| 1. |
- Abbas, Taimoor, et al.
(författare)
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Directional Analysis of Vehicle-to-Vehicle Propagation Channels
- 2011
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Ingår i: IEEE Vehicular Technology Conference.
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Konferensbidrag (refereegranskat)abstract
- This paper presents a double directional analysis of vehicle-to-vehicle channel measurements conducted in three different traffic scenarios. Using a high-resolution algorithm, we derive channel parameters like Angle-of-Arrival (AOA), Angle-of-Departure (AOD), propagation delay and Doppler shift and identify underlying propagation mechanisms by combining these estimates with maps of the measurement sites. The results show that first-order reflections from a small number of interacting objects can account for a large part of the received signal in the absence of line-of-sight (LOS). This effect is especially pronounced in the two traffic scenarios where the road is not lined with buildings. We also found that the direction spread is low (and conversely that the antenna correlation is high) in such scenarios, which suggests that beam forming rather than diversity-based methods should be used if multiple antenna elements are used. The situation is reversed, however, in the third scenario, a narrow urban intersection, where a larger number of higher-order reflections is found to result in a higher direction spread.
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| 2. |
- Bernadó, Laura, et al.
(författare)
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Complexity reduction for vehicular channel estimation using the filter-divergence measure
- 2011
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Ingår i: 2010 Conference Record of the Forty Fourth Asilomar Conference on Signals, Systems and Computers. - 9781424497225 - 9781424497218
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Konferensbidrag (refereegranskat)abstract
- In vehicular communications systems the channel estimation filter suppresses the additive noise in channel estimates obtained from pilot symbols. Vehicular channels show local stationarity for a finite region in time and frequency, only. Such a process can be divided into consecutive stationarity regions, allowing to calculate a Wiener filter. We analyze the increase of the mean square error (MSE) when using a mismatched Wiener filter calculated for a past stationarity region. The MSE increase of the filter is related to a new metric, the filter divergence directly observable at the receiver side. By accepting an increase of MSE, measured by the filter-divergence, the same filter coefficients can be used for several stationarity regions, allowing computational complexity reduction in a real system.
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| 3. |
- 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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| 4. |
- Kåredal, Johan, et al.
(författare)
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Path loss modeling for vehicle-to-vehicle communications
- 2011
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Ingår i: IEEE Transactions on Vehicular Technology. - 1939-9359. ; 60:1, s. 323-328
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Tidskriftsartikel (refereegranskat)abstract
- Vehicle-to-vehicle (V2V) communications have received increasingattention lately, but there is a lack of reported results regarding important quantities such as path loss. This paper presents parameterized path loss models for V2V communications based on extensive sets of measurement data collected mainly under line-of-sight conditions in four different propagation environments: highway, rural, urban, and suburban. The results show that the path loss exponent is low for V2V communications, i.e., path loss slowly increases with increasing distance. We compare our results to those previously reported and find that, while they confirm some of the earlier work, there are also differences that motivate the need for further studies.
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| 5. |
- Mecklenbräuker, Christoph, et al.
(författare)
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Vehicular channel characterization and its implications for wireless system design and performance
- 2011
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Ingår i: Proceedings of the IEEE. - 0018-9219. ; 99:7, s. 1189-1212
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Tidskriftsartikel (refereegranskat)abstract
- To make transportation safer, more efficient, and less harmful to the environment, traffic telematics services are currently being intensely investigated and developed. Such services require dependable wireless vehicle-to-infrastructure and vehicle-to-vehicle communications providing robust connectivity at moderate data rates. The development of such dependable vehicular communication systems and standards requires accurate models for the propagation channel in all relevant environments and scenarios. Key characteristics of vehicular channels are shadowing by other vehicles, high Doppler shifts, and inherent non-stationarity, which have major impact on the data packet transmission reliability and latency. This paper provides an overview of the existing vehicular channel measurements in a variety of important environments, and the observed channel characteristics (such as delay spreads and Doppler spreads) therein.We briefly discuss the available vehicular channel models and their respective merits and deficiencies. Finally, we discuss the implications for wireless system design with a strong focus on IEEE 802.11p. On the road towards a dependable vehicular network, room for improvements in coverage, reliability, scalability, and delay are highlighted which require evolutionary improvements in the IEEE 802.11p standard. Multiple antennas at the on-board units and road-side units are recommended to exploit spatial diversity for increased diversity and reliability. Evolutionary improvements in the PHY and MAC are required to yield dependable systems. Extensive references are provided.
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