Types of Transmission Media In Computer Networks

There are two types of transmission media including guided media and unguided media. In guided transmission media, waves are guided along a solid medium such as a transmission line. Transmission and reception in unguided transmission media are achieved through the antenna.

In this article, we will be discussing what is transmission media and its types in detail. We will try to understand the functionalities and advantages of this communication channel.

Tables of Content

• What is transmission media in computer network?
• What are the different types of transmission media?
• Pros and Cons of transmission medium
• Factors to consider while designing transmission media
• What Can Cause Transmission Impairment?
• Applications of Transmission media

What is Transmission Media in Computer Networks?

Transmission media in Computer Networks is a communication channel that transmits information from the source/transmitter to the receiver. It is a physical path for data transfer through electromagnetic signals. Information is carried over in the form of bits through LAN. It can mediate the propagation of signals for telecommunication. Signals are imposed on a wave that is suitable for the chosen medium. These media lie underneath the physical layer that regulates them. While designing a transmission, it is important to keep the following pointers in mind:

• The bandwidth should be greater since it will result in a higher data transmission rate of a signal.
• Noise should be less. Otherwise, the data signal can be distorted.

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What are the Types of Transmission Media in Computer Networks?

If you are wondering how many types of transmission media in computer networks are there, then take a look at this section. Broadly, there are two types of transmission media in computer networks including guided and unguided media. These two types of transmission media in computer networks have further subtypes. Let us discuss these in detail.

1. Guided Transmission Media

Guided media is a type of transmission media in computer networks which is also known as wired or bounded media. These transmission media consist of wires through which the data is transferred. Guided media is a physical link between transmitter and recipient devices. Signals are directed in a narrow pathway using physical links. These media types are used for shorter distances since physical limitation limits the signal that flows through these transmission media.

1.1 Twisted Pair Cable

In this type of transmission media, two insulated conductors of a single circuit are twisted together to improve electromagnetic compatibility. These are the most widely used transmission medium cables. These are packed together in protective sheaths. They reduce electromagnetic radiation from pairs and crosstalk between the neighbouring pair. Overall, it improves the rejection of external electromagnetic interference. These are further subdivided into unshielded and shielded twisted pair cables. 

1.1.1 Unshielded Twisted Pair Cable(UTP): These consist of two insulated copper wires that are coiled around one another. These types of transmission media block interference without depending on any physical shield. The unshielded twisted pair are very affordable and are simple to set up. These provide a high-speed link. 

1.1.2 Shielded Twisted Pair (STP): This twisted cable consisted of a foil shield to block external interference. The insulation within these types of twisted cables allows a greater data transmission rate. These are used in fast-data-rate Ethernet and in data and voice channels of telephone lines.  

1. 2 Optical Fibre Cable

Also known as fiber optic cable, these types of transmission media are thin strands of glass that guide light along their length. These contain multiple optical fibres and are very often used for long-distance communications. Compared to other materials, these cables can carry huge amounts of data and run for miles without using signal repeaters. Due to lesser requirements, they have less maintenance costs and it improves the reliability of the communication system. These can be unidirectional as well as bidirectional in nature. 

1.3 Coaxial cable

These guided transmission media contain an insulation layer that transmits information in baseband mode and broadband mode. Coaxial cables are made of PVC/Teflon and two parallel conductors that are separately insulated. Such cables carry high-frequency electrical signals without any big loss. The dimensions of cable and connectors are controlled to give them constant conductor spacing for efficient functioning as a transmission line.

1.3.1 Hardline Coaxial Cable: This is one of the types of transmission media in computer networks that are used for high signal strength applications including long-distance telephone lines. These look like any regular coaxial cable but these are 1.75" thick. This type of cable has the capability to carry hundreds of channels of cable TV. Such cables have sufficient internet capacity for medium-sized office buildings.

1.3.2 RG-6 Coaxial Cable: This is mainly used for cable and satellite signal transmission for the purpose of residential and commercial installation. These are thin and are easily bendable for wall or ceiling installation. Such cables are preferred for relaying cable television signals.

1.3.3 Triaxial Cable: Also known as Triax, these are the electrical cables that come with an add-on layer of insulation and a second conducting sheet. These cables provide greater bandwidth as well as rejection of interference as compared to coax. However, triaxal cables are expensive types of transmission media.

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1.4 Stripline 

This is a transverse electromagnetic (TEM) type of transmission media that is built on the inner layers of multi-layer printed circuit boards. These are used in high or low-level RF signals that require isolation from surrounding circuitry. It is a type of printed circuit transmission line in which a signal trace is sandwiched between the upper and lower ground place. Stripline minimizes emissions of electromagnetic radiation and is completely enclosed within a homogeneous dielectric. Along with the reduced emissions, it also shields against incoming spurious signals. 

1.5 Microstripline

While Microstripline is similar to stripline, it is not sandwiched and is present above the ground plane. These can be fabricated with any technology where the conductor is separated from the ground plane by a dielectric layer called subtrate. These transmission media convert microwave frequency signals. Microstrip is also used for building microwave components such as couplers, filters, power dividers, antennas, etc. In comparison with the traditional waveguide technology, it is less expensive.

