| 1. |
- Kattge, Jens, et al.
(författare)
-
TRY plant trait database - enhanced coverage and open access
- 2020
-
Ingår i: Global Change Biology. - : Wiley-Blackwell. - 1354-1013 .- 1365-2486. ; 26:1, s. 119-188
-
Tidskriftsartikel (refereegranskat)abstract
- Plant traits-the morphological, anatomical, physiological, biochemical and phenological characteristics of plants-determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to biodiversity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of trait-based plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traits-almost complete coverage for 'plant growth form'. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and trait-environmental relationships. These traits have to be measured on individual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives.
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| 2. |
- Abrahamsson, Henrik, et al.
(författare)
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Connected Vehicles in Cellular Networks : Multi-Access Versus Single-Access Performance
- 2018
-
Ingår i: TMA 2018 - Proceedings of the 2nd Network Traffic Measurement and Analysis Conference. - : Institute of Electrical and Electronics Engineers Inc.. - 9783903176096
-
Konferensbidrag (refereegranskat)abstract
- Connected vehicles can make roads traffic safer and more efficient, but require the mobile networks to handle time-critical applications. Using the MONROE mobile broadband measurement testbed we conduct a multi-access measurement study on buses. The objective is to understand what network performance connected vehicles can expect in today's mobile networks, in terms of transaction times and availability. The goal is also to understand to what extent access to several operators in parallel can improve communication performance. In our measurement experiments we repeatedly transfer warning messages from moving buses to a stationary server. We triplicate the messages and always perform three transactions in parallel over three different cellular operators. This creates a dataset with which we can compare the operators in an objective way and with which we can study the potential for multi-access. In this paper we use the triple-access dataset to evaluate single-access selection strategies, where one operator is chosen for each transaction. We show that if we have access to three operators and for each transaction choose the operator with best access technology and best signal quality then we can significantly improve availability and transaction times compared to the individual operators. The median transaction time improves with 6% compared to the best single operator and with 61% compared to the worst single operator. The 90-percentile transaction time improves with 23% compared to the best single operator and with 65% compared to the worst single operator.
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| 3. |
- Abrahamsson, Henrik, et al.
(författare)
-
DTMsim - DTM channel simulation in ns
- 2001. - 1
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Dynamic Transfer Mode (DTM) is a ring based MAN technology that provides a channel abstraction with a dynamically adjustable capacity. TCP is a reliable end to end transport protocol capable of adjusting its rate. The primary goal of this work is investigate the coupling of dynamically allocating bandwidth to TCP flows with the affect this has on the congestion control mechanism of TCP. In particular we wanted to find scenerios where this scheme does not work, where either all the link capacity is allocated to TCP or congestion collapse occurs and no capacity is allocated to TCP. We have created a simulation environment using ns-2 to investigate TCP over networks which have a variable capacity link. We begin with a single TCP Tahoe flow over a fixed bandwidth link and progressively add more complexity to understand the behaviour of dynamically adjusting link capacity to TCP and vice versa.
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| 4. |
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| 5. |
- Abrahamsson, H, et al.
(författare)
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TCP over high speed variable capacity links: A simulation study for bandwidth allocation
- 2002
-
Konferensbidrag (refereegranskat)abstract
- New optical network technologies provide opportunities for fast, controllable bandwidth management. These technologies can now explicitly provide resources to data paths, creating demand driven bandwidth reservation across networks where an applications bandwidth needs can be meet almost exactly. Dynamic synchronous Transfer Mode (DTM) is a gigabit network technology that provides channels with dynamically adjustable capacity. TCP is a reliable end-to-end transport protocol that adapts its rate to the available capacity. Both TCP and the DTM bandwidth can react to changes in the network load, creating a complex system with inter-dependent feedback mechanisms. The contribution of this work is an assessment of a bandwidth allocation scheme for TCP flows on variable capacity technologies. We have created a simulation environment using ns-2 and our results indicate that the allocation of bandwidth maximises TCP throughput for most flows, thus saving valuable capacity when compared to a scheme such as link over-provisioning. We highlight one situation where the allocation scheme might have some deficiencies against the static reservation of resources, and describe its causes. This type of situation warrants further investigation to understand how the algorithm can be modified to achieve performance similar to that of the fixed bandwidth case.
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| 6. |
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| 7. |
- Ahlgren, Bengt, et al.
(författare)
-
Design considerations for a network of information
- 2008. - 7
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Konferensbidrag (refereegranskat)abstract
- The existing Internet ecosystem is a result of decades of evolution. It has managed to scale well beyond the original aspirations. Evolution, though, highlighted a certain degree of inadequacies that is well documented. In this position paper we present the design considerations for a re-architected global networking architecture which delivers dissemination and non-dissemination objects only to consenting recipients, reducing unwanted traffic, linking information producers with consumers independently of the hosts involved, and connects the digital with the physical world. We consider issues ranging from the proposed object identifier/locator split to security and trust as we transition towards a Network of Information and relate our work with the emerging paradigm of publish/subscribe architectures. We introduce the fundamental components of a Network of Information, i.e., name resolution, routing, storage, and search, and close this paper with a discussion about future work.
