Browsing by Author "Ahmad, Shakeel"
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Item Open Access Adaptive unicast video streaming with rateless codes and feedback.(IEEE, 2010-02) Ahmad, Shakeel; Hamzaoui, Raouf; Al-Akaidi, Marwan, 1959-Video streaming over the Internet and packet-based wireless networks is sensitive to packet loss, which can severely damage the quality of the received video. To protect the transmitted video data against packet loss, application-layer forward error correction (FEC) is commonly used. Typically, for a given source block, the channel code rate is fixed in advance according to an estimation of the packet loss rate. However, since network conditions are difficult to predict, determining the right amount of redundancy introduced by the channel encoder is not obvious. To address this problem, we consider a general framework where the sender applies rateless erasure coding to every source block and keeps on transmitting the encoded symbols until it receives an acknowledgment from the receiver indicating that the block was decoded successfully. Within this framework, we design transmission strategies that aim at minimizing the expected bandwidth usage while ensuring successful decoding subject to an upper bound on the packet loss rate. In real simulations over the Internet, our solution outperformed standard FEC and hybrid ARQ approaches. For the QCIF Foreman sequence compressed with the H.264 video coder, the gain in average peak signal to noise ratio over the best previous scheme exceeded 3.5 decibels at 90 kilobits per second.Item Metadata only Bayesian Early Mode Decision Technique for View Synthesis Prediction-Enhanced Multiview Video Coding(IEEE, 2013-11) Khattak, Shadan; Hamzaoui, Raouf; Maugey, Thomas; Ahmad, Shakeel; Frossard, PascalView synthesis prediction (VSP) is a codingmode that predicts video blocks from synthesised frames. It is particularly useful in a multi-camera setup with large inter-camera distances. Adding a VSP-based SKIP mode to a standard Multiview Video Coding (MVC) framework improves the rate-distortion (RD) performance but increases the time complexity of the encoder. This letter proposes an earlymode decision technique for VSP SKIP-enhanced MVC. Our method uses the correlation between the RD costs of the VSP SKIP mode in neighbouring views and Bayesian decision theory to reduce the number of candidate coding modes for a given macroblock. Simulation results showed that our technique can save up to 36.20% of the encoding time without any significant loss in RD performance.Item Open Access The community network game project: Enriching online gamers experience with user generated content.(IARIA, 2010-11) Ahmad, Shakeel; Bouras, Christos; Hamzaoui, Raouf; Papazois, Andreas; Perelman, Erez; Shani, Alex; Simon, Gwendal; Tsichritzis, GeorgeOne of the most attractive features of Massively Multiplayer Online Games (MMOGs) is the possibility for users to interact with a large number of other users in a variety of collaborative and competitive situations. Gamers within an MMOG become members of active communities with common interests and shared adventures. The EU-funded Community Network Game (CNG) project will provide MMOG players new tools for the generation, distribution, and insertion of user generated content (UGC) without changing the game code and without adding new processing or network loads to the MMOG central servers. The UGC considered by the CNG project includes 3D objects and graphics as well as video. We present the objectives of the project, focusing on its main scientific and technological contributions.Item Metadata only Community tools for massively multiplayer online games(2011-11) Ahmad, Shakeel; Bouras, Christos; Hamzaoui, Raouf; Liu, Jiayi; Papazois, Andreas; Perelman, Erez; Shani, Alex; Simon, Gwendal; Tsichritzis, GeorgeOne of the most attractive features of Massively Multiplayer Online Games (MMOGs) is the possibility for users to interact with a large number of other users in a variety of collaborative and competitive situations. Gamers within an MMOG typically become members of active communities with mutual interests, shared adventures, and common objectives. We present the EU funded Community Network Game (CNG) project. The CNG project provides tools to enhance collaborative activities between online gamers and offers new tools for the generation, distribution and insertion of user-generated content in MMOGs. CNG allows the addition of new engaging community services without changing the game code and without adding new processing or network loads to the MMOG central servers. The user-generated content considered by the CNG project includes 3D objects and graphics, as well as screen-captured live video of the game, which is shared using peer-to-peer technology. We survey the state of the art in all areas related to the project and present its concept, objectives, and innovations.Item Open Access Efficient Broadcasting for Route Discovery in Mobile Ad-hoc Networks(International Symposium on Performance Evaluation of Computer and Telecommunication Systems (SPECTS), 2014) Adarbah, H. Y.; Ahmad, Shakeel; Arafeh, B.; Duffy, A. P.Broadcasting is used in on-demand routing protocols to discover routes in Mobile Ad-hoc Networks (MANETs). On-demand routing protocols, such