5,547 research outputs found
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
Proceedings of the Second International Mobile Satellite Conference (IMSC 1990)
Presented here are the proceedings of the Second International Mobile Satellite Conference (IMSC), held June 17-20, 1990 in Ottawa, Canada. Topics covered include future mobile satellite communications concepts, aeronautical applications, modulation and coding, propagation and experimental systems, mobile terminal equipment, network architecture and control, regulatory and policy considerations, vehicle antennas, and speech compression
Near-Instantaneously Adaptive HSDPA-Style OFDM Versus MC-CDMA Transceivers for WIFI, WIMAX, and Next-Generation Cellular Systems
Burts-by-burst (BbB) adaptive high-speed downlink packet access (HSDPA) style multicarrier systems are reviewed, identifying their most critical design aspects. These systems exhibit numerous attractive features, rendering them eminently eligible for employment in next-generation wireless systems. It is argued that BbB-adaptive or symbol-by-symbol adaptive orthogonal frequency division multiplex (OFDM) modems counteract the near instantaneous channel quality variations and hence attain an increased throughput or robustness in comparison to their fixed-mode counterparts. Although they act quite differently, various diversity techniques, such as Rake receivers and space-time block coding (STBC) are also capable of mitigating the channel quality variations in their effort to reduce the bit error ratio (BER), provided that the individual antenna elements experience independent fading. By contrast, in the presence of correlated fading imposed by shadowing or time-variant multiuser interference, the benefits of space-time coding erode and it is unrealistic to expect that a fixed-mode space-time coded system remains capable of maintaining a near-constant BER
A study and experiment plan for digital mobile communication via satellite
The viability of mobile communications is examined within the context of a frequency division multiple access, single channel per carrier satellite system emphasizing digital techniques to serve a large population of users. The intent is to provide the mobile users with a grade of service consistant with the requirements for remote, rural (perhaps emergency) voice communications, but which approaches toll quality speech. A traffic model is derived on which to base the determination of the required maximum number of satellite channels to provide the anticipated level of service. Various voice digitalization and digital modulation schemes are reviewed along with a general link analysis of the mobile system. Demand assignment multiple access considerations and analysis tradeoffs are presented. Finally, a completed configuration is described
Multiuser MIMO-OFDM for Next-Generation Wireless Systems
This overview portrays the 40-year evolution of orthogonal frequency division multiplexing (OFDM) research. The amelioration of powerful multicarrier OFDM arrangements with multiple-input multiple-output (MIMO) systems has numerous benefits, which are detailed in this treatise. We continue by highlighting the limitations of conventional detection and channel estimation techniques designed for multiuser MIMO OFDM systems in the so-called rank-deficient scenarios, where the number of users supported or the number of transmit antennas employed exceeds the number of receiver antennas. This is often encountered in practice, unless we limit the number of users granted access in the base stationâs or radio portâs coverage area. Following a historical perspective on the associated design problems and their state-of-the-art solutions, the second half of this treatise details a range of classic multiuser detectors (MUDs) designed for MIMO-OFDM systems and characterizes their achievable performance. A further section aims for identifying novel cutting-edge genetic algorithm (GA)-aided detector solutions, which have found numerous applications in wireless communications in recent years. In an effort to stimulate the cross pollination of ideas across the machine learning, optimization, signal