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Full-Text Articles in Engineering
Mimo Antenna Systems For Wireless Handheld Devices, Ahmed H. Abdelgawwad
Mimo Antenna Systems For Wireless Handheld Devices, Ahmed H. Abdelgawwad
Theses and Dissertations
Mobile communications have seen tremendous growths in the last decades in the form of smartphones, watches, wireless enabled Personal Digital Assistants (PDAs) and so on. The current and future wireless communication systems require high data-rate capabilities to support high speed needs of users in modern applications. Multiple-input multiple-output (MIMO) antenna systems have become the most promising candidate to support the increased data demand. Therefore, they have emerged as an integral part of the new 5G wireless standard. One key challenge regarding MIMO systems for the handheld is to be able to successfully accommodate multiple miniature platform integrated antennas within a …
Optimization Methods For A Reconfigurable Ota Chamber, Matthew David Arnold
Optimization Methods For A Reconfigurable Ota Chamber, Matthew David Arnold
Theses and Dissertations
Multiple-input multiple-output (MIMO) technology has enabled increased performance of wireless communication devices. The increased complexity associated with MIMO devices requires more realistic testing environments to ensure device performance. This testing can be accomplished by either very accurate but expensive anechoic chambers, less accurate but inexpensive mode-stirred chambers, or the newly introduced reconfigurable over-the-air chamber (ROTAC) that combines the benefits of both anechoic chambers and reverberation chambers. This work focuses on efficient optimization methods to quantify the performance of the ROTAC. First, an efficient optimization technique that combines convex optimization and a simple gradient descent algorithm is developed that can be …
Polarization Diversity In The Presence Of Multipath Propagation, Grant Taylor Wagner
Polarization Diversity In The Presence Of Multipath Propagation, Grant Taylor Wagner
Theses and Dissertations
The possibility of polarization diversity using left and right hand circular polarization (LHCP and RHCP) in the presence of multipath propagation is examined. We show that there are differences in the received signal for LHCP and RHCP for a number of realistic scenarios. Because multipath propagation can produce different LHCP and RCHP signals, there exists the possibility for diversity improvement involving the two polarizations.
Improved Channel Probing For Secret Key Generation With Multiple Antenna Systems, Britton T. Quist
Improved Channel Probing For Secret Key Generation With Multiple Antenna Systems, Britton T. Quist
Theses and Dissertations
Establishing secret keys from the commonly-observed randomness of reciprocal wireless propagation channels has recently received considerable attention. In this work we propose improved strategies for channel estimation between MIMO or beamforming systems for secret key generation. The amount of mutual information that can be extracted from the channel matrix estimates is determined by the quality of channel matrix estimates. By allocating increased energy to channel estimation for higher gain beamforming combinations at the expense of low-gain combinations, key establishment performance can be increased. Formalizing the notion of preferential energy allocation to the most efficient excitations is the central theme of …
Discrete-Time Implementation, Antenna Design, And Mimo For Near-Field Magnetic Induction Communications, Ronald Brett Gottula
Discrete-Time Implementation, Antenna Design, And Mimo For Near-Field Magnetic Induction Communications, Ronald Brett Gottula
Theses and Dissertations
Near-field magnetic induction (NFMI) is a short range wireless technology that uses loop antennas coupled by a magnetic field. NFMI antennas are electrically small and thus extremely inefficient and narrow band, making system design for multi-user and high-bitrate applications challenging. The goals of this thesis are to develop a test platform suitable for NFMI antenna testing, to model, design and test NFMI antennas that have high bandwidth-efficiency, and to explore the possibility of using MIMO (multiple-input multiple-output) to increase the capacity of the NFMI channel. This thesis provides system implementations, test results, and channel modeling to aid in the design …
Robust Signaling, Scheduling And Authentication In The Multi-User Multiple-Input-Multiple-Output Channel, Yan Shi
Theses and Dissertations
Multiple-input multiple-output (MIMO) networks are known to be able to achieve throughput performance superior to that available from single-input single-output (SISO) systems. However, when applying MIMO in multi-user networks, achieving this throughput advantage requires efficient precoding and optimal network scheduling. Furthermore, MIMO radios can help ensure security in a multi-user network. Previous work has proposed various precoding techniques for the MIMO broadcast channel, based either on channel state information (CSI) or channel distribution information (CDI), which achieve optimal or near- optimal MIMO channel throughput. The performance of these techniques largely depends on the availability of the channel information at the …
Studies On The Performance And Impact Of Channel Estimation In Mimo And Ofdm Systems, Michael David Larsen
Studies On The Performance And Impact Of Channel Estimation In Mimo And Ofdm Systems, Michael David Larsen
Theses and Dissertations
