无线网络中基于机会网络编码的加权广播重传

在无线广播网链路状态不同和丢包率高的条件下,基于机会网络编码的数据分发策略面临传输效率低和计算复杂度高的问题。针对这一问题,该文提出一种新的基于机会网络编码的加权广播重传(Weighted Opportunistic Network Coding Retransmission, WONCR)方案。该方案通过构建加权数据包分布矩阵(Weighted Packet Distribution Matrix, WPDM),在重传过程中采用新的调度算法进行编码数据包的选取,并将选取的数据包进行XOR编码后再重传。机会仿真结果表明,WONCR方案提高了传输效率,且计算开销较小,实现了无线广播网中高效、可靠的数据分发。     

Maximizing Network Lifetime of Broadcasting Over Wireless Stationary Ad Hoc Networks

We investigate the problem of extending the network lifetime of a single broadcast session over wireless stationary ad hoc networks where the hosts are not mobile. We define the network lifetime as the time from network initialization to the first node failure due to battery depletion. We provide through graph theoretic approaches a polynomial-time globally optimal solution, a variant of the minimum spanning tree (MST), to the problem of maximizing the static network lifetime. We make use of this solution to develop a periodic tree update strategy for effective load balancing and show that a significant gain in network lifetime over the optimal static network lifetime can be achieved. We provide extensive comparative simulation studies on parameters such as update interval and control overhead and investigate their impact on the network lifetime. The simulation results are also compared with an upper bound to the network lifetime. A preliminary version of this paper appeared in IEEE ICC 2003 [35]. This research was funded in part by NSF grant ANI-0093187, ONR award #: N00014-04-1-0479 and Collaborative Technology Alliance (CTA) from ARL under DAAD19-01-2-0011. All statements and opinions are that of the authors and do not represent any position of the U.S government Intae Kang received his B.S. degree in physics from Seoul National University, Seoul, Korea and M.S. degree in electrical engineering from the Johns Hopkins University, Baltimore, MD. He is currently working toward the Ph.D. degree in the Department of Electrical Engineering at the University of Washington, Seattle, WA. His current research interests are in the area of ad hoc and sensor networks. In particular, he is interested in energy efficient routing, topology control, medium access control, mobility management, and modeling and performance analysis of network protocols using directional/smart antennas. Radha Poovendran has been an assistant professor at the Electrical Engineering Department of the University of Washington at Seattle since September 2000. He received his Ph.D. in Electrical Engineering from the University of Maryland, College Park in 1999. His research interests are in the areas of applied cryptography for multiuser environment, wireless networking, and applications of Information Theory to security. He is a recipient of Faculty Early Career Award from the National Science Foundation (2001), Young Investigator Award from the Army Research Office (2002), Young Investigator Award from the Office of Naval Research (2004), and the 2004 Presidential Early Career Award for Scientists and Engineers, for his research contributions in the areas of wired and wireless multiuser security. He is also a co-recipient of the 2002 Outstanding Teaching as well as the Outstanding Advisor Awards from the Department of Electrical Engineering of the University of Washington.     

Extension of Coupled Mode Analysis to Periodic Large Arrays of Identical Waveguides for Photonic Crystals Applications

Coupled-mode theory, developed for several parallel waveguides, is extended to the case of infinite 2-D photonic crystals. Periodic boundary conditions, applied to a system of coupled identical waveguides, are used to compute the photonic band structures. This approach is shown to be more efficient than the usual numerical methods when tested on finite, but large-sized, arrays. Photonic crystals made of single-mode and multimode waveguide arrays are examined     

IP多播和广播技术在PPPoE协议上的扩展

本文探讨了ＩＰ多播和广播技术在ＰＰＰｏＥ协议上的应用，并就其性能不足之处提出了一种改进方法。     

Opportunistic Scheduling for Wireless Network Coding

This letter addresses a scheduling problem for wireless network coding (WNC). In our previous work, we have theoretically shown that the optimum number of nodes to be included into a network?coded packet as well as its transmission rate depends on time?varying link condition between a transmitting node and receiving nodes [1]. Based on this observation, this letter designs practical scheme which opportunistically selects scheduled nodes, packets to be coded and an employed modulation level according to time?varying channel conditions and packet length. The numerical results show that the proposed opportunistic scheduling can improve the overall throughput as compared with non?opportunistic approach.     

大规模分簇超宽带传感网的生存期渐近界

本文考虑了n个传感节点和一个Sink组成的跳时脉冲无线电超宽带(TH-IR UWB)传感网,其中n个传感节点按照Poisson点过程分布在正方形上.推导结果表明密集分簇TH-IR UWB传感网的生存期界随着节点数的增加而增加;而扩展网络的生存期界随着节点数的增加而减小.研究也表明分簇网络的生存期界远大于非分簇网络的生存...     

Design Considerations for Large Roof-integrated Photovoltaic Arrays

This paper describes calculations and modeling used in the design of the photovoltaic (PV) array built on the roof of the Georgia Tech Aquatic Center, the aquatic sports venue for the 1996 Olympic and Paralympic Games. The software package PVFORM (version 3.3) was extensively utilized; because of its importance to this work, it is thoroughly reviewed here. Procedures required to adapt PVFORM to this particular installation are described. The expected behavior and performance of the system, including maximum power output, annual energy output and maximum expected temperature, are then presented, and the use of this information in making informed design decisions is described. Finally, since the orientation of the PV array is not optimal, the effect of the unoptimized array orientation on the system's performance is quantified. © 1997 John Wiley & Sons, Ltd.     

