Browsing by Subject "Wireless"
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Item Open Access Restructuring Wireless Systems using PHY Layer Information(2012) Sen, SouvikWireless and mobile systems play an increasingly important role in our lives. Fueled by an array of innovative services and applications, mobile data traffic is surging rapidly. Traditionally, wireless traffic growth is met by acquiring new spectrum. However, wireless spectrum demand is soon going to surpass it's availability. Thus, there is an urgent need for major innovations in wireless network architecture, so that our spectrum utilization can achieve its full potential. Motivated by this problem, we explore an alternative design of physical layer aware wireless systems.
Typical approaches towards improving wireless performance is confined within the physical (PHY) or link layers of the networking stack, providing only partial so- lutions. In this thesis, we advocate to consider the entire network architecture holis- tically. We show how rich PHY layer information can be utilized to address existing challenges in wireless networking - contention resolution, rate control, interference management, etc. We design, implement, and experimentally evaluate protocols to understand network-wide implications of PHY-aware systems. We also pursue the observation that PHY layer not only encode bits but also contain rich information about the ambience, and hence can be viewed as a sensor. This sensing informa- tion can be further coupled with other phone sensors, thereby benefitting pervasive mobile services and applications. We demonstrate how this synergy can contribute towards designing precise indoor localization systems, an important building block for next generation mobile applications.
Item Open Access Simulations of an Integrated RF/Wireless Coil Design for Simultaneous Magnetic Resonance Image Acquisition and Data Transfer(2019) Bresticker, Julia ElizabethA novel integrated RF/wireless coil design, termed an integrated RF/wireless coil, which enables simultaneous MR image acquisition and wireless data transfer, has recently been proposed. The integrated RF/wireless coil design allows radio-frequency (RF) currents to flow on the coil simultaneously at the Larmor frequency, for MR image acquisition, and at the 2.4 GHz wireless communication frequency, for wireless data transfer from within the MRI scanner bore to a wireless Access Point (AP) on the scanner room wall. The integrated RF/wireless coil design provides a low-cost solution for wireless data transmission between the scanner bore and the console room that requires no mechanical modifications to the existing MRI system, which can 1) reduce the need for cumbersome cabling networks in the scanner, 2) increase patient comfort, and 3) decrease patient set up time.
In previous work, the radiated energy emitted from the integrated RF/wireless coil was not optimized for wireless data transfer between the coil in the scanner bore and the AP on the scanner room wall. The wireless data transfer from an integrated RF/wireless coil is optimal when the maximum amount of radiated power in the wireless communication band is transferred from the integrated RF/wireless coil to the AP, and the power deposited into the subject in the scanner is minimized. However, measurements of the radiated power from the integrated RF/wireless coil in the MRI environment (i.e., in the scanner bore and on a human) are not practical because they would require an excessively large anechoic chamber. Thus, electromagnetic simulations are performed to determine the optimal integrated RF/wireless coil design (e.g., size, position on the subject) that maximizes the radiated power delivered from the coil to an AP while 1) ensuring no degradation in SNR compared to a traditional RF coil and 2) minimizing the radiated power deposited into the subject in the scanner bore.
In this work, 3-D finite element electromagnetic co-simulations with an RF circuit designer are performed to optimize the gain of an integrated RF/wireless coil on a human phantom in the scanner bore and the corresponding S21 power transmission (i.e., link budget) between the coil and an AP on the scanner room wall. These simulations are verified by constructing an integrated RF/wireless coil and by using it to perform free-space radiated gain pattern measurements in an anechoic chamber and to acquire SNR maps of a uniform water phantom in an MRI scanner.
Item Open Access Technology for Brain-Machine Interfaces(2012) Hanson, Timothy LarsBrain-machine interfaces (BMIs) use recordings from the nervous system to extract volitional and motor parameters for controlling external actuators, such as prosthetics, thereby bypassing or replacing injured tissue. As such, they show enormous promise for restoring mobility, dexterity, or communication in paralyzed patients or amputees. Recent advancements to the BMI paradigm have made the brain -- machine communication channel bidirectional, enabling the prosthetic to inform the user about touch, temperature, strain, or other sensory information; these devices are hence called brain-machine-brain interfaces (BMBIs).
