Communication Hardware & Media
1. Guided (Wired) Transmission Media
Copper (Twisted Pair)
Uses electrical signals to transmit data. Commonly used in LANs (Ethernet).
Pros: Cheap, easy to install, flexible.
Cons: Low bandwidth, high attenuation, susceptible to EMI (Electromagnetic Interference).
Cons: Low bandwidth, high attenuation, susceptible to EMI (Electromagnetic Interference).
Fiber Optic
Uses pulses of light through glass fibers. Used for long-distance backbones.
Pros: Huge bandwidth, very low attenuation, immune to EMI.
Cons: Expensive, fragile, requires specialized equipment to splice.
Cons: Expensive, fragile, requires specialized equipment to splice.
2. Unguided (Wireless) Transmission Media
Radio, Microwave, and Satellite
Uses electromagnetic waves to transmit data through the air or vacuum.
| Type | Description | Use Case |
|---|---|---|
| Radio Waves | Omnidirectional waves; can pass through walls. | Wi-Fi, Bluetooth. |
| Microwaves | Directional (Line-of-Sight). Requires towers. | Mobile phone networks (4G/5G). |
| Satellites | Microwaves sent to space and relayed back. | Global GPS, Satellite TV, Starlink. |
3. Performance Metrics
- Bandwidth: The maximum rate of data transfer across a path (bits per second).
- Attenuation: The gradual loss of signal strength as it travels through a medium.
- Propagation Delay: The time it takes for a signal to travel from sender to receiver (critical for Satellites due to distance).
4. Summary Table
| Media | Bandwidth | Distance (max) | Interference |
|---|---|---|---|
| Twisted Pair | Up to 10 Gbps | ~100 meters | High |
| Fiber Optic | 100+ Gbps | 100+ kilometers | None |
| Satellite | Variable | Global | Affected by weather |
⚠️ AS-Level Exam Term: Crosstalk
This is a type of EMI where signals from one wire "leak" into another nearby wire. This is why copper wires are twisted in pairs—to cancel out this interference.