Unequal Error Protection Scheme Research Articles

Content-Based Image Unequal Error Protection Strategies for an Open Loop MIMO System

The paper deals with strategies for optimizing the transmission of JPEG2000 coded images over a MIMO quasi-static Rayleigh fading channel, by exploiting different available MIMO STBC (Space Time Block Codes), as well as the image content to be transmitted. The aim is to propose a link adaptation scheme based on the variable radio channel’s conditions, by establishing an UEP (Unequal Error Protection) scheme that leads to the best tradeoff between the robustness to errors and the image visual quality. Comparisons are made with the EEP (Equal Error Protection) case, in terms of the PSNR (Peak Signal to Noise Ratio) fidelity metric, as well as the subjective image quality.

On Rate-adaptive LDPC-based Cross-layer SVC over Bursty Wireless Channels

Recent studies have indicated that a significant improvement in wireless video throughput can be achieved by Cross Layer Design with Side-information (CLDS) protocols. In this paper, we derive the operational rate of a CLDS protocol operating over a realistic wireless channel. Then, a Rate-Distortion (R-D) empirical model for above-capacity Scalable Video Coding (SVC) is deduced to estimate the loss of video quality incurred under inaccurate rate estimation scenarios. Finally, we develop a novel Unequal Error Protection (UEP) scheme which leverages the characteristics of LDPC codes to reduce the distortion of video quality in case of typically-observed burst wireless errors. The efficacy of the proposed rate adaptation architecture over conventional protocols is demonstrated by realistic video simulations using actual IEEE 802.11b wireless traces.

Analysis and modeling of optimal error protection for embedded codestreams

Efficient utilization of bandwidth is key to providing mobile multimedia services such as wireless imaging. As such, efficient allocation of the available parity budget for error protection of the associated codestreams is essential for ensuring quality of service. Computing the optimal parity allocation to the codestream packets may not be possible in real-time due to the huge number of ways the parity can be assigned to the codestream packets. This is particularly true for systems having limited resources, such as mobile handheld devices. As a result, it is important to provide an error-protection scheme that gives good error-protection performance while imposing low computational and memory demands on the system. We therefore analyze how different parameters such as signal-to-noise ratio and source distortion-rate function affect the optimal unequal error protection (UEP) scheme for embedded codestreams. We also propose to approximate the optimal UEP using suitable mathematical models in order to reduce the complexity that otherwise would occur with computing the optimal UEP. We investigate several models for their fitness in approximating the optimal UEP using different performance metrics. The simulation results show that most of these models provide an excellent trade-off between performance and complexity.

Message-Wise Unequal Error Protection Based on Low-Density Parity-Check Codes

We propose a practical message-wise unequal error protection (UEP) scheme using low-density parity-check (LDPC) codes, where one or more special messages are more protected than other ordinary messages. In contrast to the information theoretic cavity coding scheme, which discards the codewords of ordinary messages near those of special messages, the proposed coding scheme performs codeword flipping to separate the codewords of special and ordinary messages without discarding any codewords. To better distinguish the original and flipped codewords, the LDPC codes with all-odd degree check nodes are employed. The decoder performs message type detection and codeword flipping detection based on the unsatisfied check nodes in iterative decoding. We provide performance analysis for both the message type detection and the codeword flipping detection. Moreover, we provide an asymptotic analysis on the detection error exponent to reveal the relationship between the proposed practical coding scheme and the information theoretically optimal cavity coding. Simulation results are provided to show that the proposed practical message-wise UEP schemes offer capacity-approaching protections to both types of messages as if only one type is transmitted.

Application of unequal error protection method with low density parity check codes in scalable video coding

Based on the analysis of Joint Source Channel Coding(JSCC) theory,an Unequal Error Protection(UEP) scheme for Scalable Video Coding(SVC) with Low Density Parity Check(LDPC) codes was proposed.It can minimize the total end-to-end distortion of the reconstructed video.This article proposed a bit allocation algorithm that can optimally allocate bits to each frame depending on their contribution in the reconstructed video.LDPC codes with different code rate were applied for different layers in order to provide UEP.The simulation results show that the proposed algorithm yields competitive results against the Lagrangian-based algorithm.The complexity of the algorithm is smaller and the Peak Signal-to-Noise Ratio(PSNR) of the reconstructed video is improved obviously.

