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1
Faragher, Ramsey Michael. "Effects of multipath interference on radio positioning systems". Thesis, University of Cambridge, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612008.
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Cheng, Cheng. "GNSS Multipath and Interference Mitigation Using Bayesian Methods". Thesis, Toulouse, ISAE, 2015. http://www.theses.fr/2015ESAE0011.
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Les récepteurs GNSS sont utilisés pour estimer la position et la vitesse d’un véhicule à partir de signauxtransmis par des satellites. L’estimation est habituellement réalisée en plusieurs étapes. Lesparamètres des signaux qui concernent le délai de propagation, la phase et la fréquence Dopplerde la porteuse, sont estimés et exploités pour estimer des mesures de pseudo-distances et de delta-distances.Ces mesures sont ensuite utilisées comme observation de la position et de la vitesse parl’algorithme de navigation qui délivre l’état du véhicule. En environnement GNSS dégradé les signauxémis par les satellites GPS peuvent subir des réflexions, des réfractions, et suivre ainsi deschemins multiples, communément connus sous le nom de multi-trajets. Ces signaux induisent desdéformations du signal à différents niveaux dans les récepteurs. En particulier il en résulte une distorsiondes fonctions de corrélation et des fonctions de discrimination, ce qui conduit à des erreursdans les estimées de pseudo-distances et de delta-distances et, en conséquence, à une erreur depositionnement. Bénéficiant d’un état de l’art des approches développées pour l’atténuation deseffets des interférences, de nouvelles techniques sont proposées dans cette thèse afin de réduirel’impact des MT sur les performances des récepteurs, et d’améliorer ainsi la précision de positionnementGPSGlobal Navigation Satellite Systems (GNSS) receivers calculate the user position, velocity and timeby using the signals received from a set of navigation satellites. In constricted environments, suchas urban canyons or other intensive obstruction scenarios, the signal transmitted by the satelliteis subject to reflection or diffraction and can follow different paths, commonly known as multipath(MP) interferences, before arriving at the antenna of the GNSS receiver. The MP interferencesaffect the signal processing results at different stages in the receiver. For instance, MP signals modifythe correlation and discriminator functions and can introduce errors in pseudo-range (PR) andcarrier phase measurements, resulting finally in GNSS-based positioning errors. Therefore the MPinterference can be considered as a dominant error source in these complex situations. This thesisinvestigates MP mitigation techniques based on signal processing methods at different stages ofthe GNSS receiver. By analyzing and comparing the state-of-the-art MP mitigation approaches, innovativeMP mitigation techniques are proposed in order to reduce the impact of MP interferenceson the GNSS receiver, and to improve the positioning accuracy based on GNSS
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Rice, Michael, i Qiang Lei. "SHF MULTIPATH CHANNEL MODELING RESULTS". International Foundation for Telemetering, 2005. http://hdl.handle.net/10150/604799.
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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, NevadaThis paper presents the results of land-based SHF channel modeling experiments. Channel modeling data were collected at Edwards AFB, California at S-Band, X-Band and Ku-band. Frequency domain analysis techniques were used to evaluate candidate channel models. A graphical user interface (GUI) was developed to search for the optimum channel parameters. The model parameters corresponding to different frequencies were compared for multipath events captured at approximately the same locations. A general trend was observed where the magnitude of the first multipath reflection decreased as frequency increased and the delay remained relatively unchanged.
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Seco, Granados Gonzalo. "Antenna arrays for multipath and interference mitigation in GNSS receivers". Doctoral thesis, Universitat Politècnica de Catalunya, 2000. http://hdl.handle.net/10803/6876.
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Esta tesis aborda la sincronización de una o varias réplicas de una señal conocida recibidas en un entorno con propagación multicamino e interferencias direccionales. Uno de los hilos conductores de este trabajo es la aplicación sistemática del principio de máxima verosimilitud (ML) junto con un modelo de señal en el cual las armas espaciales no tienen estructura, y en cual el ruido es Gaussiano y presenta una matriz de correlación desconocida. Esta última suposición es fundamental a la hora de obtener estimadores capaces de atenuar las señales interferentes que presentan algún tipo de estructura, y esto se consigue sin necesidad de recurrir a la estimación de ciertos parámetros de dichas señales. Por otra parte, la suposición de que las armas espaciales carecen de estructura tiene ventajas desde un punto de vista práctico, al mismo tiempo que simplifica la estimación del resto de parámetros ya que las estimaciones de estas firmas se pueden calcular de forma cerrada. Esto constituye un primer paso hacia la eliminación de las búsquedas en múltiples dimensiones, que es otro de los objetivos perseguidos en este trabajo.En la primera parte de la tesis se deduce la solución de máxima verosimilitud para el problema general de estimación de retardos cuando el ruido tiene correlación espacial desconocida. Se demuestra que el criterio resultante para los retardos es consistente y asintóticamente eficiente, pero también es altamente no-lineal debido a la presencia del determinante de una matriz y no permite, por tanto, el uso de procedimientos sencillos de optimización. Asimismo, se demuestra y se argumenta intuitivamente que el criterio _ optimo ML se puede aproximar por una función de coste más sencilla que es asintóticamente equivalente. A diferencia de otros problemas de estimación, en el caso tratado aquí, el primer término del desarrollo de Taylor del estimador ML no conserva la eficiencia asintótica. La característica esencial de la nueva función de coste es que depende linealmente de la matriz de proyección sobre el subespacio de las señales y, por lo tanto, admite ser minimizada mediante el algoritmo IQML, que es eficiente desde el punto de vista computacional. Además, la existencia de métodos de inicialización sencillos y robustos a las interferencias, los cuales se basan en el uso de una matriz de pesos igual a la identidad y posiblemente también en el algoritmo ESPRIT, hace que el esquema de estimación propuesto pueda ser viable para un diseño práctico. La nueva función de coste se puede aplicar de la misma manera a la estimación del retardo en un canal FIR. En este caso, el algoritmo IQML se puede modificar de forma que, en cada iteración, la estimación del retardo se obtiene a partir de las raíces de un polinomio cuyo orden es igual a la longitud del canal.
El objetivo perseguido por los estimadores presentados en la segunda parte de la tesis es aprovechar una particularidad de los sistemas GNSS (Global Navigation Satellite Systems), que consiste en que la dirección de llegada de la señal directa puede ser conocida a priori. Basándose en esta información adicional y suponiendo que el array está calibrado, se propone un modelo simplificado, aunque al mismo tiempo aproximado, para la señal recibida. En este modelo todas las señales excepto la señal directa se engloban en un término con correlación espacial desconocida. Se analizan los estimadores ML del retardo y de la fase de portadora de la señal directa. El sesgo producido por las componentes multicamino al utilizar estos estimadores se reduce de forma muy importante con respecto al sesgo que sufren otros métodos. De hecho, el error cuadrático medio de los estimadores propuestos es en muchas ocasiones muy próximo o incluso inferior al mínimo error que se puede alcanzar con modelos más detallados del canal multicamino. Asimismo, se presentan dos algoritmos de estimación del retardo basados en el cálculo de las raíces de un polinomio. Se demuestra también que las estimaciones ML se pueden obtener a partir de la señal de salida de un conformador de haz híbrido. Debido a que el propio conformador depende de las estimaciones del retardo y de la amplitud de la señal directa, el uso de un algoritmo iterativo surge de forma natural. La formulación mediante el conformador híbrido proporciona una interpretación alternativa interesante de la estimación ML, y podrá ser apropiada para una realización práctica. Finalmente, se demuestra analíticamente y numéricamente que el estimador propuesto para el retardo es robusto frente a errores en el valor nominal del vector de enfoque de la señal directa, y se presenta una manera de extender el margen tolerable de errores de apuntamiento.
En la última parte de la tesis se trata la sincronización de un usuario deseado que transmite una secuencia de entrenamiento conocida en un sistema de comunicaciones DS-CDMA.
El modelo de señal utilizado agrupa el ruido, y la interferencia externa y de acceso múltiple en un término de ruido equivalente que presenta una matriz de correlación espacio-temporal desconocida. Partiendo de este modelo, se deduce un estimador del retardo que es una aproximación para un numero grande de muestras del estimador ML exacto y que es apropiado para canales con desvanecimientos lentos y noselectivos en frecuencia. El estimador propuesto es una técnica de un solo usuario y es resistente al efecto near-far. Su importancia radica en el hecho de que aprovecha la estructura de las señales en el dominio temporal y espacial, lo que contrasta con otros métodos existentes que, a pesar de utilizar un array de antenas, sólo utilizan la estructura de las señales en uno de los dos dominios. En un sistema de comunicaciones móviles, el usuario deseado está interferido por un número generalmente elevado de señales de otros usuarios y por posibles interferencias externas. En concordancia con este hecho, los resultados numéricos han mostrado que el uso conjunto de todos los grados de libertad espacio-temporales es indispensable para la correcta adquisición y seguimiento del retardo en sistemas con una carga elevada de usuarios y/o en presencia de interferencias externas.
The thesis deals with the synchronization of one or several replicas of a known signal received in a scenario with multipath propagation and directional interference. A connecting theme along this work is the systematic application of the maximum likelihood (ML) principle together with a signal model in which the spatial signatures are unstructured and the noise term is Gaussian with an unknown correlation matrix. This last assumption is key in obtaining estimators that are capable of mitigating the disturbing signals that exhibit certain structure. On the other hand, the assumption of unstructured spatial signatures is interesting from a practical standpoint and facilitates the estimation. The elimination of the multidimensional searches required by many estimators is one of the main objectives of the thesis.
In the first part of the thesis, the maximum likelihood solution to the general time delay estimation problem for the case of noise with unknown spatial correlation is derived. The resulting criterion for the delays is shown to be consistent and asymptotically efficient; but it is highly non-linear, and does not lead to simple optimization procedures. It is shown that the optimal ML criterion can be approximated by an asymptotically equivalent cost function. The cost function depends linearly on the projection matrix onto the subspace spanned by the signals, and hence it can be minimized using the IQML algorithm. The existence of simple initialization schemes based on identity weightings or ESPRIT makes the approach viable for practical implementation. The proposed cost function can be applied to the estimation of the delay in a FIR channel. In this case, each iteration of IQML comes down to rooting a polynomial.
The goal of the estimators presented in the second part of the thesis is to take advantage of one particularity of the GNSS (Global Navigation Satellite Systems) systems, such as GPS and GLONASS, consisting in that the direction-of-arrival of the line-of-sight signal may be known a priori. A simplified and approximate model for the received signal is proposed. The ML estimators of the time delay and carrier phase of the direct signal largely reduce the bias produced by multipath components. Their RMSE is in many situations very close to or even better than the best possible performance attainable with more detailed models of the multipath channel. It is also shown that the ML estimates can be obtained from the output signal of a hybrid beamformer.
In the last part of the thesis, the synchronization of a desired user transmitting a known training sequence in a DS-CDMA communication system is addressed. Multiple-access interference, external interference and noise are assumed to have unknown space-time correlation. A large-sample ML code-timing estimator that operates in frequency-nonselective, slowly fading channels is derived. It is a single-user and near-far resistant method. It is shown that the use of all spatial and temporal degrees of freedom is indispensable for the correct acquisition and tracking of the synchronization parameters in heavily loaded systems and/or in the presence of external interference.
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McMurdie, Andrew, i Eric Perrins. "iNET Preamble Detector Performance in the Presence of Multipath Interference". International Foundation for Telemetering, 2014. http://hdl.handle.net/10150/578172.
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ITC/USA 2014 Conference Proceedings / The Fiftieth Annual International Telemetering Conference and Technical Exhibition / October 20-23, 2014 / Town and Country Resort & Convention Center, San Diego, CAThe iNET preamble can be used to estimate the frequency offset and multipath channel in an aeronautical telemetry link. To accomplish this, the receiver must be able to identify the start of the preamble within the received data stream in the presence of uncompensated frequency offset and unknown multipath channel. In this paper, we explore the performance of seven candidate preamble detectors in the presence of a frequency offset and over multipath channels typically encountered in aeronautical telemetry. A non-coherent post-detection integration (NCPDI) detector considered in this paper demonstrates the best detection performance for a reduced complexity.
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Abdulrahman, Majeed Carleton University Dissertation Engineering Systems and Computer. "DFE for interference and multipath suppression in a CDMA system". Ottawa, 1993.
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Perrins, Erik. "ON THE PERFORMANCE OF MULTI-H CPM IN MULTIPATH INTERFERENCE". International Foundation for Telemetering, 2002. http://hdl.handle.net/10150/606378.
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International Telemetering Conference Proceedings / October 21, 2002 / Town & Country Hotel and Conference Center, San Diego, CaliforniaThe performance of multi-h CPM over multipath interference channels is evaluated with computer simulations using the optimal coherent receiver and a suboptimal noncoherent receiver. For channels with high-amplitude short-delay multipath reflections, the simulations show that both receivers reach an error floor in their performance as the amplitude of the multipath reflections grows. The rate of degradation for the noncoherent receiver is worse than for the coherent receiver. For channels with low-amplitude long-delay reflections the coherent and noncoherent receivers had losses of 1 dB and 3 dB respectively relative to their respective unfaded performance.
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Davis, Adam Todd. "DYNAMIC BEHAVIOR OF MULTIPATH INTERFERENCE IN ARTM CHANNEL SOUNDING DATA". International Foundation for Telemetering, 2000. http://hdl.handle.net/10150/606500.
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International Telemetering Conference Proceedings / October 23-26, 2000 / Town & Country Hotel and Conference Center, San Diego, CaliforniaData collected during July 1999 at Edwards EAFB by the Advanced Range Telemetry (ARTM) program is examined to characterize the dynamic behavior of multipath interference in an aeronautical telemetry channel. Multipath fade events are analyzed in the frequency domain to show how these fades appear, evolve, and disappear from the channel. A channel model and examples from the channel sounding data are used to show the dynamic nature of these fade events. The Doppler power spectrum is used to quantify the exact time-varying nature of the multipath fade events. The coherence time, or the amount of time the channel can be viewed as unchanging, is obtained from the Doppler power spectrum and is calculated to be 100 ms in the data sets examined in this paper. This implies that adaptive multipath mitigation techniques must have an adaptation bandwidth of 10 Hz.
