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Postprint This is the accepted version of a paper published in IEEE Communications Magazine. This paper has been peer-reviewed but does not include the final publisher proof-corrections or journal pagination. Access to the published version may require subscription. Abstract— One of the key challenges of the emerging Cognitive Radio based IEEE 802.22(More)
— Recently, secondary usage of spectrum has been considered in order to better exploit spectral resources and overcome the under-utilization of licensed spectrum. Since the licensed user still keeps primary access rights to its spectrum in such a secondary usage scenario, potential Secondary Users (SUs) have to vacate the spectrum in case the licensed user(More)
To facilitate a functional analysis of neuronal connectivity in a mammalian nervous system that is tightly packed with billions of cells, we developed a new technique that uses inducible genetic manipulations in fluorescently labeled single neurons in mice. Our technique, single-neuron labeling with inducible Cre-mediated knockout (SLICK), is achieved by(More)
In this paper we review contributions regarding dynamic, i.e., channel-state adaptive schemes for OFDM systems. As the wireless broadband channel is frequency-selective, the OFDM transmission scheme provides an efficient technique to overcome this impairment. However, the OFDM transmission scheme provides further advantages. Various system metrics can be(More)
In wireless local area networks often a station can potentially associate with more than one access point. Therefore, a relevant question is which access point to select "best" from a list of candidate ones. In IEEE 802.11, the user simply associates to the access point with the strongest received signal strength. However, this may result in a significant(More)
Within the last decade the OFDM transmission scheme has become part of several standards for wireless systems. Today, OFDM is even a candidate for 4G wireless systems. It is well known that dynamic OFDMA systems potentially increase the spectral efficiency. They exploit diversity effects in time, space, and frequency by assigning system resources(More)
— OFDM systems are known to overcome the impairment of the wireless channel by splitting the given system-bandwidth into parallel sub-carriers, on which data-symbols can be transmitted simultaneously. This enables the possibility of enhancing the system's performance by deploying adaptive (dynamic) mechanisms, namely power and modulation adaption and(More)
The simulation models of wireless networks rapidly increase in complexity to accurately model wireless channel characteristics and the properties of advanced transmission technologies. Such detailed models typically lead to a high computational load per simulation event that accumulates to extensive simulation runtimes. Reducing runtimes through(More)
Developing complex technical systems requires a systematic exploration of the given design space in order to identify optimal system configurations. However, studying the effects and interactions of even a small number of system parameters often requires an extensive number of simulation runs. This in turn results in excessive runtime demands which severely(More)