2. Unguided Transmission Media

Also known as unbounded or wireless media, they help in transmitting electromagnetic signals without using a physical medium. Here, air is the medium. There is no physical connectivity between the transmitter and receiver. These types of transmission media are used for longer distances however they are less secure than guided media. There are three main types of wireless transmission media. 

2.1  Radio Waves

Radio waves are transmitted in every direction throughout free space. Since these are omnidirectional, sent waves can be received by any antenna. These waves are useful when the data is multicasted from one sender to multiple receivers. Radio waves can cover large areas and even penetrate obstacles such as buildings and walls. The frequency of these waves ranges between 3 kHz to 1GHz. Due to its omnidirectional nature, issues such as interference might arise when another signal with the same bandwidth or frequency is sent.  

2.2 Infrared

These waves are useful for only very short-distance communication. Unlike radio waves, they do not have the ability to penetrate barriers. Their range varies between 300GHz – 400THz. Since they have larger bandwidth, the data rate is very high for infrared waves. These have less interference and are more secure. 

2.3 Microwaves

For these waves, it is important for the transmitter and receiver antenna to be aligned. This is why it is known as line-of-sight transmission. Due to this, they are suitable for shorter distances. They comprise of electromagnetic waves with frequencies ranging between 1-400 GHz. Microwaves provide bandwidth between the range of 1 to 10 Mbps. The distance covered by the signal is proportional to the height of the antenna. For travelling to longer distances, the height of the tower should be increased. These are further sub-categorized as terrestrial and satellite-type microwave transmission. 

2.3.1 Terrestrial type microwave transmission: In this type, high directional antennas are used for line of sight propagation paths that use frequencies between 4-12 GHz. These are parabolic antennas having diameters that range from 12 inches to feet depending on their spacing. 

2.3.2 Satellite-type microwave transmission: Signals are transmitted to those spaces where satellites are positioned and they retransmit the signal to appropriate locations. Since they only receive and retransmit the signal, they act as repeaters. It is a much more flexible and reliable method of communication in comparison with cables and fibre systems. 

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Pros and Cons of Transmission Media in Computer Networks

The following table summarises the advantages and disadvantages of transmission media:

Considerable Factors While Designing Transmission Media

While designing transmission medium in computer networks, it is important to consider the following factors:

• It is also important to consider the cost incurred on its installation, maintenance and future upgrades of transmission medium. Factors such as infrastructure complexity, material quality and labour also add to the overall cost. An important part of designing the transmission medium is making it affordable.
• Greater bandwidth of the transmission medium allows a higher data transmission rate of the signal.
• Another factor to be considered while designing transmission media environmental conditions. The transmission medium should be able to withstand fluctuations in temperature, moisture or any wear and tear.
• Another important factor is the maximum distance to which the transmission medium can transmit data without major signal degradation. For long-distance transmission, repeaters, amplifiers as well as specialized media such as fiber optics will be required to maintain the quality of the signal. The type of transmission of transmission media will be chosen according to the range and application.
• Due to transmission impairment, the received signal may get destroyed since it does not seem identical to the transmitted signal.
• Interference occurs whenever any external signal from nearby devices disrupts the transmitted signals. This may lead to errors and signal distortion which is quite common when the design of the transmission medium is poor. To minimize interference, it is important to perform proper shielding as well as grounding and manage frequency. This will improve the integrity of the signal.

What Can Cause Transmission Impairment?

The following reasons can contribute to transmission impairment:

• Attenuation: Attenuation refers to the gradual decrease of signal strength as it travels over long distances or through a medium. This happens due to energy loss caused by resistance or absorption in the medium. Amplifiers or repeaters are often used to restore the signal strength.
• Distortion: It is the change in structure or shape of the signal as different parts of the signal travel at varying speeds. This can result from medium limitations or issues with multiplexing. It leads to misinterpretation of data unless corrected by equalizers or filters.
• Noise: These are unwanted signals that interfere with the transmitted signal, reducing its clarity. Examples include thermal noise from electrons, crosstalk from adjacent wires, or sudden impulse noise. Shielding and error correction techniques can help in mitigating noise.
• Interference: External signals, such as electromagnetic waves from nearby devices can overlap with the communication signal. This is common in wireless systems with multiple overlapping frequencies. Proper frequency management and shielding can reduce interference.
• Poor Equipment: Outdated or faulty devices such as routers, cables, or connectors can degrade the transmission quality. These may cause delays, interruptions, or loss of data. Regular maintenance and upgrading hardware improve performance.
• Environmental Factors: Weather conditions such as rain, fog, or extreme temperatures can impact signal transmission, especially for wireless or optical systems. For example, rain can cause attenuation in microwave or satellite links. Environmental shielding and robust designs help reduce these effects.

Applications of Transmission Media in Computer Networks

Conclusion 

We hope that you have now learned about the types of transmission media in computer networks. Based on the data rate and distance between the transmitter and receiver, a suitable transmission media can be selected. One can also select the transmission type based on whether they require a physical medium or not.