共查询到18条相似文献,搜索用时 62 毫秒
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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。 相似文献
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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 相似文献
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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。 相似文献
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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。 相似文献
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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 相似文献
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一种先进的话音加密同步技术的设计及实现 总被引:1,自引:0,他引:1
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。 相似文献
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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。 相似文献
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Shamima Kabir M.K. Abdullah Sabira Khatun S.B. Ahmad Anas M.A. Mahdi 《Optical Fiber Technology》2005,11(4):1199
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. 相似文献
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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。 相似文献
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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。 相似文献
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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. 相似文献
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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 相似文献
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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 相似文献