Abstract

Abstract
The operation of networked control systems strongly depends on the performance of its communication infrastructure. Therefore, their evaluation becomes an important aspect to be considered, particularly in situations where network traffic has real-time constraints and the network operates in faulty environments. In this paper a set of faull injection experiments were performed on a Profibus-DP network in order to assess the impact of faulls in the network operation. The experiments reproduce typical conditions found in industrial applications, considering different traffic loads and faull scenarios. Several performance metrics were evaluated, such as the bus cycle time, messages response times and worst case response times. Copyright © 2007 IFAC.

Abstract
In this paper, we propose the VOA algorithm (Variable Offset Algorithm) to deal with the optimization of communication efficiency in dense WSN s with star topologies. The use of the VOA algorithm has been assessed by means of an experimental setup. The results highlight that the use of the VOA algorithm, implemented as a light middleware at the application layer, clearly enhances the communication efficiency in a WSN with star topology. © 2010 IEEE.

Abstract
In this paper, a new traffic separation mechanism is proposed for IEEE 802.11e networks. Such Traffic Separation Mechanism (TSm) allows the coexistence of CSMA standard stations with modified (real-time) stations in the same network domain. A station implementing the proposed TSm scheme has the same operating behavior as a standard IEEE 802.11e network station, except in what concerns the evaluation of the backoff delay. For the case of stations implementing the TSm scheme, whenever they have traffic to transfer, they eventually impose its transfer prior to the transfer of any other message with lower priority. This behavior guarantees the highest transmitting probability to the TSm stations in an open communication environment, where multiple IEEE 802.11e standard stations may coexist with a subset of TSm-enabled real-time stations.

Abstract
The paper proposes a dependability model which the evaluation of Profibus-DP networks in scenarios transient faults which affect data communications. The behavior of Profibus-DP communication stack is including: cyclic process data exchange between and slave stations; configuration, parameterization and agnostics of slave stations. The model is based on a level Stochastic Petri Net formalism referred as Activity Networks (SAN), supported by the Mobius High modeling power, state-of-the-art analytical and lation solutions, and a flexible and integrated are their main features. Dependability measures are lished from the fulfillment of the real-time (deadlines) defined on process data messages between master and slave stations. The reward concept used to define the measures, which are obtained by of a simulation approach. A case study is proposed to assess the model performance.

Abstract
The paper presents a framework to evaluate dependability of PROFIBUS-DP networks. An hierarchical modeling approach is proposed, which considers both the effects of different kinds of faults - permanent, transient and common-cause square and the interaction between hardware and software components. Stochastic Petri Nets are used as the modeling technique to obtain dependability models, with emphasis in the use of analytical/numerical methods to provide model's solutions. In scenarios where its difficult to apply this approach, compact simulation models are derived.