《有线电视HFC网络双向改造技术交流.pptVIP

有线电视HFC网络双向改造技术交流 天柏宽带 市场发展部 李颖然 天柏集团 天柏在中国 目录 HFC网络概述 双向网络改造的基本原则 主流双向网络改造技术对比 天地通BIOC双向网络改造方案介绍 HFC有线电视网络 RF频率 Radio Frequency (RF) Above Audio to InfraRed Down Stream (DS) (Forward) Cable company to subscriber 55-750 (860) MHz 模拟电视频道 模拟/数字混传 光发射机 光接收机 同轴电缆的传输特性 分配器和分支器 放大器 多级放大器 有线电视基本概念1 CATV - Community Antenna TV NTSC - National Television Systems Committee: U.S. TV technical standard, named after the organization that created it in 1941. Uses a 6 MHz wide modulated signal PAL - Phase Alternating Line. The TV system used in most of Europe and many other places, in which the color carrier phase definition changes in alternate scan lines. Utilizes an 8 MHz wide modulated signal SECAM - TV system used in France and some former Soviet bloc countries. Utilizes an 8 MHz wide modulated Signal. 有线电视基本概念2 Carrier-to-Noise - C/N (also CNR): The difference in amplitude between the desired RF carrier and the noise in that portion of the spectrum Signal-to-Noise - S/N (also SNR): Similar to C/N but relates to a BaseBand signal Ingress Noise - Over-the-air signals that are inadvertently coupled into the nominally closed coaxial cable distribution system. Difficult to track down and intermittent in nature. QPSK - Quadrature Phase Shift Keying. A digital modulation method in which the there are 2 data bits represented with each baud symbol. 有线电视基本概念3 Carrier - or RF carrier. A signal on which another, lower-frequency signal is modulated in order to transport the lower-frequency signal to another location. FDM - Frequency Division Multiplexing. A data transmission method in which a number of transmitters share a transmission medium, each occupying a different frequency. Headend - The location where the Cable company aggregates, combines, mixes, and modulates all signals in order to send them downstream and receive upstream signals 有线电视基本概念4 dB - Decibel. A measure of the relative strength of two signals. Multiplication becomes addition and Division becomes subtraction. dBm