Truong Cong Thang

Adaptive streaming of audiovisual content using MPEG DASH

HTTP streaming has become a cost effective means for multimedia delivery nowadays. In this paper, we study the use of MPEG DASH standard to stream audiovisual content. We first describe a novel estimation method for connection throughput. Then, employing the extensibility feature of DASH syntax, we present a systematic method for selecting the best audio and video alternatives given the estimated throughput. The experiments show that our solution is stable to short-term fluctuations while responding quickly to large fluctuations.

An Evaluation of Bitrate Adaptation Methods for HTTP Live Streaming

HTTP streaming has become a cost-effective means for multimedia delivery nowadays. For adaptivity to networks and terminals, a provider should generate multiple representations of an original video as well as the related metadata. Recently, there have been various adaptation methods to support adaptive HTTP streaming. In this paper, we investigate typical adaptation methods in the context of live video streaming. We first discuss the trade-off among typical adaptation methods. The evaluation and comparison are then carried out not only in terms of bitrate and buffer behaviors but also in terms of the perceptual impact on end users. It is found that the perceptual impact depends not only on adaptation method but also on the content itself. We also show that the preparation of representation sets may affect the behaviors of some adaptation methods.

Bit error rate analysis of rectangular QAM/FSO systems using an APD receiver over atmospheric turbulence channels

We theoretically analyze the performance of free-space optical (FSO) systems using rectangular quadrature-amplitude modulation (QAM) and an avalanche photodiode (APD) receiver over atmospheric turbulence channels. Both log-normal and gamma-gamma channel models are used in the analysis for the cases of weak/moderate and strong atmospheric turbulence. The system bit error rate, when Gray code mapping is employed, is theoretically derived taking into account various link conditions and system parameters, including the APD shot noise, thermal noise, channel attenuation and geometrical loss, atmospheric turbulence strengths, and link distances. The numerical results show that using APD with a proper selection of the average gain could greatly benefit the performance of the system; as a matter of fact, in the case of optimal gain, the system using an APD receiver could provide 7 dB gain in comparison with the one with a positive-instrinsic-negative receiver. We also quantitatively discuss the impact of link conditions and system parameters on the selection of optimal APD gain.

Adaptive video streaming over HTTP with dynamic resource estimation

Adaptive hypertext transfer protocol (HTTP) streaming has become a new trend to support adaptivity in video delivery. An HTTP streaming client needs to estimate exactly resource availability and resource demand. In this paper, we focus on the most important resource which is bandwidth. A new and general formulation for throughput estimation is presented taking into account previous values of instant throughput and round trip time. Besides, we introduce for the first time the use of bitrate estimation in HTTP streaming. The experiments show that our approach can effectively cope with drastic changes in connection throughput and video bitrate.

SVC adaptation: Standard tools and supporting methods

Recently, scalable video coding (SVC) has emerged as a promising video format for applications of multimedia communication. An SVC bitstream can be easily truncated (adapted) in spatial, temporal, and SNR dimensions to meet various characteristics of terminals and connections. Though SVC allows simple and flexible truncation of a coded bitstream, there still need to be efficient means to support the adaptation in different scenarios. In this paper, we review standard tools and supporting methods for SVC adaptation. We point out the practical questions and accordingly describe potential solutions to these questions. The paper also discusses two key standard tools in detail, namely MPEG-21 AdaptationQoS and SVC priority_id.

Buffer-based bitrate adaptation for adaptive HTTP streaming

Live and on-demand video streaming has recently contributed a significant part of the Internet traffic. In order to guarantee the best possible user experience, multimedia service is required to support large fluctuations in different network conditions. One of the cost effective means for multimedia delivery nowadays is HTTP streaming. The key challenge of this technology is how to change adaptively video bitrates according to network variation and client buffer while bestowing upon users the best possible video quality. In this paper, we propose a novel rate-adaptation method on client side, which allows clients to estimate buffer level in the future, and thus achieving a balance between the need for high video quality and buffer stability. The experiments show that our method performs well under varying network conditions.

Design and performance evaluation of VLC indoor positioning system using optical orthogonal codes

In this paper, a VLC indoor positioning system utilizing optical orthogonal codes (OOCs) is proposed. The use of OOC is to distinguish different transmitted signals at the receiver, the trilateration method then calculate the position of receiver based on these distinguished signals. To expand the scale of system and use efficiently OOC resource, a strategy of reusing/combining codeword is proposed. We also create a combination of simulation and mathematical modeling to investigate the performance of proposed system. Numerical results confirm that the proposed system can achieve a good positioning accuracy level in average.

Multilayer adaptation for MGS-based SVC bitstream

Medium grained scalability (MGS) of scalable video coding is expected to be of high interest due to the advantage of packet-based scalability. In this paper, we study multilayer adaptation for MGS-based bitstream. Our adaptation method not only considers which packets to be dropped, but also modifies layer dependency of NAL units to maintain bitstream conformance. Compared to conventional method of SVC, the proposed method can both expand the range of supported bitrates and improve the quality.

Mixed mmWave RF/FSO Relaying Systems Over Generalized Fading Channels With Pointing Errors

This paper studies the performance of mixed millimeter-wave radio-frequency (mmWave RF), free-space optics (FSO) systems in a highly scalable and cost-effective solution for fifth-generation (5G) mobile backhaul networks. The mmWave RF and FSO fading channels are, respectively, modeled by the Rician and the generalized Malaga (M) distributions. The effect of pointing errors due to the misalignment between the transmitter and the receiver in the FSO link is also included. Novel accurate closed-form expressions for the cumulative distribution function, the probability density function, and the moment generating function (MGF) in terms of Meijers G functions are derived. Capitalizing on these new results, we analytically derive precise closed-form expressions for various performance metrics of the proposed system, including the outage probability, the average bit error rate (ABER), and the average capacity. Additionally, new asymptotic results are provided for the outage probability, the MGF, and the ABER in terms of simple elementary functions by applying the asymptotic expansion of the Meijers G function at high signal-to-noise ratios (SNRs). Numerical results further validate the mathematical analysis by Monte-Carlo simulations.

Performance of TCP over free-space optical atmospheric turbulence channels

This paper presents an analytical study of the performance of transmission control protocol (TCP) over free-space optical (FSO) turbulence channels when the automatic-repeat request, selective-repeat (ARQ-SR) scheme is employed. Different TCP versions, including Tahoe, Reno, and selective acknowledgement, are considered. In the TCP throughput analysis, a three-dimensional Markov model is used. In addition, to analyze the joint effect of ARQ-SR and FSO turbulence channels in terms of both TCP throughput and energy consumption, a newly defined joint throughput ¿ energy-efficiency parameter is analytically derived. In the numerical results, we discuss cross-layer design strategies for the selection of FSO system parameters and the ARQ-SR scheme in order to maximize the TCP throughput and to achieve the trade-off between the energy consumption and the throughput under various conditions of the FSO turbulence channel.