【作者】 卢冀；

【导师】 吴成柯；

【作者基本信息】 西安电子科技大学 ， 通信与信息系统， 2011， 博士

【摘要】 多媒体技术是当今信息技术领域发展迅速和活跃的技术之一,是新一代电子技术发展和竞争的焦点。随着通信网络基础设施的发展,多媒体(包括数据、视频等信息)业务在网络通信中占据越来越重要的地位。然而,由于通信网络不能提供可靠的数据传输,特别是无线网络信道存在的衰落和干扰会导致信息传输过程中受到随机错误和突发错误的影响,导致多媒体信息在网络中传输时会发生误码或数据包丢失等传输错误,因此设计鲁棒的多媒体(尤其是视频)传输方案和有效的差错控制机制是目前多媒体传输必须解决的问题；而且,新一代网络应用技术(物联网,泛在网)的兴起,使更多的具有不同带宽、丢包率等性能的终端或设备互联互通,因此如何在具有异构性的网络中设计有效的多媒体传输方案是亟待解决的问题之一。综上所述,如何在新网络技术的应用下提高多媒体信息的传输效率保证多媒体业务的QoS是多媒体通信领域研究的关键问题。网络编码已被证明可以使网络端到端的信息流量达到信道容量的上限(最大流最小割定理)；另一方面,可分级视频编码是一种适合于异构网络视频流传输的编码技术。网络编码和可分级视频编码的结合是解决上述多媒体传输问题的重要手段。本文从基于网络编码的多媒体传输技术入手,对数据及视频流的网络通信问题中的若干关键技术进行深入的研究,并取得了一些成果,这将对下一代网络多媒体传输技术的实现具有重要意义。本文的主要工作及取得的研究成果如下：1.提出一种基于随机线性网络编码(RLNC)的可分级视频编码(SVC)视频流鲁棒性传输系统方案。通过对SVC码流分级原理的分析,建立一种分层码流的状态模型并提出一种分层码流的数据分割方法。进一步结合RLNC分布传输方法和SVC分层方法的优点,从视频流打包、传输和延迟三个方面对SVC视频特性进行了研究,并分别导出了其特性表达式,设计了适合于SVC码流传输的数据包结构、码流组织方法和码流传输算法,提出的算法可以有效地提高视频流重建质量并降低传输延时。2.提出一种基于随机线性网络编码的可分级视频码流的网络传输不等错误保护算法。在表示可分级视频码流传输顺序的状态模型的基础上,提出分层码流失真的计算方法并推导出了其近似计算公式,在一定丢包率的限制下,采用局部率失真优化方法,提出一种随机线性网络编码数据包传输系统的适用于可分级视频码流的不等错误保护算法,该算法通过采用高效的分级码流失真分析和计算方法,有效地提高了视频传输的效率和视频重建质量。3.提出基于机会式网络编码的无线网络传输算法。在研究机会式网络编码技术的基础上,提出了两种适用于单跳无线网络的数据包重传方法,它们在基站分别以最小传输次数下限和最大组合数据包数为约束条件选择编码数据包,再传输采用机会式网络编码方法生成的组合重传包,在终端从收到的单个或多个组合重传包中恢复丢包。提出的方法有效地减少数据包的传输次数,并提高无线网络数据包的传输效率。4.在引入一种无线单跳网络广播传输模型的基础上,提出三种无线网络广播传输的实用算法,分别是随机算法、哈希算法和直接算法。它们采用不同的策略选择多个丢包编码组合成重传包,并通过从编码组合数据包中恢复丢包的方式来提高广播传输的吞吐量效率,其中随机算法简便实用,哈希算法性能好、复杂度低,直接算法可降低数据包传输的延迟,适用于视频业务。在一定条件下,提出的算法都可以使广播传输的平均传输带宽达到基于机会式网络编码传输方法的最佳值。以上三种算法适用于目前及第四代移动无线通信网络,例如WiMAX和LTE网络。5.提出一种基于网络编码的无线视频流混合自动重传(HARQ)方法。该方法在基站采用网络编码技术依次组合不同终端的未恢复数据包,使多个终端可以较快的恢复其数据包,提高终端收到数据包的效率和单位时间内重建视频的质量。提出的算法结合了FEC方法和基于网络编码ARQ方法的优点,给出了FEC最优编码冗余的计算方法和分级视频流数据包的编码方法,该方法不但能有效地提高无线广播吞吐量,而且提高了视频的重建质量,适用于无线网络视频流的传输。针对提出的所有算法,论文都通过大量的软件仿真、测试及与相关算法的比较来验证其有效性和先进性。更多还原

