HFC网络中上行信道三种协议的比较

讨论了基于ＨＦＣ（混合光纤同轴电缆）网络上行多址接入信道的数据通信，比较了几种适于ＨＦＣ中ＭＡＣ（媒体输入控制）层上行数据流的协议，包括分布式协议Ｒ－ＡＬＯＨＡ，集中式协议Ｕ－ｎｉＬＮＫ以及一种新的协议ＰＣＵＰ（流水线循环上行流协议）最后得出ＰＣＵＰ协议比较适合ＨＦＣ网中的双向交互式业务的结论。     

EMX—500交换机系统带数据丢失的原因分析

ＥＭＸ－５００交换机系统带数据丢失的原因分析江苏省徐州邮电局朱小枫ＥＭＸ－５００交换机的系统带最初是由ＭＯＴＯＲＯＬＡ公司提供的，它共有３个组成部分，即ＰＡＴＣＨ，ＳＹＳＧＥＮ（ＳＹＳＴＥＮＧＥＮＡＲＡＴＩＯＮ）和空的ＣＨＡＮＧＥＪＯＵＮＡＬ。前两部...     

无冲突NC—IPRMA协议下的数据——话音综合

提出了一个面向微蜂窝通信的支持数据－－话音综合业务的无冲突分组预约多址协议－－ＮＣ－ＩＰＲＭＡ协议,通过Ｍ／Ｍ／Ｎ∞／Ｍ,排队模型分析了ＮＣ－ＩＰＲＭＡ协议的话音子系统性能,通过系统仿真分析了数据－－话音综合性能。研究结果表明,在支持数据－－话音综合业务方面,ＮＣ－ＩＰＲＭＡ协议比ＰＲＭＡ和ＩＰＲＭＡ协议更高效,这包括更高的认道利用率,更短的数据分组时延和更大的话音终端容量。由于采用排队等待方式接     

基于ATM的无源光网络媒质接入控制协议的设计

针对基于ＡＴＭ的无源光网络（ＡＴＭ－ＰＯＮ）设计了一种媒质接入控制（ＭＡＣ）协议。该协议的设计遵照ＩＴＵ－Ｔ有关ＡＴＭ－ＰＯＮ的建议Ｇ．９８３．１（１９９８年１０月）中所定义的帧结构。该协议能够支持ＣＢＲ／ＶＢＲ、ＡＢＲ和ＵＢＲ等多种业务,并能够保证用户公平地接入和充分地利用网络的资源。其中ＣＢＲ／ＶＢＲ业务的优先级最高,同时也确保ＡＢＲ业务至少能以最小信元通信。系统的剩余带宽资源被分配给ＵＢＲ业     

多视极化合成孔径雷达图象的分类和极化通道优化

本文提出了一个新的最大似然（ＭＬ）分类算法对多视全极化合成孔径雷达（ＳＡＲ）图象进行分类，给出了应用ＮＡＳＡ／ＪＰＬ机载Ｌ波段四视全极化ＳＡＲ实没数据的试验结果，证明了新算法的有效性。此外，本文还针所提算法应用于部分的多视全极化ＳＡＲ数据中，实现了地貌类型分类的极化通道优化。     

MC68HC05SR3芯片介绍

ＭＣ６８ＨＣ０５ＳＲ３芯片介绍黄小平一、基本结构及特征ＭＣ６８ＨＣ０５ＳＲ３ＨＯＭＯＳ微控制器是低功耗单片微控制器Ｍ６８ＨＣ０５家族的一员。这个Ｓ位的微控制器单元（ＭＣＵ）包含有在片振荡器，ＣＵＰ、ＲＡＭＥＯＭ、Ｉ／Ｏ，定时器及Ａ／Ｄ。ＭＣ６８ＨＣ０...     

Si／Ag／Si和Si／Au／Si薄膜分形晶化的TEM和EDS研究

本文利用透射电镜（ＴＥＭ）和Ｘ射线能谱（ＥＤＳ）对ａ－Ｓｉ：Ｈ／Ａｇ／ａ－Ｓｉ：Ｈ和ａ－Ｓｉ：Ｈ／Ａｕ／ａ－Ｓｉ：Ｈ薄膜的分形晶化行为进行了研究。结果表明薄膜的分形晶化强烈依赖于退火条件，分形的形成可用随机逐次触发形核和生长（ＲＳＮＧ）来加以解释。尽管膜内存在明显的互扩散，Ｓｉ分形区厚度与均匀基体区厚度相近。但在ａ－Ｓｉ：Ｈ／Ａｇ／ａ：Ｓｉ：Ｈ膜中存在部分较大的Ａｇ晶粒凸出膜面。     

