Classification of Transmission Media
I’m Nethmi Wijebandara, Undergraduate, University of Moratuwa. From this article, I’m going to give an idea about the main deviations under the umbrella term of Transmission media.
Transmission media can be defined as a communicational channel which transfers information from sender’s end to receiver’s end. So, the data is transmitted as electromagnetic signals. The main task of such transmission media is to transfer information as bits through Local Area Network (LAN).
This transmission media can be divided into two major parts such as guided media and unguided media.
1. Guided media
Guided media means signals are transferred via a physical medium. It can be known as Bounded media as well. Basically guided media can be divided into three parts such as;
I. Twisted pair
Twisted pair can be further classified into two parts such as;
a. Unshielded twisted pair — Mostly used for telecommunication purposes. There are some categories such as ;
Category 1 — telephone lined containing low speed data
Category 2 — supports up to 4Mbps
Category 3 — supports up to 16Mbps
Category 4 — supports up to 20Mbps which is also compatible with long-distance communication.
Category 5 — supports up to 200Mbps.
Features:
b. Shielded twisted pair — Widely used for signals with higher transmission rate. This contains a mesh surrounded by the wire.
II. Coaxial cable
This is the most common and widely using transmission media. The reason behind this coaxial cable is it has two conductors parallel to each other. This has higher frequency than twisted pair cables. So that, it is commonly used as TV wires. The inner conductor is made by copper and there is an outer conductor made by copper mesh. There is a middle conductor which works as a non-conductive cover deviates inner and outer conductors. It is responsible for data transferring while outer conductor prevents from Electromagnetic interferences.
This can be divided into two parts such as;
· Baseband — transmits a particular signal at high speed.
·Broadband — transmits multiple simultaneous signals.
However, coaxial cables are more expensive and a single failure may affect for the downfall of the whole network.
III. Fiber optics
This is a cable which uses electrical signals for communication. It has optical fibers coated in plastic which is used to send data as light pulses. There is a plastic coating which protects optical fibers from cold, heat and the electromagnetic effects of other wire types. This can be considered as more faster transmission media than copper cables.
Basic elements:
1. Core — the light transmission area of the fiber.
2. Cladding — Provides the lower refractive index at the core interface. It reflects within the core as the light waves are moving through fiber.
3. Jacket — The defensive coating which is created by plastic. This protects the strength of fiber, absorb shock and extra fiber protection.
However, fiber optic cables are far more better than copper cables because of the great bandwidth, faster speed, capacity to transmit data for a longer distance, better reliability and the thinner and sturdier nature of the cables.
2. Unguided media
Unguided transmission is able to transmit electromagnetic waves excluding a physical medium. So that, this can be called as wireless transmission. Here, air is used for the easy flow of electromagnetic energy. They can be categorized into three as:
I. Radio waves
They are electromagnetic waves which can transmit every direction in free space. Radio waves can be declared as omnidirectional waves which has 3KHz to 1KHz range of frequency.
Radio waves can be applied for multicasting whenever there is one sender and multiple receivers. It is also beneficial to use in wide area networks. Therefore, radio transmission provides higher transmission rate.
II. Microwaves
This can be divided into two major parts as;
a. Terrestrial microwave transmission
Here, the microwave transmits the focused beam of a radio signal from one ground-based microwave antenna to other antenna. It has a frequency range from 1GHz to 100GHz. This works as a line of sight transmission.
The specialty of transmission is its ability to avoid land acquisition because it doesn’t need installation of cables. The communication is also so easy as a result of that. Apart from that, the communication process over the oceans can be done by microwave transmission.
However, this has some issues such as eavesdropping, out of phase signal, susceptible to weather condition and limited bandwidth.
b. Satellite microwave transmission
This has become a new trend as it is more flexible than using cables or fiber optic systems. The communication can be done with any place in the globe using satellite communication. As a result of that, this satellite microwave transmission can cover a wider area even better than terrestrial microwaves.
Now a days, this technology is using for mobile and wireless communication applications and weather forecasting, TV and Radio broadcasting and telecasting as well.
However, there are some disadvantages in these microwaves as it has high initial cost and a regular need to maintain the satellites which are places in the orbit. Apart from that, as the satellite has a lifetime mainly from 12–15 years, new launches should be done and planned to replace their functions.
III. Infrared transmission
This is used to communicate over short ranges as data transfers between mobile phones, TV remotes and closed area devices. There is a frequency from 300GHz to 400THz. However, they have a high bandwidth along with better security using minimum interference. However, these waves cannot penetrate the walls and they are unreliable outside the buildings on account of sunlight interference with infrared waves.
By understanding guided and unguided transmission media, we can conclude that, the various types of transmission media are used based on the purpose, cost, effectiveness and efficiency.
I hope you had a deep understanding about this classification of transmission media. Thank you!
