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Building wireless sensor networks based on the IEEE 802.15.4 standard is an interesting option, as the standard enables low-power, low data rate wireless communication. Many authors analyzed and optimized the operational phase of such networks. In contrast, the initial phase, containing the 802.15.4 association procedure, has mostly been neglected. In this paper, we therefore propose four optimization...
Cognitive radio (CR) is a key enabler of wireless in industrial applications especially for those with strict quality-of-service (QoS) requirements. The cornerstone of CR is spectrum occupancy prediction that enables agile and proactive spectrum access and efficient utilization of spectral resources. Hidden Markov Models (HMM) provide powerful and flexible tools for statistical spectrum prediction...
Realistic traffic modeling plays a key role in efficient Dynamic Spectrum Access (DSA) which is considered as enabler for the employment of wireless technologies in critical industrial automation applications (IAA). The majority of models of spectrum usage are not suitable for this specific use case as they are based on measurement campaigns conducted in urban or controlled laboratory environments...
In applications with strict requirements regarding reliability and real time capability such as factory and process automation, it is critical to detect sources of interference that might corrupt data packets leading to retransmissions and delays. To tackle this issue we propose a method for measuring and quantifying radio interference using higher-order statistics. Unlike traditional energy detectors...
In the course of increasing the production flexibility and dynamics, the replacement of wired industrial monitoring and control systems by wireless solutions is ongoing. To offer a similar degree of reliability as wired solutions, the IEEE 802.15.4e, targeting factory automation, defines the Time Slotted Channel Hopping (TSCH) mechanism. It appears promising to reach a timely, reliable and energy...
In factory automation where reliable low-delay communication is essential to maintain the required Quality of Service (QoS), efficient medium access schemes play quite an important role. Therefore we propose a centralized cognitive medium access method that utilizes prediction of whitespaces to avoid collisions as well as improve utilization of transmission opportunities. Our simulation results show...
The paper is devoted to modeling wireless mesh networks (WMN) through mixed-integer programming (MIP) formulations that allow to precisely characterize the link data rate capacity and transmission scheduling using the notion of time slots. Such MIP models are formulated for several cases of the modulation and coding schemes (MCS) assignment. We present a general way of solving the max–min fairness...
Developed societies have a high level of preparedness for natural or man-made disasters. But such incidents cannot be completely prevented, and when an incident like an earthquake or an accident in a chemical or nuclear plant hits a populated area, rescue teams need to be employed. In such situations it is a necessity for rescue teams to get a quick overview of the situation in order to identify possible...
Wireless mesh networks (WMNs) are a convenient type of Internet access networks, because they are self-configuring and self-healing wireless multi-hop networks. This is in particular true for IEEE 802.11 based WMNs as they cover large areas, are easy and cheap to setup, and provide sufficient capacity. Despite these advantages, WMNs have not yet entered the mass market. One of the reasons for this...
The problem how to determine the capacity of and achieve fairness in mesh networks is one of the key topics in practical and theoretical research on mesh networks. Max-min fairness is one way to define fairness and several algorithms how to compute max-min fair rate allocations are already published. In this paper we make two major contributions to this area of research: First, we formulate an algorithm...
During the last years so-called ``Thin Client'' architectures have become very popular. Thin Clients are simple end user devices, which are provided with content and services by powerful servers. Originally this concept was developed for Local Area Networks (LANs), which provide a high Quality of Service. If they are used in Wide Area Networks (WANs) they need to be adjusted accordingly in order to...
The IEEE 802.11 standard supports a variety of modulation and coding schemes (MCSs). In 802.11-based wireless mesh networks (WMNs) it is hence possible to adapt the link rate to the channel conditions. In particular, smaller link rates may be accepted for an increased spatial reuse. In an earlier study, we showed that this effect is suitable for increasing the max-min fair share throughput in a WMN...
Models and proposals for capturing the energy consumption of sensor nodes are plentiful. The majority of those approaches roughly agree about the energy consumed in the states of the sensor node duty cycle, but the costs of radio operations are abstracted very differently. In our work, we establish a general framework whose modular structure allows to compare existing abstractions and to investigate...
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