You searched for +publisher:"Virginia Tech" +contributor:("Buehrer, R. Michael").
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Virginia Tech
1.
Biskaduros, Zachary Jon.
Collaborative Localization Enhancement to the Global Positioning System using Inter-Receiver Range Measurements.
Degree: MS, Electrical Engineering, 2013, Virginia Tech
URL: http://hdl.handle.net/10919/23152 
► The localization of wireless devices, e.g. mobile phones, laptops, and handheld GPS receivers, has gained much interest due to the benefits it provides, including quicker…
(more)
▼ The localization of wireless devices, e.g. mobile phones, laptops, and handheld GPS receivers, has gained much interest due to the benefits it provides, including quicker emergency personnel dispatch, location-aided routing, as well as commercial revenue opportunities through location based services. GPS is the dominant position location system in operation, with 31 operational satellites producing eight line of sight satellites available to users at all times making it very favorable for system implementation in all wireless networks. Unfortunately when a GPS receiver is in a challenging environment, such as an urban or indoor scenario, the signal quality often degrades causing poor accuracy in the position estimate or failure to localize altogether due to satellite availability. Our goal is to introduce a new solution that has the ability to overcome this limitation by improving the accuracy and availability of a GPS receiver when in a challenging environment. To test this theory we created a simulated GPS receiver using a MATLAB simulation to mimic a standard GPS receiver with all 31 operational satellites. Here we are able to alter the environment of the user and examine the errors that occur due to noise and limited satellite availability. Then we introduce additional user(s) to the GPS solution with the knowledge (or estimate) of the distances between the users. The new solutions use inter-receiver distances along with pseudoranges to cooperatively determine all receiver location estimates simultaneously, resulting in improvement in both the accuracy of the position estimate and availability.
Advisors/Committee Members: Buehrer, R. Michael (committeechair), Reed, Jeffrey Hugh (committee member), Ruohoniemi, John Michael (committee member).
Subjects/Keywords: localization; geolocation; collaborative position location; collaborative global positioning system
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APA (6th Edition):
Biskaduros, Z. J. (2013). Collaborative Localization Enhancement to the Global Positioning System using Inter-Receiver Range Measurements. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/23152
Chicago Manual of Style (16th Edition):
Biskaduros, Zachary Jon. “Collaborative Localization Enhancement to the Global Positioning System using Inter-Receiver Range Measurements.” 2013. Masters Thesis, Virginia Tech. Accessed February 28, 2021.
http://hdl.handle.net/10919/23152.
MLA Handbook (7th Edition):
Biskaduros, Zachary Jon. “Collaborative Localization Enhancement to the Global Positioning System using Inter-Receiver Range Measurements.” 2013. Web. 28 Feb 2021.
Vancouver:
Biskaduros ZJ. Collaborative Localization Enhancement to the Global Positioning System using Inter-Receiver Range Measurements. [Internet] [Masters thesis]. Virginia Tech; 2013. [cited 2021 Feb 28].
Available from: http://hdl.handle.net/10919/23152.
Council of Science Editors:
Biskaduros ZJ. Collaborative Localization Enhancement to the Global Positioning System using Inter-Receiver Range Measurements. [Masters Thesis]. Virginia Tech; 2013. Available from: http://hdl.handle.net/10919/23152
Virginia Tech
2.
Thornton, Charles E. III.
Learning Schemes for Adaptive Spectrum Sharing Radar.
Degree: MS, Electrical Engineering, 2020, Virginia Tech
URL: http://hdl.handle.net/10919/98788
► Society's newfound dependence on wireless transmission systems has driven demand for control of the electromagnetic (EM) spectrum to an all-time high. In particular, federal spectrum…
(more)
▼ Society's newfound dependence on wireless transmission systems has driven demand for control of the electromagnetic (EM) spectrum to an all-time high. In particular, federal spectrum auctions and the fifth generation of wireless technologies have contributed to the scarcity of frequency bands below 6GHz. These frequencies are widely used by both radar and communications systems due to favorable propagation characteristics. However, current radar systems typically occupy a fixed bandwidth and are tend to be poorly equipped to share their allocated spectrum with other users, which has become a necessity given the growth of wireless traffic.
In this thesis, we study learning algorithms which enable a radar to optimize its electromagnetic pulses based on feedback from received signals. In particular, we are interested in reinforcement learning algorithms which allow a radar to learn optimal behavior based on rewards defined by a human. Using these algorithms, radar system designers can choose which metrics may be most important for a given radar application which can then be optimized for the given setting. However, scaling reinforcement learning to real-world problems such as radar optimization is often difficult due to the massive scope of the problem. Here we attempt to identify potential issues with implementation of each algorithm and narrow in on algorithms that are well-suited for real-time radar operation.
Advisors/Committee Members: Buehrer, R. Michael (committeechair), Saad, Walid (committee member), Dhillon, Harpreet Singh (committee member).
Subjects/Keywords: Statistical Learning; Spectrum Sharing; Radar; Interoperability; Deep Learning
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APA (6th Edition):
Thornton, C. E. I. (2020). Learning Schemes for Adaptive Spectrum Sharing Radar. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/98788
Chicago Manual of Style (16th Edition):
Thornton, Charles E III. “Learning Schemes for Adaptive Spectrum Sharing Radar.” 2020. Masters Thesis, Virginia Tech. Accessed February 28, 2021.
http://hdl.handle.net/10919/98788.
MLA Handbook (7th Edition):
Thornton, Charles E III. “Learning Schemes for Adaptive Spectrum Sharing Radar.” 2020. Web. 28 Feb 2021.
Vancouver:
Thornton CEI. Learning Schemes for Adaptive Spectrum Sharing Radar. [Internet] [Masters thesis]. Virginia Tech; 2020. [cited 2021 Feb 28].
Available from: http://hdl.handle.net/10919/98788.
Council of Science Editors:
Thornton CEI. Learning Schemes for Adaptive Spectrum Sharing Radar. [Masters Thesis]. Virginia Tech; 2020. Available from: http://hdl.handle.net/10919/98788
Virginia Tech
3.
Marinkovich, Aaron James Angelo.
Coordinated Beamforming for Millimeter-wave Terrestrial Peer-to-Peer Communication Networks.
Degree: MS, Electrical Engineering, 2020, Virginia Tech
URL: http://hdl.handle.net/10919/100589
► Wireless communication links can interfere with each other. Interference can be mitigated by adjusting the antennas with which the links are formed. One method of…
(more)
▼ Wireless communication links can interfere with each other. Interference can be mitigated by adjusting the antennas with which the links are formed. One method of mitigating interference is coordinated beamforming. Coordinated beamforming can be defined as a method of adjusting antennas to jointly optimize the strength of the links operating in a network. In this work, we explore coordinated beamforming in terrestrial mobile peer-to-peer communication networks and demonstrate its efficacy. Networks with varying numbers of links are simulated in scenarios with and without obstructions. The coordinated beamforming schemes presented in this work significantly improve link strength statistics in these scenarios. Greater improvement was found in networks with higher numbers of links and in networks in terrain with obstructions.
Advisors/Committee Members: Ellingson, Steven W. (committeechair), Dhillon, Harpreet Singh (committee member), Buehrer, R. Michael (committee member).
Subjects/Keywords: Coordinated Beamforming; Beamforming; Millimeter-wave Communication; Peer-to-Peer Communication; Terrestrial Communication Network
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APA (6th Edition):
Marinkovich, A. J. A. (2020). Coordinated Beamforming for Millimeter-wave Terrestrial Peer-to-Peer Communication Networks. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/100589
Chicago Manual of Style (16th Edition):
Marinkovich, Aaron James Angelo. “Coordinated Beamforming for Millimeter-wave Terrestrial Peer-to-Peer Communication Networks.” 2020. Masters Thesis, Virginia Tech. Accessed February 28, 2021.
http://hdl.handle.net/10919/100589.
MLA Handbook (7th Edition):
Marinkovich, Aaron James Angelo. “Coordinated Beamforming for Millimeter-wave Terrestrial Peer-to-Peer Communication Networks.” 2020. Web. 28 Feb 2021.
Vancouver:
Marinkovich AJA. Coordinated Beamforming for Millimeter-wave Terrestrial Peer-to-Peer Communication Networks. [Internet] [Masters thesis]. Virginia Tech; 2020. [cited 2021 Feb 28].
Available from: http://hdl.handle.net/10919/100589.
Council of Science Editors:
Marinkovich AJA. Coordinated Beamforming for Millimeter-wave Terrestrial Peer-to-Peer Communication Networks. [Masters Thesis]. Virginia Tech; 2020. Available from: http://hdl.handle.net/10919/100589
Virginia Tech
4.
Cooke, Corey.
Attenuation Field Estimation Using Radio Tomography.
Degree: MS, Electrical and Computer Engineering, 2011, Virginia Tech
URL: http://hdl.handle.net/10919/34748
► Radio Tomographic imaging (RTI) is an exciting new field that utilizes a sensor network of a large number of relatively simple radio nodes for inverse…
(more)
▼ Radio Tomographic imaging (RTI) is an exciting new field that utilizes a sensor network of a large number of relatively simple radio nodes for inverse imaging, utilizing similar mathematical algorithms to those used in medical imaging. Previous work in this field has almost exclusively focused on device-free object location and tracking. In this thesis, the application of RTI to propagation problems will be studied – specifically using RTI to measure the strength and location of attenuating objects in an area of interest, then using this knowledge of the shadowing present in an area for radio coverage prediction.
In addition to radio coverage prediction, RTI can be used to improve the quality of RSS-based position location estimates. Because the traditional failing of RSS-based multilateration is ranging error due to attenuating objects, RTI has great potential for improving the accuracy of these estimates if shadowing objects are accounted for.
In this thesis, these two problems will primarily be studied. A comparison with other inverse imaging, remote sensing, and propagation modeling techniques of interest will be given, as well as a description of the mathematical theory used for tomographic image reconstruction. Proof-of-concept of the efficacy of applying RTI to position location will be given by computer simulation, and then physical experiments with an RTI network consisting of 28 Zigbee radio sensors will be used to verify the validity of these assertions. It will be shown in this thesis that RTI does provide noticeable improvement in RSS-based position location accuracy in cluttered environments, and it produces much more accurate RSS estimates than a standard exponential path-loss model is able to provide.
Advisors/Committee Members: Buehrer, R. Michael (committeechair), Ellingson, Steven W. (committee member), Pratt, Timothy J. (committee member).
Subjects/Keywords: radio tomography; location estimation; propagation modeling; attenuation field estimation
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APA (6th Edition):
Cooke, C. (2011). Attenuation Field Estimation Using Radio Tomography. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/34748
Chicago Manual of Style (16th Edition):
Cooke, Corey. “Attenuation Field Estimation Using Radio Tomography.” 2011. Masters Thesis, Virginia Tech. Accessed February 28, 2021.
http://hdl.handle.net/10919/34748.
MLA Handbook (7th Edition):
Cooke, Corey. “Attenuation Field Estimation Using Radio Tomography.” 2011. Web. 28 Feb 2021.
Vancouver:
Cooke C. Attenuation Field Estimation Using Radio Tomography. [Internet] [Masters thesis]. Virginia Tech; 2011. [cited 2021 Feb 28].
