Amount Of Forward Error Correction Research Articles

Layered Internet Video Adaptation (LIVA): Network-Assisted Bandwidth Sharing and Transient Loss Protection for Video Streaming

As video traffic increases in the Internet and competes for limited bandwidth resources, it is important to design bandwidth-sharing and loss-protection schemes that account for video characteristics, beyond the traditional paradigm of fair-rate allocation among data flows. Ideally, such a scheme should handle both persistent and transient congestion as video streaming applications demand low-latency transmissions and low packet-loss ratios. This paper presents a novel scheme, layered Internet video adaptation (LIVA), in which network nodes feed back virtual congestion levels to video senders to assist both media-aware bandwidth sharing and transient-loss protection. The video senders respond to such feedback by adapting the rates of encoded scalable bitstreams based on their respective video rate-distortion (R-D) characteristics. The same feedback is employed to calculate the amount of forward error correction (FEC) protection for combating transient losses. Simulation studies show that LIVA can minimize the total distortion of all participating video streams and hence maximize their overall quality. At steady state, video streams experience no queueing delays or packet losses. In the face of transient congestion, the network-assisted adaptive FEC promptly protects video packets from losses. Our Linux-based demonstration showcases how LIVA can be implemented in a simple manner in real systems. We also present a solution for LIVA streams to coexist with TCP flows based on explicit congestion notification signaling. Finally, our theoretical analysis guarantees system stability for an arbitrary number of streams with round-trip delays below a prescribed limit.

A novel unequal loss protection approach for scalable video streaming over wireless networks

This paper presents an adaptive unequal loss protection (ULP) scheme for robust transmission of scalable video streaming over wireless networks. By jointly exploiting the temporal dependency between frames in a group of pictures (GOP) and the quality dependency between the scalable layers in each frame, the proposed scheme adoptively assigns unequal amount of forward error correction (FEC) codes across packets to each layer and adjusts the sending rate by dynamically selecting the number of layers to transmit, according to the available network bandwidth and the packet loss rate. To prevent the video transmission error propagation, an algorithm is developed to achieve efficient FEC assignment for the base layers in a GOP in the sense of minimizing the decoder distortion. The simulation results show that the proposed adaptive ULP scheme can provide better video quality under varying network conditions and can achieve more graceful degradation as packet loss increasing and available bandwidth decreasing.

Modeling Best-Effort and FEC Streaming of Scalable Video in Lossy Network Channels

Video applications that transport delay-sensitive multimedia over best-effort networks usually require special mechanisms that can overcome packet loss without using retransmission. In response to this demand, forward-error correction (FEC) is often used in streaming applications to protect video and audio data in lossy network paths; however, studies in the literature report conflicting results on the benefits of FEC over best-effort streaming. To address this uncertainty, we start with a baseline case that examines the impact of packet loss on scalable (FGS-like) video in best-effort networks and derive a closed-form expression for the loss penalty imposed on embedded coding schemes under several simple loss models. Through this analysis, we find that the utility (i.e., usefulness to the user) of unprotected video converges to zero as streaming rates become high. We then study FEC-protected video streaming, re-derive the same utility metric, and show that for all values of loss rate inclusion of FEC overhead substantially improves the utility of video compared to the best-effort case. We finish the paper by constructing a dynamic controller on the amount of FEC that maximizes the utility of scalable video and show that the resulting system achieves a significantly better PSNR quality than alternative fixed-overhead methods

An embedded packet train and adaptive FEC scheme for effective video adaptation over wireless broadband networks

With the rapid growth of wireless broadband technologies, such as WLAN and WiMAX, quality streaming video contents are available through portable devices anytime, anywhere. The layered multicast system using scalable video codecs has been proposed as an efficient architecture for video dissemination taking account of user and link diversities. However, in the wired/wireless combined best-effort based heterogeneous IP networks which provide more fluctuation in available bandwidth and end-to-end delay, the performance of streaming systems has been greatly degraded due to frequent packet loss, resulting from either wired congestion or wireless fading/shadowing. In this paper, we present a real-time embedded packet train probing scheme for estimating end-to-end available bandwidth so as to accomplish effective congestion and error control. This is facilitated by effective classification of packet loss sources, delay trend detection algorithm and flexible transmission rate of packets. Under the proper wireless channel modelling and estimation, our layered structure can allow appropriate subscription of video layers and adaptively insert necessary amount of forward error correction (FEC) packets so as to achieve QoS optimized system for scalable video multicasting.

