1,720,963 research outputs found
Performance assessment of DVB-T and wireless communication systems by means of cross-layer measurements
Full text linkThis thesis deals with the study and the application of measurement methods for the analysis of digitally modulated signals, deployed for wireless communications and television broadcasting. The goal is to develop methods allowing to efficiently assess the performance of transmission - reception systems upon the varying of transmission parameters and of the channel. In this way guidelines for the optimization of transmission set-up and of the network planning can be obtained, thus reducing the environmental impact of EM fields
and at the same time providing an adequate quality of service. The methods developed, known as cross-layer measurements, provide an analysis of the signal to be simultaneously carried out at different layers. In this way correlation relationships between physical layer parameters and higher layer ones (transport, network, application) can be obtained. These cross-layer measurements are applied to a DVB-T transmission platform (Part I), in collaboration with Digilab, Bozen, and furthermore, they are deployed for the assessment of coexistence problems of IEEE 802.11b and IEEE 802.15.4 wireless networks (Part II)
Characterization of the environmental EM field radiated by bluetooth devices
No full textAn improved method for the characterization of the environmental Electromagnetic (EM) field radiated by a single Bluetooth device is proposed. The method is based on suitable EM field measurements and on a proper usage of a swept-tuned spectrum analyzer. The interference of a second Bluetooth module used for enabling the transmission of the device under test is also efficiently overcome. In this way, the use of a DUT controller is avoided. Results of suitable experimental tests supporting the method idea are also discussed
Misure per l'ottimizzazione di un sistema di trasmissione DVB-T tramite canale di ritorno
No full textIn questa memoria viene discussa l’utilità delle misure di qualità video a livello di utente finale al fine
di ottimizzare il setup di sistemi di trasmissione televisiva digitale terrestre (DVB-T). Obiettivo del
lavoro è di mettere in evidenza come tali tipologie di misure possono risultare adeguate ed efficaci al
fine di realizzare, mediante opportuno canale di ritorno, regolazioni automatiche e in tempo reale del
setup di un sistema trasmissivo DVB-T
Assessment of code rate effects on DVB-T systems performance in the presence of interference
No full textEffects of code rate on the performance of Digital Video Broadcasting-Terrestrial (DVB-T) systems in the presence of in-channel interference are here assessed. In particular, major parameters at physical and application layers are considered, and two types of interfering phenomena are enlisted: Additive White Gaussian Noise (AWGN) and impulsive interference. The purpose is to deduce helpful information for optimizing the choice of code rate in some real-life configurations, thus allowing broadcasters and system designers to gain low bit error rate and high throughput. A number of experiments are carried out upon the varying of code rate and other system parameters, and the obtained results are shown. A proper testbed including a real DVB-T platform is arranged, and a cross-layer measurement approach is exploited
Analisi delle prestazioni di un sistema DVB-T in presenza di interferenza impulsiva co-canale
No full textIn questo lavoro si sono confrontate le prestazioni in presenza di interferenza co-canale dovuta a rumore
di tipo impulsivo, generato in base al modello proposto in letteartura. La metodologia di misura adottata, di
tipo cross-layer, prende in considerazione sia il layer fisico, tramite la stima della potenza del segnale
ricevuto e la qualità della modulazione, sia il layer applicativo, tramite la valutazione della qualità video
percepita dall’utente finale
Experimental analysis of WLAN interference effects on IEEE 802.15.4 wireless sensor networks
No full textInterference effects of Wireless Local Area
Networks (WLANs) on Wireless Sensor Networks
(WSNs) are here investigated. In particular, the
performance of a IEEE 802.15.4 WSN upon the
varying of some meaningful parameters and in the
presence of a near operating IEEE 802.11b WLAN is
analyzed. The purpose is to deduce helpful information
for network designers, users and standardization
committees for optimizing the performance and
reliability of a IEEE 802.15.4 WSN when operating in
the presence of an interfering WLAN. Experiments are
conducted through a proper test system, and different
WSN configurations are considered
Cross-layer measurement for the analysis of a DVB-T system performances at the end user level
No full textCross-layer relationships among three different levels of a DVB-T broadcasting system are investigated. In particular, the "modulation layer", the "physical layer" and the "end user layer" are considered and the following parameters are analyzed and compared: modulation error ratio (MER), power intensity at the receiver connector and video quality metric (VQM) indices. Meaningful results from experimental tests performed on a suitable test bench and a DVB-T transmission platform are also presented. They allow to deduce cross-layer relationships and guidelines for the optimization of the DVB-T system performanc
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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