| 1. |
- Bin Redhwan, Sakib, et al.
(författare)
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Evaluation of the effect of base station antenna polarization on the performance of CoMP transmission techniques based on synchronous multi-link measurements
- 2016
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Ingår i: 2016 IEEE 27th Annual IEEE International Symposium on Personal, Indoor and Mobile Radio Communications - (PIMRC). - 9781509032549 - 9781509032556
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Konferensbidrag (refereegranskat)abstract
- In this paper, the effect of polarization on the downlink achievable sum-rate of multi-user Cooperative Multi-Point (CoMP) systems is studied using synchronous multi-link channel measurements with two different antenna arrangements. In the first setup, four dual-polarized antenna patches with inter-patch distance varied from half wavelength to 8 m are considered at the base station (BS). In the second setup, two BSs located 60 m apart are used, each is provided with dual-polarized antennas spaced half a wavelength apart. Based on the BS antenna element selection, scenarios with different antenna polarizations at the BSs are considered. We consider four virtual users each is equipped with two antennas (V and H-polarized) with half-wavelength inter-element distance. The users are equally spaced with inter-user distance of about 0.5 m and moving in different routes. For each setup, the 8 × 4 MIMO multi-user channels are used to evaluate the achievable sum-rate of the system, where the minimum mean square error (MMSE) beamforming at both the BS and the mobile station (MS) is used. It is found that the performance improvement gained from using dual-polarized antennas at the BS vanishes if the BS antenna elements are distributed over large distance (i.e., having a large antenna array aperture). However, in the measured environment, for the case of having two BSs each of which is provided with co-located antennas, using dual-polarized antennas provide about 40% improvement in the ergodic sum-rate compared to using single-polarized antennas.
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| 2. |
- Bourdoux, Andre, et al.
(författare)
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D1.2 MaMi Channel Characteristics: Measurement Results
- 2015
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This deliverable presents channel measurement results for the scenariosOpen exhibition and Crowded auditiorium. The measurement procedureand equipment are described. Massive MIMO (MaMi) channel characteristicsand key parameters are extracted and used in an extended COST 2100channel model for MaMi. The initial validation performed shows that themodel is capable of reproducing the statistics in terms of temporal behaviorof the user separability, singular value spread, capacity and sum-rate anddirectional characteristics. The model can be used for system and link levelMaMi simulations.
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| 3. |
- Dahman, Ghassan, et al.
(författare)
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Cross-Correlation of Large-Scale Parameters in Multi-Link Systems : Analysis using the Box-Cox Transformation
- 2018
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Ingår i: IEEE Access. - 2169-3536. ; 6, s. 13555-13564
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Tidskriftsartikel (refereegranskat)abstract
- Spatially distributed transmission points connected to the same source, known as distributed antenna systems, can improve system performance compared to single-link traditional systems. However, the anticipated gain depends heavily on the cross-correlation properties of the large-scale parameters (LSPs) of the different links. Usually, measured LSPs—except the large-scale fading—have non-Gaussian distributions. Therefore, in order to study their multi-link cross-correlation properties, scenario- and parameter-specific adhoc transformations are applied such that the LSPs have Gaussian distributions in the transform domain [1], [2]. In this work, we propose using the Box-Cox transformation as a general framework for homogenizing this conversion step. The Box-Cox transformation is by nature not distribution specific; therefore, it can be used regardless of the empirical distributions of the studied LSPs. We demonstrate the applicability of the proposed framework by studying multi-link fully-coherent propagation measurements of four base stations and one mobile station in a suburban microcell environment at 2.6 GHz. The inter- and intra-link crosscorrelation of four LSPs—the large-scale fading, and the delay, azimuth, and elevation spreads—are analyzed and their distributions are modeled. Based on our analysis, it is found that, for the investigated environment: 1) the LSPs of the different links can be modeled using unimodal and bimodal Gaussian distributions, and 2) the inter- and intra-link cross-correlation coefficients of the different studied LSPs can be modeled using the Truncated Gaussian distribution. The proposed models are validated using the Kolmogorov-Smirnov test and their parameters are provided.
