Ieee 802.11N/Ac - Siemens SIMATIC NET System Manual

1.5.5

IEEE 802.11n/ac

Overview
The IEEE 802.11ac standard is a further development of the IEEE 802.11n standard and is
downward compatible with the standards IEEE 802.11a, IEEE 802.11h and IEEE 802.11n.
The mechanisms of the PHY and MAC layer implemented in the IEEE 802.11n standard
have been improved.
The following table contains the most important differences.
Frequency band
Channel bandwidth
Spatial streams (data streams)
MIMO
Modulation scheme
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.
Industrial Ethernet
System Manual, 09/2019, C79000-G8976-C242-10
Basics of communication with Industrial Ethernet
IEEE 802.11n
2.4 GHz and 5 GHz
20 MHz, 40 MHz
1 to 4
Single-User MIMO
OFDM (BPSK, QPSK, 16-QAM,
64-QAM)
1.5 Wireless LAN
IEEE 802.11ac
5 GHz
20 MHz, 40 MHz, 80 MHz
Optional: 160 MHz
1 to 8
Up to 4 per client
Multi-User MIMO
OFDM (BPSK, QPSK, 16-QAM,
64-QAM, 128-QAM, optional
256-QAM)
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