| 1. |
|
|
| 2. |
- Almhöjd, Ulrica S., et al.
(författare)
-
Analysis of carious dentine using FTIR and ToF-SIMS.
- 2014
-
Ingår i: Journal of Oral Health and Dental Management. - 1583-5588. ; 13:3, s. 735-744
-
Tidskriftsartikel (refereegranskat)abstract
- Abstract Apart from the Maillard reaction, other processes, such as esterification, take place in carious tissue. The aim of the present study was to analyse sound and carious dentine in terms of ester groups and their reaction with hydrazine derivate using Fourier Transform Infrared Spectroscopy (FTIR) and Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS). Carious and sound dentine from human premolars were excavated in three series (Experimental Parts I-III) and separated into inner and outer layers of carious dentine. The excavated tooth material was analysed with FTIR (Part I). Carious and sound dentine were also exposed to different chemical treatments and analysed with FTIR-Attenuated Total Reflectance (FTIR-ATR; Part II) and ToF-SIMS (Part III). The FTIR absorption spectra showed that the carious tissue contained ester groups, not detected in sound dentine. The results also indicated a higher occurrence of ester groups in the inner dental caries layer than in the outer ones. Potential binding to these ester groups by hydrazine derivative was observed after different chemical treatments with both FTIR-ATR and ToF-SIMS. The results of the present study revealed ester groups unique to the carious dentine which, after reaction with hydrazine derivative, form a covalent bond not found in sound dentine. The staining of carious unique groups would be clinically helpful in detection and prevention unnecessary removal of sound dentine.
|
|
| 3. |
- Andersson, Jens A, et al.
(författare)
-
User profiling for pre-fetching or caching in a catch-up TV network
- 2016
-
Ingår i: 2016 IEEE International Symposium on Broadband Multimedia Systems and Broadcasting (BMSB). - 9781467390446
-
Konferensbidrag (refereegranskat)abstract
- We investigate the potential of different pre-fetching and/or caching strategies for different user behaviour with respect to surfing or browsing in a catch-up-TV network. To this end we identify accounts and channels associated with strong or weak surfing or browsing respectively and study the distributions of hold times for the different types of behaviour. Finally we present results from a request prediction model and a caching simulation for the different types of behaviour and find that the results are relatively similar.
|
|
| 4. |
- Angelin, Lars, et al.
(författare)
-
A Congestion Control Algorithm for Signalling Networks Based on a State Machine Controlled by Network Delays
- 1995
-
Konferensbidrag (refereegranskat)abstract
- Congestion control in Signaling System number 7 faces new challenges as mobile com-munication systems and Intelligent Networks grow rapidly. New services change traffic patterns, add to signalling network load, and raise demands on shorter service completion times. To handle new demands, the congestion control mechanisms must foresee an over-load situation, and respond to it so that the network can maintain high throughput. With the introduction of a state machine and a memory function for each signaling link it is possible to predict the completion time of a service session and to detect an emerging congestion. If the predicted completion time of a service session is too long, the session is annihilated. This is the foundation of a congestion control mechanism that reacts fast on information supplied by the network. The congestion control mechanism enables the network to main-tain a high throughput during overload.
|
|
| 5. |
- Angelin, Lars, et al.
(författare)
-
A Congestion Control Mechanism for Signaling Networks based on Network Delays
- 1995
-
Konferensbidrag (refereegranskat)abstract
- Congestion control in Signaling System #7 faces new challenges as mo-bile communication systems and Intelligent Networks grow rapidly. New ser-vices change traffic patterns, add to signalling network load, and raise demands on shorter service completion times. To handle new demands, the congestion control mechanisms must foresee an overload situation, and respond to it so that the network can maintain high probability for successful service comple-tion. With the introduction of a state machine and a memory function for each signaling link it is possible to predict the completion time of a service session and to detect an emerging congestion. If the predicted completion time of a service session is too long, the session is annihilated. This is the foundation of a congestion control mechanism that reacts fast on information supplied by the congested part of the network. The congestion control mechanism increases the ratio of successfully completed service sessions during congestion by several hundred percent.
|
|
| 6. |
- Angelin, Lars, et al.
(författare)
-
A Network Approach to Signalling Network Congestion Control
- 1995
-
Konferensbidrag (refereegranskat)abstract
- Congestion control in Signaling System #7 faces new challenges as mobile communication systems and Intelligent Networks grow rapidly. New services change traffic patterns, add to signalling network load, and raise demands on shorter service completion times. To handle new demands, the congestion control mechanisms must foresee an overload situation, and respond to it so that the net-work can maintain high probability for successful service completion. By measur-ing the time consumption for the initial Message Signalling Units of a service session it is possible to predict the duration of the service session and to detect an emerging congestion. If the predicted duration of the service session is too long, the service session is annihilated. This is the foundation of a congestion control mechanism that reacts fast and on information supplied by the congested part of the network. The congestion control mechanism increases the ratio of successfully completed services during congestion by several hundred percent.
|
|
| 7. |
- Angelin, Lars, et al.
