| 1. |
- Hofer, Markus, et al.
(författare)
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Real-Time Geometry-Based Wireless Channel Emulation
- 2018
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Ingår i: IEEE Transactions on Vehicular Technology. - 0018-9545.
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Tidskriftsartikel (refereegranskat)abstract
- Connected autonomous vehicles and industry 4.0 productions scenarios require ultra-reliable low-latency communication links. The varying positions of transmitter, reflecting objects and receiver cause a non-stationary time- and frequency-selective fading process. In this paper, we present the necessary hardware architecture and signal processing algorithms for a real-time geometry-based channel emulator, that is needed for testing of wireless control systems. We partition the non-stationary fading process into a sequence of local stationarity regions and model the channel impulse response as sum of propagation paths with time-varying attenuation, delay and Doppler shift. We implement a subspace projection of the propagation path parameters, to compress the time-variant channel impulse response. This enables a low data-rate link from the host computer, which computes the geometry-based propagation paths, to the software defined radio (SDR) unit, that implements the convolution on a field programmable gate array (FPGA). With our new architecture, the complexity of the FPGA implementation becomes independent of the number of propagation paths. Our channel emulator can be parametrized by all known channel models. Without loss of generality we use a parameterization by a geometry-based stochastic channel model (GSCM), due to its non-stationary nature. We provide channel impulse response measurements of the channel emulator, using the RUSK Lund channel sounder for a vehicular scenario with 617 propagation paths. A comparison of the time-variant power delay proflie (PDP) and Doppler spectral density (DSD) of simulated and emulated channel impulse response showed a close match with an error smaller than -35 dB. The results demonstrate that our channel emulator is able to accurately emulate non-stationary fading channels with continuously changing path delays and Doppler shifts.
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| 2. |
- Hofer, Markus, et al.
(författare)
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Validation of a Real-Time Geometry-Based Stochastic Channel Model for Vehicular Scenarios
- 2018
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Ingår i: 2018 IEEE 87th Vehicular Technology Conference, VTC Spring 2018 - Proceedings. - 2577-2465. - 9781538663554 ; 2018-June, s. 1-5
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Konferensbidrag (refereegranskat)abstract
- The performance of wireless communication systems is fundamentally determined by wireless communication channel properties. Wireless vehicular communication channels exhibit multipath propagation and non-stationary channel statistics. Methods and tools for the repeatable test of wireless communication systems and signal processing algorithms in such environments are urgently needed to enable the development of reliable communication links with low-latency. In this paper we present the measurement and validation of a real time channel emulation method for non-stationary vehicular scenarios based on a geometry-based stochastic channel model.
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| 3. |
- Nilsson, Mikael, et al.
(författare)
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On Multilink Shadowing Effects in Measured V2V Channels on Highway
- 2015
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Konferensbidrag (refereegranskat)abstract
- Shadowing from vehicles can degrade the performance of vehicle-to-vehicle (V2V) communication systems significantly. It is thus important to characterize and model the influence of common shadowing objects like cars properly. For multilink systems it is essential to model the joint effects on the different links. However, the multilink shadowing effects in V2V channels are not yet well understood. In this paper we present a measurement based analysis of multilink shadowing effects in V2V communication systems with cars as blocking objects. In particular we analyze and characterize the joint large scale fading process for multilink communication at 5.9 GHz between four cars in a highway scenario. From our analysis it is found that the coherence time of the large scale fading process for different links can vary from a few seconds to minutes. The results show that it is essential to consider the correlation of the large scale fading processes as the correlation coefficients can have both large negative and large positive values. There is also a clear indication that multihop techniques provide an efficient way to overcome the issue with shadowed cars in V2V systems.
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| 4. |
- Vlastaras, Dimitrios, et al.
(författare)
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A model for power contributions from diffraction around a truck in Vehicle-to-Vehicle communications
- 2017
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Ingår i: 15th International Conference on Intelligent Transport Systems (ITS) Telecommunications. - 9781509052752
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Konferensbidrag (refereegranskat)abstract
- Channel modeling studies in vehicle-to-vehicle (V2V) communications have shown that larger road users act as blocking objects for the communication of surrounding vehicles, dramatically altering the statistical properties of the wireless channel. Without a strong line-of-sight component, packet delivery depends on other propagation mechanisms that are statistically more likely to add destructively so that the signal falls below the noise threshold of the receiver. An analytical model to understand dominant propagation mechanisms in these scenarios is a very powerful tool to predict system performance for important safety scenarios, facilitating both application development and vehicle antenna design. In this paper we present an analytical model for the power contributions from diffraction around a truck. The model is later verified using real life channel measurements from a rural road scenario. A general conclusion is that the channel between the vehicles is highly sensitive to lateral position, and even longitudinal position in the vicinity immediately behind the truck. Finally we conclude that non line-of-sight communication in rural environments is possible using only diffraction as a propagation mechanism, and that antenna diversity significantly increases communication reliability.
