Today Wireless Sensor Networks (WSNs) can be found in many application areas, e.g. they are used in smart home systems or in industrial settings in order to monitor and control machinery. The latter usually requires a guaranteed performance of the network. This mainly addresses the real-time capability of the network, i.e. knowledge of possible delays which occur on the multi-hop route between sender and receiver is needed. In this paper, a novel approach to model multi-hop networks with a fixed number of nodes uniformly distributed on a square area is proposed. Accordingly, no explicit knowledge of the routing and the topology is needed. That is, no specific network is reflected, but a class of random networks sharing common properties is modelled. In our model, all nodes generate frames according to a Poisson process with the same rate and send them to a common gateway. Based on this scenario, we deduce a mathematical model for the probability of simultaneous transmissions assuming that a generic CSMA MAC protocol is implemented. We use this result in order to derive an expression for the mean delays arising on the links, i.e. the medium access and queueing delay, of the multi-hop route in the special case of the IEEE 802.15.4 MAC and PHY protocols being used. The model results correspond well to an OMNeT++ simulation if the offered traffic does not exceed a certain limit. Beyond this limit, up to the capacity of the network, the model still captures the behaviour of the simulation but the deviation grows.

In autonomous platooning of vehicles, robust Cooperative Adaptive Cruise Control (CACC) systems are required for guaranteeing reliable and stable driving performance. Cruise control systems should meet two requirements: prevent collisions between vehicles in any event and prevent amplification of distance errors along the platoon. The absence of one of these requirements causes weak road utilization and fuel efficiency and eventually leads to decreased safety. By usage of suitable control system parameters and deployment of appropriate means of communication between members of a platoon, these risks may be minimized. In this research, an evaluation platform for stability and risk-of-collision of autonomous vehicle platoons is developed. It allows for performance analysis for a large range of controller specifications and network characteristics by extensive simulation based on real-world vehicle parameters. The experiments show platoon performance limits caused by communication constraints and control system specifications. First results suggest that the choice of controller parameters strongly affects communication system requirements. Larger distances and more aggressive controller gains can reduce demands on the radio link to a great extent. The contribution of this work is twofold: firstly, platoon performance of correlated network errors is evaluated broadly and secondly, performance dependencies between communication limitations and the control design are shown.

On-board commercial passenger aircraft Wireless Sensor Networks (WSNs) are anticipated to be used for implementing machine-to-machine communication also referred to as Wireless Avionics Intra-Communications (WAIC). These systems enable safety-related wireless avionics and aim to reduce electrical wiring harness contributing by 5% of the total weight of an aircraft. The globally harmonized frequency band designated for WAIC usage is shared with aeronautical Radio Altimeters (RAs). Literature lacks consideration of the impact of on-board RAs on WAIC systems; thus, we close this gap by performing a detailed study and propose two mitigation techniques based on channel hopping. Our simulations show that harmful RA signals infer doubled to tripled delays as well as packet error rates up to 90% when WAIC systems use the frequency band without applying appropriate techniques for increasing communication robustness. With the developed mitigation techniques, we show delays can be kept at levels comparable to non-interfered performance while increasing the usable spectrum by 50% simultaneously. Our evaluations show that the presented mitigation techniques enable reliable usage of WAIC systems in commercial aircraft allowing increased spectrum usage.

In recent years the usage of Wireless Sensor Networks (WSNs) for industrial applications (robotics, process automation, monitoring and control of critical systems) is gaining momentum. The dependability is one of the main pillars for the requirements in these application areas and can be defined in terms of reliability and maintainability. The definition of reliability is dependent on the application requirements. The motivation of this work is to model dependable WSNs so that e.g. the topology or configuration in general can be determined for given requirements regarding the metrics introduced.