| 1. |
- Abbas, Taimoor, et al.
(author)
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A Measurement Based Shadow Fading Model for Vehicle-to-Vehicle Network Simulations
- 2015
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In: International Journal of Antennas and Propagation. - : Hindawi Publishing Corporation. - 1687-5869 .- 1687-5877.
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Journal article (peer-reviewed)abstract
- The vehicle-to-vehicle (V2V) propagation channel has significant implications on the design and performance of novel communication protocols for vehicular ad hoc networks (VANETs). Extensive research efforts have been made to develop V2V channel models to be implemented in advanced VANET system simulators for performance evaluation. The impact of shadowing caused by other vehicles has, however, largely been neglected in most of the models, as well as in the system simulations. In this paper we present a shadow fading model targeting system simulations based on real measurements performed in urban and highway scenarios. The measurement data is separated into three categories, line-of-sight (LOS), obstructed line-of-sight (OLOS) by vehicles, and non-line-of-sight due to buildings, with the help of video information recorded during the measurements. It is observed that vehicles obstructing the LOS induce an additional average attenuation of about 10 dB in the received signal power. An approach to incorporate the LOS/OLOS model into existing VANET simulators is also provided. Finally, system level VANET simulation results are presented, showing the difference between the LOS/OLOS model and a channel model based on Nakagami-m fading.
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| 2. |
- Abbas, Taimoor, et al.
(author)
-
Directional Analysis of Vehicle-to-Vehicle Propagation Channels
- 2011
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In: IEEE Vehicular Technology Conference.
-
Conference paper (peer-reviewed)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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| 3. |
- Abbas, Taimoor, et al.
(author)
-
Directional Analysis of Vehicle-to-Vehicle Propagation in Different Traffic Environments
- 2010
-
In: [Host publication title missing].
-
Conference paper (other academic/artistic)abstract
- This paper presents a double directional analysis of vehicle-to-vehicle channel measurements conducted in two different traffic environments. Using a high-resolution algorithm, we derive channel parameters like angle-of- arrival, angle-of-departure, propagation delay and Doppler’s spread and identify underlying propagation mechanisms by combining these estimates with maps of the measurement sites. The results show that single-bounce interaction with static objects is the dominating effect in the absence of line-of-sight, and that the contribution from other vehicles is small. We also find that in the absence of line-of-sight the direction spread at both sides of link is large which indicates possible diversity gain using multi-antenna arrangements.
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| 4. |
- Abbas, Taimoor, et al.
(author)
-
Initial Investigation to study the Effect of Antenna Placement in Vehicle-to-Vehicle Communications
- 2011
-
In: [Host publication title missing].
-
Conference paper (other academic/artistic)abstract
- In this paper we present an analysis of the effects of antenna placement on the radio channel properties for Vehicle-to-Vehicle communications based on measurements performed in three different propagation scenarios; highway, urban and rural. Four omni-directional antennas were mounted at four different positions: roof, bumper, left-side mirror and inside windscreen of two standard station wagons (Volvo V70). The channel transfer functions were measured for all antenna combinations with a wideband MIMO channel sounder. The results from this initial analysis show that the antenna mounted on the left-side mirror outperforms other antennas when vehicles are moving in convoy and are aligned well to each other. Whereas, if the TX and RX are moving in opposite direction, i.e., towards each other, bumper antenna shows good performance as long as LOS is available in between the antenna elements. In total some kind of diversity arrangement with complementary antennas seems to be the preferred solution, to decrease the effect of shadowing.
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| 5. |
- Abbas, Taimoor, et al.
(author)
-
Measurement-Based Analysis: The Effect of Complementary Antennas and Diversity on Vehicle-to-Vehicle Communication
- 2013
-
In: IEEE Antennas and Wireless Propagation Letters. - 1548-5757. ; 12:1, s. 309-312
-
Journal article (peer-reviewed)abstract
- In vehicle-to-vehicle (V2V) communication systems the antennas are prone to shadowing and the antenna gain is dissimilar even for same antenna elements if mounted at different positions on the car. This paper investigates the impact of antenna placement based on channel measurements performed with four omni-directional antennas mounted on the roof, bumper, windscreen and left-side mirror of the transmitter and receiver cars. Results suggest to use antennas with complementary characteristics, e.g., antennas on each side, mounted on the roof and bumper, to exploit diversity and decrease the effect of shadowing.
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| 6. |
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| 7. |
- Almers, Peter, et al.
