Search results for "mobile"
showing 10 items of 1399 documents
Spectrogram Analysis of Multipath Fading Channels under Variations of the Mobile Speed
2016
When modelling, analysing, and simulating mobile radio channels, it is generally assumed that the speed of the mobile station (MS) is constant. In practice, however, the mobile speed varies with time. Mobile speed variations result in nonwide- sense stationary multipath fading channels, which can be modelled by a sum-of-chirps (SOCh) processes. In this paper, we analyse the local Doppler power spectral density (PSD) of SOCh processes by using the concept of the spectrogram. The spectrogram provides an estimate of the local Doppler PSD and gives insight into how the Doppler PSD changes over time if the MS increases or decreases its speed. A closed-form solution is presented for the spectrogr…
Energy efficient optimisation for large‐scale multiple‐antenna system with WPT
2018
In this study, an energy-efficient optimisation scheme for a large-scale multiple-antenna system with wireless power transfer (WPT) is presented. In the considered system, the user is charged by a base station with a large number of antennas via downlink WPT and then utilises the received power to carry out uplink data transmission. Novel antenna selection, time allocation and power allocation schemes are presented to optimise the energy efficiency of the overall system. In addition, the authors also consider channel state information cannot be perfectly obtained when designing the resource allocation schemes. The non-linear fractional programming-based algorithm is utilised to address the …
Diagnosis of Sensor Faults in PMSM and Drive System Based on Structural Analysis
2021
This paper presents a model-based fault diagnosis method to detect sensor faults in permanent magnet synchronous motor (PMSM) drives based on structural analysis technique. The structural model is built based on the dynamic model of the PMSM in matrix form, including unknown variables, known variables, and faults. The Dulmage-Mendelsohn (DM) decomposition is applied to evaluate the redundancy of the model and obtain redundant testable sub-models. These testable redundant sub-models are used to form residuals to observe the system state, and distinguish between healthy and faulty conditions. This work investigates faults in eleven sensors in a PMSM drive, thus nine structured residuals are d…
A Novel Priority-Based Ambulance-to-Traffic Light Communication for Delay Reduction in Emergency Rescue Operations
2019
Rescue operations are very critical and sensitive. Only one-second delay could make a serious difference between life and death. Therefore, the delay in rescue operations must be reduced as much as possible. The siren signal can be used to warn other vehicles nearby the ambulance. However, it has no impact on the traffic lights, which is normally a main cause of delay in rescue operations. For this reason, many ambulances get stuck and experience long delay at the intersections, which should not happen by any means. To enhance the rescue operations, this paper proposes a novel Priority-based Ambulance-to-Traffic Light Communication (PATCom). PATCom allows information exchanging between traf…
An ontology-based recommendation system for people with autism and technology apps
2018
The research about the use of technology for persons with autism spectrum disorders (ASD) has rapidly increased in the last decade. This fact has accompanied with the sharp development and use of apps for mobile devices by these people and their caregivers. The election of the adequate apps for persons with autism is a very difficult task, with many variables involved with the person with ASD, the family, the practitioners and the community where they live. This paper describes a recommendation system that reuse an ontology, which supports the information about the apps and all the variables previously cited. The data about the apps are automatically obtained from recognized web repositorie…
Modelling and Analysis of Non-Stationary Multipath Fading Channels with Time-Variant Angles of Arrival
2017
In mobile radio channel modelling, it is generally assumed that the angles of arrival (AOAs) are independent of time. This assumption does in general not agree with real-world channels in which the AOAs vary with the position of a moving receiver. In this paper, we first present a mathematical model for the time-variant AOAs. This model serves as the basis for the development of two non-stationary multipath fading channels models. The statistical properties of both channel models are analysed with emphasis on the time-dependent autocorrelation function (ACF), time-dependent mean Doppler shift, time-dependent Doppler spread, and the Wigner-Ville spectrum. It is shown that these characteristi…
Portable low-cost open-source wireless spectrophotometer for fast and reliable measurements
2020
This article is based upon COST Action CA16215 and supported by the ERDF , European-Union Project No.1.1.1.2/16/I/001.
Colorimetric Characterization of Mobile Devices for Vision Applications
2015
Purpose: Available applications for vision testing in mobile devices usually do not include detailed setup instructions, sacrificing rigor to obtain portability and ease of use. In particular, colorimetric characterization processes are generally obviated. We show that different mobile devices differ also in colorimetric profile and that those differences limit the range of applications for which they are most adequate. Methods: The color reproduction characteristics of four mobile devices, two smartphones (Samsung Galaxy S4, iPhone 4s) and two tablets (Samsung Galaxy Tab 3, iPad 4), have been evaluated using two procedures: 3D LUT (Look Up Table) and a linear model assuming primary constan…
Characteristics and Measures for Mobile-Masquerader Detection
2006
Personal mobile devices, as mobile phones, smartphones, and communicators can be easily lost or stolen. Due to the functional abilities of these devices, their use by an unintended person may result in a severe security incident concerning private or corporate data and services. Organizations develop their security policy and mobilize preventive techniques against unauthorized use. Current solutions, however, are still breakable and there still exists strong need for means to detect user substitution when it happens. A crucial issue in designing such means is to define what measures to monitor.
A Taxonomy for App-Enabled Devices: Mastering the Mobile Device Jungle
2018
While the term application is known for a long time, what we now refer to as mobile apps has facilitated task-oriented, interoperable software. The term was initially only used for smartphones and tablets, but desktop software now is also referred to as apps. More important than the wording, however, is the trend towards app-enablement of many further kinds of devices such as smart TVs and wearables. App-enabled devices usually share some characteristics and developing apps is often similar. However, many complexities must be mastered: Device fragmentation and cross-platform app development already are challenging when only considering smartphones. When trying to grasp the field as a whole,…