Types of Transmission Media
Definition of Transmission Media
In data communication terminology, a transmission medium is a physical path between the transmitter and the receiver.
It is the channel through which data is sent from one place to another. For any networking to be effective, raw stream of data is to be transported from one device to other over some medium. Various transmission media can be used for transfer of data.
Transmission Media is broadly classified into the following types.
1. Types of Transmission Media
I) Guided Media :
In guided media, transmitted data travels through cabling system that has a fixed path. For example, copper wires, fibre optic wires, etc.
- Features :
High Speed, Secure, Used for comparatively shorter distances
- There are 3 major types of Guided Media :
Twisted Pair Cable :
It consists of 2 separately insulated conductor wires wound about each other. Generally, several such pairs are bundled together in a protective sheath. They are the most widely used Transmission Media. Twisted Pair is of two types:
-- Unshielded Twisted Pair (UTP) :
UTP consists of two insulated copper wires twisted around one another. This type of cable has the ability to block interference and does not depend on a physical shield for this purpose. It is used for telephonic applications.
- Advantages :
Least expensive
Easy to install
High-speed capacity
Susceptible to external interference
Lower capacity and performance in comparison to STP
Short distance transmission due to attenuation
— Shielded Twisted Pair (STP) :
This type of cable consists of a special jacket (a copper braid covering or a foil shield) to block external interference. It is used in fast-data-rate Ethernet and in voice and data channels of telephone lines.
- Advantages :
Better performance at a higher data rate in comparison to UTP
Eliminates crosstalk
Comparatively faster
Comparatively difficult to install and manufacture
More expensive
Bulky
Coaxial Cable :
It has an outer plastic covering containing an insulation layer made of PVC or Teflon and 2 parallel conductors each having a separate insulated protection cover. The coaxial cable transmits information in two modes: Baseband mode(dedicated cable bandwidth) and Broadband mode(cable bandwidth is split into separate ranges). Cable TVs and analog television networks widely use Coaxial cables.
- Advantages :
High Bandwidth
Better noise Immunity
Easy to install and expand
Inexpensive
- Disadvantages :
Single cable failure can disrupt the entire network
Optical Fiber Cable :
It uses the concept of reflection of light through a core made up of glass or plastic. The core is surrounded by a less dense glass or plastic covering called the cladding. It is used for the transmission of large volumes of data.
The cable can be unidirectional or bidirectional. The WDM (Wavelength Division Multiplexer) supports two modes, namely unidirectional and bidirectional mode.
- Advantages :
Increased capacity and bandwidth
Lightweight
Less signal attenuation
Immunity to electromagnetic interference
Resistance to corrosive materials
- Disadvantages :
Difficult to install and maintain
High cost
Fragile
Stripline :
Stripline is a transverse electromagnetic (TEM) transmission line medium invented by Robert M. Barrett of the Air Force Cambridge Research Centre in the 1950s. Stripline is the earliest form of the planar transmission line.
It uses a conducting material to transmit high-frequency waves it is also called a waveguide. This conducting material is sandwiched between two layers of the ground plane which are usually shorted to provide EMI immunity.
Microstripline :
In this, the conducting material is separated from the ground plane by a layer of dielectric.
I) Unguided Media :
In unguided media, transmitted data travels through free space in form of electromagnetic signal. For example, radio waves, lasers, etc.
Each transmission media has its own advantages and disadvantages in terms of bandwidth, speed, delay, cost per bit, ease of installation and maintenance, etc.
- Features :
The signal is broadcasted through air, Less Secure, Used for larger distances, There are 3 types of Signals transmitted through unguided media.
- Radio Waves :
These are easy to generate and can penetrate through buildings. The sending and receiving antennas need not be aligned.
Frequency Range:3KHz — 1GHz. AM and FM radios and cordless phones use Radio waves for transmission.
- Microwaves :
It is a line of sight transmission i.e. the sending and receiving antennas need to be properly aligned with each other. The distance covered by the signal is directly proportional to the height of the antenna.
Frequency Range:1GHz — 300GHz. These are majorly used for mobile phone communication and television distribution.
- Infrared :
Infrared waves are used for very short distance communication. They cannot penetrate through obstacles. This prevents interference between systems.
Frequency Range:300GHz — 400THz. It is used in TV remotes, wireless mouse, keyboard, printer, etc.