Cooperative Diverse Opportunistic Network Coding for Wireless Networks

Wireless Personal Communications - Opportunistic network coding (ONC) increases communication networks’ throughput by XORing two or more packets together. However, it has shown that ONC...     

Optical Beamforming Network Based on Fiber-Optical Delay Lines and Spatial Light Modulators for Large Antenna Arrays

An optical beamformer for antenna arrays based on fiber-optical delay lines for feeding subarrays and spatial light modulators to change the radio-frequency phase of independent antenna elements is proposed. The architecture has the potential to control antenna arrays of a large number of elements. Preliminary experimental results to show the feasibility of the concept are provided     

一种获取大阵元数低冗余度线阵排列的方法

 寻找大阵元数的低冗余度线阵(LRLA)排列,是一维综合孔径微波辐射计天线阵列设计的一个难点.本文在总结了低冗余度线阵排列的一般结构规律的基础上,提出了一种排列结构约束搜索的方法,能以较短的计算时间获得较优的大阵元数LRLA排列;作为该方法的应用实例,导出了多种LRLA排列的解析解,它们可以迅速地给出任意阵元数对应的多种LRLA排列.本文提出的方法及在此基础上得到的LRLA排列,对综合孔径辐射计的阵列设计具有参考价值.     

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。     

延长网络生存时间的AODV路由改进算法

AODV(Ad Hoc on-demand distance vector)路由协议是Ad Hoc网络中一种具有代表性的按需路由协议。传统的AODV是以“最小跳数”为参数建立和更新路由的。随着网络负荷的增加,以这种方式建立和更新路由容易引起网络中部分节点较其它节点更多地参与通信,在这些节点发生拥塞的可能性将更大,频率将更高,这会增加网络能耗,缩短网络生存时间。针对这一问题,笔者提出了通过控制拥塞对AODV进行节能改进的一种算法—Lengthen Lifetime AODV(LLAODV)。     

机会网络中的数据转发机制分析

机会网络作为一种新兴移动无线自组织网络,在军事及民用领域展现出广泛的应用前景,数据转发机制是其核心问题。论文针对机会网络中的数据转发机制展开讨论,首先对机会网络数据转发机制与传统路由机制进行综合比较,在此基础上介绍数据转发机制面临的问题和性能评估标准,并根据数据转发机制主要特点对其进行了分类,最后对机会网络中的典型数据转发机制进行归纳。     

无线Mesh网络中的组播机会路由研究

 针对无线Mesh网络组播中包丢失严重的问题,提出了保持包的IP层不变,而改变包的目的MAC域,进而MAC层以单播形式向组成员发送包的M2U(Multicast to Unicast) 优化解决方案.为了满足组成员增加时不影响用户的性能,提出在M2U中引入了机会路由的M2UO（Multicast to Unicast Opportunistic Routing）算法,对候选节点采用单播形式发送包,对其它节点采用组播形式发送包.在实际网络环境中的大量实验表明,优化组播减小了数据包的丢失率,提高了网络的吞吐量,具有较好的组播视频流效果.     

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。     

Uplink Arrays for the Deep Space Network

Deep-space communication and navigation is faced with two challenges in the future: (1) the potential retirement of the largest antennas of NASA's Deep Space Network and (2) an anticipated need for increasing ground system capacity so as to support higher data rates to and from missions operating at remote locations in the solar system, as well as in anticipation of a larger number of simultaneously flying missions. In the transmitting, or uplink, direction, one approach to increasing the effective transmitted power is to array multiple antennas. This is attractive mainly because it promises a lower construction cost than equivalent (large) single antenna systems. In addition, it has the potential for increasing the reliability of the uplink and reducing maintenance costs. This paper introduces the concept of uplink arraying by examining technological challenges and possible solutions to them. Arraying principles are presented and error sources described. The main challenge is to maintain carrier phase alignment among the antennas, and this must be done by periodic calibration. Presently, two calibration methods are being developed at the Jet Propulsion Laboratory as part of an uplink arraying demonstration effort. These methods are briefly discussed.     

无锡电台音频编播网备份系统建设

随着音频编播网在广播电台的普及应用,其安全问题非常突出。建设音频编播网的备份系统,不仅确保了广播节目的正常播出,同时又为音频网停机检修、网络升级、系统改造创造了十分有利的条件。另外该系统是利用网络升级换代淘汰下来的设备和现有的备份设备构成的,提高了设备的利用率。     

功能扩展架构下广播总控系统的建设

本文主要介绍了安徽广播总控系统的设计思路和理念,不仅详细介绍了广播总控的音频方案,而且特别阐述了监测全覆盖广播总控系统的建设与实际应用情况.现总控系统还拓展与延伸了传统总控多项功能.     

机会网络中消息冗余度动态估计的缓存管理策略

机会网络以存储-携带-转发的方式实现节点间通信,高效的节点缓存管理策略能够充分利用有限的缓存空间。该文提出了一种基于消息冗余度动态估计的自适应缓存管理机制,利用消息携带节点的活跃程度和当前网络状态下消息副本数量,预测给定消息的投递状态,节点以消息冗余程度为参数确定消息的转发以及携带优先级。结果表明,所提出的节点活跃度和消息副本数的估计方法比较准确,同时所提出的缓存管理策略能有效提高消息成功投递率,降低网络平均时延和网络负载率。