How do NEXT and PS NEXT differ?
NEXT loss is a measure of the unwanted signal coupling from a transmitter at the near-end into neighboring pairs measured at the near-end. Faintly hearing the neighbor’s conversation during your own telephone call is an example of crosstalk. In a LAN, NEXT occurs when a strong signal on one pair is picked up by an adjacent pair. Early LAN protocols only utilized two pairs essentially rendering the other two dormant. Because NEXT is measured by one pair’s effect onto one other pair, the NEXT measurement was adequate. Now, protocols such as Gigabit Ethernet utilize all four pairs in full duplex transmission. PS NEXT addresses this by measuring the individual NEXT effects on any one pair by the other three pairs when all pairs are operating simultaneously.