| 1. |
- Donders, G. G. G., et al.
(författare)
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Variability in diagnosis of clue cells, lactobacillary grading and white blood cells in vaginal wet smears with conventional bright light and phase contrast microscopy
- 2009
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Ingår i: European Journal of Obstetrics, Gynecology, and Reproductive Biology. - : Elsevier BV. - 0301-2115 .- 1872-7654. ; 145:1, s. 109-112
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Tidskriftsartikel (refereegranskat)abstract
- Objective: Study the reproducibility of wet smear interpretation of clue cells, lactobacillary grades and leukocyte dominance with conventional bright light and phase contrast microscopy. Study design: Sets of vaginal specimens were taken from unselected consecutive women attending an outpatient gynaecology clinic. Air-dried vaginal fluid on a microscope slide was rehydrated with isotonic saline before examination by six independent international investigators. Some investigators initially used a conventional bright light microscope, followed by phase contrast technique. Results: Using phase contrast microscopy, an excellent inter-observer agreement was obtained among all investigators for clue cells detection (Kappa values from 0.69 to 0.94) and lactobacillary grades (Kappa 0.73-0.93). When conventional light microscopes were used, poor agreement was obtained for these criteria (Kappa index 0.37-0.72 and 0.80, respectively), but switching to phase contrast microscopy by the same investigators, improved Kappa to 0.83-0.85 and 0.88, respectively. The inter-observer agreement for estimation of the leukocyte/epithelial cell ratio (Kappa index 0.17-0.67) was poor, irrespective of the type of microscopy applied. Intra-observer agreement of clue cell detection and lactobacillary grading was also found to be excellent if phase contrast microscopy was used (Kappa 0.87-0.93), and poor with conventional bright light microscopy (Kappa 0.45-0.66). Conclusion: Clue cells and the lactobacillary grades are reliably identified by phase contrast microscopy in wet smears, with excellent intra- and inter-observer reproducibility agreement, and better than when simple bright light microscopy was used. Evaluation of leukocyte grading, on the other hand, was inconsistent among the different microscopists, irrespective of the type of microscope used. We propose to grade the leukocytes in a different way than searching for leukocyte dominance over epithelial cells, namely by counting them per high power field and per epithelial cell. (c) 2009 Elsevier Ireland Ltd. All rights reserved.
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| 2. |
- Bakke, Kristin A, et al.
(författare)
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Levetiracetam reduces the frequency of interictal epileptiform discharges during NREM sleep in children with ADHD
- 2011
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Ingår i: European journal of paediatric neurology. - : Elsevier BV. - 1090-3798 .- 1532-2130. ; 15:6, s. 532-538
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Symptoms of attention deficit hyperactivity disorder (ADHD) are more common in children with epilepsy than in the general paediatric population. Epileptiform discharges in EEG may be seen in children with ADHD also in those without seizure disorders. Sleep enhances these discharges which may be suppressed by levetiracetam. AIM: To assess the effect of levetiracetam on focal epileptiform discharges during sleep in children with ADHD. METHOD: In this retrospective study a new semi-automatic quantitative method based on the calculation of spike index in 24-h ambulatory EEG recordings was applied. Thirty-five ADHD children, 17 with focal epilepsy, one with generalised epilepsy, and 17 with no seizure disorder were evaluated. Follow-up 24-h EEG recordings were performed after a median time of four months. RESULTS: Mean spike index was 50 prior to levetiracetam treatment and 21 during treatment. Seventeen children had no focal interictal epileptiform discharges in EEG at follow-up. Five children had a more than 50% reduction in spike index. Thus, a more than 50% reduction in spike index was found in 22/35 children (63%). Out of these an improved behaviour was noticed in 13 children (59%). CONCLUSION: This study shows that treatment with levetiracetam reduces interictal epileptiform discharges in children with ADHD. There is a complex relationship between epilepsy, ADHD and epileptiform activity, why it is a need for prospective studies in larger sample sizes, also to ascertain clinical benefits.
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| 3. |
- Eriksson, Jonas, et al.
(författare)
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On Coding of Scheduling Information in OFDM
- 2009
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Ingår i: Proceedings of the 69th IEEE Vehicular Technology Conference. - 9781424425174
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Konferensbidrag (refereegranskat)abstract
- Control signaling strategies for scheduling information in cellular OFDM systems are studied. A single-cell multiuser system model is formulated that provides system capacity estimates accounting for the signaling overhead. Different scheduling granularities are considered, including the one used in the specifications for the 3G Long Term Evolution (LTE). A greedy scheduling method is assumed, where each resource is assigned to the user for which it can support the highest number of bits. The simulation results indicate that the cost of control signaling does not outweigh the scheduling gain, when compared with a simple round-robin scheme that does not need signaling of scheduling information. Furthermore, in the studied scenario, joint coding and signaling of scheduling information over all selected users is found to be superior to separate coding and signaling for each user. The results also indicate that the scheduling granularity used for LTE provides better performance than the full granularity.
