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Performance Evaluation of Pattern Reconfigurable Antennas in MIMO SystemsZhou, Yu 17 August 2012 (has links)
With the fast adoption of LTE and IEEE 802.11N, more devices are employing multiple antennas to boost the data rate and reliability of the communication link. Traditionally, fixed antennas are used in such devices. In recent years, reconfigurable antennas have been sought out to further boost the performance, which can adaptor to the changing wireless channel by altering their radiation characteristics, and maintain or exceed the performance of fixed antennas. This thesis studies the possibility of performance increase using pattern reconfigurable antennas as receivers. Their performance potential was first estimated using simulations, and then demonstrated using two electrically steerable passive array radiator (ESPAR) antennas against a pair of monopole antennas on a hardware bit error rate (BER) testbed. The former produces equal performance in BER with certain pattern combinations and excels in theoretical capacity with substantial lead making pattern reconfigurable antenna a potent option as receiver in MIMO-related
applications.
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HYPERSPECTRAL IMAGE COMPRESSIONHallidy, William H., Jr., Doerr, Michael 10 1900 (has links)
International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Systems & Processes Engineering Corporation (SPEC) compared compression and decompression algorithms and developed optimal forms of lossless and lossy compression for hyperspectral data. We examined the relationship between compression-induced distortion and additive noise, determined the effect of errors on the compressed data, and showed that the data could separate targets from clutter after more than 50:1 compression.
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LINK AVAILABILITY AND BIT ERROR CLUSTERS IN AERONAUTICAL TELEMETRYJefferis, Robert P. 10 1900 (has links)
International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Radio frequency power margins in well planned line-of-sight (LOS) air-to-ground digital data transmission systems usually produce signal to noise ratios (SNR) that can deliver error free service. Sometimes field performance falls short of design and customer expectations. Recent flight tests conducted by the tri-service Advanced Range Telemetry (ARTM) project confirm that the dominant source of bit errors and short term link failures are “clusters” of severe error burst activity produced by flat fading, dispersive fading and poor antenna patterns on airborne vehicles. This paper introduces the techniques used by ARTM to measure bit error performance of aeronautical telemetry links.
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BIT ERROR PERFORMANCE ANALYSIS OF BPSK IN THE PRESENCE OF MULTIPATH FADINGde Gaston, David E. 10 1900 (has links)
International Telemetering Conference Proceedings / October 23-26, 2000 / Town & Country Hotel and Conference Center, San Diego, California / The presence of multipath fading has been shown to degrade the performance of a wireless channel.
This paper quantifies the effects of multipath interference on signal performance based on the estimated
parameters of the multipath signal. Theoretical results are compared with actual results obtained
through the Advanced Range Telemetry (ARTM) program.
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ENHANCED PERFORMANCE OF FQPSK-B RECEIVER BASED ON TRELLIS-CODED VITERBI DEMODULATIONLee, Dennis, Simon, Marvin, Yan, Tsun-Yee 10 1900 (has links)
International Telemetering Conference Proceedings / October 23-26, 2000 / Town & Country Hotel and Conference Center, San Diego, California / Commercial FQPSK-B receivers traditionally use symbol-by-symbol detection and have a 2 dB Eb=No loss relative to ideal QPSK at a bit error rate (BER) of 10^(-5). An enhanced FQPSK-B receiver using a Viterbi algorithm (VA) to perform trellis decoding is simulated and shown to have a 1.2 dB Eb=No improvement over symbol-by-symbol detection for 10^(-5)5 BER at the cost of increased complexity. A simplified Viterbi receiver with a reduced trellis and significantly less complexity is introduced with only a slight BER degradation compared to the full Viterbi receiver. In addition, a theoretical bit error probability expression for the symbol-by-symbol FQPSK-B receiver is derived and compared with simulation results.
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Optimal communications system design for array-based electric generationOrozco, Ricardo 03 November 2011 (has links)
The world's demand for energy is an ongoing challenge, which has yet to be overcome.
The efforts to find clean energy alternatives to fossil fuels have been hampered by the
lack of investment in technology and research. Among these clean energy alternatives
are ocean waves and wind. Wind power is generated through the use of wind generators
that harness the wind's kinetic energy; it has gained worldwide popularity as a large-scale
energy source, but only provides less than one percent of global energy consumption.
