一种广播方式的视频点播系统方案

介绍了“广播式视频点播”方案，可以解决传统VOD系统存在的用户数量有限的问题，就其节目制作、播控和传输描述了系统的原理结构，并对系统所采用的MPEG-4编解码、组播及IP over DVB等关键技术作了简要介绍。     

Novel limited feedback scheme under the MIMO broadcast system

By deducing the distribution of the normalized channel covariance matrix, a novel limited feedback scheme is proposed under multiple users (MU) multiple-input multiple-output (MIMO) broadcast channel (BC) system. The proposed scheme has advantages in three aspects. First, it has no constraints on the number of users or antennas. Second, each user's feedback bits are independent of the number of receiving antennas. Third, the proposed scheme avoids the storage of large-size codebook on the transceivers. Simulation results show that the performance of the proposed scheme is close to the perfect channel state information (CSI) case and it just needs a small number of feedback bits.     

Queueing analysis of a threshold based priority scheme for ATMnetworks

A threshold-based priority scheme in which a tuning parameter is used to provide adequate quality of service to real-time traffic while providing the best possible service to the non-real-time traffic is proposed. The priority scheme is a generalization of the static priority scheme and the one-limited scheme and is more flexible than both. For this scheme, the authors carry out a queueing analysis and obtain the joint distribution of the queue-lengths. They show by numerical examples how the parameter of this scheme can be tuned dynamically, so that the tuning function can be integrated with the call admission policy     

Improvement of nonrepudiable threshold multi-proxy threshold multi-signature scheme with shared verification

In 2005, Bao, et al. [Appl. Math. and Comput., vol.169, No.2, 2005] showed that Tzeng, et al.’s nonrepudiable threshold multi-proxy multi-signature scheme with shared verification was insecure, and proposed an improved scheme with no Share Distribution Center (SDC). This paper shows that Bao, et al.’s scheme suffers from the proxy relationship inversion attack and forgery attack, and pro- poses an improvement of Bao, et al.’s scheme.     

LATS: a load-adaptive threshold scheme for tracking mobile users

Mobile user tracking is a major issue. We propose a novel approach for user tracking, in which the tracking activity is adapted to both user and system activity. The basic idea is to make the user-location update-rate dependent not only on the user activity (such as the call profile and mobility pattern). Rather, it is also made dependent on the signaling load, which reflects the actual cost of the update operation. Thus, at low-signaling load locations, the users are to transmit location update messages more frequently. To carry out this approach, we propose a load-adaptive threshold scheme (LATS): the network determines for each cell a registration threshold level (which depends on the cell load) and announces it, as a broadcast message, to the users. The user computes its own registration priority and then transmits a registration message only if its priority exceeds the announced threshold level. Thus, whenever the local load on the cell is low, the registration activity increases, while in loaded cells the registration activity decreases. Our analysis shows that the LATS reduces the paging cost, in comparison with other dynamic methods, without increasing the wireless cost of registration. Moreover, if higher user density is coupled with less mobility (e.g., consider vehicles), then the LATS strategy offers further performance improvement. The load-adaptive strategy can be used in addition to any other dynamic tracking strategy. Furthermore, the computational complexity imposed on the user is identical to that required by an equivalent load-insensitive scheme     

Computation of threshold function Chow parameters by graphical means †

Existing methods of computing Chow parameter tabulations for threshold functions generally employ a complex generation algorithm based on a 2-monotonic lattice. It is here shown that the Torng map is a preferable form of this lattice, and that a simple generation algorithm based on self-duality can be adopted to generate the positive canonical threshold function representatives. Translation of these representative functions into appropriate minimum-integer weights and thresholds then produces the desired standard Chow parameter tabulations. The complete procedure has little complexity and is ideally suitable for hand computation: its latter limitation is when the volume of the data becomes too great to hand-compile.     

足球现场节目两地联播方案的实验及总结

足球现场直播,具有很强的现场感染力.因此,广播的足球现场直播节目通常具有很高的收听率.但是足球现场两地联播,具有较高的技术要求.介绍了广东广播电视台一次足球现场节目两地联播方案的具体实验过程,并对方案的实施效果和经验进行了总结.     