Adaptive unequal loss protection for scalable video streaming over ip networks

Video streaming over IP networks faces many challenges due to the varying network conditions such as time-varying packet loss and fluctuating bandwidth. In this paper, we focus on streaming scalable video over IP networks in order to enhance the received video quality. We present an adaptive video transmission scheme, which combines unequal loss protection and layer selecting. In this scheme, we estimate the packet loss effects on video quality using model-based distortion estimation approach, both for the base layer and the enhancement layers. Based the estimated distortion, the scheme adaptively assigns the unequal amount of forward error correction to each layer and adjusts the sending rate by dynamically selecting the appropriate number of layers to transmit, according to the packet loss rate and the available network bandwidth. The scheme can provide a graceful degradation of received video quality as packet loss increasing and available bandwidth decreasing. Simulations results show that our scheme can provide reasonable video quality under varying network conditions.

Unequal loss protection for H.263 compressed video

We study the application of unequal loss protection (ULP) algorithms to motion-compensated video over lossy packet networks. In particular, we focus on streaming video applications over the Internet. The original ULP framework applies unequal amounts of forward error correction to embedded data to provide graceful degradation of quality in the presence of increasing packet loss. In this letter, we apply the ULP framework to baseline H.263, a video compression standard that targets low bit rates, by investigating reorderings of the bitstream to make it embedded. The reordering process allows a receiver to display quality video, even at the loss rates encountered in wireless transmissions and the current Internet.

Analysis of link-level hybrid FEC/ARQ-SR for wireless links and long-lived TCP traffic

Since the TCP protocol uses the loss of packets as an indication of network congestion, its performance degrades over wireless links, which are characterized by a high bit error rate. Different solutions have been proposed to improve the performance of TCP over wireless links, the most promising one being the use of a hybrid model at the link level combining Forward Error Correction (FEC), Automatic Repeat Request with Selective Repeat (ARQ-SR), and an in-order delivery of packets to IP. The drawback of FEC is that it consumes some extra bandwidth to transmit the redundant information. ARQ-SR consumes extra bandwidth only when packets are lost, its drawback is that it increases the round-trip time (RTT), which may deteriorate the performance of TCP. Another drawback of ARQ-SR is that a complete packet can be retransmitted to correct a small piece of errored data. We study in this paper the performance of TCP over a wireless link implementing hybrid FEC/ARQ-SQ. The study is done by simulating and modeling long-lived TCP transfers over wireless links showing Bernoulli errors. We are motivated by how to tune link-level error recovery, e.g. amount of FEC, persistency of ARQ, so as to maximize the performance of TCP. We provide results for different physical characteristics of the wireless link (delay, error rate) and for different traffic loads (number of TCP connections).

Error-resilient image and video transmission over the internet using unequal error protection

This paper presents a new bit-plane-wise unequal error protection algorithm for progressive bitstreams transmitted over lossy networks. The proposed algorithm protects a compressed embedded bitstream generated by a 3-D SPIHT algorithm by assigning an unequal amount of forward error correction (FEC) to each bit-plane. The proposed algorithm reduces the amount of side information needed to send the size of each code to the decoder by limiting the number of quality levels to the number of bit-planes to be sent while providing a graceful degradation of picture quality as packet losses increase. We also apply our proposed algorithm to transmission of JPEG 2000 coded images over the Internet. To get additional error-resilience at high packet loss rates, we extend our algorithm to multiple-substream unequal error protection. Simulation results show that the proposed algorithm is simple, fast and robust in hostile network conditions and, therefore, can provide reasonable picture quality for video applications under varying network conditions.

