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

Basics of PSTN

PSTN 

PUBLIC SWITCHED TELEPHONE NETWORK

PSTN is the global collection of interconnects originally designed to support circuit-switched voice communication. The PSTN provides the traditional Plain Old Telephone Service (POTS) to residences and many other establishments. Parts of the PSTN are also utilized for DSL, VoIP and other Internet-based network technologies.

The basic PSTN network link supports 64 Kbps bandwidth. In residences, the PSTN phone line caring this bandwidth is typically a copper cable. Traditional dial-up modems utilize nearly 56 Kbps of this bandwidth when connected to a phone line. The PSTN utilizes the SS7 signaling protocol.

Transfer of information in the PSTN takes place over land lined trunked lines consisting of fiber optic cables, copper cables, microwave link and satellite link. 

-DR

Basics of Radio (RF)

Radio frequency (RF) 

RF radiation is a subset of electromagnetic radiation with a wavelength of 100km to 1mm, which is a frequency of 3 KHz to 300 GHz, respectively.

This range of electromagnetic radiation constitutes the radio spectrum and corresponds to the frequency of alternating current electrical signals used to produce and detect radio waves.

RF can refer to electromagnetic oscillations in either electrical circuits or

radiation through air and space. Like other subsets of electromagnetic radiation, RF travels at the speed of light.

In order to receive radio signals, for instance from AM/FM radio stations, a radio antenna must be used. However, since the antenna will pick up thousands of radio signals at a time, a radio tuner is necessary to tune in to a particular frequency (or frequency range). This is typically done via a resonator (in its simplest form, a circuit with a capacitor and an inductor).

The resonator is configured to resonate at a particular frequency (or frequency band), thus amplifying sine waves at that radio frequency, while ignoring other sine waves. Usually, either the inductor or the capacitor of the resonator is adjustable, allowing the user to change the frequency at which it resonates.

Electrical currents that oscillate at RF have special properties not shared by direct current signals. One such property is the ease with which they can ionize air to create a conductive path through air.

This property is exploited by 'high frequency' units used in electric arc welding, although strictly speaking these machines do not typically employ frequencies within the HF band. Another special property is an electromagnetic force that drives the RF current to the surface of conductors, known as the skin effect.

Another property is the ability to appear to flow through paths that contain insulating material, like the dielectric insulator of a capacitor.

The degree of effect of these properties depends on the frequency of the signals.

-DR