Image transmission using unequal error protection combined with two-fold turbo coding

Two-fold turbo codes have been recently introduced as the least complex member of the multifold turbo code family, and they have been shown to outperform their conventional symmetric and asymmetric cousins in the waterfall region. This article introduces a simple method that allows two-fold turbo codes to offer bi-level unequal error protection. Also, the application of the unequal error protection to a still image coding technique, i.e. huesaturation-luminance coding, is explained and the pixel error performance results under Gaussian conditions are presented. According to the simulation results, the proposed scheme outperforms its conventional counterpart by up to 0.7 dB. Furthermore, with the new unequal error protection coding scheme, under certain channel conditions, significant savings in decoder iterations are achieved, without compromising the received image quality. Although the unequal error protection is limited to bi-level within the scope of this article, same technique can be used to provide multilevel error protection.

The MPEG-4 video compression standard incorporates several techniques to create error-resilient coded video. These techniques are effective against a certain level of errors. However, wireless channels often have very high error rates; thus channel coding is needed to reduce the number of errors in the compressed bitstream that is sent to the MPEG-4 video decoder. The structure of an MPEG-4 compressed bitstream lends itself to using unequal error protection to ensure fewer errors in the important portions of the bitstream. This paper discuses how unequal error protection can be used with the MPEG-4 error resilience tools and describes several experiments using both unequal and equal error protection on video sent through a simulated GSM channel. The results of these experiments show that when the bit error rate is high, unequal error protection can improve reconstructed video quality by as much as 1 dB compared with equal error protection.

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.

In this paper we propose a new image transmission scheme for an image which has been compressed using wavelet image compression and coded with a Variable Length Code. The proposed scheme applies Unequal Error Protection (UEP) at three different stages, namely the source coding, channel coding and retransmission stage. UEP at the source coding stage is employed to unequally protect the image subbands against error propagation, which arises due to variable length coding. At the channel coding stage, UEP is applied by the use of Rate Compatible Punctured Convolutional codes to unequally allocate coding redundancy to the image subbands. Finally at the retransmission stage, UEP is applied by assigning different synchronization error tolerances to the image subbands. Gains of over 4 dB in terms of Peak to Peak Signal to Noise Ratio (PSNR) is achieved by employing the integrated UEP scheme as compared to a standard Equal Error Protection Scheme.

In this contribution we investigate the performance of the UMTS Long Term Evolution (LTE) physical layer using turbo coding and 64QAM with Gray mapping. We show how the mapping of systematic and parity bits to the six different bit positions defining one complex 64QAM symbol influences the convergence of the turbo decoder and thereby the bit error rate (BER) performance as well as number of necessary decoding iterations. Exploiting the unequal error protection (UEP) property of Gray mapped 64QAM results in an SNR performance gain of approximately 2 dB for the non-iterative system and in addition leads to a significant reduction of the necessary decoding iterations when iterative decoding is performed.

This paper presents a new unequal error protection (UEP) image transmission system that incorporates a Lifting Wavelet Transform (LWT) and Reed Solomon (RS) coded cooperation scheme to increase image transmission diversity, as well as save transmission bandwidth. Having a partner to assist direct communication increases the resilience of low frequency subband data against an error-prone fading channel. Low frequency subbands are partitioned into two sets of data and transmitted using the RS coded cooperation scheme. High frequency subbands data are transmitted directly to a base station. Results show that the new UEP image transmission system using LWT based RS coded cooperation scheme achieves diversity gains of around 10dB, with channel SNR from 10 to 20dB, compared with the image transmission system with non-cooperative system under slow Rayleigh fading channel for all levels of LWT decomposition. In addition, the new UEP image transmission system using LWT based RS coded cooperation scheme with one level of wavelet decomposition offers around 37.5% bandwidth gain (ß), compared with the system without LWT, which incurs a reduction of 3dB in reconstructed image quality.

In view of increasing use of video transmission over wireless channels, a lot of research efforts have been made to trade-off the error resiliency and transmission bandwidth requirements. This in turn has led to development of various unequal error protection (UEP) schemes. In this paper, the performance of optimized 2-layered and 3-layered UEP schemes using hierarchical 64 QAM (64-HQAM) for wavelet-transformed images coded with set partitioning in hierarchical trees (SPIHT) algorithm and transmitted over additive white Gaussian noise (AWGN) channel is investigated. A look-up table (LUT) based approach to select the optimal values of modulation parameters of 64-HQAM for different channel conditions is suggested so as to reduce the computational complexity. Simulation results show that 3-layered optimized 64-HQAM-based UEP outperforms corresponding non-optimized UEP. Also, 3-layered optimized UEP scheme using 64-HQAM performs slightly better as compared to optimized 2-layered UEP scheme using 64-HQAM.

In this paper, a power water-filling scheme for unequal error protection (UEP) based on set partitioning in hierarchical trees (SPIHT) coded image transmission over multiple input multiple output(MIMO) channels is proposed. SPIHT coded image information is divided into different sub-streams according to their different importance, which is allocated to different channels. Then unequal error protection (UEP) of image with singular value decomposition and power water-filling policy is achieved. The simulation results show that the quality of reconstructed image of using UEP is better than equal error protection (EEP).

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.

We present a dynamic unequal error protection (UEP) framework for the embedded image bit streams over noisy channels. A general source model for M-rate UEP schemes is derived and an optimization algorithm for 2-rate dynamic UEP schemes is developed. To facilitate the design and implementation of UEP schemes, we also derived a necessary condition and an upper bound for UEP gains. Simulation results demonstrate about 0.3 dB improvements over equal error protection (EEP) schemes at the price of negligible overheads while the progressiveness of the original bit streams is still kept.

In this paper we propose an image coding scheme based on Block Turbo Codes (BTC) for protecting SPIHT coded images transmitted over wireless channels. An Unequal Error Protection (UEP) scheme using different product codes is also presented. The optimization of the UEP scheme under a transmission budget constraint is investigated. Performance of the proposed system are first evaluated over Gilbert-Elliott (GE) channels. They are then compared to the well-known system of Sherwood and Zeger, through numerical simulations over a single path Rayleigh fading channel. Then, we present an optimized mobile image transmission framework involving a multiuser asynchronous DS-CDMA transmission system over Rayleigh multipath channels. Simulation results for the 512x512 Lena image, transmitted over the ITU Vehicular A channel, show that a significant gain in PSNR is obtained by using the SIC/RAKE multiuser detector in comparison with a conventional detection by the RAKE receiver. Furthermore, performance are also improved when introducing the UEP scheme.

An investigation of unequal error protection (UEP) methods applied to JPEG image transmission using turbo codes is presented. The JPEG image is partitioned into two groups, i.e., DC components and AC components according to their respective sensitivity to channel noise. The highly sensitive DC components are better protected with a lower coding rate, while the less sensitive AC components use a higher coding rate. Simulation results are given to demonstrate how the UEP schemes outperforms the equal error protection (EEP) scheme in terms of bit error rate (BER) and peak signal to noise ratio (PSNR).

In this paper, based on the characteristics of multilevel codes (MLC) and space-time block codes (STBC), a concatenation scheme (MLC-STBC) combining MLC and STBC is presented over Rayleigh fading channels. The unequal error protection (UEP) of MLC-STBC in Rayleigh fading channels for image transmission is investigated. Furthermore, taking 8ASK modulation as the example, a non-uniform signal constellation for realizing UEP of MLC-STBC is designed. Both theoretical analysis and computer simulation show that MLC-STBC scheme is a high rate and high power efficiency scheme, UEP is its inherent character and non-uniform signal constellation can improve its UEP ability. Its UEP character can enhance the transmission quality in the same bandwidth over a Rayleigh fading channel. MLC-STBC is an excellent scheme for image transmission.

In this paper, we focus on network coding design for the wireless sensor networks (WSNs), where multiple source nodes communicate with a common destination node with the help of multiple relay nodes in a two-hop fashion. Specifically, we propose an unequal error protection (UEP) distributed network-channel coding (DNCC) scheme based on Luby-transform (LT) codes. We analyse three properties of the proposed UEP DNCC scheme, i.e. effective weights, turning points, and thresholds of the source nodes' number. Also, we derive the upper and lower bit error rate (BER) bounds for the proposed UEP DNCC scheme over Rayleigh fading channels under maximum-likelihood (ML) decoding. Based on the analysis, it is observed that the proposed UEP DNCC scheme can achieve all protection levels required when the number of source nodes is large enough. Simulation results show that our UEP DNCC scheme can provide desirable UEP to all source nodes.

In this paper, we address the problem of providing unequal error protection (UEP) with LDPC codes built on finite sets of order strictly greater than 2 (nonbinary codes). The main interest of providing UEP with nonbinary LDPC codes is that future standards are likely to prefer nonbinary coding schemes because of their better robustness to the codeword length and the modulation size. However, the problem of giving UEP properties with nonbinary LDPC codes is much more difficult than with binary LDPC codes. We present a first attempt to solve this difficult problem, based on LDPC codes built on finite groups. The framework and the basis about group LDPC codes are first presented in details, and the framework is used to give examples of UEP nonbinary LDPC codes that actually achieve different UEP properties at the bit level while the symbol error properties are kept equally protected.