In the first chapter an intraoperative BMI is investigated in human patients undergoing surgery for implantation of a deep brain stimulation (DBS) treatment electrodes. While the BMI was marginally effective, we found high levels of behavioral and tremor tuning among cells recorded from the surgical targets, the subthalamic nucleus (STN) and ventral intermediate nucleus (VIM) of the thalamus. Notably, this tremor or behavior tuning was not mutually exclusive with oscillatory behavior, suggesting that physiological tuning persists even in the face of pathological oscillations. We then used nonlinear means for extracting tremor tuning, and found a significant population, consistent with double-frequency or co-modulation to tremor within the basal ganglia. Synchrony was then assessed over long and short timescales between pairs of neurons, and it was found that tremor tuning implies synchrony: all units exhibiting tremor tuning showed synchrony to at least one other unit.
BMBIs rely on a host of both scientific knowledge and technology for effective function, and this technology is currently in intensive research. In this dissertation two technologies for BMBIs, corresponding to the two directions of communication, are designed, described, and tested. The first one is a high compliance, digitally controlled, high-side current-regulated microstimulator for intracortical microstimulation (ICMS). The device is validated on the bench, tested in monkeys, and used for multiple experimental setups. Due to careful control of parasitic charge injection, the microstimulator is ideally suited for interleaving stimulation and recording as employed in some BMBIs.
The second technology described is a wireless, scalable, 128 channel neural recording system. The device features aggressive digital filtering to maximize signal quality, has spike sorting and compression on the transceiver, can be fully configured over the air through a custom wireless bridge and client software, and can run for over 30 hours on one battery. This system has been tested in a monkey while in its home cage, where the wireless system permitted unfettered, continuous recording and continuous access to a simplified BMI. A full description of the development and device is described, as well as results showing convincing 1D and suggestive 2D BMI control.
Item Open Access The Impact of Spectrum Quality on Wireless Telecom Competition(2012-04-16) Zhu, StephenThis paper explores the metrics used by FCC and others for evaluating competition between wireless telecom carriers. It focuses on the impact of wireless spectrum quality on the results of FCC spectrum auctions and the estimated market shares of wireless carriers. In this case, it is revealed that quality is affected by the physical attributes of and the policies that are imposed at auction. Further, accounting for quality can lead to changes in the perception of concentration in local markets. The findings here give insights that can be used to better evaluate the competitive landscape of telecom in the future.Item Open Access The iPRES-W Coil: Advancements in Wireless Technology for Magnetic Resonance Imaging(2022) Cuthbertson, JonathanAbstractPurpose: Integration of wireless data transfer in magnetic resonance imaging (MRI) would allow for the reduction of wired connections between the scanner subsystems and the control computers located outside the scanner room, which add to the cost and complexity of the scanner, reduce patient comfort, and impede the application of next-generation MRI technologies.
Methods:In this dissertation, a novel RF coil design, termed the wireless integrated parallel reception, excitation, and shimming (iPRES-W) coil design, is further developed to remove some of these wired connections by offering a compact and easy-to-integrate MR-compatible wireless data transfer solution, which requires no scanner modifications or additional antenna systems in the bore. The iPRES-W coil design allows both a direct current (DC) and radio-frequency (RF) currents at the Larmor frequency and in a wireless communication band to flow on the same coil element to enable simultaneous MR image acquisition and wireless data transfer, which enables: wireless localized B0 shimming; wireless peripheral system data transfer to augment imaging (e.g., respiratory tracking using a respiratory belt); wireless transfer of the scanner control signal to control on-coil electronics (e.g., Q-spoiling); and wireless power harvesting to power components of the iPRES-W system. To demonstrate the performance and utility of the iPRES-W coil design in clinically relevant applications, this dissertation has four aims: 1. To develop an iPRES-W spine coil array to perform simultaneous MR imaging and wireless localized B0 shimming of the spinal cord; 2. To develop a dual-stream iPRES-W head coil array for simultaneous MR imaging of the brain and multiple wireless data streams for control of separate peripheral systems, specifically, wireless localized B0 shimming and respiratory tracking using a respiratory belt; 3. To further develop an integrated RF/wireless coil design for wireless transfer of the scanner trigger signal to perform the Q-spoiling required for MR image acquisition; 4. To design a wireless power harvesting system to convert the high-energy RF energy emitted by the scanner during the transmit cycle into a DC voltage to charge the batteries to power in-bore electronics and B0 shim currents.
