Various Transmission Media in Computer Networks

What is Transmission Media?

In the process of communication, there are five elements, they are – sender, receiver, message, medium, and feedback. The medium which is used in the communication is called the transmission medium. It is the physical medium that helps in the transmission or transfer of the message. The information is carried between the source and the destination. However, the speed of transmission depends on the transmission medium being used. Information is first converted into bits and then transferred to the intended user or its destination. If the network is copper-based, then bits are converted to electrical signals and if the network is a fiber-based network, then the data bits are converted into light signals.

You might have studied this in the OSI (Open System Interconnection) model. The physical layer of the OSI Model helps in the physical transmission of the data. In a coaxial cable, bits are converted to electrical signals whereas, if there is fiber optic cable, then the physical layer converts it to light signals. The company can use any transmission media for their communication depending on their requirements. All of the transmission has its own unique or distinct features and limitations. They may vary in terms of bandwidth, speed, quality, time that is taken in transfer, cost incurred, and installation process.

Types of Transmission Media

These media are divided into two categories. They are:

• Guided Transmission Media – Guided media is also called wired or bounded media. In this, data transmission takes place physically. Twisted pair cable, coaxial cable, and fiber optic cable are different types of wired media that are being used widely.
• Unguided Transmission Media – Unguided media is also called wireless or unbounded media. In this, the air is the medium that helps to carry data signals. Electromagnetic waves are used in transmission which is carried by air. They do not use any physical medium. Wireless media is having three categories, they are radio waves, microwaves, and infrared.

Guided Transmission Media

Three types of wired transmission media are:

1. Twisted Pair Cable – Twisted pair cable is made using a pair of cables that twisted with each other. If we compare this medium with other media, then it is quite cheap and least expensive. Also, the installation of it is very easy. In twisted pair cable, wires are arranged in a twisted pattern (or spiral pattern). These are insulated copper wires and are lightweight cables. More the turns in the wire per foot more the noise will be reduced. Analog and digital both the signals can be transmitted using this media. This cable is of two types:
2. Shielded Twisted Pair – The STP cable is covered by a mesh due to which it is more secure and also the transmission rate is high. Its capacity is more than unshielded cable, it has higher attenuation (attenuation – week signal due to increased distance),
3. Unshielded Twisted Pair – Unshielded does not contain any mesh that surrounds the cable. It is cheap and has an easy installation. Using this the speed of the LAN can be increased.

Advantages of Twisted-Pair Cable

• It is cheap and easy to install.
• Greater transmission rate.
• Capacity is high.

Disadvantages of Twisted-Pair Cable

• Higher attenuation rate.
• Shielded cable is costlier than coaxial and unshielded cable.
• Useful in a short distance (due to attenuation).

• Coaxial Cable – It is a widely used media. Coaxial cable is highly used in Television/ Cable wires. In this, two conductors are used due to which it is named coaxial. These two conductors are placed parallel to each other. These cables provide a greater frequency, then twisted pair cable. The inner conductor is made using copper and copper mesh is used to make the outer conductor. The core of the coaxial cable is made using non-conductive material. The outer conductor is separated from the inner conductor using this middle core. Coaxial cable is of two types:

1. Broadband – Transmission of multiple signals is done simultaneously. This is called broadband transmission.
2. Baseband – Transmission of one signal at one time is called baseband transmission. It provides high-speed transmission.

Advantages of Coaxial Cable

• Transmission speed is high.
• Bandwidth is high.
• Its shielding is better than twisted pair cable.

Disadvantages of Coaxial Cable

• Expensive than twisted pair.
• The entire network can fail if faults are in a single cable.

• Fiber Optic Cable – Communication is done using electrical signals when it comes to fiber optic cable. Optical fibers are covered in plastic; fiber optic holds these wires. With the help of these optic fibers, data is sent using light pulses. Due to the plastic covering, the cable is protected from heat and cold. Also, various types of electromagnetic interferences can be prevented with the help of plastic coating. Optical fiber has main three elements. They are core, cladding, and a jacket.
• Core – Core is a place where light is transmitted. An increased area of the core will provide more space for light transmission. It is covered with plastic or glass.
• Cladding – Cladding is a layer of glass. It is used to lower the refractive index. It is used so that the light is passed through the fiber.
• Jacket – Jacket is used for protection. Fiber strength is maintained and it also absorbs shock thereby providing more protection.

Advantages of Fiber Optic Cable

• It provides greater bandwidth.
• Faster speed.
• Useful in long-distance communication.
• It has a lightweight and signals attenuation is also less.

Disadvantages of Fiber Optic Cable

• It is expensive as compared to other media.
• It is fragile.
• It is unidirectional, if two-way communication is required, then two cables will be required.
• Maintenance and installation are difficult.

Unguided Transmission Media

Three types of wireless media are:

1. Radio Waves – Radio waves are electromagnetic waves. These are omnidirectional means they are spread in all directions in free space. Any sending antenna can send the signals and in air and any receiving antenna will receive it. It is not necessary to align the antennas. FM radio is an example of radio waves. Also, it is used in multicasting (one sender and multiple receivers), cordless phones, television, etc.

Advantages of Radio Waves

• Covers a large area.
• Penetrate through walls.
• High transmission rate.

Disadvantages of Radio Waves

• Cannot pass through solid objects.
• Contains Noise.
• Electromagnetic Interference.

2. Microwaves

They are of two types:

• Terrestrial Microwave – Terrestrial Microwave transmission is based on a particular geographical area. Data is transmitted from one antenna to another antenna. It is a unidirectional wave that means data can be sent in both directions. In this transmission, it is necessary to align the antennas. The antenna is located in the mountains so that they are in direct sight of each other. For a shorter distance, it is not much expensive but for long distances it is expensive.
• Satellite Microwave – Satellite is an object which is used for data transmission. It is more flexible than the other type of microwave. It covers a very huge area. It working is also easy to understand. An earth station sends data to the satellite, then the satellite amplifies the signals and sends it back to the earth station. It is used for many purposes as it has global coverage. Mobile communication, weather forecasting, broadcasting different radio/TV signals, etc.

The advantages of Microwave

• The satellite covers a large area.
• The cost incurred in the transmission is less.
• Installation is easy.
• The terrestrial microwave is less expensive.
• Maintenance of terrestrial microwave is easy as compared to satellite.

The disadvantage of Microwave

• Transmission through satellite is very expensive.
• Installation is difficult in a satellite.
• The maintenance of the satellite is expensive and difficult.
• It can contain an intruder and they can also eavesdrop.
• Bad weather conditions can hamper the quality and speed of the signal.
• The satellite needs continuous monitoring.

3. Infrared – Infrared is another wireless transmission media used in communication. It is used for a short coverage area. It creates a small network like data transmission between two mobile phones, or laptops, or a mobile and a laptop, etc. Examples of infrared transmissions are TV remote, transfer between laptops or cell phones, etc.

Advantages of Infrared

• It is more security due to less area.
• Useful in small or closed areas.
• Great bandwidth.
• The data transfer rate is also very high.

Disadvantages of Infrared

• These waves cannot pass through walls.
• Interference can be caused by sunlight.
• Covers a short-range.
• Disturbance can be caused due to other transmissions.

These are the different types of transmission media available. The quality of the transmission will depend upon the media used. If an organization is small scale and has a low budget, they can use wired media as it is less expensive, provides greater bandwidth, installation is easy, etc. Whereas, if a company is very large or company as an internet service provider, they can use wireless transmission media as it provides a wider coverage area, high speed, etc. An organization can install an antenna and look after its maintenance. Some of the wireless media is easy to install while others are expensive. It is your choice which one to use.