| 1. |
- Bodin, Ulf, et al.
(författare)
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Effects on TCP from radio-block scheduling in WCDMA high speed downlink shared channels
- 2003
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Ingår i: Quality for all. - Berlin : Encyclopedia of Global Archaeology/Springer Verlag. - 9783540201922 ; , s. 214-223
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Konferensbidrag (refereegranskat)abstract
- Avoiding delay jitter is essential to achieve high throughput for TCP. In particular, delay spikes can cause spurious timeouts. Such timeouts force TCP into slow-start, which may reduce congestion window sizes drastically. Consequently, there may not always be data available for transmission on bottleneck links. For HS-DSCH, jitter can occur due to varying interference. Also, properties of the radio-block scheduling influence the jitter. We evaluate, through simulations, effects on TCP from scheduling. Our evaluation shows that round-robin (RR) schedulers can give more jitter than SIR schedulers. SIR schedulers discriminates low SIR users to improve spectrum utilization while RR schedulers distribute transmission capacity fairly. The high jitter with RR scheduling cause however both lower utilization and decreased fairness in throughput among users than with SIR scheduling. The Eifel algorithm makes TCP more robust against delay spikes and reduces thereby these problems
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| 2. |
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| 3. |
- Fodor, Gábor, et al.
(författare)
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Intercell Interference Coordination in OFDMA Networks and in the 3GPP Long Term Evolution System
- 2009
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Ingår i: Journal of Communications. - : Academic Publishers. - 1796-2021 .- 2374-4367. ; Vol. 4:No. 7, s. 445-453
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Tidskriftsartikel (refereegranskat)abstract
- Intercell interference coordination (ICIC) in or-thogonal frequency division multiple access (OFDMA) net¬works in general and in the 3GPP Long Term Evolution system in particular has received much attention both from the academia and the standardization communities. Under¬standing the trade-offs associated with ICIC mechanisms is important, because it helps identify the architecture and protocol support that allows practical systems to realize potential performance gains. In this paper we review some of the recent advances in ICIC research and discuss the assumptions, advantages and limitations of some of the proposed mechanisms. We then proceed to describe the architecture and protocol support for ICIC in the 3GPP LTE system. We make the point that the 3GPP standard is formed in a flexible way such that network operators can employ the most suitable ICIC mechanism tailored to their actual deployment scenario, traffic situation and preferred performance target.
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| 4. |
- Gunnarsson, Fredrik, et al.
(författare)
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Channel Characterization and HSDPA Bit Rate Prediction of a Dense City Network
- 2009
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Ingår i: Proceedings of the 69th IEEE Vehicular Technology Conference. - 9781424425174
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Konferensbidrag (refereegranskat)abstract
- In radio network simulations, the channel model is one of the key inputs and it has a large impact on the network performance, especially for HSDPA. When evaluating the benefits of different features in system simulations it is therefore important that the chosen channel model is a good approximation of the radio environment of the evaluated type of area. In this paper an assessment of the radio channel characteristics in a densely planned European city center is presented. Live traffic measurements are compared to "real network" simulations results using a range of different channel models. The results show that the 3GPP Typical Urban channel model does not reproduce the measured performance from the dense urban environment in a good way; only half the capacity compared to what was calculated from the measurements was achieved. Instead, ITU Pedestrian A models the environment in a better way.
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| 5. |
- Gunnarsson, Fredrik, et al.
(författare)
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Downtilted Base Station Antennas - A Simulation Model Proposal and Impact on HSPA and LTE Performance
- 2008
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Ingår i: Proceedings of the 68th IEEE Vehicular Technology Conference. - 9781424417223 - 9781424417216 ; , s. 1-5
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Konferensbidrag (refereegranskat)abstract
- This paper proposes a low-complexity model for vertical antenna radiation patterns, e.g. for inclusion in system- level simulations. They can be seen as extensions to the horizontal radiation pattern model used in 3GPP simulation scenarios. The model is verified against and compared to predicted and measured data from real networks. The impact on system-level performance is also investigated. It is seen that using the proposed model, simulated geometry distributions and soft handover statistics closely matching those of real networks may be achieved. The analysis also concludes that many real networks have better cell isolation than what is modeled by the 3GPP antenna model. As a consequence, the horizontal radiation pattern model significantly under-estimates the system level performance in such networks. Furthermore, the proposed model is used to assess the LTE and HSPA system-level performance for realistic scenarios.
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| 6. |
- Landström, Anders, et al.
(författare)
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Measurement-Based Stochastical mmWave Channel Modeling
- 2016
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Ingår i: 2016 IEEE Globecom Workshops (GC Wkshps). - Piscataway, NJ : IEEE Communications Society. - 9781509024827
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Konferensbidrag (refereegranskat)abstract
- Emerging mmWave technology will require newchannel models. Compared to the lower frequency bands,mmWaves will be more reflected and absorbed but less diffracted.Hence, placement of individual physical structures in the en-vironment will affect the propagation much more than before,providing a challenge for channel modeling. At the same time,however, an increasing amount of information about the topologyof the physical environment, in particular for buildings, is madeavailable through better measurement equipment and servicesfor obtaining 3D data. We propose a Monte-Carlo approachfor channel modeling where interactions between mmWaves andthe surrounding small-scale environment can be included, givena stochastic representation. This method is not only suitablefor assessment of basic effects such as material reflection andabsorption, but can also in the future be extended to variousadditional effects such as weather, traffic, foliage, etc. Theframework is verified against 15 GHz measurements from anurban environment, demonstrating how major reflection pathscan be replicated by modeling the closest buildings.IndexTerms
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| 7. |
- Landström, Anders, et al.