(författare)
-
On the Robustness of a Congestion Control Algorithm for Signaling Networks Based on a State Machine
- 1996
-
Konferensbidrag (refereegranskat)abstract
- Sessions of a signaling service with high real time demands which are subject to unaccept-able delays may be obsolete or prematurely terminated by the customer; in either way, they are a burden to the signaling network. It would ease the load of the network and im-prove the performance of all sessions in progress, if such delayed sessions could be abort-ed as quickly as possible. By measuring the network delay on individual signals of a service session, it is possible to perform signaling network congestion control that consid-ers the state in the entire signaling network. Under the assumption that a session comprises a sequence of signals between one originating node and an arbitrary number of destination nodes, it is possible to predict the total duration of a session. The prediction is calculated from previously completed signals using a state machine, which is defined per signaling link. The annihilation of sessions, for which the prediction exceeds a predefined time limit, is an embryo of a simple signaling network congestion control mechanism (CCM). This simple CCM increases the number of successfully completed services with a few hundred percent under favorable circumstances. The state machine approach has been proven to function well in all types of environments. The robustness and stability of the proposed CCM is demonstrated and the fairness in the admission of signaling services into the net-work at very high loads are also shown.
|
|
| 8. |
- Ardelius, John, et al.
(författare)
-
On the effects of caching in access aggregation networks
- 2012
-
Ingår i: ICN 2012, Helsinki, Finland. - : Association for Computing Machinery (ACM). - 9781450314794
-
Konferensbidrag (refereegranskat)abstract
- All forecasts of Internet trac point at a substantial growth over the next few years. From a network operator perspective, efficient in-network caching of data is and will be a key component in trying to cope with and profit from this increasing demand. One problem, however, is to evaluate the performance of different caching policies as the number of available data items as well as the distribution networks grows very large.In this work, we develop an analytical model of an aggregation access network receiving a continuous flow of requests from external clients. We provide exact analytical solutions for cache hit rates, data availability and more. This enables us to provide guidelines and rules of thumb for operators and Information-Centric Network designers.Finally, we apply our analytical results to a real VoD trace from a network operator and show that substantial bandwidth savings can be expected when using in-network caching in a realistic setting.
|
|
| 9. |
- Ardelius, John, et al.
(författare)
-
On the effects of caching in access aggregation networks
- 2012. - 6
-
Konferensbidrag (refereegranskat)abstract
- All forecasts of Internet traffic point at a substantial growth over the next few years. From a network operator perspective, efficient in-network caching of data is and will be a key component in trying to cope with and profit from this increasing demand. One problem, however, is to evaluate the performance of different caching policies as the number of available data items as well as the distribution networks grows very large. In this work, we develop an analytical model of an aggregation access network receiving a continuous flow of requests from external clients. We provide exact analytical solutions for cache hit rates, data availability and more. This enables us to provide guidelines and rules of thumb for operators and Information-Centric Network designers. Finally, we apply our analytical results to a real VoD trace from a network operator and show that substantial bandwidth savings can be expected when using in-network caching in a realistic setting.
|
|
| 10. |
|
|
| 11. |
|
|
| 12. |
- Arvidsson, Inger, et al.
(författare)
-
Are neck-shoulder disorders associated with habitual neck extension in computer work?
- 2006
-
Ingår i: Meeting diversity in ergonomics.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- A common clinical conception is that prolonged neck extension during computer work is associated with an increased risk of neck-shoulder disorders. The aim of this study was to find out whether neck postures in computer work differed between females cases with neck-shoulderdisorders, compared to healthy referents. Based on physical examinations, 13 cases and 11 referents were selected among 70 female air traffic controllers with the same computer work and identical work stations. Neck angles were measured by inclinometry, during an ordinary work period of about 1 h. Results: Average neck angles (50thpercentile) in cases and referents was -10° (SP 8) and -9 (SD 10) respectively; p=0.9. Hence, we did not find any association between neck-shoulder disorders and neck extension during computer work.
|
|
| 13. |
- Arvidsson, Inger, et al.
(författare)
-
Changes in physical workload with implementation of mouse-based information technology in air traffic control
- 2006
-
Ingår i: International Journal of Industrial Ergonomics. - : Elsevier BV. - 0169-8141 .- 1872-8219. ; 36:7, s. 613-622
-
Tidskriftsartikel (refereegranskat)abstract
- Effects on physical workload were quantified when introducing new information technology in air traffic control. Seven female and 7 male air traffic controllers were studied in an old control system, and during simulated-but similar-work in a new, mouse-based system. Postures, movements and muscular load were recorded (inclinometry for head, neck, back and upper arms; goniometry for wrists; elect romyography for the trapezius and forearm extensor muscles). The new system was associated with lower movement velocities than the old one (examples: [50th percentiles] head flexion: 2 vs. 5 degrees/s, P < 0.01; right arm elevation: 3 vs. 6 degrees/s; P < 0.01; [90th percentile] wrist flexion: 19 vs. 50 degrees/s, P < 0.01), less varying postures (head: 95th-5th percentile range 17 degrees vs. 34 degrees; P < 0.01), and less muscular rest in the right forearm extensors (3.5% vs. 9% of time; P < 0.05). The old/new system differences were amplified at high work intensities. The new air traffic control system caused a major change of physical exposures, probably associated with an increased risk of musculoskeletal disorders in arms and hands. Relevance to industry While this study concerned the specific changes in the introduction of a new air traffic control system, we believe that the findings are applicable to similar technological developments in other settings. (c) 2006 Elsevier B.V. All rights reserved.
|
|
| 14. |
|
|
| 15. |
- Arvidsson, Inger, et al.
