In this section, we will explain what is transmission media and its different types.
What is Transmission media
In a data communication system, data travels from sender to receiver. In between the sender and receiver, there is a physical link to carry the data. This physical link is known as the transmission media or communication channel.
The data may be in the form of text, numbers, images, audio or video. But, when it traverses through the transmission media, it is converted into electromagnetic or electrical signals.
The transmission media can be defined as the means through which data can be transmitted from the transmitting station to the receiving station. The physical layer of the OSI model defines the different types of transmission media and how data travels through these various media.
The transmission channel can be physical wire or wireless. The wired media includes coaxial cable, twisted pair cable, and fibre optics cable etc. Whereas, the wireless media may be infrared, Bluetooth, radiofrequency or satellite link.
Types of transmission media
The transmission media is categorized into two broad categories :
- Guided or wired media
- Unguided or wireless media
The guided transmission media is also known as bounded or wired media. It is the actual physical and tangible media that carries the data from transmitting station to the receiver.
The guided media is limited by its physical length. That means when the physical length of the cable is increased to a greater distance, its transmission speed decreases. It is due to the attenuation caused by the metallic properties of the conducting wire. Generally, copper is considered to be a good conductor of electricity. Coaxial cable and twisted pair cable is made up of copper. Whereas, optical fibre cable is made up of glass material because optical energy i.e. light is passed through the cable. Since light can travel a greater distance, the transmitting range of optical fibre is quite greater than the metallic cable.
The unguided media is also termed as the unbounded or the wireless media.
The unguided media uses free space to broadcast signals from transmitting station and received by the remote stations that are tuned to the transmitting channel or frequency.
The transmitted signal travels through the air in the form of electromagnetic waves. The electromagnetic spectrum ranges from 3 kHz to 900 THz.
The whole range of the frequency spectrum is divided into several frequency bands. Not all frequency band are used for wireless communication.
The frequency band such as radio frequency, infrared and microwave bands are used by unguided media for data transmission.