172 research outputs found

    Adaptive Video Streaming for Wireless Networks with Multiple Users and Helpers

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    We consider the optimal design of a scheduling policy for adaptive video streaming in a wireless network formed by several users and helpers. A feature of such networks is that any user is typically in the range of multiple helpers. Hence, in order to cope with user-helper association, load balancing and inter-cell interference, an efficient streaming policy should allow the users to dynamically select the helper node to download from, and determine adaptively the video quality level of the download. In order to obtain a tractable formulation, we follow a "divide and conquer" approach: i) Assuming that each video packet (chunk) is delivered within its playback delay ("smooth streaming regime"), the problem is formulated as a network utility maximization (NUM), subject to queue stability, where the network utility function is a concave and componentwise non-decreasing function of the users' video quality measure. ii) We solve the NUM problem by using a Lyapunov Drift Plus Penalty approach, obtaining a scheme that naturally decomposes into two sub-policies referred to as "congestion control" (adaptive video quality and helper station selection) and "transmission scheduling" (dynamic allocation of the helper-user physical layer transmission rates).Our solution is provably optimal with respect to the proposed NUM problem, in a strong per-sample path sense. iii) Finally, we propose a method to adaptively estimate the maximum queuing delays, such that each user can calculate its pre-buffering and re-buffering time in order to cope with the fluctuations of the queuing delays. Through simulations, we evaluate the performance of the proposed algorithm under realistic assumptions of a network with densely deployed helper nodes, and demonstrate the per-sample path optimality of the proposed solution by considering a non-stationary non-ergodic scenario with user mobility, VBR video coding.Comment: final version to appear in IEEE Transactions on Communication

    Ontwerp en evaluatie van content distributie netwerken voor multimediale streaming diensten.

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    Traditionele Internetgebaseerde diensten voor het verspreiden van bestanden, zoals Web browsen en het versturen van e-mails, worden aangeboden via één centrale server. Meer recente netwerkdiensten zoals interactieve digitale televisie of video-op-aanvraag vereisen echter hoge kwaliteitsgaranties (QoS), zoals een lage en constante netwerkvertraging, en verbruiken een aanzienlijke hoeveelheid bandbreedte op het netwerk. Architecturen met één centrale server kunnen deze garanties moeilijk bieden en voldoen daarom niet meer aan de hoge eisen van de volgende generatie multimediatoepassingen. In dit onderzoek worden daarom nieuwe netwerkarchitecturen bestudeerd, die een dergelijke dienstkwaliteit kunnen ondersteunen. Zowel peer-to-peer mechanismes, zoals bij het uitwisselen van muziekbestanden tussen eindgebruikers, als servergebaseerde oplossingen, zoals gedistribueerde caches en content distributie netwerken (CDN's), komen aan bod. Afhankelijk van de bestudeerde dienst en de gebruikte netwerktechnologieën en -architectuur, worden gecentraliseerde algoritmen voor netwerkontwerp voorgesteld. Deze algoritmen optimaliseren de plaatsing van de servers of netwerkcaches en bepalen de nodige capaciteit van de servers en netwerklinks. De dynamische plaatsing van de aangeboden bestanden in de verschillende netwerkelementen wordt aangepast aan de heersende staat van het netwerk en aan de variërende aanvraagpatronen van de eindgebruikers. Serverselectie, herroutering van aanvragen en het verspreiden van de belasting over het hele netwerk komen hierbij ook aan bod

