
Introduction to transmission media
It is the physical media through which communication takes place in Computer Networks. Its primary function is to carry the information through LAN ( local area network) in bits. It is operated by various physical components and is therefore placed beneath the physical layer while being worked on by physical elements from the physical layer.
There are two types of transmission media: wired and wireless.
Medium parameters are more essential in wired media, but signal qualities are more relevant in wireless media.
Classification of Transmission media

Guided Transmission Media (wired transmission media)
It's also known as bounded transmission media because it's limited in the communication network. The transmission signals properties of this Guided Media are restricted and focused in a fixed constricted channel, which can be done via bodily wired contacts. The Guided Media has a high transmission velocity, which is one of its distinguishing characteristics. Other factors that influence users' decisions to utilise guided media over unguided media include the security of transmission and the ability to regulate the network's coverage within a smaller geographical area.
The type of connecting material utilised to create this network is further divided into three types.
- Twisted Pair Cables
- Fibre Optics
- Coaxial Cables
Twisted Pair Cables
These cables are made by twisting two distinct insulated cables together to make a single cable. Shields are often formed of insulating materials, allowing both cables to transmit independently. This twisted wire is then enclosed inside a protective coating to make it easier to use.
There are two types of twisted-pair cables:
Shielded twisted pair cable (STP)
Shielded cables are simply transmission media with superior casing to block all peripheral invasions throughout the transmission process.
These cables are well-known for their great performance, preventing signal crossover and allowing for quicker transmission rates.
Telephone lines in home utilities are a common application for Shielded Twisted Pair Cable. Shielded twisted pair cables, like any other media, have drawbacks, such as installation complexity, the need for a large volume of wires, and the fact that they are more expensive than other cables.

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Unshielded twisted pair cable (UTP)
This type of cable lacks a casing and has many properties that are inversely proportional to shielded cables.
These cables are less expensive, easier to install, and have faster-transmitting capabilities. It also allows for external interferences, resulting in lower performance qualities.

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Fibre Optics
These cables are glass-based cables that use light signals for transmission purposes. It uses the principle of reflections for the transmission of light signals. It is well-known for allowing bulky data to be transmitted with greater bandwidth and with fewer electromagnetic interferences during transmission.
In most cases, these cables are preferred over twisted cables because the material is non-corrosive and weightless.
Some disadvantages of Fibre Optics:
- Difficulties in maintenance or installation.
- Expensive than other types of transmission media.

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Coaxial Cable
It is made of plastic layering on the outside, and two conducting materials placed parallel to one another while being wrapped in individual insulating layers around them. It is used to transmit data using dedicated cables or a single cable divided into different bandwidths, which are referred to as Baseband mode and Broadband mode, respectively.
This cable type is commonly used to provide a television network in homes. It has several advantages, including a wide bandwidth range, ease of installation or maintenance, and is less expensive than other cable types.

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Also See, Basic Networking Commands
Unguided Transmission Media (wireless transmission media)
It is a wireless transmission medium with no physical medium to connect to network nodes or servers. They are less secure than guided media because electromagnetic signal waves are transmitted in the air over a larger geographical area. (See Unguided Media)
In terms of the signals used for transmission, this type of transmission media is classified into three types.
- Radio Waves
- Micro Waves
- Infrared
Radio Waves
These are the most basic type of transmission signals, requiring no complicated steps to create and transmit. This signal typically has a frequency range of 3 kHz to 1 GHz, and the signal types can be AM or FM.
The primary applications of this transmission medium are cordless phones for domestic or official use and radio devices used as a component in mass media communication. These radio waves can be used for either terrestrial or satellite communication.

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Micro Waves
There are two types of microwave transmission:
Terrestrial Microwave
It is a method of transmitting a focused beam of a radio signal from one ground-based microwave transmission antenna to another. These are electromagnetic waves with frequencies ranging from 1GHz to 1000GHz.
It is based on line-of-sight transmission, which means that the antennas mounted on the towers are in direct sight of each other.

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Advantages:
- It is cheaper than cables.
- It provides easy communication in terrains as the installation of cables in terrain is a difficult task.
- It is free from the land acquisition as it doesn't require any cables.
Disadvantages:
- Any environmental change, such as rain or wind, can cause the signal to be distorted.
- Allocation of bandwidth is limited.
- Out of phase signal.
Satellite Microwave
It is more dependable nowadays because it is more adaptable than cable and fiber optic systems. Using satellite communication, we can communicate with any location on the planet.
The satellite receives the signal transmitted from the earth station and amplifies it. The signal is amplified and retransmitted to another earth station.

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Advantages:
- Its coverage area is more than terrestrial microwave transmission.
- It is easy to install.
- The transmission cost is independent of the distance from the center of the coverage area.
Disadvantages:
- The satellite must be monitored and controlled on a regular basis in order to remain in orbit.
- Satellite design and development take more time and money.
- The satellite has a lifespan of 12-15 years. As a result, another launch of the satellite is required before it becomes inoperable.
Infrared
It is another method of transmitting data inside a small area that cannot pass through obstacles and does not allow for interference. These waves have a frequency range of 300 GHz to 400 THz and can be used for wireless peripheral devices such as remote controls, keyboards, printers, and so on.
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You can also read about the network models in computer network.
Also see, Message Switching in Computer Networks, Memory hierarchy in computer network, Subnetting in Computer Networks