Collaborative Research: Design and Restoration Techniques for Fault Tolerant Wireless Access Networks

在过去的十年中，支持移动通信的无线网络的部署有所增加，用户数量呈指数级增长。大多数无线网络作为无线接入网发挥作用，以提供对主要驻留在有线网络中的资源的不受束缚访问的手段。这种无线接入网络包括模拟和数字蜂窝电话网络、个人通信系统网络、许多无线局域网和移动数据服务。总的来说，尽管与有线网络相比，提供的服务质量和范围有所下降，但移动性的新颖性已经满足了当前无线接入网络的用户。随着正在进行的研究扩展了无线接入网络的功能，以更高的数据速率包括多媒体服务，公众对移动服务的需求和依赖将会增加。最终，用户将要求同样可靠的服务保证，这是基于有线的电信和数据网络的特点。公共交换电话网已经认识到在故障情况下提供通信服务的重要性，并对使这些网络具有生存能力和自愈能力给予了极大的关注。然而，很少重视对无线接入网络的理解或提高其生存性。无线接入网络的独特方面（例如，用户移动性、无线信道环境、节能等）意味着有线网络的生存性技术具有有限的适用性。该项目的目标是开发无线接入网络生存能力的综合处理方法。该项目将有两个主要重点。首先是生存性网络的设计与分析。将发展分析无线接入网生存能力的技术。这包括确定在正常和异常（故障）操作模式下对量化移动网络性能有用的指标，并确定评估指标的方法。给定适当的度量，将开发包含生存性策略的无线接入网络拓扑设计和容量分配算法。这包括蜂窝站点架构和将蜂窝连接到固定基础设施的网络拓扑。将讨论初始拓扑设计和修改现有拓扑以提高生存性的问题。其次，将开发流量恢复算法，其目的是在故障发生后充分利用可用的网络资源。这项工作将集中于基于优先级的流量恢复技术的设计和分析，以在最大限度地减少网络拥塞的同时为用户提供服务连续性。将开发涉及网络层之间协调策略的多层方法。恢复算法将适合于网络组件的自动调用，从而形成一个自愈网络。特别强调将分析故障后立即发生的瞬时网络拥塞，并将其影响纳入网络设计和流量恢复算法。另外一个重点将放在尽量减少无线接入网故障对所附有线传输和信令网络的影响上。这项工作将首先解决当前的无线接入网络（即pc），但随后将解决不断发展的无线接入架构，包括移动数据服务（例如，CDPD、GPRS）和下一代系统（例如，无线ATM）。该研究将使用优化、排队和通信理论等技术进行。此外，由于涉及的复杂性，将使用模拟与经验数据和启发式算法的使用相结合。本研究的意义在于其对有限的无线接入网生存性知识基础的贡献。研究结果将有助于未来设计和部署可生存的无线接入网。

The past decade has seen an increase in the deployment of wireless networks supporting mobile communication and an exponential growth rate in the number of users. The majority of wireless networks function as wireless access networks to provide a means for untethered access to resources that reside primarily in a wired network. Such wireless access networks include analog and digital cellular phone networks, Personal Communication Systems networks, many wireless local area networks, and mobile data services. In general, the novelty of mobility has satisfied users of current wireless access networks, despite the decrease in the quality and scope of service offerings as compared to wireline networks. As ongoing research extends the capabilities of wireless access networks to include multimedia services at higher data rates, an increase in the public's demand for and dependence on mobile services will result. Ultimately, users will demand the same reliable service guarantees, that is characteristic of wireline based telecommunications and data networks. The critical importance of providing communication service in the face of failures has been recognized in the public switched telephone network and a great deal of attention has been paid to making these networks survivable and self-healing. However, little emphasis has been placed on understanding or improving the survivability of wireless access networks. The unique aspects of wireless access networks (e.g., user mobility, wireless channel environment, power conservation, etc.) implies that survivability techniques for wired networks have limited applicability. The objective of this project is to develop a comprehensive treatment of survivability for wirelessaccess networks. The project will have two main thrusts. First is survivable network design and analysis. Techniques for analyzing the survivability of wireless access networks will be developed. This includes identifying metrics that are useful for quantifying mobile network performance during normal and abnormal (failure) operating modes and determining a methodology for estimating the metrics. Given appropriate metrics, wireless access network topology design and capacity allocation algorithms which incorporate survivability strategies will be developed. This includes the cell-site architecture and the topology of the network interconnecting the cells to the fixed infrastructure. Both initial topology design and the problem of modifying an existing topology to improve the survivability will be addressed. Secondly, traffic restoration algorithms will be developed which aim at making the best use of available network resources after a failure. This work will concentrate on the design and analysis of priority based traffic restoration techniques to provide users service continuity while minimizing network congestion. A multi-layer approach involving a coordinated strategy among network layers will be developed. The restoration algorithms will be suitable for automatic invocation by network components, resulting in a self-healing network. Special emphasis will be placed on the analysis of transient network congestion immediately following failures andincorporating its effect into the network design and traffic restoration algorithms. An additional focus will be placed on minimizing the effects of wireless access network failures on the attached wired transport and signaling networks. The work will initially address current wireless access networks (i.e., PCS), but will later address evolving wireless access architectures including mobile data services (e.g., CDPD, GPRS) and next generation systems (e.g., wireless ATM). The research will be conducted using techniques from optimization, queueing and communication theory. Additionally, due to the complexities involved, simulation combined with the use of empirical data and heuristic algorithms will be used. The significance of this research will be its contributions to the limited base of knowledge of wireless access network survivability. The results of the work should benefit the future design and deployment of survivable wireless access networks.