模块化路由软件实现技术分析与研究

本文针对目前互联网上存在的三套独立的开源模块化路由软件:MRT、GateD、GNU Zebra,从其软件体系结构及单个路由协议实现技术方面做了全面的总结和比较。为我们设计路由软件提供了很好的启示。     

Linux下动态内存分配安全性分析

介绍了在Linux系统下由malloc、free等一系列函数实现的动态内存分配算法,分析了这种算法实现可能带来的安全问题及其产生的原因,并提出了相应的解决办法.     

约束逻辑编程中宽数据算术运算算法

提出了一种在利用约束逻辑编程生成RTL数据通路模拟矢量的方法中处理宽数据的新方法。该方法解决了现有CLP求解器所能处理的最大整数限制问题。该文设计并实现了宽数据加法、减法和乘法运算的分解算法，运算分解扩展了现有CLP的功能，使其能适应实际的数据通路设计。实验结果表明方法是有效的。     

基于Linux的快速开发工具Kylix

描述了对Borland产品的理解 ,特别是对Kylix的理解     

基于GCC的VLIW编译系统研究

VLIW机器在单个机器周期中同时发射并执行多个的并行操作,从而获得较高的指令级并行度,这些操作之间的依赖分析和调度工作则被完全交给相应的编译器执行,因此VLIW的并行性能能否充分发挥取决于VLIW体系结构相关编译器的质量。GNU开发的GCC是被最广泛使用的编译系统之一,它具有多语言、多平台支持的能力和开放的结构,能够运用各种成熟的常规编译优化技术生成高效的代码。文章分析了VLIW及GCC的结构特点,提出了一种基于GCC的VLIW编译系统设计方案,利用GCC进行RTL中间代码一级的体系结构无关优化和少量体系结构相关优化,在汇编代码一级针对VLIW结构进行体系结构相关的优化,从而充分利用GCC的成熟编译技术快速开发高效的VLIW多语言编译系统。     

基于IEEE 802.11n的MANET网络移动终端的设计与实现

自组织网络和嵌入式系统都是当前的研究热点,本文结合这两方面,设计并实现了基于IEEE 802.11n Draft 2.0的移动自组织网络(MANET,Mobile Ad hocNetwork)的终端节点,并利用此移动终端搭建出MANET网络,最终在此网络上实现了稳定快速的数据、语音视频的通信.除了通过无线接入点(AP)实现作为因特网的无线接入子网,本文设计的移动终端由于采用最新技术,拥有更良好的性能,更有利于地震灾害、军事通信、移动会议等的临时通信网络的建立.移动终端作为一嵌入式系统,其硬件核心采用基于英特尔最新的Xscale架构的PXA270处理器,软件系统主要采用移植,二次开发开源软件(GNU/Linux2.6、AODV路由协议等)来实现.根据实验结果,论文还分析了MANET网络拓扑结构剧变导致网络性能下降的原因并提出解决方案.     

A distributed polling service‐based MAC protocol testbed

Medium access control (MAC) protocols play a vital role in wireless networking. It is well‐known that the high control overhead of IEEE 802.11 MAC is the limiting factor on the throughput and delay performance of wireless networks. In our prior work, three polling service‐based medium access control protocols (PSMACs) are developed to amortize the high control overhead over multiple frame transmissions, thus achieving higher efficiency. Both analysis and simulations are conducted to validate the efficacy of the proposed protocols. In this paper, we extend this work by implementing the distributed version of PSMAC, i.e., PSMAC 2, on the GNU Radio and universal software radio peripheral (GNU Radio/USRP) platform. We discuss various design considerations and challenges of prototyping PSMAC 2 and carry out extensive experimental studies with the GNU Radio/USRP PSMAC testbed. Our experimental results are found to be consistent with the theoretical study reported in our prior work and validate the advantages of PSMAC under a realistic wireless channels. Copyright © 2013 John Wiley & Sons, Ltd.     

Improved SDR Frequency Tuning Algorithm for Frequency Hopping Systems

Frequency hopping (FH) is a common characteristic of a wide variety of communication systems. On the other hand, software‐defined radio (SDR) is an increasingly utilized technology for implementing modern communication systems. The main challenge when trying to realize an SDR FH system is the frequency tuning time, that is, the higher the hopping rate, the lower the required frequency tuning time. In this paper, significant universal hardware driver tuning options (within GNU Radio software) are investigated to discover the tuning option that gives the minimum frequency tuning time. This paper proposes an improved SDR frequency tuning algorithm for the generation of a target signal (with a given target frequency). The proposed algorithm aims to improve the frequency tuning time without any frequency deviation, thus allowing the realization of modern communication systems with higher FH rates. Moreover, it presents the design and implementation of an original GNU Radio Companion block that utilizes the proposed algorithm. The target SDR platform is that of the Universal Software Radio Peripheral USRP‐N210 paired with the RFX2400 daughter board. Our results show that the proposed algorithm achieves higher hopping rates of up to 5,000 hops/second.