It is a generally accepted fact that software ages over time. This requires software products to be replaced once their ageing inhibits the goals of the organization owning the product. However, few techniques are available for quantifying the negative effects of ageing software. In this extended abstract, we present an approach to quantifying the ageing of a software architecture. The approach can, among others, be used to decide upon the retirement of a software product line. Validation of the approach is in progress, but not reported upon in this extended abstract.
As the number of wireless sensor network applications continues to grow, the need for specialized task scheduling mechanisms, aware of the sensor devices' capabilities and real-time resource availability, is becoming more and more apparent. In this paper, we therefore propose a generic model for task scheduling in heterogeneous networks, which we subsequently use to schedule distributed reasoning tasks, originating from a real-world WSN monitoring and management application. By means of simulation, we evaluate several developed scheduling heuristics and compare the results to an optimal solution of the same WSN task scheduling problem, obtained using ILP. Experiments show that our heuristics produce acceptable task schedules while maintaining a low resource footprint.
Energy harvesting has been steadily gaining interest in the wireless sensor network community. Instead of minimizing the energy consumption and maximizing a network’s operational time, the main challenge in energy harvesting sensor networks is to maximize the utility of the application subject to the harvested energy. One major challenge is to maximize the data delivery rates by exploiting the spatial variations of environmental energy. While there exists a multiplicity of energy-aware routing protocols for sensor networks without energy harvesting capabilities, only a small number of routing protocols have been published which explicitly account for energy harvesting. In this paper, we analyze and compare three state-of-the-art routing algorithms. While the original algorithms assume an idealized medium access control (MAC), a lossless wireless channel and global knowledge, we show that these assumptions lead to delusive results. We detail these findings by showing the influence of a low-power MAC protocol, a realistic wireless channel and the protocol overhead. Moreover, we show how to optimize the parameters of the MAC protocol for a given network configuration. By conducting various evaluations, we identify that our modified version of the R-MPRT algorithm outperforms the evaluated algorithms in scenarios where little energy is harvested from the environment.
The scale and complexity of advanced cyber-physical systems (CPSs) are steadily growing. Most new-generation CPSs being developed or to be developed involve networked embedded computing (NEC) devices. The state of the art in software engineering for such network-based CPSs is weak. Major problems faced are the low quality of network-based CPS software and the low productivity of CPS software engineers. One type of desirable advance in enhancing the state of the art is to establish high-level programming tools boosting the productivity of software engineers. Here additional types of desirable advance are discussed. Specifically, the establishment of methods and tools for quantitatively analyzable fault tolerance design as well as for design of time-constrained security enforcement is proposed.
Using directional antenna in ad hoc networks, offer many benefits in contrast to their classical omni-directional counterparts. The most important benefits are the significant improvement in spatial reuse, reduction of the radio interference, increase in coverage range and subsequently an increase in network capacity on the whole. On the other hand, directional transmission increases the hidden terminal problem and the problem of deafness. To best utilize directional antennas, a suitable Medium Access Control (MAC) protocol must be designed. Current MAC protocols, such as the IEEE 802.11 standard for Wireless LANs, assume the omni-directional antenna at its Physical layer and thus does not fully exploit the capabilities of a directional antenna. In this paper, we propose a MAC protocol for wireless ad hoc networks which fully exploits the potentials of directional antennas. We evaluate our work through simulation studies performed on the network simulator – NS2. Numerical results show that our protocol offers significant improvement in throughput when compared to the performance of traditional 802.11 MAC protocol and D-MAC which is a Directional MAC protocol for ad hoc networks.
