Lecture 5 - Wireless Medium

Guided Medium to Unguided Medium

• Mobility: The rise of mobile devices created a demand for wireless connectivity. (Early devices were fixed components)
• Electromagnetic Waves were used as the carrier to transmit data through the environment.
• Benefits of Wireless:
  • High speed.
  • Good penetration through obstacles.
  • Wide accessibility.
  • Cost-effectiveness.

Types of Wireless Data Transmission and Technologies

• List of Technologies:
  • Radio Frequency (RF) Transmission
  • Microwave Transmission
  • Infrared Transmission
  • Lightwave Transmission

Radio Frequency Transmission

• Key Points:
  • EM Waves: RF signals are electromagnetic waves.
  • Frequency Range: Typically 3 kHz to 300 GHz.
  • Advantages:
    • Can penetrate obstacles and travel long distances.
    • Relatively inexpensive to generate and transmit.
  • • Short and Long Range: Radio communication is used for both short-range (walkie-talkies) and long-range (AM/FM radio) communication.

Microwave Transmission

• Key Points:
  • Frequency Range: 300 MHz to 300 GHz.
  • Applications: Short and long-range communications, satellite communication, terrestrial microwave links.
  • Advantages:
    • Relatively inexpensive.
    • High bandwidth.
  • Types:
    • Satellite Transmission (SMTS): Uses satellites to relay signals over long distances.
    • Terrestrial Microwave Transmission System (TMTS): Uses ground-based towers to relay signals.

Terrestrial Microwave Transmission System (TMTS)

• Line-of-Sight: Requires a clear path between towers, as signals cannot penetrate obstacles well.
• Directional Antennas: Use parabolic antennas to focus signals.
• Frequency and Speed: Typically uses frequencies in the lower GHz range (4-6 GHz or 21-23 GHz) and speeds of 1 Mbps to 10 Mbps.

Satelite Microwave Transmission System (SMTS)

• How It Works: Satellites in orbit relay signals between ground stations.
• Process:
  • Uplink: Signals are transmitted from a ground station to the satellite.
  • Downlink: The satellite amplifies the signal and transmits it back to another ground station.

Satellite Communication

• Components:
  • Space Segment: The satellites orbiting Earth.
  • Ground Segment: Earth-based transmission and receiving stations.
• Applications:
  • Television distribution, long-distance telephone calls, private business networks, GPS, internet services, satellite phones.

 Characteristics of Satellite Technology

• Advantages: Covers the benefits of using satellite communication.
• Disadvantages:
  • Limited Repair: Difficult and expensive to repair satellites once they are in orbit.
  • Delay: High latency (delay) due to the long distance signals travel.
  • Attenuation: Signal strength decreases over long distances.
  • Mostly One-Way: Primarily used for one-way communication (e.g., satellite TV or radio).
• Best Use Cases:
  • Connecting very remote locations.
  • Emergency and secure communication (military, rescue).

 Infrared Transmission

• Key Points:

  • EM Waves: Infrared radiation is part of the electromagnetic spectrum with longer wavelengths than visible light.
  • Short Range: Used for short-distance communication.
  • Line-of-Sight: Usually requires a clear line of sight between the transmitter and receiver, as IR signals don’t penetrate solid objects well.

• Types:

  • Point-to-Point: Direct communication between two devices.
  • Diffuse Point: A broadcast system where signals are reflected off surfaces to reach multiple devices.

• Components:

  • Transmitter: Photo LED (light-emitting diode).

  • Receiver: Photodiode.

• How it Works: The LED emits modulated light that is captured by the photodiode.

• Applications: Mobile phones, TVs, security systems, laptops, remote controls.

Wi-Fi (Wireless Fidelity)

• History: Introduced in the late 1990s, based on IEEE 802.11 standards.
• Applications: LANs, internet access, short-to-medium-range communication.
• Components: Wi-Fi Access Point (AP) and Stations (devices connected to the network).
• Frequencies: Uses 2.4 GHz, 5 GHz, and 6 GHz.

Cellular Technology

GSM

• Global System for Mobile Communication (GSM)
• Time-Division Multiple Access (TDMA): A technique for sharing the radio spectrum.
• SIM Card: A removable card that stores subscriber information and authentication keys.

GRPS (2.5G)

• Packet Switching: Allows for more efficient data transmission.
• Data Capability: Enabled mobile internet access (email, basic web browsing), though speeds were still limited.

Summary

• Connection media are essential for data communication.
• Different connection technologies have their own advantages and limitations.
• Factors like speed, capacity, cost, and environmental conditions affect the choice of technology.

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