Autonomous time synchronization among radio ports in wirelesspersonal communications

In digital wireless access communications systems, a large number of radio ports are deployed to provide wide-area coverage. Achieving time synchronization among ports is beneficial to these systems, especially for systems providing access to the infrastructure networks such as local exchange networks. This leads to better cochannel interference management and easier control for automatic link transfer. This paper describes a practical “over-the-air” algorithm which is autonomously performed by individual ports and hierarchically controlled by the ports having the most reliable timing. This process involves only small overhead for demodulating special timing bits transmitted by other ports and adjusting timing accordingly. Computer simulations based on a time division multiple access (TDMA) system with port spacing of 2000-3000 feet and 500 kb/s transmission rate are used as an example to evaluate possible impacts on wireless access     

基于WDM的I/O端口访问设计及实现

32位操作系统的保护机制限制了用户态应用程序对端口的直接访问。文章讨论了I/O管理器的结构、内核态设备驱动程序模型及实现原理。在屏蔽位矩阵IOPM硬件保护技术的基础上，重点分析了基于WDM驱动程序对I/O端口的访问方法，并给出了程序实例。实际应用表明，此方法具有较强的I/O端口管理能力。     

我国部分进口交换机接入本地网网管系统情况

本文概要介绍Ｓ１２４０等８种进口交换机接入我国本地网网管系统的情况。     

双口RAM在大屏幕LED显示系统中的应用开发

双口RAM与常规RAM的最大区别是双口RAM具有两套独立的地址、数据和控制线,允许两个独立的CPU或控制器同时异步地访问存储单元,双口RAM由片内的仲裁逻辑来确定哪一侧的CPU可以访问内部RAM单元.IDT7132是2kB的标准双口RAM.文中重点介绍采用以自顶向下方法设计的基于CLD(复杂可编程逻辑器件)的大屏幕LED(发光二极管)显示系统中双口RAM的应用,并给出了系统设计方法及相关硬件电路.本设计中IDT7132双口RAM用来连接单片机信号处理模块和CPLD扫描模块.     

A flexible multiport RAM compiler for data path

A multiport RAM compiler with flexible layout and port organization has been developed using 1.0-μm CMOS technology. A new memory cell with an additional column-enable gate yielded a controllability over the aspect ratio of the memory cell array. The targeted feature is the flexibility in both layout and port organization. Fast access time and fully static and asynchronous port operation are also goals. A wide bit-word organization range including 16 b×2048 words and 72 b×512 words was also obtained. This compiler generates up to 32 K three-port RAM and 16 K six-port RAM. In addition to READ and WRITE ports, READ/WRITE ports are also available. The operations of the ports are fully static and asynchronous to each other. The RAM requires no DC power consumption. The address access times of the generated three-port RAMs are, for example, 5.0 ns for 1 K and 11.0 ns for 32 K     

The Impact of Unbalanced Availability on the Grade of Service of Wireless Systems

Cellular wireless systems, such as mobile systems and fixed wireless access systems may encounter the problem of limited availability, where users of the system do not enjoy equal access opportunity to the systems' radio ports. The problem of limited availability was encountered in the early age of telephony but it has not yet been analyzed in the context of its impact on wireless system capacity. Two common scenarios where limited availability is encountered are discussed in this paper. One where there is an overlap in the coverage of two neighboring stations and the other where the coverage of one radio port is completely contained within that of the other. The paper analyzes two possible policies of radio port selection for the users who can access more than one port. One access policy is that of a completely random choice, while by the other the user selects only one of the free ports. The analysis demonstrates that system capacity may drop substantially if a proper balance is not maintained.     

LEO-Mesh卫星光网络容量规划

利用低轨卫星网格状结构光网络的空间对称性,推导了网络流量平衡特性,进而以最小丢包率为目标,采用Lagrange乘数法对各端口容量进行优化配置.在由m条轨道、每个轨道n颗卫星构成的Mesh型卫星光网络中,轨道内端口容量与m成反比,与对地接入端口速率比约为n/8;轨道间端口容量与n成反比,与对地接入速率比约为m/8.在初始配置下,丢包率在m=n时取得极小值;经优化配置之后,各端口利用率趋于平均,丢包率较优化前有明显下降,且随着卫星数量增加呈持续下降趋势.     

