Browsing by Subject "Beamforming"

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A pulsed multiband UWB transmitter and receiver with beamforming for high data-rate WPAN applications
(2019-05-10) Ko, Jaegan; Gharpurey, Ranjit; Abraham, Jacob; Heath, Robert; Humphreys, Todd; Rudell, Jacques Christophe
Personal devices for recording high-quality video and photographs, and display systems for their playback are ubiquitous. Currently, the resolution for ultra high definition (UHD) video format is more than 33 megapixels (7680x4320), while cameras for mobile phones have reached the range of 40 megapixels. The media files used or generated in such devices can be very large. Sharing and using these files across devices such as smartphones, personal computers, and external storage drives, requires fast-transfer capability, which can be of the order of Gbps or higher. Additionally, high-resolution monitors and televisions also require streaming of display data at similar rates unless video compression is employed, which may not be desirable since it can cause noticeable latency or visual defects. With the popularity of smartphones and mobile devices, it is preferable to perform the tasks of transferring files and display streaming by employing power-efficient wireless data links, in order to ensure a good user experience. This dissertation presents an ultra-wideband (UWB) wireless communication system for such high data-rate and short-range applications. The proposed pulsed, multiband signaling with frequency hopping complies with the UWB regulation in Europe. This regulation is chosen merely for the purpose of demonstration. The approach itself can be easily adapted to different frequency bands, and hence is inherently flexible. It enables low-power implementation by adopting a low-complexity architecture, that allows for pulse-based signaling with subband channelization. Moreover, dividing the target spectrum into multiple narrow subbands reduces the power overhead in implementing beamforming at the receiver. Beamforming helps to increase the signal-to-noise ratio (SNR) and provides directivity in the receiver for immunity against multipath and interference, which enhances overall link robustness. A 1-Gbps wireless communication link is demonstrated over a range of 2-meters, as part of this research, employing prototype integrated transceiver ICs that were implemented in a 65-nm CMOS technology. The transmitter IC consumes 221 mW, and the receiver IC with 4-element beamforming dissipates 211 mW. The system employs UWB spectrum from 6-8.5 GHz
An optimization paradigm for wideband antenna arrays : integrating electromagnetics and information theory
(2021-12-03) Saab, Sandy; Heath, Robert W., Jr, 1973-; Incorvia , Jean Anne; Mezghani, Amine; Porter, Emily; de Veciana, Gustavo
As larger bandwidths are used in multiple-antenna wireless systems, the frequency selectivity of the antenna arrays starts to impact rate. Therefore, optimizing the achievable rate in compact antenna arrays becomes important especially for future wireless networks that can require octaves of bandwidth. With the emergence of 6G technologies, using terahertz (THz) frequency bands become inevitable to achieve terabit rates. Hence, in this dissertation, we focus on combining wireless communication theory and electromagnetics theory to provide a new platform that addresses the challenges in future wireless networks. In this dissertation, we introduce a circuit-level analysis of compact wideband antennas at sub-6GHz bands. We present an approach that combines the mathematics of information theory with the physics behind antenna theory. Then, we focus on designing antenna arrays for future 6G technologies that can maintain a full rank channel in the presence of a line-of-sight (LoS) component. Lastly, we introduce a passive reflective intelligent surface (RIS) that helps in redirecting the signal efficiently to the intended user. In Chapter 2 of the dissertation, we focus on optimizing the achievable rate in compact antenna arrays. We present a system model that incorporates the effects of mutual coupling (MC) of wideband physically realizable single-input multiple-output (SIMO) and multiple-input single-output (MISO) antenna systems. For the SIMO system setup, we extract the noise correlation matrices for two different antenna array configurations (parallel and co-linear). We optimize the inter-element spacing in each alignment while maximizing the achievable rate and fixing the transmit power. Then, we compare the two compact antenna designs to a perfectly matched single omni-directional antenna while accounting for MC. Likewise, for the MISO antenna system, we derive the optimal beamformer that maximizes the achievable rate using the same antenna configurations as the SIMO system. Then, we study the impact of MC and develop a new single-port matching technique for wideband antenna arrays. Finally, we provide reciprocity plots to compare the performance of the SIMO-MISO systems using different channel models. In Chapter 3 of the dissertation, we present an optimized antenna port switching technique for a LoS multiple-input multiple-output (MIMO) system operating at THz frequencies. MIMO technology