IEEE 802.11 WiFi STANDARDS
IEEE 802.11 Standards is a part of IEEE 802 which is popularly known as WiFi used in Network connectivity. Many 802.11 wifi standards were introduced depending on the need.
IEEE 802.11 wifi standard
- IEEE 802.11standard was the original version released in 1997.
- It has two variations both having the same speed but it uses different RF spread spectrums.
- IEEE 802.11 Standard uses either frequency-hopping spread spectrum (FHSS) or direct-sequence spread spectrum (DSSS) transmission scheme for transmitting the data.
- It provides a 1 Mbps or 2 Mbps data rate in the 2.4 GHz band with three non-overlapping channels.
IEEE 802.11b WiFi standard
- 802.11b was released in July 1999.
- It supports 2.4GHz radio frequency with a maximum data rate of 11Mbps at 20MHz bandwidth with Three non-overlapping channels.
- It uses a High-rate direct-sequence spread spectrum (HR-DSSS) Transmission scheme with the QPSK modulation technique.
- 802.11b uses CCK (Complementary Code Keying) for encoding the data for communications.
- Uses single user single input single output antennas(SU-SISO).
- Distance Cover: 38m(indoor) & 140 (out).
IEEE 802.11a WiFi standard
- 802.11 a was introduced in 1999.
- It supports 5GHz radio frequency with a maximum theoretical data rate of 54 Mbps in 20MHz bandwidth with 12 non-overlapping channels.
- The data rate decreases automatically from the maximum of 54Mbps to minimum of 6 Mbps(54/48/36/24/12/9/6 Mbps) to a maintain the connectivity when a client is moving away from the Access point
- With an increase in the distance or attenuation, the data rates also decrease.
- It uses the orthogonal frequency-division multiplexing (OFDM) transmission technique with 52 sub-carrier channels having maximum modulation of 64QAM.
- Uses single user single input single output antennas(SU-SISO)
- Distance Cover: 35m (Indoor) & 120 m (outdoor)
- This standard was made to avoid interference with other devices which uses a 2.4GHz radio frequency.
IEEE 802.11g WiFi standard
- 802.11g was introduced in 2003.
- It supports 2.4GHz radio frequency with maximum data rates of 54Mbps in 20MHz bandwidth with 3 non-overlapping channels.
- It uses the orthogonal frequency-division multiplexing (OFDM) transmission technique with 52 sub-carrier channels having maximum modulation of 64QAM.
- Uses single user single input single output antennas(SU-SISO)
- It is also backward compatible with 802.11b using DSSS and CCK.
- Distance Cover: 38m(indoor) & 140 (out).
IEEE 802.11n WiFi standard
- 802.11n was published in 2009.
- It has made a big change in wireless networks.
- It supports both 2.4GHz and 5GHz radio Frequencies with the max data rate of 600Mbps in 40MHz of 4×4 spatial streams.
- The main purpose of this standard is to improve network throughput from 54Mbps to 72.2Mbps in a 1×1 spatial stream of 20MHz bandwidth.
- Uses single user multiple input multiple output antennas (SU-MIMO)
- Distance Cover: 38m(indoor) & 140 (out)
- Backward capability with 802.11 a/b/g.
Features Included in IEEE 802.11n standard :
Single user multiple input, multiple output antennas(SU-MIMO)
2. Frame aggregation A-MPDU & A-MSDU
3. Channel bonding (40MHz channels)
4. Block Acknowledgments (BLOCK ACK)
5. Short Guard Interval (short GI)
6. 802.11n interoperability (HT mode)
7. RIFS (Reduced inter-framespacing)
8. HT power management
IEEE 802.11ac WiFi standard
- 802.11 ac was released in two waves.
- 802.11ac wave1 was released in Jan 2014 and wave2 was released in June 2016.
- WiFi 5 is a standard for Very High Throughput (Very High Throughput) applications
- It supports 5GHz radio frequency with 24 non-overlapping having maximum data rates of 6.9Gbps in 160MHz bandwidth at 8×8 spatial streams.
- It was the first WiFi standard developed that could theoretically achieve gigabit speeds as opposed to megabit speeds.
Features Included in IEEE 802.11ac standard :
- Wider WiFi Channels
- Channel Bonding (can combine 8 of these to obtain a 160 MHz channel for a single client)
- Downlink MU-MIMO – Multiple-Input Multiple-Output
- Maximum Spatial Streams(8×8)
- Explicit beam forming
- More Data Transfer with 256-QAM
- 400-ns (nanosecond) short guard interval.