Results:The results from this dissertation demonstrate that the iPRES-W coil modifications did not degrade the signal-to-noise ratio (SNR) when implemented onto different radio-frequency coil structures (e.g., a conventional RF coil element and novel adaptive imaging receive (AIRTM) coil element). Wireless localized B0 shimming with the iPRES-W spine array and dual-stream iPRES-W head coil array substantially reduced the B0 root-mean-square-error (RMSE) by 70.1% and -41.2% in the spinal cord and frontal brain region, which corresponded to reduced DTI and EPI distortions, respectively. The wireless performance of the iPRES-W and iRFW coil elements measured in an anechoic chamber were minimally impacted by the introduction of a saline phantom representing tissue or during wireless Q-spoiling, respectively. The power harvesting experiments performed showed that the 4-channel power harvesting coil array could convert RF energy from the scanner into a DC voltage for recharging MR-compatible batteries for various scan parameters and imaging sequences.
Conclusions:The iPRES-W and iRFW coil designs can be integrated into different coil structures and arrays to perform simultaneous imaging, wireless localized B0 shimming, and wireless transfer of peripheral device data (e.g., respiratory tracking with a respiratory belt), with no SNR degradation, minimal change in wireless performance, and without scanner modifications or additional antenna systems within the scanner bore. Additionally, the power harvesting array can supply wireless power to charge MR-compatible batteries for various scan types and parameters.
Item Open Access The iPRES-W Coil: An MRI RF Coil for Simultaneous MR Image Acquisition, Wireless Communication, and Localized B0 Shimming(2018) Cuthbertson, JonathanMagnetic resonance imaging (MRI) generates anatomical images by utilizing a homogeneous static magnetic field (B0) generated by a magnet and radiofrequency (RF) signals transmitted to and received from the subject by RF coils. To enhance the acquired signal strength and improve the image signal-to-noise ratio, receive RF coils are placed close to the surface of the subject and multiple RF coil elements are typically combined to form an RF coil array. The number of RF coil elements in an array has continually increased over the years, requiring large cables, connectors, and added electronic components to be connected to the MRI scanner for imaging, which increases the integration complexity, cost, and weight of the RF coil arrays. Additionally, RF coil arrays are typically heavy and rigid, which makes them difficult and time consuming to setup and uncomfortable for the subjects. Finally, additional shim coils are required to correct for B0 inhomogeneities induced by the subject and to improve the image quality, but they currently provide suboptimal results. This work presents a highly innovative RF coil design to address all of these concerns.
First, a novel integrated RF/wireless coil design was proposed to enable simultaneous MR image acquisition and wireless communication with a single coil, thereby reducing or eliminating the wired connections for data transfer between the coil and the MRI scanner. Second, the RF/wireless coil design was combined with the integrated parallel reception, excitation, and shimming (iPRES) coil design to enable simultaneous MR image acquisition, wireless communication, and localized B0 shimming with a single coil, thereby further improving the B0 homogeneity and image quality (iPRES-W coil). Finally, the iPRES-W coil design was integrated with: 1) the revolutionary AIR coil technology to perform the same three functions, but with a flexible and ultra-lightweight coil, thereby increasing patient comfort and offering more flexible coil design opportunities and 2) a wireless bidirectional DC power supply for B0 shimming to further eliminate any cables between the MRI scanner and RF coil (iPRES-W AIR coil).
Experiments were conducted to demonstrate that the modifications made to the RF coil, to enable wireless communication and B0 shimming, did not degrade its imaging performance. Additionally, experiments were conducted to test the wireless data connection, transmission rate, and quality of the wireless link for the RF/wireless and iPRES-W coil designs. Finally, experiments were conducted to demonstrate the ability of the iPRES-W coil to simultaneously perform localized B0 shimming during wireless data transmission and image acquisition. The results presented show no degradation in image quality with the modifications made, excellent B0 shimming performance, and the ability to wirelessly transmit data within the MRI scanner bore. The iPRES-W coil design requires no modifications to the current MRI scanner and leads to a highly scalable, cost effective, wireless solution for a more efficient, comfortable, and beneficial MRI experience.