Due to infrastructure limitations on installations of wind turbines at locations where high
winds exist, wind energy faces critical challenges difficult to overcome to continue
improving electricity generation. Ocean wave energy on the other hand seems like a
promising adjunction to wind energy. Ocean energy comes in a variety of forms such as
marine currents, tidal currents, geothermal vents and waves. Most of today's research
however is based on wave energy. It has been estimated that approximately 257 Terawatt
hour per year (TWh/year) could be extracted from ocean waves alone. This amount of
energy could be enough to meet the U.S. energy demands of 28 TWh/year. Technologies
such as point absorbers, attenuators and overtopping devices are examples of wave
energy converters. Point absorbers use a floating structure with components that move
relative to each other due to the wave action. The relative motion is used to drive
electromechanical or hydraulic energy converters. The total energy throughput of a
single point absorber however, does not justify for the great engineering cost and effort
by researchers. Thus the need to explore other alternatives of wave conversion that result
in no extra-added cost but yet increases throughput.
Our research focuses on exploring a novel method to maximize wave energy conversion
of an array-based point absorber wave farm. Unlike previous research, our method
incorporates a predictive control algorithm to aid the wave farm with the prediction of
dynamics and optimal control trajectory over a finite time and space horizon of ocean
waves. By using a predictive control algorithm, wave energy conversion throughput can
be increased as opposed to a system without. This algorithm requires that the wave
characteristics of the incoming wave be provided in advance for appropriate processing.
This thesis focuses on designing an efficient and reliable wireless
communications system capable of delivering wave information such as speed, height
and direction to each point absorber in the network for further processing by the
predictive control algorithm. This process takes place in the presence of harsh
environmental conditions where the random shape of waves and moving surface can
further affect the communication channel. In this work we focus on the physical layer
where the transmission of bits over the wireless medium takes place. Specifically we are
interested in reducing the bit error rate with a unique relaying protocol to increase packet
transmission reliability. We make use of cooperative diversity and existing protocols to
achieve our goal of merit and improve end-to-end system performance. / Graduation date: 2012
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Probability of Bit Error on a Standard IRIG Telemetry Channel Using the Aeronautical Fading Channel ModelNelson, N. Thomas 10 1900 (has links)
International Telemetering Conference Proceedings / October 17-20, 1994 / Town & Country Hotel and Conference Center, San Diego, California / This paper analyzes the probability of bit error for PCM-FM over a standard IRIG channel subject to multipath interference modeled by the aeronautical fading channel. The aeronautical channel model assumes a mobile transmitter and a stationary receiver and specifies the correlation of the fading component. This model describes fading which is typical of that encountered at military test ranges. An expression for the bit error rate on the fading channel with a delay line demodulator is derived and compared with the error rate for the Gaussian channel. The increase in bit error rate over that of the Gaussian channel is determined along with the power penalty caused by the fading. In addition, the effects of several channel parameters on the probability of bit error are determined.
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Analysis of OFDMA resource allocation with limited feedbackLeinonen, J. (Jouko) 22 September 2009 (has links)
Abstract
Radio link adaptation, multiple antenna techniques, relaying methods and dynamic radio resource assignment are among the key methods used to improve the performance of wireless communication networks. Opportunistic resource block (RB) allocation in downlink orthogonal frequency division multiple access (OFDMA) with limited feedback is considered. The spectral efficiency analysis of multiuser OFDMA with imperfect feedback path, multiple antenna methods and relaying methods is a particular focus.
The analysis is derived for best-M feedback methods and for a RB-wise signal-to-noise ratio (SNR) quantization based feedback strategy. Practical resource fair round robin (RR) allocation is assumed at the RB assignment, i.e., each user gets the same portion of the available RBs. The fading of each RB is modelled to be independent and identically distributed (IID). This assumption enabled a communication theoretic approach for the performance evaluation of OFDMA systems The event probabilities related to the considered OFDMA systems are presented so that the feedback bit error probability (BEP) is a parameter in the expressions. The performance expressions are derived for the BEP in the case of binary phase-shift keying (BPSK) modulation and single antenna methods. Asymptotic BEP behavior is considered for the best-M feedback methods when the mean SNR tends to infinity. The system outage capacity and the average system spectral efficiency are investigated in the case of multiple antenna schemes. Antenna selection and space-time block coding (STBC) are considered in multiple antenna schemes when each RB is allocated exclusively to a single user. Simple OFDMA-spatial division multiple access (SDMA) schemes are also analyzed when zero forcing (ZF) detection is assumed at the receiver.
