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Zhou, Jun. "Antenna aided interference mitigation for cognitive radio." Thesis, University of Edinburgh, 2009. http://hdl.handle.net/1842/10676.
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Spyropoulos, Ioannis. "Interference management in multiple-antenna wireless networks." Diss., [La Jolla] : University of California, San Diego, 2009. http://wwwlib.umi.com/cr/ucsd/fullcit?p3378675.
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Thesis (Ph. D.)--University of California, San Diego, 2009.Title from first page of PDF file (viewed Oct. 21, 2009). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 82-86).
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Anderson, Adam L. "Unitary space-time transmit diversity for multiple antenna self-interference suppression /." Diss., CLICK HERE for online access, 2004. http://contentdm.lib.byu.edu/ETD/image/etd500.pdf.
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Lundin, Andreas. "Interference and Energy Conservation in Phased Antenna Arrays and Young’s Double Slit Experiment." Thesis, Uppsala universitet, Institutet för rymdfysik, Uppsalaavdelningen, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-188035.
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The interest in creating and detecting electromagnetic waves carryingangular momentum in such a way that they form helical wavefronts,so called "twisted light'', has increased in recent decades.One possible way of generating such waves at radio frequenciesis to use a circular phased antenna array, where a larger relativephasing of the antenna elements corresponds to more twist of thewavefront per wavelength.However, analytical computations of the radiated power, and in turn theamountof emitted angular momentum, displays a quite rapid decrease with increasedphasing. This decrease in intensity may cause problems when alarge range of twisting is desired; for instance, as a means to encodeand transmit information. We have found that the decrease in radiatedpower does not haveany explicit relation to the beam being endowed with angular momentum.Instead, the decrease in emitted power can be explained byelectromagnetic couplingof the antenna elements in the array and that energy conservationholds, because an equal decrease in power is seen at the input of the array.We also show that a similar discrepancy is seen between the incomingand the total diffracted power in Young's classic double slit experiment,which, having only two slits, cannot provide any twisted light.The source of that discrepancy should be of a different origin.Although an explanation in terms of surface plasmons was recently givenin the literature, that is only applicable to metal screens. A general explanation of the problem therefore remains to be found.
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Chan, Chung Ph D. Massachusetts Institute of Technology. "Single antenna interference cancellation in asynchronous GSM/GPRS networks." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/36760.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2005.Includes bibliographical references (p. 73-74).
In this project, we have proposed a decorrelator-based single antenna interference cancellation algorithm for the asynchronous GSM/GPRS network. The algorithm is tested according to the current SAIC/DARP performance requirement in the computer simulation, and is shown to give various gains in different test scenarios.
by Chung Chan.
M.Eng.
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Kogon, Stephen Michel. "Adaptive array processing tecniques for terrain scattered interference mitigation." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/14927.
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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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Amihood, Patrick. "Performance analysis of interference suppression techniques for multiple antenna systems." Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2007. http://wwwlib.umi.com/cr/ucsd/fullcit?p3274524.
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Thesis (Ph. D.)--University of California, San Diego, 2007.Title from first page of PDF file (viewed October 3, 2007). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 114-119).
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Geoghegan, Mark, and Louis Boucher. "Space-Time Coding Solution to the Two-Antenna Interference Problem." International Foundation for Telemetering, 2014. http://hdl.handle.net/10150/577388.
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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, CAIn order to provide reliable line-of-sight communications, test aircraft typically use two transmit antennas to create top and bottom hemispherical patterns that cover the full range of possible aircraft orientations. The two transmit signals are normally generated by a single transmitter with the power being split between the two antennas. Although this configuration is straightforward and easy to implement, problems can arise due to the two signals constructively and destructively interfering with each other. This can result in the composite antenna pattern having periodic nulls with a depth and geometric spacing dependent upon the amplitude and phase differences of the two transmitted signals. This problem is usually addressed by either unevenly splitting the transmit power between the two antennas, or by using two separate transmitters at different frequencies. Unfortunately, these methods have drawbacks that require either system performance or cost trade-offs. This paper discusses the use of Space-Time Coding to eliminate this antenna interaction by transmitting modified waveforms that simultaneously allow for both full power transmission and single-channel operation. This approach effectively restores the nominal antenna performance, thereby resulting in better overall coverage and less pattern-induced dropouts. Telemetry performance results from recent flight testing are presented to validate the benefits of this approach.
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De, Lorenzo David S. "Navigation accuracy and interference rejection for GPS adaptive antenna arrays /." May be available electronically:, 2007. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
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Rice, Michael, and 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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Ponnekanti, S. "Efficient antenna based interference cancellation systems for narrowband and broadband signals." Thesis, University of Newcastle Upon Tyne, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282764.
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Anderson, Adam Lane. "Unitary Space-Time Transmit Diversity for Multiple Antenna Self-Interference Suppression." BYU ScholarsArchive, 2004. https://scholarsarchive.byu.edu/etd/154.
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A common practice for government defense agencies and commercial aeronautical companies is to use dual antennas on test flight air vehicles in order to overcome occlusion issues during high-speed telemetric maneuvers. The dual antennas, though never being masked at the same time, unfortunately lead to a drastic increase in nulls in the signal pattern. The result of this interference pattern can be compared to the effect of fading in a multiple-input multiple-output (MIMO) multi-path scattering environment. Confidence in this comparison leads to the use of unitary space-time MIMO codes to overcome the signal self-interference. The possibility and performance of several of these codes will be examined. Such criteria as training for channel estimation, use of shaped offset quadrature phase shift keying (SOQPSK), hardware facility, and data throughput will be compared for each code. A realistic telemetry channel will be derived to increase accuracy of simulated results and conclusions.
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Hinton, Danielle A. (Danielle Ayodele) 1978. "Protocols for multi-antenna ad-hoc wireless networking in interference environments." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/62416.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 231-242).
