Arnaldo S. R. Oliveira

Design and Optimization of Flexible and Coding Efficient All-Digital RF Transmitters

All-digital transmitters are getting increased attention due to its closer proximity to the ideal software-defined radio (SDR) transmitter. In this paper we propose a new transmitter architecture that addresses two key limitations of current approaches, namely, the poor coding efficiency and the high quality factor requirements of the RF output reconstruction filter that significantly limit the practical usability and dissemination of these new flexible RF transmitters. The proposed architecture combines a maximum coding efficiency of 79.3% and a signal-to-noise ratio (SNR) of 50 dB, while maintaining the high flexibility inherent to the all-digital transmitters and where the RF output carriers operating in the microwave frequency range are generated inside a single field-programmable gate array (FPGA) device. The obtained results also show the feasibility and potential of using FPGA-based architectures for implementing digital RF transmitters.

The ARPA-MT Embedded SMT Processor and Its RTOS Hardware Accelerator

The high-level modeling and parameterization capabilities of current hardware description languages, as well as the huge integration capacity and flexibility provided by modern field-programmable gate arrays (FPGAs), open the way to designing processors tuned to given applications and favoring specific properties. This paper presents the Advanced Real-time Processor Architecture (ARPA)-MultiThreaded processor-a customizable, synthesizable, and time-predictable processor model optimized for multitasking real-time embedded systems, which efficiently explores modern FPGA technology. A fundamental processor component is the ARPA operating system (OS) coprocessor designed for hardware implementation of the basic real-time OS management functions, such as timing, task scheduling, synchronization and switching, efficient interrupt handling, and verification of the timing constraints. The hardware implementation of these functions allows executing them faster and more predictably, reducing the OS overhead, and improving its determinism. The performance evaluation has shown reductions of one to two orders of magnitude in the execution time of some functions of a real-time executive, in comparison with an analogous software implementation.

An IEEE 802.11p/WAVE implementation with synchronous channel switching for seamless dual-channel access (poster)

The emerging interest in vehicular networks (VANET) led to the deployment of several small and medium-scale testbeds to evaluate the characteristics of this technology in real-world scenarios. Despite this, due to the low availability and high cost of IEEE 802.11p/WAVE fully compliant hardware and software, many of these experiments have been performed with other communication standards, which generate, in many cases, misleading results, that are not representative of real-world vehicular communications. As a mean of solving this problem, this paper presents the implementation and validation of a fully compliant MAC/PHY solution developed in the scope of the DRIVE-IN project, which will be used in a 500-node testbed. Contrarily to what happens with most of the solutions existent in the market, our system complies with the strict channel switching timings using GPS time synchronization, providing access to two different types of wireless channels (e.g. control and service channels as defined in IEEE 1609.4) in a seamless way for the end user. This feature allows safety-critical and control messages to be sent in a dedicated channel, with very low latency, while another channel may be used for less critical services (e.g. infotainment applications, advertisement). The results of the conducted tests show that indeed it is possible to assure the support of critical safety services in the presence of other traffic.

Flexible, efficient and robust real-time communication with server-based Ethernet Switching

The information exchanged in Networked Embedded Systems is steadily increasing in quantity, size, complexity and heterogeneity, with growing requirements for arbitrary arrival patterns and guaranteed QoS. One of the networking protocols that is becoming more common in such systems is Ethernet and its real-time Ethernet variants. However, they hardly support all the referred requirements in an efficient manner since they either favour determinism or throughput, but not both. A potential solution recently proposed by the authors is the Server-SE protocol that uses servers to confine traffic associated to specific applications or subsystems. Such an approach is dynamically reconfigurable and adaptive, being more bandwidth efficient while providing composability in the time domain. This paper proposes integrating the servers inside the Ethernet switch, boosting both the flexibility and the robustness of Server-SE, allowing, for example, the seamless connection of any Ethernet node. The switch is an FTT-enabled Ethernet Switch and the paper discusses two specific ways of integrating the servers, namely in software or in hardware. These options are described and compared analytically and experimentally. The former favours flexibility in the servers design and management while the latter provides lower latency.

Gigasample Time-Interleaved Delta-Sigma Modulator for FPGA-Based All-Digital Transmitters

This paper presents the architecture and implementation of an FPGA-based all digital transmitter with a baseband sampling rate of 1 GHz. Hardware complexity and operation frequency analysis are performed to find the best hardware topology to improve the transmitter performance. The used polyphase decomposition techniques for delta sigma modulators considerably improve the bandwidth and SNR figures of merit of state-of-the-art FPGA integrated RF transmitters. The experimental results obtained show the feasibility of this approach and the improvement in the signal modulator oversampling ratio, enabling higher bandwidth in all-digital transmitters.

