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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
181

Karinių aeronavigacinių žemėlapių optimizavimas / Optimization of military airnavigation charts

Ovodas, Donatas 27 December 2012 (has links)
Disertaciniame darbe pasitelkiant kompleksinė vertinimo metodika analizuojami karinių aeronavigacinių žemėlapių ženklai, ženklų sistemos ir užrašai. Šios analizės pagrindu tobulinami sutartiniai ženklai, optimizuojamas žemėlapio turinys ir pateikiama vieningos Lietuvos karo aeronavigacinių duomenų bazės struktūrą. Kompleksiškai parengta tyrimo metodika rėmėsi Lietuvoje nusistovėjusia teminių žemėlapių ir ženklų kartosemiotine vertinimo praktika. Įvairūs ženklų ir užrašų vertinimo aspektai leido tiksliai ir nuodugniai atlikti aeronavigacinių ženklų ir užrašų vertinimą. Analizės metu nustatyta kad ne visi karinių aeronavigacinių žemėlapių ženklai atitinka kartosemiotikos reikalavimų, todėl galėtu būti keičiami. Karinių aeronavigacinių ženklų analizė ir tobulinimas rėmėsi ankščiau vykdytais psichofiziologinio suvokimo tyrimais bei išvadomis. Siūlomi nauji aeronavigacinių žemėlapių ženklai pilnai atitinka psichofiziologinių tyrimų rekomendacijas. Išnagrinėjus karinius NATO šalių aeronavigacinius žemėlapius ir atsižvelgiant į vieningą žemėlapių sistemą, klasifikacijos požymius ir atitinkamus klasifikacijų reikalavimus, darbe pateikta apibendrinta NATO šalių karinių aeronavigacinių žemėlapių klasifikacija, kurioje yra numatyta galimybė sugebėti integruoti naujai atsirandančių žemėlapių grupes. / This dissertation provides an overall in-depth use evaluation methodology that assists in analysing of military aeronautical maps, sign system and records. On the basis of this research of signs and their conventions an optimised map and content of a unified Lithuanian military aeronautical database structures is suggested for improvement. Methodically prepared research was collected and based on already established and consistent thematic maps, signs and carto-semiotic assessment practices already used in Lithuania. A variety of illustrations and aspect assessments established an accurate and in-depth aeronautical value of signs and their practices. The analysis highlighted that not all carto-semiotic characters and signs of military aeronautical charts meet the criteria, and therefore could be changed. Previous military aeronautical sign analysis and their improvements were based on exercises of psycho-physiological studies of perception with their conclusions. Therefore a set of new aeronautical map characters that fully comply with psycho-physiological research recommendations are proposed. Through the examination of NATO's military aeronautical maps, charts and a look at a unified system of classifications, and its requirements, the dissertation summarises the overall work of the NATO’s military aeronautical maps and their classifications, which provides the possibility of integration for the newly emerging sign and map groups.
182

TELEMETRY LINK RELIABILITY IMPROVEMENT VIA “NO-HIT” DIVERSITY BRANCH SELECTION

Jefferis, Robert P. 10 1900 (has links)
International Telemetering Conference Proceedings / October 18-21, 2004 / Town & Country Resort, San Diego, California / Multipath propagation consisting largely of specular reflection components is known to be the major channel impairment in many aeronautical mobile telemetry (AMT) applications. Adaptive equalizers are not effective against flat fading commonly created by strong power delay profile components representing small fractions of the transmitted symbol period. Avoidance and diversity techniques are the only practical means of combating this problem. A new post-detection, no-hit diversity branch selector is described in this paper. Laboratory and limited flight test data comparing non-diversity, selection diversity and intermediate frequency (IF) combining techniques are presented.
183

SIMULATION OF THE AERONAUTICAL RADIO CHANNEL FOR TELEMETRY APPLICATIONS

Mwangi, Patricia A. W., Haj-Omar, Amr, Montaque, Kishan 10 1900 (has links)
ITC/USA 2006 Conference Proceedings / The Forty-Second Annual International Telemetering Conference and Technical Exhibition / October 23-26, 2006 / Town and Country Resort & Convention Center, San Diego, California / The aeronautical channel is an air to ground channel characterized by multipath, high doppler shifts, Rayleigh fading and noise. Use of a channel sounder ensures proper estimation of the parameters associated with the impulse response of the channel. These estimates help us to characterize the radio channels associated with aeronautical telemetry. In order to have a satisfactory channel characterization, the amplitudes, phase shifts and delays associated with each multipath component in the channel model must be determined.
184

REDUCED COMPLEXITY TRELLIS DETECTION OF SOQPSK-TG

Nelson, Tom 10 1900 (has links)
ITC/USA 2006 Conference Proceedings / The Forty-Second Annual International Telemetering Conference and Technical Exhibition / October 23-26, 2006 / Town and Country Resort & Convention Center, San Diego, California / The optimum detector for shaped offset QPSK (SOQPSK) is a trellis detector which has high complexity (as measured by the number of detection filters and trellis states) due to the memory inherent in this modulation. In this paper we exploit the cross-correlated, trellis-coded, quadrature modulation (XTCQM) representation of SOQPSK-TG to formulate a reduced complexity detector. We show that a factor of 128 reduction in the number of trellis states of the detector can be achieved with a loss of only 0.2 dB in bit error rate performance as compared to optimum at P(b) = 10^(-5).
185

