D-Link DWS-4026 User Manual page 422

D-Link Unified Access System
Field
Protection
No ACK
U-APSD Mode
Frag Threshold
Short Retries
Long Retries
Transmit Lifetime
Receive Lifetime
Station Isolation
Primary Channel
Short Guard Interval
Multicast Tx Rate
(Mbps)
Page 422 Basic Setup
Table 261: Advanced Radio Configuration
Description
The protection feature contains rules to guarantee that 802.11 transmissions do not cause
interference with legacy stations or applications. By default, these protection mechanisms are
enabled (Auto). With protection enabled, protection mechanisms will be invoked if legacy
devices are within range of the AP.
You can disable (Off) these protection mechanisms; however, when protection is off, legacy
clients or APs within range can be affected by 802.11n transmissions. Protection is also
available when the mode is 802.11b/g. When protection is enabled in this mode, it protects
802.11b clients and APs from 802.11g transmissions.
Select Enable to specify that the AP should not acknowledge frames with QosNoAck as the
service class value.
Select Enable to enable Unscheduled Automatic Power Save Delivery (U-APSD), which is a
power management method. U-U-APSD is recommended if VoIP phones access the network
through the AP. In U-APSD, the client sends a trigger frame and the AP delivers the buffered
frames for the client. The frame delivery is not scheduled by the AP. This is advantageous so
that when the client wakes up, it can send a trigger and get the buffered frames.
The fragmentation threshold limits the size of packets transmitted over the network.
Acceptable values are even numbers from 256-2345. Packets that are under the configured
size are not fragmented. A value of 2346 means that packets are not fragmented.
The value in this field indicates the maximum number of transmission attempts on frame sizes
less than or equal to the RTS Threshold. The range is 1-255.
The value in this field indicates the maximum number of transmission attempts on frame sizes
greater than the RTS Threshold. The range is 1-255.
Shows the number of milliseconds to wait before terminating attempts to transmit the MSDU
after the initial transmission.
Shows the number of milliseconds to wait before terminating attempts to reassemble the
MMPDU or MSDU after the initial reception of a fragmented MMPDU or MSDU.
When this option is selected, the AP blocks communication between wireless clients. It still
allows data traffic between its wireless clients and wired devices on the network, but not
among wireless clients. This feature is disabled by default.
This setting is editable only when a channel is selected and the channel bandwidth is set to
40 MHz. A 40-MHz channel can be considered to consist of two 20-MHz channels that are
contiguous in the frequency domain. These two 20-MHz channels are often referred to as the
Primary and Secondary channels. The Primary Channel is used for 802.11n clients that
support only a 20-MHz channel bandwidth and for legacy clients.
Use this setting to set the Primary Channel as the upper or lower 20-MHz channel in the
40-MHz band.
The guard interval is the dead time, in nanoseconds, between OFDM symbols. The guard
interval prevents Inter-Symbol and Inter-Carrier Interference (ISI, ICI). The 802.11n mode
allows for a reduction in this guard interval from the a and g definition of 800 nanoseconds to
400 nanoseconds. Reducing the guard interval can yield about 10% improvement in data
throughput.
Select one of the following options:
• Enable—The AP transmits data using a 400 ns guard Interval when communicating with
clients that also support the short guard interval.
• Disable—The AP transmits data using an 800 ns guard interval.
Select the 802.11 rate at which the radio transmits multicast frames. The rate is in Mbps. The
lowest rate in the 5 GHz band is 6 Mbps.
Software User Manual
Document 34CSFP6XXUWS-SWUM100-D7
12/10/09