50 research outputs found

    Methods for Control, Calibration, and Performance Optimization of Phased Array Systems

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    Phased array radar systems have proven advantageous in a variety of research applications, offering faster volume scans and unparalleled time-resolution as compared to traditional parabolic dish antenna systems that rely solely on mechanical systems for controlling the direction of radiation. As such, research has accelerated the development of practical phased array systems to realize their full vision. In particular, next generation phased array systems aim to provide additional advantages in the form of re-configurable beam patterns, adaptive digital beamforming, multiple-input multiple-output (MIMO) radar modes, and other software-defined technologies. However, to fully realize a paradigm shift in phased array technology, especially as the ratio of array to sub-array size becomes greater, this requires a corresponding increase in novel digital backend architectures to fully achieve this vision. Therefore, new methods for control, calibration, and performance optimization are required to enable next-generation phased array systems to reach their potential. In this thesis, a variety of practical engineering challenges related to phased array system design are discussed, with system-level implications and relevant theory included where necessary. For instance, for the first time, as explained in this thesis, a GPS disciplined, time-interleaved measurement technique that leveraged real-time control of a beamformer was developed to enable accurate post-processing correction of the phase drift that results from clocking differences between noncoherent physically separated bistatic nodes. In addition, laboratory efficacy of digital predistortion using the memory-polynomial model has been confirmed for the purpose of maximizing an element's usable power while minimizing spectral spreading and achieving desirable output linearity during operation, and a novel method for training predistortion models comprised of a combined software-defined and physical mechanism for measuring transmitter front-end distortion for elements within a digital-at-every element array has been proposed and verified in the lab

    A cross-stack, network-centric architectural design for next-generation datacenters

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    This thesis proposes a full-stack, cross-layer datacenter architecture based on in-network computing and near-memory processing paradigms. The proposed datacenter architecture is built atop two principles: (1) utilizing commodity, off-the-shelf hardware (i.e., processor, DRAM, and network devices) with minimal changes to their architecture, and (2) providing a standard interface to the programmers for using the novel hardware. More specifically, the proposed datacenter architecture enables a smart network adapter to collectively compress/decompress data exchange between distributed DNN training nodes and assist the operating system in performing aggressive processor power management. It also deploys specialized memory modules in the servers, capable of performing general-purpose computation and network connectivity. This thesis unlocks the potentials of hardware and operating system co-design in architecting application-transparent, near-data processing hardware for improving datacenter's performance, energy efficiency, and scalability. We evaluate the proposed datacenter architecture using a combination of full-system simulation, FPGA prototyping, and real-system experiments

    Solutions for the optimization of the software interface on an FPGA-based NIC

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    The theme of the research is the study of solutions for the optimization of the software interface on FPGA-based Network Interface Cards. The research activity was carried out in the APE group at INFN (Istituto Nazionale di Fisica Nucleare), which has been historically active in designing of high performance scalable networks for hybrid nodes (CPU/GPU) clusters. The result of the research is validated on two projects the APE group is currently working on, both allowing fast prototyping for solutions and hardware-software co-design: APEnet (a PCIe FPGA-based 3D torus network controller) and NaNet (FPGA-based family of NICs mainly dedicated to real-time, low-latency computing systems such as fast control systems or High Energy Physics Data Acquisition Systems). NaNet is also used to validate a GPU-controlled device driver to improve network perfomances, i.e. even lower latency of the communication, while used in combination with existing user-space software. This research is also gaining results in the "Horizon2020 FET-HPC ExaNeSt project", which aims to prototype and develop solutions for some of the crucial problems on the way towards production of Exascale-level Supercomputers, where the APE group is actively contribuiting to the development of the network / interconnection infrastructure

    High-speed, low cost test platform using FPGA technology

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    The object of this research is to develop a low-cost, adaptable testing platform for multi-GHz digital applications, with concentration on the test requirement of advanced devices. Since most advanced ATEs are very expensive, this equipment is not always available for testing cost-sensitive devices. The approach is to use recently-introduced advanced FPGAs for the core logic of the testing platform, thereby allowing for a low-cost, low power-consumption, high-performance, and adaptable test system. Furthermore to customize the testing system for specific applications, we implemented multiple extension testing modules base on this platform. With these extension modules, new functions can be added easily and the test system can be upgraded with specific features required for other testing purposes. The applications of this platform can help those digital devices to be delivered into market with shorter time, lower cost and help the development of the whole industry.Ph.D

    Digital Signal Processor Based Real-Time Phased Array Radar Backend System and Optimization Algorithms

