Transmission media, also known as communication channels, are the physical pathways through which data signals travel from one device to another in a network. There are two main categories of transmission media: guided media and unguided media.
Guided Media:
Guided media, also referred to as wired or bounded media, use physical cables or wires to transmit data signals. They provide a direct physical connection between devices and offer greater reliability and security compared to unguided media. Common types of guided media include:
- Twisted Pair Cable:
- Consists of pairs of insulated copper wires twisted together.
- Used in telephone lines, Ethernet networks, and DSL (Digital Subscriber Line) connections.
- Available in two main categories: unshielded twisted pair (UTP) and shielded twisted pair (STP).
- Coaxial Cable:
- Consists of a central conductor surrounded by an insulating layer, a metallic shield, and an outer insulating layer.
- Used in cable television (CATV) networks, broadband internet connections, and Ethernet networks.
- Offers higher bandwidth and better shielding compared to twisted pair cable.
- Optical Fiber:
- Transmits data signals using light pulses through a glass or plastic fiber.
- Offers high bandwidth, low attenuation, and immunity to electromagnetic interference.
- Used in long-distance telecommunications, internet backbone networks, and high-speed LANs (Local Area Networks).
Unguided Media:
Unguided media, also known as wireless or unbounded media, transmit data signals through the air without the use of physical cables. They rely on electromagnetic waves to carry signals between devices and are suitable for mobile and remote communication. Common types of unguided media include:
- Radio Waves:
- Used for wireless communication in applications such as radio broadcasting, Wi-Fi networks, and Bluetooth devices.
- Travel long distances and can penetrate obstacles, but are susceptible to interference and attenuation.
- Microwaves:
- Transmit data signals using high-frequency electromagnetic waves.
- Used for point-to-point communication links, satellite communication, and microwave radio relay systems.
- Require clear line-of-sight between transmitting and receiving antennas.
- Infrared Waves:
- Transmit data signals using infrared light waves.
- Used in short-range communication applications such as remote controls, infrared data transmission (IrDA), and proximity sensors.
- Require direct line-of-sight between transmitting and receiving devices.
Guided and unguided media each have their advantages and limitations, and the choice between them depends on factors such as distance, bandwidth requirements, reliability, and environmental conditions. By understanding the characteristics of different transmission media, network engineers can design and implement communication systems that meet the specific needs of their applications.