A fundamental question for the design of future wireless networks concerns the nature of spectrum management and the protocols that govern use of the spectrum. In the oligopoly model, spectrum is owned and centrally managed, and the protocols tend to reflect this centralized nature. In the common's model, spectrum is a public good, and protocols must support ad hoc communication. This work presents the design, tradeoffs and parameter optimization for a new protocol (Simultaneous Transmissions in Interference (STI-MAC)) for ad hoc wireless networks. The key idea behind the STI-MAC protocol is 'channel stuffing,' that is, allowing network nodes to more efficiently use spatial, time and frequency degrees of freedom. This is achieved in three key ways. First, 'channel stuffing' is achieved through multiple antennas that are used at the receiver to mitigate interference using Minimum-Mean-Squared-Error (MMSE) receivers, allowing network nodes to transmit simultaneously in interference limited environments. The protocol also supports the use of multiple transmit antennas to beamform to the target receiver. Secondly, 'channel stuffing' is achieved through the use of a control channel that is orthogonal in time to the data channel, where nodes contend in order to participate on the data channel. And thirdly, 'channel stuffing' is achieved through a protest scheme that prevents data channel overloading. The STI-MAC protocol is analyzed via Monte-Carlo simulations in which transmitter nodes are uniformly distributed in a plane, each at a fixed distance from their target receiver; and as a function of network parameters including the number of transmit and receive antennas, the distance between a transmitter-receiver pair (link-length), the average number of transmitters whose received signal is stronger at a given receiver than its target transmitter (link-rank), number of transmitter-receiver pairs, the distribution on the requested rate, the offered load, and the transmit scheme. The STI-MAC protocol is benchmarked relative to simulations of the 802.11(n) (Wi-Fi) protocol. The key results of this work show a 3X gain in throughput relative to 802.11(n) in typical multi-antenna wireless networks that have 20 transmitter-receiver pairs, a link-length of 10 meters, four receive antennas and a single transmit antenna. We also show a reduction in delay by a factor of two when the networks are heavily loaded. We find that the link-rank is a key parameter affecting STIMAC gains over Wi-Fi. In simulations of networks with 40 transmit-receiver pairs, link-rank of three, a link-length of 10 meters, and eight transmit and receive antennas in which the transmitter beamforms to its target receiver in its strongest target channel mode, we find gains in throughput of at least 5X over the 802.11(n) protocol.
by Danielle A. Hinton.
Ph.D.
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Li, Haoming. "Fiber-connected massively distributed antenna systems : energy efficiency and interference management." Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/45199.
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The density of wireless access nodes keeps increasing to provide ubiquitous wireless access and meet the ever-increasing traffic demand. However, the shrinking distance among neighboring access nodes causes excessive interference and the increasing number of access nodes incurs a higher power consumption. A careful management of interference ensures a high system capacity. An improved energy efficiency in wireless access network prevents the fast growth of wireless communication systems from aggravating the global energy crisis. In this thesis, we propose a novel architecture, Fiber-connected Massively Distributed Antennas (FMDA), to address the challenges of managing interference and improving energy efficiency in wireless access networks.
A FMDA system is composed of a centralized processing system connected to a large number of antennas via optical cables. The centralized processing system processes all the radio signals and allocates all the radio resources to better manage interference; each antenna contains much simpler circuits than conventional access nodes and therefore allows a massive deployment and reduces the antenna power consumption. We first propose a novel multi-cell wireless local area network (WLAN) system based on our proposed FMDA architecture, where the centralized processing system can see the entire spectrum usage across the coverage area and control the radio signals to be sent to each antenna, thus allowing a better management of inter-cell interference. We then propose an antenna scheduling scheme in a novel cellular system composed of fiber-connected femto access nodes to manage the excessive inter-femtocell interference and reduce the energies consumed by non-sleeping access nodes, thus simultaneously improving the spectral and energy efficiency.
When the number of cooperating antennas increases, the power consumption of signal processing spikes, thus drastically degrading the overall energy efficiency due to much smaller radio transmission power levels. Focusing on two typical indoor environments, office buildings and large public venues, we propose two low-complexity downlink transmission schemes to address these energy efficiency challenges.
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Yano, Kazuto. "Study on CDMA non-linear interference cancellers with multi-antenna reception." 京都大学 (Kyoto University), 2005. http://hdl.handle.net/2433/144502.
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Kyoto University (京都大学)0048
新制・課程博士
博士(情報学)
甲第11843号
情博第172号
新制||情||38(附属図書館)
23603
UT51-2005-K509
京都大学大学院情報学研究科通信情報ｼｽﾃﾑ専攻
(主査)教授 吉田 進, 教授 森広 芳照, 教授 佐藤 亨
学位規則第4条第1項該当
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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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Carlsson, Robin. "Investigation and Implementation of Coexistence Tool for Antennas." Thesis, Linköpings universitet, Kommunikationssystem, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-112797.
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With the increase of the number of radios and antennas on today’s systems, the risk of co-site interference is very high. Intermodulation product and antenna coupling are two common sources of interference. The thesis investigates some features of a radio system, like antenna types, receiver parameters, intermodulation products and isolation, and suggests how this knowledge can be used to minimize the risk of co-site interference. The goal is to maximize the isolation between the antennas, by good frequency planning, the use of filters and taking great care in antenna placement. A first version of an analysis software was developed where transmitters and receivers can be paired and evaluated. An intermodulation product calculator was also implemented, to easily find which products are an issue and where they originate. The goal of the software is to be simple to use and easy to adapt to different setups and situations. It should also be easy to upgrade with new features.
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Schodorf, Jeffrey Brian. "Array processing techniques for interference suppression in mobile communications systems." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/12971.
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Tasneem, Khawaja Tauseef. "Reduced Complexity Detection Techniques for Multi-Antenna Communication Systems." Thesis, University of Canterbury. Electrical and Computer Engineering, 2013. http://hdl.handle.net/10092/8611.
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In a multiuser system, several signals are transmitted simultaneously within the same frequency band. This can result in significant improvements both in spectral efficiency and system capacity. However, a detrimental effect of the shared transmissions (both in time and bandwidth), is that the signal received at the base station (BS) or access point (AP) suffers from cochannel interference (CCI) and inter-symbol interference (ISI). This situation presents challenges to receiver design. To combat the destructive nature of multipath fading, a receiver often employs multiple antennas to collect the faded superimposed versions of the transmitted signals. The multiple signals are combined and processed in such a way that the effects of CCI and ISI are minimized and the desired information is reliably recovered. The situation is even more challenging when the system is operating under overload, i.e. when there are fewer receive antennas than there are transmitted signals. Multiuser detection (MUD) is used to simultaneously estimate the information sent by the transmitters. To do this, the receiver exploits differences among the cochannel signals (through unique spatial signatures in this case).
We consider a cochannel communication system where multiple transmitted signals arrive at a receiver (equipped with multiple receive antennas) after propagating through a Rayleigh fading channel. It is assumed that the receiver is operating in an overloaded scenario. For such systems, an optimum maximum a posterior probability (MAP) detector estimates the transmitted signal by maximizing the probability of correct decision. The MAP detector reduces to the maximum likelihood (ML) detector when all the transmitted signals are equiprobable. The computational complexity of both MAP and ML detectors increases exponentially with the number of transmitted signals and the channel memory. For large systems suffering severe CCI and ISI, this is clearly not a good choice for real-time implementation due to the associated computational expenses. The main factors that influence the complexity of MAP / ML detection are: (i) the number of transmitted signals (or equivalently the number of users sharing the system resources), (ii) modulation alphabet size, and (iii) length of the channel memory. On the other hand, linear detection approaches fail to offer acceptable performance while other nonlinear sub-optimum approaches incur high computational costs for reasonably improved system performance and exhibit an irreducible error-floor at medium to high signal to noise ratio (SNR) values.