Available from: http://hdl.handle.net/10919/34748.
Council of Science Editors:
Cooke C. Attenuation Field Estimation Using Radio Tomography. [Masters Thesis]. Virginia Tech; 2011. Available from: http://hdl.handle.net/10919/34748
Virginia Tech
5.
Sollenberger, Eric Paul.
Iterative Leakage-Based Precoding for Multiuser-MIMO Systems.
Degree: MS, Electrical Engineering, 2016, Virginia Tech
URL: http://hdl.handle.net/10919/71398
► This thesis investigates the application of an iterative leakage-based precoding algorithm to practical multiuser-MIMO systems. We consider the effect of practical impairments including imperfect channel…
(more)
▼ This thesis investigates the application of an iterative leakage-based precoding algorithm to practical multiuser-MIMO systems. We consider the effect of practical impairments including imperfect channel state information, transmit antenna correlation, and time-varying channels. Solutions are derived which improve performance of the algorithm with imperfect channel state information at the transmitter by leveraging knowledge of the second-order statistics of the error. From this work we draw a number of conclusions on how imperfect channel state information may impact the system design including the importance of interference suppression at the receiver and the selection of the number of co-scheduled users. We also demonstrate an efficient approach to improve the convergence of the algorithm when using interference-rejection-combining receivers. Finally, we conduct simulations of an LTE-A system employing the improved algorithm to show its utility for modern communication systems.
Advisors/Committee Members: Buehrer, R. Michael (committeechair), Dhillon, Harpreet Singh (committee member), Dietrich, Carl B. (committee member).
Subjects/Keywords: multiuser; MIMO; linear precoding; leakage; imperfect CSI; LTE-A
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APA (6th Edition):
Sollenberger, E. P. (2016). Iterative Leakage-Based Precoding for Multiuser-MIMO Systems. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/71398
Chicago Manual of Style (16th Edition):
Sollenberger, Eric Paul. “Iterative Leakage-Based Precoding for Multiuser-MIMO Systems.” 2016. Masters Thesis, Virginia Tech. Accessed February 28, 2021.
http://hdl.handle.net/10919/71398.
MLA Handbook (7th Edition):
Sollenberger, Eric Paul. “Iterative Leakage-Based Precoding for Multiuser-MIMO Systems.” 2016. Web. 28 Feb 2021.
Vancouver:
Sollenberger EP. Iterative Leakage-Based Precoding for Multiuser-MIMO Systems. [Internet] [Masters thesis]. Virginia Tech; 2016. [cited 2021 Feb 28].
Available from: http://hdl.handle.net/10919/71398.
Council of Science Editors:
Sollenberger EP. Iterative Leakage-Based Precoding for Multiuser-MIMO Systems. [Masters Thesis]. Virginia Tech; 2016. Available from: http://hdl.handle.net/10919/71398
Virginia Tech
6.
Bettadapura, Raghuprasad Shivatejas.
Echo Delay Estimation to Aid Source Localization in Noisy Environments.
Degree: MS, Electrical Engineering, 2014, Virginia Tech
URL: http://hdl.handle.net/10919/50517
► Time-delay estimation (TDE) finds application in a variety of problems, be it locating fractures or steering cameras towards the speaker in a multi-participant conference application.…
(more)
▼ Time-delay estimation (TDE) finds application in a variety of problems, be it locating
fractures or steering cameras towards the speaker in a multi-participant conference application. Underwater acoustic OFDM source localization is another important application of TDE. Existing underwater acoustic source localization techniques use a microphone array consisting of three or four sensors in order to effectively locate the source. Analog-to-digital (ADC) converters at these sensors call for a non-nominal investment in terms of circuitry and memory. A relatively inexpensive source localization algorithm is needed that works with the output of a single sensor. Since an inexpensive process for estimating the location of the source is desired, the ADC used at the sensor is capable only of a relatively low sampling rate. For a given delay, a low sampling rate leads to sub-sample interval delays, which the desired algorithm must be able to estimate. Prevailing TDE algorithms make some a priori assumptions about the nature of the received signal, such as Gaussianity, wide-sense stationarity, or periodicity. The desired algorithm must not be restrictive in so far as the nature of the transmitted signal is concerned.
A time-delay estimation algorithm based on the time-frequency ratio of mixtures (TFRM) method is proposed. The experimental set-up consists of two microphones/sensors placed at some distances from the source. The method accepts as input the received signal which consists of the sum of the signal received at the nearer sensor and the signal received at the farther sensor and noise. The TFRM algorithm works in the time-frequency domain and seeks to perform successive source cancellation in the received burst. The key to performing source cancellation is to estimate the ratio in which the sources combine and this ratio is estimated by means of taking a windowed mean of the ratio of the spectrograms of any two pulses in the received burst. The variance of the mean function helps identify single-source regions and regions in which the sources mix.
The performance of the TFRM algorithm is evaluated in the presence of noise and is compared against the Cramer-Rao lower bound. It is found that the variance of the estimates returned by the estimator diverge from the predictions of the Cramer-Rao inequality as the farther sensor is moved farther away. Conversely, the estimator becomes more reliable as the farther sensor is moved closer.
The time-delay estimates obtained from the TFRM algorithm are used for source localization. The problem of finding the source reduces to finding the locus of points such that the difference of its distances to the two sensors equals the time delay. By moving the pair of sensors to a different location, or having a second time delay sensor, an exact location for the source can be determined by finding the point of intersection of the two loci.
The TFRM method does not rely on a priori information about the signal. It is
applicable to OFDM sources as well as sinusoidal and chirp sources.
Advisors/Committee Members: Beex, Aloysius A. (committeechair), Buehrer, R. Michael (committee member), Reed, Jeffrey Hugh (committee member).
Subjects/Keywords: Sub-sample delays; sensors; source localization; time-frequency ratio of mixtures (TFRM); chirplet signal decomposition.
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APA (6th Edition):
Bettadapura, R. S. (2014). Echo Delay Estimation to Aid Source Localization in Noisy Environments. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/50517
Chicago Manual of Style (16th Edition):
Bettadapura, Raghuprasad Shivatejas. “Echo Delay Estimation to Aid Source Localization in Noisy Environments.” 2014. Masters Thesis, Virginia Tech. Accessed February 28, 2021.
http://hdl.handle.net/10919/50517.
MLA Handbook (7th Edition):
Bettadapura, Raghuprasad Shivatejas. “Echo Delay Estimation to Aid Source Localization in Noisy Environments.” 2014. Web. 28 Feb 2021.
Vancouver:
Bettadapura RS. Echo Delay Estimation to Aid Source Localization in Noisy Environments. [Internet] [Masters thesis]. Virginia Tech; 2014. [cited 2021 Feb 28].
Available from: http://hdl.handle.net/10919/50517.
Council of Science Editors:
Bettadapura RS. Echo Delay Estimation to Aid Source Localization in Noisy Environments. [Masters Thesis]. Virginia Tech; 2014. Available from: http://hdl.handle.net/10919/50517
Virginia Tech
7.
Rao, Raghunandan M.
Perspectives of Jamming, Mitigation and Pattern Adaptation of OFDM Pilot Signals for the Evolution of Wireless Networks.
Degree: MS, Electrical and Computer Engineering, 2016, Virginia Tech
URL: http://hdl.handle.net/10919/77485
► Wireless communication networks have evolved continuously over the last four decades in order to meet the traffic and security requirements due to the ever-increasing amount…
(more)
▼ Wireless communication networks have evolved continuously over the last four decades in order to meet the traffic and security requirements due to the ever-increasing amount of traffic. However this increase is projected to be massive for the fifth generation of wireless networks (5G), with a targeted capacity enhancement of 1000× w.
r.t. 4G networks. This enhanced capacity is possible by a combination of major approaches (a) overhaul of some parts and (b) elimination of overhead and redundancies of the current 4G. In this work we focus on OFDM reference signal or pilot tones, which are used for channel estimation, link adaptation and other crucial functions in Long-Term Evolution (LTE). We investigate two aspects of pilot signals pertaining to its evolution - (a) impact of targeted interference on pilots and its mitigation and (b) adaptation of pilot patterns to match the channel conditions of the user.
We develop theoretical models that accurately quantify the performance degradation at the user’s receiver in the presence of a multi-tone pilot jammer. We develop and evaluate mitigation algorithms to mitigate power constrained multi-tone pilot jammers in SISO- and full rank spatial multiplexing MIMO-OFDM systems. Our results show that the channel estimation performance can be restored even in the presence of a strong pilot jammer. We also show that full rank spatial multiplexing in the presence of a synchronized pilot jammer (transmitting on pilot locations only) is possible when the channel is flat between two pilot locations in either time or frequency.
We also present experimental results of multi-tone broadcast pilot jamming (Jamming of Cell Specific Reference Signal) in the LTE downlink. Our results show that full-band jamming of pilots needs 5 dB less power than jamming the entire downlink signal, in order to cause Denial of Service (DoS) to the users. In addition to this, we have identified and demonstrated a previously unreported issue with LTE termed ‘Channel Quality Indicator (CQI) Spoofing’. In this scenario, the attacker tricks the user terminal into thinking that the channel quality is good, by transmitting interference transmission only on the data locations, while deliberately avoiding the pilots. This jamming strategy leverages the dependence of the adaptive modulation and coding (AMC) schemes on the CQI estimate in LTE.
Lastly, we investigate the idea of pilot pattern adaptation for SISO- and spatial multiplexing MIMO-OFDM systems. We present a generic heuristic algorithm to predict the optimal pilot spacing and power in a nonstationary doubly selective channel (channel fading in both time and frequency). The algorithm fits estimated channel statistics to stored codebook channel profiles and uses it to maximize the upper bound on the constrained capacity. We demonstrate up to a 30% improvement in ergodic capacity using our algorithm and describe ways to minimize feedback requirements while adapting pilot patterns in multi-band carrier aggregation systems. We conclude this work by identifying…
Advisors/Committee Members: Reed, Jeffrey Hugh (committeechair), Marojevic, Vuk (committee member), Buehrer, R. Michael (committee member).
Subjects/Keywords: Pilot Pattern Adaptation; OFDM systems; Long-Term Evolution (LTE)/LTE Cell-Specific Refe; Multi-tone Pilot Jamming; Channel Quality Indicator (CQI) Spoofing; Mitigation
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APA (6th Edition):
Rao, R. M. (2016). Perspectives of Jamming, Mitigation and Pattern Adaptation of OFDM Pilot Signals for the Evolution of Wireless Networks. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/77485
Chicago Manual of Style (16th Edition):
Rao, Raghunandan M. “Perspectives of Jamming, Mitigation and Pattern Adaptation of OFDM Pilot Signals for the Evolution of Wireless Networks.” 2016. Masters Thesis, Virginia Tech. Accessed February 28, 2021.
http://hdl.handle.net/10919/77485.
MLA Handbook (7th Edition):
Rao, Raghunandan M. “Perspectives of Jamming, Mitigation and Pattern Adaptation of OFDM Pilot Signals for the Evolution of Wireless Networks.” 2016. Web. 28 Feb 2021.
Vancouver:
Rao RM. Perspectives of Jamming, Mitigation and Pattern Adaptation of OFDM Pilot Signals for the Evolution of Wireless Networks. [Internet] [Masters thesis]. Virginia Tech; 2016. [cited 2021 Feb 28].
Available from: http://hdl.handle.net/10919/77485.
Council of Science Editors:
Rao RM. Perspectives of Jamming, Mitigation and Pattern Adaptation of OFDM Pilot Signals for the Evolution of Wireless Networks. [Masters Thesis]. Virginia Tech; 2016. Available from: http://hdl.handle.net/10919/77485
Virginia Tech
8.
Taylor, Ryan Charles.
Received Signal Strength-Based Localization of Non-Collaborative Emitters in the Presence of Correlated Shadowing.
Degree: MS, Electrical Engineering, 2013, Virginia Tech
URL: http://hdl.handle.net/10919/23078
► RSS-based localization is a promising solution for estimating the position of a non-collaborative emitter using a network of collaborative sensors. This paper examines RSS-based localization…
(more)
▼ RSS-based localization is a promising solution for estimating the position of a non-collaborative emitter using a network of collaborative sensors. This paper examines RSS-based localization and differential RSS (DRSS) localization in the presence of correlated shadowing with no knowledge of the emitter\'s reference power. A new non-linear least squares (NLS) DRSS location estimator that uses correlated shadowing information to improve performance is introduced. The existing maximum likelihood (ML) estimator and Cram\\é
r Rao lower bound (CRLB) for RSS-based localization given do not account for correlated shadowing. This paper presents a new ML estimator and CRLB for RSS-based localization that account for spatially correlated shadowing and imperfect knowledge of the emitter\'s reference power. The performance of the ML estimator is compared to the CRLB under different simulation conditions. The ML estimator is shown to be biased when the number of sensors is small or the shadowing variance is large. The effects of correlated shadowing on an RSS-based location estimator are thoroughly examined. It is proven that an increase in correlated shadowing will improve the accuracy of an RSS-based location estimator. It is also demonstrated that the ideal sensor geometry which minimizes the average error becomes more compact as correlation is increased. A geometric dilution of precision (GDOP) formulation is derived that provides a metric for the effect of the position of the sensors and emitter on the location estimator performance. A measurement campaign is conducted that characterizes the path loss at 3.4 GHz. The measurements are compared to the log-distance model. The errors between the model and the measurements, which should theoretically be Gaussian, have a Kurtosis value of 1.31. The errors were determined to be spatially correlated with an average correlation coefficient of 0.5 at a distance of 160 meters. The performance of the location estimators in simulation is compared to the performance using measurements from the measurement campaign. The performance is very similar, with the largest difference between the simulated and actual results in the ML estimator. In both cases, the new NLS DRSS estimator outperformed the other estimators and achieved the CRLB.
Advisors/Committee Members: McGwier, Robert W. (committeechair), Beex, Aloysius A. (committee member), Buehrer, R. Michael (committee member).
Subjects/Keywords: Received Signal Strength; Differential Received Signal Strength; Localization; Cram' er Rao Lower Bound; Correlated Shadowing
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APA (6th Edition):
Taylor, R. C. (2013). Received Signal Strength-Based Localization of Non-Collaborative Emitters in the Presence of Correlated Shadowing. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/23078
Chicago Manual of Style (16th Edition):
Taylor, Ryan Charles. “Received Signal Strength-Based Localization of Non-Collaborative Emitters in the Presence of Correlated Shadowing.” 2013. Masters Thesis, Virginia Tech. Accessed February 28, 2021.
http://hdl.handle.net/10919/23078.
MLA Handbook (7th Edition):
Taylor, Ryan Charles. “Received Signal Strength-Based Localization of Non-Collaborative Emitters in the Presence of Correlated Shadowing.” 2013. Web. 28 Feb 2021.
Vancouver:
Taylor RC. Received Signal Strength-Based Localization of Non-Collaborative Emitters in the Presence of Correlated Shadowing. [Internet] [Masters thesis]. Virginia Tech; 2013. [cited 2021 Feb 28].
Available from: http://hdl.handle.net/10919/23078.
Council of Science Editors:
Taylor RC. Received Signal Strength-Based Localization of Non-Collaborative Emitters in the Presence of Correlated Shadowing. [Masters Thesis]. Virginia Tech; 2013. Available from: http://hdl.handle.net/10919/23078
Virginia Tech
9.
Xiao, Yao.
Vehicle Detection in Deep Learning.
Degree: MS, Computer Engineering, 2019, Virginia Tech
URL: http://hdl.handle.net/10919/91375
► Computer vision techniques are becoming increasingly popular. For example, face recognition is used to help police find criminals, vehicle detection is used to prevent drivers…
(more)
▼ Computer vision techniques are becoming increasingly popular. For example, face recognition is used to help police find criminals, vehicle detection is used to prevent drivers from serious traffic accidents, and written word recognition is used to convert written words into printed words. With the rapid development of vehicle detection given the use of deep learning techniques, there are still concerns about the performance of state-of-the art vehicle detection techniques. For example, state-of-the-art vehicle detectors are restricted by the large variation of scales. People working on vehicle detection are developing techniques to solve this problem. This thesis proposes an advanced vehicle detection model, utilizing deep learning techniques to detect the potential objects’ information.
Advisors/Committee Members: Abbott, Amos L. (committeechair), Buehrer, R. Michael (committee member), Pillis, Daniel (committee member).
Subjects/Keywords: Vehicle Detection; Deep Learning; Convolutional Neural Networks; Image Processing; Architecture Design
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APA (6th Edition):
Xiao, Y. (2019). Vehicle Detection in Deep Learning. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/91375
Chicago Manual of Style (16th Edition):
Xiao, Yao. “Vehicle Detection in Deep Learning.” 2019. Masters Thesis, Virginia Tech. Accessed February 28, 2021.
http://hdl.handle.net/10919/91375.
MLA Handbook (7th Edition):
Xiao, Yao. “Vehicle Detection in Deep Learning.” 2019. Web. 28 Feb 2021.
Vancouver:
Xiao Y. Vehicle Detection in Deep Learning. [Internet] [Masters thesis]. Virginia Tech; 2019. [cited 2021 Feb 28].
Available from: http://hdl.handle.net/10919/91375.
Council of Science Editors:
Xiao Y. Vehicle Detection in Deep Learning. [Masters Thesis]. Virginia Tech; 2019. Available from: http://hdl.handle.net/10919/91375
Virginia Tech
10.
Agrawal, Ambuj.
Implementation of Application Layer Protocol for an Active RFID System.
Degree: MS, Electrical and Computer Engineering, 2011, Virginia Tech
URL: http://hdl.handle.net/10919/34961
► The emerging technology of active RFID tags has strong potential in the areas of real time health monitoring, sorting of cargo, and large scale inventory…
(more)
▼ The emerging technology of active RFID tags has strong potential in the areas of real time health monitoring, sorting of cargo, and large scale inventory management because of their longer communication range and larger data storage capacity. The market of active RFID is growing very rapidly and therefore there has been an increase in the number of companies engaging in this field. But very often it is found that the products available in the market are not always suited to the application at hand. To overcome this problem, off the shelf active RFID products which were reconfigurable and followed a standard PHY and MAC layer protocol were used for this work. By reprogramming the application layer protocol of the RFID hardware, these devices were made suitable for the desired application. This also allowed the RFID tags to extend their functionality by interfacing extra modules with themselves. The work presented in this thesis describes the way in which the microcontroller on board the active RFID tags and readers can be programmed so that the functionality of the RFID hardware can be changed as per requirements. It also shows that extra modules can be added to the tag by successfully interfacing an accelerometer module with the tag.
Advisors/Committee Members: Manteghi, Majid (committeechair), Schaumont, Patrick Robert (committee member), Buehrer, R. Michael (committeecochair).
Subjects/Keywords: TagSense Inc.; accelerometer; CC2591; CC2520; ATmega328P
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APA (6th Edition):
Agrawal, A. (2011). Implementation of Application Layer Protocol for an Active RFID System. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/34961
Chicago Manual of Style (16th Edition):
Agrawal, Ambuj. “Implementation of Application Layer Protocol for an Active RFID System.” 2011. Masters Thesis, Virginia Tech. Accessed February 28, 2021.
http://hdl.handle.net/10919/34961.
MLA Handbook (7th Edition):
Agrawal, Ambuj. “Implementation of Application Layer Protocol for an Active RFID System.” 2011. Web. 28 Feb 2021.
Vancouver:
Agrawal A. Implementation of Application Layer Protocol for an Active RFID System. [Internet] [Masters thesis]. Virginia Tech; 2011. [cited 2021 Feb 28].
Available from: http://hdl.handle.net/10919/34961.
Council of Science Editors:
Agrawal A. Implementation of Application Layer Protocol for an Active RFID System. [Masters Thesis]. Virginia Tech; 2011. Available from: http://hdl.handle.net/10919/34961
Virginia Tech
11.
Jewell, Victoria Rose.
Use of GIS in Radio Frequency and Positioning Applications.
Degree: MS, Electrical Engineering, 2014, Virginia Tech
URL: http://hdl.handle.net/10919/50499
► GIS are geoprocessing programs that are commonly used to store and perform calculations on terrain data, maps, and other geospatial data. GIS offers the latest…
(more)
▼ GIS are geoprocessing programs that are commonly used to store and perform calculations on terrain data, maps, and other geospatial data. GIS offers the latest terrain and building data as well as tools to process this data. This thesis considers three applications of GIS data and software: a Large Scale Radio Frequency (RF) Model, a Medium Scale RF Model, and Indoor Positioning. The Large Scale RF Model estimates RF propagation using the latest terrain data supplied in GIS for frequencies ranging from 500 MHz to 5 GHz. The Medium Scale RF Model incorporates GIS building data to model WiFi systems at 2.4 GHz for a range of up to 300m. Both Models can be used by city planners and government offcials, who commonly use GIS for other geospatial and geostatistical information, to plan wireless broadband systems using GIS. An Indoor Positioning Experiment is also conducted to see if apriori knowledge of a building size, location, shape, and number of floors can aid in the RF geolocation of a target indoors. The experiment shows that correction of a target to within a building's boundaries reduces the location error of the target, and the vertical error is reduced by nearly half.
Advisors/Committee Members: Buehrer, R. Michael (committeechair), Reed, Jeffrey Hugh (committee member), Sforza, Peter M. (committee member).
Subjects/Keywords: RF Propagation; GIS; Indoor Positioning
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APA (6th Edition):
Jewell, V. R. (2014). Use of GIS in Radio Frequency and Positioning Applications. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/50499
Chicago Manual of Style (16th Edition):
Jewell, Victoria Rose. “Use of GIS in Radio Frequency and Positioning Applications.” 2014. Masters Thesis, Virginia Tech. Accessed February 28, 2021.
http://hdl.handle.net/10919/50499.
MLA Handbook (7th Edition):
Jewell, Victoria Rose. “Use of GIS in Radio Frequency and Positioning Applications.” 2014. Web. 28 Feb 2021.
Vancouver:
Jewell VR. Use of GIS in Radio Frequency and Positioning Applications. [Internet] [Masters thesis]. Virginia Tech; 2014. [cited 2021 Feb 28].
