Transmission Media
Transmission media refers to the physical pathway or wireless channel used to transmit data from one device to another within a network. It can be either wired or wireless, and the selection of a particular medium depends on factors such as distance, bandwidth requirements, cost, and susceptibility to interference.
Transmission media is classified into two main categories:
- Guided (Wired) Media
- Twisted Pair Cable
- Coaxial Cable
- Optical Fibre Cable
- Unguided (Wireless) Media
- Radio Waves
- Microwaves
- Infrared Waves
Guided (Wired) Media
Guided or wired transmission media refers to physical cables that guide and direct the transmission of data signals from one device to another. The data remains confined within the cable, making this medium more secure, reliable, and less prone to interference compared to wireless media.
1. Twisted Pair Cable
A Twisted Pair Cable consists of two insulated copper wires twisted around each other. The twisting reduces electromagnetic interference (EMI) and improves signal quality. It is the most commonly used transmission medium in computer networks. In simple words Two copper wires twisted together to send data.
Twisting the wires helps to:
- Cancel electromagnetic noise
- Reduce signal loss
- Prevent interference from nearby wires
Twisted pair cables are mainly of two types:
Unshielded Twisted Pair (UTP)
UTP (Unshielded Twisted Pair) is a type of twisted pair cable that consists of two insulated copper wires twisted together without any additional metallic shielding. It is the most widely used cable in computer networking.
Key Features
- No metal shield → lightweight and flexible
- Low cost
- Easy to install
- Suitable for short to medium distances
- Most commonly used in LAN (Local Area Network)
Advantages
- Inexpensive
- Easy to install and maintain
- Lightweight and flexible
- Widely available
- Suitable for home and office networks
Disadvantages
- More susceptible to interference than STP
- Not suitable for long-distance communication
- Lower bandwidth compared to Coaxial and Fiber Optic cables
Shielded Twisted Pair (STP)
STP (Shielded Twisted Pair) is a type of twisted-pair cable that includes an additional metallic shield around the twisted copper wires.This shielding helps protect the cable from electromagnetic interference (EMI) and radio frequency interference (RFI).
An STP cable contains:
- Two insulated copper wires
- Twisted together
- Metallic foil or braided shielding around the pair
- Outer protective jacket
This shielding can be applied to:
- Each individual pair, or
- All pairs together
The shield helps to:
- Block external electromagnetic noise
- Prevent signal leakage
- Improve signal quality
- Support higher bandwidths than UTP
Uses of STP Cable
- Industrial areas with high interference
- Power plants
- Factories
- Hospitals
- High-speed LANs
- Environments close to big electrical equipment
Advantages
- Better noise protection: Ideal for areas with heavy electrical interference.
- Higher performance than UTP: More reliable data transmission.
- Reduces cross-talk: Minimal interference between pairs.
- Suitable for high-speed networks: Often used in industrial or data-heavy environments.
Disadvantages
- More expensive than UTP: Due to shielding material.
- Difficult to install: Thicker and less flexible.
- Needs proper grounding: If not grounded, the shielding becomes ineffective.
- Heavier cable: Harder to manage in large installations.
2. Coaxial Cable
A Coaxial Cable is a type of guided (wired) transmission medium that consists of a central copper conductor surrounded by insulation, a metallic shield, and an outer protective layer. The design allows it to carry signals with less interference than twisted pair cables and over longer distances. In simple words, A cable with one wire inside another, used for TV, internet, and CCTV. it is called Coaxial because the center conductor and the outer shield share the same axis → co-axial.
Types of Coaxial Cable
1. Baseband Coaxial Cable
- Used for digital data
- Short-distance communication
2. Broadband Coaxial Cable
- Used for analog signals
- Supports long-distance and higher bandwidth
Where Coaxial Cable is Used?
- Cable TV networks
- CCTV camera systems
- Internet service connections
- Early Ethernet networks
- Satellite TV communication
Advantages
- Better shielding than twisted pair
- Less signal loss
- Higher bandwidth
- Good for long-distance communication
- More reliable and durable
Disadvantages
- More expensive than twisted pair
- Thicker and less flexible
- Difficult to install
- If the cable breaks, the whole network segment fails
3. Optical Fibre Cable
An Optical Fibre Cable is a high-speed transmission medium that uses light signals to carry data. It consists of thin strands of glass or plastic fibers through which data travels as pulses of light. It uses the concept of total internal reflection of light through a core made up of glass. The core is surrounded by a less dense glass or plastic covering called the coating. It is used for the transmission of large volumes of data. The cable can be unidirectional or bidirectiona.
Types of Optical Fibre
Single-Mode Fibre (SMF)
- Very thin core
- Light travels in one straight path
- Used for long-distance communication
Multi-Mode Fibre (MMF)
- Thicker core
- Multiple light paths
- Used for short-distance communication (LANs)
Where Optical Fibre is Used?