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    This dissertation presents an implementation of multifunctional large-scale phased array radar based on the scalable DSP platform. The challenge of building large-scale phased array radar backend is how to address the compute-intensive operations and high data throughput requirement in both front-end and backend in real-time. In most of the applications, FPGA or VLSI hardware are typically used to solve those difficulties. However, with the help of the fast development of IC industry, using a parallel set of high-performing programmable chips can be an alternative. We present a hybrid high-performance backend system by using DSP as the core computing device and MTCA as the system frame. Thus, the mapping techniques for the front and backend signal processing algorithm based on DSP are discussed in depth. Beside high-efficiency computing device, the system architecture would be a major factor influencing the reliability and performance of the backend system. The reliability requires the system must incorporate the redundancy both in hardware and software. In this dissertation, we propose a parallel modular system based on MTCA chassis, which can be reliable, scalable, and fault-tolerant. Finally, we present an example of high performance phased array radar backend, in which there is the number of 220 DSPs, achieving 7000 GFLOPS calculation from 768 channels. This example shows the potential of using the combination of DSP and MTCA as the computing platform for the future multi-functional large-scale phased array radar

    Operating System Support for High-Performance Solid State Drives

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    A Symbiotic Approach to Designing Cross-Layer QoS in Embedded Real-Time Systems

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    International audienceNowadays there is an increasing need for embedded systems to support intensive computing while maintaining traditional hard real-time and fault-tolerant properties. Extending the principle of multi-core systems, we are exploring the use of distributed processing units interconnected via a high performance mesh network as a way of supporting distributed real-time applications. Fault-tolerance can then be ensured through dynamic allocation of both computing and communication resources. We postulate that enhancing QoS (Quality of Service) for real-time applications entails the development of a cross-layer support of high-level requirements, thus requiring a deep knowledge of the underlying networks. In this paper, we propose a new simulation/emulation/experimentation framework, ERICA, for designing such a feature. ERICA integrates both a network simulator and an actual hardware network to allow implementation and evaluation of different QoS-guaranteeing mechanisms. It also supports real-software-in-the-loop, i.e. running of real applications and middleware over these networks. Each component can evolve separately or together in a symbiotic manner, also making teamwork more flexible. We present in more detail our discrete-event simulation approach and the in-silicon implementation with which we cross-check our solutions in order to bring real performance aspects to our work. We also discuss the challenges of running real-software-in-the-loop in a real-time context, i.e. how to bridge it with a network simulator, and how to deal with time consistency

    Development of FPGA-based High-Speed serial links for High Energy Physics Experiments