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| 8. |
- Ahlgren, Bengt, et al.
(författare)
-
Dimensioning links for IP telephony
- 2001. - 1
-
Ingår i: Proceedings of the 2nd IP-Telephony Workshop (IPtel 2001), 2-3 April 2001, New York City, New York, USA.
-
Konferensbidrag (refereegranskat)abstract
- Packet loss is an important parameter for dimensioning network links or traffic classes carrying IP telephony traffic. We present a model based on the Markov modulated Poisson process (MMPP) which calculates packet loss probabilities for a set of super positioned voice input sources and the specified link properties. We do not introduce another new model to the community, rather try and verify one of the existing models via extensive simulation and a real world implementation. A plethora of excellent research on queuing theory is still in the domain of ATM researchers and we attempt to highlight its validity to the IP Telephony community. Packet level simulations show very good correspondence with the predictions of the model. Our main contribution is the verification of the MMPP model with measurements in a laboratory environment. The loss rates predicted by the model are in general close to the measured loss rates and the loss rates obtained with simulation. The general conclusion is that the MMPP-based model is a tool well suited for dimensioning links carrying packetized voice in a system with limited buffer space.
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| 9. |
- Ahlgren, Bengt, et al.
(författare)
-
Dimensioning Links for IP Telephony
- 2000. - 1
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Transmitting telephone calls over the Internet causes problems not present in current telephone technology such as packet loss and delay due to queueing in routers. In this undergraduate thesis we study how a Markov modulated Poisson process is applied as an arrival process to a multiplexer and we study the performance in terms of loss probability. The input consists of the superposition of independent voice sources. The predictions of the model is compared with results obtained with simulations of the multiplexer made with a network simulator. The buffer occupancy distribution is also studied and we see how this distribution changes as the load increases.
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| 10. |
- Arndt, D. S., et al.
(författare)
-
STATE OF THE CLIMATE IN 2017
- 2018
-
Ingår i: Bulletin of The American Meteorological Society - (BAMS). - : American Meteorological Society. - 0003-0007 .- 1520-0477. ; 99:8, s. S1-S310
-
Forskningsöversikt (refereegranskat)
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| 11. |
- Biyani, Pravesh, et al.
(författare)
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Early Estimation of Voice over IPQuality
- 2003
-
Konferensbidrag (refereegranskat)abstract
- Users of Voice over IP (VoIP) applications are sensitive to the quality of an ongoing call. We hypothesize that the quality of a VoIP session can be estimated from the first few seconds of the session and this can be generalized to other VoIP calls. Our approach is an in-band probing mechanism and does not require any external monitoring schemes or network support. We show by post processing VoIP data from globally distributed sites that it is possible to determine the quality after an initial number of seconds. One application is admission control, where it would be possible to reject poor quality calls before they are fully established.
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| 12. |
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| 13. |
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| 14. |
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| 15. |
- Filippini, Ilario, et al.
(författare)
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Non-cooperative RSU Deployment in Vehicular Networks
- 2012
-
Ingår i: 9th Annual Conference on Wireless On-demand Network Systems and Services (WONS), 2012. - : IEEE conference proceedings. ; , s. 79-82
-
Konferensbidrag (refereegranskat)abstract
- This work considers the issue of distributing contents to vehicles through roadside communication infrastructure. Within this scenario, this work studies the dynamics of infrastructure deployment by using game theoretic tools. A strategic game is used to model the case in which the operators perform their deployment decisions concurrently, whereas an extensive game is used to study the dynamics in case one operator is the deployment leader and moves first. The equilibria of the aforementioned games are then assessed as a function of several parameters (nominal infrastructure capacity, interference, vehicle flows). Simulations are used to validate the analytical findings.
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| 16. |
- Goldhahn, Joerg, et al.
(författare)
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Evidence for anti-osteoporosis therapy in acute fracture situations-Recommendations of a multidisciplinary workshop of the International Society for Fracture Repair
- 2010
-
Ingår i: BONE. - : Elsevier BV. - 8756-3282. ; 46:2, s. 267-271
-
Tidskriftsartikel (refereegranskat)abstract
- The International Society for Fracture Repair convened a multidisciplinary workshop to assess the current evidence around the interaction between anti-osteoporosis drugs and the healing of incident fractures, with a view to making recommendations for clinical practice. The consensus was that there is no evidence-based reason to withhold anti-resorptive therapy while a fracture heals, whether or not the patient was taking such therapy when the fracture occurred. The workshop also considered existing models of service provision for secondary prevention and concluded that the essential ingredient for reliable delivery is the inclusion of a dedicated coordinator role. Several unresolved issues were defined as subjects for further research, including the question of whether continuous long-term administration of anti-resorptives may impair bone quality. The rapidly changing area requires re-assessment of drugs and their interaction with fracture healing in the near future.
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| 17. |
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| 18. |
- Hadfield, James, et al.