Designing a costumized Ethernet switch for safe hard real-time communication

The use of switched Ethernet for precise and safe real-time communication still suffers from undesired phenomena that range from the blocking caused by long non-preemptive frames to lack of protection against errors in the time domain and also couplings across virtual LANs and even priority levels via internal switch shared resources. In this paper we propose a novel switch architecture enhanced with resource reservation mechanisms, based on the Flexible Time-Triggered paradigm, which enforces strict service differentiation, blocking-free forwarding and timing errors confinement. Experimental results of a preliminary 4-port prototype based on an FPGA validate the desired properties and exhibit the potential of the enhanced Ethernet switch.

A synthesizable ethernet switch with enhanced real-time features

The use of switched Ethernet for safe real-time communication still suffers from undesired phenomena, such as blocking caused by long non-preemptive frames, lack of protection against errors in the time domain, couplings across virtual LANs and priority levels via internal switch shared resources. Recently, a few solutions were proposed to cope with such phenomena. One such solution is based on an enhanced switch following the Flexible Time-Triggered paradigm, which enforces strict service differentiation with any kind of traffic scheduling, blocking-free forwarding and timing errors confinement. In this paper we propose a new architecture following an hardwaresoftware co-design approach that simplifies the development of the enhanced switch features by detaching the traffic scheduling from the traffic switching. The paper shows experimental results with an actual switch prototype that confirm the desired switch properties.

Automatic accident detection with multi-modal alert system implementation for ITS

The rapid technological growth is now providing global opportunities to enable intelligent transportation system (ITS) to tackle road accidents which is considered one of the worlds largest public injury prevention problem. For this purpose, eCall is an initiative by European Union (EU) with the purpose to bring rapid assistance to an accident location. This paper1 presents HDy Copilot, an application for automatic accident detection integrated with multimodal alert dissemination, via both eCall and IEEE 802.11p (ITS-G5). The proposed accident detection algorithm receives inputs from the vehicle, via ODB-II, and from the smartphone sensors, namely the accelerometer, the magnetometer and the gyroscope. An Android smartphone is used as human machine interface, so that the driver can configure the application, receive road hazard warnings issued by other vehicles in the vicinity and cancel countdown procedures upon false road vehicle crash detection. The HDy Copilot is developed for Android OS as it provides open source APIs that allow access to its hardware resources. The application is implemented, tested and connected to an IEEE 802.11p based prototype. The generated results show that the application successfully detects collisions, rollovers, performs the eCall along with sending Minimum Set of Data (MSD) and Decentralized Environmental Notification Message (DENM).

All-Digital Transmitter With a Mixed-Domain Combination Filter

In this brief, we present a new reconfigurable filtering technique for all-digital transmitters using signal interference and cancellation. The proposed method allows the change of some filtering characteristics digitally. This technique is used to reduce the quantization noise from the all-digital transmitters output, reducing the analog output filter requirements. Without a narrow band filter, a greater degree of flexibility for the transmitters carrier frequency and bandwidth is attained, improving its suitability for multiband and multistandard operation. The results show the quantization noise reduction without an output analog filter, contributing to an increase of the transmitters coding efficiency up to more than 95%.

An interactive WebGIS observatory platform for enhanced support of integrated coastal management

ABSTRACT Oliveira, A., Jesus, G., Gomes, J.L., Rogeiro, J., Azevedo, A., Rodrigues, M., Fortunato, A.B., Dias, J.M., Tomas, L.M., Oliveira, E.R. Alves, F.L., den Boer, S., 2014. An interactive WebGIS observatory platform for enhanced support of coastal management. In: Green, A.N. and Cooper, J.A.G. (eds.), Proceedings 13th International Coastal Symposium (Durban, South Africa), Journal of Coastal Research, Special Issue No. 70, pp. 507–512, ISSN 0749-0208. A new WebGIS observatory platform is presented, tailored for risk assessment and emergency preparation and response in coastal areas. The tool combines a sophisticated forecast modeling system for multi-scale analysis of water bodies, including waves, hydrodynamics and oil spills prediction, with real-time monitoring networks for forcing and continuous validation purposes. Tailor-made visualization and analysis products, conceptualized for multiple uses through a service-oriented framework, provide an easy and interactive access to both data and predictions. The system was customized for oil spills risk assessment and the rapid response to an oil spill emergency, and applied to the Aveiro lagoon. The tool addresses oil spill problems in two complementary ways: 1) a detailed risk assessment through georeferenced hazard and vulnerability maps and GIS layers of information to support the definition of contingency plans; and 2) the visualization of georeferenced oil spill predictions produced by a real-time oil spill forecasting system. Improvements relative to existing risk systems are 1) the possibility of selecting quick-access predictions for fast emergency response or high-quality, georeferenced GIS prediction products, 2) the flexibility in accessing products to evaluate local impacts of oil spills both in the water column and in the intertidal areas, and 3) the enhanced hazard and risk analysis through a combination of a multi-scenarios approach with the historical database of spill predictions, forced by daily hydrodynamic forecasts. Dependability of information, for both model results and monitoring data, is being implemented through innovative ways, targeting the robustness and quality control of the WebGIS platform.