- High-speed broadband
- Internet backbone
- Telephone networks
- Cable TV distribution
- Data centers
- Medical imaging (endoscopy)
- Military communication
Advantages
- Very high bandwidth (fastest data transmission)
- Long-distance communication without signal loss
- Immune to electromagnetic interference
- High security (difficult to tap or hack)
- Lightweight and durable
- Suitable for high-speed networks (5G, FTTH)
Disadvantages
- Expensive installation
- Requires special equipment to splice or join
- Fragile (glass fibers can break easily)
- Not easy to repair
Unguided (Wireless) Transmission Media
Unguided transmission media refers to wireless communication channels where data is transmitted through the air using electromagnetic waves, without any physical cable. Unguided media is mainly divided into three types:
Features:
- The signal is broadcasted through air
- Less Secure
- Used for larger distances
1. Radio Waves
Radio waves are a type of unguided (wireless) transmission media that carry data through the air using electromagnetic waves. They are widely used for long-distance communication because they can travel through walls, buildings, and obstacles. The range of radio waves is 3 kHz to 1 GHz. This range makes radio waves suitable for broadcasting and wireless communication.
Characteristics of Radio Waves
- Travel in all directions (omnidirectional)
- Can pass through obstacles
- Suitable for long distances
- Used for both indoor & outdoor communication
Where Radio Waves Are Used?
- FM/AM Radio broadcasting
- Television signals
- Mobile phone communication
- Wi-Fi (wireless networks)
- Walkie-talkies
- Bluetooth
- Wireless microphones
Advantages of Radio Waves
- Can travel long distances
- Omnidirectional → no need for line-of-sight
- Low cost of transmission
- Can penetrate buildings, walls, and obstacles
- Supports mobility (used in mobile networks)
Disadvantages of Radio Waves
- Prone to interference (from electrical appliances, other radio devices)
- Less security (signals can be intercepted easily)
- Limited bandwidth compared to microwave or fiber
- Affected by atmospheric conditions
2. Microwaves
Microwaves are high-frequency electromagnetic waves used as an unguided (wireless) transmission medium for communication. They travel in straight lines and require line-of-sight between the sender and receiver. The range of microwaves are 1 GHz to 300 GHz. This high frequency enables fast data transmission.
Characteristics of Microwaves
- Travel in straight lines (line-of-sight)
- Cannot pass through buildings, mountains, or obstacles
- Support high data rates
- Used for long-distance and intercity communication
Where Microwaves Are Used?
- Satellite communication (DTH TV)
- Mobile networks (4G/5G backhaul)
- Radar systems
- Microwave links between telecom towers
- WiMAX technology
- Wireless backbone networks
Advantages of Microwaves
- High bandwidth
- Suitable for long-distance communication
- Faster data transmission
- Less interference than radio waves
- Used where cables cannot be laid easily
Disadvantages of Microwaves
- Require line-of-sight: Cannot pass through obstacles.
- Affected by weather: Rain, fog, storms can weaken signals.
- Expensive installation: Towers and antennas are costly.
- Security issues: Microwave signals can be intercepted
Infrared
Infrared communication uses infrared light waves to transmit data wirelessly over short distances. hey cannot penetrate through obstacles. This prevents interference between systems. Frequency Range:300GHz - 400THz. It is used in TV remotes, wireless mouse, keyboard, printer, etc.
Characteristics of Infrared
- Used for short-range communication
- Requires direct line-of-sight (cannot penetrate walls)
- Safe, low-cost, and easy to implement
- Suitable for indoor use
Where Infrared is Used?
- TV remote controls
- Air-conditioner remotes
- Infrared sensors
- Wireless keyboards and mice (older devices)
- Short-distance file transfer (IrDA)
- Security systems & alarms
Advantages of Infrared
- Very safe and free from interference
- Low-cost technology
- Good security (signals do not pass through walls)
- Useful for indoor point-to-point communication
Disadvantages of Infrared
- Short range (typically 5–20 meters)
- Cannot pass through walls or obstacles
- Requires line-of-sight
- Affected by sunlight or strong lighting
Difference Between Radio Waves, Micro Waves, and Infrared Waves
| Basis | Radiowave | Microwave | Infrared wave |
|---|---|---|---|
| Direction | These are omni-directional in nature. | These are unidirectional in nature. | These are unidirectional in nature. |
| Penetration | At low frequency, they can penetrate through solid objects and walls but high frequency they bounce off the obstacle. | At low frequency, they can penetrate through solid objects and walls. at high frequency, they cannot penetrate. | They cannot penetrate through any solid object and walls. |
| Frequency range | Frequency range: 3 KHz to 1GHz. | Frequency range: 1 GHz to 300 GHz. | Frequency range: 300 GHz to 400 GHz. |
| Security | These offers poor security. | These offers medium security. | These offers high security. |
| Attenuation | Attenuation is high. | Attenuation is variable. | Attenuation is low. |
| Government License | Some frequencies in the radio-waves require government license to use these. | Some frequencies in the microwaves require government license to use these. | There is no need of government license to use these waves. |
| Usage Cost | Setup and usage Cost is moderate. | Setup and usage Cost is high. | Usage Cost is very less. |
| Communication | These are used in long distance communication. | These are used in long distance communication. | These are not used in long distance communication. |
Applications of Transmission Media in Computer Networks
| Transmission Media | Application |
|---|---|
| Unshielded Twisted Pair (UTP) | Local Area Networks (LAN), telephones |
| Shielded Twisted Pair (STP) | Industrial networks, environments with high interference |
| Optical Fiber Cable | Long-distance communication, internet backbones |
| Coaxial Cable | Cable TV, broadband internet, CCTV |
| Radio | Wireless communication, AM/FM radio, mobile phones |
| Infrared | Remote controls, short-range communication |
| Microwave | Satellite communication, radar, long-distance links |