Transmission Media in Networking || Guided Media (Wired Media) & Unguided Media (Wireless Media)

Transmission media are the physical pathways or channels that carry data between devices in a network. It plays a vital role in the Physical Layer (Layer 1) of the OSI model by supporting electrical, optical, or electromagnetic signal transmission for efficient data transfer. Simply put, when information moves from one device to another in the critical data transfer process, it travels through a medium or communication channel to reach its destination. This channel is known as transmission media.

Types of Transmission Media

Transmission media are broadly classified into two categories:

1.    Guided Media (Wired Media):

·         Data is transmitted through a physical medium, such as cables.

·         Examples include twisted-pair cables, coaxial cables, and fiber optics.

2.    Unguided Media (Wireless Media):

·        Data is transmitted without a physical medium, typically using electromagnetic waves.

·        Examples include radio waves, microwaves, and infrared

Guided Media (Wired Media)

Transmission media in which the connection between two devices is established through a physical method, such as a cable or wire, is referred to as wired transmission media or guided media. Wired media is also known as bounded media because it has a specific limit. Guided media enables the fast and secure transmission of data over short distances, and fibre is used for long-distance connections.

Twisted-Pair Cable

A twisted-pair cable is a copper cable used to transmit data or voice. It contains two insulated copper wires twisted around each other to reduce electromagnetic interference (EMI) from external sources and other cables nearby.

1.      Unshielded Twisted Pair (UTP): Commonly used in Ethernet networks.

2.      Shielded Twisted Pair (STP): Includes a shield to reduce interference.

UTP (Unshielded Twisted Pair) – This is an Unshielded Twisted Pair Cable, which means it does not have any separate shielding or cover, as you can see in the image. This type of cable usually supports data transfer speeds from 10 Mbps to 10 Gbps across distances up to 100 meters.

STP (Shielded Twisted Pair) –  This is a Shielded Twisted Pair Cable. It includes an additional shield that enhances data security and increases data transfer speed.

• Applications: LANs, telephone lines.
• Advantages: Inexpensive, easy to install.
• Disadvantages: Limited bandwidth and distance.

Coaxial Cable

Coaxial cable is made of copper wire, covered by insulation, and wrapped with a brass copper mesh for protection. It can transmit data up to 185 meters. While it’s easy to install, the cable is flexible yet fragile, making it more likely to break. Coaxial cables are widely used in cable TV, analog TV systems, and CCTV setups. There are mainly two types: the 50-ohm cable used for digital signals, and the 75-ohm cable used for analog signals. Though effective, coaxial cables are heavier than other cables and are among the most commonly used.

Coaxial cables are categorised by their Radio Government(RG) ratings.

Category	Impedance	Use
RG-59	75 ohm	Cable TV
RG-58	50 ohm	Thin Ethernet
RG-11	50 ohm	Thick Ethernet

• Applications: Cable TV, internet services, and CCTV systems.
• Advantages: High bandwidth, less interference.
• Disadvantages: Bulkier and costlier than twisted-pair cables.

Fiber Optic Cable

Optical fiber cable is the fastest medium for transferring data. Made from pure silica glass, it was developed in 1970. Fiber optics have revolutionized the internet world. Today, countries across the globe are connected through the internet, where fiber cables play a key role. This advanced transmission medium supports high-speed, long-distance data transfer, making it essential for modern communication systems.

In this cable, data travels in the form of a light signal, and upon reaching the data destination, the light signal is converted into a digital signal. It is extensively used in submarine communications, meaning that Fiber Optic Cable is employed to connect the network of one country with that of another country, facilitating international network connectivity.

Types of Fiber Optic Cables

1.      Single-Mode Fiber (SMF)

·        Has a very small core (about 8–10 microns).

·        Transmits data using a single light mode.

·        Best for long-distance communication (up to hundreds of kilometres).

·        Used in internet backbones, telecom networks.

