Transmission Media In Computer Networks
Transmission media is the part of the physical layer that provides a path through which data is transmitted from one place to another in computer networks. It is also known as a transmission channel, Communication media, or communication channel.
Important
The amount of data that can be transferred through a communication medium in a unit of time is called bandwidth.
- The bandwidth of the digital signal is measured in bits per second or bytes per second.
- The bandwidth of Analog’s signal is measured in cycles per second or Hertz.
Types of Transmission Media
There are two major types of Transmission Media. One is guided transmission media, and the other is unguided transmission media.
Physical transmission media is known as Guided Transmission Media, and Wireless transmission media is known as Unguided Transmission Media. A descriptive diagram of transmission media is given below.
1. Guided Transmission Media
There are three major types of guided media
i.) Twisted Pair Cable
Twisted pair cable consists of two insulated copper wires that are twisted around each other. there are two types of twisted pair cable
- Unshielded Twisted Pair (UTP) consists of pairs of insulated copper wires twisted together without any shielding around them to block external interference.
- Shielded Twisted Pair (STP) features additional shielding around the wires to minimize electromagnetic interference (EMI).
Twisted pair cables are commonly utilized in telephone lines, LANs, DSL internet, CCTV systems, audio setups, and device connections because of their affordability and ease of installation.
ii.) Coaxial Cable
Coaxial Cable consists of a central copper conductor, which carries the data signals, surrounded by insulation, a metallic shield, and an outer insulating jacket. The shield is used to protect the signal from external interference, providing better protection against electromagnetic interference (EMI) than twisted pair cables.
There are two main types of Coaxial Cable:
- Standard Coaxial Cable: This is the most common type, which consists of the central copper core, insulation, metal shielding, and the outer jacket.
- Shielded Coaxial Cable: This variant features additional layers of shielding, such as a foil wrap or braided wire mesh, to provide extra protection against signal degradation and external interference.
Coaxial cables are widely used in applications where signal integrity is important, such as in cable television (CATV), broadband internet connections (via cable modems), CCTV security systems, satellite communications, and RF (radio frequency) transmission. Their ability to maintain high-quality signal transmission over longer distances, combined with their shielding, makes them ideal for these applications.
iii.) Optical Fiber Cable
Fiber optic cable consists of a core made of glass or plastic fibers through which data is transmitted as light signals. These cables are designed for high-speed data transfer over long distances with minimal signal loss. There are two main types of fiber optic cables:
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Single-mode fiber (SMF):
It has a small core and allows only one mode of light to travel, making it suitable for long-distance communication with higher bandwidth and minimal signal distortion. -
Multi-mode fiber (MMF):
It has a larger core and allows multiple light modes to propagate, which is ideal for shorter distances due to modal dispersion that can affect signal quality over long ranges.
Fiber optic cables are widely used in internet backbone connections, cable television (CATV), high-speed data networks, medical imaging, and industrial applications due to their high bandwidth capacity, resistance to electromagnetic interference, and secure data transmission.
