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1
Pyk, Axel. "Multipath TCP : Performance in a LTE Environment." Thesis, Linköpings universitet, Databas och informationsteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-129123.
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The market penetration of mobile access devices with multiple network interfaces has increased dramatically over the last few years. As a consequence, the quest for a widespread multi-path transport protocol that takes advantage of all available interfaces simultaneously to increase data throughput and improve robustness, has received considerable attention. One prominent protocol introduced by the IETF is Multipath TCP (MPTCP). MPTCP is an extension to the predominant single-path transport protocol, the Transport Control Protocol (TCP) that enables multihomed devices to aggregate available resources transparently to the applications. Combining multiple radio access technologies, like LTE and Wi-Fi, with diverse characteristics in terms of transmission rates and fluctuations opens for novel challenges that may disrupt and even harm the data throughput. Therefore MPTCP must take path heterogeneity into account. For MPTCP to supersede single-path TCP it is required that MPTCP always achieve at least the throughput of the best individual TCP path. This thesis investigates if MPTCP with uncoupled congestion control fulfills this condition, and if so, how much it improves the throughput. By examining the protocol in a deterministic emulated environment defined by the characteristics of LTE, we conclude two key factors impacting the outcome: the download size and the difference in characteristics between the paths. Our experiments show that MPTCP overall fulfills this task, especially during path homogeneity with near aggregated results. But we also show that MPTCP may decrease data throughput with 16% compared to TCP during path heterogeneity. Hence MPTCP does not always fulfill the goal of throughput. We therefore conclude further intelligence is needed for the packet scheduling mechanism to avoid throughput degradation in the initial phase of a transmission.
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Condo, Neira Edith. "Antenna Evaluation for VehicularApplications in Multipath Environment." Licentiate thesis, Chalmers University of Technology, Sweden, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:ri:diva-30075.
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Antennas are essential components in any wireless communication system. To evaluate them is challenging, especially when new technologies are emerging. Future intelligent transport systems, where vehicular communications play an important role will cover important aspects such as traffic safety and traffic efficiency. These applications will be covered by technologies such as IEEE 802.11p and LTE. For these emerging technologies, traditional methods for measuring the vehicular antennas such as anechoic chamber measurements or expensive and time-consuming field measurements may not be enough or suitable. Thus a new method for evaluating the antennas performance is desirable. A method that includes the multipath environment to give an idea of the antenna performance in the whole system and at the same time be able to be applied at early stages of product development. This thesis aims to provide such method. The thesis is divided in two parts. The first part contains an overview and background of important concepts needed for development of methods for evaluation of vehicular antennas. In the second part, the papers that constitute the core of this work are appended. In Paper A, we evaluate the vehicle’s antenna performance using only simulations. We start by defining the multipath environment for vehicle-tovehicle and vehicle-to-infrastructure (V2X) communication. Then, the V2X environment is simulated using a multipath simulation tool to evaluate the vehicle’s antennas radiation patterns placed at different positions on the vehicle. This will result in the received power cumulative distribution functions (CDFs) for the voltage samples at the receiving antennas port. In Paper B, we present the design and evaluation of an antenna module for IEEE 802.11p and LTE technologies. The module is designed taking into consideration the available space and suitable placement on the vehicle. The proposed module is in accordance with the requirements for LTE and IEEE 802.11p technologies. This is validated with the analysis of the antenna efficiencies, S-parameters, radiation patterns, and diversity performance for the simulated and measured antenna module. Finally, Paper C presents a method for the evaluation of V2V antennas in a simulated measurement-based multipath environment. Here, a measurement campaign is performed to obtain the parameters (i.e., the angular received power spectrum) that define a realistic V2V multipath environment. These parameters are then introduced in a multipath simulation tool where the antennas radiation patterns are evaluated. Results are expressed in terms of received power CDFs. This method is validated by comparing the simulated and measured received power for two roof-top vehicle antennas.
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Tuncay, Orbay. "Wireless Strain Gauge System in a Multipath Environment." The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1222089977.
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Basciftci, Cagri Halis. "Direction Finding With Tdoa In A Multipath Land Environment." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608756/index.pdf.
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In this thesis, the problem of Angle of Arrival estimation of radar signals with Time Difference of Arrival method in an outdoor land multipath environment with limited line of sight is analyzed. A system model is proposed. Effects of system, channel and radar parameters on the Angle of Arrival estimation performance are investigated through Monte Carlo simulations.
Improving effect of utilization of diversity on the estimation performance is observed. Performances of the space diversity with noncoherent and selective combining are compared.
Finally a realistic scenario is studied and performance of the proposed system is investigated.
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Atilaw, Tsige Yared. "Characterization of the Multipath Environment of Ionospheric Scintillation Receivers." Master's thesis, University of Cape Town, 2015. http://hdl.handle.net/11427/16475.
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Includes bibliographical referencesGlobal Navigation Satellite Systems (GNSS) are used to provide information on position, time and velocity all over the world at any time of the day. Currently there are four operational GNSS and one of them is GPS (Global Positioning System) that is developed and maintained by U.S Department of Defence (DoD), which is widely used and accessible all over the world. The accuracy of the output or even the availability of the navigation system depends on current space weather conditions, which can cause random fluctuations of the phase and amplitude of the received signal, called scintillation. Interference of GNSS signals that are reflected and refracted from stationary objects on the ground, with signals that travel along a direct path via the ionosphere to the antenna, cause errors in the measured amplitude and phase. These errors are known as multipath errors and can lead to cycle slip and loss of lock on the satellite or degradation in the accuracy of position determination. High elevation cut off angles used for filtering GNSS signals, usually 15-30°, can reduce non-ionospheric interference due to multipath signals coming from the horizon. Since a fixed-elevation threshold does not take into consideration the surrounding physical environment of each GPS station, it can result in a significant loss of valuable data. Alternatively, if the fixed-elevation threshold is not high enough we run the risk of including multipath data in the analysis. In this project we characterized the multipath environment of the GPS Ionospheric Scintillation and TEC (Total Electron Content) Monitor (GISTM) receivers installed by SANSA (South African National Space Agency) at Gough Island (40:34oS and 9:88° W), Marion Island (46:87° S and 37:86° E), Hermanus (34:42° S and19:22° E) and SANAE IV (71:73° S and 2:2° W) by plotting azimuth-elevation maps of scintillation indices averaged over one year. The azimuth-elevation maps were used to identify objects that regularly scatter signals and cause high scintillation resulting from multipath effects. After identifying the multipath area from the azimuth-elevation map, an azimuth-dependent elevation threshold was developed using the MATLAB curve fitting tool. Using this method we are able to reduce the multi-path errors without losing important data. Using the azimuth-dependent elevation threshold typically gives 5 to 28% more useful data than using a 20° fixed-elevation threshold.
