- WiFi standards are defined by the IEEE 802.11 working group and specify the physical layer (PHY) and medium access control (MAC) protocols for wireless LANs
- Each standard operates in specific frequency bands and provides different data rates, range capabilities, and features
- Standards are backward compatible (newer APs can support older client devices, but performance limited to lowest common denominator)
Evolution and Frequency Bands
- 2.4 GHz band: Longer range but more congested (only 3 non-overlapping channels: 1, 6, 11)
- 5 GHz band: Shorter range but less congested with more available channels (up to 25 non-overlapping channels)
- 6 GHz band: Latest addition with even more spectrum availability and reduced interference
| Standard | Year | Frequency | Max Data Rate | Range | Key Features |
|---|---|---|---|---|---|
| 802.11 | 1997 | 2.4 GHz | 2 Mbps | ~20m indoor | Original standard (legacy) |
| 802.11b | 1999 | 2.4 GHz | 11 Mbps | ~35m indoor | DSSS modulation |
| 802.11a | 1999 | 5 GHz | 54 Mbps | ~25m indoor | OFDM modulation |
| 802.11g | 2003 | 2.4 GHz | 54 Mbps | ~35m indoor | OFDM + backward compatible with 11b |
| 802.11n (Wi-Fi 4) | 2009 | 2.4/5 GHz | 600 Mbps | ~50m indoor | MIMO, channel bonding (40 MHz) |
| 802.11ac (Wi-Fi 5) | 2013 | 5 GHz only | 6.93 Gbps/1Gbs in Net+ | ~35m indoor | MU-MIMO, 80/160 MHz channels |
| 802.11ax (Wi-Fi 6) | 2019 | 2.4/5 GHz | 9.6 Gbps | ~30m indoor | OFDMA, BSS coloring, TWT |
| 802.11ax (Wi-Fi 6E) | 2020 | 2.4/5/6 GHz | 9.6 Gbps | ~30m indoor | Adds 6 GHz band support |
Key Technologies and Improvements
- MIMO (Multiple Input Multiple Output): Uses multiple antennas to increase throughput and reliability
- 802.11n introduced up to 4x4 MIMO
- 802.11ac added MU-MIMO (Multi-User MIMO) for simultaneous transmission to multiple clients
- Channel Bonding: Combines adjacent channels for higher bandwidth
- 802.11n: 40 MHz channels (2x 20 MHz)
- 802.11ac: 80 MHz and 160 MHz channels
- OFDMA (Orthogonal Frequency Division Multiple Access): WiFi 6 feature allowing multiple users to share a single channel simultaneously
- BSS Coloring: WiFi 6 feature that reduces interference by marking frames from different networks
Practical Deployment Considerations
- Legacy device impact: Mixed environments with older standards reduce overall network performance (protection mechanisms add overhead)
- Channel planning:
- 2.4 GHz: Use channels 1, 6, 11 only to avoid overlap
- 5 GHz: More flexibility but consider DFS (Dynamic Frequency Selection) restrictions on some channels
- Power and range trade-offs: Higher frequencies = higher speeds but shorter range and more wall penetration loss
Vocabulary
- DSSS (Direct Sequence Spread Spectrum): Modulation technique used by 802.11b
- OFDM (Orthogonal Frequency Division Multiplexing): More efficient modulation used by 802.11a/g and later
- TWT (Target Wake Time): WiFi 6 power saving feature for IoT devices
- DFS (Dynamic Frequency Selection): Radar detection requirement for certain 5 GHz channels
- Protection Mechanisms: Overhead added when mixing different WiFi standards on same network
Notes
- Real-world speeds are typically 50-70% of theoretical maximums due to protocol overhead, interference, and environmental factors
- When designing networks, consider that walls reduce signal strength by 3-15 dB depending on material (drywall vs concrete)
- For enterprise deployments, always disable legacy standards (802.11b) if not needed to improve overall network performance
- WiFi 6E requires new hardware but provides significant benefits in high-density environments due to clean 6 GHz spectrum
- Remember that wireless is half-duplex - devices can’t transmit and receive simultaneously on the same frequency, unlike wired Ethernet which is full-duplex