Fixed Broadband Communications Systems

Three fixed‐line media are of main interest to broadband telecommunications: twisted pair copper wires traditionally used for the telephony system; coaxial copper cables used for inter‐exchange links and cable TV broadcasting; and optical fibre systems used for international and long‐distance telephony and telecommunications backhaul. This chapter presents a chronological account of major milestones in fixed‐line data and digital voice systems. The performance of twisted pair copper wire systems is affected by interference from other telephone connections. This interference is generally known as crosstalk, and exists in two main types: near end crosstalk (NEXT) far end crosstalk (FEXT). While much of additive noise is random and therefore difficult to remove, the crosstalk interference signals are deterministic and therefore it is possible to calculate and remove them from the received signal. Asymmetric digital subscriber line (ADSL)/very‐high‐bit‐rate DSL (VDSL) standards have evolved to deliver higher transmission rates in both upstream and downstream.