Distortion Optimized Multipath Video Streaming

This paper addresses the problem of choosing the best streaming policy for distortion optimal multipath video delivery, under delay constraints. The streaming policy consists in a joint selection of the video packets to be transmitted, as well as their sending time, and the transmission path. A simple streaming model is introduced, which takes into account the video packet importance, and the dependencies among packets, and allows to compute the quality perceived by the receiver, as a function of the streaming policy. We derive an optimization problem based on the video abstraction model, under the assumption that the server knows the state of the network. A detailed analysis of the timing constraints in multipath video streaming provides helpful insights that lead to an efficient algorithm to solve the NP-hard policy optimization problem. We eventually propose a fast heuristic-based algorithm, that still provides close to optimal performance. Thanks to its limited complexity, this novel algorithm is finally implemented in live streaming scenarios, where it only induces a negligible distortion penalty compared to the optimal strategy. Simulation results finally show that the proposed scheduling solutions perform better than common scheduling algorithms, and represent very efficient strategies for both stored and live video streaming scenarios

Packet Selection and Scheduling for Multipath Video Streaming

This paper addresses the problem of choosing the best streaming policy for distortion optimal multipath video delivery, under delay constraints. The streaming policy consists in a joint selection of the video packets to be transmitted, as well as their sending time, and the transmission path. A simple streaming model is introduced, which takes into account the video packet importance, and the dependencies among packets, and allows to compute the quality perceived by the receiver, as a function of the streaming policy. We derive an optimization problem based on the video abstraction model, under the assumption that the server knows, or can predict the state of the network. A detailed analysis of the timing constraints in multipath video streaming provides helpful insights that lead to an efficient algorithm to solve the NP-hard streaming policy optimization problem. We eventually propose a fast heuristic-based algorithm, that still provides close to optimal performance. Thanks to its limited complexity, this novel algorithm is finally demonstrated in live streaming scenarios, where it only induces a negligible distortion penalty compared to an optimal strategy. Simulation results finally show that the proposed scheduling solutions perform better than common scheduling algorithms, and represent very efficient multipath streaming strategies for both stored and live video services

Distributed Media Rate Allocation in Multipath Networks

The paper addresses the media-specific rate allocation problem in multipath networks. The streaming rate on each path is determined such that the end- to-end media distortion is minimized, when the receiving client aggregates packets received via multiple network channels. As it is difficult for the media server to have the full knowledge about the network status, we propose a distributed path selection and rate allocation algorithm. The network nodes participate to the optimization strategy, based on their local view of the network status. This eliminates the need for end-to-end network monitoring, and allows for the deployment of large scale rate allocation solutions. We design an optimal rate allocation algorithm, where the media client iteratively updates the best set of streaming paths. According to this rate allocation, each intermediate nodes then forwards incoming media flows on the outgoing paths, in a distributed manner. The proposed algorithm is shown to quickly converge to the optimal rate allocation solution, and hence to lead to stable rate allocation solutions. We also propose a greedy distributed algorithm that achieves close-to-optimal end-to-end distortion performance in a single pass. Both algorithms are shown to outperform simple heuristic- based rate allocation approaches for numerous random network topologies, and therefore offer an interesting solution for media-specific rate allocation over large scale multi-path networks

Optimal FEC Rate for Media Streaming in Active Networks

This paper addresses the problem of optimal channel rate allocation for media streaming in active networks, where intermediate nodes are able to perform basic FEC decoding/encoding operations. FEC performance is analyzed in the case of hop-by-hop FEC protection, and compared with an end-to-end FEC scenario, in order to demonstrate the benefits of FEC operations in the intermediate nodes. An optimization problem is formulated, based on a distortion model for video streaming over lossy channels. Finally, the two streaming scenarios are compared in the particular case of MPEG-4 video, under a constrained end-to- end delay. FEC operations in intermediate nodes are shown to become especially useful when the links on the streaming path have quite heterogenous characteristics

Media Flow Rate Allocation in Multipath Networks

We address the problem of joint path selection and video source rate allocation in multipath streaming in order to optimize a media specific quality of service. An optimization problem is proposed, which aims at minimizing a video distortion metric based on sequence-dependent parameters, and transmission channel characteristics, for a given network infrastructure.An in-depth analysis of the media distortion evolution allows us to define a low complexity algorithm for an optimal rate allocation in multipath network scenarios. In particular, we show that a greedy allocation of rate along paths with increasing error probability leads to an optimal solution. We argue that a network path shall not be chosen for transmission, unless all other available paths with lower error probability have been chosen. Moreover, the chosen paths should be used at their maximum available end-to-end bandwidth. Simulation results show that the optimal rate allocation carefully trades off total encoding/transmission rate, with the end-to-end transmission error probability and the number of chosen paths. In many cases, the optimal rate allocation provides more than 2

Joint Synchronization, Routing and Energy Saving in Multi-hop Hybrid Networks

Multi-hop hybrid networks can help providing both high bandwidth and broad coverage for wireless data networks. We focus on CSMA/CA-based networks and take IEEE 802.11 as a concrete example. We show that the three fundamental operations of synchronization, routing and energy saving can be implemented in an integrated way. Our integrated solution is based on the periodic computation of a broadcast tree among the nodes reporting to the same Access Point, starting from the Access Point itself. We use the nodes that are tree vertices as relays for both data and control packets. We propose a distributed neighbor discovery protocol and a simple centralized algorithm for computing the broadcast tree. Our analysis and simulation results show that the proposed solution has low protocol overhead in terms of message passing and execution time, and performs well even if nodes are mobile

