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National Repository of Grey Literature 12 records found  previous11 - 12  jump to record: Search took 0.01 seconds. 
Studies of Influences of Oscillators Frequency Instabilities in Satellite Communication Systems
 Baran, Ondřej ; Baláž, Igor (referee) ; Šimša, Jan (referee) ; Kasal, Miroslav (advisor)
The dissertation thesis deals with a study of an influence of a simultaneous incidence of an additive thermal noise and a multiplicative phase noise on the useful signal transmission in narrowband satellite communication systems. While the additive thermal noise affects the useful signal only on the receiver side of the communication system, the multiplicative phase noise is produced in all system oscillators. One investigates how the receiver filter bandwidth reduction takes effect on the influence of individual noise types. The thesis is divided into four units. The first one (chapters 4 and 5) solves the ways of modeling of both noise types. In the second part (chapter 6), on the simple example, the primary analysis of the phase noise influence is made. Basic modulation schemes used in the satellite communication are also discussed (chapter 7). Third part (chapter 8) is devoted to the modeling of a general digital system with a M PSK modulation made directly on the main carrier wave. The last part (chapter 9) describes the modeling of a digital system with a BPSK modulation on the auxiliary subcarrier wave followed by an SSB modulation on the main carrier wave. General conclusions are deduced from obtained simulation results.
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Simulation of UMTS system
 Predajňa, Martin ; Prokopec, Jan (referee) ; Kejík, Petr (advisor)
The bachelor’s thesis deals with modeling of UMTS system in downlink. It is focused on signal processing in physical layer and observes BER depending on parameters of model of real environment by setting different interruption. Basic architecture of UMTS system, channel coding and multiplexing of transport channels to physical channels is described in this thesis. Radio frame structure for downlink dedicated physical data channel is also described there. Using of pseudorandom sequences in CDMA systems and their properties are key parameters for observation of BER. Simulation uses single-user model in basic band, which enables to observe the influence of noise and narrowband jamming. These channel properties have impact on BER, which is used for evaluation of UMTS system. The orthogonality of sequences is influenced by multi access interference so detection of required signal (which uses correlation properties of spreading sequences) is limited.
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