(author)
-
Antenna subset selection in measured indoor channels
- 2007
-
In: IET Microwaves, Antennas & Propagation. - : Institution of Engineering and Technology (IET). - 1751-8725. ; 1, s. 1092-1100
-
Journal article (peer-reviewed)abstract
- Antenna subset selection can greatly reduce the implementation complexity of multiple input multiple output (MIMO) systems while retaining most of their benefits. This paper investigates the diversity gain and capacity of such systems in wireless personal area networks. Considered scenarios include both the communication between access point to a laptop, and between two handheld devices. We analyse the performance of different antenna selection algorithms and signal combining methods in measured dual-polarised narrowband and wideband propagation channels. We find that line-of-sight and non-line-of-sight situations have fairly similar behaviour. Different polarisations result in similar signal-to-noise ratio gains when the multiple antennas are used for diversity, but result in noticeably different capacities in spatial-multiplexing systems. We also find that radiofrequency (RF) preprocessing of the signals is less effective for handheld handsets with non-uniform antenna arrangements than for uniform linear arrays. For communications between handheld devices, simple selection (of one out of four antennas) shows extremely high performance gains compared to no-selection. Finally, we compare bulk selection (same antenna subset is used for all frequency sub-channels) to per-tone selection (different antenna subsets can be used for each frequency sub-channel) for wideband channels. Bulk selection together with RF preprocessing performs almost as well as per-tone selection for some scenarios.
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| 8. |
- Almers, Peter, et al.
(author)
-
Exercises
- 2005
-
In: Wireless Communications. - 9780470848883 - 047084888X - 0470848871 ; , s. 561-593
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Book chapter (other academic/artistic)
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| 9. |
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| 10. |
- Bernadó, Laura, et al.
(author)
-
Complexity reduction for vehicular channel estimation using the filter-divergence measure
- 2011
-
In: 2010 Conference Record of the Forty Fourth Asilomar Conference on Signals, Systems and Computers. - 9781424497225 - 9781424497218
-
Conference paper (peer-reviewed)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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| 11. |
- Bernadó, Laura, et al.
(author)
-
In-tunnel vehicular radio channel characterization
- 2011
-
In: [Host publication title missing]. - 1550-2252. - 9781424483327
-
Conference paper (peer-reviewed)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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| 12. |
- Bernadó, Laura, et al.
(author)
-
Multi-dimensional K-factor analysis for V2V radio channels in open sub-urban street crossings
- 2010
-
In: [Host publication title missing]. - 9781424480173 ; , s. 58-63
-
Conference paper (peer-reviewed)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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| 13. |
- Bernadó, Laura, et al.
(author)
-
Non-WSSUS Vehicular Channel Characterization at 5.2 GHz - Spectral Divergence and Time-Variant Coherence Parameters
- 2008
-
Conference paper (peer-reviewed)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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| 14. |
- Bernadó, Laura, et al.
(author)
-
Parametrization of the local scattering function estimator for vehicular-to-vehicular channels
- 2009
-
In: [Host publication title missing]. ; , s. 1-5
-
Conference paper (peer-reviewed)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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| 15. |
- Johansson, Anders J, et al.
(author)
-
MIMO channel measurements for personal area networks
- 2005
-
In: [Host publication title missing]. - 1550-2252. - 0780388879 ; 61:1, s. 171-176
-
Conference paper (peer-reviewed)abstract
- This paper analyzes MIMO propagation channels for personal area networks. Such channels show important differences to propagation channels in wide-area networks, due to the different environments in which the systems are operated, as well as due to different mobility models, ranges, and presence of humans in the environment, and the impact of the antenna arrangement. We present results from a recent measurement campaign for this type of channel. We first analyze the requirements for measurement setups, especially in terms of different positions and orientations of the antenna arrays, to obtain meaningful results. We then analyze the measured data and present results for path loss, power delay profiles, spatial correlation and temporal correlation.
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| 16. |
- Khan, Muhammad Gufran, et al.
(author)
-
Measurements and Analysis of UWB Channels in Industrial Environments
- 2005
-
Conference paper (peer-reviewed)abstract
- Communication in industrial environments is an important scenario for ultra wideband (UWB) systems. The characteristics of this environment differ considerably from office environments, where most of the channel measurements reported in the literature are performed. In this paper, we present the results and analysis of UWB channel measurements in an industrial environment. We investigate both peer-to-peer non-line-of-sight (P-P NLOS) and base station NLOS (BS NLOS) scenarios. The measurements are performed in the frequency range 3.1 to 8 GHz, at distances 2-16 m, using a vector network analyzer in conjunction with virtual antenna arrays. From these measurements, we extract channel model parameters such as power delay profiles, pathloss exponents, rms delay spread and the percentage of energy captured by RAKE receivers with a finite number of fingers. In addition, Saleh- Valenzuela parameters such as ray and cluster power decay constants and distribution of cluster interarrival times are extracted.
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| 17. |
- Kåredal, Johan, et al.
