Design and Validation of a Software Defined Radio Testbed for DVB-T Transmission

This paper describes the design and validation of a Software Defined Radio (SDR) testbed, which can be used for Digital Television transmission using the Digital Video Broadcasting - Terrestrial (DVB-T) standard. In order to generate a DVB-T-compliant signal with low computational complexity, we design an SDR architecture that uses the C/C++ language and exploits multithreading and vectorized instructions. Then, we transmit the generated DVB-T signal in real time, using a common PC equipped with multicore central processing units (CPUs) and a commercially available SDR modem board. The proposed SDR architecture has been validated using fixed TV sets, and portable receivers. Our results show that the proposed SDR architecture for DVB-T transmission is a low-cost low-complexity solution that, in the worst case, only requires less than 22% of CPU load and less than 170 MB of memory usage, on a 3.0 GHz Core i7 processor. In addition, using the same SDR modem board, we design an off-line software receiver that also performs time synchronization and carrier frequency offset estimation and compensation

A Heterogeneous System Architecture for Low-Power Wireless Sensor Nodes in Compute-Intensive Distributed Applications

Wireless Sensor Networks (WSNs) combine embedded sensing and processing capabilities with a wireless communication infrastructure, thus supporting distributed monitoring applications. WSNs have been investigated for more than three decades, and recent social and industrial developments such as home automation, or the Internet of Things, have increased the commercial relevance of this key technology. The communication bandwidth of the sensor nodes is limited by the transportation media and the restricted energy budget of the nodes. To still keep up with the ever increasing sensor count and sampling rates, the basic data acquisition and collection capabilities of WSNs have been extended with decentralized smart feature extraction and data aggregation algorithms. Energy-efficient processing elements are thus required to meet the ever-growing compute demands of the WSN motes within the available energy budget. The Hardware-Accelerated Low Power Mote (HaLoMote) is proposed and evaluated in this thesis to address the requirements of compute-intensive WSN applications. It is a heterogeneous system architecture, that combines a Field Programmable Gate Array (FPGA) for hardware-accelerated data aggregation with an IEEE 802.15.4 based Radio Frequency System-on-Chip for the network management and the top-level control of the applications. To properly support Dynamic Power Management (DPM) on the HaLoMote, a Microsemi IGLOO FPGA with a non-volatile configuration storage was chosen for a prototype implementation, called Hardware-Accelerated Low Energy Wireless Embedded Sensor Node (HaLOEWEn). As for every multi-processor architecture, the inter-processor communication and coordination strongly influences the efficiency of the HaLoMote. Therefore, a generic communication framework is proposed in this thesis. It is tightly coupled with the DPM strategy of the HaLoMote, that supports fast transitions between active and idle modes. Low-power sleep periods can thus be scheduled within every sampling cycle, even for sampling rates of hundreds of hertz. In addition to the development of the heterogeneous system architecture, this thesis focuses on the energy consumption trade-off between wireless data transmission and in-sensor data aggregation. The HaLOEWEn is compared with typical software processors in terms of runtime and energy efficiency in the context of three monitoring applications. The building blocks of these applications comprise hardware-accelerated digital signal processing primitives, lossless data compression, a precise wireless time synchronization protocol, and a transceiver scheduling for contention free information flooding from multiple sources to all network nodes. Most of these concepts are applicable to similar distributed monitoring applications with in-sensor data aggregation. A Structural Health Monitoring (SHM) application is used for the system level evaluation of the HaLoMote concept. The Random Decrement Technique (RDT) is a particular SHM data aggregation algorithm, which determines the free-decay response of the monitored structure for subsequent modal identification. The hardware-accelerated RDT executed on a HaLOEWEn mote requires only 43 % of the energy that a recent ARM Cortex-M based microcontroller consumes for this algorithm. The functionality of the overall WSN-based SHM system is shown with a laboratory-scale demonstrator. Compared to reference data acquired by a wire-bound laboratory measurement system, the HaLOEWEn network can capture the structural information relevant for the SHM application with less than 1 % deviation

