一点对多点通信系统多址协议的研究

研究一点对多点通信系统多址连接协议,有效地对通信系统信道按需分配。叙述小容量多点通信系统所采用的轮询方式,以及中、大容量系统所采用的S—ALOHA 随机请求多址协议,以增加系统吞吐量和降低平均等待时间。     

ABR点对多点通信反馈合并算法研究

对当前研究很活跃的ABR多点通信中的一个分支点对多点通信的反馈合并算法做了一个评述,将各种解决反馈合并算法按照解决合并噪声,合并延迟,合并丢失问题进行了分类,比较了各种算法的优点和不足之处。对ABR多点通信的后续研究有一定的指导作用。     

数字无线中继线型点对多点通信系统及组成

介绍一种新的农村通信系统。数字无线中继线型一点对多点通信系统的工作原理,技术指标及系统组成。     

多点通信中的可靠性机制

多点通信可以实现组成员之间迅速有效的信息交换.可靠性是多点通信研究中的一个重要问题,其实现机制与点到点方式中有所不同.分析了多点通信可靠性方面所提出的新问题和解决方法,并简要介绍了一个实用性协议.     

一种采用SCPC/FM的地面一点对多点通信系统

本文提出一种在地面采用卫星通信SCPC/FM体制实现一点对多点通信的方案,着重介绍了这种通信系统的原理、组网方式以及一些关键部件,如中心转发器线性化功放、频道按需分配与信令系统、SCPC/FM调制解调组件、集成化积木化微波收发信机等的特点和研制方案。     

其它电信与业务及其传输技术

Y2001-62878-2 0115139为 IP 点对多点通信的无名服务=Anonymisation set-vices for IP multicast[会,英]/Grosch.C.//Proceedingsof the 25th Conference on Local Computer Networks(LCN2000).—2～9(PC)Y2001-62878-208 0115140保密点对多点通信的密钥分配=On key distribution insecure multicasting(会,英]/Wu,K P.& Ruan.S.J//Proceedings of the 25th Conference on Local Com-purer Networks(LCN2000).—208～212(PC)点对多点通信已广泛地应用于从一个发送端向多个接收端传送信息。因此,保密点对多点通信便成为分布式环境中的重要设计问题。本文提出了解决密钥分配问题的新方法。参13     

蓝牙语音网络通信研究

对蓝牙语音网络通信进行了研究,分析了蓝牙网络的构成和通信机制;从理论上研究了微微网的语音通信中点对点与一点对多点通信,分析了同步面向连接(SCO)链路的配置;对于蓝牙散射网的语音通信,根据蓝牙协议和散射网的特点分析了其实现所面临的困难。     

多点通信的路由问题

多点通信是网络支持多媒体业务的关键技术之一。文章在讨论多点通信路由算法的基础上,分析了几种实际应用的路由协议。之后介绍了多点通信在In-ternet上的应用,并结合多媒体业务的发展指出了路由算法的几个发展方向。     

多点通信的路由问题

多点通信是网络支持多媒体业务的关键技术之一。文章在讨论多点通信路由算法的基础上，分析了几种实际应用的路由协议。之后介绍了多点通信在Ｉｎｔｅｒｎｅｔ上的应用，并绫殉媒体业务发展的指出了路由算法的几个发展方向。     

CAN总线在雷达中的应用和开发

作为现场总线的CAN,是一种开放式互联网络,用以支持多主实时、分布式控制串行通信。在复杂的雷达系统工程中使用CAN总线,可有效提高通信的实时性和可靠性。本文从雷达应用的实际出发,采用自项向下的设计方法,首先建立具有典型特征的CAN总线网络,为解决多点通信的总线冲突提供一种有效解决方案;继而给出基于芯片级的CAN节点软硬件设计,构建符合雷达系统工程需要的单个CAN接口,以接入模块化的单部雷达综合通信链路。工程实施的结果与建模仿真结果相吻合,说明采用CAN总线较好地解决了总线自客错问题。     

