available to the engineering and scientific community. QNATS will include the facility to analyze systems in which arrival and service mechanisms change with time, as well as queueing nodal capacity and the number of servers. Also considered will be deterministic additions/deletions of entities from queueing nodes as a function of time. QNATS will allow for time-dependent interarrival- and service-time distributions that are general in shape, rather than the often unrealistic time-dependent exponential/Poisson distributions of textbook models. QNATS models will be easy to build and QNATS analysis will be able to deliver results quickly enough to be used interactively via web services Queueing models are among the most widely used techniques to design and improve the performance of manufacturing, service-sector, digital-telecommunications and computer systems. In fact, queueing models are useful for assessing the performance of additions to the Cyberinfrastructure itself. Virtually any system in which discrete entities contend for resources from one or more service nodes can be represented as a network of queues. For example, time-dependent, infinite-server queueing networks have become a standard model for analysis of cellular telecommunication systems. Other applications come from a large variety of fields, including population processes in biology, migration/immigration processes, and epidemiology. QNATS will allow engineers and scientists in many fields to avoid the disastrous consequences that can occur when time-varying system characteristics are ignored or are approximated by their time-averaged values, leading to severe underestimation of system congestion.