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| 2. |
- Abbas, Taimoor, et al.
(författare)
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Validation of a Non-Line-of-Sight Path-Loss Model for V2V Communications at Street Intersections
- 2013
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Ingår i: 13th International Conference on ITS Telecommunications.
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Konferensbidrag (refereegranskat)abstract
- In this paper a non-line-of-sight (NLOS) path-loss and fading model developed for vehicle-to-vehicle (V2V) communication at 5:9 GHz is validated with independent and realistic measurement data. The reference NLOS model is claimed to be flexible and of low complexity, and incorporates specific geometric aspects in a closed-form expression.We validated the accuracy of the model with the help of realistic channel measurements performed in selected street intersections in the city of Lund and Malm¨o, Sweden. The model fits well, with a few exceptions, to most of the measurements taken at different intersections which have variable geometry and scattering environment. It is found that the model can be made more general if an intersection dependent parameter, that depends on the property and number of available scatterers in that particular intersection, is included in the model.
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| 3. |
- Alonso, Arrate, et al.
(författare)
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Capacity evaluation of measured vehicle-to- vehicle radio channels at 5.2 GHz
- 2010
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Konferensbidrag (refereegranskat)abstract
- Reliability in Ricean multiple-input-multipleoutput (MIMO) channels is crucial for safety-related vehicle-tovehicle (V2V) applications. In Ricean channels, there is a signalto- noise ratio-dependent critical data rate below which signaling with zero outage is possible. The link will be more reliable the higher this critical data rate is. We present results of spectral efficiency and outage probability from channel sounder measurements of V2V MIMO radio channels in the 5.2 GHz band. Our results show that MIMO channels with higher spatial correlation lead to lower ergodic capacity and a reduced critical data rate. However, for fixed output power the temporal evolution of the ergodic capacity and critical data rate shows that the channel with the strongest line of sight (LoS) component also has the highest capacity.
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| 4. |
- Alonso, Arrate, et al.
(författare)
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Temporal evolution of channel capacity in vehicular MIMO channels in the 5 GHz band
- 2010
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Ingår i: EMTS 2010: 2010 URSI International Symposium on Electromagnetic Theory. - 9781424451548 - 9781424451531 ; , s. 938-941
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Konferensbidrag (refereegranskat)abstract
- Reliability in Ricean multiple-input-multiple-output (MIMO) channels is crucial for safety related vehicle-tovehicle (V2V) applications. Due to the time variability of vehicular communication channel, it is very significant to study the temporal evolution of channel characterization criteria. We present evaluation results of the temporal evolution of the spectral efficiency from channel sounder measurements of vehicle-to-vehicle MIMO radio channels in the 5.2 GHz band. Our results show that MIMO channels with higher spatial correlation lead to lower ergodic capacity and a reduced signalto- noise ratio-dependent critical data rate. The temporal evolution of the ergodic capacity and critical data rate shows that the channel with the strongest line of sight (LoS) component also has the highest capacity. We also present a detailed analysis of the environmental factors affecting the capacity pattern throughout the measurement run. Dynamic scatterers introduce capacity bursts instantaneously; the trend stays congruent with the theory.
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| 5. |
- Bernado, Laura, et al.
(författare)
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Delay and Doppler Spreads of Non-Stationary Vehicular Channels for Safety Relevant Scenarios
- 2014
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Ingår i: IEEE Transactions on Vehicular Technology. - 1939-9359. ; 63:1, s. 82-93
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Tidskriftsartikel (refereegranskat)abstract
- Abstract in UndeterminedVehicular communication channels are characterized by a nonstationary time-frequency-selective fading process due to rapid changes in the environment. The nonstationary fading process can be characterized by assuming local stationarity for a region with finite extent in time and frequency. For this finite region, the wide-sense stationarity and uncorrelated scattering assumption approximately holds, and we are able to calculate a time-frequency-dependent local scattering function (LSF). In this paper, we estimate the LSF from a large set of measurements collected in the DRIVEWAY'09 measurement campaign, which focuses on scenarios for intelligent transportation systems (ITSs). We then obtain the time-frequency-varying power delay profile (PDP) and the time-frequency-varying Doppler power spectral density (DSD) from the LSF. Based on the PDP and the DSD, we analyze the time-frequency-varying root-mean-square (RMS) delay spread and the RMS Doppler spread. We show that the distribution of these channel parameters follows a bimodal Gaussian mixture distribution. High RMS delay spread values are observed in situations with rich scattering, whereas high RMS Doppler spreads are obtained in drive-by scenarios.
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| 6. |
- Bernadó, Laura, et al.
