This is not your usual Abstract since the intent of this presentation is to give a selected overview of my research at USF and explore areas of potential joint work during my sabbatical at UCSD and possible future collaborations. There are two thematic areas of my research: Wireless Body Area Networks and Optimization of 5G Networks.
Some of the topics that I will cover are:
This talk provides a discussion of one of the central design challenges associated with next-generation “5G”
wireless systems - that of effectively converging 3GPP-based mobile networks with the global Internet.
Although the trend towards “flat” IP-based architectures for cellular networks is well under way with LTE,
significant architectural evolution will be needed to achieve the goal of supporting the needs of mobile
devices and applications as “first-class” services on the Internet. Several emerging mobility service scenarios
Wireless electronic devices are everywhere in our daily lives with applications ranging from data communication to energy transfer and biomedical sensing. Power amplifier (PA) interfaces the antenna and governs the energy efficiency of a wireless transceiver. Its linearity is also of paramount importance to ensure the signal fidelity. Moreover, its broadband operation is highly desired for high-speed communication and high-resolution sensing. However, integrating a PA in silicon entails challenges due to the PA’s nature of large-signal and highly dynamic operation.
The mm-wave frequency spectrum has gained prominence in recent years to support high-data rate energy efficient wireless communication for the future 5G standards and other IoT applications. Mass-deployment and adoption of such technologies rely on silicon integration of the mm-wave transceivers. However, achieving high data-rates at mm-wave frequencies over long distance wireless links require efficient Watt-level transmitters and power amplifiers – a challenge in low breakdown voltage silicon technologies.
For high data rates and massive connectivity, next-generation cellular networks are expected to deploy many small base stations. While such dense deployment provides the benefit of bringing radio closer to end users, it also increases the amount of interference from neighboring cells. Consequently, efficient and effective management of interference is expected to become one of the main challenges for high-spectral-efficiency, low-power, broad-coverage wireless communications.
In this talk, I will present several unconventional analog IC design techniques. First, I will talk about how we can make use of noise, which is usually deemed as an undesirable thing, to estimate the conversion residue and increase the SNR of a SAR ADC. It is an interesting example of stochastic resonance, in which the increase in noise can lead to not SNR degradation but SNR enhancement. Second, I will talk about how we can perform data conversion below the Nyquist rate by exploiting the sparsity of the input signal.
This talk address the problem of performing statistical inference for large scale data sets i.e., Big Data. The volume and dimensionality of the data may be so high that it cannot be processed or stored in a single computing node. We propose a scalable, statistically robust and computationally efficient bootstrap method, compatible with distributed processing and storage systems. The proposed method combines distributed bootstrap with computationally efficient fixed point equations.
A central concept in matrix analysis is the decomposition of a matrix into a product of orthogonal (or unitary) matrices and a diagonaltriangular one, e.g., unitary diagonalization of a symmetric matrix, and more generally the singular-value decomposition, and the QR decomposition. Such decompositions are of particular importance for multi-antenna point-to-point physical-layer communications, where the channel gains are represented by a (channel) matrix.
Can one revisit the main concepts of information theory in a deterministic setting? Shortly after Shannon’s work came about, this was the program set by the great Soviet mathematician Andrey Kolmogorov. In this talk, we review Kolmogorov’s program and cast his results in the context of square-integrable, band-limited signals subject to perturbation. For this class of signals, spectral concentration properties are well known, and closed form formulas can be obtained.
The ubiquity of mobile phones coupled with the availability of highly scalable NoSQL databases and containerized cloud computing infrastructure has enabled Niantic to create coherent augmented realities encompassing millions of users in a single, consistent experience overlaid on top of the real world in multiple titles, first on Ingress and subsequently on Pokémon GO. The latter has been downloaded over 500 million times and has inspired players to walk more than 4.6 billion kilometers.
As we continue to depend on the rapidly expanding wireless ecosystem, we are challenged with threats related to user privacy, data confidentiality, and critical system availability. A significant portion of these threats is attributed to the broadcast nature of wireless transmissions. Using commodity radio hardware, unauthorized parties can easily eavesdrop on over-the-air transmissions and breach the privacy of communicating users by tracking their whereabouts and movements, and inferring their associations, health state, and preferences.
Modern communication systems are rapidly increasing in complexity fueled by high customer demand for data-rich media streaming over the airwaves. With limited, and sometimes fragmented, available spectrum, very complex modulation schemes with relatively high signal bandwidth are used to be able to “pack” such high data contents for wireless streaming. As a result, tremendous pressure is now put on RFIC designers to deliver circuits that can handle such complex modulation and maintain the required high signal integrity while still be power efficient.
Wireless networks have been traditionally used for communications. However, wireless signals also have the potential to extend our senses, enabling us to see moving objects through walls and behind closed doors. Specifically, as these signals travel in the medium, they traverse occlusions and bounce off different objects before arriving at a receiver; hence, they carry information about the environment. The key challenge in extracting this information is that we live in a sea of waves which interact with each other and with the environment in complex ways.
