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Impedance-matched ferrite-loaded waveguide nonreciprocal phase shifters are designed using tJte method of field expansion into eigenmodes, which includes higher order mode interaction between the step discontinuities. Computer-optimized Ku-band ferrite stepped design examples, of 45°and 90°nonreciprocal differential phase shifts, attain typically about 2°phase error and less than-25 dB input reflection within a bandwidth of about 5 percent. Compact designs are achieved by thicker uniform ferrite slabs with dielectric transformer sections at each end. The theory is verified by comparison with available results from measurements and other methods.

Many of the benefits of an Internet of Things sensor network model stem from the extremely long service life of its base sensing layer. When data from the base sensing layer is provided by very low power technologies, such as Bluetooth Low Energy, a class of vulnerabilities called Denial of Sleep attacks can be especially devastating to the network. These attacks can reduce the lifespan of the sensing nodes by several orders of magnitude, rendering the network largely unusable. This paper investigates a Denial of Sleep attack against the Bluetooth Low Energy protocol that allows a malicious actor to rapidly drain the battery of a targeted sensing node, including power analysis, simulation results, and an example implementation. The outcome will be utilized to build better defenses and more predictable environments.

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In the busy and crowded environment of health care, accurate location information of mobile medical devices and personnel (e.g. patients or physicians) is often a major challenge. In this paper, we present a real-time asset tracking system deployed within a hospital clinic setting, which tracked a set of mobile assets using small WiFi tags. The deployed system utilized radio signals received from wireless access points to estimate location of tagged assets. The system performed with resolution of within 1.5 meters, which is an acceptable range in such an environment. We developed a web-based graphical interface and a data management system which was capable of tracking and reporting status of an asset and providing an alert signal when it moved out of a designated area. Additionally, detailed logs of asset tracking information were available for archival purposes. This deployment demonstrates the feasibility of a Wi-Fi based positioning system in dynamic medical environments.