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| 4. |
- Dahman, Ghassan, et al.
(författare)
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Estimating the Cross-Correlation Properties of Large-Scale Parameters in Multilink Distributed Antenna Systems : Synchronous Measurements Versus Repeated Measurements
- 2017
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Ingår i: IEEE Transactions on Vehicular Technology. - 0018-9545. ; 66:9, s. 7633-7642
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Tidskriftsartikel (refereegranskat)abstract
- It is essential to capture the cross-correlation properties of large-scale parameters (LSPs) among different base station links in cooperative multilink systems in order to make realistic performance assessments. In this work, propagation measurements are used to study the cross-correlation properties of different LSPs, namely large-scale fading, delay spread, azimuth spread, and elevation spread of four links. The interlink cross-correlation coefficients of these LSPs are assessed based on two different measurement approaches: 1) synchronous measurements, where the values of the LSPs of the considered links are estimated from the same measurement run; and 2) repeated measurements, where the values of the LSPs of the considered links are estimated from different measurement runs. Repeated measurements are attractive because they are simpler and less expensive. In this paper, we address the following question: Can repeated measurements be used instead of synchronous measurements in order to estimate the LSPs' cross-correlation properties of different links? Based on analysis of wideband synchronous and repeated multilink measurements in a suburban microcell environment at 2.6 GHz, we found that: 1) the mean values of the cross-correlation coefficients are preserved with repeated measurements, and 2) the estimates of the cross-correlation coefficients from repeated measurements are less spread around the mean value than those from synchronous measurements. These findings are explained based on detailed investigation of specific measured cases and further supported by results obtained from Monte Carlo simulations.
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| 5. |
- Dahman, Ghassan, et al.
(författare)
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Experimental Evaluation of the Effect of BS Antenna Inter-Element Spacing on MU-MIMO Separation
- 2015
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Ingår i: IEEE International Conference on Communications. - 9781467364324 ; 2015-September
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Konferensbidrag (refereegranskat)abstract
- In this paper, multiple-input multiple-output (MIMO) channel measurements in an outdoor micro-cell environment are used to study the effect of base-station (BS) inter-element spacing on multi-user MIMO signal separation. Users with two dual-polarized patch antennas at the mobile station (MS), and four equally-spaced dual-polarized patch antennas at the BS are considered. At the BS, the inter-element spacing (i.e., the spacing between the four dual-polarized patch antennas), is varied from half a wavelength to 8 m. For each BS inter-element spacing, the 4×8 MIMO channels are used to evaluate the system's capability separating closely located users. This evaluation is done by means of the correlation matrix distance metric (between each pair of closely located users) and the sum-rate capacity of the system (when 8 equally-spaced closely located users are served simultaneously). It is found that the system is capable of separating closely located users as long as the distance between them and the BS is less than the Fraunhofer distance associated with the BS antenna array. In the measured environment, for both LOS and NLOS propagation conditions, users located as close as 0.5 m from each other, having the same orientation, are separated successfully in the multi-user MIMO sense.
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| 6. |
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| 7. |
- Dahman, Ghassan, et al.
(författare)
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On the probability of non-shared multipath clusters in cellular networks
- 2015
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Ingår i: IEEE Wireless Communications Letters. - 2162-2345. ; :99
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Tidskriftsartikel (refereegranskat)abstract
- In Space Division Multiple Access (SDMA) systems, users are separated based on their positions. The base-station (BS) signals typically reach the users through multipath clusters. The goal of this work is to find the probability that a randomly selected user will receive the signal from the BS via at least one nonshared (by any other user) multipath cluster. This probability, referred to as PSuccess, provides (under some conditions) the limit of the probability that the BS is able to communicate successfully with a randomly selected user using SDMA without causing significant interference to other users. In order to find PSuccess, we first derive a model describing the probability distribution function (pdf) of the non-overlapping area of a set of circles, that have the same radius and are spatially distributed according to a Poisson distribution. Then, the proposed model for this pdf is used to express PSuccess as a function of the user’s intensity and the clusters’ intensity. Simulations, using the COST 2100 model, for outdoor and indoor scenarios, are used to validate the derived expression for PSuccess with a very good agreement, where the maximum error was 0:04.