Available from: http://hdl.handle.net/10919/50499.
Council of Science Editors:
Jewell VR. Use of GIS in Radio Frequency and Positioning Applications. [Masters Thesis]. Virginia Tech; 2014. Available from: http://hdl.handle.net/10919/50499
Virginia Tech
12.
Tait, Daniel Beale.
Electromagnetic Vector-Sensor Direction-of-Arrival Estimation in the Presence of Interference.
Degree: MS, Electrical Engineering, 2020, Virginia Tech
URL: http://hdl.handle.net/10919/99961
► Electromagnetic vector-sensors are specialized sensors capable of capturing the full electromagnetic field vectors at a single point in space. Direction-of-arrival (DOA) estimation is the problem…
(more)
▼ Electromagnetic vector-sensors are specialized sensors capable of capturing the full electromagnetic field vectors at a single point in space. Direction-of-arrival (DOA) estimation is the problem of estimating the spatial-angular parameters of one or more wavefronts impinging on an array. For a single electromagnetic vector-sensor, the array elements are not spatially displaced, but it is still possible to estimate the direction-of-arrival through the Poynting vector, which relates the electric and magnetic field vectors to the direction of propagation of an electromagnetic wave. Although direction-of-arrival estimation is a well-established area of research, there is limited discussion in the open literature regarding signal-selective DOA estimation in the presence of interference for a single electromagnetic vector-sensor. This research investigates this problem and discusses how the high-resolution Uni-Vector-Sensor-ESPRIT (UVS-ESPRIT) algorithm may be applied to non-deterministic sources. ESPRIT based algorithms capable of selectively estimating the source DOA are formulated based on the cyclostationarity and higher-order statistics of the sources, which are approaches known to be robust to interference. The approach based on higher-order statistics is also robust to spatially colored noise and is capable of estimating the DOA of more sources than sensor elements. The formulation of the UVS-ESPRIT for higher-order statistics relies on the application of the independent component analysis algorithm JADE, an unsupervised learning technique. Overall, this research investigates signal-selective direction-of-arrival estimation using an ESPRIT-based algorithm for a single electromagnetic vector-sensor.
Advisors/Committee Members: Buehrer, R. Michael (committeechair), Dhillon, Harpreet Singh (committee member), Ellingson, Steven W. (committee member).
Subjects/Keywords: Direction-of-Arrival Estimation; Array Signal Processing; ESPRIT; Independent Component Analysis; Cyclostationarity; Higher-Order Statistics
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APA (6th Edition):
Tait, D. B. (2020). Electromagnetic Vector-Sensor Direction-of-Arrival Estimation in the Presence of Interference. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/99961
Chicago Manual of Style (16th Edition):
Tait, Daniel Beale. “Electromagnetic Vector-Sensor Direction-of-Arrival Estimation in the Presence of Interference.” 2020. Masters Thesis, Virginia Tech. Accessed February 28, 2021.
http://hdl.handle.net/10919/99961.
MLA Handbook (7th Edition):
Tait, Daniel Beale. “Electromagnetic Vector-Sensor Direction-of-Arrival Estimation in the Presence of Interference.” 2020. Web. 28 Feb 2021.
Vancouver:
Tait DB. Electromagnetic Vector-Sensor Direction-of-Arrival Estimation in the Presence of Interference. [Internet] [Masters thesis]. Virginia Tech; 2020. [cited 2021 Feb 28].
Available from: http://hdl.handle.net/10919/99961.
Council of Science Editors:
Tait DB. Electromagnetic Vector-Sensor Direction-of-Arrival Estimation in the Presence of Interference. [Masters Thesis]. Virginia Tech; 2020. Available from: http://hdl.handle.net/10919/99961
Virginia Tech
13.
Emenonye, Don-Roberts Ugochukwu.
Application of Machine Learning to Multi Antenna Transmission and Machine Type Resource Allocation.
Degree: MS, Electrical Engineering, 2020, Virginia Tech
URL: http://hdl.handle.net/10919/99956
► Wireless communication systems is a well researched area of engineering that has continually evolved over the past decades. This constant evolution and development has led…
(more)
▼ Wireless communication systems is a well researched area of engineering that has continually
evolved over the past decades. This constant evolution and development has led to well
formulated theoretical baselines in terms of reliability and efficiency. This two part thesis
investigates the possibility of improving these wireless systems with machine learning.
First, with the goal of designing more resilient codes for transmission, we propose to redesign
the transmit and receive blocks of the physical layer. We focus on jointly optimizing the
transmit and receive blocks to produce a set of transmit codes that are resilient to channel
impairments. We compare our results to the current conventional codes for various transmit
and receive antenna configuration.
The second part of this work investigates the possibility of designing a distributed multi-access scheme for machine type devices. In this scheme, MTDs pseudo-randomly transmit
their data by randomly selecting time slots. This results in the possibility of a large number
of collisions occurring in the duration of these slots. To alleviate the resulting congestion,
we employ a heterogeneous network and investigate the optimal MTD-BS association which
minimizes the long term congestion experienced in the overall network. Our results show
that we can derive the optimal MTD-BS algorithm when the number of MTDs is less than
the total number of slots.
Advisors/Committee Members: Buehrer, R. Michael (committeechair), Dietrich, Carl B. (committeechair), Dhillon, Harpreet Singh (committee member).
Subjects/Keywords: Machine Type Communication; Space Time Block Coding; Deep Learning; Reinforcement Learning
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APA (6th Edition):
Emenonye, D. U. (2020). Application of Machine Learning to Multi Antenna Transmission and Machine Type Resource Allocation. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/99956
Chicago Manual of Style (16th Edition):
Emenonye, Don-Roberts Ugochukwu. “Application of Machine Learning to Multi Antenna Transmission and Machine Type Resource Allocation.” 2020. Masters Thesis, Virginia Tech. Accessed February 28, 2021.
http://hdl.handle.net/10919/99956.
MLA Handbook (7th Edition):
Emenonye, Don-Roberts Ugochukwu. “Application of Machine Learning to Multi Antenna Transmission and Machine Type Resource Allocation.” 2020. Web. 28 Feb 2021.
Vancouver:
Emenonye DU. Application of Machine Learning to Multi Antenna Transmission and Machine Type Resource Allocation. [Internet] [Masters thesis]. Virginia Tech; 2020. [cited 2021 Feb 28].
Available from: http://hdl.handle.net/10919/99956.
Council of Science Editors:
Emenonye DU. Application of Machine Learning to Multi Antenna Transmission and Machine Type Resource Allocation. [Masters Thesis]. Virginia Tech; 2020. Available from: http://hdl.handle.net/10919/99956
Virginia Tech
14.
Krishnan, Shankar.
Spatio-Temporal Correlation in the Performance of Cache-Enabled Cellular Networks.
Degree: MS, Electrical Engineering, 2016, Virginia Tech
URL: http://hdl.handle.net/10919/71809
► Exact characterization and performance analysis of wireless networks should incorporate dependencies or correlations in space and time, i.e., study how the network performance varies spatially…
(more)
▼ Exact characterization and performance analysis of wireless networks should incorporate dependencies or correlations in space and time, i.e., study how the network performance varies spatially and temporally while having prior information about the performance at previous locations and time slots. This spatio-temporal correlation in wireless networks is usually characterized by studying metrics such as joint coverage probability at two spatial locations/time slots or spatio-temporal correlation coefficient. While developing models and analytical expressions for studying the two extreme cases of spatio-temoral correlation - i) uncorrelated scenario and ii) fully correlated scenario are easier, studying the intermediate case is non-trivial. In this thesis, we develop realistic and tractable analytical frameworks based on random spatial models (using tools from stochastic geometry) for modeling and analysis of correlation in cellular networks.
With an ever increasing data demand, caching popular content in the storage of small cells (small cell caching) or the memory of user devices (device caching) is seen as a good alternative to offload demand from macro base stations and reduce backhaul loads. After providing generic results for traditional cellular networks, we study two applications exploiting spatio-temporal correlation in cache-enabled cellular networks. First, we determine the optimal cache content to be stored in the cache of a small cell network that maximizes the hit probability and minimizes the reception energy for the two extreme cases of correlation. Our results concretely demonstrate that the optimal cache contents are significantly different for the two correlation scenarios, thereby indicating the need of correlation-aware caching strategies. Second, we look at a distributed caching scenario in user devices and show that spatio-temporal correlation (user mobility) can be exploited to improve the network performance (in terms of coverage probability and local delay) significantly.
Advisors/Committee Members: Dhillon, Harpreet Singh (committeechair), Saad, Walid (committeechair), Buehrer, R. Michael (committee member).
Subjects/Keywords: Stochastic Geometry; Correlation; Caching; Mobility; Poisson point process
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APA (6th Edition):
Krishnan, S. (2016). Spatio-Temporal Correlation in the Performance of Cache-Enabled Cellular Networks. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/71809
Chicago Manual of Style (16th Edition):
Krishnan, Shankar. “Spatio-Temporal Correlation in the Performance of Cache-Enabled Cellular Networks.” 2016. Masters Thesis, Virginia Tech. Accessed February 28, 2021.
http://hdl.handle.net/10919/71809.
MLA Handbook (7th Edition):
Krishnan, Shankar. “Spatio-Temporal Correlation in the Performance of Cache-Enabled Cellular Networks.” 2016. Web. 28 Feb 2021.
Vancouver:
Krishnan S. Spatio-Temporal Correlation in the Performance of Cache-Enabled Cellular Networks. [Internet] [Masters thesis]. Virginia Tech; 2016. [cited 2021 Feb 28].
Available from: http://hdl.handle.net/10919/71809.
Council of Science Editors:
Krishnan S. Spatio-Temporal Correlation in the Performance of Cache-Enabled Cellular Networks. [Masters Thesis]. Virginia Tech; 2016. Available from: http://hdl.handle.net/10919/71809
Virginia Tech
15.
Patterson, Cameron Webster.
An Economic Model of Subscriber Offloading Between Mobile Network Operators and a WLAN Operator.
Degree: MS, Electrical Engineering, 2014, Virginia Tech
URL: http://hdl.handle.net/10919/50660
► With increasing mobile data demand there is a push towards heterogeneous networks. Small-scale operators (SSOs) of WLANs are becoming more prevalent, while Mobile Network Operators…
(more)
▼ With increasing mobile data demand there is a push towards heterogeneous networks. Small-scale operators (SSOs) of WLANs are becoming more prevalent, while Mobile Network Operators (MNOs) seek an outlet for their customers' data usage. These conditions prompt the need for an effective relationship between the two parties for the purpose of offloading cellular data traffic to WLANs in a way that is economically beneficial to all involved. This thesis presents a model of such a relationship, in which the SSO sets a strategic offloading price per subscriber and several MNOs can choose how many subscribers they want to offload in order to minimize their costs. We determine the optimal offloading price, identify how the SSO incorporates its own network's quality of service (QoS) into its price decision, and examine the way in which the MNOs' cost structures affect their ability to offload. This model can be applied by both MNOs and SSOs to make informed network deployment decisions, even before engaging in an offloading relationship.
Advisors/Committee Members: MacKenzie, Allen B. (committeechair), Silva, Luiz A. (committee member), Buehrer, R. Michael (committee member).
