MLT-3 encoding
MLT-3 encoding is a line code (a signaling method used in a telecommunication system for transmission purposes) that uses three voltage levels. An MLT-3 interface emits less electromagnetic interference and requires less bandwidth than most other binary or ternary interfaces that operate at the same data rate (see PCM for discussion on bandwidth / quantization tradeoffs), such as Manchester code or Alternate Mark Inversion.
MLT-3 cycles through the voltage levels -1, 0, +1, and 0. It moves to the next state to transmit a 1 bit, and stays in the same state to transmit a 0 bit.
MLT-3 was first introduced by Cisco Systems as a coding scheme for FDDI copper interconnect (TP-PMD[1], aka CDDI). Later, the same technology was used in the 100BASE-TX physical medium dependent sublayer, given the considerable similarities between FDDI and 100BASE-[TF]X physical media attachment layer (section 25.3 of IEEE802.3-2002 specifies that ANSI X3.263:1995 TP-PMD should be consulted, with minor exceptions).
It shall be noted that signaling specified by 100BASE-T4 Ethernet, while it has three levels, is not compatible with MLT-3. It uses selective base-2 to base-3 conversion with direct mapping of base-3 digits to line levels (8B6T code).
External links
References
- ^ American National Standards Institute (1994). "FDDI twisted pair physical layer medium dependent (TP-PMD)". American National Standard X3T12 (incorporates X3.263). - initial implementation; also see patent