1. What IEEE 802.11 Is
IEEE 802.11 is a family of standards created by the Institute of Electrical and Electronics Engineers (IEEE) for wireless local area networking (WLAN). It defines:
- Physical layer (PHY): radio frequency, modulation, coding
- MAC layer: framing, addressing, medium access control
- Interoperability: ensures devices from different vendors can talk
Think of it as the “rulebook” for Wi-Fi.
2. Wi-Fi Generations
Marketing names (Wi-Fi 4, 5, 6…) are Wi-Fi Alliance simplifications of IEEE 802.11 amendments:
| Wi-Fi Gen | IEEE Name | Year Ratified | Max Theoretical Speed |
|---|---|---|---|
| Wi-Fi 1 | 802.11b | 1999 | 11 Mbps |
| Wi-Fi 2 | 802.11a | 1999 | 54 Mbps |
| Wi-Fi 3 | 802.11g | 2003 | 54 Mbps |
| Wi-Fi 4 | 802.11n | 2009 | 600 Mbps |
| Wi-Fi 5 | 802.11ac | 2013 | ~6.9 Gbps |
| Wi-Fi 6 | 802.11ax | 2019 | ~9.6 Gbps |
| Wi-Fi 6E | 802.11ax (6 GHz) | 2021 | ~9.6 Gbps |
| Wi-Fi 7 | 802.11be | ~2024 | >40 Gbps |
3. Detailed 802.11 Standards
802.11 (1997)
- Frequency: 2.4 GHz ISM band
- Speed: 1–2 Mbps
- Modulation: DSSS (Direct Sequence Spread Spectrum) or FHSS (Frequency Hopping Spread Spectrum)
- Very early, almost obsolete immediately.
802.11a (1999)
- Frequency: 5 GHz band
- Speed: Up to 54 Mbps
- Modulation: OFDM (Orthogonal Frequency Division Multiplexing)
- Pros: Less interference than 2.4 GHz
- Cons: Shorter range due to higher frequency absorption.
802.11b (1999)
- Frequency: 2.4 GHz
- Speed: Up to 11 Mbps
- Modulation: DSSS + CCK (Complementary Code Keying)
- Became widely popular due to low cost and decent range.
802.11g (2003)
- Frequency: 2.4 GHz
- Speed: Up to 54 Mbps (like 802.11a)
- Modulation: OFDM for high rates, DSSS for low rates
- Fully backward compatible with 802.11b.
802.11n (Wi-Fi 4) (2009)
- Frequency: 2.4 GHz & 5 GHz (dual-band)
- Speed: Up to 600 Mbps
- Channel Widths: 20 MHz, 40 MHz
- MIMO: Up to 4 spatial streams
- Introduced frame aggregation for better efficiency.
802.11ac (Wi-Fi 5) (2013)
- Frequency: 5 GHz only
- Speed: ~6.9 Gbps (theoretical)
- Channel Widths: 20, 40, 80, 160 MHz
- MIMO: Up to 8 spatial streams
- Introduced MU-MIMO (downlink only in Wave 1; uplink added later)
- Introduced 256-QAM modulation.
802.11ax (Wi-Fi 6/6E) (2019, 6E in 2021)
- Frequency: 2.4, 5, and 6 GHz (6E)
- Speed: ~9.6 Gbps (theoretical)
- OFDMA: Divides channels into smaller subcarriers (Resource Units) for multiple users
- MU-MIMO: Both downlink and uplink
- Target Wake Time (TWT): Power saving for IoT devices
- Introduced 1024-QAM modulation.
802.11be (Wi-Fi 7) (~2024)
- Frequency: 2.4, 5, and 6 GHz
- Speed: >40 Gbps
- Channel Widths: Up to 320 MHz
- MIMO: Up to 16 spatial streams
- Multi-Link Operation (MLO): Use multiple bands simultaneously
- 4096-QAM modulation.
4. Frequencies, Channel Widths & Modulation
- 2.4 GHz: Longer range, more interference (microwaves, Bluetooth). 3 non-overlapping 20 MHz channels (1, 6, 11 in the U.S.).
- 5 GHz: More channels, less interference, shorter range.
- 6 GHz (Wi-Fi 6E & 7): Massive spectrum availability, very low interference, but shortest range.
- Modulation evolution: BPSK → QPSK → 16-QAM → 64-QAM → 256-QAM → 1024-QAM → 4096-QAM (more bits per symbol, higher throughput, shorter range at high modulation).
5. Security Evolution
- WEP (802.11-1997) → Weak, broken.
- WPA (2003) → TKIP, better but still weak.
- WPA2 (2004) → AES-CCMP, robust.
- WPA3 (2018) → SAE handshake, better encryption, forward secrecy.
6. Summary Table
| IEEE Std. | Wi-Fi Name | Year | Band(s) | Max Speed | Key Features |
|---|---|---|---|---|---|
| 802.11 | — | 1997 | 2.4 GHz | 2 Mbps | DSSS/FHSS |
| 802.11a | — | 1999 | 5 GHz | 54 Mbps | OFDM |
| 802.11b | Wi-Fi 1 | 1999 | 2.4 GHz | 11 Mbps | DSSS + CCK |
| 802.11g | Wi-Fi 3 | 2003 | 2.4 GHz | 54 Mbps | OFDM, backward compatible |
| 802.11n | Wi-Fi 4 | 2009 | 2.4/5 GHz | 600 Mbps | MIMO, 40 MHz |
| 802.11ac | Wi-Fi 5 | 2013 | 5 GHz | ~6.9 Gbps | MU-MIMO, 256-QAM |
| 802.11ax | Wi-Fi 6/6E | 2019/2021 | 2.4/5/6 GHz | 9.6 Gbps | OFDMA, TWT, 1024-QAM |
| 802.11be | Wi-Fi 7 | ~2024 | 2.4/5/6 GHz | >40 Gbps | MLO, 320 MHz, 4096-QAM |