一种新型的数字图像/话音传输系统的实现方案

提出了一种采集与传输数字图像／话音的方法，介绍了其总体方案以及设计重点，包括乒乓存储结构的改进、数据复接和控制逻辑的实现等。     

基于协议分析仪的传输与话音测试单元

为了满足电信部门对2M链路信令、传输、话音的测试要求,本文设计在协议分析仪信令处理单元的基础上增加了话音监测与误码检测单元的功能     

基于CSMA/CD的教学实验的设计与实现

设计并实现了一种适用于教学的基于CSMA／CD机制的实验,重点给出了CSMA／CD机制的原理以及与此相关的信道共享技术、早期冲突、晚期冲突、以太网捕获等。实验界面知识点丰富,有助于学生掌握上述知识要点,在教学实践中获得了很好的效果。     

分组卫星话音／数据综合的混合多址协议性能研究

本文讨论了一种用于分组话音／数据综合的混合多址协议，该协议是固定分配与随机访问的混合，并且赋予话音分组优先传输权，从而保证了无重传话音分组有较小的丢失概率。本文进行了详细的理论分析，并得出了性能比较特性，所得结果认为这是一个兼顾话音／数据综合的较好协议，且具有一定的灵活性。     

基于NS-2的CSMA/CD实验设计

计算机网络是高校计算机专业和大部分理工类非计算机专业必修课,在教学过程中设计实验,让学生动手验证抽象的计算机网络原理,是提高教学质量必不可少的环节,传统的构建计算机网络实验室的方法成本高,师生受时空限制。文中设计并实现了NS-2环境下的以太网络实验,给出了一般实验设计流程,克服了构建真实物理环境实验的成本高、灵活性差等缺点,同时对流程稍作修改,便可设计更多的计算机网络技术实验,具有扩展性强、灵活性高的特点。     

话音质量的一种新的评价方法

本文利用五种新的模糊综合评判方法：模糊树法ＦＴ对通信网的通话质量进行综合评判。最后采用ＦＴ评估出通信网的通话质量。     

一种基于FFT对称性的多维话音置乱系统

本文提出了一种基于ＦＦＴ对称性的多维话音置乱系统。该系统首先将话音样值序列进行时域置乱和伪谱掩盖，然后扩展变换为一个满足ＦＦＴ对称性要求的特殊序列。对该序列进行ＩＦＦＴ变换和分段置乱，经Ｄ／Ａ变换后即可在普通电话信道中传输。该系统的理论密钥量高达（１９８！）＊（１６！）种，具有数字加密系统的抗破译能力。与一般话音置乱系统显著不同的是，该系统即使不采用任何加密措施，信道中传送的信号也是不可懂的，因而     

一种先进的话音加密同步技术的设计及实现

介绍了一种应用于数字话密机的密码同步技术,较详细地说明了它的工作原理及其优点,并讨论了在其实现过程中所需解决的有关技术问题。     

自适应p-持续CSMA/CD介质访问控制策略

针对IEEE802．3局域网介质随机访问协议l-持续CSMA／CD，在同一个冲突域内，它的性能在重荷载下有明显缺陷的问题，本文分析了p-持续CSMA／CD协议，提出了一种新的关于概率p的自适应算法。该算法基于对网络流量的分析，在OSI物理层通过信道信息量的在线实时检测，根据反馈控制的原理，在数据链路层动态地调整控制输入参数p，从而控制站点发送分组数据帧的行为，使信道处于最佳的传输状态，提高信道的效率。     

Performance evaluation of a buffer-based CSMA/CD protocol for single channel optical Ethernet LAN

Using CSMA/CD, Ethernet suffers capture effect that makes it unsuitable for supporting real-time multimedia traffic. It does not guarantee delay bound and behaves poorly under heavy load conditions, leading to excessive delay, throughput degradation and packet loss because of excessive collisions. Aim of this paper is to increase throughput and reduce average packet transfer delay of CSMA/CD-based LAN by reducing collisions and eliminating packet loss. Here, each user has a finite buffer capacity that helps to reduce collisions and Ethernet capture effect. At the same time, to eliminate packet loss, a new special-jamming signal is used. The network performance in terms of throughput, average packet transfer delay and percentage of collision based on the proposed protocol shows significant improvements. Throughput is increased more than 10% whereas average packet transfer delay and percentage of collision are reduced to less than 1.5 ms and 3%, respectively, compared to conventional protocol.     

