Motivated by the ever increasing demand of wireless communication for larger capacity and higher quality, wireless communication system grows from a single-pair point-to-point communication system to a multiple-transceiver pair communication network. Various new communication techniques, for example, cooperative communication, interference management, multi-carrier communication, are employed to enhance the system capacity and improve the communication quality. Even for some single-pair communication scenarios, due to the different quality demands for different types of information messages, more advanced coding schemes should be designed to provide more protection for more important information messages, for example, the system emergency message. This thesis proposes several coding schemes to address the above questions. More specifically, the proposed coding schemes are summarized as follows. Message-wise error protection is a new unequal error protection scheme where in a codebook some special messages are more protected than other ordinary messages. We propose the first practical coding scheme for message-wise error protection based on LDPC codes, where codeword flipping is employed to separate the special message codewords from the ordinary message codewords. We consider a half-duplex 4-node joint relay system with two sources, one relay, and one destination, where the relay combines the information from both sources and transmits it to the destination together with both sources. We propose joint network and channel coding schemes based on the superposition coding (SC) and the Raptor coding (RC), and design practical Raptor codes for the proposed coding schemes. We propose novel coding and decoding methods for a fully connected K-user Gaussian interference channel. Each transmitter encodes its information into multiple layers and transmits the superposition of those layers. Each receiver performs a twofold task by first identifying which interferers it should decode and then determining which layers of them should be decoded. We propose practical coding schemes that employ the quadrature amplitude modulations (QAM) and Raptor codes. We propose group decoding and the associated rate allocation schemes for the multi-relay assisted interference channels, where both the relays and the destinations employ constrained group decoding. We consider two types of relay systems, the hopping relay system with no direct source-destination links, and the inband relay system with direct source-destination links. For each relay type, our objective is to design the relay assignment and group decoding strategies at the relays and destinations, to maximize the minimum information rate among all source-destination pairs. We consider a distributed storage system employing some existing regenerate codes where the storage nodes are scattered in a wireless network. The existing full-downloading approach, where the data collector downloads all symbols from a subset of the storage nodes for data reconstruction, becomes less efficient in wireless networks. This is because that, due to fading, the wireless channels may not offer sufficient bandwidths for full downloading. We propose a partial downloading scheme that allows downloading a portion of the symbols from any storage node, and formulate a cross-layer wireless resource allocation problem for data reconstruction employing such partial downloading. We derive necessary and sufficient conditions for the data reconstructability for partial downloading, in terms of the numbers of downloaded symbols from the storage nodes. We also propose channel and power allocation schemes for partial downloading in wireless distributed storage systems.

Silicon photonics has grown rapidly since the first Si electro-optic switch was demonstrated in 1987, and the field has never grown more quickly than it has over the past decade, fueled by milestone achievements in semiconductor processing technologies for low loss waveguides, high-speed Si modulators, Si lasers, Si detectors, and an enormous toolbox of passive and active integrated devices. Silicon photonics is now on the verge of major commercialization breakthroughs, and optical communication links remain the force driving integrated and Si photonics towards the first commercial telecom and datacom transceivers; however other potential and future applications are becoming uncovered and refined as researchers reveal the benefits of manipulating photons on the nanoscale. This thesis documents an exploration into the unique guided-wave and nonlinear properties of deeply-scaled high-index-contrast sub-wavelength Si waveguides. It is found that the tight confinement inherent to single-mode channel waveguides on the silicon-on-insulator platform lead to a rich physics, which can be leveraged for new devices extending well beyond simple passive interconnects and electro-optic devices. The following chapters will concentrate, in detail, on a number of unique physical features of Si waveguides and extend these