基于空分多址的车联网信标消息同步广播协议

依据车联网中专用短距离通信DSRC协议的标准,车辆通过周期地广播包含车辆状态信息的信标消息,实现邻居节点感知的链路层服务,并且信标消息以随机方式共享传输安全消息的控制信道。然而,这种方式可能导致严重信道竞争和数据丢失,降低邻居节点感知率。为此,提出基于空分多址的信标消息同步广播协议SDMA-SB。通过SDMA-SB协议,使得车辆以分布式方式同步地广播信标,实现车辆在同一个信标时区内有序地广播,降低信道竞争概率,进而提高邻居节点感知效率。SDMA-SB协议先建立有序化的道路模型,然后依据距离信息为同一路段车辆选择一个控制信道间隔CCHI作为信标时区,再根据距离计算广播信标所需的等待时间,并保证车辆等待时间的惟一性。仿真结果表明,与传统的信标广播协议相比,提出的SDMA-SB协议提高了邻居感知率以及信息的新鲜度。     

Ad Hoc网络中一种基于自裁减的广播算法

为解决简单泛洪式广播算法所引起的AdHocN络的广播风暴问题,提出了一种基于自裁减的广播算法。算法根据自裁减广播策略,通过设定延时机制和优先转发机制对网络节点是否需要转发广播包进行判定。最后,将算法应用于AODV协议,并与标准AODV协议在不同节点最大移动速度的场景下进行了转发节点数、到达率、端到端平均时延和归一化路由开销等参数的比较,以验证提出算法的有效性。     

基于路段连通性和方向转发策略的机会路由协议

文章针对车载自组织网络中由于道路拓扑的限制以及障碍物的存在导致车辆节点互相隐藏,造成的网络频繁连接中断的问题,综合考虑车辆位置、方向和速度、车辆密度信息,利用十字路口路段连通性和方向转发策略选择下一跳,提出了基于路段连通性和方向转发策略的车载机会路由协议。由仿真结果可知,在城市场景中,尤其当车辆节点比较稀疏时,本协议相比GPSR和GPCR协议具有更高的包投递率和较低的平均端到端传输时延。     

VANETs城市场景下基于自适应时延的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.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”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和贪婪转发GF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.     

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。     

一种基于可靠最远转发的车载网广播协议

许多车载自组网应用依赖于可靠高效的广播,但车载自组网节点高速移动,网络连通性随场景和时间动态变化的特性给广播协议的设计带来巨大挑战。为了应对这种挑战,该文在分析和验证简单最远转发机制具有低可靠性的同时,提出一种基于广播方向的可靠最远转发策略,并结合捎带确认机制设计了一种新的自组网多跳广播协议。与简单最远转发相比,可靠最远转发能明显降低转发节点失效的概率,提高消息单跳传播的可靠性;捎带确认机制使得协议能够适应网络连通性较差的场景,提升了消息全网传播的可靠性。仿真结果表明,提出的协议能在各种场景中实现高可靠性、低冗余的广播。     

一种基于战术互联网的广播

战术互联网是AdHoc网络技术在军事领域的重要应用，广播是战术互联网中基本的信息发布方式，也是AdHoc网络技术研究的一个重要问题。首先把AdHoc网络广播算法分为邻居决定转发和自身决定转发，然后仿真分析几种典型的广播算法；最后根据战术互联网的特点，结合现有的AdHoc网络广播，提出一种新的战术互联网广播协议（TIBP）。仿真结果表明：TIBP在战术互联网环境下具有较高的效率。     

基于时间预测的广播协议

随着无限通信技术的成熟,使得通过信息交换和交通信息分发式改善交通安全和预防交通拥堵成为可能。为了分发紧急信息给驾驶员,广播技术通常被采纳,但是又经常受到隐藏节点、干扰、信息冗余和竞争问题的影响。提出一种事件驱动的基于时间预测的广播(TPB,Time-based Predictions Broadcast),适合双向多车道高速公路上的车辆合作防碰撞。信息中继节点的选择基于接收车辆节点的位置、速度、方向。仿真结果表明该协议能够有效地分发紧急信息,降低时延,信息跳数减少,重播次数减少。因此通过中继节点的选择能够减少信息冗余,降低"广播风暴"发生的概率。     

