Abstract
Energy consumption is a major issue in Wireless Sensor Networks (WSNs), as nodes are powered by chemical batteries with an upper bounded lifetime. Estimating the lifetime of batteries is a difficult task, as it depends on several factors, such as operating temperatures and discharge rates. Analytical battery models can be used for estimating both the battery lifetime and the voltage behavior over time. Still, available models usually do not consider the impact of operating temperatures on the battery behavior. The target of this work is to extend the widely-used Kinetic Battery Model (KiBaM) to include the effect of temperature on the battery behavior. The proposed Temperature-Dependent KiBaM (T-KiBaM) is able to handle operating temperatures, providing better estimates for the battery lifetime and voltage behavior. The performed experimental validation shows that T-KiBaM achieves an average accuracy error smaller than 0.33%, when estimating the lifetime of Ni-MH batteries for different temperature conditions. In addition, T-KiBaM significantly improves the original KiBaM voltage model. The proposed model can be easily adapted to handle other battery technologies, enabling the consideration of different WSN deployments.

Abstract
In the design of Wireless Sensor Networks (WSN), lifetime estimation is an important issue. This benchmark is closely related to the energy consumption of nodes. However, this assessment is not a trivial task. In such context, we propose an innovative energy measurement system for WSN. The designed system was employed for energy consumption measurements on a MicaZ node. With these measurements, a set of polynomial functions could be designed to emulate a realistic energy discharging curve for WSN nodes. These functions were then implemented in the OMNeT++ simulator to emulate the behavior of batteries discharging, potentially benefiting performance assessment of WSN. ©2013 International Information Institute.

Abstract
Wireless sensor networks can provide valuable information for a lot of measurement, tracking, surveillance, automation, and general-purpose monitoring applications. Information as humidity, temperature, pressure, infrared images, and noises will be sensed and packetized for distribution over the network, but corruption during transmission may compromise the accuracy of the retrieved information and even put people in danger. In fact, the sensed data may have different relevancies for the applications, altering the impact of packet corruptions. We propose a relevance-based partially reliable transmission approach to provide data delivery with different reliability guaranties, exploiting the relevancies of transmitted data when choosing the proper error recovery service. In this context, some error scenarios are investigated, considering different configurations of error bursts. We expect that the proposed partially reliable transmission mechanism can save energy over the network while assuring acceptable quality for sensing monitoring.

Abstract
X-by-wire applications have extremely demanding reliability requirements that are increasingly being addressed through the adoption of distributed and fault-tolerant architectures. The development of these applications is facilitated by the availability of high-level services such as agreement or reliable broadcast (RB). Some dependable communication buses, e.g., TTP-C, already provide these services, whereas FlexRay does not. In this paper, we present an approach to evaluate the reliability of a family of RB protocols implemented both on top of FlexRay and on top of ordinary time-division multiple access (TDMA). In particular, we evaluate the impact of the acknowledgment policy on the reliability of these protocols. We express the reliability as the probability of violation of the agreement and validity properties of the protocol during a mission. For that, we develop an analytical model based on discrete-time Markov chains, which considers a comprehensive set of faults (permanent, transient, omissive, and asymmetric) affecting both nodes and channels, and their effects on the protocol execution. The structure of the model is quite flexible and easily adaptable to other TDMA-based protocols. To assess the sensitivity of the protocol to both internal and external factors, we carried out a large number of experiments considering several network configurations and fault rates. The results show that for FlexRay, the negative-acknowledgment policy provides the same reliability as the positive-acknowledgment policy. However, for TDMA-based protocols that lack FlexRay's ability to distinguish silence from the loss of a message, the negative-acknowledgment policy leads to lower reliability, and its fitness for safety-critical applications depends on the system configuration and environment conditions.

Abstract
In this paper we propose a novel approach, named Real-Time Alternative-Route Definition (RT-ARounD), to support real-time message streams over large-scale wireless sensor networks. Starting from a standard cluster-tree topology, where each cluster has active and inactive periods, the proposal selects a set of nodes to build a mesh topology which is used during the inactive periods of the respective clusters to transmit messages with real-time requirements. This new topology is built considering shortest path routes between source and sink nodes. In that way, the number of hops that a real-time message needs to transverse can be drastically reduced, thereby improving the real-time responsiveness of the overall network. Moreover, the use of the inactive period guarantees that the normal cluster-tree operation remains unaffected.

Abstract
Availability is a major design issue that should play an important role when deploying and operating wireless sensor networks, specially for critical monitoring applications. Actually, sensing redundancy can be exploited to enhance the attainable availability level of sensor networks, since redundant nodes can replace faulty nodes. When employing camera enabled sensors, the perception of sensing redundancy is considerably changed" when compared to scalar sensors, with direct impact on network availability. In such way, some characteristics as deployment density, viewing angle and sensing range should be properly evaluated in wireless visual sensor networks, in order to better estimate the network availability. Nevertheless, when deploying visual sensors on occluded environments, viewed areas and resulted overlapping may be significantly altered, redefining sensing redundancy. We then propose an algorithm to automatically select redundant nodes in wireless visual sensor networks deployed on areas with occlusion, according to network configurations and application availability requirements. Additionally, an algorithm to adjust cameras' orientations in occluded environments is also proposed. Mathematical assessment of the proposed algorithms are performed, allowing the discussion of how parameters of deployed networks can influence applications monitoring availability.