attributes towards new and interesting devices. Linear optical properties and nonlinear optical properties are investigated, both of which are strongly affected by tight optical confinement of the guided waveguide modes. As will be shown, tight optical confinement directly results in strongly vectoral modal components, where the electric and magnetic fields of the guided modes extend into all spatial dimensions, even along the axis of propagation. In fact, the longitudinal electric and magnetic field components can be just as strong as the transverse fields, directly affecting the modal group velocity and energy transport properties since the longitudinal fields are shown to contribute no time-averaged momentum. Furthermore, the vectoral modal components, in conjunction with the tensoral nature of the third-order susceptibility of Si, lead to nonlinear properties which are dependent on waveguide orientation with respect to the Si parent crystal and the construction of the modal electric field components. This consideration is used to maximize effective nonlinearity and realize nonlinear Kerr gratings along specific waveguide trajectories. Tight optical confinement leads to a natural enhancement of the intrinsically large effective nonlinearty of Si waveguides, and in fact, the effective nonlinearty can be made to be almost 10^6 times greater in Si waveguides than that of standard single-mode fiber. Such a large nonlinearity motivates chip-scale all-optical signal processing techniques. Wavelength conversion by both four-wave-mixing (FWM) and cross-phase-modulation (XPM) will be discussed, including a technique that allows for enhanced broadband discrete FWM over arbitrary spectral spans by modulating both the linear and nonlinear waveguide properties through periodic changes in waveguide geometry. This quasi-phase-matching approach has very real applications towards connecting mature telecom sources detectors and components to other spectral regimes, including the mid-IR. Other signal processing techniques such as all-optical modulation format conversion via XPM will also be discussed. This thesis will conclude by looking at ways to extend the bandwidth capacity of Si waveguide interconnects on chip. As the number of processing cores continues to scale as a means for computational performance gains, on-chip link capacity will become an increasingly important issue. Metallic traces have severe limitations and are envisioned to eventually bow to integrated photonic links. The aggregate bandwidth supported by a single waveguide link will therefore become a crucial consideration as integrated photonics approaches the CPU. One way to increase aggregate bandwidth is to utilize different eigen-modes of a multimode waveguide, and integrated waveguide mode-muxes and demuxes for achieving simultaneous mode-division-multiplexing and wavelength-division-multiplexing will be demonstrated.

Analog-to-digital converters (ADCs) are analog pre-processing systems that convert the real life analog signals, the input of sensors or antenna, to digital bits that are processed by the system digital back-end. Due to the various issues associated with CMOS technology scaling such as reduced signal swings and lower transistor gains, the design of ADCs has seen a number of challenges in medium to high resolution and wideband digitization applications. The various chapters of this thesis focus on efficient design techniques for ADCs that aim to address the challenges associated with design in scaled CMOS technologies. This thesis discusses the design of three analog and mixed-signal prototypes: the first prototype introduces current pre-charging (CRP) techniques to generate the reference in Multiplying Digital-to-Analog Converters (MDACs) of pipeline ADCs. CRP techniques are specifically applied to Zero-Crossing Based (ZCB) Pipeline-SAR ADCs in this work. The proposed reference pre-charge technique relaxes power and area requirements for reference voltage generation and distribution in ZCB Pipeline ADCs, by eliminating power hungry low impedance reference voltage buffers. The next prototype describes the design of a radiation-hard dual-channel 12-bit 40MS/s pipeline ADC with extended dynamic range, for use in the readout electronics upgrade for the ATLAS Liquid Argon Calorimeters at the CERN Large Hadron Collider. The design consists of two pipeline A/D channels with four MDACs with nominal 12-bit resolution each, that are verified to be radiation-hard beyond the required specifications. The final prototype proposes Switched-Mode Signal Processing, a new design paradigm that achieves rail-to-rail signal swings with high linearity at ultra-low supply voltages. Switched-Mode Signal Processing represents analog information in terms of pulse widths and replaces the output stage of OTAs with power-efficient rail-to-rail Class-D stages, thus producing Switched-Mode Operational Amplifiers (SMOAs). The SMOAs are used to implement a Programmable Gain Amplifier (PGA) that has a programmable gain from 0-12dB.