门禁系统的CSMA／CD协议仿真

作为一种安防产品,门禁系统已经广泛使用于企业、住宅等场所,其通信的稳定性决定了产品的优劣。设计的基于ARM和RFID的自制门禁系统可以把若干台门禁控制器通过CS—MA／CD网络相互连接起来组成网络系统应用。然后通过转化与计算机相连,用门禁管理软件对各个门禁控制器进行实时监控。主要阐述CSMA／CD协议在系统中的具体设计,并进行了仿真测试,效果良好。     

带有网络分割的CSMA／CD技术

通过在ＣＳＭＡ／ＣＤ局域网中引入网络分割这一新概念，建立了以太网模拟模型，改善了ＣＳＭＡ／ＣＤ技术在重负载下的性能。     

An efficient protocol for providing integrated voice/data services to mobiles over power-limited satellite channels

Various mobile satellite communication systems are being developed for providing integrated voice/data services over a shared satellite transponder which is power-limited in nature. A common strategy is to use slotted ALOHA request channels to request channel assignments for voice/data calls from a network management station. To maximize efficiency in a system with a power-limited satellite transponder, it is proposed that the bursty nature of voice sources be exploited by the NMS to ‘over-assign’ channels. This may cause problems of inefficiency, potential instability as well as a degradation in the quality of service offered to the customers. Augmenting this with the introduction of simple state-dependent control procedures provides systems which exhibit more desirable operational features. This approach is proposed and examined in this paper.     

Reservation CSMA/CD: a multiple access protocol for LAN's

A multiple-access protocol for local area networks is described. It is basically a hybrid of carrier-sense multiple access with collision detection (CSMA/CD) and the broadcast recognizing access method (BRAM). CSMA/CD, which is contention-based, works well under light traffic, but message collisions degrade system performance when the channel becomes heavily loaded. BRAM, which is collision-free, has no longer delays at low load, but its efficiency improves as the load increases. Performance models are developed for the hybrid protocol and for the Ethernet protocol, a proven commercial implementation of CSMA/CD-type protocols. It is found that the hybrid protocol gives better performance for a wide range of scenarios     

动态p-坚持CSMA/CD协议的统计改进

p-坚持CSMA/CD协议在计算机终端数据发送上有着广泛的应用。针对计算机终端中p-坚持CSMA/CD协议的信道利用率的问题进行研究,为了能更好的利用信道发送数据,提高信道利用率,采用了统计方法中的贝叶斯决策统计理论,通过全概率公式拆分,对p-坚持CSMA/CD协议中的参数p进行动态自适应拟合的一种CSMA/CD协议方法,并进行改进使之有更好的信道利用率。用MATLAB2010a进行模拟仿真实验,得出改进后的自适应p-坚持CSMA/CD协议比静态的p-坚持CSMA/CD协议对信道有高20%左右的利用率。     

Analyzing a CSMA/CD protocol through a Systems of CommunicatingMachines Specification

A model for the specification and analysis of communication protocols called Systems of Communicating Machines is used to specify a CSMA/CD (carrier-sense multiple access with collision detection) protocol, and to analyze it for safety and certain restricted liveness properties. The model uses a combination of finite state machines and variables in the specification of each machine, and the communication between machines is accomplished through shared variables. The Ethernet bus is modeled as a single variable shared by all communicating processes. Collisions are modeled by simultaneous writes to this variable