Dissertations / Theses on the topic 'Adaptive antennas'
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Hwang, Seung-Hyeon. "Adaptive antenna techniques for smart antennas and radar systems." Related electronic resource: Current Research at SU : database of SU dissertations, recent titles available full text, 2005. http://wwwlib.umi.com/cr/syr/main.
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Bustamante, Roberto M. "Adaptive multiple beam antennas." Thesis, University of Surrey, 1986. http://epubs.surrey.ac.uk/842903/.
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This work assesses the performance of reflector antennas under adaptive control. In this study, a conventional reflector antenna is given adaptive control by placing additional feeds in the reflector focal plane. The antenna effectively becomes a Multiple Beam Antenna (MBA). This configuration has received far less attention than the Sidelobe Canceller which achieves spatial discrimination by placing low gain elements in the periphery of the reflector. The applications that motivate this work involve rotating radar antennas subject to main beam interference or multiple targets that must be resolved within a 3-db beamwidth. The possibility of the interference being correlated with the wanted signal is also considered. Within the context of these applications the assessment addresses: The basic (main-beam and sidelobe) cancellation performance of this type of antenna. The influence of beam characteristics such as crossover levels, gain, sidelobe levels, etc. in performance. The Control Laws that avoid cancellation of a wanted signal while rejecting interference even if knowledge in signal direction is only approximate. Algorithms to solve adaptively the above Control Laws at speeds consistent with rotating antennas and rapidly changing interference. The use of the beamformer output to generate a reference signal to avoid cancellation of the wanted signal. An algorithm, so far used in the frequency domain, applied in this work to the space domain with the purpose of avoiding cancellation of the wanted signal in the presence of correlated interference such as multipath. The construction of an experimental antenna is also undertaken and it is demonstrated that adaptive nulling is readily achieved in practice.
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Schlub, Robert Walter, and n/a. "Practical Realization of Switched and Adaptive Parasitic Monopole Radiating Structures." Griffith University. School of Microelectronic Engineering, 2004. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20040610.112148.
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Switched and adaptive parasitic monopole array radiating structures are investigated. Antenna design is orientated toward increasing practicability for implementation in terrestrial wireless communication systems. A number of antennas are designed with the aid of optimization and commercial simulation software. Simulation procedure was verified with the experimental manufacture and measurement of the arrays. The antennas presented in this thesis comprise an active monopole surrounded by a ring of parasitic monopoles. Parasitic radiators are constructed with static loading to enable simple experimental realization. Beam positions of an electrically steered equivalent antenna are thus simulated. Antenna symmetry ensures the beam can be reproduced throughout the azimuth. Complex antenna geometries require antenna design through optimization. A genetic algorithm is employed with HFSS and NEC for electromagnetic analysis. The robust optimization method couples with simulation software flexibility to provide an effective design tool for arbitrary structures. The genetic algorithm is employed strictly for design and not complete structural optimization. Dual band, five and six element switched parasitic antennas are presented. Lumped elemental loading along the radiators provide resonance and directed radiation at two GSM frequencies. Load value, radiator dimension and spacing are incorporated as design parameters. Experimentally built, 10dB return loss bandwidths of 17.2% and 9.6% and front to back ratios of 12.6dB and 8.4dB at 900MHz and 1900MHz respectively are measured. To reduce the ground requirements of monopole arrays, a skirted ground structure for switched parasitic antennas is analyzed. A six element switched parasitic monopole array with conductive ground skirt exhibits a front to back ratio of 10.7dB and main lobe gain of 6.4dBi at 1.575GHz. Radiation is not elevated despite lateral ground terminating at the parasitic elements. Skirt height is observed to linearly control radiation elevation, depressing the principal lobe through 40 degrees from 23 degrees above the horizontal. The Electronically Steerable Passive Array Radiator or ESPAR antenna is an adaptive parasitic monopole array. An ESPAR radiating structure incorporating a conductive ground skirt is designed for operation at 2.4GHz. Utility is confirmed with a frequency sensitivity analysis showing consistent electrical characteristics over an 8.1% bandwidth. The antenna design is improved with optimization to reduce average principal lobe elevation from 25 degrees to 9.7 degrees.
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Schlub, Robert Walter. "Practical Realization of Switched and Adaptive Parasitic Monopole Radiating Structures." Thesis, Griffith University, 2004. http://hdl.handle.net/10072/366803.
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Switched and adaptive parasitic monopole array radiating structures are investigated.
Antenna design is orientated toward increasing practicability for implementation in terrestrial wireless communication systems. A number of antennas are designed with the aid of optimization and commercial simulation software. Simulation procedure was verified with the experimental manufacture and measurement of the arrays. The antennas presented in this thesis comprise an active monopole surrounded by a ring of parasitic monopoles. Parasitic radiators are constructed with static loading to enable simple experimental realization. Beam positions of an electrically steered equivalent antenna are thus simulated. Antenna symmetry ensures the beam can be reproduced throughout the azimuth. Complex antenna geometries require antenna design through optimization. A genetic algorithm is employed with HFSS and NEC for electromagnetic analysis. The robust optimization method couples with simulation software flexibility to provide an effective design tool for arbitrary structures. The genetic algorithm is employed strictly for design and not complete structural optimization. Dual band, five and six element switched parasitic antennas are presented. Lumped elemental loading along the radiators provide resonance and directed radiation at two GSM frequencies. Load value, radiator dimension and spacing are incorporated as design parameters. Experimentally built, 10dB return loss bandwidths of 17.2% and 9.6% and front to back ratios of 12.6dB and 8.4dB at 900MHz and 1900MHz respectively are measured. To reduce the ground requirements of monopole arrays, a skirted ground structure for switched parasitic antennas is analyzed. A six element switched parasitic monopole array with conductive ground skirt exhibits a front to back ratio of 10.7dB and main lobe gain of 6.4dBi at 1.575GHz. Radiation is not elevated despite lateral ground terminating at the parasitic elements. Skirt height is observed to linearly control radiation elevation, depressing the principal lobe through 40 degrees from 23 degrees above the horizontal. The Electronically Steerable Passive Array Radiator or ESPAR antenna is an adaptive parasitic monopole array. An ESPAR radiating structure incorporating a conductive ground skirt is designed for operation at 2.4GHz. Utility is confirmed with a frequency sensitivity analysis showing consistent electrical characteristics over an 8.1% bandwidth. The antenna design is improved with optimization to reduce average principal lobe elevation from 25 degrees to 9.7 degrees.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Microelectronic Engineering
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Petrus, Paul. "Blind adaptive antenna arrays for mobile communications." Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-07112009-040414/.
