Line code: Difference between revisions

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== Disparity ==

Most long-distance communication channels cannot reliably transport a [[DC component]]. The DC component is also called the ''disparity'', the ''bias'', or the [[DC coefficient]]. The disparity of a bit pattern is the difference in the number of one bits vs the number of zero bits. The ''running disparity'' is the [[running total]] of the disparity of all previously transmitted bits.<ref>{{cite documentweb |author=Jens Kröger |url=https://www.psi.ch/mu3e/ThesesEN/BachelorKroeger.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://www.psi.ch/mu3e/ThesesEN/BachelorKroeger.pdf |archive-date=2022-10-09 |url-status=live |title=Data Transmission at High Rates via Kapton Flexprints for the Mu3e Experiment |date=2014 |page=16}}</ref> The simplest possible line code, [[Unipolar encoding|unipolar]], gives too many errors on such systems, because it has an unbounded DC component.

Most line codes eliminate the DC component{{snd}} such codes are called [[DC-balanced]], zero-DC, or DC-free. There are three ways of eliminating the DC component: