Cross-layer fault tolerance in networks-on-chip

The design of Networks-on-Chip follows the Open Systems Interconnection (OSI) reference model. The OSI model defines strictly separated network abstraction layers and specifies their functionality. Each layer has layer-specific information about the network that can be exclusively accessed by the methods of the layer. Adhering to the strict layer boundaries, however, leads to methods of the individual layers working in isolation from each other. This lack of interaction between methods is disadvantageous for fault diagnosis and fault tolerance in Networks-on-Chip as it results in solutions that have a high effort in terms of the time and implementation costs required to deal with faults. For Networks-on-Chip cross-layer design is considered as a promising method to remedy these shortcomings. It removes the strict layer boundaries by the exchange of information between layers. This interaction enables methods of different layers to cooperate, and thus, deal with faults more efficiently. Furthermore, providing lower layer information to the software allows hardware methods to be implemented as software tasks resulting in a reduction of the hardware complexity. The goal of this dissertation is the investigation of cross-layer design for fault diagnosis and fault tolerance in Networks-on-Chip. For fault diagnosis a scheme is proposed that allows the interaction of protocol-based diagnosis of the transport layer with functional diagnosis of the network layer and structural diagnosis of the physical layer by exchanging diagnostic information. The techniques use this information for optimizing their own diagnosis process. For protocol-based diagnosis on the transport layer, a diagnosis protocol is proposed that is able to locate faulty links, switches, and crossbar connections. For this purpose, the technique utilizes available information of lower layers. As proof of concept for the proposed interaction scheme, the diagnosis protocol is combined with a functional and a structural diagnosis approach and the performance and diagnosis quality of the resulting combinations is investigated. The results show that the combinations of the diagnosis protocol with one of the lower layer techniques have a considerably reduced fault localization latency compared to the functional and the structural standalone techniques. This reduction, however, comes at the expense of a reduced diagnosis quality. In terms of fault tolerance, the focus of this dissertation is on the design and implementation of cross-layer approaches utilizing software methods to provide fault tolerance for network layer routings. Two approaches for different routings are presented. The requirements to provide information of lower layers to the software using the available Network-on-Chip resources and interfaces for data communication are discussed. The concepts of two mechanisms of the data link layer are presented for converting status information into communicable units and for preventing communication resources from being blocked. In the first approach, software-based packet rerouting is proposed. By incorporating information from different layers, this approach provides fault tolerance for deterministic network layer routings. As specialization of software-based rerouting, dimension-order XY rerouting is presented. In the second approach, a reconfigurable routing for Networks-on-Chip with logical hierarchy is proposed in which cross-layer interaction is used to enable hierarchical units to manage themselves autonomously and to reconfigure the routing. Both approaches are evaluated regarding their performance as well as their implementation costs. In a final study, the cross-layer diagnosis technique and cross-layer fault tolerance approaches are combined. The information obtained by the diagnosis technique is used by the fault tolerance approaches for packet rerouting or for routing reconfiguration. The combinations are evaluated regarding their impact on Networks-on-Chip performance. The results show that the crosslayer information exchange with software has a considerable impact on performance when the amount of information becomes too large. In case of crosslayer diagnosis, however, the impact on Networks-on-Chip performance is significantly lower compared to functional and structural diagnosis

A Scalable and Adaptive Network on Chip for Many-Core Architectures

In this work, a scalable network on chip (NoC) for future many-core architectures is proposed and investigated. It supports different QoS mechanisms to ensure predictable communication. Self-optimization is introduced to adapt the energy footprint and the performance of the network to the communication requirements. A fault tolerance concept allows to deal with permanent errors. Moreover, a template-based automated evaluation and design methodology and a synthesis flow for NoCs is introduced

1-D broadside-radiating leaky-wave antenna based on a numerically synthesized impedance surface

A newly-developed deterministic numerical technique for the automated design of metasurface antennas is applied here for the first time to the design of a 1-D printed Leaky-Wave Antenna (LWA) for broadside radiation. The surface impedance synthesis process does not require any a priori knowledge on the impedance pattern, and starts from a mask constraint on the desired far-field and practical bounds on the unit cell impedance values. The designed reactance surface for broadside radiation exhibits a non conventional patterning; this highlights the merit of using an automated design process for a design well known to be challenging for analytical methods. The antenna is physically implemented with an array of metal strips with varying gap widths and simulation results show very good agreement with the predicted performance

Beam scanning by liquid-crystal biasing in a modified SIW structure

A fixed-frequency beam-scanning 1D antenna based on Liquid Crystals (LCs) is designed for application in 2D scanning with lateral alignment. The 2D array environment imposes full decoupling of adjacent 1D antennas, which often conflicts with the LC requirement of DC biasing: the proposed design accommodates both. The LC medium is placed inside a Substrate Integrated Waveguide (SIW) modified to work as a Groove Gap Waveguide, with radiating slots etched on the upper broad wall, that radiates as a Leaky-Wave Antenna (LWA). This allows effective application of the DC bias voltage needed for tuning the LCs. At the same time, the RF field remains laterally confined, enabling the possibility to lay several antennas in parallel and achieve 2D beam scanning. The design is validated by simulation employing the actual properties of a commercial LC medium

Maintenance Management of Wind Turbines

“Maintenance Management of Wind Turbines” considers the main concepts and the state-of-the-art, as well as advances and case studies on this topic. Maintenance is a critical variable in industry in order to reach competitiveness. It is the most important variable, together with operations, in the wind energy industry. Therefore, the correct management of corrective, predictive and preventive politics in any wind turbine is required. The content also considers original research works that focus on content that is complementary to other sub-disciplines, such as economics, finance, marketing, decision and risk analysis, engineering, etc., in the maintenance management of wind turbines. This book focuses on real case studies. These case studies concern topics such as failure detection and diagnosis, fault trees and subdisciplines (e.g., FMECA, FMEA, etc.) Most of them link these topics with financial, schedule, resources, downtimes, etc., in order to increase productivity, profitability, maintainability, reliability, safety, availability, and reduce costs and downtime, etc., in a wind turbine. Advances in mathematics, models, computational techniques, dynamic analysis, etc., are employed in analytics in maintenance management in this book. Finally, the book considers computational techniques, dynamic analysis, probabilistic methods, and mathematical optimization techniques that are expertly blended to support the analysis of multi-criteria decision-making problems with defined constraints and requirements