We develop receiver signal processing techniques for the frequency-flat fading channel (where all the multipaths of the transmitted signal arrive at the receiver within a symbol period). We develop an ant colony optimization (ACO) assisted soft iterative detection approach for binary phase-shift keying (BPSK) modulated signals which employs a simplified MAP criteria to extract the most probable signals from the search space. The structure of the receiver is such that it can continue operating under overloaded conditions. The technique achieves near maximum likelihood (ML) performance in critically loaded cases using much lower complexity. For the challenging case of overload it still offers performance close to ML at low to moderate SNR values. Second, an integrated framework comprising of ACO metaheuristic and a recursively defined ML search criteria is developed to handle multilevel modulations. The proposed receiver is capable of achieving near-ML performance for the considered system with significant savings in computational complexity. The receiver framework is independent of the system loading condition, and therefore it remains suitable for overloaded scenarios. Due to the branch and bound nature of the algorithm, an exact expression for the complexity cannot be determined. Instead, an upper bound on computational complexity is developed.
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Hrabar, Silvio. "Analysis of electromagnetic interference between mobile telephone and implanted medical device." Thesis, Brunel University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341092.
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Gaur, Sudhanshu. "Interference management in MIMO networks." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24769.
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Thesis (Ph.D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2008.Committee Chair: Mary Ann Ingram; Committee Member: Geoffrey Li; Committee Member: Gregory Durgin; Committee Member: Prasad Tetali; Committee Member: Raghupathy Sivakumar.
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Jo, Jung-Hyuck. "Site-specific prediction of propagation, interference and network performance in wireless communications." Diss., Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/15660.
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Annalingam, Dheveegar David. "Blind adaptive multi user interference cancellation detectors and antenna array for CDMA systems." Thesis, University of Sussex, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.435615.
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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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Cheng, Chin-Yuan. "Numerical electromagnetic modeling of a small aperture helical-fed reflector antenna." Ohio : Ohio University, 1998. http://www.ohiolink.edu/etd/view.cgi?ohiou1176838193.
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Bharadwaj, Vivek. "Ultra-Wideband for Communications: Spatial Characteristics and Interference Suppression." Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/33183.
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Ultra-Wideband Communication is increasingly being considered as an attractive solution for high data rate short range wireless and position location applications. Knowledge of the statistical nature of the channel is necessary to design wireless systems that provide optimum performance. This thesis investigates the spatial characteristics of the channel based on measurements conducted using UWB pulses in an indoor office environment. The statistics of the received signal energy illustrate the low spatial fading of UWB signals. The distribution of the Angle of arrival (AOA) of the multipath components is obtained using a two-dimensional deconvolution algorithm called the Sensor-CLEAN algorithm. A spatial channel model that incorporates the spatial and temporal features of the channel is developed based on the AOA statistics. The performance of the Sensor-CLEAN algorithm is evaluated briefly by application to known artificial channels.
UWB systems co-exist with narrowband and other wideband systems. Even though they enjoy the advantage of processing gain (the ratio of bandwidth to data rate) the low energy per pulse may cause these narrow band interferers (NBI) to severely degrade the UWB system's performance. A technique to suppress NBI using multiple antennas is presented in this thesis which exploits the spatial fading characteristics. This method exploits the vast difference in fading characteristics between UWB signals and NBI by implementing a simple selection diversity scheme. It is shown that this simple scheme can provide strong benefits in performance.Master of Science
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Wu, Terence. "Antenna integration for wireless and sensing applications." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41098.
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As integrated circuits become smaller in size, antenna design has become the size limiting factor for RF front ends. The size reduction of an antenna is limited due to tradeoffs between its size and its performance. Thus, combining antenna designs with other system components can reutilize parts of the system and significantly reduce its overall size. The biggest challenge is in minimizing the interference between the antenna and other components so that the radiation performance is not compromised. This is especially true for antenna arrays where the radiation pattern is important.
Antenna size reduction is also desired for wireless sensors where the devices need to be unnoticeable to the subjects being monitored. In addition to reducing the interference between components, the environmental effect on the antenna needs to be considered based on sensors' deployment.
This dissertation focuses on solving the two challenges: 1) designing compact multi-frequency arrays that maintain directive radiation across their operating bands and 2) developing integrated antennas for sensors that are protected against hazardous environmental conditions.
The first part of the dissertation addresses various multi-frequency directive antennas arrays that can be used for base stations, aerospace/satellite applications. A cognitive radio base station antenna that maintains a consistent radiation pattern across the operating frequencies is introduced. This is followed by multi-frequency phased array designs that emphasize light-weight and compactness for aerospace applications. The size and weight of the antenna element is reduced by using paper-based electronics and internal cavity structures.
The second part of the dissertation addresses antenna designs for sensor systems such as wireless sensor networks and RFID-based sensors. Solar cell integrated antennas for wireless sensor nodes are introduced to overcome the mechanical weakness posed by conventional monopole designs. This can significantly improve the sturdiness of the sensor from environmental hazards. The dissertation also introduces RFID-based strain sensors as a low-cost solution to massive sensor deployments. With an antenna acting as both the sensing device as well as the communication medium, the cost of an RFID sensor is dramatically reduced. Sensors' strain sensitivities are measured and theoretically derived. Their environmental sensitivities are also investigated to calibrate them for real world applications.
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Hunukumbure, Mythri. "Code orthogonality and interference effects in multi-antenna deployments for 3rd generation mobile systems." Thesis, University of Bristol, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.419659.
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Salam, Naser. "Signal processing for multiple receive antenna systems in the presence of multiple access interference." Thesis, University of Ottawa (Canada), 2004. http://hdl.handle.net/10393/26761.
Full textAbstract:
In wireless communications systems employing DS-CDMA, the base stations with multiple antennas receive signals from different mobiles that are affected by fading and noise as well as interference from other users, thus diminishing the capacity. This dissertation considers a base station with multiple receive antennas which are weighted spatially by using maximal ratio combining. Moreover, at the transmitter side, the thesis examines the use of pilot signals along with the data stream for channel estimation purpose. For each user, the pilot signals are transmitted in parallel with the data signal using orthogonal signature waveforms to those of the data signal. The proposed receiver in this thesis uses a decorrelator detector to not only to decorrelate the data signal from the MAI components, but also to decorrelate the pilot signal to achieve good channel gain estimation. The study shows that the proposed system has a good resistance toward the near-far problem, give good space receiver performance efficiency comparing it with conventional space receivers and it has Less power assigned to the pilot power stream to obtain best channel estimation within a certain fading rate.