usually requires a rich scattering environment to work properly and uses non-line-of-sight (NLoS) components. When MIMO is used in high-frequency point-to-point microwave links, however, the channel will have a dominant LoS component. For a LoS MIMO system to maintain spatial diversity, the signal streams should remain orthogonal to each other. Therefore, we design an optimally spaced uniform linear array (ULA) and non-uniform linear array (NULA) that preserves the orthogonality between the signals in a mesh grid network. We present a novel technique that selects the proper antenna ports to be activated which results in preserving the signal stream orthogonality and achieves a good condition number for the channel matrix. Finally, we provide bit error rate (BER) plots to show the performance and flexibility of this novel approach. In Chapter 4 of the dissertation, we design a reconfigurable intelligent surface, which controls the state of the imposing electromagnetic waves at THz frequencies. Since at THz frequencies there is significant and severe path loss, current beamforming techniques use costly phased arrays or bulky reflector antennas that hinder and limit their applications. Furthermore, THz frequencies are highly susceptible to frequent link outages due to misalignment and obstruction thus severely affecting the overall system throughput and reliability. As a result, the designed RIS controls the properties of an electromagnetic signal and acts as a reflector and directs the impinging wave to its proper receiver (i.e. user equipment, base station). The reflective surface controls the phase of the reflected wave from each unit-cell, hence steers the reflected signal from the surface of the array to reach the intended user equipment and improves the user’s signal-to-noise ratio (SNR). To show the effectiveness of our design, we provide plots of the beam-steering angle of the RIS.
Beam-Enabled Acoustic Link Establishment (BEALE) for underwater acoustic networks
(2013-05) Watkins, Karen Piecara; Nettles, Scott M.
There is growing interest in developing reliable, high performance, underwater acoustic networks (UWANs). However, the acoustic communication channel, with its slow sound propagation, high signal attenuation, and low bandwidth, presents significant challenges to network designers. One advantage offered by the acoustic channel is the ability to form directional communication beams, which improve signal strength and reduce interference. The work presented here describes a novel medium access control protocol for UWANs designated Beam-Enabled Acoustic Link Establishment (BEALE). BEALE addresses the inherent challenges of the acoustic channel by incorporating two techniques: link-level scheduling and dynamic directional beam steering. BEALE neighbors exchange packets based on a link-level schedule negotiated between the two nodes. This scheduling allows nodes to steer transmit and receive beams in the appropriate direction at the appropriate time while minimizing control overhead. Using steered, directional beams increases the gain between sender and receiver, reduces the senders interference with other nodes, and, at the receiver, rejects possible interference from other nodes and noise sources common in the ocean, resulting in increased spatial reuse. The core protocol has been modeled in a UWAN simulator developed specifically for this research. The results demonstrate significant improvement in throughput and packet loss over two benchmark UWAN random access protocols when evaluated over a variety of spatial node topologies and traffic patterns. The core BEALE protocol is further enhanced herein by a Half-Duplex Sliding Window algorithm. The HDX Sliding window is shown through point-to-point simulation to markedly improve bandwidth utilization and error rate in large Bandwidth Delay Product (BDP) situations. Extension of the HDX Sliding Window to more complex multi-flow, two-way and multi-hop cases requires an additional level of communication coordination provided by the BEALE Sliding Window Scheduler presented here. The functional challenges and novel concept of the scheduler are described in detail. The BEALE protocol performance promotes a rich list of potential future research, such as rigorous characterization of the BEALE Sliding Window Scheduler, BEALE accommodation of mobile nodes, conceptual operability of a BEALE-enabled network of a central multi-beam sink node supporting large numbers of simple source nodes, and rate adaptation.
Beamforming and subsurface source localization in bearing, range and depth
(2004-12-18) Dunn, Lawrence Robert; Wilson, Gary Ray
This thesis serves as a satisfactory introduction to the use of beamforming to localize an underwater source of acoustic energy in bearing, range and depth, including the necessary background material in acoustics and computation. Plane wave beam-forming is introduced, as is beamforming with a Pekeris waveguide and a waveguide with a depth dependent sound velocity profile. Under certain circumstances the filtering of unwanted signals is considered, and throughout the thesis a heavy emphasis is placed on the theory of linear algebra and its implications to the beamforming process.