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Gupte, Abhishek. "Symbol Synchronization of GFSK Modulated Signals in a Multipath Environment." International Foundation for Telemetering, 2009. http://hdl.handle.net/10150/605965.
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ITC/USA 2009 Conference Proceedings / The Forty-Fifth Annual International Telemetering Conference and Technical Exhibition / October 26-29, 2009 / Riviera Hotel & Convention Center, Las Vegas, NevadaThis paper investigates the performance of a symbol synchronization technique when used for bandlimited modulation formats in multipath environments. The performance was analyzed using Gaussian Frequency Shift Keying as the modulation format, and assume the receiver has no channel state information The symbol synchronization algorithm calculates the minimum sample variance of eye diagrams over varying symbol rate estimates. The system performance was measured through simulations run at various signal-to-noise ratios and over a range of single-reflection multipath channels.
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La, Tosa Vincenzo. "Ultra Wideband multipath exploitation for anchor-less localization and indoor environment characterization." Rennes 1, 2010. http://www.theses.fr/2010REN1S194.
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Dans le contexte générale des réseaux de capteurs, cette thèse présente des algorithmes exploitant la diversité multitrajet des signaux Ultra Large Bande reçus afin de déterminer conjointement la position des noeuds radio au sein d'une pièce et de caractériser cette dernières, sans infrastructure préalable. En accord avec une approche à complexité croissante, un scénario de plus en plus réaliste est adopté tout au long du travail (e. G. On part d'une pièce carrée avec des noeuds statiques et on termine avec une pièce rectangulaire où les noeuds sont mobiles). Les performances des algorithmes ont été évaluées par simulation numérique et permettent de conclure que l'estimation de la dimension principale de la pièce est assez fiable, alors que les coordonnées des noeuds restent affectées par une dispersion significative. Ces résultats sont d'autant plus intéressants qu'ils ont été obtenus avec des antennes existantes et, pour certains, dans le cadre du standard IEEE 802. 15. 4aIn the context of Wireless Sensor Networks (WSNs), this thesis presents some algorithms exploiting the multipath diversity of received Impulse Radio - Ultra Wide Band (IR-UWB) signals for joint anchor-less localization and environment characterization, relying on standard communications. According to the stated problem, the proposed algorithms only involve Single Input Single Output (SISO) links and two communicating nodes. The multipath scenario is addressed with increasing complexity (e. G. From static nodes in a square room to mobile nodes in a rectangular room). For different algorithms, estimation performance is assessed through simulations, highlighting a globally low errors for the estimation of the main room dimension, whereas estimated nodes coordinates can be affected by a significant dispersion. These performances are all the more interesting that they are obtained considering realistic antennas and, in the last part of the work, in the frame of the IEEE 802. 15. 4a standard
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Kafaru, Olutumininu Olufolabomi. "An environment-dependent approach to wideband modelling and computer simulation of UHF mobile radio propagation in built-up areas." Thesis, University of Liverpool, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.253411.
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Liya, Badrun Naher. "Characterization of persistent multipath components in indoor and outdoor environment at 30 GHz." Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/63143.
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Millimeter-wave (mm-wave) frequency bands are under active consideration for use as short-range
mobile broadband links in fifth generation (5G) cellular access networks. Although channel characteristics
such as path loss, delay spread and fading distributions have been extensively studied for
mm-wave channels, the study of the time-varying nature of the channel is still in its early stages.
In this work, we studied the lifetime of multipath components of the mm-wave channel, usually referred
to as persistence. An important time-varying characteristic of the mm-wave channel, persistence
may affect the capacity, and beam training and beam tracking process of mm-wave systems.
We developed a 30-GHz vector-network-analyzer-based channel sounder suitable for characterizing
multipath persistence and verified its performance through a three-stage verification procedure;
time and frequency domain verifications, two-ray verification, and measurements conducted using
the National Institute of Standards and Technology (NIST) mm-wave channel sounder verification
artifact.
The primary goal of this work was to characterize multipath persistence based on measurements
conducted at 30 GHz in indoor and outdoor urban microcell environments. Through analysis of our
measurement data, we confirmed that the log-logistic distribution provides an accurate description
of persistence and showed how the physical attributes of the channel influence the parameters of
the distribution. We also verified that a weak correlation exists between average received power
and length of the persistent path. We further showed that the rate of angular change of a multipath
component throughout its lifetime follows a Laplace distribution and that the angular rate depends
on the distance of reflectors from the transmitter-receiver path. We used these results to propose
a simulation model that can be used to make simple ray tracing simulations more realistic and to
assess the effect of persistence and variations in the angular rate on the capacity, and beam training
and tracking process of mm-wave systems.Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate
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Bird, Corey D. "Investigation and suppression of multipath communication signals with applications to a marine environment." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq23119.pdf.
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Bayes, Terence. "Spread spectrum system analysis, development, and testing, in a multipath UHF radio environment." Thesis, University of Leeds, 1989. http://etheses.whiterose.ac.uk/2578/.
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Direct Sequence Spread Spectrum systems presently find use in navigation and military communication systems. In recent years, however, interest has also been shown in the potential of such systems for Land Mobile Radio applications. In particular the broadband Spread Spectrum signal would be useful in combating the effects of narrowband fading experienced in the UHF radio environment. In addition, vast improvements in the performance of digital integrated circuits is leading to the concept of the all-digital radio receiver. One such device made feasible by progress in miniaturisation is the Digital Matched Filter. This work examines the operation of the Digital Matched Filter. It's applicability to Direct Sequence Spread Spectrum Systems is studied with a view to the possible implementation of such schemes in the Land Mobile Radio environment. Emphasis is placed on achieving maximum utilisation of the Digital Matched Filter resource. Information obtained from Digital Matched Filters in a complex baseband receiver is shown to assist rapid code synchronization, RF carrier recovery, and measurement of the multipath transmission channel profile. A practical transmitter/receiver pair is described, and the results obtained suggest that future designers of Direct Sequence Spread Spectrum receivers may obtain benefits from the Digital Matched Filter approach, particularly in the area of rapid code synchronization.
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Tan, Kok Chye. "Development, simulation and evaluation of the IEEE 802.11a physical layer in a multipath environment." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2001. http://handle.dtic.mil/100.2/ADA390986.
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Thesis (M.S. in Electrical Engineering) Naval Postgraduate School, March 2001.Thesis advisor(s): McEachen, John. "March 2001." Includes bibliographical references (p. 169-170). Also available in print.