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| 8. |
- Flordelis, Jose, et al.
(författare)
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Exploiting antenna correlation in measured massive MIMO channels
- 2016
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Ingår i: 2016 IEEE 27th Annual International Symposium on Personal, Indoor, and Mobile Radio Communications, PIMRC 2016. - 9781509032549
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Konferensbidrag (refereegranskat)abstract
- We investigate antenna correlation of an M-antenna massive multiple-input multiple-output (MIMO) setup with the purpose of obtaining a low-rank representation of the instantaneous massive MIMO channel. Low-rank representation bases using short-term and long-term antenna correlation statistics are defined, and their performance is evaluated with data sets obtained from channel measurements in both indoor and outdoor environments at 2.6 GHz. Our results indicate that the short-term bases can capture a larger amount of the channel energy compared to the long-term ones, but they have a limited timespan, one coherence time or less. On the other hand, the long-term bases are stable over time-spans of a few seconds. Hence, they can be obtained relatively easily. We also investigate a rank-p vector-scalar LMMSE channel estimator that exploits antenna correlation. Our results show that the investigated estimator can achieve a performance similar to that of full-rank LMMSE at a (2p + 1)/M times lower cost. The investigated estimator may be used in conjunction with estimators that exploit correlation in the frequency and time domains or, alternatively, in situations in which these estimators cannot be used, e.g., when pilot separation is larger than the channel coherence bandwidth or time.
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| 9. |
- Flordelis, Jose, et al.
(författare)
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Initial Characterization of Massive Multi-User MIMO Channels at 2.6 GHz in Indoor and Outdoor Environments
- 2015
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The channel properties have a large influence on user separability in massive multi-user multiple-input multiple-output (massive MIMO) systems. In this paper we present spatio-temporal characteristics obtained from massive MIMO channel measurements at 2.6 GHz. The results are based on data acquired in both indoor and outdoor scenarios where a base station equipped with 64 dual-polarized antenna elements communicates simultaneously with nine single-antenna users. In the outdoor scenarios the base station is placed at two rooftops with different heights and the users are confined to a five-meter diameter circle and move rando mly at pedestrian speeds. In the indoor scenarios, the users are located close to each other in a lecture theater and the base station is placed at various locations in the room. We report on the observed distribution of the delay spreads and angular spreads. Furthermore, the multi-user performance in terms of singular value spread of the MU-MIMO channel is also reported. Finally, statistics of the coherence time and coherence bandwidth of the propagation channel in various scenarios are given. The results are important for the design and analysis of massive MU-MIMO systems, as well as in the development of realistic massive MU-MIMO channel models.
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| 10. |
- Flordelis, Jose, et al.
(författare)
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Measurements of Large-Scale Parameters of a Distributed MIMO Antenna System in a Microcell Environment at 2.6 GHz
- 2013
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Ingår i: Antennas and Propagation (EuCAP), 2013 7th European Conference on. - 2164-3342. ; , s. 747-3026
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Konferensbidrag (refereegranskat)abstract
- Multi-site multi-antenna measurements for semiurban microcell environment at 2.6 GHz are performed with four base stations (BSs) and one mobile station (MS). Three BSs are provided with four antenna elements in closely spaced copolarized configuration, and one BS is provided with a single antenna element. The MS is equipped with a cylindrical uniform array consisting of 64 dual-polarized antenna elements and moves along some predefined routes. The values of large-scale fading (LSF) from 19 measurement runs with a total of 1900 snapshots at different locations are extracted. The cross-correlation properties of the LSF between different BS links are analyzed. It was found that, in the selected propagation environment, the influence of the BS location on the LSF cross-correlation properties is negligible. However, the location of the MS has a significant influence on the LSF cross-correlation properties of the different BS links.
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