as AODV (Ad-hoc On-demand Distance Vector) routing, commonly employ pure flooding based broadcasting. However, pure flooding generates excessively redundant routing traffic that may lead to broadcast storm problem (BSP) and deteriorate the performance of MANETs significantly. Probabilistic broadcasting schemes were proposed in the literature to address BSP. However, these schemes do not consider thermal noise and interference which exist in real life MANETs, and therefore, do not perform well in real life MANETs. This paper presents a novel Channel Adaptive Probabilistic Broadcast (CAPB) scheme to disseminate RREQ packets efficiently. The proposed CAPB scheme determines the probability of rebroadcasting RREQ packets on the fly according to the current SINR (Signal to Interference plus Noise Ratio) and node density in the neighborhood. The proposed scheme and two related state of the art (SoA) schemes from the literature ( [1] and [2]) are implemented in the standard AODV routing protocol to replace the pure flooding based broadcast. Simulation results show that the proposed scheme outperforms the standard AODV and the two competitors in terms of routing overhead, throughput and end-to-end delay significantly.Item Open Access Enhanced Collision Resolution and Throughput Analysis for the 802.11 Distributed Coordination Function(Wiley, 2021-08) Kobbaey, Thaeer; Hamzaoui, Raouf; Ahmad, Shakeel; Al-Fayoumi, Mustafa; Thomos, NikolaosThe IEEE 802 standards rely on the distributed coordination function (DCF) as the fundamental medium access control method. DCF uses the binary exponential backoff (BEB) algorithm to regulate channel access. The backoff time determined by BEB depends on a contention window (CW) whose size is doubled if a station suffers a collision and reset to its minimum value after a successful transmission. Doubling the size of CW reduces channel access time, which decreases the throughput.Resetting it to its minimum value harms fairness since the station will have a better chance of accessing the channel compared to stations that suffered a collision. We propose an algorithm that addresses collisions without instantly increasing the CW size. Our algorithm aims to reduce the collision probability without affecting the channel access time and delay. We present extensive simulations for fixed and mobile scenarios. The results show that, on average, our algorithm outperforms BEB in terms of throughput and fairness. Compared to exponential increase exponential decrease (EIED), our algorithm improves, on average, throughput and delay performance. We also propose analytical models for BEB, EIED, and our algorithm. Our models extend Bianchi’s popular Markov chain-based model by using a collision probability that is dependent on the station transmission history. Our models provide a better estimation of the probability that a station transmits in a random slot time, which allows a more accurate throughput analysis. Using our models, we show that both the saturation throughput and maximum throughput of our algorithm are higher than those of BEB and EIED.Item Open Access Error resilient packet-switched video telephony with adaptive rateless coding and reference picture selection.(EUROSIS, 2010-12) Dawood, Muneeb; Hamzaoui, Raouf; Ahmad, Shakeel; Al-Akaidi, Marwan, 1959-Providing high-quality video for packet-switched wireless video telephony on hand-held devices is a challenging task due to packet loss, limited available bandwidth, and complexity constraints. We propose a low-complexity channel-adaptive error resilience technique that combines application-layer forward error correction (FEC) with rateless codes, retransmission, and reference picture selection. Experimental results for H.264 video sequences show that the proposed technique achieves significant peak-signal-to-noise ratio (PSNR) and percentage degraded video duration (PDVD) improvements over previous techniques in networks involving two wireless links.Item Open Access Error-resilient packet switched H.264 mobile video telephony with LT coding and reference picture selection.(EURASIP, 2009-08) Dawood, Muneeb; Hamzaoui, Raouf; Ahmad, Shakeel; Al-Akaidi, Marwan, 1959-Packet switched video telephony over wireless networks for hand-held devices requires low-delay, low-complexity error control mechanisms to deal with packet loss. We present an efficient solution for 3G networks based on LT coding, reference picture selection, and cross-layer optimization. Experimental results on a 3G network simulator for H.264 compressed standard video sequences show that our method achieves significant peak-signal-to-noise ratio and percentage degraded video duration improvements over a state of the art technique.Item Metadata only Error-resilient packet-switched mobile video telephony with channel-adaptive rateless coding and early reference picture selection(Springer, 2016-02) Dawood, Muneeb; Hamzaoui, Raouf; Ahmad, Shakeel; Al-Akaidi, Marwan, 1959-Providing high-quality video for packet-switched wireless video telephony on handheld devices is a challenging task due to packet loss, varying bandwidth, and end-to-end delay constraints. While many error resilience techniques have been proposed for video transmission over wireless channels, only a few were specifically designed for mobile video