基于跨层码率适配和差错控制的3D视频无线传输方法

针对纹理视频加深度序列的3D视频无线传输,本文提出一种基于跨层优化的码率适配和差错控制方法.通过最小化端到端3D视频失真,均衡调整和配置应用层3D视频编码的码率和帧内编码更新比例,以及物理层的调制和编码模式,达到信源码率适配信道带宽以及应用层差错控制和物理层信道保护强度相互平衡的目的,进而提高接收端的3D虚拟视点视频质量.实验结果表明,提出的方法能有效的提高3D视频无线传输的性能.     

基于HMM的视频自适应信道选择传输

提出了一种基于隐马氏模型(HMM)的可伸缩性视频编码的自适应传输方案.该方案中,使用了多输入多输出(MIMO)系统的多信道质量排序.作为信道状态信息(CSI)反馈到发送端.根据该信息,发送端实时进行不同信道的分配,从而保证可伸缩性视频编码中的基本层数据被分配在当前最佳质量的信道上传输.在获取这样的CSI方法上,通过HMM建模,利用接收端的费诺译码复杂度作为观察变量,更为精确地获取多个信道的质量排序.当信道质量都变差时,采用不等保护(UEP)对基本层进行重点保护.仿真结果表明该方案有效地提高了视频的恢复质量.     

基于预测方法的无线体域网跨层优化研究

为改善无线体域网的能效和传输可靠性,该文针对其具有资源有限、信道质量波动频繁、所传输数据有异构性等特点,提出一种基于链路质量预测的跨层优化方案。通过对物理层、网络层和MAC层的松散耦合,自适应地选择传感器节点的传输功率,并且建立高效节能的端到端路由。仿真结果显示,该方案相对于已有的单层协议,整体提高了体域网的能量效率和传输可靠性。     

支持区分服务的自适应链路层HARQ控制策略

提出了一种用于无线实时流媒体传输的自适应链路层HARQ控制策略,针对不同的信道状况或业务服务质量的要求动态选择混合AQR方案.该策略采用跨层设计的方法,基于增强型GM(1,1)预测当前的网络状态,自适应地调整ARQ参数Nmax;另一方面,在应用层采用自适应FEC策略,在视频源数据和冗余数据之间动态分配网络带宽.理论分析和仿真验证表明,该策略能使接收方获得最大的可播放帧率,有效地提高流媒体传输的可靠性和实时性.     

一种改进的可分级视频编码方法及其网络传输研究

该文提出了一种改进的可分级视频编码方法。为了适应流媒体的分层传输要求,该方法通过对DCT系数量化残差的位平面编码产生视频流的增强层部分,其基本层码流由更多的子基本层组成,各子基本层通过宏块级DCT系数重排及VLC重组生成。同时,该文设计了一种针对该分层视频流数据的网络传输自适应不等重丢包保护(AUPLP)策略,在估计当前可利用带宽资源的基础上,实时调整不同层数据的保护力度,并控制传输截断的层数。仿真结果表明,与传统方法相比该文方案在低带宽时可获得平均1.2dB的编码增益,AUPLP的应用也大大改善了视频流媒体的传输质量。     

混合网络下可分级视频的跨层码流提取优化算法

针对混合网络中传输带宽受限以及误码率较高的特点,文章在可分级视频编码的基本码流提取方法基础上,提出一种新的基于应用层和传输层信息的码流提取跨层优化算法。文章还进一步结合信道获取传输带宽等信息以及在应用层得到提取网络抽象层单元的码率以及丢弃单元造成的效应,来保证视频传输的服务质量。     

用于分级视频流的无线信道顽健传输方案

提出一种针对分级视频流的无线信道传输自适应不等丢包保护方案.在估计当前网络可用带宽及丢包率的基础上,对视频流各层数据进行不等FEC保护及选择适当的传输层数以控制发送速率.为抑制传输误码扩散,提出基本层的FEC包分配算法,利用COP中各帧之间的不同重要性对各基本层数据进行不等丢包保护,使解码端的失真度达到最小.实验结果表明该方案可大大增强分级视频数据的抗误码能力,明显改善视频流媒体的传输质量.     

