Evaluation of the aggregate interference in 2.4 GHz ISM band in home, office and hospital environments

Abstract. In the last years, the wireless body area network (WBAN) research has grown considerably and the idea to apply WBAN to the medical and healthcare issues could materialize. A possible WBAN could exploit the ISM (industrial, scientific and medical) band, clustered around 2.4 GHz. The ISM band is just used by other communication systems and non-communication systems. These systems transmit signals, defined aggregate interference, that could hinder the WBAN communications. In this thesis, the ISM band is investigated in order to understand if the amount of interference is too high to allow implementation of a new WBAN or if the coexistence between WBAN and the other systems is still possible. The ISM band analyses are carried out using data collected in real-life measurements, in environments where a patient monitored by a WBAN could usually stay. Data was collected in an office and a home environments, situated in Florence, Italy, in “San Giuseppe” hospital located in Empoli, Italy and in Oulu University Hospital, situated in Oulu, Finland. In each location, data are collected during a week using a spectrum analyzer (SA). The information measured by the SA is the power, expressed in dBm. In this work, a spectrum occupancy evaluation (SOE) has been developed to analyze the occupancy percentage of every frequency channel of the ISM band. The occupancy value is determined by a threshold, which divides the interference samples from the noise samples. In this work, the occupancy is evaluated using both a fixed threshold and a dynamic threshold, which value directly depends on the samples’ values. The results achieved using fixed and dynamic thresholds are discussed and compared. In addition, a time domain analysis has been carried out in order to know the amplitude, the time distribution and the size of the interference contributions. The time domain results allow to predict the interference behavior, making possible the extraction of a statistical interference modelling. The final results of the analyses depend strongly on the measurement location, the time and the measurement equipment. However, in most cases, the occupancy value is below 10%. Hence, the amount of interference is not so high as to prevent the implementation of a new WBAN or to determine an added smartness to the WBAN

Analysis of Spectrum Occupancy Using Machine Learning Algorithms

In this paper, we analyze the spectrum occupancy using different machine learning techniques. Both supervised techniques (naive Bayesian classifier (NBC), decision trees (DT), support vector machine (SVM), linear regression (LR)) and unsupervised algorithm (hidden markov model (HMM)) are studied to find the best technique with the highest classification accuracy (CA). A detailed comparison of the supervised and unsupervised algorithms in terms of the computational time and classification accuracy is performed. The classified occupancy status is further utilized to evaluate the probability of secondary user outage for the future time slots, which can be used by system designers to define spectrum allocation and spectrum sharing policies. Numerical results show that SVM is the best algorithm among all the supervised and unsupervised classifiers. Based on this, we proposed a new SVM algorithm by combining it with fire fly algorithm (FFA), which is shown to outperform all other algorithms.Comment: 21 pages, 6 figure

Spectral analysis for long-term robotic mapping

This paper presents a new approach to mobile robot mapping in long-term scenarios. So far, the environment models used in mobile robotics have been tailored to capture static scenes and dealt with the environment changes by means of ‘memory decay’. While these models keep up with slowly changing environments, their utilization in dynamic, real world environments is difficult. The representation proposed in this paper models the environment’s spatio-temporal dynamics by its frequency spectrum. The spectral representation of the time domain allows to identify, analyse and remember regularly occurring environment processes in a computationally efficient way. Knowledge of the periodicity of the different environment processes constitutes the model predictive capabilities, which are especially useful for long-term mobile robotics scenarios. In the experiments presented, the proposed approach is applied to data collected by a mobile robot patrolling an indoor environment over a period of one week. Three scenarios are investigated, including intruder detection and 4D mapping. The results indicate that the proposed method allows to represent arbitrary timescales with constant (and low) memory requirements, achieving compression rates up to 106 . Moreover, the representation allows for prediction of future environment’s state with ∼ 90% precision

Improved electromagnetic compatibility standards for the interconnected wireless world

© 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, 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 component of this work in other works.The future is wireless, a world where everything is interconnected. However, the current standards for ensuring the electromagnetic compatibility (EMC) and the coexistence of such wireless systems urge for a major update. It is shown how novel statistical approaches based on the amplitude probability distribution detector and time-domain measurements are better suited for estimating the degradation caused by electromagnetic interferences on digital communication systems than the established practice of determining compliance according to the quasi-peak detector levels using a pass/fail criterion. Therefore, a redefinition of the test methods and of the compliance requirements in terms of EMC standards must be a priority of the international standardization bodies. Finally, a discussion of the fundamental challenges involved in this standardization breakthrough for EMC is delivered.Postprint (author's final draft

Post-Occupancy Evaluation and IEQ Measurements from 64 Office Buildings: Critical Factors and Thresholds for User Satisfaction on Thermal Quality

The indoor environmental quality (IEQ) of buildings can have a strong influence on occupants’ comfort, productivity, and health. Post-occupancy evaluation (POE) is necessary in assessing the IEQ of the built environment, and it typically relies on the subjective surveys of thermal quality, air quality, visual quality, and acoustic quality. In this research, we expanded POE to include both objective IEQ measurements and the technical attributes of building systems (TABS) that may affect indoor environment and user satisfaction. The suite of three tools, including user satisfaction survey, workstation IEQ measurements, and TABS in the National Environmental Assessment Toolkit (NEAT) has been deployed in 1601 workstations in 64 office buildings, generating a rich database for statistical evaluation of possible correlations between the physical attributes of workstations, environmental conditions, and user satisfaction. Multivariate regression and multiple correlation coefficient statistical analysis revealed the relationship between measured and perceived IEQ indices, interdependencies between IEQ indices, and other satisfaction variables of significance. The results showed that overall, 55% of occupants responded as “satisfied” or “neutral”, and 45% reported being “dissatisfied” in their thermal quality. Given the dataset, air temperature in work area, size of thermal zone, window quality, level of temperature control, and radiant temperature asymmetry with façade are the critical factors for thermal quality satisfaction in the field. As a result, the outcome of this research contributes to identifying correlations between occupant satisfaction, measured data, and technical attributes of building systems. The presented integrated IEQ assessment method can further afford robust predictions of building performance against metrics and guidelines for IEQ standards to capture revised IEQ thresholds that impact building occupants’ satisfaction.</jats:p

HF spectrum occupancy and antennas

This paper deals with the research made during the COST 296 action in the WG2, WP 2.3 in the antennas and HF spectrum management fields, focusing the Mitigation of Ionospheric Effects on Radio Systems as the subject of this COST action.info:eu-repo/semantics/publishedVersio

One-by-one trap activation in silicon nanowire transistors

Flicker or 1/f noise in metal-oxide-semiconductor field-effect transistors (MOSFETs) has been identified as the main source of noise at low frequency. It often originates from an ensemble of a huge number of charges trapping and detrapping. However, a deviation from the well-known model of 1/f noise is observed for nanoscale MOSFETs and a new model is required. Here, we report the observation of one-by-one trap activation controlled by the gate voltage in a nanowire MOSFET and we propose a new low-frequency-noise theory for nanoscale FETs. We demonstrate that the Coulomb repulsion between electronically charged trap sites avoids the activation of several traps simultaneously. This effect induces a noise reduction by more than one order of magnitude. It decreases when increasing the electron density in the channel due to the electrical screening of traps. These findings are technologically useful for any FETs with a short and narrow channel.Comment: One file with paper and supplementary informatio