Block turbo codes for efficient image transmission over wireless channels

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.

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.

Video streaming over wireless channel encounters many challenges due to the time-varying characteristics of wireless channels and limited network bandwidth. In this paper, we investigate an adaptive forward error correction (FEC) scheme for streaming the stored MPEG-4 FGS bit-stream from the video server to the clients over wireless channel. In this scheme, the base layer is transmitted reliably and the enhancement layer is protected with unequal error protection (UEP) scheme. Taking the fine-grained characteristics of FGS into account, we propose a decodable rate maximized criterion to optimally allocate the bit rate between the source rate and the channel coding rate and dynamically adapt to the varying network condition. Experimental results show that Compared with fixed unequal error protection (UEP) and equal error protection (EEP), our proposed method can provide a better performance.

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.

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.

Multimedia delivery over Wireless Sensor Networks (WSNs) is energy critical. In this paper, we study an energy constrained cross layer optimization scheme to improve digital image quality in cross polarization discrimination (XPD) based Multiple Input Multiple Output (MIMO) WSNs. The contribution of this research can be summarized in three parts. First, link layer energy consumption and packet loss ratio in multirate XPD based MIMO WSN are modeled. Secondly, XPD based modulation optimization cross link and physical layer is proposed, achieving considerable energy efficiency. Finally, a new Position-Value (P- V) based Unequal Error Protection (UEP) scheme is studied and discussed in XPD MIMO WSNs, with more efficient resource allocation compared to traditional approaches. Simulation results show the proposed modulation optimization scheme improves energy efficiency considerably, and position based UEP achieves significant distortion-energy gain compared with traditional layer based resource allocation schemes in XPD MIMO WSNs.

In this paper, we provide a sub-channel partitioning based unequal error protection (UEP) scheme for a space-time block coded orthogonal frequency division multiplexing (STBC-OFDM) system. In such a scheme, video data is partitioned into high-priority (HP) and low-priority (LP) layers according to the importance of the data. At the receiver side, OFDM sub-channels are partitioned into high-quality (HQ) and low-quality (LQ) groups according to the estimated channel qualities. Based on the feedback of sub-channel partitioning results, the transmitter assigns HP and LP video data to the corresponding HQ and LQ sub-channels. Through theoretical analysis, we show there is indeed a significant BER difference between the HQ and LQ sub-channels, which can be exploited by UEP. Based on the analysis, we provide a criterion for determining the appropriate transmission power. Through computer simulations, we show that the proposed scheme offers significant performance gain compared to conventional methods. We also demonstrate that the scheme is the least sensitive to channel estimation errors among all compared schemes, and is hardly influenced by the Doppler spread. The feedback overhead can also be reduced with almost no performance penalty by bundling several neighboring sub-channels together and assigning them to the same group.

In a frequency selective channel for wireless applications, we provide a new resources allocation procedure that enables the transmission of scalable images in accordance with end-to-end <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Quality</i> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">of</i> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Service</i> (QoS) constraints. This scheme is based on an <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Unequal</i> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Error</i> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Protection</i> (UEP) policy with the possible truncation of the source data layers (after the source coding stage) and an optimal use of the available resources for each layer (with local flattening over the channel portion). The proposed algorithm is applied to the transmission of JPEG-2000 scalable images over an OFDM channel. We analyze the performance of our method in term of perceived quality and speed, and show better results than State-Of-The-Art UEP schemes.

Traditional unequal error protection (UEP) schemes have some limitations and problems, such as the poor UEP performance of high priority data and the seriously sacrifice of low priority data in decoding property. Based on the reasonable applications of different degree distributions in LT codes, this paper puts forward a novel UEP LT coding scheme with a simple feedback to compile these data packets separately. Simulation results show that the proposed scheme can effectively protect high priority data, and improve the transmission efficiency of low priority data from 2.9% to 22.3%. Furthermore, it is fairly suitable to apply this novel scheme to multicast and broadcast environments since only a simple feedback introduced.

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.