一种多串口映射TCP端口的核数据采集系统设计

为解决多种数据类型兼容的并行采集困难、接入计算机串口资源匮乏、采集数据传输误码率高等诸多问题,设计并实现了多串口映射TCP端口(MSMTPS)的多种核辐射数据类型连续并行采集系统。采用以太网实现核辐射数据采集系统与计算机的数据交互,系统由STM32F103处理器与W5500以太网芯片构成,具有多个串口同时与以太网口交互的能力。为接收不同辐射数据的串口分配队列缓冲区,使多个串口与同一个TCP端口映射,基于TCP端口与上位机建立连接,实现多类串口与单网络端口双向快速传输。测试使用3个串口,分别以0.5 s,1 s,5 s时间间隔发送,各发送498 bytes,499 bytes,499 bytes数据,连续发送10 min。结果显示系统传输稳定,无误码,符合设计要求。     

基于Dempster-Shafer证据理论的端口扫描检测方法

端口扫描是通过对目标系统端口试探性的访问来判断端口是否开放的行为.它往往是攻击者入侵行为的第一步.端口扫描检测是入侵监测系统不可缺少的一部分,而当前端口扫描的检测方法不多,并且准确性不高.为提高扫描检测的准确性,本文使用Dempster-Shafer证据理论对两种扫描检测方法产生的数据进行融合:一种是基于端口分布特征的扫描检测方法,该方法简单且具有较高的检测率;另一种是基于序列假设测试的扫描检测方法,该方法充分利用了端口扫描的本质特征.实验结果表明,同单独使用基于端口分布特征或序列假设测试的方法相比,这种基于Dempster-Shafer证据理论的扫描检测方法对端口扫描的检测准确得多.     

On service provisioning using light-trails in WDM optical networks with waveband switching

As the number of wavelengths in a single optical fiber increases, so does the number of ports needed for wavelength switching in optical cross-connects (OXCs), which may significantly increase the cost and difficulty associated with controlling large OXCs. Waveband switching (WBS) treats several wavelengths as a bundle that is switched through a single port if they share the same switch route, so that the number of ports needed can be reduced. On the other hand, light-trails in wavelength division multiplexing (WDM) optical networks allow intermediate nodes on established optical paths to access the data paths whereas light-paths only allow two end nodes to access the data paths. Therefore, light-trails offer significantly better flexibility for service provisioning and traffic grooming. In this article, we study service provisioning using light-trails in WDM optical networks with the WBS capability under a static traffic model. For comparison, integer linear programs are formulated for establishing light-trails with and without WBS. Numerical studies show that in certain cases, service provisioning with WBS in light-trail networks can reduce the number of ports needed while providing a more flexible sub-wavelength service provisioning capability. However, contrary to intuition, in most cases applying the WBS technique requires more ports in OXCs in light-trail networks. This study provides insights into the network design problem that applies the WBS technology to light-trail based optical networks.     

基于云进化算法的3D NoC测试端口优化选择

针对于三维片上网络测试时,如何选择测试端口以提高测试效率的难题,采用基于云模型的进化算法对三维片上网络测试端口进行位置寻优,并对IP核的测试数据进行合理分配,在测试功耗约束条件下,以重用片上网络作为测试访问机制,基于XYZ路由算法和非抢占式测试调度方式,对三维片上网络IP核实施并行测试,以提高测试效率。研究结果表明,该方法可对测试端口的位置及组合方案进行精确寻优,且有效减少了测试时间。     

Scalable register file organisation for a multiple issuemicroprocessor

The scalability of a register file as employed in microprocessors is investigated. Results are presented which show the dependence of the register file access time against the number of registers, and the number of ports. A new organisation which scales better in terms of cycle time is proposed     

OXC port dimensioning strategies in optical networks-a nodal perspective

In this letter, we investigate optical cross-connect (OXC) port dimensioning strategies for supporting bandwidth-on-demand (BoD) services in optical networks. At a given node, the bandwidth-on-demand traffic load consists of two components; an access component, which is generated by demands originating at that node, and a transit component, which is generated by demands that transit electronically through the node. Given the BoD load at a node, as well as a target BoD average blocking probability, we calculate the optimal static allocation of the OXC ports between client-side ports and network-side ports. We also introduce a dynamic sharing strategy of the network-side ports and propose a method for determining the optimal port allocation under this strategy.     

