| 1. |
- Abbas, Taimoor, et al.
(författare)
-
Measurements Based Channel Characterization for Vehicle-to-Vehicle Communications at Merging Lanes on Highway
- 2013
-
Ingår i: 2013 IEEE 5th International Symposium on Wireless Vehicular Communications, WiVeC 2013 - Proceedings. - : IEEE. - 9781467363396
-
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.
|
|
| 2. |
|
|
| 3. |
- Abbas, Taimoor, et al.
(författare)
-
Validation of a Non-Line-of-Sight Path-Loss Model for V2V Communications at Street Intersections
- 2013
-
Ingår i: 13th International Conference on ITS Telecommunications.
-
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.
|
|
| 4. |
- Bernadó, Laura, et al.
(författare)
-
Non-WSSUS Vehicular Channel Characterization at 5.2 GHz - Spectral Divergence and Time-Variant Coherence Parameters
- 2008
-
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.
|
|
| 5. |
- Chung, P. J., et al.
(författare)
-
Broadband ML estimation under model order uncertainty
- 2010
-
Ingår i: Signal Processing. - : Elsevier BV. - 0165-1684. ; 90:5, s. 1350-1356
-
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.
|
|
| 6. |
- Mecklenbräuker, Christoph F., et al.
(författare)
-
Eigenbeam transmission over line-of-sight MIMO channels for fixed microwave links
- 2011
-
Ingår i: Proceedings - ITG/IEEE Workshop on Smart Antennas (WSA). - 9781612840741
-
Konferensbidrag (refereegranskat)abstract
- We propose and analyze eigenbeam transmission over line-of-sight (LOS) multiple-input multiple-output (MIMO) channels with linear reception. In particular, we consider fixed point-to-point microwave links for which the singular value decomposition of the LOS MIMO channel matrix is analytically derived. We demonstrate that the Tx eigenbeams can be defined without channel state information at the transmitter and that the beams admit an insightful physical interpretation. We also evaluate the performance of a lattice-reduction aided linear receiver through numerical simulations.
|
|
| 7. |
- Mecklenbräuker, Christoph F., et al.
(författare)
-
Sequential Bayesian Sparse Signal Reconstruction Using Array Data
- 2013
-
Ingår i: IEEE Transactions on Signal Processing. - : Institute of Electrical and Electronics Engineers (IEEE). - 1941-0476 .- 1053-587X. ; 61:24, s. 6344-6354
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, the sequential reconstruction of source waveforms under a sparsity constraint is considered from a Bayesian perspective. Let the wave field, which is observed by a sensor array, be caused by a spatially-sparse set of sources. A spatially weighted Laplace-like prior is assumed for the source field and the corresponding weighted Least Absolute Shrinkage and Selection Operator (LASSO) cost function is derived. After the weighted LASSO solution has been calculated as the maximum a posteriori estimate at time step, the posterior distribution of the source amplitudes is analytically approximated. The weighting of the Laplace-like prior for time step is then fitted to the approximated posterior distribution. This results in a sequential update for the LASSO weights. Thus, a sequence of weighted LASSO problems is solved for estimating the temporal evolution of a sparse source field. The method is evaluated numerically using a uniform linear array in simulations and applied to data which were acquired from a towed horizontal array during the long range acoustic communications experiment.
|
|
| 8. |
- Molisch, Andreas, et al.
(författare)
-
A Survey on Vehicle-to-Vehicle Propagation Channels
- 2009
-
Ingår i: IEEE Communications Magazine. - 0163-6804. ; 16:6, s. 12-22
-
Tidskriftsartikel (refereegranskat)abstract
- Traffic telematics applications are currently under intense research and development for making transportation safer, more efficient, and more environmentally friendly. Reliable traffic telematics applications and services require vehicle-to-vehicle wireless communications that can provide robust connectivity, typically at data rates between 1 and 10 Mb/s. The development of such VTV communications systems and standards require, in turn, accurate models for the VTV propagation channel. A key characteristic of VTV channels is their temporal variability and inherent non-stationarity, which has major impact on data packet transmission reliability and latency. This article provides an overview of existing VTV channel measurement campaigns in a variety of important environments, and the channel characteristics (such as delay spreads and Doppler spreads) therein. We also describe the most commonly used channel modeling approaches for VTV channels: statistical as well as geometry-based channel models have been developed based on measurements and intuitive insights. Extensive references are provided.
|
|
| 9. |
- Nuckelt, Jörg, et al.
(författare)
-
Comparison of Ray Tracing and Channel-Sounder Measurements for Vehicular Communications
- 2013
-
Ingår i: [Host publication title missing].
-
Konferensbidrag (refereegranskat)abstract
- This paper presents the results of an accuracy study of a deterministic channel model for vehicle-to-vehicle (V2V) communications. Channel simulations obtained from the ray-tracing model developed by TU Braunschweig are compared to data gathered during the DRIVEWAY V2V channel measurement campaign at 5.6 GHz in the city of Lund in summer 2009. The analysis focuses on PDP and channel gains in an urban four-way intersection scenario. Despite of some implementation-based limitations of the ray-tracing model, a very good agreement between simulation and measurement results is achieved. Most relevant power contributions arising from multiple-bounce specular reflections as well as single-bounce non-specular reflections are captured by the deterministic model. We also discuss the question to what extent roadside obstacles like traffic signs, parked cars or lamp posts have to be considered when characterizing the V2V channel.
|
|
| 10. |
- Paier, Alexander, et al.
(författare)
-
Characterization of Vehicle-to-Vehicle Radio Channels from Measurements at 5.2GHz
- 2009
-
Ingår i: Wireless Personal Communications. - : Springer Science and Business Media LLC. - 1572-834X .- 0929-6212. ; 50:1, s. 19-32
-
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.
|
|