(author)
-
A geometry-based stochastic MIMO model for vehicle-to-vehicle communications
- 2009
-
In: IEEE Transactions on Wireless Communications. - 1536-1276. ; 8:7, s. 3646-3657
-
Journal article (peer-reviewed)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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| 18. |
- Kåredal, Johan, et al.
(author)
-
A measurement-based fading model for wireless personal area networks
- 2008
-
In: IEEE Transactions on Wireless Communications. - 1536-1276. ; 7:11, s. 4575-4585
-
Journal article (peer-reviewed)abstract
- Personal area networks (PANs) are wireless communications systems with high data rates but small coverage area. PAN propagation channels differ from the well-explored propagation channels of wide-area networks due to several reasons: (i) the distances are typically very small, (ii) the antenna arrangements can be quite different, and (iii) the influence from human presence in the environment is different. The current paper presents results of a channel measurement campaign, where measurements are conducted over distances of 1-10 m using several multi-antenna devices, combined to create different PAN scenarios. For each measured Tx-Rx separation, channel realizations are obtained by small spatial movements of the antenna devices, and by rotating the persons holding the devices. From the results, we draw two main conclusions: (i) The small-scale amplitude statistics, analyzed as the variations over a small sampling area and frequency subchannels, cannot be described in a satisfactory way using only the Rayleigh or Ricean distributions, rather a mixed distribution, the generalized gamma distribution, is more suitable; (ii) it is advantageous to distinguish between two types of large-scale fading: body shadowing (due to the orientation of the person holding the device) and shadowing due to surrounding objects (lateral movement). We also define and parameterize a complete statistical model for all fading.
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| 19. |
- Kåredal, Johan, et al.
(author)
-
A measurement-based statistical model for industrial ultra-wideband channels
- 2007
-
In: IEEE Transactions on Wireless Communications. - 1536-1276. ; 6:8, s. 3028-3037
-
Journal article (peer-reviewed)abstract
- The results of three ultra-wideband (UWB) measurement campaigns conducted in two different industrial environments are presented. A frequency range of 3.1 - 10.6 or 3.1 - 5.5 GHz was measured using a vector network analyzer and a virtual array technique enabling the investigation of smallscale statistics. The results show that the energy arrives in clusters, and that the abundance of metallic scatterers present in the factory hall causes dense multipath scattering. The latter produces a small-scale fading that is mostly Rayleigh distributed; the only exception being the delay bin containing the line-of-sight component. The power delay profile can be modeled by a generalized Saleh-Valenzuela model, where different clusters have different ray power decay constants. It is also noted that the number of multipath components required to capture a majority of the energy is quite large. More than a hundred components can be needed to capture 50% of the total available energy.
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| 20. |
- Kåredal, Johan, et al.
(author)
-
A MIMO channel model for wireless personal area networks
- 2010
-
In: IEEE Transactions on Wireless Communications. - 1536-1276. ; 9:1, s. 245-255
-
Journal article (peer-reviewed)abstract
- Recent years have seen an increasing attention given to wireless Personal Area Networks (PANs), which are typically networks with small transmitter-receiver (TX-RX) separation. The desire for high data rates has led to an interest in deploying multiple-input multiple-output (MIMO) transmission for such systems, but up until this date there exists, to the authors’ best knowledge, no MIMO channel model that enables performance simulations of such systems. An important characteristic of PANs, and at the same time an important difference to regular wireless local area networks, is the interaction between the antenna array and the user. In conjunction with the irregular antenna arrangements that are typical for PAN devices, this has been shown to lead to flexible channel statistics. In this paper we present a MIMO model for PANs that incorporates these effects by prescribing different small-scale statistics and path gains to different antenna elements. The proposed model can thus be seen as a generalization of the classical MIMO model for LOS situations. The model is compared to several sets of measurement data and found to provide a very good description of the essential PAN channel characteristics. We also provide a detailed parameterization of the model for a particular PAN scenario.
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| 21. |
- Kåredal, Johan, et al.
(author)
-
Characterization of a computer board-to-board ultra-wideband channel
- 2007
-
In: IEEE Communications Letters. - 1089-7798. ; 11:6, s. 468-470
-
Journal article (peer-reviewed)abstract
- In this paper we present the results of an extensive ultra-wideband (UWB) measurement campaign performed inside the chassis of two desktop computers. The purpose of the campaign is to analyze the possibility of board-to-board communications, replacing cable connections. Measurements of the propagation channel are performed over a frequency range of 3.1 - 10.6 GHz using a vector network analyzer and antennas small enough to enable integration on a circuit board. The results show that the propagation environment is very uniform, with small variations in the path gain between different positions within a computer. We also performed interference measurements, showing that the interference is restricted to certain subbands.
