2,115 research outputs found
A Measurement Based Shadow Fading Model for Vehicle-to-Vehicle Network Simulations
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.Comment: 10 pages, 12 figures, submitted to Hindawi International Journal of
Antennas and Propagatio
Evaluating the Impact of Transmission Power on Selecting Tall Vehicles as Best Next Communication Hop
The relatively low height of antennas on communicating vehicles in Vehicular Ad Hoc Networks (VANETs) makes one hop and as well multi-hop Vehicle-to-Vehicle (V2V) communication susceptible to obstruction by other vehicles on the road. When the transmitter or receiver (or both) is a Tall vehi- cle, (i.e., truck), the V2V communication suffer less from these obstructions. The transmission power control is an important feature in the design of (multi- hop) VANET communication algorithms. However, the benefits of choosing a Tall vehicle when transmission power is varied are not yet extensively re- searched. Therefore, the main contribution of this paper is to evaluate the im- pact of transmission power control on the improved V2V communication capa- bilities of tall vehicles. Based on simulations, it is shown that significant bene- fits are observed when a Tall vehicle is selected rather than a Short vehicle as a next V2V communication hop to relay packets. Moreover, the simulation exper- iments show that as the transmission power is increasing, the rate of Tall vehi- cles that are selected as best next V2V communication hop is significantly growing
Propagation mechanism modelling in the near region of circular tunnels
ArtĂculo sobre comunicaciones ferroviarias.
Abstract: Along with the increase in operating frequencies in advanced radio communication systems utilised inside tunnels, the location of the break point is further and further away from the transmitter. This means that the near region lengthens considerably and even occupies the whole propagation cell or the entire length of some short tunnels. To begin with, this study analyses the
propagation loss resulting from the free-space mechanism and the multi-mode waveguide mechanism in the near region of circular tunnels, respectively. Then, by conjunctive employing the propagation theory and the three-dimensional solid geometry, a general analytical model of the dividing point between two propagation mechanisms is presented for the first time. Moreover, the model is validated by a wide range of measurement campaigns in different tunnels at different frequencies. Finally, discussions on the
simplified formulae of the dividing point in some application situations are made. The results in this study can be helpful to grasp the essence of the propagation mechanism inside tunnels
Propagation Mechanism modeling in the Near-Region of Arbitrary Cross-Sectional Tunnels.
Along with the increase of the use of working frequencies in advanced radio communication systems, the near-region inside tunnels lengthens considerably and even occupies the whole propagation cell or the entire length of some short tunnels. This paper analytically models the propagation mechanisms and their dividing point in the near-region of arbitrary cross-sectional tunnels for the first time. To begin with, the propagation losses owing to the free space mechanism and the multimode waveguide mechanism are modeled, respectively. Then, by conjunctively employing the propagation theory and the three-dimensional solid geometry, the paper presents a general model for the dividing point between two propagation mechanisms. It is worthy to mention that this model can be applied in arbitrary cross-sectional tunnels. Furthermore, the general dividing point model is specified in rectangular, circular, and arched tunnels, respectively. Five groups of measurements are used to justify the model in different tunnels at different frequencies. Finally, in order to facilitate the use of the model, simplified analytical solutions for the dividing point in five specific application situations are derived. The results in this paper could help deepen the insight into the propagation mechanisms in tunnels
CMD: A Multi-Channel Coordination Scheme for Emergency Message Dissemination in IEEE 1609.4
In the IEEE 1609.4 legacy standard for multi-channel communications in
vehicular ad hoc networks(VANETs), the control channel (CCH) is dedicated to
broadcast safety messages while the service channels (SCH's) are dedicated to
transmit infotainment service content. However, the SCH can be used as an
alternative to transmit high priority safety messages in the event that they
are invoked during the service channel interval (SCHI). This implies that there
is a need to transmit safety messages across multiple available utilized
channels to ensure that all vehicles receive the safety message. Transmission
across multiple SCH's using the legacy IEEE 1609.4 requires multiple channel