Designing MIMO interference alignment networks
(2012-08) Nosrat Makouei, Behrang; Heath, Robert W., Jr, 1973-; Andrews, Jeffrey G.; Evans, Brian L.; Hasenbein, John; Nettles, Scott; Vishwanath, Sriram
Wireless networks are increasingly interference-limited, which motivates the development of sophisticated interference management techniques. One recently discovered approach is interference alignment, which attains the maximum sum rate scaling (with signal-to-noise ratio) in many network configurations. Interference alignment is not yet well understood from an engineering perspective. Such design considerations include (i) partial rather than complete knowledge of channel state information, (ii) correlated channels, (iii) bursty packet-based network traffic that requires the frequent setup and tear down of sessions, and (iv) the spatial distribution and interaction of transmit/receive pairs. This dissertation aims to establish the benefits and limitations of interference alignment under these four considerations. The first contribution of this dissertation considers an isolated group of transmit/receiver pairs (a cluster) cooperating through interference alignment and derives the signal-to-interference-plus-noise ratio distribution at each receiver for each stream. This distribution is used to compare interference alignment to beamforming and spatial multiplexing (as examples of common transmission techniques) in terms of sum rate to identify potential switching points between them. This dissertation identifies such switching points and provides design recommendations based on severity of the correlation or the channel state information uncertainty. The second contribution considers transmitters that are not associated with any interference alignment cooperating group but want to use the channel. The goal is to retain the benefits of interference alignment amid interference from the out-of-cluster transmitters. This dissertation shows that when the out-of-cluster transmitters have enough antennas, they can access the channel without changing the performance of the interference alignment receivers. Furthermore, optimum transmit filters maximizing the sum rate of the out-of-cluster transmit/receive pairs are derived. When insufficient antennas exist at the out-of-cluster transmitters, several transmit filters that trade off complexity and sum rate performance are presented. The last contribution, in contrast to the first two, takes into account the impact of large scale fading and the spatial distribution of the transmit/receive pairs on interference alignment by deriving the transmission capacity in a decentralized clustered interference alignment network. Channel state information uncertainty and feedback overhead are considered and the optimum training period is derived. Transmission capacity of interference alignment is compared to spatial multiplexing to highlight the tradeoff between channel estimation accuracy and the inter-cluster interference; the closer the nodes to each other, the higher the channel estimation accuracy and the inter-cluster interference.
Field studies comparing SASW, beamforming and MASW test methods and characterization of geotechnical materials based on Vs
(2011-08) Yuan, Jiabei; Stokoe, Kenneth H.; Gilbert, Robert B.; Kallivokas, Loukas F.; Wilson, Clark R.; Cox, Brady R.; Joh, Sungho
Estimating S-wave velocities (Vs) from Rayleigh-wave velocities (VR) is widely used in field seismic testing for geotechnical engineering purposes. In this research, two widely used surface-wave methods, the Spectral-Analysis-of-Surface-Waves (SASW) and Multichannel-Analysis-of-Surface-Waves (MASW) methods, are evaluated and compared in field experiments. An experimental parametric study was undertaken of the SASW and MASW methods. Conventional seismic sources in the SASW method are sledge hammers, bulldozers and vibroseises. For MASW testing, sledge hammers and small shakers are usually used as the seismic sources. In this research, MASW testing was performed with traditional and non-traditional sources at a site owned by the City of Austin, Texas. Experimental dispersion curves and Vs profiles from SASW tests are used as references for the field parametric study with the MASW method. The source type, source offset, receiver spacing and number of receivers were varied to evaluate the impact of each variable on the field experimental dispersion curve. Two type of receivers, 1-Hz and 4.5-Hz natural-frequency geophones, were also compared in these tests. A second part of this research involved studying the use of characterizing geotechnical materials based on Vs. This work included two projects. The first project involved basalt on the Big Island of Hawaii. To develop empirical ground motion prediction models for the purpose of earthquake hazard mitigation and seismic design on the Big Island, the subsurface site conditions beneath 22 strong motion stations were investigated by SASW tests. Vs profiling was performed to depths of more than 100 ft. Vs30, the average Vs in the top 30 m, was also calculated to assign NEHRP site classes to different testing locations. Different materials, mainly thought to be stiff basalt, were characterized and grouped based on the Vs values. These groups were then compared with reference curves for sand and gravel (Menq, 2003) to differentiate the groups. The second project dealing with charactering geotechnical materials based on Vs involved of soil/rock profiles at a project site in British Columbia, Canada. The goals in terms of this research were to: (1) compare the Vs profiles from the different test locations to investigate the stiffnesses of different geologic materials, the variability in the material stiffnesses, and the estimated depth to bedrock, and (2) to compare the Vs profiles to existing geological and geotechnical information such as nearby boreholes, cone penetration tests and seismic cone penetration tests. Good agreement between SASW Vs profiles and boring records is expected when lateral variability at the site is low. However, when lateral variability is significant, then the difference between localized measurements, like borings and CPT results, and global measurements, like SASW Vs results, can further contribute to understanding the site conditions as shown at the site in British Columbia, Canada.