processing, and wireless communications research communities, we will review the broadly applicable principles of various GA-assisted optimization techniques, which were recently proposed also for employment inmultiuser MIMO OFDM. In order to stimulate new research, we demonstrate that the family of GA-aided MUDs is capable of achieving a near-optimum performance at the cost of a significantly lower computational complexity than that imposed by their optimum maximum-likelihood (ML) MUD aided counterparts. The paper is concluded by outlining a range of future research options that may find their way into next-generation wireless systems
Turbo-Coded Adaptive Modulation Versus Space-Time Trellis Codes for Transmission over Dispersive Channels
Decision feedback equalizer (DFE)-aided turbocoded wideband adaptive quadrature amplitude modulation (AQAM) is proposed, which is capable of combating the temporal channel quality variation of fading channels. A procedure is suggested for determining the AQAM switching thresholds and the specific turbo-coding rates capable of maintaining the target bit-error rate while aiming for achieving a highly effective bits per symbol throughput. As a design alternative, we also employ multiple-input/multiple-output DFE-aided spaceâtime trellis codes, which benefit from transmit diversity and hence reduce the temporal channel quality fluctuations. The performance of both systems is characterized and compared when communicating over the COST 207 typical urban wideband fading channel. It was found that the turbo-coded AQAM scheme outperforms the two-transmitter spaceâtime trellis coded system employing two receivers; although, its performance is inferior to the spaceâtime trellis coded arrangement employing three receivers. Index TermsâCoded adaptive modulation, dispersive channels, spaceâtime trellis codes
MSAT-X: A technical introduction and status report
A technical introduction and status report for the Mobile Satellite Experiment (MSAT-X) program is presented. The concepts of a Mobile Satellite System (MSS) and its unique challenges are introduced. MSAT-X's role and objectives are delineated with focus on its achievements. An outline of MSS design philosophy is followed by a presentation and analysis of the MSAT-X results, which are cast in a broader context of an MSS. The current phase of MSAT-X has focused notably on the ground segment of MSS. The accomplishments in the four critical technology areas of vehicle antennas, modem and mobile terminal design, speech coding, and networking are presented. A concise evolutionary trace is incorporated in each area to elucidate the rationale leading to the current design choices. The findings in the area of propagation channel modeling are also summarized and their impact on system design discussed. To facilitate the assessment of the MSAT-X results, technology and subsystem recommendations are also included and integrated with a quantitative first-generation MSS design
Analysis and Simulation of the Signals Transmission in the DVB-H/SH Standards
Tato disertaÄnĂ prĂĄce se zabĂœvĂĄ analĂœzou, simulacĂ a mÄĆenĂm zpracovĂĄnĂ a pĆenosu signĂĄlĆŻ digitĂĄlnĂ televize pro pĆĂjem mobilnĂho TV vysĂlĂĄnĂ ve standardech DVB-H a DVB-SH. Tyto standardy vychĂĄzejĂ z pĆedpokladu, ĆŸe pĆĂjem signĂĄlu je charakterizovĂĄn modely pĆenosovĂœch kanĂĄlĆŻ s vĂcecestnĂœm ĆĄĂĆenĂm. Tyto, tzv. ĂșnikovĂ© kanĂĄly, jsou charakterizovĂĄny hlavnÄ zpoĆŸdÄnĂm a ziskem jednotlivĂœch cest. V zĂĄvislosti na dalĆĄĂch parametrech (rychlost pĆijĂmaÄe, DopplerovskĂ© spektrum), je moĆŸnĂ© rozdÄlit ĂșnikovĂ© kanĂĄly do tĆech hlavnĂch skupin: mobilnĂ, pĆenosnĂ© a fixnĂ. DĂĄ se pĆedpoklĂĄdat, ĆŸe v rĆŻznĂœch modelech kanĂĄlĆŻ bude pĆenĂĄĆĄenĂœ signĂĄl rĆŻznÄ ovlivnÄn. Proto je potĆebnĂ© najĂt optimĂĄlnĂ parametry systĂ©mĆŻ (DVB-H/SH) pro kvalitnĂ pĆĂjem vysĂlanĂœch sluĆŸeb mobilnĂ televize, coĆŸ je hlavnĂm cĂlem tĂ©to disertaÄnĂ prĂĄci. Pro tento ĂșÄel byly vytvoĆeny dvÄ vhodnĂ© aplikace (jedna pro DVB-H a jedna pro DVB-SH) s GUI v prostĆedĂ MATLAB, kterĂ© umoĆŸĆujĂ simulovat a analyzovat mĂru zkreslenĂ signĂĄlu v pĆĂpadÄ mobilnĂch, pĆenosnĂœch a fixnĂch scĂ©nĂĄĆĆŻ pĆenosu. NavĂc, tyto aplikace obsahujĂ i druhĂœ samostatnĂœ simulĂĄtor pro nastavenĂ a modifikaci parametrĆŻ jednotlivĂœch pĆenosovĂœch cest. DĂky tomu je moĆŸnĂ© zhodnotit vliv parametrĆŻ celĂ©ho systĂ©mu a kanĂĄlovĂœch modelĆŻ na dosaĆŸenou chybovost (BER a MER) a kvalitu pĆenosu. Ve vĆĄech pĆenosovĂœch scĂ©nĂĄĆĂch (v zĂĄvislosti na pomÄru C/N) byly zĂskanĂ©, vyhodnocenĂ© a diskutovanĂ© zkreslenĂ signĂĄlĆŻ. NavĂc, u standardu DVB-H, vĆĄechny zĂskanĂ© vĂœsledky ze simulacĂ byly ovÄĆeny mÄĆenĂm. RozdĂly mezi dosaĆŸenĂœmi vĂœsledky (simulace a mÄĆenĂ) byly rovnÄĆŸ podrobeny diskuzi. Tuto disertaÄnĂ prĂĄci je moĆŸnĂ© rozdÄlit do ÄtyĆ hlavnĂch ÄĂĄstĂ. PrvnĂ ÄĂĄst disertaÄnĂ prĂĄce se zabĂœvĂĄ reĆĄerĆĄĂ souÄasnĂ©ho vĂœvoje v oblasti digitĂĄlnĂho televiznĂho vysĂlĂĄnĂ na mobilnĂ terminĂĄly ve standardech DVB-H/SH. Na konci tĂ©to ÄĂĄsti jsou jasnÄ popsĂĄny cĂle tĂ©to disertaÄnĂ prĂĄce. DruhĂĄ ÄĂĄst prĂĄce je zamÄĆenĂĄ na struÄnĂœ popis blokovĂ©ho diagramu vysĂlaÄĆŻ v obou standardech DVB-H/SH. DĂĄle jsou struÄnÄ popsĂĄny modely pĆenosovĂœch kanĂĄlĆŻ, kterĂ© se pouĆŸĂvajĂ pro modelovĂĄnĂ pĆenosu signĂĄlu. StruÄnĂœ popis vytvoĆenĂœch aplikacĂ, i s vĂœvojovĂœm diagramem, kterĂ© jsou vhodnĂ© pro simulaci a analĂœzu pĆenosu v DVB-H/SH, jsou popsĂĄny v tĆetĂ ÄĂĄsti prĂĄce. ÄtvrtĂĄ a nejdelĆĄĂ ÄĂĄst tĂ©to disertaÄnĂ prĂĄce se zabĂœvĂĄ vyhodnocenĂm zĂskanĂœch vĂœsledkĆŻ ze simulacĂ a mÄĆenĂ.This dissertation thesis deals with the analysis, simulation and measurement of the signal processing and transmission in DVB-H and DVB-SH standards. These standards are based on the assumption that signal reception is characterized by the transmission channels with echoes. These, so called fading channels, are mainly characterized by the path delays and path losses. Depending on the other, additional features (speed of the receiver, Doppler spectrum, etc.), it can be possible divided these channels onto three main groups: mobile, portable and fixed. Of course, signal transmission in different transmission channel models are affected differently. Therefore, it is needed found the optimal system parameters in both, DVB-H and DVB-SH standards, for the quality reception of the broadcasted mobile TV services, which is the main goal of this thesis. For this purpose, two appropriate applications (one for DVB-H and one for DVB-SH) with GUI were created in MATLAB, which enable simulated and analyzed the signal distortions in mobile, portable and fixed transmission scenarios. Moreover, these applications also contain a second application with GUI for the easy set and modification of the parameters of the used channel models. Therefore, it is possible to evaluate the effect of parameters of whole system and channel models on the achieved error rate (BER and MER) and quality of the transmission. In all mentioned transmission scenarios, the signal distortions (depending on the Carrier-to-Noise ratio) were obtained, evaluated and discussed in this dissertation thesis. Furthermore, in case of DVB-H, all obtained results from the simulations, were verified by the measuring. Differences between the obtained results (simulation and measuring) are also discussed. This dissertation thesis can be divided into four main parts. The first part of this dissertation thesis, after the short introduction, deals with present state-of-the-art and literature survey in mobile broadcast DVB-H/SH standards. At the end of this part are clearly outlined the main aims of this dissertation thesis. Second part is focused on the brief description of the functional block diagram of transmitters in both, DVB-H/SH standards. Furthermore, there are briefly described the transmission fading channel models, which are commonly used for the modeling of the signal transmission. The brief description of program applications with flowcharts, appropriate for the simulation of the transmission in the DVB-H/SH standards, are presented and described in the third part of this thesis. Finally, the fourth and longest part of this thesis is focused on the evaluation and comparison of obtained results from the simulations and measurements.
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