(författare)
-
Discrepancies in pain presentation caused by adverse psychosocial conditions as compared to pain due to high physical workload?
- 2012
-
Ingår i: Work: A Journal of Prevention, Assessment & Rehabilitation. - 1875-9270. ; 41, s. 2472-2475
-
Tidskriftsartikel (refereegranskat)abstract
- Disorders in the musculoskeletal system have been associated with a high physical workload as well as psychosocial and individual factors. It is however not obvious which of these factors that is most important to prevent. Musculoskeletal disorders in neck and upper extremity was assessed by interview and clinical examination in 79 teachers and 93 assisting nurses, all females. Psychosocial work environment was assessed by questionnaire. The physical workload was recorded by technical measurements of postures, movements and muscular load, in 9 teachers and 12 nurses. The physical workload was lower among the teachers, but they had a more demanding psychosocial work environment. Among the nurses, but not in the teachers, the neck-shoulder disorders were associated with a high body mass index (BMI). The teachers reported neck-shoulder complaints to a higher extent than the nurses, but had much lower prevalence of diagnoses in the clinical examination (12% vs. 25%; POR 0.3 CI 0.1 - 1.2; adjusted for age and BMI). The results suggest that adverse psychosocial conditions among the teachers give rise to a different kind of pain in the neck-shoulder region than from physical overload, troublesome but not as severe as the one afflicting the nurses.
|
|
| 16. |
|
|
| 17. |
|
|
| 18. |
- Arvidsson, Inger, et al.
(författare)
-
Neck postures in air traffic controllers with and without neck/shoulder disorders.
- 2008
-
Ingår i: Applied Ergonomics. - : Elsevier BV. - 1872-9126 .- 0003-6870. ; 39:2, s. 255-260
-
Tidskriftsartikel (refereegranskat)abstract
- Prolonged computer work with an extended neck is commonly believed to be associated with an increased risk of neck–shoulder disorders. The aim of this study was to compare neck postures during computer work between female cases with neck–shoulder disorders, and healthy referents. Based on physical examinations, 13 cases and 11 referents were selected among 70 female air traffic controllers with the same computer-based work tasks and identical workstations. Postures and movements were measured by inclinometers, placed on the forehead and upper back (C7/Th1) during authentic air traffic control. A recently developed method was applied to assess flexion/extension in the neck, calculated as the difference between head and upper back flexion/extension. Results: cases and referents did not differ significantly in neck posture (median neck flexion/extension: −10° vs. −9°; p=0.9). Hence, the belief that neck extension posture is associated with neck–shoulder disorders in computer work is not supported by the present data.
|
|
| 19. |
|
|
| 20. |
|
|
| 21. |
|
|
| 22. |
|
|
| 23. |
- Arvidsson, Inger, et al.
(författare)
-
Rationalization in meat cutting - Consequences on physical workload.
- 2012
-
Ingår i: Applied Ergonomics. - : Elsevier BV. - 1872-9126 .- 0003-6870. ; 43:6, s. 1026-1032
-
Tidskriftsartikel (refereegranskat)abstract
- Meat cutting is associated with several ergonomic risk factors and a high risk of musculoskeletal disorders. The development of new production systems points to an increased degree of mechanization; instead of subdividing split carcasses of pigs with a knife, the halves are trisected by an electrical saw into 'sixth-parts', resulting in shorter work cycles for the workers. Recently, machine-directed line-production systems have been implemented. This study evaluates differences in the physical workload between the production systems. The postures and movements (inclinometry and goniometry) and muscular load (electromyography) of workers in the split-carcass- (five subjects), sixth-part- (ten) and line-production systems (five) were recorded. Most measures showed a statistically significant trend of declining physical exposure with increasing degrees of mechanization. For example, movement velocities of the upper arm were higher in the split-carcass system (50th percentile: mean 209°/s) than in the sixth-part (103°/s) and line production (81°/s). However, the latter two were not statistically significantly different. A novel method for quantifying posture variation, based on inclinometry, showed that the split-carcass system implied the highest variation of the upper arm postures "within-minute" (i.e., a high range of motion each minute), but the lowest "between-minute" (i.e., a low variation during the course of the workday). In conclusion, the physical workload in the line-production system was significantly lower than in the split-carcass one, and tended also to be lower than in the sixth-part system. However, there may be disadvantages in line production, such as machine-directed work pace and shorter work cycles.
|
|
| 24. |
|
|
| 25. |
- Arvidsson, Per-Ola, et al.