A framework for error protection of region of interest coded images and videos

In this paper, we propose a framework for unequal error protection (UEP) of image and video streaming over a wireless channel. Our framework of allocating the parity symbols associated with error control coding to the image or video codestream takes advantage of the different levels of importance that particular spatial regions of visual multimedia content has to human observers. As such, it provides stronger protection against transmission impairments to those parts of an image or video stream that correspond to the regions of interest (ROIs) while weaker protection is applied to the background (BG). For this purpose, an image or video stream represented by a sequence of packets is split into smaller cells in such a way that certain cells contain the parts of a codestream that represent ROIs and the last cell carries solely BG information. The available parity budget obtained from the given code rate is then distributed among these cells based on their contribution to the overall perceptual quality of a reconstructed image or video. A dynamic programming approach is utilized to facilitate optimal allocation of parity to ROIs and BG for ROI based UEP. The performance of the proposed ROI based UEP scheme is analyzed and compared with both the optimal UEP without ROI processing and equal error protection (EEP) in terms of an objective perceptual quality metric, the structural similarity (SSIM) index. Performance results validate the effectiveness of our framework and the superior performance of the proposed UEP scheme compared to EEP. The performance of the proposed UEP scheme matches well with that of the optimal UEP without ROI processing, especially, for multiple spatial description image and video coding while computational complexity can be kept much lower.

Lightweight multimedia packet prioritization model for unequal error protection

In this paper, we analyze the effect of packet losses in multimedia sequences and propose a priority model for the packets, where the highest priorities are given to the packets whose loss has stronger effect in the perceived Quality of Experience (QoE). The proposed model assigns priorities to each of the media packets based on the audiovisual coding structure: type of frame, position of the packet within the frame and position of the frame within the GOP. This model can be used as a basis for Unequal Error Protection (UEP) strategies where, from a window of consecutive packets, only a fraction of them are protected and the others may potentially get lost. The experiments conducted show that this strategy strongly reduces the Mean Square Error (MSE) of the received sequence compared to the situation where the same ratio of packet losses is produced randomly. The strategy provides a good MSE gain even when the bit budget assigned to encode the priority of each packet is small. The prioritization model and the priority label signalization are fully compatible with current standards for multimedia distribution, and therefore they can be immediately applied to existing multimedia delivery services, such as IPTV platforms.

A novel hierarchical QAM-based unequal error protection scheme for H.264/AVC video over frequency-selective fading channels

A novel unequal error protection (UEP) scheme based on the hierarchical quadrature amplitude modulation (QAM) is proposed for H.264/AVC video transmission over frequency selective fading channels. In order to avoid the situation that data with higher priority in the H.264/AVC video streams to be mapped onto subcarriers in deep fading, an OFDM subcarrier classification strategy with two signal-to-noise ratio (SNR) thresholds is presented. Simulation results show that the proposed UEP scheme outperforms the state-of-the-art UEP method by up to 1.6 dB in terms of the quality of the reconstructed video.

Bit-Rate Allocation for Broadcasting of Scalable Video Over Wireless Networks

Scalable video coding technique has been desired for many years to fulfill the requirement of reliable transmission of video over heterogeneous networks. It allows for simple solutions in adaptation to network constraint and user capabilities by providing a full scalability including temporal, spatial and quality scalability. Various coding structures will dramatically affect the overall performance of the system. In this paper, we develop a new joint source and channel coding scheme for wireless broadcasting making use of H.264/SVC considering the various clients' statistics such as the accessing bandwidth and the error rate. First, an effective algorithm is carried out to distribute proper amount of source codes and channel codes to the base layer to guarantee that all the clients can receive the video with a minimum quality. Second, to deal with the burst packet loss, we propose to apply the unequal error protection (UEP) scheme on the enhancement layers using the interleaved packetization to make sure that all the lower layers can be decoded if an enhancement layer is correctly received. To maximize the system-defined utility function, fast algorithms are designed to dynamically allocate the source coding rate and the channel coding rate for the scalable bit-stream given the clients' distribution. Experiments are conducted to verify the performance of the proposed algorithm against the other two schemes, where equal error protection (EEP) and UEP schemes with different coding structures are employed. The results demonstrate the superiority of the proposed scheme and the improvement is up to 2 dB.