Detection and estimation, two classical statistical signal processing problems with wellestablished theories, are traditionally studied under the fixed-sample-size and centralized setups, e.g., Neyman-Pearson target detection, and Bayesian parameter estimation. Recently, they appear in more challenging setups with stringent constraints on critical resources, e.g., time, energy, and bandwidth, in emerging technologies, such as wireless sensor networks, cognitive radio, smart grid, cyber-physical systems (CPS), internet of things (IoT), and networked control systems. These emerging systems have applications in a wide range of areas, such as communications, energy, the military, transportation, health care, and infrastructure. Sequential (i.e., online) methods suit much better to the ever-increasing demand on time-efficiency, and latency constraints than the conventional fixed-sample-size (i.e., offline) methods. Furthermore, as a result of decreasing device sizes and tendency to connect more and more devices, there are stringent energy and bandwidth constraints on devices (i.e., nodes) in a distributed system (i.e., network), requiring decentralized operation with low transmission rates. Hence, for statistical inference (e.g., detection and/or estimation) problems in distributed systems, today's challenge is achieving high performance (e.g., time efficiency) while satisfying resource (e.g., energy and bandwidth) constraints. In this thesis, we address this challenge by (i) first finding optimum (centralized) sequential schemes for detection, estimation, and joint detection and estimation if not available in the literature, (ii) and then developing their asymptotically optimal decentralized versions through an adaptive non-uniform sampling technique called level-triggered sampling. We propose and rigorously analyze decentralized detection, estimation, and joint detection and estimation schemes based on level-triggered sampling, resulting in a systematic theory of event-based statistical signal processing. We also show both analytically and numerically that the proposed schemes significantly outperform their counterparts based on conventional uniform sampling in terms of time efficiency. Moreover, they are compatible with the existing hardware as they work with discrete-time observations produced by conventional A/D converters. We apply the developed schemes to several problems, namely spectrum sensing and dynamic spectrum access in cognitive radio, state estimation and outage detection in smart grid, and target detection in multi-input multi-output (MIMO) wireless sensor networks.

The continuing growth of microelectronics in speed, scale, and complexity has led to a looming bandwidth bottleneck for traditional electronic interconnects. This has precipitated the penetration of optical interconnects to smaller, more localized scales, in such applications as data centers, supercomputers, and access networks. For this next generation of optical interconnects, the silicon photonic platform has received wide attention for its ability to manifest, more economical, high-performance photonics. The high index contrast and CMOS compatibility of the silicon platform give the potential to intimately integrate small footprint, power-efficient, high-bandwidth photonic interconnects with existing high-performance CMOS microelectronics. Within the silicon photonic platform, traditional photonic elements can be manifested with smaller footprint and higher energy-efficiency. Additionally, the high index contrast allows the successful implementation of silicon microring-based devices, which push the limits on achievable footprint and energy-efficiency metrics. While laboratory demonstrations have testified to their capabilities as powerful modulators, switches, and filters, the commercial implementation of microring-based devices is impeded by their susceptibility to fabrication tolerances and their inherent temperature sensitivity. This work develops and demonstrates methods to resolve the aforementioned sensitivities of microring-based devices. Specifically, the use of integrated heaters to thermally tune and lock microring resonators to laser wavelengths, and the underlying control systems to enable such functionality. The first developed method utilizes power monitoring to show the successful thermal stabilization of a microring modulator under conditions that would normally render it inoperational. In a later demonstration, the photodetector used for power monitoring is co-integrated with the microring modulator, again demonstrating thermal stabilization of a microring modulator and validating the use of defect-enhanced silicon photodiodes for on-chip control systems. Secondly, a generalized method is developed that uses dithering signals to generate anti-symmetric error signals for use in stabilizing microring resonators. A control system utilizing a dithering signal is shown to successfully wavelength lock and thermally stabilize a microring resonator. Characterizations are performed on the robustness and speed of the wavelength locking process when using dithering signals. An FPGA implementation of the control system is used to scale to a WDM microring demultiplexer, demonstrating the simultaneous wavelength locking of multiple microring resonators. Additionally, the dithering technique is adopted to create control systems for microring-based switches, which have traditionally posed a challenging problem due to their multi-state configurations. The aforementioned control systems are rigorously tested for applications with high speed data and analyzed for power efficiency and scalability to show that they can successfully scale to commercial implementations and be the enabling factor in the commercial deployment of microring-based devices.