Subjects/Keywords: Cellular; WLAN; Wi-Fi; heterogeneous wireless network; pricing; economic model; optimization
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APA (6th Edition):
Patterson, C. W. (2014). An Economic Model of Subscriber Offloading Between Mobile Network Operators and a WLAN Operator. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/50660
Chicago Manual of Style (16th Edition):
Patterson, Cameron Webster. “An Economic Model of Subscriber Offloading Between Mobile Network Operators and a WLAN Operator.” 2014. Masters Thesis, Virginia Tech. Accessed February 28, 2021.
http://hdl.handle.net/10919/50660.
MLA Handbook (7th Edition):
Patterson, Cameron Webster. “An Economic Model of Subscriber Offloading Between Mobile Network Operators and a WLAN Operator.” 2014. Web. 28 Feb 2021.
Vancouver:
Patterson CW. An Economic Model of Subscriber Offloading Between Mobile Network Operators and a WLAN Operator. [Internet] [Masters thesis]. Virginia Tech; 2014. [cited 2021 Feb 28].
Available from: http://hdl.handle.net/10919/50660.
Council of Science Editors:
Patterson CW. An Economic Model of Subscriber Offloading Between Mobile Network Operators and a WLAN Operator. [Masters Thesis]. Virginia Tech; 2014. Available from: http://hdl.handle.net/10919/50660
Virginia Tech
16.
Jakubisin, Daniel J.
Array Processing for Mobile Wireless Communication in the 60 GHz Band.
Degree: MS, Electrical and Computer Engineering, 2012, Virginia Tech
URL: http://hdl.handle.net/10919/31130
► In 2001, the Federal Communications Commission made available a large block of spectrum known as the 60 GHz band. The 60 GHz band is attractive…
(more)
▼ In 2001, the Federal Communications Commission made available a large block of spectrum known as the 60 GHz band. The 60 GHz band is attractive because it provides the opportunity of multi-Gbps data rates with unlicensed commercial use. One of the main challenges facing the use of this band is poor propagation characteristics including high path loss and strong attenuation due to oxygen absorption. Antenna arrays have been proposed as a means of combating these effects. This thesis provides an analysis of array processing for communication systems operating in the 60 GHz band. Based on measurement campaigns at 60 GHz, deterministic modeling of the channel through ray tracing is proposed. We conduct a site-specific study using ray tracing to model an outdoor and an indoor environment on the
Virginia Tech campus. Because arrays are required for antenna gain and adaptability, we explore the use of arrays as a form of equalization in the presence of channel-induced intersymbol interference. The first contribution of this thesis is to establish the expected performance achieved by arrays in the outdoor environment. The second contribution is to analyze the performance of adaptive algorithms applied to array processing in mobile indoor and outdoor environments.
Advisors/Committee Members: Ellingson, Steven W. (committee member), da Silva, Claudio R. C. M. (committeecochair), Buehrer, R. Michael (committeecochair).
Subjects/Keywords: communications; array processing; 60 GHz band; channel estimation; tracking; convergence; coherence time
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APA (6th Edition):
Jakubisin, D. J. (2012). Array Processing for Mobile Wireless Communication in the 60 GHz Band. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/31130
Chicago Manual of Style (16th Edition):
Jakubisin, Daniel J. “Array Processing for Mobile Wireless Communication in the 60 GHz Band.” 2012. Masters Thesis, Virginia Tech. Accessed February 28, 2021.
http://hdl.handle.net/10919/31130.
MLA Handbook (7th Edition):
Jakubisin, Daniel J. “Array Processing for Mobile Wireless Communication in the 60 GHz Band.” 2012. Web. 28 Feb 2021.
Vancouver:
Jakubisin DJ. Array Processing for Mobile Wireless Communication in the 60 GHz Band. [Internet] [Masters thesis]. Virginia Tech; 2012. [cited 2021 Feb 28].
Available from: http://hdl.handle.net/10919/31130.
Council of Science Editors:
Jakubisin DJ. Array Processing for Mobile Wireless Communication in the 60 GHz Band. [Masters Thesis]. Virginia Tech; 2012. Available from: http://hdl.handle.net/10919/31130
Virginia Tech
17.
Kozy, Mark Alexander.
Creation of a Cognitive Radar with Machine Learning: Simulation and Implementation.
Degree: MS, Electrical Engineering, 2019, Virginia Tech
URL: http://hdl.handle.net/10919/89948
► In this thesis we develop methods for creating and implementing algorithms for a cognitive radar. A cognitive radar is a radar that is able to…
(more)
▼ In this thesis we develop methods for creating and implementing algorithms for a cognitive radar. A cognitive radar is a radar that is able to sense its environment and avoid any other communication system that may interfere with its operation. We discuss the predictive methods we used to sense and avoid the other communication systems as well as how we implemented this using a software defined radar based on the USRP X310.
Advisors/Committee Members: Buehrer, R. Michael (committeechair), Reed, Jeffrey H. (committee member), Ruohoniemi, John Michael (committee member).
Subjects/Keywords: Cognitive radar; machine learning; reinforcement learning; tracking radar; software defined radio
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APA (6th Edition):
Kozy, M. A. (2019). Creation of a Cognitive Radar with Machine Learning: Simulation and Implementation. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/89948
Chicago Manual of Style (16th Edition):
Kozy, Mark Alexander. “Creation of a Cognitive Radar with Machine Learning: Simulation and Implementation.” 2019. Masters Thesis, Virginia Tech. Accessed February 28, 2021.
http://hdl.handle.net/10919/89948.
MLA Handbook (7th Edition):
Kozy, Mark Alexander. “Creation of a Cognitive Radar with Machine Learning: Simulation and Implementation.” 2019. Web. 28 Feb 2021.
Vancouver:
Kozy MA. Creation of a Cognitive Radar with Machine Learning: Simulation and Implementation. [Internet] [Masters thesis]. Virginia Tech; 2019. [cited 2021 Feb 28].
Available from: http://hdl.handle.net/10919/89948.
Council of Science Editors:
Kozy MA. Creation of a Cognitive Radar with Machine Learning: Simulation and Implementation. [Masters Thesis]. Virginia Tech; 2019. Available from: http://hdl.handle.net/10919/89948
Virginia Tech
18.
Overfield, Jacob Ivan.
Impact of MIMO Transmission on CAF-Based Geolocation.
Degree: MS, Electrical Engineering, 2013, Virginia Tech
URL: http://hdl.handle.net/10919/51857
► The Cross Ambiguity Function (CAF) is often used for passive geolocation of an emitter based on the time difference of arrival (TDOA) and frequency difference…
(more)
▼ The Cross Ambiguity Function (CAF) is often used for passive geolocation of an emitter based on the time difference of arrival (TDOA) and frequency difference of arrival (FDOA) of the received signals. CAF performance has been thoroughly investigated in regards to traditional single-input single-output (SISO) signals. Little is known about how the CAF will respond to signals from multiple-input multiple-output (MIMO) systems which utilize multiple antennas. This thesis focuses on characterizing the CAF's magnitude distribution in order to determine the probability of correctly determining the correct TDOA/FDOA bin, and the resulting impact on geolocation. The received signals are studied in the presence of additive white Gaussian noise (AWGN) as well as multi-channel propagation effects such as phase ambiguities and offsets due to multi-antenna transmission.
Two and four transmit antennas using either a form of spatial multiplexing or space-time block coding are the focus of this work because they are mostly commonly found in currently deployed communication systems. The effects of these transmit schemes are studied with respect to TDOA/FDOA error and the resulting position error. The analysis is performed using a detection theory framework as opposed to estimation theory in order to empha- size the impact of MIMO transmission on determining the correct TDOA/FDOA bin. A simple method using the CAF magnitude as a decision statistic is also presented so that TDOA/FDOA errors can be detected and filtered in an attempt to improve positioning estimates.
Advisors/Committee Members: Buehrer, R. Michael (committeechair), Ruohoniemi, John Michael (committee member), Reed, Jeffrey Hugh (committee member).
Subjects/Keywords: MIMO; SISO; CAF; Cross Ambiguity Function; Complex Ambiguity Function; Geolocation; TDOA; Differential Delay; FDOA
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APA (6th Edition):
Overfield, J. I. (2013). Impact of MIMO Transmission on CAF-Based Geolocation. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/51857
Chicago Manual of Style (16th Edition):
Overfield, Jacob Ivan. “Impact of MIMO Transmission on CAF-Based Geolocation.” 2013. Masters Thesis, Virginia Tech. Accessed February 28, 2021.
http://hdl.handle.net/10919/51857.
MLA Handbook (7th Edition):
Overfield, Jacob Ivan. “Impact of MIMO Transmission on CAF-Based Geolocation.” 2013. Web. 28 Feb 2021.
Vancouver:
Overfield JI. Impact of MIMO Transmission on CAF-Based Geolocation. [Internet] [Masters thesis]. Virginia Tech; 2013. [cited 2021 Feb 28].
Available from: http://hdl.handle.net/10919/51857.
Council of Science Editors:
Overfield JI. Impact of MIMO Transmission on CAF-Based Geolocation. [Masters Thesis]. Virginia Tech; 2013. Available from: http://hdl.handle.net/10919/51857
Virginia Tech
19.
McDermott, Kevin Patrick.
On the Improvement of Positioning in LTE with Collaboration and Pressure Sensors.
Degree: MS, Electrical Engineering, 2015, Virginia Tech
URL: http://hdl.handle.net/10919/54019
► The ability to find the location of a mobile user has become of utmost importance. The demands of first responders necessitates the ability to accurately…
(more)
▼ The ability to find the location of a mobile user has become of utmost importance. The demands of first responders necessitates the ability to accurately identify the location of an individual who is calling for help. Their response times are directly influenced by the ability to locate the caller. Thus, applications such as Enhanced 911 and other location-based services warrant the ability to quickly and accurately calculate location. The FCC has also put in place a timeline for indoor location accuracy requirements that must be met by the mobile communications service providers. In order to meet these requirements, there are many means of performing indoor geolocation that require research; in this thesis two specific methods of identifying the location of a user will be investigated.
In the first part, the indoor localization of a target, whose exact location is unknown, in a LTE network is studied. In this problem the time difference of arrival of the LTE uplink signals sent from the target to an observer are used as the means to estimate the target position. The two-dimensional location of a user is then estimated through the use of a nonlinear least-squares algorithm. To improve this approach, a cooperative localization technique in uplink LTE is proposed in which the User Equipment (UE) communicates with base stations as well as other handsets. Through simulated results it is shown that utilizing collaboration can improve location estimation and outperform non-collaborative localization.
In the second part, the indoor localization of a target, focusing on its third dimension or elevation, is studied through the use of barometric pressure sensors in mobile handsets. Finding the third dimension of location, or the correct height above the ground level which equates to the floor in a building that a UE is on, cannot be performed with two-dimensional measurement models. For this problem, the pressure sensors are used to accurately find an immediate pressure measurement and allow for the altitude of a handset to be calculated. This altitude can be translated into an estimation for a specific floor of a building given the use of a ground floor pressure reference. Through simulation results it is then shown that the accuracy of third dimension or indoor-floor localization can be improved with the use of collaborative pressure sensors of other mobile handsets.