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CALLA, ALBERTH RONAL TAMO. "EVALUATION OF INTERFERENCE AMONG SATELLITE COMMUNICATIONS NETWORKS: JOINT EFFECT OF THE PROBABILISTIC MODELING OF EARTH STATION ANTENNA LOCATIONS AND ANTENNA SIDELOBE GAINS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2013. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=23373@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
FUNDAÇÃO DE APOIO À PESQUISA DO ESTADO DO RIO DE JANEIRO
PROGRAMA DE EXCELENCIA ACADEMICA
Num ambiente onde diversos sistemas de comunicação compartilham uma determinada faixa de frequências, cada um dos sistemas envolvidos opera sujeito às interferências geradas pelos demais sistemas. Neste ambiente, cresce a importância de uma avaliação precisa dos efeitos de interferência. Dada a complexidade do problema, o cálculo de interferências é usualmente feito considerando-se diversas situações de pior caso e hipóteses simplificadoras. Estas situações incluem, por exemplo, a hipótese de que a degradação devida a chuvas está presente apenas no enlace vítima, não afetando os enlaces interferentes, a hipótese de que as estações terrenas envolvidas estão localizadas nos pontos mais desfavoráveis (em termos de interferência) de suas área de serviço e a consideração de um diagrama de referência para os diagramas de radiação das antenas. Estas hipóteses implicam num cálculo de interferências conservador, no qual os níveis de interferência obtidos são maiores do que os níveis reais. No presente trabalho, como alternativa à consideração de que as estações terrenas envolvidas estão localizadas nos pontos mais desfavoráveis das áreas de serviço, as posições geográficas das estações terrenas são modeladas probabilisticamente, sendo caracterizadas por vetores aleatórios. Neste caso, a razão portadora interferência resultante é também uma variável aleatória cujo comportamento estatístico é avaliado no trabalho. Resultados numéricos são obtidos para situações envolvendo sistemas multifeixes de comunicações por satélite operando na Banda Ka. Estes resultados são comparados àqueles obtidos sob a hipótese de que as estações terrenas envolvidas estão localizadas nos pontos mais desfavoráveis das áreas de serviço. Finalmente, o efeito conjunto da modelagem probabilística tanto das posições geográficas das estações terrenas quanto dos ganhos nos lóbulos laterais de suas antenas, foi avaliado.
When multiple communication systems share a particular frequency band, each system operates subject to interference generated by the others. In this environment, an accurate assessment of the effects of interference is very important. Given the complexity of the problem, interference calculations is usually done considering a number of worst case conditions and simplifying assumptions. They include, for example, the hypothesis that the degradation due to rain is only present in the victim link and do not affect any of the interfering links, the hypothesis that earth stations involved are located at the most unfavorable sites (in terms of interference) within their service areas, and the use of a reference diagram for radiation antenna patterns. These hypotheses imply a conservative calculation of interference in which obtained interference levels are higher than their actual levels. In this work, as an alternative to the assumption that the earth stations are located at the most unfavorable sites of their service areas, a probabilistic model is used. In the proposed model the geographic locations of the ground stations are characterized by random vectors. As a consequence, the resulting carrier interference ratio is also a random variable and its statistical behavior is also evaluated in this work. Numerical results are obtained for particular situations involving multiple multi-beam satellite communication networks operating in the Ka band. The results are compared to those obtained under the assumption that the Earth stations are located at the most unfavorable sites of their service areas. Finally, the joint effect of modeling both, the ground station locations and their antena sidelobe gains, as random quantities was evaluated.
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Ho, Zuleita, Eduard Jorswieck, and Sabrina Engelmann. "Information Leakage Neutralization for the Multi-Antenna Non-Regenerative Relay-Assisted Multi-Carrier Interference Channel." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-121245.
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In heterogeneous dense networks where spectrum is shared, users' privacy remains one of the major challenges. On a multi-antenna relay-assisted multi-carrier interference channel, each user shares the spectral and spatial resources with all other users. When the receivers are not only interested in their own signals but also in eavesdropping other users' signals, the cross talk on the spectral and spatial channels becomes information leakage. In this paper, we propose a novel secrecy rate enhancing relay strategy that utilizes both spectral and spatial resources, termed as information leakage neutralization. To this end, the relay matrix is chosen such that the effective channel from the transmitter to the colluding eavesdropper is equal to the negative of the effective channel over the relay to the colluding eavesdropper and thus the information leakage to zero. Interestingly, the optimal relay matrix in general is not block-diagonal which encourages users' encoding over the frequency channels. We proposed two information leakage neutralization strategies, namely efficient information leakage neutralization (EFFIN) and local-optimized information leakage neutralization (LOPTIN). EFFIN provides a simple and efficient design of relay processing matrix and precoding matrices at the transmitters in the scenario of limited power and computational resources. LOPTIN, despite its higher complexity, provides a better sum secrecy rate performance by optimizing the relay processing matrix and the precoding matrices jointly. The proposed methods are shown to improve the sum secrecy rates over several state-of-the-art baseline methods.
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Li, Qiang. "On multiple-antenna communications: signal detection, error exponent and and quality of service." Texas A&M University, 2007. http://hdl.handle.net/1969.1/85827.
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Motivated by the demand of increasing data rate in wireless communication,
multiple-antenna communication is becoming a key technology in the next generation
wireless system. This dissertation considers three different aspects of multipleantenna
communication.
The first part is signal detection in the multiple-input multiple-output (MIMO)
communication. Some low complexity near optimal detectors are designed based on
an improved version of Bell Laboratories Layered Space-Time (BLAST) architecture
detection and an iterative space alternating generalized expectation-maximization
(SAGE) algorithm. The proposed algorithms can almost achieve the performance of
optimal maximum likelihood detection. Signal detections without channel knowledge
(noncoherent) and with co-channel interference are also investigated. Novel solutions
are proposed with near optimal performance.
Secondly, the error exponent of the distributed multiple-antenna communication
(relay) in the windband regime is computed. Optimal power allocation between the
source and relay node, and geometrical relay node placement are investigated based
on the error exponent analysis.
Lastly, the quality of service (QoS) of MIMO/single-input single- output(SISO)
communication is studied. The tradeoff of the end-to-end distortion and transmission
buffer delay is derived. Also, the SNR exponent of the distortion is computed for MIMO communication, which can provide some insights of the interplay among time
diversity, space diversity and the spatial multiplex gain.
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Tsai, Jiann-An. "Combined Space-Time Diversity and Interference Cancellation for MIMO Wireless Systems." Diss., Virginia Tech, 2002. http://hdl.handle.net/10919/27509.