无线局域网MAC标准

８０２１１为无线局域网标准，其物理层的无线媒体决定了它与现有的有线局域网（ＬＡＮ）的媒体访问控制（ＭＡＣ）层不同，具有独特的媒体访问控制机制，各站以载波侦听多路访问／碰撞避免（ＣＳＭＡ／ＣＡ）的方式共享无线媒体。本文结合具体设计研制过程，介绍ＭＡＣ的分布式协调功能（ＤＣＦ）和点协调功能（ＰＣＦ）、及ＭＡＣ帧格式等。     

INFORMATION FOR AUTHORS

ＩＮＦＯＲＭＡＴＩＯＮＦＯＲＡＵＴＨＯＲＳ￥／／ＳＥＭＩＣＯＮＤＵＣＴＯＲＰＨＯＴＯＮＩＣＳＡＮＤＴＥＣＨＮＯＬＯＧＹ（ＳＰＡＴ）ｉｓｐｕｂｌｉｓｈｅｄｑｕａｒｔｅｒｌｙｗｉｔｈｔｈｅｐｕｒｐｏｓｅｏｆｐｒｏｖｉｄｉｎｇｔｈｅｐｕｂｌｉｃａｔｉｏｎｏ...     

SONET／SDH155Mbit／s分插复用器中光群路单元板的参考设计

分插复用器（ＡＤＭ）是组成同步数字传输网（ＳＤＨ／ＳＯＮＥＴ网）的基本单元,它可以同ＳＤＨ的终端复用器（ＴＭ）、同步数字交叉连接设备（ＳＤＸＣ）及网络管理设备（ＴＭＮ）等网络单元（ＮＥ）一起组成配置灵活的ＳＤＨ传输网络。光群路单元板（ＯＡＵ板）是ＡＤＭ的核心部分。本文简要介绍ＡＤＭ的功能组成与ＯＡＵ板的参考设计。     

CIP:基于IP网络的一种远程多媒体实时教学系统通信协议的设计与实现

文章描述了一个基于IP网络的远程多媒体实时教学系统中的通信协议模型CIP（Class Initation Protocol)，该协议通过借鉴H．323与SIP协议，并结合实际教学的特点，满足远程多媒体实时教学的需求，在简单介绍了系统的总体设计框架后，给出了系统通信报文格式及协议模型，最后，描述了系统如何使用该协议进行通信。     

无线传感器网络UDHR协议的设计与实现

针对无线传感器网络(WSN)数据流的特点,提出一种WSN上下行路由异构的协议(UDHR),上下行路由可采用不同的算法,适合于时间驱动、事件驱动以及查询的数据收集模式.利用OMNeT++平台对UDHR协议进行建模仿真,结果表明该协议开销小、扩展性好、健壮稳定.并且在自主开发的Testbed平台上实现了该路由协议,利用该平台可实时观察整个WSN网络拓扑变化、网络开销、监测每个节点能量消耗以及数据收集等情况.     

基于流量工程的自动交换光网络新路由协议研究

为了研究基于流量工程的自动交换光网络(ASON)路由协议,采用基于源标签交换路由(LSR)路由泛供、仅广播链路可用带宽的增减的方法,得到了该协议能使LSR根据准确的带宽信息和波长可用信息选择路由的结果.结果表明,当链路中每个节点信息负荷量较小时,该协议拥有最小的链路阻塞率;与传统的路由机制相比,它能减少4～7倍的控制开销.     

基于PON网络的安全量子VPN方案

该文提出了一个新的无源光网络PON组成模型。利用该模型设计了一个具有身份认证功能的高效量子密钥分配方案,以满足无源光网络中光线路终端对光网络单元的身份认证和两者间的相互量子密钥分配,以及实现光虚拟专用网内部光网络单元间的量子密钥分配。安全性分析和实验方案表明了该协议的绝对安全性和可行性。将共享密钥作为通信双方的会话密钥,对内部传输数据进行加密,最终实现量子虚拟专用网。     

An OFDM-TDMA/SA MAC Protocol with QoS Constraints for Broadband Wireless LANs

Orthogonal frequency division multiplexing (OFDM) is an important technique to support high speed transmission of broadband traffic in wireless networks, especially broadband wireless local area networks (LANs). Based on OFDM, a new multiple access scheme, called OFDM-TDMA with subcarrier allocation (OFDM-TDMA/SA), is proposed in this paper. It provides more flexibility in resource allocation than other multiple access schemes such as OFDM-TDMA, OFDM-frequency division multiple access (OFDM-FDMA), and orthogonal frequency division multiple access (OFDMA). With OFDM-TDMA/SA, a medium access control (MAC) is designed for broadband wireless LANs. It optimizes bit allocation in subcarriers so that maximum bits are transmitted in each OFDM symbol under a frequency selective fading environment. The OFDM-TDMA/SA MAC protocol also supports three classes of traffic such as guaranteed, controlled-load, and best effort services. Based on the optimum subcarrier bit-allocation algorithm and considering heterogeneous QoS constraints of multimedia traffic, a hierarchical scheduling scheme is proposed to determine the subcarriers and time slots in which a mobile terminal can transmit packets. In such a way, the OFDM-TDMA/SA MAC protocol significantly increases system throughput in a frequency selective fading environment and guarantees QoS of multimedia traffic. Computer simulation is carried out to evaluate the performance of the OFDM-TDMA/SA MAC protocol. Results show that the new MAC protocol outperforms other MAC protocols for OFDM-based wireless LANs. This work was supported by the State of Georgia Yamacraw Project (E21-105).     