Advisors/Committee Members: Buehrer, R. Michael (committeechair), Dietrich, Carl B. (committee member), Marojevic, Vuk (committee member).
Subjects/Keywords: localization; collaborative position location; communications; geolocation; UTDOA
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APA (6th Edition):
McDermott, K. P. (2015). On the Improvement of Positioning in LTE with Collaboration and Pressure Sensors. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/54019
Chicago Manual of Style (16th Edition):
McDermott, Kevin Patrick. “On the Improvement of Positioning in LTE with Collaboration and Pressure Sensors.” 2015. Masters Thesis, Virginia Tech. Accessed February 28, 2021.
http://hdl.handle.net/10919/54019.
MLA Handbook (7th Edition):
McDermott, Kevin Patrick. “On the Improvement of Positioning in LTE with Collaboration and Pressure Sensors.” 2015. Web. 28 Feb 2021.
Vancouver:
McDermott KP. On the Improvement of Positioning in LTE with Collaboration and Pressure Sensors. [Internet] [Masters thesis]. Virginia Tech; 2015. [cited 2021 Feb 28].
Available from: http://hdl.handle.net/10919/54019.
Council of Science Editors:
McDermott KP. On the Improvement of Positioning in LTE with Collaboration and Pressure Sensors. [Masters Thesis]. Virginia Tech; 2015. Available from: http://hdl.handle.net/10919/54019
Virginia Tech
20.
Zhou, Zhou.
MIMO-OFDM Symbol Detection via Echo State Networks.
Degree: MS, Electrical Engineering, 2019, Virginia Tech
URL: http://hdl.handle.net/10919/95945
► 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…
(more)
▼ 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.
Advisors/Committee Members: Liu, Lingjia (committeechair), Buehrer, R. Michael (committee member), Ellingson, Steven W. (committee member).
Subjects/Keywords: Echo State Network; MIMO-OFDM; Symbol Detection; Bit Error Rate
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APA (6th Edition):
Zhou, Z. (2019). MIMO-OFDM Symbol Detection via Echo State Networks. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/95945
Chicago Manual of Style (16th Edition):
Zhou, Zhou. “MIMO-OFDM Symbol Detection via Echo State Networks.” 2019. Masters Thesis, Virginia Tech. Accessed February 28, 2021.
http://hdl.handle.net/10919/95945.
MLA Handbook (7th Edition):
Zhou, Zhou. “MIMO-OFDM Symbol Detection via Echo State Networks.” 2019. Web. 28 Feb 2021.
Vancouver:
Zhou Z. MIMO-OFDM Symbol Detection via Echo State Networks. [Internet] [Masters thesis]. Virginia Tech; 2019. [cited 2021 Feb 28].
Available from: http://hdl.handle.net/10919/95945.
Council of Science Editors:
Zhou Z. MIMO-OFDM Symbol Detection via Echo State Networks. [Masters Thesis]. Virginia Tech; 2019. Available from: http://hdl.handle.net/10919/95945
Virginia Tech
21.
Clark, William H. IV.
Blind Comprehension of Waveforms through Statistical Observations.
Degree: MS, Electrical Engineering, 2015, Virginia Tech
URL: http://hdl.handle.net/10919/52908
► This paper proposes a cumulant based classification means to identify waveforms for a blind receiver in the presence of time varying channels, which is built…
(more)
▼ This paper proposes a cumulant based classification means to identify waveforms for a blind receiver in the presence of time varying channels, which is built from the work done on cumulants in static channels currently in the literature. Results show the classification accuracy is on the order or better than current methods in use in static channels that do not vary over an observation period. This is accomplished by making use of second through tenth order cumulants in a signature vector that the search engine platform has the means of differentiating. A receiver can then blindly identify waveforms accurately in the presence of multipath Rayleigh fading with AWGN noise.
Channel learning occurs prior to classification in order to identify the consistent distortion pattern for a waveform that is observable in the signature vector. Then using a database look-up method, the observed waveform is identified as belonging to a particular cluster based on the observed signature vector. If the distortion patterns are collected from a variety of channel types, the database can then classify both the waveform and the rough channel type that the waveform passed through. If the exact channel model or channel parameters is known and used as a limiter, significant improvement on the waveform classification can be achieved. Greater accuracy comes from using the exact channel model as the limiter.
Advisors/Committee Members: McGwier, Robert W. (committeechair), Clancy, T. Charles (committee member), Buehrer, R. Michael (committee member).
Subjects/Keywords: communications; modulation classification; cumulant; search engine platform
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APA (6th Edition):
Clark, W. H. I. (2015). Blind Comprehension of Waveforms through Statistical Observations. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/52908
Chicago Manual of Style (16th Edition):
Clark, William H IV. “Blind Comprehension of Waveforms through Statistical Observations.” 2015. Masters Thesis, Virginia Tech. Accessed February 28, 2021.
http://hdl.handle.net/10919/52908.
MLA Handbook (7th Edition):
Clark, William H IV. “Blind Comprehension of Waveforms through Statistical Observations.” 2015. Web. 28 Feb 2021.
Vancouver:
Clark WHI. Blind Comprehension of Waveforms through Statistical Observations. [Internet] [Masters thesis]. Virginia Tech; 2015. [cited 2021 Feb 28].
Available from: http://hdl.handle.net/10919/52908.
Council of Science Editors:
Clark WHI. Blind Comprehension of Waveforms through Statistical Observations. [Masters Thesis]. Virginia Tech; 2015. Available from: http://hdl.handle.net/10919/52908
22.
Selvi, Ersin Suleyman.
Cognitive Radar Applied To Target Tracking Using Markov Decision Processes.
Degree: MS, Electrical Engineering, 2018, Virginia Tech
URL: http://hdl.handle.net/10919/81968
► The radio-frequency spectrum is a precious resource, with many applications and users, especially with the recent spectrum auction in the United States. Future platforms and…
(more)
▼ The radio-frequency spectrum is a precious resource, with many applications and users, especially with the recent spectrum auction in the United States. Future platforms and devices, such as radars and radios, need to be adaptive to their spectral environment in order to continue serving the needs of their users. This thesis considers an environment with one tracking radar, a single target, and a communications system. The radar-communications coexistence problem is modeled as a Markov decision process (MDP), and reinforcement learning is applied to drive the radar to optimal behavior.
Advisors/Committee Members: Buehrer, R. Michael (committeechair), Michaels, Alan J. (committeechair), MacKenzie, Allen B. (committee member).
Subjects/Keywords: Cognitive radar; target tracking; Markov decision process; interference mitigation; spectrum coexistence
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APA (6th Edition):
Selvi, E. S. (2018). Cognitive Radar Applied To Target Tracking Using Markov Decision Processes. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/81968
Chicago Manual of Style (16th Edition):
Selvi, Ersin Suleyman. “Cognitive Radar Applied To Target Tracking Using Markov Decision Processes.” 2018. Masters Thesis, Virginia Tech. Accessed February 28, 2021.
http://hdl.handle.net/10919/81968.
MLA Handbook (7th Edition):
Selvi, Ersin Suleyman. “Cognitive Radar Applied To Target Tracking Using Markov Decision Processes.” 2018. Web. 28 Feb 2021.
Vancouver:
Selvi ES. Cognitive Radar Applied To Target Tracking Using Markov Decision Processes. [Internet] [Masters thesis]. Virginia Tech; 2018. [cited 2021 Feb 28].
Available from: http://hdl.handle.net/10919/81968.
Council of Science Editors:
Selvi ES. Cognitive Radar Applied To Target Tracking Using Markov Decision Processes. [Masters Thesis]. Virginia Tech; 2018. Available from: http://hdl.handle.net/10919/81968
23.
Teague, Kory Alan.
Approaches to Joint Base Station Selection and Adaptive Slicing in Virtualized Wireless Networks.
Degree: MS, Electrical Engineering, 2018, Virginia Tech
URL: http://hdl.handle.net/10919/85966
► 5G, the next generation cellular network standard, promises to provide significant improvements over current generation standards. For 5G to be successful, this must be accompanied…
(more)
▼ 5G, the next generation cellular network standard, promises to provide significant improvements over current generation standards. For 5G to be successful, this must be accompanied by similarly significant efficiency improvements. Wireless network virtualization is a promising technology that has been shown to improve the cost efficiency of current generation cellular networks. By abstracting the physical resource—such as cell tower base stations— from the use of the resource, virtual resources are formed. This work investigates the problem of selecting virtual resources (e.g., base stations) to construct virtual wireless networks with minimal cost and slicing the selected resources to individual networks to optimally satisfy individual network demands. This problem is framed in a stochastic optimization framework and two approaches are presented for approximation. The first approach converts the framework into a deterministic equivalent and reduces it to a tractable form. The second approach uses a genetic algorithm to approximate resource selection. Approaches are simulated and evaluated utilizing a demand model constructed to emulate the statistics of an observed real world urban network. Simulations indicate that the first approach can provide a reasonably tight solution with significant time expense, and that the second approach provides a solution in significantly less time with the introduction of marginal error.
Advisors/Committee Members: MacKenzie, Allen B. (committeechair), Silva, Luiz A. (committee member), Buehrer, R. Michael (committee member).
Subjects/Keywords: Wireless Network Virtualization; Resource Allocation; Two-Stage Stochastic Optimization; Genetic Algorithm
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APA (6th Edition):
Teague, K. A. (2018). Approaches to Joint Base Station Selection and Adaptive Slicing in Virtualized Wireless Networks. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/85966
Chicago Manual of Style (16th Edition):
Teague, Kory Alan. “Approaches to Joint Base Station Selection and Adaptive Slicing in Virtualized Wireless Networks.” 2018. Masters Thesis, Virginia Tech. Accessed February 28, 2021.
http://hdl.handle.net/10919/85966.
MLA Handbook (7th Edition):
Teague, Kory Alan. “Approaches to Joint Base Station Selection and Adaptive Slicing in Virtualized Wireless Networks.” 2018. Web. 28 Feb 2021.
Vancouver:
Teague KA. Approaches to Joint Base Station Selection and Adaptive Slicing in Virtualized Wireless Networks. [Internet] [Masters thesis]. Virginia Tech; 2018. [cited 2021 Feb 28].
Available from: http://hdl.handle.net/10919/85966.
Council of Science Editors:
Teague KA. Approaches to Joint Base Station Selection and Adaptive Slicing in Virtualized Wireless Networks. [Masters Thesis]. Virginia Tech; 2018. Available from: http://hdl.handle.net/10919/85966
24.
Fletcher, Michael John.
Enhanced Implementations for Arbitrary-Phase Spread Spectrum Waveforms.
