共查询到20条相似文献,搜索用时 15 毫秒
1.
J.A. García Rosa Rodriguez-Sánchez J. Fdez-Valdivia 《Journal of Visual Communication and Image Representation》2010,21(7):741-750
For progressive transmission, the limited bit-reserves of low transmission cost seem to provide a limit to the growing low-cost bit-allocation and to the sustainable amount of significant coefficients for which we allocate our exhaustible low-cost bit-reserves. Following a bit-saving path in the progressive image transmission, bit streams are prioritized in response to the use of a prioritization protocol, but only a part of the prioritized low-cost bit streams is to be transmitted to the decoder at this time. The level of transmission technology may also be augmented by investing part of the gross income in transmission improvement. The rest of prioritized bit streams, which were not sent to the decoder at their prioritization time, is to be added to a knowledge base from bit-saving.It is a bit-saving just reducing the amount of transmitted bits at the present time, but additions to the knowledge base may be transmitted later following an improved transmission technology at higher bit rates. Our aim is to find the paths of transmission, bit-reserves use, and sustained improvement in transmission technology which maximizes utility of future transmission. It uncovers the exact role and relevance of knowledge from bit-saving in the optimal transmission path. 相似文献
2.
VBF-NC (Vector Based Forwarding-Network Coding) is a reliable transport protocol for UWASNs (Underwater Acoustic Sensor Networks). It transfers packets, coded by network coding, over relay node sets, which are established by VBF (Vector Based Forwarding) routing protocol. However, only the error correction function of network coding is used by VBF-NC, the most important inbeing of network coding, which cannot only improve the throughput of network but also reduce transmission overhead, is not used by VBF-NC. So, in this paper, a network coding based protocol, called Multiple Paths and Network Coding (MPNC), is proposed. In MPNC, three disjoint paths are established firstly, and then, two groups of packets A and B, coded by network coding, are transmitted over the two side paths individually, and another group of packets C (C = A ⊕ B) are transmitted over the middle path. The results of mathematical analysis and simulations show that, compared with VBF-NC, MPNC not only improve the throughput of network but also has a higher data delivery ratio and lower energy consumption without reducing the data transmission reliability. 相似文献
3.
J.A. García Rosa Rodriguez-Sánchez J. Fdez-Valdivia A. Garrido 《Signal Processing: Image Communication》2012,27(1):39-53
In progressive image transmission, there exist some risks which may appear during the processing. A first class of risks is the diminishing coding performance when the occurrence of insignificant coefficients at each transmission time is a small-probability event. It may be a catastrophic transmission risk which can lead to major and irreversible bit losses. In a second class of risks, the performance of the transmission technique diminishes though the occurrence of insignificant sample is still a large-probability event.This paper shows a “Test of Transmission Risks” which can be used to analyze, for a given image, the performance of the state of the art in progressive transmission from the viewpoint of the catastrophic transmission risks. To this aim we make use of a decision making tool based on axioms requiring sensitivity to coding situations where the occurrence of insignificant sample at the transmission time may be either a small-probability or a large-probability event. 相似文献
4.
能源互联网的一个本质特征是通过先进的通信网络实现能源供给与消费间的双向互动。以光纤通信为基础的高可靠通信网络优化配置以满足多业务的服务质量(QoS)需求成为亟需解决的关键问题。从电力光纤传输网络的可靠性入手,并考虑电力通信业务的多QoS传输需求,设计一种基于复合量度的电路配置优化方法。有别于传统最短路配置算法,新方法在一次配置过程中同时规划m条可行配置方案,并且通过分析路径集的带宽、时延、丢包率、衰耗和成本等不同量度和光路全程可靠性,最终获得满足可靠性和传输QoS需求的光路配置方案,并给出优先选择序列。多电路优化配置将有效提升电力通信的可靠性,也可为未来多路流量分摊提供电路配置保证。通过某城区35~500 kV电力通信站网实例仿真计算,新配置方法能够一次获取4条同时满足业务多QoS需求的传输电路,实现主备电路保护。对电力光纤传输网络的规划和运行优化,提高电力通信网的资源调配能力和可靠性提供参考。 相似文献
5.
A fast progressive image transmission scheme using block truncation coding by pattern fitting 总被引:2,自引:0,他引:2
Bibhas Chandra Dhara Bhabatosh Chanda 《Journal of Visual Communication and Image Representation》2012,23(2):313-322
In this paper, we have proposed a novel progressive image transmission scheme. In the present method, the concept of the BTC-PF is used for faster decoding. Here, images are decomposed into a number of blocks based on smoothness criterion. The smooth blocks are encoded by block means and the others are by BTC-PF method. To encode a block by BTC-PF method, the codebook is organized like a full search progressive transmission tree which helps greatly in efficient progressive transmission. The present method provides good image quality at low bit-rate and faster decoding compared to other spatial domain progressive transmission methods. We extend this method for color images also. In color image coding, each color plane is encoded separately and then the encoded information of the planes are transmitted in interleaving manner to obtain color images right from the early stages. 相似文献
6.