WDM-PON中基于码型动态切换的组播实现方案

提出了一种利用码型动态切换的机制来实现波分复用无源光网络中组播业务的传输.组播业务采用DPSK调制格式,下行单播业务采用动态切换的Manchester/NRZ调制格式.其中Manchester调制格式是由下行单播数据和同频的时钟信号通过电逻辑异或门产生.实验验证了同时传输5Gb/s下行点对点信号和1.25Gb/s组播信号的WDM-PON组播传输方案的可行性.     

Implementation of smart-card access control with threshold scheme

We describe an electronic implementation of a security scheme to control access to a building. Access to the building by a person alone is not possible but access by a group of authorized people whose number satisfies a prescribed threshold is permissible. The scheme makes use of the shared-secret symmetry cryptography together with smart-card technology. The access key of a person is carefully encoded and stored on a smart card which can also be used for many other purposes. Access records are kept on these smart cards in a distributive fashion and with duplication. Innocent people are able to present information regarding their recent accesses to the building and yet practically cannot be accused of fabricating these records. The scheme permits the use of a standalone controller and eliminates the need for expensive wiring to a remote central database of authorized users.     

基于ECC和ID签名的WSN广播快速认证方案

广播认证是无线传感器网络(WSN)的一种基本安全服务,针对现有认证方案的计算量大、认证速度慢等问题,提出一种基于椭圆曲线加密(ECC)和身份(ID)签名的WSN广播快速认证方案.对现有EIBAS签名认证方案进行改进,通过节点间的合作,共享中间计算结果来减少邻居节点的计算量,以此提高认证速度,减少能量消耗.同时,提出一种安全机制,通过对多个邻居共享数据的对比来抵御恶意节点的攻击.实验结果表明,该方案相对于传统的椭圆曲线加密算法能够提高约42％的签名认证速度,降低约36％的能耗,大大延长网络生命周期.     

基于双线性的无线传感器网络门限广播方案

广播是无线传感器网络中主要传输方式之一,是节约能量的主要通信方式,其安全直接影响到整个网络的安全。文中提出了基于Shamir门限秘密共享与双线性对的广播方案,在无线传感器网络中实现基站"一对多"广播,以节省各节点能量;该方案在节点接收广播之后,节点能够对广播来源、正确性进行认证;最后对该方案进行安全性分析与广播认证属性进行分析,发现该方案不仅具有较好安全性并能满足无线传感器网络的安全需求。     

Security analysis and improvement of new threshold multi-Proxy multi-Signature scheme

Kang, et al. [Journal of Electronics（China）, 23（2006）4] proposed a threshold multi-proxy multi-signature scheme, and claimed the scheme satisfies the security requirements of threshold multi-proxy multi-signature. However, in this paper, two forgery attacks are proposed to show that their schemes have serious security flaws. To overcome theses flaws, an improvement on Kang, et al.＇s scheme is proposed.     

Performance of a broadcast packet switch

The results of a simulation study undertaken to evaluate a high-performance packet-switching fabric supporting point-to-point and multipoint communications are presented. This switching fabric contains several components, each based on conventional binary routing networks. The most novel element is the copy network, which performs the packet replication needed for multipoint connections. Results characterizing the performance of the copy network are presented. Several architectural alternatives for conventional binary routing networks are also evaluated. For example, the performance gains obtainable by using cut-through switching in the context of binary routing networks with small buffers are quantified. One surprising result is that networks constructed from nodes with more then two input and output ports can perform less well than those constructed from binary nodes. This result is quantified and explained     

A reduced sampling schedule for estimating the parameters of theglucose minimal model from a labeled IVGTT

The minimal model of tracer glucose disappearance allows the measurement in man of important metabolic parameters from a labeled IVGTT (intravenous glucose tolerance test). Usually 30 blood samples are drawn to measure the insulin and the labelled glucose concentration time courses, which provide the data base for the model identification. In this paper, we address the problem of reducing the number of blood samples withdrawn without, however, deteriorating parameter estimation. By using a stepwise approach, largely based on optimal experiment design theory, we have derived a reliable reduced sampling schedule, which comprises only 14 total samples. The practical application of this reduced schedule has been validated by applying it in a new set of human experiments, completely independent of the ones used in the design phase.     