(författare)
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Comprehensive global genome dynamics of Chlamydia trachomatis show ancient diversification followed by contemporary mixing and recent lineage expansion
- 2017
-
Ingår i: Genome Research. - : Cold Spring Harbor Laboratory Press. - 1088-9051 .- 1549-5469. ; 27:7, s. 1220-1229
-
Tidskriftsartikel (refereegranskat)abstract
- Chlamydia trachomatis is the world's most prevalent bacterial sexually transmitted infection and leading infectious cause of blindness, yet it is one of the least understood human pathogens, in part due to the difficulties of in vitro culturing and the lack of available tools for genetic manipulation. Genome sequencing has reinvigorated this field, shedding light on the contemporary history of this pathogen. Here, we analyze 563 full genomes, 455 of which are novel, to show that the history of the species comprises two phases, and conclude that the currently circulating lineages are the result of evolution in different genomic ecotypes. Temporal analysis indicates these lineages have recently expanded in the space of thousands of years, rather than the millions of years as previously thought, a finding that dramatically changes our understanding of this pathogen's history. Finally, at a time when almost every pathogen is becoming increasingly resistant to antimicrobials, we show that there is no evidence of circulating genomic resistance in C. trachomatis.
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| 19. |
- Hagsand, Olof, et al.
(författare)
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Measuring Internet telephony quality : Where are we today?
- 1999
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Ingår i: Conference Record / IEEE Global Telecommunications Conference. - Rio de Janeiro, Braz. ; , s. 1838-1842
-
Konferensbidrag (refereegranskat)abstract
- Users of Internet telephony applications demand good quality audio playback. This quality is largely dependent on the instantaneous network conditions. In this paper we describe a scheme for measuring network connections as well as a motivation for including a new metric when assessing quality. The tests included a wide range of geographically distributed sites and our results can give useful feedback to users, operators and developers of Voice over IP applications. The results indicate that Internet telephony is feasible on todays Internet but we should envisage some problems if the Internet continues to grow at the rate so far.
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| 20. |
- Hagsand, Olof, et al.
(författare)
-
Self-Admission Control for IP Telephony using Early Quality Estimation
- 2004
-
Ingår i: Lecture Notes in Computer Science. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 0302-9743 .- 1611-3349. ; 3042, s. 381-391
-
Tidskriftsartikel (refereegranskat)abstract
- If quality of service could be provided at the transport or the application layer, then it might be deployed simply by software upgrades, instead of requiring a complete upgrade of the network infrastructure. In this paper, we propose a self-admission control scheme that does not require any network support or external monitoring schemes. We apply the admission control scheme to IP telephony as it is an important application benefiting from admission control. We predict the quality of the call by observing the packet loss over a short initial period using an in-band probing mechanism. The quality prediction is then used by the application to continue or to abort the call. Using over 9500 global IP telephony measurements, we show that it is possible to accurately predict the quality of a call. Early rejection of sessions has the advantage of saving valuable network resources plus not disturbing the on-going calls.
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| 21. |
- Hagsand, Olof, et al.
(författare)
-
Self-admission control for ip telephony using early quality estimation
- 2004. - 1
-
Ingår i: NETWORKING 2004, Networking Technologies, Services, and Protocols; Performance of Computer and Communication Networks; Mobile and Wireless Communications (Third International IFIP-TC6 Networking Conference, Athens, Greece, May 9-14, 2004. Proceedings). - Berlin, Heidelberg : Springer. - 9783540219590 ; , s. 381-391
-
Bokkapitel (refereegranskat)abstract
- If quality of service could be provided at the transport or the application layer, then it might be deployed simply by software upgrades, instead of requiring a complete upgrade of the network infrastructure. In this paper, we propose a self-admission control scheme that does not require any network support or external monitoring schemes. We apply the admission control scheme to IP telephony as it is an important application benefiting from admission control. We predict the quality of the call by observing the packet loss over a short initial period using an in-band probing mechanism. The quality prediction is then used by the application to continue or to abort the call. Using over 9500 global IP telephony measurements, we show that it is possible to accurately predict the quality of a call. Early rejection of sessions has the advantage of saving valuable network resources plus not disturbing the on-going calls.
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| 22. |
- Hagsand, Olof, et al.
(författare)
-
Sicsophone : A low-delay Internet telephony tool
- 2003
-
Ingår i: PROCEEDINGS OF THE 29TH EUROMICRO CONFERENCE - NEW WAVES IN SYSTEM ARCHITECTURE. - Belek, Turkey : IEEE. - 0769519962 ; , s. 189-195
-
Konferensbidrag (refereegranskat)abstract
- The end to end delay is a critical factor in the perceived quality of service for Voice over IP applications. Sicsophone is a complete VoIP system that couples the low level features of audio hardware with a standard jitter buffer playout algorithm. Using, the sound card directly eliminates intermediate buffering as well as providing fine control over timers needed by a soft real-time application such as VoIP A statistical based approach for inserting packets into audio buffers is used in conjunction with a scheme for inhibiting unnecessary fluctuations in the system. We also present mouth-to-ear delay measurements for selected VoIP applications and show that several hundreds of milliseconds can be saved by using the techniques described in this paper A prototype for both UNIX and Windows platforms has been implemented, demonstrating that our system adapts to network: conditions whilst maintaining low delays.
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| 23. |
- Hagsand, Olof, et al.
