CDMA数字直放站在村通工程中的应用研究

主要研究CDMA数字直放站的技术原理,并根据该原理及CDMA网络覆盖的特征分析CDMA数字直放站的应用,对比与传统模拟直放站、射频拉远单元的异同,阐述数字直放应用的注意事项,最后对CDMA数字直放站在村通工程中的应用实例进行了分析。     

光纤直放站数字化前后在现网的适用性对比分析

文章首先具体分析了传统模拟光纤直放站应用于GSM网络的弊端,然后从多个角度阐述了新一代数字光纤直放站应用于GSM网络的优势,最后得出结论:数字光纤直放站克服了传统光纤直放站的各种弱点,可以很好地满足网络建设的需求,是当前GSM网络覆盖系统中最好的覆盖增强系统之一.     

浅谈数字光纤直放站原理及工程应用

文章主要介绍了数字光纤直放站的实现原理和应用场景,并分别和传统的模拟光纤直放站以及分布式基站作比较。     

3G数字直放站的研究与设计

文章分析了3G数字直放站的结构,结合目前工业界提出的基站与直放站接口规范,提出了数字直放站的设计方案。与模拟直放站相比,该方案具有高性能、低成本的优点,适合3G网络的广泛覆盖建设。     

基于ICS技术的数字直放站系统设计

ICS数字直放站是直放站系统发展的热点领域和重要方向。这里介绍了基于LMS算法的干扰抵消系统的基本原理,根据软件无线电基本理论给出了系统的硬件具体实现,基于FPGA平台描述了系统各软件模块的实现方法,测试结果表明干扰抵消比高达30 dB,通道时延小于8 ns。该系统通用性和扩展性强,可以移植到各种同频干扰抵消系统中。     

基于OBSAI规范的3G数字直放站设计

分析了3G数字直放站的功能结构,并重点分析了工业界提出的基站与直放站接口规范,最后结合OBSAI规范的要求介绍了数字直放站的设计方案.本方案的射频和中频部分采用专用芯片,接口规范的实现采用FPGA,这样能用相同的硬件兼顾多种接口标准.与模拟直放站相比,该方案具有高性能、低成本的优点,适合3G网络的广泛覆盖建设.     

LTE网络城中村覆盖解决方案探讨

传统的无线信号覆盖方式都无法有效地解决城中村的覆盖问题,宏基站、传统室内分布建设不仅成本高、实施难度大,覆盖也不理想。文章将介绍模拟五类线系统、数字光纤直放站对城中村的覆盖。     

移动通讯直放站

美国Peninsula Wireless Communications公司的系列移动通讯直放站可为移动通讯系统的无缝覆盖提供经济有效的解决方案。该公司现有的产品主要包括CMRF直放站、微波—微蜂窝直放站以及光纤—微蜂窝直放站三个系列。近期还将推出高功率的远距离移动通讯直放机。 CMRF直放站具有450、800及900MHz三种型号,可与各类模拟及数字移动电话系统兼容。该直放站与小型基地站     

几种节能减排直放站介绍

一、上行降噪无线直放站移动通信网络中,模拟直放站可以简单有效地扩大覆盖范围,优化网络覆盖,但会带来对网络引入噪声的负面影响。传统模拟直放站靠牺牲上行增益控制噪声,基站与直放站系统在上行覆盖与基站底噪抬高的两端作权衡:直放站数量少时,可以适当调高上行增益,微量抬高基站底噪;直放站数量多时,必须降低上行增益控制基站底噪抬高,这样会造成直放站覆盖区域上下行严重的不平衡;以单个基站为信源的直放站数量多到一定限度时不宜再增加。     

一种数字中频系统的设计

随着高性能的模/数、数/模转换器件(ADC、DAC)和现场可编程门阵列(FPGA)的出现,基于软件无线电(SDR)的数字中频技术被广泛地应用到3G直放站中.在分析了WCDMA直放站中频单元基本原理和结构的基础上,比较了模拟处理和数字处理的优劣,提出了一种数字中频系统的设计,并对其中的关键技术,如采样率的选择、滤波器的设计等进行了具体阐述.     

800 Mbit/s Digital Transmission System Over Coaxial Cable

800 Mbit/s digital transmission systems, using nonredundant three-level and four-level codes, have been studied as a means of providing an economically attractive digital transmission system. These systems have been designed to be compatible with a 60 MHz analog system in repeater spacing and repeater size, so as to be easily introduced into the existing network. These systems with 11 520 telephone channels, exceed the 60 MHz analog system in both capacity and economy. Due to repeater construction factors, it became clear that the three-level code is more suitable. This paper describes the design and performance of 800 Mbit/s digital transmission systems and repeaters.     