(författare)
-
Violaxanthin accessibility and temperature dependency for de-epoxidation in spinach thylakoid membranes
- 1997
-
Ingår i: Photosynthesis Research. - 0166-8595. ; 52:1, s. 39-48
-
Tidskriftsartikel (refereegranskat)abstract
- Using DTT and iodoacetamide as a novel irreversible method to inhibit endogenous violaxanthin de-epoxidase, we found that violaxanthin could be converted into zeaxanthin from both sides of the thylakoid membrane provided that purified violaxanthin de-epoxidase was added. The maximum conversion was the same from both sides of the membrane. Temperature was found to have a strong influence both on the rate and degree of maximal violaxanthin to zeaxanthin conversion. Thus only 50% conversion of violaxanthin was detected at 4 degreesC, whereas at 25 degreesC and 37 degreesC the degree of conversion was 70% and 80%, respectively. These results were obtained with isolated thylakoids from non-cold acclimated leafs. Pigment analysis of sub-thylakoid membrane domains showed that violaxanthin was evenly distributed between stroma lamellae and grana partitions. This was in contrast to chlorophyll a and beta-carotene which were enriched in stroma lamellae fractions while chlorophyll b, lutein and neoxanthin were enriched in the grana membranes. In combination with added violaxanthin de-epoxidase we found almost the same degree of conversion of violaxanthin to zeaxanthin (73-78%) for different domains of the thylakoid membrane. We conclude that violaxanthin de-epoxidase converts violaxanthin in the lipid matrix and not at the proteins, that violaxanthin does not prefer one particular membrane region or one particular chlorophyll protein complex, and that the xanthophyll cycle pigments are oriented in a vertical manner in order to be accessible from both sides of the membrane when located in the lipid matrix.
|
|
| 26. |
- Arvidsson, Åke, et al.
(författare)
-
Analysis of the Accuracy of Bursty Traffic Models
- 1993
-
Konferensbidrag (refereegranskat)abstract
- Traffic models are an essential component of performance analyses of telecommunication networks. This paper investigates the modeling of bursty traffic streams in both single source and multiple source environments. Using a ranking scheme it is shown that, for the single server case, the switched Poisson process models performed the best and that for the multiple source case, models based on the switched Poisson process, or its discrete version (switched Bernoulli) together with the threshold model may give the closest match to the performance of the “real data“. The results also seem to suggest that for traffic for which there is no known, ideal model, a traffic-oriented fitting method performs better than a model oriented one. This study has concentrated on a particular set of “real data” and it has not tried to consider the many different types of bursty traffic, since, at the time of commencing this study, there was little real data available
|
|
| 27. |
- Arvidsson, Åke, 1957-, et al.
(författare)
-
Analysis of user demand patterns and locality for YouTube traffic
- 2013
-
Ingår i: 25th International Teletraffic Congress. - : IEEE Communications Society. - 9781479907991
-
Konferensbidrag (refereegranskat)abstract
- Video content, of which YouTube is a major part, constitutes a large share of residential Internet traffic. In this paper, we analyse the user demand patterns for YouTube in two metropolitan access networks with more than 1 million requestsover three consecutive weeks in the first network and more than 600,000 requests over four consecutive weeks in the second network.In particular we examine the existence of “local interest communities”, i.e. the extent to which users living closer to each other tend to request the same content to a higher degree, and it is found that this applies to (i) the two networks themselves; (ii) regions within these networks (iii) households with regions and (iv) terminals within households. We also find that different types of access devices (PCs and handhelds) tend to form similar interest communities.It is also found that repeats are (i) “self-generating” in the sense that the more times a clip has been played, the higher the probability of playing it again, (ii) “long-lasting” in the sense that repeats can occur even after several days and (iii) “semi regular”in the sense that replays have a noticeable tendency tooccur with relatively constant intervals.The implications of these findings are that the benefits from large groups of users in terms of caching gain may be exaggerated, since users are different depending on where they live and what equipment they use, and that high gains can be achieved in relatively small groups or even for individual users thanks totheir relatively predictable behaviour.
|
|
| 28. |
- Arvidsson, Åke, et al.
(författare)
-
Analysis of user demand patterns and locality for YouTube traffic
- 2013
-
Ingår i: In the Proceedings of the 25th International Teletraffic Congress (ITC).
-
Konferensbidrag (refereegranskat)abstract
- Video content, of which YouTube is a major part, constitutes a large share of residential Internet traffic. In this paper, we analyse the user demand patterns for YouTube in two metropolitan access networks with more than 1 million requests over three consecutive weeks in the first network and more than 600,000 requests over four consecutive weeks in the second network. In particular we examine the existence of "local interest communities", i.e. the extent to which users living closer to each other tend to request the same content to a higher degree, and it is found that this applies to (i) the two networks themselves; (ii) regions within these networks (iii) households with regions and (iv) terminals within households. We also find that different types of access devices (PCs and handhelds) tend to form similar interest communities. It is also found that repeats are (i) "self-generating" in the sense that the more times a clip has been played, the higher the probability of playing it again, (ii) "long-lasting" in the sense that repeats can occur even after several days and (iii) "semiregular" in the sense that replays have a noticeable tendency to occur with relatively constant intervals. The implications of these findings are that the benefits from large groups of users in terms of caching gain may be exaggerated, since users are different depending on where they live and what equipment they use, and that high gains can be achieved in relatively small groups or even for individual users thanks to their relatively predictable behaviour.
|
|
| 29. |
- Arvidsson, Åke, et al.
(författare)
-
Congestion Control in Intelligent Networks for Real Time Performance and Profit Optimisation
- 1996
-
Konferensbidrag (refereegranskat)abstract
- Current developments in technologies and markets stress the importance of exible and robust performance optimisation and congestion control. In intelligent networks, congestion control has traditionally taken a purely technical view and focused on pro- tecting individual nodes from harmful overloads. We take a profit oriented, network wide view and develop a congestion control mechanism to ensure real time performance under profit maximisation. Numerical studies in a simulator show that the proposed mechanism is robust and, in particular in overloaded states, provides a substantial improvement in comparison to conventional load control mechanisms.
|
|
| 30. |
- Arvidsson, Åke, 1957-, et al.