基于H.264 SVC无线视频传输的自适应差错保护方法

提出了一种针对H.264可分级编码(H.264 SVC)的自适应前向纠错编码保护方案.通过比较不同的纠错方案,提出了划分丢包率区间的概念,并根据不同区间的丢包率自适应地选择最佳的纠错方案.仿真结果表明,与单一保护方法相比,所提自适应方法能够取得更好的保护效果,更适于在无线信道中进行视频传输.     

基于OFDM技术的视频传输研究

移动衰落信道中的图像传输已成为继移动数字话音通信迅速普及发展后的下一代通信的更高级通信形式。该文以OFDM技术为基础,重点研究了多径衰落信道中视频的传输问题。该文首先给出了确定保护间隔的原则,然后以此为基础对整个宽带无线视频传输系统进行了仿真分析。并且将仿真结果与QAM调制方式下的视频传输性能进行了比较,可以看出OFDM技术在实现宽带无线视频业务方面具有很高优越性。     

分布式视频转码服务调度算法研究

针对分布式环境下视频转码服务的任务请求自适应接收问题以及处理后视频序列分段向客户端的端传输控制问题,通过分析视频转码处理对资源占用的特点以及流式媒体服务实现的过程,提出了基于处理节点资源与客户信道质量反馈的视频转码任务自适应接收策略和用于实现客户端流畅视频服务的视频任务分段传输控制算法。实验表明,相比现有算法,该自适应客户请求接入策略能够依据客户端的信道质量选择最适合的任务版本;在用户播放缓冲区有限的条件下,提出的传输控制算法可以达到更小的任务失败几率。     

无线衰落信道中H.264视频流的可靠传输

本文提出了一种无线衰落信道中进行H.264视频传输的不等差错保护方案.这种方案通过对视频流的不同重要性的部分进行不同码率的删余卷积信道编码和一种特殊的重传机制来实现不等差错保护机制.仿真结果显示,该方案可以有效改善视频传输的性能,提高视频传输的鲁棒性.     

Adaptive cross-layer protection strategies for robust scalable video transmission over 802.11 WLANs

Robust streaming of video over 802.11 wireless local area networks poses many challenges, including coping with bandwidth variations, data losses, and heterogeneity of the receivers. Currently, each network layer (including physical layer, media access control (MAC), transport, and application layers) provides a separate solution to these challenges by providing its own optimized adaptation and protection mechanisms. However, this layered strategy does not always result in an optimal overall performance for the transmission of video. Moreover, certain protection strategies can be implemented simultaneously in several layers and, hence, the optimal choices from the application and complexity perspective need to be identified. In this paper, we evaluate different error control and adaptation mechanisms available in the different layers for robust transmission of video, namely MAC retransmission strategy, application-layer forward error correction, bandwidth-adaptive compression using scalable coding, and adaptive packetization strategies. Subsequently, we propose a novel adaptive cross-layer protection strategy for enhancing the robustness and efficiency of scalable video transmission by performing tradeoffs between throughput, reliability, and delay depending on the channel conditions and application requirements. The results obtained using the proposed adaptive cross-layer protection strategies show a significantly improved visual performance for the transmitted video over a variety of channel conditions.     

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.     

Maximum-throughput delivery of SVC-based video over MIMO systems with time-varying channel capacity

In this paper, we present a novel scalable video transmission strategy over multi-input multi-output (MIMO) wireless systems with time-varying channel capacity. It is a great challenge to simultaneously guarantee the QoS for video delivery and maximize the system throughput over time-varying MIMO channel. We demonstrate that, by making full use of estimated channel state information (CSI) through feedback, a cascade of adaptive operations can be designed to satisfy maximum throughput for scalable video over MIMO systems. These operations include power allocation based on water-filling (WF), adaptive channel selection (ACS), and novel throughput maximizing power reallocation (PR). The proposed ACS transmission scheme enables overall increase in data throughput among enhancement layers by adaptively launching base layer bit-stream to proper sub-channel. Then, after initial power allocation with WF and proper adaptive mode selection, we obtain the surplus power across enhancement layer sub-channels which can be reallocated to some sub-channels by the proposed PR scheme. With such power reallocation, certain enhancement layers will be able to reach new level of QAM modulation through PR so as to maximize the system data throughput. We present in this paper some detailed analysis on these adaptive operations. We also present some simulation results to demonstrate that maximum throughput video transmission over MIMO wireless systems indeed can be achieved based on scalable video coding (SVC) and a sequence of appropriately designed adaptive operations.     

