Pedro Figueiredo e Silva

Received signal strength models for WLAN and BLE-based indoor positioning in multi-floor buildings

This paper investigates the similarities and differences of the signal strength fluctuations and positioning accuracy in indoor scenarios for three types of wireless area networks: two Wireless Local Area Networks (WLANs) at 2.4 GHz and 5 GHz frequency, respectively, and one Wireless Personal Area Network (WPAN), namely the Bluetooth Low Energy (BLE). Two path-loss models based on weighted centroids and non-negative least squares estimation are presented: one including a floor loss factor, and the other one ignoring the floor losses, and the three signal types are compared in terms of the path-loss parameters, channel fluctuations and positioning accuracy, namely the distance errors and floor detection probabilities. The comparison is done based on real-field measurement data collected from a university building in Tampere, Finland. It is shown that all these three signal types have similar shadowing variances and close path-loss parameter values, and that a path-loss model considering floor losses gives the best floor detection probability, but not necessarily the smallest distance error.

Autonomous orbit determination for future GEO and HEO missions

The use of GNSS space receivers for autonomous orbit determination is receiving increasing interest due to the important economical and operational benefits made possible by the reduced on-ground operations and the improved pointing performance when associated to one Star Tracker. However, the exploitation of GNSS for navigating satellites in orbits beyond the GNSS constellations has not yet gained full acceptance among spacecraft designers, manufacturers and operators. With GPS modernization and upcoming Galileo as well as with evolving receiver technologies, the feasibility for the use of GNSS in geostationary and higher orbits must be thoroughly assessed as the number of factors involved and its impact on navigation performance is significant when compared to land user receivers. This paper describes the feasibility of GNSS receiver and Orbital Filter for Autonomous Orbit Determination and the main expected performances under different missions, environment and receiver architectures. The most critical factors affecting navigation performance are presented and studied in detail using a Software Simulation Tool in a dedicated test campaign. Main results of the test campaign are then presented, illustrating the achievable performances for GEO/GTO and HEO orbits under the different GNSS sensor configurations. The presented results show that the usage of GNSS receiver technologies with the advent of Galileo and GPS modernization offer new possibilities and superior performance for autonomous orbit determination, promising important economical and operational benefits for next generation of space users in either GEO or HEO orbits.

ATENEA: Advanced techniques for deeply integrated GNSS/INS/LiDAR navigation

The ATENEA (Advanced Techniques for Navigation Receivers and Applications) project aims to join deeply integrated GNSS/INS receiver architectures and LIDAR techniques to provide an advanced navigation solution. The approach is suitable for a wide range of surveying applications in difficult environments, being Urban Mapping selected as reference case. ATENEA tackles the most challenging issues of this type of applications, showing how the use of Galileo signals, integrated positioning and observable processing can in one shot solve the more severe technical issues (robustness and continuity), increase accuracy and drastically reduce the system cost. The goal of the ATENEA project is to develop an advanced technology concept for seamless navigation at the cm-level regardless of the environment.

Indoor location based services challenges, requirements and usability of current solutions

Indoor Location Based Services (LBS), such as indoor navigation and tracking, still have to deal with both technical and non-technical challenges. For this reason, they have not yet found a prominent position in people’s everyday lives. Reliability and availability of indoor positioning technologies, the availability of up-to-date indoor maps, and privacy concerns associated with location data are some of the biggest challenges to their development. If these challenges were solved, or at least minimized, there would be more penetration into the user market. This paper studies the requirements of LBS applications, through a survey conducted by the authors, identifies the current challenges of indoor LBS, and reviews the available solutions that address the most important challenge, that of providing seamless indoor/outdoor positioning. The paper also looks at the potential of emerging solutions and the technologies that may help to handle this challenge.

Indoor positioning technology assessment using analytic hierarchy process for pedestrian navigation services

Indoor positioning is one of the biggest challenges of many Location Based Services (LBS), especially if the target users are pedestrians, who spend most of their time in roofed areas such as houses, offices, airports, shopping centres and in general indoors. Providing pedestrians with accurate, reliable, cheap, low power consuming and continuously available positional data inside the buildings (i.e. indoors) where GNSS signals are not usually available is difficult. Several positioning technologies can be applied as stand-alone indoor positioning technologies. They include Wireless Local Area Networks (WLAN), Bluetooth Low Energy (BLE), Ultra-Wideband (UWB), Radio Frequency Identification (RFID), Tactile Floor (TF), Ultra Sound (US) and High Sensitivity GNSS (HSGNSS). This paper evaluates the practicality and fitness-to-the-purpose of pedestrian navigation for these stand-alone positioning technologies to identify the best one for the purpose of indoor pedestrian navigation. In this regard, the most important criteria defining a suitable positioning service for pedestrian navigation are identified and prioritised. They include accuracy, availability, cost, power consumption and privacy. Each technology is evaluated according to each criterion using Analytic Hierarchy Process (AHP) and finally the combination of all weighted criteria and technologies are processed to identify the most suitable solution.

Overview of positioning technologies from fitness-to-purpose point of view

Even though Location Based Services (LBSs) are being more and more widely-used and this shows a promising future, there are still many challenges to deal with, such as privacy, reliability, accuracy, cost of service, power consumption and availability. There is still no single low-cost positioning technology which provides position of its users seamlessly indoors and outdoors with an acceptable level of accuracy and low power consumption. For this reason, fitness of positioning service to the purpose of LBS application is an important parameter to be considered when choosing the most suitable positioning technology for an LBS. This should be done for any LBS application, since each application may need different requirements. Some location-based applications, such as location-based advertisements or Location-Based Social Networking (LBSN), do not need very accurate positioning input data, while for some others, e.g. navigation and tracking services, highly-accurate positioning is essential. This paper evaluates different positioning technologies from fitness-to-purpose point of view for two different applications, public transport information and family/friend tracking.

Design of a very high sensitivity acquisition system for a space GNSS receiver

Increasing the GNSS receiver sensitivity and robustness in very harsh environments has become a central topic for the GNSS community. This paper addresses the design of a very High Sensitivity (HS) acquisition scheme for weak GNSS signal detection down to 5/10 dB-Hz in the particular space environment of the Lunar Low Orbit. A theoretical analysis for the determination of optimal extended coherent integration time and non-coherent accumulations allowing the achievement of pre-defined acquisition metrics will be presented and then validated by means of simulations. Complete data navigation bits and secondary code synchronization achieved thanks to the use of external aiding sources or self-assistance techniques is considered along the analysis which will provide results for weak GNSS signal acquisition in the GPS L1/L5 and Galileo E1/E5 frequency bands. Presence of a Doppler aiding source is considered and a detailed study on the required Doppler aiding accuracy is also presented.

GRANADA Factored Correlator Model blockset verification using an FPGA-Based GNSS receiver

The Factored Correlator Model (FCM) is an analytical model for the outputs of a GNSS receivers correlators. The FCM precludes the need for simulation of the lower-level signal processing stages, significantly increasing simulation speed and considerably decreasing processing and memory requirements, while still keeping a high level of realism. Results for the FCM validation using statistical models (available from previous Galileo studies) and the GRANADA Bit-True Simulator have been presented in the past. However, FCM results have never been compared to those of a real hardware receiver, whose performance is influenced by effects that have not been taken into account in the FCM (as quantization and fixed-point arithmetic, just to name a few). This paper shall present the verification and validation results of the FCM using a real hardware signal processing chain, up to the correlator outputs, implemented on an FPGA, in the scope of ongoing projects. It shall also highlight the new features of the latest GRANADA FCM Blockset release and demonstrate its applicability and value for receiver algorithms design.

GNSS/INS/LiDAR integration in urban environment: Algorithm description and results from ATENEA test campaign

The ATENEA (Advanced Techniques for Navigation Receivers and Applications) project aims to join deeply integrated GNSS/INS receiver architectures and LIDAR techniques to provide an advanced navigation solution. The approach is suitable for a wide range of surveying applications in difficult environments, being Urban Mapping selected as reference case. This paper presents the integrated GNSS+INS+LiDAR navigation filter, and detailed results of the test campaign carried out using both synthetic and real data. These results validate the ATENEA concept and open the possibilities of using such system for reliable navigation in urban environments.

Ledipasvir / Sofosbuvir for The Treatment of Chronic Hepatitis C: A Cost-Effectiveness Analysis Across Different Genotype 1 Clinical Subgroups

Almeida JM1, Félix J1, Ferreira D1, Mota M1, Afonso-Silva M1, Silva P1, Vandewalle B1, Velosa J2, Marinho R2, Aldir I3, Carvalho A4, Valente C4, Macedo G5, Sarmento e Castro R6, Pedroto I6 1Exigo Consultores; 2Hospital Santa Maria, Centro Hospitalar de Lisboa Norte, E.P.E.; 3Hospital Egas Moniz, Centro Hospitalar de Lisboa Ocidental, E.P.E.; 4Centro Hospitalar e Universitário de Coimbra, E.P.E.; 5Centro Hospitalar de São João, E.P.E.; 6Centro Hospitalar do Porto, E.P.E.