《本期重点导读》

本期【节目制作与广播】栏目刊登了"广播系统工程"专题,精选了几篇有关广播系统工程的文章。其中霍欣有关"广播电台转播系统浅析"的文章,主要对广播电台转播系统进行了论述,包括单频率转播、多频率并机转播、透传转播等主要转播模式,电话耦合器、卫星转播车、光端机、TELOS等传输设备,主控机房的调音台、矩阵、AXIA等转播设备、播出机房的简单介绍、转播工作流程、转播应急流程等方面。转播是广     

“神舟十四号”首次出舱转播系统概述

本文介绍了直播“神舟十四号”首次出舱的转播系统,重点分析了转播车与航天城机房内交换机进行设备级联的具体配置流程以及如何根据节目需求利用切换台功能实现多视窗画面效果。     

纯高清的系统 人性化的细节（上）——由湖南台T2区演播厅群视频系统高清化建设引发的思考

湖南电视台近年来相继购置了高清车、卫星车、音频车等大型转播设备，并统筹实施播出、总控机房、新闻机房、T2区演播厅群导控机房、全台网等大型技术项目建设。台内T2区演播厅群导控机房及演播厅相关设施由2007年9月进入设计阶段，本文主要介绍了对导控机房视频系统的具体设计和实施过程，并就在现代电视系统设计中如何对技术细节的把握进行了详细的介绍。     

国内体育赛事场馆转播技术及发展

近几年中国已成功地举办了三届国际大型综合性运动会，这些世界级赛事的成功转播使以主转播商（机构）为主进行运行的转播技术得到逐步的提高，场馆转播设施运作和相关技术规范及操作流程也日趋完善。本文对这些国际大型赛事场馆转播的主要设施设备和技术工艺流程进行概述性分析，并对今后的技术发展方向进行展望。     

关于县区级台电视高标清同播机房建设的几点浅议

对区县电视台来说,高清化改造不是简单的设备更新和技术指标提升,也是对资金、技术、人才等方面的考验.本文以2014年我台新建的高标清同播机房为例,介绍区县电视台在系统节目上载方式、上下变换、AFD、总控调度以及外来信号转播等方面的考虑,同时对机房标准化建设、基础设施配置、消防安全、三级防雷、强弱电接地等实用性功能与可扩展性进行探讨.     

2016里约奥运会羽毛球公共信号制作

本文介绍了2016里约奥运会羽毛球公共信号制作,从转播系统、机房布局、信号制作讯道配置、信号EVS配置等方面进行了说明。     

虚拟演播室系统在CCTV北京奥运报道的应用

中央电视台用于第29届奥运会转播的五套高清机房中,CCTV1和CCTV2均采用虚拟演播室进行直播报道工作.本文在介绍虚拟演播室的特点与优势、跟踪系统、软件应用等基础上,阐述了应用于此次奥运会转播报道的高清ProSet虚拟演播室的系统方案.     

浅谈虚拟演播室技术在29届北京奥运会中的应用

中央电视台用于第29届奥运会转播的五套高清机房中,CCTV-1和CCTV-2均采用虚拟演播室进行直播报道工作。本文在介绍虚拟演播室的特点与优势,跟踪系统,软件应用等基础上,阐述了应用于此次奥运会转播报道的高清ProSet虚拟演播室的系统方案。     

先控模块化UPS中标郑州电视台机房项目

在刚刚结束的郑州电视台机房改造UPS项目招标中，先控模块化UPS产品凭借其方案合理、节能环保、升级便利、占地面积小等特点，在众多的竞争对手中脱颖而出一举中标。这次中标的是先控IMS系列60kVA和150kVA机型，分别为电视台的信息传输设备和数据转播设备提供安全电力保障。     

调频广播信号监视器的设计原理

地市级广播电视发射（转播）台,由于经费紧张,机房监视监听设备配备不足。为保障安全优质播出,笔者设计制作了一部调频广播信号监视器,并简要介绍了调频广播信号监视器的设计原理,制作过程从略。     

一种适用于无线传感器网络的 高效节能广播机制

 针对无线传感器网络结点体积小、内存与计算能力小、靠电池供电、结点密度高以及网络规模大的特点,提出了高效广播协议(EBP,Effective Broadcast Protocol).通过对广播过程中一个结点转播之后其邻域内其它结点的转播,即引发新转播的讨论,完成了对最佳引发新转播的分析.EBP广播协议以此为依据选择转播结点,不需要任何邻结点信息就可以高效完成广播,算法的控制开销和存储开销大大降低.EBP广播机制简单有效,在无线传感器网络中具有良好的扩展性.     

