Abstract
WirelessHART currently appears as a leading solution for interconnection of wireless devices in industrial process control applications. However, the lack of knowledge about the influence of transient faults in WirelessHART networks can lead to the choice of less reliable topologies. In this work,we propose a simulation model to evaluate WirelessHART networks in the presence of transient faults. We assume that these faults result from noisy environments that disturb communications between devices. The model was developed using the Stochastic Petri Net (SPN) formalism, supported by the Mobius tool. For further developments, we target the development of an application that automates the assessment of a WirelessHART network in transient fault scenarios.

Abstract
In this paper, we propose a TDMA-based communication approach to be used upon the EDCA communication mechanism defined in the IEEE 802.11e standard. This approach allows the coexistence of realtime (RT) traffic together with uncontrolled (external) traffic sources. In the context of this paper, RT traffic means small sized packets generated in periodic intervals, which must be delivered before the end of the message stream period. The target of this paper is to highlight some limitations of the EDCA mechanism when supporting RT communication and to compare these results with those obtained with the proposed TDMA approach. We have assessed these two mechanisms considering an open communication environment, where there are RT and non-RT stations operating in the same frequency band. Furthermore, a realistic error-prone model channel was used to measure the impact of interferences against an error-free channel. We show that the proposed TDMA approach offers an almost constant access delay and it also improves the EDCA behavior in what concerns the average functional throughput and the average deadline losses.

Abstract
This work has the objective to present the first development results of a WirelessHART module for the ns-3. Our focus is the implementation of the Physical layer in order to provide the basis for the development of the superior layers such as MAC and Application. Thus, we presente an energy consumption model, a Gilbert/Elliot error model and an analysis for the currently avaliable ns-3 propagation loss models. For further development we mainly aim for the implementation of the time slot scheduler ( Network Manager) and the development of an inter protocol simulation with mutual interference.

Abstract
The paper proposes a simulation model which enables the evaluation of IEEE 802.11e EDCA networks, focusing in the behavior of the Enhanced Distributed Channel Access (EDCA) function associated to Quality of Service (QoS) stations. When compared with currently used simulation models, the proposed model provides a more accurate implementation of some aspects (timeouts, EIFS), a flexible implementation, and an easiness of use. Besides, a large number of different types of performance measures can be obtained. The model is based on a high level Stochastic Petri Net formalism referred as Stochastic Activity Networks (SAN), able to produce very compact and efficient models, and which is supported by the Mobius tool.

Abstract
Recently, the IEEE 802.11 a standard was published as an amendment to the original IEEE 802.11 standard. This amendment is intended to provide differentiated levels of QoS to the supported applications. The 802.11e amendment incorporates an. additional coordination function called Hybrid Coordination. Fraction. (HCF) that uses both a contention-based channel access method, called the Enhanced Distributed Channel Access (EDCA) and a controlled channel access, referred to as the HCF Controlled Channel Access (HCCA). Under the EDCA mechanism, it is a common assumption to consider the highest access category (voice) adequate to support real-time communication. In this paper, we analyze the timing behavior of the EDCA function, when it is used to support real-tune traffic. Basically, we assess the behavior of the voice category in open communication environments (i.e., a communication environment subject to eternal disturbances) when this access category is used to transfer small sized packets, generated in periodic intervals. We show that the transmission opportunity (TXOP) mechanism included in. the IEEE 802.11e amendment improves the system throughput, for the case of message streams with small packet sizes. However, the impact of external disturbances upon the transfer of real-tune messages is highly relevant. For instance, the average access delay for the real-time messages is more than one order of magnitude larger when. the external disturbance increases the network load from just 10% to 30%. Furthermore, both the number of packet losses anal the average size of the MAC queues forecast an. unacceptable number of deadline losses for the real-time message streams, even for intermediate load cases.

Abstract
In this paper, a new Traffic Separation mechanism (TSm) is proposed for CSMA-based networks. The TSm mechanism is intended to be used as an underlying traffic separation mechanism, able to prioritize traffic in CSMA-based networks. It allows the coexistence of standard CSMA (non-modified) stations with TSm (modified) stations in the same communication domain. When a station implementing the TSm mechanism has a high-priority message to transfer, it will impose its transfer prior to any message from standard CSMA stations. This behavior guarantees the highest transmitting probability to the TSm-enabled station in open communication environments. Therefore, the TSm approach can be used as an underlying mechanism to build real-time communication systems upon CSMA-based networks. The behavior of the TSm mechanism was assessed by simulation in the case of a relevant CSMA-based network (IEEE 802.11). The simulation analysis shows that the TSm mechanism guarantees values for both the throughput and the average access delay that significantly improve the results obtained for standard IEEE 802.11 stations.