Approximate Performance Analysis for Linear Codes in Superposition Schemes over Gaussian Broadcast Channels

Unequal error-protection schemes obtained by means of two-level superposition coding are considered. Their performance over Gaussian broadcast channels (GBCs) is investigated with optimal maximum-likelihood decoding as well as with a suboptimal decoding strategy based on interference cancellation. We focus on GBCs without fading and, assuming that linear codes are used, we evaluate, for both decoding strategies, analytical approximations of the word-error rate based on a suitable application of the union bound. As in the case of turbo codes and turbo-coded modulations in schemes without superposition, the derivation of the approximations exploits the concept of uniform interleaving. The analytical expressions obtained are in excellent agreement with the simulation results, and thus provide a useful tool for analysis and design of practical superposition-coding schemes. Unlike the existing design tools, which rely on the assumption of infinite-length superposition codes, the proposed approach allows us to study the effectiveness of finite-length coding schemes with known distance spectrum.

Highly scalable JPEG image transmission with unequal error protection and optimal feedback

This paper investigates the performance of three different Unequal Error Protection (UEP) schemes for progressive JPEG image transmission using delay-constrained hybrid ARQ, with iterative bit and symbol combining. The first UEP scheme considers only the optimization of channel code-rates and keeps the number of retransmissions fixed for all the subbands of the image. The second one optimizes both the channel code-rates and retransmissions, while the third only considers the optimal allocation of retransmission requests. The UEP schemes are designed with two different coding techniques. The first one employs Rate Compatible Punctured Turbo Codes (RCPT) with iterative bit combining and, is suitable for applications requiring high power efficiency. For the second one we propose a new coding strategy, Rate Compatible Punctured Turbo Trellis Coded Modulation (RCPTTCM) with iterative symbol combining, which provides high scalability and bandwidth efficiency. Gains of over 9 dB in Peak-Signal-to-Noise-Ratio are obtained with the UEP schemes as compared to their corresponding Equal Error Protection (EEP) schemes.

DIRECT MAPPING OVSF-BASED TRANSMISSION SCHEME FOR UNDERWATER ACOUSTIC MULTIMEDIA COMMUNICATION

Underwater communication networks are currently being developed for use in underwater control systems, underwater telemetry systems, and underwater image transmission systems. The transmission bandwidth and transmission rates of an underwater communication system are low, and its transmission delay is high. In this paper, we propose a direct mapping orthogonal variable spreading factor (OVSF)-based transmission system for underwater acoustic multimedia communication. An important feature of this transport architecture is that a power assignment mechanism, an OVSF scheme, a direct mapping strategy, an unequal error protection scheme, and adaptive modulation are employed for transmitting messages that can tolerate various bit error rates. For confirming the effectiveness of this transport architecture, we perform a simulation using measured data of a G.729 audio signal and a JPEG2000 image signal. The simulation results show that the proposed system can achieve maximum transmission data rates or minimum transmission power. In addition, the OVSFbased transport architecture is a feasible platform in underwater acoustic multimedia communication.

Transmission of 3D Scenes over Lossy Channels

This paper introduces a novel error correction scheme for the transmission of three-dimensional scenes over unreliable networks. We propose a novel Unequal Error Protection scheme for the transmission of depth and texture information that distributes a prefixed amount of redundancy among the various elements of the scene description in order to maximize the quality of the rendered views. This target is achieved exploiting also a new model for the estimation of the impact on the rendered views of the various geometry and texture packets which takes into account their relevance in the coded bitstream and the viewpoint required by the user. Experimental results show how the proposed scheme effectively enhances the quality of the rendered images in a typical depth-image-based rendering scenario as packets are progressively decoded/recovered by the receiver.

On unequal error protection for LZSS compressed data

An unequal error protection scheme for Lempel–Ziv–Storer–Szymanski (LZSS) compressed data is proposed. The novel method divides the compressed data into short blocks, which allows for near-real-time operation. The error protection is obtained through the application of BCH codes and block interleavers. Compared to other methods found in the literature, the proposed scheme is either more efficiency in terms of compression efficient or in terms of decoding delay.

Expanding window fountain codes for unequal error protection

A novel approach to provide unequal error protection (UEP) using rateless codes over erasure channels, named Expanding Window Fountain (EWF) codes, is developed and discussed. EWF codes use a windowing technique rather than a weighted (non-uniform) selection of input symbols to achieve UEP property. The windowing approach introduces additional parameters in the UEP rateless code design, making it more general and flexible than the weighted approach. Furthermore, the windowing approach provides better performance of UEP scheme, which is confirmed both theoretically and experimentally.