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| 22. |
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| 23. |
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| 24. |
- Kåredal, Johan, et al.
(author)
-
Measurement-based modeling of vehicle-to-vehicle MIMO channels
- 2009
-
In: IEEE International Conference on Communications. ; , s. 3470-3475
-
Conference paper (peer-reviewed)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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| 25. |
- Kåredal, Johan
(author)
-
Measurement-Based Modeling of Wireless Propagation Channels - MIMO and UWB
- 2009
-
Doctoral thesis (other academic/artistic)abstract
- Future wireless systems envision higher speeds and more reliable services but at the same time face challenges in terms of bandwidth being a limited resource. Two promising techniques that can provide an increased throughput without requiring additional bandwidth allocation are multiple-input multiple-output (MIMO) systems and ultra-wideband (UWB) systems. However, the performance of such systems is highly dependent on the properties of the wireless propagation channel, and an understanding of the channel is therefore crucial in the design of future wireless systems. Examples of such systems covered by this thesis are wireless personal area networks (papers I and II), vehicle-to-vehicle communications (paper III), board-to-board communications inside computers (paper IV) and sensor networks for industrial applications (paper V). Typically, channel models are used to evaluate the performance of different transmission and reception schemes. Channel modeling is the focus of this thesis, which contains a collection of papers that analyze and model the behavior of MIMO and UWB propagation channels. Paper I investigates the fading characteristics of wireless personal area networks (PANs), networks that typically involve human influence close to the antenna terminals. Based on extensive channel measurements using irregular antenna arrays, typical properties of PAN propagation channels are discussed and a model for the complete fading of a single link is presented. Paper II extends the model from paper I to a complete MIMO channel model. The paper combines the classical LOS model for MIMO with results from paper I by prescribing different fading statistics and mean power at the different antenna elements. The model is verified against measurement data and the paper also provides a parameterization for an example of a PAN scenario. Paper III presents a geometry-based stochastic MIMO model for vehicle-to-vehicle communications. The most important propagation effects are discussed based on the results from extensive channel measurements, and the modeling approach is motivated by the non-stationary behavior of such channels. The model distinguishes between diffuse contributions and those stemming from interaction with significant objects in the propagation channel, and the observed fading characteristics of the latter are stochastically accounted for in the model. Paper IV gives a characterization of UWB propagation channels inside desktop computer chassis. By studying measurement results from two different computers, it is concluded that the propagation channel only shows minor differences for different computers and positions within the chassis. It is also found out that the interference power produced by the computer is limited to certain subbands, suggesting that multiband UWB systems are more suitable for this type of applications. Paper V describes a UWB channel model based on the first UWB measurements in an industrial environment. Analyzing results from two different factory halls, it is concluded that energy arrives at the receiver in clusters, which motivates the use of a classical multi-cluster model to describe the channel impulse response. Parts of the results from this paper were also used as input to the channel model in the IEEE 802.15.4a UWB standardization work. In summary, the work within this thesis leads to an increased understanding of the behavior of wireless propagation channels for MIMO and UWB systems. By providing three detailed simulation models, two for MIMO and one for UWB, it can thus contribute to a more efficient design of the wireless communications systems of tomorrow.
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| 26. |
- Kåredal, Johan, et al.
(author)
-
Path loss modeling for vehicle-to-vehicle communications
- 2011
-
In: IEEE Transactions on Vehicular Technology. - 1939-9359. ; 60:1, s. 323-328
-
Journal article (peer-reviewed)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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| 27. |
- Kåredal, Johan, et al.
(author)
-
Radio channel measurements at street intersections for vehicle-to-vehicle applications
- 2010
-
In: IEEE 71st Vehicular Technology Conference (VTC 2010-Spring), 2010. - 1550-2252. ; , s. 1-5
-
Conference paper (peer-reviewed)abstract
- This paper presents the results of an empirical study of wireless propagation channels for vehicle-to-vehicle communications in street intersections, a scenario especially important for collision avoidance applications. The results are derived from a channel measurement campaign performed at 5.6 GHz in four different types of urban intersections. We present results on typical power delay profiles, pathloss and delay spreads and discuss important propagation mechanisms. By comparing the results of the different intersections, we find that absence of line-of-sight is problematic for system coverage, especially when there are few other significant scattering objects in and around the intersection. Roadside buildings can create important propagation paths that account for a considerable part of the total received power.
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| 28. |
- Kåredal, Johan, et al.