With the rapid development of energy harvesting technologies, a new paradigm of wireless communications that employs energy harvesting transmitters has become a reality. The renewable energy source enables the flexible deployment of the transmitters and prolongs their lifetimes. To make the best use of the harvested energy, many challenging research issues arise from the new paradigm of communications. In particular, optimal resource (energy, bandwidth, etc.) allocation is key to the design of an efficient wireless system powered by renewable energy sources. In this thesis, we focus on several resource allocation problems for energy harvesting communications, including the energy allocation for a single energy harvesting transmitter, and the joint energy and spectral resource allocation for energy harvesting networks. More specifically, the resource allocation problems discussed in this thesis are summarized as follows. We solve the problem of designing an affordable optimal energy allocation strategy for the system of energy harvesting active networked tags (EnHANTs), that is adapted to the identification request and the energy harvesting dynamic. We formulate a Markov decision process (MDP) problem to optimize the overall system performance which takes into consideration of both the system activity-time and the communication reliability. To solve the problem, both a static exhaustive search method and a modified policy iteration algorithm are employed to obtain the optimal energy allocation policy. We develop an energy allocation algorithm to maximize the achievable rate for an access-controlled energy harvesting transmitter based on causal observations of the channel fading states. We formulate the stochastic optimization problem as a Markov decision process (MDP) with continuous states and define an approximate value function based on a piecewise linear fit in terms of the battery state. We show that with the approximate value function, the update in each iteration consists of a group of convex problems with a continuous parameter and we derive the optimal solution to these convex problems in closed-form. Specifically, the computational complexity of the proposed algorithm is significantly lower than that of the standard discrete MDP method. We propose an efficient iterative algorithm to obtain the optimal energy-bandwidth allocation for multiple flat-fading point-to-point channels, maximizing the weighted sum-rate given the predictions of the energy and channel state. For the special case that each transmitter only communicates with one receiver and the objective is to maximize the total throughput, we develop efficient algorithms for optimally solving the subproblems involved in the iterative algorithm. Moreover, a heuristic algorithm is also proposed for energy-bandwidth allocation based on the causal energy and channel observations. We consider the energy-bandwidth allocation problem in multiple orthogonal and non-orthogonal flat-fading broadcast channels to maximize the weighted sum-rate given the predictions of energy and channel states. To efficiently obtain the optimal allocation, we extend the iterative algorithm originally proposed for multiple flat-fading point-to-point channels and further develop the optimal algorithms to solve the corresponding subproblems. For the orthogonal broadcast channel, the proportionally-fair (PF) throughput maximization problem is formulated and we derive the equivalence conditions such that the optimal solution can be obtained by solving a weighted throughput maximization problem. The algorithm to obtain the proper weights is also proposed. We consider the energy-subchannel allocation problem for energy harvesting networks in frequency-selective fading channels. We first assume that the harvested energy and subchannel gains can be predicted and propose an algorithm to efficiently obtain the energy-subchannel allocations for all links over the scheduling period based on controlled water-filling. The proposed algorithm is shown to be asymptotically optimal when the bandwidth of the subchannel goes to zero. A causal algorithm is also proposed based on the Q-learning technique that makes use of the statistics of the energy harvesting and channel fading processes.

