Transmission Media or Communication Channels

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What is Transmission media?

• Transmission media is a communication channel that carries the information from the sender to the receiver. Data is transmitted through electromagnetic signals.
• The main functionality of the transmission media is to carry the information in the form of bits through LAN(Local Area Network).
• It is a physical path between transmitter and receiver in data communication.
• In a copper-based network, the bits in the form of electrical signals.
• In a fiber-based network, the bits in the form of light pulses.
• In OSI(Open System Interconnection) phase, transmission media supports Layer 1. Therefore, it is considered to be a Layer 1 component.
• The electrical signals can be sent through the copper wire, fiber optics, atmosphere, water, and vacuum.
• The characteristics and quality of data transmission are determined by the characteristics of medium and signal.
• Transmission media is of two types are wired media and wireless media. In wired media, medium characteristics are more important whereas, in wireless media, signal characteristics are more important.
• Different transmission media have different properties such as bandwidth, delay, cost, and ease of installation and maintenance.
• The transmission media is available in the lowest layer of the OSI reference model, i.e., Physical layer.

Some factors need to be considered for designing the transmission media:

• Bandwidth: All the factors are remaining constant, the greater the bandwidth of a medium, the higher the data transmission rate of a signal.
• Transmission impairment: When the received signal is not identical to the transmitted one due to the transmission impairment. The quality of the signals will get destroyed due to transmission impairment.
• Interference: An interference is defined as the process of disrupting a signal when it travels over a communication medium on the addition of some unwanted signal.

Causes Of Transmission Impairment

• Attenuation: Attenuation means the loss of energy, i.e., the strength of the signal decreases with increasing the distance which causes the loss of energy.
• Distortion: Distortion occurs when there is a change in the shape of the signal. This type of distortion is examined from different signals having different frequencies. Each frequency component has its own propagation speed, so they reach at a different time which leads to the delay distortion.
• Noise: When data is traveled over a transmission medium, some unwanted signal is added to it which creates the noise.

We can group the communication media in two categories :

1. Guided Media: It includes wires and cables
2. Unguided Media: It includes waves through air, water, or vacuum.

Guided Media

Guided Media is also known as Wired or Bounded transmission media. A signal travelling the media is directed and confined by the physical limits of the medium.

Advantage of guided media

• More secure
• Provides high speed
• Used for shorter distances

Disadvantage of guided media

• Need Physical link
• Time Consuming

UnGuided Media

UnGuided/Wireless Transmission Media transfer electromagnetic waves without using a physical medium or conductor. It is also referred to as Unbounded or Wireless transmission media.

Advantages of unguided media

1. The signal is broadcaster through free space (air).
2. Unguided signals can travel in several ways: sky propagation, ground propagation,  and line-of-sight propagation.
3. The electromagnetic spectrum, ranging from 3 kHz to 900 THz, used for wireless communication.

Disadvantages of unguided media

1.Very costly.
2.Radio waves travel through Lowest portion of atmosphere