Unequal Error Protection Method Research Articles

ANALYSIS OF CHANNEL CODING PERFORMANCE FOR IMAGE TRANSMISSION OVER COOPERATIVE RELAY NETWORKS

In this paper, we examine and investigate the effects of noise-induced transmission errors on the performance of image transmission over cooperative relay networks with various error-correction capabilities. MAP decoder is used to decode the data sent across the cooperative network. First, the relationships between lengths of the code, peak signal-to-noise ratio, and signal-to-noise ratio are analyzed. Second, the comparison between the performances of different channel coding is introduced in conjunction with the set partitioning in hierarchical trees algorithm as a source code. The genetic algorithm, as an efficient optimization technique, is applied for solving the problem of optimal unequal error protection method to reduce the transmission rate and to improve the transmitted image quality. Many useful and significant results that are introduced in this paper can be used in the enhancement of image transmission over the cooperative networks. Compared to traditional methods, the suggested method is more practical for the transmission of images with high-quality via smart devices.

A UEP Method for Imaging Low-Orbit Satellites Based on CCSDS Recommendations

Remote sensing satellites allow continuous information acquisition from large areas of the earth and have been intensively applied in a number of applications, from agriculture to defense. A major challenge in remote sensing is that satellite communication systems present bandwidth restrictions and several issues typical of time-variant channels, which justifies the need for signal coding techniques. In that sense, this letter proposes an unequal error protection method for aerospace applications using the recommendations for source and channel coding created by the Consultative Committee for Space Data System (CCSDS) as frameworks. The proposed method makes use of the CCSDS-recommended convolutional code to ensure a channel coding step as low complex as possible, which allows implementation in a wide range of embedded platforms. This letter exploits the natural data division delivered by the compressor to unequally protect the information. The proposed method, which relies on a multiobjective optimization problem, allows one to find rate arrangements that minimize the distortion of the received image for a given value of an average coding rate within a granular range. The system performance is evaluated over an additive white Gaussian noise channel model. The obtained results show that the proposed method presents several advantages over an equal error protection strategy, and paves the way for scenarios with stringent energy and bandwidth constraints.

Unequal error protection based on expanding window fountain for object-based 3D audio

This paper proposes an unequal error protection (UEP) coding method to improve the transmission performance of three-dimensional (3D) audio based on expanding window fountain (EWF). Different from other transmissions with equal error protection (EEP) when transmitting the 3D audio objects. An approach of extracting the important audio object is presented, and more protection is given to more important audio object and comparatively less protection is given to the normal audio objects. Objective and subjective experiments have shown that the proposed UEP method achieves better performance than equal error protection method, while the bits error rates (BER) of the important audio object can decrease from 10–3 to 10–4, and the subjective quality of UEP is better than that of EEP by 14%.

Unequal Error Protection of Memories in LDPC Decoders

Memories are one of the most critical components of many systems: due to exposure to energetic particles, fabrication defects and aging they are subject to various kinds of permanent and transient errors. In this scenario, Unequal error protection (UEP) techniques have been proposed in the past to encode stored information, allowing to detect and possibly recover from errors during load operations, while offering different levels of protection to partitions of codewords according to their importance. Low-density parity-check (LDPC) codes are used in many communication standards to encode the transmitted information: at reception, LDPC decoders heavily rely on memories to store and correct the received information. To ensure efficient and reliable decoding of information, the need to protect the memories used in LDPC decoders is of primary importance. In this paper we present a study on how to efficiently design UEP techniques for LDPC decoder memories. The devised UEP method is divided in four adjustable levels, each one offering a different degree of protection. The full UEP, along with simplified versions, has been implemented within an existing decoder and its area occupation and power consumption evaluated. Comparison with the literature on the subject shows an unmatched level of protection from errors at a small complexity and energy cost.

Compressed sensing‐based unequal error protection by linear codes

In many wireless communication systems, data can be divided into different importance levels. For these systems, unequal error protection (UEP) techniques are used to ensure lower bit error rate for the more important classes. Moreover, if the precise characteristics of the channel are known, UEP can be used to correctly recover the more important classes even under severe receiving conditions. In this study, a UEP scheme based on compressed sensing via a linear program is proposed. Discrete wavelet transform (DWT) is chosen as the sparsifying basis, and then DWT-coded information is divided into two-layered coded streams, each of which is transmitted differentially by applying an unequal number of information bits in linear codes according to the time-varying characteristic of the corrupted channel. In this proposed transmission scheme, the more important information is to guarantee error-free transmission. At the decoder, one can simply reconstruct the signal via the l 1-minimisation algorithm. Simulation results show that the proposed scheme can achieve a higher peak signal-to-noise ratio (PSNR) and obviously improve the error resilience compared to the equal error protection scheme and other UEP methods. More importantly, with the increase of channel corrupted ratio, the drop rate of PSNR is much slower than other solutions. It indicates that the proposed method has better robustness for severe channel conditions.