Silicon has numerous benefits as a photonic integrated circuit platform, including optical transparency from 1.1 µm to greater than 5 µm, tight optical confinement due to its high index of refraction, high third order non-linearity, and lack of two photon absorption at wavelengths above 2.2 µm. Additionally, silicon photonics has the added benefit of decades of fabrication knowledge from the CMOS industry. Despite these advantages, an enormous challenge exists in two areas, optical sources for silicon photonic integrated circuits, and on the other end, optical detectors for silicon photonic integrated circuits. The same bandgap energy that leads to the optical transparency at telecom and mid-infrared wavelengths, limits both generation and detection in this same regime. This dissertation focuses on the detection problem, exploring the use of defect-mediated sub-bandgap optical absorption in ion-implanted silicon nano-wire waveguides. Section I of this dissertation focuses on fabrication and the ion-implantation process, including a primer on Shockley-Read-Hall theory and its application to defect-mediated sub-bandgap optical absorption. Section II examines the devices for use at telecom wavelengths. In Chapter 4, the fabrication and characterization of metal-semiconductor-metal ion-implanted silicon nano-wire waveguide photodiodes is examined. These devices require minimal fabrication, are compatible with standard CMOS fabrication processes, and exhibited responsivities as high as 0.51 A/W and frequency responses greater than 2.6 GHz. With improved fabrication tolerances, frequency responses of greater than 10 GHz are expected. Chapter 5 examined these ion-implanted photodiodes in a p-i-n configuration as a high speed data interconnect, demonstrating error free operation at 10 Gbs with expected sensitivities approaching that of Ge detectors. Section III extends the above research to longer wavelengths, starting with data reception at 1.9 µm in Chapter 6, exhibiting an approximate 5 dB penalty in sensitivity compared to the same diodes at 1.55 µm, at a data rate of 1 Gbs, limited by RC due to the 2 mm length of the device. Chapter 7 goes even further, characterizing Si+ implanted silicon nano-wire waveguides for operation between 2.2 µm and 2.35 µm. These devices showed responsivities as high as 9.9 mA/W, with internal quantum efficiencies approaching 5%. Chapter 8 concludes with the characterization of Zn+ implanted silicon nano-wire waveguides operating in the same wavelength regime, exhibiting higher overall responsivity, albeit at a much higher reverse bias. These long wavelength devices open up new areas of research for silicon photonics, allowing for CMOS compatible detectors operating into the mid-infrared region, useful for chemical sensing, free-space communications, and medical imaging.

Today, the Internet traffic is growing at a near exponential rate, driven predominately by data center-based applications and Internet-of-Things services. This fast-paced growth in Internet traffic calls into question the ability of the existing optical network infrastructure to support this continued growth. The overall optical networking equipment efficiency has not been able to keep up with the traffic growth, creating a energy gap that makes energy and cost expenditures scale linearly with the traffic growth. The implication of this energy gap is that it is infeasible to continue using existing networking equipment to meet the growing bandwidth demand. A redesign of the optical networking platform is needed. The focus of this dissertation is on the design and implementation of energy efficient, cross-layer enabled, dynamic optical networking platforms, which is a promising approach to address the exponentially growing Internet bandwidth demand. Chapter 1 explains the motivation for this work by detailing the huge Internet traffic growth and the unsustainable energy growth of today's networking equipment. Chapter 2 describes the challenges and objectives of enabling agile, dynamic optical networking platforms and the vision of the Center for Integrated Access Networks (CIAN) to realize these objectives; the research objectives of this dissertation and the large body of related work in this field is also summarized. Chapter 3 details the design and implementation of dynamic networking platforms that support wavelength switching granularity. The main contribution of this work involves the experimental validation of deep cross-layer communication across the optical performance monitoring (OPM), data, and control planes. The first experiment shows QoS-aware video streaming over a metro-scale test-bed through optical power monitoring of the transmission wavelength and cross-layer feedback control of the power level. The second experiment extends the performance monitoring capabilities to include real-time monitoring of OSNR and polarization mode dispersion (PMD) to enable dynamic wavelength switching and selective restoration. Chapter 4 explains the author's contributions in designing dynamic networking at the sub-wavelength switching granularity, which can provide greater network efficiency due to its finer granularity. To support dynamic switching, regeneration, adding/dropping, and control decisions on each individual packet, the cross-layer en- abled node architecture is enhanced with a FPGA controller that brings much more precise timing and control to the switching, OPM, and control planes. Furthermore, QoS-aware packet protection and dynamic switching, dropping, and regeneration functionalities were experimentally demonstrated in a multi-node network. Chapter 5 describes a technique to perform optical grooming, a process of optically combining multiple incoming data streams into a single data stream, which can simultaneously achieve greater bandwidth utilization and increased spectral efficiency. In addition, an experimental demonstration highlighting a fully functioning multi-node, agile optical networking platform is detailed. Finally, a summary and discussion of future work is provided in Chapter 6. The future of the Internet is very exciting, filled with not-yet-invented applications and services driven by cloud computing and Internet-of-Things. The author is cautiously optimistic that agile, dynamically reconfigurable optical networking is the solution to realizing this future.