Full textAbstract:
There is increasing interest in the exploitation of multiple-input and multiple-output (MIMO) channels to enhance the capacity of wireless systems.
In this study, we develop and evaluate a channel model, evaluate the corresponding channel capacity, and design and analyze a simple orthogonal transmit waveform for MIMO channels in mobile radio environments.
We also evaluate the system performance of various interference cancellation techniques when employing multiple-receive antenna in interference-limited systems.
The first part of this dissertation presents two major contributions to MIMO systems.
The analytical expression for space-time MIMO channel correlation is derived for a Rayleigh fading channel. The information-theoretic channel capacity based on this correlation is also evaluated for a wide variety of mobile radio channels.
The second part of this dissertation presents two major contributions to the area of orthogonal waveform design. We analyze the bit-error-rate (BER) performance of a proposed space-time orthogonal waveform for MIMO mobile radio communications.
The application of the proposed space-time orthogonal waveform to a conventional cellular system is also evaluated and briefly discussed.
Finally, this dissertation investigates a number of interference cancellation techniques for multiple-receive antenna systems. Both adaptive beamforming and multiuser detection are evaluated for various signal waveforms over a variety of mobile radio channels.Ph. D.
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Haghpanahan, Roohollah. "Metamaterials and their applications on antenna gain enhancement." Thesis, Brunel University, 2015. http://bura.brunel.ac.uk/handle/2438/12869.
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This thesis is devoted to potential applications of metamaterials in antenna structures as well as metamaterials behaviour, characterisation, structure design, simulation and extraction of parameters. The focus of this work is on the practical application of metamaterial structures for antenna performance enhancement. This thesis comprises three key parts; In the first part, theory of metamaterials is investigated including fields, polarisation, effective and average parameters, parameters extraction and transmission line (TL) model. In part two, zero index metamaterials (ZIM) theory is studied. The use of ZIM to form a highly directive medium is illustrated. A comparative study between different ZIM structures is conducted with a special attention to their operational bandwidth. ANSYS HFSS is used to model ZIM structures where simulation results show a bandwidth between 7.4% and 14.0%. Then two novel ZIM structures with a bandwidth of up to 33% are proposed. The first proposed ZIM is used to form a highly directive shell. Four directive shells are designed and placed around the dipole antenna where a gain increase of up to 6.8 dBi is obtained along the desired direction. Further, proposed ZIM cells are integrated with a quasi-Yagi antenna in order to increase its gain. Simulation results demonstrate gain enhancement for frequencies over which the proposed structure expresses ZIM properties. In part three, a new technique is stablished to design a metamaterial lens. The new technique is based on wave interference phenomena where engineered wave interference results in a desired spatial energy distribution. It is shown theoretically that having 180° phase difference between interfering waves results in a focused emission. Both hypothetical and metamaterial realisation models of a 180° phase shifter for a patch antenna are designed and simulated where a gain enhancement of 8 dBi and 5.77 dBi are achieved, respectively. Further, the concept of intended phase shift between interfering waves is used to design a novel bi-reflectional ground plane which can focus the reflected emission and consequently, increase the antenna directivity. In the theoretical model, the Perfect-E and Perfect-H planes are combined to form a bi-reflectional plane, whereas the practical model is designed using the copper cladding for the Perfect-E plane and the mushroom structure for the perfect-H plane. Both square and hexagonal geometries are used to form the mushroom structure. Simulation results confirm a gain enhancement of 5.4 dBi for the design using the square mushroom structure and a gain enhancement of 3.3 dBi for the design using the hexagonal mushroom structure.
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Rosenlind, Johanna. "The Impulse-Radiating Antenna." Thesis, Karlstad University, Faculty of Technology and Science, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-4527.
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As the interest in intentional electromagnetic interference (IEMI) increases, so does the need of a suitable antenna which endures those demanding conditions. The ultrawideband (UWB) technology provides an elegant way of generating high-voltage UWB pulses which can be used for IEMI. One UWB antenna, invented solely for the purpose of radiating pulses, is the impulse radiating antenna (IRA). In the course of this master thesis work, a suitable geometry of the IRA is suggested, and modelled, for the high-voltage application of 90 kV.
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Schmidt, David A. [Verfasser], Wolfgang [Akademischer Betreuer] Utschick, and Michael L. [Akademischer Betreuer] Honig. "Communications in Multi-Antenna Interference Networks / David Schmidt. Gutachter: Michael L. Honig. Betreuer: Wolfgang Utschick." München : Universitätsbibliothek der TU München, 2011. http://d-nb.info/1019589841/34.
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Tasdemir, Emrah Verfasser], Tobias G. [Akademischer Betreuer] Noll, and Gerd [Akademischer Betreuer] [Ascheid. "Blind interference mitigation in multi-antenna GNSS receivers / Emrah Tasdemir ; Tobias G. Noll, Gerd Ascheid." Aachen : Universitätsbibliothek der RWTH Aachen, 2018. http://d-nb.info/1176422197/34.
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Taşdemir, Emrah [Verfasser], Tobias G. Akademischer Betreuer] Noll, and Gerd [Akademischer Betreuer] [Ascheid. "Blind interference mitigation in multi-antenna GNSS receivers / Emrah Tasdemir ; Tobias G. Noll, Gerd Ascheid." Aachen : Universitätsbibliothek der RWTH Aachen, 2018. http://d-nb.info/1176422197/34.
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Hicks, James. "Overloaded Array Processing with Spatially Reduced Search Joint Detection." Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/9611.
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An antenna array is overloaded when the number of cochannel signals in its operating environment exceeds the number of elements. Conventional space-time array processing for narrow-band signals fails in overloaded environments. Overloaded array processing (OAP) is most difficult when signals impinging on the array are near equal power, have tight excess bandwidth, and are of identical signal type. In this thesis, we first demonstrate how OAP is theoretically possible with the joint maximum likelihood (JML) receiver. However, for even a modest number of interfering signals, the JML receiverà Âs computational complexity quickly exceeds the real-time ability of any computer. This thesis proposes an iterative joint detection technique, Spatially Reduced Search Joint Detection, (SRSJD), which approximates the JML receiver while reducing its computational complexity by several orders of magnitude. This complexity reduction is achieved by first exploiting spatial separation between interfering signals with a linear pre-processing stage, and second, performing iterative joint detection with a (possibly) tail-biting and time"-varying trellis. The algorithm is sub-optimal but is demonstrated to well approximate the optimum receiver in modest signal to interference ratios. SRSJD is shown to demodulate over 2M zero excess bandwidth synchronous QPSK signals with an M element array. Also, this thesis investigates a temporal processing technique similar to SRSJD, Temporally Reduced Search Joint Detection (TRSJD), that separates co-channel, asynchronous, partial response signals. The technique is demonstrated to separate two near equal power QPSK signals with r= .35 root raised-cosine pulse shapes."Master of Science
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Bayram, Saffet. "Overloaded Array Processing: System Analysis, Signal Extraction Techniques, and Time-delay Estimation." Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/36039.
