| 1. |
- Abbas, Taimoor, et al.
(författare)
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Measurements Based Channel Characterization for Vehicle-to-Vehicle Communications at Merging Lanes on Highway
- 2013
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Ingår i: 2013 IEEE 5th International Symposium on Wireless Vehicular Communications, WiVeC 2013 - Proceedings. - : IEEE. - 9781467363396
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Konferensbidrag (refereegranskat)abstract
- This paper presents results for vehicle-to-vehicle channel characterization based on measurements conducted for the merging lane scenarios on a highway. We present power delay profiles as well as channel gains and analyze important propagation mechanisms to see the impact of line-of-sight (LOS) and the antenna radiation pattern on the total received power. It is found that the absence of LOS and strong scattering objects, close to the point where the ramp merges with a highway, may result in poor received signal strength. The probability of dropping packets also increases where there is LOS between TX and RX but the antenna pattern is not omni-directional. A dip in the antenna pattern affects the received signal strength severely which poses a challenge for vehicle-to-vehicle communication in safety critical situations.
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| 5. |
- 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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| 6. |
- 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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| 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. |
- Christoph, Mecklenbräuker, et al.
(författare)
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Vehicle-to-Vehicle Communications
- 2012
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Ingår i: Pervasive Mobile and Ambient Wireless Communications, Roberto Verdone and Alberto Zanella, editors. Springer. - London : Springer London. - 9781447123149 ; , s. 577-608
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 10. |
- Chung, P. J., et al.
(författare)
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Broadband ML estimation under model order uncertainty
- 2010
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Ingår i: Signal Processing. - : Elsevier BV. - 0165-1684. ; 90:5, s. 1350-1356
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Tidskriftsartikel (refereegranskat)abstract
- The number of signals hidden in data plays a crucial role in array processing. When this information is not available, conventional approaches apply information theoretic criteria or multiple hypothesis tests to simultaneously estimate model order and parameter. These methods are usually computationally intensive, since ML estimates are required for a hierarchy of nested models. In this contribution, we propose a computationally efficient solution to avoid this full search procedure and address issues unique to the broadband case. Our max-search approach computes ML estimates only for the maximally hypothesized number of signals, and selects relevant components through hypothesis testing. Furthermore, we introduce a criterion based on the rank of the steering matrix to reduce indistinguishable components caused by overparameterization. Numerical experiments show that despite model order uncertainty, the proposed method achieves comparable estimation and detection accuracy as standard methods, but at much lower computational expense. (C) 2009 Elsevier B.V. All rights reserved.
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