The accelerated growth in performance of microprocessors and the emergence of chip multiprocessors, which are now widely leveraged in current data centers and high-performance computing (HPC) systems, have motivated the need for developing novel interconnection networks solutions to meet the growing need for data transmissions across all levels of the infrastructure. This work posits that, given the unique characteristics of optics---advantages and limitations---purpose-driven systems-level designs are necessary in order to harness the tremendous performance and efficiency opportunities that can be enabled by photonic interconnects. First, an enhanced optically connected network architecture is presented featuring advanced photonic functionalities to support a wider class of bandwidth-intensive traffic patterns characteristic of cloud computing systems. This proposed architectural framework can enable a rich set of photonic resources to be allocated on-demand to optimize communications between various applications within the data center. A prototype of the proposed optical network architecture is constructed and a demonstration of two unique functionalities, serving to validate the physical layer feasibility of the system, is presented. An instantiation of this architectural framework is presented that enables physical layer data duplication in order to more effectively support reliable group data delivery in the data center. Compared to the conventional solutions that duplicate data in the network or application layer, this architecture achieves efficient data transmission over the ultra-fast, loss-free, energy-efficient and low cost optical paths, with simplified flow control, congestion control, and group membership management. Both an end-to-end hardware experiment and large-scale simulations were carried out to evaluate the efficacy of the design. Next, the challenges associated with interfacing to photonically-switched networks are explored. In particular, various interface designs aimed at addressing the unique challenges imposed by optical-packet switched networks are proposed and evaluated. First, an overview of the data vortex network optical packet switch architecture is given. A high-speed optical packet formatter and interface is then presented along with the results of end-to-end data exchanges across the interface connected to a data vortex network. Finally, the design of a low-power all-optical interface alternative is validated with an end-to-end demonstration. Finally, various unique photonic switching node designs are introduced for a variety of applications|a nanosecond-scale bidirectional 2 x —2 switch to construct efficient optical fat-tree architectures, a 4 x —4 switch capable of operating as both a nanosecond-scale optical packet switch and as an optical circuit switch, and a non-blocking 4 x —4 switch designed for constructing on-chip photonic integrated networks.

In recent years the proliferation of wireless devices such as tablets and smartphones has resulted in an unprecedented crowding of the radio spectrum around the world. The high density of radio signals being transmitted at any one time has necessitated the use of high-performance radio-frequency (RF) filters prior to any receiver signal path in order to protect the device against interference. State-of-the-art filter technologies based on piezoelectric resonators provide good rejection of interfering signals, but do not scale well to cover the large range of frequencies currently allocated for cellular communications. This thesis presents measurements and analysis of a new active resonator technology, known as a graphene resonant channel transistor (G-RCT), that has the potential to be used in micron-scale RF filters that are capable of covering these larger bandwidths. A compact model for G-RCTs is developed that accurately replicates the AC, DC, and frequency tuning characteristics of the device, enabling the design and simulation of hybrid electromechanical circuits. The device noise is also modeled, and analytical expressions for the noise figure of circuits using G-RCTs are derived. Finally, expressions for third-order intermodulation distortion are derived and validated with measurements.