Hongli Luo

Quality of service provision in mobile multimedia - a survey

The prevalence of multimedia applications has drastically increased the amount of multimedia data. With the drop of the hardware cost, more and more mobile devices with higher capacities are now used. The widely deployed wireless LAN and broadband wireless networks provide the ubiquitous network access for multimedia applications. Provision of Quality of Service (QoS) is challenging in mobile ad hoc networks because of the dynamic characteristics of mobile networks and the limited resources of the mobile devices. The wireless network is not reliable due to node mobility, multi-access channel and multi-hop communication. In this paper, we provide a survey of QoS provision in mobile multimedia, addressing the technologies at different network layers and cross-layer design. This paper focuses on the QoS techniques over IEEE 802.11e networks. We also provide some thoughts about the challenges and directions for future research.

An Optimized Scheduling Scheme to Provide Quality of Service in 802.11e Wireless LAN

802.11 WLAN technology has been widely used recently to transmit heterogeneous data. The transmission of multimedia data has its quality of service (QoS) requirements. Hybrid Coordination Function (HCF) is proposed to provide service differentiation to support real-time transmission by 802.11e working group. HCF is composed of connection-based Enhanced Distributed Coordination Access (EDCA) and contention-free control-based HCF Controlled Channel Access (HCCA). The simple scheduler in HCCA proposed by 802.11e working group generates constant bit rate service, which is not efficient for the multimedia data with variable bit rates. An efficient scheduling scheme for the 802.11e wireless LAN is proposed in this paper. The allocation of the transmission opportunity to each wireless station is based on the optimization performance index and uses the queue length of the wireless station as feedback information. Simulation results demonstrate that the proposed scheduling can achieve a better QoS for different traffic class under heavy traffic load.

Video streaming over the internet with optimal bandwidth resource allocation

In this paper, an adaptive framework for video streaming over the Internet is presented. The framework is a joint design of packet scheduling and rate control with optimal bandwidth resource allocation. The transmission rate is dynamically adjusted to obtain maximal utilization of the client buffer and minimal allocation of the bandwidth. Under the constraint of the transmission rate, a prioritized packet scheduling is designed to provide a better visual quality of video frames. The packet scheduling is a refined bandwidth allocation which takes into account of varying importance of the different packets in a compressed video stream. Moreover, the proposed approach is scalable with increasing multimedia flows in the distributed Internet environment. Comparisons are made with the most current streaming approaches to evaluate the performance of the framework using the H.264 video codec. The extensive simulation results show that the average Peak Signal to Noise Ratio (PSNR) increases in our proposed approach. It provides a better quality of the decoded frames, and the quality of the decoded frames changes more smoothly. The achieved video quality among different users also has a lower fluctuation, which indicates a fair sharing of network resources.

Optimal bandwidth allocation scheme with delay awareness in multimedia transmission

Recently, efficient network resource management and quality-of-service (QoS) guarantee become more and more important for multimedia applications and services, especially when considering network delays. An optimal bandwidth allocation scheme is introduced. It achieves maximal utilization of the client buffer and minimal allocation of bandwidth for each client. The proposed scheme allocates bandwidth to multiple clients requesting services from a server by adjusting the transmission rates based on the client buffer occupancy, the playback requirements of the individual client and the network delays. Simulations for the single client and multiple client scenarios are conducted under different network congestion levels. The simulation results show that our approach performs better in comparison with the fixed rate allocation approach and the rate by playback requirement approach, since it avoids underflows and overflows efficiently and provides QoS for more clients with limited available bandwidth in the network.

A Multi-Buffer Scheduling Scheme for Video Streaming

In this paper, we propose a multi-buffer scheduling scheme for streaming video systems. A transmission rate is obtained via a rate control algorithm, which optimally utilizes the network bandwidth and client buffer resources. The server side maintains multiple buffers for packets of different importance levels. It schedules the transmission of each packet based on the source buffer size and playback deadline to reduce the end-to-end distortion. The performance of proposed scheme is evaluated in terms of peak signal-to-noise ratio (PSNR) in the simulations, and the simulation results demonstrate the improvement of the average PSNR values compared with two other scheduling schemes

Optimal resource utilization in multimedia transmission

Efficient utilization of network resources is essential in the provision of quality multimedia services. Different approaches have been proposed to shape the multimedia streams as a transmission schedule with smoothed traffic burst. In this paper, we concentrate on the problem of efficient use of bandwidth and client buffer. For this purpose, an optimal transmission schedule is proposed to provide the minimal allocation of the bandwidth and maximal utilization of the client buffer. Simulation results show that the shaping results obtained can dynamically adjust the transmission rate according to the buffer packet sizes and playback rates at the client to avoid the loss of packets, and at the same time achieve the minimal bandwidth allocation and maximal utilization of the client buffer.

Self-adjusted network transmission for multimedia data

High bandwidth requirements in multimedia transmission make the efficient use of limited network resource a challenging task, especially when multiple clients make their requests to the server simultaneously. We propose a self-adjusted network transmission mechanism for multiple clients. Instead of assigning a fixed bandwidth for each client, the server determines the transmission rate for each client connection according to the buffer packets and playback rate at each client. Transmission rates are adjusted when the total requested bandwidth is larger than the network bandwidth. In addition, the proposed mechanism can minimize the bandwidth allocation and maximize the client buffer utilization. A simulation is performed and the simulation results show that the proposed mechanism can dynamically change the transmission rate for each client to avoid overflow of the client buffer, and achieve the optimal utilization of the limited network resource in multiple client network environments.

The protection of QoS for multimedia transmission against denial of service attacks

In this paper, a secure and adaptive multimedia transmission framework is proposed to maintain the quality of service (QoS) of the multimedia streams during the denial-of service (DoS) attacks. A DoS attack generates a large amount of traffic, which will occupy the bandwidth and degrade the quality of video. The proposed framework consists of two components: intrusion detection and adaptive transmission management. The intrusion detection component monitors the incoming traffic to the server, detects the attacks, and interacts with the adaptive transmission management component; while the adaptive transmission management component is designed to improve QoS of the video via the efficient utilization of the network resources. With the detection of the DoS attacks, the bandwidth occupied by the attacks can be reduced and protected for video transmission. The results of our preliminary simulations in NS2 show that the quality of the multimedia stream can still be maintained during an attack.

An end-to-end video transmission framework with efficient bandwidth utilization

We present a new framework for streaming video over Internet in this paper. The sending rate is dynamically adjusted to obtain a maximal utilization of the client buffer and minimal bandwidth allocation. To guarantee a more reliable and better quality of delivery of the video frames, retransmission and selective drop of different frame packets are integrated into our framework. Under severe network congestion, an adaptive playback schedule can provide relative high video quality at a low frame rate. Comparisons are made with the most current streaming approaches using the H.26L video coder to evaluate the performance of the framework. Simulations results show that PSNR is increased in our approach, which provides a better quality of the decoded frames, and the quality of the decoded frames also changes more smoothly

An optimal resource utilization scheme with end-to-end congestion control for continuous media stream transmission

In this paper, we propose an optimal resource utilization scheme with end-to-end congestion control for continuous media stream transmission. This scheme can achieve minimal allocation of bandwidth for each client and maximal utilization of the client buffers. By adjusting the server transmission rate in response to client buffer occupancy, playback requirements in the client, variations in network delays and the packet loss rate, an acceptable quality-of-service (QoS) level can be maintained at the end systems. Our proposed scheme can also achieve end-to-end TCP-friendly congestion control, which the multimedia flows can share fairly with the TCP flows instead of starving the TCP flows and the packet loss rate is reduced. Simulations to compare with different approaches under different network congestion levels and to show how our approach achieves end-to-end congestion control and inter-protocol fairness are conducted. The simulation results show that our proposed scheme can generally achieve high network utilization, low losses and end-to-end congestion control.