Microsecond-Accuracy Time Synchronization Using the IEEE 802.15.4 TSCH Protocol

International audienceTime-Slotted Channel Hopping from the IEEE 802.15.4-2015 standard requires that network nodes are tightly time-synchronized. Existing implementations of TSCH on embedded hardware are characterized by tens-of-microseconds large synchronization errors; higher synchronization accuracy would enable reduction of idle listening time on receivers, in this way decreasing the energy required to run TSCH. For some applications, it would also allow to replace dedicated time synchronization mechanisms with TSCH. We show that time synchronization errors in the existing TSCH implementations on embedded hardware are caused primarily by imprecise clock drift estimations, rather than by real unpredictable drift variance. By estimating clock drift more precisely and by applying adaptive time compensation on each node in the network, we achieve microsecond accuracy time synchronization on point-to-point links and a <2 microsecond end-to-end error in a 7-node line topology. Our solution is implemented in the Contiki operating system and tested on Texas Instruments CC2650-based nodes, equipped with common off-the-shelf hardware clock sources (20 ppm drift). Our implementation uses only standard TSCH control messages and is able to keep radio duty cycle below 1%

An Exploratory Analysis Of A Time Synchronization Protocol For UAS

This dissertation provides a numerical analysis of a Receiver Only Synchronization (ROS) protocol which is proposed for use by Unmanned Aircraft Systems (UAS) in Beyond Visual Line of Sight (BVLOS) operations. The use of ROS protocols could reinforce current technologies that enable transmission over 5G cell networks, decreasing latency issues and enabling the incorporation of an increased number of UAS to the network, without loss of accuracy. A minimum squared error (MSE)-based accuracy of clock offset and clock skew estimations was obtained using the number of iterations and number of observations as independent parameters. Although the model converged after only four iterations, the number of observations needed was considerably large, of no less than about 250. The noise, introduced in the system through the first residual, the correlation parameter and the disturbance terms, was assumed to be autocorrelated. Previous studies suggested that correlated noise might be typical in multipath scenarios, or in case of damaged antennas. Four noise distributions: gaussian, exponential, gamma and Weibull were considered. Each of them is adapted to different noise sources in the OSI model. Dispersion of results in the first case, the only case with zero mean, was checked against the Cramér-Rao Bound (CRB) limit. Results confirmed that the scheme proposed was fully efficient. Moreover, results with the other three cases were less promising, thus demonstrating that only zero mean distributions could deliver good results. This fact would limit the proposed scheme application in multipath scenarios, where echoes of previous signals may reach the receiver at delayed times. In the second part, a wake/sleep scheme was imposed on the model, concluding that for wake/sleep ratios below 92/08 results were not accurate at p=.05 level. The study also evaluated the impact of noise levels in the time domain and showed that above -2dB in time a substantial contribution of error terms disturbed the initial estimations significantly. The tests were performed in Matlab®. Based on the results, three venues confirming the assumptions made were proposed for future work. Some final reflections on the use of 5G in aviation brought the present dissertation to a close

Aggregated Reverse Time Transfer

Monitoring mechanisms are a critical component of the security and maintenance of high precision timing networks. Any and all guarantees of determinism and correctness are invalidated if a synchronous network malfunctions or is compromised by an attacker. Existing mechanisms allow for a comprehensive view of the distribution of time throughout a network, but they do not scale to large networks. I propose a new method called aggregated reverse time transfer (ARTT), which redefines the existing mechanisms to include a new aggregation scheme that serves the dual purpose of distributed data summarization and anomaly detection for networks of any size. With this thesis I provide a full specification and implementation of the ARTT mechanism, test both the outlier detection and model accuracy on a real timing network, and detail the steps necessary to perform stable-state outlier detection and aggregation on large-scale networks

GTSO: Global Trace Synchronization and Ordering Mechanism for Wireless Sensor Network Monitoring Platforms