(author)
-
Shadowing effects in MIMO channels for personal area networks
- 2006
-
In: [Host publication title missing]. - 1550-2252. ; , s. 173-177
-
Conference paper (peer-reviewed)abstract
- In this paper we analyze the effects of body shadowing in multiple-input-multiple-output (MIMO) channels used for personal area networks (PANs). We give physical reasoning to why PANs may experience two different types of shadowing, and to support our argument, we present results from a measurement campaign for three different PAN channels with human influence. The campaign is performed using different types of multi-element antenna devices; an access point, a body-worn device and two hand-held devices, conducted over a series of distances between 1-10 m. For each distance, a number of channel realizations are obtained by moving the antenna devices over a small area, and by rotating the persons holding the devices. The results show that it is suitable to distinguish between body shadowing (due to the rotation of the person holding the device) and shadowing due to surrounding objects (lateral movement). We also present a statistical model where the two types of shadowing are described as separate log-normal processes. Furthermore, we find that body shadowing has a big influence on the capacity of the investigated PAN channels. © 2006 IEEE.
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| 29. |
- Kåredal, Johan, et al.
(author)
-
Statistical analysis of the UWB channel in an industrial environment
- 2004
-
In: [Host publication title missing]. - 0780385217 ; , s. 81-85
-
Conference paper (peer-reviewed)abstract
- In this paper, we present a statistical model for the ultra-wideband (UWB) channel in an industrial environment. Based on a set of measurements in a factory hall, we find that the abundance of metallic scatterers causes dense multipath scattering. This can be seen to produce mostly a Rayleigh distributed small-scale fading signal, with only a few paths exhibiting Nakagami distributions. For the power delay profile, we suggest a generalization of the Saleh-Valenzuela model where clusters with different excess delays have different ray power decay constants; the decay constants follow a linear dependence on the delay. This model provides an excellent fit to the measured data. We also note that for non-line-of-sight scenarios at larger distances, several hundred multipath components need to be collected to capture 50% of the available energy
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| 30. |
- Kåredal, Johan, et al.
(author)
-
UWB channel measurements in an industrial environment
- 2004
-
In: [Host publication title missing]. - 0780387945 ; , s. 3511-3516
-
Conference paper (peer-reviewed)abstract
- In this paper, we present the (to our knowledge) first measurement results for ultra-wideband channels in industrial environments, i.e., a factory hall. The measurements are done with virtual arrays, which allows analysis of the small-scale fading statistics, as well as a directional analysis. We find that there is dense multipath scattering due to the abundance of metallic scatterers in the considered environment. Multiple scatterer clusters can be identified both in the delay and the angular domain. Typical rms delay spreads lie between 30 ns for LOS scenarios and 40 ns for NLOS scenarios. For non-LOS scenarios at large distances, the maximum of the power delay profile is observed some 40 ns after the arrival of the first multipath components. We also draw conclusions about the behavior of typical UWB system designs in the measured channels
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| 31. |
- Mecklenbräuker, Christoph, et al.
(author)
-
Vehicular channel characterization and its implications for wireless system design and performance
- 2011
-
In: Proceedings of the IEEE. - 0018-9219. ; 99:7, s. 1189-1212
-
Journal article (peer-reviewed)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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| 32. |
- Molisch, Andreas, et al.
(author)
-
A comprehensive model for ultrawideband propagation channels
- 2005
-
In: [Host publication title missing]. - 0780394143 ; 6, s. 3648-3653
-
Conference paper (peer-reviewed)abstract
- This paper describes a comprehensive statistical model for UWB propagation channels that is valid for a frequency range from 3-10 GHz. It is based on measurements and simulations in the following environments: residential indoor, office indoor, built-up outdoor, industrial indoor, farm environments, and body area networks. The model is independent of the used antennas. It includes the frequency dependence of the pathloss, as well as several generalizations of the Saleh-Valenzuela model, like mixed Poisson times of arrival and delay dependent cluster decay constants. The model can thus be used for realistic performance assessment of UWB systems. It was accepted by the IEEE 802.15.4a working group (WG) as standard model for evaluation of UWB system proposals.
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| 33. |
- Molisch, Andreas, et al.
(author)
-
A comprehensive standardized model for ultrawideband propagation channels
- 2006
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In: IEEE Transactions on Antennas and Propagation. - 0018-926X. ; 54:11, s. 3151-3166
-
Journal article (peer-reviewed)abstract
- A comprehensive statistical model is described for ultrawideband (UWB) propagation channels that is valid for a frequency range from 3-10 GHz. It is based on measurements and simulations in the following environments: residential indoor, office indoor, builtup outdoor, industrial indoor, farm environments, and body area networks. The model is independent of the used antennas. It includes the frequency dependence of the path gain as well as several generalizations of the Saleh-Valenzuela model, like mixed Poisson times of arrival and delay-dependent cluster decay constants. A separate model is specified for the frequency range below 1 GHz. The model can thus be used for realistic performance assessment of UWB systems. It was accepted by the IEEE 802.15.4a Task Group as standard model for evaluation of UWB system proposals. This paper also presents a critical assessment of the applicability of the model and possible generalizations and improvements.