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In airborne communication systems such as airborne cell-extender repeaters the receiver faces the challenge of demodulating the signal of interest (SOI) in the presence of excessive amounts of Co-Channel Interference (CCI) from a large number of sources. This results in the overloaded environment where the number of near-equal power co-channel interferers exceeds the number of antenna array elements. This thesis first analyzes the interference environment experienced by an airborne cellular repeater flying at high altitudes. Link budget analysis using a two-ray propagation model shows that the antenna array mounted on an airborne receiver has to recover the SOI out of hundreds of co-channel interfering signals. This necessitates use of complex overloaded array signal processing techniques. An extensive literature survey on narrowband signal extraction algorithms shows that joint detection schemes, coupled with antenna arrays, provide a solution for narrowband overloaded array problem where as traditional beamforming techniques fail. Simulation results in this thesis investigates three "promising" overloaded array processing algorithms, Multi-User Decision Feedback Equalizer (MU-DFE), Iterative Least Squares with Projection (ILSP), and Iterative Least Squares with Enumeration (ILSE). ILSE is a non-linear joint maximum-likelihood detector, is shown to demodulate many more signals than elements even when the users are closely spaced and the channel is blindly estimated.
Multi-user time delay estimation is one of the most important aspects of channel estimation for overloaded array processing. The final chapter of the thesis proposes a low-complexity data-aided time-delay estimation structure for embedding in a Per Survivor Processing (PSP) trellis for overloaded array processing. An extensive analysis proves that the multi-user delay estimation is separable, which leads to the proposed multi-user algorithm that estimates the user delays with a bank of simple data-aided synchronization loops to reduce the complexity. This thesis shows simulation results for the single-user case where the low-complexity Delay Locked Loop (DLL) structure, working at a low oversampling rate of 2 samples per symbol, estimates and compensates for any integer or non-integer sample delay within ±Tsym(symbol period).
Two extensions to this technique are proposed to provide efficient multi-user delay estimation. The first multi-user structure employs a bank of DLLs, which compensate for the timing offset of each user simultaneously. This multi-user algorithm is suitable for CDMA-type applications, where each user has a distinct PN-code with good auto- and cross-correlation properties. We show that for spreading gain of 31, the presence of an interpolator enables us to reduce the oversampling factor from 4 to 2 samples per chip. Thus, the requirements of the A/D converter are relaxed without sacrificing system performance. Furthermore, we show that the proposed scheme meets the requirements of multi-user interference cancellation techniques for residual worst-case timing errors, i.e., residual timing error < 0.2 Tc, as reported in [200]. Finally, the thesis recommends a similar multi-user structure for narrowband TDMA-type system, which is based on bank of DLLs with whitening pre-filters at the front end of each branch.Master of Science
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Altan, Hal. "MOBILE GROUND TRACKING STATION DESIGN MODIFICATIONS AND PLACEMENT PREPARATION FOR CROWDED AIRSPACE." International Foundation for Telemetering, 2007. http://hdl.handle.net/10150/604566.
Full textAbstract:
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, NevadaAs the frequency spectrum becomes more crowded each day, preparation for placement of tracking ground station in tracking environment gains more importance. Existence of high power weather ground radars, airport approach equipment, and various other RF sources in the environment necessitates the test teams to be more cautious. This paper discusses, implemented design changes to an S-band antenna system to reduce the in-band interfering power, calculation of the effects from nearby interferers, analysis of the environment during placement of the mobile ground system by Honeywell telemetry teams.
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Normando, Paulo Garcia. "Alinhamento de interferÃncia espacial em cenÃrios realistas." Universidade Federal do CearÃ, 2013. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=10874.
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CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel SuperiorDevido ao rÃpido crescimento e os agressivos requisitos de vazÃo nas atuais redes sem fio, como os sistemas celulares de 4 a GeraÃÃo, a interferÃncia se tornou um problema que nÃo pode mais ser negligenciado. Neste contexto, o Alinhamento de InterferÃncia (IA) tem surgido como uma tÃcnica promissora que possibilita transmissÃes livres de interferÃncia com elevada eficiÃncia espectral. No entanto, trabalhos recentes tÃm focado principalmente nos ganhos teÃricos que esta tÃcnica pode prover, enquanto esta dissertaÃÃo visa dar um passo na direÃÃo de esclarecer alguns dos problemas prÃticos de implementaÃÃo da tÃcnica em redes celulares, bem como comparÃ-la com outras tÃcnicas bem estabelecidas. Uma rede composta por trÃs cÃlulas foi escolhida como cenÃrio inicial de avaliaÃÃo, para o qual diversos fatores realistas foram considerados de modo a realizar diferentes anÃlises. A primeira anÃlise foi baseada em imperfeiÃÃes de canal, cujos resultados mostraram que o IA à mais robusto aos erros de estimaÃÃo de canal que o BD (do inglÃs, Block Diagonalization), enquanto as duas abordagens sÃo igualmente afetadas pela correlaÃÃo entre as antenas. O impacto de uma interferÃncia externa nÃo-coordenada, que foi modelada por diferentes matrizes de covariÃncia de modo a emular vÃrios cenÃrios, tambÃm foi avaliado. Os resultados mostraram que as modificaÃÃes feitas nos algoritmos de IA podem melhorar bastante seus desempenho, com uma vantagem para o algoritmo que suprime um Ãnico fluxo de dados, quando sÃo comparadas as taxas de erro de bit alcanÃadas por cada um. Para combinar os fatores das anÃlises anteriores, as variaÃÃes temporais de canal foram consideradas. Neste conjunto de simulaÃÃes, alÃm da presenÃa da interferÃncia externa, os prÃ-codificadores sÃo calculados atravÃs de medidas atrasadas de canal, levando a resultados que corroboraram com as anÃlises anteriores. Um fato recorrente percebido em todas as anÃlises anteriores à o dilema entre aplicar os algoritmos baseados em BD, para que se consiga alcanÃar maiores capacidades, ou enviar a informaÃÃo atravÃs de um enlace mais confiÃvel utilizando o IA. Uma maneira de esclarecer este dilema à efetivamente realizar simulaÃÃes a nÃvel sistÃmico, para isto foi aplicado um simulador sistÃmico composto por um grande nÃmero de setores. Como resultado, todas as anÃlises realizadas neste simulador mostraram que a tÃcnica de IA atinge desempenhos intermediÃrios entre a nÃo cooperaÃÃo e os algoritmos baseados na prÃ-codificaÃÃo conjunta. Uma das principais contribuiÃÃes deste trabalho foi mostrar alguns cenÃrios em que a tÃcnica do IA pode ser aplicada. Por exemplo, quando as estimaÃÃes dos canais nÃo sÃo tÃo confiÃveis à melhor aplicar o IA do que os esquemas baseados no processamento conjunto. TambÃm mostrou-se que as modificaÃÃes nos algoritmos de IA, que levam em consideraÃÃo a interferÃncia externa, podem melhorar consideravelmente o desempenho dos algoritmos. Finalmente, o IA se mostrou uma tÃcnica adequada para ser aplicada em cenÃrios em que a interferÃncia à alta e nÃo à possÃvel ter um alto grau de cooperaÃÃo entre os setores vizinhos.
