| 191. |
- Kåredal, Johan, et al.
(författare)
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Path loss modeling for vehicle-to-vehicle communications
- 2011
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Ingår i: IEEE Transactions on Vehicular Technology. - 1939-9359. ; 60:1, s. 323-328
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Tidskriftsartikel (refereegranskat)abstract
- Vehicle-to-vehicle (V2V) communications have received increasingattention lately, but there is a lack of reported results regarding important quantities such as path loss. This paper presents parameterized path loss models for V2V communications based on extensive sets of measurement data collected mainly under line-of-sight conditions in four different propagation environments: highway, rural, urban, and suburban. The results show that the path loss exponent is low for V2V communications, i.e., path loss slowly increases with increasing distance. We compare our results to those previously reported and find that, while they confirm some of the earlier work, there are also differences that motivate the need for further studies.
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| 192. |
- Kåredal, Johan, et al.
(författare)
-
Radio channel measurements at street intersections for vehicle-to-vehicle applications
- 2010
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Ingår i: IEEE 71st Vehicular Technology Conference (VTC 2010-Spring), 2010. - 1550-2252. ; , s. 1-5
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Konferensbidrag (refereegranskat)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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| 193. |
- Kåredal, Johan, et al.
(författare)
-
Shadowing effects in MIMO channels for personal area networks
- 2006
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Ingår i: [Host publication title missing]. - 1550-2252. ; , s. 173-177
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Konferensbidrag (refereegranskat)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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| 194. |
- Kåredal, Johan, et al.
(författare)
-
Statistical analysis of the UWB channel in an industrial environment
- 2004
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Ingår i: [Host publication title missing]. - 0780385217 ; , s. 81-85
-
Konferensbidrag (refereegranskat)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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| 195. |
- Kåredal, Johan, et al.
(författare)
-
UWB channel measurements in an industrial environment
- 2004
-
Ingår i: [Host publication title missing]. - 0780387945 ; , s. 3511-3516
-
Konferensbidrag (refereegranskat)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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| 196. |
- Larsson, Erik G, et al.
(författare)
-
Massive MIMO for Next Generation Wireless Systems
- 2014
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Ingår i: IEEE Communications Magazine. - : Institute of Electrical and Electronics Engineers. - 0163-6804 .- 1558-1896. ; 52:2, s. 186-195
-
Tidskriftsartikel (refereegranskat)abstract
- Multi-user MIMO offers big advantages over conventional point-to-point MIMO: it works with cheap single-antenna terminals, a rich scattering environment is not required, and resource allocation is simplified because every active terminal utilizes all of the time-frequency bins. However, multi-user MIMO, as originally envisioned, with roughly equal numbers of service antennas and terminals and frequency-division duplex operation, is not a scalable technology. Massive MIMO (also known as large-scale antenna systems, very large MIMO, hyper MIMO, full-dimension MIMO, and ARGOS) makes a clean break with current practice through the use of a large excess of service antennas over active terminals and time-division duplex operation. Extra antennas help by focusing energy into ever smaller regions of space to bring huge improvements in throughput and radiated energy efficiency. Other benefits of massive MIMO include extensive use of inexpensive low-power components, reduced latency, simplification of the MAC layer, and robustness against intentional jamming. The anticipated throughput depends on the propagation environment providing asymptotically orthogonal channels to the terminals, but so far experiments have not disclosed any limitations in this regard. While massive MIMO renders many traditional research problems irrelevant, it uncovers entirely new problems that urgently need attention: the challenge of making many low-cost low-precision components that work effectively together, acquisition and synchronization for newly joined terminals, the exploitation of extra degrees of freedom provided by the excess of service antennas, reducing internal power consumption to achieve total energy efficiency reductions, and finding new deployment scenarios. This article presents an overview of the massive MIMO concept and contemporary research on the topic.
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| 197. |
- Leitinger, Erik, et al.