(författare)
-
Sicsophone: A Low-Delay Internet Telephony Tool
- 2002. - 1
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The end to end delay is a critical factor in the perceived quality of service for Voice over IP applications. The described solution is a complete system-level platform and complements QoS work in the network and application areas. We describe a VoIP system that couples the low level features of audio hardware with a jitter buffer playout algorithm. Using the sound card directly eliminates intermediate buffering as well as providing fine control over timers needed by a soft real-time application such as VoIP. A statistical based approach for inserting packets into audio buffers is used in conjunction with a scheme for inhibiting unnecessary fluctuations in the system. We give comparisons for the performance of the playout algorithm against idealised playout conditions. We also present mouth to ear delay measurements for selected VoIP applications and show that several hundreds of milliseconds can be saved by using the techniques described in this paper. A prototype for both UNIX and Windows platforms (NT and 9X) has been implemented, demonstrating that our system adapts to network conditions whilst maintaining low delays.
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| 24. |
- Harris, Simon R., et al.
(författare)
-
Whole-genome analysis of diverse Chlamydia trachomatis strains identifies phylogenetic relationships masked by current clinical typing
- 2012
-
Ingår i: Nature Genetics. - : Nature Publishing Group. - 1061-4036 .- 1546-1718. ; 44:4, s. 413-419
-
Tidskriftsartikel (refereegranskat)abstract
- Chlamydia trachomatis is responsible for both trachoma and sexually transmitted infections, causing substantial morbidity and economic cost globally. Despite this, our knowledge of its population and evolutionary genetics is limited. Here we present a detailed phylogeny based on whole-genome sequencing of representative strains of C. trachomatis from both trachoma and lymphogranuloma venereum (LGV) biovars from temporally and geographically diverse sources. Our analysis shows that predicting phylogenetic structure using ompA, which is traditionally used to classify Chlamydia, is misleading because extensive recombination in this region masks any true relationships present. We show that in many instances, ompA is a chimera that can be exchanged in part or as a whole both within and between biovars. We also provide evidence for exchange of, and recombination within, the cryptic plasmid, which is another key diagnostic target. We used our phylogenetic framework to show how genetic exchange has manifested itself in ocular, urogenital and LGV C. trachomatis strains, including the epidemic LGV serotype L2b.
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| 25. |
- Hess, Andrea, et al.
(författare)
-
Exploring communication and mobility behaviour of 3G network users and its temporal consistency
- 2015
-
Konferensbidrag (refereegranskat)abstract
- Over the past decade, telecommunication network operators have more and more realized the added value of data analytics for their network deployment efficiency. Early studies targeted the global network perspective by localizing peak loads, both in terms of area and time period. Due to their higher granularity and information richness, current telecommunication datasets allow increasingly deeper insights into the network activities of the users. Existing network traffic classification studies tend to divide users into groups without considering the transitions between different groups caused by individual behavioral traits, which we expect to show observable regularities. Our approach defines a profiling model that characterizes the user behavior as well as its temporal dynamics from two perspectives: w.r.t. (i) the network load the users generate, and (ii) their mobility patterns. The model is evaluated with two unsupervised clustering algorithms of different complexity (namely, XMeans and EM) by means of a 3G trace dataset from a European operator.
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| 26. |
- John, Wolfgang, et al.
(författare)
-
ANIARA Project - Automation of Network Edge Infrastructure and Applications with Artificial Intelligence
- 2023
-
Ingår i: Ada User Journal. - 1381-6551. ; 42:2, s. 92-95
-
Tidskriftsartikel (refereegranskat)abstract
- Emerging use-cases like smart manufacturing and smart cities pose challenges in terms of latency, which cannot be satisfied by traditional centralized infrastructure. Edge networks, which bring computational capacity closer to the users/clients, are a promising solution for supporting these critical low latency services. Different from traditional centralized networks, the edge is distributed by nature and is usually equipped with limited compute capacity. This creates a complex network to handle, subject to failures of different natures, that requires novel solutions to work in practice. To reduce complexity, edge application technology enablers, advanced infrastructure and application orchestration techniques need to be in place where AI and ML are key players.
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| 27. |
- Labiran, Clare, et al.