2.      Multi-Mode Fiber (MMF)

·        Has a larger core (about 50–62.5 microns).

·        Allows multiple light modes to travel simultaneously.

·        Ideal for short-distance connections (up to 2 km).

·        Used in LANs, data centers.

 

• Description: Uses light signals to transmit data through glass or plastic fibers.
• Applications: High-speed internet, telecommunications, long-distance data transmission.
• Advantages: Extremely high bandwidth, long distances, immune to electromagnetic interference.
• Disadvantages: Expensive, requires specialised equipment for installation and maintenance.

Unguided Media (Wireless Media)

In unguided transmission, electromagnetic energy freely travels through the air. This method allows signals to be sent over long distances without using physical cables. However, the signals transmitted through the air are more likely to face interference, signal loss, and security issues due to open transmission. Unguided media is commonly used in wireless communication such as radio, satellite, and Wi-Fi systems.

Radio Waves Transmission

Radio signals are easy to generate and use. Radio waves are electromagnetic waves that radiate in all directions through open space. They typically have a frequency range of 3KHz to 1GHz. These signals are commonly used in radio broadcasting and wireless phones for communication.

• Description: Electromagnetic waves with long wavelengths used for broadcasting.
• Applications: FM/AM radio, TV broadcasts, mobile communication.
• Advantages: Wide coverage, easy to deploy.
• Disadvantages: Prone to interference and security concerns.

Microwaves Transmission

Microwave signals are used in mobile phone communication and TV networks. They have a frequency range from 1GHz to 300GHz. The range of the signal also depends on the antenna height. For effective transmission, it’s essential to align the sender and receiver properly, ensuring clear signal communication.

Description: High-frequency waves used for point-to-point communication.

• Applications: Satellite communication, cellular networks, Wi-Fi.
• Advantages: High speed, suitable for long distances.
• Disadvantages: Requires line-of-sight; affected by weather conditions.

Infrared (IR) Transmission

Infrared waves are used for short-distance communication, but can be blocked by obstacles between devices. Their frequency range spans from 300 GHz to 400 THz. Infrared technology is commonly found in TV remotes, wireless mice, keyboards, printers, and other devices.

• Description: Uses infrared light for short-range communication.
• Applications: Remote controls, short-distance wireless communication.
• Advantages: Secure, no interference with radio waves.
• Disadvantages: Limited range, requires line-of-sight.

Satellite Communication Transmission

Satellite communication transmission is a wireless method of sending and receiving data, voice, and video signals using satellites orbiting the Earth. It enables long-distance communication by relaying signals between a transmitter and a receiver through a satellite link, making it essential for remote areas, global broadcasting, GPS, the internet, and military communications.

 

• Description: Data is transmitted to a satellite in space and then relayed to the receiver.
• Applications: Global positioning systems (GPS), TV broadcasting.
• Advantages: Wide area coverage, supports remote locations.
• Disadvantages: High latency, expensive.

Comparison of Transmission Media

Feature	Twisted Pair	Coaxial Cable	Fiber Optics	Wireless Media
Bandwidth	Low to Medium	Medium	Very High	Varies (Medium-High)
Distance	Short to Medium	Medium	Long	Varies (Short-Long)
Interference	High	Low	None	High
Cost	Low	Moderate	High	Moderate

Factors to Consider When Choosing Transmission Media

1.      Distance: Fiber optics for long distances, twisted pair for short distances.

2.      Cost: Twisted-pair is cost-effective; fiber optics are expensive.

3.      Bandwidth: High-speed requirements favor fiber optics or wireless media.

4.      Environment: Wireless for areas where cabling is impractical.

5.      Interference: Fiber optics for immunity to interference; shielded cables for moderate resistance.

Transmission media are the backbone of communication networks, enabling data exchange between devices. The choice between guided and unguided media depends on factors like cost, distance, bandwidth requirements, and environmental conditions. As technology evolves, newer, faster, and more efficient transmission media continue to shape the future of networking.