Distributed Fountain Codes With Adaptive Unequal Error Protection in Wireless Relay Networks

In wireless relay networks (WRNs), multiple source nodes communicate with a single destination node through a common relay network. Different source nodes may have different error protection or recovery time requirements. In this paper, we focus on unequal error protection (UEP) distributed network coding (DNC) design for WRNs. Specifically, we propose a continuous UEP method based on fountain codes with the objective of satisfying the UEP or unequal recovery time (URT) requirements. Then based upon this UEP method, we develop an adaptive UEP DNC scheme to realize adaptive UEP in WRNs. We analyze the properties of the proposed adaptive UEP DNC scheme and derive the upper and lower bit error rate (BER) bounds for it over Rayleigh fading channels under maximum-likelihood (ML) decoding. Simulation results show that the proposed adaptive UEP DNC scheme has desirable UEP and URT properties. The transmitted data from the source nodes in different protection groups can be recovered successfully under their performance requirements in a shorter time by using the adaptive UEP DNC scheme.

Unequal Error Protection for Streaming Media Based on Rateless Codes

This paper presents an Unequal Error Protection (UEP) method for streaming media. Previous researches have shown that UEP rateless codes can provide a low-complexity solution for downloading scalable information. However, the randomized generator of rateless codes leads to uncertainty of decoding probability and decoding priority of input data, and thus it is not suitable for streaming applications. In this paper, a novel UEP method is presented for streaming media. The proposed method, which consists of a hierarchical coding graph as well as low-complexity encoding and decoding operations, preserves the advantage of the UEP rateless codes and characterizes the decoding probability and decoding priority by formulas. The proposed hierarchical coding graph guarantees that high-priority input data are recovered before low-priority ones, so important information can be recovered with low latency, low computation, and high probability. In addition, data in different layers of the proposed UEP are dependently encoded, so that data in different layers can help decode each other. For heterogeneous clients, the proposed UEP codes can help a decoder with recovery of different amount of information according to the network condition and computation ability. Besides, we also extend the proposed UEP codes to a rateless version for downloading of media. Compared with the previous finite-length and rateless UEP codes, our method can recover more high-priority data even in serious packet loss rate (PLR), and the decoding order of data can be assigned by the server.

Coded Hierarchical Modulation for Wireless Progressive Image Transmission

A robust coded scheme for progressive multimedia transmission is proposed for additive white Gaussian noise, flat Rayleigh fading channels, and frequency-selective channels using different unequal error protection methods in combination. Hierarchical modulation is coupled with a packetization/combining strategy and an efficient channel encoder consisting of a cyclic redundancy check outer coder concatenated with an inner rate-compatible punctured convolutional coder. Distortion-optimal hierarchical parameters are jointly chosen with the set of channel coding parameters on a packet-switched wireless network with fixed length packets. A lower bound for the performance improvement of the proposed system is derived and shown to give significant gains at lower packet sizes and higher transmission rates. The proposed system is also shown to outperform several existing schemes for realistic wireless channels.

Unequal Error Protection Using Fountain Codes With Applications to Video Communication

Application-layer forward error correction (FEC) is used in many multimedia communication systems to address the problem of packet loss in lossy packet networks. One powerful form of application-layer FEC is unequal error protection which protects the information symbols according to their importance. We propose a method for unequal error protection with a Fountain code. When the information symbols were partitioned into two protection classes (most important and least important), our method required a smaller transmission bit budget to achieve low bit error rates compared to the two state-of-the-art techniques. We also compared our method to the two state-of-the-art techniques for video unicast and multicast over a lossy network. Simulations for the scalable video coding (SVC) extension of the H.264/AVC standard showed that our method required a smaller transmission bit budget to achieve high-quality video.

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.

Distortion optimal transmission of multi-layered FGS video over wireless channels

We analytically model the distortion of a scalable video bitstream containing a Base Layer (BL) and one or more Enhancement Layers (ELs). Utilizing our distortion model, we propose a pair of low complexity Unequal Error Protection (UEP) methods for transmitting BL and EL bitstreams over a wireless channel. Our one dimensional Forward Error Correction (FEC) UEP methods protect each bitstream against both temporally correlated bit errors caused by fading and packet erasures caused by network buffering. Our methods use optimal symbol interleaving to combat tandem loss effects. We illustrate the performance advantage of our methods over a baseline Equal Error Protection (EEP) and a number of UEP methods for different available budgets and channel conditions.