Due to the rapid growth and the aggressive throughput requirements of current wireless networks, such as the 4th Generation (4G) cellular systems, the interference has become an issue that cannot be neglected anymore. In this context, the Interference Alignment (IA) arises as a promising technique that enables transmissions free of interference with high-spectral efficiency. However, while recent works have focused mainly on the theoretical gains that the technique could provide, this dissertation aims to go a step further and clarify some of the practical issues on the implementation of this technique in a cellular network, as well as compare it to other well-established techniques. As an initial evaluation scenario, a 3-cell network was considered, for which several realistic factors were taken into account in order to perform different analyses. The first analysis was based on channel imperfections, for which the results showed that IA is more robust than Block Diagonalization (BD) regarding the Channel State Information (CSI) errors, but both are similarly affected by the correlation among transmit antennas. The impact of uncoordinated interference was also evaluated, by modeling this interference with different covariance matrices in order to mimic several scenarios. The results showed that modifications on the IA algorithms can boost their performance, with an advantage to the approach that suppresses one stream, when the Bit Error Rate (BER) is compared. To combine both factors, the temporal channel variations were taken into account. At these set of simulations, besides the presence of an external interference, the precoders were calculated using a delayed CSI, leading to results that corroborate with the previous analyses. A recurring fact on the herein considered analyses was the dilemma of weather to apply the Joint Processing (JP)-based algorithms in order to achieve higher sum capacities or to send the information through a more reliable link by using IA. A reasonable step towards solving this dilemma is to actually perform the packet transmissions, which was accomplished by employing a system-level simulator composed by a large number of Transmission Points (TPs). As a result, all analyses conducted with this simulator showed that the IA technique can provide an intermediate performance between the non-cooperation and the full cooperation scheme. Concluding, one of the main contributions of this work has been to show some scenarios/cases where the IA technique can be applied. For instance, when the CSI is not reliable it can be better to use IA than a JP-based scheme. Also, the modifications on the algorithms to take into account the external interference can boost their performance. Finally, the IA technique finds itself in-between the conventional transmissions and Coordinated Multi-Point (CoMP). IA achieves an intermediate performance, while requiring a certain degree of cooperation among the neighboring sectors, but demanding less infrastructure than the JP-based schemes.
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Haghdad, Mehdi. "Smart antenna and non-feedback IF equalization techniques for LEO satellite communications in a complex interference environment /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2003. http://uclibs.org/PID/11984.
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Ghani, Sarfraz M. "Improving the Performance of Wireless Systems via Selective Interference Nulling and Adaptive Medium Access Control Design." Thesis, Virginia Tech, 2006. http://hdl.handle.net/10919/34041.
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Escalating demands for high performance wireless systems requires the confluence of smart communication methods, network protocols and ongoing advances in fabrication technologies, in order to bring smaller form factor mobile handsets to market. On par with these trends, this thesis focuses on two main areas, namely, Multiple Antenna Systems and Adaptive MAC Design to improve wireless system performance.
The first part of this research work presents a mathematical framework for characterizing the performance of cellular mobile radio systems equipped with smart antennas at the mobile handset to suppress a few dominant cochannel interferers (CCI) out of a total of L active independent but non-identically distributed Rayleigh faded CCI signals. Earlier works on this subject chose an unrealistic i.i.d assumption for the cochannel interferers. Since the CCI signals are of dissimilar signal strengths in practical operating environments, the premise of i.n.d fading statistics for the cochannel interferers is more realistic. In the subsequent section an analytical framework to investigate the benefits of a hybrid antenna array using selective interference nulling (SIN) and maximal ratio combining (MRC) in mobile radio environments is developed.
In the second part of this thesis, we explore the performance gains that can be achieved by exploiting the synergy resulting from the combination of the MAC and the physical layer of a wireless network. As in a traditional design, the physical layer is responsible for providing error protection for the transmission packets while the MAC layer allocates transmission bandwidth to the contending users. However, in the proposed scheme the MAC layer makes slot assignment decisions based on the channel state information (CSI) from the physical layer.Master of Science
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Haghdad, Mehdi, and Kamilo Feher. "SMART ANTENNA (DIVERSITY) AND NON-FEEDBACK IF EQUALIZATION TECHNIQUES FOR LEO SATELLITE COMMUNICATIONS IN A COMPLEX INTERFERENCE ENVIRONMENT." International Foundation for Telemetering, 2003. http://hdl.handle.net/10150/605382.
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International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, NevadaAn improved performance smart diversity was invented to improve the signal performance in a combined selective fading, Additive White Gaussian Noise (AWGN), Co-channel interference (CCI) and Doppler shift environment such as the LEO satellite channel. This system is also applicable to aeronautical and telemetry channels. Smart diversity is defined here as a mechanism that selects at each moment the best branch in a n-branch diversity system based on the error quality with no default branch and no prioritization. The predominant novelty of this discovery is the introduction of multi level analog based Pseudo Error Detectors (PSED) in every branch. One of the advantages of PSED is that it is a non redundant error detection system, with no requirement for overhead and no need for additional valuable spectrum. This research was motivated by problems in LEO satellite systems due to low orbit and high relative speed with respect to the ground stations. The system is independent of the modulation techniques and is applicable to both coherent and non-coherent detections. The results from simulations using dynamic simulation techniques and hardware measurements over dynamic channels show significant improvement of both the Bit Error Rate (BER) and the Block Error Rate (BLER).
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Prothro, Joel Thomas. "Improved Performance of a Radio Frequency Identification Tag Antenna on a Metal Ground Plane." Thesis, Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/16303.
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Bandeira, Carlos Igor Ramos. "Interference alignment in wireless communication systems: precoding design, scheduling and channel imperfections." reponame:Repositório Institucional da UFC, 2012. http://www.repositorio.ufc.br/handle/riufc/7883.
