9.7. Summary
In the telco loop plant, there are numerous types of digital subscriber lines deployed. The DSLs deployed can be categorized in two different types: (1) symmetric echo-canceled (EC) DSLs and (2) asymmetric (FDM) DSLs. The first class of EC DSLs includes ISDN, HDSL, and SDSL; the second class includes ADSL. The modulation technologies for the DSLs include 2B1Q for ISDN, HDSL, CAP for HDSL and MSDSL, DMT for ADSL, and CAP for RADSL.
Most echo-canceled systems, including ISDN, HDSL, and SDSL, transmit the same frequency spectra in the downstream direction as the respective system uses in the upstream direction. Assuming the same transmit power for each of these systems, the worst-case crosstalk performance occurs when the cable is filled ...
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