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Jones, Haley M., and Haley Jones@anu edu au. "On multipath spatial diversity in wireless multiuser communications." The Australian National University. Research School of Information Sciences and Engineering, 2001. http://thesis.anu.edu.au./public/adt-ANU20050202.152811.
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The study of the spatial aspects of multipath in wireless communications environments
is an increasingly important addition to the study of the temporal aspects
in the search for ways to increase the utilization of the available wireless channel
capacity. Traditionally, multipath has been viewed as an encumbrance in wireless
communications, two of the major impairments being signal fading and intersymbol
interference. However, recently the potential advantages of the diversity offered by
multipath rich environments in multiuser communications have been recognised.
Space time coding, for example, is a recent technique which relies on a rich scattering
environment to create many practically uncorrelated signal transmission
channels. Most often, statistical models have been used to describe the multipath
environments in such applications. This approach has met with reasonable success
but is limited when the statistical nature of a field is not easily determined or is
not readily described by a known distribution.¶
Our primary aim in this thesis is to probe further into the nature of multipath
environments in order to gain a greater understanding of their characteristics and
diversity potential. We highlight the shortcomings of beamforming in a multipath
multiuser access environment. We show that the ability of a beamformer to resolve
two or more signals in angle directly limits its achievable capacity.¶
We test the probity of multipath as a source of spatial diversity, the limiting
case of which is co-located users. We introduce the concept of separability to define
the fundamental limits of a receiver to extract the signal of a desired user from
interfering users signals and noise. We consider the separability performances of
the minimum mean square error (MMSE), decorrelating (DEC) and matched filter
(MF) detectors as we bring the positions of a desired and an interfering user closer
together. We show that both the MMSE and DEC detectors are able to achieve
acceptable levels of separability with the users as close as λ/10.¶
In seeking a better understanding of the nature of multipath fields themselves,
we take two approaches. In the first we take a path oriented approach. The
effects on the variation of the field power of the relative values of parameters such
as amplitude and propagation direction are considered for a two path field. The
results are applied to a theoretical analysis of the behaviour of linear detectors
in multipath fields. This approach is insightful for fields with small numbers of
multipaths, but quickly becomes mathematically complex.¶
In a more general approach, we take a field oriented view, seeking to quantify
the complexity of arbitrary fields. We find that a multipath field has an intrinsic
dimensionality of (πe)R/λ≈8.54R/λ, for a field in a two dimensional circular region, increasing only linearly with the radius R of the region. This result implies that there is no such thing as an arbitrarily complicated multipath field. That is, a field generated by any number of nearfield and farfield, specular and diffuse
multipath reflections is no more complicated than a field generated by a limited
number of plane waves. As such, there are limits on how rich multipath can
be. This result has significant implications including means: i) to determine a
parsimonious parameterization for arbitrary multipath fields and ii) of synthesizing
arbitrary multipath fields with arbitrarily located nearfield or farfield, spatially
discrete or continuous sources. The theoretical results are corroborated by examples
of multipath field analysis and synthesis.
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Wu, Yating. "Code tracking for direct-sequence spread-spectrum systems under multiuser environment and multipath fading channels /." access full-text access abstract and table of contents, 2009. http://libweb.cityu.edu.hk/cgi-bin/ezdb/thesis.pl?phd-ee-b30082602f.pdf.
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Thesis (Ph.D.)--City University of Hong Kong, 2009."Submitted to Department of Electronic Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy." Includes bibliographical references (leaves 105-111)
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Belanger, Scott Patrick. "Maximum likelihood TDOA/DD estimation in a multipath propagation environment using the expectation-maximization algorithm." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/15371.
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Law, Eugene. "HOW WELL DOES A BLIND, ADAPTIVE CMA EQUALIZER WORK IN A SIMULATED TELEMETRY MULTIPATH ENVIRONMENT." International Foundation for Telemetering, 2004. http://hdl.handle.net/10150/604926.
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International Telemetering Conference Proceedings / October 18-21, 2004 / Town & Country Resort, San Diego, CaliforniaThis paper will present the results of experiments to characterize the performance of a blind, adaptive constant modulus algorithm (CMA) equalizer in simulated telemetry multipath environments. The variables included modulation method, bit rate, received signal-to-noise ratio, delay of the indirect path relative to the direct path, amplitude of the indirect path relative to the direct path, and fade rate. The main measured parameter was bit error probability (BEP). The tests showed that the equalizer usually improved the data quality in the presence of multipath.
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Kelkar, Anand, Norm Lamarra, and Thomas Vaughan. "Development of a Synthetic Beamforming Antenna - From Drawing Board to Reality." International Foundation for Telemetering, 2009. http://hdl.handle.net/10150/606144.
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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, NevadaFollowing-up on an ITC 2006 paper, "From RF to bits with Synthetic Beamforming", we follow the development and fielding of a Digital Beamforming (DBF) Antenna. This antenna, built for an airborne Telemetry application, supports 10 individual polarization-diverse beams and immediately converts RF to IF at the antenna element through a suite of LNBs. The IF is then digitized and all subsequent processing is performed through an array of 200+ FPGAs, including DBF, optimal combining, demodulation, and IF upconversion. We present our Model-Based Design approach, which allowed us to develop and test the system incrementally and rapidly, particularly during the transition from factory testing to flight operations, where several unexpected problems were discovered. Our software tool set enabled us to dissect the System behavior via post-mission replay, and our detailed simulations were instrumental in developing mitigation quickly. The System-level impacts and root causes of some of these issues are also discussed. We believe the flexibility of DBF and the modular software architecture were key in quickly mitigating many of these unforeseen real-world issues without hardware modification.
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Ritchie, Douglas Allen. "Factors That Affect the Global Positioning System and Global Navigation Satellite System in an Urban and Forested Environment." Digital Commons @ East Tennessee State University, 2007. https://dc.etsu.edu/etd/2089.
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The purpose of this study was to evaluate the accuracy in real time measurements acquired from GPS and GLONASS satellite observations using RTK techniques in an urban and forested environment. To determine this accuracy, 2 data sets of 3-dimensional coordinates were created and compared at 14 stations situated at East Tennessee State University. One data set included coordinates determined by conventional land survey methods; the second was solved by RTK GPS/GLONASS. Once the magnitude of any deviation in the coordinate positions was determined, the contributions to the accuracies from cycle slips, multipath, satellite availability, PDOP, and fixed or float solutions were evaluated. Three points in the urban environment varied from the conventional data set. Multipath was assumed to be the major bias in these points. Seven points in the forested environment varied from the conventional data set. The use of float solutions and high PDOP may have caused this bias.
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Alheid, Amani Abdullatif. "Multipath TCP over heterogeneous environments." Thesis, University of Bristol, 2017. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.720819.