On optimal multilayer cyclotomic space-time code designs 总被引:2,自引:0,他引:2
Wang G. Xia X.-G. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2005,51(3):1102-1135
High rate and large diversity product (or coding advantage, or coding gain, or determinant distance, or minimum product distance) are two of the most important criteria often used for good space-time code designs. In recent (linear) lattice-based space-time code designs, more attention is paid to the high rate criterion but less to the large diversity product criterion. In this paper, we consider these two criteria together for multilayer cyclotomic space-time code designs. In a previous paper, we recently proposed a systematic cyclotomic diagonal space-time code design over a general cyclotomic number ring that has infinitely many designs for a fixed number of transmit antennas, where diagonal codes correspond to single-layer codes in this paper. In this paper, we first propose a general multilayer cyclotomic space-time codes. We present a general optimality theorem for these infinitely many cyclotomic diagonal (or single-layer) space-time codes over general cyclotomic number rings for a general number of transmit antennas. We then present optimal multilayer (full-rate) cyclotomic space-time code designs for two and three transmit antennas. We also present an optimal two-layer cyclotomic space-time code design for three and four transmit antennas. The optimality here is in the sense that, for a fixed mean transmission signal power, its diversity product is maximized, or equivalently, for a fixed diversity product, its mean transmission signal power is minimized. It should be emphasized that all the optimal multilayer cyclotomic space-time codes presented in this paper have the nonvanishing determinant property. 相似文献
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基于Internet的实时视频信号传输研究进展 总被引:9,自引:0,他引:9
随着Internet带宽和计算机处理能力的迅速提高,实时Internet视频传输在科研和工业领域引起了极大的研究兴趣。本文介绍了实时Internet视频传输的基本方法,针对Internet分组的丢失特性,讨论了具有差错复原能力的视频压缩与编码技术,详细介绍了Internet视频传输的信源/信道联方编码技术,并对今后的研究方向进行了概括的描述。 相似文献
9.
《Communications, IEEE Transactions on》2007,55(7):1439-1439
10.
网络编码方法能有效提高数据传输效率,但采用该方法的机会网络数据转发机制均未考虑传输中的编码数据迭代冗余副本控制问题。为了充分降低译码复杂度并减少迭代冗余副本,提出了相遇持续时间估计及编码机会感知方法,进而设计了带有传输容量估计的编码冗余控制数据转发机制。节点以分布式的方式感知数据编码机会,为不同扩散程度的数据确定相应的优先级,并根据传输容量估计结果完成转发控制,以充分利用节点间的相遇持续时间。结果表明,所提出机制有效地减少了网络中的冗余副本,使译码所需的数据量趋于理论上的最小值,改善了网络资源利用率。 相似文献
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12.
Christian Hoene Holger Karl Adam Wolisz 《International Journal of Communication Systems》2006,19(3):299-316
Quality models predict the perceptual quality of services as they calculate subjective ratings from measured parameters. In this article, we present a new quality model that evaluates Voice over IP (VoIP) telephone calls. In addition to packet loss rate, coding mode and delay, it takes into account the impairments due to changes in the transmission configuration (e.g. switching the coding mode or re‐scheduling the playout time). Moreover, this model can be used at run time to control the transmission of such calls. It is also computationally efficient and open source. To demonstrate the potential of our model, we apply it to select the ideal coding and packet rate in bandwidth‐limited environments. Furthermore, we decide, based on model predictions, whether to delay the playout of speech frames after delay spikes. Delay spikes often occur after congestion and cause packets to arrive too late. We show a considerable improvement in perceptual speech quality if our model is applied to control VoIP transmissions. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
13.
A joint sensing and transmission power control policy for RF energy harvesting cognitive radio networks 下载免费PDF全文
We consider a radio frequency energy harvesting cognitive radio network in which a secondary user (SU) can opportunistically access channel to transmit packets or harvest radio frequency energy when the channel is idle or occupied by a primary user. The channel occupancy state and the channel fading state are both modeled as finite state Markov chains. At the beginning of each time slot, the SU should determine whether to harvest energy for future use or sense the primary channel to acquire the current channel occupancy state. It then needs to select an appropriate transmission power to execute the packet transmission or harvest energy if the channel is detected to be idle or busy, respectively. This sequential decision‐making, done to maximize the SU's expected throughput, requires to design a joint spectrum sensing and transmission power control policy based on the amount of stored energy, the retransmission index, and the belief on the channel state. We formulate this as a partially observable Markov decision process and use a computationally tractable point‐based value iteration algorithm. Section 5 illustrate the significant outperformance of the proposed optimal policy compared with the optimal fixed‐power policy and the greedy fixed‐power policy. 相似文献
14.
提出了一种基于JPEG2000的动态多感兴趣区域编码新方法,可以广泛地应用于各种交互式的客户/服务器应用环境.通过利用空信息包的特性和LRCP渐进方式,服务器在无需重新编码的前提下完成了原始码流的重组,从而实现了在渐进传输过程中的任意时刻,均可以有效地满足客户动态定义感兴趣区域及改变各个感兴趣区域优先级的需求.同时,由于和原始的JPEG2000码流结构保持完全一致,利用该算法同样可以实现感兴趣区域或整幅图像的无损压缩编码及渐进传输.实验结果表明:所提算法具有高度的灵活性,可以实现在低运算需求时的快速编解码. 相似文献
15.
