Elad Alon, Ph.D. - US grants

Abstract (Proposal No.1201755)

Communication between integrated circuits, such as the CPU and peripheral blocks, occurs over a high-speed bus, which requires physical wire traces on a printed circuit board. In most mobile computing and communication platforms, such as a smart phone or tablet, the form factor is constrained by the requirement to connect to this bus. We propose a sub-THz (~300 GHz) wireless bus that eliminates this constraint, allowing integrated circuits to be placed anywhere inside of the device with communication links established wirelessly and automatically. New circuit, antenna, and system architectures will be explored to enable an energy efficient realization of the key components of such a system. Two prototypes at 240 GHz and 360 GHz will demonstrate the feasibility of the proposal.

Intellectual Merit: The described technology could have tremendous impact on the design of a new generation of ultra thin and small devices, allowing chips to be placed in the most optimal positions, either to increase the aesthetics of the design or enable better engineering. The link is established using the sub-THz frequency spectrum (~300 GHz) using on-chip electronics and antennas in standard CMOS technology. To be competitive with the wired links, the link must be extremely energy efficient and must not occupy a bigger footprint on the silicon die than existing systems. Antennas at sub-THz frequencies are in fact extremely small and can be comparable in size to traditional bonding pads, which are used to connect to the physical traces. Moreover, due to the large carrier frequency, only modest fractional bandwidth is needed to support high throughputs using simple modulation schemes.

Broader Impacts: Wireless communication is a rapidly growing field and its importance to the national economy cannot be overstated. While in the previous decades the semiconductor industry was driven largely by the digital microprocessor market, today the combination of high performance computation on a portable device combined with voice and data communication is the major driver. This research is intended to advance the state of ?smart? phones, tablets, and ultra-portable laptops. A wireless chip-to-chip communication channel, or a wireless bus, will enable integrated circuits to be minimized (by removing IO pads/pins), allow the board real-estate to be used with increased flexibility, reducing the number of planes in the printed circuit board and reduce the required amount of waste.

Proposal No:1551239, EAGER-Neural dust stimulation for closed loop neuromodulation

One of the most important challenges that remains in neuroengineering is the development and demonstration of a clinically viable neural interface which can both record from and stimulate many individual neurons and lasts a lifetime. These chronic or long-term neural interfaces are of increasing interest for both central (CNS) and peripheral nervous system (PNS) interventions. Creating lasting, durable, untethered interfaces raises a variety of issues, ranging from the nature of the physical substrate (avoiding the biotic and abiotic effects that presumably lead to performance degradation at the electrode-tissue interface, the density and spatial coverage of the sensing sites), the type of signals measured, and the computation and communication capabilities (how much signal processing on-chip data to transmit wirelessly) under the power budget of the whole system. This proposal seeks to extend our recently published Neural Dust platform to allow for stimulation of nerves via neural dust motes. We believe this to be an aggressive vision which would open the door to a vast array of interventions, including untethered neural recording of human nerves and neurons, untethered stimulation of these processes and record-and-stimulate closed loop systems. Such a vision will require a number of fundamental technological innovations that will have impact across domains including basic neuroscience, clinical interventions of neurological disorders, and prosthetics. For example, the ability to precisely monitor and modulate peripheral nerve activity with a minimally invasive medical device would enable a wide-range of therapeutic opportunities. This closed-loop neuromodulation cannot be done with existing technologies because they suffer from one of two major drawbacks: lack of spatial resolution or high degree of invasiveness.

We recently proposed an ultra-miniature as well as extremely compliant system that could enable massive scaling in the number of recordings from the brain or the peripheral nervous system, providing a path towards truly chronic BMI. At the core of this vision is a platform for powering, receiving and transmitting information from inside a peripheral nerve to outside the body using aggressive, state-of-the-art circuit design and the recent demonstration of ultrasonic, piezocrystal "neural dust? motes. The work envisioned in this proposal will leverage recent application specific integrated circuit (ASIC) technology to build stimulating motes that can address individual neurons (or peripheral fibers) and will demonstrate untethered stimulation of nerve fibers, paving the way to closed-loop record-and-stim technology using neural dust. This is a very aggressive, high risk direction which leverages existing neural dust developments with a very high potential payoff (as it enables untethered closed-loop neuromodulation systems). Our long term vision is a system capable of recording and stimulation in closed-loop.

Fifth-generation (5G) wireless systems are expected to provide enormous improvements in data rates available to users, as well as much improvement overall user experience. Massive multiple-input multiple-output (MIMO) arrays consist of hundreds of antenna elements, serving many users and are considered to be a cornerstone of 5G wireless systems, and are expected to dramatically improve both the radio spectrum utilization and user experience. At the same time, the use of millimeter-wave (mm-wave) frequencies is supposed to provide additional spectrum for new services in the years to come, and small physical antenna separation makes mm-wave attractive for massive MIMO. While there has been substantial progress in the development of the theoretical concepts associated with the design of massive MIMO systems, very little work has been done to actually design a mm-wave massive MIMO system and on the network techniques needed to scale these systems to dozens of simultaneous spatial streams. This proposal addresses the key challenges in the development of signal processing algorithms, network protocols, and a prototype hardware design to enable scalable low-latency mm-wave MIMO networks with high degrees of spatial multiplexing. It will provide a path to a hundred-fold improvement in user data rates.

By integrating the theoretical system aspects with its practical development, this proposal addresses critical challenges for the development of mm-wave massive MIMO technologies. In particular, this project aims to achieve: (1) a mm-wave massive MIMO array architecture suitable for low-cost and energy-efficient deployment at massive scale, (2) an optimized scalable signal processing approach to massive MIMO array processing, which includes hybrid beamforming, distributed channel estimation and distributed beamforming, (3) a medium-access control (MAC) technique suitable for low-latency, low-coherence time applications by leveraging a full-duplex frame to enable rapid user acquisition, synchronization, tracking, and paging, (4) practical in-band full-duplex operation, realized through a combination of antenna array design, spatial filtering, and adaptive analog and digital cancellation, (5) practical front-end circuits with linearity and phase noise suitable for a large number of simultaneous spatial streams, and (6) a mm-wave massive MIMO test bed designed in a modular manner to enable future development and performance measurements of signal processing and MAC techniques. In addition to cross-disciplinary training of students involved in this project, interaction of project members with industry leaders will dramatically accelerate the penetration of 5G wireless communications.