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Pham, Tien D. "Adaptive antennas in multipath wireless communications." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq35282.pdf.
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Da, Silveira Marthinus Willem. "Analysis of spatially distributed adaptive antenna array systems in cellular networks." Pretoria : [s.n.], 2005. http://upetd.up.ac.za/thesis/available/etd-06032005-090336/.
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Mousari, Bafrooei Seyed Pedram. "Reflector feeds for large adaptive reflector antennas." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/NQ57513.pdf.
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Tyler, Neville Roy. "Robust adaptive antennas for mobile wireless networks." Thesis, King's College London (University of London), 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.418121.
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Piazza, Daniele Dandekar Kapil. "Reconfigurable antennas for adaptive MIMO communication systems /." Philadelphia, Pa. : Drexel University, 2009. http://hdl.handle.net/1860/3037.
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Moon, Jang-Wook. "Jamming mitigation through collaboration." [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0011395.
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Zarei, Hossein. "RF variable phase shifters for multiple smart antenna transceivers /." Thesis, Connect to this title online; UW restricted, 2004. http://hdl.handle.net/1773/5964.
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Yang, Ho. "Partially adaptive space-time processing." Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/13028.
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Cheung, Bing-Leung Patrick. "Simulation of Adaptive Array Algorithms for OFDM and Adaptive Vector OFDM Systems." Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/34915.
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The increasing demand for high data rate services necessitates the adoption of very wideband waveforms. In this case, the channel is frequency-selective, that is, a large number of resolvable multipaths are present in this environment and fading is not highly correlated across the band. Orthogonal frequency division multiplexing (OFDM) is well-known to be effective against multipath distortion. It is a multicarrier communication scheme, in which the bandwidth of the channel is divided into subcarriers and data symbols are modulated and transmitted on each subcarrier simultaneously. By inserting guard time that is longer than the delay spread of the channel, an OFDM system is able to mitigate intersymbol interference (ISI). Deploying an adaptive antenna array at the receiver can help separate the desired signal from interfering signals which originate from different spatial locations. This enhancement of signal integrity increases system capacity. In this research, we apply adaptive array algorithms to OFDM systems and study their performance in a multipath environment with the presence of interference. A novel adaptive beamforming algorithm based on the minimum mean-squared error (MMSE) criterion, which is referred to as frequency-domain beamforming, is proposed that exploits the characteristics of OFDM signals. The computational complexity of frequency-domain beamforming is also studied. Simulation results show employing an adaptive antenna array with an OFDM system significantly improves system performance when interference is present. Simulations also show that the computational complexity of the algorithm can be reduced by half without significant performance degradation. Adaptive array algorithms based on the maximum signal-to-noise ratio (MSNR) and the maximum signal-to-interference-plus-noise ratio (MSINR) criteria are also applied to adaptive vector OFDM systems (AV-OFDM). Simulation results show that the adaptive algorithm based on the MSNR criterion has superior performance in the multipath environment but performs worse than the one based on the MSINR criterion under the flat fading channel.Master of Science
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Cardieri, Paulo. "Resource Allocation and Adaptive Antennas in Cellular Communications." Diss., Virginia Tech, 2000. http://hdl.handle.net/10919/29051.
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The rapid growth in demand for cellular mobile communications and emerging fixed wireless access has created the need to increase system capacity through more efficient utilization of the frequency spectrum, and the need for better grade of service. In cellular systems, capacity improvement can be achieved by reducing co-channel interference.
Several techniques have been proposed in literature for mitigating co-channel interference, such as adaptive antennas and power control. Also, by allocating transmitter power and communication channels efficiently (resource allocation), overall co-channel interference can be maintained below a desired maximum tolerable level, while maximizing the carried traffic of the system.
This dissertation presents investigation results on the performance of base station adaptive antennas, power control and channel allocation, as techniques for capacity improvement. Several approaches are analyzed. Firstly, we study the combined use of adaptive antennas and fractional loading factor, in order to estimate the potential capacity improvement achieved by adaptive antennas.
Next, an extensive simulation analysis of a cellular network is carried out aiming to investigate the complex interrelationship between power control, channel allocation and adaptive antennas. In the first part of this simulation analysis, the combined use of adaptive antennas, power control and reduced cluster size is analyzed in a cellular system using fixed channel allocation.
In the second part, we analyze the benefits of combining adaptive antennas, dynamic channel allocation and power control. Two representative channel allocation algorithms are considered and analyzed regarding how efficiently they transform reduced co-channel interference into higher carried traffic. Finally, the spatial filtering capability of adaptive antennas is used to allow several users to share the same channel within the same cell. Several allocation algorithms combined with power control are analyzed.Ph. D.
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Chua, Marcial K. "1 GHz programmable analog phase shifter for adaptive antennas." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq29404.pdf.
