ADSL For Internet Services & Applications

Nowadays with the fast development of telecommunication industry and computer technology, people are much more urgent towards the broadband services like long-range education, long-range medical treatment, video on demand etc, which need a characteristic of communication network —broadband.The so-called broadband access, to residential customer, is that the data rate beyond 2Mb/s (several times or even several thousands times than the traditional dialing connection.), and 24 hours on line. Currently broadband access technologies available classes as: optical access, copper access and wireless access. Obviously the existing copper network is the result of continuous investment and preferment during the last several years, thus exploiting the transmission potential of the common copper line and adopting new technology and new equipments to deliver high-speed signal will have important economical significance.With the breakthrough of the communication technology and the implement of the optical fiber, the backbone has already realized high-speed and broadband. Therefore, whether the access network, regarded as the "last mile" of the information highway, still remains can smash its "bottleneck" limitation of analogue and low-speed has become the crux of the development of communication network.This article starts from the various access technologies, and explicates various copper access technologies separately in chapter one. The second chapter introduces the DSL technology like HDSL, ADSL, and VDSL chiefly, together with a comparison between ADSL and HFC. The ADSL, as one of the most important technologies in the copper access, this article interprets its modulation technology, including QAM, CAP, and DMT. Meanwhile it illuminates DMT technology in detail and then compares DMT recommended by ITU-T with other modulation technologies. At last the article mainly focuses on the LMS of DMT and then depicts the application and future development of ADSL.