Network correlated data gathering with explicit communication: NP-completeness and algorithms 总被引:2,自引:0,他引:2
Cristescu R. Beferull-Lozano B. Vetterli M. Wattenhofer R. 《Networking, IEEE/ACM Transactions on》2006,14(1):41-54
We consider the problem of correlated data gathering by a network with a sink node and a tree-based communication structure, where the goal is to minimize the total transmission cost of transporting the information collected by the nodes, to the sink node. For source coding of correlated data, we consider a joint entropy-based coding model with explicit communication where coding is simple and the transmission structure optimization is difficult. We first formulate the optimization problem definition in the general case and then we study further a network setting where the entropy conditioning at nodes does not depend on the amount of side information, but only on its availability. We prove that even in this simple case, the optimization problem is NP-hard. We propose some efficient, scalable, and distributed heuristic approximation algorithms for solving this problem and show by numerical simulations that the total transmission cost can be significantly improved over direct transmission or the shortest path tree. We also present an approximation algorithm that provides a tree transmission structure with total cost within a constant factor from the optimal. 相似文献
16.
介绍了将多重描述编码与分层传输技术相结合,适用于实时视频传输的分层多重描述编码方法。采用多重描述编码方法对视频信号进行处理,能够避免因丢包而请求重传所带来的时延,有利于视频信息的实时传输,但它并不能满足带宽不同的终端用户都能得到最优的重构图像质量。这里所介绍的分层多重描述编码能够有效地实现同时对不同能力的终端用户进行实时的视频传输。 相似文献
17.
无线视频传输容错算法研究新进展 总被引:9,自引:2,他引:9
视频信号经过压缩编码后通过Rayleigh衰减无线信道传输,容易受到突发性错误的影响,造成视频传输质量下降。容错(error resilience)是保证无线视频传输质量的重要措施。本文首先对几种无线信道模型进行了概括与比较,然后总结了各种容错算法的优缺点和最新研究进展情况。重点讨论了在传输层实施的前向纠错编码(FEC)和反馈差错控制,在编码器端根据不同的信道传输特性所采用的容错算法,包括帧内刷新、长期限存储、分层编码和多描述编码。本文还通过一种传输方案对容错策略的组合实施情况进行了分析。最后探讨了无线视频传输容错算法的发展趋势和挑战,提出了几个值得重视的发展方向。 相似文献
18.
针对当前大多数据传输协议没有充分利用无线信道的广播特性这一问题,本文提出了基于网络编码的机会路由协议NCOR(Network Coding based Opportunistic Routing protocol).首先,通过分析网络端到端传输代价,本文提出了最优转发集构造机制以最小化传输代价.此后,NCOR在转发集内执行节点协作式编码传输以保证传输可靠性.最后,理论分析了NCOR的传输可靠性结论.仿真实验表明NCOR可适用于不同的链路环境,且在保证可靠传输的同时,大幅降低了网络能耗. 相似文献
19.
Reliable transmission of images and video over wireless networks must address both potentially limited bandwidths and the possibilities of loss. When bandwidth sufficient to transmit the bit stream is unavailable on a single channel, the data can be partitioned over multiple channels with possibly unequal bandwidths and error characteristics at the expense of more complex channel coding (i.e., error correction). This paper addresses the problem of efficiently channel coding and partitioning pre-encoded image and video bit streams into substreams for transmission over multiple channels with unequal and time-varying characteristics. Within channels, error protection is unequally applied based on both data decoding priority and channel packet loss rates, while cross-channel coding addresses channel failures. In comparison with conventional product codes, the resulting product code does not restrict the total encoded data to a rectangular structure; rather, the data in each channel is adaptively coded according to the channel's varying conditions. The coding and partitioning are optimized to achieve two performance criteria: maximum bandwidth efficiency and minimum delay. Simulation results demonstrate that this approach is effective under a variety of channel conditions and for a broad range of source material. 相似文献
20.
利用空时分组编码技术提高数据传输速率的研究 总被引:2,自引:0,他引:2
未来的通信对移动通信业务的要求越来越高,随着从单纯语音业务到多媒体业务的转变,通信中数据传输速率成为抑制日后发展的因素之一。因此人们努力研究各种高效的编码、调制以及传输的技术,用以提高数据的传输速率。空时编码是近年提出的重要技术之一,这种技术已经在第三代移动通信(3G)方案中广泛应用。本文在介绍简单的空时分组编码原理的基础上,着重研究了对共道信号产生的干扰进行抵消抑制的技术。采用具有干扰抵消技术的空时分组编码系统进行并行数据传输可以充分利用干扰信号之间的相关性进行有效的抵消处理,在原有的信道上能够极大的提高数据的传输速率。文中提出了一种利用多种调制方式抗干扰性能的不同,对共道信号进行分步解码来削弱共道干扰的影响的空时分组编码并行传输策略。这种方法能够进一步提高信号传输的性能,为提高通信系统的数据传输速率做出了保证。 相似文献