一种多路卫星节目转播服务器的设计

在MPEG-2TS流播出服务器和多路数字卫星节目收录服务器的基础上,设计了一种基于实时收录系统的多路卫星节目转播服务器,通过卫星节目收录系统,将收到的多路实时卫星节目在服务器内部进行选择、切换和复用,然后通过ASI接口转发到HFC网络.测试表明转播服务器能够稳定地进行节日转播,节目之间切换流畅.     

Tree-Based Data Broadcast in IEEE 802.15.4 and ZigBee Networks

This paper studies efficient and simple data broadcast in IEEE 802.15.4-based ad hoc networks (e.g., ZigBee). Since finding the minimum number of rebroadcast nodes in general ad hoc networks is NP-hard, current broadcast protocols either employ heuristic algorithms or assume extra knowledge such as position or two-hop neighbor table. However, the ZigBee network is characterized as low data rate and low cost. It cannot provide position or two-hop neighbor information, but it still requires an efficient broadcast algorithm that can reduce the number of rebroadcast nodes with limited computation complexity and storage space. To this end, this paper proposes self-pruning and forward node selection algorithms that exploit the hierarchical address space in ZigBee networks. Only one-hop neighbor information is needed; a partial list of two-hop neighbors is derived without exchanging messages between neighboring nodes. The ZigBee forward node selection algorithm finds the minimum rebroadcast nodes set with polynomial computation time and memory space. Using the proposed localized algorithms, it is proven that the entire network is covered. Simulations are conducted to evaluate the performance improvement in terms of the number of rebroadcast nodes, number of duplicated receivings, coverage time, and communication overhead     

Novel Advanced Broadcast Scheme for Efficient Safety Message Collision Alleviation in Vehicular Networks

Safety message broadcasting may cause a broadcast storm in vehicular ad-hoc network without an effective feedback mechanism. In particular, with increasing number of vehicles, serious collisions and incurred long delays are not acceptable for emergency safety messages. In this paper, we proposed an advanced broadcast scheme by the functionality of distributed coordination function and multi-channel operation in dedicated short range communication to decrease collision probability and increase received ratio of safety messages. The proposed scheme can increases safety message transmission efficiency and reduce the latency by delicately designing a rebroadcast probability, choosing the channel and selecting the backoff timer. After broadcasting in the control channel, transmitters return to their original service channel. Then, the vehicles receiving the safety message should inform the others in the same service channel to switch to the control channel for the safety message. Afterwards, the vehicles broadcast the safety message once and go back to the original service channel. This method can inform the other vehicles in different channels to increase the broadcast penetration. The proposed scheme can work without global positioning system (GPS). However, GPS can adapt the rebroadcast probability on hot spots to enhance the efficiency of the proposed scheme. Through detailed simulations, the proposed scheme is shown to be more efficient compared to the existing ones.     

A reliability enhanced density adaptive data dissemination scheme for VANETs

In this paper, a reliability enhanced and density adaptive data disseminating scheme is proposed for Vehicular Ad hoc NETworks (VANETs). The distributed on demand inquiring and re-sponding mechanism is employed to get nodes’ connectivity information. The announcing-listening process is also designed to find the nodes with bigger additional degree to rebroadcast, by which the relaying node is selected freely from density’s influence. Simultaneously, a reliability parameter is de-signed to choose redundant relays for each hop. According to the importance of the broadcast, the parameter is set by the source node properly. Simulation results show that the scheme has achieved good performances such as low forwarding ratio, short latency and low load. The broadcast coverage ratio is ensured against the influence of key link errors and relaying nodes failure by paying suitable additional communication.     