(författare)
-
A Belief Propagation Algorithm for Multipath-Based SLAM
- 2019
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Ingår i: IEEE Transactions on Wireless Communications. - 1536-1276. ; 18:12, s. 5613-5629
-
Tidskriftsartikel (refereegranskat)abstract
- We present a simultaneous localization and mapping (SLAM) algorithm that is based on radio signals and the association of specular multipath components (MPCs) with geometric features. Especially in indoor scenarios, robust localization from radio signals is challenging due to diffuse multipath propagation, unknown MPC-feature association, and limited visibility of features. In our approach, specular reflections at flat surfaces are described in terms of virtual anchors (VAs) that are mirror images of the physical anchors (PAs). The positions of these VAs and possibly also of the PAs are unknown. We develop a Bayesian model of the SLAM problem and represent it by a factor graph, which enables the use of belief propagation (BP) for efficient marginalization of the joint posterior distribution. The resulting BP-based SLAM algorithm detects the VAs associated with the PAs and estimates jointly the time-varying position of the mobile agent and the positions of the VAs and possibly also of the PAs, thereby leveraging the MPCs in the radio signal for improved accuracy and robustness of agent localization. The algorithm has a low computational complexity and scales well in all relevant system parameters. Experimental results using both synthetic measurements and real ultra-wideband radio signals demonstrate the excellent performance of the algorithm in challenging indoor environments.
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| 198. |
- Leitinger, Erik, et al.
(författare)
-
Factor graph based simultaneous localization and mapping using multipath channel information
- 2017
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Ingår i: 2017 IEEE International Conference on Communications Workshops, ICC Workshops 2017. - 9781509015252 ; , s. 652-658
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Konferensbidrag (refereegranskat)abstract
- Radio-based localization has the potential to provide centimeter-level position information. In this paper we apply joint probabilistic data association to multipath-assisted simultaneous localization and mapping (SLAM) for this purpose. In multipath-assisted localization, position-related information in multipath components (MPCs) is exploited to increase the accuracy and robustness of indoor tracking. Based on a recently introduced loopy belief propagation multipath-assisted localization scheme that performs probabilistic data association jointly with agent state estimation, we build a method for SLAM without using apriori known environment maps. The proposed method is highly accurate and robust in localizing a mobile agent while building up an environment feature map. It scales well in all relevant systems parameters and has a very low computational complexity.
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| 199. |
- Leitinger, Erik, et al.
(författare)
-
On the Use of Mpc Amplitude Information in Radio Signal Based Slam
- 2018
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Ingår i: 2018 IEEE Statistical Signal Processing Workshop, SSP 2018. - 9781538615706 ; , s. 851-855
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Konferensbidrag (refereegranskat)abstract
- In this paper we present a Bayesian framework for utilizing the amplitude information of multipath components (MPCs) in radio-signal-based simultaneous localization and mapping (SLAM). The developed algorithm exploits the complex amplitudes of MPC parameters that are provided by the radio channel parameter estimator. With this information, the algorithm can adapt the probabilities of detecting features within a radio signal in a time-variant way. The algorithm increases the life-time of used features and it better explores 'weak' MPCs, i.e., MPCs with low signal-to-interference-plus-noise-ratios (SINRs) in dense multipath.
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| 200. |
- Li, Xuhong, et al.
(författare)
-
A Belief Propagation Algorithm for Multipath-based SLAM with Multiple Map Features: A mmWave MIMO Application
- 2024
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- In this paper, we present a multipath-based simultaneous localization and mapping (SLAM) algorithm that continuously adapts mulitiple map feature (MF) models describing specularly reflected multipath components (MPCs) from flat surfaces and point-scattered MPCs, respectively. We develop a Bayesian model for sequential detection and estimation of interacting MF model parameters, MF states and mobile agent's state including position and orientation. The Bayesian model is represented by a factor graph enabling the use of belief propagation (BP) for efficient computation of the marginal posterior distributions. The algorithm also exploits amplitude information enabling reliable detection of weak MFs associated with MPCs of very low signal-to-noise ratios (SNRs). The performance of the proposed algorithm is evaluated using real millimeter-wave (mmWave) multiple-input-multiple-output (MIMO) measurements with single base station setup. Results demonstrate the excellent localization and mapping performance of the proposed algorithm in challenging dynamic outdoor scenarios.
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