Efficient Cellular Network with Network Coding in Disaster Area

Wireless Personal Communications - Intermittent connectivity due to the difficult topography in disaster area prevents a direct transmission from the base station to the demand users. An analytical...     

Efficient Stereoscopic Video Coding Using Joint Disparity-Motion Estimation

The goal of this paper is to determine dense disparity and motion fields jointly and efficiently, given a sequence of stereoscopic images. At each time instant, the motion field of left sequences is estimated by using the current disparity field, the next disparity field, and the motion field of right sequences. The improved concepts for the proposed joint estimation are based on an edge-preserving regularization, an ambiguous vector region detection, and a median filtering for block-based vector generation. The reported approach is verified by processing a set of stereo sequences. Results are given with real stereoscopic data.     

Network Coding for Efficient Multicast Routing in Wireless Ad-hoc Networks

Network coding is a powerful coding technique that has been proved to be very effective in achieving the maximum multicast capacity. It is especially suited for new emerging networks such as ad-hoc and sensor networks. In this work, we investigate the multicast routing problem based on network coding and put forward a practical algorithm to obtain the maximum flow multicast routes in ad-hoc networks. The "conflict phenomenon" that occurs in undirected graphs will also be discussed. Given the developed routing algorithm, we will present the condition for a node to be an encoding node along with a corresponding capacity allocation scheme. We will also analyze the statistical characteristics of encoding nodes and maximum flow in ad-hoc networks based on random graph theory.     

采用数字同相编解码卫星传输的调频同步广播系统

音频信号采用数字同相编解码,是针对DVB-S卫视频道传输音频信号,接收端解码后音频信号的时延不确定这一问题,而采用的技术措施不仅很好地解决了利用DVB-S卫视频道传输音频信号的调频同步系统实现信号在相干区“同相”的难题,而且使多站点调频同步系统的调试变得非常简单,从而很容易实现大范围多站点的系统同步.     

应用神经网络的图像分类矢量量化编码

矢量量化作为一种有效的图像数据压缩技术，越来越受到人们的重视。设计矢量量化器的经典算法ＬＢＧ算法，由于运算复杂，从而限制了矢量量化的实用性。本文讨论了应用神经网络实现的基于边缘特征分类的矢量量化技术。它是根据人的视觉系统对图象的边缘的敏感性，应用模式识别技术，在对图像编码前，以边缘为特征对图像内容分类，然后再对每类进行矢量量化。除特征提取是采用离散余弦变换外，图像的分类和矢量量化都是由神经网络完成     

Efficient Error Control Decoder Architectures for Noncoherent Random Linear Network Coding

Random linear network coding is an efficient technique for disseminating information in networks, but it is highly susceptible to errors. Kötter-Kschischang (KK) codes and Mahdavifar-Vardy (MV) codes are two important families of subspace codes that provide error control in noncoherent random linear network coding. List decoding has been used to decode MV codes beyond half distance. Existing hardware implementations of the rank metric decoder for KK codes suffer from limited throughput, long latency and high area complexity. The interpolation-based list decoding algorithm for MV codes still has high computational complexity, and its feasibility for hardware implementations has not been investigated. In this paper we propose efficient decoder architectures for both KK and MV codes and present their hardware implementations. Two serial architectures are proposed for KK and MV codes, respectively. An unfolded decoder architecture, which offers high throughput, is also proposed for KK codes. The synthesis results show that the proposed architectures for KK codes are much more efficient than rank metric decoder architectures, and demonstrate that the proposed decoder architecture for MV codes is affordable.     

Spectrally Efficient Differential Space–Time Coding Using Non-Full-Diverse Constellations

In this paper, a method is proposed to construct spectrally efficient unitary space–time codes for high-rate differential communications over multiple-antenna channels. Unlike most of the known methods which are designed to maximize the diversity product (the minimum determinant distance), our objective is to increase the spectral efficiency. The simulation results indicate that for high spectral efficiency and for more than one receive antenna, the new method significantly outperforms the existing alternatives. In the special case of two transmit antennas, which is the main focus of this paper, the relation between the proposed code and the Alamouti scheme helps us to provide an efficient maximum-likelihood (ML) decoding algorithm. Also, we demonstrate that similar ideas can be applied to designing codes for more than two transmit antennas. As an example, we present a construction for 4-by-4 unitary constellations which has a good performance, compared with the other known codes.     

Enhancing Emergency Messages Dissemination in Vehicular Networks Using Network Coding

Vehicular ad-hoc networks play an important role in providing safety on the road. Vehicles generate and exchange emergency and control messages to avoid dangerous situations. According to IEEE 1609.4 standard, all these messages share the same control channel interval even if the emergency messages are with a highest priority. Besides that, network’s characteristics, such as vehicle density and high mobility, would make the diffusion of emergency messages a challenging task. Especially with the absence of acknowledgements and retransmission. Network coding could be seen as a solution where a block of data packets could be sent on the same transmission process. Firstly, we analyze the messages’ dissemination, and we propose a thoroughly model for success probability according to the emergency messages’ generation probabilities. Further, we propose a new network coding access scheme. The emergency messages take the priority in the channel access and it could be retransmitted several times. Thus, the scheme deals with the emergency messages’ loss and latency. NS-3 simulations show that our model increases emergency messages’ reliability.

