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.