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Hatzichristos, George. "Classification of digital modulation types in multipath environments." Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2001. http://handle.dtic.mil/100.2/ADA390810.
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Young, Andrew F. "Classification of digital modulation types in multipath environments." Thesis, Monterey California. Naval Postgraduate School, 2008.
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Approved for public release, distribution unlimitedAs the digital communications industry continues to grow and evolve, the applications of this discipline continue to grow as well. This growth, in turn, has spawned an increasing need to seek automated methods of classifying digital modulation types. This research is a revision of previous work, using the latest mathematical software including MATLAB version 7 and Simulink ®. The program considers the classification of nine different modulation types. Specifically, the classification scheme can differentiate between 2, 4, and 8 PSK, 256-QAM from other types of M-QAM signals, and also M-FSK signals from PSK and QAM signals in various types of propagation channels, including multipath fading and a variety of signal-to-noise levels. This method successfully identifies these modulation types without the benefit of a priori information. Higher-order statistical parameters are selected as class features and are tested in a classifier for their ability to identify the above modulation types. This study considers the effects due to realistic multipath propagation channels and additive white Gaussian noise. Using these features, and considering all fading conditions, it was determined that the classifier was correct for a randomly sent signal under randomly high or low SNR levels (low: 0dB to 8dB; high: 50dB to 100dB) over 83.9% of the time.
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Olofsson, Ivar. "Enhancements in LTE OTDOA Positioning for Multipath Environments." Thesis, Linköpings universitet, Kommunikationssystem, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-131821.
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By using existing radio network infrastructure, a user can be positioned even where GPS and other positioning technologies lack coverage. The LTE Positioning Protocol (LPP) supports user Reference Signal Time Difference (RSTD) reports based on the Time of Arrival (TOA) for a Positioning Reference Signal (PRS). In the current reporting format, only one RSTD for each base station is considered, but for indoor environments this is easily biased due to fading and multipath issues, resulting in a Non-Line of Sight (NLOS) bias. With a rich User Equipment (UE) feedback that can represent the multipath channel for each Base Station (BS), the positioning accuracy can be increased. This thesis develops and evaluates a UE reporting format representing multiple TDOA candidates, and a probabilistic positioning algorithm, in terms of positioning accuracy and amount of data reported. By modeling time measurements as Gaussian Mixture (GM), the time information can be compressed with arbitrary resolution and used in a Maximum-Likelihood (ML) estimation to find the position. Results were obtained through simulation in a radio network simulator and post-processing of simulation data in Matlab. The results suggest that several TOA candidates improve the positioning accuracy, but that the largest improvement comes from a noise based threshold by increasing LOS detectability reducing the NLOS bias, while suppressing noise. The results also suggest that the accuracy for the method can be further improved by combining multiple time measurement occasions.
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Larson, Kristin. "Characterizing multipath in satellite navigation measurements for urban environments." Diss., Connect to online resource, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1435237.
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Ljungzell, Erik. "Multipath-assisted Single-anchor Outdoor Positioning in Urban Environments." Thesis, Linköpings universitet, Reglerteknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-149051.
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An important aspect of upcoming fifth-generation (5G) cellular communication systems is to improve the accuracy with which user equipments can be positioned. Accurately knowing the position of a user equipment is becoming increasingly important for a wide range of applications, such as automation in industry, drones, and the internet of things. Contrary to how existing techniques for outdoor cellular positioning deal with multipath propagation, in this study the aim is to use, rather than mitigate, the multipath propagation prevalent in dense urban environments. It is investigated whether it is possible to position a user equipment using only a single transmitting base station, by exploiting position-related information in multipath components inherent in the received signal. Two algorithms are developed: one classical point-estimation algorithm using a grid search to find the cost function-minimizing position, and one Bayesian filtering algorithm using a point-mass filter. Both algorithms make use of BEZT, a set of 3D propagation models developed by Ericsson Research, to predict propagation paths. A model of the signal received by a user equipment is formulated for use in the positioning algorithms. In addition to the signal model, the algorithms also require a digital map of the propagation environment. The algorithms are evaluated first on synthetic measurements, generated using BEZT, and then on real-world measurements. For both the synthetic and real-world measurement sets, the Bayesian point-mass filter outperforms the classical algorithm. It is observed how, given synthetic measurements, the algorithms yield better estimates in non-line-of-sight regions than in regions where the user equipment has line-of-sight to the transmitting base station. Unfortunately, these results do not generalize well to the real-world measurements, where, overall, neither algorithm is able to provide reliable and robust position estimates. However, as multipath-assisted positioning, to the best of our knowledge, has not been used for outdoor cellular positioning before, there are plenty of algorithm extensions, modifications, and problem aspects left to be studied - some of which are discussed in the concluding chapters.
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Glans, Fredrik. "Enhanced positioning in harsh environments." Thesis, Linköpings universitet, Reglerteknik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-94523.
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Today’s heavy duty vehicles are equipped with safety and comfort systems, e.g. ABS and ESP, which totally or partly take over the vehicle in certain risk situations. When these systems become more and more autonomous more robust positioning is needed. In the right conditions the GPS system provides precise and robust positioning. However, in harsh environments, e.g. dense urban areas and in dense forests, the GPS signals may be affected by multipaths, which means that the signals are reflected on their way from the satellites to the receiver. This can cause large errors in the positioning and thus can give rise to devastating effects for autonomous systems. This thesis evaluate different methods to enhance a low cost GPS in harsh environments, with focus on mitigating multipaths. Mainly there are four different methods: Regular Unscented Kalman filter, probabilistic multipath mitigation, Unscented Kalman filter with vehicle sensor input and probabilistic multipath mitigation with vehicle sensor input. The algorithms will be tested and validated on real data from both dense forest areas and dense urban areas. The results show that the positioning is enhanced, in particular when integrating the vehicle sensors, compared to a low cost GPS.
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Lim, Hong Meng. "On the average capacity of MIMO channels in outdoor multipath urban environments." Thesis, University of Birmingham, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.420409.
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McKinley, Michael Dean. "Improved frequency domain measurement techniques for characterizing power amplifier and multipath environments." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24722.
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Thesis (Ph.D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2009.Committee Chair: James Stevenson Kenney; Committee Member: Gregory David Durgin; Committee Member: Madhavan Swaminathan
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Obst, Marcus. "Bayesian Approach for Reliable GNSS-based Vehicle Localization in Urban Areas." Doctoral thesis, Universitätsbibliothek Chemnitz, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-162894.
