An Applicability Study of ADSL in Japanese Subscriber Lines

Abstract

The ADSL technology is standardized in US by ANSI to enable digital transmission speed of 1.5Mbps-6Mbps over existing copper phone access line. The ADSL technology extracts almost full capability, up to the theoretical limitation imposed by Shannon's Theory, of the access line. The limitation is solely determined by loss and cross talk noise of the access line. The ADSL technology is not so sensitive to bridged taps or AM radio wave, which are commonly seen hazards of phone access lines. But, in Japan, phone access lines are different from those in US. In Japanese phone cables, 4 wires are twisted together, and pulp as well as polyethylene is used as insulating material. As a result the access lines in Japan suffers more loss and crosstalk. Moreover, the ISDN modulation method in Japan generates a lot more nose to ADSL than that in US. The ANSI ADSL technology is first evaluated with access line environment in Japan. Then, three approaches; separation of ISDN and ADSL access line, ADSL power increase, ISDN filter capability enhancement are proposed and evaluated. It can be concluded that the ADSL technology is applicable also in Japan.