An Experimental 800 Mbit/s Four-Level Repeater Compatible with the 60 MHz Analog System

The design and performance of an experimental 800 Mbit/s repeater for four-level digital transmission over a coaxial cable is described in this paper. The 800 Mbit/s digital system exceeds the 60 MHz analog system, both in capacity and in economy. The repeater is designed to operate in repeater housings located at 1.6 km maximum spacing to be compatible with the 60 MHz analog sytsem. A nonredundant four-level line code has been employed, using a newly developed quantized feedback dc restoration technique. The most important item in realizing the high-speed multilevel repeater is the reduction of intersymbol interference. A simple quantized feedback scheme and an adjustable three-tap transversal equalizer have been used to compensate for intersymbol interference. The experimental repeater has been tested for 1.1-1.7 km repeater spacings using 2.6/9.5 mm coaxial cable. The results show that an 800 Mbit/s repeater with 1.6 km maximum repeater spacing is feasible.     

Transmission of Analog Video and Digital Signals Over Analog-Repeatered Coaxial Lines

The transmission of digital telephony or data, alone and together with analog video, over analog-repeatered coaxial-cable lines is discussed. Expressions for the total random noise power and the signal-to-noise ratio (SNR) are derived. These expressions include the effects of thermal noise and the intermodulation distortion due to nonlinearity in the analog repeater amplifiers. The dependence of the SNR on system parameters, particularly the signal level and the repeater spacing, for systems that carry digital telephony, video, or both, is discussed and its implications on system design are noted.     

An interpolating clock synthesizer

A digital alternative to analog phase-locked loop (PLL)-based clock generators for microprocessors, denoted an interpolating clock synthesizer (ICS), is described. Using ROM-based digital waveform synthesis, the ICS implements a wide range of frequency multiples having the form P/Q, where P and Q are integers. The ICS outputs two synthesized clocks, one for the I/O interface having a 1/1 frequency multiple and one for the core having one of eight dynamically-selectable frequency multiples (1/1, 3/2, 5/3, 2/1, 5/2, 3/1, 15/4, and 5/1). The ICS uses a synchronous delay line as a coarse (T_p/30) timing reference, while through digital delay interpolation it achieves a fine delay resolution of 0.04 ns. Using a completely digital precision phase detector, the ICS achieves a DC skew of ±0.05 ns     

光纤直放站用光发射模块的设计

提出一种新的设计思路,采用数字激光驱动芯片MAX3669来设计一种用于光纤直放站的模拟光发射模块,解决了模拟光发射模块设计中LD驱动和自动光功率控制APC等技术难点,提高了模块的稳定性和集成度,测试结果显示模块的各项指标满足行业规定的标准。     

VSB‐Based Digital On‐Channel Repeater with Interference Cancellation System

This paper investigates the design and performance of a digital on‐channel repeater (DOCR) for use in Advanced Television Systems Committee (ATSC) digital television (DTV) broadcasting. The main drawback of a DOCR is the echo interference caused by coupling between transmitter and receiver antennas, which induces system instability and performance degradation. In order to overcome this problem, an echo canceller based on the adaptive echo channel estimation (ECE) technique has been researched and applied for a DOCR. However, in the case of ATSC, the pilot signal, which is used for carrier synchronization, may cause a DC offset error and reduce the isolation performance of the echo canceller for a DOCR in an ATSC network. Moreover, since the multipath fading effect of a radio channel usually occurs in a real environment, it should be minimized to improve the overall performance of a DOCR. Therefore, due to the limited isolation performance of echo canceller and the multipath fading effect, an interference cancellation system (ICS) is proposed for a DOCR in an ATSC network. The performance of the proposed DOCR with an ICS is evaluated by software simulation and hardware test results.     

基于单载波传输的数字同频转发器设计与实现

提出了基于单载波传输方案的数字同频转发技术的实现方式,该技术克服了传统转发技术的缺陷,提高了天线间的隔离度和输出信号的质量,可广泛应用于城市复杂的信道环境下的盲区覆盖.     

Markov Process Analysis of PCM Line Monitors

In PCM transmission systems, ensuring repeater timing and regenerative capabilities requires monitored enforcement of the ones density of the line waveform. One possible corrective monitor action is to pre-empt information bits and insert ones when necessary, and thus introduce errors into the pulse stream. The analysis of the resultant error rates for classes of digital and analog implementations of a PCM monitor is accomplished via theoretical consideration of certain stationary Markov processes.