Graceful degradation of speech recognition performance over packet-erasure networks

This paper explores packet loss recovery for automatic speech recognition (ASR) in spoken dialog systems, assuming an architecture in which a lightweight client communicates with a remote ASR server. Speech is transmitted with source and channel codes optimized for the ASR application, i.e., to minimize word error rate. Unequal amounts of forward error correction, depending on the data's effect on ASR performance, are assigned to protect against packet loss. Experiments with simulated packet loss in a range of loss conditions are conducted on the DARPA Communicator (air travel information) task. Results show that the approach provides robust ASR performance which degrades gracefully as packet loss rates increase. Transmitting at 5.2 Kbps with up to 200 ms added delay, leads to only a 7% relative degradation in word error rate even under extremely adverse network conditions.

On the synergy between adaptive physical layer and multiple-access control for integrated voice and data services in a cellular wireless network

We propose a novel design to exploit the synergy between the multiple-access control (MAC) layer and the physical layer of a cellular wireless system with integrated voice and data services. As in a traditional design, the physical layer (channel encoder and modulator) is responsible for providing error protection for transmitting the packets over the hostile radio channel, while the MAC layer is responsible for allocating the precious bandwidth to the contending users for voice or data connections. However, a distinctive feature of our proposed design is that in the physical layer, a variable-rate adaptive channel encoder is employed to dynamically adjust the amount of forward error correction according to the time-varying wireless channel state such that the MAC layer, which is a reservation-based time-division multiple-access protocol, is able to make informed decisions as to bandwidth allocation. Specifically, based on the channel state information provided by the physical layer, the MAC protocol gives higher priority to users with better channel states. This novel synergistic mechanism between the two protocol layers can utilize the system bandwidth more effectively. The multiple-access performance of the proposed scheme is compared with two baseline systems. The first baseline system consists of the same reservation-based MAC protocol but with a traditional fixed-rate physical layer. The second system consists of the same reservation-based MAC protocol and the same channel adaptive physical layer, but without interaction between the two layers. All three protocols have a request queue, which stores the previous requests that survive the contention but are not allocated information slots. Our extensive simulation results demonstrate that significant performance gains are achieved through the exploitation of the synergy between the two protocol layers.

Unequal loss protection: graceful degradation of image quality over packet erasure channels through forward error correction

We present the unequal loss protection (ULP) framework in which unequal amounts of forward error correction are applied to progressive data to provide graceful degradation of image quality as packet losses increase. We develop a simple algorithm that can find a good assignment within the ULP framework. We use the set partitioning in hierarchical trees coder in this work, but our algorithm can protect any progressive compression scheme. In addition, we promote the use of a PMF of expected channel conditions so that our system can work with almost any model or estimate of packet losses. We find that when optimizing for an exponential packet loss model with a mean loss rate of 20% and using a total rate of 0.2 bits per pixel on the Lenna image, good image quality can be obtained even when 40% of transmitted packets are lost.

Forward error correction and design of spread spectrum based multiple access networks

Spread spectrum technology is a natural choice for use in wireless multiple access networks. This paper addresses the problem of performance evaluation and design of spread spectrum based multiple access networks when forward error correction is employed. Although the use of forward error correction increases the probability of a transmission being received successfully, the effective throughput is decreased due to the increased number of redundant bits that are needed. Using an equilibrium point analysis we develop approximations for performance measures of interest. Asymptotic approximations that require reduced computational effort are also developed. We characterize the interaction between key system parameters and determine the amount of forward error correction that should be provided. Trade-offs involved in designing spread spectrum based multiple access networks that are stable and deliver high throughput while maintaining minimal delays are highlighted. Extensive numerical results are presented in the paper.