A time domain approach for avoiding crosstalk in optical blockingmultistage interconnection networks

Crosstalk in multistage interconnection networks can be avoided by ensuring that a switch is not used by two connections simultaneously, in order to support crosstalk-free communications among N inputs and N outputs, a space domain approach dilates an N×N network into one that is essentially equivalent to a 2N×2N network. Path conflicts, however may still exist in dilated networks. This paper proposes a time domain approach for avoiding crosstalk. Such an approach can be regarded as “dilating” a network in time, instead of space. More specifically, the connections that need to use the same switch are established during different time slots. This way, path conflicts are automatically avoided. The time domain dilation is useful for overcoming the limits on the network size while utilizing the high bandwidth of optical interconnects. We study the set of permutations whose crosstalk-free connections can be established in just two time slots using the time domain approach. While the space domain approach trades hardware complexity for crosstalk-free communications, the time domain approach trades time complexity. We compare the proposed time domain to the space domain approach by analyzing the tradeoffs involved in these two approaches     

Context-aware cooperative testbed for energy analysis in beyond 4G networks

The complexity of heterogeneous wireless networks in synergy with battery powered mobile devices is driving new stringent requirements in terms of power efficiency to ensure that battery life, environmental and thermal criteria can be met. Modern mobile devices are equipped with multiple interfaces, which allow them to exploit the benefits offered by heterogeneous networking environments, but on the other hand, drain battery swiftly. In this paper, architecture for a context-based node and a testbed platform for the analysis of energy consumption of heterogeneous cooperative communications are presented. The demonstrative testbed comprises a WiFi Access Point, which provides WiFi coverage in the infrastructure mode, as well as nodes capable of communicating through short-range ultra-wideband WiMedia. The testbed includes a context aware module that provides and stores information related to different nodes in the system. The paper shows how context information can be used to save the energy of mobile devices and extend their battery lifetime using short-range communications. The testbed is used as a proof-of-concept for the practical implementation of the cooperative communications concept. The obtained results show that significant amount of energy can be saved using context information along cooperation among multiple interfaces, in comparison to direct communications.     

机动通信网分级分布式网络规划设计

为提高机动通信网络规划的科学性、准确性,充分发挥指战员能动性和通信装备效能,提出了一种分级分布式网络规划方法,阐明了分级资源管理和分级分布式网络规划两种应用模式。所提方法支持规划任务的分解和资源段的下发,并能融合各级规划结果,形成全网规划态势。此外,对分布式数据融合过程中必然会出现的冲突设计了检查及处理流程,并根据引起冲突的资源类型,明确了判定规则和处理办法。     

大型DCS设备中上位机通信误差消除方法

针对大型DCS设备上位机与下位机同时进行通信时,DCS上位机可能同时接收多个下位机的控制器发来的指令,在时域指令信号方面形成冲突,造成DCS系统的上位机与终端之间通信成功率降低。为解决这一问题,提出一种大型DCS设备中上位机通信误差消除方法,算法利用一种时间空闲间隔的有效填充法、信号间的通信机制,解决上位机与控制器之间时域信号冲突。并利用信号预测检测技术,提前对下个时隙进行调整,减少冲突的可能性。解决时域内的信号冲突问题。实验结果表明,该方法在DCS系统较大的情况下,能较好地协调上位机与控制终端之间的联系,提高了多机器人的通信成功率。     

Mode selection schemes for unicasting device‐to‐device communications supported by network coding

