Search results for " propagation"
showing 10 items of 488 documents
Modelling the Complex Dynamics of Public Opinion Propagation in Micro-Blogging.
2018
The purpose of this paper is to attempt to analyze the propagation of public opinion in micro-blogging. We proposed a Micro-blogging read-post model based on a well-known diffusion model and presented its system of equations. We carried out a global qualitative analysis of the model with latent and constant recruitment, then studied the existence and stability of the public opinion vanishing and prevailing equilibrium points. An empirical study of the model was conducted using data automatically collected from a typical case on Sina Weibo, a microblogging platform with the largest number of registered users and active users in China. Simulation results showed that our model can fit data in …
Performance of power control in inter-cell interference coordination for frequency reuse
2010
To mitigate inter-cell interference in 3G evolution systems, a novel inter-cell interference coordination scheme called soft fractional frequency reuse is proposed in this article, which enables to improve the data rate in cell-edge. On this basis, an inter-cell power control is presented for the inter-cell interference coordination, and the inter-cell balanced signal to interference plus noise ratio (SINR) among users is established for power allocation, which enables mitigation of inter-cell interference. Especially, the power control is based on a novel exponential kernel equation at higher convergence speed than the traditional arithmetic kernel equations. Numerical results show that th…
Downlink radio resource allocation for coordinated cellular OFDMA networks
2010
Base station coordination is considered as a promising technique to mitigate inter-cell interference and improve the cell-edge performance in cellular orthogonal frequency division multiple-access (OFDMA) networks. The problem to design an efficient radio resource allocation scheme for coordinated cellular OFDMA networks incorporating base station coordination has been only partially investigated. In this contribution, a novel radio resource allocation algorithm with universal frequency reuse is proposed to support base station coordinated transmission. Firstly, with the assumption of global coordination between all base station sectors in the network, a coordinated subchannel assignment al…
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 effect of automated taxa identification errors on biological indices
2017
In benthic macroinvertebrate biomonitoring systems, the target is to determine the status of ecosystems based on several biological indices. To increase cost-efficiency, computer-based taxa identification for image data has recently been developed. Taxa identification errors can, however, have strong effects on the indices and thus on the determination of the ecological status. In order to shift the biomonitoring process towards automated expert systems, we need a clear understanding on the bias caused by automation. In this paper, we examine eleven classification methods in the case of macroinvertebrate image data and show how their classification errors propagate into different biological…
Towards Efficient Control of Mobile Network-Enabled UAVs
2019
| openaire: EC/H2020/815191/EU//PriMO-5G The efficient control of mobile network-enabled unmanned aerial vehicles (UAVs) is targeted in this paper. In particular, a downlink scenario is considered, in which control messages are sent to UAVs via cellular base stations (BSs). Unlike terrestrial user equipment (UEs), UAVs perceive a large number of BSs, which can lead to increased interference causing poor or even unacceptable throughput. This paper proposes a framework for efficient control of UAVs. First, a communication model is introduced for flying UAVs taking into account interference, path loss and fast fading. The characteristics of UAVs make such model different compared to traditiona…
Interchannel Interference and Mitigation in Distributed MIMO RF Sensing
2021
In this paper, we analyze and mitigate the cross-channel interference, which is found in multiple-input multiple-output (MIMO) radio frequency (RF) sensing systems. For a millimeter wave (mm-Wave) MIMO system, we present a geometrical three-dimensional (3D) channel model to simulate the time-variant (TV) trajectories of a moving scatterer. We collected RF data using a state-of-the-art radar known as Ancortek SDR-KIT 2400T2R4, which is a frequency-modulated continuous wave (FMCW) MIMO radar system operating in the K-band. The Ancortek radar is currently the only K-band MIMO commercial radar system that offers customized antenna configurations. It is shown that this radar system encounters th…
A method to estimate the path gains and propagation delays of underwater acoustic channels using the arrival phase information of the multipath compo…
2017
Abstract We propose a method for the estimation of the channel parameters of underwater acoustic channels (UACs) by using a pseudo-noise (PN) sequence. For the channel sounding, the PN sequence is coherently modulated on a carrier frequency by using a binary phase-shift keying (BPSK) modulation scheme. For the demodulation, the arrival phases of the received BPSK signals must be known at the receiver. In practice, however, the arrival phases of the received signal are unknown. We propose to demodulate the received BPSK signal by using an hypothetical arrival phase, which will be increased from 0 to 2 π . The demodulated signal obtained by using the hypothetical arrival phase is then correla…
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 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…