利用网络处理器构建弹性分组环模块

弹性分组环作为解决城域网的问题的一个方案被提出后,迅速成为研究的热点,但专用的RPR芯片还未商品化。提出了一种利用不支持RPR协议的网络处理器借助协议转换器来构建RPR模块的设计方案。协议转换器的主要功能是RPR/Ethernet帧转换和接口转换。文章介绍了RPR模块的结构和功能,并讨论了协议转换器的实现。     

WSN中最小代价前向协议的研究与改进

对无线传感器网络（WSN）中的最小代价前向协议进行了研究，通过引入随机选择和数据融合功能改进原有协议。用跳数作为代价分析了改进后的协议性能，并进行计算机仿真，结果表明改进后的协议具有更低的网络负荷和更长的生命周期。     

Protocol for the application of cooperative MIMO based on clustering in sparse wireless sensor networks

Wireless sensor networks (WSN) using cooperative multiple-input multiple-output (MIMO) communication are effective tools to collect data in several environments. However, how to apply cooperative MIMO in WSN remains a critical challenge, especially in sparse WSN. In this article, a novel clustering scheme is proposed for the application of cooperative MIMO in sparse WSN by extending the traditional low-energy adaptive clustering hierarchy (LEACH) protocol. This clustering scheme solves the problem that the cluster heads (CH) cannot find enough secondary cluster heads (SCH), which are used to cooperate and inform multiple-antenna transmitters with CHs. On the basis of this protocol, the overall energy consumption of the networks model is developed, and the optimal number of CHs is obtained. The simulation results show that this protocol is feasible for the sparse WSN. The simulation results also illustrate that this protocol provides significant energy efficiencies, even after allowing for additional overheads.     

ETPS-MAC: Energy Traffic Priority Scheduling-based QoS-aware MAC protocol for hierarchical WSNs

The evolution of the wireless sensor network (WSN) in recent years has reached its greatest heights and applications are increasing day by day, one such application is Smart Monitoring Systems (SMSs) which is in vision of implementation in every urban and rural areas. The implementation of WSN architecture in SMS needs an intelligent scheduling mechanism that efficiently handles the dynamic traffic load without sacrificing the energy efficiency of network. This paper presents a centralized TDMA scheduling based medium access control (MAC) protocol, called Energy Traffic Priority Scheduling MAC (ETPS-MAC) that accommodates variable traffic load while maintaining Quality-of-Service (QoS) assurance in hierarchical WSNs. The ETPS-MAC protocol employs priority scheduling algorithm which considers two factors for assigning priority, the energy factor and the traffic load factor to avoid packet buffering and maintains minimum data packet delay in case of high traffic load. Moreover, a novel rank-based clustering mechanism in FPS-QMAC protocol prolongs the network lifetime by minimizing the distance between the cluster head (CH) and the base station (BS). Both analytical and simulation models demonstrate the superiority of the ETPS-MAC protocol in terms of energy consumption, transmission delay, data throughput and message complexity when compared with the existing TDMA based MAC protocols.     

Analysis of Priority R‐ALOHA (PR‐ALOHA) protocol

With the exception of required time synchronization, the Reservation‐ALOHA (R‐ALOHA) protocol is simple to implement and suitable for medium access control in ad hoc wireless networks. In this paper, we propose an innovative protocol, referred to as Reservation ALOHA with priority (PR‐ALOHA) that provides differentiated services on the basis of traffic priority. To date, the carrier sense multiple access/collision avoidance (CSMA/CA) protocol has been widely used for this purpose by employing an interframe spacing (IFS) for priority service, that is, nodes ready for packet transmissions are required to wait for an IFS amount of time, where a shorter IFS is used to gain faster access to the radio channel. However, sensing and collision avoidance mechanisms make CSMA/CA unsuitable for delay‐sensitive applications, that is, congested scenarios with high traffic. In contrast, the proposed PR‐ALOHA protocol may be considered a good candidate for such applications. In this paper, the performance of the PR‐ALOHA protocol is investigated analytically and by simulation. Its comparison with regular R‐ALOHA is also carried out. Modeling and simulation results of PR‐ALOHA show that PR‐ALOHA improves the performance of high‐priority traffic with limited effect on normal network traffic. Thus, PR‐ALOHA may be useful in vehicular communications, where traffic may be separated into emergency messages having high priority and multimedia messages having low priority. Copyright © 2013 John Wiley & Sons, Ltd.