Transmission Media

Transmission media enable the transfer of electronic signals, typically binary pulses, between computers. These signals span frequencies from radio waves to microwaves and infrared light, each requiring different media. Radio frequencies, often used in LANs, can be transmitted via twisted pair or coaxial cables. Microwaves are used for focused transmissions between two points, such as between earth stations and satellites. 

Transmission Media characteristics 

1.  Cost: Cost is a key factor in networking decisions. Newer technologies tend to be faster but more expensive. Network designers must balance cost and robustness. 
2. Installation Requirements: Some transmission media require skilled labor, increasing costs and causing delays. A physical layout of the network is needed before installation
3. Bandwidth: Bandwidth measures a medium's data transmission capacity, typically in bits per second. Shorter cables have higher bandwidth, while longer cables may cause signal deterioration
4. Band Usage (Baseband or Broadband): Baseband uses the entire medium's capacity for one channel, common in LANs. Broadband allows multiple channels to share bandwidth, using techniques like Frequency Division Multiplexing (FDM) for analog signals.
5. Attenuation: Attenuation refers to signal weakening over distance. Repeaters can regenerate signals to counteract this effect. 
6. Electromagnetic Interference (EMI): EMI distorts signals due to external noise. Crosstalk, a type of EMI, occurs when signals from adjacent wires interfere with each other, posing a problem in networks with many cables.