José Alberto Fonseca

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—The requirement for flexible operation is becoming increasingly important in modern industrial systems. This requirement has to be supported at all system levels, including the field level in process industry, as well as the cell and machine control levels in manufacturing industry, where fieldbus-based communication systems are commonly found.(More)
—Currently, there is a trend towards the implementation of industrial communication systems using wireless networks. However, keeping up with the timing constraints of real-time traffic in wireless environments is a hard task. The main reason is that real-time devices must share the same communication medium with timing unconstrained devices. The VTP-CSMA(More)
The amount of information that must be exchanged in modern Digital Computer Control Systems (DCCS) and real-time industrial automation is now reaching the limits that are achievable with traditional fieldbuses. Currently, Ethernet is increasingly used in DCCS, however, the available solutions to guarantee real-time behaviour in Ethernet are not well suited(More)
An atomic broadcast protocol is a very important building block of any fieldbus based dependable distributed embedded system. Under certain error scenarios native CAN mechanisms do not enforce atomic broadcast and inconsistent message duplicates or omissions may occur. The probability of those error scenarios depend on an important factor , the CAN bit(More)
Non-preemptive scheduling is known for its lower efficiency in meeting temporal constraints when compared to preemptive scheduling. However, it is still used in certain cases such as in message scheduling over serial broadcast buses and in light multi-tasking kernels for embedded systems based on simple microprocessors. These cases are typically found in(More)
In this paper, we analyze the timing behavior of the EDCA communication mechanism defined in the IEEE 802.11e standard, when it is used to support real-time (RT) traffic. 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. Otherwise, the(More)