60,751 research outputs found
Communication Subsystems for Emerging Wireless Technologies
The paper describes a multi-disciplinary design of modern communication systems. The design starts with the analysis of a system in order to define requirements on its individual components. The design exploits proper models of communication channels to adapt the systems to expected transmission conditions. Input filtering of signals both in the frequency domain and in the spatial domain is ensured by a properly designed antenna. Further signal processing (amplification and further filtering) is done by electronics circuits. Finally, signal processing techniques are applied to yield information about current properties of frequency spectrum and to distribute the transmission over free subcarrier channels
Advanced Algorithms for Satellite Communication Signal Processing
DizertaÄnĂ prĂĄce je zamÄĆena na softwarovÄ definovanĂ© pĆijĂmaÄe urÄenĂ© k ĂșzkopĂĄsmovĂ© druĆŸicovĂ© komunikaci. KomunikaÄnĂ kanĂĄly druĆŸicovĂœch spojĆŻ zahrnujĂcĂch komunikaci s hlubokĂœm vesmĂrem jsou zatĂĆŸeny vysokĂœmi ĂșrovnÄmi ĆĄumu, typicky modelovanĂ©ho AWGN, a silnĂœm DopplerovĂœm posuvem signĂĄlu zpĆŻsobenĂœm mimoĆĂĄdnou rychlostĂ pohybu objektu. DizertaÄnĂ prĂĄce pĆedstavuje moĆŸnĂ© postupy ĆeĆĄenĂ vĂœpoÄetnÄ efektivnĂ digitĂĄlnĂ downkonverze ĂșzkopĂĄsmovĂœch signĂĄlĆŻ a systĂ©mu odhadu kmitoÄtu nosnĂ© ĂșzkopĂĄsmovĂœch signĂĄlĆŻ zatĂĆŸenĂœch DopplerovĂœm posuvem v ĆĂĄdu nĂĄsobkĆŻ ĆĄĂĆky pĂĄsma signĂĄlu. Popis navrhovanĂœch algoritmĆŻ zahrnuje analytickĂœ postup jejich vĂœvoje a tam, kde je to moĆŸnĂ©, i analytickĂ© hodnocenĂ jejich chovĂĄnĂ. Algoritmy jsou modelovĂĄny v prostĆedĂ MATLAB Simulink a tyto modely jsou vyuĆŸity pro ovÄĆenĂ vlastnostĂ simulacemi. Modely byly takĂ© vyuĆŸity k experimentĂĄlnĂm testĆŻm na reĂĄlnĂ©m signĂĄlu pĆijatĂ©m z druĆŸice PSAT v laboratoĆi experimentĂĄlnĂch druĆŸic na Ășstavu radioelektroniky.The dissertation is focused on software defined receivers intended for narrowband satellite communication. The satellite communication channel including deep space communication suffers from a high level of noise, typically modeled by AWGN, and from a strong Doppler shift of a signal caused by the unprecedented speed of an object in motion. The dissertation shows possible approaches to the issues of computationally efficient digital downconversion of narrowband signals and the carrier frequency estimation of narrowband signals distorted by the Doppler shift in the order of multiples of the signal bandwidth. The description of the proposed algorithms includes an analytical approach of its development and, if possible, the analytical performance assessment. The algorithms are modeled in MATLAB Simulink and the models are used for validating the performance by the simulation. The models were also used for experimental tests on the real signal received from the PSAT satellite at the laboratory of experimental satellites at the department of radio electronics.