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Lau, Buon Kiong. "Applications of Adaptive Antennas in Third-Generation Mobile Communications Systems." Thesis, Curtin University, 2002. http://hdl.handle.net/20.500.11937/2019.
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Adaptive antenna systems (AAS's) are traditionally of interest only in radar and sonar applications. However, since the onset of the explosive growth in demand for wireless communications during the 1990's, researchers are giving increasing attention to the use of AAS technology to overcome practical challenges in providing the service. The main benefit of the technology lies in its ability to exploit the spatial domain, on top of the temporal and frequency domains, to improve on transceiver performance. This thesis presents a unified study on two classes of preprocessing techniques for uniform circular arrays (UCA's). UCA's are of interest because of their natural ability to provide a full azimuth (i.e. 360') coverage found in typical scenarios for sensor array applications, such as radar, sonar and wireless communications. The two classes of preprocessing techniques studied are the Davies transformation and the interpolated array transformations. These techniques yield a mathematically more convenient form - the Vandermonde form - for the array steering vector via a linear transformation. The Vandermonde form is useful for different applications such as direction-of-arrival (DOA) estimation and optimum or minimum variance distortionless response (MVDR) beamforming in correlated signal environment and beampattem synthesis. A novel interpolated array transformation is proposed to overcome limitations in the existing interpolated array transformations. A disadvantage of the two classes of preprocessing techniques for UCA's with omnidirectional elements is the lack of robustness in the transformed array steering vector to array imperfections under certain conditions. In order to mitigate the robustness problem, optimisation problems are formulated to modify the transformation matrices.Suitable optimisation techniques are then applied to obtain more robust transformations. The improved transformations are shown to improve robustness but at the cost of larger transformation errors. The benefits of the robustification procedure are most apparent in DOA estimation. In addition to the algorithm level studies, the thesis also investigates the use of AAS technology with respect to two different third generation (3G) mobile communications systems: Enhanced Data rates for Global Evolution (EDGE) and Wideband Code Division Multiple Access (WCDMA). EDGE, or more generally GSM/EDGE Radio Access Network (GERAN), is the evolution of the widely successful GSM system to provide 3G mobile services in the existing radio spectrum. It builds on the TDMA technology of GSM and relies on improved coding and higher order modulation schemes to provide packet-based services at high data rates. WCDMA, on the other hand, is based on CDMA technology and is specially designed and streamlined for 3G mobile services. For WCDMA, a single-user approach to DOA estimation which utilises the user spreading code and the pulse-shaped chip waveform is proposed. It is shown that the proposed approach produces promising performance improvements. The studies with EDGE are concerned with the evaluation of a simple AAS at the system and link levels.Results from, the system and link level simulations are presented to demonstrate the effectiveness of AAS technology in the new mobile communications system. Finally, it is noted that the WCDMA and EDGE link level simulations employ the newly developed COST259 directional channel model, which is capable of producing accurate channel realisations of macrocell environments for the evaluation of AAS's.
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Lau, Buon Kiong. "Applications of Adaptive Antennas in Third-Generation Mobile Communications Systems." Curtin University of Technology, Australian Telecommunications Research Institute, 2002. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=12983.
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Adaptive antenna systems (AAS's) are traditionally of interest only in radar and sonar applications. However, since the onset of the explosive growth in demand for wireless communications during the 1990's, researchers are giving increasing attention to the use of AAS technology to overcome practical challenges in providing the service. The main benefit of the technology lies in its ability to exploit the spatial domain, on top of the temporal and frequency domains, to improve on transceiver performance. This thesis presents a unified study on two classes of preprocessing techniques for uniform circular arrays (UCA's). UCA's are of interest because of their natural ability to provide a full azimuth (i.e. 360') coverage found in typical scenarios for sensor array applications, such as radar, sonar and wireless communications. The two classes of preprocessing techniques studied are the Davies transformation and the interpolated array transformations. These techniques yield a mathematically more convenient form - the Vandermonde form - for the array steering vector via a linear transformation. The Vandermonde form is useful for different applications such as direction-of-arrival (DOA) estimation and optimum or minimum variance distortionless response (MVDR) beamforming in correlated signal environment and beampattem synthesis. A novel interpolated array transformation is proposed to overcome limitations in the existing interpolated array transformations. A disadvantage of the two classes of preprocessing techniques for UCA's with omnidirectional elements is the lack of robustness in the transformed array steering vector to array imperfections under certain conditions. In order to mitigate the robustness problem, optimisation problems are formulated to modify the transformation matrices.Suitable optimisation techniques are then applied to obtain more robust transformations. The improved transformations are shown to improve robustness but at the cost of larger transformation errors. The benefits of the robustification procedure are most apparent in DOA estimation. In addition to the algorithm level studies, the thesis also investigates the use of AAS technology with respect to two different third generation (3G) mobile communications systems: Enhanced Data rates for Global Evolution (EDGE) and Wideband Code Division Multiple Access (WCDMA). EDGE, or more generally GSM/EDGE Radio Access Network (GERAN), is the evolution of the widely successful GSM system to provide 3G mobile services in the existing radio spectrum. It builds on the TDMA technology of GSM and relies on improved coding and higher order modulation schemes to provide packet-based services at high data rates. WCDMA, on the other hand, is based on CDMA technology and is specially designed and streamlined for 3G mobile services. For WCDMA, a single-user approach to DOA estimation which utilises the user spreading code and the pulse-shaped chip waveform is proposed. It is shown that the proposed approach produces promising performance improvements. The studies with EDGE are concerned with the evaluation of a simple AAS at the system and link levels.
