A multiprocessor implementation of joyce

Joyce is a programming language for parallel computers based on CSP and Pascal. A Joyce program defines concurrent agents which communicate through unbuffered channels. This paper describes a multiprocessor implementation of Joyce.     

A hierarchical multiprocessor bandwidth reservation scheme with timing guarantees

A multiprocessor scheduling scheme is presented for supporting hierarchical containers that encapsulate sporadic soft and hard real-time tasks. In this scheme, each container is allocated a specified bandwidth, which it uses to schedule its children (some of which may also be containers). This scheme is novel in that, with only soft real-time tasks, no utilization loss is incurred when provisioning containers, even in arbitrarily deep hierarchies. Presented experiments show that the proposed scheme performs well compared to conventional real-time scheduling techniques that do not provide container isolation.

SNMP协议分析与协议栈的实现

对SNMP体系结构进行了研究,对SNMP协议及其消息格式进行了分析,对SNMP消息的传输与接收进行了研究;提出支持SNMPv1、v2c以及v3的管理器协议栈模型,分模块设计和实现了管理器协议栈的核心引擎;在通讯子模块中使用了缓冲重发机制和多线程机制等关键技术,在安全子模块中实现了USM模型。     

无线传感器网络分层带宽自适应路由协议

在无线传感器网络(WSNs)中,节点能量使用严格受限,限制了网络的使用寿命。固定环带宽度的分层路由协议是一种有效的解决方法。在此基础上,提出了一种引入环带宽度自适应调整的路由机制。该机制根据节点剩余能量和传输数据能耗自动调整环带宽度,并决定节点是否参与网内数据报文的传输。采用Matlab作为仿真工具对该路由机制进行了仿真分析,结果表明:该算法通过调整环带宽度的方式能够有效延长网络使用寿命和维持网内负载均衡。     

MOSS协议及其实现

MOSS协议是一种安全电子邮件协议,它提供对MIME对象进行数字签名和数据加密的服务,分析了MOSS协议,MOSS协议中使用的算法以及MOSS协议中两种重要的MIME封装类型,并描述了如何利用MOSS协议来保证信息的安全性以及它的具体实现。     

优先级继承协议在Linux中的实现

随着Linux被越来越多地用于实时系统中,实时性能也日益受到关注。通过将Linux的内核改造为可抢占式内核,可缩短系统的响应延时,提高Linux的实时性,但同时也带来了优先级逆转的问题。为了解决优先级逆转问题,基于可抢占式的Linux内核,对Linux内核相关源代码进行修改,实现了优先级继承协议。经过测试证明,采用优先级继承协议的抢占式Linux内核能够解决优先级逆转的问题,满足系统的实时要求。     

用C语言实现继承的研究

C语言在嵌入式软件开发中被广泛使用,但由于开发人员和应用场景等原因,面向对象、设计模式等优秀的软件开发方法始终没有很好地运用起来。时至今日,物联网等应用的兴起给嵌入式软件开发带来新的挑战,而传统的面向过程开发方法已经难以支撑这些复杂的应用。因此,有必要在嵌入式软件开发中引入面向对象、设计模式等优秀的软件开发方法。面向对象是现在软件方法的根基,继承是面向对象的三大特性之一,本文结合C语言的特性,对使用C语言实现继承进行了讨论。     

Parallel implementation of OPS5 on the encore multiprocessor: Results and analysis

Until now, most results reported for parallelism in production systems (rulebased systems) have been simulation results-very few real parallel implementations exist. In this paper, we present results from our parallel implementation of OPS5 on the Encore multiprocessor. The implementation exploits very finegrained parallelism to achieve significant speed-ups. For one of the applications, we achieve 12.4 fold speed-up using 13 processes. Our implementation is also distinct from other parallel implementations in that we parallelize a highly optimized C-based implementation of OPS5. Running on a uniprocessor, our C-based implementation is 10–20 times faster than the standard lisp implementation distributed by Carnegie Mellon University. In addition to presenting the performance numbers, the paper discusses the details of the parallel implementation-the data structures used, the amount of contention observed for shared data structures, and the techniques used to reduce such contention.     

Verification of a multiprocessor cache protocol using simulation relations and higher-order logic

We present a formal verification method for concurrent systems. The technique is to show a correspondence between state machines representing an implementation and specification behavior. The correspondence is called asimulation relation, and is particularly well suited for theorem provers. Since the method does not rely on enumerating all the states, it can be applied to systems with an infinite or unknown number of states. The method is illustrated by proving the correctness of a particularly subtle example that is likely to be of increasing importance: a directory based multiprocessor cache protocol. The proof is carried out using the HOL (higher-order logic) theorem prover.     