Item Open Access Using Coding to Improve Localization and Backscatter Communication Performance in Low-Power Sensor Networks(2016) Cnaan-On, Itay MenachemBackscatter communication is an emerging wireless technology that recently has gained an increase in attention from both academic and industry circles. The key innovation of the technology is the ability of ultra-low power devices to utilize nearby existing radio signals to communicate. As there is no need to generate their own energetic radio signal, the devices can benefit from a simple design, are very inexpensive and are extremely energy efficient compared with traditional wireless communication. These benefits have made backscatter communication a desirable candidate for distributed wireless sensor network applications with energy constraints.
The backscatter channel presents a unique set of challenges. Unlike a conventional one-way communication (in which the information source is also the energy source), the backscatter channel experiences strong self-interference and spread Doppler clutter that mask the information-bearing (modulated) signal scattered from the device. Both of these sources of interference arise from the scattering of the transmitted signal off of objects, both stationary and moving, in the environment. Additionally, the measurement of the location of the backscatter device is negatively affected by both the clutter and the modulation of the signal return.
This work proposes a channel coding framework for the backscatter channel consisting of a bi-static transmitter/receiver pair and a quasi-cooperative transponder. It proposes to use run-length limited coding to mitigate the background self-interference and spread-Doppler clutter with only a small decrease in communication rate. The proposed method applies to both binary phase-shift keying (BPSK) and quadrature-amplitude modulation (QAM) scheme and provides an increase in rate by up to a factor of two compared with previous methods.
Additionally, this work analyzes the use of frequency modulation and bi-phase waveform coding for the transmitted (interrogating) waveform for high precision range estimation of the transponder location. Compared to previous methods, optimal lower range sidelobes are achieved. Moreover, since both the transmitted (interrogating) waveform coding and transponder communication coding result in instantaneous phase modulation of the signal, cross-interference between localization and communication tasks exists. Phase discriminating algorithm is proposed to make it possible to separate the waveform coding from the communication coding, upon reception, and achieve localization with increased signal energy by up to 3 dB compared with previous reported results.
The joint communication-localization framework also enables a low-complexity receiver design because the same radio is used both for localization and communication.
Simulations comparing the performance of different codes corroborate the theoretical results and offer possible trade-off between information rate and clutter mitigation as well as a trade-off between choice of waveform-channel coding pairs. Experimental results from a brass-board microwave system in an indoor environment are also presented and discussed.
Item Open Access Wireless Electrophysiology of Locomotor Behaviors in Unrestrained Rhesus Macaques(2014) Schwarz, David AlexanderIn recent years, large-scale brain recordings in nonhuman primates have been a driving force for both fundamental neuroscience and the field of brain-machine interfaces (BMIs). This required monkey implants connected to external amplifiers and computers with ever increasing number of cables. As shown with our recent demonstration of 2,000 neurons recorded in one monkey, a tethered recording system begins to get bulky and complex, particularly for our BMI and neurophysiological research. To address this problem, we developed a multichannel wireless recording framework. The system was been tested in freely moving rhesus monkey by integrating wireless neural recordings with external computers performing BMI decoding, behavioral manipulanda and optical tracking. This technology can be applied to primate behavior research and, in the near future, wireless, fully implantable human neuroprosthetics, which is of great significance to those suffering from locomotor deficiencies, such as those brought on by spinal cord injury and stroke. Aided with these advances, I was able to study monkeys in unrestrained locomotion while their cortical activity was continuously monitored. I also explored unrestrained behaviors and how they showed distinct transitions in neural dynamics as monkeys engaged in different behavioral activities or learned new motor skills, such as bipedal walking. I was able to decode them many of these behavioral states from cortical activity with neural classifiers. Lastly, monkeys were able to perform BMI tasks continuously for many hours, allowing us to prove the relevance of unrestrained noise in BMI performance. Lastly, I present my role in developing two brain actuated movement platforms, a robotic exoskeleton under the guise of the WalkAgain project, and a microelectrode BMI enabled wheelchair. This body of work should assist those on the path to the next generation of clinical neuroprostheses and neural communication systems.