802.11 PROTOCOL INTELLIGENCE
Wi-Fi Generations - 1997 to Wi-Fi 7
Every Wi-Fi generation adds new PHY capabilities on top of the same 802.11 MAC framework. The CSMA/CA mechanism from 1997 still runs in every Wi-Fi 7 deployment. Understanding what changed per generation - and what stayed the same - is foundational for CWNA and protocol analysis.
IEEE 802.11-2020 802.11be-2024 CWNA Domain
Legacy
1997
2 Mbps
Wi-Fi 1
1999
11 Mbps
Wi-Fi 2
1999
54 Mbps
Wi-Fi 3
2003
54 Mbps
Wi-Fi 4
2009
600 Mbps
Wi-Fi 5
2013
6.93 Gbps (Wave 2)
Wi-Fi 6 / 6E
2021
9.6 Gbps
Wi-Fi 7
2024
46 Gbps
Wi-Fi 8
~2028
100+ Gbps (target)
Legacy 802.11 IEEE 1997
First standard - baseline for all future 802.11
2 Mbps
2.4 GHz
Key features
▸First Wi-Fi standard
▸FHSS: 79×1 MHz hops
▸DSSS: 11-chip Barker sequence
▸CSMA/CA MAC
▸DCF + optional PCF
▸Optional infrared PHY
PHY Details
PHY FHSS / DSSS / IR
Modulation GFSK / DBPSK / DQPSK
Channels 3 non-overlap (2.4)
CWNA EXAM NOTE
Know FHSS vs DSSS distinction, slot time 20µs, SIFS 10µs
Wi-Fi 1 802.11b IEEE 1999 WFA: 802.11b
HR-DSSS via CCK pushed 802.11 to practical speeds. WEP security was fatally flawed.
11 Mbps
2.4 GHz
Key features
▸CCK coding: 5.5 & 11 Mbps
▸22 MHz channel width
▸Long preamble 192µs / Short 96µs
▸WEP (RC4) - already broken by 2001
▸WFA certification begins 2000
▸Still most deployed 2.4 GHz legacy
PHY Details
PHY HR-DSSS
Modulation DBPSK / DQPSK / CCK
Channels 3 non-overlap (1/6/11)
CWNA EXAM NOTE
CCK: 8-chip complex spreading. Rates: 1/2/5.5/11 Mbps. Long vs short preamble.
Wi-Fi 2 802.11a IEEE 1999 WFA: 802.11a
OFDM in 5 GHz. Same time as 802.11b but commercially slower to deploy. Still the OFDM blueprint used in all future standards.
54 Mbps
5 GHz
Key features
▸5 GHz: no microwave interference
▸OFDM: 52 subcarriers, 312.5 kHz spacing
▸8 data rates: 6/9/12/18/24/36/48/54 Mbps
▸SIFS=16µs, slot=9µs (faster than 802.11b)
▸DFS not yet required in original spec
▸Less range than 2.4 GHz (higher freq attenuation)
PHY Details
PHY OFDM
Modulation BPSK → 64-QAM
Channels 23 non-overlap (UNII-1/2/3)
CWNA EXAM NOTE
OFDM subcarrier spacing 312.5 kHz. 64-point FFT. Know UNII band boundaries.
Wi-Fi 3 802.11g IEEE 2003 WFA: 802.11g
54 Mbps in 2.4 GHz. Protection overhead in mixed b/g cut effective throughput ~50%.
54 Mbps
2.4 GHz
Key features
▸ERP-OFDM: 54 Mbps in 2.4 GHz
▸Backward compat: ERP-DSSS/CCK at 11 Mbps
▸Protection mode (CTS-to-self) in mixed b/g
▸ERP IE in Beacon: NonERP_Present bit
▸Short slot time 9µs (pure-g network)
▸Long slot time 20µs (mixed b/g network)
PHY Details
PHY ERP-OFDM
Modulation BPSK → 64-QAM + CCK compat
Channels 3 non-overlap (2.4)
CWNA EXAM NOTE
Protection mode, CTS-to-self, NonERP_Present. Short vs long slot time.
Wi-Fi 4 802.11n IEEE 2009 WFA: Wi-Fi 4
MIMO and aggregation transformed throughput. First dual-band standard. Most important generation for understanding modern MAC behavior.
600 Mbps
2.4 / 5 GHz
Key features
▸MIMO: up to 4×4 spatial streams
▸Channel bonding: 20 → 40 MHz
▸A-MPDU aggregation (max 64 KB, 64 subframes)
▸Block ACK: compressed 64-bit bitmap
▸Short Guard Interval: 400ns (+11% throughput)
▸STBC: spatial diversity without MIMO receiver
▸HT-Mixed and HT-Greenfield preambles
▸SMPS: spatial multiplexing power save
PHY Details
PHY HT-OFDM (MIMO)
Modulation BPSK → 64-QAM (MCS 0-76)
Channels 3 (2.4) / 23+ (5)
CWNA EXAM NOTE
MCS index 0-76, 20/40 MHz, HT-MF vs HT-GF, A-MPDU/Block ACK, SMPS.
Wi-Fi 5 802.11ac IEEE 2013 WFA: Wi-Fi 5
256-QAM + wider channels + DL MU-MIMO = Gbps class. UL MU-MIMO missing (added in ax).
