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Abstract-This paper proposes the use of Adaptive LDPC AL-FEC codes for content download services over erasure channels. In Adaptive LDPC codes, clients inform the content download server of the losses they are experiencing. Using this information, the server makes FEC parity symbols available to the client at an optimum code rate. This paper presents an analytical model of the proposed Adaptive LDPC codes. The model is validated through measurements realized with an application prototype. Additionally, results show the performance of these codes in different scenarios, compared to the performance of nonadaptive AL-FEC, Optimum LDPC AL-FEC codes and an almost ideal rateless code. Adaptive LDPC AL-FEC codes achieve download times similar to almost ideal rateless codes with less coding complexity, at the expense of an interaction channel between server and clients.

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Abstract. Multimedia content adaption strategies are becoming increasingly important for effective video streaming over the actual heterogeneous networks. Thus, evaluation frameworks for adaptive video play an important role in the designing and deploying process of adaptive multimedia streaming systems. This paper describes a novel simulation framework for rate-adaptive video transmission using the Scalable Video Coding standard (H.264/SVC). Our approach uses feedback information about the available bandwidth to allow the video source to select the most suitable combination of SVC layers for the transmission of a video sequence. The proposed solution has been integrated into the network simulator NS-2 in order to support realistic network simulations. To demonstrate the usefulness of the proposed solution we perform a simulation study where a video sequence was transmitted over a three network scenarios. The experimental results show that the Adaptive SVC scheme implemented in our framework provides an efficient alternative that helps to avoid an increase in the network congestion in resource-constrained networks.Improvements in video quality, in terms of PSNR (Peak Signal to Noise Ratio) and SSIM (Structural Similarity Index) are also obtained.

De Fez Lava, I.; Fraile Gil, F.; Belda Ortega, R.; Guerri Cebollada, JC. (2012). Performance evaluation of AL-FEC LDPC codes for push content applications in wireless unidirectional environments. Multimedia Tools and Applications. 60(3):669-688. doi:10.1007/s11042-011-0841-y. that depends on the packet loss rate.

A performance evaluation of real time services (such as video streaming) over mobile ad-hoc networks using both hierarchical and flat routing protocols is showed in this paper. A variety of workload and scenarios, as characterized by mobility, load and size of the ad hoc network have been simulated using NS-2. We use OLSR as the flat routing protocol and our own implementation of HOLSR (which uses HNA messages) as the hierarchical one. We make a complete comparison between these protocols focused on video evaluation. The simulations lets us compare the quality of service (QoS) of the video streaming paying attention to objective parameters (PSNR, packet delivery ratio, packet delay). Results indicate that traffic overload is reduced and video quality is improved using hierarchical protocols.

This paper presents a performance evaluation of the scalable video streaming over mobile ad hoc networks. In particular, we focus on the rate-adaptive method for streaming scalable video (H.264/SVC). For effective adaptation a new cross-layer routing protocol is introduced. This protocol provides an efficient algorithm for available bandwidth estimation. With this information, the video source adjusts its bit rate during the video transmission according to the network state. We also propose a free simulation framework that supports evaluation studies for scalable video streaming. The simulation experiments performed in this study involve the transmission of SVC streams with Medium Grain Scalability (MGS) as well as temporal scalability over different network scenarios. The results reveal that the rate-adaptive strategy helps avoid or reduce the congestion in MANETs obtaining a better quality in the received videos. Additionally, an actual ad hoc network was implemented using embedded devices (Raspberry Pi) in order to assess the performance of the proposed adaptive transmission mechanism in a real environment. Additional experiments were carried out prior to the implementation with the aim of characterizing the wireless medium and packet loss profile. Finally, the proposed approach shows an important reduction in energy consumption, as the study revealed.