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Nowadays, satellite-based localization is a well-established technical solution to support several navigation tasks in daily life. Besides the application inside of portable devices, satellite-based positioning is used for in-vehicle navigation systems as well. Moreover, due to its global coverage and the availability of inexpensive receiver hardware it is an appealing technology for numerous applications in the area of Intelligent Transportation Systems (ITSs). However, it has to be admitted that most of the aforementioned examples either rely on modest accuracy requirements or are not sensitive to temporary integrity violations. Although technical concepts of Advanced Driver Assistance Systems (ADASs) based on Global Navigation Satellite Systems (GNSSs) have been successfully demonstrated under open sky conditions, practice reveals that such systems suffer from degraded satellite signal quality when put into urban areas. Thus, the main research objective of this thesis is to provide a reliable vehicle positioning concept which can be used in urban areas without the aforementioned limitations. Therefore, an integrated probabilistic approach which preforms fault detection & exclusion, localization and multi-sensor data fusion within one unified Bayesian framework is proposed. From an algorithmic perspective, the presented concept is based on a probabilistic data association technique with explicit handling of outlier measurements as present in urban areas. By that approach, the accuracy, integrity and availability are improved at the same time, that is, a consistent positioning solution is provided. In addition, a comprehensive and in-depth analysis of typical errors in urban areas within the pseudorange domain is performed. Based on this analysis, probabilistic models are proposed and later on used to facilitate the positioning algorithm. Moreover, the presented concept clearly targets towards mass-market applications based on low-cost receivers and hence aims to replace costly sensors by smart algorithms. The benefits of these theoretical contributions are implemented and demonstrated on the example of a real-time vehicle positioning prototype as used inside of the European research project GAlileo Interactive driviNg (GAIN). This work describes all necessary parts of this system including GNSS signal processing, fault detection and multi-sensor data fusion within one processing chain. Finally, the performance and benefits of the proposed concept are examined and validated both with simulated and comprehensive real-world sensor data from numerous test drives.
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Thai, Khac Phuc Hung. "Radar "Around the corner" : détection et localisation de cibles masquées en milieu urbain." Thesis, Ecole nationale supérieure Mines-Télécom Atlantique Bretagne Pays de la Loire, 2018. http://www.theses.fr/2018IMTA0102/document.
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Les applications des techniques radar au milieu urbain constituent un domaine émergent. Une des difficultés principales est liée à la complexité du milieu de propagation induit par les bâtiments présents dans la scène. En effet, la présence de ces bâtiments génère d’une part des zones d’ombre à l’intérieur desquelles une cible n’est pas en visibilité directe, et d’autre part de nombreux multi-trajets produits par les possibles réflexions et diffractions sur les surfaces environnantes. Ces multi-trajets sont souvent vus comme une gêne, limitant les capacités de détection en radar. Or ils peuvent aussi être exploités à l’avantage du radar afin de détecter et localiser des cibles situées dans les zones d’ombre (cible en NLOS). L’objectif de ce travail de thèse est donc la mise en place de méthodes de traitement du signal permettant la détection et la localisation d’une cible en NLOS en milieu urbain et l’application de ces techniques pour détecter et localiser une cible en NLOS à partir de signaux réels. Pour cela, nous avons proposé dans un premier temps deux solutions pour la détection et la localisation de la cible en exploitant les multi-trajets. Dans un deuxième temps, nous avons développé deux filtres particulaires pour pister une cible en milieu urbain en présence de multi-trajets. Ces algorithmes ont été appliqués aux données réelles issues d’une expérimentation et ont montré des résultats prometteurs : même avec une connaissance approximative de la géométrie de la scène, il a été possible de détecter, localiser et suivre une cible en exploitant uniquement l’information fournie par les retards des multi-trajetsThe applications of radar techniques to the urban environment constitute an emerging subject. One of the main difficulties is related to the complexity of the propagation environment induced by the buildings present in the scene. Indeed, the presence of these buildings generates on the one hand shadow areas within which a target is not in line of sight, and on the other hand, many multipaths produced by reflections and diffractions on the surrounding surfaces. Classically, these multipaths are often seen as an inconvenience, limiting radar detection capabilities. However, these multipaths can also be exploited to the advantage of the radar to detect and locate targets located in the shadow areas (target in NLOS). The objective of this thesis work is therefore to develop signal processing methods allowing the detection and localization of a target located in shadow areas in urban environment and to apply these techniques for detecting and locating a target in NLOS from realistic or even real signals. For this, we first proposed two solutions for detection and localization of a target by exploiting multipath information. In a second step, we developed two particle filters to track a target in urban environment in the presence of multipaths. These algorithms have been applied to real data and showed promising results: even with an approximate knowledge of the geometry of the scene, it has been possible to detect, locate and track a target by exploiting only the information on multipath delays
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Habib, Istepanian Robert S. "Use of microcontrollers for diver monitoring by underwater acoustic biotelemetry in multipath environments." Thesis, Loughborough University, 1994. https://dspace.lboro.ac.uk/2134/32923.
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Biomedical Telemetry (Biotelemetry) is a special facet of bio-instrumentation which provides a means for transmitting physiological or biological information from one site to another. There are numerous situations in which it is desirable to monitor critical physiological reflexes and responses from freely swimming swimmers or divers. The design and implementation of a novel multi-channel digital acoustic biotelemetry system using a single-chip microcontroller is described. It is intended for monitoring the electrocardiogram (ECG), heart rate, breathing rate and depth of a free swimming diver, but the system has a modular design that can be adapted for the transmission of digital data representing any parameter. The use of the microcontroller enables the digital data to be transmitted in a priority interrupt format from each sensor with programmable pulse width timing. A portable receiver contains an identical microcontroller and is designed to scan three crystal-controlled frequencies to provide a logical output for each detected signal. These signals are captured by a portable data logger and interfaced to a computer for further processing. This automated arrangement greatly reduces the probability of data error by increasing immunity to multipath and reverberation effects.
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Hibbard, Daniel James. "The Impact of Signal Bandwidth on Indoor Wireless Systems in Dense Multipath Environments." Thesis, Virginia Tech, 2004. http://hdl.handle.net/10919/9945.
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Recently there has been a significant amount of interest in the area of wideband and ultra-wideband (UWB) signaling for use in indoor wireless systems. This interest is in part motivated by the notion that the use of large bandwidth signals makes systems less sensitive to the degrading effects of multipath propagation. By reducing the sensitivity to multipath, more robust and higher capacity systems can be realized. However, as signal bandwidth is increased, the complexity of a Rake receiver (or other receiver structure) required to capture the available power also increases. In addition, accurate channel estimation is required to realize this performance, which becomes increasingly difficult as energy is dispersed among more multipath components.
