E-carrier

A hierarchy of standards for digital transmission, E-carrier is based on the original North American T-carrier digital carrier system, although the specifics are quite different with respect to signaling rates, framing conventions, line coding technique, and PCM companding technique (A-law rather than µ-law). In many respects E-carrier is a considerable improvement over T-carrier. For example, E-1 supports 30 DS-0 payload channels, compared with T1 at 24 channels, and the higher E-carrier levels build on that difference. E-carrier also supports non-intrusive signaling and control through two channels reserved for such purposes. As a result, E-carrier supports clear channel communications of a full 64 kbps per DS-0, compared to 56 kbps data with T-carrier. The DS-0 (Digital Signal level Zero) is the fundamental building block of E-carrier, as it is with T-carrier and J-carrier, the Japanese version.Through time division multiplexing (TDM), E-carrier interleaves DS-0 channels at various signaling rates to create the services that comprise the European digital hierarchy, as detailed in Table E-3.

Table E-3: European Digital Hierarchy: E-Carrier

E-carrier Level	Data Rate (Mbps)	Number of 64 kbps Channels (DS-0s)	Number of E-1s
E-1	2.048	30	1
E-2	8.448	120	4
E-3	34.368	480	16
E-4	139.268	1920	64
E-5	565.148	7680	256

See digital signal hierarchy for a side-by-side comparison of the North American, European, and Japanese digital hierarchies. See also carrier, channel, companding, digital, DS-0, E-1, E-2, E-3, E-4, E-5, J-carrier, PCM, signaling rate, T-carrier, and TDM.