单模光纤参数对布里渊散射阈值的影响

应用自发布里渊散射模型和受激布里渊散射模型,在1550nm通信窗口,分别对短距离和长距离普通单模光纤中的布里渊散射阈值进行了研究.对于短距离传输,分析了自发布里渊阈值增益系数与光纤数值孔径以及有效长度的依赖关系.     

Single threshold optimization and a novel double threshold scheme for non‐line‐of‐sight identification

Non‐line‐of‐sight (NLOS) identification is a critical issue in wireless location system. The traditional method only considers the probability of false alarm to obtain the single threshold to identify the wireless propagation environment as line of sight (LOS) or NLOS. However, the probability of missed detection is rarely discussed. In this paper, firstly, the optimal single threshold is derived through minimizing the total error probability, which is the sum of the probability of false alarm and the probability of missed detection. Further, if the prior probabilities for the LOS and NLOS environment are available, a novel double threshold method based on the optimal single threshold is proposed to perform NLOS identification. By comparing the total error probability, we show through simulation results that the performance of the optimal single threshold is better than that of the traditional single threshold. Moreover, the novel double threshold NLOS identification scheme is feasible and better than the optimal single threshold scheme. It is also shown that the analytical results are consistent with the simulated ones.Copyright © 2012 John Wiley & Sons, Ltd.     

徐州市拾屯广播电视站光纤网络设计方案

拾屯广播电视站位于徐州市区西北 ,机房距徐州市有线广播电视中心机房 13.98ｋｍ。拾屯光纤网设计采用二级光纤实现 ,按 12个光节点设计 ,一期开通 6个 ,每个光节点用 2根纤芯 ,一主一备。1　技术要求(1)本系统采用 75 0ＭＨｚ邻频系统 ,其中 5～ 6 5ＭＨｚ传送上行信号 ,87～ 75 0ＭＨｚ为下行传播频带 ,87～ 5 5 0ＭＨｚ用于传输下行的电视信号及广播 ,5 5 0～ 75 0ＭＨｚ用于数字电视、数据等数字业务。(2 )下行电视的频带内可以传输 5 4套ＰＡＬ -Ｄ制式电视节目。(3)一级光纤网Ｃ/Ｎ =5 1ｄＢ ,两级光纤网Ｃ/Ｎ≥4 8ｄＢ。(4)ＣＴＢ≤ …     

光输出反馈损耗调制型双稳激光器特性与器件参量之间的关系

报导了光输出反馈损耗调制型双稳Ａｒ离子激光器的实验结果，激光谐振腔内放置一个用作损耗调制器的的电光晶体ＬｉＮｂＯ３。利用光探测器的非线性饱和特性控制腔内损耗，器件的双稳特性随各参量（激光输出到光探测器的反馈系数η、反馈损耗调制系数Ｂ、光探测器的饱和光强ＩＤ，输入光信号强度Ｉ以及激光器的泵浦电流ｉＡ）变化的规律，与半经典理论计算的结果完全一致。     

Design of a broadcast packet switching network

An overview is given of a system designed to handle a heterogeneous and dynamically changing mix of applications. It is based on fiber-optic transmission systems and high-performance packet switching and can handle applications ranging from low-speed data to voice to full-rate video. A novel feature is a flexible multipoint connection capability suitable for broadcast and conferencing applications. The architecture of a switching systems that can be used to support this network is described     

巴林左旗村村响播控平台及终端建设方案研究

为了更好地落实村村响工作,充分发挥广播电视在精神文明建设中的重要作用,笔者根据自治区广电局的文件精神和市广电局村村响工程的建设技术指导意见,结合巴林左旗自然地理等实际情况,特制定本建设方案。