CMTS双下行信道的研究

Research of CMTS with Dual Downlink Channel

在当前的信息化社会里,人们对视频点播、可视电话、互联网等宽带业务的需求不断增大。这使得通信网络的宽带化成为必然,作为一种重要的接入技术,HFC正以其独特的带宽优势得到了越来越多的关注。利用电缆调制解调器Cable Mdoem在HFC网上传送数据,具有用户实际使用带宽高、投入设备成本低、扩展灵活、光纤网络建设成本低、网络维护更容易等优点,北美地区的Cable Modem用户已占宽带用户的大多数,随着有线电视网络改造的扩大,我国的Cable Modem用户也在不断增加。但是,目前Cable Modem系统的前端设备CMTS缺乏对多下行信道的支持,造成了信道资源的紧张状况,所以对支持多下行信道的CMTS进行研究是非常必要的。本文首先分析了实现双下行信道CMTS的重要性,然后给出了双下行信道CMTS和CM的交互工作原理,以及基于VxWorks操作系统和BROADCOM公司最新的CMTS系列芯片实现双下行信道CMTS的过程,最后对CMTS双下行信道的动态切换和时间同步等关键问题进行了研究。

In the current information society,people＇s demand on broadband services such as VOD,videotelephone and Internet is increasing.This makes the broadband communications network become inevitable,as an important access technology,HFC is gaining more and more attention for its unique bandwidth.Data transmission in HFC by Cable Mdoem has high bandwidth,low-cost in equipment,flexible expansion,low-cost in fiber-optic network＇s construction,easy network＇s maintenance,etc.In North America Cable Modem users have accounted for most in broadband users,domestic Cable Modem users are also increasing with the expansion of cable TV network＇s reconstruction.However,the current front-end equipment CMTS in Cable Modem system is lack of multi-downlink channel＇s support,resulting in the intension of channel resources,thus it＇s very necessary to research the CMTS with multi-downlink channel.In this paper,the importance of CMTS with dual downlink channel＇s realization is analysised firstly,then the interactive work principle between CMTS with dual downlink channel and CM and the process of CMTS with dual downlink channel based on VxWorks operating system and most advanced CMTS series chip in the company BROADCOM is given.Finally,dynamic channel switching and time synchronization on CMTS with dual downlink channel and other key issues are researched.