Device‐to‐device (D2D) communication in a cellular spectrum increases the spectral and energy efficiency of local communication sessions, while also taking advantage of accessing licensed spectrum and higher transmit power levels than when using unlicensed bands. To realize the potential benefits of D2D communications, appropriate mode selection algorithms that select between the cellular and D2D communication modes must be designed. On the other hand, physical‐layer network coding (NWC) at a cellular base station—which can be used without D2D capability—can also improve the spectral efficiency of a cellular network that carries local traffic. In this paper, we ask whether cellular networks should support D2D communications, physical‐layer NWC, or both. To this end, we study the performance of mode selection algorithms that can be used in cellular networks that use physical‐layer NWC and support D2D communications. We find that the joint application of D2D communication and NWC scheme yields additional gains compared with a network that implements only one of these schemes, provided that the network implements proper mode selection and resource allocation algorithms. We propose 2 mode selection schemes that aim to achieve high signal‐to‐interference‐plus‐noise ratio and spectral efficiency, respectively, and take into account the NWC and D2D capabilities of the network.     

GSM&GPRS在无线抄表系统中的应用与比较

合理地将GSM的SMS短信业务和GPRS分组数据业务用于远程无线水表抄表系统,不但可以对用户用水量进行有效的实时监控,而且成本较低,可靠性高。以无线抄表系统为基础,描述了系统数据传输常用的GSM短信业务和GPRS分组数据业务,以两者的技术复杂性、实现方法、费用、延时等进行对比,结果表明GSM适合通信频率低,数据量小,且对延时不敏感的场合;GPRS适合通信频率高,数据量大,实时性高的场合。结合无线抄表系统的特点,设计了大多时间采用GPRS模式而网络繁忙时采用SMS模式的数据传输方案,并通过软件控制,实现自动切换。结果表明该方案比采用单一方案费用更低,数据的可靠性几乎可达100%。     

Ka频段卫星信道的衰减特性

在Ka及以上高频段卫星通信系统中,其链路信号的衰减很严重,主要是大气、降雨、闪烁对卫星信道的影响。本文主要研究了雨衰和对流层闪烁产生衰减的机理与特性,提出雨衰采用DAH模型,闪烁采用Van de Kamp模型。然后根据实测气象数据,计算我国各参考站点的雨衰和闪烁值。为抗衰减对策的提出提供理论依据,为工程设计提供具体的参考数据。     

Mode instabilities in complex-coupled DFB semiconductor lasers

The authors investigate the mode stability of complex-coupled lasers with gain gratings and predict unstable mode solutions for moderate output powers when antiphase coupling is used. These instabilities are likely to have a negative impact on the performance of optical communications systems     

Relay Selection Strategy in the Secure Cooperative Communications System

With the low cost and low hardware complex considerations, cooperative systems are a tendency in the future communications. This work considers the secure cooperative communications systems. For a practical situation in the system, the scenario includes multiple source stations, multiple relay stations, multiple destination stations, and eavesdroppers. To analyze the optimal relay selection in the system, we begin with the performance analysis for a single source station and a single destination station. By applying two cooperative models, the amplify-and-forward (AF) mode and decode-and-forward (DF) mode, the secrecy capacity is derived. Then, we apply the derived results to the considered environment to find the optimal relay assignment. By the way, the relay selection can be obtained by the exhaustive search algorithm. However, there are a lot of steps needed if the number of source stations is large. Hence, applying the characters of the cooperative modes in the relay selection, the pre-selection step is proposed with a mathematical derivation. It could be used for the practical situation without a long-time calculation.     

一种保密通信系统的研究

基于混沌同步的保密通信方式相比传统保密通信方式有很大的优势,发展前景光明。通常混沌同步保密通信方式用混沌掩盖来实现,需要两个信道,其中一个信道传输混沌同步信号使系统保持同步,另一路则传输用混沌信号掩盖后的保密信息。在频谱资源日益紧张的情况下,由于这种通信方式对于信道资源的利用率相对较低,因此经济效益较差。本文提出了一个新的系统,用一个信道轮动传输信息和同步信号,对系统进行了详细分析,重点研究了系统传输的时隙分配并给出了仿真验证,证明了该系统能极大地提高信道利用率,同时对该系统的实际应用作了详细分析。