Computer Networks Part II: Transmission Media

Computer Networks - Part II: Transmission Media

• Transmission media carries signals from one computer to another.
• Two types:
  • Guided media (Wired Technology): Data signals are physically transferred through a wired medium.
  • Unguided media (Wireless Technology): Data is transmitted through waves.
• Twisted pair cable (Ethernet Cable): A common transmission medium consisting of two insulated wires twisted in a spiral pattern.
  • Used for short and medium-range communication.
  • Suitable for cables longer than a few hundred meters.
  • Twisting of wires prevents cross-talk.
  • Two types:
    • Shielded Twisted Pair (STP): Used in older telephone networks and for network and data communications to reduce outside interference.
    • Unshielded Twisted Pair (UTP): Used for television signals and by corporations in building security systems.
• Advantages of Twisted Pair Cable:
  • Simple, lightweight, easy to install and maintain
  • Capable of carrying signals over long distances
  • Physically flexible
  • Inexpensive for low-speed applications
• Disadvantages of Twisted Pair Cable:
  • Low bandwidth capabilities, not suitable for broadband applications
  • Prone to noise signals
  • Easy to break due to its thin structure

Coaxial Cable

• Consists of a central copper wire surrounded by PVC insulation, a copper mesh sleeve, and another layer of PVC
• More expensive than twisted pair cable but performs better.
• Advantages:
  • Better data transmission characteristics than twisted pair
  • Used for broadband communication (multiple channels simultaneously)
  • Offers high bandwidth (up to 400 Mbps)
  • Can be used as a basis for a shared cable network
  • Better transmission quality than twisted pair
• Disadvantages:
  • More expensive than twisted pair
  • Difficult to manage and reconfigure

Fiber Optic Cables

• Made of thin strands of glass or glass-like material that transmit light.
• Light sources: laser diodes (LD) or light-emitting diodes (LED)
• Modulation techniques are used for data transmission
• Three parts: core, cladding, and protective coating
• Advantages:
  • Immune to electrical and magnetic interference
  • Suitable for harsh industrial environments
  • Guarantees secure transmission and has a high capacity
• Disadvantages:
  • Difficult to install and maintain
  • Expensive

Infrared Communication

• Infrared light transmits data through the air.
• Requires a transceiver in both communicating devices.
• Line-of-sight transmission; sensitive to atmospheric conditions (fog)
• Advantages:
  • Low power consumption
  • Simple and inexpensive circuitry
  • Relatively secure due to short range
• Disadvantages:
  • Short range
  • Obstructions (walls, buildings) prevent transmission

Radio Waves

• Transmission using radio frequencies.
• Used in various applications (radio, television, GPS, wireless networks).
• Transmitters encode messages onto sine waves, and receivers decode them.
  • Advantages:
    • Offers mobility
    • Suitable for long-distance communication
    • Can pass through obstacles relatively easily
  • Disadvantages :
    • Insecure communication channels
    • Susceptible to weather changes

Microwave Waves

• Electromagnetic waves in the 2 to 40 GHz frequency range
• Line-of-sight transmission; requires repeaters for long distances.
  • Advantages:
    • Does not require laying cables
    • High-capacity
    • Suitable for long-distance communications
  • Disadvantages:
    • Signals weaken with distance, requiring frequent amplification
    • Installations and maintenance are very expensive
    • Affected by weather conditions

Network Protocols (Protocols)

• Sets of rules for communication between network devices.
• Defines standardized data formats and error correction techniques.
• Includes HTTP, FTP, TCP/IP, SLIP/PPP, SMTP, POP3, HTTPS, TELNET, and VoIP
• HTTP: Protocol for transferring hypertext over the web
• FTP: Protocol for transferring files over the internet
• TCP/IP: Common internet protocol used for communication.

Post Office Protocol Version 3 (POP3)

• Protocol to receive emails, storing them on the server until picked up.

Remote Access Protocol (Telnet)

• Protocol for connecting to remote computers

Chat Protocol and VoIP (Voice over Internet Protocol)

• Real-time informal communication over the Internet (e.g., chatting).
• VoIP enables voice transfer over the internet, using packet switching instead of public switched telephone networks.

Internet/Computer Protocols (GSM, GPRS, 2G, 3G, 4G, 5G)

• GSM: Digital cellular system; frequently used for mobile communication
• GPRS: Data transfer technology used for mobile devices in many countries
• 2G, 3G, 4G, 5G: Successively improved generations of wireless mobile technology, offering improved data speeds and functionalities.

Mobile Processors

• Central Processing Unit (CPU) chips designed for mobile devices such as tablets and smartphones.
• Consume lower voltages and generate less heat than processors in desktop computers.

Network Devices (Modem, RJ45 connector, Repeater, Hub)

• Modem: Converts digital signals to analog signals (and vice versa), for transmission over telephone lines
• RJ45 connector: Standard 8-pin connector for Ethernet cables (network cables)
• Repeater: Regenerates and retransmits signals to extend network
• Hub: A network device that connects multiple devices on a network.

Network Topologies (Bus, Star, Tree, Mesh)

• Bus: A single cable connects all devices, and data travels across the cable to all connected devices.
• Star: Each device is connected to a central hub, which manages the communication between devices.
• Tree: A combination of star and bus network topologies, incorporating a hierarchical structure.
• Mesh: Each device is connected to multiple other devices, with multiple possible paths for data transmission.