42 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
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
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 study on the impact of antenna characteristics on non-stationary V2I channel parameters in tunnels
This paper analyses the experimentally-assessed dual-polarized (DP) mobile channel in a tunnel environment at 1.35 GHz under traffic conditions. We investigate the impact of antenna polarization and radiation pattern on the non-stationary vehicle-to-infrastructure (V2I) channel. Basic channel evaluation metrics are examined including path gain, co-polarization ratio (CPR), and cross-polarization discrimination (XPD). In addition, the stationarity region is estimated using the channel correlation function approach, and used to calculate the time-varying delay and Doppler power profiles. Statistical models are presented for parameters like CPR, XPD, RMS delay and Doppler spreads, where the lognormal distribution provides the best fit. The polarization and the opening angle of the antennas into the propagation channel are found to strongly influence the observed non-stationarity of the channel. They impact the degree of multipath richness that is captured, thus providing different path gain, delay and Doppler spreads. Based on our analysis, the directional antenna with vertical polarization provides the longest stationarity time of 400 ms at 90 km/h, as well as the highest path gain and lowest dispersion. Furthermore, the DP channel capacity is calculated and its dependence on different normalization approaches is investigated. We propose a more accurate normalization for the DP channels that takes the conservation of energy into account. Moreover, the subchannels correlation coefficients are determined. While the condition number is found to be low on average, the correlation results show high correlation among the DP subchannels. As conclusion, we show how the CPR and XPD play the main role in providing multiplexing gain for DP tunnel channels
Massive radio channel sounder architecture for 5G mobility scenarios : MaMIMOSA
This paper presents a real-time 64 x 16 massive MIMO channel sounder based on space-frequency division multiplexing and antenna subarray switching, giving a large possibility of antenna allocation and frequency tone between 2 and 12 GHz. This channel sounder called Massive MIMOSA or MaMIMOSA belongs to the new generation of software radio design based systems. The architecture of the proposed approach was designed with the highest flexibility thus opening a wide range of applications depending upon the investigated scenarios. Currently, the system is being setup using a massive 10 x 10 antenna array operating around 6 GHz with 80 MHz bandwidth for SG V2X applications. The channel sounder can be powered with vehicle batteries to perform day long measurements when electrical outlets are not available. The output file gives the measured Massive MIMO matrix in a friendly compact binary format. It will be operational in early 2020
Time- and Frequency-Varying -Factor of Non-Stationary Vehicular Channels for Safety Relevant Scenarios
Vehicular communication channels are characterized by a non-stationary time-
and frequency-selective fading process due to fast changes in the environment.
We characterize the distribution of the envelope of the first delay bin in
vehicle-to-vehicle channels by means of its Rician -factor. We analyze the
time-frequency variability of this channel parameter using vehicular channel
measurements at 5.6 GHz with a bandwidth of 240 MHz for safety-relevant
scenarios in intelligent transportation systems (ITS). This data enables a
frequency-variability analysis from an IEEE 802.11p system point of view, which
uses 10 MHz channels. We show that the small-scale fading of the envelope of
the first delay bin is Ricean distributed with a varying -factor. The later
delay bins are Rayleigh distributed. We demonstrate that the -factor cannot
be assumed to be constant in time and frequency. The causes of these variations
are the frequency-varying antenna radiation patterns as well as the
time-varying number of active scatterers, and the effects of vegetation. We
also present a simple but accurate bi-modal Gaussian mixture model, that allows
to capture the -factor variability in time for safety-relevant ITS
scenarios.Comment: 26 pages, 12 figures, submitted to IEEE Transactions on Intelligent
Transportation Systems for possible publicatio
Propagation and Wireless Channel Modeling Development on Wide-Sense Vehicle-to-X Communications
The need for improving the safety and the efficiency of transportation systems has become of extreme importance. In this regard, the concept of vehicle-to-X (V2X) communication has been introduced with the purpose of providing wireless communication technology in vehicular networks. Not like the traditional views, the wide-sense V2X (WSV2X) communications in this paper are defined by including not only vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communications but also train-to-X (T2X) communications constituted of train-to-train (T2T) and train-to-infrastructure (T2I) communications. All the information related to the wide-sense V2X channels, such as the standardization, scenarios, characters, and modeling philosophies, is organized and summarized to form the comprehensive understanding of the development of the WSV2X channels
An enhanced approach to virtually increase quasi-stationarity regions within geometric channel models for vehicular communications
Vehicular communication channels are intrinsically
non-stationary, as they present high mobility and abundant dynamic
scatterers. Quasi-stationary regions can assess the degree
of non-stationarity within a determined scenario and time variant
observation of the channel can be extracted. These regions can
aid geometrical models as to increase channel sampling intervals
or to develop hybrid stochastic-geometric channel models. In this
work, a new methodology for the use of virtual quasi-stationary
regions within geometric channel models is proposed, in order to
leverage the inherent location information to virtually increase
their size. Overall, the use of delay-shifted channel responses
improves the mean correlation coefficient between consecutive
locations, ultimately reducing computation time for time-variant
geometric channel models.The authors wish to acknowledge the support received under Grant RYC2021-031949-I, funded by
MCIN/AEI/10.13039/501100011033 and NextGenerationEU/PRTR; and under
Grant PID2021-127409OB-C31, funded by MCIU/AEI/FEDER, UE
Propagation channel characterisation and modelling for high-speed train communication systems
High-mobility scenarios, e.g., High-Speed Train (HST) scenarios, are expected to be
typical scenarios for the Fifth Generation (5G) communication systems. With the
rapid development of HSTs, an increasing volume of wireless communication data
is required to be transferred to train passengers. HST users demand high network
capacity and reliable communication services regardless of their locations or speeds,
which are beyond the capability of current HST communication systems. The features
of HST channels are significantly different from those of low-mobility cellular
communication systems. For a proper design and evaluation of future HST wireless
communication systems, we need accurate channel models that can mimic the
underlying channel characteristics, especially the non-stationarity for different HST
scenarios. Inspired by the lack of such accurate HST channel models in the literature,
this PhD project is devoted to the modelling and simulation of non-stationary
Multiple-Input Multiple-Output (MIMO) channels for HST communication systems.
In this thesis, we first give a comprehensive review of the measurement campaigns
conducted in different HST scenarios and address the recent advances in HST channel
models. We also highlight the key challenges of HST channel measurements and
models. Then, we study the characterisation of non-stationary channels and propose
a theoretical framework for deriving the statistical properties of these channels.
HST wireless communication systems encounter different channel conditions due to the
difference of surrounding geographical environments or scenarios. HST channel models
in the literature have either considered large-scale parameters only and/or neglected
the non-stationarity of HST channels and/or only consider one of the HST scenarios.
Therefore, we propose a novel generic non-stationary Geometry-Based Stochastic
Model (GBSM) for wideband MIMO HST channels in different HST scenarios, i.e.,
open space, viaduct, and cutting. The corresponding simulation model is then developed
with angular parameters calculated by the Modified Method of Equal Area
(MMEA). The system functions and statistical properties of the proposed channel
models are thoroughly studied. The proposed generic non-stationary HST channel
models are verified by measurements in terms of stationary time for the open space
scenario and the Autocorrelation Function (ACF), Level Crossing Rate (LCR), and
stationary distance for the viaduct and cutting scenarios. Transmission techniques which are capable of utilising Three-Dimensional (3D) spatial
dimensions are significant for the development of future communication systems.
Consequently, 3D MIMO channel models are critical for the development and evaluation
of these techniques. Therefore, we propose a novel 3D generic non-stationary
GBSM for wideband MIMO HST channels in the most common HST scenarios. The
corresponding simulation model is then developed with angular parameters calculated
by the Method of Equal Volume (MEV). The proposed models considers several timevarying
channel parameters, such as the angular parameters, the number of taps, the
Ricean K-factor, and the actual distance between the Transmitter (Tx) and Receiver
(Rx). Based on the proposed generic models, we investigate the impact of the elevation
angle on some of the channel statistical properties. The proposed 3D generic
models are verified using relevant measurement data.
Most standard channel models in the literature, like Universal Mobile Telecommunications
System (UMTS), COST 2100, and IMT-2000 failed to introduce any of the HST
scenarios. Even for the standard channel models which introduced a HST scenario,
like IMT-Advanced (IMT-A) and WINNER II channel models, they offer stationary
intervals that are noticeably longer than those in measured HST channels. This has
inspired us to propose a non-stationary IMT-A channel model with time-varying parameters
including the number of clusters, powers, delays of the clusters, and angular
parameters. Based on the proposed non-stationary IMT-A channel model, important
statistical properties, i.e., the time-variant spatial Cross-correlation Function (CCF)
and time-variant ACF, are derived and analysed. Simulation results demonstrate
that the stationary interval of the developed non-stationary IMT-A channel model
can match that of relevant HST measurement data.
In summary, the proposed theoretical and simulation models are indispensable for the
design, testing, and performance evaluation of 5G high-mobility wireless communication
systems in general and HST ones in specific