    Bayesian learning approach on benefit scale parameter

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    학위논문 (박사) -- 서울대학교 대학원 : 공과대학 협동과정 기술경영·경제·정책전공, 2021. 2. 이종수.본 연구는 혜택기반모형에 혜택 척도 모수를 도입한 혜택척도모형을 제안한다. 혜택척도모형은 정보가 희소한 이산선택실험에서 데이터를 보다 효과적으로 사용할 수 있다는 장점이 있는데, 본 연구에서는 베이지안 학습 방법에 기반하여 의사결정 중요도 정보를 추출하여 모형 추정에 활용하고 구현하는 방법을 보였다. 제안한 혜택척도모형은 표준 다항로짓과 혜택기반모형보다 우수한 모형 적합도를 보였고, 우수한 예측력을 제공하였으며, 우수한 혜택 할당 확률의 수렴을 보였으며, 다른 해석을 제공하였다. 혜택척도모형을 확장한 색인혜택척도모형은 모형 적합도 수준에서 표준 다항로짓에서 개선이 없는 수준이었는데, 이는 속성을 혜택으로 할당되는 방식을 연구자가 가정하는 것에는 신중한 접근이 필요하며, 개인이 속성을 혜택으로 할당하는 방식이 실제로 이질적이라는 증거로 판단된다. 또한, 혜택척도모형에서 척도 모수에 인구통계변수를 포함하여 혜택 차원의 이질성을 포착할 수 있는 가능성을 확인하였다. 본 연구에서는 또한, 한계효용체감의 범위가 혜택 단위 뿐 아니라 전체 효용 단위로도 발생할 수 있음을 보였다.This study proposes a benefit-scale model that introduces the scale parameter to the benefit-based model. The benefit-scale model has the advantage of being able to use data more effectively in discrete choice experiments when information is sparse. In this study, we show a method of extracting and implementing decision importance information based on the Bayesian learning method. The proposed benefit scale model shows better model fit, predictive power, and convergence in assignment probabilities than the standard multinomial logit and benefit-based model and provides different interpretations. The indexed benefit-scale model, which is an applied model of the benefit-scale approach, showed no improvement in model fit compared to the standard model. This indicates that a careful approach is required when the researcher assumes that attributes are assigned to benefits, and that assignment probability is indeed heterogeneous. In addition, the possibility of capturing the heterogeneity in scale was tested and confirmed by including demographic variables in the scale parameter. It was also shown in this study that satiation can take place in both benefit level and utility-as-a-whole level. For empirical validation of the model, Over-the-top(OTT) service data and alternative fuel vehicle data were used. This study provides service planning implications for IPTV or cable TV service operators and product planning implications for electric vehicle manufacturers.Abstract v Contents vii List of Tables xi List of Figures xiv Chapter 1. Introduction 1 1.1 Research background 1 1.2 Research objective 3 1.3 Research outline 3 Chapter 2. Literature Review 4 2.1 Choice Theories and Models 4 2.1.1 Valuation Rules 8 2.1.2 Integration Rules 10 2.1.3 Choice Rules 16 2.2 Satiation 21 2.3 Factor Approach 23 2.4 Research Motivation 26 Chapter 3. Model 28 3.1 Benefit-based Model 28 3.1.1 Overview of the Model 28 3.1.2 Model Specification 29 3.1.3 Schematic illustration of the Model 32 3.1.4 Estimation procedure 36 3.2 Satiation in utility level model 37 3.2.1 Model specification 37 3.2.2 Estimation procedure 38 3.3 Benefit-scale Model 39 3.3.1 Overview of the Model 39 3.3.2 Model specification 41 3.3.3 Estimation Procedure 42 3.4 Indexed Benefit-scale model 44 3.4.1 Overview of the Model 44 3.4.2 Estimation Procedure 44 3.5 Demographic Indexed Benefit-scale Model 47 3.5.1 Model Specification 47 3.5.2 Estimation Procedure 47 Chapter 4. Empirical Studies 50 4.1 The Study on OTT services 50 4.1.1 Introduction 50 4.1.2 Data 51 4.1.3 MNL & Benefit-based(BB) Model: Estimation Results 55 4.1.4 Satiation in Utility(SU) Model: Estimation Results 62 4.1.5 Benefit-scale(BS) Model: Estimation Results 65 4.1.6 Indexed Benefit-scale(IBS) Model: Estimation Results 74 4.1.7 Demographic Indexed Benefit-scale(DIBS) Model: Results 77 4.1.8 Conclusion and Implications 80 4.2 The Study on Alternative Fuel Vehicle 85 4.2.1 Introduction 85 4.2.2 Data 86 4.2.3 MNL & Benefit-based Model: Estimation Results 92 4.2.4 Satiation in Utility Model: Estimation Results 96 4.2.5 Benefit-scale Model: Estimation Results 99 4.2.6 Indexed Benefit-scale Model: Estimation Results 106 4.2.7 Demographic Indexed Benefit-scale Model: Results 109 4.2.8 Conclusion and Implications 112 Chapter 5. Summary and Conclusion 116 5.1 Concluding Remarks and Contributions 116 5.2 Limitations and Future Studies 117 Bibliography 118 Appendix 1: Improvement in convergence of assignment probability 133 Appendix 2: Discussion on existence of local solutions 134 Appendix 3: Discussion on sensitivity of scale parameters prior 135 Appendix 4: Discrete Choice Experiment questionnaire: OTT service 137 Appendix 5: Discrete Choice Experiment questionnaire: Alternative Fuel Vehicle 141 Abstract (Korean) 145Docto

    An evaluation of SMOS L-band vegetation optical depth (L-VOD) data sets:high sensitivity of L-VOD to above-ground biomass in Africa