Results from, the system and link level simulations are presented to demonstrate the effectiveness of AAS technology in the new mobile communications system. Finally, it is noted that the WCDMA and EDGE link level simulations employ the newly developed COST259 directional channel model, which is capable of producing accurate channel realisations of macrocell environments for the evaluation of AAS's.
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Juswardy, Budi. "Integrated broadband microphotonic beamformer for adaptive nulling in smart antennas." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2010. https://ro.ecu.edu.au/theses/1843.
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The tremendous growth of the wireless communications sector and the problem of limited available spectrum that can be used to cater the wireless demand have spurred the need for better data transmission capacity and signal rates for wireless communication systems. Smart antennas are the promising technology for improving the wireless communication systems performance. Smart antennas are system that consist of antenna arrays capable of adaptively adjusting the beam pattern, thereby enhancing the desired signals (beam steering) and suppressing the interference signals (null steering), which is also known as Space Division Multiple Access (SDMA). SDMA systems allow significant improvement in the area of capacity, signal bandwidth, signal-to-interference ratio, and frequency reuse. Due to the increasing complexity of the smart antennas system, innovations and improvements in miniaturisation, power consumption, and cost are needed. These breakthroughs could be achieved by combining the microelectronic and photonic technologies, leading to an innovative software-driven broadband MicroPhotonic beamforming system.
This thesis presents a doctoral study of integrated MicroPhotonic smart antenna beamformers. The beamformers presented in this study is based on microminiaturisation of hotonic and electronic components, which processes RF-modulated optical signals and adaptively synthesises multiple broadband null for interference suppression. Two types of beamformer are investigated in this thesis; the first form is based on delaying the input RF signal via discrete, high-resolution true-time delay (TTD) through the use of free space optics. The second type is based on continuous TTD generation using an Opto-VLSI processor in conjunction with high-dispersive optical fibres.
Design, simulation and proof-of-concept demonstration of some of the photonic building blocks and RF components of smart antennas that employ the MicroPhotonic beamformer are presented. These smart antennas are designed for use in adaptive broadband phased-array antenna applications including multimedia wireless transmission and RADAR.
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Fiacco, Mauro. "Intelligent picocells for adaptive indoor coverage and capacity." Thesis, University of Surrey, 2001. http://epubs.surrey.ac.uk/844492/.
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This dissertation presents and develops the Intelligent Picocell as a solution for high bit rate, efficient bandwidth indoor wireless communication. The research has examined different aspects of the indoor radio propagation environment and system implementation in order to highlight key benefits of the proposed architecture. Explosive growth in demand for indoor wireless communications motivates research into this novel radio architecture. The architecture should be capable of tailoring capacity and coverage to the needs of the specific indoor environment, while maximising spectral efficiency. The Intelligent Picocell is based on an evolution of the distributed antenna concept to provide macrodiversity, microdiversity and interference cancellation. The architecture is fully scalable to large numbers of users and can provide plug-and-play operation, with no need for detailed system planning beyond the antenna locations. The research examines different aspects of picocell system performance and design, including: Investigation on the indoor radio environment. Through measurements, the effects of building features on path loss and shadowing are analysed and propagation models are proposed for simulating picocell systems. Analysis of the Intelligent Picocell architecture, two algorithms are proposed for interference reduction, one based on a distributed narrowband optimum combiner and the other on a dynamic channel assignment and allocation scheme. Through simulation, it was demonstrated that the mobile transmitted power for an Intelligent Picocell is lower than the power required in a distributed antennas system. It was also shown that the capacity of the system depends on the number of antennas distributed in the building. Key words: Intelligent picocell, adaptive antennas, diversity, distributed antennas, dynamic channel allocation, propagation measurements.
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Dietrich, Carl B. "Adaptive Arrays and Diversity Antenna Configurations for Handheld Wireless Communication Terminals." Diss., Virginia Tech, 2000. http://hdl.handle.net/10919/27291.
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This dissertation reports results of an investigation into the performance of adaptive beamforming and diversity combining using antenna arrays that can be mounted on handheld radios. Handheld arrays show great promise for improving the coverage, capacity, and power efficiency of wireless communication systems.
Diversity experiments using a handheld antenna array testbed (HAAT) are reported here. These experiments indicate that signals received by the antennas in two-element handheld antenna arrays with spacing of 0.15 wavelength or greater can be combined to provide 7-9 dB diversity gain against fading at the 99% reliability level in non line-of-sight multipath channels. Thus, peer-to-peer systems of handheld transceivers that use antenna arrays can achieve reliability comparable to systems of single-antenna handheld units, with only one-fifth the transmitter power, resulting in lower overall power consumption and increased battery life. Similar gains were observed for spatial, polarization, and pattern diversity.
Adaptive beamforming with single- and multi-polarized four-element arrays of closely spaced elements was investigated by experiment using the HAAT, and by computer simulation using a polarization-sensitive vector multipath propagation simulator developed for this purpose. Small and handheld adaptive arrays were shown to provide 25 to 40 dB or more of interference rejection in the presence of a single interferer in rural, suburban, and urban channels including line-of-sight and non line-of-sight cases. In multipath channels, these performance levels were achieved even when there was no separation between the transmitters in azimuth angle as seen from the receiver, and no difference in the orientations of the two transmitting antennas. This interference rejection capability potentially allows two separate spatial channels to coexist in the same time/frequency channel, doubling system capacity.Ph. D.
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Huang, Fei, and 黄菲. "Design and analysis of transmission protocols in wireless networks with smart antennas." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B46421610.
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Abusultan, Monther Younis. "Digital implementation of direction-of-arrival estimation techniques for smart antenna systems." Thesis, Montana State University, 2010. http://etd.lib.montana.edu/etd/2010/abusultan/AbusultanM0510.pdf.