On account of the wireless channel interference, transmission data tends to be erroneously decoded at the receiver. Even received with errors in some extent, the video can still be successfully recovered because of its error resilience, e.g. videos encoded with H.264/AVC. According to recent research, when a bit sequence is modulated to constellation symbols, different bit positions of symbols may have different probabilities of error occurrence. To exploit whether differential protection could be provided to different data bits of a video streaming based on this feature, our experiment implements this UEP (unequal error protection) scheme together with the data partitioning mechanism in H.264/AVC video encoding standards. The experiment results show the UEP scheme gains 5 dB of PSNR improvement in average than the EEP (equal error protection) scheme. While once massive errors occur, packets must be discarded and retransmissions are required, so additional resource consumption is unavoidable. To solve this problem, unequal loss protection (ULP) for H.264 bit stream is proposed in this paper. And we find a fact through experiments that when bandwidth resource is limited, insignificant partial data of H.264 bit stream could be discarded selectively without arousing obvious video quality degradation. Our simulation shows that when the unimportant network abstraction layer units (NALU) of H.264 bit stream are discarded, approximately 20 % of bandwidth resource is saved.

Resource allocation for multimedia selective encryption and energy efficient transmission has not been fully investigated in literature for wireless sensor networks (WSNs). In this article, we propose a new cross-layer approach to optimize selectively encrypted image transmission quality in WSNs with strict energy constraint. A new selective image encryption approach favorable for unequal error protection (UEP) is proposed, which reduces encryption overhead considerably by controlling the structure of image bitstreams. Also, a novel cross-layer UEP scheme based on cipher-plain-text diversity is studied. In this UEP scheme, resources are unequally and optimally allocated in the encrypted bitstream structure, including data position information and magnitude value information. Simulation studies demonstrate that the proposed approach can simultaneously achieve improved image quality and assured energy efficiency with secure transmissions over WSNs.

A modified set partitioning in hierarchical trees (SPIHT) algorithm based on wavelet coefficient blocks, which is more appropriate to robust image transmission over noisy channels when using unequal error protection (UEP) scheme, is presented. According to the algorithm characteristic of traditional SPIHT coding that scanning once can process four wavelet coefficients, our approach divides the wavelet transform coefficient matrix into corresponding coefficient blocks and encodes every block with different strategies. When the maximum value of the coefficient block is less than the current threshold, only one bit is used for coding, thus to reduce the loss of coding efficiency caused by repeat coding and early coding for non-important coefficients. Simulation results show that the proposed algorithm combined with UEP can provide a better peak signal to noise ratio (PSNR) performance for image transmission over noisy channel, especially at low bit rate.

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.

Distributed Speech Recognition (DSR) systems rely on efficient transmission of speech information from distributed clients to a centralized server. Wireless or network communication channels within DSR systems are typically noisy and bursty. Thus, DSR systems must utilize efficient Error Recovery (ER) schemes during transmission of speech information. Some ER strategies, referred to as forward error control (FEC), aim to create redundancy in the source coded bitstream to overcome the effect of channel errors, while others are designed to create spread or delay in the feature stream in order to overcome the effect of bursty channel errors. Furthermore, ER strategies may be designed as a combination of the previously described techniques. This chapter presents an array of error recovery techniques for remote speech recognition applications. This chapter is organized as follows. First, channel characterization and modeling are discussed. Next, media-specific FEC is presented for packet erasure applications, followed by a discussion on media-independent FEC techniques for bit error applications, including general linear block codes, cyclic codes, and convolutional codes. The application of unequal error protection (UEP) strategies utilizing combinations of the aforementioned FEC methods is also presented. Finally, framebased interleaving is discussed as an alternative to overcoming the effect of bursty channel erasures. The chapter concludes with examples of modern standards for channel coding strategies for distributed speech recognition (DSR). 8.1. Distributed Speech Recognition Systems Throughout this chapter various error recovery and detection techniques are discussed. It is therefore necessary to present an overview of a complete experimental DSR system, including feature extraction, a noisy channel model, and an automatic speech recognition engine at the server end (Fig. 8.1). 2 Bengt J. Borgstrom, Alexis Bernard, and Abeer Alwan Feature Extraction Source Coding Channel Coding Channel Decoding Source Decoding Speech Recognition Client Server Noisy Channel input speech