运用接入新技术,组建农村用户接入网

运用接入新技术组建农村用户接入网已势在必行。本文针对我国经济水平低、地区间发展不平衡等实际情况，对组建我国农村用户接入网的有关策略进行了论述。     

综合复用技术中基于HDLC的MCC驱动设计

首先介绍了综合复用技术在业务QoS和安全性保障方面的独特优点,然后重点描述了综合复用技术中一种典型的基于HDLC的MCC驱动的开发设计,包括设计思路、HDLC分析、MCC硬件原理、数据处理原理、MCC初始化过程和E1实现模型等.     

DSL技术及其应用研究

论述了DSL技术的原理，详细阐述了在面对电缆调制解调器，宽带卫星和无线接入技术对DSL业务竞争的情况下，DSL与POTS和光纤技术集成，DSL与ATM技术集成，以及标准化的HDSL架构将成为DSL技术发展中的3大主流趋势的原因及其解决方法。     

基于DMT的HDSL／ADSL系统中的回波抵消技术

高比特率数字用户环路是在光纤用户网普及之前向用户提供宽带业务的一种过渡手段。ＤＭＴ（离散多音频调制）是一种多载频调制，由于性能优越，被广泛应用于ＨＤＸＳＬ和ＡＤＳＬ系统中。采用加波抵消的方法，可以提高系统传输速率、增加传输距离。本文着 基于ＤＭＴ的ＨＤＳＬ和ＡＤＳＬ系统中的回波抵消技术－－ＴＡＦＤＥＣ方法，即将频域的回波抵消器（ＥＣ）和时域的回波合成器（ＣＥＳ）结合起来，以达到减少运算量，降低复杂     

基于HDSL的采煤工作面实时监控监测系统的设计

在煤矿综合监控监测系统中，通信线路数据流量是一个瓶颈问题。结合当前宽带接入的相关技术，提出了基于HDSL（high bit rate digital subscriber line)的工作面综合监控监测系统，使用PowerPC和实时操作系统为核心，提高通信能力和实时处理能力。给出了系统模型和设计方法。     

接入网技术及其应用

介绍了各种类型的接入网技术及在国内外的应用情况,并对其发展前景进行了展望和预测。     

Splice-induced impairments on very-high-speed digital data communications over copper telephone networks

The effects of splice-induced crosstalk, insertion loss and echo on very-high-speed digital data communications over copper telephone networks are analysed and evaluated. Sealing current is used to mitigate the adverse effects of the splices. The specifications of sealing current (i.e. magnitude, shape, frequency of application) have significant ramifications on the operations of the digital communication systems. For proper operation of echo-cancellers (i.e. fast adaptation and tracking) on full-duplex transceivers operating at 800 kbit/s, and to achieve a bit error ratio of 10^?7, the magnitude and the rate of the change of splice fluctuations must be controlled. It is shown that the effects of crosstalk and insertion loss are not as severe as the occurrence of echo due to rapid fluctuations of splice impedance. The admissible ranges of splice fluctuations for a series of worst-case scenarios are computed, and their effects on the performance of the echo-canceller are discussed. If the splice fluctuation is restricted to 0·1 Ω on a 20 Ω splice, with the splice in the vicinity of the transceiver, the echo is —36 dB with respect to the far-end received signal, which is an acceptable level on a 9 kft subscriber loop with an American Wire Gauge of 26. However, quantification of the dynamics (i.e. the rate of change) of splice fluctuations requires laboratory experiments and field measurements.     

HDSL技术原理及其维护注意事项

文章从理论层面简要介绍了高比特率数字用户线(HDSL)接入技术的基本原理,并对HDSL的线路编码、回波抵消和自适应均衡3项关键技术作了进一步阐述和横向比较。同时,从应用层面指出电路开放和系统维护中经常产生的一些问题的解决方法,并列举出相关注意事项,最后对今后的维护工作提出了一些建设性的建议。     

xDSL技术及其应用

ｘＤＳＬ技术是一种调制技术，在双绞铜线的两端分别接入ｘＤＳＬ调制解调器，即可利用其高频带特性传送高速数据，本文全面阐述了实现用户线高速比的ｘＤＳＬ技术及其应用。     

Lubrication effects on head–disk spacing loss

As flying heights are reduced to 10 nm or less, maintaining good flyability becomes critical to ensuring the robustness of the head–disk interface. One way to reduce the head–disk interference during low flying is to minimize the media portion of the head–disk spacing loss. In this work, both Touchdown RPM and Pump down Pressure tests were used to measure this parameter. Experimental results from this study show that the free lubricant thickness is a major contributor to the loss and results in the observed hysteresis between the Touchdown and Take off Pressures (or RPM).