| 1. |
- Almquist, Mathias, et al.
(författare)
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The Prefetch Aggressiveness Tradeof in 360 degrees Video Streaming
- 2018
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Ingår i: PROCEEDINGS OF THE 9TH ACM MULTIMEDIA SYSTEMS CONFERENCE (MMSYS18). - New York, NY, USA : ASSOC COMPUTING MACHINERY. - 9781450351928 ; , s. 258-269
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Konferensbidrag (refereegranskat)abstract
- With 360 degrees video, only a limited fraction of the full view is displayed at each point in time. This has prompted the design of streaming delivery techniques that allow alternative playback qualities to be delivered for each candidate viewing direction. However, while prefetching based on the users expected viewing direction is best done close to playback deadlines, large buffers are needed to protect against shortfalls in future available bandwidth. This results in conflicting goals and an important prefetch aggressiveness tradeoff problem regarding how far ahead in time from the current playpoint prefetching should be done. This paper presents the first characterization of this tradeoff. The main contributions include an empirical characterization of head movement behavior based on data from viewing sessions of four different categories of 360 degrees video, an optimization-based comparison of the prefetch aggressiveness tradeoffs seen for these video categories, and a data-driven discussion of further optimizations, which include a novel system design that allows both tradeoff objectives to be targeted simultaneously. By qualitatively and quantitatively analyzing the above tradeoffs, we provide insights into how to best design tomorrows delivery systems for 360 degrees videos, allowing content providers to reduce bandwidth costs and improve users playback experiences.
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| 2. |
- Borghol, Youmna, et al.
(författare)
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Characterizing and modelling popularity of user-generated videos
- 2011
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Ingår i: Performance evaluation (Print). - : Elsevier. - 0166-5316 .- 1872-745X. ; 68:11, s. 1037-1055
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Tidskriftsartikel (refereegranskat)abstract
- This paper develops a framework for studying the popularity dynamics of user-generated videos, presents a characterization of the popularity dynamics, and proposes a model that captures the key properties of these dynamics. We illustrate the biases that may be introduced in the analysis for some choices of the sampling technique used for collecting data; however, sampling from recently-uploaded videos provides a dataset that is seemingly unbiased. Using a dataset that tracks the views to a sample of recently-uploaded YouTube videos over the first eight months of their lifetime, we study the popularity dynamics. We find that the relative popularities of the videos within our dataset are highly non-stationary, owing primarily to large differences in the required time since upload until peak popularity is finally achieved, and secondly to popularity oscillation. We propose a model that can accurately capture the popularity dynamics of collections of recently-uploaded videos as they age, including key measures such as hot set churn statistics, and the evolution of the viewing rate and total views distributions over time.
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| 3. |
- Borghol, Youmna, et al.
(författare)
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The Untold Story of the Clones: Content-agnostic Factors that Impact YouTube Video Popularity
- 2012
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Ingår i: Proc. ACM SIGKDD Conference on Knowledge Discovery and Data Mining (KDD) 2012. - New York, NY, USA : Association for Computing Machinery (ACM). - 9781450314626 ; , s. 1186-1194
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Konferensbidrag (refereegranskat)abstract
- Video dissemination through sites such as YouTube can have widespread impacts on opinions, thoughts, and cultures. Not all videos will reach the same popularity and have the same impact. Popularity differences arise not only because of differences in video content, but also because of other "content-agnostic" factors. The latter factors are of considerable interest but it has been difficult to accurately study them. For example, videos uploaded by users with large social networks may tend to be more popular because they tend to have more interesting content, not because social network size has a substantial direct impact on popularity.In this paper, we develop and apply a methodology that is able to accurately assess, both qualitatively and quantitatively, the impacts of various content-agnostic factors on video popularity. When controlling for video content, we observe a strong linear "rich-get-richer" behavior, with the total number of previous views as the most important factor except for very young videos. The second most important factor is found to be video age. We analyze a number of phenomena that may contribute to rich-get-richer, including the first-mover advantage, and search bias towards popular videos. For young videos we find that factors other than the total number of previous views, such as uploader characteristics and number of keywords, become relatively more important. Our findings also confirm that inaccurate conclusions can be reached when not controlling for content.
