In Computer Network, the transmission media is a channel between sender and receiver. The data from sender is sent to receiver through transmission media.
The transmission media is categorized in following two types:
- Guided media
- UnGuided media
Table of contents
- Guided Media
- Unguided Media
In Guided media, signals are transmitted through a physical path. The features of guide media are high speed and security. Guided media also known as Wired or Bounded transmission media.
There are three types of Guided media:
- Twisted pair
- Coaxial cable
- Optical fiber cable
1. Twisted Pair
Twisted pair cable is made up of two insulated wires twisted with each other. One wire carries the signal from source to destination and the other wire is for ground reference. Twisting is done to avoid the exterior electromagnetic interference. It is the most widely used transmission media.
Advantages of Twisted pair cable:
- Installation is easy
- Lightweight cable
- High speed
- Can carry both analog and digital data
- Cheaper than other transmission media
- If some part of twisted pair cable is damaged, it does not affect the entire network
Disadvantages of Twisted pair cable:
- Poor security
- Not durable, easy to break
- Attenuation is high
- Supports only lower bandwidth.
Applications of Twisted Pair Cables:
- In telephone lines.
- Local area networks such as small office and data centres.
Types of twisted pair cable
There are two types of twisted pair cables:
- Unshielded Twisted-Pair Cable
- Shielded Twisted-Pair Cable
Unshielded Twisted-pair cable
Unshielded twisted pair cable is widely used in telecommunications. Unshielded Twisted pair (UTP) cable is categorized as follows:
Category 1 UTP: Mostly used in telephone lines as it supports only low-speed data.
Category 2 UTP: It supports upto 4Mbps.
Category 3 UTP: It supports upto 16Mbps.
Category 4 UTP: It supports upto 20Mbps. It can also be used for long-distance communications/
Category 5 UTP: It supports upto 200Mbps.
Advantages of Unshielded Twisted-Pair Cable
- It can supports high data speed, which can be used in high speed LAN implementation.
- Very easy to setup and install
- It is flexible and cheap option for physical transmission media
Disadvantages of Unshielded Twisted-Pair Cable
- Bandwidth is limited.
- Noise reduction is not possible
- Not ideal for longer distance communications due to the attenuation.
Shielded Twisted-pair cable
Shielded twisted pair cable contains the metal foil surrounding the twisted copper wires to avoid external interference.
Advantages of Shielded Twisted-Pair Cable
- Better performance than unshielded twisted pair cable.
- Installation is easy.
- Supports higher bandwidth and high speed because it’s shielded.
Disadvantages of Shielded Twisted-Pair Cable
- Expensive. It is more expensive than Unshielded twisted pair cable.
- Difficult to manufacture and heavy weight.
2. Coaxial cable
Coaxial cable has a centre conductor enclosed in a insulating cover, which in turn is enclosed in a metal foil shield. The whole cable is covered in a plastic cover. The metal foil shield protects against the noise.
As the name suggests, it consists two conductors parallel to each other.
The inner conductor is made up of copper and the outer conductor is made up of copper mesh. These two conductors are separated by insulating cover.
The inner centre conductor is used for data transfer while the outer copper mesh conductor protects against the noise (Electromagnetic interference).
Types of Coaxial Cable
BaseBand Transmission cable: It is used for transmission of single signal at high speed. It is used for digital transmission.
BroadBand Transmission cable: It is used for transmission of multiple signals simultaneously. It is used for analog transmission.
Advantages Of Coaxial cable:
- High speed data transmission.
- Better noise reduction compared to twisted pair cable.
- High bandwidth.
Disadvantages Of Coaxial cable:
- It is more expensive than twisted pair cable.
- The whole network consists of a a single cable so any fault can cause the failure of entire network.
3. Fiber-Optic Cable
Fiber-Optic Cable is also known as optical-fiber cable. It is made of glass and the transmission of data is based on the concept of reflection of light through glass.
In fiber optic cable, the optical fibers are coated in plastic. These optical fibers send the data by pulses of light.
The plastic coating protects the cable from temperature, electromagnetic inference and other types of wiring issues.
Components of a fiber optic cable:
Core: The core of the fiber optic cable contains optical fibers and is responsible for data transmission in form of light pulses.
Cladding: The core is enclosed in a layer of glass and this layer is called cladding. The main use of cladding is to reflect the light so that the light can be transmitted from source to the destination through reflection.
Jacket: The jacket is the outer layer of fiber optic cable which is made up of plastic and the whole purpose of jacket is to protect the cable.