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Adaptive antenna arrays use multiple antenna elements to form directional patterns in order to improve the performance of wireless communication systems. The antenna arrays also have the ability to detect the direction of incoming signals. These two capabilities allow a smart antenna system to adaptively beamform to more efficiently communicate between nodes. The direction-of-arrival estimation is a crucial component of the smart antenna system that uses open-loop adaptive approach. Historically this estimation has been accomplished using a personal computer. Implementing the estimation in the digital domain has the potential to provide a low cost and light weight solution due to recent advances in digital integrated circuit fabrication processes. Furthermore, digital circuitry allows for more sophisticated estimation algorithms to be implemented using the computational power of modern digital devices. This thesis presents the design and prototyping of direction-of-arrival (DOA) estimation for a smart antenna system implemented on a reconfigurable digital hardware fabric. Two DOA estimation algorithms are implemented and the performance tradeoffs between a custom hardware approach and a microprocessor-based system are compared. The algorithms were implemented for a 5.8 GHz, 8-element circular antenna array and their functionality was verified using a testbed platform. The implementation and analysis presented in this work will aid system designers to understand the tradeoffs between implementing algorithms in custom hardware versus an embedded system and when a hybrid approach is more advantageous.
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Kim, Sang-youb. "A fast estimation algorithm of array response vector for adaptive smart antenna systems /." Digital version accessible at:, 2000. http://wwwlib.umi.com/cr/utexas/main.
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Arnott, Robert. "Array processing for digital mobile radio." Thesis, Imperial College London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.338780.
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Chen, Junying, and 陈俊颖. "Design space exploration of real-time bedside and portable medical ultrasound adaptive beamformer acceleration." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B50434354.
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This work explored the design considerations on the real-time medical ultrasound adaptive beamformer implementations using different computing platforms: CPU, GPU and FPGA. Adaptive beamforming has been well considered as an advanced solution for improving the image quality of medical ultrasound imaging machines. Although it provides promising improvements in lateral resolution, image contrast and imaging penetration depth, the use of adaptive beamforming is substantially more computationally demanding than conventional delay-and-sum beamformers. In order not to compromise the real-time performance of medical ultrasound systems, an accelerated solution is desirable.
In this work, CPU implementation was used as a baseline implementation, based on which the intrinsic characteristics of the algorithm were analyzed. After the analysis of a particular adaptive beamforming algorithm, minimum-variance adaptive beamforming, two design parameters M and L were found to affect the implementation performance in two aspects: computational demand and image quality. The trends of the two aspects were contradictory with respect to the increment of M and L values. In our experiments, when M and L increased, the computational demand increased in a cubic curve; meanwhile, the image quality did not have much improvement when the increased values of M and L entered certain ranges. Since we targeted at a real-time solution without sacrificing the good image quality that adaptive beamforming proposed, a tradeoff was made on the selection of M and L values to balance the two contradictory requirements.
Built upon the theoretical algorithmic analysis of the real-time adaptive beamformer realization, the implementations were developed with FPGA and GPU. While a dedicated hardware solution might be able to address the computational demand of the particular design, the need for an efficient algorithm exploration framework demanded a reprogrammable platform solution that was high-performance and easily reconfigurable. Besides, although a simple processor could provide convenient algorithm exploration via software development environment, real-time performance was usually not achievable. As a result, a reprogrammable medical ultrasound research platform for investigating advanced imaging algorithms was constructed in our project. The use of FPGA and GPU for implementing the real-time adaptive beamformer on our platform was explored. In our test cases, both FPGA- and GPUbased solutions achieved real-time throughput exceeding 80 frames-per-second, and over 38x improvement when compared to our baseline CPU implementation.
Moreover, the implementations were also evaluated in terms of portability, data accuracy, programmability, and system integration. Due to its high power consumption, high-performance GPU solution is best suited for bedside applications, while FPGAs are more suitable for portable and hand-held medical ultrasound machines. Besides, while the development time on GPU platform remains much lower than its FPGA counterpart, the FPGA solution is effective in providing the necessary I/O bandwidth to enable an end-to-end real-time reconfigurable medical ultrasound image formation system.published_or_final_version
Electrical and Electronic Engineering
Doctoral
Doctor of Philosophy
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Torlak, Murat. "Estimation and capacity of channels in smart antenna wireless communication systems /." Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.
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Yang, Weidong. "Vector channel study and related issues in selective transceiving /." Digital version accessible at:, 2000. http://wwwlib.umi.com/cr/utexas/main.
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Kavak, Adnan. "Vector propagation channel studies for smart antenna wireless communication systems /." Full text (PDF) from UMI/Dissertation Abstracts International, 2000. http://wwwlib.umi.com/cr/utexas/fullcit?p3004302.
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Chen, Runhua. "A layered space-time coded MIMO architecture for high-data-rate wireless communications /." View Abstract or Full-Text, 2002. http://library.ust.hk/cgi/db/thesis.pl?ELEC%202002%20CHEN.
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Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2002.Includes bibliographical references (leaves 84-88). Also available in electronic version. Access restricted to campus users.
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Zhu, Xu. "Wireless MIMO antenna systems for frequency selective fading channels /." View Abstract or Full-Text, 2003. http://library.ust.hk/cgi/db/thesis.pl?ELEC%202003%20ZHU.
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Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2003.Includes bibliographical references (leaves 116-118). Also available in electronic version. Access restricted to campus users.
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Ali, Maha Abdelmoneim Mohamed. "DESIGN AND ANALYSIS OF ADAPTIVE AND RECONFIGURABLE ANTENNAS FOR WIRELESS COMMUNICATION." Doctoral diss., University of Central Florida, 2004. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4399.