一种可变带宽数字下变频器设计与实现

针对数字下变频器资源消耗多、信号处理时间长、运算效率低和难以处理多种带宽信号等问题,在研究数字下变频和多相结构运算特点的基础上,提出一种多相带通滤波结构设计,并利用恒速乘法、乘法器复用和多速率输入输出控制等技术实现了这一结构。软硬件仿真表明:该结构不仅能够实现多种带宽信号的正交数字下变频,而且,具有很高的运算效率和硬件资源利用率、较短的信号处理时间。     

基于SSL协议的SET协议模拟实现

安全问题是关系到电子商务服务是否能够广泛开展的重要因素。一个安全电子支付系统需要特殊的安全机制。目前，在电子商务中使用的安全协议主要有两种，即SSL协议和SET协议。SSL协议是免费的，但是它有重大缺陷。SET协议要安全许多，然而却非常昂贵，且现有的实现缺乏灵活性。SSL协议的实现版本openssl里附带有一个非常完备的加密函数库和一整套的使用和管理CA数字证书的方法。主要讨论如何在SSL协议的基础上利用openssl开发包和组件技术来实现SET协议功能，并提高SET协议使用的灵活性。     

Automated protocol implementation with RTAG

The RTAG (real-time asynchronous grammars) programming language is discussed. The language is based on an attribute grammar notation for specifying protocols. Its main design goals are: (1) to support concise and easily understood expression of complex real-world protocols; and (2) to serve as the basis of a portable software system for automated protocol implementation. The algorithms used in generating implementations from given specifications are sketched, and a Unix-based automated implementation system for RTAG is described     

A load balancing mechanism for large scale multiprocessor systems and its implementation

In large scale multiprocessor systems, the distance between processors should be taken into account by software to reduce the network traffic and the communication overhead. A load balancing method based on P³ (Processing Power Plane) model is proposed to enable programmers to specify distributing computational load, keeping the locality of the computation. In this method, a process is allocated to a rectangle on a hypothetical processing power plane. The size of the rectangle represents the processing power given to the process, and the distance between rectangles represents the communication cost between them. This plane is divided to processors, and the region of the processor may be dynamically reshaped to alleviate imbalance on P³. Mechanism for realization of the method has been implemented on the Multi-PSI/version, 2, which is a parallel processing system with 64 processing elements connected to form a 2-dimensional mesh network. A packet transmission mechanism of the Multi-PSI/version 2 is described, which realizes the process distribution along with the balancing method.     

基于移动主机的传输控制协议的研究与实现

基于无线网络的特点,提出了一种新的基于移动主机的传输层控制协议。该协议将以接收端为中心的传输层协议与以发送端为中心的传输层协议有机结合,以更好适应无线局域网。通过仿真实验验证了该协议的可行性。     

基于线性回归机制的带宽测量方法设计及实现

拓展了变包模型以获取某个网段内主干链路的带宽.分析了带宽测量的基本原理,之后讨论了获取网络链路带宽的方法,解决了路由器判定、路径分解以及探测结果组织获取等3个问题.着重讨论了减少探测量的方法、并行调度机制以及回归步骤等关键问题,最后给出了带宽测量系统的实现及实验结果.     

一种基于MANET的多播协议的设计与实现

传统的应用于有线网络的多播方法很难适应MANET所具有的拓扑结构变化和带宽有限等特点,无法有效地应用于MANET。提出了采用按需路由发现策略的MANET多播路由协议MFGRP。在MFGRP协议中不需要维护全局的路由信息,通过按需路由发现过程,动态更新路由信息和建立网格。多播数据包在转发组成员间进行有限泛洪,使协议能够降低带宽的占用及减少路由更新信息的传播。模拟实验显示协议在带宽较低、多播组成员数量变化较大的移动分组无线网环境中,具有较好的可靠性和工作效率。     

吉比特数据链路层协议的设计与实现

针对利用DDR接口进行互联的网络系统,设计了一种吉比特（Gbps）数据链路协议,详细描述了协议如何解决数据链路协议必需解决的一般性问题和该特定网络系统所带来的新问题,介绍了协议是如何帮助系统完成数据通信的,并给出了该协议采用FPGA技术的实现方法以及系统的测试结果。     

LTE空中接口协议栈的研究与实现

针对LTE (long term evolution)空中接口技术标准应用在小型无线通信系统时存在设计冗余的问题,通过对协议栈数据处理过程的研究,从PDCP (packet data convergence protocol)、RLC (radio link control)、MAC (media access control)子层模块的功能和需求着手,提出了双缓冲队列机制,并设计了一个针对小型无线通信系统的空中接口协议栈.在Xilinx Virtex-6硬件开发板上实现了该协议栈,并验证该空中接口协议栈的功能和性能均能满足小型无线通信系统对通信质量和速率的需求.     

IEC104规约与DL/T 645规约转换的设计与实现

介绍了DL/T 645规约与IEC60870-5-104规约转换的模型及其软件实现,实现了智能配变终端既能实时监测电能表的数据,又能实时与主站通信。经过反复调试运行,验证了该规约转换的可靠性。     

Improving the efficiency of automated protocol implementation using Estelle

Correctness and runtime efficiency are essential properties of software in general and of high-speed protocols in particular. Establishing correctness requires the use of FDTs during protocol design, and to prove the protocol code correct with respect to its formal specification. Another approach to boost confidence in the correctness of the implementation is to generate protocol code automatically from the specification. However, the runtime efficiency of this code is often insufficient. This has turned out to be a major obstacle to the use of FDTs in practice. One of the FDTs currently applied to communication protocols is Estelle. We show how runtime efficiency can be significantly improved by several measures carried out during the design, implementation and runtime of a protocol. Recent results of improvements in the efficiency of Estelle-based protocol implementations are extended and interpreted.