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A Perspective on the IEEE 802.11e Protocol for the Factory Floor

Lucia Lo BelloEmanuele ToscanoSalvatore Vittorio

出版	INTECH Open Access Publisher, 2010
主題	Technology & Engineering / Automation
ISBN	95330702429789533070247
URL	http://books.google.com.hk/books?id=vYvFoAEACAAJ&hl=&source=gbs_api

註釋

This chapter addressed the case for wireless networks in automation and the significant efforts currently made by a large community of researchers, from both academia and industry, to investigate suitable solutions to adapt the IEEE 802.11e standard to the industrial communication needs on the factory floor. This chapter provided an overview of current literature concerning the use of IEEE 802.11e in industrial environment, focusing on real-time performance of both EDCA and HCCA mechanisms. The limits of such protocols have been discussed and some notable works to improve their real-time performance have been presented. Such works can be used and combined to improve the support for real-time industrial traffic. As an example, studies on the EDCA admission control algorithms that limit the workload in a wireless network might take advantage of some analytic models predicting the performance of the protocol from the workload and the protocol parameters to provide probabilistic guarantees. Finally, this chapter discusses the results from case studies that analyse the performance of IEEE 802.11e networks in realistic industrial scenarios. Despite the significant effort of researchers, there are still some open issues concerning the introduction of wireless local area networks (WLANs) in the factory floor. The most relevant is how to achieve performance guarantees while using an unreliable and non-deterministic wireless channel. Other open issues are: the integration with pre-existing wired networks, so as to form hybrid architectures that are still able to meet the performance requirements; the support for mobility and handover under real-time and reliability constraints; security and privacy of industrial communications; scalability of real-time wireless networks. All these issues are currently object of notable research efforts. Among these efforts, there is the Flexible Wireless Automation in Real-Time Environments (flexWARE) collaborative project, funded by the European Commission under the 7FP. This project aims at providing real-time communication on the factory floor with wireless local area networks (WLANs), with a special focus on security, flexibility and node mobility. The outcome of the flexWARE project will be a turnkey system that can overcome the restrictions of the state-of-the-art wireless real-time systems, which are bounded to a single cell, rather than a multiple cell network covering the whole factory, and will define a platform that fulfils the requirements of flexible wireless communications. In the flexWARE architecture, the wireless infrastructure is integrated with a real-time backbone network that can be used to connect different nodes spread over the entire factory floor. Moreover, such an infrastructure can transparently switch between access points. In addition, it can provide time synchronization, location awareness and security. All these features are offered without compromising on the real-time feature of the whole system.