Evaluation of Response Times in Industrial WLANs

The adoption of wireless communication technologies in industrial environments for supporting (soft) real-time applications heavily depends on the ability to grant bounded response times for messages, at least from a probabilistic point of view. This aspect is particularly important in factory automation systems, where response times are considered much more significant than other performance indices, such as throughput, that are usually considered in different application areas. The ever-increasing availability on the market of products and solutions based on the IEEE 802.11 standard and the introduction of the 802.11e amendment for enhancing the quality of service (QoS) and prioritizing traffic make this kind of communication technology interesting also for adoption in (loosely coupled) distributed control systems. This paper reports on some experimental measures and the related analysis that have been carried out on real 802.11g/e networks for better understanding the statistical distribution of response times and can be of help in characterizing these solutions when used to support noncritical real-time traffic.