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    High Energy Physics (HEP) experiments generate high volumes of data which need to be transferred over long distance. Then, for data read out, reliable and high-speed links are necessary. Over the years, due to their extreme high bandwidth, serial links (especially optical) have been preferred over the parallel ones. So that, now, high-speed serial links are commonly used in Trigger and Data Acquisition (TDAQ) systems of HEP experiments, not only for data transfer, but also for the distribution of trigger and control systems. Examples of their wide use can be found at CERN, where each of the four big experiments mounted on the Large Hadron Collider (LHC) uses a huge amount of serial links in its read out system. Again at LHC, the Timing, Trigger and Control system (TTC), which broadcasts the timing signals, from the LHC machine to the experiments, uses optical serial link to distribute signals over kilometers of distance (diameter of LHC is 27 Km). Also for upgrades of LHC, physical layer components and protocol chips (ASIC) have been designed and are now under development: the Versatile Link and the GBT protocol (and ASICs) whose peculiarity relies in their radiation hardness. This PhD project is intended to respond to the requests of HEP experiments, developing: - a high-speed self-adapting serial link, which can be easily used in different application fields; - the serial interface of a read out board in the end-cap region of ATLAS Experiment at LHC; - the interface board for the barrel read out system of the ATLAS Experiments. Both the two last projects have required the development of fixed latency, high-speed serial links. In order to take advantage of flexibility, re-programmability and system integration of SRAM-based Field Programmable Gate Array devices (FPGAs), their serializer-deserializer (SERDES) embedded modules have been chosen for the development of the links. However, as a drawback, FPGA embedded SERDESes are typically designed for applications that do not require a deterministic latenc. Then, an accurate study of their architecture has been necessary, in order to find a configuration and a clocking scheme to guarantee a deterministic transmission delay in data transfers. The frequency agile, auto-adaptive serial link is capable to analyze the incoming data stream, by scanning the Unit Interval, and to find the highest transmission line rate, according to a given tolerated Bit Error Ratio (BER). It uses a new feature (RX eye margin analysis) of the RX side of the Xilinx 7 series FPGAs high-speed transceivers (GTX/GTH), in order to measure and display the receiver eye margin after the equalizer. When the new eye scan functionality is running, an additional sampler is activated in the GTX. It acquires a new sample (Offset Sample), with programmable (horizontal and vertical) offsets from the data sample point (Data Sample) used in standard operation. An eye scan measurement run is performed by acquiring a large number of Data Samples (which can range from tens of thousands to 1014 or more) and by counting the number of times the Offset Sample has a different value with respect to the Data Sample; the latter number is often called Error Count. The BER at a specific vertical and horizontal offset is given by the ratio between the Error Count and the Sample Count. By repeating the eye scan measurement for each horizontal and vertical offset in the Unit Interval (or in a part of the U.I.) a 2-D BER map can be produced which is usually called Statistical Eye. The auto-adaptive derail ink is designed around an FPGA-embedded microprocessor, which drives the programmable ports of the GTX, in order to perform a 2-D eye-scan, and takes care of the reconfiguration of the GTX parameters, in order to fully benefit from the available link bandwidth. Xilinx provides a standalone tool that allows performing the Eye Scan Analysis on the receiver side of the GTX/GTH transceiver, using the MicroBlaze Micro Controller System macro; the toolkit also includes the Eye Scan algorithm (providing the C code). Moreover, Xilinx supplies the hardware sources files for the implementation of a link based on the XAUI protocol, in which the GTXs are arranged in a loopback configuration. The original contribution of this work consists in the build-up, design and optimization of a full architecture, on top of the basic Xilinx tool, which: - drives the programmable ports of the GTX in order to modify the line rate of the link; - runs consecutive eye scans for various line rate; - analyses the results of the different scans, in order to find the maximum line rate sustainable by the link; - manages the synchronization between the transmitter and the receiver of the link, that will be needed at each line rate change. The application can be deployed as a monitoring tool in HEP experiments, in order to remotely monitor a transmission system or detect issues in the serial link physical layer. An application example could be some of the many experiments at Large Hadron Collider (LHC) at CERN, which have been intensively using different serial links, both for transmission of TTC signals and for trigger and data readout. Besides, this solution could be easily adapted in wide, different frameworks, as it can be used on top of any user’s existing link, as it has no specific requirement about link specification or protocol. The other two serial interface developed in this project are in the framework of the ATLAS experiment. ATLAS is one of the four detectors installed on the LHC proton-proton collider built at CERN. It was designed to collide two opposing particle beams at an energy of 14 TeV and to reach a luminosity of 1034 cm-2/s. In order to reach the design parameters, the LHC system will be upgraded in several phases. In order to take advantage of the improved LHC operation, the ATLAS detector must be upgraded following the same schedule as the LHC upgrade. The main focus of the Phase-I ATLAS upgrade (to be completed by 2018) is on the Level-1 trigger where upgrades are planned for both the muon and the calorimeter trigger systems. In particular, for the end-cap region of the muon spectrometer, the installation of a new set of precision tracking and trigger detectors was approved, called the ‘New Small Wheels’ (NSW). It will be instrumented with micro-mesh gaseous structure detectors (MM) and small-strip Thin Gap Chambers (sTGC). These detectors will solve two points of particular importance at high luminosity: high rate of fake high-pt level-1 muon triggers, and high L1 muon rate with the current momentum threshold. With the introduction of new detectors, new electronics need to be developed, in particular new trigger electronics for both the MM and sTGC. I was involved in the development of serial interface of the FPGA-based sTGC trigger board that uses information from the coarse sTGC readout pads. The sTGC pad trigger board receives serial information coming from 24 front-end chips at 4.8 Gb/s. On the board, data are deserialised, aligned and analyzed by the trigger algorithm. The trigger logic processes the data and choses two candidates at each Bunch Crossing. The result is then serialised and used for selective fine-grained strip readout. I developed the pad trigger board interface logic. The data format from the front-end chips has been agreed upon, and defines the requirements on the receiver and decoding logic. The number of output lines is 24 and the data are 8B/10B formatted. While the receiver uses the Xilinx Kintex-7 GTX transceivers, the output lines are driven by double data rate (DDR) shift registers at 640 Mb/s. A fixed latency in the sTGC trigger chain was guaranteed through the implementation and configuration of all serialisers and deserialisers. In order to test the project, I also developed a simple microprocessor-based protocol for accessing the board via terminal (rs232). A demonstrator board is now being developed. Another Phase-I Level-1 trigger upgrade consists of a new Muon to Central Trigger Processor Interface (MUCTPI). The MUCTPI receives muon candidate information from each of the muon detectors, selects muon candidates and sends them to the Central Trigger Processor (CTP). In the first runs of ATLAS, the L1 Barrel trigger candidate data were transferred to the MuCTPI via copper cables. In order to cope with the trigger upgrade, serial optical links are necessary. The optical links will provide a much higher bandwidth (up to 6.4 Gb/s) which will be used to transfer additional information from the sector logic modules, for example data for more than two muon candidates. They will also provide a lower transmission latency. I developed the interface board between the new MUCTPI and the Resistive Plate Chambers (RPC) muon trigger, using the Xilinx Artix-7 FPGA GTP transceivers. I took care of the study of feasibility of the new serial optical transmitter and the logic for the new data format. Also in this case, the fixed latency has been a requirement to be fulfilled
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