Relay enhanced dynamic OFDMA with single and multiple antennas at each end is considered for fixed infrastructure amplify-and-forward (AF) relaying methods. The average spectral efficiency has been derived for the best-M and RB-wise one bit feedback schemes, antenna selection and STBC methods.
The best choice for a combination of multiple antenna scheme and feedback strategy depends on several system parameters. The proposed analytical tools enable easy evaluation of the performance of the investigated schemes with different system parameters. The fundamental properties of the combinations of feedback and multiple antenna schemes are extensively studied through numerical examples. The results also demonstrate that the analytical results with idealized IID fading assumption are close to those obtained via simulations in a practical frequency selective channel when RBs are selected properly. Dynamic RB allocation is attractive for practical OFDMA systems since significant performance gain over random allocation can be achieved with a practical allocation principle, very low feedback overhead and an imperfect feedback channel.
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System Performance of an Over-Water Propagation for an LMDS LinkTan, Chin Khee 10 May 2001 (has links)
The growth of broadband Internet access has paved the way for the development of many newer existing technologies. As the costs of implementing broadband access soar, the best alternative will be to use wireless technologies. At a carrier frequency of about 28 GHz, the potential benefits of Local Multipoint Distribution Service (LMDS) will eventually outweigh those of its current competitors in the wired market. Since the rural communities will reap the most benefits from this technology due to its low costs, studies on the channel behavior and terrain relationships must be done.
This thesis aims to provide a preliminary study on the effects of propagating an LMDS signal over a lake surface. Currently, there is not enough information to prove the feasibility of deploying an LMDS system for this terrain. Some background on the technology and rough surface theory is provided for the reader to better understand the environment that is being investigated. Simulation results are presented as a guide to assist future researchers to conduct a field measurement campaign. A block diagram of a potential measurement system is also provided to aid in the development of the tools necessary for the measurement of an actual channel. / Master of Science
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MIMO-OFDM Symbol Detection via Echo State NetworksZhou, Zhou 30 October 2019 (has links)
Echo state network (ESN) is a specific neural network structure composed of high dimensional nonlinear dynamics and learned readout weights. This thesis considers applying ESN for symbol detection in multiple-input, multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM) systems. A new ESN structure, namely, windowed echo state networks (WESN) is introduced to further improve the symbol detection performance. Theoretical analysis justifies WESN has an enhanced short-term memory (STM) compared with the standard ESN such that WESN can offer better computing ability. Additionally, the bandwidth spent as the training set is the same as the demodulation reference signals defined in 3GPP LTE/LTE-Advanced systems for the ESN/WESN based symbol detection. Meanwhile, a unified training framework is developed for both comb and scattered pilot patterns. Complexity analysis demonstrates the advantages of ESN/WESN based symbol detector compared to conventional symbol detectors such as linear minimum mean square error (LMMSE) and sphere decoder when the system is employed with a large number of OFDM sub-carriers. Numerical evaluations show that ESN/WESN has an improvement of symbol detection performance as opposed to conventional methods in both low SNR regime and power amplifier (PA) nonlinear regime. Finally, it demonstrates that WESN can generate a better symbol detection result over ESN. / Artificial neural networks (ANN) are widely used in recognition tasks such as recommendation systems, robotics path planning, self-driving, video tracking, image classifications, etc. To further explore the applications of ANN, this thesis considers using a specific ANN, echo state network (ESN) for a wireless communications task: MIMO-OFDM symbol detection. Furthermore, it proposed an enhanced version of the standard ESN, namely, windowed echo state network (WESN). Theoretical analyses on the short term memory (STM) of ESN and WESN show that the later one has a longer STM. Besides, the training set size of this ESN/WESN based method is chosen the same as the pilot symbols used in conventional communications systems. The algorithm complexity analysis demonstrates the ESN/WESN based method performs with lower complexity compared with conventional methods, such as linear mean square error (LMMSE) and sphere decoding. Comprehensive simulations examine how the symbol detection performance can be improved by using ESN and its variant WESN when the transmission link is non-ideal.
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