Joint source-channel rate allocation in parallel channels.

A fast rate-optimal rate allocation algorithm is proposed for parallel transmission of scalable images in multichannel systems. Scalable images are transmitted via fixed-length packets. The proposed algorithm selects a subchannel, as well as a channel code rate for each packet, based on the signal-to-noise ratios (SNRs) of the subchannels. The resulting scheme provides unequal error protection of source bits and significant gains are obtained over equal error protection schemes. An application of the proposed algorithm to JPEG2000 transmission shows the advantages of exploiting differences in SNRs between subchannels. Multiplexing of multiple sources is also considered, and additional gains are achieved by exploiting information diversity among the sources.     

Progressive transmission of images over fading channels using rate-compatible LDPC codes.

In this paper, we propose a combined source/channel coding scheme for transmission of images over fading channels. The proposed scheme employs rate-compatible low-density parity-check codes along with embedded image coders such as JPEG2000 and set partitioning in hierarchical trees (SPIHT). The assignment of channel coding rates to source packets is performed by a fast trellis-based algorithm. We examine the performance of the proposed scheme over correlated and uncorrelated Rayleigh flat-fading channels with and without side information. Simulation results for the expected peak signal-to-noise ratio of reconstructed images, which are within 1 dB of the capacity upper bound over a wide range of channel signal-to-noise ratios, show considerable improvement compared to existing results under similar conditions. We also study the sensitivity of the proposed scheme in the presence of channel estimation error at the transmitter and demonstrate that under most conditions our scheme is more robust compared to existing schemes.     

Selective Error Detection for Error-Resilient Wavelet-Based Image Coding

This paper introduces the concept of a similarity check function for error-resilient multimedia data transmission. The proposed similarity check function provides information about the effects of corrupted data on the quality of the reconstructed image. The degree of data corruption is measured by the similarity check function at the receiver, without explicit knowledge of the original source data. The design of a perceptual similarity check function is presented for wavelet-based coders such as the JPEG2000 standard, and used with a proposed ldquoprogressive similarity-based ARQrdquo (ProS-ARQ) scheme to significantly decrease the retransmission rate of corrupted data while maintaining very good visual quality of images transmitted over noisy channels. Simulation results with JPEG2000-coded images transmitted over the binary symmetric channel, show that the proposed ProS-ARQ scheme significantly reduces the number of retransmissions as compared to conventional ARQ-based schemes. The presented results also show that, for the same number of retransmitted data packets, the proposed ProS-ARQ scheme can achieve significantly higher PSNR and better visual quality as compared to the selective-repeat ARQ scheme.     

Robust JPEG image transmission using unequal error protection and code combining

JPEG image transmission over noisy channels is highly problematic due to the sensitivity of the JPEG bit stream to error propagation. The use of resynchronization markers and channel coding do not alleviate the problem completely thus making retransmissions inevitable. In packetized image transmission, image packets are repeated n times, to ensure reliable transmission. This paper proposes a new unequal error protection (UEP) scheme which jointly optimizes the allocation of channel code rates and number of repeats to image packets, subject to a constraint on the maximum overall transmission rate. The coding scheme used is the rate compatible punctured convolutional code coupled with the code‐combining technique. An unequal allocation of headers to the image packets is also performed in order to reduce the overall distortion due to error propagation. Simulation results show that the proposed UEP scheme provides a gain of more than 8 dB in peak‐to‐peak signal‐to‐noise ratio over a tandem scheme. The flexibility of the proposed scheme, and the major performance gains obtained, make the scheme appealing for applications like, web‐based image browsing, multi‐hop networks, and wireless image transmission. Copyright © 2007 John Wiley & Sons, Ltd.     

基于抗差错算术编码的不等差错保护图像传输方法

JPEG2000图像的分层特性要求采用不等差错保护方法以实现高效传输,本文提出了一种新型的不等差错保护方法,对不同位平面采用不同码率的抗差错算术码进行编码.与基于信道编码的不等差错保护方法相比,该方法保持了压缩码流的结构,避免了复杂的信道成帧过程.与已有的基于抗差错算术码的等差错保护方法相比,该方法提高了传输图像的质量.     

Iterative decoding of serially concatenated arithmetic and channel codes with JPEG 2000 applications.

In this paper, an innovative joint-source channel coding scheme is presented. The proposed approach enables iterative soft decoding of arithmetic codes by means of a soft-in soft- out decoder based on suboptimal search and pruning of a binary tree. An error-resilient arithmetic coder with a forbidden symbol is used in order to improve the performance of the joint source/channel scheme. The performance in the case of transmission across the AWGN channel is evaluated in terms of word error probability and compared to a traditional separated approach. The interleaver gain, the convergence property of the system, and the optimal source/channel rate allocation are investigated. Finally, the practical relevance of the proposed joint decoding approach is demonstrated within the JPEG 2000 coding standard. In particular, an iterative channel and JPEG 2000 decoder is designed and tested in the case of image transmission across the AWGN channel.     