Comparison Table of Guided Media
| Feature | Twisted Pair Cable | Coaxial Cable | Fiber Optic Cable |
|---|---|---|---|
| Bandwidth | Low to medium. Suitable for voice and basic data transmission. | Medium to high. Can handle more data than twisted pair. | Very high. Ideal for high-speed internet, cable TV, and backbone networks. |
| Signal Type | Uses electrical signals (voltage) to carry data. | Also uses electrical signals but better shielded, so less signal loss. | Transmits data using light pulses, allowing faster and clearer transmission. |
| Max Distance Without Repeater | Up to 100 meters | Up to 500 meters – 1 km | Up to 40 km (Single-mode) Up to 2 km (Multi-mode) |
| Cost | Cheapest among all. Commonly used and easy to produce. | More expensive than twisted pair but still affordable. | Expensive due to materials and installation complexity. |
| Noise Resistance | Low. Prone to electromagnetic and radio frequency interference (EMI/RFI). | Better noise immunity due to shielding, but still vulnerable over long distances. | Excellent. Immune to EMI, RFI, and other types of interference. |
| Speed | Up to 1 Gbps (Cat5e/Cat6). Higher categories (Cat6a/Cat7) support higher speeds. | Can support up to 10 Gbps in some configurations. | It can reach terabits per second (Tbps), making it the fastest guided medium. |
| Installation | Easy to install and maintain. Flexible and lightweight. | Moderate difficulty. Thicker and less flexible than twisted pair. | Difficult and delicate installation. Fibers are fragile and require special handling. |
| Security | Moderate. Easier to tap or intercept if physical access is available. | Better security due to shielding, but still possible to tap. | Very secure. Hard to tap or intercept without being detected due to light-based data transmission. |
| Common Use | Telephone lines, LANs, DSL connections. | Cable TV, internet access, CCTV systems. | Internet backbone, long-distance telecom, medical imaging, and high-speed enterprise networks. |
Advantages of Guided Transmission Media
- Less Interference: Guided media are less prone to electromagnetic interference compared to unguided media, like wireless communication.
- Better Security: Data transmitted through physical cables is harder to intercept, providing better security.
- High Speed and Bandwidth: Especially in fiber optic cables, guided media can support very high data transfer rates.
- Reliable Transmission: Signal loss is lower and more predictable, which makes the communication more stable and reliable.
- Controlled Environment: Since the signals travel through a physical path, it is easier to manage and maintain the transmission quality.
- Cost-Effective for Short Distances: Media like twisted pair cables are inexpensive and easy to install, especially over short distances.
Disadvantages of Guided Transmission Media
Guided transmission media (wired or bounded media) refers to physical paths, like cables, that transmit data signals. Common types include twisted pair cables, coaxial cables, and fiber-optic cables.
Here are the main disadvantages of guided transmission media:
- Limited Mobility: Devices must be physically connected by cables, which restricts movement and flexibility. Not ideal for environments requiring frequent changes in layout or device positions.
- Installation Complexity and Cost: Laying down cables can be expensive and labor-intensive, especially over long distances or through buildings. Maintenance and upgrades may require rewiring or physical access to cables.
- Physical Damage and Wear: Cables are prone to physical damage due to bending, cutting, corrosion, or environmental factors. Regular wear and tear can degrade performance over time.
- Limited Scalability: Expanding the network might require laying additional cables, which can be disruptive and costly.
- Signal Attenuation: Signals weaken over long distances, requiring repeaters or amplifiers to maintain strength (especially in copper-based media).
- Interference and Crosstalk: Especially in twisted pair and coaxial cables, electromagnetic interference (EMI) and crosstalk between wires can affect signal quality.
2. Unguided Transmission Media
Unguided transmission media refers to communication channels that transmit data through the air (or space) without using physical conductors like cables or wires. Instead of copper or fiber optics, it uses electromagnetic waves (radio, microwave, infrared, etc.) to carry signals. It is essential for wireless communication.
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About Carrier Wave !! The carrier wave is always a higher frequency than the message signal, and this high frequency is what allows efficient and reliable transmission over distances. Radio waves, microwaves, and infrared waves are often used as carrier waves. However, microwaves used in microwave ovens for cooking do not function as carrier waves. |
Unguided media can be broadly divided based on the frequency of the waves used. The following three major types of guided transmission media are given below
1. Radio Waves
Radio waves are a type of electromagnetic wave with the longest wavelengths and lowest frequencies in the electromagnetic spectrum. They are widely used in wireless communication systems because they can travel long distances, penetrate buildings, and carry information effectively through the air. Radio waves are generated by transmitters and received by antennas. They are the foundation of technologies like radio broadcasting, mobile phones, Wi-Fi, Bluetooth, and satellite communication.
