Non-FIFO processing of flows by network nodes is not a rare phenomenon. Unfortunately, the state-of-the-art analytical tool for the computation of performance bounds in packet-switched networks, network calculus, cannot deal well with non-FIFO systems. The problem lies in its conventional service curve definitions. Either the definition is too strict to allow for a concatenation and consequent beneficial end-to-end analysis, or it is too loose and results in infinite delay bounds. Hence, in this paper, we propose a new service curve definition and demonstrate its strength with respect to achieving both finite delay bounds and a concatenation of systems resulting in a favorable end-to-end delay analysis. In particular, we show that the celebrated pay bursts only once phenomenon is retained even without any assumptions on the processing order of packets. This seems to contradict previous work [15]; the reasons for this are discussed.

Abstract In this paper, we propose a system leveraging peculiarities of the wireless medium, such as the broadcast nature of wireless communication and the unpredictability of indoor signal propagation to achieve effective protection against attacks based on the injection of fake data. Using a real‐world WSN deployment and a realistic implementation of an attacker, we analyze this protection scheme and demonstrate that neither position change, transmission power manipulation, nor complete knowledge of wireless parameters can help an attacker to successfully attack the network. As a result, this work demonstrates how the chaotic nature of radio communication, which is often considered a disadvantage in regard to security objectives, can be exploited to enhance protection and support implementation of lightweight security mechanisms. Copyright © 2009 John Wiley & Sons, Ltd.

Networked sensors and actuators for purposes from production monitoring and control to home automation are in increasing demand. Until recently, the main focus laid on wired systems, although their deployment requires careful planning and expensive infrastructure that may be difficult to install or modify. Hence, solutions based on wireless sensor networks (WSNs) are gaining popularity to reduce cost and simplify installation. Clearly, one of the key issues rising from the switch to wireless communication lies in security; while an air gap is among the most effective security measures in wired networks, wireless communication is not as easy to isolate from attack. In this paper, we propose a system leveraging the peculiarities of the wireless medium, such as the broadcast nature of wireless communication and the unpredictability of indoor signal propagation to achieve effective protection against attacks based on the injection of fake data. Using a real-world WSN deployment and a realistic implementation of an attacker, we analyze this protection scheme and demonstrate that neither position change, transmission power manipulation, nor complete knowledge of wireless parameters can help an attacker to successfully attack the network. As a result, this work demonstrates how the chaotic nature of radio communication, which is often considered a disadvantage in regard to security objectives, can be used to enhance protection and support implementation of lightweight security mechanisms.

Many wireless sensor networks (WSNs) are used to collect and aggregate data from potentially hostile environments. Catering to this, early application scenarios did not put tight constraints on performance properties like delay, but rather focused on ruggedness and energy conservation. Yet, there is a growing number of sceanarios like e.g. production monitoring, intrusion detection, or health care systems which depend on the sensor network to provide performance guarantees in order to be able to act upon the phenomena being sensed in a timely fashion. Nevertheless, these applications still face the traditional issue of energy-efficiency. In this paper, we present means to find energy-efficient medium assignments in time-slotted multi-hop networks that satisfy given real-time constraints. Specifically, we present a way to find the optimal length of time slots and periods in TDMA schemes. We also present a software to compute those values for typical sink-tree WSNs. Index Terms--Wireless Sensor Networks, Energy-Efficiency, Real-time guarantees, Optimal TDMA, Network calculus.