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Modern radar and communication systems have experienced a tremendous increase in the number of antennas onboard, on the ground, and in orbital space. This places a burden due to the confined volume and limited weight requirements especially in space applications. The reconfigurable antenna is a promising and exciting new type of antenna, where through the use of appropriate switches the antenna can be structurally reconfigured, to maintain the elements near their resonant dimensions for several frequency bands. This increases the bandwidth of the antenna dramatically, which enables the use of one antenna for several applications. Four novel reconfigurable antenna elements were designed to work at 2.45 GHz and at 5.78 GHz, to cover the transition period when wireless communication will shift to the 5.78 GHz band.
The four elements designed are: the reconfigurable Yagi, the reconfigurable corner-fed triangular loop antenna, the reconfigurable center-fed equilateral triangular loop antenna and the reconfigurable rectangular-spiral antenna. None of these antennas have been reported in the literature. Simulation results for all four antennas were obtained using IE3D. Fabrication and measurements for the Yagi antenna was done and the measured results agree with simulations. All four antennas have very good performance with respect to the 3dB beamwidth and directivity. However the reconfigurable rectangular-spiral antenna is the most compact in size among all four antennas. It is (20 mm x 20 mm) in size. At 2.45 GHz it has a 3dB beamwidth of 87° and directivity of 6.47dB. As for the 5.78GHz frequency the 3dB beamwidth is 82.5° and the directivity is 7.16dB. This dissertation also introduces the use of reconfigurable antenna elements in adaptive arrays.
An adaptive array that can null interference and direct its main lobe to the desired signal while being reconfigurable to maintain functionality at several frequency bands has the potential to revolutionize wireless communications in the future. Through several examples, at both the design frequencies, it is shown that the reconfigurable and adaptive antenna arrays are successful in nulling noises incident on the array. These examples illustrate how reconfigurable elements and adaptive arrays can be combined very beneficially for use in wireless communication systems.Ph.D.
School of Electrical Engineering and Computer Science
Engineering and Computer Science
Electrical Engineering and Computer Science
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Irfanullah, Irfanullah. "Adaptive Beamforming for Antennas on General Wedge- and Cylindrical-Shaped Surfaces." Diss., North Dakota State University, 2014. https://hdl.handle.net/10365/27051.
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Adaptive beamforming antennas capable of accommodating the growing number of wireless subscribers throughout the world has become an essential part of modern wireless systems. In this work, the beamforming of a conformal antenna on a changing conformal surface is studied by relating the varying position of each antenna element in the array to the weighting coefficients (i.e, array weights) required to give a desired antenna beam formation. In particular, the beamforming of a 1 x 4 array on a changing wedge- and cylindrical-shaped surface is studied using the projection method on a wavefront of a transmitted wave in a particular direction. To validate the theory, a 1 x 4 prototype antenna with individual voltage-controlled phase shifters and attenuators is used to implement the computed weights of each individual antenna element for measurements in an anechoic chamber. Overall agreement between theory, simulations and measurements is shown throughout the work. Furthermore, the effects of mutual coupling and changing conformal surfaces on the behavior of the beamforming pattern and array weights is investigated and summarized.
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Rong, Zhigang. "Simulation of Adaptive Array Algorithms for CDMA Systems." Thesis, This resource online, 1996. http://scholar.lib.vt.edu/theses/available/etd-09182008-063401/.
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Williams, Ian E. "Multipath Mitigation for Aeronautical Telemetry with Multiple Antennas." International Foundation for Telemetering, 2009. http://hdl.handle.net/10150/606143.
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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, NevadaFrequency selective multipath is a key performance limiter for aeronautical telemetry applications. Our research explores multipath mitigation techniques with ARTM Tier-1 waveforms using linear adaptive filters, multiple receive antennas and error-based best source selection. Single antenna adaptive equalization alone is unable to substantially improve performance under certain channel conditions. Analytical investigations demonstrate that nonlinear channel phase response is the principal cause of performance loss. In this adverse environment, spatial diversity with multiple receive antennas along with error-based best source selection are capable of improving bit error rate performance by 5dB for each additional antenna.
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Papathanassiou, Apostolos. "Adaptive antennas for mobile radio systems using time division CDMA and joint detection Adaptive Antennen für Mobilfunksysteme mit zeitgeschlitztem CDMA und gemeinsamer Detektion der Teilnehmersignale /." [S.l.] : [s.n.], 2000. http://deposit.ddb.de/cgi-bin/dokserv?idn=959795111.
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Matthews, James Christopher Gordon. "Patch moment method modelling of wire fed vehicular structures as adaptive antennas." Thesis, University of Sheffield, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.412702.
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Li, Haipeng. "An adaptive mac protocol for wireless multi-hop networks with multiple antennas." College Park, Md. : University of Maryland, 2005. http://hdl.handle.net/1903/2988.
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Thesis (M.S.) -- University of Maryland, College Park, 2005.Thesis research directed by: Dept. of Electrical and Computer Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Jiang, Meilong. "Robust cross-layer scheduling design in multi-user multi-antenna wireless systems." Click to view the E-thesis via HKUTO, 2006. http://sunzi.lib.hku.hk/hkuto/record/B38346758.
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Jiang, Meilong, and 江美龍. "Robust cross-layer scheduling design in multi-user multi-antenna wireless systems." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2006. http://hub.hku.hk/bib/B38346758.
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Palantei, Elyas. "Switched Parasitic Smart Antenna: Design and Implementation for Wireless Communication Systems." Thesis, Griffith University, 2012. http://hdl.handle.net/10072/366219.