Policy allocation for transmission of embedded bit streams over noisy channels with feedback - [Transactions letters]

An efficient policy allocation algorithm for the transmission of embedded bit streams over noisy channels with feedback is proposed. The transmission is based on the type- II hybrid ARQ/FEC protocol and uses a nested sequence C of channel codes to protect the packets. There are also constraints on the total bit budget and on the allowed number of retransmissions per packet. The allocation algorithm assigns different protection policies, each policy being a subset of C, to different packets to maximize the average number of correctly received source bits. We study the performance and the complexity of the proposed scheme through the transmission of images encoded by JPEG2000 over mobile channels with correlated Rayleigh fading. We demonstrate by simulations that the proposed multiplepolicy scheme provides significant improvements over a purely FEC scheme with no feedback and also the existing fixed-policy schemes. Our results show that feedback is particularly helpful for poor channel conditions and that the proposed scheme is very robust against changes in the channel signal-to-noise ratio (SNR) and the mobile speed.     

JPEG image transmission over mobile network with an efficient channel coding and interleaving

This article studies improving of coloured JPEG image transmission over mobile wireless personal area network through the Bluetooth networks. This article uses many types of enhanced data rate and asynchronous connectionless packets. It presents a proposed chaotic interleaving technique for improving a transmission of coloured images over burst error environment through merging it with error control scheme. The computational complexity of the used different error control schemes is considered. A comparison study between different scenarios of the image transmission is held in to choose an effective technique. The simulation experiments are carried over the correlated fading channel using the widely accepted Jakes’ model. Our experiments reveal that the proposed chaotic interleaving technique enhances quality of the received coloured image. Our simulation results show that the convolutional codes with longer constraint length are effective if its complexity is ignored. It reveals also that the standard error control scheme of old Bluetooth versions is ineffective in the case of coloured image transmission over mobile Bluetooth network. Finally, the proposed scenarios of the standard error control scheme with the chaotic interleaver perform better than the convolutional codes with reducing the complexity.     

一种基于JPEG2000的自适应联合信源信道编码方法

针对JPEG2000图像在噪声条件未知的信道上有效和可靠传输问题,本文提出了一种基于反馈的自适应联合信源信道编码方案.首先采用基于子空间的信噪比估计方法实时估计信道的信噪比SNR,进而求得信道的误码率,解决了对信道的自适应问题.其次,充分利用了JPEG2000的码流质量分级特点,建立了实用的目标函数,从而根据数据包对重建图像贡献的不同,实施不同的保护,以低复杂度的运算实现了码率优化分配的自适应过程.仿真结果表明,和现有的联合信源信道编码算法相比,这种自适应联合优化编码方法可以取得较好的效果.     

A power-based unequal error protection system for digital cinema broadcasting over wireless channels

This paper deals with the efficient and robust wireless broadcasting of JPEG2000 digital cinema (DC) streams from studios to theatres. Several unequal error protection (UEP) techniques have been proposed in literature for the transmission of JPEG2000 images. Some are based on variable forward error correction (FEC) coding applied to different parts of the stream according to their importance. Alternatively, UEP can be achieved by means of unequal power allocation (UPA) schemes based on differentiated transmission power over the stream. On the other hand, in DC applications UPA achieves weak performance if considered as the only protection strategy, unless high-power budget is assigned to transmission. This work proposes a novel hybrid FEC–UPA system adopting the resilience tools of the JPEG2000 wireless (JPWL) standard. The JPWL stream is partitioned into a certain number of packet groups to which “light” FEC coding is applied. Groups are then transmitted through separate wavelet packet division multiplexing (WPDM) sub-channels at different power. Both stream partitioning and UPA are driven by the sensibilities of the JPWL packets to the channel errors. The novelty of the proposed technique relies on the use of JPWL error resilience tools for the codestream partitioning, on optimized UPA among JPWL packets based on genetic algorithms (GA) and supported by “light” FEC channel coding. The proposed system is compared to the state of the art UEP techniques on JPEG2000 transmission. The performance is evaluated in case of transmission over wireless channels with both sparse and packet error statistics. Experiments show that the proposed approach allows achieving an average peak signal-to-noise ratio (PSNR) on the reconstructed frames compliant to the standard quality required by DC applications (40 dB) for bit error rate (BER) up to 10⁻⁴.     