(författare)
-
Detecting user dissatisfaction and understanding the underlying reasons
- 2013
-
Ingår i: ACM SIGMETRICS / International conference on measurement and modeling of computer systems, SIGMETRICS '13, Pittsburgh, PA, USA, June 17-21, 2013. - : Association for Computing Machinery (ACM). - 9781450319003
-
Konferensbidrag (refereegranskat)abstract
- Quantifying quality of experience for network applications is challenging as it is a subjective metric with multiple dimensions such as user expectation, satisfaction, and overall experience. Today, despite various techniques to support differentiated Quality of Service (QoS), the operators still lack of automated methods to translate QoS to QoE, especially for general web applications.In this work, we take the approach of identifying unsatisfactory performance by searching for user initiated early terminations of web transactions from passive monitoring. However, user early abortions can be caused by other factors such as loss of interests. Therefore, naively using them to represent user dissatisfaction will result in large false positives. In this paper, we propose a systematic method for inferring user dissatisfaction from the set of early abortion behaviors observed from identifying the traffic traces. We conduct a comprehensive analysis on the user acceptance of throughput and response time, and compare them with the traditional MOS metric. Then we present the characteristics of early cancelation from dimensions like the types of URLs and objects. We evaluate our approach on four data sets collected in both wireline network and a wireless cellular network.
|
|
| 31. |
- Arvidsson, Åke, 1957-, et al.
(författare)
-
Detecting user dissatisfaction from passive monitoring
- 2013
-
Ingår i: Proceedings of Eurocon 2013, International Conference on computer as a tool, Zagreb, Croatia, July 1-4, 2013. - : IEEE Communications Society. - 9781467322300
-
Konferensbidrag (refereegranskat)abstract
- In an increasingly competitive environment it is more important than ever for operators to keep their end users satisfied. User satisfaction is often characterised in terms of Quality of Experience (QoE), a subjective metric with multiple dimensions such as expectations, content, terminal, environment, cost and performance. QoE is typically quantified as MOS, mean opinion score, which is obtained by averaging the ranks of a number of voluntary users for controlled combinations content/terminals/performance etc. While this approach has many advantages, there are also a number of difficulties such as representativeness (the number of users as well as the number of objects and devices all have to be kept small); validity (the results may be biased by the situation, the setting, the renumeration and so on); and applicability (it is not clear how different numbers map to notions such as “acceptable” or “unacceptable” and operators alone cannot do very much about factors such as content).We thus investigate the possibilities of detecting user opinions in the above, simplified, terms and from the network itself; with actual expectations, content, terminals, environments, costs and performance for virtually all users all the time. To this end we revisit the earlier suggestion that user opinions be reflected in their behaviour such that poor performance may result in interrupted requests. These works have, however, considered single flows hence we extend that idea to web pages which are groups of flows. In this paper we present our methods to group flows, interpret users, and characterise performance and we make a first assessment of the correlations between web page interruptions and network performance characteristics.
|
|
| 32. |
- Arvidsson, Åke
(creator_code:cre_t)
-
Distance-Based Selection
- 2022
-
Patent (övrigt vetenskapligt/konstnärligt)abstract
- Avståndsbaserat val av peers bestående av två enheter. Den ena tar emot en förfrågan om en peer, tar emot en lista av tänkbara sådana med information ur vilken avstånden till dessa kan beräknas och sammanställer en lista av kandidater och avstånd. Den andra enheten tar emot denna sammanställningen och väljer peer med lämplig tonvikt på avstånden.
|
|
| 33. |
- Arvidsson, Åke
(författare)
-
Distance Based Server Selection in 5G Networks
- 2022
-
Konferensbidrag (refereegranskat)abstract
- Distance aware selection of servers and other net-worked resources is necessary to take full advantage of the 5G ecosystem, where the new radio and edge computing both contribute to significantly reduced latencies, but where propagation times to distant servers may add noticeable delays. The literature on server selection, and in particular on distance aware server selection, is, however, surprisingly thin. The few approaches we have come across are either relatively complex, based on continuous measurements, or both and not reflected in current standards. The present work therefore aims at simple but accurate mechanisms which build on and are backward compatible with present standards. We briefly describe the existing alternatives for distance aware selection as reflected in the standards, and propose include location information in server URLs such that distances can be explicitly calculated and evaluated by selecting entities. Moreover, we present three distinct and simple approaches to encode locations, two of which advantageously can be combined. The performance of the methods are then subject to a comprehensive performance evaluation where a large number of varied scenarios are considered. The results reveal that simple geographical coordinates should be restricted to very dense networks (typically networks which form full meshes) whereas a combination of the other approaches work well in other networks (in our case networks based on trees, stars or loops). Contrary to earlier proposals, our proposals consistently provide upper bounds on distances which eliminates the uncertainties that surrounds approximate solutions.
|
|
| 34. |
- Arvidsson, Åke, 1957-, et al.