在VANETs城市场景下的基于自适应时延的Geocast路由协议

基于广播式的Geocast路由协议能够在特定的地理区域内高效地发布数据。然而,广播模式引起冗余重播,易导致广播风暴问题。另外,由于城市场景下建筑物的影响,现有的多数广播抑制方案难以应用于城市环境。为此,提出面向城市的基于自适应时延的Geocast路由协议UGAD(Urban Geocast based on Adaptive Delay)。UGAD采用了基于自适应时延的广播抑制方案,降低发生广播风暴的概率。同时,考虑到交叉路口的地理优势,给位于交叉路口的车辆 “优惠”的时延,使其具有优先转发数据包权力,从而提高数据包到达率。此外,考虑到城市道路的复杂性,UAGD采用基于交叉路口转发IF(Intersection forwarding)和贪婪转发GF(Greedy forwarding)两个模式,依据不同的道路情况选择不同的转发模式,从而降低冗余重播,并保持高的数据包到达率。最后,针对城市场景进行仿真,结果表明提出的UGAD具有高的数据包到达率,低的数据包重播率。     

Performance Analysis of Adjusted Probabilistic Broadcasting in Mobile Ad Hoc Networks

Broadcasting in Mobile Ad Hoc Networks (MANETs) is a fundamental data dissemination mechanism with a number of important applications in, e.g., route discovery, address resolution. However, broadcasting induces what is known as the “broadcast storm problem” which causes severe degradation in network performance due to excessive redundant retransmission, collision, and contention. Broadcasting in MANETs has traditionally been based on flooding, which simply swamps the network with large number of rebroadcast messages in order to reach all network nodes. Although probabilistic flooding has been one of the earliest suggested schemes to broadcasting, there has not been so far any attempt to analyse its performance behaviour in a MANET environment. In an effort to fill this gap, this paper investigates using extensive ns-2 simulations the effects of a number of important system parameters in a typical MANET, including node speed, pause time, traffic load, and node density on the performance of probabilistic flooding. The results reveal that most of these parameters have a critical impact on the reachability and the number of saved rebroadcast messages achieved by probabilistic flooding.     

数字节目虚拟现实交互系统的实现与应用

技术革新推动着经济、文化、思维方式、生活方式等各个领域的革新.在中国的电视领域,技术也同样会带来革新效应,在直播、转播、节目制作、电视包装等诸多领域,技术一直在不断地推陈出新,其中,现实与虚拟的结合一直是一个持续性的课题.实现数字技术的跨界、融合与应用,就如同将不同的元素放在一起不断实验,得到的成果却往往为传统产业打开一扇未来之门.本文以"幻维数码"在国内率先开发、研制、推广应用的"魔幻演播系统"为例,剖析在当下中国的演播环境中,虚拟现实技术的融合与应用将对中国电视演播产生的革新影响力.     

A method for rebroadcasting signals in an optical backplane bussystem

A guided-wave optical backplane bus system intended for use in high-performance board-to-board interconnects is described. Its multiplexed polymeric holograms can implement optical signal broadcast between boards so that all boards share common optical channels. By introducing an active coupler to the doubly multiplexed hologram at the center board, signals received from any board can be rebroadcast to all other boards. We describe the design concepts for a centralized optical backplane and the resulting performance and assembly advantages over previously developed guided-wave and free-space optical backplane bus systems used for broadcasting signals. These advantages include equalized fan-out power, increased interconnect distance, and simpler fabrication     

Energy and Spatial Reuse Efficient Network-Wide Real-Time Data Broadcasting in Mobile Ad Hoc Networks

In this paper, we present NB-TRACE, which is an energy-efficient network-wide voice broadcasting architecture for mobile ad hoc networks. In the NB-TRACE architecture, the network is organized into overlapping clusters through a distributed algorithm, where the clusterheads create a nonconnected dominating set. Channel access is regulated through a distributed TDMA scheme maintained by the clusterheads. The first group of packets of a broadcast session is broadcast through flooding, where each data rebroadcast is preceded by an acknowledgment to the upstream node. Nodes that do not get an acknowledgment for a predetermined time, except the clusterheads, cease to rebroadcast, which prunes the redundant retransmissions. The connected dominating set formed through this basic algorithm is broken in time due to node mobility. The network responds to the broken links through multiple mechanisms to ensure the maintenance of the connected dominating set. We compare NB-TRACE with four network layer broadcast routing algorithms (Flooding, Gossiping, Counter-based broadcasting, and Distance-based broadcasting) and three medium access control protocols (IEEE 802.11, SMAC, and MH-TRACE) through extensive ns-2 simulations. Our results show that NB-TRACE outperforms other network/MAC layer combinations in minimizing energy dissipation and optimizing spatial reuse, while producing competitive QoS performance.