Description
2.4 IEEE 802.11n
SCALANCE W780/W740 to IEEE 802.11n Web Based Management
30 Configuration Manual, 08/2018, C79000-G8976-C267-13
With IEEE 802.11n, data can be transferred via two directly neighboring channels. The two
20 MHz channels are put together to form one channel with 40 MHz. This allows the channel
bandwidth to be doubled and the data throughput to be increased.
To be able to use channel bonding, the recipient must support 40 MHz transmissions. If the
recipient does not support 40 MHz transmissions, the band is automatically reduced to 20
MHz. This means that IEEE 802.11n can also communicate with IEEE 802.11a/b/g devices.
The channel bundling is set on the "AP (Page 287)" WBM page with the "HT Channel Width
[MHz]" parameter.
With IEEE 802.11n, it is possible to group together individual data packets to form a single
larger packet; this is known as frame aggregation. There are two types of frame aggregation:
● Aggregated MAC Protocol Data Unit (A-MPDU)
With A-MPDU, multiple MPDU data packets with the same destination address are
bundled and sent as one large A-MPDU.
● Aggregated Mac Service Data Unit (A-MSDU)
With A-MSDU, multiple MSDU data packets with the same destination address are
chained together and sent.
The SCALANCE W devices support both types of frame aggregation. You make the settings
on the WBM page "AP 802.11n (Page 285)".
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.
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