Contribution to Efficient Use of Narrowband Radio Channel
PĆedklĂĄdanĂĄ prĂĄce se soustĆedĂ na problematiku vyuĆŸĂvĂĄnĂ ĂșzkopĂĄsmovĂ©ho rĂĄdiovĂ©ho kanĂĄlu rĂĄdiovĂœmi modemy, kterĂ© jsou urÄenĂ© pro prĆŻmyslovĂ© aplikace pozemnĂ pohyblivĂ© rĂĄdiovĂ© sluĆŸby, specifikovanĂ© v dominantnĂ mĂĆe EvropskĂœm standardem ETSI EN 300 113. Tato rĂĄdiovĂĄ zaĆĂzenĂ se pouĆŸĂvajĂ v kmitoÄtovĂœch pĂĄsmech od 30 MHz do 1 GHz s nejÄastÄji pĆidÄlovanou ĆĄĂĆkou pĂĄsma 25 kHz a ve vÄtĆĄinÄ svĂœch instalacĂ jsou vyuĆŸĂvĂĄna ve fixnĂch nebo mobilnĂch bezdrĂĄtovĂœch sĂtĂch. Mezi typickĂ© oblasti pouĆŸitĂ patĆĂ zejmĂ©na datovĂĄ telemetrie, aplikace typu SCADA, nebo monitorovĂĄnĂ transportu strategickĂœch surovin. Za hlavnĂ znaky popisovanĂ©ho systĂ©mu lze oznaÄit komunikaÄnĂ pokrytĂ znaÄnĂœch vzdĂĄlenostĂ, danĂ© pĆedevĆĄĂm vysokou vĂœkonovou ĂșÄinnosti datovĂ©ho pĆenosu a vyuĆŸĂvanĂ efektivnĂch pĆĂstupovĂœch technik na rĂĄdiovĂœ kanĂĄl se semiduplexnĂm komunikaÄnĂm reĆŸimem. StriktnĂ poĆŸadavky na elektromagnetickou kompatibilitu umoĆŸĆujĂ tÄmto zaĆĂzenĂm vyuĆŸĂvat spektrum i v oblastech kmitoÄtovÄ blĂzkĂœm jinĂœm komunikaÄnĂm systĂ©mĆŻm bez nutnosti vklĂĄdĂĄnĂ dodateÄnĂœch ochrannĂœch frekvenÄnĂch pĂĄsem. ĂzkopĂĄsmovĂ© rĂĄdiovĂ© komunikaÄnĂ systĂ©my, v souÄasnosti pouĆŸĂvajĂ pĆevĂĄĆŸnÄ exponenciĂĄlnĂ digitĂĄlnĂ modulace s konstantnĂ modulaÄnĂ obĂĄlkou zejmĂ©na z dĆŻvodĆŻ velice striktnĂch omezenĂ pro velikost vĂœkonu vyzĂĄĆenĂ©ho do sousednĂho kanĂĄlu. DosahujĂ tak pouze kompromisnĂch hodnot komunikaÄnĂ ĂșÄinnosti. Ăpravy limitĆŻ pĆĂsluĆĄnĂœch rĂĄdiovĂœch parametrĆŻ a rychlĂœ rozvoj prostĆedkĆŻ ÄĂslicovĂ©ho zpracovĂĄnĂ signĂĄlu v nedĂĄvnĂ© dobÄ, dnes umoĆŸĆujĂ ekonomicky pĆijatelnĂ© vyuĆŸitĂ spektrĂĄlnÄ efektivnÄjĆĄĂch modulaÄnĂch technik i v tÄch oblastech, kde je prioritnĂ vyuĆŸĂvĂĄnĂ ĂșzkĂœch rĂĄdiovĂœch kanĂĄlĆŻ. CĂlem pĆedklĂĄdanĂ© disertaÄnĂ prĂĄce je proto vĂœzkum postupĆŻ smÄĆujĂcĂ ke sjednocenĂ vĂœhodnĂœch vlastnostĂ lineĂĄrnĂch a nelineĂĄrnĂch modulacĂ v modernĂ konstrukci ĂșzkopĂĄsmovĂ©ho rĂĄdiovĂ©ho modemu. ĂÄelem tohoto vĂœzkumu je efektivnĂ a âekologickĂ©â vyuĆŸĂvĂĄnĂ pĆidÄlenĂ© ÄĂĄsti frekvenÄnĂho spektra. Mezi hlavnĂ dĂlÄĂ problĂ©my, jimiĆŸ se pĆedklĂĄdanĂĄ prĂĄce zabĂœvĂĄ, lze zaĆadit zejmĂ©na tyto: Nyquistova modulaÄnĂ filtrace, navrhovanĂĄ s ohledem na minimalizaci neĆŸĂĄdoucĂch elektromagnetickĂœch interferencĂ, efektivnĂ ÄĂslicovĂ© algoritmy frekvenÄnĂ demodulace a rychlĂ© rĂĄmcovĂ© a symbolovĂ© synchronizace. SouÄĂĄstĂ prĂĄce je dĂĄle analĂœza navrhovanĂ©ho ĆeĆĄenĂ z pohledu celkovĂ© konstrukce programovÄ definovanĂ©ho rĂĄdiovĂ©ho modemu v rovinÄ simulacĂ pĆi vyĆĄetĆovĂĄnĂ robustnosti datovĂ©ho pĆenosu rĂĄdiovĂœm kanĂĄlem s bĂlĂœm GaussovskĂœm ĆĄumem nebo kanĂĄlem s Ășnikem v dĆŻsledku mnohacestnĂ©ho ĆĄĂĆenĂ signĂĄlu. ZĂĄvÄr prĂĄce je pak zamÄĆen na prezentovĂĄnĂ vĂœsledkĆŻ praktickĂ© ÄĂĄsti projektu, v nĂĆŸ byly testovĂĄny, mÄĆeny a analyzovĂĄny dvÄ prototypovĂ© konstrukce rĂĄdiovĂ©ho zaĆĂzenĂ. Tato finĂĄlnĂ ÄĂĄst prĂĄce obsahuje i praktickĂĄ doporuÄenĂ, vedoucĂ k vyĆĄĆĄĂmu stupni vyuĆŸitelnosti spektrĂĄlnÄ efektivnÄjĆĄĂch komunikaÄnĂch reĆŸimĆŻ v oblasti budoucĂ generace ĂșzkopĂĄsmovĂœch zaĆĂzenĂ pozemnĂ pohyblivĂ© rĂĄdiovĂ© sluĆŸby.he industrial narrowband land mobile radio (LMR) devices, as considered in this dissertation project, has been subject to European standard ETSI EN 300 113. The system operates on frequencies between 30 MHz and 1 GHz, with channel separations of up to 25 kHz, and is intended for private, fixed, or mobile, radio packet switching networks. Data telemetry, SCADA, maritime and police radio services; traffic monitoring; gas, water, and electricity producing factories are the typical system applications. Long distance coverage, high power efficiency, and efficient channel access techniques in half duplex operation are the primary advantages the system relays on. Very low level of adjacent channel power emissions and robust radio receiver architectures, with high dynamic range, enable