telephony. We propose a low-complexity channel-adaptive error resilience technique for packet-switched mobile video telephony, which combines rateless coding, feedback, and reference picture selection. In contrast to previous approaches, our technique uses cumulative feedback at every transmission opportunity and predicts when decoding is likely to fail so that reference picture selection can be triggered at an early stage. Experimental results for H.264 video sequences show that the proposed technique can achieve improvements of 1.64 dB in peak signal-to-noise ratio over benchmark techniques in simulated Long-Term Evolution networks.Item Metadata only Evaluating P2P Live Streaming Systems: the CNG Case(2011-08) Ahmad, Shakeel; Bouras, Christos; Buyukkaya, Eliya; Hamzaoui, Raouf; Kapoulas, Vaggelis; Papazois, Andreas; Shani, Alex; Simon, GwendalMany peer-to-peer (P2P) systems have been proposed for the provision of scalable live video streaming services over the Internet. While the literature contains surveys of the architectures of these systems, there is a lack of work on methodologies for their evaluation. We identify the main issues in the evaluation of P2P live streaming systems and use the Community Network Game (CNG) project as an example to illustrate them. The evaluation of the P2P system consists of two phases: a laboratory one using the ns-2 network simulator and an online field test with Massively Multiplayer Online Games (MMOG) players.Item Metadata only Fast encoding techniques for Multiview Video Coding(Elsevier, 2013) Khattak, Shadan; Hamzaoui, Raouf; Ahmad, Shakeel; Frossard, PascalItem Metadata only Level-based peer-to-peer live streaming with rateless codes(IEEE, 2012) Buyukkaya, Eliya; Ahmad, Shakeel; Dawood, Muneeb; Liu, Jiayi; Zhou, F.; Hamzaoui, Raouf; Simon, G.Item Open Access Low-Complexity Multiview Video Coding(2012-05) Khattak, Shadan; Hamzaoui, Raouf; Ahmad, Shakeel; Frossard, PascalWe consider the problem of complexity reduction in Multiview Video Coding (MVC). We provide a unique comprehensive study that integrates and compares the different low complexity encoding techniques that have been proposed at different levels of the MVC system. In addition, we propose a novel complexity reduction method that takes advantage of the relationship between disparity vectors along time. The relationship is exploited with respect to the motion activity in the frame, as well as with the position of the frame in the Group of Pictures. We integrate this technique into our unique comprehensive framework and evaluate the performance of the resulting system in different setups. We show that the effective combination of complexity reduction techniques results in saving up to 93% in encoding time at the cost of only 0.08 dB in peak signal-to-noise ratio (PSNR) and 1.64% increase in bitrate compared to the standard MVC implementation (JMVM 6.0).Item Metadata only Minimizing server throughput for low-delay live streaming in content delivery networks.(ACM, 2012-06) Zhou, F.; Ahmad, Shakeel; Buyukkaya, Eliya; Hamzaoui, Raouf; Simon, G.Large-scale live streaming systems can experience bottlenecks within the infrastructure of the underlying Content Delivery Network. In particular, the “equipment bottleneck" occurs when the fan-out of a machine does not enable the concurrent transmission of a stream to multiple other equipments. In this paper, we aim to deliver a live stream to a set of destination nodes with minimum throughput at the source and limited increase of the streaming delay. We leverage on rateless codes and cooperation among destination nodes. With rateless codes, a node is able to decode a video block of k information symbols after receiving slightly more than k encoded symbols. To deliver the encoded symbols, we use multiple trees where inner nodes forward all received symbols. Our goal is to build a diffusion forest that minimizes the transmission rate at the source while guaranteeing on-time delivery and reliability at the nodes. When the network is assumed to be lossless and the constraint on delivery delay is relaxed, we give an algorithm that computes a diffusion forest resulting in the minimum source transmission rate. We also propose an effective heuristic algorithm for the general case where packet loss occurs and the delivery delay is bounded. Simulation results for realistic settings show that with our solution the source requires only slightly more than the video bit rate to reliably feed all nodes.Item Open Access Optimal packet loss protection of progressively compressed 3D meshes(IEEE, 2009-11) Ahmad, Shakeel; Hamzaoui, Raouf; Al-Akaidi, Marwan, 1959-We consider a state of the art system that uses layered source coding and forward error correction with Reed- Solomon codes to efficiently transmit 3D meshes over lossy packet networks. Given a transmission bit budget, the performance of this system can be optimized by determining how many layers should be sent, how each layer should be packetized, and how many parity bits should be allocated to each layer such that the expected distortion at the receiver is minimum. The previous solution for this optimization problem uses exhaustive search, which is not feasible when the transmission bit budget is large.We propose instead an exact algorithm that solves this