(författare)
-
Genotyping markers used for multi locus VNTR analysis with ompA (MLVA-ompA) and multi sequence typing (MST) retain stability in Chlamydia trachomatis
- 2012
-
Ingår i: Frontiers in Cellular and Infection Microbiology. - : Frontiers Media SA. - 2235-2988. ; 2
-
Tidskriftsartikel (refereegranskat)abstract
- We aimed to evaluate the stability of the Chlamydia trachomatis multi locus VNTR analysis (MLVA-ompA) and multi sequence typing (MST) systems through multiple passages in tissue culture. Firstly, we analyzed the stability of these markers through adaptation of C. trachomatis to tissue culture and secondly, we examined the stability of a four-locus MLVA-ompA and a five-locus MST system after multiple passages in tissue culture. Marker sequences were monitored through successive chlamydial developmental cycles to evaluate the stability of the individual DNA markers through many bacterial divisions and this, in turn, informed us of the usefulness of using such typing systems for short and long-term molecular epidemiology. Southampton genitourinary medicine (GUM) clinic isolates from endocervical swabs collected from C. trachomatis positive women were passaged through tissue culture. MLVA-ompA typing was applied to primary swab samples and to the same samples after C. trachomatis had been passaged through cell culture (eight passages). Sequence data from time-zero and passage-eight isolates were aligned with reference sequences to determine the stability of the markers. The Swedish new variant (nvCT) underwent 72 passages in cell culture and the markers of the two schemes were similarly analyzed. Analysis of genetic markers of the MLVA-ompA typing system before and after the isolates were introduced to tissue culture showed no change in the dominant sequence. The nvCT that had been passaged 72 times over the duration of a year also showed no variation in the dominant sequence for both the genotyping schemes. MLVA-ompA and MST markers are stable upon adaptation of C. trachomatis to tissue culture following isolation of strains from primary endocervical swab samples. These markers remain stable throughout multiple rounds of cell-division in tissue culture, concomitant with the incubation period and appearance of symptoms normally associated with host-infection. Both genotyping schemes are, therefore, suitable for epidemiology of C. trachomatis.
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| 28. |
- Leister, Wolfgang, et al.
(författare)
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An architecture for adaptive multimedia streaming to mobile nodes
- 2008. - 1
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Ingår i: Proceedings of the 6th International Conference on Advances in Mobile Computing and Multimedia.
-
Konferensbidrag (refereegranskat)abstract
- We describe the adimus architecture which addresses the problem of maintaining the subjective quality of multimedia streaming for a mobile user. In contrast to other works, the entire end-to-end path of the video stream is considered. Adaptation mechanisms for maintaining quality include time-critical handovers, overlay routing and network estimation techniques. Our architecture is built on overlays that provides the necessary functionality for a video streaming service. The paper highlights the key components that ADIMUS advocates to support quality streaming from server to mobile client.
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| 29. |
- Marsh, Ian
(författare)
-
A lightweight measurement platform for home internet monitoring
- 2017
-
Ingår i: 2017 IFIP Networking Conference, IFIP Networking 2017 and Workshops. - 9783901882944
-
Konferensbidrag (refereegranskat)abstract
- CheesePi is a lightweight measurement platform with the goal of performing active measurements directly from within users' homes. As an always on device, it provides better context on the network state, than those available from browser interaction (Speedtest, etc.) In this demonstration, we will show the frontend of CheesePi and how we incorporate data from several sources around Sweden into a dashboard. A testbed of CheesePi nodes has been deployed, where we have conducted several tests. The presentation will highlight how to make unbiased and neutral measurements of the telecommunications infrastructure (Table III). Measurements are of sufficient quality to be useful by an operator, plus requirements mandated by academia [3], regulatory bodies [1] and the IETF [4]. © 2017 IFIP.
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| 30. |
- Marsh, Ian
(författare)
-
A new proposal for congestion control in Ambient networks
- 2005. - 1
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This report describes the protocol design of TCP with Forward Error Correction (TCP-FEC). The performance of TCP can be significantly improved by generating and sending redundant segments in addition to the normal TCP data segments. Data losses in the network can be recovered from the redundant or the original data packets. Additionally by adding correcting codes to the TCP transmissions, both isolated and bursty losses can be handled. The advantage for the application is that the long retransmission times can be avoided if the repair can be done locally. The advantage for the network is two-fold, excessive retransmissions do not further congest the network and wireless losses can be repaired at the receiver. This technical report details TCP-FEC from a design, migration and protocol perspective in the highly heterogeneous wireless environments envisaged by the sixth framework Ambient Networks project\footnote{This work was supported by the EU Ambient Networks Project IST-2002-507134-AN}.
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| 31. |
- Marsh, Ian, et al.
(författare)
-
A systematic study of PESQ’s behavior(from a networking perspective)
- 2006
-
Ingår i: 5th International Conference MESAQIN 2006: MEASUREMENT OF AUDIO AND VIDEO QUALITY IN NETWORKS, 5-6 June 2006, Prague, Czech Republic..
-
Konferensbidrag (refereegranskat)abstract
- In this paper we study, in a systematic way, how the behavior of PESQ estimations varies with the networkloss process. We assess the variability of the estimations with respect to the network conditions and the speech content, and also their accuracy, by comparing the estimates with subjective assessments.
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| 32. |
- Marsh, Ian, et al.
(författare)
-
A VoIP measurement infra-structure
- 2002. - 1
-
Konferensbidrag (refereegranskat)abstract
- Time, day, location and instantaneous network conditions largely dictate the quality of Voice over IP calls. In this paper we describe a VoIP measurement infrastructure to measure the delay, loss and jitter of simulated phone calls on the Intern et. We measure the quality by transmitting a simulated voice call between chosen sites and carefully recording the subsequent packet arrivals at the receiver. We have gathered more than 25,000 sample VoIP sessions from nine global sites. This is our second and more detailed attempt at measuring VoIP quality. This second phase has also focused on the effects of packet size, network asymmetry and silence suppression on measuring jitter, delay and loss. We have made the sessions and tools available for future investigations. Generally the quality of VoIP is excellent within the US and Europe and has improved since our last measurements. Finally this paper concludes with what we have learnt from two efforts of measuring VoIP quality on Wide Area Networks.