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| 4. |
- Interdonato, Giovanni, 1986-, et al.
(författare)
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Downlink Training in Cell-Free Massive MIMO : A Blessing in Disguise
- 2019
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Ingår i: IEEE Transactions on Wireless Communications. - : Institute of Electrical and Electronics Engineers (IEEE). - 1536-1276 .- 1558-2248. ; 18:11, s. 5153-5169
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Tidskriftsartikel (refereegranskat)abstract
- Cell-free Massive MIMO (multiple-input multipleoutput) refers to a distributed Massive MIMO system where all the access points (APs) cooperate to coherently serve all the user equipments (UEs), suppress inter-cell interference and mitigate the multiuser interference. Recent works 1, 2 demonstrated that, unlike co-located Massive MIMO, the channel hardening is, in general, less pronounced in cell-free Massive MIMO, thus there is much to benefit from estimating the downlink channel. In this study, we investigate the gain introduced by the downlink beamforming training, extending the analysis in 1 to non-orthogonal uplink and downlink pilots. Assuming singleantenna APs, conjugate beamforming and independent Rayleigh fading channel, we derive a closed-form expression for the peruser achievable downlink rate that addresses channel estimation errors and pilot contamination both at the AP and UE side. The performance evaluation includes max-min fairness power control, greedy pilot assignment methods, and a comparison between achievable rates obtained from different capacitybounding techniques. Numerical results show that downlink beamforming training, although increases pilot overhead and introduces additional pilot contamination, improves significantly the achievable downlink rate. Even for large number of APs, it is not fully efficient for the UE relying on the statistical channel state information for data decoding.
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| 5. |
- Interdonato, Giovanni, et al.
(författare)
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How Much Do Downlink Pilots Improve Cell-Free Massive MIMO?
- 2016
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Ingår i: 2016 IEEE GLOBAL COMMUNICATIONS CONFERENCE (GLOBECOM). - : IEEE. - 9781509013289 ; , s. 1-7
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Konferensbidrag (refereegranskat)abstract
- In this paper, we analyze the benefits of including downlink pilots in a cell-free massive MIMO system. We derive an approximate per-user achievable downlink rate for conjugate beamforming processing, which takes into account both uplink and downlink channel estimation errors, and power control. A performance comparison is carried out, in terms of per-user net throughput, considering cell-free massive MIMO operation with and without downlink training, for different network densities. We take also into account the performance improvement provided by max-min fairness power control in the downlink. Numerical results show that, exploiting downlink pilots, the performance can be considerably improved in low density networks over the conventional scheme where the users rely on statistical channel knowledge only. In high density networks, performance improvements are moderate.
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| 6. |
- Interdonato, Giovanni, et al.
(författare)
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On the Performance of Cell-Free Massive MIMO with Short-Term Power Constraints
- 2016
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Ingår i: 2016 IEEE 21ST INTERNATIONAL WORKSHOP ON COMPUTER AIDED MODELLING AND DESIGN OF COMMUNICATION LINKS AND NETWORKS (CAMAD). - : IEEE. - 9781509025589 ; , s. 225-230
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Konferensbidrag (refereegranskat)abstract
- In this paper we consider a time-division duplex cell-free massive multiple-input multiple-output (MIMO) system where many distributed access points (APs) simultaneously serve many users. A normalized conjugate beamforming scheme, which satisfies short-term average power constraints at the APs, is proposed and analyzed taking into account the effect of imperfect channel information. We derive an approximate closed-form expression for the per-user achievable downlink rate of this scheme. We also provide, analytically and numerically, a performance comparison between the normalized conjugate beamforming and the conventional conjugate beamforming scheme in [1] (which satisfies long-term average power constraints). Normalized conjugate beamforming scheme reduces the beamforming uncertainty gain, which comes from the users lack of the channel state information knowledge, and hence, it improves the achievable downlink rate compared to the conventional conjugate beamforming scheme.
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| 7. |
- Interdonato, Giovanni, 1986-, et al.