for a systemâs coexistence with various communication standards, without the additional guard band frequency intervals. On the other hand, the strict limitations of the referenced standard as well as the state of the technology, has hindered the increase in communication efficiency, with which the system has used its occupied bandwidth. New modifications and improvements are needed to the standard itself and to the up-to-date architectures of narrowband LMR devices, to make the utilization of more efficient modes of system operation practically realizable. The main objective of this dissertation thesis is therefore to find a practical way how to combine the favorable properties of the advanced nonlinear and linear digital modulation techniques in a single digital modem solution, in order to increase the efficiency of the narrowband radio channel usage allocated to the new generation of the industrial LMR devices. The main attention is given to the particular areas of digital modem design such as proposal of the new family of the Nyquist filters minimizing the adjacent channel interference, design and analysis of the efficient algorithms for frequency discrimination, fast frame and symbol
Low-Complexity Sub-band Digital Predistortion for Spurious Emission Suppression in Noncontiguous Spectrum Access
Noncontiguous transmission schemes combined with high power-efficiency
requirements pose big challenges for radio transmitter and power amplifier (PA)
design and implementation. Due to the nonlinear nature of the PA, severe
unwanted emissions can occur, which can potentially interfere with neighboring
channel signals or even desensitize the own receiver in frequency division
duplexing (FDD) transceivers. In this article, to suppress such unwanted
emissions, a low-complexity sub-band DPD solution, specifically tailored for
spectrally noncontiguous transmission schemes in low-cost devices, is proposed.
The proposed technique aims at mitigating only the selected spurious
intermodulation distortion components at the PA output, hence allowing for
substantially reduced processing complexity compared to classical linearization
solutions. Furthermore, novel decorrelation based parameter learning solutions
are also proposed and formulated, which offer reduced computing complexity in
parameter estimation as well as the ability to track time-varying features
adaptively. Comprehensive simulation and RF measurement results are provided,
using a commercial LTE-Advanced mobile PA, to evaluate and validate the
effectiveness of the proposed solution in real world scenarios. The obtained
results demonstrate that highly efficient spurious component suppression can be
obtained using the proposed solutions
Reconstruction of the gravitational wave signal during the Virgo science runs and independent validation with a photon calibrator
The Virgo detector is a kilometer-scale interferometer for gravitational wave
detection located near Pisa (Italy). About 13 months of data were accumulated
during four science runs (VSR1, VSR2, VSR3 and VSR4) between May 2007 and
September 2011, with increasing sensitivity.
In this paper, the method used to reconstruct, in the range 10 Hz-10 kHz, the
gravitational wave strain time series from the detector signals is
described. The standard consistency checks of the reconstruction are discussed
and used to estimate the systematic uncertainties of the signal as a
function of frequency. Finally, an independent setup, the photon calibrator, is
described and used to validate the reconstructed signal and the
associated uncertainties.
The uncertainties of the time series are estimated to be 8% in
amplitude. The uncertainty of the phase of is 50 mrad at 10 Hz with a
frequency dependence following a delay of 8 s at high frequency. A bias
lower than and depending on the sky direction of the GW is
also present.Comment: 35 pages, 16 figures. Accepted by CQ
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