Communication Channels and Technologies

Posted on Feb 8, 2025 in Computer Engineering

Communication Channels

A communication channel routes messages from sender to receiver. Channels can be guided (e.g., copper wires, optical fiber) or unguided (e.g., air, vacuum).

Types of Communication Channels

  • Dedicated Links: Establish an exclusive channel between two interlocutors.
    • Point-to-Point: One sender and one receiver.
    • Multipoint: Multiple callers at either end.
  • Shared Networks: Callers connect to a network node to contact others.
    • Dissemination (Broadcast): Transmitter sends data to multiple receivers (e.g., TV).
    • Switching (Circuit-Switched/Packet-Switched): A temporary channel is established for communication (e.g., telephone, internet).

Signal Transmission

Information is converted into electrical signals for transmission. These signals can be:

  • Periodic Sinusoidal: Characterized by amplitude, period, and frequency.
  • Random: Amplitude changes over time (e.g., voice).

Modulation

Modulation is used to transmit baseband signals by modifying a carrier signal. Common types include:

  • Amplitude Modulation (AM): Carrier amplitude varies with the modulating signal.
  • Frequency Modulation (FM): Carrier frequency varies with the modulating signal.

Digital Modulation

Analog signals are sampled and quantized, with each sample encoded in binary for transmission.

Transmission Media

Copper Cables

  • Coaxial: Central conductor insulated and shielded by a metallic mesh.
  • Twisted Pair: Pairs of wires twisted together.

Optical Fibers

  • Single Mode: Small core diameter, minimal signal distortion.
  • Multimode: Larger core diameter, more distortion, shorter transmission distances.

Electromagnetic Waves

Electromagnetic waves are used in wireless communication. Wavelength is related to frequency and the speed of light.

Wireless Communication Links

  • Proximity: Short-range communication (e.g., Wi-Fi, Bluetooth).
  • Terrestrial: Long-range communication between ground stations (e.g., TV, radar).
  • Space: Communication via satellites (e.g., meteorology, telephony).

Satellite Orbits

  • LEO (Low Earth Orbit)
  • MEO (Medium Earth Orbit)
  • HEO (Highly Elliptical Orbit)
  • GEO (Geostationary Orbit)

Applications of Communication Technologies

  • Telecommunications and Navigation
  • Positioning and Location
  • Observation and Meteorology
  • Cartography and Research