Comparison of Error Protection Methods for Audio-Video Broadcast over DVB-H

The paper discusses methods for robust audio-video broadcast over the digital video broadcasting-handheld (DVB-H) system. DVB-H includes a link-layer forward error correction (FEC) scheme known as multiprotocol encapsulation (MPE) FEC, which provides equal error protection (EEP) to the transmitted media streams. Several approaches for unequal error protection (UEP) have been proposed in the literature, and the applicability of some of them to DVB-H is analyzed in the paper. A link-layer UEP method based on priority segmentation of the media streams is chosen for more detailed analysis. According to the method, audio and the most important coded video pictures are protected by MPE-FEC more robustly compared to the remaining coded pictures. In order to compare EEP and UEP in a DVB-H environment, an error-prone DVB-H channel was simulated, audio-visual clips were sent through it, and a comprehensive subjective quality evaluation was conducted in a controlled laboratory environment. The results of the subjective evaluation revealed that the use of UEP improves the subjective quality of some test clips noticeably when the channel conditions were severe, while in other tested channel conditions and clips, UEP and EEP performed equally well.

An unequal error protection method for progressively transmitted 3D models

In this paper, we present a packet-loss resilient system for the transmission of progressively compressed three-dimensional (3D) models. It is based on a joint source and channel coding approach that trades off geometry precision for increased error resiliency to optimize the decoded model quality on the client side. We derive a theoretical framework for the overall system by which the channel packet loss behavior and the channel bandwidth can be directly related to the decoded model quality at the receiver. First, the 3D model is progressively compressed into a base mesh and a number of refinement layers. Then, we assign optimal forward error correction code rates to protect these layers according to their importance to the decoded model quality. Experimental results show that with the proposed unequal error protection approach, the decoded model quality degrades more gracefully (compared to either no error protection or equal error protection methods) as the packet-loss rate increases.

Unequal error protection for MPEG-2 video transmission over wireless channels

This paper proposes an unequal error protection (UEP) method for MPEG-2 video transmission. Since the source and channel coders are normally concatenated, if the channel is noisy, more bits are allocated to channel coding and fewer to source coding. The situation is reversed when the channel conditions are more benign. Most of the joint source channel coding (JSCC) methods assume that the video source is subband coded, the bit error sensitivity of the source code can be modeled, and the bit allocations for different subband channels will be calculated. The UEP applied to different subbands is the rate compatible punctured convolution channel coder. However, the MPEG-2 coding is not a subband coding, the bit error sensitivity function for the coded video can no longer be applied. Here, we develop a different method to find the rate-distortion functions for JSCC of the MPEG-2 video. In the experiments, we show that the end-to-end distortion of our UEP method is smaller than the equal error protection method for the same total bit-rate.

Feedback and error protection strategies for wireless progressive video transmission

Simple but meaningful models for a mobile radio channel are introduced and a channel-coding system based on high-memory rate-compatible punctured convolutional codes with an appropriate sequential decoding algorithm, the far-end error decoder (FEED), are presented. In combination with puncturing, we devise a method for unequal error protection (UEP) and error localization within a progressively coded source message without any additional error detection code. The FEED-based channel-coding system does not aim to minimize the bit or word error probability, but to delay the first error within a data frame as far as possible. This channel-coding scheme and the FEED algorithm can be used efficiently with automatic repeat request (ARQ). We present different ARQ strategies. For all forward error-correction (FEC) schemes, bounds are specified which allow the estimation of the performance and appropriate rate allocation. We briefly discuss an efficient fine granular scalable video compression scheme, the progressive texture video codec (PTVC). The proposed scheme generates an embedded bit-stream for each frame and allows reference frames to be adjusted. These source and channel-coding algorithms are used to design several video communication systems based on FEC and ARQ methods. The resulting systems are presented and compared. Performance estimations based on bounding techniques and optimized rate-allocation algorithms are derived and applied. Experimental results show the improvement potential of the proposed systems compared to standard schemes. Video communication over very low bit-rate mobile channels with varying channel conditions is thus made possible.

Soft source decoding with applications

Motivated by previous results in joint source-channel coding and decoding, we consider the problem of decoding of variable-length codes using soft channel values. We present results of decoding of selected codes using the maximum a posteriori (MAP) decoder and the sequential decoder, and show the performance gains over decoding using hard decisions alone. The objective behind this work is to provide motivation for decoding of data compressed by standard source coding schemes, that is, to view the compressed bitstreams as being the output of variable-length coders and to make use of the redundancy in the bitstreams to assist in decoding. In order to illustrate the performance achievable by soft decoding, we provide results for decoding of MPEG-4 reversible variable-length codes as well as for decoding of MPEG-4 overhead information, under the assumption that this information is transmitted without channel coding over an additive white Gaussian noise channel. Finally, we present a method of unequal error protection for an MPEG-4 bitstream using the MAP and sequential source decoders, and show results comparable to those achievable by serial application of source and channel coding.