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| 5. |
- Vlastaras, Dimitrios, et al.
(författare)
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Impact of a Truck as an Obstacle on Vehicle-to-Vehicle Communications in Rural and Highway Scenarios
- 2014
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Ingår i: 6th International Symposium on Wireless Vehicular Communications. - 9781479944507
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Konferensbidrag (refereegranskat)abstract
- Shadowing from other vehicles can degrade the performance of vehicle-to-vehicle communication systems significantly. It is thus important to characterize and model the influence of common shadowing objects like trucks in a proper way. However, the scenario of a truck as an obstacle in highly dynamic rural and highway environments is not yet well understood. In this paper we analyze the distance dependent path loss and the additional shadowing loss due to a truck through dynamic measurements. We further characterize the large scale fading and the delay and Doppler spreads as a measure of the channel dispersion in the time and frequency domains. It has been found that a truck as an obstacle reduces the received power by 12 and 13 dB on average, for roof antenna, in rural and highway scenarios, respectively. Also, the dispersion in time and frequency domains is highly increased when the line-of-sight is obstructed by the truck.
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| 6. |
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| 7. |
- Vlastaras, Dimitrios, et al.
(författare)
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Universal Medium Range Radar and IEEE 802.11p Modem Solution for Integrated Traffic Safety
- 2013
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Ingår i: 13th International Conference on ITS Telecommunications. ; , s. 193-197
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Konferensbidrag (refereegranskat)abstract
- Vehicles in the future are anticipated to have the ability to communicate and exchange useful information in order to avoid collisions. However, for this cooperation to be possible all vehicles will have to be equipped with compatible wireless IEEE 802.11p modules that implement intelligent transport systems operating in the 5 GHz frequency band standard (ITS-G5 or WAVE). During the implementation phase of the system there will be many older vehicles without such equipment that can cause hazard as information about them will not be available to vehicles equipped with IEEE 802.11p modules. In this paper we present a system, to be used as a road side unit (RSU), developed explicitly for vehicle-to-infrastructure (V2I) communication that can solve the aforementioned traffic safety problems. The system consists of a universal medium range radar (UMRR) and an IEEE 802.11p modem integrated together to detect vehicles, with or without communication capabilities, and forward their position and speed vectors to vehicles, with IEEE 802.11p modules installed, for collision avoidance. Tests have been performed by using our system in parallel with vehicles in which IEEE 802.11p modules are installed and comparing the content in the Cooperative Awareness Messages obtained from both systems. Accuracy tests have also been performed in order to verify the accuracy of the system in the time and spatial domains.
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| 8. |
- Vlastaras, Dimitrios, et al.
(författare)
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Vehicle Detection through Wireless Vehicular Communication
- 2014
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Ingår i: Eurasip Journal on Wireless Communications and Networking. - : Springer Science and Business Media LLC. - 1687-1472 .- 1687-1499. ; 2014:1, s. 146-153
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Tidskriftsartikel (refereegranskat)abstract
- Vehicles in the future are anticipated to have the ability to communicate and exchange useful information in order to avoid collisions. However, for this cooperation to be possible, all vehicles will have to be equipped with compatible wireless modules, based on, e.g. IEEE 802.11p (used in ITS-G5 or WAVE), which implements intelligent transport systems operating in the 5 GHz frequency band. During the implementation phase of the system, there will be many older vehicles without such equipment that can cause hazard as information about them will not be available to vehicles equipped with IEEE 802.11p modules. In this paper, we present a system to be used as a roadside unit (RSU), developed explicitly for infrastructure-to-vehicle (I2V) communication that can solve the aforementioned traffic safety problems. The system consists of a universal medium-range radar (UMRR) and an IEEE 802.11p modem integrated together to detect vehicles, with or without communication capabilities, and forward their position and speed vectors to vehicles, with IEEE 802.11p modules installed, for collision avoidance. Tests have been performed by using our system in parallel with vehicles in which IEEE 802.11p modules are installed and comparing the content in the Cooperative Awareness Messages obtained from both systems. Accuracy tests have been performed in order to verify the system, and Kalman filtering is applied on the radar data to improve the accuracy of the system further.
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