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| 33. |
- Marsh, Ian
(författare)
-
CheesePi : Research, results, and the regulator
- 2017
-
Ingår i: ANRW 2017 - Proceedings of the Applied Networking Research Workshop, Part ofIETF-99 Meeting. - New York, NY, USA : ACM. - 9781450351089 ; , s. 7-12
-
Konferensbidrag (refereegranskat)abstract
- In October 2015 we presented CheesePi at the Research and Applications of Internet Measurements (RAIM) workshop in Yokohama, Japan. In this followup paper, 18 months on, we present our findings. These range from simple round trip delay measurements to entire quality campaigns over several weeks. A significant portion of the research has been done in conjunction with the Swedish regulator, which we bring to the fore. CheesePi is a lightweight platform with the goal of performing measurements from within users' homes. Since the goal is to measure Internet quality delivered by ISPs, measurement fairness is of prime concern. This paper covers the regulator's demands, ISPs feedback, our research interests, the users' needs of nearly two years work.
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| 34. |
- Marsh, Ian, et al.
(författare)
-
Data-driven traffic flow : A state-of-the-art report
- 2021
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This state-of-the-art report is the first of two reports. Both are the result of a Swedish project, the Swedish Energy Authority’s TENS project, which spanned from 2018-2021. This report lays out the background, related work, state of the art, related projects as well as mapping out the area for the newcomer to the area. Examples are from Sweden due to the available data, as well as the locally installed infrastructure. We dedicate some space to the data gathering process as well as basic traffic flow principles. It should be seen as introductory material to the topic, getting the laymen up to speed in data processing issues arising from using traffic sensors. A second (sister) report contains technical results from our work in the above named Swedish project.
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| 35. |
- Marsh, Ian, et al.
(författare)
-
Data-driven traffic flow : Summary of experiments
- 2021
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This final report is the second of two reports. Both are the result of a Swedish project, the Swedish Energy Authority’s TENS project, which spanned from 2018-2021. Other reports from the project provide results from estimating emissions from traffic measurements as well as simulation studies. Like any European capital, Stockholm suffers from many problems related to its road network. The main factor is traffic jams, which are aggravated with difficult weather conditions in winter but also due to accidents, popular events and holidays. Therefore, this report provides the results from a data-driven approach to estimating traffic flow. This work aims at predicting and understanding the behavior of this network based on data collected at several places. More specifically, the goal is to predict and model the traffic flow i.e macroscopic information, on ground measurements (MCS), using floating microscopic (INRIX) data. We focus on estimating the fundamental traffic law relationships, the flow using time series and future directions. Methods and results are in the related work section.
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| 36. |
- Marsh, Ian, et al.
(författare)
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Dimensioning Links for IP Telephony
- 2001
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Ingår i: In Proceedings of the 2nd IP-Telephony Workshop, pages 14-24, New York, USA, April 2001.. ; , s. 14-24
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Konferensbidrag (refereegranskat)abstract
- Packet loss is an important parameter for dimensioning networklinks or traffic classes carrying IP telephony traffic. We present amodel based on the Markov modulated Poisson process (MMPP) whichcalculates packet loss probabilities for a set of superpositioned voice inputsources and link properties. We do not introduce another new model tothe community, rather try and verify one of the existing models via extensivesimulation and a real world implementation. A plethora of excellentresearch on queuing theory is still in the domain of ATM researchers,hence we attempt to highlight their validity to the IP (Telephony) community.Packet level simulations show reasonable correspondence with the predictionsof the model. Our main contribution is the verification of theMMPP model with measurements in a laboratory environment. The lossrates predicted by the model are in general close to the measured lossrates and the loss rates obtained by simulation. The general conclusionis that the MMPP-based model is a tool well suited for dimensioninglinks carrying packetised voice in a system with limited buffer space.
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| 37. |
- Marsh, Ian, et al.
(författare)
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Evolving 5G : ANIARA, an edge-cloud perspective
- 2021
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Ingår i: Proceedings of the 18th ACM International Conference on Computing Frontiers 2021, CF 2021. - New York, NY, USA : Association for Computing Machinery, Inc. - 9781450384049 ; , s. 206-207
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Konferensbidrag (refereegranskat)abstract
- ANIARA (https://www.celticnext.eu/project-ai-net) attempts to enhance edge architectures for smart manufacturing and cities. AI automation, orchestrated lightweight containers, and efficient power usage are key components of this three-year project. Edge infrastructure, virtualization, and containerization in future telecom systems enable new and more demanding use cases for telecom operators and industrial verticals. Increased service flexibility adds complexity that must be addressed with novel management and orchestration systems. To address this, ANIARA will provide en-ablers and solutions for services in the domains of smart cities and manufacturing deployed and operated at the network edge(s). © 2021 Owner/Author.
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| 38. |
- Marsh, Ian, et al.
