Cheng-Han Lin

A novel realistic simulation tool for video transmission over wireless network

The objective of this paper is to present a novel realistic simulation tool-set for evaluating video delivered quality over wireless network. This tool-set integrates EvalVid and NS-2. With the integration, researchers can easily analyze their designed mechanisms, such as network protocols or QoS control schemes in a realistic simulation environment. We used a case study about video transmission over wireless network to demonstrate the simulation with the tool-set. From the results, we found that the quality of video transmission with burst packet errors is superior to the random distributed packet errors in the same packet error rate. In addition, in the same packet error rate, unicast transmission leads to better video delivered quality than multicast transmission because of retransmission. Also, using the tool-set researchers can assess video quality not only with the evaluation metrics, but also with real video sequences. In brief, researchers who utilize our proposed QoS assessment framework will be benefited in verifying their designs regarding video transmission over wireless network

An adaptive cross-layer mapping algorithm for MPEG-4 video transmission over IEEE 802.11e WLAN

This paper proposes an adaptive cross-layer mapping algorithm to improve the transmission quality of MPEG-4 video stream over an IEEE 802.11e wireless network. Instead of classifying video data to a specific access category in an 802.11e network, we propose an algorithm that dynamically maps MPEG-4 video packets to appropriate access categories according to both the significance of the video data and the network traffic load. Our proposed cross-layer architecture passes information about the significance of video packets from the application layer to the media access control layer. The queue length of a specific access category is used to deduce the network traffic load. We conducted a performance evaluation of our proposed cross-layer approach under both light and heavily loaded network conditions. Our simulation results demonstrate: (a) superior performance of our proposed approach (under both light and heavy loads) over 802.11e (Enhanced Distributed Channel Access (EDCA) and static mapping schemes, (b) not only guarantees prioritized transmission of essential video data but also provides efficient queue length utilization.

The Packet Loss Effect on MPEG Video Transmission in Wireless Networks

The purpose of this paper is to study the packet loss effect on MPEG video transmission quality in wireless networks. First, we consider the distribution of packet losses in wireless network, including distributed and burst packet losses. Besides, we also discuss the additional packet drops by the play-out buffer at the received end, and the effect of the transmission packet size on the video delivered quality. From the results, we find that the effect of burst packet losses on the video delivered quality is less than distributed packet losses in the same packet loss rate. Moreover, the smaller size of the play-out buffer leads to more packet drops and worse video quality. Finally, if there is no video recovery for video transmission, the video delivered quality of the larger packet size will be better than smaller packet size

A RED-FEC Mechanism for Video Transmission Over WLANs

This paper proposes a Random Early Detection Forward Error Correction (RED-FEC) mechanism to improve the quality of video delivered over Wireless Local Area Networks (WLANs). In contrast to previous FEC schemes, in which the rate determination information is fed back from the receiver side, in our proposed method, the redundancy rate is calculated directly at the wireless Access Point (AP) in accordance with the network traffic load, as indicated by the AP queue length. An analytical model is developed to predict the effective packet loss rate of a video stream delivered over a WLAN with RED-FEC protection. The numerical results show that the proposed RED-FEC mechanism consistently achieves higher recovery efficiency than a conventional FEC scheme under high and low network loading conditions.

xAn Enhanced Adaptive FEC Mechanism for Video Delivery over Wireless Networks

This paper proposes an enhanced adaptive FEC (EAFEC) algorithm implemented in the access point (AP) to improve video delivery over wireless networks. Unlike traditional static FEC mechanisms, which add redundant data to transmission data in a fixed number, the number of redundant FEC data for the EAFEC mechanism is determined by the AP, which is based on both network traffic load and wireless channel state. The algorithm is based on two factors. One of them is the queue length in the access point, indicating network traffic load; the second factor is packet retransmission times, indicating wireless channel state. EAFEC usage would tune FEC data number generated in such a way that it would not unnecessarily add more traffic to the network in already congested scenario. Our work shows that the EAFEC algorithm improves system performance by dynamically tuning FEC strength to the current loss in the wireless channel. We use NS-2 simulation experiments to prove our algorithm

A Theoretical Framework for End-to-End Video Quality Prediction of MPEG-based Sequences

This paper presents a novel theoretical framework for end-to-end video quality prediction of MPEG-based video sequences. The proposed framework encloses two discrete models: (i) A model for predicting the video quality of an encoded signal at a pre-encoding stage and (ii) A model for mapping QoS-sensitive network parameters (i.e. packet loss) to video quality degradation. The efficiency of both the discrete models is experimentally validated, proving by this way the accuracy of the proposed framework.

A framework for end-to-end video quality prediction of MPEG video

This paper proposes, describes and evaluates a novel framework for video quality prediction of MPEG-based video services, considering the perceptual degradation that is introduced by the encoding process and the provision of the encoded signal over an error-prone wireless or wire-line network. The concept of video quality prediction is considered in this work, according to which the encoding parameters of the video service and the network QoS conditions are used for performing an estimation/prediction of the video quality level at the user side, without further processing of the actual encoded and transmitted video content. The proposed prediction framework consists of two discrete models: (i) a model for predicting the video quality of an encoded signal at a pre-encoding stage by correlating the spatiotemporal content dynamics to the bit rate that satisfies a specific level of user satisfaction; and (ii) a model that predicts primarily the undecodable frames (and subsequently the perceived quality degradation caused by them) based on the monitored averaged packet loss ratio of the network. The proposed framework is experimentally tested and validated with video signals encoded according to MPEG-4 standard.

Cross-Layer Unequal Error Protection Mechanism with an Interleaved Strategy for Video Streaming over Wireless Networks

Video streaming applications over wireless networks present many challenges owing to the high packet error rate and the error characteristics of consecutive packets. In order to solve these problems, this paper proposes a cross-layer Unequal Error Protection (UEP) Forward Error Correction (FEC) mechanism with an interleaved strategy for video streaming over wireless networks. The proposed novel UEP mechanism uses a playable frame rate (PFR) model to determine the appropriate FEC redundancy for a varied type video frame. The UEP mechanism requires the video information to be obtained from the application layer in order to allocate FEC redundancy to each video frame in the Internet Protocol (IP) layer. Moreover, this paper aims to find out the appropriate length and depth of interleaving to overcome errors in consecutive packets. Our simulation results demonstrate that the proposed mechanism outperforms a related FEC mechanism with interleaving terms of playable frame rate.

An exponential-linear backoff algorithm for contention-based wireless networks

In this paper, a backoff mechanism, Exponential Linear Backoff Algorithm (ELBA), is proposed to improve system performance over contention-based wireless networks. In the ELBA, the variation of contention window size is combined both exponentially and linearly, dependent on the network load, as indicated by the number of consecutive collisions. In the ELBA scheme, a threshold is set to determine the network load. If the contention window size is smaller than the threshold, a light network load, the contention window is tuned exponentially. Conversely, if the contention window size is larger than the threshold, a heavy network load, the contention window size is tuned linearly. The numerical results show that the ELBA provides a better system throughput and collision rate in both light and heavy network loads than the related backoff schemes, including binary exponential backoff (BEB), exponential increase exponential decrease (EIED) and linear increase linear decrease (LILD).