Forward Error Correction for Multipath Media Streaming

We address the problem of joint optimal rate allocation and scheduling between media source rate and error protection rate in scalable streaming applications over lossy multipath networks. Starting from a distortion representation of the received media information at the client, we propose a novel optimization framework in which we analyze the performance of the most relevant forward error correction and scheduling techniques. We describe both optimal and heuristic algorithms that find solutions to the rate allocation and scheduling problem, and emphasize the main characteristics of the compared techniques. Our results show that efficient unequal error protection schemes improve the quality of the streaming process. At the same time we emphasize the importance of priority scheduling of the information over the best available network paths, which outperforms traditional first-in-first-out models or network flooding mechanisms

Explosion risk assessment for already installed equipment

The equipment of installations for the processing, transport or storage of flammable substances which may generate an explosive atmosphere, in or around them, must be assessed in terms of the risk of explosions, both when they are put into operation or when the installation is modified and periodically for verify that the initial level of protection is maintained. The purpose of the assessment is to establish appropriate protective measures to prevent sources of ignition that could initiate explosive atmospheres. Explosion risk assessment is an obligation of the employer who must draw up an explosion protection document, as regulated in GD 1058/2006 transposing European Directive 1999/92/EC. The explosion risk assessment process focuses primarily on the formation of explosive atmospheres and then on the presence and activation of ignition sources. The principle of explosion protection is to reduce the probability of an ignition source occurring at the same time as the explosive atmosphere, to a minimum acceptable level according to the applicable norms and standards. The paper presents some aspects regarding the evaluation of the risk of explosions to already installed equipment, assembled in an installation, depending on the specific conditions

Height and body-mass index trajectories of school-aged children and adolescents from 1985 to 2019 in 200 countries and territories: a pooled analysis of 2181 population-based studies with 65 million participants

Summary Background Comparable global data on health and nutrition of school-aged children and adolescents are scarce. We aimed to estimate age trajectories and time trends in mean height and mean body-mass index (BMI), which measures weight gain beyond what is expected from height gain, for school-aged children and adolescents. Methods For this pooled analysis, we used a database of cardiometabolic risk factors collated by the Non-Communicable Disease Risk Factor Collaboration. We applied a Bayesian hierarchical model to estimate trends from 1985 to 2019 in mean height and mean BMI in 1-year age groups for ages 5–19 years. The model allowed for non-linear changes over time in mean height and mean BMI and for non-linear changes with age of children and adolescents, including periods of rapid growth during adolescence. Findings We pooled data from 2181 population-based studies, with measurements of height and weight in 65 million participants in 200 countries and territories. In 2019, we estimated a difference of 20 cm or higher in mean height of 19-year-old adolescents between countries with the tallest populations (the Netherlands, Montenegro, Estonia, and Bosnia and Herzegovina for boys; and the Netherlands, Montenegro, Denmark, and Iceland for girls) and those with the shortest populations (Timor-Leste, Laos, Solomon Islands, and Papua New Guinea for boys; and Guatemala, Bangladesh, Nepal, and Timor-Leste for girls). In the same year, the difference between the highest mean BMI (in Pacific island countries, Kuwait, Bahrain, The Bahamas, Chile, the USA, and New Zealand for both boys and girls and in South Africa for girls) and lowest mean BMI (in India, Bangladesh, Timor-Leste, Ethiopia, and Chad for boys and girls; and in Japan and Romania for girls) was approximately 9–10 kg/m2. In some countries, children aged 5 years started with healthier height or BMI than the global median and, in some cases, as healthy as the best performing countries, but they became progressively less healthy compared with their comparators as they grew older by not growing as tall (eg, boys in Austria and Barbados, and girls in Belgium and Puerto Rico) or gaining too much weight for their height (eg, girls and boys in Kuwait, Bahrain, Fiji, Jamaica, and Mexico; and girls in South Africa and New Zealand). In other countries, growing children overtook the height of their comparators (eg, Latvia, Czech Republic, Morocco, and Iran) or curbed their weight gain (eg, Italy, France, and Croatia) in late childhood and adolescence. When changes in both height and BMI were considered, girls in South Korea, Vietnam, Saudi Arabia, Turkey, and some central Asian countries (eg, Armenia and Azerbaijan), and boys in central and western Europe (eg, Portugal, Denmark, Poland, and Montenegro) had the healthiest changes in anthropometric status over the past 3·5 decades because, compared with children and adolescents in other countries, they had a much larger gain in height than they did in BMI. The unhealthiest changes—gaining too little height, too much weight for their height compared with children in other countries, or both—occurred in many countries in sub-Saharan Africa, New Zealand, and the USA for boys and girls; in Malaysia and some Pacific island nations for boys; and in Mexico for girls. Interpretation The height and BMI trajectories over age and time of school-aged children and adolescents are highly variable across countries, which indicates heterogeneous nutritional quality and lifelong health advantages and risks