(författare)
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Hierarchical caching simulation with visualisation
- 2013
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Ingår i: Proceedings - UKSim 15th International Conference on Computer Modelling and Simulation, UKSim 2013. - 9780769549941 ; , s. 622-627
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Konferensbidrag (refereegranskat)abstract
- Within the Internet, intermediary storage is increasingly being used to hold popular files that need to be geographically distributed. Known as Content Distribution Networks (CDNs), storage in the network can alleviate load on servers, intermediary links plus potentially reduce download time for data consumers. Well known CDNs such as Akamai, Amazon, NetFlix or even Dropbox have become household names. However, understanding the behavior of caches, an essential part of the CDNs is non-trivial. This Is because the system Ls highly dynamic: content, requests, topologies, eviction policies, spatial and temporal diversities make exact predictions of what to store and what to evict difficult. Thus, we have taken a two-pronged approach to this problem. First was to build a hierarchical simulator and second was to visualize the cache dynamics for a quantitative and qualitative understanding of the system. Ultimately, we would like to be able to optimally place, dimension and manage the caches we introduce into the Internet infrastructure and use and manage them without superfluous configuration.
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| 39. |
- Marsh, Ian, et al.
(författare)
-
IEEE 802.11b voice quality assessment using cross-layer information
- 2006. - 1
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Konferensbidrag (refereegranskat)abstract
- This paper reports on the suitability of IEEE 802.11b networks for carrying real-time voice traffic, considering particularly the end terminals. More specifically we looked at such networks in different operating circumstances: an outdoor environment, an office environment, and the influence of competing traffic. Additionally we have investigated the link protocol in combination with the application layer. Based on over 2500 recorded sessions, it can be generally concluded that the 802.11b protocol can support real-time voice; particularly if the link transmission rate is immediately lowered after an unsuccessful initial transmission. However, we did find situations where the voice quality deteriorated below commonly accepted values, such as when competing with high-rate TCP traffic, when intervening obstacles blocked the transmission path, and with certain uses of the RTS/CTS mechanism.
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| 40. |
- Marsh, Ian, et al.
(författare)
-
IEEE 802.11b voice quality assessment using crosslayer information.
- 2006
-
Konferensbidrag (refereegranskat)abstract
- This paper reports on the suitability of IEEE802.11b networks for carrying real-time voice traffic, considering particularly the end terminals. More specifically we looked at such networks in different operating circumstances:an outdoor environment, an office environment,and the influence of competing traffic. Additionally wehave investigated the link protocol in combination with theapplication layer. Based on over 2500 recorded sessions,it can be generally concluded that the 802.11b protocolcan support real-time voice; particularly if the link transmissionrate is immediately lowered after an unsuccessful initial transmission. However, we did find situations where the voice quality deteriorated below commonly accepted values, such as when competing with high-rate TCP traffic,when intervening obstacles blocked the transmission path,and with certain uses of the RTS/CTS mechanism.
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| 41. |
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| 42. |
- Marsh, Ian, et al.
(författare)
-
Modelling the arrival process for packet audio
- 2003
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Ingår i: QUALITY OF SERVICE IN MULTISERVICE IP NETWORKS, PROCEEDINGS. - 3540006044 ; , s. 35-49
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Konferensbidrag (refereegranskat)abstract
- Packets in an audio stream can be distorted relative to one another during the traversal of a packet switched network. This distortion can be mainly attributed to queues in routers between the source and the destination. The queues can consist of packets either from our own flow, or from other flows. The contribution of this work is a Markov model for the time delay variation of packet audio in this scenario. Our model is extensible, and show this by including sender silence suppression and packet loss into the model. By comparing the model to wide area traffic traces we show the possibility to generate an audio arrival process similar to those created by real conditions. This is done by comparing the probability density functions of our model to the real captured data.
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| 43. |
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| 44. |
- Marsh, Ian
(författare)
-
Quality aspects of audio communication
- 2003. - 1
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The Internet is increasingly being used to carry real-time voice traffic. Users of real-time voice services are sensitive to variable audio quality. The quality of packet audio is largely determined by the mouth-to-ear delay and the packet loss. The contribution of this thesis is to provide techniques to improve the packet audio quality: dimensioning links specifically for packet voice communication, modelling the packet audio arrival process at a receiver, measuring connectivity quality in wide area networks, and reducing delays in end systems.
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| 45. |
- Marsh, Ian, 1965-
(författare)
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Quality aspects of internet telephony
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Internet telephony has had a tremendous impact on how people communicate.Many now maintain contact using some form of Internet telephony.Therefore the motivation for this work has been to address the quality aspectsof real-world Internet telephony for both fixed and wireless telecommunication.The focus has been on the quality aspects of voice communication,since poor quality leads often to user dissatisfaction. The scope of the workhas been broad in order to address the main factors within IP-based voicecommunication.The first four chapters of this dissertation constitute the backgroundmaterial. The first chapter outlines where Internet telephony is deployedtoday. It also motivates the topics and techniques used in this research.The second chapter provides the background on Internet telephony includingsignalling, speech coding and voice Internetworking. The third chapterfocuses solely on quality measures for packetised voice systems and finallythe fourth chapter is devoted to the history of voice research.The appendix of this dissertation constitutes the research contributions.It includes an examination of the access network, focusing on how calls are multiplexed in wired and wireless systems. Subsequently in the wireless case, we consider how to handover calls from 802.11 networks to the cellularinfrastructure. We then consider the Internet backbone where most of ourwork is devoted to measurements specifically for Internet telephony. The applications of these measurements have been estimating telephony arrival processes, measuring call quality, and quantifying the trend in Internet telephony quality over several years. We also consider the end systems, since they are responsible for reconstructing a voice stream given loss and delay constraints. Finally we estimate voice quality using the ITU proposal PESQ and the packet loss process.The main contribution of this work is a systematic examination of Internet telephony. We describe several methods to enable adaptable solutions for maintaining consistent voice quality. We have also found that relatively small technical changes can lead to substantial user quality improvements.A second contribution of this work is a suite of software tools designed to a certain voice quality in IP networks. Some of these tools are in use within commercial systems today.
