Back to Computer Networks
Physical Layer
Transmission media, signal encoding, and multiplexing techniques
Key Concepts
Signal transmission, encoding schemes, multiplexing methods
Applications
Network cabling, wireless communication, signal processing
Exam Focus
Media comparison, encoding techniques, multiplexing calculations
Physical Layer Topics
Transmission Media Details
Guided Transmission Media
Twisted Pair Cable
Categories: UTP (Unshielded), STP (Shielded)
Bandwidth: Up to 100 MHz
Applications: Ethernet, Telephone systems
Advantages: Low cost, easy installation
Disadvantages: Limited bandwidth, susceptible to interference
Coaxial Cable
Categories: Thin coax (10Base2), Thick coax (10Base5)
Bandwidth: Up to 1 GHz
Applications: Cable TV, Legacy Ethernet
Advantages: Higher bandwidth than twisted pair
Disadvantages: More expensive, rigid
Fiber Optic Cable
Categories: Single-mode, Multi-mode
Bandwidth: Up to 100 THz
Applications: Long-distance communication, Backbone networks
Advantages: Very high bandwidth, immune to interference
Disadvantages: Expensive, difficult installation
Unguided Transmission Media
Radio Waves
Frequency: 3 KHz - 1 GHz
Propagation: Ground wave, Sky wave
Applications: AM/FM radio, TV broadcasting
Characteristics: Omnidirectional, can penetrate walls
Microwaves
Frequency: 1 GHz - 300 GHz
Propagation: Line of sight
Applications: Satellite communication, Cellular networks
Characteristics: Unidirectional, affected by weather
Infrared
Frequency: 300 GHz - 400 THz
Propagation: Line of sight
Applications: Remote controls, Short-range communication
Characteristics: Cannot penetrate walls, high security
📝 Exam Preparation Tips
Key Topics to Remember
- • Compare guided vs unguided transmission media
- • Understand different encoding techniques (NRZ, Manchester)
- • Know multiplexing methods and their applications
- • Practice bandwidth and efficiency calculations
- • Remember signal characteristics and frequencies
Common Exam Questions
- • "Compare fiber optic vs copper cables" (5 marks)
- • "Explain Manchester encoding with diagram" (4 marks)
- • "Calculate efficiency of FDM system" (3 marks)
- • "Differentiate between FDM and TDM" (6 marks)
- • "Draw signal waveforms for NRZ encoding" (4 marks)