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| 34. |
- Molisch, Andreas, et al.
(author)
-
A Survey on Vehicle-to-Vehicle Propagation Channels
- 2009
-
In: IEEE Communications Magazine. - 0163-6804. ; 16:6, s. 12-22
-
Journal article (peer-reviewed)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.
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| 35. |
- Molisch, Andreas, et al.
(author)
-
Propagation aspects of vehicle-to-vehicle communications - an overview
- 2009
-
In: [Host publication title missing]. ; , s. 179-182
-
Conference paper (peer-reviewed)abstract
- Vehicle-to-vehicle (VTV) wireless communications have many envisioned applications in traffic safety, congestion avoidance, etc., but the development of suitable communications systems and standards requires accurate models for the VTV propagation channel. This paper provides an overview of existing VTV channel measurement campaigns, describing the most important environments, and the delay spread and Doppler spreads obtained in them. Statistical as well as geometry-based channel models have been developed based on measurements and intuitive insights. A key characteristic of VTV channels is the nonstationarity of their statistics, which has major impact on the system performance. Extensive references are provided.
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| 36. |
- Paier, Alexander, et al.
(author)
-
Car-to-car radio channel measurements at 5 GHz: Pathloss, power-delay profile, and delay-Doppler spectrum
- 2007
-
In: [Host publication title missing]. - 9781424409792 ; , s. 224-228
-
Conference paper (peer-reviewed)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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| 37. |
- Paier, Alexander, et al.
(author)
-
Characterization of Vehicle-to-Vehicle Radio Channels from Measurements at 5.2GHz
- 2009
-
In: Wireless Personal Communications. - : Springer Science and Business Media LLC. - 1572-834X .- 0929-6212. ; 50:1, s. 19-32
-
Journal article (peer-reviewed)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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| 38. |
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| 39. |
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| 40. |
- Paier, Alexander, et al.
(author)
-
First results from car-to-car and car-to-infrastructure radio channel measurements at 5.2GHZ
- 2007
-
In: [Host publication title missing]. - 9781424411443 ; , s. 1-5
-
Conference paper (peer-reviewed)abstract
- Car-to-car and car-to-infrastructure (henceforth called C2X) communications are constantly gaining importance for road-safety and other applications. In order to design efficient C2X systems, an understanding of realistic C2X propagation channels is required, but currently, only few measurements have been published. This paper presents a description of an extensive measurement campaign recently conducted in an urban scenario, a rural scenario, and on a highway. We focused on 4 ÿ 4 multiple-input multiple-output (MIMO) measurements at a center frequency of 5.2 GHz with high Doppler resolution. As first results from evaluating the measurement data we present the power-delay profile and the delay-Doppler spectrum from a selected, especially interesting measurement run from an urban measurement route. We observe dispersed Doppler contributions between zero and the Doppler shift corresponding to the relative speed of the cars, and very concentrated (in the Doppler domain), contributions from double reflections. Surprisingly, we also found paths with larger delays and zero Doppler shifts.
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| 41. |
- Paier, Alexander, et al.
(author)
-
Non-WSSUS vehicular channel characterization in highway and urban scenarios at 5.2 GHz using the local scattering function
- 2008
-
In: ; , s. 9-15
-
Conference paper (peer-reviewed)abstract
- The fading process in high speed vehicular traffic telematic applications at 5 GHz is expected to fulfill the wide-sense stationarity uncorrelated scattering (WSSUS) assumption for very short time-intervals only. In order to test this assumption we apply the concept of a local time– and frequency–variant scattering function, which we estimate from measurements of vehicle-to-vehicle wave propagation channels by means of a multi-window spectrogram. The obtained temporal sequence of local scattering functions (LSF) is used to calculate a collinearity measure. We define the stationarity time as the support of the region where the collinearity exceeds a certain threshold. The stationarity time is the maximum time duration over which the WSSUS assumption is valid. Measurements from an highway with vehicles driving in opposite directions show stationarity times as small as 23 ms whereas vehicles driving in the same direction show stationarity times of 1479 ms.
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| 42. |
- Paier, Alexander, et al.
