Editing Multipath propagation (section)

==In wired media==
Multipath propagation is similar in [[power line communication]] and in telephone [[local loop]]s. In either case, [[Impedance matching|impedance mismatch]] causes [[signal reflection]]. 

High-speed power line communication systems usually employ multi-carrier modulations (such as [[OFDM]] or [[wavelet]] OFDM) to avoid the [[intersymbol interference]] that multipath propagation would cause. The [[ITU-T]] [[G.hn]] standard provides a way to create a high-speed (up to 1 gigabit per second) [[local area network]] using existing home wiring ([[power line communication|power lines]], phone lines, and [[ethernet over coax|coaxial cables]]). G.hn uses OFDM with a [[cyclic prefix]] to avoid ISI. Because multipath propagation behaves differently in each kind of wire, G.hn uses different OFDM parameters (OFDM symbol duration, guard interval duration) for each media.

[[DSL modem]]s also use orthogonal frequency-division multiplexing to communicate with their [[DSLAM]] despite multipath. In this case the reflections may be caused by mixed [[wire gauge]]s, but those from [[bridge tap]]s are usually more intense and complex. Where OFDM training is unsatisfactory, bridge taps may be removed.