The following table indicates two waves of IEEE 802.11ac overview :
| IEEE 802.11ac key features | Wave 1 | Wave 2 |
| Wifi channel bandwidth | 20/40/80MHz | 20/40/80/160MHz |
| MIMO | SU-MIMO | MU-MIMO |
| Spatial streams | 4 | 8 |
| Beam forming | explicit Beam forming only | explicit Beam forming only |
| QAM | 256 QAM | 256 QAM |
| Frequency Bands | 5GHz | 5GHz |
Difference between IEEE 802.11n and IEEE 802.11ac standards
| IEEE 802.11n | IEEE 802.11ac |
| 802.11n supports 2.4 GHz and 5 GHz radio frequency bands with 20 and 40 MHz bandwidth | 802.11ac supports 5 GHz radio frequency with 20, 40, 80, 80+80 and 160 MHz bandwidth |
| It supports BPSK, QPSK, 16-QAM, and 64-QAM | It supports BPSK, QPSK, 16-QAM, 64-QAM and 256-QAM |
| Supports SU-MIMO | It supports MU-MIMO |
| It supports many versions of beamforming | Supports only explicit beam forming (null data packet) |
| It supports up to four spatial streams | AP supports up to eight spatial streams and client supIEEE 802.11 Wi-fi STANDARDSports up to four spatial streams |
| Supports single-user transmission only | It supports single-user and multi-user transmission |
| It includes significant MAC enhancements like A-MSDU and A-MPDU | It supports similar MAC enhancements with high data rates Like A-MPDU and A-MSDU. |
| Max Theoretical speed of 600Mbps | Max Theoretical speed of 6.9Gbps |
IEEE 802.11ax WiFi standard
- 802.11ax Wi-Fi standard is also known as Wi-Fi 6.
- It uses 2.4GHz 5Ghz and 6GHz radio frequencies with maximum data rates of 9.6Gbps at 160MHz bandwidth with 8×8 spatial streams.
- It supports OFDMA with 1024QAM maximum frequency modulation.
- Bandwidth: 20MHZ,40MHZ,80MHZ,160MHZ.
Features of IEEE 802.11ax Features :
- Introduced OFDMA(Orthogonal frequency division multiple access)
- BSS coloring
- Supports Down-link and up-link in OFDMA
- Downlink and uplink multi-user MIMO
- Transmit beamforming
- Higher-order modulation
- OFDMA with 1024 QAM
- Long Symbol Time and Guard Intervals
- Target wake time (TWT) power-saving mechanism
- Dual NAV timers
- Backward capability up to 802.11ac
| Wi-fi Standards | 802.11a | 802.11b | 802.11g | 802.11n | 802.11ac | 802.11ax |
| Year of Published | 1999 | 1999 | 2003 | 2009 | 2014(wave1) 2016(wave2) | 2018 |
| Supported Radios | 5GHz | 2.4GHz | 2.4GHz | 5GHz | 5GHz | 2.4GHz/5GHz |
| Max Data rates | 11Mbps | 54Mbps | 54Mbps | 600Mbps | 1.73Gbps(wave1) 6.9Gbps(wave2) | 9.6Gbps |
| Bandwidth | 20MHz | 20MHz | 20MHz | 20/40MHz | 20/40/80MHz | 20/40/80/160MHz |
| Transmission scheme | DSSS-CCK | OFDM | OFDM | OFDM | OFDM | OFDMA |
| Modulation technique | QPSK | 64QAM | 64QAM | 64QAM | 256QAM | 1024QAM |
| Sub carrier spacing | 312.5KHz | 312.5KHz | 312.5KHz | 312.5KHz | 312.5KHz | 78.125KHz |
| Number of streams | 1 | 1 | 1 | Up to 4 | Up to 8 | Up to 8 |
| Radios | SISO | SISO | SISO | SU-MIMO | MU-MIMO | MU-MIMO |
| Symbol duration | 3.2μsec | 3.2μsec | 3.2μsec | 3.2μsec | 3.2μsec | 12.8μsec |
| Guard Interval | 0.8μsec | 0.8μsec | 0.8μsec | 0.4μsec 0.8μ sec | 0.4μsec 0.8μ sec | 0.4μ sec 0.8μ sec |
