Matthias Wellens

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Several measurement campaigns have shown that numerous spectrum bands are vacant although licenses have been issued by the regulatory agencies. Dynamic spectrum access (DSA) has been proposed in order to alleviate this problem and increase the spectral utilization. In this paper we present our spectrum measurement setup and discuss lessons learned during(More)
Dynamic spectrum access (DSA) has been proposed as a solution to the spectrum scarcity problem. However, the models for spectrum use, that are commonly used in DSA research, are either limited in scope or have not been validated against real-life measurement data. In this paper we introduce a flexible spectrum use model based on extensive measurement(More)
In this poster we discuss research challenges one needs to overcome to introduce intelligent methods to wireless communications. Recent research on cognitive radios has started to introduce machine learning and reasoning techniques to wireless networks. However, while these first steps with cognitive radios are certainly exciting, they have been very(More)
Dynamic spectrum access is an integral part of the Cognitive Radio paradigm. However, efficient spectrum sensing techniques are crucial on the way towards systems, which use idle spectrum bands opportunistically and increase the overall spectral efficiency. Current spectrum occupancy was evaluated in few measurement campaigns at different locations mostly(More)
There is need to develop better models and characterization methods for spectrum usage and radio environments of cognitive radios. Currently different theoretical and simulation based approaches towards enabling dynamic spectrum access would greatly benefit from the possibility to generate synthetic data for testing purposes. Such Radio Environment Maps(More)
Communication between cars can be exploited for various applications. Security enhancements as well as interactive games played by occupants of different cars are only two examples. The IEEE 802.11p standard will specify physical and MAC-layer for such scenarios. As one of the design goals is to partially reuse existing WLAN technology we investigate in(More)
Dynamic spectrum access to unused licensed spectrum has been proposed as solution to the spectrum scarcity problem. Reliable detection of any primary user signal is crucial for the required interference-free operation. It has been shown that cooperative sensing has the potential to alleviate propagation effects such as fast fading or shadowing and thus to(More)
Present mobile devices often support multiple communication technologies. If software developers want to control the configuration or monitor the characteristics of active links their applications will have to use different programming interfaces for each technology and supported platform. We propose an architecture for a Unified Link-Layer API (ULLA) to(More)
We propose to use multiscale entropy analysis in characterisation of network traffic and spectrum usage. We show that with such analysis one can quantify complexity and predictability of measured traces in widely varying timescales. We also explicitly compare the results from entropy analysis to classical characterisations of scaling and self-similarity in(More)