(author)
-
Overview of vehicle-to-vehicle radio channel measurements for collision avoidance applications
- 2010
-
In: [Host publication title missing]. ; , s. 1-5
-
Conference paper (peer-reviewed)abstract
- In this paper we present an overview of a vehicle-to-vehicle radio channel measurement campaign at 5.6GHz. The selected measurement scenarios are based on important safety-related applications. We explain why these scenarios are interesting from the aspect of radio propagation. Further we describe the power-delay profile and the Doppler spectral density of two situations especially suitable for collision avoidance applications: A traffic congestion situation where one car is overtaking another one, and a general line-of-sight obstruction between the transmitter and the receiver car. The evaluations show that in these situations the radio channel is highly influenced by the rich scattering environment. Most important scatterers are traffic signs, trucks, and bridges, whereas other cars do not significantly contribute to the multipath propagation.
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| 43. |
- Paier, Alexander, et al.
(author)
-
Spatial diversity and spatial correlation evaluation of measured vehicle-to-vehicle radio channels at 5.2 GHz
- 2009
-
In: [Host publication title missing]. - 9781424436774 ; , s. 326-330
-
Conference paper (peer-reviewed)abstract
- In this contribution, we estimate the spatial diversity order and spatial correlations from channel sounder measurements of doubly-selective vehicle-to-vehicle MIMO radio channels in the 5.2 GHz band. Ivrlac and Nossek [1] have defined a diversity measure for MIMO Rayleigh fading channels which is based on the spatial correlations of the channel. Subsequently, Nabar et al. [2] have shown the existence of an SNR-dependent critical rate for Ricean fading MIMO channels below which reliable transmission with zero outage is achievable. Here, we evaluate and discuss the temporal evolution of the spatial diversity order of doubly-selective vehicle-to-vehicle MIMO radio channels from real-world measurements by extending [I] and [2] to time-variant channels.
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| 44. |
- Santos, Telmo, et al.
(author)
-
Modeling the ultra-wideband outdoor channel - measurements and parameter extraction method
- 2010
-
In: IEEE Transactions on Wireless Communications. - 1536-1276. ; 9:1, s. 282-290
-
Journal article (peer-reviewed)abstract
- This paper presents results from one of the few existing outdoor measurement campaigns for UWB. We specifically focus on scenarios applicable for "infostations," where large amounts of data can be downloaded to a user within a limited amount of time. We describe the measurement setup, and present a novel high-resolution algorithm that allows the extraction of the scatterer's positions. Measurement data is extracted using eight meter uniform linear virtual array where incoming front waves are spherical, and thus allowing for high-precision location of the scatterers. Insight is given on how these components can be tracked in the impulse response for a spatially varying terminal. We then cluster the detected components, and investigate how the angular power variations of a given scatterer are correlated with the power variations of the other scatterers belonging to the same cluster. This results in the definition of the clusters' angular radiation pattern. Further sample measurements show how obstacles obstruct the line-of-sight component; a phenomenon that we describe mathematically by "shadowing regions," and compare these measurements with the theoretical results predicted by diffraction theory.
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| 45. |
- Santos, Telmo, et al.
(author)
-
Scatterer detection by successive cancellation for UWB - method and experimental verification
- 2008
-
In: [Host publication title missing]. - 1550-2252. - 9781424416448 ; , s. 445-449
-
Conference paper (peer-reviewed)abstract
- We present a new high delay resolution method to detect ultra-wideband (UWB) scatterers when using frequency domain measurements. Our approach makes use of the impulse response envelope amplitudes and delays measured over a distance that is larger than the region of stationarity, and detects the 2D coordinates of the channel scatterers, assuming that only single-scattering (single-interaction) processes occur. The identification methodology is based on multiple application of interference cancellation: at every step, we detect the strongest scatterer from an array of measurements, save its information, cancel it from the channel and search for the next strongest scatterer. To precisely define the strength of each scatterer, we present a method to define its birth and death locations along the measurement array. Finally, we verify the method by applying it to measurement results in an outdoor environment; the scatterer locations identified from the measurements show excellent agreement with the physically present objects like walls and columns.
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| 46. |
- Sjöberg, Katrin, et al.
(author)
-
Measuring and using the RSSI of IEEE 802.11p
- 2010
-
In: 17th World Congress on Intelligent Transport Systems, ITS 2010, Busan, South Korea, 25-29 October 2010.
-
Conference paper (peer-reviewed)abstract
- The scalability of intelligent transport systems (ITS) applications is difficult to test in a field operational test (FOT) due to the high number of ITS equipped vehicles required. Therefore, computer simulations for evaluating different wireless communication technologies for ITS different applications can serve as a complement. In this paper we present results from lab measurements conducted on the CVIS hardware platform equipped with the upcoming standard IEEE 802.11p. We have measured the packet error rate versus the signal-to-noise ratio (SNR) for different packet lengths. This lab measurement is the first step towards an outdoor measurement campaign which also considers interference. The outdoor measurements will then be fed into a computer simulator together with a realistic channel model for evaluating the scalability of VANETs in a highway scenario.