(författare)
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Voronoi-based ISD and site density characteristics for mobile networks
- 2012
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Ingår i: 2012 IEEE 76th Vehicular Technology Conference. - Piscataway, NJ : IEEE Communications Society. - 9781467318815
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Konferensbidrag (refereegranskat)abstract
- Inter-Site Distance (ISD) is a common measure for characterizing the site density in a mobile network However, obtaining a good estimation of the ISD for a real world network is not trivial since the physical layout is usually quite more complex than a perfect theoretical hexagonal grid, due to a number of unavoidable factors such as site availability and traffic density. Voronoi diagrams have been suggested for approximating cells from network layouts, providing a method for partitioning the covered area into cells defined by the proximity to the given set of sites. This yields a framework for site coverage approximation based on the actual site distribution, rather than an underlying theoretical model.We present a novel measure, based on Voronoi diagrams, for characterizing the site density of a cellular network and provide a comparison to the more traditional ISD measure. This measure improves capacity assessments and modeling of real networks.
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| 8. |
- Simonsson, Per, et al.
(författare)
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Nya gemensamma nordiska referensintervall inom klinisk kemi. Bättre bas för klinisk bedömning och samarbete
- 2004
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Ingår i: Läkartidningen. - 0023-7205. ; 101:10, s. 5-901
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Tidskriftsartikel (refereegranskat)abstract
- A project engaging the five Nordic countries has presented common reference intervals for the most frequently used biochemical and haematological analytes. The results are based on samples from up to 3000 healthy adult reference persons and are statistically calculated to include 95 % of the reference population’s values. Reference samples were analyzed together with commutable control materials traceable to reference methods (IMEP-17). Enzymes were analyzed using methods traceable to IFCC reference methods. The Swedish Society of Clinical Chemistry now recommends its member laboratories to introduce the new reference intervals and new enzyme methods during 2004.
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| 9. |
- Thurfjell, Magnus, et al.
(författare)
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Narrow Beam Channel Characteristics Measured on an 5G NR Grid-of-Beam Test-Bed
- 2018
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Konferensbidrag (refereegranskat)abstract
- Massive MIMO enabling dynamic beamforming is one key component in 5G New Radio (NR). Narrow beams improve capacity by reduced interference and extend coverage by increased antenna gain. One implementation of dynamic beamforming is Grid-of-Beams (GoB) with fixed narrow beams. In this study, the per beam characteristics are measured in a full-scale micro cell deployment with a mm-wave 5G NR test-bed. It is shown that the channel characteristics are strongly dependent on reflections captured within each beam. Channel conditions such as delay spread, singular value ratio and MIMO rank differ also between adjacent beams. Reflections may even cause significant path length difference which may call for individual synchronization per beam, e.g. meaning that beams at same transmission point may not always be considered quasi co-located (QCL)
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| 10. |
- Upton, Caryn M., et al.
(författare)
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Safety and efficacy of BCG re-vaccination in relation to COVID-19 morbidity in healthcare workers : A double- blind, randomised, controlled, phase 3 trial
- 2022
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Ingår i: eClinicalMedicine. - : Elsevier. - 2589-5370. ; 48
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Tidskriftsartikel (refereegranskat)abstract
- Background BCG vaccination prevents severe childhood tuberculosis (TB) and was introduced in South Africa in the 1950s. It is hypothesised that BCG trains the innate immune system by inducing epigenetic and functional reprogramming, thus providing non-specific protection from respiratory tract infections. We evaluated BCG for reduction of morbidity and mortality due to COVID-19 in healthcare workers in South Africa. Methods This randomised, double-blind, placebo-controlled trial recruited healthcare workers at three facilities in the Western Cape, South Africa, unless unwell, pregnant, breastfeeding, immunocompromised, hypersensitivity to BCG, or undergoing experimental COVID-19 treatment. Participants received BCG or saline intradermally (1:1) and were contacted once every 4 weeks for 1 year. COVID-19 testing was guided by symptoms. Hospitalisation, COVID-19, and respiratory tract infections were assessed with Cox proportional hazard modelling and time-to-event analyses, and event severity with post hoc Markovian analysis. This study is registered with ClinicalTrials.gov, NCT04379336. Findings Between May 4 and Oct 23, 2020, we enrolled 1000 healthcare workers with a median age of 39 years (IQR 30-49), 70.4% were female, 16.5% nurses, 14.4% medical doctors, 48.5% had latent TB, and 15.3% had evidence of prior SARS-CoV-2 exposure. Hospitalisation due to COVID-19 occurred in 15 participants (1.5%); ten (66.7%) in the BCG group and five (33.3%) in the placebo group, hazard ratio (HR) 2.0 (95% CI 0.69-5.9, p= 0.20), indicating no statistically significant protection. Similarly, BCG had no statistically significant effect on COVID-19 (p= 0.63, HR = 1.08, 95% CI 0.82-1.42). Two participants (0.2%) died from COVID-19 and two (0.2%) from other reasons, all in the placebo group. Interpretation BCG did not protect healthcare workers from SARS-CoV-2 infection or related severe COVID-19 disease and hospitalisation.
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