[EN] Monitoring is one of the best ways to evaluate the behavior of computer systems. When the monitored system is a distributed system¿such as a wireless sensor network (WSN)¿the monitoring operation must also be distributed, providing a distributed trace for further analysis. The temporal sequence of occurrence of the events registered by the distributed monitoring platform (DMP) must be correctly established to provide cause-effect relationships between them, so the logs obtained in different monitor nodes must be synchronized. Many of synchronization mechanisms applied to DMPs consist in adjusting the internal clocks of the nodes to the same value as a reference time. However, these mechanisms can create an incoherent event sequence. This article presents a new method to achieve global synchronization of the traces obtained in a DMP. It is based on periodic synchronization signals that are received by the monitor nodes and logged along with the recorded events. This mechanism processes all traces and generates a global post-synchronized trace by scaling all times registered proportionally according with the synchronization signals. It is intended to be a simple but efficient offline mechanism. Its application in a WSN-DMP demonstrates that it guarantees a correct ordering of the events, avoiding the aforementioned issues.This work was supported by the Ministerio de Economia y Competitividad by means of its project DPI2016-80303-C2-1-P. It covers the costs of publishing in open access.Navia-Mendoza, MR.; Campelo Rivadulla, JC.; Bonastre Pina, AM.; Ors Carot, R. (2018). GTSO: Global Trace Synchronization and Ordering Mechanism for Wireless Sensor Network Monitoring Platforms. Sensors. 18(1):1-22. https://doi.org/10.3390/s18010028S12218

HMP: A Hybrid Monitoring Platform for Wireless Sensor Networks Evaluation

(c) 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.[EN] Wireless sensor networks (WSNs), as an essential part of the deployment of the Internet of Things paradigm, require an adequate debugging and monitoring procedures to avoid errors in their operation. One of the best tools for WSN supervision is the so-called Monitoring Platforms that harvest information about the WSN operation in order to detect errors and evaluate performance. Monitoring platforms for the WSN can be hardware or software implemented, and, additionally, they can work in active or passive mode. Each approach has advantages and drawbacks. To benefit from their advantages and compensate their limitations, hybrid platforms combine different approaches. However, very few hybrid tools, with many restrictions, have been proposed. Most of them are designed for a specific implementation of WSN nodes; many of them are lack of a real implementation, and none of them provides an accurate solution to synchronization issues. This paper presents a hybrid monitoring platform for WSN, called HMP. This platform combines both hardware and software, active and passive monitoring approaches. This hybridization provides many interesting capabilities; HMP harvests the information both actively (directly from the sensor nodes) and passively (by means of messages captured from the WSN), causing a very low intrusion in the observed network. In addition, HMP is reusable; it may be applied to almost any WSN and includes a suitable trace synchronism procedure. Finally, HMP follows an open architecture that allows interoperability and layered development.This work was supported by the Agencia Estatal de Investigacion from the Spanish Ministerio de Economia, Industria y Competitividad, through the project Hacia el hospital inteligente: Investigacion en el diseno de una plataforma basada en Internet de las Cosas y su aplicacion en la mejora del cumplimiento de higiene de manos, under Grant DPI2016-80303-C2-1-P. The project covers the costs of publishing in open access.Navia-Mendoza, MR.; Campelo Rivadulla, JC.; Bonastre Pina, AM.; Capella Hernández, JV.; Ors Carot, R. (2019). HMP: A Hybrid Monitoring Platform for Wireless Sensor Networks Evaluation. IEEE Access. 7:87027-87041. https://doi.org/10.1109/ACCESS.2019.2925299S8702787041

The Future of the Operating Room: Surgical Preplanning and Navigation using High Accuracy Ultra-Wideband Positioning and Advanced Bone Measurement

This dissertation embodies the diversity and creativity of my research, of which much has been peer-reviewed, published in archival quality journals, and presented nationally and internationally. Portions of the work described herein have been published in the fields of image processing, forensic anthropology, physical anthropology, biomedical engineering, clinical orthopedics, and microwave engineering. The problem studied is primarily that of developing the tools and technologies for a next-generation surgical navigation system. The discussion focuses on the underlying technologies of a novel microwave positioning subsystem and a bone analysis subsystem. The methodologies behind each of these technologies are presented in the context of the overall system with the salient results helping to elucidate the difficult facets of the problem. The microwave positioning system is currently the highest accuracy wireless ultra-wideband positioning system that can be found in the literature. The challenges in producing a system with these capabilities are many, and the research and development in solving these problems should further the art of high accuracy pulse-based positioning