Hybrid Joint Source Channel Decoding for Progressive JPEG Image Transmission

In this paper, we combine two Joint Source Channel Decoding (JSCD) approaches and apply them to progressive JPEG image transmission. The first JSCD approach consists of optimizing the allocation of the channel code-rates to the different layers of the JPEG image, and is commonly referred as Unequal Error Protection (UEP). The second JSCD strategy exploits a priori probabilities obtained from source statistics as well as the residual redundancy of the source to improve channel decoding. Additionally, we propose an error resilient sub-categorization scheme for the DC layer so as to reduce the effect of the channel-induced distortion. The hybrid JSCD scheme is implemented with Rate Compatible Punctured Turbo Codes and also with the bandwidth efficient Rate Compatible Punctured Turbo Trellis Coded Modulation. Gains of over 10 dB in PSNR are obtained with the hybrid JSCD scheme as compared to a conventional JPEG image transmission scheme.     

Error Protection and Interleaving for Wireless Transmission of JPEG 2000 Images and Video

The transmission of JPEG 2000 images or video over wireless channels has to cope with the high probability and burstyness of errors introduced by Gaussian noise, linear distortions, and fading. At the receiver side, there is distortion due to the compression performed at the sender side, and to the errors introduced in the data stream by the channel. Progressive source coding can also be successfully exploited to protect different portions of the data stream with different channel code rates, based upon the relative importance that each portion has on the reconstructed image. Unequal error protection (UEP) schemes are generally adopted, which offer a close to the optimal solution. In this paper, we present a dichotomic technique for searching the optimal UEP strategy, which lends ideas from existing algorithms, for the transmission of JPEG 2000 images and video over a wireless channel. Moreover, we also adopt a method of virtual interleaving to be used for the transmission of high bit rate streams over packet loss channels, guaranteeing a large PSNR advantage over a plain transmission scheme. These two protection strategies can also be combined to maximize the error correction capabilities.     

新一代静止图像编码系统-JPEG2000

JPEG2000是最新制定的静止图像编码国际标准，JPEG2000不仅提供的率失真性能和主观图像质量优于原JPEG标准，而且在支持渐进图像传输、感兴趣区图像编码和抗误码性能上也优于传统的JPEG标准和其它编码方法。本文对JPEG2000系统的结构、特性以及其编码算法进行了分析，并给出JPEG2000与原JPEG标准的性能比较。     

A link adaptation scheme optimized for wireless JPEG 2000 transmission over realistic MIMO systems

This paper proposes a Joint Source Channel Coding solution optimized for a wireless JPEG 2000 (JPWL ISO/IEC 15444-11) image transmission scheme over a MIMO channel. To ensure robustness of the transmission, channel diversity is exploited with a Closed-Loop MIMO-OFDM scheme. This relies on the Channel State Information (CSI) knowledge on the transmitter side, which allows the MIMO channel to be decomposed into several hierarchical SISO subchannels. In the proposed scheme, the JPWL codestream is divided into hierarchical quality layer passing through the SISO subchannels. With the CSI, a global and optimal method for adjusting all the system parameters of each SISO subchannel is provided. Accordingly, adaptive modulation, Unequal Error Protection (UEP), Unequal Power Allocation (UPA) and source coding rate is provided for each quality layers. The major strength of this work is to provide an optimal method that parameterizes several variables. These have an effect on the rate-distortion trade-off under bitrate, Quality of Service (QoS) and power constraints. Finally, the proposed work allows flexible and reactive coding of a JPWL codestream adapted to the instantaneous channel status. The performance of this technique is evaluated over a realistic time-varying MIMO channel provided by a 3D-ray tracing propagation model. A significant improvement in the quality of the image is demonstrated.     

Progressive image transmission over differentially space‐time coded OFDM systems

In this paper, we consider progressive image transmission over differentially space‐time coded orthogonal frequency‐division multiplexing (OFDM) systems and treat the problem as one of optimal joint source‐channel coding (JSCC) in the form of unequal error protection (UEP), as necessitated by embedded source coding (e.g., SPIHT and JPEG 2000). We adopt a product channel code structure that is proven to provide powerful error protection and employ low‐complexity decision‐feedback decoding for differentially space‐time coded OFDM without assuming channel state information. For a given SNR, the BER performance of the differentially space‐time coded OFDM system is treated as the channel condition in the JSCC/UEP design via a fast product code optimization algorithm so that the end‐to‐end quality of reconstructed images is optimized in the average minimum MSE sense. Extensive image transmission experiments show that SNR/BER improvements can be translated into quality gains in reconstructed images. Moreover, compared to another non‐coherent detection algorithm, i.e., the iterative receiver based on expectation‐maximization algorithm for the space‐time coded OFDM systems, differentially space‐time coded OFDM systems suffer some quality loss in reconstructed images. With the efficiency and simplicity of decision‐feedback differential decoding, differentially space‐time coded OFDM is thus a feasible modulation scheme for applications such as wireless image over mobile devices (e.g., cell phones). Copyright © 2006 John Wiley & Sons, Ltd.     