switching and therefore introduces further end-to-end delays. Given that safety
messaging is a life critical application, it is important that optimal
end-to-end delay performance is derived in multi-channel VANET scenarios to
ensure reliable safety message dissemination. To tackle this challenge, three
primary contributions are in this article: first, a channel coordinator
selection approach based on the least average separation distance (LAD) to the
vehicles that expect to tune to other SCH's and operates during the control
channel interval (CCHI) is proposed. Second, a model to determine the optimal
time intervals in which CMD operates during the CCHI is proposed. Third, a
contention back-off mechanism for safety message transmission during the SCHI
is proposed. Computer simulations and mathematical analysis show that CMD
performs better than the legacy IEEE 1609.4 and a selected state-of-the-art
multi-channel message dissemination schemes in terms of end-to-end delay and
packet reception ratio.Comment: 15 pages, 10 figures, 7 table
Modeling and Simulation of Vehicular Networks: towards Realistic and Efficient Models
Vehicular Ad Hoc Networks (VANETs) have been envisioned with three types of applications in mind: safety, traffic management, and commercial applications. By using wireless interfaces to form an ad hoc network, vehicles will be able to inform other vehicles about traffic accidents, hazardous road conditions and traffic congestion. Commercial applications (e.g., data exchange, audio/video communication) are envisioned to provide incentive for faster adoption of the technology. To date, the majority of VANET research efforts have relied heavily on simulations, due to prohibitive costs of employing real world testbeds. Current VANET simulators have gone a long way from the early VANET simulation environments, which often assumed unrealistic models such as random waypoint mobility, circular transmission range, or interference-free environment Kotz et al. (2004). However, significant efforts still remain in order to enhance the realism of VANET simulators, at the same time providing a computationally inexpensive and efficient platform for performance evaluation of VANETs
Path Loss and Shadowing Modeling for Vehicle-to-Vehicle Communications in Terrestrial TV Band
Vehicle platooning is considered as one of the key use cases for
vehicle-to-vehicle (V2V) communications. However, its benefits can be realized
only with highly reliable wireless transmission. As the 5.9GHz frequency band
used for V2V suffers from high congestion, in this paper, we consider the use
of the terrestrial TV frequencies for intra-platoon communications. In order to
be able to evaluate the potential of the new bands fully, propagation models
for V2V communications at such frequencies are needed. Therefore, this paper
reports new V2V propagation measurements and their modeling results.
Particularly, we propose a Double Slope Double Shadowing model as the most
accurate one, based on a comparison of various models using the Bayesian
Information Criteria. We also investigate the space-time autocorrelation
properties of the shadowing, which turned out to be dependent on the speed of
vehicles. The proposed path loss and shadowing model differs from the ones
proposed for the 5.9GHz band. Mostly, in favor of the TV band, as shown by,
e.g., no statistically significant impact of a blocking car
On the Feasibility of Integrating mmWave and IEEE 802.11p for V2V Communications
Recently, the millimeter wave (mmWave) band has been investigated as a means
to support the foreseen extreme data rate demands of emerging automotive
applications, which go beyond the capabilities of existing technologies for
vehicular communications. However, this potential is hindered by the severe
isotropic path loss and the harsh propagation of high-frequency channels.
Moreover, mmWave signals are typically directional, to benefit from beamforming
gain, and require frequent realignment of the beams to maintain connectivity.
These limitations are particularly challenging when considering
vehicle-to-vehicle (V2V) transmissions, because of the highly mobile nature of
the vehicular scenarios, and pose new challenges for proper vehicular
communication design. In this paper, we conduct simulations to compare the
performance of IEEE 802.11p and the mmWave technology to support V2V
networking, aiming at providing insights on how both technologies can
complement each other to meet the requirements of future automotive services.
The results show that mmWave-based strategies support ultra-high transmission
speeds, and IEEE 802.11p systems have the ability to guarantee reliable and
robust communications.Comment: 7 pages, 5 figures, 2 tables, accepted to the IEEE Connected and
Automated Vehicles Symposium (CAVS
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