DSL Advances

7.1. Basic VDSL Concepts

Basic VDSL architecture presumes a shorter twisted-pair transmission line than earlier DSLs. VDSL line lengths are typically between 150 meters (500 feet) and 2000 meters (6600 feet). On such short phone lines, the very high-speed digital transmission of tens of megabits/second is possible. The existence of shorter phone lines implies a telecommunications network that increasingly uses fiber, or perhaps also wireless transmission, in that the nearest central-office portion of the access network previously carried all data via twisted-pair. All DSL technologies prior to VDSL had served the large majority of customers via copper wire pairs directly from the CO to the customer location. VDSL's short line reach, in contrast, ...