On the importance of error resilience in visual communications over noisy channels

This paper presents the importance of error resilience tools in visual communications. Error resilience tools provide a mechanism enabling transmission of visual information over channels with residual random bit errors in the received bit stream. The benefits of using error resilience tools are proven by devising the analytic relationship between the time delay in a transparent channel using automatic repeat request (ARQ) and the equivalent residual bit error rate in a nontransparent channel. The error resilience tools make it possible to achieve an acceptable visual quality even in the presence of these residual errors. Our work is related and compared to the standardization work of the next-generation still image compression system JPEG2000.The results show that partial and complete substitution of the quantization and symbol encoding in visual compression systems by robust error resilience tools provides a significant increase in robustness. Three error resilience tools are discussed: (1) substitution of the quantization and symbol encoding by a fixed length coding scheme, (2) substitution by a mixed fixed length coding and variable length coding scheme, and (3) substitution of the variable length coding by reversible variable length coding.     

一种JPEG图像传输的循环码不等差错保护策略

提出一种JPEG图像传输的循环码不等差错保护策略，该策略充分考虑JPEG各部分数据重要性的不同，对比较重要的JPEG数据，使用性能较好的差错控制编码对其进行保护；而对重要性一般的JPEG数据，使用性能一般的差错控制编码。在加性高斯白噪声信道中验证该策略，仿真结果表明该策略能保证JPEG图像的稳健传输。     

Hierarchical constellation for multi-resolution data transmission over block fading channels

We propose a new technique for multi-resolution video/image data transmission over block fading channels. The proposed scheme uses an adaptive scheduling protocol employing a retransmission strategy in conjunction with a hierarchical signal constellation (known also as nonuniform, asymmetric, multi-resolution constellation) to give different transmission priorities to different resolution levels. Transmission priorities are given in terms of average packet loss rate as well as average throughput. Basically, according to the transmission scheduling and channel state (acknowledgment signal) of the previous transmission, it dynamically selects packets from different resolution levels to transmit for the current transmission. The bits from the selected packets are assigned to different hierarchies of a hierarchical 4/16-quadrature amplitude modulation to transmit them with different error protections. The selection of packets for transmission and the assignment of these selected packets to different hierarchies of the hierarchical constellation are referred to as the scheduling protocol in our proposed scheme. We model this protocol by a finite state first order Markov chain and obtain the packet loss rate and the packet transmission rate over Nakagami-m block fading channel in closed-form. Some selected numerical results show that the proposed scheme can control the relative packet loss rate and the packet transmission rate of different resolution levels by varying the priority parameter (or equivalently, the asymmetry) of the hierarchical constellation and the maximum number of allowed retransmissions.     

基于ADV202的遥感图像实时压缩系统设计

提出了以JPEG2000图像压缩标准作为压缩算法,采用JPEG2000专用编解码芯片ADV202来实现遥感图像实时压缩系统的方案.该方案可以满足遥感图像压缩系统对实时性、低失真以及高压缩比的要求.测试结果表明,该系统工作稳定可靠,能够满足遥感图像压缩系统实时性的要求,图像压缩效果令人满意.     

Adaptive source rate control for real‐time wireless video transmission

Hybrid ARQ schemes can yield much better throughput and reliability than static FEC schemes for the transmission of data over time-varying wireless channels. However these schemes result in extra delay. They adapt to the varying channel conditions by retransmitting erroneous packets, this causes variable effective data rates for current PCS networks because the channel bandwidth is constant. Hybrid ARQ schemes are currently being proposed as the error control schemes for real-time video transmission. An important issue is how to ensure low delay while taking advantage of the high throughput and reliability that these schemes provide for. In this paper we propose an adaptive source rate control (ASRC) scheme which can work together with the hybrid ARQ error control schemes to achieve efficient transmission of real-time video with low delay and high reliability. The ASRC scheme adjusts the source rate based on the channel conditions, the transport buffer occupancy and the delay constraints. It achieves good video quality by dynamically changing both the number of the forced update (intracoded) macroblocks and the quantization scale used in a frame. The number of the forced update macroblocks used in a frame is first adjusted according to the allocated source rate. This reduces the fluctuation of the quantization scale with the change in the channel conditions during encoding so that the uniformity of the video quality is improved. The simulation results show that the proposed ASRC scheme performs very well for both slow fading and fast fading channels. This revised version was published online in July 2006 with corrections to the Cover Date.