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.     

Adaptive video protection in large scale peer‐to‐peer video streaming over mobile wireless mesh networks

Because video streaming over mobile handheld devices has been of great interest, the necessity of introducing new methods with low implementation cost and scalable infrastructures is a strong demand of the service. In particular, these requirements are present in popular wireless networks such as wireless mesh networks (WMN). Peer‐to‐peer (P2P) networks promise an efficient scalable network infrastructure for video streaming over wired and wireless networks. Limited resources of the peers in P2P networks and high error rate in wireless channels make it more challenging to run P2P streaming applications over WMNs. Therefore, it is necessary to design efficient and improved error protection methods in P2P video streaming applications over WMNs. In this paper, we propose a new adaptive unequal video protection method specially intended for large scale P2P video streaming over mobile WMNs. Using this method, different frames have different priorities in receivers along the recovery process. Moreover, we precisely and completely evaluate different aspects related to frame protection in these networks using five important performance metrics including video distortion, late arrival distortion, end‐to‐end delay, overhead and initial start‐up delay. The results obtained from a precise simulation in OMNeT++ show that the proposed adaptive method significantly outperforms other solutions by providing better video quality on mobile wireless nodes. Copyright © 2015 John Wiley & Sons, Ltd.     

Cross‐layer design for MIMO systems over spatially correlated and keyhole Nakagami‐m fading channels

Cross‐layer design is a generic designation for a set of efficient adaptive transmission schemes, across multiple layers of the protocol stack, that are aimed at enhancing the spectral efficiency and increasing the transmission reliability of wireless communication systems. In this paper, one such cross‐layer design scheme that combines physical layer adaptive modulation and coding (AMC) with link layer truncated automatic repeat request (T‐ARQ) is proposed for multiple‐input multiple‐output (MIMO) systems employing orthogonal space‐‐time block coding (OSTBC). The performance of the proposed cross‐layer design is evaluated in terms of achievable average spectral efficiency (ASE), average packet loss rate (PLR) and outage probability, for which analytical expressions are derived, considering transmission over two types of MIMO fading channels, namely, spatially correlated Nakagami‐m fading channels and keyhole Nakagami‐m fading channels. Furthermore, the effects of the maximum number of ARQ retransmissions, numbers of transmit and receive antennas, Nakagami fading parameter and spatial correlation parameters, are studied and discussed based on numerical results and comparisons. Copyright © 2009 John Wiley & Sons, Ltd.     

一种信道自适应的无线视频流差错控制机制

提出了一种自适应的无线视频流差错保护方法。该方法充分考虑MPEG-4FGS码流细粒度可扩展的特性,根据码流的重要性程度采用不等的保护措施,同时能够自适应地根据无线信道的具体状况,将信道带宽在MPEG-4FGS信源编码速率和信道编码速率之间进行最优化分配,使得接收端能获得最佳的重建视频质量。实验结果表明,在各种不同信道状况下,与均等错误保护和固定的不等错误保护方法相比,该方法均可获得更好的性能。     

无线视频通讯中的自适应差错非均匀保护方案

针对划分了重要级别的H-264视频编码数据提出五种可能的不平等保护策略，通过测试和比较，最终提出一种高误码率下无线视频可靠性传输的全局最优不平等保护策略。仿真实验表明，在无线网络带宽和信道误码率不同的情况下，这种最优策略都能使接收端信源解码后的视频图像峰值信噪比(PSNR)既稳定又具鲁棒性。