Anti-Lock Braking Systems (ABS) and Brake-by-Wire Systems (BBW) are safety-critical applications by nature. Such systems are required to demonstrate high degrees of dependability. Fault-tolerance is the primary means to achieve dependability at runtime and has been an active research area for decades. Fault-tolerance is usually achieved in traditional embedded computing systems through redundancy and voting methods. In such systems, hardware units, actuators, sensors, and communication networks are replicated where special voters vote against faulty units. In addition to traditional hardware and software redundancy, hybrid and reconfiguration-based approaches to fault-tolerance are evolving. In this article, we present a reconfiguration-based fault-tolerant approach to achieve high dependability in ABS BBW braking systems. The proposed architecture makes use of other components of less safety-critical systems to maintain high dependability in the more safety-critical systems. This is achieved by migrating safety-critical software tasks from embedded computer hardware that runs into a malfunction to other embedded computing hardware running less-critical software tasks. Or by using a different configuration in terms of the used speed sensors and type of ABS. The proposed architecture is on average 20% more reliable than conventional ABS architectures assuming equal reliabilities of different components.

The unprecedented growth in wireless communication is offering opportunities and challenges for educators. Thanks to technology advances and job opportunities, more and more students are interested in wireless communications courses. However, bridging the gap between classroom and real-world experience remains a challenge. Advanced undergraduate communications courses typically focus more on theory. Some courses are given online, and lack hands-on experiments. Driven by feedback from industry and students, we propose practical laboratory experiments that attempt to bridge the gap between classroom and real world. The laboratory exercises take advantage of the infrastructure of deployed wireless networks and allow students to measure, and analyze data, as well as to interact. The proposed labs can be used even in online courses. This paper describes the experiments proposed, the procedures and typical results. The experiments are tied to course objective.

Optical (infrared) wireless communications links offer an attractive solution for indoor applications. To enable terminal mobility and reduce temporal dispersion, a configuration known as multispot-diffusing (MSD) is used, which is a multiinput, multioutput (MIMO) architecture. In this configuration, a transmitter generates multiple narrow beams that get uniformly spread over a reflection surface accessible to a service area. A multibranch receiver with each branch having access to a diffusing spot (generated by transmitter) combines signals on its branches. This scheme creates multiple virtually ideal communications channels between a base station and terminals. This paper considers issues involved in the design of a transmitter-based holographic spot array generator. The generator produces equally-spaced diffusing spots on the room ceiling and/or walls. To overcome power limitation set by eye safety requirements, a receiver optical concentrator is proposed. Furthermore, to improve receiver signal-to-noise ratio, an optical filter that rejects optical noise is needed. Thus, functionally receiver branch optical front-end consists of an optical concentrator and an optical band-pass filter. A single holographic optical element, capable of performing both functions is proposed. Link performance is investigated by providing equivalent link model and comparing probability of error for a bare and a holographic receiver. From performance evaluations, our results show that it is possible to achieve an increase of 11 dB in the SNR and improve power budget by reducing the path loss by over 6 dB.

Spatial confinement of the paths traveled by infrared signals enables reuse of bandwidth and resources in adjacent indoor environments. This property can also result in undesirable shadowing that occurs whenever an obstacle blocks signal paths between transceivers. Shadowing compromises link reliability by increasing the error rate, and can result in service interruption. We propose spatial coding to improve link performance and alleviate the shadowing effect in multi spot diffusing, a multi-input, multi-output architecture. Spatial coding performance is compared to receiver multi-level combining. Our results show that when a channel is shadowed, 4-level combining at the receiver fails to maintain a reliable link irrespective of transmitted power. Using spatial coding over 6 channels, a reliable link is possible in the presence of a shadowed channel with an optical power penalty of 4.5 dB.

Traditionally, diffused infrared configuration has been studied with the assumption that the illuminated region is placed at room ceiling. This is done to ensure minimum path loss to a maximum number of receiver locations. In many practical situations, this arrangement might be difficult to implement, either due to the ceiling structure or the difficulty in illuminating the entire ceiling uniformly without introducing an intrusive transmitter. In this paper, we propose a new configuration, in which the upper regions of the walls are illuminated. Path loss and delay spread are used as performance measures to assess the feasibility of the proposed configuration.

Performance of a diffuse optical link may potentially be degraded by temporal dispersions resulting from surface reflections. In order to devise techniques to alleviate the adverse effect of dispersion, an accurate channel model is needed. Obtaining the impulse response (IR) for a given receiver location requires consideration not only of the direct path, but also of reflections up to nth order. The IR is only valid for a specific location and specific receiver parameters. If a receiver moves, the IR has to be recalculated. We propose a new approach for characterizing diffuse links that results in a tremendous saving in calculation and also gives more insight into the channel characteristics. The new approach is based on consolidating the dependence of receiver parameters, transmitter parameters, and the indoor environment into independent components. Thus, changing one of the parameters of the link requires recalculation of one of these components. The new model is utilized to obtain an accurate profile of delay spread and received power throughout a room.