(författare)
-
Fast transport for edge computing in 5G networks
- 2018
-
Ingår i: Proceedings of 2018 26th International Conference on Software, Telecommunications and Computer Networks (SoftCOM). - New York : IEEE Communications Society. ; , s. 41-45
-
Konferensbidrag (refereegranskat)abstract
- We consider TCP performance for cloud servicesin 5G cellular networks and show that edge clouds offer the highest throughput, but that further improvements still arepossible. To this end we devise a concept where edge clouds connected directly to the radio access network can increase their transmission rates by relying on the built in re-transmissions (through quality of service features) and on the built in userfairness (through per-user buffers and scheduler policies). We use numerical examples from measurements in real networks to demonstrate that the concept is efficient and significantly improves the effective throughput beyond what placement alone can do, and we also outline possible further improvements.
|
|
| 35. |
- Arvidsson, Åke, et al.
(författare)
-
Forecasting Cellular Mobile Traffic : An Econometric Approach
- 2006
-
Konferensbidrag (refereegranskat)abstract
- We consider the problem of explaining and forecasting the volume of cellular mobile traffic in a long-term perspective. To this end, we create a model of a market with both economic and non-economic variables, viz. the state of the economy, the current price level and the penetration effect on the market in question. We measure these variables by using publicly available data and by applying income theories and by combining theories of demand and technology diffusion. Applying the model to three markets, viz. China, Italy and Sweden, we show that it performs very well in explaining and predicting the volume of cellular mobile traffic. Noting the qualitative differences between these markets, we conclude that the model has some universality in that the results are comparable for all of them
|
|
| 36. |
- Arvidsson, Åke
(författare)
-
High Level B-ISDN/ATM Traffic Management in Real Time
- 1995
-
Ingår i: Performance Modelling and Evaluation of ATM Networks. - London : Chapman & Hall. - 0412711400 ; , s. 177-207
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- We study real time traffic management in the perspective of a four-level model of traffic variations: cells, bursts, sessions, and links. Our interest is focused on the two latter levels: Using virtual channels (VCs) and virtual paths (VPs) as the managed entities on the two levels respectively, we put forward a simple and robust strategy for traffic management in real time: All nodes simultaneously monitor offered traffics and forward the result to a network management centre (NMC); The NMC computes a new set of optimal VPs and compares the result to the existing network; If a change appears profitable, the necessary information is sent back to the nodes and the new design is implemented. Applying our strategy to control general networks subject to traffics which in advance are known only as expectations, we develop simple methods for traffic observation, the optimal observation interval, a fast and efficient algorithm to compute VP networks, a test to determine whether to implement a new design in which costs related to lost traffic are compared to processing costs, and the optimal updating interval. Running our strategy in a simulator, we discover a considerable adaptivity, large savings in transmission capacity, and a performance far better than achieved by fixed redesign according to forecasts. Finally we discuss limits to the range of variations within which our strategy can be applied. The present work applies both to networks using SDH/SONET and/or networks based on ATM, i.e. both to present public switched telephony networks and broadband inte- grated services digital networks, and is a summary and extension of earlier works within this area [3{9].
|
|
| 37. |
- Arvidsson, Åke, 1957-, et al.
(författare)
-
Load transients in pooled cellular core network nodes
- 2015
-
Ingår i: Performance evaluation (Print). - 0166-5316 .- 1872-745X. ; 90, s. 18-35
-
Tidskriftsartikel (refereegranskat)abstract
- The coverage areas of cellular networks are logically subdivided into service areas. Each service area has a local anchor node which “hides” the mobility inside the area and the entire network has a global anchor node which “hides” the mobility between areas.The concept of unique local anchor nodes per service area was invented to simplify routing but has been found to complicate expansion. The rapidly growing demand for cellular access has therefore prompted for alternative solutions with pools of local anchor nodes per service area. Such pools are now deployed by several operators all over the world.Users in pooled service areas are mapped to specific pool members according to a load distribution policy, but the mapping can change as a result of node failures or operator interventions. Such changes take a certain time to implement and cause additional load on the anchor nodes. We study these processes in detail and derive closed form expressions which allow operators to control the trade-off between rapid changes and acceptable loads.Finally we show that the key assumptions of our model are in agreement with measured data and demonstrate how the model can be applied to investigate the effects of different network settings (timers) under different user behaviour (traffic and mobility).Contrary to current solutions to this problem, which typically are slow and/or inaccurate, our results enable fast and accurate analysis of different scenarios thereby enabling operators to maximise utilisation of the existing investments and at the same time avoid potentially dangerous situations of overload.
|
|
| 38. |
- Arvidsson, Åke, et al.