Characteristics of Radio Waves
- Long Wavelength: Radio waves have wavelengths ranging from 1 millimeter to over 100 kilometers, allowing them to diffract around obstacles and follow the Earth’s curvature, making them ideal for long-range communication.
- Low Frequency: They operate in the 3 kHz to 300 GHz range, covering several communication bands from Very Low Frequency (VLF) to Extremely High Frequency (EHF), supporting diverse wireless technologies.
- Omnidirectional Propagation: Radio waves generally radiate in all directions from the transmitter, making them perfect for applications like broadcasting, mobile networks, and Wi-Fi that require wide coverage.
- Penetration Ability: These waves can penetrate non-metallic objects such as walls, glass, and wood, which makes them highly effective for indoor communication systems like Bluetooth, Wi-Fi, and cordless phones.
- Long-Distance Travel: At lower frequencies (e.g., VLF and HF), radio waves can travel great distances via ground wave and skywave propagation. This is especially useful in marine, military, and international radio communication
Radio Waves Types
Radio Waves are part of the electromagnetic spectrum and span a wide range of frequencies. These are further divided into several types (bands) based on their frequency and application. Here’s a breakdown of the main types of radio waves along with their characteristics:
| Band Name | Abbreviation | Frequency Range | Wavelength | Distance Covered | Common Uses / Applications | Internet Speed |
|---|---|---|---|---|---|---|
| Very Low Frequency | VLF | 3 kHz – 30 kHz | 10 km – 100 km | >1000 km | Submarine communication, navigation systems (LORAN), seismic monitoring | <1 kbps (Not used for the internet) |
| Low Frequency | LF | 30 kHz – 300 kHz | 1 km – 10 km | 500 – 1000 km | AM longwave radio, maritime & navigation signals | <1 kbps (Not used for the internet) |
| Medium Frequency | MF | 300 kHz – 3 MHz | 100 m – 1 km | 100 – 500 km | AM radio broadcasting, maritime communication | <1 kbps (Not used for the internet) |
| High Frequency | HF | 3 MHz – 30 MHz | 10 m – 100 m | 30 – 300 km (skywave) | Shortwave radio, amateur radio, and military communication | <10 kbps (Not commonly used for the internet) |
| Very High Frequency | VHF | 30 MHz – 300 MHz | 1 m – 10 m | 10 – 100 km | FM radio, TV broadcasts, air traffic control, 2-way radios | <100 kbps – 1 Mbps (Analog TV & Radio) |
| Ultra High Frequency | UHF | 300 MHz – 3 GHz | 10 cm – 1 m | 1 – 10 km | Wi-Fi (2.4 GHz), Bluetooth, Mobile phones (2G–4G), TV, GPS | 1 Mbps – 1 Gbps (Wi-Fi, Mobile Internet) |
| Super High Frequency | SHF | 3 GHz – 30 GHz | 1 cm – 10 cm | <1 – 5 km | Wi-Fi (5 GHz), 5G, satellite communication, radar, microwave links | 1 Gbps – 10 Gbps (5G, Satellite Internet) |
| Extremely High Frequency | EHF | 30 GHz – 300 GHz | 1 mm – 1 cm | <1 km | Advanced 5G (mmWave), remote sensing, radio astronomy, military radar | 10 Gbps and above (5G mmWave, Experimental) |
Imortant: Higher frequencies always hold shorter wavelengths, which provide higher speed (can carry many bits per cycle), cover shorter distances (shorter wavelengths always lose faster energy as they travel), and are more easily blocked by obstacles. In comparison, lower frequencies can travel further and penetrate better through buildings, water, or the ground.
2. Microwaves
Microwaves are a type of electromagnetic wave with shorter wavelengths and higher frequencies than radio waves. They lie between radio waves and infrared waves in the electromagnetic spectrum. Microwaves are widely used for communication, radar systems, and cooking due to their ability to carry high data rates, penetrate through various materials, and be easily focused into narrow beams.
