Siemens SCALANCE W1780 Configuration Manual page 22

Description
2.4 IEEE 802.11n/ac
Multi-User
Spatial mutliplexing
With spatial multiplexing, different information is sent using the same frequency. The data
stream is distributed over n transmitting antennas; in other words, each antenna sends only 1/
n of the data stream. The division of the data stream is restricted by the number of antennas.
The signal is reconstructed at the receiver end. Due to the spatial multiplexing, there is a higher
signal-to-noise ratio and a higher data throughput.
Accelerated guard interval
The guard interval prevents different transmissions being mixed together. In
telecommunications, this mixing is also known as intersymbol interference (ISI).
When the send time has elapsed, a send pause (guard interval) must be kept to before the next
transmission begins.
The guard interval of IEEE 802.11a /b/g is 800 ns. IEEE 802.11n/ac can use the reduced guard
interval of 400 ns. You specify the guard interval on the WBM page "AP 802.11n/ac
(Page 237)".
Frame aggregation
With IEEE 802.11n/ac, it is possible to bundle together individual frames to form one larger
frame, a process referred to as frame aggregation. There are two types of frame aggregation:
● Aggregated MAC Service Data Unit (A-MSDU)
Multiple MSDU frames with the same destination address are bundled and sent as one A-
MSDU. This reduces the network load. Due to their shorter maximum length, A-MSDUs are
mainly suitable for bundling several shorter frames.
● Aggregated MAC Protocol Data Unit (A-MPDU)
Multiple MPDU frames with the same destination address are bundled and sent as one large
A-MPDU. This allows the total throughput to be increased.
22
MIMO
SCALANCE W1780/W1740 according to IEEE 802.11ac Web Based Management
Client 1
Client 2
Client 3
Client 4
Configuration Manual, 11/2019, C79000-G8976-C485-03