Abstract
Due to the increased availability of low cost network technology, the use of networks to interconnect sensors, actuators and controllers is now widely accepted. Such increased availability is one of the driving factors for the implementation of smart sensor networks. To ensure the correctness of the supported applications, the communication network must provide a reliable and timely communication service. Aside from the Medium Access Control (MAC) protocol, one of the components that has a high impact in the communication delays is the local communication stack. Therefore, the usage of an adequate communication stack is of utmost importance to guarantee the timing correctness of the supported smart sensor applications. In this paper, we analyze the real-time aspects of a CAN-based smart sensor network. We assess the use of well established real-time scheduling algorithms to manage the outgoing queue of each of the local communication stacks. We show that it is possible to improve the responsiveness of applications supported by the CAN communication protocol, by using just a light scheduling middleware to adequately schedule each of the outgoing queues. We also show that implementing such middleware upon COTS communication hardware, it is possible to reduce the occurrence of priority inversions in the communication medium. Therefore it becomes possible to decrease the number of deadline misses even for highly loaded network scenarios. As a consequence, we advocate that CAN networks can be an interesting solution to support event-triggered smart sensor networks.

Abstract
A smart transducer is the integration of a sensor/actuator element, a processing unit and a network interface. Smart sensor networks are composed of smart transducer nodes interconnected through a communication network. This paper proposes a new architecture for smart sensor networks, that is driven by events (asynchronous data). The events are derived from a data compression algorithm embedded in the smart sensor, which compresses data from the sensor. The proposed architecture also provides configuration and monitoring data to manage the distributed system.

Abstract
This paper provides a comprehensive study on how to use Profibus networks to support real-time communications, that is, ensuring the transmission of the real-time messages before their deadlines. Profibus is based on a simplified Timed Token (TT) protocol, which is a well-proved solution for real-time communication systems. However, Profibus differences to the TT protocol prevent the application of the usual TT analysis. The main reason is that, conversely to the TT protocol, in the worst case, only one high-priority message is processed per token visit. The major contribution of this paper is to prove that, despite this shortcoming, it is possible to guarantee communication real-time behaviour with the Profibus protocol.

Abstract
PROFIBUS is an international standard (IEC 61158) for factory-floor communications, with some hundreds of thousands of world-wide installations. However, it does not include any wireless capabilities. In this paper we propose a hybrid wired/wireless PROFIBUS solution where most of the design options are made in order to guarantee the proper real-time behaviour of the overall network. We address the timing unpredictability problems placed by the co-existence of heterogeneous transmission media in the same network. Moreover, we propose a novel solution to provide inter-cell mobility to PROFIBUS wireless nodes.

Abstract
Fieldbus communication networks aim to interconnect sensors, actuators and controllers within distributed computer-controlled systems. Therefore, they constitute the foundation upon which real-time applications are to be implemented. A specific class of fieldbus communication networks is based on a simplified version of token-passing protcols, where each station may transfer, at most, one Single Message per Token Visit (SMTV). In this paper, we establish an analogy between non pre-emptive task scheduling in single processors and scheduling of messages on SMTV token-passing networks. Moreover, we clearly show that concepts such as blocking and interference in non pre-emptive task scheduling have their counterpart in the scheduling of messages on SMTV token-passing networks. Based on this task/message scheduling analogy, we provide pre-run-time schedulability conditions for supporting real-time messages with SMTV token-passing networks. We provide both utilisation-based and response time tests to perform the pre-run-time schedulability analysis of real-time RM/DM and EDF priority assignment schemes.

Abstract
In this paper we address the real-time capabilities of P-NET, which is a multi-master fieldbus standard based on a virtual token passing scheme. We show how P-NETS medium access control (MAC) protocol is able to guarantee a bounded access time to message requests. We then propose a model for implementing fixed priority-based dispatching mechanisms at each master's application level. in this way, we diminish the impact of the first-come-first-served (FCFS) policy that P-NET uses at the data link layer. The proposed model rises several issues well known within the real-time systems community message release jitter; pre-run-time schedulability analysis in non pre-emptive contexts; non-independence of tasks at the application level. We identify these issues in the proposed model and show how results available for priority-based task dispatching can be adapted to encompass priority-based message dispatching in P-NET networks.