optimization problem in linear time and space. We illustrate the advantages of our approach by providing experimental results for the CPM (Compressed Progressive Meshes) mesh compression techniqueItem Open Access Peer-to-peer live streaming for massively multiplayer online games(IEEE, 2012-09) Ahmad, Shakeel; Bouras, Christos; Buyukkaya, Eliya; Hamzaoui, Raouf; Papazois, Andreas; Shani, Alex; Simon, Gwendal; Zhou, FenOne of the most attractive features of Massively Multiplayer Online Games (MMOGs) is the possibility for users to interact with a large number of other users in a variety of collaborative and competitive situations. Gamers within an MMOG typically become members of active communities with mutual interests, shared adventures, and common objectives. This demonstration presents a peer-to-peer live video system that enables MMOG players to stream screen-captured video of their game. Players can use the system to show their skills, share experience with friends, or coordinate missions in strategy games.Item Open Access Peer-to-Peer Live Video Streaming with Rateless Codes for Massively Multiplayer Online Games(Springer US, 2016-08-19) Ahmad, Shakeel; Bouras, Christos; Buyukkaya, Eliya; Dawood, Muneeb; Hamzaoui, Raouf; Kapoulas, Vaggelis; Papazois, Andreas; Simon, GwendalWe present a multi-level multi-overlay hybrid peer-to-peer live video system that enables players of Massively Multiplayer Online Games to simultaneously stream the video of their game and watch the game videos of other players. Each live video bitstream is encoded with rateless codes and multiple trees are used to transmit the encoded symbols. Trees are constructed dynamically with the aim to minimize the transmission rate at the source while maximizing the number of served peers and guaranteeing on-time delivery and reliability. ns-2 simulations and real measurements on the Internet show competitive performance in terms of start-up delay, playback lag, rejection rate, used bandwidth, continuity index, and video quality.Item Open Access Practical channel-adaptive video streaming with fountain codes.(IEEE, 2008-10) Ahmad, Shakeel; Hamzaoui, Raouf; Al-Akaidi, Marwan, 1959-Video streaming is sensitive to packet loss, which can severely damage the quality of the received video. Video communication systems that rely on application-layer forward error correction (FEC) to combat packet loss are particularly suitable for pervasive computing because they can be used on top of any existing network architecture. However, since in heterogeneous environments network con- ditions are unpredictable, determining the right amount of redundancy introduced by the channel encoder is not obvious. This paper presents a practical implementation of a unicast video streaming system that solves this problem by using a rateless code and receiver feedback. In real simulations over the Internet our solution outperformed a standard approach based on fixed-rate forward error correction. For an Internet connection Konstanz-Beijing- Konstanz and the standard Foreman sequence compressed with the H.264 video coder, the gain in average peak signal to noise ratio exceeded 3.5 decibels at 90 kilobits per secondItem Metadata only Resource allocation in underprovisioned multioverlay live video sharing services(ACM, 2012-12-10) Ahmad, Shakeel; Buyukkaya, Eliya; Hamzaoui, Raouf; Simon, Gwendal; Liu, JiayiIn a multioverlay live video sharing service consisting of multiple independent peer-to-peer live video streaming systems, a user can simultaneously watch multiple live video streams. A major challenge for such services is the interoverlay bandwidth competition problem, which is to find an upload bandwidth allocation between the overlays each peer has subscribed to. So far, no solution has been proposed in the literature for the important case where the overall system is underprovisioned, that is, when peers do not have enough upload bandwidth to ensure a distribution of videos at full quality. We show that an allocation of upload resources that minimizes the wastage of resources (i.e., minimizes the upload bandwidth allocated to overprovisioned overlays) can be computed in polynomial time. Then we present a generic model that allows the design of different strategies for the management of the resource deficit in underprovisioned systems. Finally, we provide relevant simulation results to demonstrate the gains in video quality resulting from the implementation of our solutions.Item Metadata only Resource allocation in underprovisioned multioverlay peer-to-peer live video sharing services(Springer US, 2014-04) Liu, Jiayi; Ahmad, Shakeel; Buyukkaya, Eliya; Hamzaoui, Raouf; Simon, GwendalMultioverlay peer-to-peer live video streaming systems face the problem of finding a suitable peer upload bandwidth allocation among concurrent overlays. So far, no efficient solution has been proposed for the important case where the overall system is underprovisioned, that is, when peers do not have enough upload bandwidth to ensure video distribution at full quality. We design various objective functions for this upload bandwidth allocation problem and show how optimal solutions can be computed using a bipartite flow network. Simulation results show that our solutions improve on existing algorithms in terms of video quality.