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Rice, Michael, i Daniel H. Friend. "Antenna Gain Pattern Effects on Multipath Interference in Aeronautical Telemetering". International Foundation for Telemetering, 1997. http://hdl.handle.net/10150/607555.
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International Telemetering Conference Proceedings / October 27-30, 1997 / Riviera Hotel and Convention Center, Las Vegas, NevadaThis paper examines the effect of antenna gain pattern on multipath fades for a typical aeronautical telemetry system. Assuming a parabolic reflector antenna at the tracking station and a single specular reflection as the source of multipath, an expression for the fade depth which incorporates the attenuating effects of the antenna gain pattern is derived. A representative example is presented which demonstrates the utility of the expressions derived.
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Dye, Ricky G., i Lyman D. Horne. "PARAMETER CHARACTERIZATION ON A TELEMETRY CHANNEL INCLUDING THE EFFECTS OF THE SPECULAR RAY". International Foundation for Telemetering, 1995. http://hdl.handle.net/10150/608412.
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International Telemetering Conference Proceedings / October 30-November 02, 1995 / Riviera Hotel, Las Vegas, NevadaThe aeronautical channel model is a good candidate for modeling the effects of multipath interference of telemetry signals on test ranges. The aeronautical fading channel model is parameterized by the signal to noise ratio, the Doppler shift and time delay between the specular and direct components, the specular to direct power ratio, the direct to diffuse power ratio, and the bandwidth of the multipath fading process. Segments of weighting signal data measured during a test at Tyndall AFB provide data which can be used to determine typical values of the above parameters in a variety of telemetering environments. In this paper, the set of parameters which most closely model the actual telemetry channel using the Tyndall data is determined.
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Lo, Norm W. K. (Norman Wai Keung) Carleton University Dissertation Engineering Systems and Computer. "Adaptive equalization for a multipath fading channel in the presence of interference". Ottawa, 1994.
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Lim, Seau Sian. "Antenna array single- and multi-user DS-CDMA receivers". Thesis, Imperial College London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367916.
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Mowbray, Robert Stephen. "Interference and multipath cancellation for increased subscriber capacity in spread spectrum communication systems". Thesis, Edinburgh Napier University, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386003.
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CARLSON, JOHN R., i ARLEN SCHMIDT. "AIRBORNE/SHIPBORNE PSK TELEMETRY DATA LINK". International Foundation for Telemetering, 1991. http://hdl.handle.net/10150/612917.
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International Telemetering Conference Proceedings / November 04-07, 1991 / Riviera Hotel and Convention Center, Las Vegas, NevadaThis paper describes the design considerations and methodology applied to solve the practical problems posed in the creation of a high bit rate telemetry relay system and specifically the techniques implemented to enhance signal to noise performance under adverse operational conditions.
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Kamirah, Daniel K. "OFDM Performance on Aeronautical Channnels". International Foundation for Telemetering, 2009. http://hdl.handle.net/10150/606130.
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ITC/USA 2009 Conference Proceedings / The Forty-Fifth Annual International Telemetering Conference and Technical Exhibition / October 26-29, 2009 / Riviera Hotel & Convention Center, Las Vegas, NevadaThis paper provides an introduction to the Orthogonal Frequency Division Multiplexing (OFDM) scheme which has been proposed for future aeronautical telemetry applications. OFDM offers the potential for high data rates on radio channels with multipath such as aeronautical telemetry channels. This paper provides in introduction to OFDM and demonstrates how orthogonality is maintained over multipath channels by the introduction of a guard band and by the inclusion of a cyclic prefix. The simulation of OFDM in multipath is simulated and performance results are presented that show the degradation of this scheme on a multipath channel with and without the guard band and the cyclic prefix.
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Chen, Chi-She. "Using TD/CCSK spread spectrum technique to combat multipath interference in a multiple user system". Ohio : Ohio University, 1995. http://www.ohiolink.edu/etd/view.cgi?ohiou1179519410.
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Kajale, Nikhil Vijay. "UWB and WLAN Coexistence: a Comparison of Interference Reduction Techniques". [Tampa, Fla.] : University of South Florida, 2005. http://purl.fcla.edu/fcla/etd/SFE0001145.
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Ibrahim, Jihad E. "Algorithms and Architectures for UWB Receiver Design". Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/26105.
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Impulse-based Ultra Wideband (UWB) radio technology has recently gained significant research attention for various indoor ranging, sensing and communications applications due to the large amount of allocated bandwidth and desirable properties of UWB signals (e.g., improved timing resolution or multipath fading mitigation). However, most of the applications have focused on indoor environments where the UWB channel is characterized by tens to hundreds of resolvable multipath components. Such environments introduce
tremendous complexity challenges to traditional radio designs in terms of signal detection and synchronization. Additionally, the extremely wide bandwidth and shared nature of the medium means that UWB receivers must contend with a variety of interference sources. Traditional interference mitigation techniques are not amenable to UWB due to the complexity of straight-forward translations to UWB bandwidths.
Thus, signal detection, synchronization and interference mitigation are open research issues that must be met in order to exploit the potential benefits of UWB systems. This thesis seeks to address each of these three challenges by first examining and accurately characterizing common approaches borrowed from spread spectrum and then proposing new methods which provide an improved trade-off between complexity and performance.Ph. D.
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Mirbagheri, Arash. "Linear MMSE receivers for interference suppression & multipath diversity combining in long-code DS-CDMA systems". Thesis, Waterloo, Ont. : University of Waterloo, 2003. http://etd.uwaterloo.ca/etd/amirbagh2003.pdf.
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Thesis (Ph.D)--University of Waterloo, 2003."A thesis presented to the University of Waterloo in fulfilment of the thesis requirement for the degree of Doctor of Philosophy in Electrical and Computer Engineering". Includes bibliographical references. Also available in microfiche format.
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Zhang, Yunjun. "Analysis and cancellation of inter-carrier interference for OFDM systems over time-variant multipath fading channels". Thesis, University of Ottawa (Canada), 2002. http://hdl.handle.net/10393/6065.
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The orthogonality among the subcarriers of OFDM systems may be impaired by the time-selectivity of the fading channels. The loss of the orthogonality results in ICI, and if it is not treated appropriately, the system performance may not be improved only by increasing the signal-to-noise ratio. In other words, ICI results in error floors. This research work concentrates on the ICI analysis and cancellation, and also on the effects of channel time-selectivity on the OFDM systems over frequency-selective time-variant mobile fading channels. In the first part of this study, a general time-variant frequency-selective WSSUS fading channel model is further characterized to support the OFDM ICI analysis, thus the obtained results are applicable for many specific channels. We then identify the cause of the ICI, i.e. how the orthogonality among the subcarriers of OFDM systems is impaired. The average ICI power and its distribution are obtained based on the general time-variant frequency-selective WSSUS fading channel model. To mitigate the ICI caused by the channel time-selectivity for OFDM systems, in the second part of this study, an efficient ICI cancellation scheme is designed based on the obtained ICI power distribution. The simulation results indicate that a significant performance improvement can be achieved. For OFDM systems, differential encoding can be performed not only between the information bits of the same subcarrier of the consecutive OFDM symbols (inter-frame differential encoding), but also between the information bits of the adjacent subcarriers of the same OFDM symbol (inter-carrier differential encoding). In the third part of this study, we compare the performance of inter-frame and inter-carrier differential detection for OFDM systems over multipath time-variant mobile fading channels. The objective is to identify which differential encoding scheme (inter-frame or inter-carrier) is more robust to the channel time-selectivity, when OFDM systems are experiencing both frequency-selective and time-selective fading. The conditions under which the inter-carrier differential encoding outperforms the inter-frame differential encoding and vice-versa are provided.
