光码分多址技术在光接入网中的应用

无源光网络是光接入网的主要发展方向,ＦＴＴＨ是ＰＯＮ的最终方式,将ＯＣＤＭＡ,ＷＤＭ等技术用于光接入网中,是帝现接入网宽带化的途径之一。介绍了ＯＣＤＭＡ的技术报目前光接入网中多址技术的弊端,探讨了ＯＣＭＤＡ用于光接入网的可能性和优势,提出实现无源光网络多址接入的ＷＤＭ／ＣＤＭＡ方案。     

数据采集系统中用SRAM模拟双口RAM

介绍了一种在５１ 单片机采集系统中,使用普通ＳＲＡＭ,采用时分复用模似双口ＲＡＭ 的方法。使用这种方法,既可以避免使用昂贵的双口ＲＡＭ,又可减少印刷板面积,实践证明,这种方法是稳定可靠的。     

一种开环载波同步方法

本文结合ＴＤＭＡ通信方式的特点,分析了ＴＤＭＡ通信系统中载波的快速同步问题,推导了一种开环载波同步算法。并给出了计算机仿真结果,进一步验证了该算法在实际应用中的可行性。     

Performance evaluation of uplink power control algorithm over TDMA systems

Future PCS (personal communication system) cellular networks will mainly be driven by high link quality, high bandwidth utilization, low power consumption and efficient network management. Power control is one of the several major techniques which could help to achieve these goals. By exploiting power control techniques, co-channel interference could be reduced and as many links as possible could be obtained with satisfactory link quality. SIR-based (signal-to-interference ratio-based) power control was proposed as a technique for managing co-channel interference in cellular radio systems. Furthermore, new distributed autonomous feedback power control methods were introduced to achieve excellent performance without the difficult centralized control used in SIR-based methods. Unfortunately, the implementation of those power control algorithms is still challenging owing to the precision of SIR. The main aim of this paper is to investigate an uplink power control algorithm which depends indirectly on the signal-to-noise ratio in the TDMA (time division multiple access) cellular system. Simulation of the prototype hardware implementation of the receiver baseband signal processing based on the PACS (personal access communications system) specification is used as the main approach to explore the performance evaluation of this power control technique. According to simulation results, suitable values of those parameters used in this power control algorithm are derived, and the minimum frequency reuse factor under different propagation environments is also obtained for PACS under power control. © 1998 John Wiley & Sons, Ltd.     

60 GHz超高速无线网络接入机制研究

首先介绍了工作在60 GHz频段、支持1 Gbit/s以上数据速率的IEEE 802.15.3c标准和IEEE 802.11ad标准草案规定的无线接入机制的基本原理,然后对它们的特点和性能进行了详细的对比分析。研究结果显示:2种无线接入机制都采用了TDMA+CSMA/CA的混合机制,但各有所长;IEEE 802.11ad接入机制兼容性更好,能达到更高的数据速率,然而原理更复杂;IEEE 802.15.3c接入机制实现相对简单,同样也能达到Gbit/s级别的数据速率。最后,对全文进行总结并指出了未来的研究方向。     

基于HLA的联合战术信息分配系统端机工作软件仿真

联合战术信息分发系统(JTIDS)端机工作软件仿真的终端模型含用户接口、内存、任务模块、网络接口、RTI接口等模块.基于HLA/RTI仿真平台运行时,每个端机先初始化加载平台配置文件,再以静态或动态注入法配置文件得到时隙参数,进而在时隙同步的基础上完成TDMA方式收发数据.     

An accurate numerical solution study of three-dimensional natural convection in a box

This paper describes the application of the finite difference method to the simulation of three-dimensional natural convection in a box. The velocity–vorticity formulation is employed to represent the mass, momentum, and energy conservations of the fluid medium. We employ a fractional time marching technique for solving seven field variables involving three velocity, three vorticity and one temperature components. By using the fast Fourier transform (FFT) and a tridiagonal matrix algorithm (TDMA), the velocity Poisson equations are advanced in space along with the continuity equation, thus solving efficiently and easily the diagonally dominant tridiagonal matrix equations. Both vorticity and energy equations are discretized through an explicit method (Adams–Bashforth central difference scheme) as a simplified numerical scheme for solving 3D problems, which otherwise requires enormous computational effort. A natural convection in a box for the Rayleigh number equal to 10⁴, 10⁵, 10⁶ and 10⁷ as well as As = L_x / L_z aspect ratios varying from 0.25 to 4 is investigated. It is shown that the benchmark results for temperature and flow fields could be obtained using the present algorithm.     

基于动态中继选择的无人机自组网协作接入协议

对无人机自组织网络中的协作机制进行了研究,提出一种基于动态中继选择的无人机自组网协作时分信道接入协议.该协议在传输中继数据包时引入了双队列协作机制,在网络层数据包缓存队列之外引入了独立的媒体接入控制(Media access control,MAC)层中继数据包缓存队列,并且能够实现默认中继节点与辅助中继节点的动态选择...     

多宿点无线传感器网络时分多址时隙优化分配算法

针对单宿点无线传感器网络的时延大、容易出现传输瓶颈等问题,提出了多宿点无线传感器网络模型以及该模型的基于遗传算法(GA)的时分多址(TDMA)时隙分配算法。该算法根据宿点的数量以及位置将整个传感器网络划分成多个小传感器网络,并采用遗传算法对时隙分配结果进行优化。仿真结果表明,基于遗传算法的多宿点无线传感器网络TDMA时隙分配算法得到的时隙分配结果在时隙分配帧长度、数据包平均时延以及节点平均能耗方面均要优于图着色算法。     

一种基于簇首协调的时分多址路由协议

针对现有无线移动网络中采用竞争广播交互路由、控制信息,造成路由控制信息碰撞丢包的问题,提出了一种基于簇首协调的时分多址路由协议。该协议复合设计多址接入协议与路由协议,通过保障路由、控制信息的可靠传输,降低了传输延时,提高了数据传输效率。提出了一种基于超帧结构的多址接入协议,在超帧的控制信息交互阶段以时分多址的方式交互路由、控制信息,在数据信息交互阶段,以载波侦听碰撞避免的方式交互用户数据信息。为了控制节点之间的路由控制信息交互开销,簇首节点只为成功入网的节点分配时隙,并保证入网节点稳定地占有该时隙。成员节点通过交互两跳邻节点信息建立不超过3跳的簇内路由表,簇首节点通过控制信息交互获取全簇路由信息。仿真结果表明,在群组移动模式下,与AODV、OLSR等现有路由协议相比,所提出的协议在平均时延方面降低了23%,在传输效率方面提升了30%.