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Smart antenna technology in applications such as the next-G wireless communication networks may improve the quality of service (QoS). One category of smart antennas is the switched beam smart antenna (SBA). These antennas can be grouped into plug and play antennas and adaptive internal antennas. Four types of switched beam smart antennas were investigated including a six monopole array on circular ground plane with conducting sleeve, five monopoles on a circular ground plane without a conducting sleeve, a reconfigurable monopole on a cylindrical hollow ground structure, and a reconfigurable adaptive internal antenna. The first two antennas were constructed with a switched parasitic array of elements combined with an RF circuit with microcontroller. Two of the four antenna prototypes were capable for steering the beam pattern automatically based on signal strength (RSSI) or bit error rate (BER) scanning. The two remaining antennas were designed for electronic beamforming and electronic frequency tuning. Both numerical and empirical investigations were undertaken to measure performance and investigate manufacture difficulties. The numerical investigations were undertaken using both the method of moment (MoM)-NEC and the finite element method (FEM)-HFSS modeling. The fabrication and testing in an anechoic chamber were used to explore the actual performance of the designed antennas. The fabrication of the last two types of antennas was not implemented. Further work is required to find the optimal design for all antennas investigated. This study suggests significant promise for these antennas in wireless networks.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Engineering
Science, Environment, Engineering and Technology
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Petrus, Paul. "Novel Adaptive Array Algorithms and Their Impact on Cellular System Capacity." Diss., Virginia Tech, 1997. http://hdl.handle.net/10919/30375.
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This report focuses on the application of adaptive arrays to the Advanced Mobile Phone Service (AMPS) and Code Division Multiple Access (CDMA) cellular systems. Adaptive arrays have been proposed as early as in the 1960s to improve the signal quality, but most of its applications were restricted to defense purposes. Recently, there has been a surge in interest of applying adaptive arrays for cellular systems. This work introduces new blind adaptive array algorithms for AMPS and CDMA signals. The theoretical capacity limit using an adaptive array at the base station for an AMPS cellular system is derived in this work. One of the significant contributions in this research is a macrocell channel model which provides angle-of-arrival (AOA) statistics of the multipath components. Practical issues involved in the implementation of an adaptive array are addressed and the author's implementation of an 8-element adaptive array operating at 2.05 GHz is explained. This research also analyzes the capacity that can be o ered by an adaptive array in a system where CDMA users co-exist with existing AMPS users. A novel cellular CDMA system which exploits adaptive arrays is introduced and the capacity o ered by this system is compared with existing and other systems exploiting spatial dimension.Ph. D.
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Seow, Tian Beng. "Circular antenna array applications in coded DS-CDMA mobile communication systems /." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2003. http://library.nps.navy.mil/uhtbin/hyperion-image/03Mar%5FSeow.pdf.
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Srivastava, Vikash Umeshchandra. "Smart Antennas & Power Management in Wireless Networks." Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/31244.
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The proliferation of wireless ad-hoc networks especially wireless LAN (IEEE 802.11b Standard) in the commercial market in recent years has reached a critical mass. The adoption and strong support of wireless IEEE 802.11 standard, coupled with the consequent decline in costs, has made wireless LAN deployment as one of the fastest growth area in communication access technology. With the ever increasing use of wireless LAN technology the various networks are reaching their full capacity in terms of network throughput, number of users and interference level in the wireless channel.
In this thesis work I propose to the use smart antenna technology and a power management scheme in the wireless ad-hoc networks to increase the network capacity in terms of throughput, number of simultaneous communication and to lower the average transmit power and consequently co-channel interference. Power management scheme can be used to maximize the power efficiency of the transmitter by choosing an optimum transmit power level. Smart antenna or adaptive antenna array technology has reached a level of sophistication that it is feasible to use it on small mobile terminals like handheld PDA, LAPTOP and other mobile devices with limited battery power.
The simulation results of various ad â hoc network scenario shows that there are significant gains to be had if these technologies can be integrated in the existing wireless LAN physical layer and/or in the standard them self. Smart antennas along with slight modification in channel access scheme reduce co-channel interference dramatically and increases the number of simultaneous transmissions hence improves network throughput. Power management algorithm is shown to improve average transmission of a node.
We present a mathematical framework to characterize the outage probability of cellular mobile radio system with selective co-channel interference receiver in overloaded array environments. The mathematical framework outlines a general numerical procedure for computing the probability of outage of a cellular mobile radio system that is equipped with a smart antenna to suppress a few strongest co-channel interferers (CCI) out of a total of NI active interferers by null steering.Master of Science
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Maddela, Madhurima Ramadoss Ramesh. "Design of MEMS-based tunable antennas, organic transistors and MEMS-based organic control circuits." Auburn, Ala, 2008. http://repo.lib.auburn.edu/2007%20Fall%20Dissertations/Maddela_Madhurima_8.pdf.
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Church, Christopher Michael. "Estimation of Adaptive Antenna Induced Phase Biases in Global Navigation Satellite Systems Receiver Measurements." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1257792743.
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Li, Aini. "QoS-aware adaptive resource management in OFDMA networks." Thesis, Queen Mary, University of London, 2017. http://qmro.qmul.ac.uk/xmlui/handle/123456789/24652.
