Study And Achieve Of The Technology Of Subscriber Access Network

This assay is focuses on part of access network technology. The main contents are as the follows.To discuss the function of the forthcoming copper loop, city cable channel's once and twice parameters are analyzed and calculated, and simple analytic model are used to describe the characteristics of channel. The transformation of parameter related to applied HDSL technology in higher band of frequency, and the influences of near reaction and twisted subscriber line are mainly analyzed.To discuss the influence of transmission environment, the noise of the present subscribe channel and its influence on digital signal transmission are analyzed. The possible influence of pulse noise on HDSL technology's application is analyzed quantitatively, subscribe channel's interference voice is analyzed, and the influence of bridged tap on subscriber loop when it is applied under the digital condition of subscriber channel is calculated.On the basis of above-mentioned analysis of channel peculiarity, the realistic channel capacity of present twisted subscriber line is calculated and the possibility that it is expanded and the ultra-limitation of capacity of HDSL are discussed.It's discussed that the general receive & deliver structure and some crucial technologies of HDSL, including CAP, Tomlison Preceding, DFE and so on, and the direction of subsequent work is indicated. The hardware circuits that are based on subscriber loop integrated service multiplex are also achieved. In addition, some problems about subscriber access network related to fiber channel are discussed.There are some creative studies in this article:Firstly, analytical method to calculate some parameters of symmetrical cableused as subscriber line is used. The analytical result in theory is consistent with actual result. This helps to analyze the effect of every factor in collective character.Secondly, simple model to calculate pulse noises which affect subscriber channel be digitized is used. This provides data basis for the design of channel filter.Thirdly, based on the theory of transmission line, the affection to subscriber channel be digitized when there is bridged tap in subscriber loop is analyzed.Finally, the capacity in theory when average power is limited is estimated. Then noise and channel capacity in NEXT is gotten and the ultra-limitation of subscriber channel in theory in general condition is presented.