The need for reliable, high-throughput, mobile wireless communication technologies has never been greater as increases in the demand for on-the-go access to information, entertainment, and other electronic services continues. Two such technologies, which are at the forefront of current research efforts, are orthogonal frequency division multiplexing (OFDM) and multiple-input multiple-output (MIMO) systems, their union being known simply as MIMO-OFDM. The successful performance of these technologies depends upon the availability of accurate information concerning the wireless communication channel. In this dissertation, several issues related to quality of this channel state information (CSI) are studied. Specifically, the first part of this dissertation …
Offset Qpsk In Siso And Mimo Environments, Xiaoyu Dang
Offset Qpsk In Siso And Mimo Environments, Xiaoyu Dang
Theses and Dissertations
We demonstrate how the performance of offset quadrature phase-shift keying (OQPSK) and its variants of Feher-patented QPSK (FQPSK) and Shaped Offset QPSK (SOQPSK) (collectively known as the ARTM Tier-1 waveforms) in single input single output (SISO) system could change with the channel fading parameters. The bit error rate expression of offset QSPK and ATRM Tier-1 waveforms over the aeronautical telemetry multipath channel has been derived. Simulations show that for the case of a single multipath ray, the BER gets worse with increasing Γ for a fixed delay, and that the BER has a quasi-periodic property for fixed Γ and increasing …
Near-Optimal Antenna Design For Multiple Antenna Systems, Daniel N. Evans
Near-Optimal Antenna Design For Multiple Antenna Systems, Daniel N. Evans
Theses and Dissertations
Multiple-input-multiple-output (MIMO) wireless systems use multiple antenna elements at the transmitter and receiver to offer improved spectral efficiency over traditional single antenna systems. In these systems, properties of the transmit and receive antenna arrays play a key role in determining the overall performance of the system. This thesis derives an upper bound on ergodic (average) channel capacity which formally links good antenna diversity performance with good ergodic capacity. As a result of this derivation, antenna arrays with good ergodic capacity performance are designed in this thesis by designing antenna arrays with near-optimal diversity gain. Several approaches are developed to design …
Optimizing Wireless Network Throughput: Methods And Applications, Pengchang Zhan
Optimizing Wireless Network Throughput: Methods And Applications, Pengchang Zhan
Theses and Dissertations
Ever since Marconi succeeded in his first demonstration on the possibility to communicate over the air overseas about a century ago, wireless communications have experienced dramatic improvements. Today's world sees the penetration of wireless communications into human life almost everywhere, from a simple remote control for TV to a cellular phone. With a better understanding of the adverse nature of the wireless propagation channels, engineers have been able to invent various clever techniques, i.e. Multiple Input Multiple Output (MIMO) technology, spread spectrum communications, Orthogonal Frequency Division Multiplexing (OFDM) to name a few, to achieve fast and reliable communications over each …
Synthesis Of Optimal Arrays For Mimo And Diversity Systems, Britton T. Quist
Synthesis Of Optimal Arrays For Mimo And Diversity Systems, Britton T. Quist
Theses and Dissertations
This thesis proposes a method for determining the optimal antenna element radiation characteristics which maximize diversity gain given a specific power angular spectrum of the propagation environment. The method numerically constructs the eigenfunctions of the covariance operator for the scenario subject to constraints on the power radiated by each antenna as well as the level of supergain allowed in the solution. The optimal antenna characteristics are produced in terms of radiating current distributions along with their resulting radiation patterns. The results reveal that the optimal antennas can provide significantly more diversity gain than that provided by a simple practical design. …
Performance Of Mimo Space-Time Coding Algorithms On A Parallel Dsp Test Platform, Beau C. Neal
Performance Of Mimo Space-Time Coding Algorithms On A Parallel Dsp Test Platform, Beau C. Neal
Theses and Dissertations
Commercial Off The Shelf (COTS) hardware has the advantages of low cost, modularity, and is easily upgraded. For Multiple-Input Multiple-Output (MIMO) space-time algorithms to be practical they must have the processing capability to execute in real-time. This makes COTS ideal for real-time MIMO research where the processing power increases exponentially with a linear increase in antennas. The BYU Electrical Engineering wireless lab has designed and built an eight processor transmitter and a twenty processor receiver to research and develop MIMO wireless communication. The Alamouti, 2 x 2 and 4 x 4 differential space-time MIMO algorithms have been partially implemented on …
Mimo Communication Capacity: Antenna Coupling And Precoding For Incoherent Detection, Nicolas W. Bikhazi
Mimo Communication Capacity: Antenna Coupling And Precoding For Incoherent Detection, Nicolas W. Bikhazi
Theses and Dissertations
While the capacity of multiple-input multiple-output (MIMO) systems has been explored in considerable detail, virtually all literature on this topic ignores electromagnetic considerations. This dissertation explores electromagnetic effects on the capacity performance of these multi-antenna architectures. Specifically, it examines the impact of superdirectivity for compact antenna arrays, the effect of antenna mutual coupling, and MIMO performance of multi-mode optical fiber with non-linear detection. Superdirectivity can lead to abnormally large capacity bounds in a MIMO communication system, especially when the antennas are placed close together. Because superdirective behavior is difficult to achieve in practice, this work formulates an approach for limiting …