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| 46. |
- Marsh, Ian
(författare)
-
Real-time voice over wireless IP networks: The last challenge?
- 2005. - 1
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Ingår i: INFOCOM 2005 Student Workshop.
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Konferensbidrag (refereegranskat)abstract
- Wireless connectivity is needed to bring IP-based telephony into serious competition with the cellular infrastructure. Nevertheless, quality problems remain with wireless VoIP services, not least when used with unlicensed spectrum technologies. This submission summaries on-going work in the area of real-time voice quality issues using a combination of networking and real-user assessment techniques.
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| 47. |
- Marsh, Ian, et al.
(författare)
-
The design and implementation of a quality-based handover trigger
- 2006
-
Ingår i: Lecture Notes in Computer Science. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 0302-9743 .- 1611-3349. ; 3976, s. 580-591
-
Tidskriftsartikel (refereegranskat)abstract
- Wireless connectivity is needed to bring IP-based telephony into serious competition with the existing cellular infrastructure. However it is well known that voice quality problems can occur when used with unlicensed spectrum technologies such as the popular IEEE 802.11 standards. The cellular infrastructure could provide alternative network access should users roam out of 802.11 coverage or if heavy traffic loads are encountered in the 802.11 cell. Therefore, our goal is to design a handover mechanism to switch ongoing calls to the cellular network when the 802.11 network cannot sustain sufficient call quality. We have investigated load and coverage scenarios and designed, implemented and evaluated the performance of an 802.11 quality-based trigger for the handover of voice calls to the cellular network. We show that our predictive solution addresses the coverage problem and evaluate it within a real setting.
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| 48. |
- Marsh, Ian
(författare)
-
VANET communication: A traffic flow approach
- 2012. - 8
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Konferensbidrag (refereegranskat)abstract
- Macroscopic fluid traffic flow models are used in this paper to predict connectivity behavior within vehicular to vehicular (V2V) networks. The vehicular density determines the radio connectivity in sparse traffic, and may even contribute to radio interference in dense traffic situations. We propose modeling the vehicular density using an approach from physics and engineering known as traffic flow theory. It builds models of the interactions between vehicles and road infrastructure similar to fluid or gas flows in pipelines. We have developed analytic solutions for estimating vehicular densities based on a method for solving the traffic flow equations. With very general infrastructure conditions we can find the density evolution at any location and time for any (given) initial conditions. Using such an approach we show how the connectivity, reachability and broadcast capacities of V2V networks can be calculated as applications of this approach. Furthermore we can include the path loss between vehicles and include interference from dense traffic situations in line and non-line of sight situations. We parameterize the method using Bluetooth and IEEE 802.11a radio technologies to show the applicability of such an approach.
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| 49. |
- Marsh, Ian, et al.
(författare)
-
Wide Area Measurements of Voice Over IP Quality
- 2003. - 1
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Time, day, location and instantaneous network conditions largely dictate the quality of Voice over IP calls. In this paper we present the results of over 18000 VoIP measurements, taken from nine sites connected in a full-mesh configuration. We measure the quality of the routes on a hourly basis by transmitting a pre-recorded call between a pair of sites. We repeat the procedure for all nine sites during the one hour interval. Based on the obtained jitter, delay and loss values as defined in RFC 1889 (RTP) we conclude that the VoIP quality is acceptable for all but one of the nine sites we tested. We also conclude that VoIP quality has improved marginally since we last conducted a similar study in 1998.
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| 50. |
- McNamara, Liam, et al.
(författare)
-
CheesePi : A Raspberry Pi based measurement platform
- 2015. - 8
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Ingår i: IRTF & ISOC Workshop on Research and Applications of Internet Measurements (RAIM 2015).
-
Konferensbidrag (refereegranskat)abstract
- We aim to to objectively characterise the service users experience from their home Internet connections. The attributes of an Internet connection (e.g., bandwidth and loss rate) dictate the service quality that can be achieved over it. American video use is increasing rapidly with 70% of broadband users under the age of 35 getting some of their TV from online sources. Measurement of such connections is crucial, their characterisation is useful not only for human users (so people know what service they can receive) but also for the users’ devices for adaptive behaviour. Furthermore, large-scale characterisation data of individual connections can be collated into a characterisation of the whole network. In this paper we will present a distributed measurement system that we have built and the choices that comprise its design.
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