Toufik Ahmed

Bio: Toufik Ahmed is an academic researcher from University of Bordeaux. The author has contributed to research in topics: Video quality & Quality of service. The author has an hindex of 5, co-authored 16 publications receiving 61 citations. Previous affiliations of Toufik Ahmed include L'Abri.

An efficient playout smoothing mechanism for layered streaming in P2P networks

Abstract: Layered video streaming in peer-to-peer (P2P) networks has drawn great interest, since it can not only accommodate large numbers of users, but also handle peer heterogeneity. However, there’s still a lack of comprehensive studies on chunk scheduling for the smooth playout of layered streams in P2P networks. In these situations, a playout smoothing mechanism can be used to ensure the uniform delivery of the layered stream. This can be achieved by reducing the quality changes that the stream undergoes when adapting to changing network conditions. This paper complements previous efforts in throughput maximization and delay minimization for P2P streaming by considering the consequences of playout smoothing on the scheduling mechanisms for stream layer acquisition. The two main problems to be considered when designing a playout smoothing mechanism for P2P streaming are the fluctuation in available bandwidth between peers and the unreliability of user-contributed resources—particularly peer churn. Since the consideration of these two factors in the selection and scheduling of stream layers is crucial to maintain smooth stream playout, the main objective of our smoothing mechanism becomes the determination of how many layers to request from which peers, and in which order. In this work, we propose a playout smoothing mechanism for layered P2P streaming. The proposed mechanism relies on a novel scheduling algorithm that enables each peer to select appropriate stream layers, along with appropriate peers to provide them. In addition to playout smoothing, the presented mechanism also makes efficient use of network resources and provides high system throughput. An evaluation of the performance of the mechanism demonstrates that the proposed mechanism provides a significant improvement in the received video quality in terms of lowering the number of layer changes and useless chunks while improving bandwidth utilization.

COOCHING: Cooperative Prefetching Strategy for P2P Video-on-Demand System

Abstract: Most P2P VoD schemes focused on service architectures and overlays optimization without considering segments rarity and the performance of prefetching strategies As a result, they cannot better support VCR-oriented services Despite the remarkable popularity in VoD systems, there exists no prior work that studies the performance gap between different prefetching strategies In this paper we analyze and understand the performance of different prefetching strategies Our analytical characterization brings us not only a better understanding of several fundamental tradeoffs in prefetching strategies, but also important insights on the design of P2P VoD system On the basis of this analysis, we finally proposed a cooperative prefetching strategy namely "COOCHING"In this strategy, the segments requested in VCR interactivities are prefetched into session beforehand using the information collected through gossips

Delivering scalable video coding using P2P Small-World based push-pull mechanism

Abstract: Peer-to-Peer (P2P) networks have proven to enable large-scale content distribution over the Internet thanks to peers organization in overlays. However, real-time content delivery such as live and video on demand (VoD) streaming applications requires significant consideration in term of peer organization to provide concurrent users with adequately satisfying viewing experiences. In this paper, we present an adaptive video streaming mechanism that constructs overlay networks based on Small-World (SW) of peers. Our approach combines the key characteristics of P2P push and pull mechanisms to improve the packet delivery ratio and the overall quality of service. Furthermore, we tackle peer heterogeneity using scalable video coding (SVC) that is considered more promising for real-time applications over heterogeneous networks. Our mechanism is evaluated and compared with existing approach. The obtained results show the effectiveness of the proposed overlay organization in term of lowering the packet loss ratio and the delay jitter. This proves the application of our mechanism to live and VoD delivery.

On the optimal scheduling in pull-based real-time P2P streaming systems: Layered and non-layered streaming

Abstract: During the last decade, we witnessed a rapid growth in deployment of pull-based P2P streaming applications. In these applications, each node selects some other nodes as its neighbors and requests streaming data from them. This scheme allows eliminating data redundancy and recovering from data loss, but it pushes the complexity to the receiver node side. In this paper, we theoretically study the scheduling problem in pull-based P2P video streaming and we model it as an assignment problem. Then, we propose AsSched, new scheduling algorithm for layered streaming, in order to optimize the throughput and the delivery ratio of the system. In second time, we derive an optimal algorithm (NAsSched) for non layered streaming. The results of simulations show that our algorithms significantly outperform classic scheduling strategies especially in stern bandwidth constraints.

SWOR: An Architecture for P2P Scalable Video Streaming Using Small World Overlay

Abstract: In this paper we propose SWOR, an architecture to deliver Scalable Video Coding (SVC) contents over P2P network. SWOR architecture is based on twofold mechanisms: (1) organization of peers in Small-World (SW) overlay networks, (2) delivering SVC content using push-pull mechanism. SWOR is evaluated and compared with CoolStreaminglDONet (CS) on QoS metrics using NS-2 simulator. Performance evaluation demonstrates that SWOR outperforms CS and provides a significant improvement in the received video quality in terms of lowering the packet loss and transmission delay.