Full-duplex millimeter wave communication systems : theory and practice
(2023-06-12) Roberts, Ian Parker; Andrews, Jeffrey G.; Vishwanath, Sriram; Evans, Brian L; Kim, Hyeji; Chopra, Aditya
This dissertation is focused on studying, characterizing, and developing new solutions for full-duplex millimeter wave (mmWave) communication systems. Translating existing full-duplex solutions—which are largely for systems operating at lower carrier frequencies—to mmWave systems is not practically viable nor is it necessarily desirable. Instead, I propose several novel solutions for full-duplex mmWave systems, all of which harness beamforming with dense antenna arrays to cancel self-interference to levels near or even below the noise floor—unlocking the long-sought ability to simultaneously transmit and receive over the same frequency spectrum. Two trademarks of my proposed techniques are that they (i) account for a wide variety of key practical constraints and (ii) are informed by a campaign in which I collected and analyzed nearly 20 million measurements of self-interference using 28 GHz phased arrays. Numerical simulation and experimental evaluation are used to illustrate the effectiveness of the proposed techniques, validating them as enablers of full-duplex mmWave systems. Based on the aforementioned measurements, this dissertation also extensively characterizes mmWave self-interference through statistical analysis and spatial modeling, both of which are the first of their kind. Together comprising this dissertation, the characterization of self-interference and the proposed solutions serve as strides toward transforming real-world mmWave communication systems by upgrading them with full-duplex capability.
Millimeter wave link configuration robust to radio frequency impairments
(2020-08-14) Myers, Nitin Jonathan; Heath, Robert W., Jr., 1973-; Vorobyov, Sergiy A; Sanghavi, Sujay; Caramanis, Constantine; Gonzalez-Prelcic, Nuria
Millimeter wave (mmWave) bands offer several gigahertz of bandwidth that can support high data rate applications. To efficiently use the spectrum at mmWave frequencies, the wireless link between the transmitting and receiving radios must be configured properly. The link configuration problem at mmWave, however, is challenging due to the use of large antenna arrays and radio frequency (RF) impairments that are less severe in common lower frequency systems. Some of these impairments include the low resolution of RF phase shifters, carrier frequency offset, and the misfocus effect in near field systems with large arrays. An important characteristic of mmWave multiple-input multiple-output (MIMO) channels is sparsity. The sparse nature of such channels has allowed the use of compressed sensing (CS) for fast link configuration through channel estimation or beam alignment. CS techniques usually involve random sensing matrices to acquire a compressed channel representation and an optimization algorithm to estimate the sparse channel. Unfortunately, common random CS matrices result in poor link configuration under RF impairments. In the first part of this dissertation, we construct a new class of CS matrices that achieve robustness to the low resolution of RF phase shifters and the carrier frequency offset. To aid our construction, we propose a framework called FALP and develop an algorithm called Swift-Link within this framework. Swift-Link achieves better beam alignment than standard CS-based solutions at a reduced computational complexity. In the second part of this dissertation, we investigate the misfocus effect in near field beamforming. The beams in a near field communication scenario can focus RF signals in a spatial region called the focal point. The focal point, however, changes with the frequency of operation in a wideband phased array that uses a center frequency-based beamformer. This effect called misfocus, reduces the effective operating bandwidth of the near field system. To mitigate the misfocus effect, we propose a technique called InFocus that constructs beams which are well suited for massive wideband phased arrays. InFocus enables massive wideband phased array-based radios to achieve a higher data rate than comparable beamforming solutions.