(författare)
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Scalability Aspects of Cell-Free Massive MIMO
- 2019
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Ingår i: 2019 IEEE International Conference on Communications (ICC), Proceedings Shanghai, China 20–24 May 2019. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781538680889 - 9781538680896 ; , s. 1-6
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Konferensbidrag (refereegranskat)abstract
- Ubiquitous cell-free massive MIMO (multiple-input multiple-output) combines massive MIMO technology and user-centric transmission in a distributed architecture. All the access points (APs) in the network cooperate to jointly and coherently serve a smaller number of users in the same time-frequency resource. However, this coordination needs significant amounts of control signalling which introduces additional overhead, while data co-processing increases the back/front-haul requirements. Hence, the notion that the “whole world†could constitute one network, and that all APs would act as a single base station, is not scalable. In this study, we address some system scalability aspects of cell-free massive MIMO that have been neglected in literature until now. In particular, we propose and evaluate a solution related to data processing, network topology and power control. Results indicate that our proposed framework achieves full scalability at the cost of a modest performance loss compared to the canonical form of cell-free massive MIMO.
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| 8. |
- Interdonato, Giovanni, 1986-, et al.
(författare)
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Self-Learning Detector for the Cell-Free Massive MIMO Uplink : The Line-of-Sight Case
- 2020
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Ingår i: 2020 IEEE 21st International Workshop on Signal Processing Advances in Wireless Communications (SPAWC). - : IEEE. ; , s. 1-5
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Konferensbidrag (refereegranskat)abstract
- The precoding in cell-free massive multiple-input multiple-output (MIMO) technology relies on accurate knowledge of channel responses between users (UEs) and access points (APs). Obtaining high-quality channel estimates in turn requires the path losses between pairs of UEs and APs to be known. These path losses may change rapidly especially in line-of-sight environments with moving blocking objects. A difficulty in the estimation of path losses is pilot contamination, that is, simultaneously transmitted pilots from different UEs that may add up destructively or constructively by chance, seriously affecting the estimation quality (and hence the eventual performance). A method for estimation of path losses, along with an accompanying pilot transmission scheme, is proposed that works for both Rayleigh fading and line-of-sight channels and that significantly improves performance over baseline state-of-the-art. The salient feature of the pilot transmission scheme is that pilots are structurally phase-rotated over different coherence blocks (according to a pre-determined function known to all parties), in order to create an effective statistical distribution of the received pilot signal that can be efficiently exploited by the proposed estimation algorithm.
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| 9. |
- Interdonato, Giovanni, et al.
(författare)
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Utility-based Downlink Pilot Assignment in Cell-Free Massive MIMO
- 2018
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Ingår i: WSA 2018; 22nd International ITG Workshop on Smart Antennas. - : VDE Verlag GmbH. - 9783800745418
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Konferensbidrag (refereegranskat)abstract
- We propose a strategy for orthogonal downlink pilot assignment in cell-free massive MIMO (multiple-input multiple-output) that exploits knowledge of the channel state information, the channel hardening degree at each user, and the mobility conditions for the users. These elements, properly combined together, are used to define a user pilot utility metric, which measures the user's real need of a downlink pilot for efficient data decoding. The proposed strategy consists in assigning orthogonal downlink pilots only to the users having a pilot utility metric exceeding a predetermined threshold. Instead, users that are not assigned with an orthogonal downlink pilot decode the data by using the statistical channel state information. The utility-based approach guarantees higher downlink net sum throughput, better support both for high-speed users and shorter coherent intervals than prior art approaches.
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| 10. |
- Larsson, Pål G., et al.
(författare)
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A New Method for Quantification and Assessment of Epileptiform Activity in EEG with Special Reference to Focal Nocturnal Epileptiform Activity
- 2009
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Ingår i: Brain Topography. - : Springer Science and Business Media LLC. - 0896-0267 .- 1573-6792. ; 22:1, s. 52-59
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Tidskriftsartikel (refereegranskat)abstract
- Quantification of epileptiform activity in EEG has been applied for decades. This has mainly been done by visual inspection of the recorded EEG. There have been many attempts using computers to quantify the activity, usually with moderate success. In a row of contexts, including Landau-Kleffner syndrome and the syndrome of epilepsy with continuous spike wave during slow sleep, the spike index (SI) has been applied to quantify [Symbol: see text]interictal nocturnal focal epileptiform activity', which is suggested as a general term for the epileptiform activity enhanced by sleep. However, the SI has been implemented differently by different authors and has usually not been well described and never properly defined. This study suggests a definition of SI that gives a semiautomatic and relatively robust algorithm for assessment. The method employs spike detection by means of template matching of the current source density estimate. The percentage of time within an epoch with interspike interval (ISI) below a given limit, usually 3 s, is returned as the SI. This is calculated during daytime and in non-REM sleep. The standard epoch length is 10 min. The parameter selection is discussed in the context of the influence of spikes and bursts on cognition. The described method gives reproducible results in routine use, gives clinical valuable information, and is easily implemented in a clinical setting. There is only a minor added workload for the electroencephalographer.
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