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.     

Toward an improvement of H.264 video transmission over IEEE 802.11e through a cross-layer architecture

The recently developed H.264 video standard achieves efficient encoding over a bandwidth ranging from a few kilobits per second to several megabits per second. Hence, transporting H.264 video is expected to be an important component of many wireless multimedia services, such as video conferencing, real-time network gaming, and TV broadcasting. However, due to wireless channel characteristics and lack of QoS support, the basic 802.11-based channel access procedure is merely sufficient to deliver non-real-time traffic. The delivery should be augmented by appropriate mechanisms to better consider different QoS requirements and ultimately adjust the medium access parameters to the video data content characteristics. In this article we address H.264 wireless video transmission over IEEE 802.11 WLAN by proposing a robust cross-layer architecture that leverages the inherent H.264 error resilience tools (i.e., data partitioning); and the existing QoS-based IEEE 802.11e MAC protocol possibilities. The performances of the proposed architecture are extensively investigated by simulations. Results obtained indicate that compared to 802.11 and 802.11e, our cross-layer architecture allows graceful video degradation while minimizing the mean packet loss and end-to-end delays.     

Content-adaptive traffic prioritization of spatio-temporal scalable video for robust communications over QoS-provisioned 802.11e networks

In this work a low complexity traffic prioritization strategy to transmit H.264 scalable video coding (SVC) video over 802.11e wireless networks is presented (the approach applies to any DiffServ-like network). The distinguishing feature of the proposed strategy is the ability to adapt the amount of error protection to the changing characteristics of the video content. First, we estimate the perceptual impact of data losses in the different types of enhancement layers, i.e., temporal or spatial, for a large set of H.264/SVC videos. The experiments show that perceptual impairments are highly correlated with the level of motion activity in the video sequence. Then, we propose a content-adaptive traffic prioritization strategy based on the identification of the most important parts of the enhancement layers of the video sequence by means of a low complexity macroblock analysis process. The prioritization algorithm is tested by simulating a realistic 802.11e ad hoc network scenario. Simulation results show that the proposed traffic prioritization strategy consistently outperforms, particularly for dynamic video sequences, fixed a priori approaches, as well as a traditional FEC-based UEP strategy.     

Downlink media streaming with wireless fountain coding in wireline‐cum‐WiFi networks

This paper addresses the problem of streaming packetized media data in a combined wireline/802.11 network. Since the wireless channel is normally the bottleneck for media streaming in such a network, we propose that wireless fountain coding (WFC) be used over the wireless downlink in order to efficiently utilize the wireless bandwidth and exploit the broadcast nature of the channel. Forward error correction (FEC) is also used to combat errors at the application‐layer. We analytically obtain the moment generating function (MGF) for the wireless link‐layer delay incurred by WFC. With the MGF, the expected value of this wireless link‐layer delay is found and used by the access point (AP), who has no knowledge of the buffer contents of wireless receivers, to make a coding‐based decision. We then derive the end‐to‐end packet loss/late probability based on the MGF. We develop an integrated ns‐3/EvalVid simulator to evaluate our proposed system and compare it with the traditional 802.11e scheme which is without WFC capability but equipped with application‐ and link‐layer retransmission mechanisms. Through extensive simulations of video streaming, we show that streaming with WFC is able to support more concurrent video flows compared to the traditional scheme. When the deadlines imposed on video packets are relatively stringent, streaming with WFC also shows superior performance in terms of packet loss/late probability, video distortion, and video frame delay, over the traditional scheme. Copyright © 2011 John Wiley & Sons, Ltd.     

Retry Limit Based ULP for Scalable Video Transmission over IEEE 802.11e WLANs

We investigate the packet loss behavior in the IEEE 802.11e wireless local area networks (WLANs) under various retry limit settings. Considering scalable video traffic delivery over the IEEE 802.11e WLANs, our study shows the importance of adaptiveness in retry limit settings for the unequal loss protection (ULP) design. Based on the study, we present a simple yet effective retry limit based ULP which adaptively adjusts the retry limit setting of the IEEE 802.11e medium access control protocol to maintain a strong loss protection for critical video traffic transmission. The simulation results illustrate significant advantages in the delivered video quality for our proposed design.     

GOP-based channel rate allocation using genetic algorithm for scalable video streaming over error-prone networks.

In this paper, we address the problem of unequal error protection (UEP) for scalable video transmission over wireless packet-erasure channel. Unequal amounts of protection are allocated to the different frames (I- or P-frame) of a group-of-pictures (GOP), and in each frame, unequal amounts of protection are allocated to the progressive bit-stream of scalable video to provide a graceful degradation of video quality as packet loss rate varies. We use a genetic algorithm (GA) to quickly get the allocation pattern, which is hard to get with other conventional methods, like hill-climbing method. Theoretical analysis and experimental results both demonstrate the advantage of the proposed algorithm.     