Fixed Point Theory and Applications

Abstract: Preface On the Semilocal Convergence of Newton's Method Under Unifying Conditions Inequalities and Fixed Points in Menger Convex Metric Spaces Applications of the Perov's Fixed Point Theorem to Delay Integro-Differential Equations On Vector Equilibrium Problems with Multifunctions Fixed Points in Generalised Metric Spaces and the Stability of a Cubic Functional Equation Continuous Selection and Coincidence Theorems on Product G-Convex Space Sensitivity Analysis of Solution Set for a New Class of Generalised Implicit Quasi-Variational Inclusions Fixed Points in Probabilistic-Quasi-Metric Spaces Common Fixed Point Theorems for Condensed Mappings The Strongly Convergence Theorems of Fixed Points for Local Strictly F-Pseudocontractive On Generalised Non-linear Variational Inequalities A Note on a Paper of Hadic and Pap The Ishiwaka and Mann Iteration Methods On Certain Applications of Leray-Schauder Alternate Remarks on Concepts of Generalised Convex Spaces Generic Existence and Non-Existence of Approximate Fixed Points General System of Relaxed g-?-r-Pseudococoercive Non-linear Variational Inequalities and Projection Methods Three-Step Iteration Methods with Errors for Non-expansive Mappings in Uniformly Convex Banach Spaces On Nonnegative Linear Composite Games of NTU-Game Probabilistic Contractor and Non-linear Operator Equations with Set-Valued Operator in Probabilistic Normed Spaces Index.

A Survey and Synthesis of User Behavior Measurements in P2P Streaming Systems

Abstract: In terms of scalability, cost and ease of deployment, the Peer-to-Peer (P2P) approach has emerged as a promising solution for video streaming applications. Its architecture enables end-hosts, called peers, to relay the video stream to each other. P2P systems are in fact networks of users who control peers. Thus, user behavior is crucial to the performance of these systems because it directly impacts the streaming flow. To understand user behavior, several measurement studies have been carried out over different video streaming systems. Each measurement analyzes a particular system focusing on specific metrics and presents insights. However, a single study based on a particular system and specific metrics is not sufficient to provide a complete model of user behavior considering all of its components and the impact of external factors on them. In this paper, we propose a comparison and a synthesis of these measurements. First of all, we review video streaming architectures, followed by a survey on the user behavior measurements in these architectures. Then, we gather insights revealed in these measurements and compare them for consensual and contrasting points. Finally, we extract components of user behavior, their external impacting factors and relationships among them. We also point out those aspects of user behavior which require further investigations.

Performance analysis of the Libswift P2P streaming protocol

Abstract: Video distribution is nowadays the dominant source of Internet traffic, and recent studies show that it is expected to reach 90% of the global consumer traffic by the end of 2015. Peer-to-peer assisted solutions have been adopted by many content providers with the aim of improving the scalability and reliability of their distribution network. While many solutions have been proposed, virtually all of them are at the overlay level, and so rely on the standard functionality of the transport layer. The Peer-to-Peer Streaming Protocol workgroup of the IETF has adopted the Libswift transport-layer protocol that is targeted at P2P traffic. In this paper we describe the design features and a first implementation of the Libswift protocol, and a piece-picking protocol that uses the transport features of Libswift in an essential way. We investigate its performance on both high-end and power-constrained low-end devices, comparing it to the state-of-the-art in P2P protocols.

Zebroid: using IPTV data to support STB-assisted VoD content delivery

Abstract: IPTV, unlike Internet TV, delivers digital TV and multimedia services over IP-based networks with the required level of quality of service (QoS) and quality of experience (QoE). Linear programming channels in IPTV are delivered through multicast, which is highly scalable with the number of subscribers. Video-on-demand (VoD) content, on the other hand, is typically delivered using unicast, which places a heavy load on the VoD servers and all the network components leading to the end-user set-top boxes (STBs) as the demand increases. With the rapid growth of IPTV subscribers and the shift in video viewing habits, the need to efficiently disseminate large volumes of VoD content has prompted IPTV service providers to consider the use of STBs to assist in video content delivery. This paper describes our current research work on Zebroid, a potential VoD solution for fiber-to-the-node (FTTN) networks, which uses IPTV data on a recurring basis to determine how to select, stripe, and preposition popular content in selected STBs during idle hours. A STB requesting VoD content during the peak hours can then receive necessary stripes from participating STBs in the neighborhood. Recent VoD request access patterns, STB availability data, and capacity data on network components are taken into consideration in determining the parameters used in the striping algorithm of Zebroid. We show both by simulation and emulation on a realistic IPTV testbed that the VoD server load can be reduced by more than 70% during peak hours by allocating only 8 GB of storage on each STB. The savings achieved through Zebroid would also allow IPTV service providers to add more linear programming channels without expensive infrastructure upgrades.

Avoiding Quality Bottlenecks in P2P Adaptive Streaming

Abstract: This paper addresses the problem of quality bottleneck in adaptive SVC streaming. Quality bottleneck occurs in adaptive streaming systems when the desired video quality cannot be obtained even if the network capabilities are sufficient. In the context of SVC layered video streaming, we have observed that enhancement layers remain around the video source and fail to reach all the participating peers. To overcome this problem, we propose an adaptive SVC streaming solution that cooperatively integrates strategies of overlay formation, data scheduling and content adaptation. Performance evaluation using simulations shows that the proposed streaming solution reduces the quality bottleneck, increases churn-tolerance and optimizes bandwidth utilization.