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Chen, Nan. "An IEEE 802.15.4 Packet Error Classification Algorithm : Discriminating Between Multipath Fading and Attenuation and WLAN". Thesis, Mittuniversitetet, Avdelningen för informations- och kommunikationssystem, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-24918.
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In wireless sensor networks, communications are usually destroyed by signal attenuation, multipath fading and different kinds of interferences like WLAN and microwave oven interference. In order to build a stable wireless communication system, reactions like retransmission mechanisms are necessary. Since the way we must react to interference is different from the way we react to multipathfading and attenuation, the retransmission mechanism should be adjusted in different ways under those different cicumstances. Under this condition, channel diagnostics for discriminating the causes that corrupt the packets between multipath fading and attenuation (MFA) and WLAN interference are imperative. This paper presents a frame bit error rate (F-BER) regulated algorithm based on a joint RSSI-LQI classifier that may correctly diagnose the channel status. This discriminator is implemented on MicaZ sensor devices equipped with CC2420 transceivers. This discriminator is able to improve the accuracy to 91%. Although we need to wait for 2 or 3 necessary packets to make a decision, higher stability and reliability are presented when operating this discriminator.
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Norman, Terence R. "An investigation into the effects of multipath interference and their significance in the design of radio frequency identification systems". Thesis, University of Manchester, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.616285.
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This thesis investigates multipath interference and the implication of this phenomenon for the design of future radio frequency identification devices, or RFID tags. The future radio frequency identification market and the design of appropriate tags is discussed. In particular utilising microwave carrier frequencies to extend tag-to-reader range and increase product functionality is considered. It is demonstrated that whilst the broader bandwidth inherent in microwave frequencies does allow an increase in RFID product functionality multipath interference effects will severely limit the range and reliability of microwave RFID devices. Through the development of a new mathematical framework describing multipath interference phenomena a range of models of the multipath propagation environment are constructed that allow the effects of multipath interference upon range and functionality of RFID devices to be investigated. From this fuller understanding of the effect of multipath interference upon RFID tag design a novel communications protocol is postulated that mitigates multipath effects and thus extends the range and reliability of low-microwave, radio frequency identification devices.
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Jian, Wang, i Xie Yan. "Behavior Modeling of a Digital Video Broadcasting System and the Evaluation of its Equalization Methods". Thesis, Linköping University, Computer Engineering, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-54632.
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In this thesis, a single carrier ATSC DTV baseband transmitter, part of the receiver(including channel estimator and channel equalizer), were modeled. Since multi-pathinduced ISI (inter symbol interference) is the most significant impact on theperformance of single carrier DTV reception, modeling and implementation of singlecarrier channel estimator and channel equalizer have been the focus of the thesis. Westarted with the investigation of channel estimation methods. Afterwards, severalchannel estimators and equalizers were modeled and the performance of each channelequalization methods in different scenarios was evaluated. Our results show that thefrequency domain equalizer can achieve low computing cost and handle long delaypaths. Another important issue to be considered in block equalization is Inter-BlockInterference (IBI). The impact of IBI was investigated via behavior modeling. In lastpart of our thesis, two methods for IBI cancellation are compared and the proposal forhardware implementation was given.
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Pirinen, P. (Pekka). "Effective capacity evaluation of advanced wideband CDMA and UWB radio networks". Doctoral thesis, University of Oulu, 2006. http://urn.fi/urn:isbn:9514282701.
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Abstract
High radio capacity is one of the main targets in wireless network planning. The characteristics of the broadband radio channel pose serious challenges for achieving this goal. This thesis views the capacity problem from two frameworks. In the first, the effective user capacity in advanced direct sequence wideband code-division multiple-access (DS-CDMA) radio networks is evaluated. Sensitivity to various imperfections in key system parameters is studied. The analysis is based on a mathematical foundation that presents complex signal models and enables evaluation of the performance losses due to parameter estimation errors and multipath fading. The effective number of users supported in a cell is restricted by the multiple access interference (MAI) in the same cell (intracell interference) and overall background noise. The studied wideband CDMA receiver structures comprise conventional rake receivers with both the maximal ratio combining (MRC) and equal gain combining (EGC) schemes that can be supplemented with either linear decorrelating or nonlinear successive cancellation-based multiuser detectors and M-antenna spatial diversity.
The second framework focuses on direct sequence spread spectrum-based ultra wideband (UWB) indoor communications. Cochannel interference limited capacity is evaluated against the outage probability criterion in exponentially decaying lognormal multipath fading channels. Distance-dependence and spatial distribution of users is taken into account at different spatial cell configurations. Only moderate complexity partial rake receivers with noncoherent combining are employed. Total interference is composed of interpath, multipath, intracell, and intercell interference contributions. Lognormal sum approximations and simulations are used to evaluate distributions of the desired and interfering signals. The impact of the timing errors at the receiver monopulse correlation is studied.
The numerical results for the wideband CDMA framework show that effective user capacity and sensitivity depend critically on the joint impact of nonidealities in system parameters (e.g., channel profile, severity of fading, receiver algorithms). User capacities of the studied multiuser enhanced receivers were more prone to these impairments than those of the simpler single user receivers. The results should be used for network planning and optimization.
The numerical results of the UWB framework suggest that, even in the multipath rich channel, the optimal number of rake fingers can be less than half of the significant multipaths. Differences between circular, square, and hexagonal cell models proved to be minor with respect to link distance distributions. The derived link distance statistics are useful tools in the analytic piconet dimensioning and optimization.
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Altan, Han. "Dual Antenna Use on a GPS Receiver". International Foundation for Telemetering, 2008. http://hdl.handle.net/10150/606154.
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ITC/USA 2008 Conference Proceedings / The Forty-Fourth Annual International Telemetering Conference and Technical Exhibition / October 27-30, 2008 / Town and Country Resort & Convention Center, San Diego, CaliforniaDue to vehicle dynamics in mobile systems, GPS signal reception may be blocked by the body of the vehicle. This paper discusses various studies made on some vehicles such as the Space Shuttle, various aircraft, and analyzes the implementation of dual GPS antenna systems. Constructive and destructive interference characteristics of signal combining are considered. The author suggests an approach which uses a delay line on one of the antennas while analyzing the front end C/N0 needed for L1 GPS reception. An embedded Excel spreadsheet provides a front-end Noise Figure (NF) calculation tool based on user selected parameters.
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Xingwen, Ding, Zhai Wantao, Chang Hongyu i Chen Ming. "CMA BLIND EQUALIZER FOR AERONAUTICAL TELEMETRY". International Foundation for Telemetering, 2016. http://hdl.handle.net/10150/624262.
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In aeronautical telemetry, the multipath interference usually causes significant performance
degradation. As the bit rate of telemetry systems increases, the impairments of multipath
interference are more serious. The constant modulus algorithm (CMA) blind equalizer is effective
to mitigate the impairments of multipath interference. The CMA adapts the equalizer coefficients
to minimize the deviation of the signal envelope from a constant level. This paper presents the
performances of the CMA blind equalizer applied for PCM-FM, PCM-BPSK, SOQPSK-TG and
ARTM CPM in aeronautical telemetry.