Microwaves are generated by specialized devices such as magnetrons, klystrons, and solid-state oscillators. Their ability to travel in straight lines and be directed precisely makes them suitable for applications requiring focused energy and directional communication.
Characteristics of Microwaves
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Shorter Wavelength: Microwaves have wavelengths ranging from 1 millimeter to 30 centimeters, which allows them to be easily focused and reflected. This property makes them ideal for radar and point-to-point communication.
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Higher Frequency: Operating between 300 MHz and 300 GHz, microwaves fall within the Ultra High Frequency (UHF), Super High Frequency (SHF), and Extremely High Frequency (EHF) bands. These frequencies support high-bandwidth data transmission, including 5G and satellite internet.
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Line-of-Sight Propagation: Microwaves typically travel in straight lines and require a clear line of sight between the transmitter and receiver, especially at higher frequencies. This makes them suitable for satellite links, microwave towers, and radar systems.
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Absorption by Moisture: Microwaves are absorbed by water molecules, which is the principle behind microwave ovens. This property also affects signal strength during heavy rain in microwave communication (known as rain fade).
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High Bandwidth: Because of their high frequency, microwaves can support very large bandwidths, enabling high-speed internet and large-volume data transmission.
Microwave Frequency Bands and Uses
Microwaves are classified into different bands according to their frequency, each serving specific applications. Here’s a breakdown of microwave bands, their characteristics, and common uses.
| Band Name | Frequency Range | Wavelength Range | Common Applications | Typical Data Rate / Internet Speed |
|---|---|---|---|---|
| UHF (Microwave Start) | 300 MHz – 1 GHz | 30 cm – 1 m | Digital TV, mobile phones (2G), some Wi-Fi (802.11ah) | Up to 10 Mbps (mobile) |
| L-Band | 1 GHz – 2 GHz | 15 cm – 30 cm | GPS, mobile phones (3G), satellite phones, air traffic surveillance | 1 – 10 Mbps (3G, GPS) |
| S-Band | 2 GHz – 4 GHz | 7.5 cm – 15 cm | Radar, WiMAX, 4G LTE, weather radar, and some satellite communications | 10 – 100 Mbps (4G, WiMAX) |
| C-Band | 4 GHz – 8 GHz | 3.75 cm – 7.5 cm | Satellite TV, VSAT, long-distance microwave links, 5G (low-band) | 100 Mbps – 1 Gbps (Satellite, 5G) |
| X-Band | 8 GHz – 12 GHz | 2.5 cm – 3.75 cm | Military radar, weather radar, satellite downlinks | Up to 1 Gbps (specialized) |
| Ku-Band | 12 GHz – 18 GHz | 1.7 cm – 2.5 cm | Direct broadcast satellite (DTH), VSAT, satellite internet | 1 – 10 Gbps (Satellite Internet) |
| K-Band | 18 GHz – 27 GHz | 1.1 cm – 1.7 cm | Radar, space communication, Earth observation | 1 – 10 Gbps (Research/Specialized) |
| Ka-Band | 27 GHz – 40 GHz | 0.75 cm – 1.1 cm | Advanced satellite internet (e.g., Starlink), 5G mmWave | 10+ Gbps (5G mmWave, Satellite) |
| V-Band | 40 GHz – 75 GHz | 4 mm – 7.5 mm | Millimeter-wave 5G, secure military communication | 10 – 20 Gbps (mmWave) |
| W-Band | 75 GHz – 110 GHz | 2.7 mm – 4 mm | High-resolution radar, imaging, and automotive radar | 10 + Gbps (Experimental/Imaging) |
| mmWave Band | 30 GHz – 300 GHz | 1 mm – 10 mm | 5G, high-speed internet, radar, and scientific research | 10 Gbps and above |
| EHF (Microwave End) | 100 GHz – 300 GHz | 1 mm – 3 mm | Space research, advanced military radar, and radio astronomy | Ultra-high data rates (Experimental) |
Microwaves are indispensable to modern life, powering everything from microwave ovens and wireless internet to radar systems and space exploration. Their ability to carry large amounts of data with minimal delay is key to the evolution of next-gen technologies like 5G, satellite internet, and autonomous navigation.
