Broadcom NitroQAM

NitroQAM is the Broadcom name for non-standard 1024-QAM support on 802.11ac and 802.11n enabling a 25% higher data rate compared to standard rates.

Maximum Data Rate per spatial stream @ 40MHz for 802.11n and 80MHz for 802.11ac:

To make use of this technology you will need a compatible adapter and an extremely good signal.