CHANNEL ISSUES FOR DESIGN OF THE iNET RADIO LINK PROTOCOL

Britto, Elizabeth, Mwangi, Patricia 10 1900 (has links)
ITC/USA 2005 Conference Proceedings / The Forty-First Annual International Telemetering Conference and Technical Exhibition / October 24-27, 2005 / Riviera Hotel & Convention Center, Las Vegas, Nevada / This paper presents the issues related to the modeling and performance of the Radio Channel used in Telemetry. Because of the physical environment one expects stressed channel conditions due to multipath, shadowing, and high doppler shift caused by high speeds of up to mach 3. Prior work has created useful data and models for analysis of these radio channels. This paper will develop features of a channel simulator that will allow for evaluation of radio protocols for iNET. Substantial work has also been done to develop requirements for the iNET networked radio environment. This paper will map these requirements into technical features required for the radio link and consider how these will relate to the effects of the channels.
186

SPACE-TIME CODED SOQPSK IN THE PRESENCE OF DIFFERENTIAL DELAYS

Nelson, Tom 10 1900 (has links)
International Telemetering Conference Proceedings / October 18-21, 2004 / Town & Country Resort, San Diego, California / This paper presents a method of detecting the Tier I modulation SOQPSK when it is used in a space-time coded (STC) system in which there is a non-negligible differential delay between the received signals. Space-time codes are useful to eliminate data dropouts which occur on aeronautical telemetry channels in which transmit diversity is employed. The proposed detection algorithm employs a trellis to detect the data while accounting for the offset between the in-phase and quadrature-phase components of the signals as well as the differential delay. The performance of the system is simulated and presented and it is shown that the STC eliminates the BER floor which results from the data dropouts.
187

DIVERSITY BRANCH SELECTION IN REAL WORLD APPLICATION

Formeister, Richard 10 1900 (has links)
ITC/USA 2007 Conference Proceedings / The Forty-Third Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2007 / Riviera Hotel & Convention Center, Las Vegas, Nevada / Multipath propagation continues to be the dominant channel impairment in many aeronautical mobile telemetry (AMT) applications. Avoidance and diversity techniques continue to be the only practical means to combat this problem. In 2004 limited results from the development of a new post-detection, no-hit diversity selector were reported. Late breaking results from flight test were reported orally. A review of the methodology, flight test results and conclusions are presented in this paper. Also presented is an update describing enhancements of the implementation which emphasize operational flexibility as well as support for alternate demodulator products.
188

A HIGH-ACCURACY AND LOW-COMPLEXITY CARRIER-OFFSET-FREQUENCY ESTIMATOR

Palmer, Joseph 10 1900 (has links)
ITC/USA 2007 Conference Proceedings / The Forty-Third Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2007 / Riviera Hotel & Convention Center, Las Vegas, Nevada / A single-tone frequency estimator for a non-uniformly sampled sinusoid is proposed. A nonuniformly sampled sinusoid may be generated from the received training sequences of a telemetry link. The frequency of the sinusoid matches the carrier-frequency-offset (CFO) of the received signal, and estimation of this quantity allows a receiver to compensate for the CFO. The performance bounds of this type of estimator have been investigated in the literature, though little work has been published on practical algorithms. The estimator proposed in this paper is a generalization of phase-increment estimators previously described in the literature. It exhibits a low computational complexity yet converges to theoretical bounds at high SNR. The paper argues that a periodic training sequence structure, combined with the new estimator, allows for a high-accuracy and lowcomplexity CFO compensator.
189

AN INTRODUCTION TO SPECTRUM REALLOCATION LEGISLATION

Ryan, Mikel R. 10 1900 (has links)
International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, Nevada / In the past four years Congress has passed legislation mandating the reallocation of 255 MHz of radio frequency bands from Federal to non-Federal or “MIXED USE.” Several of the frequency bands supporting telemetering functions were affected, and more legislation of this nature is forecasted.
190

LINK AVAILABILITY AND BIT ERROR CLUSTERS IN AERONAUTICAL TELEMETRY

Jefferis, Robert P. 10 1900 (has links)
International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Radio frequency power margins in well planned line-of-sight (LOS) air-to-ground digital data transmission systems usually produce signal to noise ratios (SNR) that can deliver error free service. Sometimes field performance falls short of design and customer expectations. Recent flight tests conducted by the tri-service Advanced Range Telemetry (ARTM) project confirm that the dominant source of bit errors and short term link failures are “clusters” of severe error burst activity produced by flat fading, dispersive fading and poor antenna patterns on airborne vehicles. This paper introduces the techniques used by ARTM to measure bit error performance of aeronautical telemetry links.

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