Robust directional transmission beamforming techniques for smart antenna systems
(1995) Bigler, Laurie Anne, 1970-; Xu, Guanghan
Current developments in smart antenna technology include the use of adaptive antenna arrays to directively transmit and receive data from the mobile user. Implementing adaptive antennas only on uplink enhances the signal quality and provides considerable range extension for a cell site, but does not allow for significant increases in capacity. However, utilizing adaptive antennas for both uplink and downlink rejects co-channel interference to the degree that mobiles located at spatially distinct angles from the base station and mobiles located at shorter reuse distances can operate on the same frequency channel. Unfortunately, robust beamforming techniques for downlink have not been developed. Previous research studies have given theoretical performance comparisons of, primarily, DOA-based beamforming techniques for uplink transmissions. Very few RF experiments have been conducted which evaluate adaptive beamforming techniques in a real environment. In this thesis, experimental studies are conducted to evaluate adaptive beamforming techniques and determine a robust downlink transmission beamforming approach. Experimental data is presented which demonstrates the stability of strong specular DOAs over a 25 MHz frequency range, and the robust performance of a new integrated DOA-based beamforming approach for both uplink and downlink transmissions. The spatial signature beamforming approach is shown to perform better than DOA-based beamforming on uplink, but to be less robust on downlink for Frequency Division Duplex (FDD) systems. Additional research is needed to validate these results for larger frequency differences in both cellular and PCS bands
System design issues in dense urban millimeter wave cellular networks
(2018-06-21) Kulkarni, Mandar Narsinh; Andrews, Jeffrey G.; Baccelli, Francois; Veciana, Gustavo de; Heath, Robert W; Mukherjee, Sayandev
Upcoming deployments of cellular networks will see an increasing use of millimeter wave (mmWave) frequencies, roughly between 20-100 GHz. The goal of this dissertation is to investigate some key design issues in dense urban mmWave cellular networks by developing mathematical models that are representative of these networks. In the first contribution, stochastic geometry (SG) is used to study the per user rate performance of multi-user MIMO (MU-MIMO) in downlink mmWave cellular network incorporating the impact of a spatially sparse blockage dependent multipath channel and hybrid precoding. Performance of MU-MIMO is then compared with single-user beamforming and spatial multiplexing in different network scenarios considering coverage, rate and power consumption tradeoffs to suggest when to use which MIMO scheme. The second contribution reconsiders a popular received signal power model used in system capacity analysis of MIMO wireless networks employing single user beamforming. A modification is suggested to the model by introducing a correction factor. An approximate analysis is done to justify incorporating such a factor and simulations are performed to validate it's importance. Although this contribution does not study a new system design issue for mmWave cellular, it highlights a shortcoming with using the popular received signal power model to study design issues in mmWave cellular networks. The third and fourth contributions investigate resource allocation in self-backhauled mmWave cellular networks. In order to enable affordable initial deployments of mmWave cellular, self-backhauling is envisioned as a cost-saving solution. The third contribution investigates how to divide resources between uplink and downlink for access and backhaul in self-backhauled networks with single hop wireless backhauling. The performance of dynamic time division duplexing (TDD) and integrated access-backhaul (IAB) is compared with static TDD and orthogonal access backhaul (OAB) strategies using a SG based model. The last contribution of this dissertation addresses the following key question for self-backhauled networks. What is the maximum extended coverage area that a single fiber site can support using multi-hop relaying, while still achieving a minimum target per user data rate? The problem of maximizing minimum per user rates is studied considering a series of deployments with a single fiber site and varying number of relays. Several design guidelines for multi-hop mmWave cellular networks are provided based on the analytical and empirical results.
System-level design and analysis of an embedded audio signal processing application
(2016-05) Dollo, Philippe Marc; Sun, Nan; Akinwande, Deji
In this report, a design is proposed for an embedded system that implements an audio beamforming application. This design provides the key considerations for both the analog front-end, and the digital signal processing that would be included on-chip. The analog portion of the design implements a multi-order delta-sigma ADC, and the digital portion of the design implements a digital decimation filter and a beamforming filter. The objective of the project is to develop a system that could be used in a real-world implementation, with design decisions which attempt to account for system-wide specifications, rather than focusing on block-level performance alone.