In this thesis we quantify the channel response for six signal bandwidths ranging from continuous wave (CW) to 1 GHz transmission bandwidths. We present large scale and small scale fading statistics for both LOS and NLOS indoor channels based on an indoor measurement campaign conducted in Durham Hall at Virginia Tech. Using newly developed antenna positioning equipment we also quantify the spatial correlation of these signals. It is shown that the incremental performance gains due to reduced fading of large bandwidths level off as signals approach UWB bandwidths. Furthermore, we analyze the performance of Rake receivers for the different signal bandwidths and compare their performance for binary phase modulation (BPSK). It is shown that the receiver structure and performance is critical in realizing the reduced fading benefit of large signal bandwidths. We show practical channel estimation degrades performance more for larger bandwidths. We also demonstrate for a fixed finger Rake receiver there is an optimal signal bandwidth beyond which increased signal bandwidth produces degrading results.Master of Science
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Wang, Shangbo [Verfasser], Peter [Akademischer Betreuer] Jung, and Klaus [Akademischer Betreuer] Solbach. "Wireless Positioning Applications in Multipath Environments / Shangbo Wang. Gutachter: Klaus Solbach. Betreuer: Peter Jung." Duisburg, 2015. http://d-nb.info/1066206341/34.
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Valtierra, Robert Daniel. "Source location of narrow band signals in multipath environments, with application to marine mammals." Thesis, Boston University, 2013. https://hdl.handle.net/2144/11072.
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Thesis (Ph.D.)--Boston UniversityPassive acoustic localization has benefited from many major developments and has become an increasingly important focus point in marine mammal research. Several challenges still remain. This work seeks to address several of these challenges such as tracking the calling depths of baleen whales. In this work, data from an array of widely spaced Marine Acoustic Recording Units (MARUs) was used to achieve three dimensional localization by combining the methods Time Difference of Arrival (TDOA) and Direct-Reflected Time Difference of Anival (DRTD) along with a newly developed autocorrelation technique. TDOA was applied to data for two dimensional (latitude and longitude) localization and depth was resolved using DRTD. Previously, DRTD had been limited to pulsed broadband signals, such as sperm whale or dolphin echolocation, where individual direct and reflected signals are separated in time. Due to the length of typical baleen whale vocalizations, individual multipath signal arrivals can overlap making time differences of arrival difficult to resolve. This problem can be solved using an autocorrelation, which can extract reflection information from overlapping signals. To establish this technique, a derivation was made to model the autocorrelation of a direct signal and its overlapping reflection. The model was exploited to derive performance limits allowing for prediction of the minimum resolvable direct-reflected time difference for a known signal type. The dependence on signal parameters (sweep rate, call duration) was also investigated. The model was then verified using both recorded and simulated data from two analysis cases for North Atlantic right whales (NARWs, Eubalaena glacialis) and humpback whales (Megaptera noveaengliae). The newly developed autocorrelation technique was then combined with DRTD and tested using data from playback transmissions to localize an acoustic transducer at a known depth and location. The combined DRTD-autocorrelation methods enabled calling depth and range estimations of a vocalizing NARW and humpback whale in two separate cases. The DRTD-autocorrelation method was then combined with TDOA to create a three dimensional track of a NARW in the Stellwagen Bank National Marine Sanctuary. Results from these experiments illustrated the potential of the combined methods to successfully resolve baleen calling depths in three dimensions.
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Annamalai, Annamalai. "Accurate and efficient analysis of wireless digital communication systems in multiuser and multipath fading environments." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ37328.pdf.
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Lichtenstein, Joseph. "Low computational complexity bit error rate simulation for personal communications systems in multipath and fading environments." Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-06102009-063138/.
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Shytermeja, Enik. "Design and performance of a GNSS single-frequency multi-constellation vector tracking architecture for urban environments." Phd thesis, Toulouse, INPT, 2017. http://oatao.univ-toulouse.fr/19756/1/SHYTERMEJA_Enik.pdf.
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In the last decade, Global Navigation Satellites Systems (GNSS) have gained a significant position in the development of urban navigation applications and associated services. The urban environment presents several challenges to GNSS signal reception, such as multipath and GNSS Line-of-Sight (LOS) blockage, which are translated in the positioning domain in a decreased navigation solution accuracy up to the lack of an available position. For this matter, Vector Tracking (VT) constitutes a promising approach able to cope with the urban environment-induced effects including multipath, NLOS reception and signal outages. This thesis is particularly focused on the proposal and design of a dual constellation GPS + Galileo single frequency L1/E1 Vector Delay Frequency Lock Loop (VDFLL) architecture for the automotive usage in urban environment. From the navigation point of view, VDFLL represents a concrete application of information fusion, since all the satellite tracking channels are jointly tracked and controlled by the common navigation Extended Kalman filter (EKF). The choice of the dual-constellation single frequency vector tracking architecture ensures an increased number of observations and at the same time allowing the conservation of the low-cost feasibility criteria of the mobile user’s receiver. Moreover, the use of single frequency L1 band signals implies the necessity of taking into account the ionospheric error effect. In fact, even after the application of the ionosphere error correction models, a resultant ionospheric residual error still remains in the received observations. The originality of this work relies on the implementation of a dual-constellation VDFLL architecture, capable of estimating the ionosphere residual error present in the received observations. This dissertation investigates the VDFLL superiority w.r.t the scalar tracking receiver in terms of positioning performance and tracking robustness for a real car trajectory in urban area in the presence of multipath and ionosphere residual error.
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Luke, Neville. "Space-time modelling and simulation of multipass processes within a modern computer environment." Thesis, University of Sheffield, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301812.
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Andreotti, Marcus Talcir. "Global navigation satellite systems in urban and indoor environments : a new tool to visualize, understand and use multipath." Thesis, University of Nottingham, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.438521.
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Jin, Zhaozhang. "Monaural Speech Segregation in Reverberant Environments." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1279141797.
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Hemsath, James R. "Beyond Culture: Success Factors for Transnational Multiparty Collaboration." Case Western Reserve University Doctor of Management / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=casedm1556803713641637.
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Li, Gang [Verfasser]. "Innovative Imaging Synthetic Aperture Secondary Radar Concepts for Ultra-Precise Positioning and Tracking of a Backscatter Transponder in Multipath Environments / Gang Li." München : Verlag Dr. Hut, 2015. http://d-nb.info/1069019887/34.
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Shen, Guowei [Verfasser], Reiner [Akademischer Betreuer] Thomä, Jörn [Gutachter] Thielecke, and Günther [Gutachter] Schäfer. "Localization of Active Nodes within Distributed UWB Sensor Networks in Multipath Environments / Guowei Shen ; Gutachter: Jörn Thielecke, Günther Schäfer ; Betreuer: Reiner Thomä." Ilmenau : TU Ilmenau, 2012. http://d-nb.info/1178185621/34.