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BANDEIRA, C. I. R. Interference alignment in wireless communication systems: precoding design, scheduling and channel imperfections. 2012. 91 f. Dissertação (Mestrado em Engenharia de Teleinformática) - Centro de Tecnologia, Universidade Federal do Ceará, Fortaleza, 2012.Submitted by Marlene Sousa (mmarlene@ufc.br) on 2014-04-02T12:15:57Z No. of bitstreams: 1 2012_dis_cirbandeira.pdf: 1451016 bytes, checksum: e08c0d3121c26d7cb08fbfbc287c5c23 (MD5)
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In multiuser MIMO systems, the transmitter can select a subset of antennas and/or users which have good channel conditions to maximize the system throughput using various selection criteria. Furthermore, precoding can provide free interference dimensions. The Interference Alignment (IA) is based on the concept of precoding and it offers different trade-offs between complexity and performance. The basic idea of Interference Alignment consists in precoding the transmitted signals such that they are aligned at the receiver where they constitute interference, while at the same time disjointed from the desired signal. However, the Channel State Information (CSI) has been a concern because it impacts the performance of IA algorithms. Hence, we propose to analyze the performance of antenna selection and multiuser diversity together in order to allow opportunistic IA using several criteria over the disturbance of CSI. Analyses and simulations verify the behavior of the proposed scheme.
Em sistemas MIMO multiusuário, o transmissor pode selecionar um subconjunto de antenas e/ou usuários que têm bons canais para maximizar o rendimento do sistema usando vários critérios de seleção. Além disso, os pré-codificadores podem proporcionar dimensões livres de interferência. O alinhamento de interferência (IA) é baseado no conceito de pré-codificação e oferece diferentes compromissos entre complexidade e desempenho. A idéia básica do Alinhamento Interferência consiste em pré-codificar os sinais transmitidos de maneira que os mesmos sejam alinhados no receptor, em que eles constituem interferência, enquanto que ao mesmo tempo os separa do sinal desejado. No entanto, a Informação do Estado do Canal (CSI) tem sido uma preocupação para os pesquisadores porque ela tem um impacto no desempenho de algoritmos de IA. Assim, nos propomos a analisar o desempenho da seleção de antena e diversidade multiusuário em conjunto, a fim de permitir o IA oportunista usando vários critérios com relação à perturbação da CSI. Análises e simulações verificam o comportamento do esquema proposto.
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MANCHEGO, ALFREDO OMAR CORDOVA. "EFFECT OF THE PROBABILISTIC MODELING OF EARTH STATION ANTENNA SIDELOBE GAINS ON THE EVALUATION OF INTERFERENCE AMONG SATELLITE COMMUNICATION NETWORKS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2012. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=23168@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
PROGRAMA DE EXCELENCIA ACADEMICA
Quando diversos sistemas de comunicação compartilham uma determinada faixa de frequências, cada um dos sistemas envolvidos opera sujeito às interferências geradas pelos demais. Dentro de este panorama, cresce a importância de uma avaliação precisa dos efeitos de interferência. Dada a complexidade do problema, o cálculo de interferências é usualmente feito considerando diversas situações de pior caso. Estas situações de pior caso incluem, por exemplo, a hipótese de que a degradação devida a chuvas está presente apenas no enlace vítima, não afetando os enlaces interferentes, a hipótese de que as estações terrenas envolvidas estão localizadas nos pontos mais desfavoráveis (em termos de interferência) de suas área de serviço e a consideração de um diagrama de referência para os diagramas de radiação das antenas. Obviamente, estas hipóteses implicam num cálculo de interferências conservador, nos quais os níveis de interferência obtidos são maiores do que os níveis reais de interferência. No presente trabalho, como alternativa ao uso de uma envoltória, os ganhos nos lóbulos laterais das antenas envolvidas são modelados por variáveis aleatórias. Neste caso, a razão portadora interferência resultante é também uma variável aleatória. Seu comportamento estatístico é avaliado para dois tipos de modelagem dos ganhos os lóbulos laterais das antenas: como variáveis aleatórias com distribuição exponencial e como variáveis aleatórias com distribuição gama. Os resultados obtidos são comparados àqueles obtidos quando uma envoltória é utilizada na caracterização dos ganhos das antenas.
When several communication systems share a particular frequency band, each of the systems operates subject to the interference generated by the others. Within this scenario, the importance of an accurate assessment of the effects of interference is increased. Given the complexity of the problem, the evaluation of interference is usually done by considering several worst-case situations. These worst-case situations include, for example, the hypothesis that degradation due to rain affects only the victim link and do not affect the interfering links, the hypothesis that the earth stations involved are located at the most unfavorable (in terms of interference) spots in their service area and the use of reference patterns for the radiation patterns of the antennas. obviously, these assumptions imply a conservative calculation of interference in which the obtained interference levels are higher than their actual levels. In this work, as an alternative to the use of envelopes, the earth station sidelobe antenna gains are modeled as random variables. In this case, the resulting carrier to interference ratio is also a random variable. The statistical behavior of the carrier to interference ratio is then evaluated for two different modelings of the antenna sidelobe gains: as exponential distributed random variables and as gamma distributed random variables. The results are compared to those obtained when an envelope is used to characterize the antenna radiation patterns.
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O'Brien, Jonathan M. "Design and Modeling of a High-Power Periodic Spiral Antenna with an Integrated Rejection Band Filter." Scholar Commons, 2017. https://scholarcommons.usf.edu/etd/7431.
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This work details the design and fabrication of an ultra-wideband periodic spiral antenna (PSA) with a notch filter embedded directly into the radiating aperture. Prototype fabrication of the PSA reveals long assembly time due to forming the antenna element, therefore modifications are made to allow fabricating the antenna elements on a thin, flexible, Polyimide substrate. A transmission line model is develop to support the updated configuration of the antenna elements. In addition, a symmetric spurline filter is integrated into the arms of the spiral antenna in order to address the common problem of interference in ultra-wideband systems. For the first time, a placement study is conducted to show the optimal location of the filter as a function of frequency. The presented transmission line model demonstrates the ability to decouple the design of the filter and antenna by being able to predict the resonant frequency and achieved rejection after integration of the two. Measured results show a gain rejection of 21 dB along with the ability to tune the resonance of the filter from 1.1 – 2.7 GHz using a lumped capacitor. For high power applications, thermal measurements are conducted, and for the first time, thermal profiles along the top of the antenna are used to show the radiation bands in a spiral antenna. Power tests are successfully conducted up to 40 W across the entire operational bandwidth and up to 60 W for 2 GHz and below. At these elevated power levels, a large voltage is generated across the lumped capacitor used to tune the resonance of the spurline filter; this issue is addressed through the development of a capacitive wedge that is overlapped on top of the spurline stub, which increases the voltage handling to 2,756 V. Measured results reveal a reduced tuning range compared to using lumped capacitors and a gain rejection of greater than 10 dB for all configurations.