基于位置信息的移动P2P路由发现策略

由于EDSR路由协议在路由选择时采取向邻居节点全部转发路由信息的策略,在路由请求时,容易引起转发次数过多而导致网络瘫痪。提出了借助LAR协议利用目的节点的位置信息设置路由的期望域,从而构建路由选择区域,提高发起路由请求时预知目的节点位置的几率。提出了增强性LAR路由协议。当位置辅助路由协议发现路由失败时避免采用全网洪泛机制,采用基于距离的位置路由改进算法,设置距离更新门限来达到节点位置信息实时性与更新负载的平衡,通过路由选择权重值Qpath使路由选择达到最优。     

基于位置信息的移动P2P路由发现策略

由于EDSR路由协议在路由选择是采取向邻居节点全部转发路由信息的策略,在路由请求时,容易引起转发次数过多而导致网络瘫痪。本文提出借助LAR协议利用目的节点的位置信息设置路由的期望域,从而构建路由选择区域,提高发起路由请求时预知目的节点位置的几率,提出增强性LAR路由协议。当位置辅助路由协议发现路由失败时避免采用全网洪泛机制,采用基于距离的位置路由改进算法,设置距离更新门限来达到节点位置信息实时性与更新负载的平衡,通过路由选择权重值Qpath使路由选择达到最优。     

远洋船舶公共广播系统应用与改进

介绍了公共广播系统在远洋船舶中的应用，针对现代化船舶通信系统的发展与广播系统的现状，根据远洋船舶广播应用实践，提出了基于计算机控制的自动船舶公共广播系统，对其功能拓展的方案及优化改进措施进行了讨论。     

Efficient multi‐hop wireless broadcast protocol in vehicular networks using automated threshold function design

Vehicular networking applications often use multi‐hop wireless broadcasting as a primary data dissemination mechanism. Therefore, protocols that efficiently and thoroughly propagate application data while adapting to a wide range of network density, vehicle distribution pattern, channel quality, and other conditions are critical for vehicular communications. Here, we design the Statistical Vehicular Broadcast (SVB) protocol to efficiently distribute data via multi‐hop broadcast in vehicular networks. First, we present an automated optimization technique for the design of threshold functions in statistical broadcasting methods. Next, we compare and analyze known statistical techniques, including different fundamental methods, assessment delay algorithms, and failsafe mechanisms. All combinations of these techniques are given threshold functions optimized using the proposed automated procedure then are evaluated in a wide range of simulations. High‐level statistical design principles and recommendations are established based on analysis of these results. Finally, we apply those principles to design SVB. It is evaluated in JiST/SWANS and is shown to achieve a high target reachability level while consuming less bandwidth than similar protocols across urban and highway vehicular networking scenarios.Copyright © 2014 John Wiley & Sons, Ltd.     

江阴电视台数字播出系统的设计与安全

简要讲述了江阴电视台数字播出系统的构成及其特点,并针对播出系统的安全性设计提出了一些观点和想法。     

Efficient Channel Allocation Tree Generation for Data Broadcasting in a Mobile Computing Environment

