浅谈CDMA大话务情况下的优化

中国联通CDMA网络建成以来，由于还处于发展用户时期，所以没有大话务冲击，但对网络优化来说却是一个新的课题。本文介绍了广交会的大话务优化情况，广交会展馆的地理位置和网络覆盖的特殊性以及广交会人流量集中导致了话务量高度集中，为研究CDMA系统在大话务情况下实际性能提供了极好的条件。     

CDMA系统的网络优化

本文提出了衡量CDMA网络质量的主要指标，阐述了CDMA系统的网络优化流程，并对网络的覆盖与干扰、无线接通率、寻呼成功率、切换和掉话等问题的成因和定位方法进行了分析，最后提出一些常用的CDMA无线网络优化措施。     

CDMA网优中干扰的分析和处理

文章首先对CDMA网络优化的关键问题作了概述,然后分析讨论了干扰对CDMA系统性能和容量的影响,其次对CDMA系统抗干扰能力指标及强干扰源对系统的危害作了分析,最后提出了故障定位、干扰处理及抗干扰的具体方法。     

中国CDMA移动通信网络优化研讨会部分论文摘要：CDMA网优利器——系统思想与方法

文章站在网络优化指导思想的高度．提出在目前CDMA网络建设与优化新阶段．需要坚持以科学的系统思想为行动的指导，用系统观去看待和分析问题．用系统方法来解决复杂问题，从而为网络优化在思想上指明方向。     

CDMA网络优化浅谈

网络优化的目的是改善网络的通信质量。采用快速有效的网络优化方法，改善网络的性能和服务质量是移动运营商关注的主要问题之一。由于CDMA是干扰受限系统，因此CDMA网络的优化尤为重要。首先介绍了CDMA网络的性能指标，然后详细介绍了CDMA网络优化的分析流程和主要内容。并对CDMA网络优化中的测试方法以及CDMA系统参数进行了探讨。指出网络优化是一项持续性的工作。     

对CDMA网络优化的研究

CDMA的网络质量因为对用户手机使用有直接影响和较高的复杂性,已经越来越受到运营商的关注。CDMA优化的最主要目的就是完善网络的通讯质量,积极地采用有效、快速的优化方式,有效改善网络的服务质量和性能。CDMA是一种受限干扰系统,所以说,CDMA的有优化显得非常重要。文章详细论述CDMA网络的优化研究。     

浅析CDMA网络优化中呼叫失败现象及对策研究

CDMA移动通信系统的网络优化是一项技术性,专业性很强的工作,也是一项复杂的长期的工作,贯穿于网络发展的全过程。网络的规划、设计、工程建设和运行维护等工作都与网络优化密不可分。加强CDMA移动通信系统网络优化,搞好运行维护是运营商提高CDMA网络服务质量的关键。     

CDMA网络优化浅析

随着CDMA网络负载量的增加,网络问题逐渐突出,对CDMA网络进行优化十分必要。本文介绍了网络优化的基本内容和目标,基于CDMA网络运营现状,提出了CDMA网络优化的相关方案。     

CDMA 3G数据业务模型分析和预测

文章从话务使用模型和业务传输模型两个方面分析了CDMA3G网络的主要数据业务类型,明确了数据业务模型分析和预测的目标;在此基础上针对当前CDMA网络网管系统数据提取现状,结合实际话务情况,提出了优化的CDMA业务模型分析方法和预测思路。     

LAS-CDMA——新一代全IP的移动通信技术

本文将从介绍CDMA系统出发。研究它的话务模型。宽带CDMA系统链路结构,如何实现同步及软切换技术。然后介绍LAS-CDMA的技术特点,发展优势。     

国外航海雷达现状及发展趋势

航海雷达是船舶航行必备的电子设备,其性能直接关系到船舶的航行安全。对国外航海雷达的技术现状及发展情况进行了综述,并对其发展趋势展开了讨论。通过运用多种新体制、新技术,能够有效提升雷达设备可靠性,增强其在雨雪杂波、海杂波下的目标发现能力。航海雷达将会从现有的单一磁控管脉冲体制,发展为固态化、多频段配合使用的多功能航海雷达系统。     

Engineering-economic systems: a new profession

Technological advances in computers and automation over the last 20 years have far outstripped our ability to use them effectively. Profound changes in industry, government, and business will emerge as the new technology unfolds. As an example: the whole concept of a ``big' operation or company will have to be reshaped in terms of our new ability to organize and operate a system efficiently. To exploit the possibilities of this new technology rationally, broad interties between the academic and practical worlds are indispensable. The academic world contributes a philosophical structure providing vital breadth and flexibility, while the real world offers a simplifying practicality that insures workability and early realization. In the initial stages, planning for the use of the new technology must be done as a joint research and development effort between both worlds. As this joint effort grows, a more complete and integrated structure will undoubtedly evolve. A prototype form of the engineering?economic systems profession is being evolved in a program at Stanford University.     

