Siemens SIMATIC NET SCALANCE W760 Series Configuration Manual page 20

Description
2.4 IEEE 802.11n
Channel bonding
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 bonding is set on the "AP" WBM page with the "HT Channel Width [MHz]"
parameter.
Frame aggregation
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) and Aggregated MAC Service Data Unit (A-
MSDU).
The frame aggregation reduces the packet overheads. Frame aggregation can only be used
if the individual data packets are intended for the same receiving station (client).
The W700 devices support both types of frame aggregation. You specify the settings for the
A-MPDU data packet on the "AP 802.11n" WBM page.
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 can use the reduced guard
interval of 400 ns. You specify the guard interval on the "AP 802.11n" WBM page.
20
SCALANCE W760/W720 to IEEE 802.11n Web Based Management
Configuration Manual, 11/2014, C79000-G8976-C350-03