Coaxial cable Propagation Modes:
Multimode: Multiple light sources moves through different paths inside coaxial cable. Multiple data transmission simultaneously.
Singlemode: Light moves in a single path close to horizontal of the cable.
Advantages of fiber optic cable:
- High bandwidth: The fiber optic cable supports high bandwidth compared to the copper cables. Thus, it transfers more data compared to the copper cables.
- High speed: Since the data is transmitted in form of light, the transmission speed is very high.
- Longer range: unlike copper wires cable, the fiber optic cable can be used for larger distance data transmission.
- Reliable: It is more reliable than copper cables as the core is protected against the temperature and electromagnetic disturbances.
- Light weight
Unguided media does not use physical medium to transmit the data from source to destination. We already know that the Guided media uses physical medium such as cables and wires to transfer the data from source to destination. However unlike guided media, the Unguide media uses air as a transmission medium to transfer the data. Thus, it is called wireless transmission media.
The unguided media uses an antenna for transmitting and receiving the data in form of electromagnetic waves.
Why we need Unguided media?
There are certain areas where it is very difficult or not possible to install the cables and wires such as hill areas, in these areas wireless data transfer is very much required.
Types of Unguided media
- Microwave Transmission
- Radio Transmission
- Infrared Transmission
1. Microwave transmission
In microwave transmission, the range of frequency of electromagnetic waves lies somewhere between 1-300GHz. Microwave transmission is of two types:
- Terrestrial Type Microwave Transmission
- Satellite Type Microwave Transmission
Terrestrial Type Microwave Transmission
In this type of microwave transmission, both the sender and receiver antennas are in direct sight with each other.
- Frequency range: The frequency range of terrestrial microwave ranges from 4 to 6GHz.
- Bandwidth: It supports the bandwidth from 1 to 10 Mbps.
- Cost: If used in short distance communication, the implementation cost is cheap as we do not need relay towers. However when terrestrial type microwave transmission is used for long distances, the implementation cost goes high as we need relay towers to extend the signals.
- Attenuation: Attenuation means loss of signal. In terrestrial type microwave transmission, attenuation mainly depends on frequency and signal strength.
- Implementation: Implementation is difficult as the tower needs to be line of sight and the signal requirement makes it even more difficult to implement.
Advantages of Terrestrial type microwave transmission:
- It is cheaper than cable transmission
- Possible to implement in areas where cable transmission is difficult to implement such as hill areas.
Disadvantages of Terrestrial type microwave transmission:
- Not secure, susceptible to eavesdropping.
- Weather condition can affect the transmission.
- Limited bandwidth.
Satellite type microwave transmission
This type of communication uses the satellite antenna for communication. The sender antenna sends the signal to the satellite antenna which is revolving around the earth at a known height. The satellite antenna then amplifies the received signal and sends it to the receiver antenna.
Advantages of Satellite type transmission:
- The transmission can be done to the longer distances.
- Unlike terrestrial transmission where the implementation cost goes higher based on the transmission distance, the satellite communication is unaffected by the distance of the data transmission.
- Easy to install compared to terrestrial type.
Disadvantages of Satellite type transmission:
- Installation of satellite is extremely tough.
- Installation cost is high and development requires more time.
2. Radio Transmission
- Radio waves are very low frequency electromagnetic waves that are transmitted in all directions within the range.
- Radio transmission frequency ranges from 3KHz to 1GHz.
- In radio transmissions, the antennas need not be in aligned nor required to be set in a particular manner to send and receive signals.
- Since radio waves are omnidirectional (all directions), it is not possible to isolate the communication inside a building.
Advantages of Radio Transmission:
- Radio waves are mainly used for Wide Area Networks (WAN) for example: Mobile networks.
- Suitable for longer distance communications.
- Signals can penetrate walls.
- Higher data transmission rate compared to other transmission mediums.
Disadvantages of Radio Transmission:
- Waves are omnidirectional so faces interference from other signals of same frequency so disturbance can be there.
- Not possible to isolate the communication inside the building.
3. Infrared Transmission
- Infrared waves are highest frequency waves, frequency ranges from 300GHz to 400 THz.
- Suitable for short distance communication.
- Bandwidth is high so data transmit rate is high compared to other mediums.
- These waves cannot penetrate walls, thus they are ideal for isolated communications.
Advantages of Infrared Transmission:
- High speed
- High frequency signals
- High data transfer rate
- low interference
Disadvantages of Infrared Transmission:
- Sun rays interfere with the infrared rays so not ideal for outdoor communication.
- Suitable for short distance communication only.
- Cannot penetrate walls so difficult to establish a communication between two different rooms.