The research issue of broadcasting has attracted a considerable amount of attention in a mobile computing system. By utilizing broadcast channels, a server continuously and repeatedly broadcasts data to mobile users. These broadcast channels are also known as broadcast disks from which mobile users can retrieve data. Using broadcasting, mobile users can obtain the data of interest efficiently and only need to wait for the required data to present on the broadcast channel. The issue of designing proper data allocation in the broadcast disks is to reduce the average expected delay of all data items. We explore in this paper the problem of generating hierarchical broadcast programs with the data access frequencies and the number of broadcast disks in a broadcast disk array given. Specifically, we first transform the problem of generating hierarchical broadcast programs into the one of constructing a channel allocation tree with variant-fanout. By exploiting the feature of tree generation with variant-fanout, we develop a heuristic algorithm VF ^K to minimize the expected delay of data items in the broadcast program. In order to evaluate the solution quality obtained by algorithm VF ^K and compare its resulting broadcast program with the optimal one, we devise an algorithm OPT based on a guided search to obtain the optimal solution. Performance of these algorithms is comparatively analyzed. Sensitivity analysis on several parameters, including the number of data items and the number of broadcast disks, is conducted. It is shown by our simulation results that by exploiting the feature of variant-fanout in constructing the channel allocation tree, the solution obtained by algorithm VF ^K is of very high quality and is in fact very close to the optimal one resulted by algorithm OPT. Moreover, algorithm VF ^K is of very good scalability which is important for algorithm VF ^K to be of practical use to generate hierarchical broadcast programs dynamically in a mobile computing environment.     

Dynamic Leveling: Adaptive Data Broadcasting in a Mobile Computing Environment

The research issue of broadcasting has attracted a considerable amount of attention in a mobile computing system. By utilizing broadcast channels, a server is able to continuously and repeatedly broadcast data to mobile users. From these broadcast channels, mobile users obtain the data of interest efficiently and only need to wait for the required data to be present on the broadcast channel. Given the access frequencies of data items, one can design proper data allocation in the broadcast channels to reduce the average expected delay of data items. In practice, the data access frequencies may vary with time. We explore in this paper the problem of adjusting broadcast programs to effectively respond to the changes of data access frequencies, and develop an efficient algorithm DL to address this problem. Performance of algorithm DL is analyzed and a system simulator is developed to validate our results. Sensitivity analysis on several parameters, including the number of data items, the number of broadcast disks, and the variation of access frequencies, is conducted. It is shown by our results that the broadcast programs adjusted by algorithm DL are of very high quality and are in fact very close to the optimal ones.     

户外现场直播节目信号的安全传输及安全播出

对户外现场直播节目信号的安全传输及安全播出提出一些看法。     

IP广播平台在“村村响”广播工程中的应用

IP广播平台可以满足几千个节目同时在网上跑,几万个终端同时播出,采用IP广播平台建设“村村响”广播工程,构建农村公共服务体系,对农村政务、经济和灾害预警等信息的发布,丰富农村的精神文化生活有着重要意义.主要就IP广播平台在“村村响”广播工程建设中的应用做一些介绍,供同行参考.     

Variable power broadcast using local information in ad hoc networks

Network wide broadcast is a frequently used operation in ad hoc networks. Developing energy efficient protocols to reduce the overall energy expenditure in network wide broadcast can contribute toward increasing the longevity of ad hoc networks. Most of the existing work in energy efficient broadcast protocols use either a fixed transmission power model or assume global knowledge of the entire network at each node. Variable power broadcast with local knowledge has recently been proposed as a promising alternative approach for network wide broadcast in ad hoc networks.

In this paper, we present a novel approach, called INOP, for network wide broadcast. INOP is a variable power broadcast approach that uses local (two-hop neighborhood) information. INOP utilizes a novel technique for determining the transmission power level at each transmitting node. We also propose two alternative methods to cover the nodes that are not covered by the transmission of the source or a retransmitting node.

Our simulation based evaluations show that, compared to other approaches, INOP achieves better results in terms of energy efficiency, and competes with and exceeds other approaches in terms of a number of other performance metrics including traffic overhead, coverage, and convergence time. Based on these results, we can conclude that INOP improves the current state-of-the-art approaches for energy efficient broadcast in ad hoc networks.     

县级应急广播智能监控系统的设计应用

应急广播智能监控系统将视频与语音播控结合,在很多领域得到运用,对广播智能监控技术的特点进行介绍,分析智能监控技术在城市智慧广播视频中的具体应用。     

基于清流备播的数字电视应急处理系统研究

为保障数字电视的不间断播出,本文对基于清流备播的数字电视应急处理系统进行了研究,包括:背景分析、加入清流备播系统后的数字电视前端平台架构、清流备播系统架构以及基于清流备播系统的数字电视应急处理系统架构。