As the primary way of broadband access

the requirements of user rate become more stringent for DSL. Through combing the typical scenarios

we compare the distinction of realization from different scenarios

the subscriber loop as the key factor affecting the DSL rate is reported. By studying the characteristics of the subscriber loop line

this paper summaries the basic requirements of DSL line. Based on the above factors

it induces the important DSL parameters infl uencing the line rate and the relationship among them. Combined with engineering application

it raises the method to enhance the DSL rate and have carried on the discussion through the fault instance.