Cross-layer H.264 scalable video downstream delivery over WLANs

Thanks to its in-network drop-based adaptation capabilities, H.264 Scalable Video Coding is perceived as an effective approach for delivering video over networks characterized by sudden large bandwidth fluctuations, such as Wireless LANs. Performance may be boosted by the adoption of application-aware/cross-layer schedulers devised to intelligently drop video data units (NALUs), so that i) decoding dependencies are preserved, and ii) the quality perceived by the end users is maximized. In this paper, we provide a theoretical formulation of a QoE utility-optimal cross-layer scheduling problem for H.264 SVC downlink delivery over WLANs. We show that, because of the unique characteristics of the WLAN MAC operation, this problem significantly differs from related approaches proposed for scheduled wireless technologies, especially when the WLAN carries background traffic in the uplink direction. From these theoretical insights, we derive, design, implement and experimentally assess a simple practical scheduling algorithm, whose performance is very close to the optimal solution

Joint Network and Rate Allocation for Video Streaming over Multiple Wireless Networks

Abstract — We address the problem of video streaming over multiple parallel networks. In the context of multiple users, accessing different types of applications, we are looking for efficient ways of allocating network resources and selecting network paths for each application, in order to maximize the overall systems performance. Our optimization joint problem consists of finding the appropriate application rate allocation and network parameters for each individual user, such that a universal system quality metric is maximized. A specific mapping between the requirements of each considered application and the overall quality metric is introduced, and our results are compared to other solutions based on throughput optimization strategies. The superiority and robustness of our approach is shown through extensive simulations in constant and dynamic systems, when clients can join/leave the access networks. Furthermore, we introduce heuristic algorithms which can obtain good results and are inexpensive in terms of computation and execution time. I

JOINT NETWORK AND RATE ALLOCATION FOR SIMULTANEOUS WIRELESS APPLICATIONS

We address the problem of rate allocation and network/path selection for multiple users, running simultaneous applications over multiple parallel access networks. Our joint optimization problem consists of finding the appropriate application rate allocation and network parameters for each individual user, such that an overall quality metric is maximized. We compare our solution to other solutions based on throughput optimization strategies through extensive simulations, and we show the superiority of our approach. Furthermore, our solution proves to be more robust in dynamic systems, when clients can join/leave the access networks. 1

Application-aware H. 264 scalable video coding delivery over wireless LAN: experimental assessment

This paper is among the first works to document experimental results for application-aware H.264 Scalable Video Coding (SVC) support over wireless LANs. Application-aware support is achieved by introducing a bandwidth throttling device, called Virtual Bottleneck (VBN), before the WLAN access point. Throttling is set to a bandwidth slightly smaller than the actual WLAN capacity (either known or estimated), so that all packet/frame losses occur inside the VBN. Here, loss events are controlled by a scheduling mechanism devised to operate with information taken from the H.264 Network Abstraction Layer Units (NALUs). Despite its relative simplicity, the implemented scheduler exhibits effective video adaptation performance and close to optimal bandwidth efficiency. Setting up the trial was not trivial due to the lack of suitable publicly available tools. We filled this gap by implementing and integrating several separate software modules, e.g., streaming server, NALU dependency filtering, video frame concealment, etc. As a final result, the experimental trial supports the full delivery chain for an SVC stream with the only limitation of an off-line stream conversion for play-out and Peak Signal-To-Noise Ratio (PSNR) measurement purposes, due to the unavailability of real time SVC players

SVEF: an open-source experimental evaluation framework for H.264 scalable video streaming

This paper describes the H.264 scalable video coding streaming evaluation framework (SVEF). This is the first open-source framework for experimental assessment of H.264 scalable video coding (SVC) delivery over real networks. Effectively adapting of the transport of an H.264 SVC stream to time-varying, bandwidth constrained, and loss prone networks is an important research area. However, very little experimental work has been performed due to the unavailability of real-time H.264 SVC players, the limitations of existing decoding software libraries when challenged with network-imparied received SVC streams (e.g., affected by random loss of Network Abstraction Layer Units - NALUs), and the lack of solutions for SVC streaming support. SVEF overcomes these issues by developing missing components and by integrating them in a hybrid online/offline experimental framework. We believe SVEF will be of significant help to the research community interested in experimentally benchmarking their own proposed SVC adaptation approaches and delivery mechanisms. As a proof-of-concept of SVEF, we provide the experimental performance evaluation of an SVC cross-layer in-network scheduler in a wireless LAN hot spot scenario