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This article provides insight into the state of higher education in Serbia, particularly in the context of reform processes based on European Higher Education Area principles. A multidimensional approach was taken, encompassing (a) a review and analysis of legal regulations relevant to the historical context of Serbia, (b) an examination of current working conditions at accredited state and private...
Background Besides classical and electrical toothbrushes market offers tooth brushes that can be chewed, like chewing gums. The aim of this study was to show the effectiveness of chewable toothbrush versus a conventional brush in the students’ population. Methods The prospective study included 346 students. For this research, we used a e-questionnaire for “smart” phones, that students completed...
The optimization of wireless orthogonal frequency division multiplexing (OFDM) systems is based on the knowledge of the signal-to-noise ratio (SNR). Most of the existing methods for the SNR estimation operates in the frequency-domain and assumes perfect carrier frequency offset (CFO) synchronization. However, it has been shown that in real systems in the presence of the residual CFO this estimators...
Timing Synchronization at the receiver of an Orthogonal Frequency Division Multiplexing (OFDM) system is the first step towards extracting the information contained within the received OFDM frame. In this paper we will be looking at the robustness of the Schmidl and Cox timing synchronisation algorithm in a dynamic spectrum access environment where interference is present. Interference with respect...
OFDM-based cognitive radio (CR) systems are shown to be an effective solution for increasing spectrum efficiency by activating the certain group of subcarriers (subbands) in locally available spectrum. However, each CR receiver should synchronize itself to appropriate carrier frequency and to identify currently activated subbands. Moreover, energy and bandwidth efficiency of CR systems can be improved...
In this paper, the performance of Schmidl and Cox (S&C) timing estimator in cognitive radio systems under a fractional bandwidth (FBW) scenario is investigated. The synchronization preamble is appropriately modified in order to avoid transmission in the subbands where primary users (PU) are active. However, at the receiver, the timing synchronizer processes all received signal samples within the...
The reliable detection of unused spectrum while meeting a required probability of detecting primary user activity is a key functionality of cognitive radio systems. In cooperative spectrum sensing, the detection results of multiple cognitive radios are combined to a global result with high reliability. In order to transmit the local decisions a signaling channel is required. It can be realized by...
A crucial parameter required for adaptive transmission in orthogonal frequency division multiplexing (OFDM) systems is the signal-to-noise ratio (SNR). In this paper, certain modifications to previously proposed preamble-based SNR estimator for wireless OFDM systems are suggested in order to improve estimation performance. Proposed modifications, related to DFT interpolation, are based on the adaptive...
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