We introduce an adaptive pacing scheme to overcome the drawbacks of TCP in wireless mesh networks with Internet connectivity. The pacing scheme is implemented at the wireless TCP sender as well as at the mesh gateway, and reacts according to the direction of TCP flows running across the wireless network and the Internet. TCP packets are transmitted rate-based within the TCP congestion window according to the current out-of-interference delay and the coefficient of variation of recently measured round-trip times. Opposed to the majority of previous work which builds on simulations, we implement a Linux prototype of our approach and evaluate its feasibility in a real 20-node mesh testbed. In an experimental performance study, we compare the goodput and fairness of our approach against the widely deployed TCP NewReno. Experiments show that our approach, which we denote as Mesh Adaptive Pacing (MAP), can achieve up to 150% more goodput than TCP NewReno and significantly improves fairness between competing flows. MAP is incrementally deployable since it is TCP-compatible, does not require cross-layer information from intermediate nodes along the path, and requires no modifications in the wired domain.

Microcontrollers, the brains of embedded systems, have found their way into every aspect of our lives including medical devices such as pacemakers. Pacemakers provide life supporting functions to people therefore it is critical for these devices to meet their timing constraints. This thesis examines the use of hardware co-processing to accelerate the calculation time associated with the critical tasks of a pacemaker. In particular, we use an FPGA to accelerate a microcontroller’s calculation time of the Kendall Tau Rank Correlation Coefficient algorithm. The Kendall Tau Rank Correlation Coefficient is a statistical measure that determines the pacemaker’s voltage level for heart stimulation. This thesis explores three different hardware distributions of this algorithm between an FPGA and a pacemaker’s microcontroller. The first implementation uses one microcontroller to establish the baseline performance of the system. The next implementation executes the entire Kendall Tau algorithm on an FPGA with varying degrees of parallelism. The final implementation of the Kendall Tau algorithm splits the computational requirements between the microcontroller and FPGA. This thesis uses these implementations to compare system-level issues such as power consumption and other tradeoffs that arise when using an FPGA for co-processing.

Mikroprozessorgesteuerte Implantate haben sich in zahlreichen Bereichen der Medizin etabliert. Physiologische, korpereigene Parameter werden erfasst, abgespeichert und konnen durch Telemetriesysteme weitergeleitet werden. Zusatzlich stehen Therapieoptionen zur Verfugung. Dazu zahlen Neurostimulatoren, welche im Bereich der Schmerztherapie und des fortgeschrittenen Morbus Parkinson erfolgreich angewendet werden ebenso wie Systeme zur Medikamentenapplikation. Beispielhaft hat sich die Entwicklung aktiver Implantate jedoch im Bereich der Herzschrittmacher- und Defibrillatortherapie vollzogen. Die vorliegende Arbeit beschaftigt sich mit der Erforschung physiologischer kardialer Parameter und ihrer Erfassung mit Hilfe von implantierbaren Sensoren. Dabei werden grundlegende technische Aspekte, die spezielle Sensorik zur Erfassung verschiedener Parameter und die Signalverarbeitung dargestellt. Es werden die bereits heute vielfaltigen Moglichkeiten implantierbarer kardialer Monitoringsysteme diskutiert. Neue Moglichkeiten wie das Monitoring ischamischer Ereignisse werden eroffnet. / Mikroprocessor controlled implantable systems are standard in many medical specialities. Physiological parameters can be recorded, stored and transfered via telemetry systems. In addition different therapeutic options are available: neurostimulation to treat patients with refractory pain and morbus parkinson, drug pumps for infusion of insulin etc.. Cardiac pacemakers and implantable cardioverter defibrillators were the driving force in the development of implantable sensors. We investigated different physiological cardiac parameters via implantable sensors. In this paper we discuss basic technical aspects, sensors, signal conditioning and signal analysis. The spectrum of available implantable sensors is shown. New options like the monitoring of transient myocardial ischemia are presented.