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Wu, Mingyang. "Pitch tracking and speech enhancement in noisy and reverberant environments." Columbus, Ohio : Ohio State University, 2003. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1064341479.
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Thesis (Ph. D.)--Ohio State University, 2003.Title from first page of PDF file. Document formatted into pages; contains xvi, 149 p.; also includes graphics. Includes abstract and vita. Advisor: DeLiang Wang, Dept. of Computer and Information Science. Includes bibliographical references (p. 136-149).
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Ramirez-Hernandez, Ramiro A. "Additively Manufactured On-Package Multipolar Antenna Systems for Harsh Communication Channels." Scholar Commons, 2018. https://scholarcommons.usf.edu/etd/7705.
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Four main aspects are studied and explored throughout this dissertation: (1) On-Package Multipolar antenna system design for integration with commercial wireless sensor nodes for machine-to-machine communication applications; (2) Development of a novel MMIC packaging process and subsequent antenna integration for chip-to-chip communication applications, (3) Design and characterization of additively manufactured lumped passive elements for integration with MMIC and hybrid circuits, (4) Design and characterization of antennas for on- and off-metal radio frequency identification (RFID) applications.
This work presents the design of different 3-D printed tripolar antenna systems operating at 2.4 GHz. The antennas are designed for integration with commercial wireless nodes with the purpose of mitigating multipath and depolarization channel effects that might be present in many machine-to-machine (M2M) deployments. The antennas are fabricated utilizing an additive manufacturing (AM) approach that combines fused deposition modeling (FDM) of ABS plastic for dielectric parts and micro-dispensing of silver paste Du-Pont CB028 for conductive layers as the majority of the devices presented in this work. Over the air testing demonstrates a 1% channel improvement of up to 14 dB, achieved in a highly-reflective, Rayleigh-like fading environment by implementing selection diversity between three mutually orthogonal monopoles. This improvement leads to better bit error rate (BER) performance (as is also shown). Additionally, RSSI measurements show significant improvement when the prototype antenna system is integrated with commercial wireless sensor hardware. Implications of tripolar antenna integration on M2M systems include reduction in energy use, longer communication link distances, and/or greater link reliability.
In order to incorporate the proposed multipolar selection diversity technique into short range wireless chip-to-chip communications, a novel and versatile 3D printed on-chip integration approach using laser machining is subsequently demonstrated for microwave and mm-wave systems in a process herein referred to as Laser Enhanced or Laser Assisted Direct Print Additive Manufacturing (LE-DPAM). The integration process extends interconnects laterally from a MMIC to a chip carrier. Picosecond laser machining is applied and characterized to enhance the 3D printing quality. Specifically, the width of micro-dispensed printed traces is accurately controlled within micrometer range (e.g. laser cuts ~12 μm wide), additionally, 150 μm probe pads are cut in order to facilitate RF measurement. The S-parameters of a distributed amplifier integrated into the package are simulated and measured from 2 to 30 GHz. It is seen how the overall performance is significantly better than a traditional wirebonded QFN package and previously reported AM MMIC interconnections. The attenuation of the microstrip line including interconnects is only 0.2 dB/mm at 20 GHz and return loss with the package is less than 10 dB throughout the operating frequency band
A 17 GHz package integrated linearly polarized patch antenna, fabricated with a multi-layer and multi-material LE-DPAM process is then introduced for vertical interconnection with a MMIC die. Performance is successfully measured and characterized achieving a return loss greater than 19 dB at the desired design frequency. Good agreement between simulated and measured radiation patterns is also obtained with a peak gain of 4.2 dBi.
Another section of this work utilizes LE-DPAM to fabricate lumped capacitors and inductors for coplanar waveguide (CPW) circuits, especially useful for filtering and matching network implementation. Laser machining is used to achieve ~12 µm slots on printed conductors, producing aspect ratios greater than 2:1, as well as to fabricate vertical interconnects or vias that allow for the fabrication of the multilayer inductors. Inductances in the range of 0.4-3 nH are achieved, with a maximum quality factor of 21, self-resonance frequencies up to 88 GHz, and an inductance per unit of area of 5.3 nH/mm2. Interdigital capacitors in the range of 0.05-0.5 pF are fabricated, having a maximum quality factor of 750 and self-resonances up to 120 GHz. All the components are made on the center line of a CPW that is 836 µm wide. The results show that LE-DPAM enables the fabrication of compact passive circuits that can be easily interconnected with MMIC dies, which at the same time, can be manufactured as part of a larger component. This enables the fabrication of structural electronics that are functional into the mm-wave frequency range.
A final aspect of this work goes through antenna designs for specific RFID (radio frequency identification) applications. RFID tag design is generally focused specifically on either off-metal or on-metal configurations. In this work passive 2D and 3D RFID tags are presented which perform similarly in both configurations. The presented tags operate in the ISM RFID UHF bands that cover 864-868 MHz and 902-928 MHz. A matching loop consisting of two parallel stubs to ground is used for impedance matching to a passive integrated circuit, which has -18 dBm sensitivity. A planar 2D tag with a footprint of 13126.5 mm2 is first introduced, showing a simulated gain of approximately 3 dBi and a measured read range of 10 m (for 31 dBm transmit power from the reader) in both on-metal and off-metal conditions. The tag is miniaturized into a 3D geometry with a footprint of 2524.25 mm2 (520% reduction) and achieves the same broadside simulated on-metal gain. The antennas are fabricated using a DPAM process, and a meshed ground configuration is explored in order to accomplish a 50% conductive paste reduction without disrupting the performance. The proposed tags are compared with commercially available tags as well as previously published tags in terms of read range and size. The tags in this work present an improvement in terms of read range, gain, and area with respect to previous designs covering the ISM RFID UHF bands. Moreover, the performance of these tags is maintained in on- and off-metal conditions, achieving comparable performance and a reduction in volume of 11482% with respect to the best tag reported.
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Hunter, Brandon. "Channel Probing for an Indoor Wireless Communications Channel." BYU ScholarsArchive, 2003. https://scholarsarchive.byu.edu/etd/64.
