Open Access

Wireless systems continue to rapidly gain popularity. This is extremely true for data networks in the local and personal area, which are called WLAN and WPAN, respectively. However, most of those systems are working in the license-free industrial scientific medical (ISM) frequency bands, where neither resource planning nor bandwidth allocation can be guaranteed. To date, the most widespread systems in the 2.4 GHz ISM band are IEEE802.11 as stated in IEEE Std. 802-11 (1997) and Bluetooth, with ZigBee based in IEEE Std. 802.15.4 (2003) and IEEE802.15.4 as upcoming standards for short range wireless networks. In this paper we examine the mutual effects of these different communication standards. Measurements are performed with real-life equipment, in order to quantify coexistence issues.

Routing is a key feature for wireless sensor networks, as it extends the geographic range, enables larger installation and provides redundancy to packet transmission. A extensive variety of routing protocols has been designed for wireless sensor networks; however, until today, integration of unidirectional nodes poses a challenge. This paper proposes a routing algorithm to integrate unidirectional and even energy-autarkic nodes into an ad-hoc routing mechanism. It gives an insight into protocol development and various extensions, which proof the practical usability of the chosen approach as well for static and as for dynamic sensor nodes. The protocol was implemented and tested on EnOcean wireless nodes. It enables reasonable performance while causing very small overhead with regard to memory footprint and processing power.

The last several years have witnessed a paradigm shift in industry that has now ushered in the fourth industrial revolution era also referred to as Industry 4.0. This new technology promises major improvements in the industrial processes by connecting local and global networks for information exchange amongst smart machinery while integrating possibly all stages of the value chain. However, small and medium-sized enterprises (SMEs) still have many concerns about Industry 4.0 and about its potential benefits. This is generally as a result of high investment and conversion costs. An evaluation platform to test Industry 4.0 applications for enabling engineers and managers in identifying the potential benefits before making expensive decisions is attractive. With this aim, the authors present an extensible and customizable open source toolkit for the evaluation of Industry 4.0 applications by providing a complete set of capabilities from sensing of data at the shop floor to monitoring at the upper level of the enterprise.

Wireless sensor networks have found their way into a wide range of applications, among which environmental monitoring systems have attracted increasing interests of researchers. Main challenges for these applications are scalability of the network size and energy efficiency of the spatially distributed nodes. Nodes are mostly battery-powered and spend most of their energy budget on the radio transceiver module. In normal operation modes most energy is spent waiting for incoming frames. A so-called Wake-On-Radio (WOR) technology helps to optimize trade-offs between energy consumption, communication range, complexity of the implementation and response time. We already proposed a new protocol called SmartMAC that makes use of such WOR technology. Furthermore, it gives the possibility to balance the energy consumption between sender and receiver nodes depending on the use case. Based on several calculations and simulations, it was predicted that the SmartMAC protocol was significantly more efficient than other schemes being proposed in recent publications, while preserving a certain backward compatibility with standard IEEE802.15.4 transceivers. To verify this prediction, we implemented the SmartMAC protocol for a given hardware platform. This paper compares the realtime performance of the SmartMAC protocol against simulation results, and proves the measured values are very close to the estimated values. Thus we believe that the proposed MAC algorithms outperforms all other Wake-on-Radio MACs.

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.