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| 4. |
- Carlsson, Niklas, et al.
(författare)
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Caching and optimized request routing in cloud-based content delivery systems
- 2014
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Ingår i: Performance evaluation (Print). - : Elsevier. - 0166-5316 .- 1872-745X. ; 79, s. 38-55
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Tidskriftsartikel (refereegranskat)abstract
- Geographically distributed cloud platforms enable an attractive approach to large-scale content delivery. Storage at various sites can be dynamically acquired from (and released back to) the cloud provider so as to support content caching, according to the current demands for the content from the different geographic regions. When storage is sufficiently expensive that not all content should be cached at all sites, two issues must be addressed: how should requests for content be routed to the cloud provider sites, and what policy should be used for caching content using the elastic storage resources obtained from the cloud provider. Existing approaches are typically designed for non-elastic storage and little is known about the optimal policies when minimizing the delivery costs for distributed elastic storage.In this paper, we propose an approach in which elastic storage resources are exploited using a simple dynamic caching policy, while request routing is updated periodically according to the solution of an optimization model. Use of pull-based dynamic caching, rather than push-based placement, provides robustness to unpredicted changes in request rates. We show that this robustness is provided at low cost \textendash{} even with fixed request rates, use of the dynamic caching policy typically yields content delivery cost within 10\% of that with the optimal static placement. We compare request routing according to our optimization model to simpler baseline routing policies, and find that the baseline policies can yield greatly increased delivery cost relative to optimized routing. Finally, we present a lower-cost approximate solution algorithm for our routing optimization problem that yields content delivery cost within 2.5\% of the optimal solution.
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| 5. |
- Carlsson, Niklas, et al.
(författare)
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Content Delivery using Replicated Digital Fountains
- 2010
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Ingår i: Proc. IEEE/ACM International Symposium on Modeling, Analysis and Simulation of Computer and Telecommunication Systems (MASCOTS ’10). - : IEEE. - 9780769541976 ; , s. 338-348
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Konferensbidrag (refereegranskat)
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| 6. |
- Carlsson, Niklas, 1977-, et al.
(författare)
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Cross-user Similarities in Viewing Behavior for 360°Video and Caching Implications
- 2023
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Ingår i: ACM Transactions on Multimedia Computing, Communications, and Applications (TOMCCAP). - : ASSOC COMPUTING MACHINERY. - 1551-6857 .- 1551-6865. ; 19:5
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Tidskriftsartikel (refereegranskat)abstract
- The demand and usage of 360°video services are expected to increase. However, despite these services being highly bandwidth intensive, not much is known about the potential value that basic bandwidth saving techniques such as server or edge-network on-demand caching (e.g., in a CDN) could have when used for delivery of such services. This problem is both important and complicated as client-side solutions have been developed that split the full 360°view into multiple tiles, and adapt the quality of the downloaded tiles based on the user’s expected viewing direction and bandwidth conditions. This paper presents new trace-based analysis methods that incorporate users’ viewports (the area of the full 360°view the user actually sees), a first characterization of the cross-user similarities of the users’ viewports, and a trace-based analysis of the potential bandwidth savings that caching-based techniques may offer under different conditions. Our analysis takes into account differences in the time granularity over which viewport overlaps can be beneficial for resource saving techniques, compares and contrasts differences between video categories, and accounts for uncertainties in the network conditions and the prediction of the future viewing direction when prefetching. The results provide substantial insight into the conditions under which overlap can be considerable and caching effective, and inform the design of new caching system policies tailored for 360°video.
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| 7. |
- Carlsson, Niklas, et al.
