| 61. |
- Khan, Waqas Nawaz, et al.
(författare)
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Performance Evaluation of Time-Reversal on Measured 60 GHz Wireless Channels
- 2013
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Ingår i: Wireless Personal Communications. - : Springer Science and Business Media LLC. - 1572-834X .- 0929-6212. ; 71:1, s. 707-717
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Tidskriftsartikel (refereegranskat)abstract
- Time-reversal (TR) signal processing has the potential to focus the transmitted signal at a desired receive (Rx) location in both space and time. At lower frequency bands, TR in conjunction with array antennas at transmit (Tx) or Rx has been shown to significantly improve its focusing performance relative to the case of single antennas at both link ends. This work for the first time investigates TR processing for multi-antenna systems in the 60 GHz band. We consider both multiple-input-single-output and single-input-multiple-output (SIMO) channels measured in the 60 GHz band in a conference room environment and investigate the effect of array size and its orientation on spatial and temporal compression properties of TR. It is observed that the root mean square (RMS) delay spread can be reduced significantly by the application of TR in the 60 GHz band and that the orientation of the Rx array significantly affects TR performance for SIMO systems.
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| 62. |
- Kihl, Maria, et al.
(författare)
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Simulation modelling and analysis of a realistic radio channel model for V2V communications
- 2010
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Ingår i: Proceedings of ICUMT - International Congress on Ultra Modern Telecommunications and Control Systems. - 2157-0221. - 9781424472857 ; , s. 981-988
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Konferensbidrag (refereegranskat)abstract
- Realistic radio channel models are crucial for the success of vehicle-to-vehicle (V2V) system investigations. In this paper, we summarize the important parameters for V2V channel models and describe relevant measurement campaigns. Also, we develop and evaluate an ns-3 simulation model of a realistic V2V channel model that is based on measurements in Sweden. The channel model incorporates the effects of obstacles between the transmitter and receiver. We show that the resulting pathloss is very different compared with available models.
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| 63. |
- Kolmonen, Veli-Matti, et al.
(författare)
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A dual-link capacity analysis of measured time-variant radio indoor channels
- 2010
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Ingår i: 2010 IEEE 71st Vehicular Technology Conference. - 9781424425181
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Konferensbidrag (refereegranskat)abstract
- There has been extensive research about single link multiple-input multiple-output (MIMO) channels, both simulated and measured, but only few studies have targeted multilink analysis with measured channel data. Hence, in this paper, we analyze the influence of spatial separation of user terminals and the human shadowing effect on the MIMO capacity and to the signal to interference ratio (SIR) in a time-variant dual-link scenario. The paper analyses the dual-link channel capacity based on simulations as well as measurements conducted using dynamic dual-link dual-polarized wideband MIMO channel sounder in an indoor office environment, and compare the results to the singlelink capacity. Here the analysis is restricted to 4 x 4 MIMO links. The following conclusions have been obtained from the analyses: 1) Compared to the single link case, the dual-link channel capacity is more affected by the SIR than the spatial separation of the users. 2) The human shadowing introduced variations of SIR up to ±10 dB, causing large fluctuations in the dual-link capacity.
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| 64. |
- Kolmonen, Veli-Matti, et al.
(författare)
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A dynamic dual-link wideband MIMO channel sounder for 5.3 GHz
- 2010
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Ingår i: IEEE Transactions on Instrumentation and Measurement. - 0018-9456. ; 59:4, s. 873-883
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Tidskriftsartikel (refereegranskat)abstract
- Abstract in UndeterminedIn this paper, we present and evaluate the performance of a dynamic dual-link wideband multiple-input-multiple-output ( MIMO) channel sounder. The channel sounder can simultaneously measure two wideband dual-polarized links, each with a MIMO matrix size of 30 x 30 and 30 x 32. Multi-link MIMO systems, including multiuser and cooperative MIMO, are essential parts of future high-throughput wireless local area networks and fourth-generation cellular systems. To fully understand such systems, the dynamic characteristics of multilink MIMO channels have to be measured. In this paper, we present a channel sounder that enables such measurements, including double-directional parameter estimation possibility for both links. The presented dual-link MIMO channel sounder does not suffer from the deficiencies of previous "virtual multiuser" measurement systems. Furthermore, system analysis and sample results from a measurement campaign with this channel sounder at 5.3 GHz in an indoor office environment are presented.
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| 65. |
- Kolmonen, V. -M., et al.
(författare)
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Dual-link capacity analysis of measured time-variant indoor radio channels
- 2010
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Ingår i: Electronics Letters. - : Institution of Engineering and Technology (IET). - 1350-911X .- 0013-5194. ; 46:8, s. 72-592
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Tidskriftsartikel (refereegranskat)abstract
- There has been extensive research about single link multiple-input multiple-output (MIMO) channels, both simulated and measured, but only a few studies have targeted multilink analysis with measured channel data. Hence, in this presented report, the authors analyse the influence of spatial separation of user terminals and the human shadowing effect on the MIMO capacity and on the signal-to-interference ratio in indoor radio channels.
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| 66. |
- Kolmonen, Veli-Matti, et al.
(författare)
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Measurement-based evaluation of interlink correlation for indoor multi-user MIMO Channels
- 2010
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Ingår i: IEEE Antennas and Wireless Propagation Letters. - 1548-5757. ; 9, s. 311-314
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Tidskriftsartikel (refereegranskat)abstract
- Abstract in UndeterminedThe properties of the single-link multiple-input-multiple- output (MIMO) propagation channels have been analyzed in many studies based on extensive propagation measurements. In this letter, we extend the measurement-based analysis to dual-link MIMO propagation channels. Here, we examine interlink correlation by evaluating the correlation of eigenvectors obtained from multiple MIMO links. We also investigated how the physical propagation phenomena produced the interlink correlation. Results indicate that interlink correlation may exist. Sometimes it is found to be very high also for far separated receive units, depending on similarity of dominant propagation mechanisms between multiple MIMO links and also on antenna array properties.
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| 67. |
- Kuang, Yubin, et al.
(författare)
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Single Antenna Anchor-Free UWB Positioning based on Multipath Propagation
- 2013
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Ingår i: [Host publication title missing].
-
Konferensbidrag (refereegranskat)abstract
- Radio based localization and tracking usually require multiple receivers/transmitters or a known floor plan. This paper presents a method for anchor free indoor positioning based on single antenna ultra wideband (UWB) measurements. By using time of arrival information from multipath propagation components stemming from scatterers with different, but unknown, positions we estimate the movement of the receiver as well as the angle of arrival of the considered multipath components. Experiments are shown for real indoor data measured in a lecture room with promising results. Simultaneous estimation of both receiver motion, transmitter and scatterer positions is performed using an factorization based approach followed by non-linear least squares optimization. A RANSAC approach to automatic matching of data has also been implemented and tested. The resulting reconstruction is compared to ground truth motion as given by the antenna positioner. The resulting accuracy is in the order of one cm.
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| 68. |
- Kåredal, Johan, et al.
(författare)
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A MIMO channel model for wireless personal area networks
- 2010
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Ingår i: IEEE Transactions on Wireless Communications. - 1536-1276. ; 9:1, s. 245-255
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Tidskriftsartikel (refereegranskat)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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| 69. |
- 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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| 70. |
- 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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