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Havel, Ladislav. "Počítačový návrh digitálního radioreléového spoje". Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2009. http://www.nusl.cz/ntk/nusl-218029.
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The Terrestrial digital radio links are used for transmitting digital information between fixed stations on a line of sight of a radio path. Each digital radio link has many characteristics and parameters for transmission. We require technical parameters in the design of digital radio link such as data rates and capacities. In this design we should take into account most effects of the electromagnetic waves propagation, if we want to meet user technical requirements of the link and if that link may correctly transmit digital signals with minimum errors. Prediction methods for the design of terrestrial line of sight systems are still in progress. Some effects of electromagnetic waves propagation and methods of the digital radio link design depend on natural variability and climate. The goal of this diploma thesis is to investigate methods for the design of terrestrial line of sight links with taking into account of ITU recommendation. Make computer program which implement this investigate methods
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Křivka, Petr. "Počítačové modelování datového přenosu po silnoproudých vedeních". Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2011. http://www.nusl.cz/ntk/nusl-219335.
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The master‘s thesis is focused on data transfer over power lines. The influence of connected devices on data signal is studied. In this thesis, you can find the descriptions of PLC technology characteristics, sources of signal interruption and, mainly, the method of modelling the PLC channels as a multipath signal propagation environment is thoroughly discussed. There are models of PLC channels using this method projected in Simulink. The analysis of the influence of connected devices to bit error rate of a signal is processed. The devices are modelled by connected impedance.
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Bradáč, Lubomír. "Model distribuční energetické sítě". Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2012. http://www.nusl.cz/ntk/nusl-219469.
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The thesis is focused on PLC technology issues and thus the data transmission over a power-line. This work describes characteristics of the PLC technology, its usage, functional principles and used modulation techniques. The main part of the work describes individual kinds of interferences in the network. The method of necessary steps against these interferences by using the right modulation and relevant coding is also described in the thesis. On the basis of theoretical knowledge, the models of interferences are realized in Matlab/Simulink. The simulative model of power-lines with random parameters is designed and realized for each elected techniques of modulation (BPSK, QPSK, ASK, FSK). The method of PLC channels modeling is chose as a multipath signal spreading for topology with one and two branching and the dependence of their transmission functions are inquired too. The analysis of interference influence on the data transmission is performed via the created models. All acquired results are compared and evaluated in the conclusion of this thesis.
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Queiroz, Diego Véras de. "Simulação realista de redes de sensores sem fio industriais". Universidade Federal da Paraíba, 2016. http://tede.biblioteca.ufpb.br:8080/handle/tede/9248.
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A Wireless Sensor Network (WSN) can be characterized by the use of sensor nodes in varied environments for many different applications, e.g., monitoring and control systems applications in industrial environments. The use of WSNs in industrial applications must deal with typical problems of wireless networks, such as high attenuation and obstructions. In these environments, different characteristics of the channels can be observed due to its multipath profile. Changes in the topology may also cause changes in the channel characteristics as the time goes on, and it may cause differences in the average value of the received power. An alternative to deal with it and with the variation of channel quality is the development of protocols that use multiple channels. Its use allows, e.g., to achieve better use of the channel, increasing the network transmission capacity. However, there is a difficulty in evaluating and comparing different approaches due to the lack of simulators which have more accurate models. To assess the real benefits of these protocols, one should take into account a more realistic propagation model. This work presents a realistic simulation model that captures the effects of fading on a large and small scale, log-normal shadowing, the non-stationary characteristics of the channel for a long time, and the different characteristics of the different IEEE 802.15.4 standard channels. The model was then built into the open-source discrete event simulator Castalia and tested, comparing it with the default stationary model of the simulator. After integration, the protocol Tree-based Multi-Channel Protocol (TMCP) was evaluated using the proposed model. In the experiments it was possible to identify good accuracy in both the model and the TMCP protocol.
Uma Rede de Sensores sem Fio (RSSF) pode ser caracterizada pela utilização de nós sensores em variados ambientes para as mais diversas aplicações, por exemplo, para monitoramento e controle em ambiente industrial. O uso de RSSFs para implementar aplicações industriais precisa lidar com problemas típicos das redes sem fio, como alta atenuação e obstruções. Nesses ambientes, diferenças nas características dos canais podem ser observadas dado o seu perfil de multipercurso. Mudanças na topologia também podem provocar mudanças nas características dos canais ao longo do tempo, podendo causar diferença no valor médio da potência recebida. Uma alternativa para lidar com isso e com a variação da qualidade dos canais é o desenvolvimento de protocolos que utilizam múltiplos canais. Seu uso permite, por exemplo, alcançar uma melhor utilização do canal, aumentando a capacidade de transmissão da rede. No entanto, existe uma dificuldade em avaliar e comparar as diferentes abordagens devido à carência de simuladores que apresentem modelos mais precisos. Para avaliar os reais benefícios desses protocolos deve-se levar em consideração um modelo de propagação mais próximo da realidade. Esse trabalho apresenta um modelo de simulação que captura os efeitos de desvanecimento em larga escala, atenuação em pequena escala, sombreamento log-normal, as características não-estacionárias do canal em longos períodos de tempo, e as características distintas dos diferentes canais do padrão IEEE 802.15.4. O modelo foi então integrado ao simulador de eventos discretos de código aberto Castalia e testado, comparando-o com o modelo estacionário padrão do próprio simulador. A partir da integração, o protocolo Tree-based Multi-Channel Protocol (TMCP) foi implementado e avaliado utilizando o modelo proposto. Com os experimentos foi possível identificar uma ótima precisão do modelo e do protocolo TMCP.
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Ellinger, John David. "Multi-Carrier Radar for Target Detection and Communications". Wright State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=wright1463839176.
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Nguyen, Xuan Vinh [Verfasser]. "Super-resolution compressed sensing for resolving time-of-flight multipath interferences / Xuan Vinh Nguyen". Siegen : Universitätsbibliothek der Universität Siegen, 2018. http://d-nb.info/1173421858/34.
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Ma, Hang. "Using chaos to enhance multi-user time-of-arrival estimation : application to UWB ranging systems". Thesis, Toulouse, INSA, 2014. http://www.theses.fr/2014ISAT0008/document.
