What is the difference between 802.11n and 802.11ac ?

Generally, the newer 802.11ac standard increases wireless speed by introducing beamforming, and using more spatial streams that are three times wider than 802.11n. It also provides better speeds at a distance because of the quieter 5GHz band and wider channels.

802.11ac does not, however, increase range compared to 802.11n - on the contrary, the 2.4GHz frequency band has longer range and better wall penetration (however can suffer from interference because of much wider adoption).


Bellow are a list of key specs and differences:

802.11n
- primarily 2.4GHz, can also use 5GHz band
- 150 Mbps per spatial stream, maximum of 4 spatial streams.
- 64-QAM
- MIMO

802.11ac
- 5GHz band only
- 433 Mbps per spatial stream, up to 8 spatial streams
- 256-QAM
- beamforming
- MU-MIMO

Generally 802.11n works in the 2.4GHz band with speeds that are multiple of its 150 Mbps spatial streams, i.e. 150, 300, 450 Mbps speeds (one to three spatial streams). Those can also be matched with up to three streams in the 5GHz band, for combined speeds of up to 900 Mbps (450 Mbps in 2.4GHz, and 450Mbps in 5GHz). In addition, there is a proprietary extension of 802.11n that allows for 200 Mbps spatial streams (using 256-QAM), for theoretical speeds of 200,400,600 Mbps in the 2.4GHz band. This is what more recent 802.11ac devices incorporate as the 802.11n portion of their speed claims, even though 256-QAM is not part of the original 802.11n specs.

Note: 802.11n specs define the standard to support up to four spatial streams, however, current devices on the market only use up to three.