plesiochronous digital hierarchy การใช้

• Plesiochronous digital hierarchy ( PDH ) was developed as a standard for multiplexing higher order frames.
• The most common example of a plesiochronous system design is the plesiochronous digital hierarchy networking standard.
• The target was to supply the requested availability for the whole block ( Plesiochronous digital hierarchy, PDH, or Synchronous Digital Hierarchy, SDH ).
• Although originally deployed systems ( 1990s ) used plesiochronous digital hierarchy ( PDH ) links such as E1 / T1 links, more recent systems use Ethernet cabling.
• A few years before a new standard for optical transmission systems called Synchronous Digital Hierarchy ( SDH ) had been developed and ratified as a global standard as a replacement for existing Plesiochronous Digital Hierarchy ( PDH ) equipment.
• The "'plesiochronous digital hierarchy "'( "'PDH "') is a technology used in telecommunications networks to transport large quantities of data over digital transport equipment such as fibre optic and microwave radio systems.
• As is the case with level 1 of the plesiochronous digital hierarchy ( 2 Mbit / s ), the higher levels of multiplexing are carried out bit by bit ( unlike the multiplexing of 64 kbit / s channels in a 2 Mbit / s signal, which is byte by byte ), thus making it impossible to identify the lower level frames inside a higher level frame.
• At the time of the design of ATM, 155 Mbit / s Synchronous Digital Hierarchy ( SDH ) with 135 Mbit / s payload was considered a fast optical network link, and many plesiochronous digital hierarchy ( PDH ) links in the digital network were considerably slower, ranging from 1.544 to 45 Mbit / s in the USA, and 2 to 34 Mbit / s in Europe.