Search results for "Spectrogram"
showing 10 items of 34 documents
A 3D Non-Stationary Cluster Channel Model for Human Activity Recognition
2019
Author's accepted manuscript. © 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. This paper proposes a three-dimensional (3D) non- stationary fixed-to-fixed indoor channel simulator model for human activity recognition. The channel model enables the formulation of temporal variations of the received signal caused by a moving human. The moving human is modelled by …
A non-stationary relay-based 3D MIMO channel model with time-variant path gains for human activity recognition in indoor environments
2021
AbstractExtensive research showed that the physiological response of human tissue to exposure to low-frequency electromagnetic fields is the induction of an electric current in the body segments. As a result, each segment of the human body behaves as a relay, which retransmits the radio-frequency (RF) signal. To investigate the impact of this phenomenon on the Doppler characteristics of the received RF signal, we introduce a new three-dimensional (3D) non-stationary channel model to describe the propagation phenomenon taking place in an indoor environment. Here, the indoor space is equipped with a multiple-input multiple-output (MIMO) system. A single person is moving in the indoor space an…
Analysis of Activity States of Local Neuronal Microcircuits in Mouse Brain
2018
Time series of neuronal activity corresponding to different activity states in mouse brain are analyzed in the time domain and the time-frequency domain. The signals are associated with either a slow wave brain state or a persistent brain state. For both states, characteristic spectral features are identified and a simple detector is proposed that is able to identify the brain state with low latency and high accuracy. In practice, being able to monitor the brain state online and in real time is crucial for improved in vivoexperiments and, ultimately, for a causal understanding of brain dynamics.
Comparative analysis of acoustic emission signals generated by electrical discharges measured by the hydrophone and the wideband contact transducer
2005
The paper presents a comparative analysis of the acoustic emission (AE) pulses and signals generated by PDs. For this purpose the measurements of the acoustic emission signals generated by PDs were taken in the multipoint-plane system using a hydrophone placed directly in the area of discharge generation, and the AE pulses using a piezoelectric contact transducer which was on a side wall of a power transformer tub. Next, time runs and amplitude density spectra were drawn. Also the descriptors describing signals in the frequency domain were determined and the time-frequency analysis was carried out, which determined spectrograms for the energy density spectrum.
A Trajectory-Driven 3D Channel Model for Human Activity Recognition
2021
This paper concerns the design, analysis, and simulation of a 3D non-stationary channel model fed with inertial measurement unit (IMU) data. The work in this paper provides a framework for simulating the micro-Doppler signatures of indoor channels for human activity recognition by using radiofrequency-based sensing technologies. The major human body segments, such as wrists, ankles, torso, and head, are modelled as a cluster of moving point scatterers. We provide expressions for the time variant (TV) speed and TV angles of motion based on 3D trajectories of the moving person. Moreover, we present mathematical expressions for the TV Doppler shifts and TV path gains associated with each movin…
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…
The Influence of Human Walking Activities on the Doppler Characteristics of Non-stationary Indoor Channel Models
2019
This paper analyzes the time-variant (TV) Doppler power spectral density of a 3D non-stationary fixed-to-fixed indoor channel simulator after feeding it with realistic trajectories of a walking person. The trajectories of the walking person are obtained by simulating a full body musculoskeletal model in OpenSim. We provide expressions of the TV Doppler frequencies caused by these trajectories. Then, we present the complex channel gain consisting of fixed scatterers and a cluster of moving scatterers. After that, we use the concept of the spectrogram to analyze the TV Doppler power spectral density of the complex channel gain. Finally, we present expressions of the TV mean Doppler shift and …
A Framework for Activity Monitoring and Fall Detection Based on the Characteristics of Indoor Channels
2018
Author´s accepted manuscript © 2018 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. This paper concerns the Doppler power spectrum of three-dimensional non-stationary indoor fixed-to- fixed channels with moving people. In this paper, we model each moving person as a moving scatterer with time-variant (TV) speed, TV vertical angles of motion, and TV horizontal angles o…
Doppler Power Characteristics Obtained from Calibrated Channel State Information for Human Activity Recognition
2020
This paper demonstrates the time-variant (TV) Doppler power characteristics of human activities using measured channel state information (CSI). We model the measured CSI as a complex channel transfer function corresponding to a 3D non-stationary multipath fading channel consisting of a fixed transmitter, a fixed receiver, fixed scatterers representing fixed objects, and a cluster of moving scatterers representing a moving person performing some human activities. We demonstrate the relationship between the TV Doppler frequency caused by each moving scatterer and the rate of change of its corresponding TV propagation delay. Furthermore, we express the TV mean Doppler shift in terms of the pat…
Modelling, Analysis, and Simulation of the Micro-Doppler Effect in Wideband Indoor Channels with Confirmation Through Pendulum Experiments
2020
This paper is about designing a 3D no n-stationary wideband indoor channel model for radio-frequency sensing. The proposed channel model allows for simulating the time-variant (TV) characteristics of the received signal of indoor channel in the presence of a moving object. The moving object is modelled by a point scatterer which travels along a trajectory. The trajectory is described by the object&rsquo