Wi-Fi Standards
[!NOTE] This module explores the core principles of Wi-Fi Standards, deriving solutions from first principles and hardware constraints to build world-class, production-ready expertise.
1. What is Wi-Fi?
Wi-Fi is a family of wireless network protocols based on the IEEE 802.11 family of standards. It uses radio waves to transmit data.
2. The 802.11 Evolution
| Standard | Release | Band | Max Speed | Marketing Name |
|---|---|---|---|---|
| 802.11b | 1999 | 2.4 GHz | 11 Mbps | - |
| 802.11g | 2003 | 2.4 GHz | 54 Mbps | - |
| 802.11n | 2009 | 2.4/5 GHz | 600 Mbps | Wi-Fi 4 |
| 802.11ac | 2013 | 5 GHz | 1.3 Gbps | Wi-Fi 5 |
| 802.11ax | 2019 | 2.4/5/6 GHz | 9.6 Gbps | Wi-Fi 6 |
3. 2.4 GHz vs. 5 GHz
- 2.4 GHz: Longer range, better at penetrating walls. High interference (used by Microwaves, Bluetooth, Zigbee).
- 5 GHz: Faster speeds, less interference. Short range, easily blocked by walls.
4. CSMA/CA (Collision Avoidance)
Unlike Ethernet, wireless adapters cannot detect collisions while they are transmitting (they can’t listen and talk on the same frequency simultaneously). Instead of Detection, they use Avoidance.
- DIFS: Listen for a clear airwave.
- RTS/CTS: Request to Send / Clear to Send.
- Node A sends RTS to the Access Point (AP).
- AP responds with CTS, telling everyone else to be quiet.
- ACK: Receiver must send an Acknowledgement for every frame. If no ACK, sender assumes a collision and retries.
5. Interactive: Channel Interference
See why we use channels 1, 6, and 11 on 2.4 GHz.
CH 1
CH 2
CH 6
CH 11
Channels in the 2.4GHz spectrum overlap.
6. Modern Technologies
- MIMO (Multiple Input Multiple Output): Using multiple antennas to send different data streams simultaneously.
- Beamforming: Focusing the radio signal directly toward the device rather than radiating in all directions.