A bandwidth latency tradeoff for broadcast and reduction

The “fractional tree” algorithm for broadcasting and reduction is introduced. Its communication pattern interpolates between two well known patterns—sequential pipeline and pipelined binary tree. The speedup over the best of these simple methods can approach two for large systems and messages of intermediate size. For networks which are not very densely connected the new algorithm seems to be the best known method for the important case that each processor has only a single (possibly bidirectional) channel into the communication network.     

测控系统中串行接口与通信协议

分析了四种主要串行接口的电气性能以及不同的应用特点,并结合笔者的实际应用体会,对串行接口的通信协议软件编制和操作系统环境提出了值得读者注意的问题和建议．     

半双工信道上TCP/IP协议性能仿真

通过电台组网通信在特殊场合具有十分重要的应用价值.电台一般采用半双工方式通信,这种环境下TCP/IP的适用性及其性能值得研究.NS是网络模拟常用的工具,但它本身并不包含半双工链路模型.文中首先讨论在NS网络仿真软件中对半双工链路的建模,进而研究TCP/IP在半双工信道上的性能.模拟实验结果表明：只要解决半双工信道的信息冲突问题,TCP/IP在半双工链路上运行是完全可行的.     

JD103数据采集与监测系统中前端机的设计及实现

介绍的前端机是吉林大学和吉林化学工业公司电厂厂联合研制的“JD103数据采集与监测系统”中7个前端机（分布全厂7个车间）中的一个。系统已通过省级鉴定并正式投入使用,经过多年运行实践证明,系统稳定可靠,能提供详实准确的实时数据。     

基于手持电台的半双工无线传输协议的实现

提出并实现了一种基于手持无线电台的通用半双工无线数据传输协议。通过自定义数据帧及控制帧结构，确保在不可靠、低带宽无线环境下实现数据的无差错传输。利用有限状态机FSM的状态转换和事件驱动技术，详细论述该协议的实现方案，井给出了协议的实现环境。     

具有微控制器的智能仪表设计与应用

介绍了以微控制器ＭＣＵ基本系统及测控软件、通讯接口和输入／输出接口构成的全数字化智能仪表的构成与功能,与上位机ＰＣ的通讯协议,和仪表软件的抗干扰技术,同时介绍了基于智能仪表的集散型计算机测控系统的结构及所实现的功能,以及智能仪表的应用与前景。     

A retrial queue for modeling fault-tolerant systems with checkpointing and rollback recovery

In this paper we analyze a retrial queue that can be used to model fault-tolerant systems with checkpointing and rollback recovery. We assume that the service time of each job is decomposed into N modules, at the end of each of which a checkpoint is established. Checkpointing and rollback recovery consists, basically, of saving periodically the state of the system on a secure device so that, upon recovery from a system failure, the system can resume the computation from the most recent checkpoint, rather than from the beginning. Upon a successful service completion of a job, the server activates a timer and remains awake. If the timer expires without a request, the server departs for a vacation. Upon returning from the vacation, the server activates the timer again. Furthermore, both idle and vacation periods can be interrupted by the server in order to perform secondary jobs. Applications of this model can be found in power saving of mobile devices in a half-duplex communication system operating in wireless environment, and in long-running software applications. We investigate stability condition and steady state analysis. We also apply a mean value analysis to obtain useful performance measures, and prove that the model satisfies the stochastic decomposition property. Useful energy metrics are determined and constrained optimization problems are formulated and used to obtain extensive numerical results.     

数字半双工通信机制在楼宇对讲系统中的应用

针对于数字楼宇对讲系统通话声音小、对讲过程中经常出现回声和啸叫等问题,本文基于DM365硬件平台和嵌入式Linux系统设计了一款具有数字语音半双工双向通信机制的楼宇对讲系统。该系统在语音端采用短时能量加过零率的实时语音端点检测算法,能使前端输入的音频信号无衰减,实现高清晰的语音对讲。相对于其他的数字语音通信机制,该系统不仅可以有效地抑制回声。而且能减少因去噪而造成的语音信号失真。     

一种应用于WLAN的混合双工MAC协议

全双工通信技术可以提高链路容量和频谱利用率,会给现有无线局域网(WLAN)带来极大的变革。该文针对传统半双工WLAN向全双工WLAN发展的过程中多种双工站点共存的问题,提出一种混合双工媒体接入控制(MAC)协议(HYD-MAC)。该协议合理设计了请求发送/清除发送(RTS/CTS)帧,并根据网络隐藏节点状况和站点全双工能力,自适应地选择最佳的传输模式,包括同步全双工、异步全双工、条件半双工以及半双工等4种模式。给出了HYD-MAC协议在4种传输模式下的链路建立与数据传输流程,分析了HYD-MAC的饱和吞吐量和介质访问时延等网络性能。仿真结果表明,所提的HYD-MAC的性能优于传统半双工DCF协议,特别在帧长较长、站点数较少、数据传输速率较低时,HYD-MAC的性能提升效果更加明显;与经典的全双工协议相比,HYD-MAC协议通过牺牲极少的吞吐量和时延性能,可以同时满足全双工、半双工以及混合双工网络的通信需求。