Degree: MS, Electrical Engineering, 2019, Virginia Tech
URL: http://hdl.handle.net/10919/90286
► This thesis presents a series of options for enhancing the implementation of arbitrary-phase spread spectrum waveforms, a highly-secure class of wireless technologies, in order to…
(more)
▼ This thesis presents a series of options for enhancing the implementation of arbitrary-phase spread spectrum waveforms, a highly-secure class of wireless technologies, in order to reduce design complexity with minimal loss, provide methods for real-time performance adaptations, and extend the traditional application space for increased security of communications in other networks. A number of enhanced hardware prototypes were implemented to provide measurable results, achieving substantial computational resource gains and design flexibility. Given the computational resources and power constraints of devices in the Internet of Things (IoT), the signal detection loss of 2.10 dB for reducing the hardware logic utilization of the brute force fallthrough correlator by more than 76% (and eliminating the need to dedicate computationally-expensive embedded multipliers) is a very reasonable trade. While the waveform is fundamentally designed for increased security, adapting to widespread and/or commercial use may allow some sacrifice of the signal’s ability to avoid interception/detection to improve performance in undesirable operating conditions. In a similar, yet reversed, case, injecting a watermarking signature at the physical layer (PHY) of less-secure wireless technologies for receiver-side authentication also proves to be beneficial.
Advisors/Committee Members: Michaels, Alan J. (committeechair), Beex, Aloysius A. (committee member), Buehrer, R. Michael (committee member).
Subjects/Keywords: Spread Spectrum; Arbitrary-Phase; Chaotic Communications; Implementation
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APA (6th Edition):
Fletcher, M. J. (2019). Enhanced Implementations for Arbitrary-Phase Spread Spectrum Waveforms. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/90286
Chicago Manual of Style (16th Edition):
Fletcher, Michael John. “Enhanced Implementations for Arbitrary-Phase Spread Spectrum Waveforms.” 2019. Masters Thesis, Virginia Tech. Accessed February 28, 2021.
http://hdl.handle.net/10919/90286.
MLA Handbook (7th Edition):
Fletcher, Michael John. “Enhanced Implementations for Arbitrary-Phase Spread Spectrum Waveforms.” 2019. Web. 28 Feb 2021.
Vancouver:
Fletcher MJ. Enhanced Implementations for Arbitrary-Phase Spread Spectrum Waveforms. [Internet] [Masters thesis]. Virginia Tech; 2019. [cited 2021 Feb 28].
Available from: http://hdl.handle.net/10919/90286.
Council of Science Editors:
Fletcher MJ. Enhanced Implementations for Arbitrary-Phase Spread Spectrum Waveforms. [Masters Thesis]. Virginia Tech; 2019. Available from: http://hdl.handle.net/10919/90286
25.
Inti, Durga Laxmi Narayana Swamy.
Time-Varying Frequency Selective IQ Imbalance Estimation and Compensation.
Degree: MS, Electrical Engineering, 2017, Virginia Tech
URL: http://hdl.handle.net/10919/78202
► Direct-Down Conversion (DDC) principle based transceiver architectures are of interest to meet the diverse needs of present and future wireless systems. DDC transceivers have a…
(more)
▼ Direct-Down Conversion (DDC) principle based transceiver architectures are of interest to meet the diverse needs of present and future wireless systems. DDC transceivers have a simple structure with fewer analog components and offer low-cost, flexible and multi-standard solutions. However, DDC transceivers have certain circuit impairments affecting their performance in wide-band, high data rate and multi-user systems.
IQ imbalance is one of the problems of DDC transceivers that limits their image rejection capabilities. Compensation techniques for frequency independent IQI arising due to gain and phase mismatches of the mixers in the I/Q paths of the transceiver have been widely discussed in the literature. However for wideband multi-channel transceivers, it is becoming increasingly important to address frequency dependent IQI arising due to mismatches in the analog I/Q lowpass filters.
A hardware-efficient and standard independent digital estimation and compensation technique for frequency dependent IQI is introduced which is also capable of tracking time-varying IQI changes. The technique is blind and adaptive in nature, based on the second order statistical properties of complex random signals such as properness/circularity.
A detailed performance analysis of the introduced technique is executed through computer simulations for various real-time operating scenarios. A novel technique for finding the optimal number of taps required for the adaptive IQI compensation filter is proposed and the performance of this technique is validated. In addition, a metric for the measure of properness is developed and used for error power and step size analysis.
Advisors/Committee Members: Beex, Aloysius A. (committeechair), Dhillon, Harpreet Singh (committee member), Buehrer, R. Michael (committee member).
Subjects/Keywords: Direct-Down Conversion Systems; IQ Imbalance; Blind Equalization; Adaptive Filtering; Image Rejection
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APA (6th Edition):
Inti, D. L. N. S. (2017). Time-Varying Frequency Selective IQ Imbalance Estimation and Compensation. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/78202
Chicago Manual of Style (16th Edition):
Inti, Durga Laxmi Narayana Swamy. “Time-Varying Frequency Selective IQ Imbalance Estimation and Compensation.” 2017. Masters Thesis, Virginia Tech. Accessed February 28, 2021.
http://hdl.handle.net/10919/78202.
MLA Handbook (7th Edition):
Inti, Durga Laxmi Narayana Swamy. “Time-Varying Frequency Selective IQ Imbalance Estimation and Compensation.” 2017. Web. 28 Feb 2021.
Vancouver:
Inti DLNS. Time-Varying Frequency Selective IQ Imbalance Estimation and Compensation. [Internet] [Masters thesis]. Virginia Tech; 2017. [cited 2021 Feb 28].
Available from: http://hdl.handle.net/10919/78202.
Council of Science Editors:
Inti DLNS. Time-Varying Frequency Selective IQ Imbalance Estimation and Compensation. [Masters Thesis]. Virginia Tech; 2017. Available from: http://hdl.handle.net/10919/78202
26.
Jauhar, Ahmad Shujauddin.
A CMA-FRESH Whitening Filter for Blind Interference Rejection.
Degree: MS, Electrical Engineering, 2018, Virginia Tech
URL: http://hdl.handle.net/10919/85389
► Wireless communication is complicated by the fact that multiple radios may be attempting to transmit at the same frequency, time and location concurrently. This scenario…
(more)
▼ Wireless communication is complicated by the fact that multiple radios may be attempting to transmit at the same frequency, time and location concurrently. This scenario may be a due to malicious intent by certain radios (jamming), or mere confusion due to a lack of knowledge that another radio is transmitting in the same channel. The latter scenario is more common due to congested wireless spectrum, as the number of devices increases exponentially. In either case, interference results. We present a novel interference rejection method in this work, one that is blind to the properties of the interferer and adapts to cancel it. It follows the philosophy of property restoration as extolled by the constant modulus algorithm (CMA) and is a frequency shift (FRESH) filter, hence the name. The process of restoring the wireless spectrum to white noise is what makes it a whitening filter, and is also how it adapts to cancel interference. Such a filter has myriad possible uses, and we examine the use case of rejecting interference to detect or recover the signal-of-interest (SOI) that we are attempting to receive. We present performance results in both cases and compare with conventional time-invariant filters and state of the art FRESH filters.
Advisors/Committee Members: Reed, Jeffrey Hugh (committeechair), Buehrer, R. Michael (committee member), Marojevic, Vuk (committee member).
Subjects/Keywords: Cyclostationarity; FRESH filter; Constant Modulus Algorithm; Interference Rejection; Signal Detection; Hidden Node Problem; Spectrum Sharing
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APA (6th Edition):
Jauhar, A. S. (2018). A CMA-FRESH Whitening Filter for Blind Interference Rejection. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/85389
Chicago Manual of Style (16th Edition):
Jauhar, Ahmad Shujauddin. “A CMA-FRESH Whitening Filter for Blind Interference Rejection.” 2018. Masters Thesis, Virginia Tech. Accessed February 28, 2021.
http://hdl.handle.net/10919/85389.
MLA Handbook (7th Edition):
Jauhar, Ahmad Shujauddin. “A CMA-FRESH Whitening Filter for Blind Interference Rejection.” 2018. Web. 28 Feb 2021.
Vancouver:
Jauhar AS. A CMA-FRESH Whitening Filter for Blind Interference Rejection. [Internet] [Masters thesis]. Virginia Tech; 2018. [cited 2021 Feb 28].
Available from: http://hdl.handle.net/10919/85389.
Council of Science Editors:
Jauhar AS. A CMA-FRESH Whitening Filter for Blind Interference Rejection. [Masters Thesis]. Virginia Tech; 2018. Available from: http://hdl.handle.net/10919/85389
27.
Bhandari, Tapan.
Comprehensive Performance Analysis of Localizability in Heterogeneous Cellular Networks.
Degree: MS, Electrical Engineering, 2017, Virginia Tech
URL: http://hdl.handle.net/10919/78664
► The availability of location estimates of mobile devices (MDs) is vital for several important applications such as law enforcement, disaster management, battlefield operations, vehicular communication,…
(more)
▼ The availability of location estimates of mobile devices (MDs) is vital for several important applications such as law enforcement, disaster management, battlefield operations, vehicular communication, traffic safety, emergency response, and preemption. While global positioning system (GPS) is usually sufficient in outdoor clear sky conditions, its functionality is limited in urban canyons and indoor locations due to the absence of clear line-of-sight between the MD to be localized and a sufficient number of navigation satellites. In such scenarios, the ubiquitous nature of cellular networks makes them a natural choice for localization of MDs. Traditionally, localization in cellular networks has been studied using system level simulations by fixing base station (BS) geometries. However, with the increasing irregularity of the BS locations (especially due to capacity-driven small cell deployments), the system insights obtained by considering simple BS geometries may not carry over to real-world deployments. This necessitates the need to study localization performance under statistical (random) spatial models, which is the main theme of this work.
In this thesis, we use powerful tools from stochastic geometry and point process theory to develop a tractable analytical model to study the localizability (ability to get a location fix) of an MD in single-tier and heterogeneous cellular networks (HetNets). More importantly, we study how availability of information about the location of proximate BSs at the MD impacts localizability. To this end, we derive tractable expressions, bounds, and approximations for the localizability probability of an MD. These expressions depend on several key system parameters, and can be used to infer valuable system insights. Using these expressions, we quantify the gains achieved in localizability of an MD when information about the location of proximate BSs is incorporated in the model. As expected, our results demonstrate that localizability improves with the increase in density of BS deployments.
Advisors/Committee Members: Dhillon, Harpreet Singh (committeechair), MacKenzie, Allen B. (committee member), Buehrer, R. Michael (committee member).
Subjects/Keywords: Stochastic geometry; localization; localizability; cellular network; Poisson point process.
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APA (6th Edition):
Bhandari, T. (2017). Comprehensive Performance Analysis of Localizability in Heterogeneous Cellular Networks. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/78664
Chicago Manual of Style (16th Edition):
Bhandari, Tapan. “Comprehensive Performance Analysis of Localizability in Heterogeneous Cellular Networks.” 2017. Masters Thesis, Virginia Tech. Accessed February 28, 2021.
http://hdl.handle.net/10919/78664.
MLA Handbook (7th Edition):
Bhandari, Tapan. “Comprehensive Performance Analysis of Localizability in Heterogeneous Cellular Networks.” 2017. Web. 28 Feb 2021.
Vancouver:
Bhandari T. Comprehensive Performance Analysis of Localizability in Heterogeneous Cellular Networks. [Internet] [Masters thesis]. Virginia Tech; 2017. [cited 2021 Feb 28].
Available from: http://hdl.handle.net/10919/78664.
Council of Science Editors:
Bhandari T. Comprehensive Performance Analysis of Localizability in Heterogeneous Cellular Networks. [Masters Thesis]. Virginia Tech; 2017. Available from: http://hdl.handle.net/10919/78664
28.
