Abstract
In recent years, the FlexRay communication protocol been promoted as a de facto standard for in-vehicular communication. In the FlexRay protocol, the communication timeline is organized as a sequence of four segments, whereas the static segment defines a set of slots specifically designed for the transmission of synchronous messages. In this paper, we investigate the following problem: "how to allocate a minimum number of static slots to each FlexRay node, while guaranteeing that all synchronous messages will be transmitted before their deadlines." Unlike previous studies that use linear programming based techniques, we evaluate the number of allocated slots using traditional response time analysis (RTA) techniques. The use of RTA techniques allow us to consider the timing requirements imposed by the set of synchronous message streams. Unlike other approaches, the RTA-based technique proposed in this paper is able to deal with a) message stream sets where periods are not multiple of the FlexRay cycle duration, b) generation of messages at the application layer that are not synchronized with the FlexRay cycle, and c) on-line scheduling of the traffic transferred during the static segment, according to its deadline requirements. The proposed technique is integrated as a RT-Middleware in each node, to take full advantage of the proposed allocation scheme. © 2012 IEEE.

Abstract
One of the motivations for use of wireless sensor networks (WSNs) in industrial environments is related to the reduced deployment and maintenance costs, when compared to the use of wired networks for connecting single I/O points. Nevertheless, a well-known problem for the use of wireless communication in industrial environments is related to the unreliable nature of the communication medium. Therefore, the search for communication reliability in WSNs is a relevant topic of research for the scientific community. In this paper we propose an innovative message retransmission scheme, based on network coding techniques, to increase the reliability of message exchanges in industrial environments. The proposed technique: NetCod, that improve the probability of message deliver by allowing the message retransmission whenever a loss occurs is experimentally compared with state of the art techniques: BlockACK, Redundant TDMA and Master/Slave. A comparative experimental assessment of these four techniques was performed using MicaZ motes. Metrics such as: message loss, message transmission delay and power consumption were used to comparatively assess the behavior of these retransmission techniques. © 2012 IEEE.

Abstract
When packets are transmitted over braided-paths in visual sensor networks some intermediate nodes may relay most part of the traffic, turning part or the entire network inactive when they run out of energy. Due to the nature of visual monitoring, source nodes may have different relevancies for the application, according to the desired monitoring tasks and the current sensors' poses and fields of view. Based on such relevancies, packets transmitted from different source nodes will have different relaying priorities, which are associated with energy thresholds. We propose an energy-efficient relay scheme where packets are forwarded to the next hop toward the sink only if the associated energy threshold is below the current energy level of the relaying node. Doing so, energy saving is achieved potentially prolonging the network lifetime, but with reduced impact to the overall monitoring quality of the application. © 2012 IEEE.

Abstract
In this paper we present an admission control mechanism to handle real-time traffic in IEEE 802.11 networks operating in open communication environments. The proposal is based on a non-preemptive EDF scheduling algorithm, combined with a measurement-based mechanism that assesses blockage times on medium access of real-time stations due to retransmissions and delays. This proposal will be part of the upper layer of the RT-WiFi architecture that was proposed by us in previous works. The main goal is to achieve a better compromise between medium utilization and timeliness. © 2012 IEEE.

Abstract
In this paper we assess the interference caused by external (uncontrolled) traffic sources upon real-time flows in IEEE 802.11-based mesh networks. Through a set of simulations, we assess the impact of external traffic sources by analyzing the end-to-end delay, frame loss ratio and deadline miss ratio as performance metrics for a set of real-time flows. We infer the maximum interfering traffic load that can be supported so that it does not negatively impact upon the behavior of the real-time flows. We highlight that there is a critical threshold load for the network above which the network can no longer reliably support real-time flows. © 2012 IEEE.

Abstract
In this paper, a TDMA-based mechanism is proposed for IEEE 802.11 Wireless LANs. This mechanism prioritizes real-time traffic in IEEE 802.11 networks, allowing the coexistence of standard stations with modified (real-time) stations in the same network-domain. The worst-case timing analysis of the TDMA-based mechanism shows that the service interval is upper-bounded, even when the communication medium is shared with timing unconstrained stations.