【Abstract】 Multimedia technology is one of the most rapidly develop and active technologies, and is the focus of the evolution and competition in new generation electronic technologies. With the development of network infrastructure, multimedia (including data, video and so on) services take more and more important role in network communications. However, the reliable data transmission can’t be provided by the existing communication networks, especially, the bit-error or packet loss occurs when delivering the multimedia information over networks because of the random and burst errors in wireless channels caused by fading and interference. So the robust multimedia transmission scheme and effective error resilient mechanism must be designed to solve the problem of the multimedia transmission. Furthermore, the apprearance of the hot applications, such as the Internet of things and ubiquitous network, makes more and more terminals and devices with different performance of bandwidth and packet loss rate integrated. Thus how to design the effective multimedia transmission schemes for heterogeneous networks is a problem to be solved urgently. In conclusion, how to improve the data transmission efficiency and ensure the QoS requirement of forthcoming multimedia services is a key research content in the field of multimedia communication.Network coding has been proved to be very effective to make the peer to peer information flow over networks achieve the maximum capacity of that of Shannon channel. On the other hand, scalable video coding is applied to the video coding and transmission over heterogeneous networks. The combination of network coding and scalable video coding can be used to solve the multimedia transmission problems discussed above. In this thesis, based on the multimedia transmission technology with network coding, we investigate several key problems of data and video transmission in network scenario and obtain many practical results, which will help the realization of the multimedia transmission in the next generate wireless network.The main contribution and innovation of the thesis are as follows:1. A realiable scalable video (SVC) transmission system based on random linear network coding (RLNC) is proposed. By analyzing the scalable characteristics of SVC, we setup a state model to represent the transmission order of SVC streaming and present a data partition method for scalable bit streams, which helps the scalable video streaming transmission efficienctly over networks. By combining the advantage of distribution transmission feature of RLNC and scalable approach of SVC, we analyze the packetization, distortion and latency characteristic of SVC streaming, and deduce their expressions respectively. The packetization algorithms, bit stream organization algorithm and bit stream transmission algorithm derived from the characteristics are proposed to improve the reconstructed quality of video and the transmission latency.2. A novel unequal error protection algorithm based on random linear network coding (RLNC) is proposed for scalable video coding (SVC) streaming. Based on the proposed state model of scalable bit streaming, we study the rate-distortion feature of scalable bit stream. By using the RLNC-based packet transmission method, we put forward an effective distortion computation method for SVC streaming, based on which an unequal error protection algorithm for scalable video streaming is presented with the local optimal rate-distortion optimization method. The proposed algorithm effectively improves the video transmission efficiency and the quality of reconstructed video sequence. The simulation results show the effectiveness and feasibility of the new algorithm.3. Opportunity network coding-based retransmission algorithms are proposed for wireless networks. We study the opportunistic network coding, on the basis of which two retransmission algorithms are proposed for single-hop wireless networks. The proposed algorithms select the encoding packets at the base station with the constrain of the minimum number of retransmissions and the maximum combined packets in one combination retransmission packet respectively, and transmit the combination retransmission packet generating by using opportunistic network coding, then the terminals can recover their packets via one retransmission. The the proposed algorithms can effectively reduce the number of transmissions and improve the transmission efficiency of wireless packets.4. Practical broadcast transmission algorithms are proposed for wireless networks. We introduce a single-hop wireless broadcast transmission model, on the basis of which three opportunistic network coding-based broadcast transmission algorithms are presented, namely random algorithm, hash algorithm, and direct algorithm. The proposed algorithms construct the combination retransmission packet with different strategies, and improve the throughput efficiency by recovering the lost packets of different terminals from one retransmission packet. Random algorithm takes the advantage of low complexity, thus practice. Hash algorithm achieves the better performance and low complexity. Direct algorithm is designed to improve the packet transmission delay and is good for video streaming transmission in broadcast scenario. The proposed algorithm can make the average transmission bandwidth achieve the best one of network coding-based transmission schemes under certain conditions. The proposed algorithms can be applied to the existing wireless networks and the 4th generation wireless networks, such as WiMAX or LTE networks.5. A network coding-based hybrid ARQ (HARQ) algorithm is proposed for video broadcast over wireless networks. The sender applies NC technique to combine the unretrieved packets from different terminals so that multiple terminals can recover their lost packets rapidly. By combining the advantage of FEC scheme and NC-based ARQ scheme, the computation of the optimal redundancy of FEC mechanism and the construction of video streaming packets are presented. The proposed algorithm is designed so as to maximize not only wireless throughput efficiency but also reconstructed quality for video broadcast. The proposed algorithm is suitable for the transmission of the video streaming over wireless networks.All of the proposed methods in this thesis are simulated and compared with related schemes in order to verify their advantages and validities.更多还原