| 1. |
- 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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| 2. |
- Bernadó, Laura, et al.
(författare)
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Parametrization of the local scattering function estimator for vehicular-to-vehicular channels
- 2009
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Ingår i: [Host publication title missing]. ; , s. 1-5
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Konferensbidrag (refereegranskat)abstract
- Non wide-sense stationary (WSS) uncorrelated scatterering (US) fading processes are observed in vehicular communications. To estimate such a process under additive white Gaussian noise we use the local scattering function (LSF). In this paper we present an optimal parametrization of the multitaper-based LSF estimator. We do this by quantizing the mean square error (MSE). For that purpose we use the structure of a twodimensional Wiener filter and optimize the parameters of the estimator to obtain the minimum MSE (MMSE). We split the observed fading process in WSS regions and analyze the influence of the estimator parameters and the length of the stationarity regions on the MMSE. The analysis is performed considering three different scenarios representing different scattering properties. We show that there is an optimal combination of estimator parameters and length of stationarity region which provides a minimum MMSE.
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| 3. |
- Czink, Nicolai, et al.
(författare)
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Tracking time-variant cluster parameters in MIMO channel measurements: algorithm and results
- 2007
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This paper presents a joint clustering-and-tracking framework to identify time-variant cluster parametersfor geometry-based stochastic MIMO channel models.The method uses a Kalman filter for tracking and predicting cluster positions, a novel consistentinitial guess procedure that accounts for predicted cluster centroids, and the well-known KPower-Means algorithm for cluster identification.We tested the framework by applying it to three entirely different sets of MIMO channel measurementdata obtained by different channel sounders: indoor measurements conducted at 2.55GHz, outdoor rural measurements at 300 MHz, and outdoor sub-urban measurements at 2.0 GHz.The time-variant cluster parameters of interest are: (i) cluster movement, (ii) change of clusterspreads, (iii) cluster lifetimes, and birth and death rates of cluster.We find that clusters show significant movement in parameter space depending on the environment.The spreads of individual clusters change rather randomly over their lifetime, with astandard deviation up to 150% of their mean spread. The cluster lifetime is approximately exponentiallydistributed, however additionally one has to account for long-living clusters coming fromthe line-of-sight path or from major reflectors.
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| 4. |
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| 5. |
- Kåredal, Johan, et al.
(författare)
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A geometry-based stochastic MIMO model for vehicle-to-vehicle communications
- 2009
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Ingår i: IEEE Transactions on Wireless Communications. - 1536-1276. ; 8:7, s. 3646-3657
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Tidskriftsartikel (refereegranskat)abstract
- Vehicle-to-vehicle (VTV) wireless communications have many envisioned applications in traffic safety and congestion avoidance, but the development of suitable communications systems and standards requires accurate models for the VTV propagation channel. In this paper, we present a new wideband multiple-input-multiple-output (MIMO) model for VTV channels based on extensive MIMO channel measurements performed at 5.2 GHz in highway and rural environments in Lund, Sweden. The measured channel characteristics, in particular the non-stationarity of the channel statistics, motivate the use of a geometry-based stochastic channel model (GSCM) instead of the classical tapped-delay line model. We introduce generalizations of the generic GSCM approach and techniques for parameterizing it from measurements and find it suitable to distinguish between diffuse and discrete scattering contributions. The time-variant contribution from discrete scatterers is tracked over time and delay using a high resolution algorithm, and our observations motivate their power being modeled as a combination of a (deterministic) distance decay and a slowly varying stochastic process. The paper gives a full parameterization of the channel model and supplies an implementation recipe for simulations. The model is verified by comparison of MIMO antenna correlations derived from the channel model to those obtained directly from the measurements.
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| 6. |
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| 7. |
- Kåredal, Johan, et al.
(författare)
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Measurement-based modeling of vehicle-to-vehicle MIMO channels
- 2009
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Ingår i: IEEE International Conference on Communications. ; , s. 3470-3475
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Konferensbidrag (refereegranskat)abstract
- Vehicle-to-vehicle (VTV) communications are of interest for applications within traffic safety and congestion avoidance, but the development of suitable communications systems requires accurate models for the VTV propagation channel. This paper presents a new wideband MIMO (multipleinput- multiple-output) channel model for VTV channels based on extensive MIMO channel measurements performed at 5.2 GHz in rural environments in Lund, Sweden. The measured channel characteristics, in particular the non-stationarity of the channel statistics, motivate the use of a geometry-based stochastic channel model (GSCM) instead of the classical tapped-delay line model. We introduce generalizations of the generic GSCM approach and find it suitable to distinguish between diffuse and discrete scattering contributions. The time-variant contribution from discrete scatterers is tracked over time and delay using a high resolution algorithm, and our observations motivate their power being modeled as a combination of a deterministic part and a stochastic part. The paper gives a full model parameterization and the model is verified by comparison of MIMO antenna correlations derived from the channel model to those obtained directly from the measurements.
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| 8. |
- Paier, Alexander, et al.
(författare)
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Car-to-car radio channel measurements at 5 GHz: Pathloss, power-delay profile, and delay-Doppler spectrum
- 2007
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Ingår i: [Host publication title missing]. - 9781424409792 ; , s. 224-228
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Konferensbidrag (refereegranskat)abstract
- We carried out a car-to-infrastructure (C2I) and car-to-car (C2C) 4x4 multiple-input-multiple-output (MIMO) radio channel measurement campaign at 5.2GHz in Lund, Sweden. This paper presents first results on pathloss, power-delay profiles, and delay-Doppler spectra in a C2C highway scenario, where both cars were traveling in opposite directions. A pathloss coefficient of 1.8 yields the best fit with our measurement results in the mean square sense. The measured Doppler shift of the line of sight path matches exactly with theoretical calculations. Selected paths are investigated in the delay and Doppler domain. The avererage delay spread is 250 ns; Doppler shifts of more than 1000 Hz are observed.
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| 9. |
- Paier, Alexander, et al.
(författare)
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Characterization of Vehicle-to-Vehicle Radio Channels from Measurements at 5.2GHz
- 2009
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Ingår i: Wireless Personal Communications. - : Springer Science and Business Media LLC. - 1572-834X .- 0929-6212. ; 50:1, s. 19-32
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Tidskriftsartikel (refereegranskat)abstract
- The development of efficient vehicle-to-vehicle (V2V) communications systems requires an understanding of the underlying propagation channels. In this paper, we present results on pathloss, power-delay profiles (PDPs), and delay-Doppler spectra from a high speed measurement campaign on a highway in Lund, Sweden. Measurements were performed at a carrier frequency of 5.2GHz with the communicating vehicles traveling on the highway in opposite directions. A pathloss coefficient of 1.8 shows the best fit in the mean square sense with our measurement. The average root mean square (RMS) delay spread is between 263 ns and 376 ns, depending on the noise threshold. We investigate and describe selected paths in the delay-Doppler domain, where we observe Doppler shifts of more than 1000Hz.
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| 10. |
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