Magnetostatic simulations for design of superconducting magneticshields

A magnetostatic approach to numerical simulations of magnetic field attenuation by superconducting shields is demonstrated on simple geometries. Comparisons to published measurements and analytic calculations show that results are accurate for simulation of a shield in the shape of a cylindrical tube. The capabilities of the method are shown by simulations which close the cylinder with end caps having access ports or gaps. With end caps having cylindrical ports, the simulated attenuation transits smoothly between the analytical results for semi-infinite tubes of the two radii. Radial gaps between solid end caps and the cylinder allow little flux leakage for time-varying fields, but significant leakage for static fields     

基于以太网端口的用户访问控制技术

文章介绍了IEEE 802.1×这一基于以太网端口的用户访问控制协议的内容和特点,论述了采用以太网接入时在以太网交换机上实现用户认证的方法,并给出了一个宽带城域网应用的解决方案。     

基于PC机的某雷达天控系统设计

介绍一种基于PC机的天控系统设计方法。除介绍必要的硬件之外，着重介绍在软件设计当中如何实现硬件端口的访问，及WINDOWS循环必须的定时器等问题。希望对于用户自行设计基于WINDOWS的控制系统具有一定参考意义。     

Performance of simulcast wireless techniques for personalcommunication systems

Broadband analog transport facilities using fiber or fiber/coax cable can play a significant role in the evolution of the network infrastructure for personal communications services (PCSs). Low-power PCS systems require a dense grid of radio ports to provide connectivity to the telephone network. Analog transport has a number of important advantages over digital transmission facilities, including the flexibility to support a variety of air interface formats, shared infrastructure cost with other services such as video distribution, and centralized call processing allowing the use of low cost and simple radio ports. A simulcast technique can be used in such systems to permit low rates of handoff (no handoff within each simulcast area) and sharing of hardware resources among multiple radio ports. This paper provides a detailed model and a simulation analysis of the cochannel interference and noise performance as well as the resource sharing benefit of a simulcast PCS system. Several potential PCS air interfaces are considered, including time division multiple access (TDMA) and code division multiple access (CDMA) techniques. Our investigation shows that the impact of multiple antenna noise in a simulcast system is offset by the improved signal-to-interference (SIR) ratio brought about by distributed antennas. Even with distributed antennas, multiple antenna noise places a limit on the maximum number of radio ports that can be assigned to each simulcast group. This limit, however, is shown to have little impact on the achievable resource sharing benefit of simulcasting (i.e., grouping beyond this limit has diminishing returns). A saving of 40% to 60%, in terms of the required central hardware resources, is typical for both TDMA and CDMA systems in suburban environments     

Protection-against-collision optical packet network

An optically transparent packet network controlled by a simple medium access circuit is presented. The system, based on frequency division multiplexing and tunable transmitters, has no internal blocking and is optically self-routing. It provides internal collision-free traffic by allowing access to the network only if the addressed channel (output port) is available. A packet denied access to the network is reflected back to its input port, which is thus informed of the packet status. Therefore, the traffic is not bogged down by acknowledgments between input and output ports. To achieve this result, each input of the network is controlled by a protection-against-collision (PAC) circuit located at a central hub. The PAC circuit uses the packet for probing the energy present in the addressed channel. The resulting signal controls an optical switch connecting the input port to the network. Thus, full optical connectivity is provided between ports controlled by electrical signals derived from simple optical power measurements     

基于云进化算法的NoC测试端口优化选择方法

针对片上网络(NoC)中大量节点的测试难题,提出了一种结合二维云进化算法优化选取NoC中测试端口位置,提高测试效率的方法。该方法结合NoC网格结构特点,采用重用测试访问机制和XY路由方式,由测试功耗限制确定端口对数,通过二维云模型对端口坐标进行统一建模,云进化算法自适应控制遗传变异的程度和搜索空间的范围,在测试功耗约束条件下,优化选取最佳测试端口的位置,达到总测试时间最少的目的。以SoCIN结构电路为仿真平台,分别对4×4网格和8×8网格结构NoC进行了实验仿真,结果表明,在NoC节点测试问题上,云进化算法能快速收敛到最优解,有效提高整体测试效率。     

Performance evaluation of a switch using priority-based dynamic capacity allocation scheme

Performance-analysis of a switching system using priority-based dynamic capacity allocation is presented. The system provides connectivity between a number of point-to-multipoint communication access clusters. The scheduling of traffic transmission at each access cluster is based on a priority scheme with priority given to real-time (rt) traffic over nonreal-time (nrt) traffic. An analytical model is developed to evaluate the covariance functions of both rt and nrt traffic arriving at the output ports. Aggregate traffic arrival streams are approximated to 2-state Markov-modulated Poisson processes (MMPPs) by matching their statistical characteristics. Analytical and simulation results on performance of an example 4 /spl times/ 4 switch for different traffic loads are discussed.