Browsing by Author "Güvenç, I."

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    Adaptation of two types of processing gains for UWB impulse radio wireless sensor networks
    (The Institution of Engineering and Technology, 2007) Güvenç, I.; Arslan, H.; Gezici, Sinan; Kobayashi, H.
    Ultrawideband impulse radio systems offer two kinds of processing gains that can be adapted based on the interference level in the system so that quality of service requirements are fulfilled. An adaptive assignment scheme for two types of multiple-access parameters in cluster-based wireless sensor networks is investigated. A mathematical framework is developed for asynchronous communications using a Gaussian approximation method to model the multiple-access interference in two cases: one with fixed frame duration, where the goal is to increase the average throughput, and the other with fixed symbol duration, where the goal is to increase the network lifetime. Extension of the analysis to multipath channels is carried out, and the validity of the Gaussian approximation is investigated using the Kullback-Leibler distance.
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    Cognitive-radio systems for spectrum, location, and environmental awareness
    (IEEE, 2010) Celebi, H.; Güvenç, I.; Gezici, Sinan; Arslan, H.
    In order to perform reliable communications, a system needs to have sufficient information about its operational environment, such as spectral resources and propagation characteristics. Cognitive-radio technology has capabilities for acquiring accurate spectrum, location, and environmental information, due to its unique features such as spectrum, location, and environmental awareness. The goal of this paper is to give a comprehensive review of the implementation of these concepts. In addition, the dynamic nature of cognitive-radio systems - including dynamic spectrum utilization, transmission, the propagation channel, and reception - is discussed, along with performance limits, challenges, mitigation techniques, and open issues. The capabilities of cognitive-radio systems for accurate characterization of operational environments are emphasized. These are crucial for efficient communications, localization, and radar systems.