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.     

基于802.11e的无线Mesh网络中视频传输优化方案

针对无线Mesh网络环境下视频数据传输的延迟、吞吐量、丢包率等问题,改进了一种数据映射方案,将不同重要程度的数据与IEEE 802.11e中的接入类别相对应,优先发送级别高的数据。对压缩视频数据传输进行了仿真实验,并对仿真结果进行了分析,证明了在不同的网络业务负载下,改进的映射方案对网络性能有一定的改善。     

End-to-End Performance Improvement of the Wireless Channel for Video Transmission

Real time video transmission in wireless environment considers various parameters of wireless channel like information rate, error resiliency, security, end-to-end latency, quality of service etc. The available internet protocols are transmission control protocol and user datagram protocol (UDP). But most of the real-time applications uses UDP as their transport protocol. UDP is a fast protocol suitable for delay sensitive applications like video and audio transmission as it does not provide flow control or error recovery and does not require connection management. Due to the tremendous growth in wired and wireless real-time applications, some improvements should be made in the existing systems or protocols. Various techniques to improve end-to-end performance of system for real time video transmission over wireless channel are available in literature. Authors claim that the solution suggested in the paper provide more reliability in wireless video transmission. In the proposed solution, adaptive redundant packets are added in every block (or datagram) transmitted in order to achieve a desired recovery rate at the receiver. The suggested method dose not use any retransmission mechanism. The network simulator NS-2 is used to evaluate the method and the simulation results indicate that the proposed method can guarantee satisfied end-to-end performance by increased packet delivery ratio, reduced end-to-end delay and hence increased network throughput for video transmission in wireless network.     

无线视频传输的跨层动态映射算法

在IEEE 802.11e EDCA机制和基于场景的马尔可夫链模型基础上,提出跨层动态映射算法来改善无线视频传输的服务质量（QoS）。根据视频帧的重要性和网络的负荷情况,将来自应用层的视频帧信息动态地映射到MAC层中合适的队列中去,并且采用网络仿真工具NS2进行仿真,来比较IEEE 802.11e EDCA机制以及跨层动态映射算法。仿真结果表明跨层动态映射算法能明显提高传输后的视频质量。     

Frame distortion estimation for unequal error protection methods in scalable video coding (SVC)

In many multimedia applications, coded video is transmitted over error prone heterogeneous networks. Because of the predictive mechanism used in video coding, transmission error would propagate temporally and spatially and would result in significant quality losses. In order to address this problem, different error resilience methods have been proposed. One of the techniques, which is commonly used in video streaming, is unequal error protection (UEP) of scalable video coding (SVC). In this technique, different independent layers of an SVC stream are protected differently and based on their importance by using forward error correction (FEC) codes. Accurately analyzing the importance or utility of each video part is a critical component and would lead to a better protection and higher quality of the received video. Calculation of the utility is usually based on multiple decoding of sub-bitstreams and is highly computationally complex. In this work, we propose an accurate low complexity utility estimation technique that can be used in different applications. This technique estimates the utility of each network abstraction layer (NAL) by considering the error propagation to future frames. We utilize this method in an UEP framework with the scalable extension of H.264/AVC codec and it achieves almost the same performance as highly complex estimation techniques (an average loss of 0.05 dB). Furthermore, we propose a low delay version of this technique that can be used in delay constrained application. The estimation accuracy and performance of our proposed technique are studied extensively.     

Multiview coding and error correction coding for 3D video over noisy channels

We consider the joint source–channel coding problem of stereo video transmitted over AWGN and flat Rayleigh fading channels. Multiview coding (MVC) is used to encode the source, as well as a type of spatial scalable MVC. Our goal is to minimize the total number of bits, which is the sum of the number of source bits and the number of forward error correction bits, under the constraints that the quality of the left and right views must each be greater than predetermined PSNR thresholds at the receiver. We first consider symmetric coding, for which the quality thresholds are equal. Following binocular suppression theory, we also consider asymmetric coding, for which the quality thresholds are unequal. The optimization problem is solved using both equal error protection (EEP) and a proposed unequal error protection (UEP) scheme. An estimate of the expected end-to-end distortion of the two views is formulated for a packetized MVC bitstream over a noisy channel. The UEP algorithm uses these estimates for packet rate allocation. Results for various scenarios, including non-scalable/scalable MVC, symmetric/asymmetric coding, and UEP/EEP, are provided for both AWGN and flat Rayleigh fading channels. The UEP bit savings compared to EEP are given, and the performances of different scenarios are compared for a set of stereo video sequences.     

