Extreme Networks Summit WM User Manual page 91

The 40MHz channel width is achieved by bonding the primary channel (20MHz) with an extension
channel that is either 20MHz above (bonding up) or 20MHz below (bonding down) of the primary
channel.
Depending on the radio protocols, channel bonding can be predefined:
802.11b/g/n - Channels can bond up or down as long as the band edge is not exceeded, but some
channels have predefined bonding directions.
802.11a/n - Bonding pairs are predefined.
Channel bonding is enabled by selecting the Channel Width on the 802.11b/g/n and 802.11a/n tabs.
When selecting Channel Width, the following options are available:
20MHz - Channel bonding is not enabled:
802.11n clients use the primary channel (20 MHz)
Non-802.11n clients, beacons, and multicasts use the 802.11a/b/g radio protocols.
40MHz - Channel bonding is enabled:
802.11n clients that support the 40MHz frequency can use 40MHz, 20MHz, or the 802.11a/b/g
radio protocols.
802.11n clients that do not support the 40MHz frequency can use 20MHz or the 802.11a/b/g
radio protocols.
Non-802.11n clients, beacons, and multicasts use the 802.11a/b/g radio protocols.
If the primary channel allows for both bonding types (up and down), you can click the channel
bond type from the Channel Bonding drop-down list.
If the primary channel allows for one of the bonding types (up or down), the channel bond type
is displayed in the Channel Bonding drop-down list.
Auto - Channel bonding is automatically enabled or disabled, switching between 20MHz and
40MHz, depending on how busy the extension channel is. If the extension channel is busy above a
prescribed threshold percentage, which is defined in the 40MHz Channel Busy Threshold box,
channel bonding is disabled.
Channel selection - primary and extension
The primary channel of the Altitude 802.11n AP is selected from the Request New Channel drop-down
list. If auto is selected, the ACS feature selects the primary channel. Depending on the primary channel
that is selected, channel bonding may be allowed: up, down, both, or neither.
Guard interval
The guard intervals ensure that individual transmissions do not interfere with one another. The Altitude
802.11n AP provides a shorter guard interval that increases the channel throughput. When a 40MHz
channel is used, you can select the guard interval to improve the channel efficiency. The guard interval
is selected from the Guard Interval drop-down list. Longer guard periods reduce the channel efficiency.
Aggregate MSDU and MPDU
The Altitude 802.11n AP provides aggregate Mac Service Data Unit (MSDU) and aggregate Mac
Protocol Data Unit (MPDU) functionality, which combines multiple frames together into one larger
frame for a single delivery. This aggregation reduces the overhead of the transmission and results in
Summit WM User Guide, Software Version 5.3
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