Wireless Transmission Media - IT 709

Overview of Transmission Media

• Transmission methods fall into two main categories: guided and unguided media.
• Guided media include twisted pairs, coaxial cables, and fiber optics which direct electromagnetic waves along a physical path.
• Unguided media involve transmission through the atmosphere or outer space, without a physical guiding medium.

Wireless Transmission Media

• The electromagnetic spectrum includes various types of waves: radio, microwave, infrared, and visible light, essential for wireless communication.
• Higher frequency waves like ultraviolet, X-rays, and gamma rays could transmit data efficiently but are difficult to produce, modulate, and are harmful to health.
• Information capacity of a signal is proportional to its bandwidth and received power, making fiber optics favorable due to high bandwidth.

Electromagnetic Spectrum

• The spectrum includes bands like LF (Low Frequency), MF (Medium Frequency), and HF (High Frequency), denoting different ranges of wavelength and frequency.
• Recent bands are humorously labeled Very, Ultra, Super, Extremely High Frequencies, with the absence of names for frequencies beyond these.

Radio Transmission

• Radio waves are generated easily, travel long distances, and penetrate buildings, making them popular for communication.
• Radio waves are omnidirectional, allowing signal reception without precise transmitter-receiver alignment.
• VLF, LF, and MF bands are effective for indoor signal penetration, though they have low bandwidth, limiting data communication.

Microwave Transmission

• Microwaves travel in straight lines above 100 MHz, allowing for focused signals via parabolic antennas, which improves signal-to-noise ratio.
• They form the foundation for long-distance telephone transmission prior to optical fiber technology.
• Repeaters are necessary for maintaining signal over long distances, requiring precise tower placement to avoid obstacles.

Multipath Fading and Water Absorption

• Microwaves can experience multipath fading, resulting in signal cancellation when delayed waves arrive out of phase with direct waves.
• At frequencies around 4 GHz, water absorption becomes significant, particularly during rain, requiring alternate routing for affected links.

Lightwave Transmission

• Free-space optics allows unguided optical signaling, often used to connect LANs through rooftop lasers.
• Optical signals provide high bandwidth, enhanced security against tapping, and easy installation without licensing requirements.
• Environmental factors like heat-induced air turbulence can affect the stability of optical signals.

Communication Satellites

• Satellites act as relay stations, receiving signals on one frequency, amplifying them, and transmitting on another.
• Types of satellites include Geostationary (GEO), Medium-Earth Orbit (MEO), and Low-Earth Orbit (LEO), each with specific uses in television, phone networking, and business communications.
• Global coverage requires consideration of satellite altitude and round-trip delay times for operational efficiency.

This quiz covers the essentials of wireless transmission media within the context of mobile communications and technology. Topics include the electromagnetic spectrum, radio transmission, and microwave transmission. Perfect for students in IT 709, it aims to solidify understanding of these critical concepts.