The following table contains the most important differences.
IEEE 802.11n IEEE 802.11ac
Frequency band 2.4 GHz and 5 GHz 5 GHz
Channel bandwidth 20 MHz, 40 MHz 20 MHz, 40 MHz, 80 MHz
Optional: 160 MHz
Spatial streams (data streams) 1 to 4 1 to 8
Up to 4 per client
MIMO Single-User MIMO Multi-User MIMO
Modulation scheme OFDM (BPSK, QPSK, 16-QAM,
64-QAM)
OFDM (BPSK, QPSK, 16-QAM,
64-QAM, 128-QAM, optional
256-QAM)
MIMO antenna technology
MIMO (Multiple Input - Multiple Output) is based on an intelligent multiple antenna system. The
transmitter and the receiver have several spatially separate antennas. These separated
antennas transmit the data streams (spatial streams) at the same time. Up to four data streams
are possible with IEEE 802.11n and up to eight data streams with IEEE 802.11ac.
The data streams are transmitted over spatially separate paths and return over different paths
due to diffraction, refraction, fading and reflection (multipath propagation). The multipath
propagation means that at the point of reception a complex, space- and time-dependent pattern
results as a total signal made up of the individual signals sent. MIMO uses this unique pattern
by detecting the spatial position of characteristic signals. Here, each spatial position is different
from the neighboring position. The specific characteristics of each sender enable the recipient
to separate several signals from each other.
Single-User MIMO
With Single-User MIMO, the same frame is sent over multiple data streams to a single WLAN
client. A single-user MIMO can operate up to four devices alternately, but only one device at a
time.
Multi-User MIMO
With multi-user MIMO, multiple frames are sent simultaneously to different multi-user MIMO
clients over the same frequency range. A multi-user MIMO therefore supplies up to four multi-
user MIMO clients with data simultaneously.
Description
2.4 IEEE 802.11n/ac
SCALANCE W1780/W1740 according to IEEE 802.11ac Web Based Management
Configuration Manual, 11/2019, C79000-G8976-C485-03 21
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