(författare)
-
Load transients in pooled cellular core network nodes
- 2015
-
Ingår i: Performance evaluation (Print). - : Elsevier BV. - 0166-5316 .- 1872-745X. ; 90, s. 18-35
-
Tidskriftsartikel (refereegranskat)abstract
- The coverage areas of cellular networks are logically subdivided into service areas. Each service area has a local anchor node which “hides” the mobility inside the area and the entire network has a global anchor node which “hides” the mobility between areas. The concept of unique local anchor nodes per service area was invented to simplify routing but has been found to complicate expansion. The rapidly growing demand for cellular access has therefore prompted for alternative solutions with pools of local anchor nodes per service area. Such pools are now deployed by several operators all over the world. Users in pooled service areas are mapped to specific pool members according to a load distribution policy, but the mapping can change as a result of node failures or operator interventions. Such changes take a certain time to implement and cause additional load on the anchor nodes. We study these processes in detail and derive closed form expressions which allow operators to control the trade-off between rapid changes and acceptable loads. Finally we show that the key assumptions of our model are in agreement with measured data and demonstrate how the model can be applied to investigate the effects of different network settings (timers) under different user behaviour (traffic and mobility). Contrary to current solutions to this problem, which typically are slow and/or inaccurate, our results enable fast and accurate analysis of different scenarios thereby enabling operators to maximise utilisation of the existing investments and at the same time avoid potentially dangerous situations of overload.
|
|
| 39. |
- Arvidsson, Åke
(författare)
-
Management of Reconfigurable Virtual Path Networks
- 1994
-
Ingår i: The Fundamental Role of Teletraffic in the Evolution of Telecommunication Networks. - Amsterdam : Elsevier. - 9920106445 ; , s. 931-940
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- We study dynamically rearrangable end-to-end transport networks by means of SDH/SONET and/or ATM virtual paths. The concept and its advantages are brie y reviewed and we propose a new algorithm for designing such networks. Our algorithm provides integer solutions, handles non-linear equivalent bandwidths, finds its own paths, and allows for an arbitrary design optimisation criterion. It is found to perform equal to or better than an earlier, comparable though more restricted, algorithm. We also put forward a strategy for managing virtual paths in real time. It consists of a repeated cycle of on-line measurement of offered traffics followed by the design and implementation of a new virtual path network. Methods and parameters for traffic measurements and network updating frequency are studied and optimised. Applying the strategy to rearrangeable networks subject to variable traffics in a simulator, we discover considerable gains and a robustness in our parameter settings.
|
|
| 40. |
- Arvidsson, Åke, 1957-, et al.
(författare)
-
Modelling user experience of adaptive streaming video over fixed capacity links
- 2021
-
Ingår i: Performance evaluation (Print). - 0166-5316 .- 1872-745X. ; 148, s. 1-12
-
Tidskriftsartikel (refereegranskat)abstract
- Streaming video continues to experience unprecedented growth. This underscores the need to identify user-centric performance measures and models that will allow operators to satisfy requirements for cost-effective network dimensioning delivered with an acceptable level of user experience. This paper presents an analysis of two novel metrics in the context of fixed capacity links: (i) the average proportion of a video’s playing time during which the quality is reduced and (ii) the average proportion of videos which experience reduced quality at least once during their playing time, based on an M/M/∞ system. Our analysis is shown to hold for the more general M/G/∞ system for metric (i), but not for (ii) and simulation studies show an unexpected form of sensitivity of metric (ii) to the flow duration distribution, contrary to the norm of increasing variance causing worse performance. At typical operational loads these new metrics provide a more sensitive and information rich guide for understanding how user experience degrades, than the widely used average throughput metric does. We further show that only the combined use of this existing and our new metrics can provide a holistic perspective on overall user performance.
|
|
| 41. |
- Arvidsson, Åke, et al.
(författare)
-
Modelling user experience of adaptive streaming video over fixed capacity links
- 2021
-
Ingår i: Performance evaluation (Print). - : Elsevier BV. - 0166-5316. ; 148, s. 1-12
-
Tidskriftsartikel (refereegranskat)abstract
- Streaming video continues to experience unprecedented growth. This underscores the need to identify user-centric performance measures and models that will allow operators to satisfy requirements for cost-effective network dimensioning delivered with an acceptable level of user experience. This paper presents an analysis of two novel metrics in the context of fixed capacity links: (i) the average proportion of a video’s playing time during which the quality is reduced and (ii) the average proportion of videos which experience reduced quality at least once during their playing time, based on an M/M/∞ system. Our analysis is shown to hold for the more general M/G/∞ system for metric (i), but not for (ii) and simulation studies show an unexpected form of sensitivity of metric (ii) to the flow duration distribution, contrary to the norm of increasing variance causing worse performance. At typical operational loads these new metrics provide a more sensitive and information rich guide for understanding how user experience degrades, than the widely used average throughput metric does. We further show that only the combined use of this existing and our new metrics can provide a holistic perspective on overall user performance.
|
|
| 42. |
- Arvidsson, Åke
(författare)
-
On Dynamic Capacity Management in Voice/Frame Relaying Networks
- 1992
-
Konferensbidrag (refereegranskat)abstract
- We consider call admission and capacity management in a dynamically reconfigurable network that carries a multitude of traffics. Our approach is a heuristic capacity as- signment algorithm designed to maximise an arbitrary profit function. The algorithm is based on the concept of equivalent circuits, i.e. a given relationship between transmis- sion capacities and call handling capabilities expressed as effective numbers of circuits. Such relationships are examined for the two traffics of our application, voice and frame relaying. Methods and results are independent of the transfer mode used.
