E-carrier
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The E-carrier is a member of the series of
E1 frame structure
An E1 link operates over two separate sets of wires, usually
Special timeslots
One timeslot (TS0) is reserved for framing purposes, and alternately transmits a fixed pattern. This allows the receiver to lock onto the start of each frame and match up each channel in turn. The standards allow for a full cyclic redundancy check to be performed across all bits transmitted in each frame, to detect if the circuit is losing bits (information), but this is not always used. An alarm signal may also be transmitted using timeslot TS0. Finally, some bits are reserved for national use.[1]
One timeslot (TS16) is often reserved for signalling purposes, to control call setup and teardown according to one of several standard telecommunications protocols. This includes
When using E1 frames for data communication, some systems use those timeslots slightly differently, either
- TS0: Framing, TS1–TS31: Data traffic — This is named Channelized E1, and is used where the framing is required, it allows any of the 32 timeslots to be identified and extracted.
- TS0–TS31: Data traffic — Often referred to as Clear Channel E1 or Unchannelized, it is used where no framing is required, timeslot extraction is not required and the full bandwidth (2 Mb/s) is required.
Hierarchy levels
The
Note, because bit interleaving is used, it is very difficult to demultiplex low level tributaries directly, requiring equipment to individually demultiplex every single level down to the one that is required.
See also
- D 0 (DS0)
- Digital Signal 1 (DS1, T1)
- HDB3encoding scheme
- List of device bandwidths
- Multiplexing
- Plesiochronous Digital Hierarchy
- STM-1
- T-carrier
- Time-division multiplexing
- Nonblocking minimal spanning switch - discussion of practical telephone switches.
- Clos network - the mathematics of telephone switches.
References
- ^ E1 Environment Archived 2013-10-14 at the Wayback Machine, RAD data communications University Tutorials
- ^ "Signaling System No. 7 (SS7/C7): Protocol, Architecture, and Services, Lee Dryburgh, Jeff Hewett, 2004". Archived from the original on 1 January 2012. Retrieved 26 May 2010.
External links