(författare)
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In-tunnel vehicular radio channel characterization
- 2011
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Ingår i: [Host publication title missing]. - 1550-2252. - 9781424483327
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Konferensbidrag (refereegranskat)abstract
- Abstract in UndeterminedInside a tunnel, electromagnetic wave propagation differs strongly from the well understood "open-air" situation. The characterization of the tunnel environment is crucial for deploying vehicular communication systems. In this paper we evaluate vehicle-to-vehicle (V2V) radio channel measurements inside a tunnel. We estimate the time-varying root mean square (rms) delay and Doppler spreads, as well as the excess delay and the maximum Doppler dispersion. The fading process in V2V communications is inherently non-stationary. Hence, we characterize the stationarity time, for which we can consider the fading process to be wide sense stationary. We show that the spreads, excess delay, and maximum Doppler dispersion are larger on average when both vehicles are inside the tunnel compared to the "open-air" situation. The temporal evolution of the stationarity time is highly influenced by the strength of time-varying multipath components and the distance between vehicles. Furthermore, we show the good fit of the rms delay and Doppler spreads to a lognormal distribution, as well as for the stationarity time. From our analysis we can conclude that the IEEE 802.11p standard will be robust towards inter-symbol and inter-carrier interference inside a tunnel.
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| 7. |
- Bernadó, Laura, et al.
(författare)
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Multi-dimensional K-factor analysis for V2V radio channels in open sub-urban street crossings
- 2010
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Ingår i: [Host publication title missing]. - 9781424480173 ; , s. 58-63
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Konferensbidrag (refereegranskat)abstract
- In this paper we analyze the small-scale fading statistics for vehicle-to-vehicle (V2V) communications in a typical open sub-urban street crossing. The two cars approach the crossing from two different streets and the channel conditions vary from non line-of sight (NLOS) to line-of-sight (LOS). The small-scale fading of the first delay bin is Ricean distributed with a time-varying K-factor. The later delay bins are mostly Rayleigh distributed. The antenna arrays used for recording the multiple-input multiple-output channels are linear and consist of 4 elements with directional radiation patterns. We investigate the K-factor variation of the first delay bin in time, frequency, and space dimensions, where the measurement has a duration of 20 s, a bandwidth of 240 MHz, and 16 individual single-input single- output channels. We observe that the large/small K-factor values are not necessarily correlated with the received power. We show that the K-factor can not be assumed to be constant in any of the considered domains, not even in the frequency domain, as it has been always done for relative bandwidths up to 10%. The narrow- band K-factor for each frequency bin corroborates the need to consider its frequency variation. The antenna radiation patterns, and the illuminated objects by them at different time instances are the cause of these variations. We conclude that a multi- dimensional varying K-factor models the large-scale statistical behaviour more accurately than a constant K-factor.
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| 8. |
- Bernadó, Laura, et al.
(författare)
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Non-WSSUS Vehicular Channel Characterization at 5.2 GHz - Spectral Divergence and Time-Variant Coherence Parameters
- 2008
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Konferensbidrag (refereegranskat)abstract
- The scattering environment in vehicle-to-vehicle communication channels at 5.2 GHz changes rapidly. Hence the wide-sense stationary (WSS) uncorrelated scattering (US) assumption for the fading process is valid for short time intervals only. We characterize the spectral divergence of the local scattering function (LSF) sequence in order to assess the non-WSSUS characteristics in different scenarios. We find that the vehicle-to-vehicle channels violate the wide-sense stationarity much stronger than the US assumption. Additionally, we use the LSF to quantify the time dependence of the channel coherence time and bandwidth. Both parameters vary strongly over time depending on the chosen scenario. Furthermore the effect of the antenna radiation pattern on the fading process is quantified, which can cause the strength of a multipath component to change by more than 40 dB in drive-by experiments.
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| 9. |
- Bernado, Laura, et al.
(författare)
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The (in-) validity of the WSSUS assumption in vehicular radio channels
- 2012
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Ingår i: [Host publication title missing]. - 2166-9589 .- 2166-9570. - 9781467325684 ; , s. 1757-1762
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Konferensbidrag (refereegranskat)abstract
- The assumption of wide-sense-stationarity (WSS) and uncorrelated scattering (US) of wireless propagation channels is widespread for the design and analysis of wireless propagation channels. However, the assumption is only valid within a limited range. In this paper, we investigate the extension of this range not only in time (WSS), but also in frequency (US), for measured vehicular propagation channels. We do this by using the collinearity of the local scattering function, which is a bounded spectral distance metric, and thus allows us to set an indicative threshold, which in turn enables a WSS and a US test. We prove that the fading process in vehicular communications is strongly non-WSS, which agrees with results previously reported in the literature. Furthermore, for the first time (to the authors' knowledge), we show their non-US behavior as well, mainly in scenarios with rich scattering. The dimensions of the minimum stationarity region are on the order of 40 ms in time and 40MHz in frequency.
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| 10. |
- Bernado, Laura, et al.
(författare)
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Time- and Frequency-Varying K -Factor of Non-Stationary Vehicular Channels for Safety-Relevant Scenarios
- 2015
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Ingår i: IEEE Transactions on Intelligent Transportation Systems. - 1524-9050. ; 16:2, s. 1007-1017
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Tidskriftsartikel (refereegranskat)abstract
- 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 $K$-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 Rician distributed with a varying K-factor. The later delay bins are Rayleigh distributed. We demonstrate that the K-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 bimodal Gaussian mixture model, which allows to capture the K-factor variability in time for safety-relevant ITS scenarios.
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