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| 47. |
- Thiel, Andreas, et al.
(author)
-
In-situ vehicular antenna integration and design aspects for vehicle-to-vehicle communications
- 2010
-
In: [Host publication title missing]. - 9781424464319 ; , s. 1-5
-
Conference paper (peer-reviewed)abstract
- Vehicle-to-vehicle (V2V) communications aim to enhance driver safety and traffic efficiency by using the recently designated frequency bands in the 5.9 GHz range in Europe. Due to the time-frequency selective fading behavior of the vehicular communication channel, multi-antenna techniques can provide enhanced link conditions by means of diversity processing. This paper highlights the integration of a four-element (N =4) linear array antenna into the roof-top compartment of a vehicle to conduct Multiple-Input Multiple-Output (MIMO) high-resolution mobile-to-mobile channel measurements.
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| 48. |
- Wyne, Shurjeel, et al.
(author)
-
A cluster-based analysis of outdoor-to-indoor office MIMO measurements at 5.2 GHz
- 2006
-
In: [Host publication title missing]. - 1550-2252. ; , s. 22-26
-
Conference paper (peer-reviewed)abstract
- In this paper, we present a cluster based analysis of an outdoor-to-indoor Multiple-Input Multiple-Output (MIMO) measurement campaign, and extract model parameters for the COST273 channel model. The measurements were performed at 5.2 GHz for 159 measurement locations in an office building. Multipath component (MPC) parameters have been extracted for these positions using a high-resolution algorithm. We analyze the clustering of MPCs, i.e., grouping together of MPCs with similar DOAs, DODs, and delays. We compare cluster identification by visual inspection to automatic identification by the recently proposed algorithm of Czink et al. In the paper we include results on the intercluster properties such as the distribution of the number of clusters and the cluster powers, as well as intracluster properties such as the angle and delay spreads within the clusters. In particular, we extract parameters for the COST 273 channel model, a standardized generic model for MIMO propagation channels. © 2006 IEEE.
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| 49. |
- Wyne, Shurjeel, et al.
(author)
-
Outdoor-to-indoor office MIMO measurements, and analysis at 5.2 GHz
- 2008
-
In: IEEE Transactions on Vehicular Technology. - 0018-9545 .- 1939-9359. ; 57:3, s. 1374-1386
-
Journal article (peer-reviewed)abstract
- The outdoor-to-indoor wireless propagation channel is of interest for cellular and wireless local area network applications. This paper presents the measurement results and analysis based on our multiple-input-multiple-output (MIMO) measurement campaign, which is one of the first to characterize the outdoor-to-indoor channel. The measurements were performed at 5.2 GHz, the receiver was placed indoors at 53 different locations in an office building, and the transmitter was placed at three "base station" positions on a nearby rooftop. We report on the root-mean-square (RMS) angular spread, building penetration, and other statistical parameters that characterize the channel. Our analysis is focused on three MIMO channel assumptions often used in stochastic models. 1) It is commonly assumed that the channel matrix can be represented as a sum of a line-of-sight (LOS) contribution and a zero-mean complex Gaussian distribution. Our investigation shows that this model does not adequately represent our measurement data. 2) It is often assumed that the Rician K-factor is equal to the power ratio of the LOS component and the other multipath components (MPCs). We show that this is not the case, and we highlight the difference between the Rician K-factor often associated with LOS channels and a similar power ratio for the estimated LOS MPC. 3) A widespread assumption is that the full correlation matrix of the channel can be decomposed into a Kronecker product of the correlation matrices at the transmit and receive array. Our investigations show that the direction-of-arrival (DOA) spectrum noticeably depends on the direction-of-departure (DOD), therefore, the Kronecker model is not applicable, and models with less-restrictive assumptions on the channel, e.g., the Weichselberger model or the full correlation model, should be used.
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| 50. |
- Wyne, Shurjeel, et al.
(author)
-
Outdoor to indoor office MIMO measurements at 5.2 GHz
- 2004
-
In: IEEE Vehicular Technology Conference. - 1550-2252. - 0780385217 ; 1, s. 101-105
-
Conference paper (peer-reviewed)abstract
- This paper presents the results of one of the first measurement campaigns for the double-directional characterization of outdoor to indoor wireless propagation channels. Such channels play a vital role for cellular systems with multiple antenna elements at transmitter and receiver, i.e. multiple-input multiple-output (MIMO) systems. Measurements were performed at 5.2 GHz between 53 different receiver locations in an office building, and three "base station" positions on a nearby rooftop. In the paper we present results for angular-delay profiles, RMS angular spread, and other statistical parameters characterizing delay and angular dispersion.
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