146 research outputs found
Stationarity analysis of V2I radio channel in a suburban environment
Due to rapid changes in the environment, vehicular communication channels no longer satisfy the assumption of wide-sense stationary uncorrelated scattering. The non-stationary fading process can be characterized by assuming local stationarity regionswith finite extent in time and frequency. The local scattering function (LSF) and channel correlation function (CCF) provide a framework to characterize the mean power and correlation of the non-stationary channel scatterers, respectively. In this paper, we estimate the LSF and CCF from measurements collected in a vehicle-to-infrastructure radio channel sounding campaign in a suburban environment in Lille, France. Based on the CCF, the stationarity region is evaluated in time as 567 ms and used to capture the non-stationary fading parameters. We obtain the time-varying delay and Doppler power profiles fromthe LSF, and we analyze the corresponding root-mean-square delay and Doppler spreads. We show that the distribution of these parameters follows a lognormal model. Finally, application relevance in terms of channel capacity and diversity techniques is discussed. Results show that the assumption of ergodic capacity and the performance of various diversity techniques depend on the stationarity and coherence parameters of the channel. The evaluation and statistical modeling of such parameters can provide away of tracking channel variation, hence, increasing the performance of adaptive schemes
Analysis of the Local Quasi-Stationarity of Measured Dual-Polarized MIMO Channels
It is common practice in wireless communications to assume strict or
wide-sense stationarity of the wireless channel in time and frequency. While
this approximation has some physical justification, it is only valid inside
certain time-frequency regions. This paper presents an elaborate
characterization of the non-stationarity of wireless dual-polarized channels in
time. The evaluation is based on urban macrocell measurements performed at 2.53
GHz. In order to define local quasi-stationarity (LQS) regions, i.e., regions
in which the change of certain channel statistics is deemed insignificant, we
resort to the performance degradation of selected algorithms specific to
channel estimation and beamforming. Additionally, we compare our results to
commonly used measures in the literature. We find that the polarization, the
antenna spacing, and the opening angle of the antennas into the propagation
channel can strongly influence the non-stationarity of the observed channel.
The obtained LQS regions can be of significant size, i.e., several meters, and
thus the reuse of channel statistics over large distances is meaningful (in an
average sense) for certain algorithms. Furthermore, we conclude that, from a
system perspective, a proper non-stationarity analysis should be based on the
considered algorithm
Including general environmental effects in K-factor approximation for rice-distributed VANET channels
© 2014. This paper presents a method of approximating the Rician K-factor based on the instantaneous static environment. The strongest signal propagation paths are resolved in order to determine specular and diffuse powers for approximation. The model is experimentally validated in two different urban areas in New South Wales, Australia. Good agreement between the model and experimental data was obtained over short-range communication links, demonstrating the suitability of the model in urban VANETs. The paper concludes with recommendations for methods to account for vehicles in the simulation and incorporating additional phenomena (such as scattering) in the approximation
Experimental characterization of non-stationary V2I radio channel in tunnels
The fading process in vehicular communications is inherently non-stationary. In this paper, vehicle-to-infrastructure (V2I) radio channel measurements are performed inside a tunnel for low and medium traffic conditions to estimate the stationarity time, in addition to the time-varying RMS delay and Doppler spreads. Furthermore, we show the good fit of the spreads to a lognormal distribution, as well as for the Rician K-factor of the fading amplitude. From our analysis we conclude that the traffic density has an impact on the large-scale parameters as it increases delay and Doppler spreads, while reducing the correlation between them as well as the average K-factor. Larger traffic densities may be required to impact the stationarity time
Experimental characterization of V2I radio channel in a suburban environment
This paper describes the results of the experimental vehicle-to-infrastructure radio channel sounding campaign at 1.35 GHz performed in a suburban environment in Lille, France. Based on the channel measurements acquired in vertical and horizontal polarizations, a multitaper estimator is used to estimate the local scattering function for sequential regions in time, from which Doppler and delay power profiles are deduced. We analyze second order statistics such as delay and Doppler spreads, as well as small-scale fading amplitude. A similar behavior between both polarizations is observed. In both cases, the statistical distributions of the RMS delay and Doppler spreads are best fitted to a lognormal model. The small-scale fading of the strongest path is found to be Rician distributed, while the later delay taps show occasional worse-than-Rayleigh behavior
Methodologies for Future Vehicular Digital Twins
The role of wireless communications in various domains of intelligent
transportation systems is significant; it is evident that dependable message
exchange between nodes (cars, bikes, pedestrians, infrastructure, etc.) has to
be guaranteed to fulfill the stringent requirements for future transportation
systems. A precise site-specific digital twin is seen as a key enabler for the
cost-effective development and validation of future vehicular communication
systems. Furthermore, achieving a realistic digital twin for dependable
wireless communications requires accurate measurement, modeling, and emulation
of wireless communication channels. However, contemporary approaches in these
domains are not efficient enough to satisfy the foreseen needs. In this
position paper, we overview the current solutions, indicate their limitations,
and discuss the most prospective paths for future investigation.Comment: Submitted to IEEE Intelligent Transportation Systems Magazin
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