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Dans les décennies à venir, la connaissance d’informations très précises concernant la position d’un objet permettra de créer des applications révolutionnaires dans les domaines sociaux, médicaux, commerciaux et militaires. La technologie Ultra-Wideband (UWB) est considérée comme un bon candidat permettant de fournir des capacités de localisation précise grâce à la mesure de l’estimation du temps d'arrivée (TOA). Dans cette thèse, des algorithmes de mesure de distance dans le cas multi-utilisateurs pour des systèmes UWB sont étudiés afin d'atteindre une bonne précision pour une faible complexité, avec de la robustesse aux interférences multi-utilisateur et dans le cas d’un grand nombre d'utilisateurs. Au cours de la dernière décennie, les signaux chaotiques ont reçu une attention significative en raison d'un certain nombre de caractéristiques intéressantes. Les signaux chaotiques sont des signaux non périodiques, déterministes ou considérés comme pseudo-aléatoires provenant de systèmes dynamiques non linéaires. Leur bonne autocorrélation et leurs faibles propriétés d’inter corrélation les rendent particulièrement résistants aux évanouissements par trajets multiples et capables d'atténuer les interférences multi-utilisateur (MUI). En raison de leur grande sensibilité aux conditions initiales, il est possible de générer un grand nombre de signaux chaotiques pour accroître la capacité globale du système. Dans cette thèse, deux nouveaux algorithmes d'estimation de TOA sont proposés dans un cadre multi-utilisateur avec une faible complexité et une bonne robustesse. Le nombre d'utilisateurs pris en charge par ces deux algorithmes est beaucoup plus grand que dans le cas des estimateurs de TOA actuels. Cependant, l'utilisation de séquences d'étalement classique et d’impulsion limite l'amélioration des performances et la capacité du système. Afin d’apporter des améliorations, des signaux chaotiques sélectionnés sont utilisés comme séquences d'étalement ou impulsion dans les algorithmes proposés. Grâce à l'utilisation de signaux chaotiques, notre algorithme est non seulement amélioré, mais permet également l’utilisation d’un plus grand nombre d'utilisateurs par comparaison avec l’algorithme utilisant des signaux classiquesIn the coming decades, highly accurate position information has the potential to create revolutionary applications in the social, medical, commercial and military areas. Ultra-Wideband (UWB) technology is considered as a potential candidate for enabling accurate localization capabilities through Time-of-Arrival (TOA) based ranging techniques. Over the past decade, chaotic signals have received significant attention due to a number of attractive features. Chaotic signals are aperiodic, deterministic, and random-like signals derived from nonlinear dynamical systems whose good autocorrelation, low cross-correlation and sensitivity to the initial conditions make them particularly suitable to ranging systems. In this thesis, two new multiuser TOA estimation algorithms are proposed with low complexity and robustness to MUI, the number of users supported by which is much larger than current multiuser TOA estimators. While, the use of classic spreading sequences and ranging pulse constrain the further improvement of ranging performance and system capacity. For breaking through the limit brought by the classic signals, the selected chaotic signals are employed as the spreading sequences or ranging pulse in our proposed algorithms. With the use of chaotic signals, our proposed algorithm not only obtains the additional improvement, but also with capability to support larger number of users comparing with its counterpart using classic signals
34
Troublefield, Robert C. "DIGITAL RECEIVER PERFORMANCE". International Foundation for Telemetering, 2000. http://hdl.handle.net/10150/606794.
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International Telemetering Conference Proceedings / October 23-26, 2000 / Town & Country Hotel and Conference Center, San Diego, CaliforniaBit errors often occur in a wireless communications link when impairments alter the transmitted signal. It is advantageous to be able to predict how well a system will tolerate transmission problems. This paper details laboratory performance measurements and comparisons in terms of evaluating configurations of a digital receiver for Feher patented Quadrature Phase Shift Keying (FQPSK-B) demodulation. The transmitted signal is subjected to calibrated levels of impairments while the receiver performance is monitored in real-time.
35
Shang, Lei, i lei shang@ieee org. "Modelling of Mobile Fading Channels with Fading Mitigation Techniques". RMIT University. Electrical and Computer Engineering, 2006. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20061222.113303.
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This thesis aims to contribute to the developments of wireless communication systems. The work generally consists of three parts: the first part is a discussion on general digital communication systems, the second part focuses on wireless channel modelling and fading mitigation techniques, and in the third part we discuss the possible application of advanced digital signal processing, especially time-frequency representation and blind source separation, to wireless communication systems. The first part considers general digital communication systems which will be incorporated in later parts. Today's wireless communication system is a subbranch of a general digital communication system that employs various techniques of A/D (Analog to Digital) conversion, source coding, error correction, coding, modulation, and synchronization, signal detection in noise, channel estimation, and equalization. We study and develop the digital communication algorithms to enhance the performance of wireless communication systems. In the Second Part we focus on wireless channel modelling and fading mitigation techniques. A modified Jakes' method is developed for Rayleigh fading channels. We investigate the level-crossing rate (LCR), the average duration of fades (ADF), the probability density function (PDF), the cumulative distribution function (CDF) and the autocorrelation functions (ACF) of this model. The simulated results are verified against the analytical Clarke's channel model. We also construct frequency-selective geometrical-based hyperbolically distributed scatterers (GBHDS) for a macro-cell mobile environment with the proper statistical characteristics. The modified Clarke's model and the GBHDS model may be readily expanded to a MIMO channel model thus we study the MIMO fading channel, specifically we model the MIMO channel in the angular domain. A detailed analysis of Gauss-Markov approximation of the fading channel is also given. Two fading mitigation techniques are investigated: Orthogonal Frequency Division Multiplexing (OFDM) and spatial diversity. In the Third Part, we devote ourselves to the exciting fields of Time-Frequency Analysis and Blind Source Separation and investigate the application of these powerful Digital Signal Processing (DSP) tools to improve the performance of wireless communication systems.
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Bouatit, Mohamed Nacer. "Optimisation du routage, tolérance aux pannes et gestion de l'énergie et de l'interférence pour la transmission des flux multimédia temps réel dans les réseaux de capteur sans fil". Thesis, Paris, CNAM, 2018. http://www.theses.fr/2018CNAM1188/document.