|
|
| 43. |
- Arvidsson, Åke
(författare)
-
On the Usage of Virtual Paths, Virtual Channels, and Buffers in ATM Traffic Management
- 1995
-
Konferensbidrag (refereegranskat)abstract
- Traffic in ATM networks can be described by numerous parameters. On a per session basis, one may use peak rate, average rate, sustainable rate, average burst duration, average silence duration, and others. In a longer time scale, parameters like the average and peakedness of connection request interarrival times, the average and variance of session holding times, and so on are proposed. Theoretically, users should provide the former parameters and network operators the latter. In reality, however, few users can be expected to provide all sorts of statistical information about their traffic in advance, and operators do not have enough experience to prepare traffic forecasts for new services and applications. Moreover, even if the information could be provided, the lack of simple yet valid traffic models for ATM networks means that it is far from clear how such information should be used. Realising that ATM networks, which are already being built, at least for the next few years will have to operate under these uncertain conditions, we propose a robust and forgiving network design and traffic management strategy. The idea is to use only little information about offered traffics and then dynamically control resource allocations, so as to provide acceptable quality of service combined with high utilisation. The network design is based on the idea of keeping congestion at the edges of the net- work, so that the operating areas of fast congestion control mechanisms are minimised. Traffic variations are characterised by a model of six layers, each of which is assigned a corresponding layer in a traffic management model. We define the functionalities of each level in the latter modell and review possible implementations. In particular, we report on an implementation of two of these layers and discuss in some detail how a third one could be added.
|
|
| 44. |
- Arvidsson, Åke, et al.
(författare)
-
On the Validity of Some Markovian Models in ATM Traffic Modelling
- 1995
-
Konferensbidrag (refereegranskat)abstract
- Markov modulated models are often used to model traffic in a network. How well the processes really capture the essentials of real traffic is less known. We review some of these models and apply a number of associated fitting methods to an Ethernet traffic in different timescales. The fitted models are then used as input to a buffer where buffer occupancies are used as a measure of the goodness of the models. Also, the ability of a fitting method to correctly model the traffic when applied to traffic generated from a model that the fitting method was intended for is examined.
|
|
| 45. |
- Arvidsson, Åke, et al.
(författare)
-
Performance Comparison of Bursty Traffic Models
- 1991
-
Konferensbidrag (refereegranskat)abstract
- Models of bursty arrival processes are reviewed and compared with re- spect to their in uence on the performance of a single server system. Considerable variations are found between different models fitted to the same traffic, though some models exhibit similar behaviour. Comparing the ability of the models to reproduce the performance of an explicitly given parcel they all tend to fail.
|
|
| 46. |
|
|
| 47. |
|
|
| 48. |
- Arvidsson, Åke, et al.
(författare)
-
Profit Optimal Congestion Control in Intelligent Networks
- 1997
-
Ingår i: 15th International Teletraffic Congress on Teletraffic Contributions for the Information. - WASHINGTON, DC : ELSEVIER SCIENCE PUBL B V. - 0444825983 ; , s. 911-920
-
Bokkapitel (refereegranskat)abstract
- Current developments in technologies and markets stress the importance of exible and robust performance optimisation and congestion control. In intelligent networks, conges- tion control has traditionally taken a mainly technical view and focused on protecting individual nodes from harmful overloads. We take a profit oriented, network wide view and develop a congestion control mechanism to ensure profit maximisation under real time performance. Numerical studies in a simulator show that the proposed mechanism is robust and, in particular in overloaded states, provides a substantial improvement in comparison to conventional load control mechanisms.
|
|
| 49. |
- Arvidsson, Åke
(författare)
-
Real Time Management of Virtual Paths
- 1994
-
Konferensbidrag (refereegranskat)abstract
- We propose a simple and robust automatic strat- egy for managing SDH/SONET and/or ATM virtual paths in real time to handle slow traffic variations. It consists of on-line measurements of offered traffics followed by the design and possi- ble implementation of a new virtual path network in a repeated cycle. Methods and parameters for traffic measurements and network updating are studied and optimised to achieve maximal traffic carrying capability at minimal cost. Applying our strat- egy to networks subject to partially unknown, variable traffics we discover a considerable adaptivity, large savings in transmis- sion capacity, and a performance far better than achieved by deterministic management.
|
|
| 50. |
- Arvidsson, Åke
(författare)
-
Real Time Traffic Management by Dynamic Bandwidth Allocation
- 1995
-
Konferensbidrag (refereegranskat)abstract
- We introduce a six layer model of traffic variations and a corresponding model of management actions. In particular, we traffic study real time traffic management on the traffic and session levels which correspond to variations on the hour and minute levels. Using virtual paths (VPs) and virtual channels (VCs) as the managed entities on the two levels respectively, we put forward a simple and robust strategy for traffic management in real time: For slow variations, i.e. on the traffic level, all nodes simultaneously monitor offered traffics and forward the result to a network management centre (NMC); The NMC computes a new set of optimal VPs compares the result to the existing network; If a change appears profitable, the necessary information is sent back to the nodes and the new design is implemented. For fast variations, i.e. on the session level, dynamic routing schemes similar to those of public switched telephone networks are employed. Applying our strategy to control general networks subject to traffics which in advance are known only as expectations, we develop simple methods for traffic observation, derive the optimal observation interval, brie y review algorithms to compute VP networks, develop a cost optimal test to determine whether to implement a new design or not, and derive the optimal updating interval. Running our strategy in a simulator, we discover a considerable adaptivity and a performance far better than obtained by alternative methods.
|
|
