Abstract — This paper presents a new framework for multimedia streaming that integrates the application and network layer functionalities to meet such stringent application requirements as delay and loss. The coordination between these two layers provides more robust media transmission even under severe network conditions. In this framework, a multiple description source coder is used to produce multiple independently-decodable streams that are routed over partially link-disjoint (non-shared) paths to combat bursty packet losses. We model multi-path streaming and propose a multi-path selection method that chooses a set of paths maximizing the overall quality at the client. Overlay infrastructure is then used to achieve multi-path routing over these selected paths. The simulation results show that the average peak signal-to-noise ratio (PSNR) improves by up to 8.1 dB, if the same source video is routed over intelligently selected multiple paths instead of the shortest path or maximally link-disjoint paths. In addition to PSNR improvement in quality, the enduser experiences a more continual streaming quality. I.

Abstract. Mobile ad hoc networks (MANETs) consist of a collection of wireless mobile nodes which dynamically exchange data among themselves without the reliance on a fixed base station or a wired backbone network. MANET nodes are typically distinguished by their limited power, processing, and memory resources as well as high degree of mobility. In such networks, the wireless mobile nodes may dynamically enter the network as well as leave the network. Due to the limited transmission range of wireless network nodes, multiple hops are usually needed for a node to exchange information with any other node in the network. Thus routing is a crucial issue to the design of a MANET. In this paper, we specifically examine the issues of multipath routing in MANETs. Multipath routing allows the establishment of multiple paths between a single source and single destination node. It is typically proposed in order to increase the reliability of data transmission (i.e., fault tolerance) or to provide load balancing. Load balancing is of especial importance in MANETs because of the limited bandwidth between the nodes. We also discuss the application of multipath routing to support application constraints such as reliability, load-balancing, energy-conservation, and Quality-of-Service (QoS). 1

Multiple description coding (MDC) has received a lot of interest lately, because it allows to split one source of information in multiple entities, where each of the entities is decodable in a stand--alone fashion. The more of these entities are received the more information of the original source can be restored. This opens the door for new applications in many fields of mobile communications. Unfortunately the multiple description coding comes with the price of higher bandwidth requirements. This overhead is caused by the coding process itself and the related network transport. In this work we present a solid investigation of the overhead arising from the splitting process for video coding. The overhead caused by the underlying network protocols is highlight. Furthermore we investigate the quality of the decoded video in absence of specific streams. A main conclusion we draw here is that we have to consider the scenario carefully whether or not multiple description coding should be chosen over single description coding.

Layered (LC) and multiple description coding (MDC) have been proposed as source coding techniques that are robust to channel errors for video transmission. LC and MDC have similar characteristics: they both generate multiple sub-bitstreams, and it is permissible to drop some portion of the data from the sub-bitstreams during transmission for both methods. However, they are different in the sense that the sub-bitstreams for LC have different levels of importance while all sub-bitstreams for MDC are equally important. Since these two encoding techniques have similar properties, some performance comparisons between LC and MDC have recently been reported. However, these studies are still not conclusive because several scenarios have not been carefully considered. Furthermore, they have been performed in different environments. In this paper, we further investigate the error-resilience capabilities of these two encoding techniques through extensive experimentation. Although some of our conclusions agree with those in the literature, we believe that this paper provides the most comprehensive performance comparison yet between LC and MDC.

Internet transmission is characterized by variations in throughput, delay, and packet loss, which can severely affect the quality of multimedia presentations delivered over the network. Still, Internet video streaming has experienced phenomenal growth in the last few years, owing to the extensive research in video coding and transmission. In this paper, we review several recent advances for network-adaptive video streaming that, we believe, will benefit the design of video streaming systems in the future. Employed in different system components, these techniques have the common objective of providing efficient, robust, scalable and low-latency streaming video. They range from purely server or source encoder-based techniques, through transmission schemes that could be implemented either at the sender or at the receiver, to purely client-based techniques. We discuss each of them in detail, presenting also related work and experimental results. We end the paper with a summary of the reviewed techniques and a brief discussion of future research directions.

this paper show an average PSNR improvement of up to 8.1 dB than conventional MDC scheme. The challenge that the authors faced in this paper was finding a set of paths to minimize the cost function that estimated average streaming distortion in terms of network statistics, media characteristics and application requirements [6]. To remedy this problem, they proposed a fast heuristics--based solution by exploiting the infrastructure features of the internet in [6]. Their simulations run over several random internet topologies show that the proposed heuristic approach is capable of finding a good set of paths in a much shorter time than the methods they used in [5]. This heuristic is therefore very well suited for time critical applications such as VoIP and video conferencing

Layered (LC) and multiple description coding (MDC) have been proposed as source coding techniques that are robust to channel errors for video transmission. In this paper, we investigate and study the error-resilience capabilities of these two encoding techniques through extensive experimentation, and explore the environments where they perform best. Although some of our conclusions agree with those in the literature, we believe that this paper provides the most comprehensive performance comparison yet between LC and MDC. I.

The past decade has witnessed a growing interest in deploying automatic speech recognition (ASR) in communication networks. The networks such as wireless networks present a number of challenges due to e.g. bandwidth constraints and transmission errors. The introduction of distributed speech recognition (DSR) largely eliminates the bandwidth limitations and the presence of transmission errors becomes the key robustness issue. This paper reviews the techniques that have been developed for ASR robustness against transmission errors. In the paper, a model of network degradations and robustness techniques is presented. These techniques are classified into three categories: error detection, error recovery and error concealment (EC). A one-frame error detection scheme is described and compared with a frame-pair scheme. As opposed to vector level techniques a technique for error detection and EC at the sub-vector level is presented. A number of error recovery techniques such as forward error correction and interleaving are discussed in addition to a review of both feature-reconstruction and ASR-decoder based EC techniques. To enable the comparison of some of these techniques, evaluation has been conduced on the basis of the same speech database and channel. Special attention is given to the unique characteristics of DSR as compared to streaming audio e.g. voice-over-IP. Additionally, a technique for adapting ASR to the varying quality of networks is presented. The frame-error-rate is here used to adjust the discrimination threshold with the goal of optimising out-of-vocabulary detection.

Abstract — 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. I.

Abstract. In this paper, we present error-resilient Internet video transmission using path diversity and ratedistortion optimized reference picture selection. Under this scheme, the optimal packet dependency is determined adapting to network characteristics and video content, to achieve a better trade-off between coding efficiency and forming independent streams to increase error-resilience. The optimization is achieved within a rate-distortion framework, so that the expected end-to-end distortion is minimized under the given rate constraint. The expected distortion is calculated based on an accurate binary tree modeling with the effects of channel loss and error concealment taken into account. With the aid of active probing, packets are sent across multiple available paths according to a transmission policy which takes advantage of path diversity and seeks to minimize the loss rate. Experiments demonstrate that the proposed scheme provides significant diversity gain, as well as gains over video redundancy coding and the NACK mode of conventional reference picture selection.