3. Infrared (IR) Waves
Infrared (IR) waves are electromagnetic waves with a higher frequency and shorter wavelength than microwaves and radio waves. They are primarily associated with heat and thermal radiation, as most objects at room temperature emit infrared radiation. IR waves are widely used in remote controls, thermal imaging, communication, night vision, and sensor technologies. Infrared waves are emitted by any object with a temperature above absolute zero and are detected using sensors or specialized cameras.
Characteristics of Infrared Waves
- Medium Wavelength: Infrared waves have wavelengths ranging from about 700 nanometers (nm) to 1 millimeter (mm), falling between visible light and microwaves in the electromagnetic spectrum.
- Moderate Frequency: They operate in the range of 300 GHz to 430 THz, providing enough energy to interact with molecular vibrations and heat emissions.
- Heat Radiation: All objects with a temperature above absolute zero emit infrared radiation. The intensity increases with temperature, making IR ideal for thermal imaging, night vision, and temperature sensing.
- Line-of-Sight Propagation: Infrared signals typically require a clear line of sight, especially for communication and remote controls. Unlike radio waves, IR waves cannot penetrate walls or opaque objects.
- Short to Medium Range Communication: IR communication is used for short-range, high-speed, and secure data transfer in devices like TV remotes, wireless headphones, and data transmission between devices (e.g., IR blasters).
Comparison: Radio Waves, Microwaves, and Infrared
| Parameter | Radio Waves | Microwaves | Infrared (IR) Waves |
|---|---|---|---|
| Position in EM Spectrum | Lowest frequency, longest wavelength | Between radio and infrared | Between microwaves and visible light |
| Wavelength Range | ~1 mm – 100 km | ~1 mm – 30 cm | ~700 nm – 1 mm |
| Frequency Range | 3 kHz – 300 GHz | 300 MHz – 300 GHz | 300 GHz – 430 THz |
| Energy Level | Lowest | Moderate | Higher than radio/microwaves, lower than visible light |
| Propagation | Omnidirectional, long-distance, diffracts around obstacles | Line-of-sight or focused beams | Line-of-sight does not penetrate walls well |
| Penetration | Penetrates buildings and obstacles well | Can penetrate through walls (limited for higher frequencies) | Poor penetration; blocked by most solids |
| Main Source | Electrical circuits, antennas | Magnetrons, klystrons, oscillators | Thermal radiation from objects, IR LEDs, lasers |
| Detection | Antennas | Waveguides, dishes | IR sensors, photodiodes, thermal cameras |
| Typical Applications | AM/FM radio, TV, mobile phones, Bluetooth, satellite communication | Radar, microwave ovens, Wi-Fi, 5G, satellite TV | Remote controls, thermal imaging, night vision, optical fibers |
| Internet Capability | High (UHF/SHF bands used in Wi-Fi, 4G/5G) | Very high (used in Wi-Fi, 5G, point-to-point links) | High (in optical communication), limited for short-range |
| Effect of Obstacles | Low to moderate effect | Moderate effect; high frequencies blocked easily | Strongly affected; blocked by walls and fog |
| Health Impact | Generally safe at low power levels | Safe at moderate levels, excessive exposure may cause heating | Generally safe; can cause heating at high power |
Transmission Impairment
There are three major types of transmission impairment, explained under
- Attenuation: The strength of the signal decreases when the distance increases, which causes the loss of energy.
- Distortion: Distortion occurs when there is a change in the shape of the signal. Changing the shape of the signal means the signal changes its amplitude.
- Noise: When data is transmitted over a communication medium, some unwanted signals may be added to it, which creates noise.