(författare)
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Ephemeral Content Popularity at the Edge and Implications for On-Demand Caching
- 2017
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Ingår i: IEEE Transactions on Parallel and Distributed Systems. - : IEEE COMPUTER SOC. - 1045-9219 .- 1558-2183. ; 28:6, s. 1621-1634
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Tidskriftsartikel (refereegranskat)abstract
- The ephemeral content popularity seen with many content delivery applications can make indiscriminate on-demand caching in edge networks highly inefficient, since many of the content items that are added to the cache will not be requested again from that network. In this paper, we address the problem of designing and evaluating more selective edge-network caching policies. The need for such policies is demonstrated through an analysis of a dataset recording YouTube video requests from users on an edge network over a 20-month period. We then develop a novel workload modelling approach for such applications and apply it to study the performance of alternative edge caching policies, including indiscriminate caching and cache on kth request for different k. The latter policies are found able to greatly reduce the fraction of the requested items that are inserted into the cache, at the cost of only modest increases in cache miss rate. Finally, we quantify and explore the potential room for improvement from use of other possible predictors of further requests. We find that although room for substantial improvement exists when comparing performance to that of a perfect "oracle" policy, such improvements are unlikely to be achievable in practice.
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| 8. |
- Carlsson, Niklas, et al.
(författare)
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Had You Looked Where Im Looking? Cross-user Similarities in Viewing Behavior for 360 degrees Video and Caching Implications
- 2020
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Ingår i: PROCEEDINGS OF THE ACM/SPEC INTERNATIONAL CONFERENCE ON PERFORMANCE ENGINEERING (ICPE20). - New York, NY, USA : ASSOC COMPUTING MACHINERY. - 9781450369916 ; , s. 130-137
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Konferensbidrag (refereegranskat)abstract
- The demand and usage of 360 degrees video services are expected to increase. However, despite these services being highly bandwidth intensive, not much is known about the potential value that basic bandwidth saving techniques such as server or edge-network on-demand caching (e.g., in a CDN) could have when used for delivery of such services. This problem is both important and complicated as client-side solutions have been developed that split the full 360 degrees view into multiple tiles, and adapt the quality of the downloaded tiles based on the users expected viewing direction and bandwidth conditions. To better understand the potential bandwidth savings that caching-based techniques may offer for this context, this paper presents the first characterization of the similarities in the viewing directions of users watching the same 360 degrees video, the overlap in viewports of these users (the area of the full 360 degrees view they actually see), and the potential cache hit rates for different video categories and network conditions. The results provide substantial insight into the conditions under which overlap can be considerable and caching effective, and can inform the design of new caching system policies tailored for 360 degrees video.
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| 9. |
- Carlsson, Niklas, et al.
(författare)
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Modeling Priority-based Incentive Policies for Peer-assisted Content Delivery Systems
- 2008
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Ingår i: NETWORKING 2008 Ad Hoc and Sensor Networks, Wireless Networks, Next Generation Internet. - Berlin, Heidelberg : Springer Berlin/Heidelberg. - 3540795480 - 9783540795483 ; , s. 421-432
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Bokkapitel (refereegranskat)abstract
- Content delivery providers can improve their service scalability and offload their servers by making use of content transfers among their clients. To provide peers with incentive to transfer data to other peers, protocols such as BitTorrent typically employ a tit-for-tat policy in which peers give upload preference to peers that provide the highest upload rate to them. However, the tit-for-tat policy does not provide any incentive for a peer to stay in the system beyond completion of its download.This paper presents a simple fixed-point analytic model of a priority-based incentive mechanism which provides peers with strong incentive to contribute upload bandwidth beyond their own download completion. Priority is obtained based on a peer's prior contribution to the system. Using a two-class model, we show that priority-based policies can significantly improve average download times, and that there exists a significant region of the parameter space in which both high-priority and low-priority peers experience improved performance compared to with the pure tit-for-tat approach. Our results are supported using event-based simulations.
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| 10. |
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