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The statistics of the amplitude, time and angle of arrival of multipaths in an indoor environment are all necessary components of multipath models used to simulate the performance of spatial diversity in receive antenna configurations. The model presented by Saleh and Valenzuela, was added to by Spencer et. al., and included all three of these parameters for a 7 GHz channel. A system was built to measure these multipath parameters at 2.4 GHz for multiple locations in an indoor environment. Another system was built to measure the angle of transmission for a 6 GHz channel. The addition of this parameter allows spatial diversity at the transmitter along with the receiver to be simulated. The process of going from raw measurement data to discrete arrivals and then to clustered arrivals is analyzed. Many possible errors associated with discrete arrival processing are discussed along with possible solutions. Four clustering methods are compared and their relative strengths and weaknesses are pointed out. The effects that errors in the clustering process have on parameter estimation and model performance are also simulated.
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Chou, Kun-Ho, and 周坤和. "The Applications of Smart Antenna System in Multipath Environment." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/62511321780860200201.
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碩士中原大學
電子工程學系
88
In wireless communications, the smart antenna system can utilize antenna array to obtain the spatial signatures from transmitted signals. Furthermore, the smart antenna system explores the differences of spatial signatures or directions-of-arrival (DOA) from the signals to get the desired signals and reduce the effects of co-channel interference and multipath fading. Thus, it can increase the channel capacity and improve the communication quality. The main topic of this thesis is to evaluate the performance of the beamforming algorithms and use the ray-tracing technique to assess the direction finding efficiency of the subspace smoothing algorithm. This thesis mainly consists of three parts. The first part introduces the smart antenna system and the characteristics of wireless communication environments. In the second part, we define the antenna processing gain (APG) in dB as the difference between two carrier-to-interference ratios (CIR) obtained by using an antenna array and the single omni-directional antenna, respectively. Based on APG, we evaluate the performance of each beamforming algorithm applied to the Wireless Local Loop (WLL) system in a multipath propagation environment. In the third part, we present a subspace smoothing technique to find the directions of arrival of multipath signals. Our simulation results show that the APG obtained by using smart antenna is higher than that obtained by using traditionally single omni-directional antenna over WLL systems. In addition, among the DOA finding approaches mentioned above, the subspace smoothing algorithms can estimate up to M-1 DOAs of direct path and multipath components, where M is the number of antennas. Keyword: Smart Antenna, Beamforming Algorithm, Subspace Smoothing
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Liu, Bing-Lung, and 劉炳龍. "Digital Beamforming in Multipath Channel Environment for Wireless Communication." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/61670522564050939979.
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碩士元智大學
電機工程研究所
89
Beamforming is a method of spatial filtering, which can eliminate unwanted spatial interferences and receive desired signal accurately. Nowaday, digital beamfoming method is widely used in many areas, like radar, sensor, and space exploration. In next generation of mobile communication system, it will be a key method for signal processing. In wireless communication system, the process of signal propagation results in multipath propagation. We usually describe this kind of channel as so called delay spread, doppler spread, and incident angles of multipath signal, so called angle spread. In this paper, we will discuss the effect of delay and angle spread of multipath signal, and performance of beamforming. And we will also discuss the situation of CCI and static state channel, and discriminate the narrowband and wideband signals from the relative size between delay spread and symbol period. From the above two situations, we use several narrowband and wideband digital beamformer, and algorithms, like LMS, RLS, MMSE,..etc, to research different aspects of beamforming performance in different multipath environments, and confirm the result by computer simulations.
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Lee, Zong-Si, and 李宗錫. "A Beamspace Diversity Combiner for Signal Acqusition in a Multipath Fading Environment." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/37570152173279800209.
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碩士國立交通大學
電信工程研究所
86
The beam diversity technique is effective in combating multipath in wireless communications. In a beam diversity system, multiple receiving branches are formed with multiple antenna beams with distinctive patterns. Thesebeams are synthesized in such a fashion that the fading phenomena observed at different branches are nearly uncorrelated. The disadvantage of such a system is the lack of adaptivity for cochannel interference (CCI) suppression. In this thesis, an adaptive beam diversity combiner is proposed for sectorized signal reception. The diversity branches are formed with several adaptive beamformers whose response patterns encompass an angular sector in the field-of-view of the receiver. With a set of juidiciously chosen weight vectors, effective diversity combining can be achieved inside the sector, and out-of-sector CCI can be suppressed via nulling. To enchance its tracking capability, the decision-directed mode is employed upon the convergence of the combiner. In a frequency selective fading channel in which intersymbol interference (ISI) is present,a joint operation of the decision-directed optimum combiner and linear equalizer is necessary, and will be discussed in the thesis. Finally, simulation results based on the GSM signal model are given to confirm the efficacy of the proposed beam diversity combiner/equalizer.
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Jones, Haley M. "On multipath spatial diversity in wireless multiuser communications." Phd thesis, 2001. http://hdl.handle.net/1885/47290.
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The study of the spatial aspects of multipath in wireless communications environments is an increasingly important addition to the study of the temporal aspects in the search for ways to increase the utilization of the available wireless channel capacity. Traditionally, multipath has been viewed as an encumbrance in wireless communications, two of the major impairments being signal fading and intersymbol interference. However, recently the potential advantages of the diversity offered by multipath rich environments in multiuser communications have been recognised. Space time coding, for example, is a recent technique which relies on a rich scattering environment to create many practically uncorrelated signal transmission channels. Most often, statistical models have been used to describe the multipath environments in such applications. This approach has met with reasonable success but is limited when the statistical nature of a field is not easily determined or is not readily described by a known distribution. ¶ ...
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Chang, Jr-Wen, and 張志文. "Adapitve Multiuser Receiver with RAKE Structure and Decision Feedback in Multiuser and Multipath Fading Environment." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/25638466489657201329.
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碩士國立中山大學
電機工程學系研究所
88
A review of adaptive decorrelating detector techniques for direct-sequence code division multiple access (CDMA) signals is given. The goal is to improve CDMA system performance and capacity by reducing interference between users. The techniques considered are implementations of multiuser receivers, for which background material is given. Adaptive algorithms improve the feasibility of such receivers. An adaptive multiuser receiver for CDMA system has been proposed to increase system capacity. The adaptive decorrelator can be used to eliminate interference from known interferers, though it is prone to noise enhancement. However the receiver is basically designed for synchronous CDMA over AWGN channels. In order to confirm the robustness of the receiver for the asynchronous cases, experimental evaluations are displayed when the relative user delays are small compared to the symbol duration and when the channel is Rayleigh multipath fading as in micro-cellular scenarios. In addition to the efficient implementation of the decorrelating detector of [1], the receiver also can be adapted to incorporate decision feedback. Successive interference cancellation techniques reduce interference by cancellation of one detected signal from another. And an efficient incorporation of decorrelator with RAKE and (DF) decision feedback receiver for frequency-selective Rayleigh fading multipath channels is also proposed. Performance evaluation of the detector via computer simulation scenarios is conducted to substantiate it's potential for real-time operation.