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The application of leaky feeder (radiating) cables is a common solution for the implementation of reliable radio communication in huge industrial buildings, tunnels and mining environment. This paper explores the possibilities of leaky feeders for 1D and 2D localization in wireless systems based on time of flight chirp spread spectrum technologies. The main focus of this paper is to present and analyse the results of time of flight and received signal strength measurements with leaky feeders in indoor and outdoor conditions. The authors carried out experiments to compare ranging accuracy and radio coverage area for a point-like monopole antenna and for a leaky feeder acting as a distributed antenna. In all experiments RealTrac equipment based on nanoLOC radio standard was used. The estimation of the most probable path of a chirp signal going through a leaky feeder was calculated using the ray tracing approach. The typical non-line-of-sight errors profiles are presented. The results show the possibility to use radiating cables in real time location technologies based on time-of-flight method.
The increasing number of transistors being clocked at high frequencies of modern microprocessors lead to an increasing power consumption, which calls for an active dynamic thermal management. In a research project a system environment has been developed, which includes thermal modeling of the microprocessor in the board system, a software environment to control the characteristics of the system’s timing behavior, and a modified Linux scheduler, which is enhanced with a prediction controller. Measurement results are shown for this development for a Freescale i.MX6Q quad-core microprocessor.
In this work we describe the implementation details of a protocol suite for a secure and reliable over-the-air reprogramming of wireless restricted devices. Although, recently forward error correction codes aiming at a robust transmission over a noisy wireless medium have extensively been discussed and evaluated, we believe that the clear value of the contribution at hand is to share our experience when it comes to a meaningful combination and implementation of various multihop (broadcast) transmission protocols and custom-fit security building blocks: For a robust and reliable data transmission we make use of fountain codes a.k.a. rateless erasure codes and show how to combine such schemes with an underlying medium access control protocol, namely a distributed low duty cycle medium access control (DLDC-MAC). To handle the well known problem of packet pollution of forward-error-correction approaches where an attacker bogusly modifies or infiltrates some minor number of encoded packets and thus pollutes the whole data stream at the receiver side, we apply homomorphic message authentication codes (HomMAC). We discuss implementation details and the pros and cons of the two currently available HomMAC candidates for our setting. Both require as the core cryptographic primitive a symmetric block cipher for which, as we will argue later, we have opted for the PRESENT, PRIDE and PRINCE (exchangeable) ciphers in our implementation.
Extended Performance Measurements of Scalable 6LoWPAN Networks in an Automated Physical Testbed
(2015)
IPv6 over Low power Wireless Personal Area Networks, also known as 6LoWPAN, is becoming more and more a de facto standard for such communications for the Internet of Things, be it in the field of home and building automation, of industrial and process automation, or of smart metering and environmental monitoring. For all of these applications, scalability is a major precondition, as the complexity of the networks continuously increase. To maintain this growing amount of connected nodes a various 6LoWPAN implementations are available. One of the mentioned was developed by the authors' team and was tested on an Automated Physical Testbed for Wireless Systems at the Laboratory Embedded Systems and Communication Electronics of Offenburg University of Applied Sciences, which allows the flexible setup and full control of arbitrary topologies. It also supports time-varying topologies and thus helps to measure performance of the RPL implementation. The results of the measurements prove an excellent stability and a very good short and long-term performance also under dynamic conditions. In all measurements, there is an advantage of minimum 10% with regard to the average times, like global repair time; but the advantage with reagr to average values can reach up to 30%. Moreover, it can be proven that the performance predictions from other papers are consistent with the executed real-life implementations.