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One important feature of the future communication network is that users in the network are required to experience a guaranteed high quality of service (QoS) due to the popularity of multimedia applications. This thesis studies QoS-aware radio resource management schemes in different OFDMA network scenarios. Motivated by the fact that in current 4G networks, the QoS provisioning is severely constrained by the availability of radio resources, especially the scarce spectrum as well as the unbalanced traffic distribution from cell to cell, a joint antenna and subcarrier management scheme is proposed to maximise user satisfaction with load balancing. Antenna pattern update mechanism is further investigated with moving users. Combining network densi fication with cloud computing technologies, cloud radio access network (C-RAN) has been proposed as the emerging 5G network architecture consisting of baseband unit (BBU) pool, remote radio heads (RRHs) and fronthaul links. With cloud based information sharing through the BBU pool, a joint resource block and power allocation scheme is proposed to maximise the number of satisfi ed users whose required QoS is achieved. In this scenario, users are served by high power nodes only. With spatial reuse of system bandwidth by network densi fication, users' QoS provisioning can be ensured but it introduces energy and operating effciency issue. Therefore two network energy optimisation schemes with QoS guarantee are further studied for C-RANs: an energy-effective network deployment scheme is designed for C-RAN based small cells; a joint RRH selection and user association scheme is investigated in heterogeneous C-RAN. Thorough theoretical analysis is conducted in the development of all proposed algorithms, and the effectiveness of all proposed algorithms is validated via comprehensive simulations.
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Gao, Bo 1981. "Computationally efficient approaches for blind adaptive beamforming in SIMO-OFDM systems." Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=115994.
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In single-input multiple-output (SIMO) systems based on orthogonal frequency division multiplexing (OFDM), adaptive beamforming at the receiver side can be used to combat the effect of directional co-channel interference (CCI). Since pilot-aided beamforming suffers from consuming precious channel bandwidth, there has been much interest in blind beamforming approaches that can adapt their weights by restoring certain properties of the transmitted signals. Within this class of blind algorithms, the recursive least squares constant modulus algorithm (RLS-CMA) is of particular interest due to its good overall CCI cancelation performance and fast convergence. Nevertheless, the direct use of RSL-CMA within a SIMO-OFDM receiver induces considerable computational complexity, since a distinct copy of the RLS-CMA must be run on each individual sub-carriers. In this thesis, we present two approaches to reduce the computational complexity of SIMO-OFDM beamforming based on the RLS-CMA, namely: frequency interpolation and distributed processing. The former approach, which exploits the coherence bandwidth of the broadband wireless channels, divides the sub-carriers into several contiguous groups and applies the RLS-CMA to a selected sub-carrier in each group. The weight vectors at other frequencies are then obtained by interpolation. The distributed processing approach relies on the partitioning of the receiving array into sub-arrays and the use of a special approximation in the RLS-CMA. This allows a partial decoupling of the algorithm which can then be run on multiple processors with reduced overall complexity. This approach is well-suited to collaborative beamforming i~ multi-node distributed relaying. Through numerical simulation experiments of a SIMO-OFDM system, it is demonstrated that the proposed modifications to the RLS-CMA scheme can lead to substantial computational savings with minimal losses in adaptive cancelation performance.
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Lim, GuBong. "H-MIMO a hybrid of spatial multiplexing and adaptive beamforming /." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file 1.65 Mb., 69 p, 2005. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:1428176.
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Perri, Eduardo Barbosa. "Efeitos de acoplamento e de banda de operação em redes de antenas adaptativas reais." Universidade de São Paulo, 2005. http://www.teses.usp.br/teses/disponiveis/3/3142/tde-21042005-142500/.
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Redes inteligentes de antenas vêm ganhando uma importância cada vez maior na expansão e no aperfeiçoamento de sistemas de telefonia celular, principalmente para sistemas de 3a geração, que necessitarão de uma banda de transmissão ainda maior. Neste sentido, são muitas as contribuições da comunidade científica para este tema, com o objetivo de determinar a direção de chegada dos sinais incidentes na rede, de diminuir a interferência de um sinal sobre o outro e de sintetizar diagramas de radiação desejados. Na maior parte dos casos, porém, as antenas utilizadas nas simulações são consideradas ideais, desprezando-se os efeitos de acoplamento mútuo entre os seus elementos. Neste trabalho, através de simulações numéricas, é analisado o impacto da utilização de antenas reais no desempenho de sistemas de antenas inteligentes, levando-se em conta todas as características intrínsecas como acoplamento mútuo e diagramas de radiação reais dos seus elementos. Além disso, são propostas soluções para a utilização de redes de antenas reais através de métodos e procedimentos que possam contribuir para melhor precisão e confiabilidade dos resultados correspondentes. Dessa forma, é apresentado um método de processamento adaptativo em rede ideal equivalente, que leva a uma solução para formação de feixe em enlace de descida de sistemas de telefonia celular, utilizando-se uma transformação de rede real em rede ideal. É também investigada a dependência de velocidade de convergência e dos erros resultantes no processo acima citado em função da escolha da geometria da rede ideal. Apresenta-se, ainda, uma nova configuração de rede com redução de acoplamento mútuo, investigando-se a melhoria de características como nível de lóbulos secundários e precisão na determinação de direção de chegada de sinais em redes de antenas inteligentes.Smart antenna arrays are becoming more important in the expansion and in the enhancement of cellular telephony systems, specially in the third-generation that will need an even larger bandwidth. In this subject, many contributions from the scientific community have been provided with the goal of determining direction-of-arrival for incident signals, eliminating interference between different signals and of synthesizing desired radiation patterns. On most cases, however, the antennas employed in the simulations are ideal antennas, where one disregards the mutual coupling effects between each pair of elements. In this work, the impact of using real antennas in the behavior of smart antenna systems is analyzed through numerical simulations, taking into account intrinsic features such as mutual coupling and real radiation patterns of its elements. On top of that, solutions are proposed for the utilization of real antenna arrays through methods and procedures that may contribute to a better precision and reliability of the related results. In this sense, it is initially presented an adaptive process method that leads to a solution for downlink beamforming in cellular systems, using a transformation of the real array into an ideal array. The dependence of convergence speed and errors on the choice of the ideal array geometry is also investigated. Next, a new array configuration with reduced mutual coupling is presented, and improvements in characteristics such as secondary lobe level and direction-of-arrival determination precision on smart antenna arrays are investigated.