as per term in technology,Transmission means sending,propagating,receiving infromation from source to destination via Coaxiel Cable,Microwave link,Optical Fiber as point to point or point to multipoint….
PDH (Plesiochronous Digital Hierarchy):
In terms of Telecom,transmission technology first introduced as PDH (Plesiochronous Digital Hierarchy) by ITU-T (International Telecommunication Union-Telephony) G.702 standard for multiplex Hierarachy and G.703 standard for Electrical Interfaces.
PDH is a traditional higer data rate digital multiplexing technology used by telecommunication to transport a large amount of information via microvave link.
The term plesiochronous is derived from Greek Plesio, meaning near and chronous, time and refers to the fact that PDH networks run in a state where different parts of the network are almost, but not quite perfectly synchronized.lets take an example of two watches running at nominal speed at same rate like 60 seconds per minute but there is no any hierarchy that two watches running at same rate.
E1 is basic unit in PDH..and its rate of 2.048 MBPS.so how its become 2.048mpbs let me explain..
Our human voice is analog in nature..and PDH it self is digital technology…for this,human voice frequenecy is from 300 to 33000 HZ band so let take voice frequency as a 4 KHZ..Now sampling it so 4*2 (nyquiest Theorem)=8 kbps (Sampling rate)—now do non uniform quantization….decoding/encoding ( in 1 sample = 8 bit) =8*8=64kbps….now 64kpbs is your one PCM line (Pulse Code Modulation) and 32*64(1 PCM line)=2.048 mbps= 1 E1.
PDH hierarchy is defined as below…
PDH signal level
Bit Rate (Mbps)
E2 (4 E1’s)
E3 (16 E1’s)
E4 (64 E1’s)
E5 (256 E1’s)
SONET ( Synchronous Optical Network):
This is standard Tehcnology used internationally in specially USA/Canada/Japan.the information are transfer in this system via LASER/LED ( Light Amplification by stimulation Emition/Light Emitting Diode) to provide more security and fast delivery data to receiver end.
Now Term Synchronous means ,SDH networks run at a state where diffrent parts of the network are exaclty synchronosed with a centralized clock.
T1 is basic unit in SONET and its rate of 1.5441 mbps.
SDH ( Synchronous Digital Hierarchy):
Ø It is a transport network
Ø fully standardized
Ø with high bandwidth
Ø for synchronous and asynchronous signals
Ø for future broadband signals and new services
Ø with standardized network management capabilities
Ø with traffic protection
Ø with a flexible multiplexing structure
Ø direct access to tributaries
Ø cross-connections without demultiplexing
SDH hierarchy is defined as below as per standard.
OPTERA METRO 4100
OPTERA METRO 4200