Forward Error Correction for Multipath Media Streaming

We address the problem of joint optimal rate allocation and scheduling between media source rate and error protection rate in scalable streaming applications over lossy multipath networks. Starting from a distortion representation of the received media information at the client, we propose a novel optimization framework in which we analyze the performance of the most relevant forward error correction and scheduling techniques. We describe both optimal and heuristic algorithms that find solutions to the rate allocation and scheduling problem, and emphasize the main characteristics of the compared techniques. Our results show that efficient unequal error protection schemes improve the quality of the streaming process. At the same time we emphasize the importance of priority scheduling of the information over the best available network paths, which outperforms traditional first-in-first-out models or network flooding mechanisms.

A new unequal error protection scheme based on FMO

This paper presents a novel scheme for video transmission over error-prone networks. The proposed scheme exploits the error resilient features of H.264/AVC and employs an unequal error protection (UEP) approach to protect effectively the streams. A novel algorithm is proposed to classify macroblocks into slice groups using the explicit mode of Flexible Macroblock Ordering (FMO). A rate distortion optimized algorithm is used to assign unequal amounts of FEC protection to the resulting slice groups according to their importance. In addition, a Converged Motion Estimation (CME) is proposed to further improve the proposed UEP scheme. The idea behind the CME is to make the macroblocks be referenced in a skewed manner, such that highly important macroblocks are converged on only a few and the use of redundancy for error protection is efficient. Simulation results show the superiority of the proposed method over other approaches for transmission of H.264/AVC streams.

A low complexity hierarchical QAM symbol bits allocation algorithm for unequal error protection of wireless video transmission

A low complexity hierarchical quadrature amplitude modulation (QAM) symbol bits allocation algorithm for unequal error protection of video transmission over wireless channels is proposed in this paper. An unequal error protection (UEP) scheme using hierarchical QAM, which takes into consideration the non-uniformly distributed importance of intracoded frame (I-frame) and predictive coded frame (P-frame) in a group of pictures (GOP), is first proposed. In order to optimally allocate the hierarchical QAM's high priority (HP), medium priority (MP) and low priority (LP) symbol bits to the H.264/AVC video, a generic solution for optimal allocation of hierarchical QAM's high priority (HP), medium priority (MP) and low priority (LP) symbol bits to the H.264/AVC video is then proposed. Finally, a low complexity symbol bits allocation algorithm, namely ranking search algorithm, which reduces the computational complexity of the proposed optimal symbol bits allocation algorithm, is proposed. Simulation results show that our proposed UEP scheme outperforms the classical equal error protection (EEP) scheme and also the previous UEP scheme.

Group-of-pictures-based unequal error protection for scalable video coding extension of H.264/AVC

We address the problem of unequal error protection (UEP) for SNR enhancement layer network abstraction layer (NAL) units of scalable video coding extension of H.264/AVC standard over wireless packet-erasure channel. We develop a UEP scheme by jointly selecting SNR NAL units and allocating unequal amounts of protection to selected NAL units for every group of pictures in the sequence. A simple heuristic algorithm is proposed to quickly derive the protection pattern. Experimental results demonstrate the proposed UEP scheme provides significant error resilience.

Design of RCPC Encoded V-BLAST MIMO System

A Vertical Bell Laboratories Layered Space-Time Multiple-Input Multiple Output (V-BLAST MIMO) enhanced with Unequal Error Protection (UEP) to achieve highly reliable wireless communication is proposed. The UEP scheme is based on Channel State Information (CSI) available at the transmitter whose calculation utilizes Singular Value Decomposition (SVD) of the MIMO matrix channel. Using Rate-Compatible Punctured Convolutional (RCPC), a different code rate is given for each sub-stream of source information, according to its level of transmit power. To analyze the system performance, an analytical BER comprising the performance of V-BLAST MIMO BPSK-modulated signals and the performance of RCPC codes in Rayleigh fading environment is presented. Simulation results show that increasing the code rate can attain a bandwidth efficiency of 33.3% in expense Eb/No, but this penalty is not severe as the high code rate is used in sub-channels with high attenuation level. It is also shown that a system with 2 transmit and 4 receive antennas will have an improved performance within only 1 dB range compared to a system with 2 transmit and 2 receive antennas. The performance of the proposed system is mostly affected by the type of puncturing matrices chosen.