Multihop Rate Adaptive Wireless Scalable Video Using Syndrome‐Based Partial Decoding

The overall channel capacity of a multihop wireless path drops progressively over each hop due to the cascading effect of noise and interference. Hence, without optimal rate adaptation, the video quality is expected to degrade significantly at any client located at a far‐edge of an ad‐hoc network. To overcome this limitation, decoding and forwarding (DF), which fully decodes codewords at each intermediate node, can be employed to provide the best video quality. However, complexity and memory usage for DF are significantly high. Consequently, we propose syndrome‐based partial decoding (SPD). In the SPD framework an intermediate node partially decodes a codeword and relays the packet along with its syndromes if the packet is corrupted. We demonstrate the efficacy of the proposed scheme by simulations using actual 802.11b wireless traces. The trace‐driven simulations show that the proposed SPD framework, which reduces the overall processing requirements of intermediate nodes, provides reasonably high goodput when compared to simple forwarding and less complexity and memory requirements when compared to DF.     

Optimized video streaming over 802.11 by cross-layer signaling

Seamless video streaming over wireless links imposes strong demands on video codecs and the underlying network. It is not sufficient that only the video codec or only the radio adapts to changes in the wireless link quality; efforts should be applied in both layers, and - if possible - synchronized. Also, the disturbing effect of possible background traffic over the same shared medium has to be taken into account. In this article we present a communication architecture for video streaming over 802.11 that is capable of adapting to changes in the link quality and sharing of the wireless channel in various use scenarios. Experimental results show that substantial improvements in the quality of the video can be obtained by applying link adaptation and cross-layer signaling techniques.     

Joint source-channel coding and power adaptation for energy efficient wireless video communications

We consider efficiently transmitting video over a hybrid wireless/wire-line network by optimally allocating resources across multiple protocol layers. Specifically, we present a framework of joint source-channel coding and power adaptation, where error resilient source coding, channel coding, and transmission power adaptation are jointly designed to optimize video quality given constraints on the total transmission energy and delay for each video frame. In particular, we consider the combination of two types of channel coding—inter-packet coding (at the transport layer) to provide protection against packet dropping in the wire-line network and intra-packet coding (at the link layer) to provide protection against bit errors in the wireless link. In both cases, we allow the coding rate to be adaptive to provide unequal error protection at both the packet and frame level. In addition to both types of channel coding, we also compensate for channel errors by adapting the transmission power used to send each packet. An efficient algorithm based on Lagrangian relaxation and the method of alternating variables is proposed to solve the resulting optimization problem. Simulation results are shown to illustrate the advantages of joint optimization across multiple layers.     

一种环境感知的无线Mesh网络自适应QoS路径选择算法

本文针对如何改善无线多跳Mesh网络的服务质量,满足无线多媒体业务对数据传输的带宽、时延、抖动的要求等问题,研究了一种基于无线信道状态和链路质量统计的MAC层最大重传次数的自适应调整算法。该算法通过对无线Mesh网络的无线信道环境的动态感知,利用分层判断法区分无线分组丢失的主要原因是无线差错还是网络拥塞导致,实时调整MAC层的最佳重传次数,降低无线网络中的分组冲突概率。基于链路状态信息的统计和最大重传策略,提出了一种启发式的基于环境感知的QoS路由优化机制HEAOR。该算法通过动态感知底层链路状态信息,利用灰色关联分析法自适应选择最优路径,在不增加系统复杂度的基础上,减少链路误判概率,提高传输效率。NS2仿真结果表明,HEAOR算法能有效减少重路由次数,降低链路失效概率,提高网络的平均吞吐率。本文提出的方法不仅能够优化MAC层的重传,而且通过发现跨层设计的优化参数实现对路径的优化选择。      

Comparison of video protection methods for wireless networks

An experimental comparison of video protection methods targeted for wireless networks is presented. Basic methods are the data partitioning, reversible variable length coding, and macroblock row interleaving as well as macroblock scattering for packet loss protection. An implementation is described, in which scalable video is protected unequally with forward error correcting codes and retransmissions. Comparisons are performed for simulated wideband code division multiple access channel, and measurements are carried out with wireless local area network, Bluetooth as well as with GSM high speed circuit switched data. For the measurements, point-to-point connections are used. The achieved video quality is examined in our real-time wireless video demonstrator. The performance is measured with peak-signal-to-noise-ratio of received video, data overhead, communication delay, number of lost video frames, and decoding frame rate. Results show that the quality of decoded video can be improved by 1 dB with transparent connections compared to connections designed for general packet data. As a conclusion, a video coding subsystem must have access to the error control in a wireless link for the best quality in varying conditions.