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    The vegetation optical depth (VOD) measured at microwave frequencies is related to the vegetation water content and provides information complementary to visible/infrared vegetation indices. This study is devoted to the characterization of a new VOD data set obtained from SMOS (Soil Moisture and Ocean Salinity) satellite observations at L-band (1.4 GHz). Three different SMOS L-band VOD (LVOD) data sets (SMOS level 2, level 3 and SMOS-IC) were compared with data sets on tree height, visible/infrared indexes (NDVI, EVI), mean annual precipitation and above-ground biomass (AGB) for the African continent. For all relationships, SMOS-IC showed the lowest dispersion and highest correlation. Overall, we found a strong (R > 0.85) correlation with no clear sign of saturation between L-VOD and four AGB data sets. The relationships between L-VOD and the AGB data sets were linear per land cover class but with a changing slope depending on the class type, which makes it a global non-linear relationship. In contrast, the relationship linking L-VOD to tree height (R = 0.87) was close to linear. For vegetation classes other than evergreen broadleaf forest, the annual mean of L-VOD spans a range from 0 to 0.7 and it is linearly correlated with the average annual precipitation. SMOS L-VOD showed higher sensitivity to AGB compared to NDVI and K/X/C-VOD (VOD measured at 19, 10.7 and 6.9 GHz). The results showed that, although the spatial resolution of L-VOD is coarse (similar to 40 km), the high temporal frequency and sensitivity to AGB makes SMOS L-VOD a very promising indicator for large-scale monitoring of the vegetation status, in particular biomass

    Mathematical analysis of scheduling policies in peer-to-peer video streaming networks

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    Las redes de pares son comunidades virtuales autogestionadas, desarrolladas en la capa de aplicación sobre la infraestructura de Internet, donde los usuarios (denominados pares) comparten recursos (ancho de banda, memoria, procesamiento) para alcanzar un fin común. La distribución de video representa la aplicación más desafiante, dadas las limitaciones de ancho de banda. Existen básicamente tres servicios de video. El más simple es la descarga, donde un conjunto de servidores posee el contenido original, y los usuarios deben descargar completamente este contenido previo a su reproducción. Un segundo servicio se denomina video bajo demanda, donde los pares se unen a una red virtual siempre que inicien una solicitud de un contenido de video, e inician una descarga progresiva en línea. El último servicio es video en vivo, donde el contenido de video es generado, distribuido y visualizado simultáneamente. En esta tesis se estudian aspectos de diseño para la distribución de video en vivo y bajo demanda. Se presenta un análisis matemático de estabilidad y capacidad de arquitecturas de distribución bajo demanda híbridas, asistidas por pares. Los pares inician descargas concurrentes de múltiples contenidos, y se desconectan cuando lo desean. Se predice la evolución esperada del sistema asumiendo proceso Poisson de arribos y egresos exponenciales, mediante un modelo determinístico de fluidos. Un sub-modelo de descargas secuenciales (no simultáneas) es globalmente y estructuralmente estable, independientemente de los parámetros de la red. Mediante la Ley de Little se determina el tiempo medio de residencia de usuarios en un sistema bajo demanda secuencial estacionario. Se demuestra teóricamente que la filosofía híbrida de cooperación entre pares siempre desempeña mejor que la tecnología pura basada en cliente-servidor

    Enabling Large-Scale Peer-to-Peer Stored Video Streaming Service with QoS Support

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    This research aims to enable a large-scale, high-volume, peer-to-peer, stored-video streaming service over the Internet, such as on-line DVD rentals. P2P allows a group of dynamically organized users to cooperatively support content discovery and distribution services without needing to employ a central server. P2P has the potential to overcome the scalability issue associated with client-server based video distribution networks; however, it brings a new set of challenges. This research addresses the following five technical challenges associated with the distribution of streaming video over the P2P network: 1) allow users with limited transmit bandwidth capacity to become contributing sources, 2) support the advertisement and discovery of time-changing and time-bounded video frame availability, 3) Minimize the impact of distribution source losses during video playback, 4) incorporate user mobility information in the selection of distribution sources, and 5) design a streaming network architecture that enables above functionalities.To meet the above requirements, we propose a video distribution network model based on a hybrid architecture between client-server and P2P. In this model, a video is divided into a sequence of small segments and each user executes a scheduling algorithm to determine the order, the timing, and the rate of segment retrievals from other users. The model also employs an advertisement and discovery scheme which incorporates parameters of the scheduling algorithm to allow users to share their life-time of video segment availability information in one advertisement and one query. An accompanying QoS scheme allows reduction in the number of video playback interruptions while one or more distribution sources depart from the service prematurely.The simulation study shows that the proposed model and associated schemes greatly alleviate the bandwidth requirement of the video distribution server, especially when the number of participating users grows large. As much as 90% of load reduction was observed in some experiments when compared to a traditional client-server based video distribution service. A significant reduction is also observed in the number of video presentation interruptions when the proposed QoS scheme is incorporated in the distribution process while certain percentages of distribution sources depart from the service unexpectedly
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