[show abstract][hide abstract] ABSTRACT: The use of wireless technologies in Factory Automation is attractive due to several advantages (mobility, cost, etc.); however, to satisfy the requirements of industrial applications, they have to be improved in terms of real-time performance. Handover is a particular weakness in cellular wireless systems, e. g., in IEEE 802.11, since it may introduce delay beyond acceptable bounds. The project “<sup>flex</sup>WARE - Flexible Wireless Automation in Real-Time Environments” aims at implementing such an infrastructure based on IEEE 802.11. To enhance overall system performance, it offers a localisation service. In this paper we present the <sup>flex</sup>WARE handover mechanism which exploits localisation to reduce the discovery phase. A performance evaluation, based on simulation and empirical measurements, shows that the mechanism results in a seamless handover for a class of industrial applications.
[show abstract][hide abstract] ABSTRACT: Characterization of the behaviour of link-layer retransmissions is helpful when designing MAC protocols and scheduling algorithms for Factory Automation WLANs. In this paper, we measure retransmission rates and consecutive retransmission occurrences of IEEE 802.11g communication links in an industrial indoor environment. The employed wireless channel at 2.4 GHz is characterized. Experimental results show that the distribution of consecutive retransmission occurrences tends to concentrate around just one retry when devices operate within their transmission range. It is also shown that smaller frames result in fewer retransmissions.
Factory Communication Systems (WFCS), 2010 8th IEEE International Workshop on; 06/2010