Dsouza, Jennifer.
Analysis of RF Front-End Non-linearity on Symbol Error Rate in the Presence of M-PSK Blocking Signals.
Degree: MS, Electrical Engineering, 2017, Virginia Tech
URL: http://hdl.handle.net/10919/79489
► Radio frequency (RF) receivers are inherently non-linear due to non-linear components contained within the RF front-end such as the low noise amplifier (LNA) and mixer.…
(more)
▼ Radio frequency (RF) receivers are inherently non-linear due to non-linear components contained within the RF front-end such as the low noise amplifier (LNA) and mixer. When receivers operate in the non-linear region, this will affect the system performance due to intermodulation products, and cross-modulation, to name a few. Intermodulation products are the result of adjacent channel signals that combine and create intermodulation distortion of the received signal. We call these adjacent channel signals blockers. Receiving blockers are unavoidable in wideband receivers and their effect must be analyzed and properly addressed. This M.S. Thesis studies the effect of blockers on system performance, specifically the symbol error rate (SER), as a function of the receiver non-linearity figure and the blocking signal power and modulation format. There have been numerous studies on the effect of non-linearity in the probability of true and false detections in spectrum sensing when blockers are present. There has also been research showing the optimal modulation scheme for effective jamming. However, we are not aware of work analyzing the effect of modulated adjacent channel blockers on communication system performance. The approach taken in this paper is a theoretical derivation followed by numerical analysis aimed to quantify the effect of receiver nonlinearity on communication system performance as a function of (1) receiver characteristics, (2) blocking signal powers, (3) signal and blocker modulation format, and (4) phase-synchronized/non-synchronized blocker reception. The work focuses on M-PSK modulation schemes. For high blocker powers and non-linearity, the Es/No (Eb/No) performance loss can be as high as 4.7 dB for BPSK modulated signal and BPSK modulated blockers when received in sync with the desired signal. When blockers have a random phase offset with respect to the desired signal, the performance degradation is about 2 dB for BPSK modulated desired and blocker signals. It was found that for an BPSK transmitted signal with phase-synchronous blockers, the SER (BER) deteriorates the most when the blocking signals are of the same modulation. The effect is reduced, but still significant, as the modulation order of the signal of interest or the blockers, or both increases.
Advisors/Committee Members: Marojevic, Vuk (committeechair), Reed, Jeffrey Hugh (committee member), Buehrer, R. Michael (committee member).
Subjects/Keywords: Symbol error rate; Non-linearity; M-PSK; Blockers; Phase-synchronous; Phase-unsynchronous; RF Front-End
…Virginia Tech researchers
have previously shown the adverse impact of RF front-end non-linearity…
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APA (6th Edition):
Dsouza, J. (2017). Analysis of RF Front-End Non-linearity on Symbol Error Rate in the Presence of M-PSK Blocking Signals. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/79489
Chicago Manual of Style (16th Edition):
Dsouza, Jennifer. “Analysis of RF Front-End Non-linearity on Symbol Error Rate in the Presence of M-PSK Blocking Signals.” 2017. Masters Thesis, Virginia Tech. Accessed February 28, 2021.
http://hdl.handle.net/10919/79489.
MLA Handbook (7th Edition):
Dsouza, Jennifer. “Analysis of RF Front-End Non-linearity on Symbol Error Rate in the Presence of M-PSK Blocking Signals.” 2017. Web. 28 Feb 2021.
Vancouver:
Dsouza J. Analysis of RF Front-End Non-linearity on Symbol Error Rate in the Presence of M-PSK Blocking Signals. [Internet] [Masters thesis]. Virginia Tech; 2017. [cited 2021 Feb 28].
Available from: http://hdl.handle.net/10919/79489.
Council of Science Editors:
Dsouza J. Analysis of RF Front-End Non-linearity on Symbol Error Rate in the Presence of M-PSK Blocking Signals. [Masters Thesis]. Virginia Tech; 2017. Available from: http://hdl.handle.net/10919/79489
29.
Ryland, Kevin Sherwood.
Software-Defined Radio Implementation of Two Physical Layer Security Techniques.
Degree: MS, Electrical Engineering, 2018, Virginia Tech
URL: http://hdl.handle.net/10919/82055
► This thesis discusses the design of two Physical Layer Security (PLS) techniques on Software Defined Radios (SDRs). PLS is a classification of security methods that…
(more)
▼ This thesis discusses the design of two Physical Layer Security (PLS) techniques on Software Defined Radios (SDRs). PLS is a classification of security methods that take advantage of physical properties in the waveform or channel to secure communication. These schemes can be used to directly obfuscate the signal from eavesdroppers, or even generate secret keys for traditional encryption methods. Over the past decade, advancements in Multiple-Input Multiple-Output systems have expanded the potential capabilities of PLS while the development of technologies such as the Internet of Things has provided new applications. As a result, this field has become heavily researched, but is still lacking implementations. The design work in this thesis attempts to alleviate this problem by establishing SDR designs geared towards Over-the-Air experimentation.
The first design involves a 2x1 Multiple-Input Single-Output system where the transmitter uses Channel State Information from the intended receiver to inject Artificial Noise (AN) into the receiver's nullspace. The AN is consequently not seen by the intended receiver, however, it will interfere with eavesdroppers experiencing independent channel fading. The second design involves a single-carrier Alamouti coding system with pseudo-random phase shifts applied to each transmit antenna, referred to as Phase-Enciphered Alamouti Coding (PEAC). The intended receiver has knowledge of the pseudo-random sequence and can undo these phase shifts when performing the Alamouti equalization, while an eavesdropper without knowledge of the sequence will be unable to decode the signal.
Advisors/Committee Members: Clancy, Thomas Charles (committeechair), Dietrich, Carl B. (committee member), Buehrer, R. Michael (committee member).
Subjects/Keywords: Physical Layer Security; Software Defined Radio; Alamouti STBC; Artificial Noise; Over-the-Air
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APA (6th Edition):
Ryland, K. S. (2018). Software-Defined Radio Implementation of Two Physical Layer Security Techniques. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/82055
Chicago Manual of Style (16th Edition):
Ryland, Kevin Sherwood. “Software-Defined Radio Implementation of Two Physical Layer Security Techniques.” 2018. Masters Thesis, Virginia Tech. Accessed February 28, 2021.
http://hdl.handle.net/10919/82055.
MLA Handbook (7th Edition):
Ryland, Kevin Sherwood. “Software-Defined Radio Implementation of Two Physical Layer Security Techniques.” 2018. Web. 28 Feb 2021.
Vancouver:
Ryland KS. Software-Defined Radio Implementation of Two Physical Layer Security Techniques. [Internet] [Masters thesis]. Virginia Tech; 2018. [cited 2021 Feb 28].
Available from: http://hdl.handle.net/10919/82055.
Council of Science Editors:
Ryland KS. Software-Defined Radio Implementation of Two Physical Layer Security Techniques. [Masters Thesis]. Virginia Tech; 2018. Available from: http://hdl.handle.net/10919/82055
Virginia Tech
30.
Rao, Raghunandan M.
Enhancing Performance of Next-Generation Vehicular and Spectrum Sharing Wireless Networks: Practical Algorithms and Fundamental Limits.
Degree: PhD, Electrical Engineering, 2020, Virginia Tech
URL: http://hdl.handle.net/10919/99796
► The impact of today's technologies has been magnified by wireless networks, due to the standardization and deployment of fifth-generation (5G) cellular networks. 5G promises faster…
(more)
▼ The impact of today's technologies has been magnified by wireless networks, due to the standardization and deployment of fifth-generation (5G) cellular networks. 5G promises faster data speeds, lower latency and higher user security, among other desirable features. This has made it capable of meeting the performance requirements of key infrastructure such as smart grid and mission-critical networks, and novel consumer applications such as smart home appliances, smart vehicles, and augmented/virtual reality. In part, these capabilities have been achieved by (a) better spectrum utilization among various wireless technologies (called spectrum sharing), and (b) serving multiple users on the same resource using large multi-antenna systems (called massive MIMO). In this dissertation, we make three contributions that enhance the performance of vehicular communications and spectrum sharing systems.
In the first contribution, we present a novel scheme wherein a vehicular communication link adapts to the channel conditions by controlling the resource overhead in real-time, to improve spectral utilization of data resources. The proposed scheme enhances those of current 4G and 5G networks, which are based on limited feedback of quantized channel statistics, fed back from the receiver to the transmitter.
In the second contribution, we show that conventional link adaptation methods fail when 4G/5G networks share spectrum with pulsed radars. To mitigate this problem, we develop a comprehensive signal processing framework, consisting of a hybrid SINR estimation method that is robust and accurate in a wide range of interference and noise conditions. Concurrently, we also propose a scheme to pass additional information that captures the channel conditions in the presence of radar interference, and analyze its performance in detail.
In the third contribution, we focus on characterizing the impact of 5G cellular interference on a radar system in shared spectrum, using mathematical tools from stochastic geometry. We model the worst-case interference scenario, and study the impact of the system parameters on the worst-case radar performance.
In summary, this dissertation advances the state-of-the-art in vehicular communications and spectrum sharing, through (a) novel contributions in protocol design and (b) development of mathematical tools for performance characterization.
Advisors/Committee Members: Reed, Jeffrey H. (committeechair), Marojevic, Vuk (committeechair), Dhillon, Harpreet Singh (committee member), Buehrer, R. Michael (committee member), Farhood, Mazen H. (committee member).
Subjects/Keywords: Link adaptation; channel state information acquisition; vehicular communications; radar-cellular coexistence; spectrum sharing; stochastic geometry
Record Details
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Share »
Record Details
Similar Records
Cite
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❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Rao, R. M. (2020). Enhancing Performance of Next-Generation Vehicular and Spectrum Sharing Wireless Networks: Practical Algorithms and Fundamental Limits. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/99796
Chicago Manual of Style (16th Edition):
Rao, Raghunandan M. “Enhancing Performance of Next-Generation Vehicular and Spectrum Sharing Wireless Networks: Practical Algorithms and Fundamental Limits.” 2020. Doctoral Dissertation, Virginia Tech. Accessed February 28, 2021.
http://hdl.handle.net/10919/99796.
MLA Handbook (7th Edition):
Rao, Raghunandan M. “Enhancing Performance of Next-Generation Vehicular and Spectrum Sharing Wireless Networks: Practical Algorithms and Fundamental Limits.” 2020. Web. 28 Feb 2021.
Vancouver:
Rao RM. Enhancing Performance of Next-Generation Vehicular and Spectrum Sharing Wireless Networks: Practical Algorithms and Fundamental Limits. [Internet] [Doctoral dissertation]. Virginia Tech; 2020. [cited 2021 Feb 28].
Available from: http://hdl.handle.net/10919/99796.
Council of Science Editors:
Rao RM. Enhancing Performance of Next-Generation Vehicular and Spectrum Sharing Wireless Networks: Practical Algorithms and Fundamental Limits. [Doctoral Dissertation]. Virginia Tech; 2020. Available from: http://hdl.handle.net/10919/99796
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Open Access Theses and Dissertations