Arq Techniques For Mimo Communication Systems, Zhihong Ding
Arq Techniques For Mimo Communication Systems, Zhihong Ding
Theses and Dissertations
Multiple-input multiple-output (MIMO) communication systems employ multiple antennas at the transmitter and the receiver. Multiple antennas provide capacity gain and/or robust performance over single antenna communications. Traditional automatic-repeat-request (ARQ) techniques developed for single-input single-output (SISO) communication systems have to be modified in order to be employed in MIMO communication systems. In this dissertation, we propose and analysis some ARQ techniques for MIMO communication systems. The basic retransmission protocols of ARQ, stop-and-wait (SW-ARQ), go-back-$N$ (GBN-ARQ), and selective repeat (SR-ARQ), designed for SISO communication systems are generalized for parallel multichannel communication systems. The generalized ARQ protocols seek to improve the channel utilization …
The Impact Of Antenna And Rf System Characteristics On Mimo System Capacity, Matthew Leon Morris
The Impact Of Antenna And Rf System Characteristics On Mimo System Capacity, Matthew Leon Morris
Theses and Dissertations
The recent growth in demand for wireless services coupled with the limited spectrum available for these services has spawned new efforts to increase the spectral efficiency of wireless links. Recent research has shown that in multipath propagation environments, the spatial characteristics of the propagation channel can be exploited to increase spectral efficiency through the use of multiple antennas at the transmitting and receiving nodes. Such multiple-input multiple-output (MIMO) systems show promise for dramatic performance gains over their single-antenna counterparts. However, MIMO system performance is influenced by many different factors. Antenna array configuration directly contributes to MIMO system performance. The ability …
An Examination Into The Statistics Of The Singular Vectors For The Multi-User Mimo Wireless Channel, Scott Nathan Gunyan
An Examination Into The Statistics Of The Singular Vectors For The Multi-User Mimo Wireless Channel, Scott Nathan Gunyan
Theses and Dissertations
Many capacity and near-capacity achieving methods in multiple-input-multipleoutput (MIMO) wireless channels make use of the singular value decomposition (SVD) of the channel matrix. For the multi-user case, the SVD of the channel matrix for each user may result in right and left singular vectors that are similar between users. This proposes another descriptive characterization of the multi-user MIMO channel. Closely aligned singular vectors between any two users could reduce the achievable signaling rates of signal processing communication methods as one user would be more difficult to resolve in space-time from another. An examination into how this alignment can be described …
Architectures For Symbol Timing Synchronization In Mimo Communications, Kejing Liu
Architectures For Symbol Timing Synchronization In Mimo Communications, Kejing Liu
Theses and Dissertations
Maximum likelihood symbol timing estimation for communication over a frequency non-selective MIMO fading channel is developed. The cases of known data (data-aided estimation) and unknown data (non-data-aided estimation) together with known channel and unknown channel are considered. The analysis shows that the log-likelihood functions and their approximations can be interpreted as SISO log-likelihood functions operating on each of the receive antennas. Previously published symbol timing estimators are shown to be special cases of the more general framework presented. Architectures based on both block processing and sequential processing using a discrete-time phase-locked loop are summarized. Performance examples over a MIMO channel …
Wideband Channel Characterization For Mimo Scenario, Justin T. Holzer
Wideband Channel Characterization For Mimo Scenario, Justin T. Holzer
Theses and Dissertations
Because broadband wireless systems benefit from accurate channel characterization, there is growing interest in broadband wireless multiple-input multiple-output (MIMO) channel models. This thesis verifies the suitability of the Saleh Valenzuela with Angle (SVA) model for wideband MIMO communication models. While recent wideband MIMO measurements have been obtained by switching a single transmit/receive pair over all possible antenna pair combinations, a simultaneous probing system is superior because of the time required for the antenna-switching channel measurements. This work provides two different wideband channel estimation algorithms based on simultaneous transmission from and reception on all antennas. Simulated data from an electromagnetic ray …
Modeling Electromagnetic Wave Propagation In Electrically Large Structures, Jon Wallace
Modeling Electromagnetic Wave Propagation In Electrically Large Structures, Jon Wallace
Theses and Dissertations
Existing unified numerical electromagnetic methods are often unable to analyze electrically large structures due to the amount of memory and processing power required, necessitating approximate analyses with limited applicability. In this research a hybrid modeling methodology is adopted to solve these complex problems more efficiently than unified numerical methods and more accurately than analytical methods. Electromagnetic modeling problems are divided into two or more levels of scale. Each level analyzes a specific level of detail and only promotes the required information to the next level. The method is demonstrated by successful application to three important problems: (1) remote sensing of …
Channel Probing For An Indoor Wireless Communications Channel, Brandon Hunter
Channel Probing For An Indoor Wireless Communications Channel, Brandon Hunter
Theses and Dissertations
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 …