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Les applications multimédias, dans les réseaux de capteurs sans fil, véhiculent des données volumineuses, qui nécessitent un taux de transmission élevé et un traitement intensif et par conséquent une consommation d'énergie importante. Transmettre efficacement ces flux hétérogènes, tout en assurant leur fiabilité et garantir les exigences de QoS, avec les ressources limitées disponibles, en particulier dans les contextes critiques, demeure un verrou scientifique ouvert. C’est pourquoi, dans le cadre de cette thèse, nous nous sommes intéressés aux aspects liés : au routage, à la tolérance aux pannes et à la gestion des interférences dans les RCMSF.Compte tenu, du très faible nombre de protocoles de routage, qui ont approché la phase expérimentale et encore moins ceux qui l’ont abordé pendant la transmission des données en temps réel, nous avons développé dans ce contexte, un protocole routage géographique baptisé GNMFT (Geographic Non-interfering Multipath Fault-tolerant),En premier lieu, nous avons amélioré le mode de sélection des nœuds, utilisé par le transfert glouton, pour faire face au problème du Minimum-local, où une fonction objective multicritères (distance, énergie et puissance de réception) relative au choix du prochain saut a été définie. Puis, nous avons introduit une phase d’optimisation des chemins construits afin d’éliminer les boucles et une approche adaptative gérant les transmissions simultanées des différents trafics.Par la suite, nous nous sommes orientés vers la tolérance aux pannes, pour assurer la fiabilité des données transmises ainsi que la connectivité du réseau. A cet effet, nous avons modélisé le nombre des paquets perdus durant la livraison des paquets et proposé deux mécanismes : un curatif pour réparer les défaillances soudaines et un préventif afin d’anticiper l’épuisement des batteries. Les deux mécanismes sont combinés avec une stratégie de basculement dynamique lors de la construction des chemins alternatives.En dernier lieu, nous avons présenté un modèle d’interférence et un troisième mécanisme qui limite les interactions entre les liens adjacents. De plus, nous avons défini également un modèle de perte de chemins dans un environnement multi-paires (source,sink) et nous avons calculé le coefficient de probabilité d’erreurs basée sur une fonction de distance qui sépare les flux de données. Une nouvelle métrique a été ajouté dans la fonction objective, relative à la somme des bruits des nœuds actifs qui interférent sur les nœuds du ForwardingSet du nœud courant.Les résultats obtenus montrent l’efficacité des approches proposées qui ont été étudiées et validées à la fois par simulation et sur un banc d’essai expérimentalMultimedia applications in WSNs convey large data (image, audio and video) that requires high transmission rate and intensive treatment and therefore high energy consumption. Effectively transmit these heterogeneous flows, while ensuring their reliability and guaranteeing QoS requirements, with the limited resources available, especially in critical contexts, remains an open scientific problem. That is why, in this thesis, we are interested in aspects related to : routing, fault tolerance and interference management in WMSNs.Given the very low number of routing protocols, that have approached the experimental phase and still less those who approached it during data transmission in real time, we developed in this context, a geographic routing protocol baptised GNMF (Geographic Non-interfering Multipath Fault-tolerant),First, we improved node's selection mode used by the greedy-forwarding, to deal with local minimum problem, where a multi-criteria objective function (distance, energy and reception power) related to next-hop choice has been defined. Then, we introduced an optimization phase of built paths to eliminate loops and an adaptive approach to manage simultaneous traffic transmissions.After that, we oriented towards fault tolerance, to ensure transmitted data reliability and network connectivity. To this end, we modeled the number of lost packets during package delivery and proposed two mechanisms. The curative is used when sudden failures occurs and the preventive to anticipate batteries depletion. Both are combined with a dynamic failover strategy during alternative paths construction.Finally, we presented an interference model and a third mechanism that limits interactions between adjacent links. In addition, we also defined a path loss model in a multipairs environment (source, sink) and computed the error probability coefficient based on a distance function that separates the data flows. A new metric has been added in the objective function, related to noise sum of the active nodes that interferes on forwarding set nodes of the current node.Obtained results show the effectiveness of the proposed approaches that have been studied and validated both by simulation and on an experimental testbed
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"Antenna arrays for multipath and interference mitigation in GNSS receivers". Universitat Politècnica de Catalunya, 2000. http://www.tesisenxarxa.net/TDX-0730101-124722/.
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Lin, Chien-Liang, i 林建良. "Interference and Multipath Suppression For GPS Reception Using Adaptive Beamforming". Thesis, 2010. http://ndltd.ncl.edu.tw/handle/72934194823341931654.
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碩士元智大學
通訊工程學系
98
The purpose of this thesis is to design a blind adaptive GPS beamformer. Although the GPS is a mature system, because the weak GPS signal will be easily affected by external interference, as well as GPS positioning mechanism is related with the reception timing, it makes the accuracy of GPS positioning vulnerable to the impact of multipath. The proposed beamformer has the ability to combat strong interference and multipath signal. Therefore the desired GPS signal can be reliable receipted in the cold boot state, and thus, it improves both the receiver system reliability and positioning accuracy. In this paper, we propose a three-step subspace beamformer by applying subspace search/projection method. Respectively, in the first step, it eliminates the low elevation multipath. In the second step, the strong directional interference is blindly canceled. By using the C/A code information, although the GPS elevation angle is not know a priori, the beamforemer can enhance the received GPS signal power in the third step. Finally, we use subspace tracking techniques, orthonormal projection approximation subspace tracking(OPAST) to reduce the computing complexity and equip the beamformer with the ability to track time-varying angles. In this study, the proposed three-step subspace beamformer is simulated in multipath and interference environment with Gaussian noise to confirm the improvment of the GPS positioning results. The Output SINR performance is simulated and analyzed. The performance results are confirmed the performance improvement of GPS receivers.
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Lin, Po-Tsun, i 林柏村. "Performance Analysis of Multipath Interference Reduction with Adaptive Array Techniques". Thesis, 2000. http://ndltd.ncl.edu.tw/handle/26784509694941416862.
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碩士逢甲大學
電機工程學系
88
Facing the problems in wireless communicaiton, including multipath-fading, limited bandwidth, and co-annelinterferences. Besides that, we also have to satisfy the requirement of the incresing number of subscribers. Thus, it becomes a necessary trend to design a smart antenna system. It can mitigate multipath fading, eliminate co-channel interferences, improve transmission efficiency and increase system capacity. The key point of it is to find a proper adaptive algorithm which can be used to change its pattern quickly and to the aim of SDMA. In this thesis, thinking of the coherent and noncoherent interferences arising from multipath, we analysis and comparion of some algorithms on reducing the above problems. At last, taking account of complex and computing load of a system, a simplified type for LCMV, called linearly constrained criterion(LC) is presented. We really hope LC can be applied to smart antenna system more suitable.
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Yeh, Ting-hung, i 葉庭宏. "FPGA Implementation of Multipath Interference Cancellation for Passive Coherent Location Systems". Thesis, 2011. http://ndltd.ncl.edu.tw/handle/g6bd2g.
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碩士國立臺灣科技大學
電機工程系
99
This work investigates airborne target detection using a passive coherent location system, which use non-cooperative commercial broadcast signals as its transmitter sources. To locate the unknown targets, we jointly combine Angle-of-Arrival and Time-Difference-of-Arrival information. Generally, a receiver in a passive coherent location system receives the reflected target signals and the interference of clutter. The prior is usually much weaker than the latter. To obtain an accurate output of Ambiguity function, we must cancel the interference from receiver. We estimate the Angle-of-Arrival information by applying Multiple Signal Classification algorithm, which is implemented using FPGA and DSP. As to the interference of clutter cancellation for Ambiguity functio we investigate some algorithms including least mean square, normalized least mean square, and extensive cancellation algorithm. Because of the limit of hardware, we select the normalized least mean square algorithm for FPGA implementation. We perform some experiments by emulating reference and clutter signal to verify the functionality of the algorithm implementation. The empirical results demonstrate satisfactory performances of interference suppression.
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WEN, ZHI-HONG, i 溫志宏. "The effect of multipath interference on the performance of packet radios". Thesis, 1990. http://ndltd.ncl.edu.tw/handle/28050506945992842997.
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Han, Di-Yar, i 韓滌亞. "The Effect of Multipath Interference on the Performance of Cellular Mobile Communication". Thesis, 1993. http://ndltd.ncl.edu.tw/handle/94594926667512451647.
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碩士國立中正大學
電機工程研究所
81
During the development of communication technology, mobile telephone has been massively applied into our daily life. However, channel allocation has become a serious problem due to the rapidly increasing utilization. In order to increase the channel capacity and solve the channel allocation problem, mobile telephone system adopts the cellular architecture. This architecture turns to its advantages of frequency reuse and co- channel interference suppression (via capture effect). In a radio communciation environment, no matter what the signal is transmitted outdoors or indoors, the phenomenon of multipath interference is unavoidable. Therefore, in this thesis, we firstly investigate the effect of multipath interference on the performance of a single cell system with finite users. In order to use Markov chain method, two new system models with 3- dimensional state vector and 2-dimensional state vector respectively are presented. With these models, the system performance under multipath interference has been successfully derived. Plus, we further propose an extended-slot method to reduce the multipath interference triggered by LOS packets occurring in the previous slot, which also results in system performance enhancement. Lastly, we analyze the effect of co- channel interference and multipath interference on the performance of multicell system.
