| 1. |
- Bartoletti, Stefania, et al.
(författare)
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Positioning methods
- 2024
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Ingår i: Positioning and Location-based Analytics in 5G and Beyond. - 9781119911463 ; , s. 21-50
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- This chapter introduces the main positioning methods, starting from the state-of-the-art and following a statistical estimation perspective. This is followed by an in-depth treatment of radio positioning, first focusing on device-based positioning and then on device-free positioning. Finally, recent approaches based on artificial intelligence methods for positioning are detailed.
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| 2. |
- Cassioli, Dajana, et al.
(författare)
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Low complexity Rake receivers in ultra-wideband channels
- 2007
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Ingår i: IEEE Transactions on Wireless Communications. - 1536-1276. ; 6:4, s. 1265-1275
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Tidskriftsartikel (refereegranskat)abstract
- One of the major issues for the design of ultra-wideband (UWB) receivers is the need to recover the signal energy dispersed over many multipath components, while keeping the receiver complexity low. To this aim we consider two schemes for reduced-complexity UWB Rake receivers, both of which combine a subset of the available resolved multipath components. The first method, called partial Rake (PRake), combines the first arriving multipath components. The second is, known as selective Rake (SRake) and combines the instantaneously strongest multipath components. We evaluate and compare the link performance of these Rake receivers in different UWB channels, whose models are based on extensive propagation measurements. We quantify the effect of the channel characteristics on the receiver performance, analyzing in particular the influence of small-scale fading statistics. We find that for dense channels the performance of the simpler PRake receiver is almost as good as that of the SRake receiver, even for a small number of fingers. In sparse channels, however, the SRake outperforms the PRake significantly. We also show that for a fixed transmitted energy there is an optimum transmission bandwidth.
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| 3. |
- Leitinger, Erik, et al.
(författare)
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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
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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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| 4. |
- Molisch, Andreas, et al.
(författare)
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A comprehensive standardized model for ultrawideband propagation channels
- 2006
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Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X. ; 54:11, s. 3151-3166
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Tidskriftsartikel (refereegranskat)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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| 5. |
- Reichert, Maximilian, et al.
(författare)
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Quantum-enhanced Doppler lidar
- 2022
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Ingår i: npj Quantum Information. - : Springer Science and Business Media LLC. - 2056-6387. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- We propose a quantum-enhanced lidar system to estimate a target’s radial velocity, which employs squeezed and frequency-entangled signal and idler beams. We compare its performance against a classical protocol using a coherent state with the same pulse duration and energy, showing that quantum resources provide a precision enhancement in the estimation of the velocity of the object. We identify three distinct parameter regimes characterized by the amount of squeezing and frequency entanglement. In two of them, a quantum advantage exceeding the standard quantum limit is achieved assuming no photon losses. Additionally, we show that an optimal measurement to attain these results in the lossless case is frequency-resolved photon counting. Finally, we consider the effect of photon losses for the high-squeezing regime, which leads to a constant factor quantum advantage higher than 3 dB in the variance of the estimator, given a roundtrip lidar-to-target-to-lidar transmissivity larger than 50%.
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| 6. |
- Widmer, Joerg, et al.
(författare)
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Enablers toward 6G positioning and sensing
- 2024
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Ingår i: Positioning and Location-based Analytics in 5G and Beyond. - 9781119911463 ; , s. 75-97
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- This chapter provides the reader with an overview of three major trends toward 6G, namely integrated sensing and communication, the ability to control radio wave propagation in the environment thanks to reconfigurable intelligent surfaces, and advances in model-based and model-free signal processing. This list of trends is by no means exhaustive, but only aims to highlight the tremendous potential for research and innovation toward 6G positioning.
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| 7. |
- Win, Moe Z., et al.
(författare)
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History and Applications of UWB
- 2009
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Ingår i: Proceedings of the IEEE. - 0018-9219. ; 97:2, s. 198-204
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 8. |
- Witrisal, Klaus, et al.
(författare)
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High-accuracy localization for assisted living : 5G systems will turn multipath channels from foe to friend
- 2016
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Ingår i: IEEE Signal Processing Magazine. - 1053-5888. ; 33:2, s. 59-70
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Tidskriftsartikel (refereegranskat)abstract
- Asisted living (AL) technologies, enabled by technical advances such as the advent of the Internet of Things, are increasingly gaining importance in our aging society. This article discusses the potential of future high-accuracy localization systems as a key component of AL applications. Accurate location information can be tremendously useful to realize, e.g., behavioral monitoring, fall detection, and real-time assistance. Such services are expected to provide older adults and people with disabilities with more independence and thus to reduce the cost of caretaking. Total cost of ownership and ease of installation are paramount to make sensor systems for AL viable. In case of a radio-based indoor localization system, this implies that a conventional solution is unlikely to gain widespread adoption because of its requirement to install multiple fixed nodes (anchors) in each room. This article therefore places its focus on 1) discussing radiolocalization methods that reduce the required infrastructure by exploiting information from reflected multipath components (MPCs) and 2) showing that knowledge about the propagation environment enables localization with high accuracy and robustness. It is demonstrated that new millimeter-wave (mm-wave) technology, under investigation for 5G communications systems, will be able to provide centimeter (cm)-accuracy indoor localization in a robust manner, ideally suited for AL.
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