In data communication terminology, a medium is a physical path between a transmitter and a receiver, also known as a “channel,” through which data goes from one place to another. Transmission media is broadly classified as follows:
1. Guided media
This term is also known as bounded or wired media. The signals transmitted in this system are directional and are transmitted in a narrow path using physical transmitters.
Configurations:
- High speed
- safe
- It can be used for short-distance communication
Here we have three types of directed media:
1-1- Twisted pair cables
It consists of two separate insulated conductive cables wrapped around each other. Typically, multiple pairs of cables are placed together within a shielded sheath. This type of cable is widely used for media transmission. There are two types of twisted pair cables:
Unshielded Twisted Pair (UTP) Cables This type of cable can block interference and does not require a shield or shield for this purpose. This type of cable is used for telephone communication applications.
Advantages:
- They are very cheap.
- They are easy to install.
- They have a high-speed capacity.
- They are sensitive to external disturbances.
- They have lower capacity and lower performance than the STP sample.
- Due to their damping properties, they can only be used for short distances.
- Shielded twisted pair (STP) cables
This type of cable has special jackets that block external disturbances. They are used for Ethernet with fast data rates and in the voice and data channels of telephone lines.
Advantages:
- They outperform unshielded twisted pair (UTP) cables in terms of performance and data rate.
- They can prevent crosstalk.
- They are significantly faster.
- They are more difficult to install and produce.
- They are more expensive.
- They are more voluminous.
1-2- coaxial cable
They have a plastic cover with two conductors inside them, each using a separate insulating shield. Coaxial cables for data transmission are made in baseband mode (in which the cable bandwidth is dedicated) and broadband mode (in which the cable bandwidth is divided into different ranges). Cable television and analog television networks widely use coaxial cables.
Advantages:
- They have high bandwidth.
- They have better noise immunity.
- They can be easily installed and developed.
- are expensive
Disadvantages:
A single cable failure can disrupt the entire network.
1-3- Optical fiber cables
In these cables, the concept of light reflection inside a transparent core made of glass or plastic is used. The core is a low-density glass or plastic covered with a coating called Cladding. They are used to transfer large amounts of information.
Cables can be unidirectional or bidirectional. WDM (wavelength division multiplexer) can support unidirectional and bidirectional modes.
Advantages:
- Increased capacity and bandwidth.
- Being lightweight.
- No attenuation in signals.
- Safety against electromagnetic waves
- Corrosion resistant
Disadvantages:
The difficulty of installation and maintenance
The price is relatively higher
being fragile
1-4- Strip line
Stripline is a transverse wave electromagnetic transmitter invented by Robert M. Barrett at the Cambridge Air Force Research Center in the 1950s. Strip lines are the primary form of flat transmission lines. They use a conductive material to transmit high-frequency waves, also known as a waveguide. This conductive material is placed between two layers in the form of a sandwich, which causes EMI (wave frequency disturbance) safety.
1-5 – microstrip line
In this section, the conductive materials are separated through plates made of non-conductive materials.
2. Undirected media
They are also known as wireless or unbounded communications, where no physical medium is used to transmit electromagnetic signals.
Configurations:
- Signals are waiting over the air.
- Their security is less.
- It can be used for long distances.
There are three ways to transfer data for unguided media via signal transmission:
2-1 Radio waves for media transmission
These are the easiest to produce and have the ability to penetrate through buildings as well. The placement of transmitter and receiver antennas here does not need any arrangement. The frequency range here is between 3KHz to 1GHz. AM and FM radios and cordless intercoms use radio waves to transmit data.
Other divisions here include terrestrial and satellite waves.
2.2 Microwaves for media transmission
This is a direct transmission method, so the receiving antennas must be properly aligned. The distance these cover is in direct proportion to the height of the antennas. The frequency range here is between 1GHz and 300GHz. These waves are widely used to cover mobile phones and televisions.
2-3 infrared waves
Infrared waves are used for communication over very short distances. They cannot pass through objects and obstacles. This will prevent system disruptions. The frequency range here is between 300GHz and 400THz. These waves are used in TV remotes, mice, keyboards and wireless printers, and other similar things.
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