基于虚拟仪器技术新型混沌信号产生器的设计

随着虚拟仪器技术的飞速发展,为研究非线性系统提供了新途径。讨论了基于虚拟仪器技术的新型混沌信号产生器的实验模式,设计了硬件系统和软件系统,并给出基于虚拟仪器技术实验系统的拓扑结构,为研究非线性系统提供可行的方案。利用此方案进行初步的实验,结果证明此实验系统具有良好的实验效果。     

MaSSIVE: the Mass Storage System IV Enterprise

The Mass Storage System IV Enterprise (MaSSIVE) a fourth-generation mass storage system that provides a file system service to teraflops computing systems, is described. A bitfile managed by MaSSIVE can be a complete, self-contained Unix file system specific to a particular MaSSIVE client. MaSSIVE will stage whole file systems from archival storage onto online storage devices and then provide its clients with raw block access to the staged file systems. It will comply with the IEEE Mass Storage System Reference Model, and will consist of cooperating processes distributed across a network of supermicrocomputers. The client interface to a file system will be implemented through a custom device driver that will permit I/O to MaSSIVE online storage drives. The device interface through a high-bandwidth data fabric to the storage device will use common device-controller-specific protocols. As file systems are unmounted by clients or clients disconnect from the data fabric, file systems can be migrated back to archive storage and removed from online storage     

Performance Modeling of System Architectures

Performance modeling of network architectures has been an integral part of network systems design for decades. As signal processing system architectures become more and more complex, models of computational performance are becoming an important part of the architectural design process. This paper will describe performance modeling, both in general, and within the context of the RASSP system design process.     

An unattended seismological observatory

Sandia Laboratory is developing and testing prototype equipment to continuously record outputs from three short-period and three long-period unattended seismometers for up to 120 days. Timing accuracy will be within 0.1 second throughout the record period. The system will be capable of recording a 70 decibel signal range. As much as 42 decibel attenuation can also be applied to each short-period data channel by an automatic gain control system to compensate for high levels of background noise. Concurrent with the development of the recording system, a playback system is being developed and tested which will convert the recorded data and timing signals to the standard Vela Uniform tape format. According to present schedules, the systems should be fully evaluated in the laboratory and in the field by the beginning of 1967.     

基于指示信息的带碰撞避免的载波侦听多址技术

本文从现有协议中DCF机制的基本和RTS/CTS两种工作模式出发，提出一种基于指示信息的带碰撞避免的载波侦听多址技术，根据不同工作模式分为三种改进模式。针对两种对数据帧长适应性较好的改进工作模式，即改进的基本模式和改进的RTS/CTS模式一，本文提出在整个网络数据传输速率固定的条件下，可设定数据帧长阈值，根据传输数据帧长与阈值关系实现两种改进模式的动态切换，最大化地缩短碰撞处理时间，降低随机回退产生的额外系统开销，提高系统性能。NS2仿真结果表明，基于指示信息的带碰撞避免的载波侦听多址技术相比于现有的DCF机制具有更好的系统性能。      

Performance of cross-layer design for orthogonal space-time block coded MIMO systems with imperfect CSI in Ricean fading channels

A cross-layer design (CLD) scheme for orthogonal space-time block coded MIMO systems with imperfect channel state information is presented by combining adaptive modulation and automatic repeat request, and the corresponding system performance is investigated over Ricean fading channel. The fading gain value is partitioned into a number of regions by which the modulation is adapted in terms of the region the fading gain falls in. The fading gain switching thresholds subject to a target packet error rate (PER) constraint are derived. According to these results, and using the generalized Marcum Q-function, we derive the theoretical formulae of average PER and spectrum efficiency (SE) of the system with CLD for both perfect and imperfect estimation in detail. As a result, closed-form expressions for average PER and SE are obtained. These expressions include some existing expressions in Rayleigh channel as special cases. With these expressions, the system performance in Ricean channel with perfect and imperfect estimation information can be evaluated effectively. Computer simulation for average PER and SE show that the theoretical analysis and simulation are consistent. The results show that the system performance will be effectively improved as Ricean factor increases, but it will be degraded as estimation errors increases.     

Building accurate and robust HMM models for practical ASR systems

In this article the relevant training aspects for building robust and accurate HMM models for large vocabulary recognition system are discussed and adjusted, namely: speech features, training steps, and the tying options for context dependent (CD) phonemes. As the basis for building HMM models the well known MASPER training scheme is assumed. First the incorporation of the voicing information and its effect on the classical extraction methods like MFCC and PLP will be shown together with the derivative features, where the relative error reductions are up to 50%. Next the suggested enhancement of the standard training procedure by introducing garbled speech models will be presented and tested on real data. As it will be shown it brings more than a 5% drop in the error rate. Finally, the options for tying states of CD phonemes using decision trees and phoneme classification will be adjusted, tested, and explained.     

QoS provisioning for multimedia wireless networks

As we move towards IP-based multimedia wireless networks with voice, video and data convergence, quality of service (QoS) provisioning will become an increasingly challenging task. One implication is that greater emphasis on managing the call admission and overall network resources will be needed. This paper presents a conservative and adaptive quality of service (CAQoS) framework for provisioning the QoS for both real-time and non-real-time traffic in a multimedia wireless network. Unlike most conventional schemes, which gradually scale down the bandwidth of ongoing connections to accommodate new connection/hand-off requests, CAQoS introduces an early scaling-down of bandwidth for new connections based on a designated provisioning model. The performance of a CAQoS system is evaluated through simulations of a realistic wireless environment. Simulation results show that CAQoS meets our design goals and outperforms conventional schemes.