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黃子豪. "A Study on Soft Multipath Interference Cancellation Techniques for MC-CDMA Systems". Thesis, 2005. http://ndltd.ncl.edu.tw/handle/12747845499732850276.
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Lin, Chih-Hung, i 林志鴻. "An Improved Multistage Parallel Interference Cancellation for CDMA in Multipath Fading Channels". Thesis, 2000. http://ndltd.ncl.edu.tw/handle/97561785394511709756.
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碩士國立清華大學
電機工程學系
88
This study introduces an improved multistage parallel interference cancellation (PIC) technique for binary phase shift keying (BPSK) modulated direct sequence code-division multiple access (DS/CDMA) systems over multipath fading channels. We study the improvement technique for multistage interference cancellation receivers, with a full or only a fractional cancellation of the estimated multiple access interference (MAI) and intersymbol interference (ISI) caused by multipaths at each receiver stage. Because the statistics of MAI and ISI are unavailable in multipath fading channels, the estimations of the MAI and ISI, especially in the earlier stages, contain significant errors. A poor estimation of MAI and ISI due to the relatively high decision bit error rate (BER) may lead to a poor cancellation or even a higher BER at the following decision stages. In this study, the H-infinity filtering is employed to estimate MAI and ISI at the initial stage, and then it can improve the system performance by effective cancellation of MAI and ISI. The H-infinity filtering approach is a robust optimization from the minimax point of view, and it tends to be more effective even in the case that the co-channel interference statistics are less valid. It minimizes the effect of the worst disturbance (including co-channel interference and additive noise). Computer simulation demonstrates that a better transmission performance can be achieved by using the H-infinity filtering algorithm at the initial stage of PIC.
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Hsiu, Tsai Pei, i 蔡佩修. "An Improved Multistage Parallel Interference Cancellation for MC-CDMA in Multipath Fading Channel". Thesis, 2001. http://ndltd.ncl.edu.tw/handle/34333895154008625857.
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碩士國立臺灣科技大學
電子工程系
89
This study introduces an improved multistage parallel interference cancellation technique for multi-carrier code-division multiple access systems over multipath fading channels. We study the improvement technique for multistage interference cancellation receivers, with a full or only a fractional cancellation of the estimated multiple access interference and intersymbol interference caused by multipaths at each receiver stage. Because the statistics of MAI and ISI are unavailable in multipath fading channels, the estimations of the MAI and ISI, especially in the earlier stages, contain significant errors. A poor estimation of MAI and ISI due to the relatively high decision bit error rate may lead to a poor cancellation or even a higher BER at the following decision stages. In this study, the filtering is employed to estimate MAI and ISI at the initial stage, and then it can improve the system performance by effective cancellation of MAI and ISI.
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King-Tai, Yang. "Space-Time Processing for Mobile Communications with Multipath Fast Fading and Co-Channel Interference". 1997. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0009-0112200611363653.
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47
Lin, Yu-hui, i 林育輝. "On the Modified PN Code Tracking Loop with Multiuser Detection and Multipath Interference Cancellation". Thesis, 2004. http://ndltd.ncl.edu.tw/handle/14722796235182723164.
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碩士國立中山大學
通訊工程研究所
92
A non-coherent PN code tracking loop with multi-user detection and simplified multi-path interference cancellation (MPIC) is proposed for direct sequence spread spectrum communications system. A decorrelator decision-feedback detector (DDFD) is first applied on the incoming signal to mitigate the multi-user interference. Then, a simplified multi-path interference cancellation (MPIC) is further used to increase signal quality. Finally, a modified code tracking loop (MCTL) is adopted for non-coherent PN code tracking. Mathematical expressions of the S-curve and tracking jitter are derived. Mean time to lose lock is also compared with traditional tracking loops. From the numerical results, we know the proposed PN code tracking loop can efficiently mitigate the interference from multi-user and multi-path and improve the performance of code tracking loop.
48
Cheng, Ming-Hsiung, i 鄭明雄. "A Design of Interference Canceller for CDMA Coherent Signal in Multipath Rayleigh Fading Channel". Thesis, 2000. http://ndltd.ncl.edu.tw/handle/65179840991933110781.
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碩士國立臺灣科技大學
電子工程系
88
In this thesis, we propose the design of adaptive antenna array receiver to cancel interference of multipath Rayleigh fading for code division multiple access mobile communication system. The Pseud-random noise code is employed in multipath fading cross correlation environment in which the receiver is the decorrelating detector. We concentrate on real time technigue in the receiver, we only receive the first arrival fading path, and the fading coefficient of the first arrival path is estimated by decorrelator detector. The fading coefficient provides the reference signal for the adaptive antenna array. This structure can solve multipath Rayleigh fading interference. Therefore, we don’t have to estimate the angle and time of the arrival multipath. The Rayleigh fading channel coefficient due to Doppler effect, is generated by a channel simulator. Multipath Rayleigh fading channel is made up of one signal through several Rayleigh fading channel. we compare, by simulation, the performance of equal power multipath and nonequal power ones in term of BER. The BER is compared with single path bound. The design can cancel interference of CDMA coherent signal of multipath Rayleigh fading by simulation result.
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Kuo, Ming-Chia, i 郭明家. "A New Rake Receiver Structure for Multipath Fading and Multiuser Interference In Communication Systems". Thesis, 2002. http://ndltd.ncl.edu.tw/handle/u3wsap.
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碩士逢甲大學
電機工程所
90
The technology of Direct Sequence Spread Spectrum has been utilized widely in mobile communication system for combating noise interference in transmission channels and keeping transmission information secret. However, the transmission bandwidth is restricted by interference when large users use common bandwidth. This problem has been a direction in processing mobile communication. On the other hand, it is known that multipath, which causes ISI and ICI, is a major reason influence the capacity of wireless TDMA communication system, and it often uses equalizer to solve the problems. In CDMA systems, diversity is one of the methods to combat multipath fading, where Rake receiver that based on path-diversity concept is applied most often. The thesis discusses the concepts of Rake receiver but also the drawbacks of Rake receiver. Therefore the thesis presents a new receiver structure, which combine a Rake receiver and adaptive decision feedback equalization, attempts to improve the immunity of the receiver to ISI, ICI and MAI.
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Lajevardi, Saina. "Imperfect Channel Knowledge for Interference Avoidance". Master's thesis, 2011. http://hdl.handle.net/10048/1740.
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This thesis examines various signal processing techniques that are required for establishing efficient (near optimal) communications in multiuser multiple-input multiple-output (MIMO) environments. The central part of this thesis is dedicated to acquisition of information about the MIMO channel state - at both the receiver and the transmitter. This information is required to organize a communication set up which utilizes all the available channel resources. Realistic channel model, i.e., the spatial channel model (SCM), has been used in this study, together with modern long-term evolution (LTE) standard.
The work consists of three major themes: (a) estimation of the channel at the
receiver, also known as tracking; (b) quantization of the channel information and its feedback from receiver to the transmitter (feedback quantization); and (c) reconstruction of the channel knowledge at the transmitter, and its use for data precoding during communication transmission.Communications