6.93 Gbps (Wave 2)
5 GHz only
Key features
▸5 GHz only - no 2.4 GHz
▸80 / 80+80 / 160 MHz channel bonding
▸256-QAM: 8 bits/symbol (vs 64-QAM 6 bps)
▸DL MU-MIMO: up to 4 users simultaneously
▸Up to 8 spatial streams
▸A-MPDU max 1 MB (vs 64 KB in 802.11n)
▸Explicit beamforming via NDP sounding mandatory
▸A-MPDU mandatory for all VHT transmissions
PHY Details
PHY VHT-OFDM
Modulation BPSK → 256-QAM (MCS 0-9)
Channels 23+ non-overlap (5)
CWNA EXAM NOTE
MCS 0-9, NSS 1-8. VHT-SIG-A/B. Wave 1 (80 MHz, 4×4 MU-MIMO) vs Wave 2 (160 MHz, 8×8).
Wi-Fi 6 / 6E 802.11ax IEEE 2021 WFA: Wi-Fi 6 / Wi-Fi 6E
Efficiency revolution. Shift from speed to capacity. OFDMA serves many devices per TXOP. BSS Color reduces OBSS deferral.
9.6 Gbps
2.4 / 5 / 6 GHz
Key features
▸OFDMA: multi-user per PPDU (UL + DL)
▸BSS Color (6-bit) - Spatial Reuse
▸Target Wake Time (TWT) - IoT battery life
▸UL MU-MIMO: 8×8 (first time UL MU added)
▸1024-QAM: 10 bits/symbol at MCS 10/11
▸HE PPDU: 4× narrower subcarriers (78.125 kHz)
▸Wi-Fi 6E: 6 GHz, 1200 MHz clean spectrum
▸PMF mandatory, WPA3 required on 6 GHz
PHY Details
PHY HE-OFDMA
Modulation BPSK → 1024-QAM (MCS 0-11)
Channels 3+23+59 = 85
CWNA EXAM NOTE
RU sizes: 26/52/106/242/484/996 tones. Trigger Frame. OBSS_PD. R-TWT.
Wi-Fi 7 802.11be IEEE 2024 WFA: Wi-Fi 7
MLO is the architectural shift - one logical device, multiple simultaneous links. Everything else (4096-QAM, 320 MHz) amplifies that foundation.
46 Gbps
2.4 / 5 / 6 GHz (MLO)
Key features
▸MLO: simultaneous multi-band operation
▸320 MHz channels (6 GHz only)
▸4096-QAM: 12 bits/symbol (MCS 12/13)
▸Preamble Puncturing: skip occupied sub-channels
▸16 spatial streams (vs 8 in ax)
▸Multi-AP Coordination (MAP)
▸TID-to-Link Mapping (TLM)
▸U-SIG preamble field for version-agnostic decode
PHY Details
PHY EHT-OFDMA
Modulation BPSK → 4096-QAM (MCS 0-13)
Channels 85 total
CWNA EXAM NOTE
MLO modes: STR, NSTR, EMLSR, EMLMR. AP MLD vs non-AP MLD. EHT-SIG (MU only).
Wi-Fi 8 802.11bn IEEE ~2028 WFA: Wi-Fi 8 (upcoming)
Multi-AP coordination at scale. AI-native resource management. Study group phase - no ratified standard yet.
100+ Gbps (target)
2.4 / 5 / 6 GHz
Key features
▸Ultra High Reliability (UHR)
▸Coordinated multi-AP OFDMA (Joint Tx)
▸Distributed MIMO across synchronized APs
▸Sub-1 ms latency target
▸AI/ML channel prediction (AIML TIG)
▸Study group: formed 2020, Draft target 2027-2028
PHY Details
PHY UHR (Ultra High Reliability)
Modulation TBD
Channels TBD
CWNA EXAM NOTE
AI/ML TIG - 4 use cases: CSI compression, enhanced roaming, DRL channel access, MAPC.
Comparison Table
| Generation | Standard | Year | Band | Max Rate | PHY | Key Addition |
|---|---|---|---|---|---|---|
| Legacy | 802.11 | 1997 | 2.4 GHz | 2 Mbps | FHSS / DSSS / IR | First Wi-Fi standard |
| Wi-Fi 1 | 802.11b | 1999 | 2.4 GHz | 11 Mbps | HR-DSSS | CCK coding: 5.5 & 11 Mbps |
| Wi-Fi 2 | 802.11a | 1999 | 5 GHz | 54 Mbps | OFDM | 5 GHz: no microwave interference |
| Wi-Fi 3 | 802.11g | 2003 | 2.4 GHz | 54 Mbps | ERP-OFDM | ERP-OFDM: 54 Mbps in 2.4 GHz |
| Wi-Fi 4 | 802.11n | 2009 | 2.4 / 5 GHz | 600 Mbps | HT-OFDM (MIMO) | MIMO: up to 4×4 spatial streams |
| Wi-Fi 5 | 802.11ac | 2013 | 5 GHz only | 6.93 Gbps (Wave 2) | VHT-OFDM | 5 GHz only - no 2.4 GHz |
| Wi-Fi 6 / 6E | 802.11ax | 2021 | 2.4 / 5 / 6 GHz | 9.6 Gbps | HE-OFDMA | OFDMA: multi-user per PPDU (UL + DL) |
| Wi-Fi 7 | 802.11be | 2024 | 2.4 / 5 / 6 GHz (MLO) | 46 Gbps | EHT-OFDMA | MLO: simultaneous multi-band operation |
| Wi-Fi 8 | 802.11bn | ~2028 | 2.4 / 5 / 6 GHz | 100+ Gbps (target) | UHR (Ultra High Reliability) | Ultra High Reliability (UHR) |
// related reference