Basics of E1/T1 Link

Basics of E1/T1 Link or Data rate

E1:

It is the Basic Data rate of communication in telecommunication. It is the lowest level of the Plesiochronous Digital Hierarchy (PDH) and is among the most common ways of transmitting voice & data over telephone and data networks. Physically E1 is transmitted as 32 timeslots.

STANDARDS OF E 

E0=64 kbits/second
E1=2.048 kbits/s
E2=8.448 Mbits/s
E3=34.368 Mbits/s
E4=139.264 Mbits/s
E5=564.992 Mbits/s

E1 Link

• E1 link operates over two separate sets of wires. Usually Twisted pair cables.
• A nominal 3volt peak signal is encoded with pulses using a method that avoids long periods without polarity changes.
• This is an ideal for voice telephone calls where the voice is sampled.
• The line data rate of E1 is 2.048 Mbits/S. full duplex [2.048 Mbits/s upstream and downstream] which is split in to 32 time slots each being allocated 8 bits in turn.
• So each time slot sends and receives an 8bits/s of sample.
• 8000 times per second = 8* 8000* 32 = 2,048,000.
• The timeslots are numbered from 0-31.
• One timeslot ( TS0 ) is reserved for framing purposes and alternately transmits a fixed pattern.

TS0= Synchronization, Alarm transport, international carrier use.
E1 has 30 circuits.

One timeslot [ TS16] is often reserved for signalling purpose to control call setup and teardown according to telecommunication protocol.

This includes channel associating Signaling ( CAS ) where a set of bits is used opening and closing the ckt. where CAS is known as per trunk signaling , a form of digital communication.

PHYSICAL E1
Here two types of physical delivery option are available for E1:

• UNBALANCED [120w]: COPPER WIRE 4 [ One pair for TX ( 4+5) one pair for RX ( 1+2)
• BALANCED [75w]: COAX with BNC connector [one cable for RX and one cable for TX]

E1 Frame

The E1 framing is the first level in the digital hierarchy. The E1 frame carries 30 voice channels in a 256-bit frame. Since 30 channels only require 240 bits; 16 bits are available for framing, signaling, error checking and supervisory communications. These extra 16 bits are divided into two groups of 8 bits each.

E3 Frame

A group of E1 circuits bundled on to higher capacity E3 links between telephone exchanges or countries. This allows a network operator to provide a end-to-end E1 circuit between customers in different countries that share single high capacity links between them.

• E3 has 480 circuits.
• E3 has 512 timeslots and data rate as 34.368 Mbits/s.

-DR