Cross-layer optimization of unequal protected layered video over hierarchical modulation

Abstract-unequal protection mechanisms have been proposed at several layers in order to improve the reliability of multimedia contents, especially for video data. The paper aims at implementing a multi-layer unequal protection scheme, which is based on a Physical-Transport-Application cross-layer design. Hierarchical modulation, in the physical layer, has been demonstrated to increase the overall user capacity of a wireless communications. On the other hand, unequal erasure protection codes at the transport layer turned out to be an efficient method to protect video data generated by the application layer by exploiting their intrinsic properties. In this paper, the two techniques are jointly optimized in order to enable recovering lost data in case the protection is performed separately. We show that the cross-layer design proposed herein outperforms the performance of hierarchical modulation and unequal erasure codes taken independently

Live video streaming over packet networks and wireless channels

The transmission of live video over noisy channels requires very low end-to-end delay. Although automatic repeat request ensures lossless transmission, its usefulness to live video streaming is restricted to short connections because of the unbounded retransmission latency. An alternative is to use forward error correction (FEC). Since finding an optimal error protection strategy can be time expensive, FEC systems are commonly designed for the worst case condition of the channel, which limits the end-to-end performance. We study the suitability of two scalable FEC-based systems to the transmission of live video over packet networks. The first one uses Reed-Solomon codes and is appropriate for the Internet. The second one uses a product channel code and is appropriate for wireless channels. We show how fast and robust transmission can be achieved by exploiting a parametric model for the distortion-rate curve of the source coder and by using fast joint source-channel allocation algorithms. Experimental results for the 3D set partitioning in hierarchical tree video coder show that the systems have good reconstruction quality even in severe channel conditions. Finally, we compare the performance of the systems to the state-of-the-art for video transmission over the Internet. 1

Channel coding for progressive images in a 2-D time-frequency OFDM block with channel estimation errors.

Coding and diversity are very effective techniques for improving transmission reliability in a mobile wireless environment. The use of diversity is particularly important for multimedia communications over fading channels. In this work, we study the transmission of progressive image bitstreams using channel coding in a 2-D time-frequency resource block in an OFDM network, employing time and frequency diversities simultaneously. In particular, in the frequency domain, based on the order of diversity and the correlation of individual subcarriers, we construct symmetric n -channel FEC-based multiple descriptions using channel erasure codes combined with embedded image coding. In the time domain, a concatenation of RCPC codes and CRC codes is employed to protect individual descriptions. We consider the physical channel conditions arising from various coherence bandwidths and coherence times, leading to a range of orders of diversities available in the time and frequency domains. We investigate the effects of different error patterns on the delivered image quality due to various fade rates. We also study the tradeoffs and compare the relative effectiveness associated with the use of erasure codes in the frequency domain and convolutional codes in the time domain under different physical environments. Both the effects of intercarrier interference and channel estimation errors are included in our study. Specifically, the effects of channel estimation errors, frequency selectivity and the rate of the channel variations are taken into consideration for the construction of the 2-D time-frequency block. We provide results showing the gain that the proposed model achieves compared to a system without temporal coding. In one example, for a system experiencing flat fading, low Doppler, and imperfect CSI, we find that the increase in PSNR compared to a system without time diversity is as much as 9.4 dB

Wireless industrial monitoring and control networks: the journey so far and the road ahead

While traditional wired communication technologies have played a crucial role in industrial monitoring and control networks over the past few decades, they are increasingly proving to be inadequate to meet the highly dynamic and stringent demands of today’s industrial applications, primarily due to the very rigid nature of wired infrastructures. Wireless technology, however, through its increased pervasiveness, has the potential to revolutionize the industry, not only by mitigating the problems faced by wired solutions, but also by introducing a completely new class of applications. While present day wireless technologies made some preliminary inroads in the monitoring domain, they still have severe limitations especially when real-time, reliable distributed control operations are concerned. This article provides the reader with an overview of existing wireless technologies commonly used in the monitoring and control industry. It highlights the pros and cons of each technology and assesses the degree to which each technology is able to meet the stringent demands of industrial monitoring and control networks. Additionally, it summarizes mechanisms proposed by academia, especially serving critical applications by addressing the real-time and reliability requirements of industrial process automation. The article also describes certain key research problems from the physical layer communication for sensor networks and the wireless networking perspective that have yet to be addressed to allow the successful use of wireless technologies in industrial monitoring and control networks

Rate Efficient Wireless Image Transmission using MIMO-OFDM

In this paper, we propose a rate efficient JPEG 2000 image transmission system over hybrid wireless networks using MIMO-OFDM. The objective is to minimize the expected end-to-end distortion given the rate constraint, which is achieved by jointly adjusting source coding schemes and channel coding rates. In this system, MIMO-OFDM is used to increase the channel capacity and mitigate the inter-symbol interference, variable rate space frequency codes and Reed Solomon codes are adopted to combat the channel errors, and error resilient source coding schemes are applied to restrict the error propagation. In case network congestion may happen, packet erasure codes are used to alleviate the packet dropping. The advantages of the proposed system lie in three aspects: adaptivity, optimality, and low complexity. Based on the characteristics of the image content, the estimated channel conditions, and the distortion constraint, the proposed low-complexity joint source channel coding and rate control algorithm adjusts the coding and transmission strategies adaptively, which can approximate the optimal solution with a tight bound

Joint Source-Channel Coding of JPEG 2000 Image Transmission Over Two-Way Multi-Relay Networks

In this paper, we develop a two-way multi-relay scheme for JPEG 2000 image transmission. We adopt a modified time-division broadcast (TDBC) cooperative protocol, and derive its power allocation and relay selection under a fairness constraint. The symbol error probability of the optimal system configuration is then derived. After that, a joint source-channel coding (JSCC) problem is formulated to find the optimal number of JPEG 2000 quality layers for the image and the number of channel coding packets for each JPEG 2000 codeblock that can minimize the reconstructed image distortion for the two users, subject to a rate constraint. Two fast algorithms based on dynamic programming (DP) and branch and bound (BB) are then developed. Simulation demonstrates that the proposed JSCC scheme achieves better performance and lower complexity than other similar transmission systems

Energy efficiency of error correction on wireless systems

Since high error rates are inevitable to the wireless environment, energy-efficient error-control is an important issue for mobile computing systems. We have studied the energy efficiency of two different error correction mechanisms and have measured the efficiency of an implementation in software. We show that it is not sufficient to concentrate on the energy efficiency of error control mechanisms only, but the required extra energy consumed by the wireless interface should be incorporated as well. A model is presented that can be used to determine an energy-efficient error correction scheme of a minimal system consisting of a general purpose processor and a wireless interface. As an example we have determined these error correction parameters on two systems with a WaveLAN interfac

Wavelet based image compression integrating error protection via arithmetic coding with forbidden symbol and map metric sequential decoding with ARQ retransmission

The phenomenal growth of digital multimedia applications has forced the communication