     

一种基于神经网络的矢量量化零冗余度信道编码方法

本文提出一种新的基于神经网络的矢量量化零冗余度信道编码方法,该方法能有效地降低矢量量化编码系统在有噪信道下的平均失真。     

Generalized Greedy Broadcasting for Efficient Media-on-Demand Transmissions

To reduce the bandwidth of media-on-demand transmissions, different broadcasting techniques have been developed over the last years. For highly demanded media, proactive schemes have a lower bandwidth requirement compared to reactive ones. While some of the proactive schemes try to obtain an efficiency near to the theoretical limit, others have been developed to lower the bandwidth by partial preloading, additional playout delay, the use of breaks within the transmission or by exploiting bandwidth variations of variable-bit-rate media. In this article we describe how one of the most efficient proactive transmission schemes can further be improved and generalized so it supports all these additional enhancements and outperforms its predecessor and the specialized schemes.     

Efficient Broadcasting in Mobile Ad Hoc Networks

This paper presents two efficient flooding algorithms based on 1-hop neighbor information. In the first part of the paper, we consider sender-based flooding algorithms, specifically the algorithm proposed by Liu et al. In their paper, Liu et al. propose a sender-based flooding algorithm that can achieve local optimality by selecting the minimum number of forwarding nodes in the lowest computational time complexity O(n logn), where n is the number of neighbors. We show that this optimality only holds for a subclass of sender-based algorithms. We propose an efficient sender-based flooding algorithm based on 1-hop neighbor information that reduces the time complexity of computing forwarding nodes to O(n). In Liu's algorithm, n nodes are selected to forward the message in the worst case, whereas in our proposed algorithm, the number of forwarding nodes in the worst case is 11. In the second part of the paper we propose a simple and highly efficient receiver-based flooding algorithm. When nodes are uniformly distributed, we prove that the probability of two neighbor nodes broadcasting the same messageneighbor nodes broadcasting the same message exponentially decreases when the distance between them decreases or when the node density increases. The analytical results are confirmed using simulation.     

广电网络的市场化运营

广电网络的运营是整个广电行业产业化经营的一个重要组成部分,建立既切合实际又适应市场经济要求的运营体制,进一步促进网络的经营管理,提高网络运营效益,是当前我们应该重视和研究解决的一个重要问题。     

无线通信中的网络编码技术

网络编码是一种提高网络吞吐量和性能的新技术,预计将成为未来网络的一项关键技术.本文概述了无线网络中的网络编码技术,无线网络被认为是网络编码最可能得到应用的领域之一,网络编码技术使无线媒质的广播属性可以得到充分利用,无线网络和传感器网络为网络编码的应用提供了巨大的机会.本文结合不同无线场景介绍了网络编码的各种编码方法,包括传统的网络编码、物理层网络编码、模拟网络编码以及复数域网络编码,并对未来发展给出了展望.     

ANTEC网管系统在广电网中的应用

HFC网络前端设备的网管主要针对安装在前端机房内的有源设备,包括各种光接收机、光发射机、前置放大器等进行监测管理,对网络设备故障的及时预警、查找、处理起到至关重要的作用,改进被动抢修为主动防御,保证系统的稳定运行,为安全播出提供强有力的保障。介绍ANTEC网管系统的硬件组成和软件配置,以及网管软件的安装和使用。     

Efficient Resource Allocation Based on Layered Coding in Single Frequency Network with Limited Feedback Scheme

Single frequency network (SFN) can provide Multimedia Broadcast Multicast Service (MBMS) over a large coverage area, so it receives more and more attention from both academia and industry. However, the application of SFN is still restricted by a large number of feedbacks. Therefore, we propose a novel multicast resource allocation algorithm based on limited feedback scheme. In the algorithm, we first design a user limited feedback scheme based on channel gain threshold to effectively reduce feedback load. The scheme determines to which base stations users should report channel state information. Next, to overcome the MBMS capacity limitation drawback, we encode the MBMS data into a base layer and multiple enhancement layers and develop a joint subcarrier and power allocation strategy to maximize the throughput of enhancement layers while guaranteeing the rate requirement of base layer. Simulation results show that the proposed algorithm significantly reduces 83 % of the feedback overhead while achieving a comparable multicast throughput performance to the case of full feedback.     

网络编码在网络安全中的应用

网络编码的思想在1999年由杨伟豪和张珍首次提出,由Ahlswede等人进一步发展和扩充,安全的网络编码也随即提出。蔡亍和杨伟豪首先针对单信源有向无圈网络给出了安全网络编码的定义和模型,其他研究者也各自提出了不同的安全模型,如J P Vilela提出了轻量级安全的网络编码,K Bhattad提出了弱安全的网络编码等,另外还有抗拜占庭攻击的网络编码。网络编码理论亦在网络纠错中得到了应用,杨伟豪和蔡宁推广了经典纠错码,引入了网络纠错码,杨胜豪在杨伟豪和蔡亍研究的基础上,研究了线性网络编码的重量性质。     

动态IP传输技术在广电宽带网中的应用

随着多媒体通信业务的发展,人们对信息的需求迅速增长。同时电视、电话已普及,电脑的家庭占有率也在不断提高,传统的电视、计算机、电话采用各自的物理传输网络,传输速率低,业务内容贫乏,已不能满     

海底光缆在广播电视网络中的应用

本主要介绍了海底光缆的类型、结构和技术指标。以及海底光缆工程中的登陆点的选择、海底路由的调查、技术指标的检验和海底光缆的保护等，对海底光缆与其它传输方式比较之优势和不足也进行了分析。