Monitoring of passive optical networks utilising an optical coding technique

Passive Optical Networks (PONs) have become the most popular fibre based access networks over the last decade. They are widely deployed for use in Fibre-to-the-Premises (FTTP) scenarios. PON is a point-to-multipoint connection (P2MP) between an optical line terminal (OLT) located at the central office (CO) and multiple optical network units (ONU) at the customer premises. The next generation of PONs (NG-PON) are likely to deploy a ring-and-spur long reach PON (LR-PON). NG-PON aims to accommodate more ONUs, extend the network coverage out to 100 km, minimize complexity and improve operational outcomes. An all fibre access network, operating over extended distances, presents a reliability risk, thereby increasing the need for a reliable and cost-effective monitoring system to enhance protection and reduce restoration time. Among existing monitoring techniques, attention is focused on approaches that use optical code division multiplexing (OCDM), also known as optical coding (OC). The OC is applied to a signal that is sent from the network management system (NMS) to the ONUs. The monitoring signal is transmitted onto a fibre and split into a number of sub-signals that are equal in number to the ONUs. Each one of the ONUs receives a sub-signal, encodes it, and then reflects it back to the NMS. The NMS has the capability to identify faulty ONUs by examining the code received from the ONUs. A review of the literature has shown that the use of OCs does improve system performance, especially in the timely detection of faults. Many of the studies, found in the literature, focus on how to implement optical spreading codes that are used in OCDM Access (OCDMA) systems and currently the optical orthogonal code (OOC) is the dominant code implemented for time-domain coding. Although the OOC code performs well, its construction is relatively complex. The available code-words (cardinality) that are offered by OOC are proportional to the code length. Implementing OOC in a high capacity PON requires a long code length causes an inevitable degradation of system performance. Therefore, an improved optical coding technique for PONs should provide code-words that conform to PON split ratios. The main objective of the research was to develop an optical spreading code, based on a prime code family for OCDMA systems, that has the capability to accommodate different PON split ratios and with characteristics that improve transmission system performance when compared to existing prime code families. The novel code presented in this thesis is identified as the extended grouped new modified prime code (EG-nMPC). The number of code-words generated by the proposed codes are substantially higher than those generated by the existing code families and more compatible to the different PON splitting ratios. In addition, with a low code weight, both power consumption and hardware complexity decreases. The code performance was evaluated using mathematical models for two transmission formats - pulse position modulation (PPM) and on-off keying (OOK) modulation. The performance of EG-nMPC was compared to other prime codes, and the results show that the proposed code improves the performance of OCDMA in terms of bit-error rate (BER). As PON is a point-to-multipoint connection oriented access network, downstream traffic is encrypted and broadcast to all ONUs, while the unencrypted upstream traffic from each ONU terminal occurs in a burst mode. The OLT carries out a ranging process to determine transmission delays between ONUs, to prevent collisions between the burst mode traffic from each of the ONUs. In this research, the burst mode traffic ranging process has been replicated in the monitoring system, with this replication providing a fixed equalization delay time for the monitoring transmissions. To investigate the ring-and-spur LR-PON reliability several protection architectures were evaluated, in term of cost and availability, to determine the optimal protection architecture. In this thesis, the reliability parameter Failure Impact Robustness (FIR), has been used to calculate the failure impact of the different components in ring-and-spur LR-PON, hence selecting the optimal protection scheme. A PON-based optical communication system model was developed and the proposed EG-nMPC code was incorporated. Fibre split ratios of 32, 64 and 128, were considered in this study. The simulation results show that the EG-nMPC code improves the performance, efficiency and accuracy of the PON transmission monitoring system. To conclude, this research aims to enhance the PON performance by a fast detection of the fault and quick restoration. This research has contributed to knowledge by identifying a new and novel spreading code that is compatible with the different PON splitting ratios for OC monitoring techniques. By using the ranging process, a fixed equalization delay time has been assigned to each ONU to manage the upstream burst traffic. The spreading code has been implemented in a real-time simulation to show the status of each fibre link. The implementation was carried out based on 1-D tree topology system. However, the proposed EG-nMPC can be exploited to enable network monitoring that is based on hybrid 1D/2D coding. This coding is complementary with the structure of LR-PON as explained in section ‎8.2.3. In addition, with the use of the FIR parameter for the different components in the ring-and-spur architecture, an optimal protection scheme for both OLT and the ring (feeder fibre), has been nominated. This protection scheme ensures that protection, availability and cost are at their optimal values

Sensor Characteristics Reference Guide

The Buildings Technologies Office (BTO), within the U.S. Department of Energy (DOE), Office of Energy Efficiency and Renewable Energy (EERE), is initiating a new program in Sensor and Controls. The vision of this program is: • Buildings operating automatically and continuously at peak energy efficiency over their lifetimes and interoperating effectively with the electric power grid. • Buildings that are self-configuring, self-commissioning, self-learning, self-diagnosing, self-healing, and self-transacting to enable continuous peak performance. • Lower overall building operating costs and higher asset valuation. The overarching goal is to capture 30% energy savings by enhanced management of energy consuming assets and systems through development of cost-effective sensors and controls. One step in achieving this vision is the publication of this Sensor Characteristics Reference Guide. The purpose of the guide is to inform building owners and operators of the current status, capabilities, and limitations of sensor technologies. It is hoped that this guide will aid in the design and procurement process and result in successful implementation of building sensor and control systems. DOE will also use this guide to identify research priorities, develop future specifications for potential market adoption, and provide market clarity through unbiased informatio

Design Development Test and Evaluation (DDT and E) Considerations for Safe and Reliable Human Rated Spacecraft Systems

A team directed by the NASA Engineering and Safety Center (NESC) collected methodologies for how best to develop safe and reliable human rated systems and how to identify the drivers that provide the basis for assessing safety and reliability. The team also identified techniques, methodologies, and best practices to assure that NASA can develop safe and reliable human rated systems. The results are drawn from a wide variety of resources, from experts involved with the space program since its inception to the best-practices espoused in contemporary engineering doctrine. This report focuses on safety and reliability considerations and does not duplicate or update any existing references. Neither does it intend to replace existing standards and policy