User’s everyday outgrowing demand for high-data-rate and high-performance mobile devices pushes industry and researchers into more sophisticated systems to fulfill those expectations. In this presentation, the challenges and suitable solutions to improve the performance of wireless transceivers are addressed. At first, a novel PA will be presented with an adaptive matching network and a nonlinearity cancelation technique.
Wireless technology and research have been evolving over the past decade to address more and more systems level challenges and a greater focus on how wireless can enable new experiences. Although traditional measures of capacity are still relevant and important, and clearly a focus of many ‘5G’ related research, there are also new requirements emerging in terms of latency, power consumption, cost, small form-factors, and application specific quality measures.
Wearable device that matches the soft human body represents an important trend for bio-integration; the resulting search for pliable electronic materials calls for strategies to bridge the gap between hard and soft – among which advanced engineering of the geometry and architecture of materials presents unique opportunities. A prominent example of geometry engineering is that nanowires of piezoelectric oxides can act as a flexible energy source; their synthesis, properties and integration into energy harvesting devices will be discussed.
In this talk, Dr. Doppler will introduce some of the connectivity challenges for wearables. Wearables range from head mounted displays for the consumption of Virtual Reality content to biostamps for medical diagnostics. I will introduce some of the limitations of current technologies and upcoming solutions that can address some of these limitations.
Time-based circuits encode analog information in the edge times of binary-valued signals. These circuits benefit from the fast transition times and high digital density offered by advanced CMOS processes, and offer a path to using digital circuits to perform analog processing of signals. Recent examples of such circuits include digital phase-locked loops and VCO-based analog-to-digital converters.
“Low-frequency” for radio astronomers is “Very HighFrequency” (VHF) for electrical engineers, i.e. up to ~300MHz. It is considered “low frequency” because it is lower than the typical operating frequency of a dish antenna. Similarly, “aperture arrays” do not involve any apertures (i.e. holes), but rather they are so named to distinguish them from dish arrays.
5G communication systems are expected to have 1000 times larger capacity using denser base station, wider communication bandwidth and higher spectral efficiency. Together with millimeter-wave communications, in-band full duplex radio system is one of potential solutions. In-band full duplex radio, which is often called STAR (simultaneous transmit and receive) system can achieve twice higher spectral efficiency theoretically.
The demand for wireless capacity and data rates continues to grow unabated. In order to meet this demand, future communication systems will incorporate a mix of potential solutions, including reconfigurable, spectrum sharing radios in the low GHz bands, and (sub) mm-wave radios.
The success of information theory in dealing with systems that incorporate feedback is limited. Even for the basic setting of fixed-length coding over a discrete memoryless channel (DMC), the effect of feedback on the fundamental limits regarding refined performance measures is not known in general and the common conjecture is that feedback does not improve any of them. However, feedback has been shown to dramatically improve these fundamental limits if one allows the decoding time to be random and impose an average delay constraint.
In-network queuing and distributed operation have been essential attributes of the classical TCP-IP networking ensuring scalability and fast growth. However, this architecture has come at the cost of excessive delay and tardy flow completion times. In recent years, and with the growth of inter-data center networking, new architectures are proposed which drastically depart from this classical approach and avoid in-network queuing all together.
Computer networks do not simply connect machines together, but run several applications on network devices, such as load balancers, intrusion detection systems, authentication portals, and more. Historically, these applications were black-boxes running on proprietary hardware, but software-defined networking (SDN) now allows anyone to write their own programs using open networking protocols (e.g., OpenFlow).So, what are the right abstractions for programming networks?
Radio frequency interference (RFI) is an hour-to-hour problem in commercial wideband satellite communications (SATCOM). In fact, there are between 2 and 3 interference incidents per hour worldwide in the commercial SATCOM industry. In response to this, there are emerging products known as interference excision devices. There are multiple product classes, but the most promising class for general purpose use is based on adaptive filters. Adaptive filters for noise cancellation have been around since the 1970s, but only recently have they been productized for use in the
Full-duplex wireless, which allows nodes to send and receive simultaneously in the same frequency band, has gain recent attention due to experimental demonstrations. In this talk, we will discuss an all-digital architecture for implementing full-duplex in systems with many antennas (10s to 100s). The new architecture, SoftNull, allows us to use current half-duplex radios on base-stations to implement full-duplex capability.
With mass production marching to 17nm CMOS technology and beyond, we are fast approaching the information resolution of the biological systems such as DNA/RNA and cellular ion channels. Electronic sensing, amplification, stimulation, data conversion and transmission can effectively realize a small proximity system with interface to the biomolecularand biological domains.
The suppression of unknown narrow band disturbances with time-varying characteristics has many industrial applications. The narrow band disturbances get mixed up with broadband noise of lower amplitude and usually appear at the output of the system. The objective is to use feedback to attenuate or reject the narrow band disturbances without amplifying the broadband noise. In this talk we present the design and analysis of an effective robust adaptive scheme that achieves the following:
Next-generation wireless networks aim to enable order-of-magnitude increases in connectivity, capacity, and speed. Such a goal can be achieved in part by utilizing larger frequency bandwidth or deploying denser base stations. However, as the number of wireless devices is exploding, it is inevitable that multiple devices communicate over the same time and spectrum. Consequently, mitigating the interference in concurrent transmission becomes the key challenge to future wireless systems.